CN112362813B - Root system drawing test system and method based on PIV technology - Google Patents

Root system drawing test system and method based on PIV technology Download PDF

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CN112362813B
CN112362813B CN202011253167.0A CN202011253167A CN112362813B CN 112362813 B CN112362813 B CN 112362813B CN 202011253167 A CN202011253167 A CN 202011253167A CN 112362813 B CN112362813 B CN 112362813B
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root system
pressure chamber
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steel
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CN112362813A (en
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高乾丰
曾铃
余慧聪
史振宁
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Changsha University of Science and Technology
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Changsha University of Science and Technology
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    • G01—MEASURING; TESTING
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    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P60/00—Technologies relating to agriculture, livestock or agroalimentary industries
    • Y02P60/20—Reduction of greenhouse gas [GHG] emissions in agriculture, e.g. CO2
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Abstract

The invention discloses a root system drawing test system and method based on a PIV (particle image velocimetry) technology, wherein the system comprises a pressure chamber, a confining pressure control device, a suction control device, a root system drawing device and a PIV testing device, the pressure chamber is integrally of a semi-cylindrical sealing structure, the side surface of the pressure chamber is transparent, a semi-cylindrical sample is placed in the pressure chamber, and the vertical side surface of the sample contains a plant root system which is split from the center along the vertical direction; confining pressure controlling means and the two-way intercommunication of pressure chamber carry out the confining pressure and adjust, and suction controlling means carries out matrix suction with the two-way intercommunication of pressure chamber and adjusts, and root system draw gear sets up in the top of sample, and PIV testing arrangement is located the side dead ahead that the pressure chamber is the transparence, surveys soil grain and plant roots's movement track and speed. The method adopts a root system drawing test system based on the PIV technology to realize drawing-resistant characteristic parameters of root systems of different ages in the root system-containing soil under the action of different confining pressures and substrate suction.

Description

Root system drawing test system and method based on PIV technology
Technical Field
The invention belongs to the field of geotechnical test equipment in the civil engineering industry, and relates to a root system drawing test system and method based on a Particle Image Velocimetry (PIV) technology.
Background
In recent years, the construction of traffic infrastructures such as roads, railways and the like in China is continuously broken through, countless artificial slopes are formed all over the country, and effective protection of the slopes is important content of current geological disaster prevention and control. Plant ecological protection is widely applied to soil slope protection as a measure capable of obviously improving the strength of shallow soil, and the mechanism of the plant ecological protection mainly lies in the mechanical soil fixation effect of plant roots. The plant root system is in the soil around the root, and the root system and the soil body jointly form a root soil composite material, when the soil body is deformed under the action of external force, the stretching of the root system can limit the deformation of the soil body, and therefore the shear strength of the soil body is improved. In the actual engineering, when the side slope shallow soil body slides, part of the root system is broken due to the fact that the tensile strength is achieved, and the part of the root system is not broken but is pulled out to cause the surrounding soil body to be loosened, so that the soil body strength and the side slope stability are obviously reduced. Therefore, the research on the anti-pulling property of the plant root system is of great significance.
At present, although documents report the single-root anti-pulling performance of some plants, the anti-pulling performance of the root system when the root system and the soil body act together is rarely analyzed, the disturbance degree and the disturbance range of the root system to the nearby soil layer when the root system is pulled off or pulled out are rarely analyzed, and the reason is mainly lack of instruments and equipment for developing the research. The existing test methods such as single pull test and direct shear test have a plurality of difficulties and problems when the anti-pull property of the plant root system is measured, and mainly comprise the following steps:
1. the soil containing root systems is almost unsaturated, and the plants can absorb water in the soil during growth, so that the pore water pressure of the soil body is reduced, and the suction of the matrix is increased. The existence of the matrix suction force can obviously change the strength and deformation characteristics of the soil body, so that the properties of the soil body are completely different from those of the conventional saturated soil body. Accordingly, the root-soil interface characteristics may also change significantly. However, the influence of the suction force of the matrix cannot be considered when the existing instrument is used for measuring the anti-pulling property of the root system.
2. Because the natural environment is different, the confining pressure born by the soil body is different, so that the tightness degree of the soil body is different, and the interaction force between the plant root system and the soil body is different accordingly. Obviously, this will further affect the resistance of the plant root system to pulling. However, the existing instrument cannot accurately control the confining pressure of the soil body during the anti-drawing test, so that the influence of the confining pressure on the drawing characteristic of the root system cannot be considered.
3. When the roadbed side slope adopts plant ecological protection, under extreme conditions, if the side slope shallow soil body slides under the action of external load, a plurality of plant roots are pulled out to the outer side of the slope body, and the disturbance to the surrounding soil body is inevitably generated, so that the stability of the side slope deep soil body is influenced. However, the existing instrument can not accurately determine the slip deformation of the plant root system in the soil body and the disturbance degree and range of the plant root system to the surrounding soil body.
In conclusion, in order to accurately measure the pulling-resistant characteristics (tensile strength, pulling resistance and root soil interface friction coefficient) of single plants in different ages in root system-containing soil under the action of different confining pressures and matrix suction and the pulling-resistant characteristics (main root tensile strength and root system pulling resistance) of root systems in different ages, analyze the deformation and movement tracks of soil bodies, single plants or root systems in the pulling process, discuss the disturbance range of the single plants or the root systems to the soil bodies, disclose relevant mechanisms, and develop a novel plant root system pulling test system, it is necessary to develop a novel plant root system pulling test system.
Disclosure of Invention
The invention aims to provide a system and a method for a root system drawing test based on a PIV technology, which aim to solve the problems that the influence of substrate suction and confining pressure on the root system drawing characteristic cannot be considered when the existing instrument is used for measuring the drawing resistance characteristic of the root system, and the existing instrument cannot accurately measure the slippage deformation of a plant root system in a soil body and the disturbance degree and range of the plant root system to the surrounding soil body.
The technical scheme adopted by the embodiment of the invention is as follows: the root system drawing test system based on the PIV technology comprises a pressure chamber, a confining pressure control device, a suction control device, a root system drawing device, a PIV test device and a data acquisition system; the pressure chamber is integrally of a semi-cylindrical sealing structure, the side surface of the pressure chamber is transparent, a semi-cylindrical sample is placed in the pressure chamber, a plant root system split from the center along the vertical direction is contained in the vertical side surface of the sample, and the top end of the plant root system is exposed out of the top of the sample; the confining pressure control device is communicated with the pressure chamber in a two-way mode and used for conducting confining pressure adjustment on a sample in the pressure chamber; the suction control device is communicated with the pressure chamber in a bidirectional way and used for carrying out matrix suction adjustment on the sample in the pressure chamber; the root system drawing device is arranged above the sample and applies drawing force to the plant root system; the PIV testing device is arranged right in front of the transparent side surface of the pressure chamber and is used for measuring and recording the movement tracks and the movement rates of soil particles and plant root systems; the data acquisition system is electrically connected with the confining pressure control device, the suction control device and the PIV testing device in a bidirectional way and is electrically connected with the signal output end of the root system drawing device;
the pressure chamber comprises a steel bottom plate, an organic glass side wall and a steel top cover, the organic glass side wall and the steel bottom plate are sequentially and fixedly connected from top to bottom to form a semi-cylindrical sealed space, the sample is located in the semi-cylindrical sealed space, the organic glass side wall is vertically arranged on the periphery of the side face of the sample, the top of the organic glass side wall is in sealed connection with the bottom face of the steel top cover, and the bottom of the organic glass side wall is in sealed connection with the top face of the steel bottom plate;
a funnel-shaped water drainage tank is arranged in the middle area of the upper surface of the steel base plate, a pottery clay plate is fixed at the top of the water drainage tank, and a sample is placed on the pottery clay plate;
one side of the steel base plate is provided with a water inlet and outlet pipe interface with a water inlet and outlet pipe valve, a confining pressure water pipe interface with a confining pressure water pipe valve and a back pressure water pipe interface with a back pressure water pipe valve, one end of the water inlet and outlet pipe interface and one end of the confining pressure water pipe interface are communicated with the inside of the pressure chamber, and the other ends of the water inlet and outlet pipe interface and the confining pressure water pipe interface are communicated with a confining pressure control device; one end of the back pressure water pipe interface is communicated with the bottom of the drainage groove, and the other end of the back pressure water pipe interface is communicated with the suction control device.
Furthermore, the top of the pressure chamber, namely the steel top cover, is provided with an exhaust hole communicated with the inside of the pressure chamber and the periphery of the sample, and an exhaust screw connected with the exhaust hole in a threaded manner is arranged in the exhaust hole; the curved side surface of the sample is wrapped with a latex film for sealing the sample;
the confining pressure control device comprises a confining pressure water pipe, a confining pressure controller, a water inlet and outlet pipe, a water cylinder and a water pump, wherein the water pump is positioned in the water cylinder and is communicated with a water inlet and outlet pipe interface of the pressure chamber through the water inlet and outlet pipe;
and the confining pressure controller is communicated with the data acquisition system in a bidirectional way.
Further, an air inlet pipe interface communicated with the inside of the pressure chamber is arranged on the top of the pressure chamber, namely the steel top cover, and the air inlet pipe interface is arranged above the sample;
the suction control device comprises a back pressure controller, an air compressor, a filter, a dryer, an air pressure controller, a safety tank, a back pressure water pipe and an air inlet pipe, wherein the back pressure controller is connected with a back pressure water pipe interface of the pressure chamber through the back pressure water pipe;
the back pressure controller and the air pressure controller are respectively communicated with the data acquisition system in a bidirectional mode.
Furthermore, a convex cavity corresponding to the upper part and the lower part of the sample is arranged on the steel top cover, a hole for extending the lower end of the root system drawing device is reserved at the top of the convex cavity, and a second sealing ring is arranged around the hole; a plurality of porous annular cushion blocks which are sequentially nested are arranged on the sample, and a metal gasket is arranged between each porous annular cushion block and the steel top cover;
root system draw gear includes horizontal clamping device and vertical draw gear, and in the hole at the protruding chamber top of vertical draw gear lower extreme process steel top cap stretched into the pressure chamber, horizontal clamping device set up in the protruding intracavity of steel top cap, and horizontal clamping device fixed at vertical draw gear lower extreme, vertical draw gear can drive horizontal clamping device and vertically move down in the pressure chamber.
Furthermore, the vertical drawing device comprises a tensile machine, a cross beam, a support, a base and a drawing rod, wherein the base is fixedly connected with the cross beam through the support, a pressure chamber is fixed on the base, and a telescopic rod of the tensile machine is arranged on the cross beam; the top of the pulling rod penetrates through the cross beam and is fixedly connected with the bottom end of a telescopic rod of the tensile machine, and the bottom of the pulling rod extends into the pressure chamber through a hole in the top of a convex cavity of the steel top cover and is connected with the horizontal clamping device; a tension sensor is fixed between a telescopic rod and a drawing rod of the tension machine, and a displacement sensor is vertically fixed at the bottom of the cross beam; the drawing rod consists of a clamping device fixing rod and a drawing telescopic rod, and the top of the drawing telescopic rod is detachably connected with the bottom of the clamping device fixing rod; a displacement measuring rod is fixedly sleeved on the drawing telescopic rod, and a pointer head of a displacement sensor contacts the displacement measuring rod;
the horizontal clamping device comprises a motor, threaded rotary rods, connecting rods, a rubber pad, clamping pieces, clamping piece fixing rods and a horizontal force sensor, the motor is a bidirectional synchronous motor, two output shafts of the motor are respectively connected with one threaded rotary rod, each threaded rotary rod is in threaded connection with a nut seat, the bottom of each nut seat is fixedly connected with the horizontally placed clamping piece fixing rods through the connecting rods, the end parts of one ends of the two clamping piece fixing rods are arranged in opposite directions, the clamping pieces are movably connected to the ends, close to each other, of the two clamping piece fixing rods respectively, the clamping piece fixing rods can slide along the insides of the clamping pieces under the driving of the threaded rotary rods, and the clamping piece fixing rods can drive the clamping pieces to move towards or away from a plant root system under the action of the threaded rotary rods after sliding to the end inside the clamping pieces; a horizontal force sensor is fixed inside the clamping piece, and one end part of the clamping piece fixing rod, which is positioned inside the clamping piece, is in contact with the horizontal force sensor embedded in the clamping piece; the contact surface of the clamping piece and the plant root system is tightly attached to the rubber pad;
the lower end of the drawing telescopic rod is detachably connected with the motor, and the horizontal clamping device is fixed at the lower end of the vertical drawing device;
and the signal output ends of the horizontal force sensor, the tension sensor and the displacement sensor are electrically connected with a data acquisition system.
Furthermore, the PIV testing device comprises a rectangular testing cavity, a synchronizer, a laser power supply, a laser head, a CCD camera, an LED lamp and a PIV connecting wire, wherein the rectangular testing cavity and the pressure chamber are both fixed on a base of a vertical drawing device of the root drawing device, the rectangular testing cavity is positioned right in front of the pressure chamber, and the rectangular testing cavity is a closed space formed by a rectangular steel top plate, a rectangular steel bottom plate, three rectangular steel side walls and a transparent side face of the pressure chamber; the laser head is arranged at the lower part of the front part of the transparent side surface of the pressure chamber, the laser head is electrically connected with the output end of the laser, and the laser power supply is electrically connected with the power supply end of the laser; a CCD camera is fixed at the central position in the steel side wall arranged on the rectangular test cavity and opposite to the transparent side surface of the pressure chamber, a synchronizer is connected with the CCD camera and a laser power supply, and the synchronizer is bidirectionally connected with a computer of the data acquisition system through a PIV connecting line; the CCD camera is taken as the center, and the LED lamps are respectively arranged in four directions around the CCD camera;
the data acquisition system comprises a computer and a data acquisition box; the input end of the data acquisition box is respectively electrically connected with the confining pressure controller of the confining pressure control device, the back pressure controller and the air pressure controller of the suction control device, and the signal output ends of the horizontal force sensor, the tension sensor and the displacement sensor of the root system drawing device, and the output end of the data acquisition box and the signal input ends of the confining pressure controller, the back pressure controller and the air pressure controller are electrically connected with a computer; and the CCD camera of the PIV testing device is in bidirectional connection with the computer.
Furthermore, the organic glass side wall is formed by hermetically connecting a curved plate organic glass side wall and a flat plate organic glass side wall, wherein the curved plate organic glass side wall is arranged at the periphery of a curved side face of the sample, the flat plate organic glass side wall is arranged right in front of a vertical side face of the sample, and the curved plate organic glass side wall and the flat plate organic glass side wall are respectively hermetically connected with the top face of the steel bottom plate and the bottom face of the steel top cover;
the latex film is rectangular when being unfolded, the width of the latex film is the same as the height of the sample, and the length of the latex film is larger than the side length of the bottom of the curved side surface of the sample; the excessive parts at the two sides of the latex film wrapping the sample are unfolded along the side wall of the flat organic glass to the direction far away from the sample, and are fixedly compacted on the side wall of the flat organic glass through an organic glass fixing plate, so that the latex film seals the sample; the organic glass fixing plate is positioned between the steel bottom plate and the steel top cover and is detachably connected with the steel bottom plate and the steel top cover;
the periphery of bent plate organic glass lateral wall is provided with a plurality of stay tubes, all is provided with the vertical preformed hole that runs through it on steel top cap and the stay tube, and steel bottom plate top surface is provided with the screw hole with the preformed hole one-to-one on the steel top cap, and steel top cap and steel bottom plate pass through the screw rod and connect, and screw rod from the top down passes in proper order behind the preformed hole on steel top cap, the stay tube screw hole threaded connection on with the steel bottom plate.
The embodiment of the invention adopts another technical scheme that: the root system drawing test method based on the PIV technology adopts the root system drawing test system based on the PIV technology and comprises the following steps:
step S1, sample preparation: laying test soil with the thickness of 50-60 mm in a test box, putting plant seeds to be tested into the center of the test box, filling the test box with the test soil, and watering and cultivating the plant seeds regularly; when the plants grow to the degree required by the test, removing flowers, stems and leaves of the plants above the soil surface, only retaining the root system, and sampling by taking the root system as the center by adopting a cylindrical mould; after demolding, vertically cutting the cylindrical sample into a semi-cylinder along the center of the root system to prepare a sample containing the root system required by the test;
step S2, sample mounting: completely saturating a pottery clay plate on a steel bottom plate of the pressure chamber with degassed distilled water, and then putting a sample containing a root system into the pressure chamber to enable the vertical side surface of the sample to be in contact with the transparent side surface of the pressure chamber; then wrapping the latex film on the side surface of the sample to enable the latex film to seal the sample; then placing a proper number of porous annular cushion blocks on the upper part of the sample, and controlling the uplifting area of the top of the sample in the root system drawing process; placing a metal gasket on the porous annular cushion block, and enabling the plant root system to be detected to penetrate out of the centers of the porous annular cushion block and the metal gasket by 2-3 cm;
step S3, installing a root system drawing device: inserting the lower end of a drawing telescopic rod of a vertical drawing device of the root drawing device into a hole at the top of a convex cavity of a steel top cover, and then fixing a motor of a horizontal clamping device of the root drawing device at the lower end of the drawing telescopic rod; finally, a steel top cover is installed, a screw rod penetrates through preformed holes in the steel top cover and the support tube and then is in threaded connection with a threaded hole in the steel bottom plate, and the support tube is located between the steel top cover and the steel bottom plate and on the periphery of the side wall of the organic glass;
step S4, device start: connecting a computer of the data acquisition system, the data acquisition box, a confining pressure controller of the confining pressure control device, a back pressure controller of the suction control device and a power supply of the air pressure controller and starting up;
step S5, root clamping: opening a tensile machine of the vertical drawing device, controlling a telescopic rod of the tensile machine to move downwards through hydraulic pressure to drive the drawing telescopic rod to move downwards, driving the horizontal clamping device to move downwards until a clamping piece of the horizontal clamping device is aligned with a part of the plant root system to be detected, which extends out of the metal gasket, and then closing the tensile machine; resetting a horizontal force sensor of a horizontal clamping device, then turning on a motor, rotating the motor, driving two clamping piece fixing rods to approach to the direction of a plant root system to be detected through two threaded rotary rods and nut seats on the threaded rotary rods through a connecting rod, simultaneously observing the reading of the horizontal force sensor in real time in the process, turning off the motor when rubber pads on the two clamping pieces clamp the plant root system to be detected, and recording the reading of the horizontal force sensor at the moment, namely the horizontal clamping force;
step S6, applying confining pressure: loosening an exhaust screw in an exhaust hole in the steel top cover, opening a water inlet and outlet pipe valve, pumping distilled water in a water cylinder through a water pump of a confining pressure control device, injecting the distilled water into the pressure chamber through a water inlet and outlet pipe, and tightening the exhaust screw to close the water inlet and outlet pipe valve when the distilled water in the pressure chamber slowly flows out of the exhaust hole; clearing the reading of the confining pressure controller, opening a confining pressure water pipe valve, setting a confining pressure value required to be applied by a test through the confining pressure controller, and observing back pressure volume change data in real time to judge whether the sample consolidation is finished;
step S7, applying suction: after the confining pressure value reaches a set value and is stable, the readings of the back pressure controller and the air pressure controller of the suction control device are reset, then a back pressure water pipe valve and an air inlet pipe valve are opened, an air compressor of the suction control device is opened, the required back pressure value and the required air pressure value are set through the back pressure controller and the air pressure controller respectively, the back pressure volume change is acquired in real time through a data acquisition box of the data acquisition system, and the back pressure volume change data is observed in real time to judge whether the suction force is balanced or not;
step S8, opening PIV: after the suction is balanced, a synchronizer of the PIV testing device is controlled by a computer of the data acquisition system to enable a laser power supply and a CCD camera to work synchronously, the laser emits laser in the transparent side surface of the pressure chamber through a laser head, an LED lamp is turned on, and the moving direction and the moving speed of the plant root system and the soil particles to be tested are recorded;
step S9, root system drawing: turning on a motor, and applying a set horizontal clamping force to the plant root system to be tested through a horizontal clamping device; then, resetting a tension sensor and a displacement sensor of the vertical drawing device, opening a tension machine, enabling the tension machine to drive a drawing telescopic rod to move at a uniform speed to apply an upward drawing force to the plant root system to be tested, and recording the displacement and the drawing force in the test in real time by the displacement sensor and the tension sensor until the plant root system to be tested is drawn out or broken;
step S10, system reset: sequentially turning on a motor and a tensile machine to reset the horizontal clamping device and the drawing telescopic rod, stopping the PIV testing device, adjusting the air pressure and the back pressure to be zero through an air pressure controller and a back pressure controller, and adjusting the confining pressure to be zero through a confining pressure controller; then closing the back pressure water pipe valve, the air inlet pipe valve and the confining pressure water pipe valve, opening the water inlet and outlet pipe valve and the exhaust screw, discharging water in the pressure chamber through the water inlet and outlet pipe, and finally opening the steel top cover of the pressure chamber to remove the sample;
and S11, analyzing and processing the test data through a computer to obtain the drawing-resistant characteristic parameters of the root systems of different ages in the root system-containing soil under the action of different confining pressures and substrate suction forces.
Further, a sample containing a single to be tested was prepared as follows: measuring the diameter of a single piece to be measured, configuring a cylindrical sample with required water content according to the requirement of a test scheme, placing the single piece to be measured in the center of the cylindrical sample, cutting the cylindrical sample into a semi-cylinder along the center of the single piece to be measured after demolding, and preparing the required sample containing the single piece to be measured;
and then repeating the steps S2-S10 on the sample containing the single root to be tested, and analyzing and processing the test data obtained by repeating the steps S2-S10 on the sample containing the single root to be tested through a computer to obtain the anti-drawing characteristic parameters of the single root to be tested in different ages in the soil containing the root system under the action of different confining pressures and substrate suction forces, so as to complete the root drawing test of the single root to be tested in different ages in the soil containing the root system under the action of different confining pressures and substrate suction forces.
The embodiment of the invention has the beneficial effects that:
1. the embodiment of the invention adopts the axis translation technology to control the substrate suction force so as to consider the influence of different substrate suction forces on the pulling-resistant property of the plant root system in the unsaturated soil body, thereby truly simulating the dry-wet condition of the natural soil body, reducing the natural environment state of the plant root system as much as possible, and solving the problem that the influence of the substrate suction force on the root system pulling-resistant property can not be considered when the pulling-resistant property of the root system is measured by the existing instrument;
2. according to the embodiment of the invention, distilled water is used as a medium, different levels of confining pressure are applied to the outer side of a sample wrapped by a latex film through a pressure controller, the size of the side pressure of a soil body and the stress history are simulated, the anti-pulling characteristics of a single root and a root system in the soil body under different confining pressure conditions are further researched, and the problem that the influence of the confining pressure on the root system pulling characteristics cannot be considered when the anti-pulling characteristics of the root system are measured by using the conventional instrument is solved;
3. the embodiment of the invention adopts a Particle Image Velocimetry (PIV) technology to measure the moving direction and speed of soil particles and plant roots in the process of the drawing test in real time, thereby discussing the disturbance degree and range of a single root and root system drawn out to the nearby soil body, revealing relevant mechanisms and solving the problem that the existing instrument can not accurately measure the slippage deformation of the plant root system in the soil body and the disturbance degree and range of the plant root system to the surrounding soil body.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a structural diagram of a root system drawing test system based on the PIV technology according to an embodiment of the present invention (a PIV test apparatus is not shown).
Fig. 2 is a partial structure diagram of a root system drawing test system based on the PIV technology according to an embodiment of the present invention.
Fig. 3 is a structural view of a pressure chamber of a root system drawing test system based on the PIV technology according to an embodiment of the present invention.
Fig. 4 is a schematic view of a confining pressure control device of a root system drawing test system based on the PIV technology in the embodiment of the invention.
Fig. 5 is a schematic view of a suction control device of a root system drawing test system based on the PIV technology according to an embodiment of the invention.
Fig. 6 is a schematic view of a vertical drawing device of a root system drawing test system based on the PIV technology in an embodiment of the invention.
Fig. 7 is a schematic view of a horizontal clamping device of a root system drawing test system based on the PIV technology according to an embodiment of the invention.
Fig. 8 is a structural diagram of a PIV testing apparatus of a root system pull-out testing system based on the PIV technology according to an embodiment of the present invention.
Fig. 9 is a schematic diagram of a data acquisition system of a root system drawing test system based on the PIV technology according to an embodiment of the invention.
In the figure, 1, a pressure chamber, 2, a confining pressure control device, 3, a suction control device, 4, a root system drawing device, 5, a PIV testing device, 6, a data acquisition system, 7, a steel bottom plate, 8, an organic glass side wall, 9, a steel top cover, 10, a supporting tube, 11, a screw rod, 12, a sample, 13, a latex film, 14, an organic glass fixing plate, 15, a clay plate, 16, a porous annular cushion block, 17, a metal gasket, 18, a water inlet and outlet pipe joint, 19, a confining pressure water pipe joint, 20, a back pressure water pipe joint, 21, a water pump, 22, a drainage tank, 23, a curved plate organic glass side wall, 24, a flat organic glass side wall, 25, a drawing rod, 26, an air inlet pipe joint, 27, an exhaust hole, 28, a second sealing ring, 29, an exhaust screw, 30, a plant root system, 31, a confining pressure water pipe, 32, a confining pressure controller, 33, a water inlet and outlet pipes, 34, a water cylinder, 35. a back pressure controller, 36 air compressor, 37 filter, 38 drier, 39 air pressure controller, 40 safety tank, 41 back pressure water pipe, 42 air inlet pipe, 43 horizontal clamping device, 44 vertical pulling device, 45 motor, 46 screw rotary rod, 47 connecting rod, 48 rubber pad, 49 clip, 50 clip fixing rod, 51 horizontal force sensor, 52 pulling force machine, 53 beam, 54 bracket, 55 base, 56 pulling force sensor, 57 displacement sensor, 58 displacement measuring rod, 59 clamping device fixing rod, 60 pulling telescopic rod, 61 rectangular testing cavity, 62 synchronizer, 63 laser power supply, 64 laser, 65 laser head, 66. camera, 67 LED lamp, 68.PIV connecting line, 69 computer, 70 data collecting box, 71 water inlet and outlet pipe valve, 72 water surrounding pipe valve, 73. back pressure water line valve, 74 intake valve.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The embodiment of the invention provides a root system drawing test system based on a PIV (particle image velocimetry) technology, which is shown in figures 1-2 and comprises a pressure chamber 1, a confining pressure control device 2, a suction control device 3, a root system drawing device 4, a PIV test device 5 and a data acquisition system 6; the pressure chamber 1 is integrally of a semi-cylindrical sealing structure, the side surface of the pressure chamber is transparent, a semi-cylindrical sample 12 is placed in the pressure chamber 1, and a plant root system 30 which is split from the center along the vertical direction is contained in the vertical side surface of the sample 12. And the top end of the plant root system 30 is exposed out of the top of the sample 12; the confining pressure control device 2 is communicated with the pressure chamber 1 in a bidirectional way and is used for adjusting the confining pressure of the sample 12 in the pressure chamber 1; the suction control device 3 is communicated with the pressure chamber 1 in a bidirectional way and is used for adjusting the substrate suction of the test sample 12 in the pressure chamber 1; the root system drawing device 4 is arranged above the sample 12 and applies drawing force to the plant root system 30; the PIV testing device 5 is arranged right in front of the transparent side face of the pressure chamber 1 and is used for measuring and recording the movement tracks and the movement rates of soil particles and the plant root system 30; the data acquisition system 6 is electrically connected with the confining pressure control device 2, the suction control device 3 and the PIV testing device 5 in a bidirectional mode and is electrically connected with the signal output end of the root system drawing device 4.
Pressure chamber 1 draws experimental main generating device for the root system, as shown in fig. 2~3, including steel bottom plate 7, organic glass lateral wall 8, steel top cap 9 and sample 12, steel top cap 9, organic glass lateral wall 8, steel bottom plate 7 from the top down fixed connection in proper order forms half cylinder form enclosure space, sample 12 is located half cylinder form enclosure space, and organic glass lateral wall 8 is vertical to be set up in the side periphery of sample 12, the 8 top of organic glass lateral wall and the bottom surface sealing connection of steel top cap 9, the 8 bottom of organic glass lateral wall and the top surface sealing connection of steel bottom plate 7.
As shown in fig. 2, the organic glass side wall 8 is formed by hermetically connecting a curved organic glass side wall 23 and a flat organic glass side wall 24, wherein the curved organic glass side wall 23 is arranged at the periphery of the curved side surface of the sample 12, the flat organic glass side wall 24 is arranged right in front of the vertical side surface of the sample 12, and the curved organic glass side wall 23 and the flat organic glass side wall 24 are hermetically connected with the top surface of the steel bottom plate 7 and the bottom surface of the steel top cover 9 respectively.
Specifically, the top surface of the steel bottom plate 7 and the bottom surface of the steel top cover 9 are vertically and correspondingly provided with grooves for fixing the organic glass side wall 8, the bottom of the organic glass side wall 8 is embedded into the groove for fixing the organic glass side wall 8 on the top surface of the steel bottom plate 7, and the grooves are connected in a sealing manner through glass cement to prevent water leakage; the top of the organic glass side wall 8 is embedded into a groove on the bottom surface of the steel top cover 9, which is used for fixing the organic glass side wall 8, and the two are hermetically connected through a first sealing ring in the groove on the bottom surface of the steel top cover 9. Adopt the sealed mode sealing connection of glass cement after the embedding between bent plate organic glass lateral wall 23 and the flat plate organic glass lateral wall 24, it is specific, the position is connected with flat plate organic glass lateral wall 24 to bent plate organic glass lateral wall 23 designs into the type of dogbone, and flat plate organic glass lateral wall 24 corresponds with bent plate organic glass lateral wall 23 and designs into the type of concavity and convexity, and flat plate organic glass lateral wall 24 passes through the embedding of concave-convex position combination with bent plate organic glass lateral wall 23, all adopts glass cement to seal inside and outside the seam after the embedding.
The periphery of bent plate organic glass lateral wall 23 is provided with a plurality of stay tubes 10, all is provided with the vertical preformed hole that runs through it on steel top cap 9 and the stay tube 10, 7 top surfaces of steel bottom plate be provided with the preformed hole one-to-one's on the steel top cap 9 screw hole, steel top cap 9 and steel bottom plate 7 pass through screw rod 11 and connect, screw rod 11 from the top down pass in proper order steel top cap 9, stay tube 10 behind the preformed hole screw thread connection on with the steel bottom plate 7. As a large water pressure needs to be applied to the pressure chamber 1 during the test, the pressure chamber 1 needs to bear a large pressure, and the supporting tube 10 plays a role of supporting and protects the organic glass side wall 8. Next, the steel top cover 9 and the steel bottom plate 7 of the pressure chamber 1 also have a function of sealing the pressure chamber 1 up and down as compared with the side wall of the pressure chamber 1, and are fixed by the screw 11.
A funnel-shaped water drainage groove 22 is formed in the middle area of the upper surface of the steel bottom plate 7, an argil plate 15 is fixed to the top of the water drainage groove 22, and the sample 12 is placed on the argil plate 15. One side of the steel bottom plate 7 is provided with a water inlet and outlet pipe interface 18 with a water inlet and outlet pipe valve 71, a confining pressure water pipe interface 19 with a confining pressure water pipe valve 72 and a back pressure water pipe interface 20 with a back pressure water pipe valve 73; one ends of the water inlet and outlet pipe connector 18 and the confining pressure water pipe connector 19 are communicated with the inside of the pressure chamber 1, and the other ends of the water inlet and outlet pipe connector 18 and the confining pressure water pipe connector 19 are communicated with the confining pressure control device 2; one end of the back pressure water pipe interface 20 is communicated with the bottom of the drainage groove 22, and the other end thereof is communicated with the suction control device 3.
The curved side surface of the sample 12 is wrapped with a latex film 13, the latex film 13 is rectangular when being unfolded flatly, the width of the latex film is the same as the height of the sample 12, and the length of the latex film is larger than the bottom side length of the curved side surface of the sample 12; the extra parts on the two sides of the latex film 13 are unfolded along the flat side wall (flat organic glass side wall 24) of the organic glass side wall 8 towards the direction far away from the sample 12, and are fixedly compacted on the flat side wall (flat organic glass side wall 24) of the organic glass side wall 8 through the organic glass fixing plate 14, so that the latex film 13 seals the sample 12. The specific method is that after the extra parts on the two sides of the latex film 13 are unfolded along the flat side wall of the organic glass side wall 8 towards the direction far away from the sample 12, the bottom of the organic glass fixing plate 14 is embedded into the top surface of the steel bottom plate 7, and the organic glass fixing plate 14 is made of rigid materials, and the latex film 13 is compressible, so that a certain extrusion force can be generated on the latex film 13 after one end of the organic glass fixing plate 14 is fixed, and the latex film 13 is tightly attached to the flat organic glass side wall 24. As shown in fig. 2, the organic glass fixing plate 14 is located between the steel bottom plate 7 and the steel top cover 9 and detachably connected to the steel bottom plate 7 and the steel top cover 9, specifically, a groove for connecting the organic glass fixing plate 14 is correspondingly formed in the top surface of the steel bottom plate 7 and the bottom surface of the steel top cover 9 up and down, the top of the organic glass fixing plate 14 is embedded into the groove for connecting the organic glass fixing plate 14 on the bottom surface of the steel top cover 9, and the bottom of the organic glass fixing plate 14 is embedded into the groove for connecting the organic glass fixing plate 14 on the top surface of the steel bottom plate 7.
Be equipped with the protruding chamber that corresponds from top to bottom with sample 12 on the steel top cap 9, the hole that the drawing rod 25 that is used for root system drawing device 4 stretches out is left at protruding chamber top, establishes second sealing washer 28 around the hole to guarantee the gas tightness of pressure chamber 1. The convex cavity of the steel top cover 9 is also provided with an air inlet pipe interface 26 which is communicated with the interior of the convex cavity and is provided with an air inlet pipe valve 74, and the pressure chamber 1 is connected with the suction control device 3 through the air inlet pipe interface 26. Further, the steel top cover 9 is provided with an exhaust hole 27 communicating with the semi-cylindrical sealed space where the sample 12 is located, an exhaust screw 29 threadedly connected to the exhaust hole 27 is provided in the exhaust hole 27, the opening and closing of the exhaust hole 27 is controlled by the exhaust screw 29 with a third seal ring, and the exhaust rate can be adjusted by the degree of tightness of the connection of the exhaust screw 29 and the exhaust hole 27, and the exhaust hole 27 is used for maintaining the balance of the air pressure inside and outside the pressure chamber 1 when water is injected into the pressure chamber 1 or when water is discharged from the pressure chamber 1.
The upper surface of the sample 12 is provided with a plurality of porous annular cushion blocks 16 which are sequentially nested, metal gaskets 17 are arranged on the porous annular cushion blocks 16, the metal gaskets 17 are located between the porous annular cushion blocks 16 and the steel top cover 9, under the condition that the plurality of porous annular cushion blocks 16 are used, the innermost porous annular cushion block 16 is not pressed by the steel top cover 9 and may be loosened in the test process, the effect of controlling the protruding area of the top of the sample cannot be achieved, the porous annular cushion blocks 16 can be restrained through the metal gaskets 17, and therefore the protruding area of the top of the sample in the root system drawing process is controlled. The different numbers of the porous annular cushion blocks 16 are used for nesting, so that the allowable protruding area of the top of the sample 12 when the plant root system 30 is pulled out can be controlled, for example, for a root system with thick rootstocks, a larger protruding area needs to be reserved, and fewer porous annular cushion blocks 16 can be used for nesting; for roots with thinner roots, only a smaller area needs to be reserved, and more porous annular cushion blocks 16 can be used.
The porous annular cushion block 16 is a porous structure, and has through holes on the top surface and the side surface for gas to flow through, and the porous annular cushion block 16 is arranged to be a porous structure because the suction control device 3 applies air pressure to the inside of the sample 12 through the air inlet pipe interface 26 in the test process, and the porous annular cushion block 16 is arranged to be a porous structure so that the air pressure can be more uniformly applied to the sample 12 from the top.
The confining pressure control device 2 is used for adjusting the circumferential pressure borne by the sample 12 in the pressure chamber 1 and simulating different stress states borne by the soil body. As shown in fig. 4, the confining pressure control device 2 comprises a confining pressure water pipe 31, a confining pressure controller 32, a water inlet and outlet pipe 33, a water cylinder 34 and a water pump 21. The water pump 21 is positioned in the water cylinder 34, the water pump 21 is communicated with the water inlet and outlet pipe connector 18 of the pressure chamber 1 through the water inlet and outlet pipe 33, and the confining pressure control device 2 can pump distilled water in the water cylinder 34 through the water pump 21 to inject water into the pressure chamber 1 or discharge water in the pressure chamber 1 to the water cylinder 34; the confining pressure controller 32 is communicated with the confining pressure water pipe interface 19 of the pressure chamber 1 through the confining pressure water pipe 31, the confining pressure controller 32 is used for controlling and measuring the confining pressure of the sample 12 in the pressure chamber 1 and the volume of water entering and exiting from the confining pressure water pipe 31 in real time, the confining pressure controller 32 is a controller capable of storing a certain amount of water inside, mainly comprises a water pump, a water storage cavity, a controller and a sensor, and can adopt an ADVDPC type advanced pressure/volume controller produced by GDS company in England. The signal output end of the confining pressure controller 32 is electrically connected with the input end of a data acquisition box 70 of the data acquisition system 6, the signal input end of the confining pressure controller 32 is electrically connected with a computer 69 of the data acquisition system 6, the computer 69 controls the confining pressure controller 32 to work, and the confining pressure controller 32 transmits the measured confining pressure of the sample 12 in the pressure chamber 1 and the change value of the volume of water entering and leaving the confining pressure water pipe 31 to the data acquisition box 70 in real time.
The suction control device 3 is mainly used for controlling the substrate suction of the sample 12 in the pressure chamber 1, as shown in fig. 5, the suction control device 3 comprises a back pressure controller 35, an air compressor 36, a filter 37, a dryer 38, an air pressure controller 39, a safety tank 40, a back pressure water pipe 41 and an air inlet pipe 42; the back pressure controller 35 is connected with the back pressure water pipe interface 20 of the pressure chamber 1 through a back pressure water pipe 41; one end of the air inlet pipe 42 is connected to the air inlet pipe connection 26 of the pressure chamber 1, and the other end thereof is connected to the air compressor 36 via the safety tank 40, the air pressure controller 39, the dryer 38, and the filter 37 in this order. An air compressor 36 is used to provide air pressure, a filter 37 is used to filter solid particles and impurities from the compressed air, and a dryer 38 may dry the compressed air. The back pressure controller 35 is used for controlling and measuring the pore water pressure of the sample 12 in the pressure chamber 1 and the volume of water flowing in and out of the back pressure water pipe 41 in real time, and the back pressure controller 35 is consistent with the internal structure of the confining pressure controller 32. The air pressure controller 39 is used to control and measure the pore air pressure applied to the test piece 12 by adjusting the air pressure output from the air compressor 36 and then outputting the air of the desired pressure to the pressure chamber 1. The signal output ends of the back pressure controller 35 and the air pressure controller 39 are electrically connected with the input end of a data acquisition box 70 of the data acquisition system 6, the signal input ends of the back pressure controller 35 and the air pressure controller 39 are electrically connected with a computer 69 of the data acquisition system 6, the computer 69 controls the back pressure controller 35 and the air pressure controller 39 to work, the back pressure controller 35 transmits the measured pore water pressure of the sample 12 and the change value of the water inlet and outlet volume of the back pressure water pipe 41 to the data acquisition box 70 in real time, and the air pressure controller 39 transmits the measured pore air pressure of the sample 12 to the data acquisition box 70 in real time. The safety tank 40 is used to collect water when the water in the sample 12 is drained from the air inlet pipe 42, preventing damage to the air pressure controller 39.
The root system drawing device 4 comprises a horizontal clamping device 43 and a vertical drawing device 44, as shown in fig. 6-7, the horizontal clamping device 43 is used for providing horizontal clamping force for the plant root system 30 in the sample 12, and the vertical drawing device 44 is used for providing vertical drawing force for the plant root system 30 in the soil body. The lower end of the vertical drawing device 44 extends into the convex cavity through a hole in the top of the convex cavity of the steel top cover 9, the horizontal clamping device 43 is arranged in the convex cavity of the steel top cover 9, the horizontal clamping device 43 is fixed at the lower end of the vertical drawing device 44, and the vertical drawing device 44 can drive the horizontal clamping device 43 to vertically move downwards in the pressure chamber 1. As shown in fig. 6, the vertical pulling device 44 includes a pulling machine 52, a cross beam 53, a bracket 54, a base 55, a pulling rod 25, a pulling force sensor 56, a displacement sensor 57 and a displacement measuring rod 58, the base 55 and the cross beam 53 are fixedly connected through the bracket 54, the pressure chamber 1 is fixed on the base 55, and a telescopic rod of the pulling machine 52 is arranged on the cross beam 53; the top of the drawing rod 25 passes through the cross beam 53 to be connected with the tensile machine 52, and the bottom of the drawing rod extends into the pressure chamber 1 through a hole at the top of the convex cavity of the steel top cover 9 to be connected with the horizontal clamping device 43; the pulling rod 25 and the housing of the horizontal clamping device 43 are made of the same material, and can be connected by welding. A tension sensor 56 is fixed between the telescopic rod of the tension machine 52 and the drawing rod 25, and a displacement sensor 57 is vertically fixed at the bottom of the cross beam 53; the drawing rod 25 is composed of a clamping device fixing rod 59 and a drawing telescopic rod 60, the top of the drawing telescopic rod 60 is detachably connected with the bottom of the clamping device fixing rod 59, specifically, an external thread is arranged at the top of the drawing telescopic rod 60, an internal thread is arranged at the bottom of the clamping device fixing rod 59, and the bottom of the clamping device fixing rod 59 is in threaded connection with the top of the drawing telescopic rod 60. The pointer head of the displacement sensor 57 contacts the displacement measuring rod 58 to record the displacement of the plant root system 30 in the vertical direction in real time, and the output ends of the tension sensor 56 and the displacement sensor 57 are connected with the data acquisition box 70 of the data acquisition system 6.
The drawing rod 25 is hollow, i.e. the drawing rod 60 and the holding device fixing rod 59 are hollow. The clamping device fixing rod 59 can be composed of an inner layer and an outer layer, the inner layer and the outer layer can move relatively, the bottom of the inner layer is provided with internal threads, and the bottom of the inner layer of the clamping device fixing rod 59 is in threaded connection with the top of the drawing telescopic rod 60; the top of the inner layer of the clamping device fixing rod 59 is connected with the bottom of the tension sensor 56, the top of the tension sensor 56 is fixedly connected with the bottom of the telescopic rod of the tensile machine 52, and the connection can be realized by adopting the modes of bolts, riveting, welding and the like. The pulling machine 52 may employ a hollow hydraulic jack.
As shown in fig. 7, the horizontal clamping device 43 includes a motor 45, a screw rod 46, a connecting rod 47, rubber pad 48, clamping piece 49, clamping piece dead lever 50 and horizontal force sensor 51, motor 45 is two-way synchronous machine, a screw thread swing arm 46 is connected respectively to two output shafts of motor 45, threaded connection has the nut seat on every screw thread swing arm 46, clamping piece dead lever 50 that every nut seat bottom was placed through connecting rod 47 fixed connection level, the nut seat on two screw thread swing arms 46 sets up in opposite directions through connecting rod 47 fixed connection's clamping piece dead lever 50 tip, the one end that two clamping piece dead levers 50 are close to each other swing joint has clamping piece 49 respectively, clamping piece dead lever 50 can follow the inside slip of clamping piece 49 under the drive of screw thread swing arm 46, clamping piece 49 is inside to be fixed with horizontal force sensor 51, clamping piece dead lever 50 is located the inside one end tip of clamping piece 49 and the contact of horizontal force sensor 51 in embedding clamping piece 49. In order to ensure the stability of the screw rod 46, it can be arranged in the horizontal clamping device shell, one end of which is fixedly connected with the output shaft of the motor 45, and the other end of which is movably connected with the horizontal clamping device shell through a bearing and the like, and the bottom of the horizontal clamping device shell is provided with an opening which facilitates the left and right movement of the connecting rod 47.
Specifically, the ends of the two clamping piece fixing rods 50 close to each other extend into the clamping piece 49 from the back of the clamping piece 49, sliding grooves are formed in the clamping piece 49 along the length direction of the clamping piece fixing rods 50, protrusions are arranged on the edges of the ends of the clamping piece fixing rods 50 extending into the clamping piece 49, the protrusions on the clamping piece fixing rods 50 are connected with the sliding grooves in the clamping piece 49 in a matched mode, and the protrusions on the clamping piece fixing rods 50 can move along the sliding grooves in the clamping piece 49; a gap is reserved between the interior of the clamping piece 49 and the clamping piece fixing rod 50, and lubricating oil is coated in the upper gap and the lower gap to reduce the resistance of the clamping piece fixing rod 50 in the movement of the clamping piece 49; the contact surface of the clamping piece 49 and the plant root system 30 is tightly attached to the rubber pad 48. The clamping piece 49 can clamp the plant root system 30 and apply horizontal clamping force through the expansion and contraction of the clamping piece fixing rod 50, the clamping piece fixing rod 50 can slide along the inside of the clamping piece 49 under the driving of the threaded rotary rod 46, and the clamping piece fixing rod 50 can drive the clamping piece 49 to move close to or far away from the plant root system 30 together under the action of the threaded rotary rod 46 after sliding to the end inside the clamping piece 49. The output of the horizontal force sensor 51 is connected to the data acquisition box 70 of the data acquisition system 6 outside the pressure chamber 1 via a connection line passing through the inner space of the draw bar 25.
The vertical drawing device 44 is arranged on the test bed, and the horizontal clamping device 43 is in threaded connection with the vertical drawing device 44 through drawing threads at the lower end of the telescopic rod 60 and threaded holes at the top of the motor 45. The wire of the horizontal clamping device 43 is led out from the inside of the hollow drawing telescopic rod 60 to the data acquisition box 70 connected to the data acquisition system 6, and the wire is provided with an interface at the top of the motor 45 and can be connected or disconnected. Before the test, the horizontal clamping device 43 is unscrewed from the drawing telescopic rod 60 of the vertical drawing device 44, the wire is disconnected, the horizontal clamping device 43 is removed, and the steel top cover 9 of the pressure chamber 1 can be opened. After the sample is installed, the wire of the horizontal clamping device 3 is connected firstly, then the horizontal clamping device 43 and the vertical drawing device 44 are connected through the thread at the top of the drawing telescopic rod 60 and the motor 45, and finally the steel top cover 9 of the pressure chamber 1 is installed, so that the whole assembly of the root drawing device 4 is realized.
The PIV testing device 5 can measure the movement locus and speed of the soil particles and the plant root system 30, and as shown in fig. 8, the PIV testing device 5 comprises a rectangular testing cavity 61, a synchronizer 62, a laser power supply 63, a laser 64, a laser head 65, a CCD camera 66, an LED lamp 67 and a PIV connecting line 68. The rectangular test cavity 61 and the pressure chamber 1 are both fixed on the base 55 of the vertical pulling device 44, the rectangular test cavity 61 is located right ahead of the pressure chamber 1, and the rectangular test cavity 61 is a closed space formed by a rectangular steel top plate, a rectangular steel bottom plate, three rectangular steel side walls and a transparent side surface (flat organic glass side wall 24) of the pressure chamber 1. The laser head 65 is arranged at the lower part of the front part of the flat organic glass side wall 24 of the pressure chamber 1, the laser head 65 is electrically connected with the output end of the laser 64, and the laser power supply 63 is electrically connected with the power supply end of the laser 64. The inside central point of steel lateral wall that rectangle test chamber 61 and dull and stereotyped organic glass lateral wall 24 set up relatively puts and is fixed with CCD camera 66, synchronizer 62 connects CCD camera 66 and laser power supply 63, synchronizer 62 passes through PIV connecting wire 68 and data acquisition system 6's computer 69 both way junction, use CCD camera 66 as the center, respectively set up an LED lamp 67 in its periphery, guarantee that CCD camera 66 shoots the face field of vision bright clear, synchronizer 62 is used for synchronizing laser power supply 63 and CCD camera 66's operating frequency, when laser 64 launches the laser, pass through CCD camera 66 record effective data.
The data acquisition system 6 is used for recording various data changes in the test process, as shown in fig. 9, the data acquisition system 6 includes a data acquisition box 70 and a computer 69, the input end of the data acquisition box 70 is electrically connected with the confining pressure controller 32 of the confining pressure control device 2, the back pressure controller 35 of the suction control device 3, the air pressure controller 39 of the suction control device 3, and the signal output ends of the horizontal force sensor 51, the tension sensor 56 and the displacement sensor 57 of the root system drawing device 4, the output end of the data acquisition box 70, the signal input ends of the confining pressure controller 32, the back pressure controller 35 and the air pressure controller 39 are electrically connected with the computer 69, the CCD camera 66 of the PIV testing device 5 is directly connected with the computer 69 in a bidirectional mode, and the test data is directly acquired by the computer 69.
The internal dimension of the pressure chamber 1 in the embodiment of the invention is as follows: the diameter is 300mm, and the height is 150 mm; the dimensions of sample 12 were: diameter of 200mm, height of 100mm, and pressureThe dimensions of the force chamber 1 and the test specimen 12 can be adjusted according to actual requirements; the measuring range of the horizontal force sensor 51 and the tension sensor 56 is 10kN, and the precision is 0.001 kN; the measuring range of the displacement sensor 57 is 0 +/-200 mm, and the precision is 0.001 mm; maximum adjustment displacement of the threaded rotary rod: 20 mm; maximum clamping force of the clamping piece: 2 kN; maximum tensile force of a tensile machine: 10 kN; the confining pressure controller 32 has a pressure control range of 0-2 MPa and a volume control range of 0-100000 mm 3 The pressure precision is 0.1kPa, and the volume precision is 0.1mm 3 (ii) a The back pressure controller 35 has a pressure control range of 0-2 MPa and a volume control range of 0-100000 mm 3 The pressure precision is 0.1kPa, and the volume precision is 0.1mm 3 (ii) a The pressure control range of the air pressure controller 39 is 0-2 MPa, and the pressure precision is 0.1 kPa; the maximum sampling frequency of the CCD camera 66 is 15 Hz; the air inlet value of the clay plate 15 is 1500 kPa.
Both the confining pressure controller 32 and the back pressure controller 35 of the present embodiment can be ADVDPC type advanced pressure/volume controller manufactured by GDS (geographic Digital Systems Instruments Ltd) of UK; the air compressor 36 can be an LAHW-1030 silent oil-free air compressor produced by Zhejiang Laoshton welding equipment, Inc.; the filter 37 can be VFL-66 vacuum special straight-through filter produced by Xiamen company; the drier 38 can be a 02/0.8MPa oil-water filter manufactured by Jinyu general equipment, Inc. in Wenling; the air pressure controller 39 may be a GDSPPC type air pressure controller manufactured by GDS corporation, england; the motor 45 can be a ZWBPD 032-4 motor produced by Shenzhen MwWei electromechanical shares Limited; the horizontal force sensor 51 and the tension sensor 56 can be ZZ210-010 type tension-pressure bidirectional mechanical sensors produced by Shanghai texture exhibition measurement and control systems, Inc.; the tensile machine 52 can be an electronic tensile testing machine produced by the test technology of Jinan Meitess, Inc.; the displacement sensor 57 can be an MTR magnetic pulling type waterproof linear displacement sensor produced by Shenzhen Milan technology Limited; the CCD camera 66, the laser 64 and the PIV connecting line 68 can be selected from a 2D2C PIV system produced by Beijing Cuntian scientific and technological development Co.Ltd; the LED lamp 67 may be a JU-LE-41489 bulb manufactured by OPPLE; the data acquisition box 70 may be implemented by an ADVDCS V2 high speed digital control and acquisition system manufactured by GDS, UK.
Example 2
Referring to fig. 1 to 9, an embodiment of the invention provides a root system drawing test method based on a PIV technology, which is used for a drawing resistance test of a root system in soil containing the root system under different confining pressure and substrate suction, and the operation steps of the root system drawing test system based on the PIV technology in the embodiment 1 are as follows:
step S1, sample preparation: laying test soil with the thickness of 50-60 mm in a test box, putting plant seeds to be tested into the center of the test box, filling the test box with the test soil, and watering and cultivating the plant seeds regularly; when the plants grow to the degree required by the test, removing flowers, stems and leaves of the plants above the soil surface, only retaining the root system, and sampling by taking the root system as the center by adopting a cylindrical mould; after demolding, vertically cutting the cylindrical sample into a semi-cylinder along the center of the root system to prepare a sample 12 containing the root system required by the test;
step S2, sample mounting: completely saturating an argil plate 15 on a steel bottom plate 7 of a pressure chamber 1 with degassed distilled water, then placing a sample 12 containing a root system into the pressure chamber 1, enabling the vertical side surface of the sample to be in contact with a transparent side surface (a flat organic glass side wall 24) of the pressure chamber 1, then wrapping a latex film 13, unfolding the excessive parts on the two sides of the latex film 13 along the flat side wall of the organic glass side wall 8 in the direction far away from the sample 12, installing an organic glass fixing plate 14 to tightly press the latex film 13, enabling the latex film 13 to seal the sample 12, then placing a proper number of porous annular cushion blocks 16 on the upper part of the sample 12, and controlling the protruding area of the top of the sample in the root system drawing process; placing a metal gasket 17 on the porous annular cushion block 16, and enabling the plant root system 30 to be detected to penetrate out of the centers of the porous annular cushion block 16 and the metal gasket 17 by 2-3 cm;
step S3, installing a root system drawing device: inserting the lower end of a drawing telescopic rod 60 of the vertical drawing device 44 into a hole at the top of a convex cavity of the steel top cover 9, and then connecting the horizontal clamping device 43 to the lower end of the drawing telescopic rod 60 in a threaded manner through threads at the lower end of the drawing telescopic rod 60 and threads at the top of a motor 45 of the horizontal clamping device 43; finally, a steel top cover 9 is installed, and a screw rod 11 penetrates through preformed holes on the steel top cover 9 and the supporting tube 10 to be in threaded connection with a threaded hole on the steel bottom plate 7;
step S4, device activation: the computer 69, the data acquisition box 70, the confining pressure controller 32, the back pressure controller 35 and the air pressure controller 39 are powered on and started;
step S5, root system clamping: opening the tensile machine 52, controlling the telescopic rod of the tensile machine 52 to move downwards through hydraulic pressure to drive the drawing telescopic rod 60 to move downwards, driving the horizontal clamping device 43 to move downwards by the drawing telescopic rod 60 until the clamping piece 49 is aligned with the part of the plant root system 30 to be detected, which extends out of the metal gasket 17, and then closing the tensile machine; resetting the horizontal force sensor 51, turning on the motor 45, rotating the motor 45, driving the two clamping piece fixing rods 50 to approach to the direction of the plant root system 30 to be detected through the two threaded rotary rods 46 and the connecting rod 47, simultaneously observing the reading of the horizontal force sensor 51 in real time in the process, turning off the motor 45 when the rubber pads 48 on the two clamping pieces 49 clamp the plant root system 30 to be detected, and recording the reading of the horizontal force sensor 51 at the moment, namely the horizontal clamping force;
step S6, applying confining pressure: loosening the exhaust screw 29 on the steel top cover 9, opening the water inlet and outlet pipe valve 71, pumping distilled water in the water cylinder 34 through the water pump 21, injecting the distilled water into the pressure chamber 1 through the water inlet and outlet pipe 33, and tightening the exhaust screw 29 and closing the water inlet and outlet pipe valve 71 when the distilled water in the pressure chamber 1 slowly flows out from the exhaust hole 27; clearing the reading of the confining pressure controller 32, opening the confining pressure water pipe valve 72, setting a confining pressure value required to be applied by the test through the confining pressure controller 32, and observing the back pressure volume change data in real time to judge whether the sample consolidation is finished;
the real-time monitoring of the change of the back pressure volume is that whether the consolidation of the sample is finished or not is judged according to whether the change of the back pressure volume in a time period exceeds a certain limit value or not, and the judgment standard of the stability of the suction consolidation is as follows: the water discharge of the sample, namely the change of the back pressure volume within 2 hours continuously does not exceed 0.01cm 3 And the total duration is not less than 48h, and whether the set value is reached can be judged through the read data of the confining pressure controller 32 or the computer 69.
Step S7, applying suction: after the confining pressure value reaches a set value and is stable, the readings of the back pressure controller 35 and the air pressure controller 39 are reset, then the back pressure water pipe valve 73 and the air inlet pipe valve 74 are opened, the air compressor 36 is opened, then the required back pressure value and the required air pressure value are set through the back pressure controller 35 and the air pressure controller 39 respectively, the back pressure volume change is collected in real time through the data collection box 70, and the back pressure volume change data is observed in real time to judge whether the suction force is balanced or not;
step S8, opening PIV: after the suction force is balanced, the computer 69 controls the synchronizer 62 to enable the laser power supply 63 and the CCD camera 66 to work synchronously, the laser 64 emits laser in the transparent side surface of the pressure chamber 1, namely the flat organic glass side wall 24 through the laser head 65, the LED lamp 67 is turned on, and the moving direction and speed of the plant root system 30 and the soil particles begin to be recorded;
step S9, root system drawing: turning on the motor 45, and applying a set horizontal clamping force to the plant root system 30 to be tested through the horizontal clamping device 43; then, the tension sensor 56 and the displacement sensor 57 are cleared, the tension machine 52 is opened, the tension machine 52 drives the drawing telescopic rod 60 to move at a uniform speed to apply an upward drawing force to the plant root system 30 to be tested, and the displacement sensor 57 and the tension sensor 56 record the displacement and the drawing force in the test in real time until the plant root system 30 to be tested is drawn out or broken;
the tension sensor 56 and the displacement sensor 57 are used for measuring longitudinal tension and longitudinal displacement after the test is started, and the tension sensor 56 and the displacement sensor 57 are cleared after the horizontal clamping force is applied, so that the influence of the horizontal clamping force application process on the two sensors is reduced, and the test error is reduced as much as possible.
Step S10, system reset: sequentially turning on the motor 45 and the tensile machine 52 to reset the horizontal clamping device 43 and the drawing telescopic rod 60, stopping the PIV testing device 5, adjusting the air pressure and the back pressure to zero through the air pressure controller 39 and the back pressure controller 35, and adjusting the confining pressure to zero through the confining pressure controller 32; then closing the back pressure water pipe valve 73, the air inlet pipe valve 74 and the confining pressure water pipe valve 72, opening the water inlet and outlet pipe valve 71 and the exhaust screw 29 of the pressure chamber 1, discharging water in the pressure chamber 1 through the water inlet and outlet pipe 33, and finally opening the steel top cover 9 of the pressure chamber 1 to dismantle the sample 12;
step S11, the test data is analyzed and processed by the computer 69, the drawing-resistant characteristic parameters (main root tensile strength and root system drawing-resistant force) of the root system of different ages in the soil containing the root system under the action of different confining pressures and matrix suction can be obtained, the deformation and motion trail of the soil body and the plant root system in the drawing process are analyzed, the disturbance range of the root system drawing process to the soil body is discussed, and the relevant mechanism is revealed.
Example 3
Referring to fig. 1 to 9, an embodiment of the invention provides another application method of a root system pulling test system based on a PIV technology, which is used for testing a pulling-resistant test of a root system of a single plant, and includes the following operation steps:
step 1, measuring the diameter of a single to be tested by using a vernier caliper, configuring a cylinder sample with required water content according to the requirement of a test scheme, placing the single to be tested (one root in a single root system) in the center of the cylinder sample, cutting the cylinder sample into a semi-cylinder along the center of the single to be tested after demolding, and preparing a sample 12 containing the single to be tested, which is required by the test;
the diameter of the single to be measured is measured to calculate the tensile strength of the single to be measured, the tensile strength is equal to the pulling resistance divided by the sectional area of the single to be measured, and the section of the single to be measured is approximately round during calculation.
Step 2, repeating the steps S2-S10 on the sample 12 containing the single to be tested;
and 3, analyzing and processing the test data through the computer 69 to obtain the drawing-resistant characteristic parameters (tensile strength, drawing-resistant force and root-soil interface friction coefficient) of the single root to be tested in different ages in the root-containing soil under the action of different confining pressures and substrate suction, analyzing the deformation and movement tracks of the soil body and the single plant in the drawing process, discussing the disturbance range of the single root in the soil body in the drawing process, and revealing a relevant mechanism.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims (9)

1. The root system drawing test system based on the PIV technology is characterized by comprising a pressure chamber (1), a confining pressure control device (2), a suction control device (3), a root system drawing device (4), a PIV test device (5) and a data acquisition system (6); the pressure chamber (1) is integrally of a semi-cylindrical sealing structure, the side surface of the pressure chamber is transparent, a semi-cylindrical sample (12) is placed in the pressure chamber (1), a plant root system (30) split from the center along the vertical direction is contained in the vertical side surface of the sample (12), and the top end of the plant root system (30) is exposed out of the top of the sample (12); the confining pressure control device (2) is communicated with the pressure chamber (1) in a two-way mode and used for conducting confining pressure adjustment on the sample (12) in the pressure chamber (1); the suction control device (3) is communicated with the pressure chamber (1) in a bidirectional way and used for adjusting the substrate suction of the sample (12) in the pressure chamber (1); the root system drawing device (4) is arranged above the test sample (12) and applies drawing force to the plant root system (30); the PIV testing device (5) is arranged right in front of the transparent side face of the pressure chamber (1) and is used for measuring and recording the movement tracks and the movement speeds of soil particles and the plant root systems (30); the data acquisition system (6) is electrically connected with the confining pressure control device (2), the suction control device (3) and the PIV testing device (5) in a bidirectional way and is electrically connected with the signal output end of the root system drawing device (4);
the pressure chamber (1) comprises a steel bottom plate (7), an organic glass side wall (8) and a steel top cover (9), the organic glass side wall (8) and the steel bottom plate (7) are sequentially and fixedly connected from top to bottom to form a semi-cylinder-shaped sealed space, a sample (12) is located in the semi-cylinder-shaped sealed space, the organic glass side wall (8) is vertically arranged on the periphery of the side face of the sample (12), the top of the organic glass side wall (8) is in sealed connection with the bottom face of the steel top cover (9), and the bottom of the organic glass side wall (8) is in sealed connection with the top face of the steel bottom plate (7);
a funnel-shaped water drainage groove (22) is formed in the middle area of the upper surface of the steel bottom plate (7), a clay plate (15) is fixed to the top of the water drainage groove (22), and the sample (12) is placed on the clay plate (15);
one side of the steel base plate (7) is provided with a water inlet and outlet pipe interface (18) with a water inlet and outlet pipe valve (71), a confining pressure water pipe interface (19) with a confining pressure water pipe valve (72) and a back pressure water pipe interface (20) with a back pressure water pipe valve (73), one ends of the water inlet and outlet pipe interface (18) and the confining pressure water pipe interface (19) are communicated with the inside of the pressure chamber (1), and the other ends of the water inlet and outlet pipe interface (18) and the confining pressure water pipe interface (19) are communicated with the confining pressure control device (2); one end of the back pressure water pipe interface (20) is communicated with the bottom of the drainage groove (22), and the other end of the back pressure water pipe interface (20) is communicated with the suction control device (3).
2. The root system drawing test system based on the PIV technology as claimed in claim 1, wherein the top of the pressure chamber (1), namely the steel top cover (9), is provided with an exhaust hole (27) communicated with the inside of the pressure chamber (1) and the periphery of the test sample (12), and an exhaust screw (29) in threaded connection with the exhaust hole (27) is arranged in the exhaust hole (27); the curved side surface of the sample (12) is wrapped with a latex film (13) for sealing the sample;
the confining pressure control device (2) comprises a confining pressure water pipe (31), a confining pressure controller (32), a water inlet and outlet pipe (33), a water cylinder (34) and a water pump (21), the water pump (21) is positioned in the water cylinder (34), the water pump (21) is communicated with a water inlet and outlet pipe interface (18) of the pressure chamber (1) through the water inlet and outlet pipe (33), and the confining pressure controller (32) is communicated with a confining pressure water pipe interface (19) of the pressure chamber (1) through the confining pressure water pipe (31);
the confining pressure controller (32) is in bidirectional communication with the data acquisition system (6).
3. The root system drawing test system based on the PIV technology as claimed in claim 1, wherein an air inlet pipe interface (26) communicated with the inside of the pressure chamber (1) is arranged on the top of the pressure chamber (1), namely the steel top cover (9), and the air inlet pipe interface (26) is arranged above the test sample (12);
the suction control device (3) comprises a back pressure controller (35), an air compressor (36), a filter (37), a dryer (38), an air pressure controller (39), a safety tank (40), a back pressure water pipe (41) and an air inlet pipe (42), the back pressure controller (35) is connected with a back pressure water pipe interface (20) of the pressure chamber (1) through the back pressure water pipe (41), one end of the air inlet pipe (42) is connected with an air inlet pipe interface (26) at the top of the pressure chamber (1), and the other end of the air inlet pipe (42) is connected with the air compressor (36) through the safety tank (40), the air pressure controller (39), the dryer (38) and the filter (37) in sequence;
the back pressure controller (35) and the air pressure controller (39) are respectively communicated with the data acquisition system (6) in a bidirectional mode.
4. The root system drawing test system based on the PIV technology as claimed in claim 1, wherein a convex cavity corresponding to the upper part and the lower part of the sample (12) is arranged on the steel top cover (9), a hole for extending the lower end of the root system drawing device (4) is reserved at the top of the convex cavity, and a second sealing ring (28) is arranged around the hole; a plurality of porous annular cushion blocks (16) which are sequentially nested are arranged on the sample (12), and a metal gasket (17) is arranged between each porous annular cushion block (16) and the steel top cover (9);
root system draw-off gear (4) include horizontal clamping device (43) and vertical draw-off gear (44), and vertical draw-off gear (44) lower extreme stretches into pressure chamber (1) through the hole at the protruding chamber top of steel top cap (9), and horizontal clamping device (43) set up in the protruding intracavity of steel top cap (9), and horizontal clamping device (43) are fixed at vertical draw-off gear (44) lower extreme, and vertical draw-off gear (44) can drive horizontal clamping device (43) vertical downstream in pressure chamber (1).
5. The root system drawing test system based on the PIV technology as claimed in claim 4, wherein the vertical drawing device (44) comprises a drawing machine (52), a cross beam (53), a support (54), a base (55) and a drawing rod (25), the base (55) and the cross beam (53) are fixedly connected through the support (54), the pressure chamber (1) is fixed on the base (55), and an expansion rod of the drawing machine (52) is arranged on the cross beam (53); the top of the drawing rod (25) penetrates through the cross beam (53) to be fixedly connected with the bottom end of a telescopic rod of the tensile machine (52), and the bottom of the drawing rod (25) extends into the pressure chamber (1) through a hole in the top of a convex cavity of the steel top cover (9) to be connected with the horizontal clamping device (43); a tension sensor (56) is fixed between the telescopic rod and the drawing rod (25) of the tensile machine (52), and a displacement sensor (57) is vertically fixed at the bottom of the cross beam (53); the drawing rod (25) consists of a clamping device fixing rod (59) and a drawing telescopic rod (60), and the top of the drawing telescopic rod (60) is detachably connected with the bottom of the clamping device fixing rod (59); a displacement measuring rod (58) is fixedly sleeved on the drawing telescopic rod (60), and a pointer head of the displacement sensor (57) contacts the displacement measuring rod (58);
horizontal clamping device (43) includes motor (45), screw thread swing arm (46), connecting rod (47), rubber pad (48), clamping piece (49), clamping piece dead lever (50) and horizontal force sensor (51), motor (45) is two-way synchronous machine, a screw thread swing arm (46) is connected respectively to two output shafts of motor (45), threaded connection has nut seat on every screw thread swing arm (46), clamping piece dead lever (50) that every nut seat bottom was placed through connecting rod (47) fixed connection level, the one end tip of two clamping piece dead levers (50) sets up in opposite directions, and the one end that two clamping piece dead levers (50) are close to each other respectively swing joint has clamping piece (49), clamping piece dead lever (50) can follow clamping piece (49) inside and slide under the drive of screw thread swing arm (46), and clamping piece dead lever (50) can drive clamping piece (49) to be close to or keep away from together under the effect of screw thread swing arm (46) after clamping piece (49) inside slides to the end The direction of the plant root system (30) moves; a horizontal force sensor (51) is fixed inside the clamping piece (49), and one end part of the clamping piece fixing rod (50) positioned inside the clamping piece (49) is contacted with the horizontal force sensor (51) embedded in the clamping piece (49); the contact surface of the clamping piece (49) and the plant root system (30) is tightly attached to the rubber pad (48);
the lower end of the drawing telescopic rod (60) is detachably connected with the motor (45), and the horizontal clamping device (43) is fixed at the lower end of the vertical drawing device (44);
and the signal output ends of the horizontal force sensor (51), the tension sensor (56) and the displacement sensor (57) are electrically connected with the data acquisition system (6).
6. The root system drawing test system based on the PIV technology as claimed in claim 1, wherein the PIV test device (5) comprises a rectangular test cavity (61), a synchronizer (62), a laser power supply (63), a laser (64), a laser head (65), a CCD camera (66), an LED lamp (67) and a PIV connecting line (68), the rectangular test cavity (61) and the pressure chamber (1) are both fixed on a base (55) of a vertical drawing device (44) of the root system drawing device (4), the rectangular test cavity (61) is located right in front of the pressure chamber (1), and the rectangular test cavity (61) is a closed space formed by a rectangular steel top plate, a rectangular steel bottom plate, three rectangular steel side walls and a transparent side face of the pressure chamber (1); the laser head (65) is arranged at the lower front part of the transparent side surface of the pressure chamber (1), the laser head (65) is electrically connected with the output end of the laser (64), and the laser power supply (63) is electrically connected with the power supply end of the laser (64); a CCD camera (66) is fixed at the center position in the steel side wall of the rectangular test cavity (61) opposite to the transparent side face of the pressure chamber (1), a synchronizer (62) is connected with the CCD camera (66) and a laser power supply (63), and the synchronizer (62) is in bidirectional connection with a computer (69) of the data acquisition system (6) through a PIV (particle image velocimetry) connecting line (68); the LED lamp (67) is arranged in each of four directions around a CCD camera (66) by taking the CCD camera as a center;
the data acquisition system (6) comprises a computer (69) and a data acquisition box (70); the input end of the data acquisition box (70) is respectively electrically connected with the confining pressure controller (32) of the confining pressure control device (2), the back pressure controller (35) and the air pressure controller (39) of the suction control device (3), and the signal output ends of the horizontal force sensor (51), the tension sensor (56) and the displacement sensor (57) of the root system drawing device (4), and the output end of the data acquisition box (70), the signal input ends of the confining pressure controller (32), the back pressure controller (35) and the air pressure controller (39) are electrically connected with the computer (69); the CCD camera (66) of the PIV testing device (5) is connected with the computer (69) in a bidirectional mode.
7. The root system drawing test system based on the PIV technology as claimed in any one of claims 1-6, wherein the organic glass side wall (8) is formed by hermetically connecting a curved organic glass side wall (23) and a flat organic glass side wall (24), wherein the curved organic glass side wall (23) is arranged at the periphery of the curved side surface of the test sample (12), the flat organic glass side wall (24) is arranged right in front of the vertical side surface of the test sample (12), and the curved organic glass side wall (23) and the flat organic glass side wall (24) are hermetically connected with the top surface of the steel bottom plate (7) and the bottom surface of the steel top cover (9) respectively;
the curved side surface of the sample (12) is wrapped with a latex film (13) for sealing the sample, the latex film (13) is rectangular when being unfolded, the width of the latex film is the same as the height of the sample (12), and the length of the latex film is greater than the bottom side length of the curved side surface of the sample (12); the parts of the two sides of the latex film (13) wrapping the sample (12) which are more than needed are unfolded along the flat organic glass side wall (24) to the direction far away from the sample (12), and are fixedly compacted on the flat organic glass side wall (24) through an organic glass fixing plate (14), so that the latex film (13) seals the sample (12); the organic glass fixing plate (14) is positioned between the steel bottom plate (7) and the steel top cover (9) and is detachably connected with the steel bottom plate (7) and the steel top cover (9);
the periphery of bent plate organic glass lateral wall (23) is provided with a plurality of stay tubes (10), all be provided with vertical preformed hole that runs through it on steel top cap (9) and stay tube (10), steel bottom plate (7) top surface be provided with the preformed hole one-to-one's on steel top cap (9) screw hole, steel top cap (9) and steel bottom plate (7) pass through screw rod (11) and connect, screw rod (11) from the top down passes steel top cap (9) in proper order, behind the preformed hole on stay tube (10) with the screw hole threaded connection on steel bottom plate (7).
8. A root system drawing test method based on the PIV technology is characterized in that the root system drawing test system based on the PIV technology of any one of claims 1-6 is adopted, and the method comprises the following steps:
step S1, sample preparation: laying test soil with the thickness of 50-60 mm in a test box, putting plant seeds to be tested into the center of the test box, filling the test box with the test soil, and watering and cultivating the plant seeds regularly; when the plants grow to the degree required by the test, removing flowers, stems and leaves of the plants above the soil surface, only retaining root systems, and sampling by taking the root systems as the centers by adopting a cylindrical mould; after demolding, vertically cutting the cylindrical sample into a semi-cylinder along the center of the root system to prepare a sample (12) containing the root system required by the test;
step S2, sample mounting: completely saturating a pottery clay plate (15) on a steel bottom plate (7) of the pressure chamber (1) by using degassed distilled water, and then putting a sample (12) containing a root system into the pressure chamber (1) to enable the vertical side surface of the sample to be in contact with the transparent side surface of the pressure chamber (1); then wrapping the latex film (13) on the side surface of the sample (12) to enable the latex film (13) to seal the sample (12); then, placing a proper number of porous annular cushion blocks (16) on the upper part of the sample (12) and controlling the top bulging area of the sample in the root system drawing process; placing a metal gasket (17) on the porous annular cushion block (16), and enabling the plant root system (30) to be detected to penetrate out of the centers of the porous annular cushion block (16) and the metal gasket (17) by 2-3 cm;
step S3, installing a root system drawing device: inserting the lower end of a drawing telescopic rod (60) of a vertical drawing device (44) of the root drawing device (4) into a hole at the top of a convex cavity of a steel top cover (9), and then fixing a motor (45) of a horizontal clamping device (43) of the root drawing device (4) at the lower end of the drawing telescopic rod (60); finally, a steel top cover (9) is installed, a screw rod (11) penetrates through preformed holes in the steel top cover (9) and the support pipe (10) and then is in threaded connection with a threaded hole in the steel bottom plate (7), and the support pipe (10) is located between the steel top cover (9) and the steel bottom plate (7) and on the periphery of the organic glass side wall (8);
step S4, device start: the computer (69) of the data acquisition system (6), the data acquisition box (70), the confining pressure controller (32) of the confining pressure control device (2), the back pressure controller (35) of the suction control device (3) and the air pressure controller (39) are connected and started;
step S5, root system clamping: opening a tensile machine (52) of the vertical drawing device (44), controlling a telescopic rod of the tensile machine (52) to move downwards through hydraulic pressure to drive a drawing telescopic rod (60) to move downwards, driving a horizontal clamping device (43) to move downwards by the drawing telescopic rod (60) until a clamping piece (49) of the horizontal clamping device is aligned with a part, extending out of the metal gasket (17), of the plant root system (30) to be detected, and then closing the tensile machine (52); clearing a horizontal force sensor (51) of a horizontal clamping device (43) and then turning on a motor (45), enabling the motor (45) to rotate, driving two clamping piece fixing rods (50) to approach to the direction of a plant root system (30) to be detected through two threaded rotary rods (46) and nut seats on the threaded rotary rods through a connecting rod (47), simultaneously observing the reading of the horizontal force sensor (51) in real time in the process, turning off the motor (45) when the plant root system (30) to be detected is clamped by rubber pads (48) on two clamping pieces (49), and recording the reading of the horizontal force sensor (51) at the moment, namely the horizontal clamping force;
step S6, applying confining pressure: loosening an exhaust screw (29) in an exhaust hole (27) on a steel top cover (9), opening a water inlet and outlet pipe valve (71), pumping distilled water in a water cylinder (34) through a water pump (21) of a confining pressure control device (2), injecting the distilled water into a pressure chamber (1) through a water inlet and outlet pipe (33), tightening the exhaust screw (29) when the distilled water in the pressure chamber (1) slowly flows out of the exhaust hole (27), and closing the water inlet and outlet pipe valve (71); clearing the reading of the confining pressure controller (32), opening a confining pressure water pipe valve (72), setting a confining pressure value required to be applied by a test through the confining pressure controller (32), and observing back pressure volume change data in real time to judge whether the sample consolidation is finished;
step S7, applying suction: after the confining pressure value reaches a set value and is stable, reading of a back pressure controller (35) and an air pressure controller (39) of the suction control device (3) is cleared, a back pressure water pipe valve (73) and an air inlet pipe valve (74) are opened, an air compressor (36) of the suction control device (3) is opened, a required back pressure value and an air pressure value are set through the back pressure controller (35) and the air pressure controller (39) respectively, back pressure volume change is collected in real time through a data collection box (70) of a data collection system (6), and back pressure volume change data are observed in real time to judge whether suction is balanced or not;
step S8, opening PIV: after the suction is balanced, a computer (69) of the data acquisition system (6) controls a synchronizer (62) of the PIV testing device (5) to enable a laser power supply (63) and a CCD camera (66) to work synchronously, a laser (64) emits laser in the transparent side surface of the pressure chamber (1) through a laser head (65), an LED lamp (67) is turned on, and the moving direction and speed of a plant root system (30) to be tested and soil particles are recorded;
step S9, root system drawing: turning on a motor (45), and applying a set horizontal clamping force to the plant root system (30) to be tested through a horizontal clamping device (43); then clearing a tension sensor (56) and a displacement sensor (57) of the vertical drawing device (44) to zero, then opening a tension machine (52), enabling the tension machine (52) to drive a drawing telescopic rod (60) to move at a uniform speed to apply an upward drawing force to the plant root system (30) to be tested, and recording the displacement and the drawing force in the test in real time by the displacement sensor (57) and the tension sensor (56) until the plant root system (30) to be tested is pulled out or pulled out;
step S10, system reset: sequentially turning on a motor (45) and a tensile machine (52), resetting a horizontal clamping device (43) and a drawing telescopic rod (60), stopping a PIV testing device (5), adjusting the air pressure and the back pressure to be zero through an air pressure controller (39) and a back pressure controller (35), and adjusting the confining pressure to be zero through a confining pressure controller (32); then closing a back pressure water pipe valve (73), an air inlet pipe valve (74) and a confining pressure water pipe valve (72), opening a water inlet and outlet pipe valve (71) and an exhaust screw (29), discharging water in the pressure chamber (1) through a water inlet and outlet pipe (33), and finally opening a steel top cover (9) of the pressure chamber (1) to remove the sample (12);
and step S11, analyzing and processing the test data through the computer (69) to obtain the drawing-resistant characteristic parameters of the roots of different ages in the soil containing the roots under the action of different confining pressures and substrate suction.
9. The PIV technology-based root system drawing test method according to claim 8, characterized in that the sample (12) containing the single root to be tested is prepared according to the following method: measuring the diameter of a single to be tested, configuring a cylinder sample with required water content according to the requirement of a test scheme, placing the single to be tested at the center of the cylinder sample, cutting the cylinder sample into a semi-cylinder along the center of the single to be tested after demolding, and preparing the required sample (12) containing the single to be tested;
and then repeating the steps S2-S10 on the sample (12) containing the single root to be detected, analyzing and processing the test data obtained by repeating the steps S2-S10 on the sample (12) containing the single root to be detected through a computer (69), obtaining the anti-pulling characteristic parameters of the single root to be detected in different ages in the soil containing the root system under the action of different confining pressures and substrate suction, and completing the root system pulling test of the single root to be detected in different ages in the soil containing the root system under the action of different confining pressures and substrate suction.
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