CN113092283B - Device and method for analyzing mechanical characteristics of soil under action of plant root system - Google Patents

Device and method for analyzing mechanical characteristics of soil under action of plant root system Download PDF

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CN113092283B
CN113092283B CN202110415157.0A CN202110415157A CN113092283B CN 113092283 B CN113092283 B CN 113092283B CN 202110415157 A CN202110415157 A CN 202110415157A CN 113092283 B CN113092283 B CN 113092283B
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root
soil
cultivation
sleeve
water
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CN113092283A (en
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毛正君
耿咪咪
毕银丽
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Xian University of Science and Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/24—Investigating strength properties of solid materials by application of mechanical stress by applying steady shearing forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/36—Embedding or analogous mounting of samples
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/36—Embedding or analogous mounting of samples
    • G01N2001/366—Moulds; Demoulding
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0016—Tensile or compressive
    • G01N2203/0017—Tensile
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0016—Tensile or compressive
    • G01N2203/0019—Compressive
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0025—Shearing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/026—Specifications of the specimen
    • G01N2203/0298—Manufacturing or preparing specimens

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  • Cultivation Receptacles Or Flower-Pots, Or Pots For Seedlings (AREA)

Abstract

The invention discloses a device and a method for analyzing mechanical characteristics of soil under the action of a plant root system, wherein the device comprises a cultivation container and a cultivation control system; a porous plate is arranged in the cultivation container, and a cultivation sleeve is arranged on the porous plate; the cultivation control system comprises a first water level sensor, a temperature sensor, a timer, a controller, a first electromagnetic valve, a second electromagnetic valve, a third electromagnetic valve, a water pumping device, a nutrient solution pumping device, a water tank, a nutrient solution tank and a heating sheet; the cultivating container is provided with a transfusion hose. The invention also provides a method for testing by adopting the analysis device, which comprises the steps of cultivating the root-soil complex sample, taking out the root-soil complex sample, carrying out a triaxial compression test, carrying out a direct shear test and carrying out a root system extraction test in the cultivating sleeve. The device has the advantages of convenient demoulding and effective obtaining of an original sample, and the mechanical property research of the soil under the action of the plant root system can be carried out by adopting the device and the method.

Description

Device and method for analyzing mechanical characteristics of soil under action of plant root system
Technical Field
The invention belongs to the technical field of civil test equipment, and particularly relates to a device and a method for analyzing mechanical properties of soil under the action of a plant root system.
Background
Along with the development of urban construction and traffic infrastructure, disasters such as slope surface soil body sliding, water and soil loss and the like caused by engineering activities are increased year by year, potential hazards are caused to cities, towns, railways and highways to a certain extent, and certain influence is brought to social and economic construction and development. Therefore, the method accelerates the vegetation recovery of the side slope, improves the stability of the side slope and reduces the water and soil loss, and is a problem which needs to be solved urgently at present. At present, the plant root system has been widely accepted and accepted by people to effectively prevent and treat natural disasters such as side slope shallow landslide and the like. The important index for measuring the soil stabilization and slope protection effect of the plant root system is the influence of the plant on the shear strength of the soil body, which is the key for understanding the strengthening effect of the plant root system on the soil body strength, and is an important way for keeping the stability of the slope excavated in engineering facilities such as railways, highways, hydropower, roadways, ports and the like and avoiding water and soil loss through the plant.
The indoor test of shear strength of present common soil includes direct shear test, triaxial compression test, unconfined compressive strength test etc. but because the sample that needs to gather when carrying out the shear strength test is more, it is experimental to be inconvenient to bring back indoor, and outdoor sample is comparatively difficult, consequently adopt remolded soil to test in the laboratory often, but because the root soil complex body soil of remolding is artificial formation, compare with the root soil complex body under the natural condition, the structure can not keep unanimous, how effectively gain the original state sample and utilize the original state sample that obtains to carry out the mechanical properties analysis of soil under the plant roots effect, be the important way that reduces experimental error, improve experimental precision.
Disclosure of Invention
The invention aims to solve the technical problem of providing a device and a method for analyzing the mechanical properties of soil under the action of a plant root system, aiming at the defects of the prior art. The device for analyzing the mechanical properties of the soil under the action of the plant root system has the advantages of being convenient to demould, capable of effectively obtaining the advantages of an undisturbed sample and capable of researching the influence of the plant root system on the strength properties of the loess.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: the utility model provides a mechanical properties analytical equipment of soil under plant roots effect which characterized in that includes: a culture container and a culture control system for culturing a root-soil complex sample; a plurality of culture sleeves are arranged on the water permeable plate;
the cultivation control system comprises a first water level sensor, a temperature sensor, a timer, a controller, a first electromagnetic valve, a second electromagnetic valve, a third electromagnetic valve, a water pumping device, a nutrient solution pumping device, a water tank, a nutrient solution tank and a heating sheet;
the first water level sensor is arranged in the cultivation container; the heating plate and the temperature sensor are both arranged on the cultivation container;
the first water level sensor, the temperature sensor, the timer, the first electromagnetic valve, the second electromagnetic valve and the third electromagnetic valve are electrically connected with the controller;
the water tank is provided with a first water inlet pipe, one end of the first water inlet pipe, far away from the water tank, is connected to the cultivation container, the water pumping device is arranged in the water tank and is communicated with the first water inlet pipe, and the first electromagnetic valve is arranged on the first water inlet pipe;
the first water inlet pipe is communicated with a second water inlet pipe, and the second electromagnetic valve is arranged on the second water inlet pipe;
a third water inlet pipe is arranged on the nutrient solution box, and a transfusion hose is arranged on the cultivation container; one end of the second water inlet pipe, which is far away from the first water inlet pipe, and one end of the third water inlet pipe, which is far away from the nutrient solution tank, are connected to the infusion hose, and the wall of the infusion hose is provided with a liquid outlet hole; the nutrient solution pumping device is arranged in the nutrient solution box and communicated with a third water inlet pipe, and the third electromagnetic valve is arranged on the third water inlet pipe.
The device for analyzing the mechanical properties of the soil under the action of the plant root system is characterized in that the cultivation sleeve comprises a plurality of pipe sections which are sequentially arranged, a connecting sleeve for connecting adjacent pipe sections is sleeved on each pipe section, and a tie for the pipe sections is arranged on each pipe section; the pipe section comprises a left half pipe section and a right half pipe section, and the shape and the structure of the left half pipe section are the same as those of the right half pipe section.
The mechanical property analytical equipment of foretell plant root system effect soil down, a serial communication port, adapter sleeve includes half adapter sleeve on the left side and half adapter sleeve on the right side, half adapter sleeve on the left side and half adapter sleeve on the right side shape and structure are all the same, cultivate with the sleeve pipe still including tying up in ribbon for the sleeve pipe on the adapter sleeve.
The mechanical property analysis device of soil under foretell plant root system effect, its characterized in that, cultivate the container for taking interbedded cultivation container, the heating plate sets up in the interlayer.
The mechanical property analysis device for soil under the action of the plant root system is characterized by further comprising a camera, an LED lamp, a bottom plate, universal wheels, a solar light panel and a storage battery capable of storing electric energy generated by the solar light panel;
the bottom plate is arranged below the cultivation container, and the bottom plate is provided with a mounting bracket for mounting the solar light panel, the camera and the LED lamp;
the mounting bracket is a height-adjustable mounting bracket;
the universal wheel is arranged at the lower part of the bottom plate.
The present invention also provides a method for manufacturing a device for analyzing mechanical properties of soil under plant root system action, including a method for manufacturing a cultivation sleeve, the method for manufacturing the cultivation sleeve including:
cutting a pipe into N sections to obtain N sectional pipes; n is more than or equal to 2;
step two, cutting each section-shaped pipe along the axial direction, and correspondingly obtaining N groups of left half pipe sections and right half pipe sections with the same shape and structure;
step three, the left half pipe section and the corresponding right half pipe section are opposite to each other to obtain N pipe sections, and the pipe sections are respectively bound along the circumferential direction of the pipe sections by using binding belts;
and step four, sequentially placing N pipe sections bound with the pipe section binding tapes to form (N-1) pipe section adjacent positions, and respectively sleeving the (N-1) connecting sleeves to the pipe section adjacent positions to obtain the cultivation sleeves.
Further, the invention also provides a method for researching by adopting the device for analyzing the mechanical properties of the soil under the action of the plant root system, which is characterized by comprising the steps of cultivating a root-soil complex sample, taking out the root-soil complex sample, performing a triaxial compression test, performing a direct shear test and performing a root system extraction test in a cultivating sleeve; the cultivation of the root soil complex sample comprises:
filling sand grains into a cultivation container to form a sand layer with the height of 5-10 cm, placing a water permeable plate on the sand layer, and vertically arranging the cultivation sleeve on the water permeable plate;
filling soil into the cultivation casing, tamping, filling and scattering plant seeds in layers;
step three, conveying water into the cultivation container, enabling the water entering the cultivation container to enter a cultivation casing after passing through a sand layer and a permeable plate, detecting the water level in the cultivation container by a first water level sensor and transmitting a detected water level signal to a controller, controlling a first electromagnetic valve to be opened by the controller until the water level in the cultivation container reaches a preset height, and closing the first electromagnetic valve to finish water conveying;
conveying nutrient solution in the nutrient solution box to a transfusion hose through a third water inlet pipe, simultaneously enabling water in the water box to flow into the transfusion hose through a second water inlet pipe, spraying the nutrient solution and the water which are converged into the transfusion hose into a sleeve for cultivation through a liquid outlet hole in the transfusion hose until the preset time is reached, and controlling a second electromagnetic valve and a third electromagnetic valve to be closed by a controller to finish nutrient solution spraying;
step five, the temperature sensor detects the temperature, and transmits a detected temperature signal to the controller, the controller compares the obtained temperature signal with a preset temperature value, and when the obtained temperature signal value is lower than the preset temperature value, the controller controls the heating sheet to heat until the temperature reaches the preset temperature value;
and step six, cultivating according to the steps till the preset cultivation time is reached, and finishing cultivation.
The method described above, wherein the method for taking out a root-soil composite sample includes:
after the culture is completed, the culture sleeve containing the root-soil complex sample is taken out of the culture container, the connecting sleeve is taken down, the sleeve is cut along the adjacent position of the pipe section, the upper section is taken, the upper section of the sleeve containing the root-soil complex sample is obtained, the root-soil complex sample is separated from the inner wall surface of the upper section of the sleeve, and the binding tape for the pipe section is removed, so that the root-soil complex sample is obtained.
The method described above is characterized in that the method for testing root extraction in the cultivation cannula includes:
after the cultivation is finished, taking out the cultivation sleeve filled with the root soil complex sample, cutting along the joint of the root system and the plant stem of the plant, and removing the stem-containing part;
cutting along the upper surface of the root-soil complex sample, removing a soil body part which is 1 cm-2 cm away from the edge of the upper surface, and clamping the root part of the upper surface of the root-soil complex sample by using a clamp; install the tensiometer in on the anchor clamps, tensiometer pulling anchor clamps, anchor clamps drive the root system and extract to the root system, when the root system extracted the process root system fracture, under the record rupture state the tensiometer reading, the diameter and the rupture length of fracture department, when the root system extracted the process root system not fracture, under the record slippage state the tensiometer reading, main root terminal department diameter and the length of sliding.
The method is characterized by further comprising a method for determining the shear strength of the root-soil composite, wherein the method for determining comprises the following steps:
step one, determining the extraction force T according to a root extraction test in a cultivation sleeve b ，T b The unit is KN;
step two, determining a shear strength measured value of the root-soil complex and a shear strength measured value of the plain soil according to a triaxial compression test and a direct shear test;
step three, the pull-out force T in the step one is used b Substituting into formula S r ＝1.2·T b A, obtaining a theoretical value S of the cohesive force of the root-soil complex r ，S r Has a unit of KPa, A is the shear cross-sectional area, and m is the unit 2 ；
Step four, subtracting the shear strength measured value of the native soil from the shear strength measured value of the root soil complex in the step two to obtain a measured value of the cohesion of the root soil complex;
step five, utilizing the theoretical value of the cohesion of the root-soil complex under different cultivation time
Figure BDA0003025590510000051
Fitting to obtain a functional relation S between the theoretical value of cohesive force of the fitted root-soil complex and time r (t); wherein a, c, d and k are fitting parameters; t is the cultivation time in years;
step six, utilizing the cohesion of the root-soil complex under different cultivation time
Figure BDA0003025590510000061
Fitting to obtain the functional relation c between the cohesive force of the root-soil complex and the time r (t); wherein a ', c', d ', k' are fitting parameters; t is the cultivation time in years;
step seven, the S of the step five r (t) and c of step six r (t) bringing in
Figure BDA0003025590510000062
Obtaining a correction coefficient k' (t); wherein, c Plain soil The unit is the cohesive force of the plain soil and KPa;
step eight, the step seven is describedThe correction coefficient k ″ (t) is substituted into the formula S (t) k ″ (t) S r +c Plain soil Obtaining the shear strength S of the root-soil complex (t) ，S (t) In units of KPa.
Compared with the prior art, the invention has the following advantages:
1. the device comprising the cultivation container, the cultivation sleeve and the cultivation control system has the advantages of convenient demoulding and effective obtaining of an original sample, and can be used for researching the influence of a plant root system on the loess strength characteristic.
2. Preferably, the cultivation sleeve comprises a plurality of pipe sections which are connected in sequence, and each pipe section comprises a left half pipe section and a right half pipe section which can be enclosed, so that the cultivation sleeve can be more conveniently peeled from an internal soil sample.
3. The method comprises a method for determining the shear strength of the root-soil complex obtained by correcting the Wu-Waldron model according to a root system pull-out strength test, wherein the method for determining the shear strength of the root-soil complex comprises the steps of bringing the influence of the cultivation time on the pull-out strength of the root system into theoretical calculation, determining the incidence relation between the correction coefficient and the time by using a fitting method, and obtaining the expression of k' and the expression of S r Calculation formula S r ＝k″·1.2·T b and/A. The accuracy of the Wu-Waldron model can be effectively improved, the effective evaluation of the soil stabilization stability of the root system based on the test result is facilitated, the theoretical basis of the mechanical mechanism of the soil protection of the plants in the soil and water conservation engineering such as slope forestation is used, and a scientific basis is provided for the selection of a proper plant engineering to strengthen the soil and water conservation.
The technical solution of the present invention is further described in detail with reference to the accompanying drawings and embodiments.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
FIG. 2 is a flow chart of the production of a cannula for incubation.
FIG. 3 is a schematic block diagram of the incubation control system.
FIG. 4 is a stress-strain relationship diagram of a root-soil composite under the condition of no consolidation and no drainage in a triaxial compression test.
FIG. 5 is a stress path diagram of a root-soil composite under the condition of no consolidation and no drainage in a triaxial compression test.
FIG. 6 is a stress-strain relationship diagram of a root-soil composite under a condition of consolidation and no drainage in a triaxial compression test.
FIG. 7 is a graph showing the relationship between the strain of the root-soil composite and the pore water pressure under the condition of consolidation and no drainage in the triaxial compression test.
FIG. 8 is a stress path diagram of a root-soil composite under a condition of consolidation and no drainage in a triaxial compression test.
FIG. 9 is a diagram of the effective stress path of the root-soil composite under the condition of consolidation and no drainage in the triaxial compression test.
FIG. 10 is a graph showing the relationship between the stress and strain of the root-soil complex in the direct shear test of the plain soil.
FIG. 11 is a graph showing the stress-strain relationship in the direct shear test of a root-soil composite sample cultured for 60 days.
FIG. 12 is a graph showing the stress-strain relationship of a root-soil composite sample in a direct shear test after 90-day incubation.
FIG. 13 is a graph showing the stress-strain relationship in a direct shear test of a root-soil composite sample cultured for 120 days.
FIG. 14 is a graph showing the stress-strain relationship of a root-soil composite sample in a direct shear test after 150 days of cultivation.
FIG. 15 is a schematic diagram of the Wu-Waldron model.
Reference numerals
1-a bottom plate; 2-cultivating container; 3, a sand layer;
411 — left half pipe section; 412 — right half pipe section;
431-left half connecting sleeve; 432-right half joint sleeve;
44-binding tapes for pipe sections; 45-binding tapes for sleeves; 5, a permeable plate;
6, a controller; 7-a water tank; 71-a first water inlet pipe;
72-a second water inlet pipe; 8-water pumping device;
9-a second level sensor; 10-nutrient solution box; 101-a third water inlet pipe;
11-nutrient solution pumping device; 12-infusion hose; 121-liquid outlet holes;
13-a first water level sensor; 14-a temperature sensor; 15-a first mounting bar;
16-solar light panel; 17-a second mounting bar; 18-a storage battery;
19-a reinforcing bar; 20-a camera; 21-LED lamps;
22-universal wheel; 23-interlayer; 25-a timer;
26-a first solenoid valve; 27-a second solenoid valve; 28-third solenoid valve.
Detailed Description
Example 1
This embodiment provides mechanical properties analytical equipment of soil under plant roots acts on, includes: a culture vessel 2 and a culture control system for culturing a root-soil complex sample; a water permeable plate 5 is arranged in the cultivation container 2, cultivation sleeves capable of scattering plant seeds are arranged on the water permeable plate 5, and the number of the cultivation sleeves is multiple;
the cultivation control system comprises a first water level sensor 13, a temperature sensor 14, a timer 25, a controller 6, a first electromagnetic valve 26, a second electromagnetic valve 27, a third electromagnetic valve 28, a water pumping device 8, a nutrient solution pumping device 11, a water tank 7, a nutrient solution tank 10 and a heating plate;
the first water level sensor 13 is disposed in the incubation container 2; the heating plate and the temperature sensor 14 are both arranged on the cultivation container 2;
the first water level sensor 13, the temperature sensor 14, the timer 25, the first electromagnetic valve 26, the second electromagnetic valve 27 and the third electromagnetic valve 28 are all electrically connected with the controller 6;
a first water inlet pipe 71 is arranged on the water tank 7, one end of the first water inlet pipe 71, which is far away from the water tank 7, is connected to the cultivation container 2, the water pumping device 8 is arranged in the water tank 7 and is communicated with the first water inlet pipe 71, and the first electromagnetic valve 26 is arranged on the first water inlet pipe 71;
the first water inlet pipe 71 is communicated with a second water inlet pipe 72, and the second electromagnetic valve 27 is arranged on the second water inlet pipe 72;
a third water inlet pipe 101 is arranged on the nutrient solution box 10, and an infusion hose 12 is arranged on the culture container 2; one end of the second water inlet pipe 72, which is far away from the first water inlet pipe 71, and one end of the third water inlet pipe 101, which is far away from the nutrient solution tank 10, are both connected to the infusion hose 12, and the pipe wall of the infusion hose 12 is provided with a liquid outlet hole 121; the nutrient solution pumping device 11 is arranged in the nutrient solution tank 10 and is communicated with a third water inlet pipe 101, and the third electromagnetic valve 28 is arranged on the third water inlet pipe 101.
In this embodiment, the plant seeds may be grass seeds, and the grass seeds may be common plant seeds;
in this embodiment, the water pump device may further include a second water level sensor 9 disposed in the water tank 7, and the second water level sensor 9 may monitor a water level in the water tank 7, so that water is conveniently replenished when the water level is lower than a predetermined water level, and the water pump device 8 is prevented from idling.
In this embodiment, the water pumping device 8 and the nutrient solution pumping device 11 are both liquid pumping devices commonly used in the field, and may be liquid delivery pumps, for example; the first solenoid valve 26, the second solenoid valve 27 and the third solenoid valve 28 are all hydraulic solenoid valves commonly used in the art.
As a possible implementation manner, the infusion hose 12 in this embodiment is annularly arranged around the top edge of the cultivation container 2, the liquid outlet hole 121 is opened on one side of the infusion hose 12 facing the inner cavity of the cultivation container 2, and the liquid in the infusion hose 12 is flushed out from the liquid outlet hole 121 and then falls into the cultivation sleeve to simulate rainfall.
In the device for analyzing mechanical properties of soil under the action of plant roots of the embodiment, the cultivation sleeve comprises a plurality of pipe sections which are arranged in sequence, a connecting sleeve for connecting adjacent pipe sections is sleeved on each pipe section, and each pipe section is provided with a pipe section binding tape 44; the plurality of pipe sections comprise a left pipe half 411 and a right pipe half 412, and the left pipe half 411 and the right pipe half 412 are identical in shape and structure. In the embodiment, the cultivation casing can be formed by sequentially connecting a plurality of pipe sections, as long as the total length is 40 cm-45 cm after connection, preferably, the cultivation casing is formed by connecting three pipe sections, the lengths of the three pipe sections are 14cm respectively, and the installation and combination flexibility can be effectively improved; the pipe section can be a pipe section which can be encircled under the action of stress and is provided with a through notch, or a plurality of pipe section parts are spliced, for example, the pipe section which is encircled by the right half pipe section 411 and the left half pipe section 412 which are opposite to each other in the embodiment is more convenient to be stripped from the internal soil sample. As a feasible implementation mode, the inner diameter of the pipe section in the embodiment is 67.8mm, the outer diameter is 75mm, and the inner diameter of the connecting sleeve is 75 mm. In this embodiment, the culture container 2 is a barrel-shaped culture container having an upper caliber of 32.5cm in outside diameter, an inner diameter of 30cm, a lower caliber of 28.1cm in outside diameter, an inner diameter of 26.1cm, and a height of 38.5 cm.
In the mechanical characteristics analytical equipment of soil under plant roots effect of this embodiment, adapter sleeve includes half left adapter sleeve 431 and half right adapter sleeve 432, half left adapter sleeve 431 and half right adapter sleeve 432 shape and structure are all the same, cultivate with the sleeve pipe still including can tie up in ribbon 45 for the sleeve pipe on the adapter sleeve. In this embodiment, the connection sleeve is a connection sleeve that can be fixed on the pipe section, for example, the connection sleeve may be a connection sleeve with a through notch that can be encircled under stress, or a connection sleeve that is a split of a plurality of connection sleeve portions, for example, the connection sleeve of the present embodiment that is composed of the left half connection sleeve 431 and the right half connection sleeve 432, and the connection sleeve with a fixed inner diameter is formed by tying the sleeve with the tie 45, so that the connection sleeve is easy to detach and simple to use.
In this embodiment, the water permeable plate 5 is provided with a groove for placing the cultivation cannula.
In the mechanical characteristics analytical equipment of soil under plant roots effect of this embodiment, cultivate container 2 for taking the cultivation container of intermediate layer 23, the heating plate sets up in intermediate layer 23.
In this embodiment, the heating sheet is connected with a heating controller; the first water level sensor 13, the second water level sensor 9 and the temperature sensor 14 are all connected with the input end of the controller 6, the first electromagnetic valve 26, the second electromagnetic valve 27, the third electromagnetic valve 28 and the heating controller are all connected with the output end of the controller 6, and the timer 25 is connected with the controller 6; as a possible implementation, the water pumping device 8 and the nutrient solution pumping device 11 are both connected to the output end of the controller 6;
the water pumping device 8 can be connected to the output end of the controller 6 through a water pumping device switching circuit connected with a power supply loop of the water pumping device 8, and the nutrient solution pumping device 11 can be connected to the output end of the controller 6 through a nutrient solution pumping device switching circuit connected with a power supply loop of the nutrient solution pumping device 11; the water pumping device switch circuit and the nutrient solution pumping device switch circuit can both be relays;
the process of the controller 6 controlling the water pumping device 8 may be: the controller 6 compares the water level signal transmitted by the first water level sensor 13 with a preset height, when the water level in the cultivation container 2 is lower than the preset height, the controller 6 opens or maintains the water pumping device 8 and the first electromagnetic valve 26 to be opened, and when the water level in the cultivation container 2 reaches the preset height, the controller 6 simultaneously controls the water pumping device 8 and the first electromagnetic valve 26 to be closed;
the process of controlling the nutrient solution pumping device 11 by the controller 6 can be as follows: spraying is performed to a preset time, and the controller 6 controls the nutrient solution pumping device 11, the second solenoid valve 27, and the third solenoid valve 28 to be closed.
In the device for analyzing mechanical properties of soil under the action of the plant root system, the device for analyzing mechanical properties further comprises a camera 20, an LED lamp 21, a bottom plate 1, a universal wheel 22, a solar light panel 16 and a storage battery 18 capable of storing electric energy generated by the solar light panel 16;
the bottom plate 1 is arranged below the cultivation container 2, and the bottom plate 1 is provided with a mounting bracket for mounting a solar light panel 16, a camera 20 and an LED lamp 21;
the mounting bracket is a height-adjustable mounting bracket;
the universal wheel 22 is mounted at the lower part of the bottom plate 1.
As a possible implementation manner, the height-adjustable mounting bracket in this embodiment is composed of a first mounting rod 15 vertically disposed on the bottom plate 1 and a second mounting rod 17 with one end vertically connected to the first mounting rod 15, the second mounting rod 17 extends toward the cultivation container 2 at the end far away from the first mounting rod 15, the second mounting rod 17 is mounted on the first mounting rod 15 through a bolt-nut assembly, the first mounting rod 15 is provided with a plurality of adaptive threaded holes, the plurality of threaded holes are distributed along the axial direction of the first mounting rod 15, and the height adjustment of the mounting bracket is realized by mounting the bolt-nut assembly on different threaded holes; preferably, the height-adjustable mounting bracket further comprises a reinforcing rod 19 connected to both the first mounting rod 15 and the second mounting rod 17, and the reinforcing rod 19 can reinforce the first mounting rod 15 and the second mounting rod 17, so that the stability of the mounting bracket is improved; in this embodiment, as a possible installation method, the solar light panel 16 is installed at the end of the first installation rod 15, the storage battery 18 and the camera 20 are installed on the second installation rod 17, and the LED lamp 21 is installed at the end of the second installation rod 17 opposite to the cultivation container 2; the whole analysis device can be moved conveniently and quickly through the movable bottom plate.
The controller 6 is installed at the side of the incubation container 2; the timer 25 is provided on the upper side of the incubation container 2; the controller 6 and the timer 25 are located on opposite sides of the incubation container 2.
Example 2
In this embodiment, there is provided a method of manufacturing the device for analyzing mechanical properties of soil under plant root system action of example 1, wherein the method of manufacturing the sleeve for cultivation includes:
cutting a pipe into N sections to obtain N sectional pipes; n is more than or equal to 2;
the pipe is a PVC pipe; the length of the section-shaped pipe can be 8 cm-15 cm; in this embodiment, the tube is cut into three segments of 14cm long tubes, and connected to obtain the cultivation cannula conforming to the standard GB/T50123-2019, and it is known by those skilled in the art that two or more than three lengths of tube segments are connected to obtain the cultivation cannula based on easier peeling of the tube segments or other purposes, and the present invention is also within the concept of the present invention;
step two, cutting each section of pipe material along the axial direction, and correspondingly obtaining N groups of left half pipe sections 411 and right half pipe sections 412 which are identical in shape and structure;
step three, the left half pipe section 411 and the corresponding right half pipe section 412 are oppositely arranged to obtain N pipe sections, and the pipe sections are respectively bound along the circumferential direction of the pipe sections by using binding belts 44; the right half pipe section 411 and the right half pipe section 412 which are opposite to each other are encircled to form a tubular body with a fixed diameter; the inner diameter of the tubular body is the inner diameter of the pipe in step one;
and step four, sequentially placing N pipe sections bound with the pipe section binding tapes 44 to form (N-1) pipe section adjacent positions, and respectively sleeving the (N-1) connecting sleeves to the pipe section adjacent positions to obtain the cultivation sleeves. The length of the cannula for incubation was 42 cm.
Or (N-1) connecting sleeve pipes are cut along the axial direction to respectively obtain (N-1) groups of left half connecting sleeves 431 and right half connecting sleeves 432 with the same shape and structure, the left half connecting sleeves 431 and the corresponding right half connecting sleeves 432 are oppositely arranged and sleeved on the adjacent positions of the pipe sections, the connecting sleeves are sleeved on the pipe sections, and the sleeves are bound along the circumferential direction of the connecting sleeves by using a binding belt 45 to obtain the sleeves for cultivation; and the inner diameter of the pipe fitting for the connecting sleeve is equal to the outer diameter of the pipe in the step one.
Example 3
The present embodiment provides a method for performing a study using the device for analyzing mechanical properties of soil under the action of a plant root system of embodiment 1, including a root-soil complex sample cultivation test, a root-soil complex sample taking-out test, a triaxial compression test, a direct shear test, and a root system extraction test in a cultivation casing;
in the method of the present embodiment, the incubation of the root-soil complex sample includes:
step one, filling sand grains into a cultivation container 2 to form a sand layer 3 with the height of 5-10 cm, placing a permeable plate 5 on the sand layer 3, and vertically arranging the cultivation sleeve on the permeable plate 5;
filling soil into the cultivation sleeve, tamping the soil in layers, stopping filling the soil until the cultivation sleeve is filled, and scattering plant seeds; the soil is loess;
step three, conveying water into the cultivation container 2, wherein the water entering the cultivation container 2 enters a cultivation casing after passing through a sand layer 3 and a permeable plate 5, a first water level sensor 13 detects the water level in the cultivation container 2 and transmits a detected water level signal to a controller 6, the controller 6 controls a first electromagnetic valve 26 to be opened until the water level in the cultivation container 2 reaches a preset height, and the first electromagnetic valve 26 is closed to finish water conveying; the preset height can be 5 cm-15 cm;
step four, nutrient solution in the nutrient solution box 10 is conveyed to the infusion hose 12 through the third water inlet pipe 101, meanwhile, water in the water box 7 flows into the infusion hose 12 through the second water inlet pipe 72, the nutrient solution and the water merged into the infusion hose 12 are sprayed into the cultivation sleeve through the liquid outlet hole 121 on the infusion hose 12, a time signal of the timer 15 is transmitted to the controller 6, the controller 6 receives the time signal and compares the time signal with the preset time, when the spraying reaches the preset time, the controller 6 controls the timer 15 to stop, and the controller 6 controls the second electromagnetic valve 27 and the third electromagnetic valve 28 to be closed, so that the spraying of the nutrient solution is completed; the preset time can be 3min by taking the spraying flow as 4 mL/min;
the process of inputting water in the third step and the process of spraying nutrient solution in the fourth step can be exchanged or carried out simultaneously;
step five, in the above process, the temperature sensor 14 detects the temperature, and transmits the detected temperature signal to the controller 6, the controller 6 compares the obtained temperature signal with a preset temperature value, and when the obtained temperature signal value is lower than the preset temperature value, the controller 6 controls the heating sheet to heat until the preset temperature value is reached; the preset temperature can be 15-30 ℃;
the camera 20 monitors the plant growth condition in real time and transmits a growth condition picture to a mobile phone end of a user, and the user adjusts the irradiation intensity of the LED lamp 21 according to the plant growth condition;
the solar panel 16 absorbs solar energy and converts the solar energy into electric energy and transmits the electric energy to the storage battery 18, and the storage battery 18 can supply power for the device;
the position of the device can be moved under the action of the universal wheels 22 by pushing the bottom plate 1; and step six, culturing according to the steps till the preset culturing time, and finishing culturing. The preset incubation time is 60 days, 90 days, 120 days or 150 days.
And selecting proper steps to carry out strength test according to requirements.
In the method of the present embodiment, the method for taking out a root-soil composite sample includes:
after the cultivation is completed, the cultivation sleeve containing the root-soil complex sample is taken out of the cultivation container 2, the connection sleeve which is close to the exposed part of the plant and is on the cultivation sleeve containing the root-soil complex sample is taken out, the adjacent part of the upper pipe section and the middle pipe section is exposed, the upper pipe section containing the root-soil complex sample is cut along the adjacent part, the internal soil sample and the root system are simultaneously cut off, and the upper pipe section part with the exposed part of the plant is taken out to obtain the upper pipe section of the sleeve containing the root-soil complex sample; the length of the upper section of the sleeve in the upper section of the sleeve of the root-soil complex sample is 14 cm; the mode of removing the connecting sleeve can be as follows: the surrounding multiple connection sleeve portions, such as the left half connection sleeve 431 and the right half connection sleeve 432, are separated directly by removing the connection sleeve with the through-cut, or alternatively, by cutting the sleeve tie 45; and circumferentially cutting the inner wall surface of the pipe section close to the overground part of the plant by using a cutter to separate the root-soil complex sample from the inner wall surface of the upper section of the sleeve, removing the tie 44 for the pipe section, and separating the opposite left half pipe section 411 from the corresponding right half pipe section 412 to obtain the root-soil complex sample.
In the method of this embodiment, the triaxial compression test includes preparing a sample for triaxial compression, and the method for preparing the sample for triaxial compression includes:
cutting and flattening the obtained root-soil complex sample, and then placing the sample between two nail discs of a soil cutting disc, wherein the cutting can be carried out in order to place the sample in the soil cutting disc; cutting the outer side of the root-soil complex sample between the two nail discs by using a soil cutting knife while rotating, then flattening the two ends to obtain a cut soil sample, and cutting exposed root systems to obtain a sample for triaxial compression; the height of the cut soil sample is 7.82 cm-9.78 cm, and the diameter is 3.91 cm;
and carrying out a triaxial compression experiment on the obtained triaxial compression sample according to GB/T50123-2019, wherein the experiment result is shown in figures 4-9.
The test results of the root-soil complex samples with the incubation time of 150 days under the working conditions of no consolidation and no drainage are shown in fig. 4 and 5, and it can be seen from fig. 4 and 5 that the stress-strain relationship curve of the root-soil complex samples shows a trend of moving upwards as a whole along with the increase of confining pressure, and the peak intensity does not appear in the shearing process, and is consistent with the change rule of the soil (i.e. plain soil, not shown) filled in the cannula for incubation; the stress path of the root-soil complex sample approaches a straight line, the slope of the stress path straight line is not greatly different under different confining pressures, the stress path straight line and the stress path straight line are parallel, and in addition, it can be seen that the dense point of the stress path always appears at the upper right of the straight line, which shows that: under the same axial strain condition, the offset stress is increased along with the increase of confining pressure, namely, the confining pressure is increased to inhibit the deformation of the soil body and increase the strength of the soil body.
FIGS. 6 to 7 show the test results of the root-soil composite samples with the incubation time of 150 days under the condition of consolidation and no drainage, and it can be seen from FIGS. 6 to 7 that the stress is rapidly increased when the strain is less than 4% during the shearing process; the increasing tendency of the stress decreases sharply with increasing shear strain. The change trend of pore water pressure in the shearing process is basically consistent, the pore water pressure is rapidly increased along with the increase of the shear strain when the shear strain is less than 4%, and the pore water pressure is relatively stable when the shear strain is more than 4%. This indicates that: the plant root system has the functions of enhancing the soil body strength and resisting deformation.
As can be seen from comparison of fig. 8 to 9 and fig. 4 to 5, the characteristics of the stress paths of the unconsolidated and unconsolidated tests are basically the same, and the stress path concentration points of the consolidated and unconsolidated tests are lower than those of the unconsolidated and unconsolidated tests; the curve shape of the effective stress path is semicircular overall, compared with the stress path dense points, the dense points of the effective stress path are moved leftwards integrally on the basis that the heights are basically consistent, and the leftward movement distance is equal to the pore water pressure stable value.
In the method of this embodiment, the method of the direct shear test includes a method of preparing a sample for the direct shear test, and the method of preparing a sample for the direct shear test includes:
cutting the root-soil complex sample, aligning the cutting edge of the cutting ring coated with vaseline with the upper surface of the cut root-soil complex sample to enable the circle center of the upper surface to coincide with the circle center of the cutting ring, and performing girdling and flattening by using the cutting ring to obtain a sample for a direct shear test; the diameter of the sample for the direct shear test is 6.18cm, and the height of the sample is 2 cm;
the obtained test sample for the direct shear test is subjected to the direct shear test according to GB/T50123-2019, and the test results are shown in figures 10 to 14.
Fig. 10 to 14 show the test results of the direct shear test of the root-soil complex samples obtained from the plain soil (without seeds) and the root-soil complex samples obtained from the cultivation for 60 days, 90 days, 120 days, and 150 days, respectively, and it can be seen from fig. 10 to 14 that the stress-strain relationship curve shows a tendency of moving upward as the vertical pressure increases. As can be seen by comparing FIGS. 10-14, in the samples of the root system at different growth stages, when the vertical pressure is lower (30kPa, 10kPa), the shear stress decreases and the decreasing amplitude is reduced continuously after reaching the peak value along with the increase of the growth time of the root system, and when the growth time is 150 days, the shear stress remains stable after reaching the peak value, which indicates that: the residual strength of the loess can be obviously improved by the plant root system.
In the method of this embodiment, the method for testing the extraction of the root system from the inside of the cultivation cannula includes:
after the cultivation is finished, taking out the cultivation sleeve filled with the root soil complex sample, cutting along the joint of the root system and the plant stem of the plant, and removing the stem-containing part;
cutting along the upper surface of the root soil complex sample, removing a soil body part which is 1 cm-2 cm away from the edge of the upper surface, and clamping the root part of the upper surface of the exposed root soil complex sample by using a clamp; enabling the root system to be exposed out of the surface for a longer time, and then brushing off redundant soil on the surface of the soil body by using a small brush, wherein the length of the exposed root system is 1 cm-2 cm; the clamp can be a carpenter clamp;
installing a tension meter on the clamp, pulling the clamp by the tension meter, driving the root system to be pulled out by the clamp, and recording the reading of the tension meter, the diameter of a fracture part and the fracture length in the fracture state when the root system is fractured in the root system pulling-out process; when the root system is not broken in the process of pulling out the root system, the reading of the tension meter in the slippage state, the diameter of the tail end of the main root and the slippage length are recorded.
Excluding the test result corresponding to the distance of 0-0.5 cm from the fixture at the root fracture position, and recording other test results; gather the test result data that anchor clamps do not have the influence to the fracture department, the purpose is in order to avoid causing the cracked influence of root system because of anchor clamps centre gripping. The method for measuring the diameter of the exposed surface root system and the diameter of the root system fracture part is implemented by a vernier caliper, wherein the vernier caliper is an Airui electronic vernier caliper, the precision of the vernier caliper is 0.01mm, and the measuring range is 0-150 mm; the tensiometer is a Weidu handheld digital display tensiometer, the measuring range is 500N, and the precision is 1%.
The method of this embodiment further includes a method for determining the shear strength of the root-soil complex in a root system extraction test in the cultivation casing, where the determining method includes calculating the shear strength of the root-soil complex according to the following formula:
S(t)＝k″(t)·S r +c plain soil
Wherein,
S r ＝k″·1.2·T b /A；
Figure BDA0003025590510000171
in the above formula, S (t) The unit is KPa for the shear strength of the root-soil complex;
S r the unit is KPa, which is the theoretical value of the cohesive force of the root-soil complex;
c plain soil The unit is the cohesive force of the plain soil and KPa;
T b pull-out force in kN;
a is the area of the shear cross section in m 2 ；
t is the incubation time in years.
The above formula is based on an improvement made by a Wu-Waldron model which is a common model for theoretical calculation of the shear strength of the soil containing the root system.
In the Wu-Waldron model, the action of plant roots in soil is called root-soil complex cohesion, and the model is based on the following assumed conditions: (1) all root systems are vertical to the damage surface; (2) no sliding extracted root system exists; (3) all root systems on the damaged surface are broken. The Wu-Waldron model principle is shown in figure 15, when the upper soil body in figure 15 generates displacement x, the root segment
Figure BDA0003025590510000172
Will increase to
Figure BDA0003025590510000173
Mean tensile stress T of the root system a Depends on the elastic modulus (E) and the change in length of the root system under stress Δ l/l 0 The relationship is formula (a):
T a ＝(Δl/l 0 )E (a)
where Δ l ═ Z (sec β -1),
Figure BDA0003025590510000174
the length of the root system after deformation under the action of the tensile force depends on the tensile stress in the root system, and a formula (b) is obtained by calculation according to the sum of the tensile stress and the tangential force on the cylindrical root system unit:
dT/dl＝4τ/D (b)
m is a point with zero root pull stress and is positioned at the lower end of the root system, tau' is a value of tau, and the integral obtains the pull stress T of N points N Comprises the following steps:
Figure BDA0003025590510000181
wherein
Figure BDA0003025590510000182
When the temperature is higher than the set temperature
Figure BDA0003025590510000183
The root system is atThe length under tensile stress l is:
l＝T N D/2τ′ (d)
taking the mean tensile stress T a Is half of the tensile stress at the N position and l to l 0 Obtaining the following formula (e)
And (f):
T α ＝T N /2＝(Δl/l)E＝2τ′EZ(secβ-1)/T N D (e)
and
T N ＝(4τ′ZE/D) 1/2 (secβ-1) 1/2 (f)
the first term on the right in the formula (f) is a constant, i.e.
T N ＝k(secβ-1) 1/2 (g)
Where k is (4 τ' ZE/D) 1/2
The force of the root system acting on the soil body above N to the soil body below N can be decomposed into tangential force (F) on the horizontal plane at N t ) And normal force (F) n ):
F t ＝A r Tsinβ＝A r k(secβ-1) 1/2 sinβ (h)
F n ＝A r Tcosβ＝A r k(secβ-1) 1/2 cosβ (i)
In the formula A r The total root cross-sectional area is obtained;
the Wu-Waldron model corrects the soil strength according to the force applied by the root system to the soil, and the calculation formula of the shear strength of the root-soil complex is a formula (j):
St＝C+ark(secβ-1) 1/2 (sinβ+cosβtanφ)+σ N tanφ (j)
according to (j), the shear strength of the root-soil complex is the shear strength of the native soil and the cohesion S of the root-soil complex r Sum of S r Comprises the following steps:
Figure BDA0003025590510000184
wherein
Figure BDA0003025590510000191
The value range of (1) is 1.1-1.3, and usually 1.2 is taken;
namely S r Comprises the following steps:
S r ＝1.2·T r ·(A r /A) (l)
wherein A is r Is the total root cross-sectional area in m 2 ；
T r The tensile strength of the root system is expressed in kPa;
a is the area of the shear cross section in m 2 。
The Wu-Waldron model is simple in principle and simple and convenient to calculate, and is the most widely applied model in the prediction research of the shear strength of the soil body containing the root system at present. The Wu-Waldron model excessively simplifies the interaction of the root and the soil, so that the difference between the model calculation result and the measured value is large, sometimes even one magnitude difference is obtained, the tensile strength of the root system is replaced by the pull-out strength of the root system, the fracture or sliding process of the root system in the soil can be reduced to a large extent, and the test result is less influenced by instrument factors and environmental factors.
The Wu-Waldron model is corrected according to the root system pull-out strength test, namely the tensile force T corresponding to the root system tensile strength in the formula (l) r ·A r Replacement by the extraction force T required for the extraction destruction of the root system b Obtaining:
S r ＝1.2·T b /A (m)
meanwhile, the method for determining the shear strength of the root-soil complex includes the steps of bringing the influence of the cultivation time on the root system extraction strength into theoretical calculation, determining the incidence relation between the correction coefficient and the time by using a richard growth curve, and specifically including:
step one, determining the extraction force T according to the root extraction test in the sleeve for cultivation b ，T b The unit is KN; the calculation results are shown in Table 1;
step two, obtaining a measured shear strength value of the root-soil complex and a measured shear strength value of the plain soil according to the triaxial compression test and the direct shear test; see table 3, wherein the cultivation time is 0 corresponding to the shear strength measured value of the native soil;
step three, the pull-out force T in the step one is used b Substituting into formula S r ＝1.2·T b Obtaining a theoretical value S of the cohesive force of the root-soil complex r ，S r Has a unit of KPa, A is the shear cross-sectional area, and m is the unit 2 (ii) a Calculating the theoretical value S of the cohesive force of the obtained root-soil complex r See table 2;
step four, subtracting the shear strength measured value of the native soil from the shear strength measured value of the root soil complex in the step two to obtain a measured value of the cohesion of the root soil complex;
step five, utilizing the theoretical value of the cohesion of the root-soil complex under different cultivation time
Figure BDA0003025590510000201
Fitting to obtain a functional relation S between the theoretical value of cohesive force of the fitted root-soil complex and time r (t); wherein a, c, d and k are fitting parameters; t is the cultivation time in years; functional relation S r The parameters in (t) are shown in Table 4;
in specific implementation, the alignment 2017 software is adopted for fitting;
step six, utilizing the measured values of the cohesion of the root-soil complex under different cultivation time
Figure BDA0003025590510000202
Fitting to obtain the function relation c between the actual measured value of the cohesion of the root-soil complex and time r (t); wherein a ', c', d 'and k' are fitting parameters; t is the cultivation time in years; functional relationship c r The parameters in (t) are shown in Table 5;
step seven, the S of the step five r (t) and c of step six r (t) bringing in
Figure BDA0003025590510000203
Obtaining a correction coefficient k' (t); wherein, c Plain soil The unit is the cohesive force of the plain soil and KPa, and the unit is measured by an indoor test;
Figure BDA0003025590510000204
step eight, substituting the correction coefficient k "(t) in step seven into the formula S (t) k" (t) S r +c Plain soil Obtaining the shear strength S of the root-soil complex sample (t) ，
Wherein S is (t) The unit is KPa, and the unit is the shear strength of the root-soil complex sample;
S r the unit is KPa, which is the theoretical value of the cohesive force of the root-soil complex;
c plain soil The unit is the cohesive force of the plain soil and KPa;
T b pull-out force in kN;
a is the area of the shear cross section in m 2 ；
t is the incubation time in years.
TABLE 1S r Calculation Process and result (c) Plain soil Taking 23.61kPa)
Figure BDA0003025590510000205
Figure BDA0003025590510000211
Wherein C is Root-containing soil Tested by the indoor direct shear test.
TABLE 2S at different growth stages r Data of
Figure BDA0003025590510000212
TABLE 3 c in different growth phases Root-containing soil Data of
Figure BDA0003025590510000213
TABLE 4S r Fitting the results by the SRichards2 equation
Figure BDA0003025590510000214
TABLE 5c Root-containing soil Fitting the results by the SRichards2 equation
Figure BDA0003025590510000215
The cultivation time is recorded into a database containing a shear strength measured value of the root-soil complex, a shear strength measured value of the native soil and a pull-out force, the cultivation time is matched with a corrected formula, and calculation and query are performed on different times and different test types through a single or any combination method.
The Wu-Waldron model is corrected according to a root system pull-out strength test, the influence of the cultivation time on the root system pull-out strength is brought into theoretical calculation, the correlation between the correction coefficient and the time is determined by utilizing a Richards growth curve, and the expression of k 'and S' are obtained r Calculation formula S r ＝k″·1.2·T b and/A. The accuracy of the Wu-Waldron model can be effectively improved, the effective evaluation of the soil stabilization stability of the root system based on the test result is facilitated, the theoretical basis of the mechanical mechanism of the soil protection of the plants in the soil and water conservation engineering such as slope forestation is used, and a scientific basis is provided for the selection of a proper plant engineering to strengthen the soil and water conservation.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims (7)

1. A method for researching by using a mechanical property analysis device of soil under the action of a plant root system is characterized in that the mechanical property analysis device of soil under the action of the plant root system comprises: a culture vessel (2) and a culture control system for culturing a root-soil complex sample; a water permeable plate (5) is arranged in the cultivation container (2), cultivation sleeves capable of scattering plant seeds are arranged on the water permeable plate (5), and the number of the cultivation sleeves is multiple;
the cultivation control system comprises a first water level sensor (13), a temperature sensor (14), a timer (25), a controller (6), a first electromagnetic valve (26), a second electromagnetic valve (27), a third electromagnetic valve (28), a water pumping device (8), a nutrient solution pumping device (11), a water tank (7), a nutrient solution tank (10) and a heating sheet;
the first water level sensor (13) is arranged in the cultivation container (2); the heating sheet and the temperature sensor (14) are both arranged on the cultivation container (2);
the first water level sensor (13), the temperature sensor (14), the timer (25), the first electromagnetic valve (26), the second electromagnetic valve (27) and the third electromagnetic valve (28) are electrically connected with the controller (6);
a first water inlet pipe (71) is arranged on the water tank (7), one end, far away from the water tank (7), of the first water inlet pipe (71) is connected to the cultivation container (2), the water pumping device (8) is arranged in the water tank (7) and communicated with the first water inlet pipe (71), and the first electromagnetic valve (26) is arranged on the first water inlet pipe (71);
the first water inlet pipe (71) is communicated with a second water inlet pipe (72), and the second electromagnetic valve (27) is arranged on the second water inlet pipe (72);
a third water inlet pipe (101) is arranged on the nutrient solution box (10), and a transfusion hose (12) is arranged on the cultivation container (2); one end of the second water inlet pipe (72) far away from the first water inlet pipe (71) and one end of the third water inlet pipe (101) far away from the nutrient solution tank (10) are both connected to the infusion hose (12), and a liquid outlet hole (121) is formed in the pipe wall of the infusion hose (12); the nutrient solution pumping device (11) is arranged in the nutrient solution box (10) and is communicated with a third water inlet pipe (101), and the third electromagnetic valve (28) is arranged on the third water inlet pipe (101);
the cultivation sleeve comprises a plurality of pipe sections which are arranged in sequence, a connecting sleeve for connecting adjacent pipe sections is sleeved on each pipe section, and a tie (44) for the pipe sections is arranged on each pipe section; the pipe sections comprise a left half pipe section (411) and a right half pipe section (412), and the left half pipe section (411) and the right half pipe section (412) are identical in shape and structure;
the method comprises the steps of cultivating a root-soil complex sample, taking out the root-soil complex sample, performing a triaxial compression test, performing a direct shear test and performing a root system extraction test in a cultivating sleeve; the cultivation of the root soil complex test sample comprises the following steps:
step one, filling sand grains into a cultivation container (2) to form a sand layer (3) with the height of 5-10 cm, placing a water permeable plate (5) on the sand layer (3), and vertically arranging the cultivation sleeve on the water permeable plate (5);
filling soil into the cultivation sleeve, tamping the soil in layers, and scattering plant seeds;
step three, conveying water into the cultivation container (2), enabling the water entering the cultivation container (2) to enter a cultivation casing pipe after passing through a sand layer (3) and a permeable plate (5), detecting the water level in the cultivation container (2) by a first water level sensor (13) and transmitting a detected water level signal to a controller (6), controlling a first electromagnetic valve (26) to be opened by the controller (6) until the water level in the cultivation container (2) reaches a preset height, and closing the first electromagnetic valve (26) to finish water conveying;
conveying nutrient solution in the nutrient solution box (10) to a transfusion hose (12) through a third water inlet pipe (101), simultaneously enabling water in the water tank (7) to flow into the transfusion hose (12) through a second water inlet pipe (72), spraying the nutrient solution and the water which are converged into the transfusion hose (12) into a sleeve for cultivation through a liquid outlet hole (121) in the transfusion hose (12) until preset time is reached, and controlling a second electromagnetic valve (27) and a third electromagnetic valve (28) to be closed by a controller (6) to finish nutrient solution spraying;
step five, the temperature sensor (14) detects the temperature, and transmits a detected temperature signal to the controller (6), the controller (6) compares the obtained temperature signal with a preset temperature value, and when the obtained temperature signal value is lower than the preset temperature value, the controller (6) controls the heating sheet to heat until the temperature reaches the preset temperature value;
culturing according to the steps to preset culturing time, and finishing culturing;
the method comprises a determination method of the shear strength of the root-soil complex, and the determination method comprises the following steps:
step one, determining the extraction force T according to a root extraction test in a cultivation sleeve b ，T b The unit is KN;
determining a shear strength measured value of the root-soil complex and a shear strength measured value of the plain soil according to a triaxial compression test and a direct shear test;
step three, the pull-out force T in the step one is used b Substituting into formula S r ＝1.2·T b A, obtaining a theoretical value S of the cohesive force of the root-soil complex r ，S r Has a unit of KPa, A is the shear cross-sectional area, and m is the unit 2 ；
Step four, subtracting the shear strength measured value of the native soil from the shear strength measured value of the root soil complex in the step two to obtain a measured value of the cohesion of the root soil complex;
step five, utilizing the theoretical value of the cohesion of the root-soil complex under different cultivation time
Figure FDA0003787613570000031
Fitting to obtain the functional relation S between the theoretical value of cohesive force of the fitted root-soil complex and time r (t); wherein a, c, d and k are fitting parameters; t is the cultivation time in years;
step six, utilizing the cohesion of the root-soil complex under different cultivation time
Figure FDA0003787613570000032
Fitting to obtain the functional relation c between the cohesive force of the root-soil complex and the time r (t); wherein a ', c', d 'and k' are fitting parameters; t is the cultivation time in years;
step seven, the S of the step five r (t) and c of step six r (t) bringing in
Figure FDA0003787613570000033
Obtaining a correction coefficient k' (t); wherein, c Plain soil The unit is the cohesive force of the plain soil and KPa;
step eight, mixingIn step seven, the correction coefficient k ″ (t) is substituted into the formula S (t) ═ k ″ (t) · S r +c Plain soil The shear strength S (t) of the root-soil composite is obtained, and the unit of S (t) is KPa.
2. The method according to claim 1, wherein said coupling sleeves comprise a left coupling sleeve half (431) and a right coupling sleeve half (432), said left coupling sleeve half (431) and said right coupling sleeve half (432) being identical in shape and structure, said cultivating sleeve further comprising a sleeve tie (45) attachable to said coupling sleeves.
3. The method according to claim 1, wherein the incubation container (2) is an incubation container with a sandwich (23), and the heating sheet is disposed in the sandwich (23).
4. The method according to claim 1, wherein the mechanical property analysis device further comprises a camera (20), an LED lamp (21), a bottom plate (1), a universal wheel (22), a solar light panel (16) and a storage battery (18) capable of storing electric energy generated by the solar light panel (16);
the bottom plate (1) is arranged below the cultivation container (2), and a mounting bracket for mounting the solar light panel (16), the camera (20) and the LED lamp (21) is arranged on the bottom plate (1);
the mounting bracket is a height-adjustable mounting bracket;
the universal wheels (22) are arranged at the lower part of the bottom plate (1).
5. The method of claim 1, wherein the method of removing the root-soil composite sample comprises:
after completion of the culture, the culture sleeve containing the sample of the root-soil complex is taken out of the culture container (2), the connecting sleeve is removed, the sleeve is cut along the adjacent position of the pipe section, the upper section of the sleeve containing the sample of the root-soil complex is taken out, the upper section of the sleeve containing the sample of the root-soil complex is obtained, the sample of the root-soil complex is separated from the inner wall surface of the upper section of the sleeve, and the tie (44) for the pipe section is removed, so that the sample of the root-soil complex is obtained.
6. The method of claim 1, wherein the root pull-out test method in the cultivation sleeve comprises:
after the cultivation is finished, taking out the cultivation sleeve filled with the root soil complex sample, cutting the cultivation sleeve along the joint of the root system and the plant stem of the plant, and removing the stem-containing part;
cutting along the upper surface of the root-soil complex sample, removing a soil body part 1-2 cm away from the edge of the upper surface, and clamping the root part of the upper surface of the exposed root-soil complex sample by using a clamp; install the tensiometer in on the anchor clamps, tensiometer pulling anchor clamps, anchor clamps drive the root system and extract to the root system, when the root system extracted the process root system fracture, under the record rupture state the tensiometer reading, the diameter and the rupture length of fracture department, when the root system extracted the process root system not fracture, under the record slippage state the tensiometer reading, main root terminal department diameter and the length of sliding.
7. A method for manufacturing a device for analyzing mechanical properties of soil under plant root system action, the device for analyzing mechanical properties of soil under plant root system action being the device for analyzing mechanical properties of soil under plant root system action as set forth in claim 1, the method for manufacturing the device for analyzing mechanical properties of soil under plant root system action comprising a method for manufacturing a cultivation sleeve, the method for manufacturing the cultivation sleeve comprising:
cutting a pipe into N sections to obtain N sectional pipes; n is more than or equal to 2;
step two, cutting each section of pipe material along the axial direction, and correspondingly obtaining N groups of left half pipe sections (411) and right half pipe sections (412) with the same shape and structure;
step three, the left half pipe section (411) is opposite to the corresponding right half pipe section (412) to obtain N pipe sections, and the pipe sections are bound by binding tapes (44) along the circumferential direction of the pipe sections respectively;
and step four, sequentially placing N pipe sections bound with the pipe section binding tapes (44) to form (N-1) pipe section adjacent positions, and respectively sleeving the (N-1) connecting sleeves to the pipe section adjacent positions to obtain the cultivation sleeves.
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