CN112946011B - Soil body pressure water supplementing freeze thawing device for simulating bidirectional freezing - Google Patents
Soil body pressure water supplementing freeze thawing device for simulating bidirectional freezing Download PDFInfo
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Abstract
The invention discloses a soil body pressure water supplementing freeze thawing device for simulating bidirectional freezing, which is characterized in that square openings are formed in a plurality of wall surfaces of a soil sample box, a movable first refrigerating plate/side plate is arranged and matched with a loading system, a weighing system and a control system, so that the vertical freezing of a soil body can be carried out, the horizontal freezing of the soil body can be carried out in the same test device, different soil body overlaying pressures can be simulated, different water head pressures are applied to the soil sample, the influence of different underground water levels on the vertical frost heaving and the thaw deformation of the soil body can be simulated, the vertical frost heaving and the thaw deformation of the soil body around an artificial freezing project can be truly obtained, the device can be used for researching the influence of different influence factors on the vertical frost heaving and the thaw deformation of the soil body under different freezing modes and pressure water supplementing conditions, and providing effective technical support for predicting and controlling the vertical frost heaving and the thaw deformation of the soil body in the artificial freezing project.
Description
Technical Field
The invention relates to the technical field of civil engineering, in particular to a soil body pressure water supplementing freeze thawing device for simulating bidirectional freezing.
Background
The artificial freezing method is a method for quickly and effectively reinforcing soil layer temporarily, and its main principle is that the refrigerant medium (commonly used saline water and liquid nitrogen) is circulated in the arranged freezing pipes, and the freezing pipes and the surrounding soil body can make heat exchange, so that the liquid water in the soil can be frozen into ice to form a closed freezing wall with a certain strength, so that the effect of resisting soil pressure and isolating underground water can be reached. The method is firstly used for the development of deep mineral resources, then along with the continuous expansion of the development of urban underground space and the expansion of urban rail transit, the great risk exists in the excavation of water-sand-rich layers and soft soil layers, and the safety risk can be effectively reduced and the method can be widely used by adopting an artificial freezing method, particularly in the Yangtze river delta region, such as Shanghai, nanjing, suzhou, changzhou and the like. However, the artificial freezing method also brings potential hazards, namely vertical frost heaving and thaw collapse deformation of the soil layer are caused, and if the deformation exceeds a certain limit value, yield fracture of the embedded pipeline and even uneven settlement of the ground surface can be caused. In the actual artificial freezing engineering, the freezing directions of the peripheral soil bodies are different, and two extreme situations exist: (1) the freezing direction is parallel to the soil consolidation direction; (2) the freezing direction is perpendicular to the soil consolidation direction, for example, the freezing of the soil on the upper and lower sides and the left and right sides of the communication channel (as shown in fig. 1). Because the horizontal permeability coefficient of the soil body is generally larger than the vertical permeability coefficient, compared with the vertical freezing, more water is gathered to the freezing frontal surface during the horizontal freezing to form segregation ice, so that the vertical frost heaving and the thawing-sinking deformation of the soil body have obvious difference. Before adopting artifical freezing method construction, need fully to master the vertical frost heaving and the thawing and sinking deformation of soil body, current test device can only realize one kind and freeze the direction: most of test devices refer to a natural frozen soil indoor test method, and can realize vertical unidirectional freezing of a soil body; few test devices can realize horizontal one-way freezing of soil bodies, only horizontal frost heaving deformation of the soil bodies is obtained, but in the manual freezing process, vertical frost heaving deformation is concerned more than horizontal frost heaving deformation, and deformation of the ground surface and deformation of underground pipelines are directly influenced. In addition, the existing device does not realize pressure water supplement in the freezing and thawing process, but underground water levels in actual engineering are different, soil bodies are usually in pressure water supplement conditions in the freezing and thawing process, and different water head pressures can directly influence the water supplement amount of the soil bodies in the freezing process so as to influence vertical frost heaving deformation, so that a soil body pressure water supplement freezing and thawing process test device capable of realizing both vertical freezing and horizontal freezing is needed to be established.
Disclosure of Invention
In view of the above circumstances, an object of the present invention is to provide a soil freezing and thawing process testing apparatus, which can achieve both vertical freezing and horizontal freezing of a soil body, and can achieve pressure water replenishment during the freezing and thawing process, and can approximately simulate the influence of different overburden pressure, different ground water heads, different temperature gradients, and other factors on vertical frost heaving and thawing deformation of the soil body, so as to provide technical support for predicting and controlling the vertical frost heaving and thawing deformation of the soil body in the engineering.
The technical scheme provided by the invention is as follows:
the utility model provides a simulation bidirectional frozen's soil body has pressure moisturizing freeze thawing apparatus which characterized in that, includes thermostated container, refrigerating system, soil sample case, graduated flask, weighing system, loading system, displacement sensor, temperature sensor and control system:
the constant temperature box is used for providing the environmental temperature required by the freeze thawing test;
the refrigeration system comprises a first refrigeration plate, a second refrigeration plate and corresponding cold baths, wherein the first refrigeration plate and the second refrigeration plate are oppositely arranged on two sides of the soil sample and are used for freezing the soil sample and manufacturing a temperature gradient;
the soil sample box is of a square box body structure with three hollowed surfaces, the soil sample box is in a vertically placed state, the top, the bottom and one side surface of the soil sample box are respectively provided with a square opening communicated with an inner cavity of the soil sample box, the top opening and the bottom opening have the same size and correspond to each other in the upper position and the lower position, the top opening is blocked by a first refrigerating plate, the bottom opening is blocked by a second refrigerating plate, the side opening is blocked by a side plate, the back surface of the soil sample box, namely the side opposite to the side opening, and a drainage air vent is arranged at a position close to the bottom;
the measuring cylinder is used for containing and measuring water bodies discharged from the water discharging air holes;
the loading system is connected with the control system and used for applying vertical downward pressure to the soil sample so as to simulate the overlying load of the soil sample;
the weighing system comprises a coil pipe and an electric lifting platform, the coil pipe is horizontally laid on the platform, water is injected into the platform, one end of the coil pipe is used for feeding water into the soil sample through a water guide pipe, and the other end of the coil pipe is bent upwards and communicated with the atmosphere in a mode that an opening faces upwards; the electric lifting platform is arranged beside the soil sample box, a loading platform of the electric lifting platform is provided with a weighing sensor, and a platform for laying the coil pipe is arranged above the weighing sensor so as to monitor the change of water amount in the coil pipe through the weighing sensor; the electric lifting platform is connected with the control system, and different underground water heads are simulated by adjusting the height of the coil pipe;
the displacement sensor is arranged on the first refrigeration plate positioned above in a vertical freezing test, is arranged on the side plate positioned above in a horizontal freezing test, and reflects the vertical frost heaving and thaw collapse deformation changes of the soil sample by monitoring the height change of the first refrigeration plate or the side plate;
the temperature sensor is inserted in the soil sample and used for monitoring the temperature of the soil sample;
and the signal output ends of the weighing sensor, the displacement sensor and the temperature sensor are respectively connected with the data acquisition instrument and the control system, and the monitoring signals are fed back to the control system.
On the basis of the above scheme, a further improved or preferred scheme further comprises:
further, the soil sample box is preferably made of transparent organic glass.
Further, the coil pipe is formed by winding a hose with an inner diameter of 4-6 mm.
Furthermore, a plurality of temperature sensors are arranged, and are uniformly inserted in the middle of the soil sample in a vertical row mode in a vertical freezing test; in the horizontal freezing test, the soil sample is uniformly inserted in the middle position of the soil sample in a horizontal row mode so as to monitor the temperature and the temperature gradient parameters of the soil sample.
Furthermore, the loading system applies pressure through the dowel bar, pressure heads are arranged at the middle parts of the outer surfaces of the first refrigeration plate and the side plates, and a pit structure matched with the shape of the output end of the dowel bar in shape is arranged on each pressure head.
Furthermore, a square water storage tank is arranged on the inner surface of the first refrigerating plate/side plate, the periphery of the water storage tank is enclosed by a circle of flange, and meanwhile, a water replenishing hole vertically penetrating through a plate body of the first refrigerating plate/side plate is also formed in the first refrigerating plate/side plate; in vertical freezing experiment/horizontal freezing experiment, the catch basin is connected into water through moisturizing hole and coil pipe, is equipped with the porous disk between catch basin and the soil sample, the porous disk is flat for block the catch basin opening of first refrigeration board/curb plate, realize the uniform water distribution to the soil sample.
Furthermore, filter paper is laid between the water permeable plate and the soil sample.
Furthermore, be equipped with the porous disk between second refrigeration board and the soil sample, the drainage bleeder vent sets up in the position that corresponds this porous disk.
Furthermore, the soil body pressure water supplementing freeze thawing device is also provided with a filling plate;
the filling plates comprise a refrigeration plate filling plate and a side plate filling plate, the shape and the size of the side plate filling plate are consistent with those of a side plate water storage tank, and when a vertical freezing test is carried out, the water permeable plate between the side plate and a soil sample is removed and then is filled into the water storage tank of the side plate; the shape and the size of the refrigerating plate filling plate and the first refrigerating plate water storage tank are consistent, and when a horizontal freezing test is carried out, the water storage tank of the first refrigerating plate is filled after the water permeable plate between the first refrigerating plate and the soil sample is removed.
Furthermore, the soil body pressure water supplementing freeze thawing device is applied to an artificial freezing method test, when a temperature gradient is formed, the first refrigerating plate is set as a warm-end refrigerating plate, the second refrigerating plate is a cold-end refrigerating plate, and the temperature of the second refrigerating plate is set as a negative temperature and is lower than that of the first refrigerating plate.
Has the advantages that:
according to the soil body pressure water supplementing freeze thawing device for simulating bidirectional freezing, square openings are formed in a plurality of wall surfaces of a soil sample box, the movable first refrigerating plate and the movable side plates are arranged and matched with the loading system, the weighing system and the control system, so that the vertical freezing of a soil body can be carried out in the same test device, the horizontal freezing of the soil body can be carried out, different soil body overlaying pressures can be simulated, different water head pressures can be applied to the soil sample, and the influence of different underground water levels on the vertical frost heaving and the thaw deformation of the soil body can be simulated. In view of the fact that the relation (parallel and vertical) between the consolidation direction and the freezing direction of the soil body can influence the vertical frost heaving and the thaw collapse deformation of the soil body, when the simulated soil body is vertically frozen, the consolidation direction of the soil body is parallel to the freezing direction, when the simulated soil body is horizontally frozen, the consolidation direction of the soil body is perpendicular to the freezing direction, the vertical frost heaving and the thaw collapse deformation of the soil body around the artificial freezing engineering can be really obtained, the method and the device can be used for exploring the influences of different influence factors (different overlying soil pressures, different underground water heads, different temperature gradients and the like) on the vertical frost heaving and the thaw collapse deformation of the soil body under different freezing modes and pressure water supplement conditions, and provide technical support for predicting and controlling the vertical frost heaving and the thaw collapse deformation of the soil body in the artificial freezing engineering. Meanwhile, the device disclosed by the invention has the advantages of novel design, reasonable structural planning, easiness in manufacturing and convenience in operation, and is suitable for popularization and use.
Drawings
FIG. 1 is a schematic view showing the deposition direction and the freezing direction of the soil around the communication channel;
FIG. 2 is a schematic structural view of a soil sample box;
FIG. 3 is a longitudinal cross-sectional view of a first refrigeration plate (warm end refrigeration plate);
fig. 4 is a longitudinal cross-sectional view of a second refrigeration plate (cold side refrigeration plate);
FIG. 5 is a longitudinal cross-sectional view of the side panel;
FIG. 6 is a top view of the coil;
FIG. 7 is a schematic structural diagram of the soil body freezing and thawing test device in vertical freezing;
fig. 8 is a schematic structural diagram of the soil body freezing and thawing test device in horizontal freezing.
In the figure, 1-a computer, 2-a data acquisition instrument, 3-a cold bath, 4-a displacement sensor, 5-filter paper, 6-a thermostat, 7-a soil sample box, 8-a soil sample, 9-a water drainage and air vent, 10-a water stop rubber ring, 11-a measuring cylinder, 12-a loading system, 13-a dowel bar, 14-a water guide pipe, 15-a warm end refrigerating plate, 16-a first water replenishing hole, 17-a wire outlet hole, 18-a side plate, 19-a fixed support, 20-a temperature sensor, 21-a second water replenishing hole, 22-a second permeable stone, 23-a cold end refrigerating plate, 24-a coil pipe, 25-a platform, 26-a weighing sensor and 27-an electric lifting platform.
Detailed Description
In order to clarify the technical solution and the working principle of the present invention, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.
The soil body pressure water supplementing freeze thawing device simulating bidirectional freezing shown in fig. 1 to 8 comprises a constant temperature box 6, a refrigerating system, a soil sample box 7, a water permeable plate, filter paper, a filling plate, a measuring cylinder 11, a loading system 12, a weighing system, a displacement sensor, a temperature sensor, a control system and other components.
The control system can adopt the computer 1, is respectively connected with the sensor, the loading system 12 and the weighing system, receives signals fed back by the sensor, and controls the loading system 12 and the weighing system based on preset instructions and/or signals fed back by the sensor in real time.
The incubator 6 is used for providing an ambient temperature required for the soil sample freeze-thaw test.
The refrigerating system comprises a first refrigerating plate, a second refrigerating plate and corresponding cold baths, and during testing, the first refrigerating plate and the second refrigerating plate are oppositely arranged on two sides of the soil sample 8 and used for freezing the soil sample and manufacturing a temperature gradient. In this embodiment, the structure is described by taking an artificial freezing method test as an example, so that the first refrigeration plate is set as the warm-end refrigeration plate 15, and the second refrigeration plate is set as the cold-end refrigeration plate 23. Two refrigeration boards all preferably adopt the brass material to make, have good heat conduction characteristic, are equipped with circuitous cold night circulation channel in the refrigeration board, and the channel both ends are equipped with cold night inlet joint and outlet joint.
As shown in fig. 3, a square water storage tank is arranged at the bottom of the warm-end refrigerating plate 15, the periphery of the water storage tank is surrounded by a circle of flange 15-4, a first water replenishing hole 16 vertically penetrating through a plate body of the warm-end refrigerating plate 15 is arranged on the warm-end refrigerating plate 15, and water enters the water storage tank through the first water replenishing hole 16; the outer side wall of the warm end refrigerating plate 15 is provided with an annular groove 15-5 for limiting and mounting the water stop rubber ring 10; the middle part of the upper surface of the warm-end refrigerating plate 15 is provided with a first pressure head 15-3, the top surface of the first pressure head 15-3 is provided with a pit structure with the shape matched with the shape of the output end of the dowel bar 13, meanwhile, the top surface of the warm-end refrigerating plate 15 is provided with a cold liquid inlet joint 15-1 and an outlet joint 15-2, and the two joints are connected with the corresponding cold bath 3 through guide pipes.
As shown in fig. 4, the cold-end refrigeration plate 23 includes an upper plate body 23-1 and a lower plate body 23-2, the size of the top view area of the upper plate body 23-1 is smaller than that of the lower plate body 23-1, a two-stage step structure is formed, and meanwhile, an annular groove 23-3 for limiting and mounting a water-stop rubber ring is formed on the return-type step surface around the upper plate body 23-1; the upper plate body 23-1 of the cold-end refrigerating plate 23 is matched with the bottom opening 7-2 of the soil sample box 7 in shape, and is embedded in the bottom opening 7-2 during installation; the left end and the right end of a plate body 23-2 at the lower part of the cold end refrigerating plate 23 are respectively provided with a cold liquid inlet joint 23-4 and an outlet joint 23-5, and the two joints are connected with corresponding cold baths through guide pipes.
As shown in fig. 5, a square water storage tank is also arranged at the bottom of the side plate 18, the periphery of the water storage tank is enclosed by a circle of flange 18-3, a second water replenishing hole 21 vertically penetrating through the plate body of the side plate 18 is arranged on the side plate 18, and water enters from the water storage tank of the side plate through the second water replenishing hole 21; the outer side wall of the side plate 18 is provided with an annular groove 18-2 for limiting and mounting a water-stopping rubber ring; the middle part of the upper surface of the side plate is provided with a second pressure head 18-1, the top surface of the second pressure head 18-1 is provided with a concave structure with the shape matched with the shape of the output end of the dowel bar 13, meanwhile, the side plate 18 is provided with a wire outlet hole 17 vertically penetrating through the plate body, and the wire outlet hole 17 is arranged at the position of the flange 18-3.
The soil sample box 7 is used for containing a soil sample 8 and is made of transparent high-strength organic glass, so that a good heat insulation effect is achieved, cracking in the loading process is prevented, and a cold-growing structure of a soil body after freezing is observed; as shown in fig. 2, the soil sample box 7 is a square box structure with three hollowed-out surfaces, and square openings communicated with an inner cavity of the box are arranged at the top, the bottom and one side surface of the box, wherein the size of the top opening 7-1 is the same as that of the bottom opening 7-2, the top opening 7-1 is blocked by a warm end refrigerating plate 15, the bottom opening 7-2 is blocked by a cold end refrigerating plate 23, the side opening 7-3 is blocked by a side plate 18, and meanwhile, a drainage vent hole 9 is arranged at a position close to the bottom of the side surface opening 7-3 of the box 7 and used for discharging melted water.
The measuring cylinder 11 is used for receiving and measuring water discharged from the water discharge vent 9.
As shown in fig. 7 and 8, the first pressure head and the second pressure head are of a pressure-bearing seat structure protruding relative to the reference surface of the warm-end refrigeration plate 15/side plate 18, the power output end of the loading system 12 is connected with the pressure head on the warm-end refrigeration plate 15 or the side plate 18 through a dowel bar 13, and the movable warm-end refrigeration plate 15 or the side plate 18 transmits vertical downward pressure to the soil sample 8 to simulate the overlying load of the soil sample.
The weighing system includes a coiled tube 24 and an electric lift table 27.
The coil pipe 24 can be bent and coiled in an S-shaped manner in a reciprocating manner by adopting a hose, as shown in fig. 6, the coil pipe 24 is horizontally laid on a platform 25, water is injected into the coil pipe when the coil pipe is used, one end 24-1 of the coil pipe feeds water into the soil sample 8 through a water guide pipe, the other end 24-2 is bent upwards and communicated with the atmosphere in an opening-upwards manner, and the inner diameter of the coil pipe can be controlled to be 4-6 mm.
The electric lifting platform 27 is arranged at the side of the soil sample box 7, a load carrying platform of the electric lifting platform is provided with a weighing sensor 26, and a platform 25 for laying the coil pipe 24 is arranged above the weighing sensor 26 so as to monitor the change of the water quantity in the coil pipe 24 through the weighing sensor 26; the electric lifting platform 27 is connected with the computer 1, and the adjusting coil pipe 24 is driven to lift according to instructions output by the computer 1 so as to simulate different underground water heads.
The displacement sensor 4 is arranged on the warm end refrigerating plate 15 positioned above in a vertical freezing test, and is arranged on the side plate 18 positioned above in a horizontal freezing test, and the change of vertical frost heaving and thaw deformation of the soil sample is reflected by monitoring the height change of the warm end refrigerating plate 15 or the side plate 18.
In this embodiment, the temperature sensors 20 are thermocouple temperature sensors, and are inserted into the soil sample 8 during the test to monitor the temperature and temperature gradient parameters of the soil sample 8, as shown in fig. 7 and 8, in the vertical freezing test, a plurality of temperature sensors 20 are uniformly inserted into the middle of the soil sample 8 in a vertical row; in the horizontal freezing test, the soil sample 8 is uniformly inserted in the middle of the soil sample in a horizontal row.
The displacement sensor 4, the temperature sensor 20 and the weighing sensor 26 are respectively connected with the data acquisition instrument 2, and send monitoring signals to the computer 1 through the data acquisition instrument 2.
The filling plates comprise a refrigeration plate filling plate made of a copper plate and a side plate filling plate made of organic glass, wherein the shape and the size of the side plate filling plate are consistent with those of a side plate water storage tank, and the filling plates are filled into the water storage tank of the side plate 18 after a water permeable plate between the side plate 18 and the soil sample 8 is removed during a vertical freezing test; the shape and the size of refrigeration board infill panel and warm end 15 catch basin are unanimous, when carrying out the level and freeze the experiment, remove warm end refrigeration board 15 and soil sample 8 between the porous disk after, fill in warm end refrigeration board 15 catch basin.
The soil body pressure water supplementing freeze thawing device can realize vertical freezing and horizontal freezing.
One) vertical freezing
When the soil sample 8 is vertically frozen, the connection and placement mode of the device is as shown in fig. 7:
the soil sample box 7 is vertically arranged in the constant temperature box 6;
the upper plate body 23-1 is embedded in the bottom opening 7-2 of the soil sample box 7 by the cold end refrigerating plate 23, and a water stop rubber ring is arranged on the contact surface of the upper plate body and the soil sample box 7 so as to seal the bottom opening 7-2 of the soil sample box 7; a second water permeable plate 22, filter paper and a soil sample 8 are sequentially placed above the cold end refrigerating plate 23;
the side plate 18 is vertically embedded in the side opening 7-3 on the right side of the soil sample box 7 to plug the side opening 7-3 of the soil sample box, a water stopping rubber ring is used for sealing between the contact surface of the side plate 18 and the soil sample box 7, the water storage tank of the side plate 18 is positioned on the left side surface of the side plate 18 at the moment, an organic glass plate with the same size as the water storage tank is filled in the water storage tank, the contact surface of the side plate 18 and the soil sample 8 is a vertical plane, and the water filling holes 21 on the side plate 18 are sealed at the moment;
the soil sample box 7 is filled with soil samples 8, a row of temperature sensors 20 are arranged at different height positions in the middle of the soil samples 8, the wiring of the temperature sensors 20 penetrates through the wire outlet holes 17 in the side plates 18 to be connected with the data acquisition instrument 2 outside the constant temperature box 6, and the wire outlet holes 17 are sealed;
the filter paper 5, the first permeable plate and the warm-end refrigerating plate 15 are sequentially placed on the top of the soil sample 8, the lower portion of the warm-end refrigerating plate 15 is embedded in an opening 7-1 in the top of the soil sample box 7, and the contact surface between the side wall of the warm-end refrigerating plate 15 and the soil sample box 7 is sealed through a water-stop rubber ring; a flange 15-5 on the bottom surface of the warm end refrigerating plate 15 is pressed on the first water permeable plate and is bonded with the first water permeable plate through a waterproof adhesive;
the first permeable plate and the second permeable plate 22 are both plane stone plates, the cross section size of the plane stone plates is the same as that of the inner cavity of the soil sample box, the plane stone plates are horizontally embedded in the soil sample box, and the filter paper is used for isolating the soil sample 8 from the corresponding permeable plates;
a loading system 12 outside the constant temperature box 6 is connected with a first pressure head 15-3 bearing the pressure of a warm end refrigerating plate 15 through a dowel bar 13; the soil sample box 7 is fixed in the constant temperature box 6 through a fixing bracket 19, so that only the warm-end refrigerating plate 15 can move up and down under the action of pressure applied by the loading system 12;
a measuring cylinder 11 is also arranged beside the soil sample box 7 in the constant temperature box 6, a water drainage air hole 9 of the soil sample box 7 is connected with the opening of the measuring cylinder 11 through a section of water guide pipe, and the water quantity drained by the soil sample in the melting process is contained and measured through the measuring cylinder 11; drainage bleeder vent 9 sets up the position of being close cold junction refrigeration board 22 upper surface, and the top is no longer than the height of second porous disk 22 upper surface to avoid impurity to flow.
One end of the coil pipe 24 is connected with the first water replenishing hole 16 of the warm-end refrigerating plate 15 through the water guide pipe 14;
cold liquid inlet joints and outlet joints of the warm-end refrigerating plate 15 and the cold-end refrigerating plate 23 are connected with corresponding cold baths positioned outside the constant temperature box 6 through guide pipes;
the displacement sensor 4 is arranged in the constant temperature box 6 and is installed at the top of the warm end refrigerating plate 15, and the signal output end of the displacement sensor is connected with the data acquisition instrument 2; the signal output end of the data acquisition instrument 2 and the control signal input ends of the loading system 12 and the electric lifting platform 27 are respectively connected with the computer 1.
II) horizontal freezing
When the soil sample 8 is horizontally frozen, the connection and placement of the device are as shown in fig. 8.
Unlike vertical freezing:
at the moment, the soil sample box 7 is transversely placed in the constant temperature box 6, the warm-end refrigerating plate 15 and the cold-end refrigerating plate 23 are in a vertical placing state, and the side plate 18 is in a horizontal state;
the organic glass plate in the water storage tank of the side plate 18 is removed, the first water permeable plate and the filter paper between the warm-end refrigerating plate 15 and the soil sample 8 are also removed, and the water storage tank of the warm-end refrigerating plate 15 is filled with copper plates with the same size, so that the contact surface of the warm-end refrigerating plate and the soil sample 8 is a vertical plane;
a third permeable plate and filter paper for isolating the third permeable plate from the soil sample 8 are arranged between the side plate 18 and the soil sample 8 filled below, the area size of the third permeable plate is the same as the size of the longitudinal section of the soil sample box 7, and the third permeable plate is embedded in the soil sample box 7; a flange 15-5 at the bottom of the side plate 18 is pressed on the third permeable plate and is bonded with the third permeable plate through water stop glue;
the water replenishing hole 14 of the side plate 18 is opened and is connected with the coil pipe 24 through the water guide pipe 14, and the water replenishing hole 16 of the warm-end refrigerating plate 15 is sealed;
after the soil sample 8 is filled in the soil sample box 7, the temperature sensors 20 are distributed at the middle height position of the soil sample 8 in a transverse arrangement mode (the wiring of the temperature sensors 20 still passes through the wire outlet holes 17 on the side plates 18 to be connected with the data acquisition instrument 2 outside the thermotank 6, and the wire outlet holes 17 are sealed);
a loading system 12 outside the incubator 6 is connected with a second pressure head 18-1 bearing pressure by a side plate 18 through a dowel bar 13, and the soil sample box 7 is fixed through a fixing bracket 19, so that only the side plate 18 can move up and down under the action of pressure applied by the loading system 12;
in the constant temperature box, the soil sample box 7 is erected, the measuring cylinder 11 is placed below the drainage air holes 9, and the water volume discharged by the soil sample in the melting process is contained and measured (a second water permeable plate 22 and filter paper for isolating the second water permeable plate 22 from the soil sample are still arranged between the cold-end refrigerating plate and the soil sample 8);
the displacement sensor 4 is arranged on the top of the measuring plate 18 and is positioned in the constant temperature box 6, and the signal output end of the displacement sensor is connected with the data acquisition instrument 2.
The connection mode of other components is basically the same as that of the vertical freezing test, and comprises the following steps:
1) The data acquisition instrument 2, the loading system 12, the electric lifting platform 27 and the computer 1 are connected;
2) The connection mode of the warm-end refrigerating plate 15 and the cold-end refrigerating plate 23 with the cold bath;
3) The connection mode among the coil pipe 24, the platform 25, the weighing sensor 26 and the electric lifting platform 27 and the like.
The soil body test process:
1. obtaining the dry density and liquid limit of undisturbed soil through a conventional geotechnical test;
2. breaking an undisturbed soil sample, putting the crushed undisturbed soil sample into an oven for 12 hours, completely drying water in the soil, grinding the dried soil through a 2mm sieve, weighing a certain mass of soil from the sieved dried soil, adding distilled water according to 1.5 times of liquid limit, and repeatedly stirring to obtain soil sample slurry;
3. placing the slurry into a soil sample box, and connecting the devices according to the structure shown in figure 7 (or figure 8); closing the water replenishing hole, opening the ventilating drain hole, slowly applying vertical pressure to the center of the warm end refrigerating plate (or the side plate) through the loading device to ensure that the final vertical pressure is the same as the overlying load borne by the undisturbed soil sample (the influence of different overlying soil pressures can be simulated by applying different pressures), and obtaining a remolded soil sample after the soil sample is stably solidified (the height change of the soil sample is less than or equal to 0.01mm within 1 hour);
it should be pointed out that, a large number of soil sample preparation tests are required to determine the quality of dry soil in the early stage, and the dry density of the prepared remolded soil sample is ensured to be approximately equal to that of undisturbed soil;
4. opening a water replenishing hole of a warm end refrigerating plate (or a side plate), connecting a coil pipe and the water replenishing hole by using a water guide pipe, then injecting enough distilled water into the coil pipe, wherein the distilled water entering a soil sample box firstly enters a water storage tank and is blocked by a water permeable plate, so that the distilled water spreads in the water storage tank and can relatively uniformly permeate into a soil sample below the water storage tank, when the distilled water continuously flows out of a ventilating water discharging hole, the soil sample box is filled with water (namely, remolded soil sample is completely saturated), the ventilating hole for water and gas permeation is closed at the moment, and according to the formulated test requirement, the height between a motor-driven lifting platform and the top surface of the soil sample is adjusted by a computer, namely, different underground water heads are simulated;
5. keeping the pressure applied to the soil unchanged, adjusting the temperature in the constant temperature box to 1 ℃, simultaneously adjusting the cold bath, and controlling the temperatures of the warm end refrigerating plate and the cold end refrigerating plate to be 1 ℃;
6. a freezing stage: when the temperature in the soil sample is stabilized at 1 ℃, keeping the temperature of the thermostat and the temperature of the warm-end refrigerating plate at 1 ℃, adjusting and controlling the cold bath of the cold-end refrigerating plate, reducing the temperature of the cold-end refrigerating plate to a specified cold-end temperature, such as-5 ℃, and freezing for 24 hours;
it should be noted that the influence of different temperature gradients on the soil sample can be simulated by changing the temperature of the bottom plate;
7. a thawing stage: and (3) closing the water replenishing hole, adjusting the cold bath, adjusting the temperature in the constant temperature box to 20 ℃ to enable the sample to start to melt, connecting the drainage air hole with the measuring cylinder by using a water guide pipe, and when the deformation of the soil sample is less than 0.05mm in every 2 hours (the descending speed of a warm-end refrigerating plate or a side plate), considering that the sample is stable in melting and sinking and finishing the melting and sinking test.
8. The data acquisition instrument can acquire the temperature and the vertical displacement of the interior of a soil body and the mass of the coil pipe in the freeze thawing process in real time, 1 data point is acquired at intervals of 5 minutes, the vertical displacement of the soil sample is an average value of readings of the displacement sensors, and the difference value between the readings of the real-time weighing sensors and the beginning of freezing is the water supplement amount of the soil sample.
The features and advantages of the device of the embodiment include:
1) Set up the rectangle hole at the lateral wall of soil sample case, adopt two kinds of modes of placing of vertical and level of soil sample case to it is fixed to combine the fixed bolster, make only warm end refrigeration board or only the curb plate can free vertical removal, and then realize can carrying out the vertical freezing of the soil body in same test device, can carry out the level of the soil body again and freeze.
2) On arranging weighing sensor in electric lift platform, arrange the platform back in with the coil pipe, arrange weighing sensor again in on, electric lift platform links to each other with the computer, and accessible computer control electric lift platform, its and the height of soil sample top surface of accurate control for the simulation exerts different head pressure to soil sample, and then the influence of different ground water level to the vertical frost heaving of soil body and melt and sink the deformation.
3) The catch basin has all been seted up to warm end refrigeration board and curb plate bottom to combine the effect of hindering of porous disk, no matter the soil body carries out vertical freezing and when the level freezes, all can guarantee the even moisturizing in soil sample top.
4) Combine coil pipe moisturizing device and weighing sensor to be used for monitoring the moisturizing volume change of freeze thawing in-process soil body, compare in traditional moisturizing device (like mahalanobis bottle etc.) have following benefit: the diameter of the coil pipe is small, the water replenishing sensitivity is high, and the hysteresis phenomenon of the traditional water replenishing device is avoided; the circular coil pipe is low in cost and easy to obtain; the coil pipe is arranged on the weighing sensor, so that the change of the soil body water supplement amount at each moment can be obtained in real time, and the test error caused by hysteresis is avoided.
5) All reserve the twice recess on warm end refrigeration board, cold junction refrigeration board and curb plate, install stagnant water rubber circle in the recess, fix each subassembly with the fixed bolster, make and connect closely between each subassembly to soil sample case is preferred to adopt the thick organic glass support of high strength, can form confined space in consequently soil sample incasement, guarantees that loading in-process soil granule and native normal water can not discharge.
6) In view of the fact that the relation (parallel and vertical) between the soil consolidation direction and the freezing direction can influence the vertical frost heaving and the thaw collapse deformation of the soil, when the device simulates the vertical freezing of the soil, the consolidation direction of the soil is parallel to the freezing direction, when the simulation soil horizontally freezes, the consolidation direction of the soil is perpendicular to the freezing direction, and the vertical frost heaving and the thaw collapse deformation of the soil around the manual freezing project can be really obtained.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the invention, but various changes and modifications may be made without departing from the spirit and scope of the invention, the scope of which is defined by the appended claims, the description and the equivalents thereof.
Claims (9)
1. The utility model provides a simulation bidirectional frozen's soil body has pressure moisturizing freeze thawing apparatus which characterized in that, includes thermostated container (6), refrigerating system, soil sample case (7), graduated flask (11), loading system (12), weighing system, displacement sensor, temperature sensor and control system:
the constant temperature box (6) is used for providing the environmental temperature required by the freeze-thaw test;
the refrigeration system comprises a first refrigeration plate, a second refrigeration plate and corresponding cold baths, wherein the first refrigeration plate and the second refrigeration plate are oppositely arranged on two sides of a soil sample (8) and are used for freezing the soil sample and manufacturing a temperature gradient;
the soil sample box (7) is used for containing a soil sample (8) required by a freezing test, and is vertically or horizontally placed in the constant temperature box (6) during the test; the soil sample box (7) is of a square box body structure with three hollowed-out surfaces, the soil sample box (7) is vertically placed, square openings communicated with an inner cavity of the soil sample box are respectively formed in the top, the bottom and one side surface of the soil sample box (7), the top opening (7-1) and the bottom opening (7-2) are identical in size and correspond to each other in the upper position and the lower position, the top opening (7-1) is blocked by a first refrigerating plate (15), the bottom opening (7-2) is blocked by a second refrigerating plate (23), the side opening (7-3) is blocked by a side plate (18), and a drainage air hole (9) is formed in the position close to the bottom of the back surface of the soil sample box (7), namely the side surface opposite to the side opening (7-3);
the measuring cylinder (11) is used for containing and measuring water bodies discharged from the water discharging air holes (9);
the loading system (12) is connected with the control system and is used for applying vertical downward pressure to the soil sample (8) so as to simulate the overlying load of the soil sample;
the weighing system comprises a coil pipe (24) and an electric lifting platform (27), the coil pipe (24) is horizontally laid on a platform (25), water is injected into the platform, one end of the coil pipe is used for feeding water into the soil sample (8) through a water guide pipe, the other end of the coil pipe is bent upwards and communicated with the atmosphere in a mode that an opening faces upwards; the electric lifting platform (27) is arranged beside the soil sample box (7), a loading platform of the electric lifting platform is provided with a weighing sensor (26), a platform (25) for laying the coil pipe (24) is arranged above the weighing sensor (26), and the change of the water amount in the coil pipe (24) is monitored through the weighing sensor (26); the electric lifting platform (27) is connected with a control system, and different underground water heads are simulated by adjusting the height of the coil pipe (24);
the inner surface of the first refrigerating plate/side plate (18) is provided with a square water storage tank, the periphery of the water storage tank is enclosed by a circle of flange, and meanwhile, the first refrigerating plate/side plate (18) is also provided with a water replenishing hole which vertically penetrates through a plate body of the first refrigerating plate/side plate; in a vertical freezing experiment/horizontal freezing experiment, the water storage tank is connected with the coil pipe (24) through a water supplementing hole for water inflow, a water permeable plate is arranged between the water storage tank and the soil sample (8), and the water permeable plate is flat and used for blocking an opening of the water storage tank of the first refrigeration plate/side plate (18) and realizing uniform water supplementation on the soil sample (8);
the displacement sensor (4) is arranged on the first refrigeration plate positioned above in a vertical freezing test, is arranged on the side plate (18) positioned above in a horizontal freezing test, and reflects the vertical frost heaving and thaw deformation changes of the soil sample by monitoring the height change of the first refrigeration plate or the side plate (18);
the temperature sensor (20) is inserted into the soil sample (8) and is used for monitoring the temperature of the soil sample (8);
and the signal output ends of the weighing sensor (26), the displacement sensor (4) and the temperature sensor (20) are respectively connected with a data acquisition instrument, and then are connected with the control system to feed back monitoring signals to the control system.
2. The soil body pressure water replenishing freeze thawing device for simulating bidirectional freezing of the soil body according to claim 1, wherein the soil sample box (7) is made of transparent organic glass.
3. The soil body pressure water replenishing freeze thawing device for simulating bidirectional freezing of the soil body according to claim 1, wherein the coil pipes (24) are formed by winding hose pipes with the inner diameter of 4-6 mm.
4. The soil body pressure water replenishing freeze thawing device for simulating bidirectional freezing according to claim 1, wherein: a plurality of temperature sensors (20) are arranged, and are uniformly inserted in the middle of the soil sample (8) in a vertical row mode in a vertical freezing test; in the horizontal freezing test, the soil sample is uniformly inserted in the middle of the soil sample (8) in a horizontal row mode so as to monitor the temperature and the temperature gradient parameters of the soil sample.
5. The soil body pressure water replenishing freeze thawing device for simulating bidirectional freezing of claim 1, wherein the loading system (12) applies pressure through a dowel (13);
the middle parts of the outer surfaces of the first refrigeration plate and the side plate (18) are respectively provided with a pressure head, and the pressure heads are provided with a concave groove structure with the shape matched with the shape of the output end of the dowel bar (13).
6. The soil body pressure-supplementing water-freezing and thawing device for simulating bidirectional freezing of the soil body according to claim 1, wherein filter paper is laid between the water permeable plate and the soil sample (8).
7. The soil body pressure water-replenishing freeze thawing device simulating bidirectional freezing of claim 1, wherein a water permeable plate is arranged between the second refrigeration plate and the soil sample (8), and the water drainage vent holes (9) are arranged at positions corresponding to the water permeable plate.
8. The soil body pressure-supplementing water-freezing and thawing device for simulating bidirectional freezing of the soil body according to claim 1, wherein a filling plate is arranged;
the filling plates comprise a refrigeration plate filling plate and a side plate filling plate, the shape and the size of the side plate filling plate are consistent with those of a side plate water storage tank, and when a vertical freezing test is carried out, the water permeable plate between the side plate (18) and the soil sample (8) is removed and then is filled into the water storage tank of the side plate (18); the shape and the size of the refrigerating plate filling plate are consistent with those of the first refrigerating plate water storage tank, and when a horizontal freezing test is carried out, the water permeable plate between the first refrigerating plate and the soil sample (8) is removed and then the water permeable plate is filled into the water storage tank of the first refrigerating plate.
9. The soil body pressure-supplementing water-freezing and thawing device for simulating bidirectional freezing according to any one of claims 1 to 8, wherein:
in the manual freezing method experiment, when making temperature gradient, will first refrigeration board sets up to warm end refrigeration board, and the second refrigeration board is the cold junction refrigeration board, promptly the temperature of second refrigeration board sets up for negative temperature and is less than first refrigeration board.
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| CN113607919B (en) * | 2021-07-29 | 2022-03-29 | 海南大学 | Frost heaving and thawing sinking test device |
| CN113933337B (en) * | 2021-10-13 | 2024-07-02 | 中国矿业大学 | Boundary active constraint bidirectional freezing frost heaving test device and application method thereof |
| CN115266810B (en) * | 2022-08-03 | 2023-05-05 | 哈尔滨工业大学 | Hot rod roadbed frost heaving test device |
| CN115808437B (en) * | 2023-01-17 | 2023-05-02 | 中国建筑第二工程局有限公司 | Subway communication channel freezing method construction model test device and method |
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