Three-dimensional soil moisture migration rule testing device and method

Abstract

The invention provides a three-dimensional soil moisture migration rule testing device. The three-dimensional soil moisture migration rule testing device comprises a test box body, a freezing circulation device, a grouting device and a variable water head simulation device, the test box body is used for placing a simulation sample and providing environment conditions similar to a field soil body for the simulation sample; the freezing circulation device is used for simulating flow characteristics of a cold source in a freezing pipe in freezing method construction; the grouting device is used for simulating a grouting process in grouting method construction; the variable water head simulation device is used for simulating water level changes; the invention also discloses a method for testing the three-dimensional soil moisture migration rule by using the three-dimensional soil moisture migration rule testing device. The testing device is easy to operate, good in using effect and capable of truly simulating the water migration and frost heaving rule of the three-dimensional soil body under freezing-grouting combined reinforcement of the water-rich sand layer under the action of the variable water head.

Description

Technical Field

[0001] The present invention belongs to the field of indoor geotechnical low-temperature testing (the present invention belongs to the technical field of experimental equipment), and specifically relates to a three-dimensional soil water migration law testing device and method. Background Art

[0002] The freezing method has been widely used in underground engineering construction in recent years due to its advantages such as good safety, wide adaptability, high flexibility, strong controllability and low pollution. However, studies have found that during the formation of the frozen soil curtain, the water in the soil will migrate to the vicinity of the frozen wall under the action of its own gravity, matrix suction and temperature gradient. After the water freezes, the volume expands, which increases the volume of the frozen soil. The frost heaving force generated at this time can easily cause large deformation of the overlying surface and adjacent buildings. In addition, the porosity of the sandy soil in the water-rich sand layer is large, the permeability coefficient is high, the groundwater is abundant and the recharge is large, the frost heaving effect is obvious, the frozen soil volume is large, the formation speed is fast, and the frost heaving has a great impact on the stratum, resulting in the inability of the existing tunnel upper line to operate normally, causing major economic losses and adverse social impacts. At the same time, the development process of the frozen wall cannot be effectively observed during the construction process, which inevitably causes local reinforcement failure and causes accidents such as tunnel water and sand gushing.

[0003] Therefore, it has become an urgent problem to carry out grouting reinforcement on the soil, understand the three-dimensional moisture migration and frost heave deformation law of the soil after grouting-freezing combined reinforcement, and provide an effective reference basis and reliable theoretical support for the design and construction of the freezing method.

[0004] The current test equipment has the following main defects: 1) Most of them are one-dimensional soil column tests, which can only study the one-dimensional moisture migration law of soil under the action of temperature gradient, and cannot truly reflect the three-dimensional moisture migration characteristics of soil under the action of freezing pipe; 2) The grouting effect is usually simulated by mixing grouting slurry with sand and soil and filling it into the sample loading bin, which is seriously inconsistent with actual construction; 3) At present, the test method can only be used to explore the moisture migration characteristics of sand with different moisture contents under the action of temperature field, and cannot be used to simulate the moisture migration law of sand at different water levels and depths. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art and to provide a three-dimensional soil moisture migration law testing device and method to solve the problem that the test device in the prior art has a simple structure and cannot simulate the actual situation of freezing and grouting.

[0006] In order to solve the above problems, the present invention provides a three-dimensional soil moisture migration law testing device, which is characterized by comprising a test box, a freezing circulation device, a grouting device and a variable head simulation device; the test box is used to place simulated samples and provide a simulated on-site soil storage environment for the simulated samples; the freezing circulation device is connected to the test box and is used to simulate the flow characteristics of the cold source in the freezing pipe during freezing construction. The freezing circulation device comprises a refrigerator, a low-temperature cooling circulating water pump and a freezing pipe. The outlet of the refrigerator is connected to the liquid inlet of the low-temperature cooling circulating water pump through a pipeline. The liquid outlet of the circulating water pump is connected to one end of the freezing pipe through a pipeline, and the other end of the freezing pipe is connected to the inlet of the refrigerator through a pipeline; the grouting device is connected to the test box to simulate the grouting process in the grouting construction; the variable head simulation device is connected to the test box to simulate the change of water level; wherein, the freezing pipe is arranged in the middle of the test box in the vertical direction, the lower end of the freezing pipe passes through the bottom of the test box and is connected to the liquid outlet of the low-temperature cooling circulating water pump through a pipeline, and the upper end of the freezing pipe passes through the upper part of the test box and is connected to the inlet of the refrigerator through a pipeline.

[0007] The above-mentioned three-dimensional soil moisture migration law testing device is characterized in that the freezing cycle device also includes a liquid storage tank, a temperature display and a valve; the liquid storage tank is arranged on the pipeline between the refrigerator and the low-temperature cooling circulating water pump, the inlet of the liquid storage tank is connected with the outlet of the refrigerator through a pipeline, and the outlet of the liquid storage tank is connected with the liquid inlet of the low-temperature cooling circulating water pump through a pipeline; the temperature display is arranged on the liquid storage tank, which is used to monitor the temperature in the liquid storage tank in real time; the valve is arranged on the pipeline between the low-temperature cooling circulating water pump and the freezing pipe, which is used to control the flow rate and flow of the cold source in the pipeline.

[0008] The above-mentioned three-dimensional soil moisture migration law testing device is characterized in that the test box includes a loading bin, an insulation bin, a bearing plate and a hydraulic jack; the loading bin is used to place simulated samples; the insulation bin is arranged at the front and rear sides of the loading bin, and is used to apply different initial temperatures to the simulated samples placed in the loading bin; the bearing plate is located at the top of the loading bin, and is used to apply corresponding overlying loads to the simulated samples in the loading bin; the hydraulic jack is connected to the bearing plate, and is used to provide thrust to the bearing plate.

[0009] The above-mentioned three-dimensional soil moisture migration law testing device is characterized in that the test box also includes a pressure measuring instrument and a pressure display instrument; the pressure measuring instrument is arranged in the sample soil body, and is used to measure the overlying load value and the stress change in the soil body during the test; the pressure display instrument is communicated with the pressure measuring instrument and is used to provide real-time feedback on the soil pressure.

[0010] The above-mentioned three-dimensional soil moisture migration law testing device is characterized in that the grouting device includes a grouting pump and an advance small tube; the grouting outlet of the grouting pump is connected to one end of the grouting pipe; the advance small tube is connected to the other end of the grouting pipe; wherein the advance small tube is arranged in the test box in the vertical direction, and the lower end of the advance small tube passes through the bottom of the test box and is connected to the grouting pipe.

[0011] The above-mentioned three-dimensional soil moisture migration law testing device is characterized in that the grouting device also includes a mixing barrel, a stirrer, an air compressor and a high-pressure hose; the mixing barrel is used to contain the prepared grouting material; the stirrer is arranged in the mixing barrel, and is used to stir the material in the mixing barrel; the air compressor is connected to the grouting pump, and is used to provide a certain grouting pressure for the slurry; one end of the high-pressure hose is connected to the mixing barrel, and the other end of the high-pressure hose is connected to the slurry inlet of the grouting pump.

[0012] The above-mentioned three-dimensional soil moisture migration law testing device is characterized in that the variable head simulation device includes a water replenishment bin, an automatic water supply controller, a pressureless water replenishment device, a seepage chamber, a leakage hole and a water bin; the water replenishment bin is used to hold the water required for simulating water level changes during the test; the water inlet of the automatic water supply controller is connected to the water replenishment bin for extracting water from the water replenishment bin; the water inlet of the pressureless water replenishment device is connected to the water outlet of the automatic water supply controller through a pipeline, and the seepage chamber is located on the left and right sides of the loading bin; the leakage hole is used to connect the seepage chamber and the loading bin, and the number of the leakage holes is multiple, and the multiple leakage holes are evenly arranged on the box wall between the seepage chamber and the loading bin; the water bin is arranged on the outside of the seepage chamber, and the water bin is connected to the seepage chamber, which can reflect the height of the water level in the seepage chamber; wherein the water outlet of the pressureless water replenishment device is connected to the seepage chamber through a pipeline.

[0013] The variable water head simulation device also includes a water level measuring instrument, which is arranged in the water tank and is used to monitor the water head height inside the water tank in real time.

[0014] The above-mentioned three-dimensional soil moisture migration law testing device is characterized in that the three-dimensional soil moisture migration law testing device also includes a data acquisition device that can monitor the moisture content, temperature and frost heave of sand in real time during the freezing process, and the data acquisition device includes a moisture sensor, a temperature sensor and a displacement meter; the moisture sensor is arranged in the sample to monitor the distribution of moisture inside the sample; the temperature sensor is also arranged in the sample to monitor the distribution of temperature field inside the sample; the displacement meter is arranged on the surface of the bearing plate to monitor the three-dimensional moisture migration law inside the sample soil during the freezing process and the internal displacement change process of the soil under the action of frost heave force in real time.

[0015] The above-mentioned three-dimensional soil moisture migration law testing device is characterized in that there are multiple moisture sensors and temperature sensors, and the multiple moisture sensors and temperature sensors are evenly arranged and buried in the sample soil.

[0016] The present invention also discloses a three-dimensional soil moisture migration law testing method, which is characterized in that the three-dimensional soil moisture migration law is tested by using the above-mentioned three-dimensional soil moisture migration law testing device, and the specific steps include:

[0017] Step 1: Test the physical and mechanical properties of the sample:

[0018] First, the moisture content, porosity, and particle size distribution of the on-site sand samples were tested; second, remolded sand was used and controlled by relative density index to ensure that the physical and mechanical properties of the remolded sand were the same as those of the on-site sand;

[0019] Step 2: Sample loading:

[0020] Add water to the prepared sand and soil to make it reach the same moisture content as the on-site sand and soil, and then keep the material sealed for 24 hours; then install the advance small guide tube and freezing tube in the loading bin; finally, divide the prepared soil sample into 5 equal parts by mass, fill them into the loading bin, and use a compactor to compact the soil sample to make the sample dense and level the surface of the sample. During the layered filling of the soil, bury the moisture sensor, temperature sensor and pressure measuring instrument in the corresponding position;

[0021] Step 3: Loading device installation:

[0022] After the sample is loaded, a load plate is placed on the surface of the loading chamber, and the displacement meter is installed on the load plate; then, a hydraulic jack is placed at the center of the load plate to apply the corresponding ground stress to the sand sample, and the soil pressure is fed back in real time through the pressure display instrument;

[0023] Step 4: Apply the initial temperature field:

[0024] After the soil stress loading is completed, the freezing circulation device is connected; then water of a certain temperature is injected into the insulation chamber to cool the soil, truly restoring the initial temperature field of the soil at different burial depths. At the same time, the internal temperature of the soil is monitored by the temperature sensor buried in advance. When the overall temperature of the sample is consistent, the grouting test is carried out;

[0025] Step 5: Slurry injection:

[0026] Pour the prepared raw materials into the mixing bucket, add a certain amount of water, and mix the slurry through the mixer; turn on the grouting pump and conduct the grouting test;

[0027] Step 6: Test the variable head simulation device:

[0028] After the slurry injection is completed, fill the seepage chamber with soils of different permeability coefficients to simulate different water level depths. At the same time, fill the water replenishment tank with water, and install a water level measuring instrument and a pressureless water replenishment device.

[0029] Step 7: Collect test data:

[0030] Turn on the refrigerator and set the test target temperature. When the temperature reaches the preset temperature, turn on the low-temperature cooling circulating water pump to freeze and replenish water to the sample soil in the test box to freeze the soil. During the test, collect test data from the moisture sensor, temperature sensor and displacement meter inside the soil.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] 1. The variable water head simulation method used in the present invention can truly simulate the three-dimensional water migration phenomenon of soil under different groundwater level depths, solving the problem that only one-dimensional water migration of soil can be measured in previous experiments.

[0033] 2. The grouting device used in the present invention can truly simulate the grouting process, solving the problem that the test results are unreliable and the test conditions are seriously deviated from the on-site construction due to excessive mixing of the grouting slurry with the soil in the previous experimental process.

[0034] 3. The freezing cycle device used in the present invention is simple in design and easy to operate. It can accurately transfer the cold source to the soil, and the insulation chambers are set on the front and rear surfaces of the sample loading chamber to simulate the initial temperature field of the strata under different tunnel burial depths.

[0035] 4. The present invention uses a method for testing the water migration law of three-dimensional soil under the action of variable water head by simulating the freezing-grouting combined reinforcement of water-rich sand layers. The method is easy to operate, can simulate the effect of the freezing-grouting combined treatment measures indoors, and can test the water migration law and surface frost heave deformation characteristics during soil freezing.

[0036] The invention is further described in detail below through the accompanying drawings and examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0038] Figure 1 Schematic diagram of various components of the testing device in an embodiment of the present invention.

[0039] Figure 2Schematic diagram of the structure of the test box in the embodiment of the present invention.

[0040] Figure 3 It is a schematic diagram of the positions and connection relationships of the loading bin, the insulation bin, the seepage chamber and the water bin in an embodiment of the present invention.

[0041] Figure 4 FIG. 4 is a top view of a load-bearing plate in an embodiment of the present invention.

[0042] Description of reference numerals:

[0043] 1—test box; 11—loading chamber; 12—insulation chamber; 13—carrying plate;

[0044] 14—Hydraulic jack; 15—Pressure measuring instrument; 16—Pressure display instrument;

[0045] 2—freezing cycle device; 21—refrigerating machine; 22—low temperature cooling circulating water pump;

[0046] 23—freezing pipe; 24—liquid storage tank; 25—temperature display instrument; 26—valve;

[0047] 3—grouting device; 31—grouting pump; 32—grouting pipe; 33—advanced small guide tube;

[0048] 34—mixing barrel; 35—mixer; 36—air compressor; 37—high-pressure hose;

[0049] 4—variable water head simulation device; 41—water replenishment tank; 42—automatic water supply controller;

[0050] 43—pressureless water replenishment device; 44—seepage chamber; 45—leakage hole;

[0051] 46—water level measuring instrument; 47—water tank; 5—data acquisition device;

[0052] 51—moisture sensor; 52—temperature sensor; 53—displacement meter. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] like Figures 1 to 3As shown, the present invention discloses a three-dimensional soil moisture migration law testing device, which is characterized in that it includes a test box 1, a freezing circulation device 2, a grouting device 3 and a variable head simulation device 4; the test box 1 is used to place a simulation sample and provide the simulation sample with an environmental condition similar to that of the on-site soil; the freezing circulation device 2 is connected to the test box 1 and is used to simulate the flow characteristics of a cold source in a freezing pipe during freezing construction, the freezing circulation device 2 includes a refrigerator 21, a low-temperature cooling circulating water pump 22 and a freezing pipe 23, the outlet of the refrigerator 21 is connected to the liquid inlet of the low-temperature cooling circulating water pump 22 through a pipeline, and the low-temperature cooling circulating water pump 22 The liquid outlet is connected to one end of the freezing pipe 23 through a pipeline, and the other end of the freezing pipe 23 is connected to the inlet of the refrigerator 21 through a pipeline; the grouting device 3 is connected to the test box 1 to simulate the grouting process in the grouting construction; the variable head simulation device 4 is connected to the test box 1 to simulate the change of water level; wherein, the freezing pipe 23 is arranged in the middle of the test box 1 in the vertical direction, and the lower end of the freezing pipe 23 passes through the bottom of the test box 1 and is connected to the liquid outlet of the low-temperature cooling circulating water pump 22 through a pipeline, and the upper end of the freezing pipe 23 passes through the upper part of the test box 1 and is connected to the inlet of the refrigerator 21 through a pipeline.

[0055] In this embodiment, an overburden load is applied to the sample soil through the test box 1 to provide a simulated on-site soil environment for the sample; the freezing effect of the freezing pipe 23 on the surrounding sample soil during the freezing method construction is simulated through the freezing circulation device 2; the grouting process of the sample soil by the grouting device 3 is simulated; and the three-dimensional water migration phenomenon of the soil under different groundwater level depths is simulated through the variable head simulation device 4. Among them, the freezing circulation device 2 mainly transfers the cold source from the freezing pipe 23 to the soil, and provides a certain pressure to the cold source to circulate in the freezing pipe; it can truly simulate the flow characteristics of the cold source during the on-site construction process and improve the accuracy of the test.

[0056] In this embodiment, the low-temperature cooling circulating water pump 22 can be used to control the flow rate and flow rate of the cold source in the freezing pipe 23 to be consistent with the on-site conditions, thereby improving the accuracy of the test.

[0057] The temperature range that the refrigerator 21 can provide in this embodiment is -50 to 30°C, with an error within ±0.05°C, which can ensure accurate application of temperature;

[0058] like Figure 1As shown, the freezing circulation device 2 also includes a liquid storage tank 24, a temperature display instrument 25 and a valve 26; the liquid storage tank 24 is arranged on the pipeline between the refrigerator 21 and the low-temperature cooling circulating water pump 22, the inlet of the liquid storage tank 24 is connected to the outlet of the refrigerator 21 through a pipeline, and the function of the liquid storage tank 24 is mainly to store the cold source of the target temperature, and the cold source can be a brine-calcium chloride solution; the outlet of the liquid storage tank 24 is connected to the liquid inlet of the low-temperature cooling circulating water pump 22 through a pipeline; the temperature display instrument 25 is arranged on the liquid storage tank 24, and is used to monitor the temperature in the liquid storage tank in real time; the temperature of the brine-calcium chloride solution can be measured in real time; the valve 26 is arranged on the pipeline between the low-temperature cooling circulating water pump 22 and the freezing pipe 23, and is used to control the flow rate and flow of the cold source in the pipeline, and the flow rate and flow of the brine-calcium chloride solution can be set to truly simulate the flow characteristics of the cold source during the on-site construction process; the valve 26 is a control valve that can control the flow rate and flow.

[0059] In this embodiment, the volume of the liquid storage tank 24 is 25L. The liquid storage tank 24 contains a coolant, which is mainly a salt water-calcium chloride solution with a specific gravity of 1.23.

[0060] The connecting pipes of the various components of the freezing cycle device 2 in this embodiment are all pipes with heat insulation function to avoid heat exchange between the cold source and the outside world during pipeline transportation, resulting in energy loss. The freezing pipe 23 is arranged in the central part of the loading bin 11, which can evenly transfer heat to the inside of the soil.

[0061] In this embodiment, the surfaces of the components and connecting pipes of the freezing cycle device 2 are wrapped with a 5 mm thick insulation layer, which can effectively reduce the heat loss of the cold source during the circulation process.

[0062] In this embodiment, a water valve is reserved on the low-temperature cooling circulating water pump 22, which can be used to adjust the flow size and flow rate of the cold source, truly simulating on-site construction.

[0063] like Figure 1 , Figure 2 and Figure 4 As shown, the test box 1 includes a loading bin 11, an insulation bin 12, a bearing plate 13 and a hydraulic jack 14. The loading bin 11 is used to place simulated samples. The bearing plate 13 and the hydraulic jack 14 can apply an overlying load to the simulated samples in the loading bin 11, thereby truly simulating the on-site soil environment. The insulation bin 12 is arranged at the front and rear sides of the loading bin 11, and is used to apply different initial temperatures to the simulated samples placed in the loading bin 11. The bearing plate 13 is located at the top of the loading bin 11, and is used to apply a corresponding overlying load to the simulated samples in the loading bin 11. The hydraulic jack 14 is connected to the bearing plate 13, and is used to provide thrust to the bearing plate 13.

[0064] In this embodiment, the loading bin 11 is a rectangular parallelepiped made of steel plate, with a wall thickness of 1.5 cm, a height of 50 cm, and a length and width of 200 cm respectively; a reserved hole is provided at the center of the bottom surface of the loading bin 11 and the center of the bearing plate 13 for placing the freezing pipe 23. In this embodiment, the loading bin 11 is made of steel plate, which avoids the problem of damage to the test device caused by excessive grouting pressure and frost heave force during grouting and freezing.

[0065] In this embodiment, the insulation chamber 12 is located on the front and rear surfaces of the sample loading chamber 11, and has a thickness of 0.6 cm. A water inlet and a water outlet are set on the outer surface of the insulation chamber 12. By controlling the water temperature entering and exiting the insulation chamber 12, different initial temperatures are applied to the simulated samples placed in the loading chamber 11.

[0066] In this embodiment, the thickness of the bearing plate 13 is 2 cm, and 1 cm thick ribs are arranged on its surface longitudinally and transversely respectively. The thickness of the ribs is 1 cm to ensure uniform application of the load; the lower end of the hydraulic jack 14 acts on the bearing plate 13, and the upper end is connected to the bracket. The bracket is used to provide a reaction force to the hydraulic jack 14, so that the bearing plate 13 can provide an overlying load for the simulated specimen.

[0067] like Figure 2 As shown, the test box 1 also includes a pressure measuring instrument 15 and a pressure display 16; the pressure measuring instrument 15 is set in the sample soil body, and is used to measure the overlying load value and the stress change in the soil body during the test; the pressure display 16 is connected to the pressure measuring instrument 15 for real-time feedback of the soil pressure. The pressure measuring instrument 15 is buried 10 cm below the bearing plate 13, and can monitor the internal pressure of the sand;

[0068] like Figure 1 and Figure 2 As shown, the grouting device 3 includes a grouting pump 31 and an advance small catheter 33; the grouting outlet of the grouting pump 31 is connected to one end of the grouting pipe 32; the advance small catheter 33 is connected to the other end of the grouting pipe 32; wherein, the advance small catheter 33 is arranged in the test box 1 along the vertical direction, and the lower end of the advance small catheter 33 passes through the bottom of the test box 1 and is connected to the grouting pipe 32.

[0069] In this embodiment, the grouting pump 31 is connected to the advance small conduit 33 through the grouting pipe, and the slurry can be directly injected into the soil; the slurry injection process can be truly simulated, avoiding the shortcomings of the current mixing method used to simulate grouting to reinforce the soil; the advance small conduit 33 adopts a steel welded pipe commonly used in the construction of subway dark tunnels, and two 8mm grouting holes are reserved in the center of the advance small conduit, with a spacing of 10cm between the grouting holes; the advance small conduit 33 is circumferentially arranged around the freezing pipe, and the circumferential and lateral spacing of the advance small conduit is 30cm;

[0070] like Figure 1 As shown, the grouting device 3 also includes a mixing barrel 34, a stirrer 35, an air compressor 36 and a high-pressure hose 37; the mixing barrel 34 is used to contain the prepared grouting material; the stirrer 35 is arranged in the mixing barrel 34, and is used to stir the material in the mixing barrel 34; the air compressor 36 is connected to the grouting pump 31, and is used to provide a certain grouting pressure for the slurry; one end of the high-pressure hose 37 is connected to the mixing barrel 34, and the other end of the high-pressure hose 37 is connected to the slurry inlet of the grouting pump 31.

[0071] In this embodiment, the grouting pump 31 is a pneumatic grouting pump, and the air compressor 36 can also provide power for the pneumatic grouting pump.

[0072] In this embodiment, the mixer 35 is located inside the mixing barrel 34, and can stir the slurry at a high speed to prevent the slurry from sedimentation; the air inlet of the pneumatic grouting pump is also connected to the air compressor 36 through a high-pressure hose to provide a certain grouting pressure for the slurry; the grouting inlet of the pneumatic grouting pump is connected to a grouting pipe, which directly extends into the mixing barrel 34 for absorbing the slurry; the slurry outlet of the pneumatic grouting pump is connected to the advance small duct 33 through the grouting pipe, and the slurry can be directly injected into the sample soil, truly simulating on-site construction; the advance small duct 33 is arranged in a ring shape around the freezing pipe.

[0073] like Figure 1 and Figure 3 As shown, the variable water head simulation device 4 includes a water replenishment tank 41, an automatic water supply controller 42, a pressureless water replenishment device 43, a seepage chamber 44, a leaking hole 45 and a water tank 47; the water replenishment tank 41 is used to hold the water required for simulating the water level change during the test; the water inlet of the automatic water supply controller 42 is connected to the water replenishment tank 41, and is used to extract the water in the water replenishment tank 41; the water inlet of the pressureless water replenishment device 43 is connected to the water outlet of the automatic water supply controller 42 through a pipeline, and the leaking hole 45 is connected to the water outlet of the automatic water supply controller 42 through a pipeline. The flow chamber 44 is located on the left and right sides of the loading bin 11; it is used to connect the seepage chamber 44 and the loading bin 11, and the number of the leakage holes 45 is multiple, and the multiple leakage holes 45 are evenly distributed on the box wall between the seepage chamber 44 and the loading bin 11; the water tank 47 is arranged on the outside of the seepage chamber 44, and the water tank 47 is connected to the seepage chamber 44, which can reflect the height of the water level in the seepage chamber 44; wherein, the water outlet of the pressureless water replenishment device 43 is connected to the seepage chamber 44 through a pipe.

[0074] In this embodiment, the variable water head simulation device 4 further includes a water level measuring instrument 46 , which is disposed in a water tank 47 and is used to monitor the water head height inside the water tank in real time.

[0075] In this embodiment, the seepage chamber 44 is welded on the left and right surfaces of the loading bin 11, and the water tank 47 is welded on the surface of the seepage chamber 44 away from the loading bin 11. The inside of the seepage chamber 44 can be filled with soil with different permeability coefficients to simulate different groundwater depths; the leakage hole 45 is arranged on the baffle connecting the seepage chamber 44 and the loading bin 11, which can ensure that the water flow migrates under the temperature gradient; there are multiple leakage holes 45 with a diameter of 2 cm, and they are evenly arranged on the baffle to ensure uniform penetration of the water flow; the water level measuring instrument 46 is located in the water tank 47 to monitor the water level; the pressureless water replenishment device 43 is connected to the seepage chamber 44 through a pipeline. Through the principle of the communicating vessel, the water level in the seepage chamber 44 is consistent with the water level in the pressureless water replenishment device 43. The water level in the pressureless water replenishment device 43 is controlled by the automatic water supply controller 42, and then the water level in the seepage chamber 44 is controlled, simulating the water migration law under different water level burials and performing pressureless and uniform water replenishment on the soil in the sample pressure bin.

[0076] like Figure 2 As shown, the three-dimensional soil moisture migration law testing device also includes a data acquisition device 5 that can monitor the moisture content, temperature and frost heave of sand in real time during the freezing process. The data acquisition device 5 includes a moisture sensor 51, a temperature sensor 52 and a displacement meter 53; the moisture sensor 51 is arranged in the sample to monitor the distribution of moisture inside the sample; the temperature sensor 52 is also arranged in the sample to monitor the distribution of the temperature field inside the sample; the displacement meter 53 is arranged on the surface of the bearing plate 13, and is used to monitor the three-dimensional moisture migration law inside the sample soil during the freezing process and the displacement change process of the soil under the action of frost heave force in real time.

[0077] In this embodiment, there are multiple moisture sensors 51 and temperature sensors 52, and the multiple moisture sensors 51 and temperature sensors 52 are evenly arranged and buried in the sample soil.

[0078] In this embodiment, the moisture sensors 51 are evenly arranged and buried 20 cm inside the soil sample, with a spacing of 5 cm.

[0079] In this embodiment, the displacement meter 53 is arranged on the surface of the middle bearing plate to monitor the displacement of the stratum caused by the frost heaving force of the soil during the freezing process. The arrangement interval is 10 cm.

[0080] The three-dimensional soil moisture migration law testing device of the present invention is simple to operate and has good use effect. It can truly simulate the three-dimensional soil moisture migration and frost heave law under the freezing-grouting combined reinforcement of the water-rich sand layer under the action of variable water head.

[0081] The present invention also discloses a method for testing the three-dimensional soil moisture migration law. The three-dimensional soil moisture migration law is tested using the above-mentioned three-dimensional soil moisture migration law testing device. The specific steps include:

[0082] Step 1: Test the physical and mechanical properties of the sample:

[0083] First, the moisture content, porosity, and particle size distribution of the on-site sand samples were tested; second, remolded sand was used and controlled by relative density index to ensure that the physical and mechanical properties of the remolded sand were the same as those of the on-site sand;

[0084] Step 2: Sample loading:

[0085] Add water to the prepared sand to make it reach the same moisture content as the on-site sand, and then keep it stuffed for 24 hours; then install the advance small guide tube 33 and the freezing tube 23 in the loading bin 11; finally, divide the prepared soil sample into 5 equal parts by mass, fill it into the loading bin 11, and use a compactor to compact the soil sample to make it dense and level the surface of the sample. During the layered filling of the soil, bury the moisture sensor 51, temperature sensor 52 and pressure measuring instrument 15 in the corresponding positions;

[0086] Step 3: Loading device installation:

[0087] After the sample is loaded, a bearing plate 13 is placed on the surface of the loading chamber 11, and the displacement meter 53 is installed on the bearing plate 13; then, a hydraulic jack 14 is placed at the center of the bearing plate 13 to apply corresponding ground stress to the sand sample, and the soil pressure is fed back in real time through the pressure display 16;

[0088] Step 4: Apply the initial temperature field:

[0089] After the soil stress loading is completed, the freezing circulation device 2 is connected; then a water flow of a certain temperature is injected into the heat preservation chamber 12 to cool the soil, and the initial temperature field of the soil at different burial depths is truly restored. At the same time, the internal temperature of the soil is monitored by the temperature sensor 52 buried in advance. When the overall temperature of the sample is consistent, the grouting test is carried out;

[0090] Step 5: Slurry injection:

[0091] Pour the prepared raw materials into the mixing barrel 34, add a certain amount of water, and mix the slurry through the mixer 35; turn on the grouting pump 31 to perform a grouting test;

[0092] Step 6: Test the variable head simulation device:

[0093] After the slurry injection is completed, the seepage chamber 44 is filled with soils with different permeability coefficients to simulate different water level depths. At the same time, the water replenishment tank 41 is filled with water, and a water level measuring instrument 46 and a pressureless water replenishment device 43 are installed.

[0094] Step 7: Collect test data:

[0095] Turn on the refrigerator 21 and set the test target temperature. When the temperature reaches the predetermined temperature, turn on the low-temperature cooling circulating water pump 22 to freeze and replenish water to the sample soil in the test box 1 to freeze the soil. During the test, the test data of the soil internal moisture sensor 51, temperature sensor 52 and displacement meter 53 are collected.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A three-dimensional soil water migration law testing device, characterized in that: include: The test box (1) is used to place the simulated sample and provide a simulated on-site soil environment for the simulated sample; A freezing circulation device (2), the freezing circulation device (2) being connected to the test box (1) and used for simulating the flow characteristics of a cold source in a freezing pipe during freezing construction, the freezing circulation device (2) comprising a refrigerator (21), a low-temperature cooling circulation water pump (22) and a freezing pipe (23), the outlet of the refrigerator (21) being connected to the liquid inlet of the low-temperature cooling circulation water pump (22) through a pipeline, the liquid outlet of the low-temperature cooling circulation water pump (22) being connected to one end of the freezing pipe (23) through a pipeline, and the other end of the freezing pipe (23) being connected to the inlet of the refrigerator (21) through a pipeline; A grouting device (3), the grouting device (3) being connected to the test box (1) and being used to simulate the grouting process in grouting construction; and a variable water head simulation device (4), wherein the variable water head simulation device (4) is connected to the test box (1) and is used to simulate the change of water level; The freezing pipe (23) is arranged in the middle of the test box (1) in the vertical direction, the lower end of the freezing pipe (23) passes through the bottom of the test box (1) and is connected to the liquid outlet of the low-temperature cooling circulation water pump (22) through a pipeline, and the upper end of the freezing pipe (23) passes through the upper part of the test box (1) and is connected to the inlet of the refrigerator (21) through a pipeline.

2. A three-dimensional soil water migration law testing device according to claim 1, characterized in that: The freezing cycle device (2) further comprises: A liquid storage tank (24), the liquid storage tank (24) being arranged on a pipeline between the refrigerator (21) and the low-temperature cooling circulating water pump (22), the inlet of the liquid storage tank (24) being connected to the outlet of the refrigerator (21) through a pipeline, and the outlet of the liquid storage tank (24) being connected to the liquid inlet of the low-temperature cooling circulating water pump (22) through a pipeline; A temperature display (25), the temperature display (25) being arranged on the liquid storage tank (24) and used for real-time monitoring of the temperature in the liquid storage tank; and a valve (26), wherein the valve (26) is arranged on the pipeline between the low-temperature cooling circulation water pump (22) and the freezing pipe (23) and is used to control the flow rate and flow of the cold source in the pipeline.

3. A three-dimensional soil water migration law testing device according to claim 1, characterized in that: The test box (1) comprises: A loading chamber (11) for placing a simulation sample; A heat preservation chamber (12), the heat preservation chamber (12) being arranged at the front side and the rear side of the loading chamber (11) and being used to apply different initial temperatures to the simulation sample placed in the loading chamber (11); A load-bearing plate (13), the load-bearing plate (13) being located on the top of the loading chamber (11) and being used to apply a corresponding overlying load to the simulated sample in the loading chamber (11); and a hydraulic jack (14), wherein the hydraulic jack (14) is connected to the bearing plate (13) and is used to provide thrust to the bearing plate (13).

4. A three-dimensional soil water migration law testing device according to claim 3, characterized in that: The test box (1) also includes: A pressure measuring instrument (15), the pressure measuring instrument (15) being arranged in the sample soil body and used for measuring the value of the overlying load and the stress change in the soil body during the test; and a pressure display instrument (16), wherein the pressure display instrument (16) is communicatively connected with the pressure measuring instrument (15) and is used for providing real-time feedback on soil pressure.

5. The three-dimensional soil water migration law testing device according to claim 1 is characterized in that: The grouting device (3) comprises: A grouting pump (31), wherein a grouting outlet of the grouting pump (31) is connected to one end of a grouting pipe (32); and an advance small conduit (33), wherein the advance small conduit (33) is connected to the other end of the grouting pipe (32); The small advance conduit (33) is arranged in the test box (1) along the vertical direction, and the lower end of the small advance conduit (33) passes through the bottom of the test box (1) and is connected to the grouting pipe (32).

6. A three-dimensional soil water migration law testing device according to claim 5, characterized in that: The grouting device (3) further comprises: A mixing barrel (34) for containing the prepared grouting material; A mixer (35), the mixer (35) is arranged in the mixing barrel (34) and is used to mix the materials in the mixing barrel (34); An air compressor (36), the air compressor (36) being connected to the grouting pump (31) and used for providing a certain grouting pressure for the slurry; and a high-pressure hose (37), one end of which is connected to the stirring barrel (34), and the other end of which is connected to the slurry inlet of the grouting pump (31).

7. A three-dimensional soil water migration law testing device according to claim 3, characterized in that: The variable water head simulation device (4) comprises: A water replenishment tank (41) is used to hold water required to simulate water level changes during the test; An automatic water supply controller (42), wherein a water inlet of the automatic water supply controller (42) is connected to the water supply tank (41) and is used to extract water from the water supply tank (41); A pressureless water supply device (43), wherein the water inlet of the pressureless water supply device (43) is connected to the water outlet of the automatic water supply controller (42) through a pipeline, A seepage chamber (44), wherein the seepage chamber (44) is located on the left and right sides of the loading bin (11); A water leakage hole (45) is used to connect the seepage chamber (44) and the loading bin (11), and the number of the water leakage holes (45) is multiple, and the multiple water leakage holes (45) are evenly arranged on the box wall between the seepage chamber (44) and the loading bin (11); and a water tank (47), wherein the water tank (47) is arranged outside the seepage chamber (44), and the water tank (47) is connected to the seepage chamber (44), and can reflect the height of the water level in the seepage chamber (44); Wherein, the water outlet of the non-pressure water replenishment device (43) is connected to the seepage chamber (44) through a pipeline; The variable water head simulation device (4) also includes a water level measuring instrument (46), which is arranged in the water tank (47) and is used to monitor the water head height inside the water tank in real time.

8. A three-dimensional soil water migration law testing device according to claim 7, characterized in that: The three-dimensional soil moisture migration law testing device further comprises a data acquisition device (5) capable of real-time monitoring of the moisture content, temperature and frost heave of the sand during the freezing process, wherein the data acquisition device (5) comprises: A moisture sensor (51), the moisture sensor (51) is arranged in the sample and is used to monitor the distribution of moisture inside the sample; A temperature sensor (52), which is also arranged in the sample and is used to monitor the distribution of the temperature field inside the sample; and a displacement meter (53), wherein the displacement meter (53) is arranged on the surface of the bearing plate (13) and is used for real-time monitoring of the three-dimensional water migration law inside the sample soil body during the freezing process and the displacement change process inside the soil body under the action of frost heave force.

9. A three-dimensional soil water migration law testing device according to claim 8, characterized in that: The number of the moisture sensors (51) and the temperature sensors (52) is multiple, and the multiple moisture sensors (51) and the temperature sensors (52) are evenly arranged and buried in the sample soil.

10. A three-dimensional soil water migration law testing method, characterized in that: The three-dimensional soil moisture migration law is tested by using a three-dimensional soil moisture migration law testing device as described in claim 9, and the specific steps include: Step 1: Test the physical and mechanical properties of the sample: First, the moisture content, porosity, and particle size distribution of the on-site sand samples were tested; second, remolded sand was used and controlled by relative density index to ensure that the physical and mechanical properties of the remolded sand were the same as those of the on-site sand; Step 2: Sample loading: Add water to the prepared sand and soil to make it reach the same moisture content as the on-site sand and soil, and then simmer for 24 hours; then, install the advance small guide tube (33) and the freezing tube (23) in the loading bin (11); finally, divide the soil sample prepared in advance into 5 equal parts by mass, fill them into the loading bin (11), and use a compactor to compact the soil sample to make the sample dense and level the surface of the sample. During the layered filling of the soil, bury the moisture sensor (51), temperature sensor (52) and pressure measuring instrument (15) in the corresponding positions; Step 3: Loading device installation: After the sample is loaded, a bearing plate (13) is placed on the surface of the loading chamber (11), and a displacement meter (53) is installed on the bearing plate (13); then, a hydraulic jack (14) is placed at the center of the bearing plate (13), and corresponding ground stress is applied to the sand sample, and the soil pressure is fed back in real time through a pressure display instrument (16); Step 4: Apply the initial temperature field: After the soil stress loading is completed, the freezing circulation device (2) is connected; then a water flow of a certain temperature is injected into the heat preservation chamber (12) to cool the soil, and the initial temperature field of the soil at different burial depths is truly restored. At the same time, the internal temperature of the soil is monitored by the temperature sensor (52) buried in advance. When the overall temperature of the sample is consistent, a grouting test is carried out; Step 5: Slurry injection: Pour the raw materials prepared in advance into a mixing bucket (34), add a certain amount of water, and mix and stir the slurry through a stirrer (35); turn on the grouting pump (31) to perform a grouting test; Step 6: Test the variable head simulation device: After the slurry injection is completed, soil with different permeability coefficients is filled in the seepage chamber (44) to simulate different water level depths, and at the same time, the water replenishment tank (41) is filled with water, and a water level measuring instrument (46) and a pressureless water replenishment device (43) are installed; Step 7: Collect test data: The refrigerator (21) is turned on, and the test target temperature is set. When the temperature reaches the predetermined temperature, the low-temperature cooling circulating water pump (22) is turned on to freeze and replenish water to the sample soil in the test box (1), so that the soil is frozen; during the test, test data of the soil internal moisture sensor (51), the temperature sensor (52) and the displacement meter (53) are collected.

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