Multifunctional frost heave test system and test method thereof

Abstract

The present invention discloses a multifunctional frost heave test system and a test method thereof, wherein the test system comprises a support frame, a test barrel body arranged on the support frame for storing soil samples, a temperature control system for controlling the temperature of the soil samples, a force application system for selectively applying a constant pressure or an infinite stiffness to the soil samples through the top of the test barrel body, a pressureless water supply system for supplying water into the soil samples through the bottom of the test barrel body, and a detection system. The present invention can carry out multi-condition coupling tests with high integration.

Description

Technical Field

[0001] The invention relates to the technical field of frozen soil research, and in particular to a multifunctional frost heave test system and a test method thereof. Background Art

[0002] Soil and rock with negative or zero temperature and containing ice are called frozen soil. When the water in the soil turns into ice, the volume increases by 9%, which is called frost heave of water in the soil. When the volume expansion of water in the soil is sufficient to cause relative displacement between soil particles, the volume expansion of the soil during freezing is formed, which is called frost heave of the soil. Frost heave is divided into two types: in-situ frost heave and partial freezing heave. In a closed system, in-situ frost heave mainly occurs in the soil. In an open system with water replenishment, water migrates to a certain location and freezes under the action of a driving mechanism, which is called partial freezing heave, and the amount of frost heave is large. When salinization occurs in frozen soil, the complex soil-water-salt interaction changes the original frost heave and water migration mechanism, and aggravates the damage of buildings (structures) under periodic temperature change conditions.

[0003] At present, the research on soil water-heat-salt-force is mainly concentrated on indoor model tests. When studying a single soil layer, the temperature of the columnar soil sample needs to be maintained uniform from top to bottom. When studying multiple soil layers, an environment with a temperature gradient change from top to bottom is provided. When simulating the influence of groundwater, the soil sample needs to be pressure-free replenished with water. In addition, it is also necessary to simulate the influence of different constraints on frozen soil. The test equipment of the existing technology has low integration and cannot carry out coupled tests under the above multiple conditions. Summary of the invention

[0004] The purpose of the present invention is to provide a multifunctional frost heave test system to address the defect that the frost heave test device in the prior art cannot meet the research requirements in many aspects.

[0005] Another object of the present invention is to provide a test method for the multifunctional frost heave test system.

[0006] The technical solution adopted to achieve the purpose of the present invention is:

[0007] A multifunctional frost heave test system comprises a support frame, a test barrel body arranged on the support frame for storing soil samples, a temperature control system for controlling the temperature of the soil samples, a force application system for selectively applying a constant pressure or an infinite stiffness to the soil samples through the top of the test barrel body, a pressureless water supply system for replenishing water into the soil samples through the bottom of the test barrel body, and a detection system, wherein:

[0008] The test barrel body comprises an inner sample barrel for storing soil samples and a cooling portion arranged on the circumferential outer wall of the inner sample barrel;

[0009] The temperature control system comprises the cooling part, a lower cold plate fixed to the bottom of the test barrel, and an upper temperature control plate which can be matched to enter the inner sample barrel and is sealed and connected to the inner wall thereof, the upper temperature control plate applies a load to the soil sample under the action of the force application system, and the bottom of the inner sample barrel is sealed and connected to the top of the lower cold plate;

[0010] The force application system includes a lever force application device, a booster rod, and an upper reaction beam. The booster rod is provided with a detachable force ring. When the upper reaction beam is fixedly connected to the support frame and the force ring is not installed on the booster rod, the upper reaction beam simulates an infinite stiffness condition by fixing the position of the upper temperature control plate. When the upper reaction beam is fixedly connected to the support frame and the force ring is installed on the booster rod, a flexible boundary condition is simulated.

[0011] The non-pressure water supply system comprises a water supply cavity arranged at the bottom of the test barrel and a communicating vessel structure for supplying water to the water supply cavity, and the water supply cavity is provided with a water supply hole facing the soil sample;

[0012] The detection system includes a displacement sensor arranged on the force ring and / or a stress sensor arranged on the booster rod and / or a temperature sensor for measuring the temperature of the soil sample and / or a displacement sensor probe for measuring the vertical displacement of the soil sample and / or a water replenishment metering device for measuring the water replenishment amount and water replenishment rate.

[0013] In the above technical solution, the support frame includes a lower base plate and a guide rod fixed on the lower base plate, a support leg is fixed to the bottom of the lower base plate, the lower cold plate is fixed to the lower base plate, the upper reaction beam is slidably connected to the upper part of the guide rod, and the upper reaction beam can be fastened to the guide rod by a fastening connector.

[0014] In the above technical solution, an insulation cover is arranged on the outside of the test barrel body, the bottom of the insulation cover is fixed on the lower cold plate or the support frame, the top of the test barrel body is provided with the upper top plate which can seal the opening of the insulation cover, the upper top plate is fixed to the lower cold plate or the support frame by a first pull rod, a through hole is formed on the upper top plate for the booster rod to pass through, and the booster rod is sealed and connected to the through hole.

[0015] In the above technical solution, the lever force applying device includes a lever assembly, a force plate, and a fulcrum block fixed to the bottom of the support frame, wherein the lever assembly includes a lever and a weight that can be selectively assembled on one end of the lever, the middle part of the lever is hinged to the force plate, the force plate is slidably connected to the guide rod located below the support frame, the bottom fulcrum of the fulcrum block is in contact with the lever, and the force plate is fixed to the upper reaction beam through a second pull rod.

[0016] In the above technical solution, the other end of the lever is provided with a balancing block which can be adjusted along the length direction thereof, and the balancing block and the weight are respectively located at the two ends of the lever.

[0017] In the above technical solution, the displacement sensor probe is fixed downward on the upper top plate, a measuring block is fixed on the booster rod, and the displacement sensor probe detects the distance between the displacement sensor probe and the measuring block to measure the displacement of the soil sample;

[0018] The temperature sensor comprises a first temperature sensor vertically inserted into the soil sample through the upper temperature control plate and / or one or more second temperature sensors horizontally inserted into the soil sample through the side wall of the test barrel;

[0019] In the above technical solution, the test barrel body includes a replaceable first test barrel body and a second double-layer barrel body, wherein the first test barrel body includes the inner sample barrel and a cooling part arranged on the circumferential outer wall of the inner sample barrel, and the second double-layer barrel body includes an inner sample barrel and an outer sample barrel, the bottom of the inner sample barrel is sealed and connected to the lower cold plate, the outer sample barrel is slidably sleeved on the outside of the inner sample barrel, a small hole for inserting a second temperature sensor is formed on the side wall of the outer sample barrel, and a strip hole for inserting the second temperature sensor is formed on the side wall of the inner sample barrel, and the length of the strip hole is greater than the aperture of the small hole.

[0020] In the above technical solution, the detection system also includes a plurality of salt sensors for testing salt content, the salt sensors are plugged into different heights of the second double-layer barrel body, and reinforcing ribs are fixed on the side walls of the inner sample barrel of the second double-layer barrel body.

[0021] In the above technical solution, the top of the booster rod is fixed to the bottom of the upper reaction beam, a force disk is fixed to the bottom, and the force disk is coaxially fixed to the top surface of the upper temperature control plate.

[0022] In the above technical solution, the booster rod includes a positioning sleeve fixed to the bottom of the upper reaction beam, a force-bearing shaft fixedly sleeved in the positioning sleeve, and an upper temperature control plate reaction rod fixed to the top of the upper temperature control plate, wherein a groove is formed on the top of the upper temperature control plate reaction rod, the stress sensor is fixed in the groove, and the force-bearing shaft can be matched and inserted into the groove to directly or indirectly act on the stress sensor;

[0023] The top of the force measuring ring is provided with a protrusion which can be matched and inserted into the positioning sleeve, and the bottom of the force measuring ring is fixed with a fixing block which can be matched and inserted into the groove to directly or indirectly act on the stress sensor.

[0024] In the above technical solution, the cooling part is a cooling jacket or cooling coil arranged outside the inner sample barrel;

[0025] The upper temperature control plate and the lower cold plate include a cavity for storing coolant and a cold plate circulating liquid inlet pipe and a cold plate circulating liquid outlet pipe connected to the cavity; or the upper temperature control plate and the lower cold plate both include an upper cooling plate and a lower cooling plate arranged up and down, a spiral groove is arranged in the lower cooling plate, and when the upper cooling plate covers the lower cooling plate, the spiral groove is sealed to form a spiral coolant channel, and the two ends of the spiral coolant channel are respectively connected to the cold plate circulating liquid outlet pipe and the cold plate circulating liquid inlet pipe.

[0026] In the above technical solution, a sealing ring is provided on the circumferential side wall of the upper temperature control plate.

[0027] In the above technical solution, the water supply plate and the lower cold plate are enclosed to form a water supply cavity, and the water supply cavity is provided with two water inlets, one of which is connected to the Martens flask through a water supply pipe, and the other is connected to a connecting hose to form a communicating vessel structure with the Martens flask;

[0028] The water replenishment metering device comprises a weighing device placed below the Martens flask and a differential pressure gauge mounted on the water replenishment pipe.

[0029] In the above technical solution, the water replenishment plate and the annular flange arranged on the lower cold plate form a water replenishment cavity, and the water replenishment plate includes a bottom water-permeable frame and a perforated plate fixed to the top of the bottom water-permeable frame, wherein the bottom water-permeable frame includes ribs arranged in a cross-grid, and the ribs are provided with penetrating water holes.

[0030] In another aspect of the present invention, the test method of the test device is to put the soil sample into the inner sample barrel, and the upper temperature control plate and the lower cold plate seal the upper and lower ends of the test barrel body, so that the soil sample is in a relatively sealed state, and the following three coupling tests can be performed:

[0031] (1) Single soil layer or temperature gradient: When the cooling unit is closed and the lower cooling plate and upper temperature control plate are opened, a temperature gradient is formed in the soil sample, simulating multiple soil layer tests. When the lower cooling plate and upper temperature control plate are closed and the cooling unit is opened, the temperature in the soil sample is fixed and uniform, simulating a single soil layer test.

[0032] (2) Open system or closed system: When the pressureless water replenishment system is turned on, an open system test is conducted to simulate groundwater recharge. When the pressureless water replenishment system is turned on, the lower cold plate and the upper temperature control plate are turned on, and the temperature gradient is used as the driving force for water replenishment. When the pressureless water replenishment system is turned off, a closed system test is conducted to simulate no groundwater recharge.

[0033] (3) Constant stress or infinite stiffness or flexible boundary conditions: When the upper reaction beam is fixedly connected to the support frame and the force ring 60 is not installed on the booster rod 54, the displacement of the soil sample is completely restricted and the test is carried out under infinite stiffness conditions;

[0034] When the upper reaction beam is movably connected to the support frame, the upper reaction beam is pulled down by the constant pulling force of the lever force applying device to perform a test under constant stress conditions;

[0035] When the upper reaction beam 2 is fixedly connected to the support frame and a force ring is installed on the booster rod, a test is carried out under flexible boundary conditions to study the expansion force variation mechanism of the soil sample. In theory, the expansion force increases with the increase of displacement.

[0036] During the test, the displacement sensor is installed on the vertical diameter of the measuring ring structure through a connecting component. It can detect the vertical deformation displacement of the ring structure. The temperature sensor collects the temperature changes of the soil sample in real time. The stress sensor can reflect the stress generated by the soil sample during the frost heave process. The displacement sensor probe measures the vertical displacement of the soil sample during the freezing and thawing process. The water replenishment measurement device measures the water replenishment amount and water replenishment rate.

[0037] In the above technical solution, when a single soil layer test is conducted, the test barrel body adopts a first test barrel body, and the temperature sensor adopts a first temperature sensor inserted into the soil sample from the upper temperature control plate;

[0038] When the temperature gradient test is performed, the test barrel body adopts a second double-layer barrel body, and the temperature sensor adopts a plurality of second temperature sensors inserted into the soil sample from the side wall of the second double-layer barrel body.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. The present invention provides a test device that can not only make temperature gradient (the temperature of the soil layer changes from top to bottom in a gradient), but also study a single soil layer (the temperature of each position in the soil layer is consistent), can be used for constant stress conditions (no force ring is installed, and the upper reaction beam is pulled down by a lever device), can be used for infinite stiffness conditions (no force ring is installed, and the upper reaction beam is locked) or boundary conditions (the force ring is installed, and the upper reaction beam is locked), can be used for open system tests (the pressureless water replenishment system is started to simulate the actual formation with groundwater recharge), and can be used for closed system tests (the pressureless water replenishment system is closed to simulate the actual formation without groundwater recharge). In this way, a variety of experimental studies are carried out, and the functions are diversified. In addition, the test device of the present invention has a simple structure, is easy to disassemble and assemble, is easy to operate, and is easy to promote and apply.

[0041] 2. The present invention adopts a lever force device, which can effectively apply a constant load to the soil sample, and through the lever structure, the lever principle is fully utilized, and a large load can be applied to the soil sample through a small weight, meeting the needs of different test conditions. At the same time, the displacement of the sample can also be completely restricted, and the restriction conditions can be converted. Thus, the functions in multiple application scenarios can be met.

[0042] 3. The replaceable double-layer barrel structure effectively avoids the lateral restriction of the soil sample expansion process by the laterally arranged temperature sensor (or other sensors such as salt sensor), hinders the expansion of the soil sample (prevents "locking"), and improves the test measurement accuracy of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is the front view of the test device.

[0044] Figure 2 This is the front view of the test device.

[0045] Figure 3 It is a side view of the test device.

[0046] Figure 4 It is a connection diagram between the test barrel, water source, upper temperature control plate, lower cold plate, upper top plate, and lower bottom plate.

[0047] Figure 5 yes Figure 1 A partial enlarged view of the figure (the position of the permeable plate is moved up for easier display).

[0048] Figure 6 It is a structural diagram of a permeable board.

[0049] Figure 7 It is a schematic diagram of the structure of the cooling jacket and the inner sample barrel.

[0050] Figure 8 It is a schematic diagram of the structure of the cooling coil and the inner sample barrel.

[0051] Fig. 9 It is a structural schematic diagram of the upper temperature control plate.

[0052] Fig.10 It is a schematic diagram of the structure of the second double-layer barrel.

[0053] Fig.11 This is a schematic diagram of the assembly structure of the force measuring ring (omitting the lever force device, pressure-free water supply system, etc.)

[0054] In the figure: 1-inner sample barrel, 2-upper reaction beam, 3-upper temperature control plate, 4-annular flange, 5-water supply pipe, 6-stress sensor, 7-displacement sensor probe, 8-force disk, 9-reinforcement wing, 10-upper top plate, 11-lower bottom plate, 12-first pull rod, 13-bolt, 14-support leg, 15-measuring block, 16-first temperature sensor, 17-second temperature sensor, 18-small hole, 19-strip hole, 20-positioning sleeve, 21-force shaft, 22-upper temperature control plate reaction rod, 23-assembly groove, 24-guide rod, 25-cooling jacket, 26-cooling coil, 27-cavity circulating liquid outlet, 28-cavity circulating liquid inlet, 29-circulating liquid inlet, 30 -circulating liquid outlet, 31-cavity, 33-cold plate circulating liquid inlet pipe, 34-upper cooling plate, 35-lower cooling plate, 36-spiral slot, 37-cold plate circulating liquid outlet pipe, 38-cold plate circulating liquid inlet pipe, 39-water permeable rack, 40-orifice plate, 41-water hole, 42-force plate, 43-fulcrum block, 44-lever, 45-balance block, 46-weight, 47-second pull rod, 48-tray, 49-connecting rod, 50-external sample barrel, 51-Marsh flask, 52-differential pressure gauge, 53-connecting plate, 54-boosting rod, 55-groove, 56-temperature sensor hole, 57-hose, 58-insulation sleeve, 59-sealing ring, 60-force ring, 61-displacement sensor. DETAILED DESCRIPTION

[0055] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0056] A multifunctional frost heave test system comprises a support frame, a test barrel disposed on the support frame, a temperature control system for controlling the temperature of the soil sample, a force application system for selectively applying different loads to the soil sample through the top of the test barrel, a pressureless water supply system for supplying water into the soil sample through the bottom of the test barrel, and a detection system, wherein:

[0057] The test barrel body comprises an inner sample barrel 1 for storing soil samples and a cooling part arranged on the circumferential outer wall of the inner sample barrel 1;

[0058] The temperature control system includes the cooling part, a lower cold plate fixed to the bottom of the test barrel, and an upper temperature control plate 3 that can be matched and sealed with the inner wall of the inner sample barrel 1. The upper temperature control plate 3 applies a load to the soil sample under the action of the force application system. The bottom of the inner sample barrel is sealed with the top of the lower cold plate (the top of the lower cold plate forms an assembly groove 23 for inserting the bottom of the test barrel, which is convenient for positioning the test barrel and sealing the inner sample barrel 1);

[0059] The force application system includes a lever force application device, a booster rod 54, and an upper reaction beam 2. A detachable force ring 60 is provided on the booster rod 54. When the upper reaction beam 2 is fixedly connected to the support frame and the force ring 60 is not installed on the booster rod 54, the upper reaction beam 2 simulates an infinite stiffness condition by fixing the position of the upper temperature control plate 3. When the upper reaction beam 2 is fixedly connected to the support frame and the force ring 60 is installed on the booster rod 54, a flexible boundary condition is simulated. When the upper reaction beam 22 is movably connected to the support frame, the upper reaction beam 2 pulled down by the lever force application device applies a load to the upper temperature control plate 3 through the booster rod 54 to simulate a constant stress condition.

[0060] The pressureless water replenishment system includes a water replenishment plate arranged at the bottom of the test barrel, and the water replenishment plate and the lower cold plate are enclosed to form a water replenishment cavity, and the water replenishment cavity is supplied with water through a communicating vessel structure. Unlike the peristaltic pump that supplies water through pressure, the present application uses pressureless water replenishment to simulate the actual formation environment conditions. After the upper temperature control plate 3 and the lower cold plate are turned on, a temperature gradient is formed in the soil sample, and under the driving force of the temperature gradient, pressureless water replenishment is performed through the communicating vessel structure.

[0061] The detection system includes a displacement sensor 61 arranged on the force ring 60 and / or a stress sensor 6 arranged on the booster rod 54 and / or a temperature sensor for measuring the temperature of the soil sample and / or a displacement sensor probe 7 for measuring the vertical displacement of the soil sample and / or a water replenishment metering device for measuring the water replenishment amount and water replenishment rate.

[0062] The soil sample is placed in the inner sample barrel 1. The upper temperature control plate 3 and the lower cold plate seal the upper and lower ends of the test barrel, so that the soil sample is in a relatively sealed state. The following three coupling tests can be carried out:

[0063] (1) Single soil layer or temperature gradient: When the cooling unit is closed and the lower cold plate and the upper temperature control plate 3 are opened, a temperature gradient is formed in the soil sample, simulating a test of multiple soil layers. When the lower cold plate and the upper temperature control plate 3 are closed and the cooling unit is opened, the temperature in the soil sample is fixed and uniform, simulating a test of a single soil layer.

[0064] (2) Open system or closed system: When the pressureless water replenishment system is turned on, an open system test is carried out to simulate groundwater recharge. When the pressureless water replenishment system is turned off, a closed system test is carried out to simulate the absence of groundwater recharge. It is the communicating vessel structure formed by the component such as the Maschine flask that makes it possible to simulate the pressureless water replenishment in the actual stratum during the test.

[0065] (3) Constant stress or infinite stiffness or flexible boundary conditions:

[0066] When the upper reaction beam 2 is fixedly connected to the support frame and the force ring 60 is not installed on the booster rod 54, the test is carried out under infinite stiffness conditions. At this time, the displacement of the soil sample is completely restricted, and the expansion force change mechanism of the soil sample is studied. In theory, the expansion force increases with the increase of displacement;

[0067] When the upper reaction beam 2 is movably connected to the support frame and the force ring 60 is not installed on the booster rod 54, the upper reaction beam 2 is pulled down by the constant pulling force of the lever force device, and the test under constant stress conditions is carried out. At this time, the soil sample is equivalent to a weight of a fixed weight being pressed on it. The pressure remains unchanged, and the expansion force is theoretically fixed and unchanged, which is equivalent to the stress generated by the overlying load.

[0068] When the upper reaction beam 2 is fixedly connected to the support frame and the force ring 60 is installed on the booster rod 54, a test under flexible boundary conditions is performed, and the pressure above the soil sample gradually increases with the expansion process.

[0069] During the test, the displacement sensor 61 is arranged on the vertical diameter of the ring structure of the force measuring ring 60 through a connecting component, and it can detect the vertical deformation displacement of the ring structure; in practice, the displacement measured by the force measuring ring 60 can be compared and verified with the displacement measured by the displacement sensor probe 7 to serve as a reference for the accuracy of the test results.

[0070] The temperature sensor collects the temperature changes of the soil sample in real time, the stress sensor 6 can reflect the stress generated by the soil sample during the frost heave process, the displacement sensor probe 7 measures the vertical displacement of the soil sample during the freeze-thaw process, and the water replenishment measurement device measures the water replenishment amount and water replenishment rate. These data can be recorded and processed manually or transmitted to the monitoring terminal for automatic processing.

[0071] The support frame includes a lower bottom plate 11 and a guide rod 24 fixed to the lower bottom plate 11, the lower cold plate is fixed to the lower bottom plate 11, and the bottom of the inner sample barrel 1 is sealed and fixed to the upper surface of the lower cold plate. The upper reaction beam 2 is slidably connected to the upper part of the guide rod 24, and the upper reaction beam 2 can be fastened to the guide rod 24 through a fastening connector, and the force plate 42 is slidably connected to the guide rod 24 located below the support frame to play a guiding role and ensure that the force plate 42 moves up and down in the vertical direction.

[0072] When the guide rod 24 and the upper reaction beam 2 are fastened together by the fastening connector, a test under infinite stiffness conditions can be performed, and the stress state, that is, the state of frost heave force, is mainly measured. The fastening connector can be a fixing bolt, and the guide rod 24 is provided with a thread. The two ends of the upper reaction beam 2 can be fixed to the two guide rods 24 respectively by the fixing bolt, and the position of the upper reaction beam 2 is fixed.

[0073] The setting of the guide rod 24 can realize the force transmission in the vertical direction without deviation. The support frame is fixed with a vertical guide rod 24. More preferably, the bottom of the guide rod 24 passes through the lower bottom plate 11 and is fixed to the lower bottom plate 11 by connecting bolts. The end of the upper reaction beam 2 is formed with a guide hole for the guide rod 24 to pass through. Furthermore, two guide rods 24 are provided, symmetrically arranged on the left and right sides of the test barrel, and the two ends of the upper reaction beam 2 are slidably connected to the two guide rods 24 respectively.

[0074] In order to maintain the stability of the temperature inside the test barrel, an insulation sleeve 58 is arranged on the outside of the test barrel, and the bottom of the insulation sleeve 58 is fixed on the lower cold plate or the lower bottom plate 11. The top of the test barrel is provided with the upper top plate 10 which can seal its opening. The upper top plate 10 is fixed to the lower bottom plate 11 or the lower cold plate by a first pull rod 12. A through hole is formed on the upper top plate 10 for the booster rod 54 to pass through. The booster rod 54 is sealed and connected to the through hole, which can play a role of heat insulation and reduce heat loss. The upper top plate 10 and the outermost insulation sleeve 58 form an enclosed space to play a role of heat insulation. The bottom of the first tie rod 12 is fixed to the lower bottom plate 11 or the lower cold plate by bolts 13, and the upper top plate 10 is fastened to the top of the first tie rod 12 by bolts 13; the upper and lower ends of the first tie rod 12 are threaded sections, and the upper top plate 10 and the lower bottom plate 11 can be fixed by the bolts 13 threadedly connected thereto. As shown in the figure, three first tie rods 12 are arranged, which are evenly distributed in a circular array with the axis of the test barrel as the axis, and the bottom of the lower bottom plate 11 is fixed with support legs 14 to place the entire test device on the test platform.

[0075] When the upper and lower cold plates or the surrounding cooling parts are turned on, the sample has no heat loss in the vertical direction, making the test more accurate and close to the real natural situation.

[0076] like Figure 2-3 As shown, the lever force applying device includes a lever assembly, a force plate 42, and a fulcrum block 43 fixed to the bottom of the support frame, wherein the lever assembly includes a lever 44, a weight 46 that can be selectively assembled on one end of the lever 44, the middle part of the lever 44 is hinged on the force plate 42, the bottom fulcrum of the fulcrum block 43 is in contact with the lever 44, and the force plate 42 is fixed to the upper reaction beam 2 through a second pull rod 47. Two second pull rods 47 are provided symmetrically to form a symmetrical pulling force. A contact groove is formed at the position where the lever 44 contacts the bottom fulcrum. In order to adapt to soil columns of different heights, the fulcrum block 43 is a plurality of replaceable fulcrum blocks 43 of different heights, or a fulcrum block 43 with adjustable height, so as to adjust the distance between the lever 44 and the lower base plate 11 when the lever 44 is balanced.

[0077] When weights 46 of different numbers or weights are assembled at the end of the lever 44, the lever 44 provides a constant pulling force to the force plate 42, and then provides a constant pulling force to the upper reaction beam 2 through the second pull rod 47, so as to realize the constant load. In the same way as the assembly of the first pull rod 12, the top of the second pull rod 47 is fastened to the upper reaction beam 2 by a fastening bolt, and the bottom is fastened to the force plate 42 by a fastening bolt. When disassembling the upper reaction beam 2, the fastening bolts can be removed.

[0078] Furthermore, in order to maintain the balance of the lever 44, the other end of the lever 44 is provided with a balancing block 45 which can be adjusted along its length direction, and the balancing block 45 and the weight 46 are respectively located at both ends of the lever 44. One section of the lever 44 is a threaded rod, and the balancing block 45 is connected to the threaded rod by threads. Before placing the weight, first adjust the balancing block 45 to balance the entire lever system, and then add the weight 46.

[0079] Furthermore, a tray 48 for placing a weight 46 is fixed to the end of the lever 44. The tray 48 is fixed to the end of the lever 44 through a connecting rod 49, and the top of the connecting rod 49 is fixedly connected to the lever 44 by a connecting screw hinge or an integral molding method. The lever 44 is directly hinged to the force plate 42 through a connecting shaft or a connecting screw, and a position near the middle of the lever 44 contacts the fulcrum block 43. The end of the lever 44 is hinged to two oppositely arranged connecting plates 53 on the top of the force plate 42 through a connecting shaft.

[0080] In order to accurately collect displacement data, the displacement sensor probe 7 is fixed downward on the upper top plate 10, and a measuring block 15 is fixed on the booster rod 54. The displacement sensor probe 7 detects the distance between the displacement sensor probe 7 and the measuring block 15 to measure the displacement of the soil sample. For example, when the soil sample frost heaves, it moves upward in the vertical direction, and the distance between the displacement sensor probe 7 and the measuring block 15 is reduced, so that the displacement of the soil sample is measured.

[0081] In order to accurately measure the temperature in the soil sample, the temperature sensor includes a first temperature sensor 16 vertically inserted into the soil sample through the upper temperature control plate 3 and / or one or more second temperature sensors 17 horizontally inserted into the soil sample through the side wall of the test barrel. When multiple second temperature sensors 17 are provided, the temperature of the soil sample at different heights can be detected. For the frost heave test under the temperature gradient (multiple soil layers), the temperature that needs to be measured is the temperature distribution on the entire soil column, because the temperature is different due to the temperature gradient on the entire soil column, so the sensor is inserted on the side wall.

[0082] The second temperature sensor is inserted into the hole in the side wall of the sample barrel. When the soil expands, multiple second temperature sensors and the test barrel impose lateral restrictions on the soil sample, forming a "locking" structure, which greatly restricts the expansion of the soil and reduces the measurement accuracy of the salt-frost heave instrument.

[0083] In order to prevent the soil sample from being lateral restricted during the frost heave process, that is, being "locked" by the test barrel, the test barrel includes a replaceable first test barrel and a second double-layer barrel, wherein the first test barrel includes the inner sample barrel 1 and a cooling portion arranged on the circumferential outer wall of the inner sample barrel 1, such as Figure 7-8 As shown, the second double-layer barrel body includes an inner sample barrel 1 and an outer sample barrel 50. Fig.10 As shown, the bottom of the inner sample barrel 1 is sealed and connected to the lower cold plate, the inner sample barrel 1 is slidably sleeved in the outer sample barrel, a small hole 18 for inserting the second temperature sensor 17 is formed on the side wall of the outer sample barrel, and a strip hole 19 for the second temperature sensor 17 to penetrate is formed on the side wall of the inner sample barrel 1, and the aperture of the strip hole 19 is larger than the aperture of the small hole 18. The strip holes are arranged one by one with the small holes, and the strip holes 19 provide space for the second temperature sensor 17 to move up and down, so that the soil sample drives the second temperature sensor 17 to move up during the frost heave process, and the outer sample barrel 50 and the second temperature sensor 17 move up relative to the inner sample barrel 1, preventing the soil sample from being locked by the test barrel body, thereby improving the accuracy of the test.

[0084] In order to test the influence of salinity, the detection system further comprises a plurality of salt sensors for testing salinity, and the salt sensors are plugged into different heights of the double-layer barrel body, and the arrangement is the same as that of the second temperature sensor 17 .

[0085] In order to prevent the inner sample barrel 1 from cracking due to excessive overburden during the overburden load test, reinforcing ribs are fixed on the side walls of the inner sample barrel 1 .

[0086] Therefore, when conducting a single soil layer test, the first test barrel is assembled on the support frame, and when conducting a gradient temperature test, the second double-layer barrel is assembled on the support frame. Different test barrels are selected according to different test requirements.

[0087] In order to visually check the changes of soil samples during frost heave, the test barrel is made of transparent material.

[0088] In order to make the booster rod 54 apply load to the upper temperature control plate 3 uniformly, the top of the booster rod 54 is fixed to the bottom of the upper reaction beam 2, and a force disc 8 is fixed to the bottom, and the force disc 8 is coaxially fixed to the top surface of the upper temperature control plate 3. Furthermore, a reinforcing wing 9 is fixed between the bottom of the booster rod 54 and the force disc 8, and the reinforcing wings 9 are distributed in a circular array around the axis of the booster rod 54. As shown in the figure, there are three reinforcing wings 9, and the angle between each two adjacent reinforcing wings 9 is 120 degrees.

[0089] In order to accurately collect data from the stress sensor 6, the booster rod 54 includes a positioning sleeve 20 fixed to the bottom of the upper reaction beam 2, a force-bearing shaft 21 inserted into the positioning sleeve 20, and an upper temperature control plate reaction rod 22 fixed to the top of the upper temperature control plate 3, wherein a groove 55 is formed on the top of the upper temperature control plate reaction rod 22, and the stress sensor 6 is fixed in the groove 55, and the force-bearing shaft 21 can be matched and inserted into the groove 55 to directly or indirectly act on the stress sensor 6;

[0090] The top of the force ring 60 is provided with a protrusion that can be matched and inserted into the positioning sleeve 20, and the bottom of the force ring 60 is fixed with a fixing block to match and insert into the groove 55 to directly or indirectly act on the stress sensor 6. Such a setting is convenient for disassembly and assembly, and can improve the accuracy of measurement. When installing the force ring 60, the protrusion on the top of the force ring 60 is inserted into the positioning sleeve 20, and the fixing block at the bottom of the force ring 60 is inserted into the groove 55. When the force ring 60 is not installed, the top of the force-bearing shaft 21 is inserted into the positioning sleeve 20, and the bottom of the force-bearing shaft 21 is inserted into the groove 55.

[0091] The cooling part is a cooling jacket 25 or a cooling coil 26 disposed outside the inner sample barrel 1. When the cooling part is a cooling jacket 25, a temperature control cavity for storing cooling liquid is formed inside the cooling jacket 25, and the top of the cooling jacket 25 is provided with a cavity circulating liquid outlet 27 connected to the temperature control cavity, and the bottom is provided with a cavity circulating liquid inlet 28 connected to the temperature control cavity. When the cooling part is a cooling coil 26, the cooling coil 26 is spirally wound on the outer wall of the test barrel, and the bottom of the cooling coil 26 is a circulating liquid inlet 29, and the top is a circulating liquid outlet 30.

[0092] The upper temperature control plate 3 and the lower cold plate can both adopt the following two structures:

[0093] First, the upper temperature control plate 3 and the lower cold plate include a cavity 31 for storing coolant and a cold plate circulating liquid inlet pipe 32 and a cold plate circulating liquid outlet pipe 33 connected to the cavity 31. The temperature of the upper temperature control plate 3 is controlled by circulating coolant. When a force disc 8 is provided on the upper temperature control plate 3, the upper temperature control plate circulating liquid inlet pipe and the upper temperature control plate circulating liquid outlet pipe pass through the force disc 8.

[0094] The second type: the upper temperature control plate 3 and the lower cold plate both include an upper cooling plate 34 and a lower cooling plate 35 arranged up and down, and a spiral groove 36 is arranged in the lower cooling plate 35. When the upper cooling plate 34 covers the lower cooling plate 35, the spiral groove 36 is sealed to form a spiral coolant channel, and the two ends of the spiral coolant channel are respectively connected to the cold plate circulating liquid outlet pipe 37 and the cold plate circulating liquid inlet pipe 38. The upper cooling plate 34 and the lower cooling plate 35 can be fastened and connected by screws, and the setting of the spiral coolant channel can optimize the cooling effect. The annular flange 4 is formed on the top of the upper cooling plate 34 of the lower cold plate to facilitate processing and molding. In addition, the upper cooling plate 34 and the lower cooling plate 35 of the upper temperature control plate 3 can be provided with a temperature sensor hole 56 for inserting the first temperature sensor 16.

[0095] In order to ensure the sealing performance between the upper temperature control plate 3 and the inner wall of the inner sample barrel 1 , a sealing ring 59 is provided on the circumferential side wall of the upper temperature control plate 3 .

[0096] Furthermore, the water replenishment cavity is provided with two water inlets, one of which is connected to the Marg flask 51 through the water replenishment pipe 5, and the other is connected to the connecting hose 57 to form a communicating vessel structure with the Marg flask 51, and the water replenishment metering device includes a weighing device placed under the Marg flask 51 and a differential pressure gauge 52 mounted on the water replenishment pipe;

[0097] The weighing device can use an electronic balance to measure the amount of water replenishment during the test. The change of the scale in the Martens flask can be photographed with a camera or manually observed to calculate the amount of water replenishment. A differential pressure gauge 52 is set on the water replenishment pipe 5 to measure the water replenishment rate. The port of the connecting hose 57 is placed at a height equivalent to the height of the differential pressure gauge 52, so as to form a communicating vessel structure to achieve pressure-free water replenishment. A connecting pipe is fixed to each of the two water inlets, extending through the perforations on the lower cold plate to connect the water replenishment pipe 5 and the connecting hose 57, and the water replenishment pipe 5 and the connecting hose 57 are sealed and connected to the perforations).

[0098] The water replenishment plate and the annular flange 4 arranged on the lower cold plate form a water replenishment cavity, and the water replenishment plate includes a bottom water-permeable frame 39 and a perforated plate 40 fixed to the top of the bottom water-permeable frame 39, wherein the bottom water-permeable frame 39 includes ribs arranged in a cross-grid, and the ribs are provided with penetrating water holes 41.

[0099] The water supplied through the water supply pipe 5 enters the water supply plate, is evenly distributed in the bottom water-permeable frame 39 through the water holes 41, and then enters the soil sample through the small holes 18 on the orifice plate 40, ensuring uniform water supply to the soil sample, preventing uneven distribution of water in the soil sample from affecting the test results, and further improving the reliability of the test results.

[0100] Example 2

[0101] Frost heave test of a single soil layer under closed system (pressureless water replenishment system closed), constant stress conditions, infinite stiffness conditions or flexible boundary conditions.

[0102] Filling soil sample:

[0103] (1) If an adjusting bolt is installed on the guide rod 24, first unscrew the adjusting bolt to make the upper reaction beam 2 and the guide rod 24 slidably connected, remove the fastening bolt between the upper reaction beam 2 and the second pull rod 47, and remove the upper reaction beam 2;

[0104] (2) Unscrew the bolts 13 and remove the upper top plate 10;

[0105] (3) Remove the upper temperature control plate from the test barrel and fill the soil sample through the top opening of the test barrel;

[0106] (4) The upper temperature control plate is pressed onto the soil sample, the upper top plate 10 is closed, the bolts 13 are tightened, the upper reaction beam 2 is installed, and the two ends of the upper reaction beam 2 are fastened to the second tie rod 47 by means of the fastening bolts;

[0107] (5) If necessary, use the adjusting bolts to fix the position of the upper reaction beam 2.

[0108] After the soil samples were filled, the frost heave test of a single soil layer under constant stress conditions in Example 2.1 and the frost heave test of a single soil layer under infinite stiffness conditions in Example 2.2 were respectively carried out. Both Examples 2.1 and 2.2 included a single freezing and freeze-thaw cycle, which was related to the temperature setting. In this example, the test barrel body was Figure 7 or Figure 8 In the first test barrel shown, the temperature is measured using a first temperature sensor. 2.1

[0110] The soil sample is loaded according to the above steps, the measuring ring 60 is not installed, the adjusting bolt is not assembled, the upper reaction beam 2 is slidably connected to the guide rod 24, a rated number of weights 46 are placed on the tray 48, the lever 44 rotates with the fulcrum block 43 as a fulcrum, the upper reaction beam 2 is pulled down by the second pull rod 47, the upper reaction beam 2 applies an upper load to the upper temperature control plate 3 through the power rod 54, and the upper temperature control plate 3 applies a constant load to the soil sample. 2.1.1

[0112] The frost heave test of a single soil layer under constant stress and single cooling is carried out. The specific operation process is: connect the cooling part to the cold bath, adjust the temperature of the cold bath to 25℃-20℃-15℃-10℃-5℃-0℃-(-5)℃-(-10)℃-(-15)℃-(-20)℃, and simulate the frost heave test of a single soil layer under single cooling. For example, the temperature change of a single soil layer from day to night, at this time, the frost heave test under single cooling is to be carried out. 2.1.2

[0114] A frost heave test was conducted under a freeze-thaw cycle of a single soil layer with constant stress. The specific operation process is: connect the cooling part to a cold bath, and adjust the temperature of the cold bath to 25℃-20℃-15℃-10℃-5℃-0℃-(-5)℃-(-10)℃-(-15)℃-(-20)℃-(-15)℃-(-10)℃-(-5)℃-0℃-5℃-10℃-15℃-20℃-25℃, simulating the macroscopic temperature changes of the soil layer throughout the year. 2.2

[0116] After the soil sample is loaded, the force ring 60 is not installed, and the upper reaction beam 2 is fastened to the guide rod 24 by adjusting bolts to completely limit the displacement of the sample. The remaining test steps refer to the operation procedures in 2.1.1 and 2.1.2, and the frost heave test under single cooling of infinite stiffness single soil layer and the frost heave test under freeze-thaw cycle of infinite stiffness single soil layer can be carried out respectively. 2.3

[0118] After the soil sample is filled, the force ring 60 is installed, and the upper reaction beam 2 is fastened to the guide rod 24 by means of the adjusting bolts. The remaining test steps refer to the operation procedures in 2.1.1 and 2.1.2, and the frost heave test under a single temperature drop of a single soil layer under flexible boundary conditions and the frost heave test under a single soil layer freeze-thaw cycle with infinite stiffness can be carried out respectively.

[0119] The measurement parameters in Examples 2.1 and 2.2 include frost heave (measured by displacement sensor probe 7), frost heave stress (measured by stress sensor 6), and temperature change of the sample (measured by first temperature sensor 16). The frost heave in Example 2.2 can only measure a tiny melting displacement (during freeze-thaw cycles), and in Example 2.3, it is also necessary to use displacement sensor 61 to measure the vertical deformation displacement of the ring structure of the force measuring ring 60. Theoretically, the displacement deformation measured by the force measuring ring 60 at this time should be the same as the displacement measured by the displacement sensor probe 7. We can perform an accuracy comparison. Moreover, the displacement measured by the force measuring ring 60 multiplied by the stiffness coefficient K of the force measuring ring is equal to the frost heave stress, F=K*ΔX. F should be consistent with that measured by the stress sensor 6.

[0120] Example 3 3.1

[0122] In the frost heave test of soil layer under temperature gradient under constant stress condition, the test device is adjusted as in Example 2.1, and the process of filling soil sample is the same as in Example 2. Fig.10 The second double-layer barrel shown has a plurality of second temperature sensors inserted into the side wall, and the plurality of second temperature sensors can measure the temperature change in the vertical direction of the soil sample. In addition, the second double-layer barrel can also be inserted with a salt sensor to measure the salt change in the soil column in the vertical direction.

[0123] 3.1.1 Open system single freezing test

[0124] The pressureless water replenishment system is turned on and connected to the Martens flask to form a communicating vessel structure for pressureless water replenishment. The circumferential cooling part is closed, and the lower cold plate and the upper temperature control plate 3 are respectively connected to the cold bath. Under the action of the temperature gradient, the water migrates in the soil layer to perform pressureless water replenishment. The lower cold plate maintains a constant temperature (generally negative temperature, -1°C in this embodiment), and the temperature of the upper temperature control plate 3 changes in the form of 25°C-20°C-15°C-10°C-5°C-0°C-(-5)°C-(-10)°C-(-15)°C-(-20)°C.

[0125] The data that need to be collected include the amount of water replenishment and the rate of water replenishment, the temperature gradient in the vertical direction of the soil sample (measured by multiple second temperature sensors), the amount of frost heave (measured by the displacement sensor probe 7) and the frost heave stress (measured by the stress sensor, theoretically equal to the overlying load).

[0126] 3.1.2 Open system freeze-thaw cycle test

[0127] The pressureless water replenishment process is the same as 3.1.1. The lower cold plate and the upper temperature control plate 3 are respectively connected to a cold bath. The lower cold plate maintains a constant temperature (generally a negative temperature, -1°C in this embodiment), and the temperature of the upper temperature control plate 3 changes in the form of 25°C-20°C-15°C-10°C-5°C-0°C-(-5)°C-(-10)°C-(-15)°C-(-20)°C-(-15)°C-(-10)°C-(-5)°C-0°C-5°C-10°C-15°C-20°C-25°C (the temperature range in this embodiment is 5°C, which can be adjusted as needed, and can also be set to a sinusoidal function change).

[0128] The data that need to be collected include the amount of water replenishment and the rate of water replenishment, the temperature gradient in the vertical direction of the soil sample (measured by multiple second temperature sensors), the amount of frost heave (measured by the displacement sensor probe 7) and the frost heave stress (measured by the stress sensor, theoretically equal to the overlying load).

[0129] 3.1.3 Closed system single freezing test

[0130] The pressureless water replenishment system is turned off, the Martens flask is not connected, and the temperature control is the same as in Example 3.1.1. The data that need to be collected include the temperature gradient in the vertical direction of the soil sample (measured by multiple second temperature sensors), the frost heave amount (measured by the displacement sensor probe 7) and the frost heave stress (measured by the stress sensor, which is theoretically equal to the overlying load).

[0131] 3.1.4 Closed system freeze-thaw cycle test

[0132] Turn off the pressureless water supply system, do not connect the Martens flask, control the temperature as in Example 3.1.2, and collect the data as in Example 3.1.3. 3.2

[0134] In the frost heave test of soil layer under temperature gradient under infinite stiffness condition, the test device is adjusted as in Example 2.2, and the process of filling soil sample is the same as in Example 2. Fig.10 The second double-layer barrel shown has multiple second temperature sensors inserted into the side wall, and the multiple second temperature sensors can measure the temperature change of the soil sample in the vertical direction. In addition, the second double-layer barrel can also be inserted with a salt sensor to measure the salt change of the soil column in the vertical direction. Using the test steps of Examples 3.1.1-3.1.4, an open system single freezing test under infinite stiffness conditions, an open system freeze-thaw cycle test closure, a closed system single freezing test, and a closed system freeze-thaw cycle test can be performed respectively. 3.3

[0136] In the frost heave test of soil layer under flexible boundary condition temperature gradient, the test device is adjusted as in Example 2.3, and the process of filling soil sample is the same as in Example 2. Fig.10 The second double-layer barrel shown has multiple second temperature sensors inserted into the side wall, and the multiple second temperature sensors can measure the temperature change in the vertical direction of the soil sample. Using the test steps of Examples 3.1.1-3.1.4, an open system single freezing test with flexible boundary conditions, an open system freeze-thaw cycle test closure, a closed system single freezing test, and a closed system freeze-thaw cycle test can be performed respectively.

[0137] In summary, in addition to the above embodiments, the present device can select one condition from a single soil layer or a temperature gradient (multiple soil layer simulation); select one condition from an open system (turn on the pressureless water replenishment system) and a closed system (turn off the pressureless water replenishment system); select one condition from constant stress, infinite stiffness and flexible boundary conditions for combination and classification, and conduct research under multiple conditions. In addition, the above test conditions can also be converted during the test. It is worth noting that when conducting a single soil layer test under open system conditions, first start the lower cold plate and the upper temperature control plate 3 to form a temperature gradient, and then turn on the pressureless water replenishment system. The temperature gradient is the driving force for the migration of soil moisture. After the water replenishment is completed, close the lower cold plate and the upper temperature control plate 3, open the circumferential cooling part, adjust the soil temperature to be uniform, and conduct the test.

[0138] For ease of explanation, spatial relative terms such as "upper", "lower", "left", "right" and the like are used in the embodiments to illustrate the relationship of one element or feature shown in the figure relative to another element or feature. It should be understood that, in addition to the orientation shown in the figure, the spatial terms are intended to include different orientations of the device in use or operation. For example, if the device in the figure is inverted, the element described as being "under" other elements or features will be positioned "on" other elements or features. Therefore, the exemplary term "under" can include both upper and lower orientations. The device can be positioned in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used here can be interpreted accordingly.

[0139] Furthermore, relational terms such as “first” and “second” and the like are merely used to distinguish one component from another having the same name, but do not necessarily require or imply any such actual relationship or order between these components.

[0140] The above is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. Multifunctional frost heave test system, characterized in that: It includes a support frame, a test barrel body arranged on the support frame for storing soil samples, a temperature control system for controlling the temperature of the soil samples, a force application system for applying a constant pressure or an infinite stiffness to the soil samples through the top of the test barrel body, a pressure-free water supply system for supplying water into the soil samples through the bottom of the test barrel body, and a detection system, wherein: The test barrel body comprises an inner sample barrel for storing soil samples and a cooling portion arranged on the circumferential outer wall of the inner sample barrel; The temperature control system comprises the cooling part, a lower cold plate fixed to the bottom of the test barrel, and an upper temperature control plate which can be matched to enter the inner sample barrel and is sealed and connected to the inner wall thereof, the upper temperature control plate applies a load to the soil sample under the action of the force application system, and the bottom of the inner sample barrel is sealed and connected to the top of the lower cold plate; The force application system includes a lever force application device, a booster rod, and an upper reaction beam. The booster rod is provided with a detachable force ring. When the upper reaction beam is fixedly connected to the support frame and the force ring is not installed on the booster rod, the upper reaction beam simulates an infinite stiffness condition by fixing the position of the upper temperature control plate. When the upper reaction beam is fixedly connected to the support frame and the force ring is installed on the booster rod, a flexible boundary condition is simulated. The pressureless water supply system comprises a water supply cavity arranged at the bottom of the test barrel and a communicating vessel structure for supplying water to the water supply cavity, and the water supply cavity is provided with a water supply hole facing the soil sample; The detection system includes a displacement sensor arranged on the force measuring ring for detecting its vertical displacement and / or a stress sensor arranged on the booster rod and / or a temperature sensor for measuring the temperature of the soil sample and / or a displacement sensor probe for measuring the vertical displacement of the soil sample and / or a water replenishment metering device for measuring the water replenishment amount and water replenishment rate; The lever force applying device comprises a lever assembly, a force plate, and a fulcrum block fixed to the bottom of the support frame, wherein the lever assembly comprises a lever and a weight that can be selectively assembled on one end of the lever, the middle portion of the lever is hinged to the force plate, the force plate is slidably connected to a guide rod located below the support frame, the bottom fulcrum of the fulcrum block contacts the lever, and the force plate is fixed to the upper reaction beam through a second pull rod; The other end of the lever is provided with a balance block which can be adjusted along its length direction, and the balance block and the weight are respectively located at the two ends of the lever; The top of the booster rod is fixed to the bottom of the upper reaction beam, a force-applying disc is fixed to the bottom, and the force-applying disc is coaxially fixed to the top surface of the upper temperature control plate; The booster rod comprises a positioning sleeve fixed to the bottom of the upper reaction beam, a force-bearing shaft fixedly sleeved in the positioning sleeve, and an upper temperature control plate reaction rod fixed to the top of the upper temperature control plate, wherein a groove is formed on the top of the upper temperature control plate reaction rod, the stress sensor is fixed in the groove, and the force-bearing shaft can be matched and inserted into the groove to directly or indirectly act on the stress sensor; The top of the force measuring ring is provided with a protrusion which can be matched and inserted into the positioning sleeve, and the bottom of the force measuring ring is fixed with a fixing block which can be matched and inserted into the groove to directly or indirectly act on the stress sensor.

2. The multifunctional frost heave test system according to claim 1, characterized in that: The support frame includes a lower base plate and a guide rod fixed on the lower base plate, a support leg is fixed to the bottom of the lower base plate, the lower cold plate is fixed to the lower base plate, the upper reaction beam is slidably connected to the upper part of the guide rod, and the upper reaction beam can be fastened to the guide rod by a fastening connector.

3. The multifunctional frost heave test system according to claim 1, characterized in that: An insulation sleeve is arranged on the outside of the test barrel body, and the bottom of the insulation sleeve is fixed on the lower cold plate or the support frame. An upper top plate which can seal the opening of the insulation sleeve is arranged on the top of the test barrel body. The upper top plate is fixed on the lower cold plate or the support frame through a first pull rod. A through hole is formed on the upper top plate for the booster rod to pass through, and the booster rod is sealed and connected to the through hole.

4. The multifunctional frost heave test system according to claim 3, characterized in that: The displacement sensor probe is fixed downward on the upper top plate, a measuring block is fixed on the booster rod, and the displacement sensor probe detects the distance between the displacement sensor probe and the measuring block to measure the displacement of the soil sample; The temperature sensor comprises a first temperature sensor vertically inserted into the soil sample through the upper temperature control plate and / or one or more second temperature sensors horizontally inserted into the soil sample through the side wall of the test barrel.

5. The multifunctional frost heave test system according to claim 1, characterized in that: The test barrel body includes a replaceable first test barrel body and a second double-layer barrel body, wherein the first test barrel body includes the inner sample barrel and a cooling portion arranged on the circumferential outer wall of the inner sample barrel, and the second double-layer barrel body includes an inner sample barrel and an outer sample barrel, the bottom of the inner sample barrel is sealed and connected to the lower cold plate, the outer sample barrel is slidably sleeved on the outside of the inner sample barrel, a small hole for inserting a second temperature sensor is formed on the side wall of the outer sample barrel, and a strip hole for inserting the second temperature sensor is formed on the side wall of the inner sample barrel, and the length of the strip hole is greater than the aperture of the small hole.

6. The multifunctional frost heave test system according to claim 5, characterized in that: The detection system also includes a plurality of salt sensors for testing salt content, the salt sensors are plugged into different heights of the second double-layer barrel body, and reinforcing ribs are fixed on the side walls of the inner sample barrel of the second double-layer barrel body.

7. The multifunctional frost heave test system according to claim 1, characterized in that: The cooling part is a cooling jacket or cooling coil arranged outside the inner sample barrel; The upper temperature control plate and the lower cold plate include a cavity for storing coolant and a cold plate circulating liquid inlet pipe and a cold plate circulating liquid outlet pipe connected to the cavity; or the upper temperature control plate and the lower cold plate both include an upper cooling plate and a lower cooling plate arranged up and down, a spiral groove is arranged in the lower cooling plate, and when the upper cooling plate covers the lower cooling plate, the spiral groove is sealed to form a spiral coolant channel, and the two ends of the spiral coolant channel are respectively connected to the cold plate circulating liquid outlet pipe and the cold plate circulating liquid inlet pipe.

8. The multifunctional frost heave test system according to claim 1, characterized in that: A sealing ring is provided on the circumferential side wall of the upper temperature control plate.

9. The multifunctional frost heave test system according to claim 1, characterized in that: The lower cold plate and the water supply plate are enclosed to form a water supply cavity, and the water supply cavity is provided with two water inlets, one of which is connected to the Martens flask through a water supply pipe, and the other is connected to a connecting hose to form a communicating vessel structure with the Martens flask; The water replenishment metering device comprises a weighing device placed below the Martens flask and a differential pressure gauge mounted on the water replenishment pipe.

10. The multifunctional frost heave test system according to claim 9, characterized in that: The water replenishment plate and the annular flange arranged on the lower cold plate form a water replenishment cavity, and the water replenishment plate includes a bottom water-permeable frame and a perforated plate fixed to the top of the bottom water-permeable frame, wherein the bottom water-permeable frame includes ribs arranged in a cross-grid, and the ribs are provided with penetrating water holes.

11. The test method of the multifunctional frost heave test system according to any one of claims 1 to 10, characterized in that: The test method of the test system is to put the soil sample into the inner sample barrel, and the upper temperature control plate and the lower cold plate seal the upper and lower ends of the test barrel, so that the soil sample is in a relatively sealed state, and the following three coupling tests can be carried out: (1) Single soil layer or temperature gradient: When the cooling unit is closed and the lower cooling plate and upper temperature control plate are opened, a temperature gradient is formed in the soil sample, simulating multiple soil layer tests. When the lower cooling plate and upper temperature control plate are closed and the cooling unit is opened, the temperature in the soil sample is fixed and uniform, simulating a single soil layer test. (2) Open system or closed system: When the pressureless water replenishment system is turned on, an open system test is conducted to simulate groundwater recharge. When the pressureless water replenishment system is turned on, the lower cold plate and the upper temperature control plate are turned on, and the temperature gradient is used as the driving force for water replenishment. When the pressureless water replenishment system is turned off, a closed system test is conducted to simulate no groundwater recharge. (3) Constant stress or infinite stiffness or flexible boundary conditions: When the upper reaction beam is fixedly connected to the support frame and no force ring is installed on the booster rod, the displacement of the soil sample is completely restricted and the test is carried out under infinite stiffness conditions; When the upper reaction beam is movably connected to the support frame, the upper reaction beam is pulled down by the constant pulling force of the lever force applying device to perform a test under constant stress conditions; When the upper reaction beam 2 is fixedly connected to the support frame and a force measuring ring is installed on the booster rod, a test under flexible boundary conditions is performed; During the test, the displacement sensor is installed on the vertical diameter of the measuring ring structure through a connecting component. It can detect the vertical deformation displacement of the ring structure. The temperature sensor collects the temperature changes of the soil sample in real time. The stress sensor can reflect the stress generated by the soil sample during the frost heave process. The displacement sensor probe measures the vertical displacement of the soil sample during the freezing and thawing process. The water replenishment measurement device measures the water replenishment amount and water replenishment rate.

12. The test method according to claim 11, characterized in that When a single soil layer test is conducted, the test barrel body adopts a first test barrel body, and the temperature sensor adopts a first temperature sensor inserted into the soil sample from the upper temperature control plate; When the temperature gradient test is performed, the test barrel body adopts a second double-layer barrel body, and the temperature sensor adopts a plurality of second temperature sensors inserted into the soil sample from the side wall of the second double-layer barrel body.

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