Lateral pressure adjustable expansive soil expansion rate measuring device and method

Abstract

The invention relates to the technical field of soil testing, and discloses a lateral pressure adjustable expansive soil expansion rate measuring device, which comprises an experiment box, a sample cylinder and a measuring module, symmetrical through holes are formed in the side wall of the sample cylinder, a lateral pressure loading system is correspondingly arranged on the outer side of each through hole, and each lateral pressure loading system comprises a rigid piston head capable of extending into the cylinder, a piston rod, a closed medium pressure cavity and a miniature constant pressure pump; the pump is connected with the pressure cavity through a pipeline, and the piston head is driven to apply adjustable lateral pressure to the sample by accurately feeding and discharging a medium; the measurement module comprises a vertical deformation and lateral pressure measurement system and integrates free expansion and lateral confinement expansion measurement functions; the rigid piston and the water medium are adopted for constant-pressure loading, the structure is simplified, operation is convenient and fast, rapid response and high-stability control over lateral pressure are achieved, the membrane embedding effect is thoroughly eliminated, a multi-stage constraint continuous test can be completed through one-time sample loading, and the test efficiency and data consistency are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of soil testing technology, and more specifically to a device and method for measuring the swelling rate of expansive soil with adjustable lateral pressure. Background Technology

[0002] Expansive soil is a special type of cohesive soil with significant water absorption expansion and water loss shrinkage characteristics. In engineering construction, this type of soil often causes geological disasters such as uneven foundation deformation and slope instability, which are extremely harmful. Therefore, accurately measuring the expansion and contraction characteristics of expansive soil under different stress states is a key basis for engineering design and disaster prevention.

[0003] Currently, commonly used instruments in laboratories for determining the swelling and shrinkage characteristics of expansive soil can be mainly divided into the following two categories: 1. Unconfined dilatometer: This device has a relatively simple structure. It allows the sample to absorb water and expand freely in water, and measures the resulting vertical deformation. However, the test conditions of this method are seriously inconsistent with the actual stress state of the soil in the foundation, and completely ignore the lateral constraint effect on the soil in actual engineering. Therefore, its test results are difficult to apply directly to engineering practice and have obvious limitations.

[0004] 2. Triaxial Consolidated Dilatometer: This system borrows the principle of triaxial testing and applies confining pressure (lateral pressure) to a cylindrical specimen wrapped with a rubber diaphragm through a liquid medium, thus taking into account the effect of lateral constraint. Although this device is closer to actual working conditions than an unconfined dilatometer, it has several inherent drawbacks: The system is complex and costly: it requires a pressure chamber, volumetric pressure tube, a precision hydraulic or pneumatic pressure source, and a complex piping system, resulting in high equipment cost, cumbersome operation procedures, and difficult maintenance; poor pressure control stability: due to the compressibility of the liquid medium, the hysteresis of pipeline pressure transmission, and the creep effect of the rubber membrane itself, it is difficult to achieve and maintain a constant confining pressure during the test, and the pressure fluctuation range is usually large (e.g., more than ±5%), which seriously affects the stability and repeatability of test data; there is a "membrane embedding effect": when the sample absorbs water and expands, the flexible rubber membrane wrapped around it will embed into the tiny cracks on the soil surface, thereby generating additional and unexpected constraint force on the expansion of the soil. This causes the measured expansion amount to be systematically smaller than the true value, introducing measurement errors that are difficult to correct accurately. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is: how to provide a test device and method with a relatively simple structure that can apply accurate and stable lateral constraint force to expansive soil samples, while avoiding measurement errors caused by the "membrane embedding effect" due to the use of flexible wrapping materials.

[0006] This invention provides the following technical solution: a lateral pressure adjustable expansive soil swelling rate measuring device, comprising an experimental chamber, a sample tube disposed inside the experimental chamber, and a measuring module for acquiring swelling information of the expansive soil inside the sample tube. The lateral pressure loading system includes a piston part that seals and penetrates the side wall of the sample tube and can move axially along its cavity. The piston part is integrally composed of a piston head that fits against the inner peripheral wall of the cavity and a piston rod fixed to the outside of the piston head. A medium conveying sleeve is sleeved along the extension direction of the piston rod at the end of the sample tube. The outer end of the medium conveying sleeve is connected to a pump, and the inner end is connected to the end side of the cavity, so that a medium pressure chamber is formed between the piston head and the end side of the cavity. The pump precisely controls the supply and discharge of the medium, so that the medium is conveyed or discharged from the medium pressure chamber through the medium conveying sleeve, thereby adjusting the pressure in the medium pressure chamber to drive the piston head to apply adjustable lateral pressure to the expansive soil sample.

[0007] Furthermore, the measurement module includes a vertical deformation measurement system, a lateral pressure measurement system, a data acquisition system, and a control system. The vertical deformation measurement system includes a free expansion pointer device installed at the center of the sample cylinder cavity and a displacement sensor connected thereto, used to monitor the vertical expansion deformation of the sample in real time under no vertical load conditions. The lateral pressure measurement system is a pressure sensor installed on the pipeline connected to the medium pressure chamber, used to monitor and feedback the lateral pressure value in real time. The data acquisition system is used to receive the lateral pressure signal from the pressure sensor and the vertical deformation signal from the displacement sensor, and transmit them to the control system. The control system processes and analyzes the acquired data, and then plots the lateral pressure-expansion rate relationship curve.

[0008] Furthermore, the sample tube includes a main tube located in the middle of the test chamber, with end caps symmetrically arranged at its left and right ends that can abut against it. The end caps slide axially in a guide rail fixed inside the test chamber. A plug is fixed above the main tube, and the plug and a socket installed on the top wall of the test chamber form a detachable connection.

[0009] Furthermore, a groove is formed at one end of the end cap near the main cylinder, and a medium pressure chamber is formed between the groove and the piston head. When the medium pressure chamber is not filled with medium, the piston head is retracted into the groove, so that the side walls of the two remain flush and fit together, thereby forming a complete wall surface, which can abut against the end wall of the main cylinder.

[0010] Furthermore, the medium conveying sleeve is inserted into the end cover and its end is aligned with the groove, and it is fixed inside the end cover, so that it can move synchronously with the end cover. When the end cover moves outward along the guide rail, it can drive the medium conveying sleeve and the piston part in the extreme contraction position to move outward together, thereby causing the wall surface formed by the end cover and the piston part to separate from the port of the main cylinder.

[0011] Furthermore, the experimental chamber is provided with side covers on both the left and right sides, and the side covers are equipped with linear drive devices for driving the end caps to move axially.

[0012] Furthermore, an isolation system is provided in the middle of the main cylinder to divide it into two chambers, each chamber being equipped with a measuring module. The isolation system includes a rotating part located at the center line of the main cylinder, sidewalls arranged on the left and right sides of the rotating part and fixed inside the main cylinder, and a driving part located on the end face of the rotating part for driving its rotation. By rotating the rotating part clockwise or counterclockwise, the corresponding channels on the sidewalls can be switched to be closed or opened, thereby realizing the delivery of the unclogging agent in the left and right symmetrical chambers.

[0013] Furthermore, the drive unit includes a toothed roller that slides longitudinally through the side wall of the main cylinder and a wedge block fixedly connected to its bottom end; the wedge block is arc-shaped, and its inner curvature matches the curvature of the circumferential side wall of the main cylinder, so that it can adhere to the circumference of the main cylinder; the width of the wedge block gradually decreases from the inside to the outside, and the longitudinal section is triangular; push-pull rods are symmetrically arranged on the left and right below it, one end of which is provided with a wedge-shaped chamfer that can be squeezed and slid relative to the wedge block, and the other end extends to the outer end of the end cap and then bends upward and is fixed to the output end of the linear drive device.

[0014] Furthermore, the rotating part includes a turntable, with a rotating shaft coaxially fixed at its center, and is rotatably mounted between the left and right sidewalls via the rotating shaft; the end face of the turntable is recessed inward to form a toothed ring groove that meshes with the toothed roller; the surface of the turntable has multiple guide grooves that radiate outward in a clockwise arc from the inside, and a sliding shaft is slidably connected in each guide groove; the sidewall includes a fixed plate, with the rotating shaft rotatably mounted at the center of the fixed plate, and a number of conveying units corresponding one-to-one with the guide grooves arranged circumferentially around it; each conveying unit includes a fixed sleeve fixed to the surface of the fixed plate and a movable block movably inserted into the fixed sleeve, the bottom end of the movable block being rigidly connected to the sliding shaft, and the sidewall of the fixed sleeve having a through groove for the sliding shaft to move; the top of the movable block has a conical structure, and a nozzle is installed there, the nozzle being connected to the supply source of the drain cleaner via a hose.

[0015] A method for determining the swelling rate of expansive soil with adjustable lateral pressure, based on the aforementioned device for determining the swelling rate of expansive soil, includes the following steps: S1. Place the prepared expansive soil sample into the sample tube. S2. Set the initial lateral pressure via the pump; this pressure can be 0 or a preset low value. S3. Allow the sample to absorb water and expand, and use a displacement sensor to record the change of its vertical deformation over time in real time. S4. At different times during the test, adjust the output pressure of the pump to adjust the lateral pressure to a new set value to achieve a staged pressurization test; S5. The data acquisition system synchronously records the lateral pressure at each level and its corresponding stable vertical expansion. S6. Based on the collected data, plot the lateral pressure-expansion rate relationship curve and calculate the lateral confined expansion modulus.

[0016] The technical effects and advantages of this invention are as follows: This invention effectively overcomes the shortcomings of traditional testing devices through an innovative design of a rigid piston and constant pressure loading with a water medium. It achieves structural simplification and convenient operation, and utilizes a micro constant pressure pump to achieve rapid response (<1 second) and high stability control (fluctuation <±1%) of lateral pressure. The rigid piston directly and uniformly contacts the sample, completely eliminating measurement errors caused by the flexible membrane embedding effect. The device integrates free expansion and multi-stage lateral confined expansion measurement functions, and can complete a series of continuous tests under constraint conditions with a single sample loading, significantly improving testing efficiency and data consistency, and providing an accurate and reliable testing method for evaluating the engineering properties of expansive soil. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the external structure of Embodiment 1 of the present invention.

[0018] Figure 2 This is a schematic diagram of the overall structure of Embodiment 1 of the present invention.

[0019] Figure 3 For the present invention Figure 2 Schematic diagram of the structure at point A in the middle.

[0020] Figure 4 This is a schematic diagram of the overall structure of Embodiment 2 of the present invention.

[0021] Figure 5 This is a schematic diagram of the three-dimensional structure in detection mode according to Embodiment 2 of the present invention.

[0022] Figure 6 For the present invention Figure 5 Schematic diagram of the structure at point B.

[0023] Figure 7 For the present invention Figure 5 Schematic diagram of the main cylinder, drive unit, and locking unit.

[0024] Figure 8 This is a schematic diagram of the main cylinder structure of the present invention.

[0025] Figure 9 For the present invention Figure 5 A schematic diagram of the unfolded structure of the central rotating part, side wall part, and driving part.

[0026] Figure 10 For the present invention Figure 9Schematic diagram of the rotating part and drive part.

[0027] Figure 11 For the present invention Figure 9 Schematic diagram of the middle sidewall structure.

[0028] Figure 12 This is a schematic diagram of the three-dimensional structure in cleanup mode according to Embodiment 2 of the present invention.

[0029] Figure 13 For the present invention Figure 12 Schematic diagram of the structure at point C.

[0030] Figure 14 For the present invention Figure 12 Schematic diagram of the rotating part and drive part.

[0031] Figure 15 For the present invention Figure 12 Schematic diagram of the middle sidewall structure.

[0032] Figure 16 For the present invention Figure 15 Schematic diagram of the fixed plate and sealing unit structure.

[0033] The attached figures are labeled as follows: 1. Experimental chamber; 2. Sample cylinder; 21. Main cylinder; 211. U-shaped sliding hole; 22. End cap; 23. Plug; 24. Socket; 3. Piston part; 31. Piston head; 32. Piston rod; 4. Medium conveying sleeve; 41. Linear channel; 42. Expansion channel; 43. Connector; 5. Pump; 6. Measuring module; 7. Guide rail; 8. Isolation system; 81. Rotating part; 811. Turntable; 8111. Guide groove; 8112. Gear ring groove; 812. Rotating shaft; 813. Sliding shaft; 82. Side wall; 821. Fixed plate; 8211. Through port; 822. Conveying unit; 8221. Fixed sleeve; 8222. Movable block; 8223. Nozzle; 823. Sealing unit; 8231. Fixed tube; 8232. Sealing plate; 8233. Spring; 83. Drive unit; 831. Toothed roller; 8311. Limiting groove; 832. Wedge; 84. Locking part; 841. Rotary lock; 842. Locking seat; 9. Push-pull rod; 10. Telescopic cylinder. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. In addition, the forms of the various structures described in the following embodiments are merely illustrative. The lateral pressure adjustable expansive soil swelling rate measuring device and method involved in the present invention are not limited to the structures described in the following embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1, refer to Figures 1 to 3 As shown, the present invention provides a lateral pressure adjustable expansive soil swelling rate measuring device, including an experimental chamber 1, a sample cylinder 2 disposed inside the experimental chamber 1, and a measuring module 6 for acquiring expansive soil swelling information in the sample cylinder 2; the lateral pressure loading system includes a piston part 3 that seals through the side wall of the sample cylinder 2 and can move axially along its cavity, the piston part 3 is integrally formed by a piston head 31 that fits against the inner peripheral wall of the cavity and a piston rod 32 fixed to the outside of the piston head 31, a medium conveying sleeve 4 located at the end of the sample cylinder 2 is sleeved along the extension direction of the piston rod 32, the outer end of the medium conveying sleeve 4 is connected to a pump 5, and the inner end is connected to the end side of the cavity, so that a variable liquid cavity, i.e. a medium pressure cavity, is formed between the piston head 31 and the end side of the cavity; the pump 5 precisely controls the supply and discharge of the medium, so that the medium is transported or discharged from the medium pressure cavity through the medium conveying sleeve 4, thereby adjusting the pressure in the medium pressure cavity to drive the piston head 31 to apply adjustable lateral pressure to the sample. In this embodiment, it should be noted that the medium delivery sleeve 4 sleeved on the surface of the piston rod 32 has a section that extends out of the side wall of the sample cylinder 2. A linear channel 41 is provided inside this section, and the end of the linear channel 41 that extends into the side wall of the sample cylinder 2 is formed into an extended channel 42. The outer end of the linear channel 41 is connected to the pump 5, and the inner end is connected to the extended channel 42. The piston rod 32 passes through it to ensure that when the piston rod 32 moves inward, the medium can only be injected into the medium pressure chamber through the continuous channel formed by the linear channel 41 and the extended channel 42. The expansion channel 42 is conical, and its radial radius gradually expands on the side near the medium pressure chamber to improve the medium conveying efficiency. The outer end of the medium conveying sleeve 4 is equipped with a connector 43 that connects the linear channel 41 and the pump 5. The connector 43 is located on the periphery of the piston rod 32, that is, it is offset from the axis of the piston rod 32 to avoid interference with the movement of the piston part 3. The end face curvature of the piston head 31 matches the curvature of the inner peripheral wall of the cavity of the sample cylinder 2, and the coaxiality error between the two is less than 0.1 mm. Measurement module 6 includes a vertical deformation measurement system, a lateral pressure measurement system, a data acquisition system, and a control system; The vertical deformation measurement system includes a free expansion pointer device installed in the center of the cavity of the sample tube 2 and a displacement sensor (such as LVDT) connected to it, which is used to monitor the vertical expansion deformation of the sample in real time under no vertical load conditions. The lateral pressure measurement system is a pressure sensor installed on the pipeline connected to the medium pressure chamber. The pressure sensor is preferably installed inside the medium conveying sleeve 4 to monitor and feedback the lateral pressure value in real time. The data acquisition system is used to receive lateral pressure signals from pressure sensors and vertical deformation signals from displacement sensors, and transmit them to the control system. The control system (CPU) processes and analyzes the collected data, and then plots the lateral pressure-expansion rate relationship curve. The medium pressure chamber is a closed cavity filled with a basically incompressible water medium or a low-compressibility liquid medium such as hydraulic oil with equivalent properties. Pump 5 is a miniature constant pressure pump, which is connected to the medium pressure chamber through a high-pressure pipeline. It is used to inject or discharge the medium into the chamber, thereby precisely controlling the pressure applied to the piston. The pump can achieve a constant pressure mode to maintain the set pressure, or a graded loading mode in which the pressure is increased in preset steps. Methods for determining expansion rate include: S1. Place the prepared expansive soil sample into the sample tube. S2. Set the initial lateral pressure using pump 5. This pressure can be 0 or a preset low value. S3. Allow the sample to absorb water and expand, and use a displacement sensor to record the change of its vertical deformation over time in real time. S4. At different times during the test, adjust the output pressure of pump 5 to adjust the lateral pressure to a new set value to achieve a staged pressurization test; S5. The data acquisition system synchronously records the lateral pressure at each level and its corresponding stable vertical expansion. S6. Based on the collected data, plot the lateral pressure-expansion rate relationship curve and calculate the lateral confined expansion modulus; To achieve rapid assembly and disassembly of sample cylinder 2, its structure is improved as follows: (Refer to...) Figures 2 to 3 As shown, the sample tube 2 includes a main tube 21 located in the middle of the test chamber 1, with end caps 22 symmetrically arranged at its left and right ends for contact with it. The end caps 22 slide axially in the guide rails 7 fixed inside the test chamber 1. A plug 23 is fixed above the main tube 21, and the plug 23 is detachably connected to a socket 24 installed on the top wall of the test chamber 1. The detachable connection is preferably a plug-in snap-fit ​​connection. The end cap 22 has a groove at one end near the main cylinder 21, and the groove and the piston head 31 form a medium pressure chamber. When the medium pressure chamber is not filled with medium, the piston head 31 is housed in the groove, so that the side walls of the two are flush and fit together, thus forming a complete wall surface, which can abut against the end wall of the main cylinder 21. Conversely, when the medium pressure chamber is gradually filled with medium, the pressure acting on one side of the piston head 31 increases, driving it to advance axially inward along the inner peripheral wall of the main cylinder 21, thereby applying lateral pressure to the sample. The expansion channel 42 is inserted into the end cap 22 and its end is aligned with the groove. The expansion channel 42 is fixed inside the end cap 22 and can move synchronously with the end cap 22. When the end cap 22 moves outward along the guide rail 7, it can drive the medium conveying sleeve 4 and the piston part 3 in the extreme contraction position to move outward together, thereby causing the wall surface formed by the end cap 22 and the piston part 3 to separate from the port of the main cylinder 21. Then, the connection between the plug 23 and the socket 24 is disconnected, and the main cylinder 21 can be taken out. The experimental chamber 1 is equipped with side covers on both the left and right sides. The pump 5 is installed inside the side cover, and the side cover is equipped with a linear drive device for driving the end cover 22 to move axially. The linear drive device is a telescopic cylinder 10, such as a hydraulic cylinder, pneumatic cylinder or electric cylinder. The linear drive device is offset from the axis of the medium conveying sleeve 4 and the piston rod 32 to avoid interference with their axial movement. In order to accommodate the movement requirements of the medium conveying sleeve 4, the connecting pipeline between the medium conveying sleeve 4 and the pump 5 must be a flexible pipeline that can be bent.

[0036] Example 2, based on Example 1, requires multiple repeated experiments, including at least two sets as controls, to ensure the accuracy of the test data. This increases the workload of disassembling / cleaning the main cylinder 21, thus necessitating further improvements to the structure of the main cylinder 21. Specifically, referring to... Figures 4 to 16 As shown, an isolation system 8 is provided in the middle of the main cylinder 21 to divide it into two chambers, and each chamber is equipped with an independent measuring module 6; In this embodiment, it should be noted that since the original cavity is divided into two independent chambers, the vertical deformation measurement system in the measurement module 6 should be set above each chamber. The data acquisition system and the control system can share a set for centralized processing, while the lateral pressure measurement system should be set on the connecting pipeline of the corresponding medium pressure chamber of each chamber. The expansive soil sample is measured simultaneously through two sets of symmetrical chambers on the left and right sides, serving as a control group for parallel testing to obtain comparative data. The test can be carried out by filling the two symmetrically arranged chambers on the left and right sides of the main cylinder 21 with equal amounts of expansive soil samples, filling them through the port, positioning them and assembling them between the end caps 22. Since the samples are compacted and adhered to the sidewalls of the isolation system 8 after the test, the cleaning difficulty is increased. How to effectively detach the compacted expansive soil samples from the chamber is a problem that needs to be further solved. Therefore, the equipment structure needs to be optimized as follows: Specifically, the isolation system 8 includes a rotating part 81 located at the center line of the main cylinder 21, sidewall parts 82 arranged on the left and right sides of the rotating part 81 and fixed inside the main cylinder 21, and a driving part 83 located on the end face of the rotating part 81 for driving its rotation; by rotating the rotating part 81 clockwise / counterclockwise, the corresponding channels on the sidewalls of the sidewall parts 82 can be switched to be closed or opened, thereby realizing the delivery of the unclogging agent in the left and right symmetrical chambers; the unclogging agent used is sodium hydroxide solution NaOH, and its mechanism of action is: this alkaline solution is suitable for cohesive soil rich in organic matter or amphoteric oxides, and can disperse soil particles and partially remove organic matter; the solution concentration is 0.1-0.5 mol / L; the driving part 83 is located on either the front or rear side of the rotating part 81. The drive unit 83 includes a toothed roller 831 that slides longitudinally through the side wall of the main cylinder 21 and a wedge 832 fixedly connected to its bottom end. The wedge 832 is arc-shaped, and its inner curvature matches the curvature of the circumferential side wall of the main cylinder 21, so that it can adhere to the circumference of the main cylinder 21. The width of the wedge 832 gradually decreases from the inside to the outside, and its longitudinal section is triangular. Push-pull rods 9 are symmetrically arranged on the left and right below it. One end of the push-pull rod 9 is provided with a wedge-shaped chamfer that can be squeezed and slid relative to the wedge 832, and the other end extends to the outer end of the end cap 22 and then bends upward and is fixed to the output end of the linear drive device. The toothed roller 831 has a limiting groove 8311 on the side near the inner wall of the main cylinder 21, and the surface of the main cylinder 21 has a U-shaped sliding hole 211 that allows the toothed roller 831 to slide through and is adapted to it. The position of the top of the limiting groove 8311 determines the downward height of the toothed roller 831. It should at least ensure that when the top of the limiting groove 8311 enters and is blocked by the U-shaped sliding hole 211, the wedge block 832 still does not contact the bottom wall of the test chamber 1. This prevents the drive unit 83 from falling freely and impacting the test chamber 1 without restraint. The main cylinder 21 has a locking part 84 on the same side as the drive unit 83, which is used to actively constrain the position of the drive unit 83. The locking part 84 includes a rotating locking member 841 rotatably disposed on the side wall of the main cylinder 21 and a locking seat 842 that can lock the rotating locking member 841. During operation, the locking head of the rotating locking member 841 is first removed from the locking seat 842, and then the rotating locking member 841 is pulled and placed into the notch at the bottom end of the wedge block 832, so that the wedge block 832 can be stably attached to the bottom wall of the main cylinder 21. This state is suitable for the sample loading stage. In the detection stage, the operation is reversed to remove the locking head of the rotating locking member 841 from the bottom end of the wedge block 832, flip it over and re-lock it into the locking seat 842. In use, after the main cylinder 21 is fixed to the bottom of the socket 24 by the plug 23, the main cylinder 21 and the end cover 22 need to be connected. At this time, the drive unit 83 falls to the lowest position under its own weight. When the telescopic shaft of the telescopic cylinder 10 drives the end cover 22 to abut against the main cylinder 21, it simultaneously drives the push-pull rods 9 on both sides to move towards the center. The wedge block 832 drives the toothed roller 831 to move upward together under the pressure of the wedge-shaped inclined surface of the push-pull rod 9, thereby driving the rotating part 81 to rotate clockwise and triggering the closing action of the side wall part 82. The rotating part 81 includes a turntable 811, with a rotating shaft 812 coaxially fixed at its center, and is rotatably mounted between the left and right sidewall parts 82 via the rotating shaft 812; the end face of the turntable 811 is recessed inward to form a toothed ring groove 8112 that meshes with the toothed roller 831; the surface of the turntable 811 has multiple guide grooves 8111 circumferentially formed from the inside out in a clockwise arc shape, and a sliding shaft 813 is slidably connected in each guide groove 8111; the sidewall part 82 includes a fixed plate 821. The rotating shaft 812 is rotatably mounted at the center of the fixed disk 821, and a number of conveying units 822 corresponding one-to-one with the guide grooves 8111 are arranged around its periphery. Each conveying unit 822 includes a fixed sleeve 8221 fixed to the surface of the fixed disk 821 and a movable block 8222 movably inserted into the fixed sleeve 8221. The bottom end of the movable block 8222 is rigidly connected to the sliding shaft 813, and the side wall of the fixed sleeve 8221 is provided with a through groove for the sliding shaft 813 to move. The end faces of the fixed disk 821 and piston head 31 that contact the sample can be adapted to the cylindrical side surface of the sample, and designed as a corresponding arc-shaped structure. This design enables the contact surface to form a more suitable fit with the side surface of the sample, thereby optimizing the contact conditions and facilitating a more uniform distribution of pressure on the sample surface during the pressure test, reducing local stress concentration, and improving the stability and accuracy of the test results. It should be understood that this arc-shaped structure is only a preferred embodiment, and other suitable contact surface shapes can also be adopted under the premise of achieving uniform pressure. The top of the movable block 8222 has a conical structure, and a nozzle 8223 is installed there. The nozzle 8223 is connected to the supply source of the drain cleaner through a hose. The hose passes through a pre-set opening on the bottom wall of the main cylinder 21, and the arrangement range of the opening does not exceed the coverage area between the two side wall portions 82. When in use, after the test of the expansive soil sample in the main cylinder 21 is completed, the main cylinder 21 needs to be removed and the compacted sample in the left and right chambers needs to be cleaned. At this time, the telescopic cylinder 10 is pulled outward by its telescopic axis, which not only drives the end cover 22 and the reset piston part 3 to disengage from the port of the main cylinder 21, but also causes the push-pull rod 9 connected to it to move outward in the opposite direction, thereby removing the stop on the wedge block 832. The drive part 83 slides down under its own weight and drives the toothed ring groove 8112, causing the turntable 811 to rotate counterclockwise. Then, the movable block 8222 connected to the sliding shaft 813 slides from the inside to the outside along the fixed sleeve 8221 under the guidance of the guide groove 8111 until the conical structure at the top of the movable block 8222 opens the sealing unit 823 and delivers the nozzle 8223 to the position aligned with the opening 8211, so that the unclogging agent can enter the chamber containing the expansive soil sample. The fixed plate 821 has openings 8211 around its perimeter that can be aligned with the nozzle 8223. On the side of the fixed plate 821 away from the expansive soil sample, sealing units 823 are symmetrically arranged on both sides of each opening 8211. The sealing unit 823 includes a fixed tube 8231 fixed to the side of the fixed plate 821 and a sealing sheet 8232 elastically telescoping within the fixed tube 8231 by a spring 8233. The sealing sheet 8232 is slidably connected to a slide rail pre-set on the side wall of the fixed plate 821. Both the fixed tube 8231 and the sealing sheet 8232 are arc-shaped. Under normal conditions, the sealing sheet 8232 closes and blocks the inside of the opening 8211 under the elastic force of the spring 8233, thus achieving a seal. When the sealing sheet 8232 is assembled, an embedding groove is formed on its inner side, into which the conical structure at the top of the movable block 8222 can be pushed. When in use, the tapered structure at the top of the movable block 8222 can radially expand the sealing plate 8232 after entering the embedding groove, so that it can be retracted into the fixed tube 8231 by the compression spring 8233, thereby providing a channel for the movable block 8222 to enter, and allowing the nozzle 8223 to finally complete the docking with the port 8211, thus completing the task of delivering the drain cleaner.

[0037] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, in accordance with the technical plan and improved concept of the present invention, should be included under the protection of the present invention.

Claims

1. A device for determining the swelling rate of expansive soil with adjustable lateral pressure, comprising an experimental chamber (1), a sample tube (2) disposed inside the experimental chamber (1), and a measuring module (6) for acquiring information on the swelling of expansive soil inside the sample tube (2), characterized in that: The lateral pressure loading system includes a piston part (3) that seals through the side wall of the sample tube (2) and can move axially along its cavity. The piston part (3) is integrally formed by a piston head (31) that fits against the inner peripheral wall of the cavity and a piston rod (32) fixed to the outside of the piston head (31). A medium conveying sleeve (4) located at the end of the sample tube (2) is sleeved along the extension direction of the piston rod (32). The outer end of the medium conveying sleeve (4) is connected to the pump (5), and the inner end is connected to the end side of the cavity, so that a medium pressure cavity is formed between the piston head (31) and the end side of the cavity. The pump (5) precisely controls the supply and discharge of the medium, so that the medium is conveyed or discharged from the medium pressure cavity through the medium conveying sleeve (4), thereby adjusting the pressure in the medium pressure cavity to drive the piston head (31) to apply adjustable lateral pressure to the expansive soil sample.

2. The lateral pressure adjustable expansive soil swelling rate measuring device according to claim 1, characterized in that: The measurement module (6) includes a vertical deformation measurement system, a lateral pressure measurement system, a data acquisition system, and a control system. The vertical deformation measurement system includes a free expansion pointer device installed in the center of the cavity of the sample tube (2) and a displacement sensor connected thereto, which is used to monitor the vertical expansion deformation of the sample in real time under no vertical load conditions. The lateral pressure measurement system is a pressure sensor installed on the pipeline connected to the medium pressure chamber, which is used to monitor and feedback the lateral pressure value in real time. The data acquisition system is used to receive the lateral pressure signal from the pressure sensor and the vertical deformation signal from the displacement sensor, and transmit them to the control system. The control system processes and analyzes the acquired data, and then plots the lateral pressure-expansion rate relationship curve.

3. The lateral pressure adjustable expansive soil swelling rate measuring device according to claim 1, characterized in that: The sample tube (2) includes a main tube (21) located in the middle of the test chamber (1), with end caps (22) symmetrically arranged at its left and right ends, which can abut against it. The end caps (22) slide axially in the guide rail (7) fixed inside the test chamber (1). A plug (23) is fixed above the main tube (21), and the plug (23) and the socket (24) installed on the top wall of the test chamber (1) form a detachable connection.

4. The lateral pressure adjustable expansive soil swelling rate measuring device according to claim 3, characterized in that: The end cap (22) near the main cylinder (21) forms a groove, and the groove and the piston head (31) form a medium pressure chamber. When the medium pressure chamber is not filled with medium, the piston head (31) is housed in the groove, so that the side walls of the two are flush and fit together, thus forming a complete wall surface, which can abut against the end wall of the main cylinder (21).

5. The lateral pressure adjustable expansive soil swelling rate measuring device according to claim 4, characterized in that: The medium conveying sleeve (4) is inserted into the end cover (22) and its end is aligned with the groove. It is fixed inside the end cover (22) and can move synchronously with the end cover (22). When the end cover (22) moves outward along the guide rail (7), it can drive the medium conveying sleeve (4) and the piston part (3) in the extreme contraction position to move outward together, thereby causing the wall surface formed by the end cover (22) and the piston part (3) to separate from the port of the main cylinder (21).

6. The lateral pressure adjustable expansive soil swelling rate measuring device according to claim 5, characterized in that: The experimental box (1) is provided with side covers on both the left and right sides, and the side covers are equipped with linear drive devices for driving the end cover (22) to move axially.

7. The lateral pressure adjustable expansive soil swelling rate measuring device according to claim 6, characterized in that: An isolation system (8) is provided in the middle of the main cylinder (21) to divide it into two chambers, and each chamber is equipped with a measuring module (6). The isolation system (8) includes a rotating part (81) located at the center line of the main cylinder (21), a side wall part (82) arranged on the left and right sides of the rotating part (81) and fixed inside the main cylinder (21), and a driving part (83) located on the end face of the rotating part (81) for driving its rotation. By rotating the rotating part (81) clockwise / counterclockwise, the corresponding channel on the side wall of the side wall part (82) can be switched to be closed or opened, thereby realizing the delivery of the unclogging agent in the left and right symmetrical chambers.

8. The lateral pressure adjustable expansive soil swelling rate measuring device according to claim 7, characterized in that: The drive unit (83) includes a toothed roller (831) that slides longitudinally through the side wall of the main cylinder (21) and a wedge (832) fixedly connected to its bottom end. The wedge (832) is arc-shaped, and its inner curvature matches the curvature of the circumferential side wall of the main cylinder (21), so that it can adhere to the circumference of the main cylinder (21). The width of the wedge (832) gradually decreases from the inside to the outside, and its longitudinal section is triangular. Push-pull rods (9) are symmetrically arranged on the left and right below it. One end of the push-pull rod (9) is provided with a wedge-shaped chamfer that can be squeezed and slid relative to the wedge (832), and the other end extends to the outer end of the end cap (22) and then bends upward and is fixed to the output end of the linear drive device.

9. The lateral pressure adjustable expansive soil swelling rate measuring device according to claim 8, characterized in that: The rotating part (81) includes a turntable (811), with a rotating shaft (812) fixed coaxially at its center, and is rotatably mounted between the left and right sidewalls (82) via the rotating shaft (812); the end face of the turntable (811) is recessed inward to form a toothed ring groove (8112) that meshes with the toothed roller (831); the surface of the turntable (811) has multiple guide grooves (8111) that radiate outward in a clockwise arc from the inside to the outside, and a sliding shaft (813) is slidably connected in each guide groove (8111); the sidewall (82) includes a fixed disk (821), with the rotating shaft (812) rotatably mounted at the center of the fixed disk (821), and its periphery A number of conveying units (822) are arranged circumferentially, corresponding one-to-one with the guide grooves (8111); each conveying unit (822) includes a fixed sleeve (8221) fixed to the surface of the fixed plate (821) and a movable block (8222) movably inserted into the fixed sleeve (8221). The bottom end of the movable block (8222) is rigidly connected to the sliding shaft (813), and the side wall of the fixed sleeve (8221) is provided with a through groove for the sliding shaft (813) to move; the top of the movable block (8222) is conical, and a nozzle (8223) is installed there. The nozzle (8223) is connected to the supply source of the drain cleaner through a hose.

10. A method for determining the swelling rate of expansive soil with adjustable lateral pressure, based on the device for determining the swelling rate of expansive soil with adjustable lateral pressure as described in claim 2, characterized in that... The method for determining the expansion rate includes the following steps: S1. Place the prepared expansive soil sample into the sample tube. S2. Set the initial lateral pressure using the pump (5), which can be 0 or a preset low value; S3. Allow the sample to absorb water and expand, and use a displacement sensor to record the change of its vertical deformation over time in real time. S4. At different times during the test, adjust the output pressure of the pump (5) to adjust the lateral pressure to a new set value to achieve a graded pressurization test; S5. The data acquisition system synchronously records the lateral pressure at each level and its corresponding stable vertical expansion. S6. Based on the collected data, plot the lateral pressure-expansion rate relationship curve and calculate the lateral confined expansion modulus.

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