A device for measuring the consolidation properties of subgrade soil

Abstract

This invention belongs to the field of soil testing technology and discloses a device for testing the consolidation performance of roadbed soil. The device includes a testing chamber, a hydraulic cylinder, and a pressure plate. The hydraulic cylinder is fixedly installed on the side wall of the testing chamber, and its moving end extends upward and is laterally fixed with a connecting plate. A pressure rod connected to the center of the upper surface of the pressure plate is fixed at the lower end of the connecting plate. The device also includes a step-by-step pressurization mechanism, located on the upper and lower surfaces of the pressure plate, with the pressurizing end located on the lower surface of the pressure plate and in contact with the soil and permeable stone surfaces inside the testing chamber. The step-by-step pressurization mechanism can apply pressure to the soil and permeable stone from the inside out. This invention uses a step-by-step pressurization structure from the inside out to discharge accumulated water and air from the interlayer. Combined with a water pump that adaptively adjusts its power according to the consolidation stage, and simultaneously collects data on settlement, moisture content, and drainage volume, it effectively eliminates detection errors caused by gaps and manual pumping, improving the accuracy of roadbed soil consolidation testing.

Description

Technical Field

[0001] This invention belongs to the field of soil testing technology, and in particular relates to a device for testing the consolidation performance of roadbed soil. Background Technology

[0002] In the construction and maintenance of roadbed engineering, soil consolidation performance is a key indicator determining the long-term stability of the roadbed, directly affecting the bearing capacity and service life of the road. The core working principle of existing roadbed soil consolidation performance testing devices is as follows: a prepared roadbed soil sample is placed into a testing chamber, and axial pressure is applied through a top pressure plate to cause the soil sample to undergo consolidation deformation. At the same time, parameters such as settlement, drainage, and moisture content are monitored to analyze consolidation characteristics, such as the device for measuring soil consolidation performance and expansion force disclosed in announcement number CN206906375U.

[0003] To optimize the contact effect between the pressure plate and the soil sample and to assist in drainage and air release, permeable stones are commonly laid on the soil surface. Although this can fill the small unevenness of the soil surface to a certain extent and reduce the initial gap between the pressure plate and the soil, in the actual measurement process, the pressure plate adopts the whole surface synchronous pressure mode. The pressure plate is in full contact with the permeable stone at an instant. Not only can it not effectively expel the air and moisture in the gap, but it will also seal them inside the soil, forming "air pockets" and "water accumulation". This causes the early sedimentation data to be distorted. Moreover, the sealed gas will be slowly compressed in the later stage, resulting in abnormal water discharge during the consolidation stage and reducing the measurement accuracy.

[0004] To address this, a device for measuring the consolidation properties of roadbed soil is proposed. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a device for measuring the consolidation performance of roadbed soil.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a device for testing the consolidation performance of roadbed soil, comprising a testing box, a hydraulic cylinder, and a pressure plate, wherein the hydraulic cylinder is fixedly installed on the side wall of the testing box, and the moving end of the hydraulic cylinder extends upward and is laterally fixedly provided with a connecting plate; a pressure rod connected to the center of the upper surface of the pressure plate is fixedly provided at the lower end of the connecting plate; and the device further comprises: The step-by-step pressurization mechanism is located on the upper and lower surfaces of the pressure plate, with the pressurization end located on the lower surface of the pressure plate and in contact with the soil and permeable stone surfaces inside the measuring chamber. The step-by-step pressurization mechanism can pressurize the soil and permeable stone from the inside out, gradually discharging the gas and water trapped in the interlayer gaps. The step-by-step pressurization mechanism and the lower surface edge area of ​​the pressure plate together form an annular water tank. A water tank is fixedly installed at the bottom of the measuring box, and multiple evenly distributed overflow holes are provided at the connection between the water tank and the measuring box. The side wall of the measuring box is provided with a pumping mechanism connected to the annular water tank and the water tank. A water level sensor is fixedly installed on the inner side wall of the water tank. The FDR dielectric soil moisture sensor is fixedly installed on the side wall of the measuring chamber, and both probes of the FDR dielectric soil moisture sensor extend into the interior of the measuring chamber. The settlement detection mechanism is installed on the side wall of the measuring chamber, and the detection end of the settlement detection mechanism is connected to the upper surface of the pressure plate.

[0007] Preferably, the progressive pressurization mechanism includes a circular pressure plate fixedly disposed at the center of the lower surface of the pressure plate. The outer periphery of the circular pressure plate is provided with a plurality of mutually movably sleeved pressure rings. The thickness of the circular pressure plate is greater than the thickness of the pressure rings. Electromagnetic telescopic mechanisms are provided on the top of both sides of the plurality of pressure rings, and the electromagnetic telescopic mechanisms are fixedly disposed on the upper surface of the pressure plate.

[0008] Preferably, the electromagnetic telescopic mechanism includes a telescopic rod fixedly disposed on the upper surface of the pressure ring, a permanent magnet block fixedly disposed at the upper end of the telescopic rod, a connecting plate fixedly disposed at the top of the permanent magnet block, an electromagnetic ring sleeved on the rod wall of the telescopic rod, and the bottom of the electromagnetic ring fixedly connected to the upper surface of the pressure plate, a spring fixedly disposed between the electromagnetic ring and the permanent magnet block, a connecting ring fixedly disposed on the upper surface of the pressure plate and located outside the electromagnetic ring, and a telescopic cover covering the outside of the spring fixedly disposed between the connecting plate and the connecting ring.

[0009] Preferably, the circular pressure plate has a plurality of evenly distributed limiting rods fixedly provided on its circumferential wall, and the lower surface of the plurality of pressure rings is provided with limiting grooves at positions corresponding to the positions of the plurality of limiting rods. The cooperation between the limiting rods and the limiting grooves ensures that the lower surface of the circular pressure plate is flush with the lower surface of the plurality of pressure rings.

[0010] Preferably, the water pumping mechanism includes a water pump fixedly installed on the side wall of the measuring chamber, a water pumping pipe fixedly installed at the suction end of the water pump, and the end of the water pumping pipe fixedly connected to the pressure plate and extending into the interior of the annular water tank, a filter screen fixedly installed inside the annular water tank and at the pipe opening of the water pumping pipe, and a water outlet pipe fixedly connected to the water tank at the output end of the water pumping mechanism.

[0011] Preferably, the settlement detection mechanism includes a support base fixedly mounted on the side wall of the measuring box, a displacement sensor fixedly mounted on the top of the support base, an L-shaped connecting rod fixedly mounted on the displacement end of the displacement sensor, and the end of the L-shaped connecting rod fixedly connected to the edge of the upper surface of the pressure plate.

[0012] Preferably, a controller is fixedly installed on the side wall of the measuring box, and the hydraulic cylinder, the step-pressurization mechanism, the pumping mechanism, the water level sensor, the FDR dielectric soil moisture sensor and the settlement detection mechanism are all electrically connected to the controller.

[0013] Preferably, a pressure sensor is fixedly provided at the lower end of the pressure rod, and the pressure-receiving end of the pressure sensor is fixedly connected to the center of the upper surface of the pressure plate. The pressure sensor is also electrically connected to the controller. The pressure plate monitors the pre-compression of the soil and permeable stone through the pressure sensor. After pre-compression, the controller starts the gradual pressurization mechanism.

[0014] Compared with existing technologies, the present invention has the following advantages: 1. This invention uses a circular pressure plate and multiple nested pressure rings on a pressure plate. When pressurizing the subgrade soil, a hydraulic cylinder extends and moves the pressure plate downward, simultaneously moving the circular pressure plate and multiple pressure rings. The circular pressure plate first contacts the center of the subgrade soil surface and the pressure sensor detects the pre-pressure applied to the subgrade soil. When the pre-pressure reaches a threshold, the hydraulic cylinder stops and the electromagnetic rings on both sides of the top of the multiple pressure rings are connected in sequence from the inside out. This causes the permanent magnet to move the telescopic rod downward synchronously. The lower end of the telescopic rod pushes the pressure ring towards the subgrade soil, and the spring between the permanent magnet and the electromagnetic ring is compressed. Finally, the multiple pressure rings are pressed down from the inside out and fit against the subgrade soil surface. This allows for gradual compaction of the subgrade soil surface, squeezing the air and stagnant water between layers to the outer annular water trough. This avoids the formation of gas and water trapped in the air when the entire layer is compressed at once, effectively eliminating data deviations caused by water and air trapped in gaps and improving the accuracy of consolidation tests.

[0015] 2. This invention involves starting a water pump, which discharges air and water collected in an annular water tank through a pumping pipe. This pumping action is based on gradually pressurizing the soil. The water is then discharged into a water tank through an outlet pipe. A water level sensor inside the tank monitors the cumulative drainage volume in real time, generating drainage data. Simultaneously, an FDR dielectric soil moisture sensor is embedded in the middle layer of the soil to monitor changes in soil moisture content in real time. In the initial stage, the moisture content decreases slightly due to the discharge of interstitial water. During the primary consolidation stage, the moisture content decreases rapidly as soil pores are compressed and a large amount of pore water is discharged. After entering the secondary consolidation stage, the rate of decrease in moisture content slows down significantly and gradually stabilizes. Meanwhile, the water level sensor in the tank tracks the changes in drainage volume synchronously. Initially, there is a brief small peak due to the discharge of interstitial water. During the primary consolidation stage, the drainage volume increases rapidly as a large amount of pore water is discharged. During the secondary consolidation stage, the drainage volume is minimal, and the cumulative drainage volume gradually becomes constant.

[0016] 3. This invention uses a pressure plate to move downwards, synchronously driving an L-shaped connecting rod. The end of the L-shaped connecting rod is fixedly connected to the displacement end of a displacement sensor. As the pressure plate moves, the displacement end moves along the detection stroke of the displacement sensor, thereby capturing the displacement change of the pressure plate in real time and indirectly monitoring soil settlement. Based on the two parameters of settlement and drainage, the consolidation is divided into three stages. The working power of the water pump is automatically adjusted to prevent the water pump from forcibly sucking out the pore water inside the soil under negative pressure. The entire process relies on the natural drainage of the soil under pressure, avoiding human error caused by manual pumping. Finally, by collecting three sets of core data on soil settlement, moisture content, and drainage, a correlation curve between the three is constructed to distinguish the soil change patterns in the three stages of instantaneous settlement, primary consolidation, and secondary consolidation, thus completing a comprehensive and accurate measurement of the consolidation performance of the roadbed soil. Attached Figure Description

[0017] Figure 1 This is a first-view perspective perspective of a device for measuring the consolidation performance of roadbed soil provided by the present invention; Figure 2 This is a second-view perspective perspective of a device for measuring the consolidation performance of roadbed soil provided by the present invention; Figure 3 This is a perspective view of the cross-section of the pressure plate of the subgrade soil consolidation performance testing device provided by the present invention; Figure 4 This is a perspective view of the structure of the lower surface of the pressure plate in the subgrade soil consolidation performance testing device provided by the present invention; Figure 5 This is a perspective view of the pressure plate, circular pressure plate, and pressure ring in a roadbed soil consolidation performance testing device provided by the present invention; Figure 6 This is a perspective view of the pressure ring and electromagnetic telescopic mechanism in a roadbed soil consolidation performance testing device provided by the present invention. Figure 7 This is a perspective view of the pressure plate and settlement detection mechanism in a roadbed soil consolidation performance testing device provided by the present invention.

[0018] In the diagram: 1. Measuring box, 2. Hydraulic cylinder, 3. Pressure plate, 4. Connecting plate, 5. Pressure rod, 6. Gradual pressurization mechanism, 61. Circular pressure plate, 62. Pressure ring, 63. Electromagnetic telescopic mechanism, 631. Telescopic rod, 632. Permanent magnet block, 633. Connecting plate, 634. Electromagnetic ring, 635. Spring, 636. Connecting ring, 637. Telescopic cover, 64. Limiting support rod, 65. Limiting groove, 7. Annular water tank, 8. Water tank, 9. Overflow hole, 10. Pumping mechanism, 101. Pumping pump, 102. Pumping pipe, 103. Filter screen cover, 104. Water outlet pipe, 11. Water level sensor, 12. FDR dielectric soil moisture sensor, 13. Settlement detection mechanism, 131. Support base, 132. Displacement sensor, 133. Displacement end, 134. L-shaped connecting rod, 14. Controller, 15. Pressure sensor. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] like Figures 1-2 The device for testing the consolidation performance of subgrade soil includes a testing chamber 1, a hydraulic cylinder 2, and a pressure plate 3. The hydraulic cylinder 2 is fixedly installed on the side wall of the testing chamber 1, and the moving end of the hydraulic cylinder 2 extends upward and is laterally fixed with a connecting plate 4. A pressure rod 5, which is connected to the center of the upper surface of the pressure plate 3, is fixed at the lower end of the connecting plate 4. The size of the pressure plate 3 matches the inner wall size of the testing chamber 1. The device also includes: The gradual pressurization mechanism 6 is set on the upper and lower surfaces of the pressure plate 3, with the pressurizing end located on the lower surface of the pressure plate 3 and in contact with the soil and permeable stone surfaces inside the measuring chamber 1. The gradual pressurization mechanism 6 can pressurize the soil and permeable stone from the inside out (the permeable stone is small-particle gravel, and a layer is laid on the top and bottom of the measuring chamber 1), gradually discharging the gas and water trapped in the interlayer gaps. The gradual pressurization mechanism 6 and the lower surface edge area of ​​the pressure plate 3 together form an annular water tank 7.

[0021] In actual use, when the moving end of the hydraulic cylinder 2 retracts and drives the pressure plate 3 to move down, the gradually pressurizing mechanism 6 first contacts the permeable stone on the upper side of the soil and the middle of the soil surface. The pressurizing mechanism 6 presses down from the inside to the outside and completely fits the permeable stone on the upper side and the soil surface, squeezing out the air and free water trapped in the gap between the soil and the permeable stone and between the permeable stone and the pressure plate 3 towards the annular water groove 7 at the edge of the pressure plate 3.

[0022] like Figures 4-6As shown, the progressive pressurization mechanism 6 includes a circular pressure plate 61 fixedly disposed at the center of the lower surface of the pressure plate 3. Multiple interlocking pressure rings 62 are provided around the circular pressure plate 61. The thickness of the circular pressure plate 61 is greater than the thickness of the pressure rings 62. Electromagnetic telescopic mechanisms 63 are provided on the top of both sides of the multiple pressure rings 62, and the electromagnetic telescopic mechanisms 63 are fixedly disposed on the upper surface of the pressure plate 3. The electromagnetic telescopic mechanism 63 includes a telescopic rod 631 fixedly disposed on the upper surface of the pressure rings 62. A permanent magnet block 632 is fixedly disposed at the upper end of the telescopic rod 631. The top of the permanent magnet block 632... A connecting plate 633 is fixedly provided in the telescopic rod 631. An electromagnetic ring 634 is sleeved on the rod wall of the telescopic rod 631. The rod wall of the telescopic rod 631 can move up and down relative to the electromagnetic ring 634. The bottom of the electromagnetic ring 634 is fixedly connected to the upper surface of the pressure plate 3. A spring 635 is fixedly provided between the electromagnetic ring 634 and the permanent magnet block 632. The spring 635 is sleeved on the telescopic rod 631. A connecting ring 636 is fixedly provided on the upper surface of the pressure plate 3 and located outside the electromagnetic ring 634. A telescopic cover 635 is fixedly provided between the connecting plate 633 and the connecting ring 636, covering the outside of the spring 635. 37. The telescopic cover 637 is a soft rubber cover that can shield and protect the electromagnetic ring 634 and the permanent magnet 632. When the electromagnetic ring 634 is energized, it generates a magnetic attraction force on the permanent magnet 632, causing the permanent magnet 632 to move the telescopic rod 631 and the lower pressure ring 62 downwards. At the same time, the spring 635 is compressed between the permanent magnet 632 and the electromagnetic ring 634. When the electromagnetic ring 634 is de-energized, the spring 635 applies an upward elastic force to the permanent magnet 632, causing the telescopic rod 631 and the lower pressure ring 62 to move upwards automatically. The circumferential wall of the circular pressure plate 61 is fixed. Multiple evenly distributed limiting rods 64 are fixedly provided. The lower surface of multiple pressure rings 62 is provided with limiting grooves 65 corresponding to the positions of the multiple limiting rods 64. The cooperation between the limiting rods 64 and the limiting grooves 65 ensures that the lower surface of the circular pressure plate 61 is flush with the lower surface of the multiple pressure rings 62. When the multiple pressure rings 62 are driven downward, the limiting grooves 65 and the limiting rods 64 are inserted and cooperate to limit the downward movement distance of the multiple pressure rings 62, thereby ensuring that the lower surface of the multiple pressure rings 62 is flush with the lower surface of the circular pressure plate 61, realizing the flat pressing of the soil and permeable stone.

[0023] In actual use, the electromagnetic rings 634 on the top of both sides of the multiple pressure rings 62 are connected in sequence from the inside out. After the electromagnetic rings 634 are energized, they generate magnetic attraction force, which forms a downward attraction effect on the permanent magnet block 632, causing the permanent magnet block 632 to drive the telescopic rod 631 to move down synchronously. The lower end of the telescopic rod 631 pushes the pressure rings 62 towards the soil. At the same time, the spring 635 between the permanent magnet block 632 and the electromagnetic ring 634 is compressed. Finally, the multiple pressure rings 62 are pressed down from the inside out and put into contact with the permeable stone and soil surface on the upper side of the soil. In this process, the middle of the soil is first compacted by the circular pressure plate 61, and then the compaction range is gradually expanded outward by the pressure rings 62. This can effectively squeeze out the air and free water trapped in the gap between the soil and the permeable stone, as well as between the permeable stone and the pressure plate 3, towards the annular water groove 7 at the edge of the pressure plate 3.

[0024] like Figure 3 As shown, the water tank 8 is fixedly installed at the bottom of the measuring box 1, and multiple evenly distributed overflow holes 9 are provided at the connection between the water tank 8 and the measuring box 1. The side wall of the measuring box 1 is provided with a pumping mechanism 10 connected to the annular water tank 7 and the water tank 8. A water level sensor 11 is fixedly installed on the inner side wall of the water tank 8, and the water level sensor 11 can detect the amount of water collected inside the water tank 8 in real time. The pumping mechanism 10 includes a pumping pump 101 fixedly installed on the side wall of the measuring box 1, and a pumping pipe 102 is fixedly installed at the suction end of the pumping pump 101. The end of pipe 102 is fixedly connected to pressure plate 3 and extends into the interior of annular water tank 7. Inside annular water tank 7 and at the opening of water pump pipe 102, filter screen cover 103 is fixedly installed. Filter screen cover 103 can block soil and permeable stone particles from entering water pump pipe 102, achieving solid-liquid isolation and preventing pipe blockage. The output end of water pump 101 is fixedly provided with water outlet pipe 104 fixedly connected to water tank 8. Water pump pipe 102 adopts telescopic corrugated pipe, which can ensure that the water pump pipe 102 is unobstructed during the up and down movement of pressure plate 3.

[0025] In actual use, during the pressurization process, the pore water inside the soil will flow into the water tank 8 through the seepage channel of the bottom permeable stone from the overflow hole 9. As the water volume in the water tank 8 gradually increases, the water level sensor 11 can detect the water volume in real time. During this process, the water pump 101 is started. The operation of the water pump 101 makes the water pipe 102 a negative pressure state. The water pump 101 discharges the air and water collected in the annular water tank 7 together through the water pipe 102. By timely pumping out the interstitial water and entrained gas collected in the annular water tank 7 by the water pump 101, the backflow of water can be avoided, the test interference caused by trapped air and trapped water can be eliminated, and the test results of the roadbed soil consolidation test can be guaranteed to be true and accurate.

[0026] like Figure 3As shown, the FDR dielectric soil moisture sensor 12 is fixedly installed on the side wall of the measuring box 1, and both probes of the FDR dielectric soil moisture sensor 12 extend into the interior of the measuring box 1. The FDR dielectric soil moisture sensor 12 is pre-embedded in the middle layer of the soil and can monitor changes in soil moisture content in real time.

[0027] In practical use, the FDR dielectric soil moisture sensor 12 detects the volumetric water content inside the soil in real time based on the frequency domain reflection principle. It can track the dynamic changes of soil moisture throughout the test process, distinguish the water content change trends in the preloading, air release and drainage stage, the primary consolidation stage, and the secondary consolidation stage, and provide reliable internal moisture data support for accurately dividing the consolidation stages of the subgrade soil and restoring the true consolidation evolution law.

[0028] like Figure 7 As shown, the settlement detection mechanism 13 is installed on the side wall of the measuring box 1, and the detection end of the settlement detection mechanism 13 is connected to the upper surface of the pressure plate 3. The settlement detection mechanism 13 includes a support base 131 fixedly installed on the side wall of the measuring box 1. A displacement sensor 132 is fixedly installed on the top of the support base 131. An L-shaped connecting rod 134 is fixedly installed on the displacement end 133 of the displacement sensor 132. The end of the L-shaped connecting rod 134 is fixedly connected to the edge of the upper surface of the pressure plate 3. The L-shaped connecting rod 134 moves synchronously with the pressure plate 3. The displacement sensor 132 adopts a sealed shell with a telescopic dustproof and waterproof sleeve to extend its service life.

[0029] In actual use, when the pressure plate 3 moves downward to apply pressure, it will simultaneously pull down the L-shaped connecting rod 134. The end of the L-shaped connecting rod 134 is fixedly connected to the displacement end 133 of the displacement sensor 132. As the pressure plate 3 moves downward, the displacement end 133 will move along the detection stroke of the displacement sensor 132, thereby capturing the displacement change of the pressure plate 3 in real time. This can indirectly realize the monitoring of soil settlement, obtain soil settlement data in real time, and provide a reliable deformation basis for judging different consolidation stages of the subgrade soil.

[0030] like Figure 7 As shown, a controller 14 is fixedly installed on the side wall of the measuring box 1. The hydraulic cylinder 2, the progressive pressurization mechanism 6, the pumping mechanism 10, the water level sensor 11, the FDR dielectric soil moisture sensor 12, and the settlement detection mechanism 13 are all electrically connected to the controller 14. A pressure sensor 15 is fixedly installed at the lower end of the pressure rod 5. The pressure sensor 15 is a strain gauge pressure sensor. The pressure-bearing end of the pressure sensor 15 is fixedly connected to the center of the upper surface of the pressure plate 3. The pressure sensor 15 is also electrically connected to the controller 14. The pressure plate 3 monitors the pre-pressurization of the soil and permeable stone through the pressure sensor 15. After pre-pressurization, the controller 14 starts the progressive pressurization mechanism 6.

[0031] The operating principle of the present invention is described as follows: The testing personnel first lay a layer of saturated permeable stone at the bottom of the testing box 1, and then evenly fill the pretreated roadbed soil into the testing box 1 to ensure that the soil density is consistent. Then, another layer of saturated permeable stone is laid on the upper surface of the roadbed soil to complete the sample preparation work before the test. The measurement work officially started. The tester started the hydraulic cylinder 2 through the controller 14. When the hydraulic cylinder 2 retracted, it moved the pressure plate 3 down synchronously through the connecting plate 4 and the pressure rod 5 until it entered the test box 1 to carry out pre-compression treatment. During this process, the circular pressure plate 61 and multiple pressure rings 62 on the lower surface of the pressure plate 3 moved down synchronously with the pressure plate 3. The circular pressure plate 61 first contacted the surface of the permeable stone and soil on the upper side. At the moment of contact, the external force was transmitted to the pressure sensor 15 through the pressure plate 3. The pressure sensor 15 detected the pre-compression stress applied to the soil by the circular pressure plate 61 in real time and fed the data back to the controller 14. When the pressure reaches 8 kPa, the controller 14 immediately stops the hydraulic cylinder 2 from retracting. Simultaneously, it sequentially activates the electromagnetic rings 634 on the top sides of multiple pressure rings 62 in an inward-outward sequence. The energized electromagnetic rings 634 generate magnetic attraction, creating a downward attraction on the permanent magnet block 632. This causes the permanent magnet block 632 to move the telescopic rod 631 downwards synchronously. The lower end of the telescopic rod 631 pushes the pressure rings 62 towards the soil. Simultaneously, the spring 635 between the permanent magnet block 632 and the electromagnetic rings 634 is compressed, ultimately achieving the sequential downward pressure of multiple pressure rings 62 from the inside out, completely contacting the upper permeable stone and soil surface. In this progressive pressurization process, the central part of the soil is first compacted by the circular pressure plate 61, and then the compaction range is gradually expanded outward by the pressure ring 62. This effectively squeezes out the air and free water trapped in the gap between the soil and the permeable stone, as well as between the permeable stone and the pressure plate 3, towards the annular water trough 7 at the edge of the pressure plate 3. At the same time, under the action of pre-compression stress, the pore water inside the soil will also flow into the water tank 8 through the seepage channel of the bottom permeable stone from the overflow hole 9. Normal water-containing soil or mud will have its internal water discharged when compressed. Here, electromagnetic pressure is used, and the pressure can be increased by increasing the current.

[0032] While receiving the pre-pressure signal from the pressure sensor 15, the controller 14 simultaneously starts the water pump 101. The water pump 101 discharges the air and water collected in the annular water tank 7 through the water pumping pipe 102, and then discharges it into the water tank 8 through the water outlet pipe 104. The water level sensor 11 inside the water tank 8 monitors the cumulative drainage volume in real time and collects drainage data. After the pre-compression has been settling for 20 minutes, the controller 14 automatically controls the hydraulic cylinder 2 to continue retracting, driving the pressure plate 3, the circular pressure plate 61 and multiple pressure rings 62 to move down synchronously, applying progressively increasing consolidation pressure to the soil. During this process, the pressure value detected by the pressure sensor 15 rises steadily from 8 kPa. According to the requirements of the roadbed soil test standard, the maximum pressure value can reach 200 kPa or be set to 100 kPa to 200 kPa according to the test requirements, and is fed back to the controller 14 in real time to achieve pressure control. Meanwhile, the FDR dielectric soil moisture sensor 12 is embedded in the middle layer of the soil to monitor the changes in soil moisture content in real time. In the initial stage, the moisture content decreases slightly due to the discharge of interstitial water. In the main consolidation stage, the moisture content decreases rapidly as the soil pores are compressed and a large amount of pore water is discharged. After entering the secondary consolidation stage, the rate of decrease in moisture content slows down significantly and gradually stabilizes. Meanwhile, the water level sensor 11 in the water tank 8 tracks the changes in drainage volume. In the early stage, a short peak occurs due to the discharge of interstitial water. In the main consolidation stage, the drainage volume increases rapidly as a large amount of pore water is discharged. In the secondary consolidation stage, the drainage volume is very small, and the cumulative drainage volume gradually becomes constant. As the pressure plate 3 moves downward, it simultaneously pulls down the L-shaped connecting rod 134. The end of the L-shaped connecting rod 134 is fixedly connected to the displacement end 133 of the displacement sensor 132. As the pressure plate 3 moves downward, the displacement end 133 will move along the detection stroke of the displacement sensor 132, thereby capturing the displacement change of the pressure plate 3 in real time and indirectly realizing the monitoring of soil settlement. It should be noted that during the pre-compression stage, as the pressure plate 3 gradually moves downward and the circular pressure plate 61 contacts the soil and permeable stone to apply pressure, the displacement end 133 will synchronously generate a displacement with the pressure plate 3. This displacement mainly corresponds to the soil surface layer, the permeable stone interlayer, and the gap between the two. The actual settlement is not the actual consolidation and settlement of the soil. When the pre-compression stress detected by the pressure sensor 15 reaches 8 kPa, it will immediately send a signal to the controller 14. After receiving the signal, the controller 14 will mark the position of the displacement end 133 at this time as the initial zero point (i.e., the reference position) for settlement detection. In the subsequent formal pressure measurement stage, the pressure plate 3 drives the circular pressure plate 61 and the pressure ring 62 to continuously apply pressure to the soil. The soil undergoes actual consolidation and compression and causes the pressure plate 3 to sink. The displacement end 133 will generate a new displacement from the initial zero point. The displacement sensor 132 collects the displacement data in real time and feeds it back to the controller 14, thereby calculating the actual settlement of the soil. The controller 14 collects three sets of core data—settlement, moisture content, and drainage—simultaneously, constructs a correlation curve between the three, distinguishes the soil change patterns in the three stages of instantaneous settlement, primary consolidation, and secondary consolidation, and finally completes a comprehensive and accurate measurement of the roadbed soil consolidation performance. During the instantaneous settling stage, the soil surface layer, the permeable stone interlayer, and the gap between them are closed under the action of the pressure plate 3, and the settling rate increases sharply. The free water retained in the soil pores is quickly squeezed into the annular water tank 7, and the instantaneous water storage capacity of the annular water tank 7 increases sharply. During the primary consolidation stage, the soil pores are continuously compressed under the action of external pressure, the settling is uniform, the pore water is stably seeped out, the annular water tank 7 maintains a uniform water inflow state, and the water storage capacity accumulates. During the secondary consolidation stage, the soil pore water is basically drained, the settling rate drops to the minimum, and only a small amount of capillary seepage water intermittently flows into the annular water tank 7. The water storage capacity of the annular water tank 7 remains at a low level for a long time. The controller 14 synchronously collects the settling rate data of the displacement sensor 132 and the drainage data of the water level sensor 11. After the instantaneous settling stage, the water accumulated in the annular water tank 7 is quickly pumped out to prevent overflow and backflow. During the main consolidation stage, a medium constant power is matched to ensure that the pore water is discharged naturally without forming negative pressure. During the secondary consolidation stage, the power is reduced to intermittent low-load operation (45W full power continuous operation during the instantaneous settling stage, constant 25W continuous operation during the main consolidation stage, and 8W intermittent start and stop during the secondary consolidation stage, operating for 30 seconds every 5 minutes). This fundamentally eliminates the problem of passively sucking out the soil moisture caused by high-power suction, completely eliminates subjective control interference, and ensures the authenticity and accuracy of the test data.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for measuring the consolidation performance of roadbed soil, comprising a measuring box (1), a hydraulic cylinder (2), and a pressure plate (3), wherein the hydraulic cylinder (2) is fixedly installed on the side wall of the measuring box (1), and the moving end of the hydraulic cylinder (2) extends upward and is laterally fixedly provided with a connecting plate (4), wherein the lower surface end of the connecting plate (4) is fixedly provided with a pressure rod (5) connected to the center of the upper surface of the pressure plate (3), characterized in that, Also includes: The step-by-step pressurization mechanism (6) is set on the upper and lower surfaces of the pressure plate (3), and the pressurization end is located on the lower surface of the pressure plate (3) and in contact with the soil and permeable stone surfaces inside the measuring box (1). The step-by-step pressurization mechanism (6) can pressurize the soil and permeable stone from the inside out, and discharge the gas and water trapped in the interlayer gap layer by layer. The step-by-step pressurization mechanism (6) and the lower surface edge area of ​​the pressure plate (3) together form an annular water tank (7). A water tank (8) is fixedly installed at the bottom of the measuring box (1), and multiple evenly distributed overflow holes (9) are provided at the connection between the water tank (8) and the measuring box (1). The side wall of the measuring box (1) is provided with a pumping mechanism (10) connected to the annular water tank (7) and the water tank (8). A water level sensor (11) is fixedly installed on the inner side wall of the water tank (8). The FDR dielectric soil moisture sensor (12) is fixedly installed on the side wall of the measuring box (1), and both probes of the FDR dielectric soil moisture sensor (12) extend into the interior of the measuring box (1). The settlement detection mechanism (13) is set on the side wall of the measuring box (1), and the detection end of the settlement detection mechanism (13) is connected to the upper surface of the pressure plate (3).

2. The device for measuring the consolidation performance of roadbed soil according to claim 1, characterized in that, The progressive pressurization mechanism (6) includes a circular pressure plate (61) fixedly disposed at the center of the lower surface of the pressure plate (3). The outer periphery of the circular pressure plate (61) is provided with a plurality of mutually movable pressure rings (62). The thickness of the circular pressure plate (61) is greater than the thickness of the pressure rings (62). The top of both sides of the plurality of pressure rings (62) are provided with electromagnetic telescopic mechanisms (63), and the electromagnetic telescopic mechanisms (63) are fixedly disposed on the upper surface of the pressure plate (3).

3. The device for measuring the consolidation performance of subgrade soil according to claim 2, characterized in that, The electromagnetic telescopic mechanism (63) includes a telescopic rod (631) fixedly disposed on the upper surface of the pressure ring (62). A permanent magnet block (632) is fixedly disposed at the upper end of the telescopic rod (631). A connecting plate (633) is fixedly disposed at the top of the permanent magnet block (632). An electromagnetic ring (634) is sleeved on the rod wall of the telescopic rod (631). The bottom of the electromagnetic ring (634) is fixedly connected to the upper surface of the pressure plate (3). A spring (635) is fixedly disposed between the electromagnetic ring (634) and the permanent magnet block (632). A connecting ring (636) is fixedly disposed on the upper surface of the pressure plate (3) and outside the electromagnetic ring (634). A telescopic cover (637) covering the outside of the spring (635) is fixedly disposed between the connecting plate (633) and the connecting ring (636).

4. The device for measuring the consolidation performance of roadbed soil according to claim 2, characterized in that, The circular pressure plate (61) has a plurality of evenly distributed limiting rods (64) fixedly provided on its circumferential wall. The lower surfaces of the plurality of pressure rings (62) are provided with limiting grooves (65) corresponding to the positions of the plurality of limiting rods (64). The cooperation between the limiting rods (64) and the limiting grooves (65) ensures that the lower surface of the circular pressure plate (61) is flush with the lower surface of the plurality of pressure rings (62).

5. The device for measuring the consolidation performance of subgrade soil according to claim 1, characterized in that, The pumping mechanism (10) includes a pump (101) fixedly installed on the side wall of the measuring box (1). The pump (101) has a pump pipe (102) fixedly installed at the suction end. The end of the pump pipe (102) is fixedly connected to the pressure plate (3) and extends into the interior of the annular water tank (7). A filter screen (103) is fixedly installed inside the annular water tank (7) at the opening of the pump pipe (102). The pump (101) has an outlet pipe (104) fixedly connected to the water tank (8) at the output end.

6. The device for measuring the consolidation performance of subgrade soil according to claim 1, characterized in that, The settlement detection mechanism (13) includes a support base (131) fixedly installed on the side wall of the measuring box (1). A displacement sensor (132) is fixedly installed on the top of the support base (131). An L-shaped connecting rod (134) is fixedly installed on the displacement end (133) of the displacement sensor (132), and the end of the L-shaped connecting rod (134) is fixedly connected to the edge of the upper surface of the pressure plate (3).

7. The device for measuring the consolidation performance of subgrade soil according to claim 1, characterized in that, The side wall of the measuring box (1) is fixedly equipped with a controller (14), and the hydraulic cylinder (2), the step pressurization mechanism (6), the pumping mechanism (10), the water level sensor (11), the FDR dielectric soil moisture sensor (12) and the settlement detection mechanism (13) are all electrically connected to the controller (14).

8. The device for measuring the consolidation performance of subgrade soil according to claim 7, characterized in that, The lower end of the pressure rod (5) is fixedly equipped with a pressure sensor (15). The pressure end of the pressure sensor (15) is fixedly connected to the center of the upper surface of the pressure plate (3). The pressure sensor (15) is electrically connected to the controller (14). The pressure plate (3) monitors the pre-pressure of the soil and permeable stone through the pressure sensor (15). After pre-pressure, the controller (14) starts the gradual pressurization mechanism (6).

Images