Expansive soil roadbed centrifugal model test device and test method thereof

Abstract

The invention discloses an expansive soil roadbed centrifugal model test device and a test method thereof, and belongs to the technical field of expansive soil roadbed tests.The expansive soil roadbed centrifugal model test device comprises a geotechnical centrifuge, a model box, a dry-wet circulation system and a data collecting and monitoring system; n g centrifugal accelerations are applied to the expansive soil roadbed model by arranging a geotechnical centrifuge, the deadweight required by the proportion reduction of the expansive soil roadbed model is compensated, and the gravity field of the real condition of the expansive soil roadbed is simulated; due to the arrangement of the dry-wet circulation system, the humidity change of the expansive soil roadbed model is simulated to the maximum extent under the condition that the geotechnical centrifuge is not shut down; various sensors are arranged in the data collecting and monitoring system, important test data are monitored in real time, the deformation process of the expansive soil roadbed is convenient to analyze, and the problem that test results are likely to be distorted when test research is conducted on the expansive soil roadbed in a normal gravity environment is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of expansive soil roadbed testing, and in particular relates to an expansive soil roadbed centrifugal model testing device and a testing method thereof. Background Art

[0002] Expansive soil is a kind of highly plastic clay with the characteristics of swelling when absorbing water, shrinking when losing water, repeated swelling and shrinking deformation, attenuation of bearing capacity when immersed in water, and development of shrinkage cracks. In expansive soil areas with distinct dry and rainy seasons, the swelling and shrinking deformation of the foundation under the action of repeated immersion / drying has the potential to damage the overlying geotechnical structures (such as railway and highway subgrades), seriously affecting the long-term service performance of the structure.

[0003] Most of the existing experimental studies on expansive soil roadbed are conducted in a normal gravity environment. As a strong nonlinear engineering material, soil modulus, strength, deformation characteristics and other mechanical properties have a great correlation with stress level. In the normal gravity acceleration model test, due to the reduction of the model size, the stress level of the soil in the model is smaller than that in the prototype, resulting in "distortion" of the test results, which will affect the test analysis and test conclusions. Summary of the invention

[0004] The invention aims to provide a centrifugal model test device for an expansive soil roadbed and a test method thereof, which solves the problem that the test results may be "distorted" when conducting test research on an expansive soil roadbed in a normal gravity environment.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0006] Provided is a centrifugal model test device for an expansive soil roadbed, which includes a geotechnical centrifuge, a model box, a dry-wet cycle system, and a data acquisition and monitoring system;

[0007] The geotechnical centrifuge comprises a centrifuge rotating shaft, a centrifuge rotating arm is arranged on the centrifuge rotating shaft, and a counterweight and a hanging basket are respectively hinged at both ends of the centrifuge rotating arm;

[0008] The model box is fixedly arranged in the hanging basket, and the interior of the model box is filled with an expansive soil roadbed model;

[0009] The dry-wet cycle system includes a humidity adjustment module and a ventilation cycle module connected to the model box;

[0010] The data acquisition and monitoring system includes a soil pressure sensor, a moisture content sensor, a displacement sensor, a soil pore water pressure sensor, a first temperature sensor, a video monitoring image acquisition module, a data acquisition instrument and a computer that are electrically connected to each other; the soil pressure sensor, the first temperature sensor, the moisture content sensor and the soil pore water pressure sensor are in multiple numbers and are all buried inside the expansive soil roadbed model; the video monitoring image acquisition module is arranged on the outer wall of the model box; the displacement sensor is arranged on the top surface of the expansive soil roadbed model; the data acquisition instrument and the computer are arranged outside the model box.

[0011] The basic principle of a centrifugal model test device for an expansive soil roadbed is as follows: a geotechnical centrifuge is set to apply a centrifugal acceleration of n g to an expansive soil roadbed model, so as to compensate for the deadweight required for the reduction in the proportion of the expansive soil roadbed model and simulate the gravity field of the actual situation of the expansive soil roadbed; a dry-wet circulation system is set to simulate the humidity change of the expansive soil roadbed model to the greatest extent without stopping the geotechnical centrifuge; a variety of sensors are set in the data acquisition and monitoring system to monitor important test data in real time, so as to facilitate the analysis of the deformation process of the expansive soil roadbed; the above-mentioned settings make the stress and humidity changes of the expansive soil roadbed model more in line with the actual situation, and thus the deformation of the expansive soil roadbed can be truly simulated and analyzed, solving the problem of "distorted" test results that may occur when conducting test research on the expansive soil roadbed in a normal gravity environment.

[0012] Furthermore, the model box is a rectangular box made of aluminum alloy with an open top, a cover plate is detachably connected to the opening, and a transparent organic glass observation window is provided on one side wall of the model box; the video monitoring image acquisition module photographs the expansive soil roadbed model through the transparent organic glass observation window. The video monitoring image acquisition module can collect the displacement of the soil of the expansive soil roadbed model during the test through the transparent organic glass observation window.

[0013] Furthermore, as a specific implementation of the video monitoring image acquisition module, the video monitoring image acquisition module includes a camera and a fill light electrically connected to the data acquisition instrument and the computer; the camera and the fill light both illuminate the expansive soil roadbed model through the transparent organic glass observation window. The camera can be a high-resolution, high-frame-rate, high-speed camera; the fill light can provide a light source, so that the image collected by the camera is clearer, and the accuracy of the test results is improved.

[0014] Furthermore, the bottom of the expansive soil roadbed model is provided with a perforated stainless steel plate and a steel bead layer in sequence from top to bottom. The arrangement of the perforated stainless steel plate and the steel bead layer makes the bottom of the expansive soil roadbed model suspended, which is convenient for the circulation of humid gas and dry gas and improves the effect of the humidity adjustment module.

[0015] Furthermore, the humidity regulating module includes a humidifying module and a drying module which are arranged inside the geotechnical centrifuge and electrically connected to the computer, and the humidifying module and the drying module both transport humidified gas and dry gas to the inside of the model box through a transport pipe.

[0016] Furthermore, the inner top surface of the cover plate is provided with a plurality of nozzles; the end of the delivery pipe is provided with a plurality of branch pipes respectively connected to the plurality of nozzles. The beneficial effect of the above technical solution is that it can improve the effect of the humidification module and the drying module, so as to quickly wet or dry the expansive soil roadbed model.

[0017] Furthermore, the ventilation circulation module includes a second temperature sensor, a humidity sensor and multiple ventilation fans installed on the cover plate; the second temperature sensor and the humidity sensor are both electrically connected to the data acquisition instrument; and the multiple ventilation fans are electrically connected to the computer.

[0018] The present invention also provides a test method of an expansive soil roadbed centrifugal model test device, which comprises:

[0019] Step 1: Prepare the test soil according to the target moisture content;

[0020] Step 2: Fill the roadbed in layers in the model box according to the void ratio required by the test, arrange various sensors in between, fill to the target height, and bury the soil deformation measurement cursor on the side of the observation window;

[0021] Step 3: hoist the model box to the hanging basket, fix all kinds of pipelines, set the target acceleration, start the geotechnical centrifuge, and consolidate the soil;

[0022] Step 4: After consolidation is completed, the geotechnical centrifuge is turned off. After the geotechnical centrifuge stops rotating, the fill soil is subjected to slope cutting to obtain an expansive soil roadbed model;

[0023] Step 5: After the model roadbed is processed, the cover plate and pipeline are installed;

[0024] Step 6: Set the target humidity curve and target acceleration, run the geotechnical centrifuge, the dry-wet cycle system automatically works, the data monitoring and acquisition system starts working, the humidity adjustment module delivers gases with different humidity according to the set target humidity curve, and adjusts the target humidity curve at any time according to various sensors in the roadbed model and on the cover plate;

[0025] Step 7: After the dry-wet cycle required for the test is completed, the geotechnical centrifuge is shut down, and the dry-wet cycle system stops working;

[0026] Step 8: The computer extracts and analyzes the various sensor data of the data acquisition and monitoring system, obtains the required corresponding variable relationships, and draws conclusions.

[0027] The beneficial effects of the present invention are as follows: a centrifugal model test device and a test method for an expansive soil roadbed in the present invention apply a centrifugal acceleration of n g to an expansive soil roadbed model by setting a geotechnical centrifuge, where g is expressed as gravity acceleration, to compensate for the deadweight required for the reduced proportion of the expansive soil roadbed model, thereby simulating the gravity field of the actual situation of the expansive soil roadbed; a dry-wet circulation system is set to simulate the humidity change of the expansive soil roadbed model to the greatest extent without stopping the geotechnical centrifuge; a variety of sensors are set in the data acquisition and monitoring system to monitor important test data in real time, so as to facilitate the analysis of the deformation process of the expansive soil roadbed; the above-mentioned settings make the stress and humidity changes of the expansive soil roadbed model more in line with the actual situation, and thus the deformation of the expansive soil roadbed can be truly simulated and analyzed, solving the problem of "distorted" test results that may occur in the test research of the expansive soil roadbed in a normal gravity environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The figure is a structural schematic diagram of a centrifugal model test device for expansive soil roadbed.

[0029] Figure 2 Schematic diagram of the cross-sectional structure of the model box.

[0030] Among them, 1. geotechnical centrifuge; 101. centrifuge shaft; 102. centrifuge arm; 103. counterweight; 104. hanging basket; 2. model box; 201. cover plate; 301. humidification module; 302. drying module; 303. conveying pipe; 304. nozzle; 305. branch pipe; 306. second temperature sensor; 307. humidity sensor; 308. ventilation fan; 401. soil pressure sensor; 402. moisture content sensor; 403. displacement sensor; 404. soil pore water pressure sensor; 405. first temperature sensor; 406. video monitoring image acquisition module; 407. data acquisition instrument; 408. computer; 5. expansive soil roadbed model; 6. stainless steel plate with holes; 7. steel ball layer. DETAILED DESCRIPTION

[0031] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0032] like Figure 1-2 As shown, the present invention provides a centrifugal model test device for expansive soil roadbed, which includes a geotechnical centrifuge 1, a model box 2, a dry-wet circulation system and a data acquisition and monitoring system.

[0033] The geotechnical centrifuge 1 comprises a centrifuge shaft 101 , on which a centrifuge arm 102 is disposed, and at both ends of the centrifuge arm 102 a counterweight 103 and a hanging basket 104 are hingedly connected respectively.

[0034] The model box 2 is fixedly arranged in the hanging basket 104, and the inside of the model box 2 is filled with an expansive soil roadbed model 5. Specifically, the model box 2 is a rectangular box body with an open top made of aluminum alloy, a cover plate 201 is detachably connected to the opening, and a transparent organic glass observation window is arranged on one side wall of the model box 2.

[0035] The dry-wet cycle system includes a humidity adjustment module and a ventilation cycle module which are connected to the model box 2 .

[0036] The data acquisition and monitoring system includes a soil pressure sensor 401, a moisture content sensor 402, a displacement sensor 403, a soil pore water pressure sensor 404, a first temperature sensor 405, a video monitoring image acquisition module 406, a data acquisition instrument 407 and a computer 408 that are electrically connected to each other; the soil pressure sensor 401, the first temperature sensor 405, the moisture content sensor 402 and the soil pore water pressure sensor 404 are in multiple numbers and are all buried inside the expansive soil roadbed model 5; the video monitoring image acquisition module 406 is arranged on the outer wall of the model box 2, and the video monitoring image acquisition module 406 photographs the expansive soil roadbed model 5 through a transparent organic glass observation window. The video monitoring image acquisition module 406 can collect the displacement of the soil of the expansive soil roadbed model 5 during the test through the transparent organic glass observation window. Specifically, as a specific implementation of the video monitoring image acquisition module 406, the video monitoring image acquisition module 406 includes a camera and a fill light electrically connected to the data acquisition instrument 407 and the computer 408; the camera and the fill light both illuminate the expansive soil roadbed model 5 through the transparent organic glass observation window. The camera can be a high-resolution, high-frame-rate, high-speed camera; the fill light can provide a light source, so that the image collected by the camera is clearer, and the accuracy of the test results is improved.

[0037] The displacement sensor 403 is arranged on the top surface of the expansive soil roadbed model 5 to monitor and collect soil displacement; the data acquisition instrument 407 and the computer 408 are arranged outside the model box 2.

[0038] Preferably, but not limited to, the humidity regulating module includes a humidifying module 301 and a drying module 302 which are arranged inside the geotechnical centrifuge 1 and electrically connected to the computer 408, and the humidifying module 301 and the drying module 302 both convey humidified gas and dry gas to the inside of the model box 2 through a conveying pipe 303. The inner top surface of the cover plate 201 is provided with a plurality of nozzles 304; the end of the conveying pipe 303 is provided with a plurality of branch pipes 305 which are respectively connected to the plurality of nozzles 304. The beneficial effect of the above technical solution is: the effect of the humidifying module 301 and the drying module 302 can be improved, so that the expansive soil roadbed model 5 can be quickly wetted or dried. The bottom of the expansive soil roadbed model 5 is sequentially provided with a perforated stainless steel plate 6 and a steel bead layer 7 from top to bottom. The arrangement of the perforated stainless steel plate 6 and the steel bead layer 7 makes the bottom of the expansive soil roadbed model 5 suspended, which is convenient for the circulation of humidified gas and dry gas, and improves the effect of the humidity regulating module.

[0039] The ventilation circulation module includes a second temperature sensor 306, a humidity sensor 307 and multiple ventilation fans 308 installed on the cover plate 201; the second temperature sensor 306 and the humidity sensor 307 are both electrically connected to the data acquisition instrument 407; and the multiple ventilation fans 308 are electrically connected to the computer 408.

[0040] The present invention also provides a test method of an expansive soil roadbed centrifugal model test device, which comprises:

[0041] Step 1: Prepare the test soil according to the target moisture content;

[0042] Step 2: fill the roadbed in layers in the model box 2 according to the void ratio required by the test, arrange various sensors in between, fill to the target height, and bury the soil deformation measurement cursor on the side of the observation window;

[0043] Step 3, hoist the model box 2 to the hanging basket 104, fix various pipelines, set the target acceleration, start the geotechnical centrifuge 1, and consolidate the soil;

[0044] Step 4: After consolidation is completed, the geotechnical centrifuge 1 is turned off. After the geotechnical centrifuge 1 stops rotating, the fill soil is subjected to slope cutting to obtain an expansive soil roadbed model 5;

[0045] Step 5: After the model roadbed is processed, the cover plate 201 and the pipeline are installed;

[0046] Step 6: Set the target humidity curve and target acceleration, run the geotechnical centrifuge 1, the dry-wet cycle system automatically works, the data monitoring and acquisition system starts working, the humidity adjustment module delivers gases with different humidity according to the set target humidity curve, and adjusts the target humidity curve at any time according to various sensors in the roadbed model and on the cover plate 201;

[0047] Step 7: After the dry-wet cycle required for the test is completed, the geotechnical centrifuge 1 is shut down, and the dry-wet cycle system stops working;

[0048] Step 8: The computer 408 extracts and analyzes the various sensor data of the data acquisition and monitoring system to obtain the required corresponding variable relationships and draw conclusions.

[0049] A centrifugal model test device for an expansive soil roadbed and a test method thereof are provided. A geotechnical centrifuge 1 is provided to apply a centrifugal acceleration of n g to an expansive soil roadbed model 5, where g is expressed as gravity acceleration, to compensate for the deadweight required for the reduced proportion of the expansive soil roadbed model 5, and to simulate the gravity field of the actual situation of the expansive soil roadbed. A dry-wet circulation system is provided to simulate the humidity change of the expansive soil roadbed model 5 to the greatest extent without stopping the geotechnical centrifuge 1. A plurality of sensors are provided in a data acquisition and monitoring system to monitor important test data in real time, so as to facilitate the analysis of the deformation process of the expansive soil roadbed. The above-mentioned settings make the stress and humidity changes of the expansive soil roadbed model 5 more in line with the actual situation, and thus the deformation of the expansive soil roadbed can be truly simulated and analyzed, and the problem of "distorted" test results that may occur in the test research of the expansive soil roadbed in a normal gravity environment is solved.

Claims

1. A centrifugal model test device for expansive soil roadbed, characterized in that: Includes geotechnical centrifuge, model box, dry-wet cycle system and data acquisition monitoring system; The geotechnical centrifuge comprises a centrifuge rotating shaft, a centrifuge rotating arm is arranged on the centrifuge rotating shaft, and a counterweight and a hanging basket are respectively hinged at both ends of the centrifuge rotating arm; The model box is fixedly arranged in the hanging basket, and the interior of the model box is filled with an expansive soil roadbed model; The dry-wet cycle system includes a humidity adjustment module and a ventilation cycle module connected to the model box; The data acquisition and monitoring system includes a soil pressure sensor, a moisture content sensor, a displacement sensor, a soil pore water pressure sensor, a first temperature sensor, a video monitoring image acquisition module, a data acquisition instrument and a computer that are electrically connected to each other; the soil pressure sensor, the first temperature sensor, the moisture content sensor and the soil pore water pressure sensor are in multiple numbers and are all buried inside the expansive soil roadbed model; the video monitoring image acquisition module is arranged on the outer wall of the model box; the displacement sensor is arranged on the top surface of the expansive soil roadbed model; the data acquisition instrument and the computer are arranged outside the model box.

2. The centrifugal model test device for expansive soil roadbed according to claim 1, characterized in that: The model box is a rectangular box made of aluminum alloy with an open top, a cover plate is detachably connected to the opening, and a transparent organic glass observation window is provided on one side wall of the model box; the video monitoring image acquisition module photographs the expansive soil roadbed model through the transparent organic glass observation window.

3. The expansive soil roadbed centrifugal model test device according to claim 2, characterized in that: The video monitoring image acquisition module includes a camera and a fill light electrically connected to the data acquisition instrument and the computer; the camera and the fill light both illuminate the expansive soil roadbed model through the transparent organic glass observation window.

4. The centrifugal model test device for expansive soil roadbed according to claim 3, characterized in that: The bottom of the expansive soil roadbed model is provided with a perforated stainless steel plate and a steel bead layer in sequence from top to bottom.

5. The expansive soil roadbed centrifugal model test device according to claim 2, characterized in that: The humidity regulating module comprises a humidifying module and a drying module which are arranged inside the geotechnical centrifuge and electrically connected to the computer. The humidifying module and the drying module both transport humidified gas and dry gas to the inside of the model box through a transport pipe.

6. The expansive soil roadbed centrifugal model test device according to claim 2, characterized in that: The inner top surface of the cover plate is provided with a plurality of nozzles; the end of the delivery pipe is provided with a plurality of branch pipes respectively connected with the plurality of nozzles.

7. The centrifugal model test device for expansive soil roadbed according to claim 2, characterized in that: The ventilation circulation module includes a second temperature sensor, a humidity sensor and a plurality of ventilation fans installed on the cover plate; the second temperature sensor and the humidity sensor are both electrically connected to the data acquisition instrument; and the plurality of ventilation fans are electrically connected to the computer.

8. A test method of the centrifugal model test device for expansive soil roadbed according to any one of claims 2 to 7, characterized in that: include: Step 1: Prepare the test soil according to the target moisture content; Step 2: Fill the roadbed in layers in the model box according to the void ratio required by the test, arrange various sensors in between, fill to the target height, and bury the soil deformation measurement cursor on the side of the observation window; Step 3: hoist the model box to the hanging basket, fix all kinds of pipelines, set the target acceleration, start the geotechnical centrifuge, and consolidate the soil; Step 4: After consolidation is completed, the geotechnical centrifuge is turned off. After the geotechnical centrifuge stops rotating, the fill soil is subjected to slope cutting to obtain an expansive soil roadbed model; Step 5: After the model roadbed is processed, the cover plate and pipeline are installed; Step 6: Set the target humidity curve and target acceleration, run the geotechnical centrifuge, the dry-wet cycle system automatically works, the data monitoring and acquisition system starts working, the humidity adjustment module delivers gases with different humidity according to the set target humidity curve, and adjusts the target humidity curve at any time according to various sensors in the roadbed model and on the cover plate; Step 7: After the dry-wet cycle required for the test is completed, the geotechnical centrifuge is shut down, and the dry-wet cycle system stops working; Step 8: The computer extracts and analyzes the various sensor data of the data acquisition and monitoring system, obtains the required corresponding variable relationships, and draws conclusions.

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