Centrifugal test device and method for bearing characteristic of unsaturated soil pile foundation under dry-wet cycle

Abstract

The invention relates to a centrifugal test device and method for the bearing characteristic of an unsaturated soil pile foundation under a dry-wet cycle, and the device comprises a centrifugal control module, a centrifugal machine, a model box, a model pile, a dry-wet cycle module, a counterforce module, a loading control module and a data collection module. The dry-wet cycle module and the counter-force module are both installed on the model box, the loading control module is installed on the counter-force module and connected with a model pile, the data acquisition module is installed in the model box, and the model box is placed on a centrifugal machine. The centrifugal control module is in communication connection with the centrifugal machine, the dry-wet cycle module, the loading control module and the data acquisition module; the method realizes the process. The influence of dry and wet working conditions on pile sinking, bearing and deformation characteristics of a pile foundation in unsaturated soil is considered, various dry and wet cycle working conditions can be simulated, and non-stop operation in the whole test process of centrifugal tests including dry and wet cycle, pile sinking and static load tests is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of centrifugal testing devices, and in particular to a centrifugal testing device and method for bearing characteristics of unsaturated soil pile foundations under dry-wet cycles. Background Art

[0002] Pile foundations are a common foundation type widely used in various types of structures. In practical engineering, the soil surrounding the pile above the groundwater level is typically unsaturated, forming a solid-liquid-gas three-phase system. Compared to pile foundations in saturated soil, pile foundations in unsaturated soil are subject to matrix suction generated by interfacial tension and permeability, which significantly alters the strength properties and stiffness parameters of the soil surrounding the pile, as well as the shear behavior of the pile-soil interface, ultimately significantly affecting the bearing capacity and deformation response of the pile foundation. Furthermore, the suction field in unsaturated soil is dynamically related to the soil saturation. Under the influence of natural and human factors (such as rainfall infiltration, evaporation, plant transpiration, and groundwater level fluctuations), the soil surrounding the pile continuously dries and wets, forming a drying-wetting cycle. This process not only changes the soil saturation distribution but also causes the evolution of hydraulic parameters such as matrix suction, which in turn affects the mechanical properties of the pile-soil interface and significantly alters the ultimate bearing capacity and settlement characteristics of pile foundations in unsaturated soil. However, existing pile foundation design methods are still based on the assumption of saturated soil and fail to fully consider the dynamic changes in foundation saturation and its effects under dry-wet cycles. This can lead to problems such as insufficient bearing capacity or excessive settlement in engineering practice. As can be seen from the above, the bearing and deformation characteristics of pile foundations in unsaturated soils change dynamically with dry-wet cycles. Whether predicting the bearing capacity of existing pile foundations or designing the bearing capacity of new piles, dry-wet cycles are a significant factor that cannot be ignored. Therefore, it is necessary to develop a dedicated model test device to conduct in-depth research on the bearing mechanism and deformation evolution of pile foundations in unsaturated soils under dry-wet cycles. This has important academic value and engineering practical significance for improving existing pile foundation design theory, refining calculation methods, and optimizing testing techniques. This will help to more accurately predict the long-term performance of pile foundations in unsaturated soils under the complex environment of dry-wet cycles, providing a more reliable design basis for engineering practice.

[0003] Centrifuge model testing solves the stress distortion problem of constant gravity model testing through mechanical similarity. It offers significant advantages over constant gravity model testing, including high stress field similarity, realistic simulation of soil mechanical behavior, simulation of the long-term effects of high gravity acceleration, and adaptability to complex boundary conditions. Therefore, it has greater application value than constant gravity model testing in geotechnical engineering fields such as pile foundations and unsaturated soil mechanics. Currently, existing centrifuge model testing devices for pile foundation bearing characteristics are unable to simulate the effects of dry-wet cycles on the bearing and deformation characteristics of unsaturated soil pile foundations (e.g., the test device for simulating the vertical and lateral bearing characteristics of pile foundations based on a geotechnical centrifuge disclosed in Chinese patent document CN104480978A; the VHM static combined loading device and centrifuge testing method disclosed in Chinese patent document CN115508060A, etc.). At the same time, existing centrifugal testing devices capable of simulating soil dry-wet cycles are still unable to carry out pile penetration and static load tests on pile foundations, and cannot be directly applied to centrifugal model tests of the bearing characteristics of unsaturated soil pile foundations (such as the slope dry-wet cycle simulation system and method for geotechnical centrifugal model tests disclosed in Chinese patent document CN 118032629A, etc.). Even if the dry-wet cycle module is directly applied to the existing centrifugal model test device for pile foundation bearing characteristics, it is impossible to achieve non-stop operation of the geotechnical centrifuge throughout the entire process, including soil dry-wet cycles, pile foundation sinking, and static load tests, which is not conducive to improving the convenience of the test and the accuracy of the test data. At present, there is still a lack of suitable supporting centrifugal testing devices and methods for conducting centrifugal model test research on the evolution of the bearing and deformation characteristics of unsaturated soil pile foundations under the action of dry-wet cycles. Therefore, if a centrifugal testing device can be invented that can directly simulate the evolution of the bearing and deformation characteristics of unsaturated soil pile foundations during the dry-wet cycle process, and can realize non-stop operation throughout the entire test process including dry-wet cycle, pile sinking and static load tests, the test error can be significantly reduced, and the mechanical behavior of unsaturated soil pile foundations under the corresponding dry-wet cycle conditions in the actual environment can be more realistically restored, thereby providing more accurate test technical means for research in this field.

[0004] Therefore, providing a centrifugal test device that can directly simulate the bearing and deformation of pile foundations in unsaturated soil under the action of dry-wet cycles, and proposing a corresponding supporting centrifugal test operation method, are of great significance for solving the bottleneck of centrifugal test research on the bearing and deformation of pile foundations in unsaturated soil under the action of dry-wet cycles, effectively revealing the bearing and settlement deformation mechanism and its evolution law of pile foundations in unsaturated soil during the dry-wet cycle process, and then guiding and improving the design, calculation and testing of pile foundations in unsaturated soil. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a centrifugal test device and method for the bearing characteristics of unsaturated soil pile foundations under dry-wet cycles.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] According to one aspect of the present invention, a centrifugal test device for the bearing characteristics of unsaturated soil pile foundations under dry-wet cycles is provided, comprising a centrifugal control module, a centrifuge, a model box, a model pile, a dry-wet cycle module, a reaction module, a loading control module and a data acquisition module, wherein the model pile is installed in the unsaturated soil of the model box, the dry-wet cycle module and the reaction module are both installed on the model box, the loading control module is installed on the reaction module and connected to the model pile, the data acquisition module is installed in the model box, the model box is placed on the centrifuge, and the centrifugal control module is communicatively connected to the centrifuge, the dry-wet cycle module, the loading control module and the data acquisition module respectively.

[0008] As a preferred technical solution, the model box includes a drain outlet, a geotextile, a pebble layer and a model soil. The pebble layer is laid on the bottom of the model box, the geotextile is laid on the pebble layer, the model soil is filled in the model box and located on the geotextile, the drain outlet is installed in the pebble layer, and the model piles are installed in the model soil.

[0009] As an optimal technical solution, the dry-wet cycle module includes a heat conducting rod, a temperature sensor and a drying control cabinet. The heat conducting rod is installed in the model soil symmetrically and at equal intervals with the model pile as the axis. The temperature sensor is installed on the heat conducting rod at equal intervals. The drying control cabinet is respectively communicated with the centrifugal control module, the heat conducting rod and the temperature sensor.

[0010] As an optimal technical solution, the dry-wet cycle module also includes a sealed water tank, an automatic exhaust valve, a water pump, a water supply pipeline, a return pipeline, a humidification pipeline, a spray pipe and a humidification control cabinet. The water outlet end of the sealed water tank is connected to the water pumping end of the water pump, the water outlet end of the water pump is connected to the humidification pipeline through the water supply pipeline, the humidification pipeline is connected to the spray pipe, the spray pipes are installed at equal intervals in the model soil, the humidification pipeline is connected to the sealed water tank through the return pipeline, and the humidification control cabinet is connected to the centrifugal control module and the water pump respectively.

[0011] As an optimal technical solution, the reaction module includes an upper frame, a lower frame, a reaction column, a reaction beam and a slide rail. The lower frame is installed on the top of the model box, the upper frame is installed on the lower frame through the reaction column, the slide rail is installed on the upper frame, and the reaction beam is installed on the slide rail.

[0012] As a preferred technical solution, the loading control module includes a loading unit and a loading control cabinet. The loading unit includes a servo motor, a linear module, a force transmission column, a pile cap, a slide, a slide connection bracket, a force transmission column joint component, a fixed aluminum plate assembly and a movable connection block.

[0013] The force transmission column, pile cap, slide, slide connecting bracket and force transmission column joint component are all installed in the linear module, the pile cap is installed on the force transmission column, the force transmission column is installed on the force transmission column joint component, the force transmission column joint component is installed in the slide, the slide and the slide connecting bracket are connected, the servo motor is installed on the linear module, the servo motor and the loading control cabinet are communicatively connected, the linear module is installed on the fixed aluminum plate assembly, and the fixed aluminum plate assembly is installed on the reaction beam through a movable connecting block.

[0014] As a preferred technical solution, the data acquisition module includes a pressure sensor, a laser displacement sensor, a moisture sensor, a soil pressure gauge, a tensiometer, a strain gauge and an end resistance sensor. The pressure sensor is installed at the connection between the pile cap and the model pile, the laser displacement sensor is installed in the model box and close to the connection between the pile cap and the model pile, the moisture sensor, soil pressure gauge and tensiometer are all installed in the model soil, the soil pressure gauge and tensiometer are also installed on the model pile, and the strain gauge and end resistance sensor are both installed on the model pile.

[0015] As a preferred technical solution, the centrifuge control module includes a dedicated computer and a remote computer. The dedicated computer is respectively connected to the centrifuge, dry-wet cycle module, loading control module and data acquisition module. The dedicated computer is connected to the remote computer.

[0016] As a preferred technical solution, the centrifuge control module includes a wireless transceiver and a wired unit, and the wireless transceiver and the wired unit are respectively connected to the centrifuge, the dry-wet cycle module, the loading control module and the data acquisition module. The dedicated computer is respectively connected to the remote computer through the wireless transceiver and / or the wired unit.

[0017] According to another aspect of the present invention, there is provided a method for a centrifugal test device for bearing characteristics of unsaturated soil pile foundations under dry-wet cycles as described above, the method specifically comprising:

[0018] Step 1: Install the centrifugal test device;

[0019] Step 2: Take the soil from the site, dry it in the sun, crush it, add water and stir it according to the saturation of the experimental design to prepare unsaturated remolded soil;

[0020] Step 3: Fill the unsaturated soil into the model box and control its moisture content and compaction degree to the specified saturation degree;

[0021] Step 4: Make a model pile and position it in the unsaturated remolded soil of the model box, and connect the model pile to the loading control module;

[0022] Step 5: Install the assembled device on the centrifuge, start the test through the centrifuge control module, and set the rotation speed of the centrifuge to the preset speed to keep the centrifuge running;

[0023] Step 6: The centrifuge control module first controls the loading control module to sink the model pile, and collects data through the data acquisition module. After the pile sinking is completed, the centrifuge waits for a first preset time and keeps running.

[0024] Step 7: The centrifugal control module controls the loading control module to load the model pile step by step, maintaining the load for a second preset time each time until the pile top settlement of the model pile reaches a stable or predetermined deformation limit, and collecting data through the data acquisition module;

[0025] Step 8: Keep the centrifuge running, the centrifuge control module simulates the dry-wet cycle working condition of the unsaturated remolded soil in the model box through the dry-wet cycle module, and collects data through the data acquisition module;

[0026] Step 9: Repeat steps 5 to 8 above to obtain data under different working conditions.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention is provided with a dry-wet cycle module and a loading control module, which takes into account the influence of dry-wet cycle on the pile sinking, bearing and deformation characteristics of pile foundations in unsaturated soil. It can remotely and automatically control the drying and wetting of unsaturated soil and simulate various dry-wet cycle working conditions of unsaturated soil. Its loading control module can remotely carry out pile sinking and static load tests, realizing non-stop operation of the entire centrifugal test including dry-wet cycle, pile sinking and static load tests, which is conducive to the speed and accuracy of centrifugal tests, can significantly reduce test errors, and more realistically restore the mechanical behavior of unsaturated soil pile foundations under corresponding dry-wet cycle conditions in actual environments.

[0029] 2. The present invention is equipped with corresponding test methods, which can directly simulate the bearing and deformation of unsaturated soil pile foundations under various dry-wet cycle conditions such as different dry-wet cycle amplitudes, dry-wet cycle paths, dry-wet cycle durations, and dry-wet cycle numbers. It can also use high gravity acceleration in a shorter time to simulate the long-term effects of dry-wet cycle conditions on the bearing and deformation of unsaturated pile foundations, thereby realizing the analysis of the load-settlement characteristics, bearing characteristics and their evolution laws of existing piles under the action of dry-wet cycles, the development, accumulation and evolution laws of the ultimate bearing capacity with the number of dry-wet cycles, and the analysis of the pile sinking characteristics, load-settlement characteristics, bearing characteristics and their evolution laws of new piles under the action of dry-wet cycles.

[0030] 3. The heat conducting rod of the present invention adopts a porous tubular design, which combines heating and steam extraction functions, making it more conducive to drying the model soil and enabling uniform drying of soil at different depths. The equipped drying control cabinet and drying control software realize remote and precise automatic control of the drying operation time, temperature and other drying degree during the operation of the centrifuge, as well as temperature monitoring and protection.

[0031] 4. The present invention adopts components such as a sealed water tank, an automatic exhaust valve, a water pump, and a water supply pipeline and a return pipeline to solve the problems of water supply, recovery, and splashing under high centrifugal force, thereby realizing humidification operation during the operation of the centrifuge; the spray pipe realizes uniform humidification of soil at different depths; the water inlet at the top of the sealed water tank is tightly connected to the return pipeline, realizing the recycling of water in the water tank during the humidification process; its humidification control cabinet and humidification control software ensure uniform and stable water supply during the humidification process, and realize remote, precise, automated control, monitoring, and protection of the water supply time, water pressure, and flow rate of the humidification operation during the operation of the centrifuge.

[0032] 5. The reaction beam and the slide rail of the present invention are connected by bolts to ensure that when the reaction beam and the loading control module move along the corresponding slide rail during pile sinking positioning, the reserved bolt holes on the reaction beam and the loading control module can completely coincide with the reserved bolt holes on the corresponding slide rail, so that they are installed and fixed with bolt fasteners to prevent the reaction beam and the loading control module from sliding or shaking at will during the operation of the centrifuge, thereby achieving stable loading of the pile sinking and static load tests during the centrifuge test.

[0033] 6. The loading control cabinet and servo motor equipped in the loading control module of the present invention can remotely control the opening and closing of the servo motor and the vertical loading of the loading unit, realizing remote automated servo control of pile driving and static load tests during centrifugal testing.

[0034] 7. During the test, the present invention only needs to be installed in the hanging basket, and there is no need to install water tanks, water pumps, control cabinets and other equipment on the geotechnical centrifuge, thereby avoiding adverse effects such as damage and modification to the geotechnical centrifuge. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the overall structure of the device of the present invention;

[0036] Figure 2 A top view of the device of the present invention;

[0037] Figure 3 It is a structural diagram of the model box of the present invention;

[0038] Figure 4 Schematic diagram of the top section of the model box of the present invention;

[0039] Figure 5 This is a structural diagram of the dry-wet cycle module of the present invention;

[0040] Figure 6 It is a top view of II-4 of the present invention;

[0041] Figure 7 It is a top view of II-3 of the present invention;

[0042] Figure 8 It is a top view of II-2 of the present invention;

[0043] Figure 9 It is a top view of II-1 of the present invention;

[0044] Figure 10 This is a top view of II-0 of the present invention;

[0045] Figure 11 This is a connection diagram of the dry-wet cycle module of the present invention;

[0046] Figure 12 Schematic diagram of the top view of the connection of the dry-wet cycle module of the present invention;

[0047] Figure 13 It is a connection diagram of the drying process of the present invention;

[0048] Figure 14 Schematic diagram of the top view of the drying process of the present invention;

[0049] Figure 15 It is a connection diagram of the humidification process of the present invention;

[0050] Figure 16 Schematic diagram of the top view of the humidification process of the present invention;

[0051] Figure 17 A schematic diagram of the structure of the loading control module of the invention;

[0052] Figure 18 This is a schematic diagram of the installation of the data acquisition module of the present invention;

[0053] Figure 19 Schematic diagram of the installation of the model box and the centrifuge of the present invention;

[0054] Figure 20 Schematic diagram of control logic of the drying process of the present invention;

[0055] Figure 21 Schematic diagram of control logic of the humidification process of the present invention;

[0056] Figure 22 A control logic diagram of the loading control module of the present invention;

[0057] Figure 23 This is a test flow chart of the present invention;

[0058] 1. Model box; 11. Drainage outlet; 12. Geotextile; 13. Pebble layer; 14. Model soil; 2. Model pile;

[0059] 311. Thermal rod; 312. Temperature sensor; 313. Drying control cabinet; 321. Sealed water tank; 322. Automatic exhaust valve; 323. Water level gauge; 324. Water pressure gauge; 325. Flow meter; 326. Water pump; 327. Water pipe; 328. Ball valve; 329. Humidification control cabinet; 3210. Spray pipe; 3211. Reducer; 3212. Elbow; 3213. Tee; 3215. Steel bracket; 3216. Positioning hole;

[0060] 41. Upper frame; 42. Lower frame; 43. Reaction column; 44. Water pipe channel; 45. Cable channel; 46. Reaction beam; 47. Slide rail; 48. Bolt hole; 49. Fastener;

[0061] 51. Loading unit; 511. Servo motor; 512. Linear module; 513. Force transfer column; 514. Pile cap; 515. Slide; 516. Slide connecting bracket; 517. Force transfer column joint component; 518. Fixed aluminum plate assembly; 519. Mobile connecting block; 5110. Mobile slider; 52. Loading control cabinet;

[0062] 61. Pressure sensor; 62. Laser displacement sensor; 63. Moisture sensor; 64. Soil pressure gauge; 65. Tensiometer; 66. Strain gauge; 67. End resistance sensor;

[0063] 7. Expand the base plate; 8. Anchor bolts; 9. Remote computer; 91. Wireless transceiver; 10. Wires and cables; A. Connect to the centrifuge power channel; B. Connect to the centrifuge signal channel; C. Connect to the centrifuge data acquisition channel; ⊙, perpendicular to the paper and outward; Perpendicular to the paper surface and inward; I, test area; II, electromechanical equipment control area; II-0, bottom plate; II-1, first platform; II-2, second platform; II-3, third platform; II-4, fourth platform; T, centrifuge; T-1, rotating arm; T-2, rotating shaft; T-3, counterweight; T-4, hanging basket. DETAILED DESCRIPTION

[0064] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0065] Example 1

[0066] like Figure 1-Figure 22 As shown, a centrifugal test device for the bearing characteristics of unsaturated soil pile foundations under dry-wet cycles includes a centrifugal control module, a centrifuge T, a model box 1, a model pile 2, a dry-wet cycle module, a reaction module, a loading control module and a data acquisition module. The model pile 2 is installed in the unsaturated soil of the model box 1, the dry-wet cycle module and the reaction module are both installed on the model box 1, the loading control module is installed on the reaction module and connected to the model pile 2, the data acquisition module is installed in the model box 1, and the model box 1 is placed on the centrifuge T. The centrifugal control module is communicatively connected to the centrifuge T, the dry-wet cycle module, the loading control module and the data acquisition module respectively.

[0067] In this embodiment, the centrifugal test apparatus is a single unit, with its interior divided into a test area I and an electromechanical equipment control area II by the side walls of the model box 1 and the upper frame 41. The apparatus includes a centrifugal control module, a model box 1, a model pile 2, a dry-wet cycle module, a reaction force module, a loading control module, a data acquisition module, and associated supporting wires and cables 10. The centrifugal control module serves as the overall control, ensuring the orderly conduct of the test, while the wires and cables 10 provide wired information transmission or power supply.

[0068] The overall concept of the present invention is as follows:

[0069] The reaction module is fixed to the upper part of the model box 1, and a dry-wet cycle module is arranged inside the model box 1; the interior is filled with model soil 14, and components for drying and wetting, such as a heat conducting rod 311, a temperature sensor 312, and a spray pipe 3210, are buried, as well as sensors such as a moisture sensor 63, an earth pressure gauge 64, and a tensiometer 65; the model pile 2 is inserted into the model soil 14 in the model box 1, and the model pile 2 is equipped with sensors such as a pressure sensor 61, a strain gauge 66, an earth pressure gauge 64, a tensiometer 65, and an end resistance sensor 67. The pile top of the model pile 2 can be installed together with the pile cap 514 of the loading unit 51;

[0070] The dry-wet cycle module includes two components: a drying system and a wetting system. It is equipped with a drying control cabinet 313 and drying control software, and a wetting control cabinet 329 and wetting control software. These are used for remote automatic control of the drying and wetting of the model soil 14, respectively. The module can simulate various dry-wet cycle conditions, including different dry-wet cycle amplitudes, dry-wet cycle paths, dry-wet cycle durations, and dry-wet cycle times.

[0071] The reaction module is divided into two layers, the upper frame 41 is used to install the loading unit 51, and the lower frame 42 contains a reserved water pipe channel 44 and a reserved cable channel 45, which are used to lay the water pipeline of the humidification system and the cable line of the drying system respectively;

[0072] The loading control module includes a loading unit 51 and a loading control cabinet 52, and is equipped with loading control software for providing vertical loads for the pile driving and static load centrifugal tests of the model pile 2, and realizing remote automatic servo control of the pile driving and static load;

[0073] The data acquisition module includes various types of sensors such as pressure sensor 61, laser displacement sensor 62, moisture sensor 63, soil pressure gauge 64, tensiometer 65, strain gauge 66, end resistance sensor 67, etc., and is equipped with data acquisition software for remote real-time monitoring and analysis of the data of the sensors in the model soil 14 and model pile 2 during the centrifugal test; the remote computer 9 is respectively installed with drying control software, wetting control software, loading control software and data acquisition software, which are used to realize non-stop operation of the geotechnical centrifuge throughout the entire test process, including soil drying and wetting cycles, pile foundation sinking, and static load tests.

[0074] In addition, the test area I mainly includes a model box 1, a model pile 2, a drying system, a humidification system, a humidification pipeline, a reaction module 4, a loading unit 51, and a data acquisition module, which are used to carry out pile sinking and static load centrifugal tests of unsaturated soil dry-wet cycle and its model pile 2; the electromechanical equipment control area II is provided with a base plate II-0 and four platforms including the first platform II-1, the second platform II-2, the third platform II-3, and the fourth platform II-4, which are respectively equipped with a steel sealed water tank 321, a water pump 326, a humidification control cabinet 329, a drying control cabinet 313 and a loading control cabinet 52, which are used to provide power supply, water supply, control equipment and part of the water supply pipeline and return pipeline for the humidification system, provide power supply and control equipment for the drying system, and provide power supply and servo control equipment for the loading unit 51, thereby monitoring, adjusting, automatically controlling and managing the electromechanical equipment of the dry-wet cycle module and the loading control module. The bottom plate II-0 of the electromechanical equipment control area II is at the same height as the bottom plate of the model box 1 of the test area I; the third platform II-3 is at the same height as the lower frame 42 of the test area I; and the fourth platform II-4 is at the same height as the upper frame 41 of the test area I. The bottom plate II-0 and each platform are made of high-strength materials such as aluminum alloy or stainless steel plates to withstand high centrifugal force requirements and avoid mechanical stress damage. The first platform II-1, the second platform II-2, and the third platform II-3 are all equipped with holes for the vertical passage of the water supply and return pipes of the humidification system. The "⊙" symbol in the figure represents that the direction of the water supply pipe of the humidification system is perpendicular to the paper and outward; The symbol represents that the water supply pipeline of the humidification system runs perpendicular to the paper surface and inward.

[0075] The model box 1 includes a drain outlet 11, a geotextile 12, a pebble layer 13 and a model soil 14. The pebble layer 13 is laid at the bottom of the model box 1, the geotextile 12 is laid on the pebble layer 13, the model soil 14 is filled in the model box 1 and located on the geotextile 12, the drain outlet 11 is installed in the pebble layer 13, and the model pile 2 is installed in the model soil 14.

[0076] In this embodiment, the centrifugal test apparatus adopts an overall square design, constructed from an aluminum alloy housing with a partially transparent acrylic observation window, balancing strength and visual observation requirements. In this embodiment, the model soil 14 filled within the model box 1 is unsaturated remolded soil. A thermal conductive rod 311 and a temperature sensor 312 are embedded in the model soil 14 to monitor the drying and drying status of the model soil 14. A steel spray pipe 3210 and a moisture sensor 63 are also embedded in the model soil 14 to monitor the wetting and wetting status of the model soil 14. Furthermore, sensors such as a tensiometer 65 and an earth pressure gauge 64 are embedded in the model soil to monitor the hydraulic state of the model soil during the dry-wet cycle, the penetration of the model pile 2, and the static load centrifugal test.

[0077] The model box 1 has a geotextile 12 and a pebble layer 13 laid below the model soil 14. The pebble layer 13 is covered with the geotextile 12, and the top of the geotextile 12 is filled with the model soil 14. The bottom of the model box 1 is provided with a plurality of drain ports 11, and the drain ports 11 are equipped with drain valves.

[0078] The wet-dry cycle module includes a heat conducting rod 311, a temperature sensor 312 and a drying control cabinet 313. The heat conducting rod 311 is installed in the model soil 14 symmetrically and at equal intervals with the model pile 2 as the axis. The temperature sensors 312 are installed on the heat conducting rod 311 at equal intervals. The drying control cabinet 313 is respectively communicated with the centrifugal control module, the heat conducting rod 311 and the temperature sensor 312.

[0079] In this embodiment, the dry-wet cycle module consists of a drying system and a humidification system. The drying system includes a heat conducting rod 311, a temperature sensor 312, a drying control cabinet 313, and drying control software. The components of the drying system are located in the electromechanical equipment control area II and the test area I, respectively. The drying control cabinet 313 is located in the electromechanical equipment control area II, while the heat conducting rod 311 and temperature sensor 312 are located in the test area I. The heat-conducting rod 311 adopts a porous tubular design and has the functions of heating and steam extraction. It is buried in the model soil 14 in multiple rows with equal spacing and axisymmetry along the model box 1, and the model soil 14 is dried by electric heating; the temperature sensor 312 is installed at different depths on the surface of the heat-conducting rod 311 and in the soil near it, and is used to monitor and feedback the temperature of the heat-conducting rod 311 and the soil during the drying process, and transmit the signal to the drying control cabinet 313; the wires and cables 10 of the heat-conducting rod 311 and the temperature sensor 312 are connected to the drying control cabinet 313 through the reserved cable channel 45 of the lower frame 42, which is used to accurately control the drying of the model soil 14.

[0080] The drying control software, installed on a remote computer 9, is used to remotely control the opening and closing of the heat-conducting rods 311 and the degree of drying of the model soil 14 during the centrifugal test. The drying circuits connecting all rows of heat-conducting rods 311 in test area I are arranged in a single-threaded, zigzag pattern above the model box 1 through reserved cable channels 45 on the left and right side beams at the bottom of the lower frame 42, providing unified power supply control for all heat-conducting rods 311. Furthermore, the drying control cabinet 313 is installed on the second platform II-2 of the electromechanical equipment control area II. The base plate of the drying control cabinet 313 utilizes an enlarged base plate 7, which is fixed to the second platform II-2 via anchor bolts 8.

[0081] The drying control cabinet 313's input is connected to the centrifuge's power channel A, and its output is connected to the centrifuge's signal channel B, which then provides feedback to the drying control software on the remote computer 9. The drying control cabinet 313 includes modules such as a power supply and distribution module, a core control module, a signal processing and acquisition module, a communication and networking module, and a protection and auxiliary module. These modules are responsible for precise control of the heating of the heat conducting rod 311 during the drying process, as well as temperature monitoring and protection functions.

[0082] The dry-wet cycle module also includes a sealed water tank 321, an automatic exhaust valve 322, a water pump 326, a water supply pipeline, a return pipeline, a humidification pipeline, a spray pipe 3210 and a humidification control cabinet 329. The water outlet end of the sealed water tank 321 is connected to the water pump end of the water pump 326, and the water outlet end of the water pump 326 is connected to the humidification pipeline through the water supply pipeline. The humidification pipeline is connected to the spray pipe 3210, and the spray pipe 3210 is installed at equal intervals in the model soil 14. The humidification pipeline is connected to the sealed water tank 321 through the return pipeline. The humidification control cabinet 329 is connected to the centrifugal control module and the water pump 326 respectively.

[0083] In this embodiment, the humidification system includes components such as a steel sealed water tank 321, a water pump 326, a steel water pipe 327, a ball valve 328, a humidification control cabinet 329, a steel spray pipe 3210, an automatic exhaust valve 322, a steel bracket 3215, and measuring instruments such as a water level gauge 323, a water pressure gauge 324, and a flow meter 325, humidification control software, and matching joints and holes such as a reducer 3211, an elbow 3212, a tee joint 3213, and a reserved positioning hole 3216. The components of the humidification system are respectively arranged in the electromechanical equipment control area II and the test area I, among which the steel sealed water tank 321, water pump 326, humidification control cabinet 329, part of the steel water pipe 327, part of the steel bracket 3215, water level gauge 323, water pressure gauge 324, flow meter 325 and other measuring instruments and accessories such as ball valve 328, automatic exhaust valve 322, reducer 3211, part of the elbow 3212 are arranged and installed in the electromechanical equipment control area II; part of the steel water pipe 327, part of the steel bracket 3215, steel spray pipe 3210, three-way joint 3213, and part of the elbow 3212 are arranged in the test area I.

[0084] A sealed steel water tank 321 provides water for the humidification system. Its outlet is connected to the pumping end of a water pump 326 via a steel water pipe 327. An automatic air vent valve 322 is installed at the top of the tank to prevent pressure fluctuations and gas accumulation within the model box 1 from affecting the water supply. A steel water pipe 327 is installed at the outlet of the water pump 326, providing a water supply line to the model box 1 in test area 1. A ball valve 328 is also installed to open and close the water supply line and control the water flow. By arranging humidification pipelines in series at equal intervals along the model box 1 in the reserved water pipe channels 44 on the left and right side beams at the top of the lower frame 42 of the test area I, multiple rows of steel spray pipes 3210 are buried axially symmetrically at equal intervals in the model soil 14 to humidify the model soil 14; and the water in the humidification pipeline that does not flow into the steel spray pipes 3210 is re-injected into the steel sealed water tank 321 through the return pipe for reuse.

[0085] Measuring instruments such as a water level gauge 323, a water pressure gauge 324, and a flow meter 325 are installed in the sealed steel water tank 321, water pump 326, and the water supply and return lines. The electrical wiring and cables 10 for the water pump 326, water level gauge 323, water pressure gauge 324, and flow meter 325 are connected to the humidification control cabinet 329 to precisely control the humidification of the model soil 14. Humidification control software is installed on a remote computer 9 to remotely control the opening and closing of the water pump 326 and the degree of humidification of the model soil 14 during the centrifugal test. Furthermore, the sealed steel water tank 321 and water pump 326 are both mounted on the baseplate II-0 of the electromechanical equipment control area II. The baseplates of both the sealed steel water tank 321 and water pump 326 utilize an enlarged baseplate 7, and both are secured to the baseplate II-0 of the electromechanical equipment control area II via anchor bolts 8. The humidification control cabinet 329 is installed on the first platform II-1 of the electromechanical equipment control area II. The bottom plate of the humidification control cabinet 329 also adopts the enlarged bottom plate 7, which is fixed to the first platform II-1 through anchor bolts 8.

[0086] The input of the humidification control cabinet 329 is connected to the centrifuge power channel A, and the output is connected to the centrifuge signal channel B, which in turn provides feedback to the humidification control software on the remote computer 9. The water pump 326 adjusts the water delivery frequency via a frequency converter within the humidification control cabinet 329, enabling the water pump 326 to precisely adjust the water delivery pressure and flow rate. The water pump 326 draws water from the sealed steel water tank 321, pressurizes the water, and delivers it at a stable pressure. This provides the water pump 326 with a high-precision voltage stabilization function, ensuring stable water supply pressure and flow rate. The entire water supply pipeline of the humidification system can be divided into three sections: water supply pipeline, humidification pipeline and return pipeline. The humidification pipeline is located in the test area I, and its water inlet end is located at the water inlet of the reserved water pipe channel 44 on the left beam at the top of the lower frame 42, and its water outlet end is located at the water outlet of the reserved water pipe channel 44 on the opposite side of the left beam; the water supply pipeline and the return pipeline are both located in the electromechanical equipment control area II, wherein the water supply pipeline runs from the water outlet of the steel sealed water tank 321 to the water inlet end of the humidification pipeline; the return pipeline runs from the water outlet end of the humidification pipeline to the water inlet of the steel sealed water tank 321.

[0087] The water supply pipeline, humidification pipeline, return water pipeline, and other water pipelines are all connected by steel water pipes 327. The diameter change is connected by a reducer 3211, the turning point is connected by an elbow 3212, and the diversion point is connected by a tee joint 3213. Specifically, the water supply pipeline is laid along the horizontal plane for a distance on the bottom plate II-0 of the electromechanical equipment control area II. It then changes from the output end of the water pump 326 to the vertical plane through the elbow 3212. The main body of the water supply pipeline vertically passes through the first platform II-1, the second platform II-2, and the third platform II-3, and then changes to a horizontal plane to the water inlet of the reserved water pipe channel 44 on the top left beam of the lower frame 42 to connect to the humidification pipeline. The humidification pipeline of the test area is arranged above the lower frame 42 along the horizontal plane through the reserved water pipe channels 44 of the left and right side beams at the top of the lower frame 42, and is arranged back and forth in a single-threaded broken line. It is connected to the return water pipeline at the outlet of the reserved water pipe channel 44 on the left beam on the opposite side. The steel water pipe 327 at the broken line of the humidification pipeline is connected with an elbow 3212.

[0088] The return water pipeline runs horizontally from the outlet of the humidification pipeline to the third platform II-3, then transitions to a vertical layout after passing through an elbow 3212. Its main body vertically passes through the third platform II-3, the second platform II-2, and the first platform II-1, where it is sealed and installed with the water inlet at the top of the steel sealed water tank 321. Furthermore, steel brackets 3215 are installed simultaneously above the left and right side beams at the top of the third platform II-3 of the electromechanical equipment control area II and the lower frame 42 of the test area I, along the horizontal layout of the water supply pipeline, humidification pipeline, and return water pipeline. These brackets are used to support and secure these horizontally arranged water supply, humidification, and return water pipelines to prevent them from shaking, falling off, or leaking under the high centrifugal forces during centrifuge operation. The steel brackets 3215 above the lower frame 42 of the test area I are evenly provided with reserved positioning holes 3216 for positioning and installing the steel spray pipe 3210, so that the humidification pipeline installed in the steel bracket 3215 is connected to the steel spray pipe 3210 below the reserved positioning hole 3216 through the three-way joint 3213.

[0089] The steel brackets 3215 of the third platform II-3 of the electromechanical equipment control area II are pre-reserved with holes for the vertical passage of water supply and return pipes. The size and location of these holes match those of the pre-reserved holes on the third platform II-3. The steel spray pipes 3210 are embedded in the model soil 14 in multiple rows, symmetrically and evenly spaced. The steel spray pipes 3210 are equipped with spray holes arranged around their surfaces to moisten the model soil 14. These holes are fitted with fine filters to prevent model soil particles from entering the holes and clogging the steel spray pipes 3210. The tops of the steel spray pipes 3210 are connected to the humidification pipelines located above the lower frame 42 via a tee joint 3213. In addition, the humidification control cabinet 329 also includes modules such as power supply and distribution module, core control module, signal processing and acquisition module, communication and network module, protection and auxiliary module, etc., which are used for precise control, monitoring and protection of the water delivery pressure and flow of the water pump 326 during the humidification process.

[0090] The reaction module includes an upper frame 41, a lower frame 42, a reaction column 43, a reaction beam 46 and a slide rail 47. The lower frame 42 is installed on the top of the model box 1, the upper frame 41 is installed on the lower frame 42 through the reaction column 43, the slide rail 47 is installed on the upper frame 41, and the reaction beam 46 is installed on the slide rail 47.

[0091] The loading control module includes a loading unit 51 and a loading control cabinet 52. The loading unit 51 includes a servo motor 511, a linear module 512, a force transmission column 513, a pile cap 514, a slide 515, a slide connecting bracket 516, a force transmission column joint component 517, a fixed aluminum plate assembly 518 and a movable connecting block 519.

[0092] The force transmission column 513, pile cap 514, slide 515, slide connecting bracket 516 and force transmission column joint component 517 are all installed in the linear module 512, the pile cap 514 is installed on the force transmission column 513, the force transmission column 513 is installed on the force transmission column joint component 517, the force transmission column joint component 517 is installed in the slide 515, the slide 515 is connected to the slide connecting bracket 516, the servo motor 511 is installed on the linear module 512, the servo motor 511 is communicatively connected to the loading control cabinet 52, the linear module 512 is installed on the fixed aluminum plate assembly 518, and the fixed aluminum plate assembly 518 is installed on the reaction beam 46 through the movable connecting block 519.

[0093] The data acquisition module includes a pressure sensor 61, a laser displacement sensor 62, a moisture sensor 63, an earth pressure gauge 64, a tension gauge 65, a strain gauge 66 and an end resistance sensor 67. The pressure sensor 61 is installed at the connection between the pile cap 514 and the model pile 2. The laser displacement sensor 62 is installed in the model box 1 and close to the connection between the pile cap 514 and the model pile 2. The moisture sensor 63, earth pressure gauge 64 and tension gauge 65 are all installed in the model soil 14. The earth pressure gauge 64 and tension gauge 65 are also installed on the model pile 2. The strain gauge 66 and end resistance sensor 67 are both installed on the model pile 2.

[0094] In this embodiment, the reaction module is located in the test area I and is fixedly connected to the top of the model box 1 through the reaction column 43. It can be divided into an upper frame 41 and a lower frame 42. On the left and right side beams at the bottom and top of the lower frame 42, there are respectively provided a reserved cable channel 45 and a reserved water pipe channel 44 for the wiring of the drying system and the humidification system. In addition, the present invention includes various types of beams, including a reaction beam 46 and a strip beam. Slide rails 47 are installed on the middle and bottom of the front side of the reaction beam 46 and on the strip beam above the reaction beam 46 for adjusting the position of the loading unit 51 on the reaction beam 46, so that the position of the pile can be determined together.

[0095] The fixed aluminum plate assembly 518 is specifically installed on the strip crossbeam on the upper part of the reaction beam 46. In addition, a movable slider 5110 is installed at the corresponding position between the fixed aluminum plate assembly 518 and the middle part of the front side of the reaction beam 46 and the lower slide rail 47, which can move synchronously on its slide rail 47.

[0096] Slide rails 47 are installed along the left and right side beams at the top of the upper frame 41. Pre-set bolt holes 48 of identical size and shape are evenly spaced on the slide rails 47. A reaction beam 46 is installed along the front and rear crossbeams on the slide rails 47. Support legs are installed at each end of the reaction beam 46, allowing the reaction beam 46 to move on the left and right side beam slide rails 47. The support legs also contain pre-set bolt holes 48 of identical size and shape, corresponding to the bolt holes on the left and right side beam slide rails 47. This ensures that when the reaction beam 46 moves on the left and right side beam slide rails 47, the support legs completely align with the pre-set bolt holes 48 on the slide rails 47. Bolt fasteners 49 are then used to secure the reaction beam 46, preventing it from sliding or shaking during centrifuge operation.

[0097] In this embodiment, a steel bar crossbeam is mounted on the upper portion of the reaction beam 46 along the direction of the reaction beam 46. A slide rail 47 is mounted on the front side of the bar crossbeam along the direction of the reaction beam 46. Similarly, slide rails 47 are mounted on the front side of the middle and bottom portions of the reaction beam 46 along the direction of the reaction beam 46. Pre-set bolt holes 48 of identical size and shape are evenly spaced on the front sides of the three slide rails 47.

[0098] The loading unit 51 is installed on the front side of the reaction beam 46, corresponding to the three slide rails 47 respectively. The back of the loading unit 51 is respectively installed with a movable connecting block 519 that can move along the front side slide rail 47 of the strip beam, a movable slider 5110 that can move along the middle front side slide rail 47 of the reaction beam 46, and a movable slider 5110 that moves along the front side slide rail at the bottom of the reaction beam.

[0099] In this embodiment, the loading control module includes a loading unit 51, a loading control cabinet 52, and loading control software. The loading unit 51 mainly includes a servo motor 511, a linear module 512, a force transmission column 513, a pile cap 514, a slide connecting bracket 516, and other pile-pressing components. The front of the loading unit 51 is equipped with a linear module 512 that can move vertically. The front of the linear module 512 is equipped with a slide connecting bracket 516, a force transmission column 513, a pile cap 514, and other pile-pressing components. The rear is equipped with a linear module fixing aluminum plate assembly 518, which is mounted on the bar beam via the movable connecting block 519 to support and fix the linear module 512 and the entire loading unit 51.

[0100] The loading unit 51, together with the linear module 512 and the pile driving assembly, is installed on the strip beam through the upper movable connecting block 519, so that the movable connecting block 519 can move left and right along the front side slide rail 47 of the strip beam, and at the same time drive the loading unit 51 to move synchronously on the front side slide rails 47 in the middle and bottom of the reaction beam 46 through the movable sliders 5110 at the two lower positions. Similarly, on the front side of the module-fixing aluminum plate assembly 518, at positions corresponding to the three slide rails 47, namely the front side slide rail 47 of the strip crossbeam, the middle portion of the reaction beam 46, and the bottom front side slide rail 47, respectively, reserved bolt holes 48 of exactly the same size and shape as their bolt holes are arranged. This ensures that when the loading unit 51 moves synchronously left and right on the three slide rails 47, the reserved bolt holes 48 on the module-fixing aluminum plate assembly 518 can completely overlap with the reserved bolt holes 48 on the three slide rails 47, thereby being installed and fixed with bolt fasteners 49, preventing the loading unit 51 from sliding or shaking during operation of the centrifuge. The loading unit 51 is driven vertically by a linear module 512 driven by a servo motor 511.

[0101] The slide connecting bracket 516 is mounted on the slide 515 of the linear module 512. The slide connecting bracket 516 includes a force transmission column joint member 517, which is mounted to the top of the force transmission column 513 through a reserved bolt hole 48. A pile cap 514 is mounted at the bottom of the force transmission column 513. The bottom end of the pile cap 514 is mounted to the top of the model pile 2 via a pressure sensor 61.

[0102] In this embodiment, the laser displacement sensor 62 is installed at the top of the lower frame 42 near the pile cap 514. The pile driving assembly is used together with the laser displacement sensor 62 and the pressure sensor 61 for pile penetration and static load testing of the pile foundation. The wires and cables 10 of the servo motor 511 are connected to the loading control cabinet 52, which controls the opening and closing of the servo motor 511 to servo control the loading unit 51. The loading control software is installed on the remote computer 9 and is used to remotely control the opening and closing of the servo motor 511 and the vertical loading of the loading unit 51 during the centrifugal test. The loading control cabinet 52 is installed on the fourth platform II-4 of the electromechanical equipment control area II. The bottom plate of the loading control cabinet 52 also adopts an enlarged bottom plate 7, which is specifically fixed to the fourth platform II-4 by anchor bolts 8. The input end of the loading control cabinet 52 is connected to the centrifuge power channel A, and the output end is connected to the centrifuge signal channel B, which is then fed back to the loading control software of the remote computer 9.

[0103] Similarly, the loading control cabinet 52 also includes modules such as a power supply and distribution module, a core control module, a signal processing and acquisition module, a communication and network module, and a protection and auxiliary module, which are used to accurately control the opening and closing of the servo motor 511 during the operation of the centrifuge, thereby realizing remote automatic control of pile penetration and static load tests without stopping the centrifuge.

[0104] In this embodiment, the model pile 2 is equipped with a number of strain gauges 66, soil pressure gauges 64, tensiometers 65, and other sensors along different sections of the pile body. These sensors are used to monitor the strain distribution of the model pile 2 and the soil pressure and suction distribution in the surrounding soil during the pile driving and static load centrifugal tests. A tip resistance sensor 67 is installed at the end of the model pile 2 to monitor the tip resistance of the model pile 2 during the centrifugal test. A pressure sensor 61 is installed at the top of the model pile 2 and is installed together with the pile cap 514 of the loading device 51. A laser displacement sensor 62 is installed nearby to monitor the pile top load, pile top axial force, and settlement of the model pile 2 during the pile driving and static load centrifugal tests.

[0105] The data acquisition module primarily includes sensors such as a pressure sensor 61, a laser displacement sensor 62, a moisture sensor 63, an earth pressure gauge 64, a tensiometer 65, a strain gauge 66, and an end resistance sensor 67, as well as data acquisition software. These sensors are connected to the centrifuge's data acquisition channel C. The data acquisition software, installed on the geotechnical centrifuge's dedicated computer, monitors and stores sensor data from the dry-wet cycle of the model soil 14, as well as the pile driving and static load tests of the model pile 2, in real time during the centrifuge test. Alternatively, a wireless transmission module can be installed, allowing remote control via a two-way wireless transceiver 91 from the data acquisition software installed on a remote computer 9. The data acquisition software can provide real-time data tables and automatically plot curves. This data acquisition software enables remote, real-time acquisition, storage, and visualization of data monitored by the data acquisition module's sensors on a computer.

[0106] The centrifuge control module includes a dedicated computer and a remote computer 9. The dedicated computer is respectively connected to the centrifuge T, the dry-wet cycle module, the loading control module and the data acquisition module. The dedicated computer is connected to the remote computer 9.

[0107] The centrifuge control module includes a wireless transceiver 91 and a wired unit, and the wireless transceiver 91 and the wired unit are respectively connected to the centrifuge T, the dry-wet cycle module, the loading control module and the data acquisition module. The dedicated computer is respectively connected to the remote computer 9 through the wireless transceiver 91 and the wired unit.

[0108] In this embodiment, the software installed on the remote computer 9 provides an operation interface, displays system status, parameter settings, and fault information, facilitates human-computer interaction, and facilitates operator monitoring and adjustment control. If the remote computer 9 is a dedicated computer for the geotechnical centrifuge, it can control the operation of the geotechnical centrifuge while performing drying and wetting control, pile driving and loading servo control, and test data collection through the centrifuge signal channel B or wireless transmission channel and centrifuge data acquisition channel C. If the remote computer 9 is not a dedicated computer for the geotechnical centrifuge, it must be equipped with a dedicated computer for the geotechnical centrifuge, which controls the operation of the centrifuge and the collection of sensor data from the data acquisition module. The remote computer 9 is then used to control the drying system, wetting system, loading control module, or data acquisition module through a two-way wireless transceiver 91.

[0109] Wireless transceivers 91 can be installed on the drying, humidifying, and loading control cabinets respectively and communicated with the remote computer 9. The remote computer 9 directly controls the dry-wet cycle module and the loading control module to perform dry-wet cycle and pile sinking and loading operations, and wirelessly controls the centrifuge dedicated computer to control the operation of the centrifuge T and collect test data. Alternatively, only one wireless transmission module can be set, and the drying, humidifying, and loading control cabinets all transmit data through the same wireless transmission module.

[0110] Data can be transmitted in wired and / or wireless ways, that is, it can be transmitted in wired and wireless ways; it can also be transmitted in wireless or wired ways. Depending on the actual situation, only one of the ways can be used.

[0111] In this embodiment, the centrifugal test device is used in conjunction with the geotechnical centrifuge T. Figure 19 As shown, the geotechnical centrifuge T includes a rotating arm T-1, a rotating shaft T-2, a counterweight T-3, a hanging basket T-4, etc. The centrifuge test device is installed in the hanging basket T-4 of the geotechnical centrifuge T to perform geotechnical centrifuge tests.

[0112] The present embodiment involves a centrifugal testing device for simulating the bearing and deformation of unsaturated soil pile foundations under the action of dry-wet cycles, which takes into account the influence of dry-wet cycles on the pile sinking, bearing and deformation characteristics of pile foundations in unsaturated soil. Its drying system and wetting system can remotely and automatically control the drying and wetting of unsaturated soil, and simulate various dry-wet cycle working conditions of unsaturated soil. Its loading control system can remotely carry out pile sinking and static load tests, realizing non-stop operation of the entire centrifugal test, including dry-wet cycles, pile sinking and static load tests, which is conducive to the speed and accuracy of centrifugal tests, can significantly reduce test errors, and more realistically restore the mechanical behavior of unsaturated soil pile foundations under corresponding dry-wet cycle conditions in actual environments, overcoming the defects and shortcomings of existing centrifugal testing devices, thereby providing more accurate test technical means for research in this field. At the same time, this centrifuge testing device and method address the bottleneck of centrifuge testing research on the bearing and deformation of unsaturated soil pile foundations under the action of dry-wet cycles. It can more accurately simulate the complex working conditions of existing and new piles under various dry-wet cycles in actual projects, conveniently conducting centrifuge testing on the bearing and deformation of unsaturated soil pile foundations under dry-wet cycles, and has excellent application and promotion value. This centrifuge testing device and method are of great significance for effectively revealing the bearing and settlement deformation mechanisms and evolution laws of unsaturated soil pile foundations during dry-wet cycles, and thus guiding and improving the design, calculation, and testing of pile foundations in unsaturated soils.

[0113] Example 2

[0114] like Figure 23 As shown, a method for a centrifugal test device for bearing characteristics of unsaturated soil pile foundations under dry-wet cycles is characterized in that the method specifically includes:

[0115] Step 1: Install the centrifugal test device;

[0116] Step 2: Take the soil from the site, dry it in the sun, crush it, add water and stir it according to the saturation of the experimental design to prepare unsaturated remolded soil;

[0117] Step 3: Fill the unsaturated soil into the model box 1 and control its moisture content and compaction degree to a specified saturation degree;

[0118] Step 4: Make a model pile 2 and position it in the unsaturated remolded soil of the model box 1, and then connect the model pile 2 to the loading control module;

[0119] Step 5: Install the assembled device on the centrifuge T, start the test through the centrifuge control module, and set the rotation speed of the centrifuge T to the preset speed to keep the centrifuge T running;

[0120] Step 6: The centrifuge control module first sinks the model pile 2 by controlling the loading control module, and collects data through the data acquisition module. After the pile sinking is completed, it waits for a first preset time and keeps the centrifuge T running.

[0121] Step 7: The centrifugal control module controls the loading control module to load the model pile 2 step by step, maintaining the load for a second preset time each time until the pile top settlement of the model pile 2 reaches a stable or predetermined deformation limit, and collects data through the data acquisition module;

[0122] Step 8: Keep the centrifuge T running. The centrifuge control module simulates the dry-wet cycle working condition of the unsaturated remolded soil in the model box 1 through the dry-wet cycle module, and collects data through the data acquisition module.

[0123] Step 9: Repeat steps 5 to 8 above to obtain data under different working conditions.

[0124] In this embodiment, the specific steps of the method are as follows:

[0125] S1: Centrifugal test apparatus equipment and piping installation and pre-test preparation. Install and lay out the steel sealed water tank 321, water pump 326, steel bracket 3215, the water pipeline for the dry-wet cycle module, the drying control cabinet 313, the humidification control cabinet 329, the loading control cabinet 52, and other equipment components, as well as measuring instruments such as the water level gauge 323, water pressure gauge 324, and flow meter 325. Connect the relevant wires and cables 10, connect the water pump 326, water level gauge 323, water pressure gauge 324, flow meter 325, and other equipment to the humidification control cabinet 329, connect the servo motor 511 to the loading control cabinet 52, fill the water tank with water, debug the equipment, and prepare for use.

[0126] S2: Prepare model soil 14. Take the on-site soil, dry it, crush it, add water and stir it according to the experimental design saturation to prepare unsaturated remolded soil.

[0127] S3: Fill the model box 1. The model soil 14 is filled and compacted in layers, and the moisture content and degree of compaction are controlled to a specified saturation. During the filling process, multiple rows of heat conducting rods 311 and steel spray pipes 3210 are pre-buried and installed at equal intervals along the model box 1. Sensors such as temperature sensors 312, moisture sensors 63, soil pressure gauges 64, and tensiometers 65 are also buried. The heat conducting rods 311 and temperature sensors 312 are connected to the drying control cabinet 313.

[0128] S4: Make a model pile 2, attach the strain gauge 66, and install sensors such as the soil pressure gauge 64, the tensiometer 65, and the end resistance sensor 67.

[0129] S5: Pile Positioning. After determining the pile sinking position, the reaction beam 46 and loading unit 51 are moved along the slide rails 47 to the target positions and secured with bolts 49. The top of the model pile 2 is assembled with the pile cap 514 of the loading unit 51. Sensors such as the pressure sensor 61 and laser displacement sensor 62 are also installed.

[0130] S6: Place the centrifugal test device in the basket and start the centrifugal test. Install the centrifugal test device in the hanging basket T-4 of the geotechnical centrifuge T. Install the counterweight T-3 on the geotechnical centrifuge T. Connect the input of each control cabinet to the centrifuge power channel A and the output to the centrifuge signal channel B. Connect the pressure sensor 61, laser displacement sensor 62, moisture sensor 63, soil pressure gauge 64, tensiometer 65, strain gauge 66, end resistance sensor 67, and other sensors to the centrifuge data acquisition channel C. Open the humidification system ball valve 328, close the drain port 11 of the model box 1, start the geotechnical centrifuge T, and use the dedicated computer for the geotechnical centrifuge T to accelerate the geotechnical centrifuge T to the target acceleration ng, and keep the centrifuge running.

[0131] S7: Pile driving. Loading control software on the remote computer 9 remotely controls the loading unit 51 to perform the pile driving operation, while data acquisition software remotely monitors the sensor data from the data acquisition module in real time. After the pile driving operation is complete, a waiting period is maintained, with the centrifuge T continuously running, to allow for rebalancing of the pile-soil stresses.

[0132] S8: Static Load Test. Using the loading control software on the remote computer 9, the loading unit 51 is remotely controlled to perform step-by-step loading, maintaining the load for a period of time each time until the pile top settlement reaches a stable or predetermined deformation limit. Sensor data is monitored during the test, and load-settlement curves are plotted to analyze the pile foundation's bearing capacity, settlement characteristics, and ultimate bearing capacity. Furthermore, time conditions can be set to conduct static load tests and analyze the evolution of the pile foundation's bearing and deformation characteristics.

[0133] S9: Dry-Wet Cycle. Based on the actual rainfall and evaporation conditions of the project, a dry-wet cycle is set. Based on the test-designed dry-wet cycle amplitude, dry-wet cycle path, dry-wet cycle duration, and number of dry-wet cycles, the drying and wetting systems are controlled by the drying and wetting control software of the remote computer 9, respectively, to perform the dry-wet cycle. Before the dry-wet cycle, the data acquisition module is used to measure the initial soil moisture content and suction. During the drying operation, the duration and temperature of the drying process are determined based on the designed drying degree, so that the soil moisture content reaches the predetermined dry state. The drying control software is used to continuously power the heat conducting rod 311, accelerating soil moisture evaporation and gradually drying the soil. During the drying process, the soil moisture content and suction are continuously monitored to ensure that the soil has dried to the designed moisture content level, at which point the drying operation is stopped. During the wetting operation, the water supply and duration are determined based on the designed wetting degree. The humidification control software was used to start the water pump 326, adjust the water supply pressure and volume, and humidify the soil through the steel sprinkler pipe 3210, so that the water evenly penetrated the model soil at different depths and around the piles. During the humidification process, the changes in soil moisture content and suction were monitored until the preset wet state of the test was reached. The humidification control software was then used to shut down the water pump 326. Furthermore, based on the dry-wet cycle conditions set for the test, the above-mentioned drying and wetting operations were repeated for multiple cycles. After each cycle, the changes in soil moisture content and suction were recorded to observe the impact of the dry-wet cycle on soil properties.

[0134] S10: Static load test after wet-dry cycle. Keep centrifuge T running. After wet-dry cycle testing the soil according to the test's established wet-dry cycle conditions, if the load-settlement characteristics, bearing characteristics, and their evolution of the existing pile foundation are analyzed, as well as the development, accumulation, and evolution of the ultimate bearing capacity with the number of wet-dry cycles, step S9 can be performed and then step S8 can be re-executed. Furthermore, if the pile foundation's sinking characteristics, load-settlement characteristics, bearing characteristics, and their evolution after wet-dry cycles are analyzed, step S9 can be performed and then steps S7 and S8 can be re-executed.

[0135] S11: End the centrifugal test. Turn off the geotechnical centrifuge T, close the humidification system ball valve 328, and remove the centrifugal test device.

[0136] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A centrifugal test device for the bearing characteristics of unsaturated soil pile foundations under dry-wet cycles, characterized in that: The invention comprises a centrifugal control module, a centrifuge (T), a model box (1), a model pile (2), a dry-wet cycle module, a reaction module, a loading control module and a data acquisition module, wherein the model pile (2) is installed in the unsaturated soil of the model box (1), the dry-wet cycle module and the reaction module are both installed on the model box (1), the loading control module is installed on the reaction module and connected to the model pile (2), the data acquisition module is installed in the model box (1), the model box (1) is placed on the centrifuge (T), and the centrifugal control module is respectively connected to the centrifuge (T), the dry-wet cycle module, the loading control module and the data acquisition module for communication.

2. The centrifugal test device for unsaturated soil pile foundation bearing characteristics under dry-wet cycles according to claim 1 is characterized in that: The model box (1) comprises a drain outlet (11), a geotextile (12), a pebble layer (13) and a model soil (14); the pebble layer (13) is laid on the bottom of the model box (1); the geotextile (12) is laid on the pebble layer (13); the model soil (14) is filled in the model box (1) and located on the geotextile (12); the drain outlet (11) is installed in the pebble layer (13); and the model pile (2) is installed in the model soil (14).

3. The centrifugal test device for unsaturated soil pile foundation bearing characteristics under dry-wet cycles according to claim 2, characterized in that: The wet-dry cycle module comprises a heat conducting rod (311), a temperature sensor (312) and a drying control cabinet (313); the heat conducting rod (311) is symmetrically installed in the model soil (14) with the model pile (2) as the axis and at equal intervals; the temperature sensor (312) is installed on the heat conducting rod (311) at equal intervals; and the drying control cabinet (313) is respectively connected to the centrifugal control module, the heat conducting rod (311) and the temperature sensor (312) in communication.

4. The centrifugal test device for unsaturated soil pile foundation bearing characteristics under dry-wet cycles according to claim 2, characterized in that: The dry-wet cycle module further comprises a sealed water tank (321), an automatic exhaust valve (322), a water pump (326), a water supply pipeline, a return pipeline, a humidification pipeline, a spray pipe (3210) and a humidification control cabinet (329). The water outlet of the sealed water tank (321) is connected to the water pump end of the water pump (326). The water outlet of the water pump (326) is connected to the humidification pipeline via the water supply pipeline. The humidification pipeline is connected to the spray pipe (3210). The spray pipe (3210) is installed at equal intervals in the model soil (14). The humidification pipeline is connected to the sealed water tank (321) via the return pipeline. The humidification control cabinet (329) is connected to the centrifugal control module and the water pump (326) respectively.

5. The centrifugal test device for unsaturated soil pile foundation bearing characteristics under dry-wet cycles according to claim 2, characterized in that: The reaction module comprises an upper frame (41), a lower frame (42), a reaction column (43), a reaction beam (46) and a slide rail (47); the lower frame (42) is mounted on the top of the model box (1); the upper frame (41) is mounted on the lower frame (42) via the reaction column (43); the slide rail (47) is mounted on the upper frame (41); and the reaction beam (46) is mounted on the slide rail (47).

6. The centrifugal test device for unsaturated soil pile foundation bearing characteristics under dry-wet cycles according to claim 5, characterized in that: The loading control module comprises a loading unit (51) and a loading control cabinet (52); the loading unit (51) comprises a servo motor (511), a linear module (512), a force transmission column (513), a pile cap (514), a slide (515), a slide connection bracket (516), a force transmission column joint component (517), a fixed aluminum plate assembly (518) and a movable connection block (519); The force transmission column (513), the pile cap (514), the slide (515), the slide connecting bracket (516) and the force transmission column joint component (517) are all installed in the linear module (512); the pile cap (514) is installed on the force transmission column (513); the force transmission column (513) is installed on the force transmission column joint component (517); the force transmission column joint component (517) is installed in the slide (515); the slide (515) is connected to the slide connecting bracket (516); the servo motor (511) is installed on the linear module (512); the servo motor (511) is communicatively connected to the loading control cabinet (52); the linear module (512) is installed on a fixed aluminum plate assembly (518); and the fixed aluminum plate assembly (518) is installed on the reaction beam (46) via a movable connecting block (519).

7. The centrifugal test device for unsaturated soil pile foundation bearing characteristics under dry-wet cycles according to claim 6, characterized in that: The data acquisition module comprises a pressure sensor (61), a laser displacement sensor (62), a moisture sensor (63), an earth pressure gauge (64), a tension gauge (65), a strain gauge (66) and an end resistance sensor (67); the pressure sensor (61) is installed at the connection between the pile cap (514) and the model pile (2); the laser displacement sensor (62) is installed in the model box (1) and close to the connection between the pile cap (514) and the model pile (2); the moisture sensor (63), earth pressure gauge (64) and tension gauge (65) are all installed in the model soil (14); the earth pressure gauge (64) and tension gauge (65) are also installed on the model pile (2); and the strain gauge (66) and end resistance sensor (67) are both installed on the model pile (2).

8. The centrifugal test device for unsaturated soil pile foundation bearing characteristics under dry-wet cycles according to claim 1, characterized in that: The centrifuge control module includes a dedicated computer and a remote computer (9), wherein the dedicated computer is respectively connected to the centrifuge (T), the dry-wet cycle module, the loading control module and the data acquisition module, and the dedicated computer is connected to the remote computer (9).

9. The centrifugal test device for unsaturated soil pile foundation bearing characteristics under dry-wet cycles according to claim 1, characterized in that: The centrifuge control module includes a wireless transceiver (91) and a wired unit. The wireless transceiver (91) and the wired unit are respectively connected to the centrifuge (T), the dry-wet cycle module, the loading control module and the data acquisition module. The dedicated computer is connected to the remote computer (9) through the wireless transceiver (91) and the wired unit.

10. A method for a centrifugal test device for bearing characteristics of unsaturated soil pile foundations under dry-wet cycles according to any one of claims 1 to 9, characterized in that: The method specifically includes: Step 1: Install the centrifugal test device; Step 2: Take the soil from the site, dry it in the sun, crush it, add water and stir it according to the saturation of the experimental design to prepare unsaturated remolded soil; Step 3: Fill the unsaturated soil into the model box (1) and control its moisture content and compaction degree to a specified saturation degree; Step 4: making a model pile (2) and positioning and installing it in the unsaturated remolded soil of the model box (1), and then connecting the model pile (2) to the loading control module; Step 5: Install the assembled device on the centrifuge (T), start the test through the centrifuge control module, and set the rotation speed of the centrifuge (T) to a preset speed to keep the centrifuge (T) running; Step 6: The centrifugal control module first controls the loading control module to sink the model pile (2), and collects data through the data collection module. After the pile sinking is completed, it waits for a first preset time and keeps the centrifuge (T) running; Step 7, the centrifugal control module then controls the loading control module to load the model pile (2) step by step, maintaining the load for a second preset time each time until the pile top settlement of the model pile (2) reaches a stable or predetermined deformation limit, and performing data acquisition through the data acquisition module; Step 8: Keep the centrifuge (T) running continuously, and the centrifuge control module simulates the dry-wet cycle working condition of the unsaturated remolded soil in the model box (1) through the dry-wet cycle module, and collects data through the data collection module (6); Step 9: Repeat steps 5 to 8 above to obtain data under different working conditions.

Images