Device and method for simulating hydro-thermal influence of seasonal frozen area environment on pile-soil foundation

Abstract

The invention belongs to the technical field of soil analysis, and particularly discloses a device and method for simulating the influence of a seasonal frozen region environment on the water heating power of a pile soil foundation. The device comprises an experiment box, an environment airflow simulation device, a pressing device, a separation device, a water supplementing device, a heating device, a moisture detection device, a temperature detection device, a compaction degree detection device, a pile body and a control system, wherein the control system is used for receiving signals of the moisture detection device, the temperature detection device and the compaction degree detection device and controlling all the devices to operate. Devices such as a removable partition plate, a thin film and a jack are arranged, and monitoring and control of soil moisture and compactness are performed, so that a real multi-layer soil environment is highly simulated, and the experiment accuracy and the result reliability are improved; in a freezing and thawing cycle process, a moisture transmission condition which is the same as that of a real multi-layer soil environment is accurately provided; the temperature gradient is constructed by the soil temperature in the box and the external atmospheric temperature, the temperature control can be optimized, the energy consumption is reduced, and an efficient and accurate platform is provided for the water thermal research of the pile-soil foundation in the seasonal frozen region.

Description

Technical Field

[0001] The invention belongs to the technical field of soil analysis, and in particular relates to a device and a method for simulating the hydrothermal influence of a seasonally frozen zone environment on a pile foundation. Background Art

[0002] In northern my country, soil undergoes significant seasonal freeze-thaw cycles, which poses a challenge to the stability of composite foundation and pavement structure and will lead to insufficient contact between composite foundation and pavement. When vehicles frequently travel on such pavement, especially in areas where the composite foundation and pavement have poor contact, the pavement material will be subjected to more concentrated loads due to the lack of sufficient support and stress dispersion. This non-uniform stress state accelerates fatigue damage of pavement materials, such as the generation and expansion of cracks, material peeling and wear, etc., which significantly shortens the service life of the pavement, increases maintenance costs, and may pose a potential threat to driving safety. Therefore, many scholars have conducted research on composite foundations in seasonally frozen areas. However, field tests often consume manpower and material resources, and more importantly, are constrained by time (it is difficult to conduct tests in winter). Indoor tests are particularly important, and equipment that accurately simulates the natural environment is the key to conducting research. At present, there are many equipment for indoor tests in frozen soil areas, but few equipment for seasonally frozen areas. This is because with the freeze-thaw changes, the moisture in the soil will also migrate, which cannot meet the moisture content of the soil in the real environment, so the soil needs to be replaced. The process of replacing the soil is complicated, which reduces the efficiency of the test. At the same time, simulating real freeze-thaw changes places high demands on experimental equipment. Summary of the invention

[0003] In view of the problems in the prior art that the soil replacement process is complicated, the test efficiency is low, and at the same time, it is difficult and costly to simulate the real freeze-thaw changes, a device and method for simulating the hydrothermal effects of the seasonally frozen zone environment on the pile foundation are proposed. The present invention provides the following technical solutions: A device for simulating the hydrothermal effects of seasonally frozen environment on pile foundations, comprising: Experimental boxes for holding various layers of soil; Ambient airflow simulation device for simulating hot and cold airflow; Compacting device for compacting soil in layers; Dividing devices for separating the layers of soil; A water supply device for adjusting the moisture content of each layer of soil; Heating device for accelerating the freezing and thawing process; Moisture detection device for detecting the moisture content of each layer of soil; A temperature detection device for detecting the temperature of each layer of soil; A compaction detection device for detecting the compactness of each layer of soil; A pile body arranged in the box and inserted into the soil; A control system for receiving signals from a moisture detection device, a temperature detection device and a compaction detection device and controlling the operation of each device.

[0004] Preferably, a detachable partition is inserted into the side of the box body, and the number of detachable partitions = the number of soil layers - 1.

[0005] Preferably, the partition device adopts a film, the lower side of the lowest layer of soil is the film, the lower side of the film is set as a support plate, an insulation cavity is formed between the lower side of the support plate and the experimental box, an insulation pipe is set in the insulation cavity, and the insulation pipe is externally connected to a constant water pump and a constant temperature water tank.

[0006] Preferably, a reaction frame is provided on the upper side of the experimental box, and the clamping device includes a hydraulic jacking device, which can specifically be a hydraulic jack. The output end of the lower end of the hydraulic jacking device is detachably connected to a loading plate, and the upper end of the hydraulic jacking device is seated and connected to the reaction frame, and the reaction frame is fixedly connected to the ground or the experimental box.

[0007] Preferably, the experimental box includes a box body and a cover plate arranged on the box body, the cover plate is provided with an air inlet hole, an exhaust hole and a loading hole, the environmental airflow simulation device is connected to the air inlet hole through a pipeline; the loading plate is arranged on the lower side of the cover plate, and the output end of the hydraulic jacking device is connected to the loading plate after passing through the loading hole.

[0008] Preferably, the cover plate is slidably connected to the experimental box, and the reaction frame is fixedly connected to the cover plate.

[0009] Preferably, the water replenishment device includes a plurality of porous drip tubes, which are arranged to penetrate the soil from top to bottom, and the outer ends of the porous drip tubes are connected to water control switches for controlling the amount of water.

[0010] The method for simulating the hydrothermal effect of seasonally frozen zone environment on pile foundation comprises the following steps: S1, construction of basic environment of experimental box; Lay a film at the bottom of the test box, then lay the bottom layer of soil, and adjust the compaction device and compact and water the soil layer by controlling the density and moisture content set by the control system to achieve a real soil environment; S2, multi-layer soil layer construction; After the compaction of the bottom soil layer is completed, a film is laid on top; the second soil layer is laid: first, the control system inputs the target compaction degree and moisture content, and adjusts the compaction degree and moisture content through the compaction device and the water replenishment device to achieve the state of the soil layer in the box to the actual soil state, and the thickness of the bottom soil layer reaches the designed thickness, and then the cycle operation is repeated to complete the laying of subsequent layers; S3, soil monitoring and pile loading; Starting from the center of the pile, temperature probes and moisture probes are arranged horizontally on both sides; and the temperature probes and moisture probes are evenly arranged in multiple layers along the height direction of the soil layer; collect instant soil moisture and temperature information and transmit it to the control system; set the load through the control system, and complete the loading of the pile through the compaction device; S4, temperature cycle simulation; The control system sets the number of cycles, and sets the temperature and period of the cycles; the control system adjusts the cooling effect of the upper environmental airflow simulation device, the temperature of the external heating device of the experimental box, and the temperature of the bottom insulation pipe to achieve a real frozen soil environment.

[0011] Preferably, in step S2, a row of removable partitions is added at the boundary of the soil layers. When the lower layer of soil reaches the target soil conditions, the removable partitions are inserted and the second layer of soil is laid. First, the control system inputs the target compaction degree and moisture content, and through the jack with a loading plate and a water replenishment device, the soil layer in the box reaches the actual soil state, and the thickness of the lowest soil layer reaches the designed thickness, and then the laying of subsequent layers is completed.

[0012] Preferably, drainage holes are provided on the film. In step S4, the frozen soil melts, and the moisture migrates downward and gathers above the film and is discharged through the drainage holes. The control system monitors the moisture through the moisture detection device, adjusts the water replenishment device, and quantitatively replenishes water to each soil layer to achieve the same soil moisture as the natural environment.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The present invention integrates computer control, and is equipped with detachable partitions, films, jacks and other devices, and monitors and controls the moisture and compaction degree of the soil, highly simulating the real multi-layer soil environment, and improving the experimental accuracy and the reliability of the results; during the freeze-thaw cycle, combined with the computer control system control, it accurately provides the same moisture transmission conditions as the real multi-layer soil environment; innovatively uses silica gel heating plates to construct a temperature gradient with the soil temperature in the box and the external atmospheric temperature, which can optimize temperature control and reduce energy consumption; the present invention provides an efficient and accurate platform for the hydrothermal research of composite foundations in seasonally frozen areas, and promotes the scientific and precise engineering analysis and design under complex geological conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is a specific structural schematic diagram of the present invention; Figure 3 It is a partial structural schematic diagram of the present invention; Figure 4 Layout diagram of temperature sensor and moisture meter; Figure 5It is the distribution map of the test soil layers; In the attached drawings, 1, experimental box; 11, box body; 12, cover plate; 2, pressing device; 21, hydraulic lifting device; 22, loading plate; 23, remote control device; 3, environmental air flow simulation device; 31, fan; 32, air inlet pipe; 33, wind diffusion device; 4, partition device; 41, film; 411, first film; 412, second film; 413, third film; 414, fourth film; 42, removable partition; 43, support plate; 5, water replenishment device; 51, water storage tank; 511, Thermometer; 52. Porous dropper; 6. Heating device; 611. Constant water pump; 612. Constant temperature water tank; 613. Insulation pipe; 621. Silicone heating plate; 622. Power supply; 71. Temperature detection device; 72. Moisture detection device; 73. Compactness detection device; 8. Pile body; 9. Control system; 91. Control center; 92. Central control device; 93. Control panel; 101. First soil layer 101; 102. Second soil layer; 103. Third soil layer; , fourth soil layer; 105. Mattress layer. DETAILED DESCRIPTION

[0015] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings of the present invention. The directional words mentioned in the following embodiments, such as "up", "down", "left" and "right", etc., are only reference to the directions of the accompanying drawings. Therefore, the directional words used are used to illustrate rather than limit the invention.

[0016] Example 1 like Figure 1-3 As shown, a device for simulating the hydrothermal effect of seasonally frozen environment on pile foundations comprises: An experimental box 1 for holding various layers of soil; Environmental airflow simulation device 3 for simulating hot and cold airflow; A compacting device 2 for compacting the soil in layers; A separation device 4 for separating the various layers of soil; A water supply device 5 for adjusting the moisture content of each layer of soil; A heating device 6 for advancing the progress of freezing and thawing; A moisture detection device 72 for detecting the moisture content of each layer of soil; A temperature detection device 71 for detecting the temperature of each layer of soil; A compaction detection device 73 for detecting the compactness of each layer of soil; A pile body 8 disposed in the box body 11 and inserted into the soil; A control system 9 is used to receive signals from the moisture detection device 72, the temperature detection device 71 and the compaction detection device 73 and control the operation of each device.

[0017] Specifically, the control system 9 includes a control center 91 , a central control device 92 and a control panel 93 for connecting various components, and the central control device 92 and the control center 91 are interconnected.

[0018] Furthermore, a detachable partition 42 is inserted into the side of the box body 11, and the number of detachable partitions 42 = the number of soil layers - 1.

[0019] Furthermore, the partition device 4 adopts a film 41, the lower side of the lowest layer of soil is the film 41, the lower side of the film 41 is set as a support plate 43, and an insulation cavity is formed between the lower side of the support plate 43 and the experimental box 1. An insulation pipe 613 is arranged in the insulation cavity, and the insulation pipe 613 is externally connected to a constant water pump 611 and a constant temperature water tank 612.

[0020] Furthermore, a reaction frame is provided on the upper side of the experimental box 1, and the clamping device 2 includes a hydraulic jacking device 21, the output end of the lower end of the hydraulic jacking device 21 is detachably connected to a loading plate 22, and the upper end of the hydraulic jacking device 21 is seated and connected to the reaction frame, and the reaction frame is fixedly connected to the ground or the experimental box 1.

[0021] Furthermore, the experimental box 1 includes a box body 11 and a cover plate 12 covered on the box body 11, the cover plate 12 is provided with an air inlet hole, an exhaust hole and a loading hole, and the environmental airflow simulation device 3 is connected to the air inlet hole through a pipeline; the loading plate 22 is arranged on the lower side of the cover plate 12, and the output end of the hydraulic jacking device 21 is connected to the loading plate 22 after passing through the loading hole.

[0022] Furthermore, the cover plate 12 is slidably connected to the experimental box 1 , and the reaction frame is fixedly connected to the cover plate 12 .

[0023] Furthermore, the water replenishment device 5 includes a plurality of porous drip tubes 52 , and the porous drip tubes 52 are arranged to penetrate the soil from top to bottom, and the outer ends of the porous drip tubes 52 are connected to water control switches for controlling the amount of water.

[0024] Specifically, the environmental airflow simulation device 3 adopts an outdoor unit, including a wind diffusion device 33 and a fan 31 connected through an air inlet pipe 32. The fan 31 can be an air conditioner. The lower end of the wind diffusion device 33 is provided with a nozzle.

[0025] Specifically, the top cover is made of steel, and 10-20 exhaust holes are set on the top side of the top cover, and the diameter of the exhaust holes is 1-5 cm. An air inlet hole with a diameter of 5 cm is set on the side of the top cover, and the air inlet pipe 32 penetrates into the inner circumference of the box body 11 through the air inlet hole. The air inlet pipe 32 is provided with 4 air holes with a diameter of 2 cm in parallel, and the air holes are connected to the wind diffusion device 33. The air inlet pipe 32 is hoisted on the top cover. The fan 31 generates hot and cold air for the experiment, which enters the interior of the box body 11 through the air inlet pipe 32, the air holes, and the wind diffusion device 33. Two loading holes are arranged on the top of the top cover, and the diameter of the loading holes is 5-10cm. A reaction frame is fixed on the upper part of the top cover, and the reaction frame includes 4 columns and 1 crossbeam. The clamping device 2 adopts a hydraulic jack and can be remotely controlled by a remote control device 23. Two hydraulic jacks are arranged on the crossbeam of the reaction frame, and the extended end of the hydraulic jack passes through the loading hole to realize vertical movement. The extended end of the hydraulic jack is connected to the loading plate 22. The two hydraulic jacks are connected to a pump station in common, and the pump station is controlled by the control end.

[0026] The top cover and the box body 11 are connected by a slidable guide rail, which includes a track and a track groove. The track is fixed on the box body 11, and the track groove is fixed on the top cover. The top cover can move horizontally along the track to achieve horizontal opening and closing of the upper top cover and the box body 11.

[0027] The box 11 is made of steel, and the top of the box 11 is open. The inside is filled with soil layers, and the first film 411, the first soil layer 101, the second film 412, the second soil layer 102, the third film 413, the third soil layer 103, the fourth film 414, the fourth soil layer 104, and the cushion layer 105 are laid from bottom to top. The pile body 8 is set at the center of the box 11, and vertically penetrates the fourth soil layer 104, the fourth film 414, the third soil layer 103, the third film 413, the second soil layer 102, the second film 412, and the first soil layer 101. During the melting process, moisture will migrate downward, gather above the film 41 and be discharged through the drainage hole on the right. Starting from the center of the pile body 8, temperature probes and moisture probes are arranged horizontally outward, one is arranged every 15 cm, and along the height direction of the soil layer, a layer of temperature probes and moisture probes are arranged every 5-10 cm, and transmitted to the data acquisition instrument through the data line, and transmitted to the central control system. The water replenishment device 5 includes a water storage tank 51 and a porous drip tube 52, and a thermometer 511 is installed on the water storage tank 51; a water replenishment hole is arranged on the left side of the box body 11, and a row of porous drip tubes 52 are arranged on each layer of soil. The porous drip tubes 52 are arranged through the water replenishment hole, and the porous drip tubes 52 run through each layer of soil. The outer end of the porous drip tube 52 is connected to a water volume control switch, and the amount of water is controlled by controlling the opening and closing size of the water volume control switch. The control switch is connected to a water pump. Four rows of drainage holes are arranged on the right side of the box body 11. The drainage holes are arranged at the bottom of each layer of soil. The drainage holes are arranged horizontally in a row with a horizontal interval of 5 cm. Three rows of removable partitions 42 are arranged on the right side of the box body 11. The removable partitions 42 are made of strip steel plates. The removable partitions 42 are located 2-3 cm above the drainage holes. The removable partitions 42 have a thickness of 2 cm and a width of 4-10 cm. The spacing between a row of removable partitions 42 is 1-2 cm. The removable partition 42 can be inserted into the groove on the left side of the box body 11.

[0028] The support plate 43 is made of steel plate, and the insulation pipe 613 is connected to the constant water pump 611 and the constant temperature water tank 612, which is controlled by the central control device 92. A silicone heating plate 621 is installed on the outside of the box 11, which is directly connected to the power supply 622 and controlled by the central control device 92. The heating device 6 includes a constant water pump 611, a constant temperature water tank 612 and a silicone heating plate 621. The temperature gradient is constructed with the soil temperature in the box and the external atmospheric temperature, which can optimize temperature control and reduce energy consumption. The present invention can be used for hydrothermal research of pile foundations in seasonally frozen areas. The present invention provides an efficient and accurate platform for hydrothermal research of composite foundations in seasonally frozen areas, and promotes the scientific and precise engineering analysis and design under complex geological conditions.

[0029] The method for simulating the hydrothermal effect of seasonally frozen zone environment on pile foundation comprises the following steps: S1, construction of basic environment of experimental box 1; A film 41 is laid at the bottom of the test box 1, and then the bottom layer of soil is laid, and the compaction device 2 and the compaction and water replenishment of the soil layer are adjusted by the density and moisture content set by the control system 9 to achieve a real soil environment; This embodiment is an improvement of the above embodiment and a refinement of the above embodiment regarding the film. The film thickness of this embodiment is 0.03mm-0.07mm, which isolates the soil layer and facilitates the timely discharge of water that migrates downward during the melting process.

[0030] S2, multi-layer soil layer construction; After the compaction of the bottom soil layer is completed, a film 41 is laid on top; the second soil layer is laid: first, the control system 9 inputs the target compaction degree and moisture content, and adjusts the compaction degree and moisture content through the compaction device 2 and the water replenishment device 5, so that the soil layer in the box reaches the state of the actual soil and the thickness of the soil layer reaches the designed thickness, and then the cycle operation is repeated to complete the laying of subsequent layers; S3, soil monitoring and pile loading; Starting from the center of the pile, temperature probes and moisture probes are arranged horizontally on both sides; and the temperature probes and moisture probes are evenly arranged in multiple layers along the height direction of the soil layer; real-time soil moisture and temperature information is collected and transmitted to the control system 9; the load is set through the control system 9, and the loading of the pile is completed through the compaction device 2; S4, temperature cycle simulation; The control system 9 sets the number of cycles, and sets the temperature and period of the cycle; the control system 9 adjusts the cooling effect of the upper environmental airflow simulation device 3, adjusts the temperature of the external heating device 6 of the experimental box 1, and adjusts the temperature of the bottom insulation pipe 613 to achieve a real frozen soil environment.

[0031] Furthermore, at the beginning of step S1, geological information is first obtained: through on-site investigation, the geological conditions of the actual engineering site are obtained, the type of soil layer, moisture content, dry density of soil, foundation bearing capacity, etc. are determined, and the scale ratio is determined.

[0032] Further, in step S2, a row of removable partitions 42 is arranged at the boundary of the soil layer, 2-3 cm above the drainage hole, the thickness of the removable partitions 42 is 2 cm, the width is 4-10 cm, and the spacing between a row of removable partitions 42 is 1-2 cm. 2 When the lower layer of soil reaches the target soil condition, the removable partitions 42 are inserted and the second layer of soil is laid. First, the control system 9 inputs the target compaction degree and moisture content, and through the jack with the loading plate 22 and the water replenishment device 5, the soil layer in the box reaches the actual soil state, and the thickness of the lowest soil layer reaches the designed thickness, and then the subsequent layers are laid.

[0033] Furthermore, in step S3, the hydrothermal parameters of the soil under the control conditions are measured first, and the changing process is recorded; before loading the pile, the steel pipe is first inserted into the foundation soil, the soil in the steel pipe is taken out and the hole wall is cleaned, and then the pre-set concrete pile model 24 is placed, and the cushion layer 105 is laid with a thickness of 5cm-10cm, and the top of the cushion layer 105 is 5cm-10cm lower than the pile top.

[0034] When loading the pile, the actual load on the pile foundation is reduced according to the scale ratio of the size, and the reduced load is set in the control system 941 to control the jack 13 to apply the load on the pile top and the cushion layer 105. The water and heat parameters of the soil and the settlement displacement of the pile under the control condition are measured, and the change process is recorded; This embodiment is an improvement of the above embodiment. In the above embodiment, the top of the pile is higher than the cushion layer, and single pile bearing capacity and pile group bearing capacity tests can be carried out. This embodiment expands the test scope to the composite foundation (pile + soil between piles + cushion layer) experiment. Through on-site investigation, the cushion layer is laid according to the same scale ratio, and the top of the cushion layer is higher than the pile top. The relevant seasonal freezing zone test of the composite foundation can be completed by directly applying a load to the top of the cushion layer through the loading plate.

[0035] Furthermore, before step S4, the top cover is pushed by the sliding guide rail to close the top cover and the box body 11. Connect the air cooling, silicone heating plate 621, constant temperature pipe and other equipment to the central control device 92. The control system 9 sets the number of cycles, and sets the temperature and cycle of the cycle. The central control system adjusts the cooling effect of the upper air cooling device 7, the temperature of the silicone heating plate 621 outside the experimental box 1, and the temperature of the constant temperature device at the bottom to achieve a real frozen soil environment. Measure the settlement displacement of the water and thermal parameter pile of the soil under control conditions, and record the change process.

[0036] This embodiment is an improvement of the above embodiment and a refinement of the above embodiment regarding the silicone heating plate. The thickness of the silicone heating plate in this embodiment is 0.8mm-3.0mm. The silicone heating plate is a planar heating element with excellent soft performance and silicone rubber coated with glass fiber cloth on the outside and high-quality nickel-chromium alloy on the inside.

[0037] Furthermore, during the freezing process, the constant temperature water pipe equipment keeps the temperature constant, the air cooling equipment operates according to the temperature set by the control system 9, the silicone heating plate 621 maintains a constant temperature of 0-3°C, the soil is frozen, and the settlement displacement of the water and thermal parameter piles of the soil under the control conditions is measured, and the change process is recorded; during the melting process, the constant temperature water pipe equipment keeps the temperature constant, the air cooling equipment operates according to the temperature set by the control system 9, and the silicone heating plate 621 maintains a constant temperature of 8-10°C. The moisture will migrate downward, gather above the film 41 and be discharged through the drainage hole. The central control device 92 monitors the moisture and adjusts the water replenishment device 5 to quantitatively replenish water for each soil layer to achieve the same soil layer moisture as the natural environment. Measure the settlement displacement of the water and thermal parameter piles of the soil under the control conditions and record the change process.

[0038] The present invention integrates computer control, and is provided with devices such as a removable partition 42, a film 41, and a jack, and monitors and controls the moisture content and compaction degree of the soil, highly simulating a real multi-layer soil environment, and improving the accuracy of the experiment and the reliability of the results; during the freeze-thaw cycle, combined with the control system 9 of the computer, the moisture transmission conditions that are the same as those in the real multi-layer soil environment are accurately provided; the innovative use of a silicone heating plate to construct a temperature gradient with the soil temperature in the box and the external atmospheric temperature can optimize temperature control and reduce energy consumption.

[0039] Example 2 The difference from Example 1 is that the compression displacement of different soil layers is calculated so as to realize the actual soil layer working condition under repeated pressurization. Specifically, the calculation of compaction displacement includes the following steps: first, combining the field investigation results of the actual working condition, establish the functional relationship between the soil confining pressure and the soil layer burial depth; second, conduct a static load triaxial test on the soil according to the confining pressure of the soil in the actual working condition, and establish the static constitutive model of different soils under specific burial depths through the test results; finally, establish a numerical model of the three-dimensional soil layer based on the finite element method, and load it in layers and stages, and calculate the displacement of different soil layers that need to be compressed to achieve the actual working condition of the soil layer under layered pressurization under constant jack load conditions.

[0040] Embodiment 3, In this experiment, the design target prefabricated pile diameter is 5cm, the pile length is 110cm, and the length of the pile in the soil is 80cm; the specific soil sample is as follows Figure 4 The arrangement of temperature sensor and moisture meter is shown in Figure 5 This experiment will test the water thermodynamic changes under freeze-thaw cycles of the conventional device and the device of the present invention.

[0041] The water requirement is calculated based on the moisture content of the test design. A layer of film 41 is laid at the bottom of the test box 1, and then the bottom layer of soil is laid. The density and moisture content are set by the control system 9, and the compaction device 2 is adjusted to compact and replenish the soil layer to achieve a real soil environment. After standing, the temperature control device in the test box is turned on to freeze the soil layer, and the construction of one layer of soil is completed; after the compaction of the bottom layer of soil is completed, a layer of film 41 is laid on top; the second layer of soil is laid: first, the control system 9 inputs the target compaction and moisture content, and adjusts the compaction and moisture content through the compaction device 2 and the replenishment device 5, so that the soil layer in the box reaches the state of actual soil, and the thickness of the soil layer reaches the designed thickness, and then the operation is cyclically operated to complete the laying of subsequent layers; Freeze-thaw process: The temperature during the thawing process was set at 15°C for 10 days, and the temperature during the freezing process was set at -12°C for 10 days, for a total of 20 days. After the thawing-freezing process was completed, the indoor temperature was adjusted to 15°C, and the thawing process continued. The thawing process lasted for 5 days, that is, on the 25th day of the test. The data of the temperature sensor and the moisture meter were recorded on the 0th, 10th, 20th, and 25th days of the test.

[0042] Table 1 - Soil temperature tested by two devices

[0043] Table 2 - Soil moisture content tested by two equipments

[0044] In order to more clearly demonstrate the advancement of the present invention. The changes in soil temperature and moisture in the freeze-thaw cycle tested by the two devices are compared, see Table 1 and Table 2. From Table 1, it can be seen that initially, the temperature of the device at a depth of 60cm-80cm is close to 2°C, while the bottom temperature of the traditional device is close to 1°C. In addition, at 10-30cm, the results of the two devices are close. The results of the traditional device deviate from the actual soil layer distribution. Because for deep soil layers, the temperature of the soil is a constant temperature close to 2°C, which shows that the present invention is advanced in simulating the temperature distribution of the soil layer.

[0045] As can be seen from Table 2, in the early stage of freeze-thaw, the moisture content of the two devices is similar. After 10 days of thawing, it can be seen that the moisture content of this device is higher than that of the traditional device at -15cm, and lower than that of the traditional device at a deeper depth. This is because during the thawing process, the water from the melting ice will migrate downward, resulting in a higher moisture content in the lower soil and a lower moisture content in the lower soil. This phenomenon does not occur in the actual environment. The real-time monitoring of moisture, drainage, water-blocking membrane, and water replenishment measures of this device can simulate real soil.

[0046] In addition, at 20 days, after thawing for 10 days and freezing and thawing for 10 days, there was less migration of water during the freeze-thaw process. The moisture content of this equipment was higher than that of the traditional equipment at -15cm, and lower than that of the traditional equipment at a deeper depth. After the freeze-thaw was completed, the ice in the deep soil continued to melt for 5 days, but it had not completely melted. Due to the migration of water when the ice melted, the moisture content of the deep soil of the traditional equipment would be higher. In addition, with the continuous decrease in moisture, the moisture content of the first two layers of this equipment was higher than that of the traditional equipment. The soil moisture distribution of this equipment is more consistent with the real environment, which shows that the present invention is advanced in simulating the soil moisture distribution.

[0047] In summary, it is shown that the results of the present invention can accurately and efficiently simulate the hydrothermal effects of the simulated seasonally frozen zone environment on the pile-soil foundation while having sufficient reliability.

Claims

1. A device for simulating the hydrothermal effects of seasonally frozen environment on pile foundations, characterized in that: include: An experimental box for holding various layers of soil (1); An environmental air flow simulation device for simulating hot and cold air flows (3); A compacting device (2) for compacting the soil in layers; a separator (4) for separating the layers of soil; A water supply device (5) for adjusting the moisture content of each layer of soil; A heating device (6) for accelerating the freezing and thawing process; a moisture detection device (72) for detecting the moisture content of each layer of soil; A temperature detection device (71) for detecting the temperature of each layer of soil; A compaction detection device (73) for detecting the compactness of each layer of soil; A pile body (8) disposed in the box body (11) and inserted into the soil; A control system (9) for receiving signals from a moisture detection device (72), a temperature detection device (71) and a compaction detection device (73) and controlling the operation of each device.

2. The device for simulating the hydrothermal effect of seasonally frozen zone environment on pile foundation according to claim 1, characterized in that: A detachable partition (42) is inserted into the side of the box body (11), and the number of detachable partitions (42) is equal to the number of soil layers-1.

3. The device for simulating the hydrothermal effect of seasonally frozen zone environment on pile foundation according to claim 1, characterized in that: The partition device (4) uses a film (41), the lower side of the lowest layer of soil is the film (41), the lower side of the film (41) is provided with a support plate (43), a heat preservation cavity is formed between the lower side of the support plate (43) and the experimental box (1), a heat preservation pipe (613) is provided in the heat preservation cavity, and the heat preservation pipe (613) is externally connected to a constant water pump (611) and a constant temperature water tank (612).

4. The device for simulating the hydrothermal effect of seasonally frozen zone environment on pile foundation according to claim 1, characterized in that: A reaction frame is arranged on the upper side of the experimental box (1); the pressing device (2) comprises a hydraulic jacking device (21); an output end at the lower end of the hydraulic jacking device (21) is detachably connected to a loading plate (22); an upper end of the hydraulic jacking device (21) is seated and connected to the reaction frame; and the reaction frame is fixedly connected to the ground or the experimental box (1).

5. The device for simulating the hydrothermal effect of seasonally frozen zone environment on pile foundation according to claim 4, characterized in that: The experimental box (1) comprises a box body (11) and a cover plate (12) arranged on the box body (11); the cover plate (12) is provided with an air inlet hole, an air outlet hole and a loading hole; the environmental air flow simulation device (3) is connected to the air inlet hole via a pipeline; the loading plate (22) is arranged on the lower side of the cover plate (12); and the output end of the hydraulic jacking device (21) passes through the loading hole and is connected to the loading plate (22).

6. The device for simulating the hydrothermal effect of seasonally frozen zone environment on pile foundation according to claim 5, characterized in that: The cover plate (12) is slidably connected to the experimental box (1), and the reaction frame is fixedly connected to the cover plate (12).

7. The device for simulating the hydrothermal effect of seasonally frozen zone environment on pile foundation according to claim 1, characterized in that: The water replenishment device (5) comprises a plurality of porous drip tubes (52), wherein the porous drip tubes (52) are arranged to penetrate the soil from top to bottom, and the outer ends of the porous drip tubes (52) are connected to water control switches for controlling the amount of water.

8. A method for simulating the hydrothermal effects of seasonally frozen zone environment on pile foundation, characterized in that: The following steps are involved: S1. Experimental box (1) Basic environment construction; A film (41) is laid at the bottom of the test box (1), and then the bottom layer of soil is laid. The compaction device (2) is adjusted to compact and replenish the soil layer with water by setting the density and moisture content of the control system (9) to achieve a real soil environment; S2, multi-layer soil layer construction; After the compaction of the bottom soil layer is completed, a film (41) is laid on top; the second soil layer is laid: first, the control system (9) inputs the target compaction degree and moisture content, and adjusts the compaction degree and moisture content through the compaction device (2) and the water replenishment device (5) to achieve the soil layer in the box to reach the actual soil state and the thickness of the bottom soil layer reaches the designed thickness, and then the operation is cyclically performed to complete the laying of subsequent layers; S3, soil monitoring and pile loading; Starting from the center of the pile, temperature probes and moisture probes are horizontally arranged on both sides; and the temperature probes and moisture probes are evenly arranged in multiple layers along the height direction of the soil layer; real-time soil moisture and temperature information is collected and transmitted to the control system (9); the load is set through the control system (9), and the loading of the pile is completed through the compaction device (2); S4, temperature cycle simulation; The control system (9) sets the number of cycles, and sets the temperature and period of the cycles; the control system (9) adjusts the cooling effect of the upper environmental airflow simulation device (3), adjusts the temperature of the external heating device (6) of the experimental box (1), and adjusts the temperature of the bottom insulation pipe (613) to achieve a real frozen soil environment.

9. The method for simulating the hydrothermal effects of seasonally frozen zone environment on pile foundation according to claim 8, characterized in that: In step S2, a row of removable partitions (42) are added at the boundary of the soil layers. When the lower soil layer reaches the target soil condition, the removable partitions (42) are inserted and the second soil layer is laid. First, the control system (9) inputs the target compaction degree and moisture content, and through the jack with the loading plate (22) and the water replenishment device (5), the soil layer in the box reaches the actual soil state and the thickness of the lowest soil layer reaches the designed thickness, and then the laying of subsequent layers is completed.

10. The method for simulating the hydrothermal effects of seasonally frozen zone environment on pile foundation according to claim 8, characterized in that: The box body (11) is provided with drainage holes. In step S4, the frozen soil melts, and the moisture migrates downward and gathers above the film (41) and is discharged through the drainage holes. The control system (9) monitors the moisture through the moisture detection device (72), adjusts the water replenishment device (5), and quantitatively replenishes water to each soil layer to achieve the same soil moisture as the natural environment.

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