A pile-soil test device considering complex field coupling

Abstract

The present invention discloses a pile-soil test device that takes into account the coupling effect of complex field states. The device comprises a seepage generation system, a transparent model box, a temperature control system, and a loading device. A pre-prepared soil sample is filled into the transparent model box; a model pile is connected to the loading device and placed into a preset position within the model box; after the test begins, the temperature control system helps create an in-situ temperature environment within the transparent model box; water in the seepage generation system is pumped into the model box via a pump, and the interaction of an inward-facing water-permeable membrane slider, an outward-facing water-permeable membrane slider, and the pump achieves the effect of inputting and outputting water into and out of the model box, thereby simulating an in-situ seepage field environment; simultaneously, the loading device applies periodic lateral loads to the pile group model, forming a model test system that couples multiple fields including temperature field, seepage field, and stress field.

Description

Technical Field

[0001] The invention relates to a testing device, in particular to a pile-soil testing device taking into account complex field coupling, and belongs to the technical field of geotechnical engineering testing. Background Art

[0002] With my country's steady economic growth, infrastructure construction is booming in regions like Northwest and Northeast my country. However, due to the mountainous terrain, high altitude, and low temperatures in these regions, infrastructure construction presents numerous challenges. Pile foundation engineering, a crucial component of this, is of undeniable importance. Due to the unique nature and structure of cold-region projects, they are particularly sensitive to temperature fluctuations. Therefore, the temperature environment is a major factor affecting the use of underground projects in cold regions. Furthermore, the presence of water in the rock and soil modifies the mechanical properties of the rock and soil through pore water pressure. When the ambient temperature drops and the water in the rock and soil reaches its freezing point, it freezes and expands in volume, generating frost heave forces within the rock and soil. Water (seepage field), heat (temperature field), and forces (stress field) in the rock and soil interact with each other, making it difficult to obtain accurate results by focusing solely on one aspect.

[0003] On the other hand, cities in my country with a high level of underground development are mostly located in plains along rivers and coasts, which have thick Quaternary cover and are typical porous media. Urban underground structures are generally controlled by multiple coupled subsurface fields. For example, the stability of underground space is closely related to the dynamics of stress and seepage fields, the dynamic changes in groundwater volume are controlled by seepage and chemical fields, and the impact of tidal forces on building structures in offshore areas is closely related to changes in temperature and seepage fields. It can be said that the factors affecting the stability of underground projects are essentially macroscopic manifestations of the coupled subsurface fields.

[0004] In current engineering practice, offshore, river, and lake-based projects are increasingly becoming the mainstream of research, especially for large-diameter piles near water. Due to their large size, full-scale testing of large-diameter piles in situ is often difficult and costly, so most researchers have begun to turn to indoor scaled-down testing. Lateral loads are increasingly impacting geotechnical engineering, particularly foundations. For example, high-rise buildings are subject to the effects of wind loads, earthquake loads, and vehicle traffic on their pile foundations, while ports and large offshore pile platforms are subject to large lateral loads such as wind loads and wave loads. Summary of the Invention

[0005] The purpose of the present invention is to address the above problems and provide a test device that can not only create complex field coupling conditions, but also study the deformation characteristics of laterally loaded pile groups under these conditions.

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

[0007] A pile-soil test device that takes into account the coupling effect of complex field states includes a seepage generation system, a transparent model box, a temperature control system, and a loading device. After the loading device is connected to the test pile, it is placed in the transparent model box filled with soil samples, and the model pile is loaded during the test. The temperature control system is connected to the transparent model box to control the temperature in the transparent model box during the test. The seepage generation device is connected to the transparent model box to periodically perform water delivery and pumping operations.

[0008] Furthermore, the seepage generation system includes a water tank, an ordinary water pipe, a special-shaped water pipe, and a pump; the small-section end of the special-shaped water pipe is connected to the pump, and the large-section end is connected to the transparent model box.

[0009] Furthermore, the transparent model box includes a transparent cover, a breathable area, a temperature control area, and a one-way water permeable area; the transparent model box is made of organic glass, the inner wall is square, the side length is 760mm, the height is 1660mm, and the wall thickness is 80mm; the top and bottom of the transparent model box are coated with insulation material.

[0010] Furthermore, the temperature control system includes an upper liquid pump, a liquid outlet pipe, an upper four-way valve, an upper temperature sensor, a temperature control box, a liquid outlet pipe, a lower four-way valve, a lower temperature sensor, and a lower liquid pump; the upper temperature sensor is embedded in the upper four-way valve; the lower temperature sensor is embedded in the lower four-way valve; the temperature control box includes a refrigeration area, a right liquid storage area, a middle liquid storage area, a heating area, and a left liquid storage area; the right liquid storage area, the middle liquid storage area, and the left liquid storage area are separated by insulation boards; inert gas is injected between the insulation boards; the refrigeration area includes a temperature sensor, a semiconductor refrigeration system, and a liquid outlet valve; the heating area includes a temperature sensor, a heating guide, and a liquid outlet valve.

[0011] Furthermore, the loading device includes a loading platform, a tray, and weights; the loading platform is buckled into the side of the transparent model box, and after the loading rope is connected to the model pile, it passes around the loading platform and connects to the tray. After the test starts, the weights are placed on the tray in sequence to apply a horizontal load to the pile body.

[0012] Furthermore, the one-way water-permeable area includes an inward water-permeable membrane slider, an outward water-permeable membrane slider, and a guide rail; the slider is placed on the guide rail and can be moved alternately by control; after the test starts, the water pump first supplies water to the transparent model box, and at this time the special-shaped water pipe is connected to the inward water-permeable membrane slider, successfully introducing the water source from the water pipe into the model box; when the water pump performs the water pumping operation, in the one-way water-permeable area, the inward water-permeable membrane slider moves forward along the guide rail, and the outward water-permeable membrane slider moves backward along the guide rail and then moves downward to reach the original position of the inward water-permeable membrane slider. At this time, the inward water-permeable membrane slider moves upward again to complete the position exchange with the outward water-permeable membrane slider, and at the same time successfully introduces the water source from the model box into the water pipe.

[0013] Furthermore, four bolts are distributed on the transparent cover. After the sample soil and model piles are placed in the transparent model box, the transparent cover is covered and locked with bolts to form a nearly closed environment in the box.

[0014] Furthermore, the ventilation area is surrounded by ventilation holes with a diameter of 2 mm to prevent the transparent box from being damaged due to the expansion and contraction of the original gas in the box due to excessive temperature changes in the box.

[0015] Furthermore, a temperature-control tube is embedded in the temperature-control zone. The cross-section of the temperature-control tube is circular and the diameter is 40 mm. Temperature-control liquid flows in the temperature-control tube. When the temperature-control liquid flows through the model box, it exchanges heat with the environment inside the model box. Since the model box is coated with insulation material on the top and bottom, a preset temperature field can be created inside the box.

[0016] Furthermore, the upper temperature sensor is built into the upper four-way valve. When the temperature control liquid flows out of the transparent model box and passes through the upper four-way valve, its temperature is automatically determined. When the temperature is higher than the preset temperature range, it enters the refrigeration area. After cooling to the preset temperature, the liquid outlet valve opens and enters the right liquid storage area; when the temperature is lower than the preset temperature range, it enters the heating area. After heating to the preset temperature, the liquid outlet valve opens and enters the left liquid storage area; when the temperature is still in the preset temperature range, it enters the middle liquid storage area; thereby realizing the recyclable use of the temperature control liquid.

[0017] The implementation of the present invention has the following beneficial effects:

[0018] 1. The present invention facilitates in-depth theoretical research on laterally loaded piles under the coupled effects of complex fields, including stress, seepage, and temperature. This research is beneficial for demonstrating the impact of these complex fields on the soil surrounding the piles and the interaction mechanism between these two fields. This research provides a scientific basis and experimental means for the construction of pile foundations under these complex field conditions, and is of great practical significance.

[0019] 2. The one-way permeable area within the transparent model box of the present invention, through the interplay of two one-way permeable membrane sliders, can simulate the periodic changes of high and low tides in water-prone areas. The presence of the irregularly shaped water pipes, based on the flow formula (for a constant flow rate, the larger the pipe cross-sectional area, the slower the liquid flow rate), reduces the flow rate of water entering and exiting the model box from the pump, increasing the initial seepage area for the water flow, and thus better aligning with reality.

[0020] 3. The temperature control system and the temperature control box of the present invention can achieve the effect of constant temperature of the temperature control liquid, thereby realizing the automatic circulation of the temperature control system, and ensuring that the temperature field in the model box can be controlled to fluctuate slightly above and below the set value during the test.

[0021] 4. The temperature control system of the present invention cooperates with the model box to create a two-dimensional temperature field in the model box. Compared with the one-dimensional temperature field created in most current tests, the two-dimensional temperature field can more efficiently reach the preset temperature of the test. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary persons in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 Schematic diagram of a pile-soil test device considering complex field coupling

[0024] Figure 2 Transparent model box structure disassembly diagram

[0025] Figure 3 Southwest view of the temperature control system structure

[0026] Figure 4 Northeast view of temperature control system structure

[0027] Figure 5 Cross-section of the internal structure of the temperature control box

[0028] Figure 6 Schematic diagram of the workflow of one-way permeable area DETAILED DESCRIPTION

[0029] 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 only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] Example

[0031] Reference Figures 1 to 6 This embodiment relates to a pile-soil test device that takes into account the coupling effect of complex field states, including a transparent model box 1, a temperature control system 2, a seepage generation system 3, and a loading device 4; after the loading device 4 is connected to the test pile 44, it is placed in the transparent model box 1 filled with soil samples, and the model pile 44 is loaded during the test. The temperature control system 2 is connected to the transparent model box 1 to control the temperature in the transparent model box 1 during the test. The seepage generation device 3 is connected to the transparent model box 1 to periodically perform water supply and pumping operations.

[0032] The transparent model box 1 includes a transparent cover 11, a ventilation area 12, a temperature control area 13, and a one-way water permeable area 14; the transparent model box 1 is made of organic glass, the inner wall is square, the side length is 760mm, the height is 1660mm, and the wall thickness is 80mm; the top and bottom of the transparent model box are coated with insulation material.

[0033] The temperature control system 2 includes a temperature control box 21, a liquid outlet pipe 22, an upper temperature sensor 23, an upper four-way valve 24, an infusion pipe 25, a lower temperature sensor 26, a lower four-way valve 27, a lower liquid pump 28, and an upper liquid pump 29; the upper temperature sensor 23 is embedded in the upper four-way valve 24; the lower temperature sensor 26 is embedded in the lower four-way valve 27; the temperature control box 21 includes a cooling area 211, a right liquid storage area 212, a middle liquid storage area 213, a heating area 214, and a left liquid storage area 215; the right liquid storage area 211, the middle liquid storage area 213, and the left liquid storage area 214 are separated by insulation boards; inert gas is injected between the insulation boards; the cooling area 211 includes a temperature sensor and a semiconductor refrigeration system 2111, and a liquid outlet valve; the heating area includes a temperature sensor and a heating guide 2141, and a liquid outlet valve.

[0034] The seepage generating system 3 includes a water tank 31 , an ordinary water pipe 32 , a pump 33 , and a special-shaped water pipe 34 ; the special-shaped water pipe 34 has a small-section end connected to the pump 33 and a large-section end connected to the transparent model box 1 .

[0035] The loading device 4 includes a loading platform 41 , a tray 42 , and a weight 43 ; the loading platform 41 is buckled into the side of the transparent model box 1 , and the loading rope is connected to the model pile 44 , then passes around the loading platform 41 and connects to the tray 42 .

[0036] Four bolts 111 are distributed on the transparent cover 11. After the sample soil and the model piles 44 are placed in the transparent model box 1, the transparent cover 11 is covered and locked with the bolts 111 to form a nearly closed environment in the box.

[0037] The ventilation area 12 is surrounded by ventilation holes with a diameter of 2 mm to prevent the original gas in the box from expanding and contracting due to excessive temperature changes in the box, which may cause damage to the transparent box.

[0038] A temperature control tube 131 is embedded in the temperature control zone 13. The cross section of the temperature control tube 131 is circular and has a diameter of 40 mm. Temperature control liquid flows in the temperature control tube 131. When the temperature control liquid flows through the model box, it exchanges heat with the environment inside the model box. Since the model box is coated with insulation material on the top and bottom, a preset temperature field can be created in the box.

[0039] The one-way water-permeable area 14 includes an inward water-permeable membrane slider 141 , an outward water-permeable membrane slider 142 , and a guide rail 143 ; the sliders are placed on the guide rail 143 and can be moved alternately by control.

[0040] The specific usage is as follows:

[0041] The first step is to prepare the cohesionless soil according to the test requirements, place the transparent model box 1, temperature control system 2, and seepage generation system 3 on a flat ground, and put the configured soil sample into the transparent model box 1.

[0042] The second step is to inject an appropriate amount of water into the water tank 31, install the loading device 4 properly, and connect it to the model pile 44. Then, connect the strain gauge of the model pile 44 to the strain collector through a wire, and then place the model pile into the model box filled with soil samples.

[0043] Step 3: Cover the model box with the transparent cover 11 and tighten it with bolts 111.

[0044] Step 4. Turn on the lower liquid pump 28 and the upper liquid pump 29 in the temperature control system 2. When the temperature control liquid flows out of the transparent model box 1 and passes through the upper four-way valve 24, its temperature is automatically determined. When the temperature is higher than the preset temperature range, it enters the refrigeration zone 211. After cooling to the preset temperature, the liquid outlet valve opens and enters the right liquid storage area 212; when the temperature is lower than the preset temperature range, it enters the heating zone 214. After heating to the preset temperature, the liquid outlet valve opens and enters the left liquid storage area 215; when the temperature is still in the preset temperature range, it enters the middle liquid storage area 213; the temperature control liquid is recycled and the required temperature field is created in the model box.

[0045] Step 5. After the temperature in the model box reaches the test temperature, turn on the pump 33 of the seepage generating system 3 to supply water to the model box. At this time, the special-shaped water pipe 34 is connected to the inward water-permeable membrane slider 141, and the water source is successfully introduced into the model box from the water pipe; after the water supply reaches the preset total seepage volume, the pump 33 performs the water pumping operation. At this time, in the one-way water-permeable area 14, the inward water-permeable membrane slider 141 moves forward along the guide rail, and the outward water-permeable membrane slider 142 moves backward along the guide rail and then moves downward to reach the original position of the inward water-permeable membrane slider 141. At this time, the inward water-permeable membrane slider 141 moves upward again to complete the position exchange with the outward water-permeable membrane slider 142. The special-shaped water pipe 34 is connected to the outward water-permeable membrane slider 141, and at the same time, the water source is successfully introduced from the model box to the water tank 31.

[0046] Step 6: After the temperature field and seepage field environment in the model box are stabilized, a certain amount of weights 43 are added to the tray 42 of the loading device 4 to apply a horizontal load to the model pile 44, and the strain data of the pile body at this time are collected using a strain collector.

Claims

1. A pile-soil test device considering complex field coupling, characterized in that: The system comprises a seepage generating system, a transparent model box, a temperature control system, and a loading device; the loading device is connected to the test pile and placed in the transparent model box filled with soil samples, and the model pile is loaded during the test; the temperature control system is connected to the transparent model box to control the temperature inside the transparent model box during the test; the seepage generating device is connected to the transparent model box to periodically perform water delivery and pumping operations; The seepage generation system includes a water tank, a common water pipe, a special-shaped water pipe, and a pump; the special-shaped water pipe has a small-section end connected to the pump, and a large-section end connected to the transparent model box; The one-way water-permeable area includes an inward water-permeable membrane slider, an outward water-permeable membrane slider, and a guide rail; the slider is placed on the guide rail and can be moved alternately by control; after the test starts, the water pump first delivers water into the transparent model box, at which time the special-shaped water pipe is connected to the inward water-permeable membrane slider, successfully introducing the water source from the water pipe into the model box; when the water pump is pumping water, in the one-way water-permeable area, the inward water-permeable membrane slider moves forward along the guide rail, and the outward water-permeable membrane slider moves backward along the guide rail and then moves downward to reach the original position of the inward water-permeable membrane slider. At this time, the inward water-permeable membrane slider moves upward again, completing the position exchange with the outward water-permeable membrane slider, and successfully introducing the water source from the model box into the water pipe; The transparent model box includes a transparent cover, a ventilation area, a temperature control area, and a one-way water permeable area; the transparent model box is made of organic glass, and the inner wall is square with a side length of 760mm, a height of 1660mm, and a wall thickness of 80mm; the top and bottom of the transparent model box are coated with insulation material; The loading device includes a loading platform, a tray, and weights; the loading platform is buckled into the side of the transparent model box, and after the loading rope is connected to the model pile, it passes around the loading platform and connects to the tray. After the test starts, the weights are placed on the tray in sequence to apply a horizontal load to the pile body.

2. A pile-soil test device considering complex field coupling according to claim 1, characterized in that: The temperature control system includes an upper liquid pump, a liquid outlet pipe, an upper four-way valve, an upper temperature sensor, a temperature control box, a liquid outlet pipe, a lower four-way valve, a lower temperature sensor, and a lower liquid pump; the upper temperature sensor is embedded in the upper four-way valve; the lower temperature sensor is embedded in the lower four-way valve; the temperature control box includes a refrigeration area, a right liquid storage area, a middle liquid storage area, a heating area, and a left liquid storage area; the right liquid storage area, the middle liquid storage area, and the left liquid storage area are separated by insulation boards; inert gas is injected between the insulation boards; the refrigeration area includes a temperature sensor, a semiconductor refrigeration system, and a liquid outlet valve; the heating area includes a temperature sensor, a heating guide, and a liquid outlet valve.

3. The pile-soil test device considering complex field coupling according to claim 1 is characterized in that: There are four bolts distributed on the transparent cover. After the sample soil and the model pile are placed in the transparent model box, the transparent cover is covered and locked with bolts to form a nearly closed environment in the box.

4. The pile-soil test device considering complex field coupling according to claim 1, characterized in that: The ventilation area is surrounded by ventilation holes with a diameter of 2 mm to prevent the original gas in the box from expanding and contracting due to excessive temperature changes in the box, which may cause damage to the transparent box.

5. The pile-soil test device considering complex field coupling according to claim 1 is characterized in that: A temperature-control tube is embedded in the temperature-control zone. The cross-section of the temperature-control tube is circular and has a diameter of 40 mm. Temperature-control liquid flows in the temperature-control tube. When the temperature-control liquid flows through the model box, heat is exchanged with the environment inside the model box. Since the model box is coated with insulation material on the top and bottom, a preset temperature field can be created inside the box.

6. The pile-soil testing device considering complex field coupling according to claim 2, characterized in that: The upper temperature sensor is built into the upper four-way valve. When the temperature-control liquid flows out of the transparent model box and passes through the upper four-way valve, its temperature is automatically determined. When the temperature is higher than the preset temperature range, it enters the refrigeration area. After cooling to the preset temperature, the liquid outlet valve opens and enters the right liquid storage area; when the temperature is lower than the preset temperature range, it enters the heating area. After heating to the preset temperature, the liquid outlet valve opens and enters the left liquid storage area; when the temperature is still within the preset temperature range, it enters the middle liquid storage area, thereby realizing the recycling of the temperature-control liquid.

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