A pile foundation deviation rectification system and method based on controllable frost heaving effect

Abstract

This invention discloses a pile foundation correction system and method based on controllable frost heave effect, belonging to the field of foundation engineering technology. The system includes at least one directional freezing unit; the directional freezing unit includes a freezing pipe and a cooling circulation unit; the freezing pipe is installed in the soil surrounding the pile foundation, located on the inclined side of the pile foundation; the cooling circulation unit forms a closed loop with the freezing pipe, and a coolant circulates inside, while the cooling circulation unit cools the coolant; the coolant in the freezing pipe causes the moisture in the soil between the freezing pipe and the pile foundation to undergo a phase change and freeze, generating a frost heave force pointing in the correction direction, and the pile foundation achieves correction under the action of the frost heave force. This invention has the advantages of directional efficiency and controllability.

Description

Technical Field

[0001] This invention belongs to the field of foundation engineering technology, and relates to a pile foundation correction method, and more particularly to a pile foundation correction system and method based on the controllable frost heave effect. Background Technology

[0002] Pile foundations, as a widely used and abundant foundation structure, have experienced tilting in some existing piles due to changes in the working environment and construction defects, affecting the structural safety of the superstructure. Traditional pile foundation correction techniques include jacking, grouting, and excavation. During jacking, the pile to be corrected loses its working capacity, resulting in high correction costs and a high risk of secondary ground settlement. Grouting, the most commonly used method, is technically simple and inexpensive, but suffers from low correction accuracy and uncontrollable grout diffusion, making targeted correction difficult. Excavation carries significant construction risks and easily disturbs the foundation, only being used when the above methods fail. Therefore, proposing a new, efficient, controllable, and cost-effective pile foundation correction method is of great practical significance.

[0003] The freezing method is a special construction technique that uses artificial refrigeration to freeze ground moisture, forming a high-strength, impermeable frozen wall. It is now widely used in coal mine shaft excavation, shield tunnel construction, diaphragm wall construction, and underground engineering leak sealing. When water undergoes a liquid-solid phase change, the water volume expands, and while soil particles cement, ice crystals fill the pores of the soil particles, improving the strength, impermeability, and stability of the ground. However, the freezing method suffers from frost heave and thaw settlement problems. Existing technologies use methods such as a cross arrangement of freezing pipes and variable-temperature pipes, and pre-embedded heating pipelines to control frost heave and thaw settlement deformation, but the control effect is significantly different from the design expectations. Summary of the Invention

[0004] This invention provides a pile foundation correction system and method based on the controllable frost heave effect to overcome the shortcomings of the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a pile foundation correction system based on controllable frost heave effect, comprising at least one directional freezing unit; the directional freezing unit includes a freezing pipe and a cooling circulation unit; the freezing pipe is disposed in the soil surrounding the pile foundation, located on the inclined side of the pile foundation; the cooling circulation unit and the freezing pipe form a closed loop, with a coolant circulating inside, and the cooling circulation unit cools the coolant; the coolant in the freezing pipe causes the moisture in the soil between the freezing pipe and the pile foundation to undergo a phase change and freeze, generating a frost heave force pointing in the correction direction, and the pile foundation achieves correction under the action of the frost heave force.

[0006] To optimize the above technical solution, the specific measures also include: Furthermore, there are multiple directional freezing units, and the freezing pipes of the multiple directional freezing units are arranged in an arc shape around the pile foundation on the inclined side of the pile foundation.

[0007] Further, the freezing pipe includes an infusion pipe, a supply pipe, a return pipe, several segmented semi-permeable membranes, and a retention semi-permeable membrane; the infusion pipe is vertically fixed in the soil surrounding the pile foundation; the supply pipe is disposed within the infusion pipe, with its upper end connected to the cooling circulation unit for inputting the refrigerant into the freezing pipe, and its lower end extending to the bottom of the infusion pipe, providing a space between it and the infusion pipe for the refrigerant to flow out; one end of the return pipe is connected to the top of the infusion pipe, and the other end is connected to the cooling circulation unit for outputting the refrigerant from the freezing pipe; the segmented semi-permeable membranes are annular, disposed between the infusion pipe and the supply pipe, with their outer and inner sides respectively connected to the inner wall of the infusion pipe and the outer wall of the supply pipe. Fixed; a plurality of segmented semipermeable membranes are vertically distributed between the infusion tube and the supply tube, dividing the infusion tube into multiple frozen sections, the average pore size of the plurality of segmented semipermeable membranes decreasing progressively from bottom to top; a retention semipermeable membrane is disposed at the connection between the return tube and the infusion tube; the average pore size of the retention semipermeable membrane is smaller than the average pore size of the uppermost segmented semipermeable membrane; the infusion tube and the supply tube contain a variety of high molecular weight polymers, the plurality of segmented semipermeable membranes separate the various molecular weight polymers into multiple frozen sections, the molecular weight of the polymers in the multiple frozen sections decreasing progressively from bottom to top, and the retention semipermeable membrane retains the polymers in the infusion tube.

[0008] Furthermore, the infusion tube has a heat insulation layer on the outer wall of the side facing away from the pile foundation; the length of the infusion tube is the same as the length of the pile foundation; the diameter of the infusion tube is not less than half the diameter of the pile foundation; and the distance between the infusion tube and the pile foundation is 4 to 5 times the diameter of the pile foundation.

[0009] Furthermore, the cooling circulation unit includes a liquid storage tank, a circulation pump, a thermocouple, a compressor, a condenser, an expansion valve, and an evaporator coil; the outlet of the liquid storage tank is connected to the upper end of the liquid supply pipe, the inlet of the liquid storage tank is connected to the return pipe, and a closed loop for circulating the refrigerant is formed between the liquid storage tank and the liquid supply pipe; the circulation pump is used to circulate the refrigerant; the thermocouple is used to measure the temperature of the refrigerant; the compressor, the condenser, the expansion valve, and the evaporator coil are connected in sequence to form a closed loop for circulating the refrigerant, and the evaporator coil is embedded in the liquid storage tank.

[0010] Furthermore, the directional freezing unit also includes a composite salt solution circulation device; the composite salt solution circulation device stores a composite salt solution and has an intake end and an exhaust end; the intake end and the exhaust end are connected to the storage tank and are used to incorporate the composite salt solution into the refrigerant; the refrigerant is a calcium chloride solution; the composite salt solution is a mixed solution of calcium chloride and ammonium chloride.

[0011] Furthermore, it also includes a reinforcement unit; the reinforcement unit is used to fix the position of the pile foundation after correction.

[0012] Furthermore, the reinforcement unit includes multiple clamps, support ears, support components, multiple grouting pipes, and a curing liquid supply device; the multiple clamps are respectively fixed to the top of the pile foundation and the freezing pipe; the support ears are fixed to the side wall of the clamps on the top of the pile foundation; the support components include walers, brackets, and rods; the walers are arc-shaped and placed on the clamps on the top of several freezing pipes, fixed to the side wall of the freezing pipes; the brackets are fixed to the inner side of the walers, located at the freezing pipes facing the inclination direction of the pile foundation; one end of the rod is fixed to the support ear, and the other end is fixed to the bracket; the curing liquid supply device stores low-carbon gel material; the grouting pipes are all set in the soil between the freezing pipes and the pile foundation, and connected to the curing liquid supply device for injecting low-carbon gel material into the soil.

[0013] Furthermore, it also includes a monitoring unit and a control unit; the monitoring and control unit includes an inclination sensor, multiple temperature sensors, and a three-dimensional laser scanning device; the inclination sensor is installed on the top of the pile foundation, with its axis parallel to the axis of the top surface of the pile foundation; the multiple temperature sensors are evenly distributed in the soil between the freezing pipe and the pile foundation to detect the temperature of the soil at different locations and depths; the three-dimensional laser scanning device is used to scan and obtain the position of the top of the pile foundation; the control unit includes finite element analysis software, a BIM platform, and a central controller; the finite element analysis software is used to simulate before freezing... The initial coolant temperature and the theoretical temperature cloud map of the soil and the theoretical displacement cloud map of the pile foundation at the initial coolant temperature are determined. The BIM platform is used to receive data from the tilt sensor and the three-dimensional laser scanning device during freezing and to form the actual displacement cloud map of the pile foundation. The central controller is used to receive data from the temperature sensor during freezing and to form the actual temperature cloud map of the soil. The central controller is also used to compare the actual temperature cloud map of the soil with the theoretical temperature cloud map of the soil, and the actual displacement cloud map of the pile foundation with the theoretical displacement cloud map of the pile foundation, and to adjust the temperature and flow rate of the coolant and the amount of the composite salt solution through a feedback algorithm.

[0014] Secondly, the present invention also provides a pile foundation correction method based on the controllable frost heave effect, implemented through the aforementioned pile foundation correction system based on the controllable frost heave effect, comprising the following steps: S1: Explore the pile foundation and the surrounding soil to obtain the length and inclination angle of the pile foundation, as well as the engineering geological and hydrogeological conditions of the soil. S2: Determine the location, insertion depth, and height above the ground surface of the freezing pipe; determine the dimensions of the clamp and the support assembly; S3: Install the tilt sensor and the three-dimensional laser scanning device, and synchronize the data from the tilt sensor and the three-dimensional laser scanning device to the BIM platform; S4: Drill holes around the pile, vertically bury the freezing pipe into the hole, and install the temperature sensor and the grouting pipe. The data from the temperature sensor is uploaded to the central controller, and the grouting pipe is connected to the curing liquid supply device. S5: Connect the low-temperature circulating unit, the composite salt solution circulating device, and the freezing pipe; S6: The finite element analysis software simulates freezing to obtain the theoretical temperature cloud map of the soil and the theoretical displacement cloud map of the pile foundation, and then the correction is carried out in stages. S7: Start the system and set the temperature and flow rate of each freezing tube; the central controller adjusts the temperature and flow rate of the refrigerant and the amount of the composite salt solution. S8: When the monitoring data shows that the pile foundation displacement reaches the threshold of this stage, the power of the compressor and the circulation pump is slowly reduced and the composite salt solution circulation device is shut down. After thermal equilibrium is reached, the next stage is entered. S9: Repeat S7 and S8 until the pile foundation is reset, and the correction is completed; S10: Install the clamp, connect the support assembly, and grout to repair until the pressure meets the requirements; the freezing pipe and the grouting pipe are retained in the soil as reinforcements, and the ground equipment is removed.

[0015] The beneficial effects of this invention are as follows: I. This invention fully utilizes the directional frost heave force and water migration potential generated by soil frost heave. By leveraging the frost heave deformation induced by water phase change in the freezing method, a frozen wall is formed around the pile. This frozen wall then triggers water migration to its location, causing refreezing and further enhancing the frost heave effect. Phase change compensation and real-time optimization of freezing parameters are employed during the freezing process to ensure a smooth process without disturbing the soil. After correction, the freezing pipe and grouting pipe work together as reinforcement within the soil, forming a permanent support structure to prevent further pile displacement. Compared to traditional correction techniques such as jacking, grouting reinforcement, and forced settlement, this invention eliminates the need for extensive excavation around the pile foundation and minimizes disturbance to surrounding buildings during construction. This achieves high efficiency and directionality in pile foundation correction, effectively reducing the cost of pile foundation correction.

[0016] Second, this invention achieves targeted freezing of the soil between the pile foundation and the freezing pipe through the heat insulation layer on the outer wall of the freezing pipe. This ensures that the frost heave force is directed from the freezing pipe to the pile foundation, while also reducing the freezing range, shortening the freezing time, and preventing frost heave deformation of unrelated soil. Furthermore, the segmented semi-permeable membrane inside the freezing pipe creates a temperature gradient that gradually increases from top to bottom, ensuring that the stress on the inclined side of the pile foundation gradually decreases from top to bottom. In addition, this invention incorporates phase change compensation by adding a composite salt solution to lower the freezing point and thermal conductivity of the coolant. This ensures the fluidity of the coolant while controlling the water phase change rate and ice crystal morphology, preventing brittle soil failure during the correction process.

[0017] Third, this invention utilizes a monitoring unit and a control unit, employing finite element analysis software to simulate freezing, obtaining the theoretical cooling rate and correction path. Then, using tilt sensors, temperature sensors, and a 3D laser scanning device, it monitors the tilt angle and displacement of the pile foundation, as well as the soil temperature at various locations around the pile, in real time. The data is fed back to a BIM platform for visualization. Finally, a PID algorithm is used to compare the theoretical values ​​from the finite element simulation with the visualized actual values, enabling real-time adjustment of freezing parameters such as coolant temperature and flow rate under multimodal conditions. This provides a control basis for directional freezing, achieving comprehensive monitoring and control of the correction process, ensuring the timeliness and accuracy of pile foundation correction. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the main structure of a pile foundation correction system based on the controllable frost heave effect; Figure 2 This is a top view schematic diagram of a pile foundation correction system based on the controllable frost heave effect; Figure 3 This is a schematic diagram of the structure of a freezing tube; Figure 4 This is a schematic diagram of the segmented semipermeable membrane in a freezing tube; Figure 5This is a schematic diagram of the structure of the freezing tube, its insulation layer, and the temperature sensor. Figure 6 This is a schematic diagram of the structure of a directional freezing unit; Figure 7 This is a top view of the freezing pipe and reinforcement unit. Figure 8 This is a structural diagram of the clamp and support ear; Figure 9 This is a schematic diagram of the grouting pipe structure; Figure 10 This is a schematic diagram of the active freeze-up control unit. The labels in the attached diagram are as follows: 11. Freezing tube; 111. Infusion tube; 112. Supply tube; 113. Return tube; 1141. Segmented semi-permeable membrane; 1142. Retention semi-permeable membrane; 115. Insulation layer; 12. Cooling circulation unit; 121. Storage tank; 122. Circulation pump; 123. Thermocouple; 124. Compressor; 125. Condenser; 126. Expansion valve; 127. Evaporator coil; 13. Compound salt solution circulation. Device; 131, suction end; 132, discharge end; 21, clamp; 22, support ear; 231, waler; 232, bracket; 233, rod; 24, grouting pipe; 241, pipe tip; 242, small hole in pipe wall; 243, pipe tail; 25, curing liquid supply device; 31, tilt sensor; 32, temperature sensor; 321, probe rod; 322, temperature probe; 33, three-dimensional laser scanning device; A, pile foundation. Detailed Implementation

[0019] The specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0020] like Figure 1 and Figure 2 As shown, this invention discloses a pile foundation correction system based on controllable frost heave effect, comprising at least one directional freezing unit. The directional freezing unit includes a freezing pipe 11 and a cooling circulation unit 12. The freezing pipe 11 is disposed in the soil surrounding pile A, located on the inclined side of pile A. A closed loop is formed between the cooling circulation unit 12 and the freezing pipe 11, with a refrigerant circulating inside, while the cooling circulation unit 12 cools the refrigerant. The refrigerant in the freezing pipe 11 causes a phase change freezing of the water in the soil between the freezing pipe 11 and pile A, generating a frost heave force pointing in the correction direction. Pile A achieves correction under the action of this frost heave force. Specifically, the freezing wall first forms at the junction of the freezing pipes 11. Simultaneously, free water migrates towards the freezing wall during the freezing process. The freezing wall absorbs the free water, refreezes, and expands, compressing the unfrozen soil and forming compressive stress pointing from the freezing wall towards the unfrozen area. Furthermore, the rigid freezing pipe 11 ensures the stability of the excavated area and also serves as part of the support structure after correction is completed.

[0021] In a preferred embodiment, there are multiple directional freezing units, and the freezing pipes 11 of the multiple directional freezing units are arranged in an arc shape on the inclined side of the pile foundation A with the pile foundation A as the center.

[0022] like Figure 3 and Figure 4 As shown, the freezing tube 11 includes an infusion tube 111, a supply tube 112, a return tube 113, several segmented semipermeable membranes 1141 and a retention semipermeable membrane 1142.

[0023] like Figure 3 As shown, the infusion pipe 111 is vertically fixed in the soil surrounding pile A. The infusion pipe 111 is a sealed pipe with a bottom cone. The connection between the bottom cone and the pipe body is reinforced to prevent damage when the infusion pipe 111 is drilled into the soil. The infusion pipe 111 is made of seamless steel, preferably duplex steel, with an anti-corrosion coating sprayed on the inner wall. This gives the infusion pipe 111 excellent mechanical strength, good thermal conductivity, and corrosion resistance, ensuring that it does not shift or deform during the freezing process, nor is it corroded or damaged by the refrigerant. A supply pipe 112 is installed inside the infusion pipe 111. Its upper end is connected to the cooling circulation unit 12 via a pipe to supply the refrigerant to the freezing pipe 11. Its lower end extends to the bottom of the infusion pipe 111, providing space between it and the infusion pipe 111 for the refrigerant to flow out. One end of the return pipe 113 is connected to the top of the delivery pipe 111, and the other end is connected to the cooling circulation unit 12 via a pipe to output the refrigerant from the freezing pipe 11. The supply pipe 112 introduces the refrigerant into the bottom of the delivery pipe 111, and the return pipe 113 transports the refrigerant filled in the delivery pipe 111 back to the cryogenic circulation unit, realizing the circulation of the refrigerant. Specifically, the center of the top surface of the delivery pipe 111 and the top of the pipe wall have circular holes of the same size, which are used to connect the supply pipe 112 and the return pipe 113 respectively, while ensuring the balanced flow rate at the inlet and outlet of the freezing pipe 11. Through the dual-pipe structure, the convective heat transfer coefficient between the refrigerant and the pipe wall is high and the flow rate is stable, thereby enabling precise control of flow rate and temperature, avoiding the local freezing lag that is prone to occur in single-pipe structures, which can cause uneven freezing of the wall.

[0024] like Figure 4As shown, the segmented semipermeable membrane 1141 is annular and positioned between the infusion tube 111 and the supply tube 112. Its outer and inner sides are bonded to the inner wall of the infusion tube 111 and the outer wall of the supply tube 112, respectively, using sealant. Several segmented semipermeable membranes 1141 are vertically distributed between the infusion tube 111 and the supply tube 112, dividing the infusion tube 111 into multiple frozen sections. The average pore size of the segmented semipermeable membranes 1141 decreases progressively from bottom to top. A retention semipermeable membrane 1142 is positioned at the connection between the return tube 113 and the infusion tube 111. The average pore size of the retention semipermeable membrane 1142 is smaller than the average pore size of the uppermost segmented semipermeable membrane 1141. Between the infusion pipe 111 and the supply pipe 112, there are polymers of various molecular weights. Several segmented semi-permeable membranes 1141 separate these polymers into multiple freezing sections. The molecular weight of the polymers in these freezing sections decreases progressively from bottom to top, and the retention semi-permeable membranes 1142 retain the polymers within the infusion pipe 111. Specifically, polymers of various molecular weights are injected from the bottom into the space between the infusion pipe 111 and the supply pipe 112 through the supply pipe 112. With the circulation of the refrigerant, the difference in the average pore size of the segmented semi-permeable membranes 1141 ensures that the molecular weight of the polymers in the multiple freezing sections decreases progressively from bottom to top. Since smaller molecular weights correspond to lower freezing points and higher heat transfer coefficients in the freezing section, a temperature gradient with progressively decreasing temperature from bottom to top is formed within the infusion pipe 111, resulting in a greater stress on the upper part of side A of the pile foundation than on the lower part. The polymer can be polyethylene glycol. The segmented semipermeable membrane 1141 and the retention semipermeable membrane 1142 should preferably be ultrafiltration membranes, which have a high retention rate and less stringent pressure requirements on the circulation pump.

[0025] like Figure 5 As shown, a heat insulation layer 115 is provided on the outer wall of the infusion pipe 111 on the side facing away from pile A. Through the heat insulation effect of the heat insulation layer 115, the directional freezing unit freezes only the soil between the freezing pipe 11 and pile A, reducing cold dissipation and preventing frost heave damage to unrelated soil. Specifically, the heat insulation layer 115 can be a heat-insulating foam such as polystyrene, tightly bonded to the outer wall of the infusion pipe 111 using polyurethane foam adhesive.

[0026] In a preferred embodiment, the length of the infusion pipe 111 is the same as the length of the pile foundation A. The diameter of the infusion pipe 111 is not less than half the diameter of the pile foundation A to meet the bending stiffness specification. The distance between the infusion pipe 111 and the pile foundation A is 4 to 5 times the diameter of the pile foundation A, thereby leaving sufficient soil between the freezing pipe 11 and the pile foundation A to provide sufficient free water.

[0027] like Figure 6 As shown, the cooling circulation unit 12 includes a liquid storage tank 121, a circulation pump 122, a thermocouple 123, a compressor 124, a condenser 125, an expansion valve 126, and an evaporator coil 127.

[0028] The outlet of the storage tank 121 is connected to the upper end of the supply pipe 112 via a pipe, and the inlet of the storage tank 121 is connected to the return pipe 113 via a pipe, forming a closed loop for circulating refrigerant between the storage tank 121 and the delivery pipe 111. After welding, the pipes are sprayed with polyurethane for insulation to reduce heat loss at the joints. The pipes have two layers: an inner layer made of low-carbon seamless steel and an outer insulation layer 115. The insulation layer 115 is sprayed with hollow ceramic insulation agent, thus achieving good sealing, thermal insulation, and low-temperature stability, preventing heat loss during refrigerant transportation.

[0029] A circulating pump 122 is located at the outlet of the liquid receiver 121 for circulating the refrigerant. A thermocouple 123 is located inside the liquid receiver 121, submerged in the refrigerant, and is used to measure the temperature of the refrigerant. A compressor 124, condenser 125, expansion valve 126, and evaporator coil 127 are connected in sequence to form a closed loop for circulating the refrigerant. The evaporator coil 127 is embedded inside the liquid receiver 121. The compressor 124 compresses the refrigerant to a high-temperature, high-pressure gaseous state; the condenser 125 cools and liquefies the compressed refrigerant; the expansion valve 126 depressurizes and expands the liquid refrigerant; and the evaporator coil 127 evaporates the low-temperature, low-pressure refrigerant while simultaneously absorbing heat from the refrigerant in the liquid receiver 121, thus cooling the refrigerant. R717 refrigerant is preferred, balancing cost, energy efficiency, and refrigeration efficiency.

[0030] The system achieves precise monitoring and control of the refrigerant temperature and flow rate through the cooling circulation unit 12.

[0031] like Figure 6 As shown, the directional freezing unit also includes a composite salt solution circulation device 13. The composite salt solution circulation device 13 stores a composite salt solution and has an intake end 131 and an outlet end 132. The intake end 131 and the outlet end 132 are connected to the liquid storage tank 121 through pipes for incorporating the composite salt solution into the refrigerant.

[0032] The refrigerant is a calcium chloride solution, which has a low freezing point, good thermal conductivity, and low corrosivity, and the temperature can be controlled within the range of -10 to -25℃. Specifically, water exhibits the fastest ice crystal growth rate at -5 to -10℃, and the crystals are mostly dendritic or needle-like, easily causing brittle damage or disturbance to the soil. At -20℃, water has a higher degree of supercooling to provide the driving force for phase change, while water molecules still retain a certain degree of migration ability. Therefore, the initial refrigerant temperature set for the simulated freezing is -15 to -25℃, and the calcium chloride solution concentration is not less than 25 wt%.

[0033] The composite salt solution is a mixture of calcium chloride and ammonium chloride. The composite salt solution circulation device 13 is used to add ammonium chloride to the refrigerant without changing the concentration of calcium chloride. The addition of ammonium chloride reduces the thermal conductivity between the refrigerant and the pipe wall. Furthermore, the low-temperature viscosity of the ammonium chloride solution is higher than that of calcium chloride. The low thermal conductivity and high viscosity synergistically slow down the cold transfer efficiency, thereby preventing brittle failure or disturbance of the soil due to excessively rapid phase change of moisture in the soil. Simultaneously, the addition of calcium chloride maintains the concentration of calcium chloride in the refrigerant, thus preventing the refrigerant's freezing point from rising and solidifying, which would affect the circulation.

[0034] In a preferred embodiment, both the cooling circulation unit 12 and the composite salt solution circulation device 13 are located on the ground surface and on the inclined side of the pile foundation A. Being located on the ground surface facilitates liquid replenishment, maintenance, etc., and being located on the inclined side of the pile foundation A reduces the length of the connecting pipes.

[0035] The system also includes a reinforcement unit. The reinforcement unit is used to fix the position of pile A after correction.

[0036] like Figure 1 , Figure 7 and Figure 8 As shown, the reinforcement unit includes multiple clamps 21, support ears 22, support components, multiple grouting pipes 24, and curing liquid supply device 25.

[0037] like Figure 1 , Figure 7 and Figure 8 As shown, multiple clamps 21 are fixed to the top of pile A and the freezing pipe 11 respectively. Support ears 22 are fixed to the side wall of the clamps 21 at the top of pile A. The support assembly includes a waler 231, a bracket 232, and a rod 233. The waler 231 is an H-shaped steel rod, arc-shaped, placed on the clamps 21 at the top of several freezing pipes 11, and fixed to the side wall of the freezing pipes 11 by expansion bolts. The bracket 232 is fixed to the inner side of the waler 231 by double welded steel plates, located at the freezing pipe 11 facing the inclined direction of pile A. The rod 233 is a steel pipe with an internal H-shaped steel section, one end fixed to the support ear 22, and the other end fixed to the bracket 232. The clamps 21, support ears 22, and support assembly, as a support structure, connect the freezing pipe 11 and pile A, preventing pile A from deflecting back due to soil settlement around the pile.

[0038] like Figure 1 and Figure 7 As shown, the curing liquid supplier stores low-carbon gel material, which is composed of cement slurry, water glass, and fly ash, ensuring the fluidity of the slurry and its strength after solidification. The grouting pipes 24 are all installed in the soil between the freezing pipe 11 and pile A, and are connected to the curing liquid supplier for injecting the low-carbon gel material into the soil. Specifically, as... Figure 9As shown, the grouting pipe 24 includes a pipe tip 241, small holes 242 in the pipe wall, and a pipe tail 243. The pipe tip 241 is conical and penetrates the frost-susceptible soil layer into the thick soil layer. The small holes 242 in the pipe wall are evenly distributed to ensure uniform coverage of the grout and prevent local loosening of the stratum. The pipe tail 243 protrudes above the ground and has a pre-reserved, holeless grout-stopping section, which is connected to the solidification liquid supply device 25 via a rubber tube. The grout reacts chemically with the minerals in the soil to generate a strong silicate or aluminosilicate network structure, cementing the loose soil into a load-bearing soil mass. After grouting is completed, the grouting pipe 24 remains in the soil as a reinforcement, effectively preventing the weakening of soil strength caused by increased porosity due to the melting of ice crystals after frost heave.

[0039] The system also includes a monitoring unit and a control unit.

[0040] like Figure 1 and Figure 2 As shown, the monitoring and control unit includes a tilt sensor 31, multiple temperature sensors 32, and a three-dimensional laser scanning device 33.

[0041] Inclination sensor 31 is installed on the top of pile A, with its axis parallel to the axis of the top surface of pile A, to ensure that the received data is the same as the actual inclination angle of pile A.

[0042] Multiple temperature sensors 32 are evenly distributed in the soil between the freezing pipe 11 and the pile foundation A to detect the soil temperature at different locations and depths. Specifically, such as... Figure 5 As shown, the temperature sensor 32 includes a probe 321, multiple temperature probes 322, and a transmission line. The probe 321 is inserted into the soil perpendicular to the ground. Multiple temperature probes 322 are integrated at different depths of the probe 321, and the temperature probes 322 are connected to a control unit via a transmission line located inside the probe 321. The temperature sensor 32 preferably uses a type K thermocouple 123 to monitor the longitudinal temperature distribution of the soil. By uniformly distributing several temperature sensors 32 along the moisture direction, a spatial temperature cloud map is formed.

[0043] A three-dimensional laser scanning device 33 is used to scan and obtain the position of the top of pile foundation A. Specifically, the three-dimensional laser scanning device 33 is located on the ground surface between the freezing pipe 11 and pile foundation A, and is erected on a tripod at a height higher than the top of pile foundation A. The three-dimensional laser scanning device 33 emits a modulated continuous laser beam that reflects off the top of pile foundation A. By measuring the phase difference between the emitted and reflected laser beams and calculating the round-trip path of the laser, the distance from the three-dimensional laser scanning device 33 to various points on the top of pile foundation A can be obtained, and visualized as a three-dimensional model of the top of pile foundation A. During the correction process of pile foundation A, the three-dimensional laser scanning device 33 performs continuous scanning to obtain a displacement cloud map of the top of pile foundation A.

[0044] The system uses multiple temperature sensors 32 to monitor the temperature of the soil around the pile in both horizontal and vertical directions, and uses tilt sensors 31 and a three-dimensional laser scanning device 33 to monitor the tilt angle and displacement path of the pile foundation A.

[0045] The control unit includes finite element analysis software, a BIM platform, and a central controller. The finite element analysis software is used to determine the appropriate initial coolant temperature and the theoretical temperature cloud map of the soil and the theoretical displacement cloud map of the pile foundation at that initial coolant temperature through simulation before freezing. The BIM platform is used to receive data from the tilt sensor 31 and the 3D laser scanning device 33 during freezing and generate an actual displacement cloud map of the pile foundation. The central controller is used to receive data from the temperature sensor 32 during freezing and generate an actual temperature cloud map of the soil. The central controller also compares the actual temperature cloud map of the soil with the theoretical temperature cloud map of the soil, and the actual displacement cloud map of the pile foundation with the theoretical displacement cloud map of the pile foundation, adjusting the temperature and flow rate of the coolant and the amount of composite salt solution used through a feedback algorithm.

[0046] Specifically, the finite element analysis software used is COMSOL. Inputting parameters such as the geometric model, basic soil parameters, and boundary conditions yields the equilibrium equations for the temperature, moisture, and stress fields. Changes in volumetric water content and volumetric ice content alter the soil's equivalent volumetric heat capacity and equivalent thermal conductivity, thus affecting temperature. A hydrothermal coupling simulation is used to generate the moisture and temperature fields. These fields are applied as loads to the stress field. The stress field is derived by calculating the volumetric expansion caused by water freezing, thus combining the temperature, moisture, and stress fields. The simulated theoretical temperature contour maps of the soil and pile foundations are uploaded to the central controller. The finite element analysis software helps determine the initial coolant temperature, and the resulting theoretical temperature and displacement contour maps provide theoretical data for the central controller's adjustments. This provides a theoretical basis for freezing construction, ensuring the controllability of the cooling process and the stability of the correction process, preventing disturbance to the soil and pile foundation A.

[0047] The BIM platform is primarily built using Revit software. Based on data from tilt sensor 31 and 3D laser scanning device 33, it constructs a real-time 3D model of the changes in pile foundation A at different stages, forming a continuous visualized displacement map of pile foundation A, which is then synchronized to the central controller as an actual displacement cloud map of the pile foundation. The BIM platform visualizes and reconstructs the data from tilt sensor 31 and 3D laser scanning device 33 into an actual displacement cloud map of the pile foundation, and coordinates it with data from temperature sensor 32 to provide actual data to the central controller.

[0048] The central controller receives data uploaded from the BIM platform and temperature sensor 32, and connects to compressor 124, circulation pump 122 and composite salt solution circulation device 13 via wires, and adjusts each freezing parameter in real time based on PID algorithm.

[0049] like Figure 10 As shown, the system's correction mechanism is as follows: The physical parameters and geometric model of the exploratory inclined pile A and the surrounding soil are input into COMSOL. Different initial coolant temperatures are set to simulate and obtain the corresponding theoretical soil temperature cloud map and theoretical pile displacement cloud map. Combining the strength indices of pile A and the soil, the optimal initial coolant temperature, theoretical soil temperature cloud map, and theoretical pile displacement cloud map are determined. The correction process is then divided into several stages based on the theoretical pile displacement cloud map, with the pile A inclination angle change and displacement threshold set for each stage. Data from the inclination sensor 31 and the 3D laser scanning device 33 are input into the BIM platform for visualization and reconstruction, obtaining the actual pile displacement cloud map during the freezing process. The data from the temperature sensor 32 is then visualized as the actual soil temperature cloud map. The central controller compares the actual soil temperature cloud map with the theoretical soil temperature cloud map, and the actual pile displacement cloud map with the theoretical pile displacement cloud map, adjusting the freezing parameters based on a PID algorithm. The freezing construction at each stage is divided into an active freezing period and a maintenance freezing period, with different freezing objectives achieved in different freezing periods. The active freezing period is the main period for correction. During this period, the soil rapidly cools to freezing temperature, resulting in significant frost heave displacement and substantial displacement of pile A. PID control of freezing parameters is introduced at this stage. If the actual temperature is higher than the theoretical temperature or the actual displacement is less than the theoretical displacement, the power of compressor 124 and the pressure of circulating pump 122 increase, the refrigerant temperature decreases, and the flow rate increases. If the actual temperature is lower than the theoretical temperature or the actual displacement is greater than the theoretical displacement, the power of compressor 124 and the pressure of circulating pump 122 decrease, the refrigerant temperature increases, and the flow rate decreases. The maintenance freezing period is the correction and stabilization period. During this period, the soil maintains its freezing temperature, with minimal frost heave displacement, and pile A displaces slowly. The freezing maintenance period continues until the displacement and tilt angle of pile A match the threshold of this correction stage. After reaching the threshold, the power of compressor 124 and the pressure of circulating pump 122 are slowly reduced to achieve thermal equilibrium. To avoid brittle failure of the soil, isotherms below zero degrees Celsius are selected from both the theoretical and actual soil temperature cloud maps. The expansion rate of the frozen wall is obtained based on the rate of increase in the isotherm coverage area. If the actual rate is greater than the theoretical rate, the concentration of the composite salt solution is increased. If the actual speed is less than the theoretical speed, the concentration of the composite salt solution is reduced. When the BIM platform detects a non-preset direction displacement of pile A using the 3D laser scanning device 33, the central controller immediately lowers the temperature of the coolant in the freezing pipe 11 in that direction to enhance freezing in that direction until the preset state is restored. When the BIM platform detects that pile A has reached the inclination angle and displacement threshold for that stage, that stage ends. After a brief period of thermal equilibrium, the next stage begins until pile A is reset, and the correction is complete.

[0050] The pile foundation correction method based on the controllable frost heave effect includes the following steps: S1: Explore pile foundation A and its surrounding soil to obtain the length and inclination angle of pile foundation A, as well as the engineering geological and hydrogeological conditions of the soil.

[0051] S2: Determine the location, insertion depth, and height above the ground of the freezing pipe 11. Determine the dimensions of the clamp 21 and the support assembly.

[0052] S3: Install tilt sensor 31 and 3D laser scanning device 33, and synchronize the data of tilt sensor 31 and 3D laser scanning device 33 to BIM platform.

[0053] S4: Drill holes around the pile, vertically embed the freezing pipe 11 into the hole, and install temperature sensor 32 and grouting pipe 24. The data from temperature sensor 32 is uploaded to the central controller, and grouting pipe 24 is connected to curing liquid supply device 25.

[0054] S5: Establish a freezing chamber and connect the low-temperature circulating unit, the composite salt solution circulating device 13, and the freezing pipe 11.

[0055] S6: The finite element analysis software simulates freezing to obtain the theoretical temperature cloud map of the soil and the theoretical displacement cloud map of the pile foundation, and then the correction is carried out in stages.

[0056] S7: Start the system and set the temperature and flow rate of each freezing tube 11. The central controller adjusts the temperature and flow rate of the refrigerant and the amount of composite salt solution used.

[0057] S8: When the monitoring data shows that the displacement of pile foundation A reaches the threshold of this stage, the power of compressor 124 and circulation pump 122 is slowly reduced and the composite salt solution circulation device 13 is turned off. After thermal equilibrium is reached, the next stage is entered.

[0058] S9: Repeat S7 and S8 until pile A is reset, and the correction is completed.

[0059] S10: Install clamp 21, connect the support components, and grout until the pressure meets the requirements. The freezing pipe 11 and grouting perforated pipe 24 are retained in the soil as reinforcement. Remove the surface equipment.

[0060] In this invention, unless otherwise stated, scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, the reagents, materials, and procedures used herein are all widely used in the relevant fields.

[0061] It should be noted that the terms such as "upper", "lower", "left", "right", "front", and "back" used in the invention are only for clarity of description and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0062] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pile foundation correction system based on controllable frost heave effect, characterized in that: Includes at least one directional freezing unit; The directional freezing unit includes a freezing pipe and a cooling circulation unit; The freezing pipe is installed in the soil surrounding the pile foundation, located on the inclined side of the pile foundation; The cooling circulation unit and the freezing pipe form a closed loop, with a refrigerant circulating inside, and the cooling circulation unit cools the refrigerant. The refrigerant inside the freezing pipe causes the moisture in the soil between the freezing pipe and the pile foundation to undergo a phase change and freeze, generating a frost heave force pointing in the direction of correction. The pile foundation achieves correction under the action of the frost heave force.

2. The pile foundation correction system based on controllable frost heave effect according to claim 1, characterized in that: The number of directional freezing units is multiple, and the freezing pipes of the multiple directional freezing units are arranged in an arc shape around the pile foundation on the inclined side of the pile foundation.

3. The pile foundation correction system based on controllable frost heave effect according to claim 2, characterized in that: The freezing tube includes an infusion tube, a supply tube, a return tube, several segmented semi-permeable membranes, and a retention semi-permeable membrane; The infusion tube is vertically fixed in the soil surrounding the pile foundation; The supply pipe is installed in the delivery pipe, with its upper end connected to the cooling circulation unit for inputting the refrigerant into the freezing pipe, and its lower end extending to the bottom of the delivery pipe, with a space between it and the delivery pipe that allows the refrigerant to flow out. One end of the return pipe is connected to the top of the delivery pipe, and the other end is connected to the cooling circulation unit to output the refrigerant from the freezing pipe; The segmented semipermeable membrane is annular and disposed between the infusion tube and the supply tube, with its outer and inner sides respectively connected and fixed to the inner wall of the infusion tube and the outer wall of the supply tube; a plurality of the segmented semipermeable membranes are distributed vertically between the infusion tube and the supply tube, dividing the infusion tube into multiple frozen sections, and the average pore size of the plurality of segmented semipermeable membranes gradually decreases from bottom to top; The semi-permeable membrane is disposed at the connection between the return tube and the infusion tube; the average pore size of the semi-permeable membrane is smaller than the average pore size of the uppermost segmented semi-permeable membrane; The infusion tube and the supply tube contain polymers of various molecular weights. Several segmented semi-permeable membranes separate the polymers of various molecular weights into multiple frozen sections. The molecular weight of the polymers in the multiple frozen sections decreases gradually from bottom to top, and the retention semi-permeable membrane retains the polymers in the infusion tube.

4. The pile foundation correction system based on controllable frost heave effect according to claim 3, characterized in that: The infusion pipe has a heat insulation layer on the outside of the pipe wall on the side facing away from the pile foundation; The length of the infusion tube is the same as the length of the pile foundation; the diameter of the infusion tube is not less than half the diameter of the pile foundation; The distance between the infusion tube and the pile foundation is 4 to 5 times the diameter of the pile foundation.

5. The pile foundation correction system based on controllable frost heave effect according to claim 3, characterized in that: The cooling circulation unit includes a liquid storage tank, a circulation pump, a thermocouple, a compressor, a condenser, an expansion valve, and an evaporator coil; The outlet of the liquid storage tank is connected to the upper end of the liquid supply pipe, and the inlet of the liquid storage tank is connected to the return pipe. A closed loop for circulating the refrigerant is formed between the liquid storage tank and the liquid supply pipe. The circulating pump is used to circulate the refrigerant; The thermocouple is used to measure the temperature of the refrigerant. The compressor, the condenser, the expansion valve, and the evaporator coil are connected in sequence to form a closed loop for circulating refrigerant, and the evaporator coil is embedded in the liquid storage tank.

6. The pile foundation correction system based on controllable frost heave effect according to claim 5, characterized in that: The directional freezing unit also includes a composite salt solution circulation device; The composite salt solution circulation device stores a composite salt solution and has an intake end and an exhaust end; the intake end and the exhaust end are connected to the storage tank and are used to incorporate the composite salt solution into the refrigerant; The coolant is a calcium chloride solution; the composite salt solution is a mixture of calcium chloride and ammonium chloride.

7. The pile foundation correction system based on controllable frost heave effect according to claim 6, characterized in that: It also includes reinforcement units; The reinforcement unit is used to fix the position of the pile foundation after correction.

8. The pile foundation correction system based on controllable frost heave effect according to claim 7, characterized in that: The reinforcement unit includes multiple clamps, support ears, support components, multiple grouting pipes, and a curing liquid supply device; Multiple clamps are respectively fixed to the pile foundation and the top of the freezing pipe; The support lug is fixed to the side wall of the clamp at the top of the pile foundation; The support assembly includes a waler, a bracket, and a rod; the waler is arc-shaped and placed on the clamps at the top of several freezing pipes, and fixed to the side wall of the freezing pipes; the bracket is fixed to the inner side of the waler and located at the freezing pipe facing the inclination direction of the pile foundation; one end of the rod is fixed to the support lug and the other end is fixed to the bracket. The curing liquid supply device stores low-carbon gel material; the grouting pipes are all installed in the soil between the freezing pipe and the pile foundation, and are connected to the curing liquid supply device to inject low-carbon gel material into the soil.

9. The pile foundation correction system based on controllable frost heave effect according to claim 7, characterized in that: It also includes a monitoring unit and a control unit; The monitoring and control unit includes a tilt sensor, multiple temperature sensors, and a three-dimensional laser scanning device; The tilt sensor is installed on the top of the pile foundation, and its axis is parallel to the axis of the top surface of the pile foundation; Multiple temperature sensors are evenly distributed in the soil between the freezing pipe and the pile foundation to detect the temperature of the soil at different locations and depths. The three-dimensional laser scanning device is used to scan and obtain the position of the top of the pile foundation; The control unit includes finite element analysis software, a BIM platform, and a central controller; The finite element analysis software is used to determine the initial coolant temperature and the theoretical temperature cloud map of the soil and the theoretical displacement cloud map of the pile foundation under the initial coolant temperature through simulation before freezing. The BIM platform is used to receive data from the tilt sensor and the three-dimensional laser scanning device during freezing, and to generate a cloud map of the actual displacement of the pile foundation. The central controller is used to receive data from the temperature sensor during freezing and form an actual soil temperature cloud map; the central controller is also used to compare the actual soil temperature cloud map with the theoretical soil temperature cloud map and the actual pile displacement cloud map with the theoretical pile displacement cloud map, and adjust the temperature and flow rate of the coolant and the amount of the composite salt solution through a feedback algorithm.

10. A pile foundation correction method based on controllable frost heave effect, characterized in that: The implementation of the pile foundation correction system based on the controllable frost heave effect as described in claim 9 includes the following steps: S1: Explore the pile foundation and the surrounding soil to obtain the length and inclination angle of the pile foundation, as well as the engineering geological and hydrogeological conditions of the soil. S2: Determine the location, insertion depth, and height above the ground surface of the freezing pipe; determine the dimensions of the clamp and the support assembly; S3: Install the tilt sensor and the three-dimensional laser scanning device, and synchronize the data from the tilt sensor and the three-dimensional laser scanning device to the BIM platform; S4: Drill holes around the pile, vertically bury the freezing pipe into the hole, and install the temperature sensor and the grouting pipe. The data from the temperature sensor is uploaded to the central controller, and the grouting pipe is connected to the curing liquid supply device. S5: Connect the low-temperature circulating unit, the composite salt solution circulating device, and the freezing pipe; S6: The finite element analysis software simulates freezing to obtain the theoretical temperature cloud map of the soil and the theoretical displacement cloud map of the pile foundation, and then the correction is carried out in stages. S7: Start the system and set the temperature and flow rate of each freezing tube; the central controller adjusts the temperature and flow rate of the refrigerant and the amount of the composite salt solution. S8: When the monitoring data shows that the pile foundation displacement reaches the threshold of this stage, the power of the compressor and the circulation pump is slowly reduced and the composite salt solution circulation device is shut down. After thermal equilibrium is reached, the next stage is entered. S9: Repeat S7 and S8 until the pile foundation is reset, and the correction is completed; S10: Install the clamp, connect the support assembly, and grout to repair until the pressure meets the requirements; the freezing pipe and the grouting pipe are retained in the soil as reinforcements, and the ground equipment is removed.

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