Method for repairing pile-soil interface defect of cast-in-place pile in permafrost region

Abstract

The invention discloses a method for repairing a pile-soil interface defect of a cast-in-place pile in a permafrost region, which comprises the following steps of: pre-burying a repairing pipe on the wall of a drilled hole, covering a pressure sensitive film on a prefabricated hole of the repairing pipe, and after a concrete cast-in-place pile is poured and fully hydrated, freezing frozen soil back to form the pile-soil interface defect. And low-temperature mud / mortar is injected into the repairing pipe in stages, and when the injection pressure is larger than the fracture pressure of the pressure sensitive film, the pressure sensitive film at the pile-soil interface defect position is fractured, so that the pile-soil interface defect is effectively filled, the construction quality of the cast-in-place pile is improved, the bearing capacity of the cast-in-place pile is remarkably improved, and the structural stability is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation engineering in permafrost regions, and particularly to a method for repairing the defects of the pile-soil interface of cast-in-place piles in permafrost regions. Background Art

[0002] Permafrost is a kind of ice-containing rock and soil mass with a temperature below 0°C. In permafrost regions, there are significant differences in the ice content of the underground soil layers. Especially near the upper limit of permafrost, thick underground ice often exists. According to the load transfer characteristics of friction pile foundations, theoretically this part of the frozen soil layer is the key area mainly bearing the upper load, that is, the freezing force at the pile-soil interface in this area mainly bears the upper load in the form of side friction resistance. However, as Figure 1 shown, when constructing cast-in-place piles in permafrost regions, the transfer of the hydration heat of concrete will significantly change the hydrothermal state of the soil around the pile. Specifically, it is manifested as the melting of the frozen soil on the pile side and the redistribution of the water in the melting zone under the action of gravity. Under the action of the infinite cold source of permafrost, when the thawed soil around the pile refreezes, the ice content distribution of the soil on the pile side changes significantly compared with the original state, often resulting in poor contact or void phenomena at the pile-soil interface. These problems not only cause a large deviation between the actual bearing capacity of cast-in-place piles in permafrost regions and the drilling prediction results, but also seriously weaken the bearing capacity and structural stability of cast-in-place piles, bringing potential safety hazards to construction projects. At present, the solutions to such problems are relatively limited and there are certain technical challenges. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for repairing the defects of the pile-soil interface of cast-in-place piles in permafrost regions for the problems of the redistribution of the water in the melting zone on the pile side caused by the thermal disturbance of the frozen soil on the pile side by the hydration heat of concrete and the formation of pile-soil interface defects during the re-freezing process.

[0004] The technical solution adopted to achieve the purpose of the present invention is as follows: A method for repairing the defects of the pile-soil interface of cast-in-place piles in permafrost regions, comprising the following steps: Step 1, embedding repair pipes: Install one or more repair pipes vertically along the circumferential direction on the hole wall of the borehole in the permafrost region. The top of each repair pipe is open, the top surface of the repair pipe is flush with the ground surface, the bottom surface is close to the bottom of the borehole, and a plurality of prefabricated holes are successively arranged at intervals along the depth direction of the borehole. The openings of the prefabricated holes face the hole wall of the borehole and are close to the hole wall of the borehole. Each prefabricated hole is covered with a single layer or multiple layers of pressure-sensitive membranes; Step 2, pouring concrete: After the repair pipes are embedded, pour concrete in the borehole to form a cast-in-place pile. During the pouring process, the soil around the concrete cast-in-place pile melts. When the melted soil refreezes, pile-soil interface defects are formed between the cast-in-place pile and the surrounding soil; Step 3, injecting low-temperature mud / mortar: Inject low-temperature mud / mortar into the repair pipe from the ground surface until the injection pressure is greater than the rupture pressure of the pressure-sensitive membrane. After the pressure-sensitive membrane at the pile-soil interface defect ruptures, the low-temperature mud / mortar enters the pile-soil interface defect through the prefabricated holes for filling. Step 4, forming a filling layer: After the injection is completed, the low-temperature mud / mortar freezes and forms a filling layer at the pile-soil interface defect, and the repair of the pile-soil interface defect is completed.

[0005] In the above technical solution, in Step 1, the repair pipe is divided into three sections, namely the top section located at the top of the borehole, the middle section located in the middle of the borehole, and the bottom section located at the bottom of the borehole. The rupture pressure of the pressure-sensitive membrane covered by the prefabricated holes in the top section of the repair pipe is the first rupture pressure, the rupture pressure of the pressure-sensitive membrane covered by the prefabricated holes in the middle section is the second rupture pressure, and the rupture pressure of the pressure-sensitive membrane covered by the prefabricated holes in the bottom section is the third rupture pressure. The first rupture pressure is greater than the second rupture pressure, and the second rupture pressure is greater than the third rupture pressure.

[0006] In the above technical solution, in Step 3, a strain gauge is pasted at the center of the surface of the pressure-sensitive membrane. The strain gauge is connected to a data acquisition system. During the process of injecting low-temperature mud / mortar into the repair pipe, the output signal of the strain gauge is recorded in real time through the data acquisition system. According to the output signal of the strain gauge, combined with the elastic modulus and Poisson's ratio of the pressure-sensitive membrane material, the pressure change borne by the pressure-sensitive membrane is calculated.

[0007] On the other hand, the present invention also includes a method for evaluating the perfusion quality of a cast-in-place concrete pile, including the following steps: Step 1, drilling in the permafrost area and detecting the ice content of each area at different depth positions. Step 2, pre-burying the repair pipe: Vertically install one or more repair pipes along the circumferential direction of the borehole wall in the permafrost area. The top of each repair pipe is open, the top surface of the repair pipe is flush with the ground surface, and the bottom surface is close to the bottom of the borehole. The repair pipe is sequentially provided with a plurality of prefabricated holes at intervals along the depth direction of the borehole. The openings of the prefabricated holes face the borehole wall and are close to the borehole wall. Each prefabricated hole is covered with a single layer or multiple layers of pressure-sensitive membranes. A strain gauge is pasted at the center of the surface of the pressure-sensitive membrane, and the strain gauge is connected to a data acquisition system. Step 3, pouring concrete: After the repair pipe is pre-buried, pour concrete in the borehole to form a cast-in-place pile. During the pouring process, due to the action of hydration heat, the soil around the cast-in-place concrete pile melts. When the melted soil refreezes, a pile-soil interface defect is formed between the cast-in-place pile and the surrounding soil. Step 4, injecting low-temperature mud / mortar to form a filling layer: Inject low-temperature mud / mortar into the repair pipe from the ground surface until the injection pressure is greater than the rupture pressure of the pressure-sensitive membrane. After the pressure-sensitive membrane ruptures, the low-temperature mud / mortar fills the defects at the pile-soil interface. The pile-soil interface defects include the first defect formed between the cast-in-place pile and the surrounding frozen soil and the second defect formed due to uneven concrete pouring during the formation of the cast-in-place pile. Step 5, perfusion quality assessment: The data acquisition system obtains whether each pressure-sensitive membrane has ruptured by collecting the signals of the strain gauges. If the position where the pressure-sensitive membrane ruptures corresponds to the area with a high ice content, it indicates that the rupture of the pressure-sensitive membrane is caused by the first defect. If the position where the pressure-sensitive membrane ruptures corresponds to the area with a low ice content, it indicates that the rupture of the pressure-sensitive membrane is caused by the second defect. If the pressure-sensitive membrane corresponding to the area with a high ice content ruptures, it indicates that the first defect has been repaired. If the pressure-sensitive membrane corresponding to the area with a low ice content ruptures, it indicates that the second defect has been repaired.

[0008] In the above technical solution, low-temperature mud / mortar is injected in stages. When injecting the bottom section, when the difference between the pressure borne by the pressure-sensitive membrane in the middle section and its rupture pressure reaches a predetermined value and / or the difference between the pressure borne by the pressure-sensitive membrane in the top section and its rupture pressure reaches a predetermined value, the system issues a warning signal to remind the construction personnel to adjust the injection pressure of the low-temperature mud / mortar to avoid inaccurate injection position of the low-temperature mud / mortar caused by premature rupture of the pressure-sensitive membrane. When injecting the middle section, when the difference between the pressure borne by the pressure-sensitive membrane in the top section and its rupture pressure reaches a predetermined value, the system issues a warning signal to remind the construction personnel to adjust the injection pressure of the low-temperature mud / mortar to avoid inaccurate injection position of the low-temperature mud / mortar caused by premature rupture of the pressure-sensitive membrane.

[0009] In the above technical solution, first inject low-temperature mud / mortar into the bottom section of the repair pipe. The injection pressure is greater than the rupture pressure of the pressure-sensitive membrane at the prefabricated hole in the bottom section. After the low-temperature mud / mortar enters the pile-soil interface defect and freezes, then inject low-temperature mud / mortar into the middle section of the repair pipe. The injection pressure is greater than the rupture pressure of the pressure-sensitive membrane at the prefabricated hole in the middle section. After the low-temperature mud / mortar enters the pile-soil interface defect and freezes, finally inject low-temperature mud / mortar into the top section of the repair pipe. The injection pressure is greater than the rupture pressure of the pressure-sensitive membrane at the prefabricated hole in the top section. The low-temperature mud / mortar enters the pile-soil interface defect and freezes. Among them, the injection pressure of the bottom section is less than that of the middle section, and the injection pressure of the middle section is less than that of the top section.

[0010] In the above technical solution, the pressure-sensitive membrane is a polyester film.

[0011] In the above technical solution, a prefabricated hole is arranged in the repair pipe every 1 to 2 meters along the depth direction of the drilling.

[0012] In the above technical solution, the diameter of the prefabricated hole is 5 mm to 1 cm, and is smaller than half of the diameter of the repair tube.

[0013] In the above technical solution, the diameter of the repair tube does not exceed 5 cm, preferably 2 to 3 cm.

[0014] In the above technical solution, the repair tube is a plastic tube, preferably a PVC tube.

[0015] In the above technical solution, when multiple repair pipes are installed along the circumference of the borehole wall in the permafrost area, the prefabricated holes of the multiple repair pipes are staggered along the depth direction of the borehole to ensure that prefabricated holes are set on any horizontal surface in the borehole.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention can effectively fill the pile-soil interface defects and improve the construction quality of cast-in-place piles by pre-buried repair pipes on the borehole wall and covering the prefabricated holes of the repair pipes with pressure-sensitive membranes; 2. After the low-temperature mud / mortar is injected in stages, the contact condition of the pile-soil interface is improved, the bearing capacity of the cast-in-place pile is significantly improved, and the stability of the structure is enhanced; 3. The present invention is simple to operate and easy to implement, does not require complicated equipment and processes, and reduces construction costs; 4. The repair method of the present invention is applicable to a variety of frozen soil conditions and engineering environments and has wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the background technology of the present invention, wherein a is pouring concrete in a borehole in permafrost, b is the initial setting of concrete in a bored pile formed by pouring concrete, and c is a pile-soil interface defect formed on the side of the bored pile.

[0018] Figure 2 It is a schematic diagram of the construction process of the present invention, wherein a is pre-embedded repair pipe, b is initial setting of concrete, c is injection of low-temperature mud / mortar in the repair pipe, d is applying different injection pressures in stages during the injection process, e is filling after the pressure-sensitive membrane is ruptured, and f is forming a filling layer on the side of the cast-in-place pile.

[0019] Figure 3 It is a schematic diagram of two repair pipes installed on the borehole wall of the present invention.

[0020] Figure 4 It is a schematic diagram of the repair tube of the present invention.

[0021] Figure 5 Schematic diagram of the repair pipe of the present invention, wherein ① is the top section of the repair pipe, ② is the middle section of the repair pipe, and ③ is the bottom section of the repair pipe.

[0022] Among them, 1: repair pipe, 2: pressure-sensitive membrane, 3: cast-in-place pile, 4: defect at the pile-soil interface, 5: filling layer. Specific embodiments

[0023] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] Embodiment 1 As Figures 2 - 4 shown, a method for repairing the defect at the pile-soil interface of a cast-in-place pile in a permafrost area includes the following steps: Step 1, embedding the repair pipe. Install one or more repair pipes 1 with a diameter of 3 cm (PVC pipes in this embodiment) vertically along the circumferential direction of the borehole wall in the permafrost area. The top of each repair pipe is open, the top surface of the repair pipe is flush with the ground surface, and the bottom surface is close to the bottom of the borehole. The repair pipe 1 is provided with a prefabricated hole with a diameter of 1 cm every 1 m along the depth direction of the borehole. The opening of the prefabricated hole faces the borehole wall and is close to the borehole wall. Each prefabricated hole is covered with a single layer or multiple layers of pressure-sensitive membranes 2. The rupture pressure of the pressure-sensitive membrane 2 is set to 0.3 MPa, and this rupture pressure is greater than the pressure at the position where the pressure-sensitive membrane 2 is located, so as to block the prefabricated hole with the pressure-sensitive membrane 2. Step 2, pouring concrete: After the repair pipe 1 is embedded, concrete is poured in the borehole to form a cast-in-place pile 3. During the pouring process, due to the effect of hydration heat, the soil around the cast-in-place concrete pile 3 melts. When the melted soil refreezes, a defect 4 at the pile-soil interface is formed between the cast-in-place pile 3 and the surrounding soil (the defect at the pile-soil interface is the void, crack or poor contact between the pile body of the cast-in-place pile and the refrozen soil, etc., and is formed due to uneven concrete pouring during the formation of the cast-in-place pile). The pressure-sensitive membrane 2 effectively prevents water or soil from entering the repair pipe 1. Step 3, injecting low-temperature mud / slurry: Inject low-temperature mud / slurry into the repair pipe 1 from the ground surface until the injection pressure is greater than the rupture pressure of the pressure-sensitive membrane 2. The pressure-sensitive membrane 2 at the defect 4 at the pile-soil interface ruptures, and the low-temperature mud / slurry enters the defect 4 at the pile-soil interface through the prefabricated hole for filling. Step 4, forming a filling layer: After the injection is completed, the low-temperature mud / slurry freezes and forms a filling layer 5 at the defect 4 at the pile-soil interface. The repair of the defect at the pile-soil interface is completed, thereby improving the contact condition between the cast-in-place pile 3 and the soil interface and increasing the bearing capacity of the cast-in-place pile 3.

[0025] Furthermore, the diameter of the repair pipe 1 in this embodiment is selected according to the actual engineering requirements and construction conditions, generally 2 - 3 cm, not exceeding 5 cm. The diameter of the prefabricated holes in the repair pipe 1 does not exceed 1 / 2 of the diameter of the repair pipe 1. The spacing between adjacent prefabricated holes and the number of prefabricated holes are adjusted accordingly according to the thickness and ice content of the frozen soil layer. The adjustment principle is that the distribution density of prefabricated holes is high in the section with high ice content and low in the section with low ice content.

[0026] Furthermore, when installing multiple repair pipes 1 vertically along the circumferential direction of the borehole wall in the permafrost area, in this embodiment, when there are 2 repair pipes 1, the prefabricated holes of the 2 repair pipes 1 are staggered along the borehole depth direction.

[0027] Embodiment 2 As Figure 5 shown, on the basis of Embodiment 1, the bursting pressure of the pressure - sensitive membrane 2 is adjusted according to the borehole depth to ensure that the low - temperature mud / mortar can be accurately injected into the pile - soil interface defect 4.

[0028] In the step 1, by changing the thickness and number of layers of the pressure - sensitive membrane 2, its bursting pressure can be flexibly adjusted to meet the construction requirements under different depths and frozen - soil conditions. The specific implementation is as follows: The repair pipe 1 is divided into three sections, namely the top section at the top of the borehole, the middle section in the middle of the borehole, and the bottom section at the bottom of the borehole. The prefabricated holes in the top section of the repair pipe 1 cover three layers of pressure - sensitive membrane 2, the prefabricated holes in the middle section cover two layers of pressure - sensitive membrane 2, and the prefabricated holes in the bottom section cover one layer of pressure - sensitive membrane 2. The pressure - sensitive membrane 2 is a polyester film, which has good low - temperature resistance and mechanical strength and can adapt to the construction environment in the permafrost area. Furthermore, the bursting pressure of one layer of pressure - sensitive membrane is 0.3 Mpa.

[0029] Furthermore, in the step 3, during construction, in order to minimize the heat input and avoid the difficulty of refreezing around the cast - in - place pile again, the low - temperature mud / mortar is injected into the repair pipe 1 in stages from the ground surface. First, the low - temperature mud / mortar is injected into the bottom section of the repair pipe. When the injection pressure is in the range of 0.3 - 0.6 MPa, the pressure - sensitive membrane 2 at the prefabricated holes in the bottom section bursts, and after the low - temperature mud / mortar enters the pile - soil interface defect 4 and refreezes, then the low - temperature mud / mortar is injected into the middle section of the repair pipe. When the injection pressure is in the range of 0.6 - 0.9 MPa, the pressure - sensitive membrane 2 at the prefabricated holes in the middle section bursts, and after the low - temperature mud / mortar enters the pile - soil interface defect 4 and refreezes, finally the low - temperature mud / mortar is injected into the top section of the repair pipe. When the injection pressure is greater than 0.9 MPa, the pressure - sensitive membrane 2 at the prefabricated holes in the top section bursts, and the low - temperature mud / mortar enters the pile - soil interface defect 4 and refreezes.

[0030] Embodiment 3 In order to calculate the pressure change borne by the pressure-sensitive membrane 2, monitor the pressure borne by the pressure-sensitive membrane 2 in real time, provide real-time data support for the construction process, and give early warnings of possible rupture of the pressure-sensitive membrane 2, and further infer the ice content distribution state of the frozen soil around the cast-in-place pile and the position and degree of the pile-soil interface defect after heat and mass transfer. On the basis of Example 1 and / or Example 2, strain gauges are evenly pasted on the center of the surface of the pressure-sensitive membrane 2, and the strain gauges are connected to the data acquisition system. During the process of injecting low-temperature mud / mortar into the repair pipe 1, the output signals of the strain gauges are recorded in real time through the data acquisition system. According to the output signals of the strain gauges, combined with the elastic modulus of the material of the pressure-sensitive membrane 2 , Poisson's ratio , thickness , radius , central displacement , use the formula to calculate the pressure borne by the pressure-sensitive membrane 2 P change, and at the same time, the position and range of the rupture of the pressure-sensitive membrane 2 can also be analyzed, and then the position and severity of the pile-soil interface defect can be preliminarily judged. Among them, the pressure borne by the pressure-sensitive membrane P The calculation formula is: ;

[0031] Furthermore, during the process of injecting low-temperature mud / mortar in stages, when injecting the bottom section, when the difference between the pressure borne by the pressure-sensitive membrane 2 in the middle section or the top section and its rupture pressure reaches a predetermined value, the system issues a warning signal to remind the construction personnel to adjust the pressure of injecting low-temperature mud / mortar to avoid inaccurate injection position of low-temperature mud / mortar caused by premature rupture of the pressure-sensitive membrane 2; When injecting the middle section, when the difference between the pressure borne by the pressure-sensitive membrane 2 in the top section and its rupture pressure reaches a predetermined value, the system issues a warning signal to remind the construction personnel to adjust the pressure of injecting low-temperature mud / mortar to avoid inaccurate injection position of low-temperature mud / mortar caused by premature rupture of the pressure-sensitive membrane 2.

[0032] Example 4 The ice content in the frozen soil will affect the degree of heat and mass transfer after the cast-in-place pile is poured, and further affect the stress state of the pile-soil interface after the pile and soil around the cast-in-place pile are frozen. For example, frozen soil with soil-ice layers or high ice content will cause the volume of the soil to decrease and voids to increase after melting. After refreezing, pile-soil interface defects will occur. At the same time, during the process of pouring concrete cast-in-place piles, uneven pouring will occur. Through the rupture data of the pressure-sensitive membrane (the position, range and pressure received by the rupture of the pressure-sensitive membrane PBy comparing it with the drilled ice content distribution, the defect conditions of the pile-soil interface or the phenomenon of uneven concrete pouring can be more comprehensively understood, the defect causes can be more accurately located and analyzed, and the concrete pouring quality can be improved.

[0033] Based on the above, the present embodiment provides a method for evaluating the pouring quality of a cast-in-place concrete pile, including the following steps: Step 1: Drill holes in the permafrost area and detect the ice content of each area at different depth positions; Step 2: Embedding of repair pipes: Vertically install one or more repair pipes along the circumferential direction of the hole wall of the drilled hole in the permafrost area. The top of each repair pipe is open, the top surface of the repair pipe is flush with the ground surface, the bottom surface is closely attached to the bottom of the drilled hole, and a plurality of prefabricated holes are sequentially spaced along the depth direction of the drilled hole. The openings of the prefabricated holes face the hole wall of the drilled hole and are closely attached to the hole wall of the drilled hole. Each prefabricated hole is covered with a single layer or multiple layers of pressure-sensitive membranes, and strain gauges are evenly pasted on the center of the surface of the pressure-sensitive membranes. The strain gauges are connected to a data acquisition system; Step 3: Pouring concrete: After the repair pipes are embedded, concrete is poured into the drilled hole to form a cast-in-place pile. During the pouring process, due to the action of hydration heat, the soil around the cast-in-place concrete pile melts. After the melted soil refreezes, a pile-soil interface defect is formed between the cast-in-place pile and the surrounding soil; Step 4: Injecting low-temperature mud / mortar to form a filling layer: Inject low-temperature mud / mortar into the repair pipes from the ground surface until the injection pressure is greater than the rupture pressure of the pressure-sensitive membrane. Then the pressure-sensitive membrane ruptures, and the low-temperature mud / mortar fills the pile-soil interface defect. The pile-soil interface defect includes a first defect formed between the cast-in-place pile and the surrounding frozen soil and a second defect formed by uneven concrete pouring during the formation of the cast-in-place pile; Step 5: Evaluation of pouring quality: The data acquisition system obtains whether each pressure-sensitive membrane ruptures (that is, the rupture data of the pressure-sensitive membrane (the position, range, and pressure value of the rupture of the pressure-sensitive membrane)) by collecting the signals of the strain gauges. If the position where the pressure-sensitive membrane ruptures corresponds to the area with a high ice content, it indicates that the rupture of the pressure-sensitive membrane is caused by the first defect. If the position where the pressure-sensitive membrane ruptures corresponds to the area with a low ice content, it indicates that the rupture of the pressure-sensitive membrane is caused by the second defect. If the pressure-sensitive membrane corresponding to the area with a high ice content ruptures, it indicates that the first defect has been repaired. If the pressure-sensitive membrane corresponding to the area with a low ice content ruptures, it indicates that the second defect has been repaired. P The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

[0034] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for repairing the defects of the pile-soil interface of cast-in-place piles in permafrost regions, characterized in that, It includes the following steps: Step 1, repair pipe embedding: Install one or more repair pipes vertically along the circumferential direction of the borehole wall in the permafrost area. The top of each repair pipe is open, the top surface of the repair pipe is flush with the ground surface, the bottom surface is close to the bottom of the borehole, and a plurality of prefabricated holes are sequentially arranged at intervals along the depth direction of the borehole. The openings of the prefabricated holes face the borehole wall and are close to the borehole wall. Each prefabricated hole is covered with a single layer or multiple layers of pressure-sensitive membranes; Step 2, concrete pouring: After the repair pipes are embedded, concrete is poured into the borehole to form a cast-in-place pile. During the pouring process, the soil around the cast-in-place concrete pile melts. When the melted soil refreezes, a pile-soil interface defect is formed between the cast-in-place pile and the surrounding soil; Step 3, injecting low-temperature mud / slurry: Inject low-temperature mud / slurry into the repair pipe from the ground surface until the injection pressure is greater than the rupture pressure of the pressure-sensitive membrane. The pressure-sensitive membrane at the pile-soil interface defect ruptures, and the low-temperature mud / slurry enters the pile-soil interface defect through the prefabricated holes for filling; Step 4, forming a filling layer: After the injection is completed, the low-temperature mud / slurry freezes and a filling layer is formed at the pile-soil interface defect, and the repair of the pile-soil interface defect is completed.

2. The repair method according to claim 1, characterized in that, In the said Step 1, the repair pipe is divided into three sections, namely the top section at the top of the borehole, the middle section in the middle of the borehole, and the bottom section at the bottom of the borehole; The rupture pressure of the pressure-sensitive membrane covering the prefabricated hole in the top section of the repair pipe is the first rupture pressure, the rupture pressure of the pressure-sensitive membrane covering the prefabricated hole in the middle section is the second rupture pressure, and the rupture pressure of the pressure-sensitive membrane covering the prefabricated hole in the bottom section is the third rupture pressure. The first rupture pressure is greater than the second rupture pressure, and the second rupture pressure is greater than the third rupture pressure.

3. The repair method according to claim 1, characterized in that, In the said Step 3, a strain gauge is pasted at the center of the surface of the pressure-sensitive membrane. The strain gauge is connected to a data acquisition system. During the process of injecting low-temperature mud / slurry into the repair pipe, the output signal of the strain gauge is recorded in real time through the data acquisition system. According to the output signal of the strain gauge, combined with the elastic modulus and Poisson's ratio of the pressure-sensitive membrane material, the pressure change borne by the pressure-sensitive membrane and the rupture position of the pressure-sensitive membrane are calculated; 4. The repair method according to claim 2, characterized in that, The low-temperature mud / slurry is injected in stages. When injecting the bottom section, when the difference between the pressure borne by the pressure-sensitive membrane in the middle section and its rupture pressure reaches a predetermined value or the difference between the pressure borne by the pressure-sensitive membrane in the top section and its rupture pressure reaches a predetermined value, the system issues a warning signal to remind the construction personnel to adjust the injection pressure of the low-temperature mud / slurry; When injecting the middle section, when the difference between the pressure borne by the pressure-sensitive membrane in the top section and its rupture pressure reaches a predetermined value, the system issues a warning signal to remind the construction personnel to adjust the injection pressure of the low-temperature mud / slurry.

5. The repair method according to claim 4, characterized in that, First, inject low-temperature mud / mortar into the bottom section of the repair pipe. The injection pressure is greater than the rupture pressure of the pressure-sensitive membrane at the prefabricated hole in the bottom section. After the low-temperature mud / mortar enters the pile-soil interface defect and freezes back, then inject low-temperature mud / mortar into the middle section of the repair pipe. The injection pressure is greater than the rupture pressure of the pressure-sensitive membrane at the prefabricated hole in the middle section. After the low-temperature mud / mortar enters the pile-soil interface defect and freezes back, finally inject low-temperature mud / mortar into the top section of the repair pipe. The injection pressure is greater than the rupture pressure of the pressure-sensitive membrane at the prefabricated hole in the top section. The low-temperature mud / mortar enters the pile-soil interface defect and freezes back. Among them, the injection pressure in the bottom section is less than that in the middle section, and the injection pressure in the middle section is less than that in the top section.

6. The repair method according to claim 1, wherein The pressure-sensitive membrane is a polyester film.

7. The repair method according to claim 1, characterized in that, One prefabricated hole is arranged every 1 to 2 meters along the drilling depth direction of the repair pipe. The aperture of the prefabricated hole is 5 mm to 1 cm and less than half of the diameter of the repair pipe.

8. The repair method according to claim 7, characterized in that, The diameter of the repair pipe does not exceed 5 cm.

9. The repair method according to claim 1, characterized in that, The repair pipe is a plastic pipe.

10. The repair method according to claim 1, wherein When installing multiple repair pipes along the circumferential direction on the borehole wall in the permafrost region, the prefabricated holes of the multiple repair pipes are staggered along the drilling depth direction.

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