Inter-wall vacuum induction-pressure grouting well wall structure strengthening method under frozen wall protection

Abstract

The invention discloses an inter-wall vacuum induction-pressure grouting well wall structure strengthening method under frozen wall protection, and belongs to the technical field of shaft well wall structure strengthening. The outer wall is constructed, a temperature sensor is pre-embedded in a joint seam, and the inner wall is constructed, and a concrete strain sensor and a grouting pipe are pre-embedded; the inner wall and the outer wall of the well bottom are connected through the cup-shaped base, the annular space between the inner wall and the outer wall is blocked, the annular space between the inner wall and the outer wall is vacuumized under the protection of the freezing wall, ice at the contact seam of the outer wall is sublimated and discharged, liquid water between the walls is sucked and discharged, and the annular space between the walls is clean. And then double-pipe cooperative pressure grouting is conducted on the annular space between the inner wall and the outer wall according to the sectioning and zoning principle, the annular space between the inner wall and the outer wall in the vertical depth range of the shaft is covered, and the outer wall connecting seam is repaired. According to the method, the slurry filling degree between the walls, the slurry stone body strength and the bonding strength between the slurry stone body and the well wall concrete can be effectively improved, so that the inner wall and the outer wall are really compounded into a whole to jointly resist the water pressure behind the wall after the frozen wall is unfrozen.

Description

Technical Field

[0001] The present invention relates to a method for strengthening the structure of an inter-wall vacuum induction-pressure grouting shaft lining under the protection of a frozen wall, which is particularly applicable to the grouting reinforcement between the double-layer shaft linings of a vertical shaft in water-rich rock strata, and belongs to the technical field of strengthening the structure of a vertical shaft lining. Background Art

[0002] The double-layer shaft lining is the main structural form of a coal mine freezing shaft. The outer wall resists the freezing pressure, and the inner wall and the outer wall form a whole through grouting to jointly resist the water and soil pressure (mainly the water pressure in the water-stable rock strata). However, during actual construction, due to the influence of the hydration heat of cement, the peripheral part of the frozen wall at the joint of the outer shaft wall temporarily melts, and the melted area refreezes as the construction continues, resulting in discontinuous ice at the joint of the outer shaft wall. When grouting is carried out under the protection of the frozen wall, it is difficult for the slurry to fill the places where the cracked ice exists. In addition, there will inevitably be free liquid water between the inner and outer shaft linings. These discontinuous ice and liquid water greatly reduce the bonding strength between the slurry stone body and the shaft lining interface, and the effect of the inner shaft wall and the outer shaft wall jointly resisting the water pressure is limited.

[0003] At present, the existing technologies for blasting grouting, negative pressure grouting and ordinary pressure grouting include: Patent ① Zhou Guoqing et al. High-energy gas fracturing grouting method for mud-cemented soft rock and soil ZL201510062323.8; Patent ② Wang Jianzhou et al. Construction method for wall grouting waterproofing and strengthening shaft wall structure under frozen wall protection ZL201710110203.X; Patent ③ Zhou Guoqing et al. Positive and negative pressure combined grouting method 201210285955.7; Patent ④ Zhou Guoqing et al. Comprehensive test system and test method for simulating deep space planet gravity field environment 201710963439.8. Negative pressure grouting methods are also proposed for different scenarios, such as Patent ① Kurose Masayuki et al. Soft-ground reinforcement method JP-2007309055-A; Patent ② Yin Aiyue et al. A diversion grouting structure and method for cold joints in interlocking pile construction 202110316141.4; Patent ③ Liu Guoguang et al. A method for concealed grouting and void risk assessment of cement concrete road slab edge 202111650844.7, and theoretical and experimental research was carried out (Zhang Libo. Simulation test study of vacuum grouting in fine sand formation, master's degree thesis of China University of Geosciences (Beijing), 20 15; Zhou Lixin. Research on the mechanism of vacuum negative pressure infiltration grouting in unsaturated fine sand formation, Master's degree thesis of China University of Geosciences (Beijing), 2021; Lv Xin et al. Experimental study and mechanism analysis of negative pressure grouting reinforcement of broken rock mass in goaf. Chinese Journal of Rock Mechanics and Engineering, 2023, 42(S2):4174-4188.), and found that negative pressure can break the surface tension of the solid-liquid interface and increase the filling degree of slurry. At the same time, vacuum can increase the strength of slurry stone by inducing slurry dehydration. The above studies are all based on the vacuum induction method to increase the pressure difference and guide the directional flow and efficient filling of slurry, but none of them involve the special grouting environment of discontinuous ice at the joint of the outer wall of the shaft and free liquid water between the inner and outer walls, especially the problem of ice sublimation in a vacuum low-temperature environment. However, the above research provides a theoretical and experimental basis for the proposal of the present invention, that is, the double-tube collaborative grouting method that simultaneously considers the frozen wall protection effect, vacuum freezing sublimation effect and vacuum dehydration effect will effectively improve the inter-wall slurry filling degree, the slurry stone body-well wall interface bonding strength and the slurry stone body strength, and truly exert the combined bearing effect of the inner and outer walls, thereby providing an innovative technical path for thinning the inner well wall thickness. Summary of the invention

[0004] Technical problem: In view of the shortcomings of the existing technology in dealing with discontinuous ice at the joints of the outer walls of deep vertical shafts and free liquid water between the inner and outer walls, the present invention provides a method for strengthening the shaft wall structure by vacuum induction-pressure grouting between the walls under the protection of a frozen wall. The vacuum and low temperature are used to sublime the residual solid ice in the joints of the outer wall, and the liquid water between the inner and outer walls is pumped away to ensure the cleanliness of the annulus between the inner and outer walls. Then, pressure grouting is used to integrate the inner and outer walls, truly exerting the combined bearing effect of the inner and outer walls and effectively reducing the thickness of the inner shaft wall.

[0005] Technical content: To achieve the above technical purpose, the present invention provides a method for strengthening the well wall structure by vacuum induction-pressure grouting between walls under frozen wall protection, comprising the following steps:

[0006] a. In water-rich rock formations, according to the short-section excavation and masonry process of frozen wells, frozen pipes are used to freeze in the construction area to form a closed cylindrical frozen wall to resist ground pressure and isolate the connection between groundwater and the wellbore. Under the protection of the frozen wall, the wellbore is excavated and the inner and outer double-layer hollow wellbore wall structure is constructed;

[0007] b. First, excavate and build a short section of the outer wall. After each excavation, build a section of the outer wall. Joints are formed between the outer wall sections, and temperature sensors are pre-buried at the joints. When the outer wall is constructed in sections to the preset position, a cup-shaped base is constructed below the outer wall. Then, the inner wall that does not contact the outer wall is continuously constructed from the cup-shaped base from bottom to top on the inner side of the outer wall to ensure that there is a sandwich space between the inner wall and the outer wall. Concrete strain gauges are pre-buried in layers in the inner wall at the same position and height as the outer wall temperature sensor; a steel grouting pipe with the same length as the thickness of the inner wall and temporarily sealed is pre-buried on the inner wall;

[0008] c. After the inner wall construction is completed, use the shaft hoisting plate and automatic detection equipment to read the temperature sensor reading, detect the temperature at the sensor installation location, and use the concrete strain gauge to detect the concrete strain of the inner wall at the installation location;

[0009] d. Adopt the hot-melt technology to seal the gap between the inner wall and the outer wall at the wellbore opening. Together with the bottom cup-shaped base, a closed annular space between the walls is formed between the inner wall and the outer wall. Since the frozen wall will experience local thawing and refreezing due to the heat of hydration of cement, residual ice will form at the outer wall joint seam and residual water will form on the inner side of the outer wall. Under the protection of the frozen wall, cancel the seal of the steel grouting pipe. Using the shaft hanging platform and the pre-embedded steel grouting pipe, successively use a mechanical pump and a molecular pump to evacuate the annular space between the walls through the steel grouting pipe. According to the measured temperature at the concrete joint seam of the outer shaft wall at the same position, combined with the gas-liquid-solid phase diagram of water, use the formula: vacuum degree = atmospheric pressure - actual pressure in the annulus to determine the vacuum degree of the annular space between the walls, ensure that the solid ice existing at the outer wall joint seam is directly gasified and extracted, and then further suck out the residual liquid water in the annular space between the walls, making the annular space between the walls a clean annular space between the walls;

[0010] e. Use the shaft construction hanging platform to connect the pressure grouting system with the pre-embedded grouting pipe. The grouting material is ordinary cement slurry or cement-clay slurry. Implement vacuum extraction - double-pipe collaborative pressure grouting in the annular space between the walls according to the principles of vertical segmentation and circumferential zoning, so that the slurry can cover the annular space between the walls and at the same time fill the outer wall joint seam, from top to bottom until the entire vertical depth range between the walls is covered.

[0011] Furthermore, install a sealed box for accommodating the temperature sensor wire at the position of the temperature sensor installed on the outer wall. At the corresponding position on the inner wall, there is also a sealed box for accommodating the temperature sensor wire and the concrete strain gauge wire. The heights and positions of the sealed boxes on the outer wall and the inner wall are the same.

[0012] Furthermore, after each construction of the temperature sensor and the sealed box on the outer wall, introduce the temperature sensor wire into the sealed box to prevent the wire from being buried by the concrete; when constructing the inner wall from bottom to top, whenever the inner wall is constructed to the position of different sealed boxes on the outer wall, introduce the concrete strain gauge wire installed near the inner edge of the inner wall into the sealed box on the inner wall, and at the same time open the sealed box on the outer wall, take out the temperature sensor wire of the same layer from the sealed box on the outer wall and introduce it into the sealed box on the inner wall.

[0013] Furthermore, there are multiple steel grouting pipes buried in the inner wall, arranged in a plum blossom pattern.

[0014] Furthermore, after the construction of the inner wall is completed, use the shaft hanging platform to open the sealed box on the inner wall, fix the temperature sensor wire and the concrete strain gauge wire in sections on the inner surface of the inner wall and lead them to the wellhead, and connect them to the automatic monitoring system for reading the information of the temperature sensor and the concrete strain gauge.

[0015] Furthermore, the ultimate vacuum degree of the mechanical pump used for vacuum extraction of the annular space between the walls is not less than [atmospheric pressure - 1×10 -4kPa, the ultimate vacuum degree of the molecular pump should be not less than [atmospheric pressure - 1×10 -9 kPa.

[0016] Furthermore, during the grouting process, the grouting pressure is monitored in real time through the pressure gauge at the end of the grouting pipe, and the circumferential and vertical strains at the inner edge of the inner wall are monitored through the concrete strain gauges embedded in the inner wall to ensure that the maximum grouting pressure does not exceed the ultimate tensile strain of the inner wall concrete.

[0017] Beneficial effects: The present invention uses a mechanical pump and a molecular pump to conduct hierarchical vacuum pumping. As the grouting range gradually expands and the annulus space between the walls gradually decreases, the vacuum degree in the annulus space between the walls will be effectively improved on the basis of the effect of the traditional mechanical pump. The vacuum degree in the annulus space between the walls shows a trend of continuing to increase with time, and the vacuum freeze-drying sublimation effect and the suction drainage effect will be fully exerted. Vacuum grouting has a high filling degree, so that not only the cracks between the outer well wall and the annular space between the inner and outer well walls, but even the tiny defects in the well wall can be filled synchronously, which is expected to transform the temporary water-stop function of the outer well wall into a permanent support function, providing an innovative technical path for reducing the thickness of the inner well wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic flow chart of the method for strengthening the structure of the well wall with vacuum induction - pressure grouting between walls under the protection of the frozen wall of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The following further describes the embodiments of the present invention with reference to the drawings:

[0020] As Figure 1 shown, a method for strengthening the structure of the well wall with vacuum induction - pressure grouting between walls under the protection of the frozen wall of the present invention comprises the following steps:

[0021] a. In the water-rich rock stratum, according to the short-section tunneling and lining technology of the freezing shaft, since the segmented construction of the outer wall will inevitably generate the joint seams of the well wall, temperature sensors are embedded at the joint seams of the well wall, and the wires of the temperature sensors are introduced into the sealed box. The outer surface of the sealed box is flush with the inner surface of the outer wall;

[0022] b. After the segmented construction of the outer wall reaches the bottom, the cup-shaped base is constructed, and then the inner wall is continuously constructed from bottom to top. When the inner wall is constructed to the different sealed boxes of the outer wall, the sealed boxes are opened, and the wires are taken out and introduced into the sealed boxes of the inner wall. The outer surface of the sealed boxes of the inner wall is flush with the inner surface of the inner wall; According to the principle that the vertical depth of the temperature sensors arranged on the outer wall is the same, concrete strain gauges are embedded in layers in the inner wall, and the wires of the concrete strain gauges and the wires of the temperature sensors on the outer wall at the same layer are introduced into the sealed boxes of the inner wall together; Steel grouting pipes with the same length as the inner wall thickness and temporary seals are embedded in a plum blossom shape. The steel grouting pipes are arranged at equal angles around the inner wall and can be arranged at different heights of the inner wall according to needs;

[0023] c. After the construction of the inner wall is completed, use the shaft hanging platform to open the inner wall seal box, lead out the wire, fix it section by section on the inner surface of the inner wall and lead it out to the wellhead, connect it to the automatic monitoring system, and read the data of each temperature sensor and concrete strain gauge through the automatic monitoring system;

[0024] d. Adopt the hot melt technology to seal the annulus near the wellhead between the inner and outer shaft walls. Under the protection of the frozen wall, use the shaft hanging platform and the pre-buried steel grouting pipe, and successively use a mechanical pump and a molecular pump to evacuate the annulus between the walls. The ultimate vacuum degree of the mechanical pump shall not be lower than [atmospheric pressure - 1×10 -4 kPa, and the ultimate vacuum degree of the molecular pump shall not be lower than [atmospheric pressure - 1×10 -9 kPa; According to the measured temperature at the joint of the outer wall concrete shaft wall at the same position, combined with the triple-phase diagram of water, determine the vacuum degree between the walls (vacuum degree = atmospheric pressure - actual pressure in the annulus). In a vacuum and low-temperature environment, ensure that the solid ice at the joint of the outer wall directly vaporizes and is discharged, and at the same time, aspirate and discharge the residual liquid water between the walls. The residual liquid water between the walls comes from the residue of concrete construction and the vacuum dehydration of the grouting slurry in the upper section, so that the annular space between the inner and outer walls becomes a clean annular space, and at the same time, ensure the cleanliness of the joint of the outer well;

[0025] e. Use the shaft construction hanging platform to connect the pressure grouting system with the pre-buried grouting pipe. The grouting material is ordinary cement slurry or cement-clay slurry. Implement vacuum evacuation - double-pipe collaborative pressure grouting in the annulus between the walls according to the principles of vertical sectioning and circumferential zoning. During the grouting process, monitor the grouting pressure in real time through the pressure gauge at the end of the grouting pipe, and monitor the circumferential and vertical strains of the inner edge of the inner wall through the concrete strain gauges pre-buried in the inner wall to ensure that the maximum grouting pressure does not exceed the ultimate tensile strain of the inner wall concrete. Finally, make the slurry cover the entire annular space between the inner and outer walls, and at the same time fill the cracks at the joints of the outer wall, from top to bottom until the entire vertical depth range between the walls is covered.

[0026] The present invention mainly aims at the grouting between the double-layer shaft walls - the strengthening of the shaft wall structure. After appropriate adjustment, it can also be used for the pre-grouting on the ground and the face grouting of deep shafts, and has a good effect on plugging the shaft leakage.

Claims

1. A method for strengthening the shaft wall structure by vacuum induction-pressure grouting under the protection of a frozen wall, characterized in that, The steps include: a. In water-rich rock formations, according to the short-section excavation and masonry process of frozen wells, frozen pipes are used to freeze in the construction area to form a closed cylindrical frozen wall to resist ground pressure and isolate the connection between groundwater and the wellbore. Under the protection of the frozen wall, the wellbore is excavated and the inner and outer double-layer hollow wellbore wall structure is constructed; b. First, excavate and build a short section of the outer wall. After each excavation, build a section of the outer wall. Joints are formed between the outer wall sections, and temperature sensors are pre-buried at the joints. When the outer wall is constructed in sections to the preset position, a cup-shaped base is constructed below the outer wall. Then, the inner wall that is not in direct contact with the outer wall is continuously constructed from the cup-shaped base from bottom to top on the inner side of the outer wall to ensure that there is a sandwich space between the inner wall and the outer wall. Concrete strain gauges are pre-buried in layers in the inner wall at the same position and height as the outer wall temperature sensor; a steel grouting pipe with the same length as the thickness of the inner wall and temporarily sealed is pre-buried on the inner wall; c. After the inner wall construction is completed, use the shaft hoisting plate and automatic detection equipment to read the temperature sensor reading, detect the temperature at the sensor installation location, and use the concrete strain gauge to detect the concrete strain of the inner wall at the installation location; d. Use hot melt technology to seal the gap between the inner wall and the outer wall at the wellhead, together with the cup-shaped base at the bottom, so that a closed inter-wall annular space is formed between the inner wall and the outer wall. As the frozen wall is affected by the heat of cement hydration, local thawing and refreezing will occur, thereby forming residual ice at the joint of the outer wall and residual water on the inner side of the outer wall. Under the protection of the frozen wall, cancel the seal of the steel grouting pipe, use the wellbore hanging plate and the pre-buried steel grouting pipe, and use the mechanical pump and molecular pump in turn to evacuate the annular space between the inner and outer walls through the steel grouting pipe. According to the measured temperature at the joint of the concrete well wall at the same position of the outer well wall, combined with the gas, liquid and solid three-phase diagram of water, the vacuum degree of the inter-wall annular space is determined by using the formula: vacuum degree = atmospheric pressure - actual pressure in the annulus, to ensure that the solid ice at the joint of the outer wall is directly gasified and extracted, and then the residual liquid water in the inter-wall annular space is further discharged by suction, so that the inter-wall annular space becomes a clean inter-wall annular space; e. Use the shaft construction hoisting platform to connect the pressure grouting system with the pre-buried grouting pipe. Ordinary cement slurry or cement-clay slurry is used as the grouting material. According to the principles of vertical segmentation and annular division, the inter-wall annular space vacuumization and double-tube coordinated pressure grouting are implemented so that the slurry can cover the annular space between the walls and fill the joints of the outer wall from top to bottom until the entire vertical depth range between the walls is covered.

2. The method for strengthening the shaft wall structure by vacuum induction-pressure grouting between the lower walls protected by the frozen wall according to claim 1, wherein, A sealing box for accommodating the temperature sensor wires is installed at the temperature sensor installed on the outer well wall to temporarily protect the temperature sensor wires. A sealing box for accommodating the outer wall temperature sensor wires and the inner wall concrete strain gauge wires is also provided at the inner wall near the inner edge and at a position corresponding to the outer wall sealing box. The height and position of the sealing boxes on the outer wall and the inner wall are the same.

3. The method for strengthening the shaft wall structure by vacuum induction-pressure grouting between the lower walls protected by the frozen wall according to claim 2, wherein, After the temperature sensors and sealing boxes at a certain layer of the outer wall are constructed, the temperature sensor wires at that layer are introduced into the sealing box to prevent the wires from being buried by concrete; when the inner wall is constructed from bottom to top, when the inner wall construction reaches different sealing boxes on the outer wall, the concrete strain gauge wires installed on the inner wall near the inner edge are introduced into the inner well wall sealing box, and at the same time, the outer wall sealing box is opened, and the temperature sensor wires at the same layer are taken out from the outer wall sealing box and introduced into the inner wall sealing box.

4. The method for strengthening the shaft wall structure by vacuum induction-pressure grouting between the lower walls protected by the freezing wall according to claim 1, characterized in that, There are multiple steel grouting pipes buried in the inner wall, arranged in a plum blossom shape.

5. The method for strengthening the shaft wall structure by vacuum induction-pressure grouting between the lower walls protected by the freezing wall according to claim 1, wherein, When the inner wall construction is completed, the inner wall sealing box is opened using the wellbore hoisting plate. The temperature sensor wires and concrete strain gauge wires are fixed in sections on the inner surface of the inner wall and led to the wellhead to the automatic monitoring system for reading the temperature sensor and concrete strain gauge information.

6. The method for strengthening the shaft wall structure by vacuum induction-pressure grouting between the lower walls protected by the frozen wall according to claim 1, wherein, The ultimate vacuum degree of the mechanical pump for evacuating the annulus between walls shall not be lower than [atmospheric pressure - 1×10 -4 kPa, and the ultimate vacuum degree of the molecular pump shall not be lower than [atmospheric pressure - 1×10 -9 kPa.

7. The method for strengthening the shaft wall structure by vacuum induction-pressure grouting between the lower walls protected by the frozen wall according to claim 1, characterized in that During the grouting process, the grouting pressure is monitored in real time by the pressure gauge at the end of the grouting pipe, and the circumferential and vertical strains of the inner edge of the well wall are monitored by the concrete strain gauge pre-buried in the inner wall to ensure that the maximum grouting pressure does not exceed the ultimate tensile strain of the inner wall concrete.

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