Monitoring and prevention method for grouting casing pipe in bedrock weathering zone

Abstract

The invention discloses a monitoring and prevention method for a grouting sleeve in a bedrock weathering zone, and belongs to the technical field of bed separation grouting, and the monitoring and prevention method specifically comprises the following steps: S1, designing the arrangement spacing of grouting positions; s2, establishing a pulping station; s21, drilling for the first time, drilling vertically downwards on the ground, inserting a surface casing, and cementing with cement to form a straight well section I; s22, drilling a hole for the second time, continuously drilling the hole at the well bottom of the straight well section I, inserting an inner-layer sleeve, and cementing the well by cement to form a straight well section II; s3, water is injected between the surface sleeve and the inner sleeve for pressure maintaining, and a pressure sensor is placed between the surface sleeve and the inner sleeve for water pressure detection; and S4, a grouting or water pumping device is connected to a hole opening of the grouting hole channel, the grouting hole channel is connected with the slurry making station through the grouting or water pumping device, and grouting is conducted along all the distributed grouting hole channels. The method has the advantages that monitoring and prevention in the separation layer grouting process can be conveniently achieved, and the separation layer grouting stability is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of off-layer grouting, in particular to a monitoring and prevention method for bedrock weathering zone grouting casing. BACKGROUND

[0002] In recent years, with the large-scale exploitation of coal resources, a large number of goaf has been formed, and the exploitation of underground coal seams will inevitably cause the settlement and migration of overlying strata, and the change of strata will further develop into water inrush, sand collapse, surface subsidence and other negative problems, among which the surface subsidence problem is particularly obvious. It not only easily causes farmland, cultivated land destruction and building damage, but also easily causes environmental problems such as soil erosion and land desertification. Therefore, for the problem of surface subsidence, off-layer grouting subsidence reduction technology has become a more concerned technology because it does not affect normal mining underground.

[0003] The maximum subsidence space of the collapsed overlying strata above the middle compaction zone in the goaf forms an off-layer space between the key stratum and the weak layer; grouting and filling in the off-layer space provide active support for the key stratum, the key stratum remains stable and does not break and sink, and the overlying stratum above the key stratum and the surface can remain small deformation or even micro-deformation, thereby achieving the goal of non-destructive mining. The implementation of multiple projects in China has reached the I-level damage level standard of the "Building, Water Body, Railway and Mine Roadway Coal Pillar Setting and Coal Mining under Pressure Specification", and the results show that off-layer grouting has a significant effect on controlling surface subsidence.

[0004] However, the commonly used method in current construction has a key problem: due to the existence of pressure during continuous grouting, the grouting casing cannot be timely plugged, and with the advance of the coal mining face, the continuous migration of the overlying strata of the working face and the formation of the shallow off-layer (the junction of the Quaternary and bedrock weathering zone), the shallow casing is easily broken, which causes the off-layer work to be interrupted, the grout to flow into the Quaternary weathering zone or to seep into the water-bearing layer of the Quaternary, causing environmental pollution; or the grout to flow to the ground along the small fracture zone of the Quaternary, causing grouting accidents. SUMMARY

[0005] In order to realize the monitoring and prevention during off-layer grouting and ensure the stability of off-layer grouting through the casing, the present application provides a monitoring and prevention method for bedrock weathering zone grouting casing.

[0006] The monitoring and prevention method for bedrock weathering zone grouting casing provided by the present application adopts the following technical scheme: The application discloses a method for monitoring and preventing a bedrock weathering zone grouting casing, which comprises the following steps: S1, designing grouting position arrangement interval, analyzing grouting layer depth according to stratum condition, calculating grouting amount, grout preparation water supply amount, designing grout solid particle size, and arranging grouting layer between sub-key layer and soft layer; S2, establishing a grout preparation station, adopting four-opening drilling structure to form a grouting hole at each grouting position; S21, first opening drilling, vertically drilling downward on the ground and inserting a surface casing, cementing, and forming a straight well section I, wherein the straight well section I is arranged in the Quaternary system in the bedrock layer; S22, second opening drilling, continuously drilling at the bottom of the straight well section I and inserting an inner casing, cementing, and forming a straight well section II, wherein the bottom of the straight well section II is located at the bottom of the main key layer, and the top of the inner casing is located at the same height as the top of the surface casing; S23, third opening drilling, continuously drilling at the bottom of the straight well section II and inserting a bottom casing I, cementing, and forming a straight well section III, wherein the bottom of the straight well section III is located at the bottom of the sub-key layer; S24, fourth opening drilling, continuously drilling at the bottom of the straight well section III and inserting a bottom casing II, cementing, and forming a grouting section, wherein the grouting section is located in the grouting layer; S3, injecting water between the surface casing and the inner casing and detecting water pressure by arranging a pressure sensor between the surface casing and the inner casing; S31, when the pressure sensor value is lower than a preset value, injecting early strength cement between the surface casing and the inner casing; and S4, connecting a grouting or water pumping device at the grouting hole mouth, connecting the grouting hole with the grout preparation station through the grouting or water pumping device, and grouting along each arranged grouting hole.

[0007] By adopting the technical scheme, if advanced migration occurs in the bedrock weathering zone and the migration deformation strength is greater than the strength of the surface casing, the pressure maintaining water between the surface casing and the inner casing leaks or flows out, the pressure sensor value is lower than the preset value, early strength cement is injected between the surface casing and the inner casing in time, and the gap between the surface casing and the inner casing is filled, so that the bedrock weathering zone migration is prevented from continuously damaging the inner casing, the grouting is ensured to be carried out smoothly, and the accident of grout flowing out of the ground is effectively avoided; the pressure sensor is used to cooperate with the early strength cement injection in time, so that the monitoring and prevention in the delamination grouting process are facilitated, and the stability of the delamination grouting is ensured.

[0008] Optionally, in the step S3, a plurality of pressure sensors are arranged along the vertical direction and connected through an optical fiber belt.

[0009] By adopting the technical scheme, the multiple pressure sensors of different depths are convenient for positioning the depth position of the leakage point, thereby being convenient for controlling the injection amount of the early strength cement according to the different depth positions of the leakage; and the multiple pressure sensors provide data redundancy, so that even if one pressure sensor fails, other pressure sensors can still provide complete data chains to judge whether leakage occurs and to position the leakage point, thereby improving the reliability of the whole monitoring system.

[0010] Optionally, in the S2, the diameter of the surface casing is 377 mm, the wall thickness is 8 mm, the diameter of the inner casing is 245 mm, the wall thickness is 8 mm, the diameter of the first bottom casing is 216 mm, the wall thickness is 9 mm, and the diameter of the second bottom casing is 127 mm, the wall thickness is 9 mm.

[0011] By adopting the technical scheme, the design of the gradually reduced casings ensures the safety of the drilling and the smooth running of the casings, thereby providing an optimal channel for subsequent grouting operation, and being conducive to ensuring the safety of the drilling process and the long-term stability of the formed hole after the setting of the casing.

[0012] Optionally, in the S3, multiple grouting pipes are arranged between the surface casing and the inner casing and are uniformly distributed around the axis of the inner casing, and the early strength cement is injected into the surface casing and the inner casing through the grouting pipes.

[0013] By adopting the technical scheme, the multiple grouting pipes can simultaneously realize the injection of the early strength cement into the surface casing and the inner casing, thereby being conducive to the uniform and stable upward movement of the early strength cement and avoiding the generation of local weak points, so as to build a uniform, complete and high-strength sealing system.

[0014] Optionally, multiple sets of limiting assemblies are arranged in the surface casing inner wall or the inner casing outer wall and correspond to the multiple grouting pipes, each set of limiting assemblies is distributed in multiple in the vertical direction, and each limiting assembly comprises a limiting ring fixedly installed on the surface casing inner wall or the inner casing outer wall, and the limiting ring is provided with a limiting hole vertically penetrating and used for passing the grouting pipe.

[0015] By adopting the technical scheme, the limiting holes of the limiting rings play a limiting and guiding role when the grouting pipes grout, thereby preventing the grouting pipes from shaking when the early strength cement is injected, and being conducive to ensuring the stability of the early strength cement injection.

[0016] Optionally, the limiting ring is provided with a pressing piece, the pressing piece comprises a pressing spring and a pressing block, a pressing sliding groove is formed in the hole wall of the limiting hole, the pressing block is slidingly fitted in the pressing sliding groove, an inclined guide surface is arranged on the top of the pressing block, one end of the pressing spring is connected to the groove wall of the pressing sliding groove, and the other end of the pressing spring is connected to the pressing block, and the pressing spring applies an elastic force to the pressing block in a direction away from the limiting hole.

[0017] By adopting the technical scheme, when the grouting pipe is arranged in each limiting hole, each pressing block is pressed and limited to the grouting pipe under the elastic force of the pressing spring, so that the stability of the position of the grouting pipe is further ensured; the inclined guide surface on the top of the pressing block has a sliding force to the pressing groove, so that the grouting pipe is conveniently inserted into the limiting hole, and the size of the limiting hole is set with a certain redundancy by the pressing block, so that the grouting pipe is also conveniently inserted into the limiting hole.

[0018] Optionally, an end of the pressing block away from the pressing spring is rotatably installed with a pressing roller, and the material of the pressing roller is selected as rubber.

[0019] By adopting the technical scheme, the rubber material of the pressing roller is beneficial to reducing the abrasion of the pressing block caused by the rigid contact with the grouting pipe, and is beneficial to the vertical movement of the grouting pipe in the limiting hole, so that the early strength cement is injected at different depths.

[0020] Optionally, the surface sleeve and the inner sleeve each include a plurality of sleeve bodies distributed along an axis thereof, and a connecting piece is arranged between two vertically adjacent sleeve bodies, the connecting piece is provided with a connecting hole vertically penetrating through, and a positioning ring is fixedly connected to an inner wall of the connecting hole, the two vertically adjacent sleeve bodies are respectively abutted to two sides of the positioning ring, and the sleeve body is fixed to the connecting piece by a bolt penetrating through the connecting piece and threadedly matched with the sleeve body.

[0021] By adopting the technical scheme, the plurality of sleeve bodies reduces the transportation and hoisting difficulty of the surface sleeve and the inner sleeve, and facilitates the stacking management, and the positioning ring is beneficial to ensuring the coaxiality of the two sleeve bodies after installation, and functions as a positioning role during installation of the two sleeve bodies, so that the sleeve body and the connecting piece are stably fixed by the bolt.

[0022] Optionally, a plurality of positioning protrusions are fixedly connected to two sides of the positioning ring, and a positioning groove corresponding to the positioning protrusion and in plug-fit cooperation with the positioning protrusion is formed in an end of the sleeve body.

[0023] By adopting the technical scheme, the cooperation of the positioning protrusion and the positioning groove further limits the sleeve body and the connecting piece during installation, and is beneficial to further ensuring the stability of the relative position of the sleeve body and the connecting piece during installation.

[0024] Optionally, two sealing pads are fixedly connected to an inner wall of the connecting piece, the two sealing pads are respectively arranged close to two ends of the connecting piece, and the two sealing pads are respectively abutted to outer circumferential surfaces of the two adjacent sleeve bodies.

[0025] By adopting the technical scheme, the sealing gasket is arranged, which is beneficial to further guarantee the sealing performance after the connection of the connecting piece and the casing body, so that the stable isolation of the substances inside and outside the casing is further realized.

[0026] In summary, the present application has at least one of the following beneficial technical effects: 1、If the overrunning migration occurs in the bedrock weathering zone, and the migration deformation strength is greater than the strength of the surface casing, the surface casing is broken, the pressure maintaining water between the surface casing and the inner casing leaks or flows away, at this time, the pressure sensor is lower than the preset value, early strength cement is injected between the surface casing and the inner casing in time, the gap between the surface casing and the inner casing is filled, thereby preventing the bedrock weathering zone migration from further damaging the inner casing, ensuring the smooth progress of grouting, and effectively avoiding the accident of slurry gushing out of the ground.

[0027] 2、The multiple pressure sensors at different depths facilitate positioning the depth position of the leakage point, so as to facilitate controlling the injection amount of early strength cement according to the leakage at different depth positions.

[0028] 3、The multiple grouting pipes uniformly distributed can simultaneously realize the injection of early strength cement in the surface casing and the inner casing, which is beneficial to uniformly and stably advancing the early strength cement upward, avoiding the generation of local weak points, and thereby constructing a uniform, complete and high-strength sealing system. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a schematic diagram of the overall structure of embodiment 1 of the present application.

[0030] Figure 2 is a schematic diagram of the main structure of the grouting hole in embodiment 1 of the present application.

[0031] Figure 3 is Figure 2 a partial enlarged schematic diagram of part A in

[0032] Figure 4 is a schematic diagram of the main structure of the limiting assembly in embodiment 2 of the present application.

[0033] Figure 5 is a schematic diagram of the main structure of the connecting piece in embodiment 3 of the present application.

[0034] Explanation of reference signs: 1, surface casing; 2, inner casing; 3, bottom hole casing 1; 4, bottom hole casing 2; 5, pressure sensor; 51, optical fiber ribbon; 6, grouting pipe; 7, straight well section 1; 8, straight well section 2; 9, straight well section 3; 10, grouting section; 11, limiting ring; 12, limiting hole; 13, pressure piece; 131, pressure spring; 132, pressure block; 1321, inclined guide surface; 133, pressure roller; 14, pressure chute; 15, casing body; 16, connecting piece; 17, connecting hole; 18, positioning ring; 19, positioning protrusion; 20, positioning groove; 21, sealing gasket. DETAILED DESCRIPTION

[0035] The following will be described in detail with reference to the accompanying drawings. Figures 1-5 The application is further described in detail.

[0036] Embodiment 1.

[0037] The application discloses a monitoring and prevention method for grouting casing in bedrock weathering zone.

[0038] Referring to Figure 1 , the monitoring and prevention method for preventing grouting casing in bedrock weathering zone from falling off and deforming comprises the following specific steps: S1: designing the arrangement interval of grouting positions, analyzing the grouting layer depth according to the stratum condition, calculating the grouting amount, the grouting water supply amount, designing the solid particle size in the slurry, and arranging the grouting layer between the sub-key layer and the soft layer. In the application, the grouting positions are two, and the interval between the two grouting positions is 150 m.

[0039] S2: establishing a grouting station, and forming grouting channels by adopting four-opening drilling structure at each grouting position.

[0040] Referring to Figure 1 and Figure 2 , S21: one-opening drilling, drilling vertically downward on the ground and inserting the surface casing 1, cementing the well, forming the straight well section 1 7, and arranging the fourth system in the bedrock layer; wherein the one-opening drilling hole diameter is 445 mm, the diameter of the surface casing 1 is 377 mm, the wall thickness is 8 mm, and the top of the surface casing 1 is higher than the wellhead of the straight well section 1 7.

[0041] S22: two-opening drilling, continuing to drill at the bottom of the straight well section 1 7 and inserting the inner casing 2, cementing the well, forming the straight well section 2 8, and arranging the bottom of the straight well section 2 8 at the bottom of the main key layer; wherein the two-opening drilling hole diameter is 311 mm, the diameter of the inner casing 2 is 377 mm, the wall thickness is 8 mm, and in the application, the top of the inner casing 2 is flush with the top of the surface casing 1.

[0042] S23: three open drilling, continue drilling at the bottom of the straight well section three 9 and insert the bottom hole casing 3, cementing, forming a straight well section three 9, the bottom of the straight well section three 9 is located at the bottom of the sub-key layer; wherein the three open drilling hole diameter is 216mm, the diameter of the bottom hole casing 1 is 178mm, and the wall thickness is 9mm.

[0043] S24: four open drilling, continue drilling at the bottom of the straight well section three 9 and insert the bottom hole casing 4, cementing, forming the grouting section 10, the grouting section 10 is located in the grouting layer; wherein the four open drilling hole diameter is 152mm, the diameter of the bottom hole casing 4 is 127mm, and the wall thickness is 9mm.

[0044] Referring to Figure 2 and Figure 3 , S3: water injection and pressure maintenance between the surface casing 1 and the inner casing 2, and a pressure sensor 5 is placed between the surface casing 1 and the inner casing 2 to detect the water pressure; specifically, the pressure sensor 5 is distributed in the vertical direction, and each pressure sensor 5 is connected by an optical fiber belt 51, in the embodiment of the application, the pressure sensor 5 is uniformly provided with four in the vertical direction, and the pressure sensor 5 is specifically selected as SCYG411 immersion type liquid level transmitter to ensure that the pressure sensor 5 has strong impact resistance, overload resistance and high stability, when the value of the pressure sensor 5 is lower than the preset value, the pressure sensor 5 will send a signal to alarm.

[0045] S31: when the value of the pressure sensor 5 is lower than the preset value, early strength cement is injected between the surface casing 1 and the inner casing 2. Wherein, a plurality of grouting pipes 6 are arranged between the surface casing 1 and the inner casing 2, which are uniformly distributed around the axis of the inner casing 2, in the embodiment of the application, the number of grouting pipes 6 is selected as four, early strength cement is injected into the space between the surface casing 1 and the inner casing 2 through each grouting pipe 6, and the grouting pipe 6 can be continuously lifted upward during the injection of early strength cement, so as to ensure the stability of the injection of early strength cement. Early strength cement is specifically selected as 425 early strength cement to ensure the structural strength after early strength cement fills the gap between the surface casing 1 and the inner casing 2.

[0046] Referring to Figure 1 and Figure 2 , S4: the grouting hole is connected with the grouting or water pumping device at the orifice, the grouting hole is connected with the grouting station through the grouting or water pumping device, and grouting is carried out along each arranged grouting hole. The grouting hole passes through the fourth system (soil layer, sand layer, gravel layer), bedrock, main key layer, sub-key layer and separation layer (grouting layer) in turn along the vertical direction.

[0047] The implementation principle of the method for monitoring and preventing the grouting casing in the bedrock weathering zone is as follows: when, in the grouting process, the advanced migration occurs in the bedrock weathering zone, and the migration deformation intensity is greater than the intensity of the surface casing 1, the surface casing 1 is broken, the pressure-maintaining water between the surface casing 1 and the inner casing 2 leaks or flows away, at this time, the pressure sensor 5 is lower than the preset value and sends an alarm signal, at this time, the early-strength cement is injected through the grouting pipe 6 between the surface casing 1 and the inner casing 2 to fill the gap between the surface casing 1 and the inner casing 2, thereby preventing the bedrock weathering zone migration from further damaging the inner casing 2, ensuring the smooth progress of grouting, and effectively avoiding the accident of slurry gushing out of the ground; the measures of the pressure sensor 5 cooperating with the early-strength cement injection in time facilitate the monitoring and prevention in the delamination grouting process, and ensure the stability of the delamination grouting.

[0048] Embodiment 2.

[0049] With reference to Figure 4 The main difference between the embodiment and the embodiment 1 is that the surface casing 1 inner wall or the inner casing 2 outer wall is provided with a plurality of sets of limiting assemblies corresponding to a plurality of grouting pipes 6, in the embodiment, the limiting assemblies are arranged on the inner casing 2 outer wall and correspond to four sets of four grouting pipes 6, and each set of limiting assemblies is uniformly distributed with a plurality of limiting rings 11 in the vertical direction.

[0050] Specifically, the limiting assembly includes a limiting ring 11 fixedly installed on the inner casing 2 outer wall by a bolt (not shown in the figure), and the limiting ring 11 is vertically provided with a limiting hole 12, and the hole diameter of the limiting hole 12 is greater than the pipe diameter of the grouting pipe 6, so that the limiting hole 12 is used for the grouting pipe 6 to pass through. When the grouting pipe 6 is inserted into each limiting hole 12, each limiting ring 11 plays a limiting and guiding role for the grouting pipe 6 during grouting, thereby facilitating the stability of the early-strength cement injection.

[0051] With reference to Figure 4 To further ensure the stability of the position of the grouting pipe 6 and facilitate the movement of the grouting pipe 6 in the vertical direction, each limiting ring 11 is provided with a pressing piece 13, specifically, the pressing piece 13 includes a pressing spring 131 and a pressing block 132, wherein the hole wall of the limiting hole 12 away from the inner casing 2 is provided with a pressing sliding groove 14, and the pressing block 132 is slidingly fitted in the pressing sliding groove 14. The top of the pressing block 132 is provided with an inclined guide surface 1321, so that when the top of the pressing block 132 is stressed, it has a sliding force into the pressing sliding groove 14, thereby facilitating the insertion of the grouting pipe 6 into the limiting hole 12.

[0052] With reference to Figure 4The other end of the pressing spring 131 is connected to the pressing block 132, so that the pressing spring 131 exerts a spring force on the pressing block 132 in a direction away from the limiting hole 12, so that when the grouting pipe 6 is arranged in each limiting hole 12, each pressing block 132 is further pressed and limited on the grouting pipe 6 under the action of the spring force of the pressing spring 131. The end of each pressing block 132 away from the pressing spring 131 is rotatably installed with a pressing roller 133, and the material of the pressing roller 133 is selected to be rubber, so as to reduce the wear of the pressing block 132 caused by rigid contact with the grouting pipe 6, and on the other hand, facilitate the vertical movement of the grouting pipe 6 in the limiting hole 12, so that the grouting pipe 6 can inject early strength cement at different depths. The implementation principle of the embodiment of the present application is the same as that of embodiment 1, and will not be repeated here.

[0053] Embodiment 3.

[0054] With reference to Figure 5 The main difference between the embodiment of the present application and embodiment 1 is that the specific structures of the surface sleeve 1 and the inner sleeve 2 are different. Specifically, the surface sleeve 1 and the inner sleeve 2 in the embodiment of the present application each include a plurality of sleeve bodies 15 distributed along the axis thereof, and a connecting piece 16 is arranged between two vertically adjacent sleeve bodies 15.

[0055] Specifically, the connecting piece 16 is provided with a connecting hole 17 vertically penetrating through the connecting piece 16, and a positioning ring 18 is fixedly connected to the inner wall of the connecting hole 17. The positioning ring 18 is located at the middle part of the connecting piece 16, and two vertically adjacent sleeve bodies 15 are respectively inserted into the two ends of the connecting hole 17 and abut against the two sides of the positioning ring 18. The sleeve body 15 is fixed to the connecting piece 16 by a bolt penetrating through the connecting piece 16 and threadedly connected to the sleeve body 15, so as to stably connect the sleeve body 15 and the connecting piece 16. The inner diameter of the positioning ring 18 is equal to the inner diameter of the sleeve body 15. The positioning ring 18 is beneficial to ensuring the coaxiality of the two sleeve bodies 15 after installation, and also plays a positioning role during installation of the two sleeve bodies 15, so as to facilitate stable fixation of the sleeve body 15 and the connecting piece 16 by the bolt.

[0056] With reference to Figure 5To further ensure the stability of the sleeve body 15 and the connecting piece 16 when connected, a plurality of positioning protrusions 19 are fixedly connected on both sides of the positioning ring 18 and are uniformly distributed in the circumferential direction around the axis of the positioning ring 18, and the end of the sleeve body 15 is provided with a positioning groove 20 corresponding to the positioning protrusions 19 and being inserted and matched with the positioning protrusions 19, so that the sleeve body 15 and the connecting piece 16 are stably positioned when installed through the inserted matching of the positioning protrusions 19 and the positioning groove 20. The inner wall of the connecting piece 16 is embedded with two sealing pads 21, the two sealing pads 21 are respectively arranged near the two ends of the connecting piece 16, and the two sealing pads 21 are respectively abutted against the outer circumferential surfaces of the two adjacent sleeve bodies 15, so as to further ensure the sealing performance of the connecting piece 16 and the sleeve body 15 after being connected, and to stably isolate the substances inside and outside the sleeve. The implementation principle of the embodiment of the present application is the same as that of the embodiment 1, and will not be described here.

[0057] The above are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, therefore: any equivalent changes made on the structure, shape, principle of the present application shall be covered within the protection scope of the present application.

Claims

1. A method for monitoring and preventing the use of a grouting casing in a bedrock weathering zone, characterized in that: The method comprises the following steps: S1: designing the arrangement interval of the grouting position, analyzing the grouting layer depth according to the stratum condition, calculating the grouting amount, the slurry preparation water supply amount, and designing the solid particle size in the slurry, and the grouting layer is between the sub-key layer and the soft layer; S2: establishing a slurry preparation station, and adopting a four-opening drilling structure to form a grouting hole at each grouting position; S21: first opening drilling, drilling vertically downward on the ground and inserting a surface casing (1), cementing the well, and forming a straight well section one (7), wherein the straight well section one (7) is arranged in the Quaternary stratum in the bedrock layer; S22: second opening drilling, continuing to drill at the bottom of the straight well section one (7) and inserting an inner casing (2), cementing the well, and forming a straight well section two (8), wherein the bottom of the straight well section two (8) is located at the bottom of the main key layer, and the top of the inner casing (2) is located at the same height as the top of the surface casing (1); S23: third opening drilling, continuing to drill at the bottom of the straight well section two (8) and inserting a bottom casing one (3), cementing the well, and forming a straight well section three (9), wherein the bottom of the straight well section three (9) is located at the bottom of the sub-key layer; S24: fourth opening drilling, continuing to drill at the bottom of the straight well section three (9) and inserting a bottom casing two (4), cementing the well, and forming a grouting section (10), wherein the grouting section (10) is located in the grouting layer; S3: injecting water to maintain pressure between the surface casing (1) and the inner casing (2), and placing a pressure sensor (5) between the surface casing (1) and the inner casing (2) to detect the water pressure; S31: when the value of the pressure sensor (5) is lower than the preset value, injecting early strength cement between the surface casing (1) and the inner casing (2); S4: connecting a grouting or water pumping device at the orifice of the grouting hole, connecting the grouting hole with the slurry preparation station through the grouting or water pumping device, and grouting along each arranged grouting hole.

2. The method for monitoring and preventing according to claim 1, characterized in that: In the step S3, a plurality of pressure sensors (5) are distributed along the vertical direction, and each pressure sensor (5) is connected through an optical fiber ribbon (51).

3. The method for monitoring and preventing according to claim 1, characterized in that: In the step S2, the diameter of the surface casing (1) is 377 mm, and the wall thickness is 8 mm, the diameter of the inner casing (2) is 245 mm, and the wall thickness is 8 mm, the diameter of the bottom casing one (3) is 216 mm, and the wall thickness is 9 mm, and the diameter of the bottom casing two (4) is 127 mm, and the wall thickness is 9 mm.

4. The method for monitoring and preventing according to claim 1, characterized in that: In the step S3, a plurality of grouting pipes (6) are arranged between the surface casing (1) and the inner casing (2) and are uniformly distributed along the circumferential direction of the inner casing (2), and the early strength cement is injected into the surface casing (1) and the inner casing (2) through the grouting pipes (6).

5. The method for monitoring and preventing according to claim 4, characterized in that: A plurality of limiting assemblies corresponding to the plurality of grouting pipes (6) are arranged on the inner wall of the surface casing (1) or the outer wall of the inner casing (2), each limiting assembly is distributed along the vertical direction, and each limiting assembly comprises a limiting ring (11) fixedly installed on the inner wall of the surface casing (1) or the outer wall of the inner casing (2), and the limiting ring (11) is provided with a limiting hole (12) vertically penetrating and used for passing the grouting pipe (6).

6. The method for monitoring and preventing according to claim 5, characterized in that: The limiting ring (11) is provided with a pressing part (13), the pressing part (13) comprises a pressing spring (131) and a pressing block (132), the hole wall of the limiting hole (12) is provided with a pressing sliding groove (14), the pressing block (132) is slidably matched in the pressing sliding groove (14), the top of the pressing block (132) is provided with an inclined guide surface (1321), one end of the pressing spring (131) is connected to the groove wall of the pressing sliding groove (14), and the other end of the pressing spring (131) is connected to the pressing block (132), the pressing spring (131) applies a spring force to the pressing block (132) in a direction away from the limiting hole (12).

7. The method for monitoring and preventing according to claim 6, characterized in that: The end of the pressing block (132) away from the pressing spring (131) is rotatably provided with a pressing roller (133), and the material of the pressing roller (133) is selected as rubber.

8. The method for monitoring and preventing according to claim 1, characterized in that: The surface sleeve (1) and the inner sleeve (2) each comprise a plurality of sleeve bodies (15) distributed along the axis thereof, connecting pieces (16) are arranged between two adjacent sleeve bodies (15) in the vertical direction, the connecting pieces (16) are provided with connecting holes (17) vertically penetrating through, the connecting holes (17) are fixedly connected with positioning rings (18), and the two adjacent sleeve bodies (15) in the vertical direction are respectively abutted on the two sides of the positioning ring (18), and the sleeve body (15) is fixed with the connecting piece (16) through the bolt penetrating the connecting piece (16) and threadedly matched with the sleeve body (15).

9. The method for monitoring and preventing according to claim 8, characterized in that: The two sides of the positioning ring (18) are fixedly connected with a plurality of positioning protrusions (19), and the end of the sleeve body (15) is provided with a positioning groove (20) corresponding to the positioning protrusion (19) and matched with the positioning protrusion (19).

10. The method for monitoring and preventing according to claim 9, characterized in that: The inner wall of the connecting piece (16) is fixedly connected with two sealing pads (21), and the two sealing pads (21) are respectively arranged close to the two ends of the connecting piece (16) and abut against the outer circumferential surfaces of the two adjacent sleeve bodies (15).

Images