Method for monitoring water pressure of surrounding rock on outer side of well wall of water-containing bedrock section of coal mine freezing vertical shaft

Abstract

The invention discloses a coal mine freezing vertical shaft water-containing bedrock section well wall outer side surrounding rock water pressure monitoring method, and belongs to the technical field of coal mine freezing vertical shaft surrounding rock water pressure monitoring. S2, packaging the water permeable box; s3, mounting a water permeable box; s4, lowering the water permeable box; step S5, hole sealing; and S6, collecting and recording data. By combining the designed permeable box with the monitoring process, the underground water pressure borne by the surrounding rock can be monitored in real time, the safety of the surrounding rock structure is ensured, and when it is monitored that the water pressure borne by the surrounding rock is close to or exceeds the allowable value of the bearing capacity of the surrounding rock, related personnel can find and take preventive remedial measures at the first time; compared with a traditional monitoring method, the method has the advantages that the accuracy and timely response are remarkably improved, and the engineering safety and stability can be better ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of water pressure monitoring of the surrounding rock of a frozen vertical shaft in a coal mine, and particularly to a method for monitoring the water pressure of the surrounding rock on the outer side of the shaft wall in the water-bearing bedrock section of a frozen vertical shaft in a coal mine. Background Art

[0002] The artificial ground freezing method (referred to as the freezing method for short) is widely used in water-rich strata, sediment layers and other environments due to its excellent water sealing performance, remarkable reinforcement effect, strong adaptability and high safety. The principle of the freezing method is to circulate a refrigerant in the freezing pipes artificially arranged, so as to take away the heat in the soil body, freeze the water-bearing soil body, form a frozen soil layer with high strength and good sealing performance, and then realize bearing the load and providing the function of sealing and waterproofing. The diameter of the frozen soil cylinder formed around each freezing pipe will increase with time, and these cylinders are connected to each other to form a dense and closed frozen soil wall (also called a freezing wall), which can resist the water and soil pressure and block the groundwater flow. Under the protection of the frozen soil wall, the formation excavation and lining construction are carried out. Therefore, when the shield method and the ordinary dewatering method are not suitable for vertical shaft construction, the freezing method is also a commonly used technical means. In addition, during construction, only need to drill holes at the corresponding positions on the ground surface, insert the freezing pipes, and circulate the refrigerant, then the soft and water-rich strata can be frozen within a certain period of time to provide guarantee for the subsequent construction.

[0003] Although the above freezing construction method is widely used in the construction of coal mine vertical shafts, after the completion of the vertical shaft construction, the current technical means are still difficult to effectively monitor the water pressure of the surrounding rock on the outer side of the shaft wall in the water-bearing formation of the vertical shaft. Since it is impossible to accurately judge whether the water pressure borne by the surrounding rock shaft wall is within the reasonable range of design, there is a lack of a reliable evaluation method for the safety, applicability and durability of the structure. This will bring great hidden dangers in areas with more abundant water volume and stronger permeability, and may lead to engineering accidents.

[0004] The above problems need to be solved urgently. For this reason, the present invention proposes a method for monitoring the water pressure of the surrounding rock on the outer side of the shaft wall in the water-bearing bedrock section of a frozen vertical shaft in a coal mine. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: how to solve the problem that the existing technical means are difficult to effectively monitor the water pressure of the surrounding rock on the outer side of the vertical shaft wall, and provides a method for monitoring the water pressure of the surrounding rock on the outer side of the shaft wall in the water-bearing bedrock section of a frozen vertical shaft in a coal mine, which has the function of monitoring the water pressure of the surrounding rock on the outer side of the shaft wall after the completion of the vertical shaft construction, and can also evaluate the safety, applicability and durability of the structure by monitoring the water pressure of the surrounding rock on the outer side of the shaft wall.

[0006] The present invention solves the above technical problems through the following technical solutions. The present invention includes the following steps:

[0007] Step S1: Selection of monitoring points

[0008] After the freezing construction is completed, select the monitoring points according to the geological exploration report, and determine the formation depth where the water pressure of the surrounding rock needs to be monitored; Step S2: Encapsulation of the water-permeable box

[0009] Install and fix multiple water pressure sensors into the water-permeable box, pull out the wires of each sensor from the water-permeable box, and then install the box cover to complete the encapsulation work;

[0010] Step S3: Installation of the water-permeable box

[0011] According to the formation depth where the water pressure of the surrounding rock needs to be monitored determined longitudinally, mark the position of the corresponding formation demarcation line on the hollow steel wire rope; then open holes on the side at a set distance below the corresponding marked position on the hollow steel wire rope, and pass the sensor wires of each water-permeable box through the side of the hollow steel wire rope and out from the top;

[0012] Step S4: Lowering of the water-permeable box

[0013] After installing the water-permeable box on the hollow steel wire rope, pull out the freezing pipes in the freezing holes serving as monitoring points, lower the water-permeable box through the hollow steel wire rope. After lowering it to the corresponding position, horizontally place a steel bar at the top of the freezing hole and weld the hollow steel wire rope to it to make the whole hollow steel wire rope in a vertical state;

[0014] Step S5: Sealing of the holes

[0015] Inject the water-permeable hole-sealing material into the freezing holes where the hollow steel wire rope is fixed until the ground surface. After all the water-permeable boxes in the freezing holes serving as monitoring points are lowered, inject the water-permeable hole-sealing material to complete the hole-sealing work;

[0016] Step S6: Data acquisition and recording

[0017] Connect all the sensor wires passing through the hollow steel wire rope to the data acquisition controller and record the initial data; take the initial data as the benchmark, compare the initial data with the design allowable value of the bearing capacity of the surrounding rock structure to obtain the monitoring result of the water pressure of the surrounding rock.

[0018] Furthermore, in the said Step S1, the specific processing process is as follows:

[0019] Step S11: After the freezing construction is completed, according to the geological exploration report, horizontally determine the radial flow direction of the groundwater, define it as the positive direction of the x-axis, take the center of the vertical shaft as the coordinate origin o(0,0), and establish the xoy plane with the ground surface as the reference plane, and the y-axis is perpendicular to the x-axis;

[0020] Step S12: Select the freezing hole that the groundwater flow first passes through on the water-facing side as the first monitoring point for the surrounding rock water pressure, and with the vertical shaft center as the center, arrange the other three monitoring points in a cross shape on the xoy plane. The distances from the centers of the four monitoring points to the vertical shaft center are the same;

[0021] Step S13: Record the depths from each formation boundary line below each monitoring point 2 to the ground surface respectively, and then determine the formation depth for which the surrounding rock water pressure needs to be monitored.

[0022] Furthermore, in the step S12, when the freezing hole that the groundwater first passes through on the water-facing side is located on the x-axis and the other freezing holes are symmetrically distributed on the x-axis and y-axis, directly use the other three freezing holes on the x-axis and y-axis as the monitoring points for the surrounding rock water pressure; when the freezing hole that the groundwater first passes through on the water-facing side is not located on the x-axis, according to the position of the freezing hole selected as the first monitoring point, evenly distribute the other three freezing holes as the monitoring points for the surrounding rock water pressure.

[0023] Furthermore, in the step S2, the water-permeable box is a hollow cylindrical structure. Three sensor circular holes for installing water pressure sensors are circumferentially opened at the middle position of the inner wall of the water-permeable box. A plurality of evenly distributed water-permeable circular holes for realizing water permeability are opened on the outer wall of the water-permeable box. A sponge for preventing blockage of the induction area of the water pressure sensor is filled in the inner cavity formed between the outer wall and the inner wall of the water-permeable box; the axes of the three sensor circular holes are on the same horizontal plane, and the included angle between adjacent two axes is 120°.

[0024] Furthermore, in the step S2, the specific processing process is as follows:

[0025] S21: Put rubber gaskets on the outsides of the three water pressure sensors respectively, and use glue to fix them in the three sensor circular holes on the inner wall of the water-permeable box;

[0026] S22: Pull out the sensor wires from the inner holes of the water-permeable box, then fill the inside of the water-permeable box with sufficient sponge, and install the box cover to complete the encapsulation work.

[0027] Furthermore, in the step S3, a plurality of water-permeable boxes are installed on the hollow steel wire rope, and the water-permeable boxes are installed from bottom to top in descending order of the sensor range.

[0028] Furthermore, in the step S3, after the sensor wires pass through the hollow steel wire rope, the upper and lower ends of each water-permeable box are respectively fixed with wire rope clamps.

[0029] Furthermore, in the step S5, the arrangement positions and quantities of the water-permeable boxes on the hollow steel wire ropes in each freezing hole used as a monitoring point are the same.

[0030] Further, in the step S6, when the water pressure of the surrounding rock of each stratum obtained by converting the data monitored and recorded by the water permeable box minus the initial data is less than 80% of the design allowable value of the bearing capacity of the surrounding rock structure, it indicates that the surrounding rock structure of the vertical shaft is safe; when the water pressure of the surrounding rock of any stratum obtained by converting the data monitored and recorded by the water permeable box minus the initial data is greater than or equal to 80% of the design allowable value of the bearing capacity of the surrounding rock structure, it indicates that there are potential safety hazards in the surrounding rock structure of the vertical shaft.

[0031] Further, in each stratum, three groups of voltage data are obtained corresponding to the three water pressure sensors of the water permeable box in the freezing holes corresponding to each monitoring point. The three groups of voltage data obtained by a single water permeable box are arithmetically averaged to obtain the average voltage data d of a single water permeable box. i , and then the average voltage data d of the four water permeable boxes corresponding to the four monitoring points in each stratum i is arithmetically averaged again to obtain the average voltage data S of each stratum. n , combined with the initial value S of the average voltage data of each stratum 0 The average voltage data S of each stratum n is converted to obtain the water pressure P of the surrounding rock of each stratum. n The calculation formula is as follows:

[0032] P n = k·(S n - S 0 )

[0033] Among them, P n is the water pressure of the surrounding rock of the corresponding stratum, k is the conversion coefficient of the water pressure sensor, S n is the average voltage data of each stratum calculated according to the monitored output voltage of each water pressure sensor, that is, the data monitored and recorded by the water permeable box subsequently, and S 0 is the average voltage data of each stratum calculated according to the zero output voltage of each water pressure sensor, that is, the initial data; i takes 1, 2, 3, and n takes 1, 2, 3, 4.

[0034] The present invention has the following advantages compared with the prior art: the monitoring method for the water pressure of the surrounding rock outside the shaft wall in the water-bearing bedrock section of the frozen vertical shaft of the coal mine can, through the designed water permeable box combined with the monitoring process of the present invention, monitor the groundwater pressure received by the surrounding rock in real time and ensure the safety of the surrounding rock structure. When it is monitored that the water pressure received by the surrounding rock approaches or exceeds its allowable bearing capacity value, relevant personnel can discover it in time and take preventive remedial measures; compared with the traditional monitoring method, it has significant improvements in accuracy and timely response, and can better ensure the safety and stability of the project. Description of the Drawings

[0035] Figure 1It is a schematic flow diagram of the method for monitoring the water pressure of the surrounding rock on the outer side of the shaft wall in the water-bearing bedrock section of the coal mine freezing vertical shaft in the embodiment of the present invention;

[0036] Figure 2 It is a schematic flow diagram of the encapsulation and lowering process of the water-permeable box in the embodiment of the present invention;

[0037] Figure 3 It is a schematic diagram of the xoy plane in the embodiment of the present invention;

[0038] Figure 4 It is a partial sectional view of the structure of the water-permeable box in the embodiment of the present invention;

[0039] Figure 5 It is a schematic installation diagram of the water-permeable box in the embodiment of the present invention;

[0040] Figure 6 It is a schematic elevation view of the formation layout of the water-permeable box in the embodiment of the present invention;

[0041] In the figure: 1, vertical shaft; 2, monitoring point; 3, freezing hole; 4, box cover; 5, rubber gasket and the application position of 502 glue; 6, water-permeable round hole; 7, sensor wire; 8, sensor round hole; 9, water pressure sensor; 10, hollow steel wire rope; 11, wire rope clamp; 12, inner hole; 13, sponge; 14, formation boundary line; 15, steel bar. Detailed implementation manner

[0042] The following makes a detailed description of the embodiments of the present invention. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0043] As Figure 1-6 shown, this embodiment provides a technical solution: a method for monitoring the water pressure of the surrounding rock on the outer side of the shaft wall in the water-bearing bedrock section of the coal mine freezing vertical shaft, including the following steps (taking single-circle freezing as an example):

[0044] Step S1: Selection of monitoring points

[0045] After the freezing construction is completed, the monitoring points 2 are selected according to the geological exploration report.

[0046] The specific process is as follows:

[0047] Step S1.1: Horizontally determine the radial flow direction of groundwater, define it as the positive direction of the x-axis, use the center of the vertical shaft 1 as the coordinate origin o(0,0), and establish the xoy plane with the ground surface as the reference plane. The y-axis is perpendicular to the x-axis; select the freezing hole 3 that the groundwater flow encounters first on the water-facing side as the first monitoring point 2 for the water pressure of the surrounding rock, and arrange the other three monitoring points 2 in a cross shape on the xoy plane with the center of the vertical shaft 1 as the center.

[0048] More specifically, when the freezing hole 3 through which the groundwater first flows on the upstream side is located on the x-axis and the other freezing holes 3 are symmetrically distributed on the x-axis and y-axis, the remaining three freezing holes 3 on the axes of the x-axis and y-axis are directly used as the monitoring points 2 for the surrounding rock water pressure;

[0049] More specifically, when the freezing hole 3 through which the groundwater first flows on the upstream side is not located on the x-axis, according to the position of the freezing hole 3 selected as the first monitoring point, the remaining three freezing holes 3 are evenly distributed as the monitoring points 2 for the surrounding rock water pressure; the specific layout can be adjusted accordingly according to the on-site geological conditions.

[0050] It should be noted that in this embodiment, each freezing hole 3 and the vertical shaft 1 are both vertically arranged.

[0051] Step S1.2: Vertically determine the formation depth where the surrounding rock water pressure needs to be monitored: Record the depths from the surface to the respective formation boundaries below each monitoring point 2, and determine the formation where the surrounding rock water pressure needs to be monitored.

[0052] Step S2: Encapsulation of the water permeable box

[0053] Put rubber washers on the outside of the three water pressure sensors 9 respectively, use 502 glue to fix them in the three sensor circular holes 8 on the inner wall of the water permeable box, pull out the sensor wires 7 from the inner hole of the water permeable box, and then fill the inner cavity formed between the outer wall and the inner wall of the water permeable box with sponge 13 for preventing the induction area of the water pressure sensor from being blocked, and install the box cover 4 to complete the encapsulation work.

[0054] Preferably, the range specifications of the water pressure sensors 9 installed inside a single water permeable box should be the same.

[0055] Preferably, the axes of the three sensor circular holes 8 on the inner wall of the water permeable box are on the same horizontal plane, and the included angle between adjacent two axes is 120°, and the diameter of the sensor circular hole 8 is 20 mm.

[0056] Preferably, connect the sensor wires 7 of the installed water pressure sensors 9 to the data acquisition controller, immerse the water permeable box in water to detect whether it works normally, record the zero output voltage of the water pressure sensor, and disconnect the connection after determining that it works normally.

[0057] In this embodiment, the diameter of the water pressure sensor 9 is 18 mm, and the inner diameter of the rubber washer is 18 mm.

[0058] Step S3: Installation of the water permeable box

[0059] According to the formation depth where the water pressure of the surrounding rock needs to be monitored determined longitudinally, mark the positions of the corresponding formation dividing lines on the hollow steel wire rope 10 (with a diameter of 20 mm); drill a hole on the side at a position 0.5 m below the corresponding mark on the hollow steel wire rope 10, and pass the sensor wire 7 of each water permeable box through the side of the hollow steel wire rope 10 and out from the top.

[0060] Preferably, the water permeable boxes should be installed from bottom to top in descending order of the sensor range.

[0061] Preferably, after the sensor wire 7 of each water permeable box is installed on the hollow steel wire rope 10, the space between the inner hole 12 of the water permeable box and the hollow steel wire rope 10 is filled with waterproof glue for further encapsulation.

[0062] Preferably, after the sensor wire 7 passes through the hollow steel wire rope 10, the upper and lower ends of each water permeable box are respectively fixed with wire rope clamps 11 (M20) to ensure that it will not slide.

[0063] Preferably, connect the sensor wire 7 installed and fixed on the hollow steel wire rope 10 to the data acquisition controller again, immerse the water permeable box in water again to detect whether it works normally, and disconnect the connection after determining that it works normally.

[0064] Step S4: Lowering the water permeable box

[0065] After installing the water permeable box on the hollow steel wire rope 10, pull out the freezing pipe in the freezing hole 3 serving as the monitoring point, lower the water permeable box through the hollow steel wire rope 10. After lowering it to the corresponding position, horizontally place a steel bar 15 (model HRB400 Ф28, length 200 mm) at the top of the freezing hole 3, and weld it to the hollow steel wire rope 10 to ensure that the whole hollow steel wire rope 10 is in a vertical state, and connect the sensor wire 7 passing through the top of the hollow steel wire rope 10 to the data acquisition controller.

[0066] Step S5: Sealing the hole

[0067] Inject the water permeable hole-sealing material into the freezing hole 3 with the hollow steel wire rope 10 fixed until it reaches the ground surface.

[0068] After the sealing of a single freezing hole 3 serving as the monitoring point 2 is completed, repeat steps S4 - S5 until the water permeable boxes in all the freezing holes 3 serving as the monitoring point 2 are lowered and the hole-sealing work is completed.

[0069] Step S7: Data acquisition and recording

[0070] Connect all the sensor wires 7 passing through the hollow steel wire rope 10 to the data acquisition controller, record the initial data; take the initial data as the benchmark, compare the initial data with the design allowable value of the bearing capacity of the surrounding rock structure to obtain the monitoring results of the water pressure of the surrounding rock.

[0071] Step S7.1: When the surrounding rock water pressure of each stratum obtained by converting the data of subsequent monitoring records minus the initial data is less than 80% of the design allowable value of the surrounding rock structure bearing capacity, it indicates that the surrounding rock structure of the vertical shaft is safe;

[0072] Step S7.2: When the surrounding rock water pressure of any stratum obtained by converting the data of subsequent monitoring records minus the initial data is greater than or equal to 80% of the design allowable value of the surrounding rock structure bearing capacity, it indicates that there are potential safety hazards in the surrounding rock structure of the vertical shaft, and reinforcement measures should be taken as early as possible to prevent them.

[0073] More specifically, in each stratum, three groups of voltage data are obtained corresponding to the three water pressure sensors of the water permeable box in the freezing hole corresponding to each monitoring point 2. The three groups of voltage data obtained by a single water permeable box are arithmetically averaged to obtain the average voltage data d of a single water permeable box i , and then the average voltage data d of the four water permeable boxes corresponding to the four monitoring points 2 in each stratum i is arithmetically averaged again to obtain the average voltage data S of each stratum n , combined with the initial value S of the average voltage data of each stratum 0 The average voltage data S of each stratum is n converted to obtain the surrounding rock water pressure P of each stratum n , and the calculation formula is as follows:

[0074] P n = k·(S n - S 0 )

[0075] Among them, P n is the surrounding rock water pressure of the corresponding stratum, k is the conversion coefficient of the water pressure sensor, S n is the average voltage data of each stratum calculated according to the monitoring output voltage of each water pressure sensor, and S 0 is the average voltage data of each stratum calculated according to the zero output voltage of each water pressure sensor, and the unit is V.

[0076] It should be noted that for the three groups of voltage data monitored and recorded by each water permeable box in each layer of the freezing hole corresponding to each monitoring point 2, when taking the average value of the three groups of voltage data of each water permeable box, if one group of voltage data has a large difference from the other two groups of voltage data, it is determined that the corresponding water pressure sensor 9 is faulty, and the voltage data of the corresponding sensor should be discarded, and the arithmetic average is taken with the other two groups of voltage data.

[0077] In addition, the change of the water pressure data of the surrounding rock during the water-rich season and the cold winter season (the change of groundwater flow) should be recorded. Through this data collection and recording process, it is possible to effectively monitor the surrounding rock of the shaft wall after construction to detect potential hidden dangers in advance and take timely measures, which serves as an important basis for evaluating the structural safety, applicability, and durability.

[0078] It should be noted that the design content of the water-permeable box in this embodiment is as follows:

[0079] The designed water-permeable box has an outer diameter of 100 mm, a height of 100 mm, an outer wall thickness of 5 mm, an inner diameter of 30 mm, an inner wall thickness of 10 mm, a bottom thickness of 5 mm, and a lid thickness of 5 mm. A plurality of 5-mm water-permeable round holes 6 are drilled on the outer wall of the water-permeable box to achieve the purpose of water permeability. The diameter of the water-permeable round holes 6 should not be too large to avoid the gravel for grouting and sealing the holes from blocking the round holes and causing water impermeability. Three sensor round holes 8 are opened in the middle of the inner wall for the installation of the water pressure sensor 9. An 18-mm inner diameter rubber gasket is sleeved outside the water pressure sensor 9, and the sensor wires 7 are pulled out from the inner hole (with a diameter of 30 mm) 12 of the water-permeable box. The inner side of the sensor round hole 8 and the rubber gasket are coated with 502 glue to fix the water pressure sensor 9. The water-permeable box is filled with sufficient sponge 13 to prevent media such as sediment from blocking the sensor sensing area, and finally the lid 4 is installed on the water-permeable box to achieve the encapsulation purpose.

[0080] It should be noted that the connection process between the hollow steel wire rope 10 and the water-permeable box is as follows: The hollow steel wire rope 10 is passed through the inner hole 12 of the water-permeable box. According to the geological exploration report and the monitoring requirements, the test layer is selected, and then the steel wire rope clamps 11 are used to lock the hollow steel wire rope 10 at the upper and lower parts of the water-permeable box respectively to fix it and prevent its position from shifting during the lowering process.

[0081] In summary, for the monitoring method of the water pressure of the surrounding rock on the outer side of the shaft wall in the water-bearing bedrock section of the freezing vertical shaft of the coal mine, through the designed water-permeable box combined with the monitoring process of the present invention, it is possible to monitor the groundwater pressure exerted on the surrounding rock in real time and ensure the safety of the surrounding rock structure. When it is monitored that the water pressure exerted on the surrounding rock approaches or exceeds the allowable value of its bearing capacity, relevant personnel can discover it in a timely manner and take preventive remedial measures; compared with the traditional monitoring method, there is a significant improvement in accuracy and timely response, which can better ensure the safety and stability of the project.

[0082] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for monitoring the water pressure of the surrounding rock outside the shaft wall of the water-bearing bedrock section of a frozen vertical shaft in a coal mine, characterized in that: The following steps are involved: Step S1: Monitoring point selection After the freezing construction is completed, the monitoring points are selected according to the geological survey report, and the depth of the formation where the surrounding rock water pressure needs to be monitored is determined; Step S2: Water-permeable box packaging Install and fix multiple water pressure sensors into the water-permeable box, pull out the wires of each sensor from the water-permeable box, and then install the box cover to complete the packaging work; Step S3: Installation of water-permeable box According to the stratum depth where the surrounding rock water pressure needs to be monitored according to the longitudinal determination, the position of the corresponding stratum boundary line is marked on the hollow wire rope; Then, a hole is opened on the side of the hollow steel wire rope at a set distance downward from the corresponding mark, and the sensor wire of each water-permeable box is passed through the side of the hollow steel wire rope and out from the top; Step S4: Lowering the water-permeable box After the water-permeable box is installed on the hollow steel wire rope, the freezing pipe in the freezing hole serving as the monitoring point is pulled out, and the water-permeable box is lowered through the hollow steel wire rope. After it is lowered to the corresponding position, a steel bar is placed horizontally on the top of the freezing hole, and the hollow steel wire rope is welded to it so that the hollow steel wire rope is in a vertical state as a whole; Step S5: Sealing the hole The permeable sealing material is injected into the freezing hole where the hollow steel wire rope is fixed to the ground surface, and the permeable boxes in all the freezing holes used as monitoring points are lowered and the permeable sealing material is injected to complete the sealing work; Step S6: Data collection and recording Connect all sensor wires passing through the hollow steel wire rope to the data acquisition controller and record the initial data; The initial data are used as a benchmark and compared with the design allowable value of the surrounding rock structure bearing capacity to obtain the surrounding rock water pressure monitoring results.

2. The method for monitoring water pressure of surrounding rock outside the shaft wall of a water-bearing bedrock section of a frozen coal mine shaft according to claim 1 is characterized in that: In step S1, the specific processing process is as follows: Step S11: After the freezing construction is completed, according to the geological survey report, the radial flow direction of groundwater is determined horizontally, which is defined as the positive direction of the x-axis, the center of the shaft is used as the coordinate origin o(0,0), and the xoy plane is established with the ground surface as the reference plane, and the y-axis is perpendicular to the x-axis; Step S12: Select the freezing hole that groundwater first flows through toward the water-facing surface as the first monitoring point of surrounding rock water pressure, and arrange the remaining three monitoring points in a cross shape on the xoy plane with the center of the shaft as the center, and the distances between the centers of the four monitoring points and the center of the shaft are the same; Step S13: respectively record the depth from each stratum boundary line below each monitoring point 2 to the ground surface, and then determine the stratum depth where the surrounding rock water pressure needs to be monitored.

3. The method for monitoring water pressure of surrounding rock outside the shaft wall of a water-bearing bedrock section of a frozen coal mine shaft according to claim 2, characterized in that: In step S12, when the freezing hole through which the groundwater flows first is located on the x-axis, and the other freezing holes are symmetrically distributed on the x-axis and the y-axis, the remaining three freezing holes on the axis of the x-axis and the y-axis are directly used as monitoring points for the surrounding rock water pressure; when the freezing hole through which the groundwater flows first is not located on the x-axis, the remaining three freezing holes are evenly distributed as monitoring points for the surrounding rock water pressure according to the position of the freezing hole selected as the first monitoring point.

4. The method for monitoring water pressure of surrounding rock outside the shaft wall of a water-bearing bedrock section of a frozen coal mine shaft according to claim 2, characterized in that: In step S2, the water-permeable box is a hollow cylindrical structure, three sensor circular holes for installing water pressure sensors are circumferentially opened in the middle position of the inner wall of the water-permeable box, and multiple evenly distributed water-permeable circular holes for achieving water permeability are opened on the outer wall of the water-permeable box. The inner cavity formed between the outer wall and the inner wall of the water-permeable box is filled with sponge for preventing blockage of the sensing area of ​​the water pressure sensor; wherein the axes of the three sensor circular holes are on the same horizontal plane, and the angle between two adjacent axes is 120°.

5. The method for monitoring water pressure of surrounding rock outside the shaft wall of a water-bearing bedrock section of a frozen coal mine shaft according to claim 4, characterized in that: In step S2, the specific processing process is as follows: S21: Put rubber washers on the outside of the three water pressure sensors respectively, and use glue to fix them into the three sensor holes on the inner wall of the water permeable box; S22: Pull the sensor wire out of the inner hole of the waterproof box, then fill the waterproof box with a sufficient amount of sponge, and install the box cover to complete the packaging work.

6. The method for monitoring water pressure of surrounding rock outside the shaft wall of a water-bearing bedrock section of a frozen coal mine shaft according to claim 4, characterized in that: In step S3, the hollow steel wire rope is installed with a plurality of water-permeable boxes, and the water-permeable boxes are installed from bottom to top in descending order of sensor range.

7. The method for monitoring water pressure of surrounding rock outside the shaft wall of a water-bearing bedrock section of a frozen coal mine shaft according to claim 6, characterized in that: In step S3, after the sensor wire passes through the hollow steel wire rope, the upper and lower ends of each water-permeable box are fixed with steel wire rope clamps respectively.

8. The method for monitoring water pressure of surrounding rock outside the shaft wall of a water-bearing bedrock section of a frozen coal mine shaft according to claim 7, characterized in that: In step S5, the arrangement positions and quantities of the water-permeable boxes on the hollow steel wire ropes in the freezing holes serving as monitoring points are the same.

9. The method for monitoring water pressure of surrounding rock outside the shaft wall of a water-bearing bedrock section of a frozen coal mine shaft according to claim 7, characterized in that: In step S6, when the surrounding rock water pressure of each stratum obtained by subtracting the initial data from the data subsequently monitored by the permeable box is less than 80% of the design allowable value of the bearing capacity of the surrounding rock structure, it indicates that the surrounding rock structure of the vertical shaft is safe; when the surrounding rock water pressure of any stratum obtained by subtracting the initial data from the data subsequently monitored by the permeable box is greater than or equal to 80% of the design allowable value of the bearing capacity of the surrounding rock structure, it indicates that there is a safety hazard in the surrounding rock structure of the vertical shaft.

10. The method for monitoring water pressure of surrounding rock outside the shaft wall of a water-bearing bedrock section of a frozen coal mine shaft according to claim 9, characterized in that: In each stratum, three water pressure sensors of the water-permeable box in the freezing hole corresponding to each monitoring point obtain three sets of voltage data. The three sets of voltage data obtained by a single water-permeable box are arithmetic averaged to obtain the voltage data mean value d of a single water-permeable box. i , and then calculate the voltage data mean d of the four permeable boxes corresponding to the four monitoring points in each layer i Perform arithmetic averaging again to obtain the mean voltage data S of each layer. n , combined with the initial value S0 of the mean voltage data of each layer, the mean voltage data S of each layer n The surrounding rock water pressure P of each layer is obtained by conversion. n , the calculation formula is as follows: P n =k·(S n -S0) Among them, P n is the surrounding rock water pressure of the corresponding formation, k is the conversion coefficient of the water pressure sensor, S n is the mean voltage data of each layer calculated according to the monitoring output voltage of each water pressure sensor, that is, the data subsequently recorded by the water permeable box monitoring; S0 is the mean voltage data of each layer calculated according to the zero-point output voltage of each water pressure sensor, that is, the initial data; i is 1, 2, 3, and n is 1, 2, 3, and 4.

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