Seismic borehole strain observation pore-forming method

Abstract

The invention discloses an earthquake borehole strain observation pore-forming method, and relates to the technical field of earthquake monitoring. Comprising the following steps of leveling treatment on the surrounding area of a well hole, graded hole forming construction, casing pipe installation and sealing treatment, drilling hole flushing with clear water, quality detection and well hole ground treatment. Through real-time monitoring, material improvement, an intelligent system and other innovations, the hole forming precision, the well hole stability and leakproofness, the well washing quality and the like are improved, the method is suitable for various complete bedrock sites for borehole strain observation, especially for a depth adjustment scheme of complex terrains such as mountains, the flexibility of the technical method is improved, and the accuracy of seismic observation data is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of earthquake monitoring, in particular to a method for drilling a hole for earthquake borehole strain observation. BACKGROUND

[0002] Earthquake is a natural disaster that seriously threatens human life and property safety, and accurate monitoring of earthquake activity is of great significance for earthquake warning and disaster prevention. Drilling strain observation is an important means to obtain crustal strain information, and the accuracy and reliability of the observation data depend largely on the quality of the hole. There is no fixed method for drilling a hole for earthquake borehole strain observation in the prior art, and the traditional drilling technology has many defects: the use of impact drilling to drill a hole leads to irregular hole walls, affecting the stability of the instrument installation; the drilling is not airtight enough, drilling strain observation is the overall stress of the stratum, and the existing drilling strain observation drilling technology ignores the airtightness of the wellbore, and surface water and underground water seepage interfere with the observation data; the core recovery rate is low, and it is difficult to accurately assess the integrity of the bedrock; the installation of the casing is not standardized, and problems such as well wall collapse may occur, and some hole drilling methods do not strictly control the drilling depth, inclination and consolidation process of the casing and the stratum, resulting in large interference of the observation data by the external environment and poor long-term stability. Therefore, there is an urgent need for a drilling technology method for earthquake borehole strain observation to meet the high standard requirements of earthquake borehole strain observation. SUMMARY

[0003] The main purpose of the present application is to provide a method for drilling a hole for earthquake borehole strain observation to solve the above problems.

[0004] To achieve the above purpose, the present application provides a method for drilling a hole for earthquake borehole strain observation, comprising the following steps: S100, drilling preparation stage: flattening the area around the wellbore; S200, hierarchical hole drilling construction: drilling a hole with a core drill with a diameter not less than 160mm, starting to take core and marking the core depth in real time when drilling into the bedrock section; after drilling not less than 1m in the complete bedrock section, using a tapered drill to perform "horn mouth" diameter change processing to ensure the concentricity of the drilling before and after the diameter change, the diameter after the diameter change is 130mm, and a diamond drill with a diameter of 130mm is used to drill at a constant speed and slowly for not less than 6m in the complete bedrock section; the total drilling depth is controlled to be not less than 30m; the inclination of the newly built wellbore is not greater than 1°, and the rebuilt wellbore maintains the same inclination as the original; S300, casing installation and sealing treatment: install casing after the variable diameter treatment or install casing after the final hole, install geological seamless casing from the ground to the variable diameter place, the inner diameter of the casing is not less than 136mm, the top end is higher than the ground by not less than 30cm and lower than the well platform height, a 3cm*8cm notch is reserved at the top end of the casing and a casing cover is arranged; the casing adopts standard thread connection, the connection place is sealed, the casing is installed in the center to ensure the concentricity with the lower well hole; cement slurry pressure grouting is used between the outer wall of the casing and the hole wall to make the casing and the formation consolidated, after the cement consolidation, the residual cement debris on the inner wall of the casing and the bottom of the well hole is removed; S400, well washing: flush the drilling hole with clean water until the rock debris, dust and cement slurry in the well hole are washed clean to ensure the smooth and clean well wall and well bottom; S500, quality detection: fill the well hole with water for well leakage test, the water level is required to drop by not more than 3cm per hour; through the downhole television inspection, it is confirmed that the inner wall of the whole hole is smooth, the well wall below the casing is complete, the well bottom is free of debris and water accumulation; the well hole inclination, well diameter of each section, lithology and rock integrity are tested, and large scale columnar chart and construction log are prepared; S600, well hole ground treatment: taking the casing as the center, a not less than 4m*4m area is treated with cement hardening to form a water impermeable treatment ground with a thickness of not less than 5cm to ensure that the ground is free of water, and the unattended site can be covered with original soil after hardening; the distance between the drilling hole and the recording room is controlled to be not more than 20m, the cable is connected to the recording room through the threading pipe embedded under the water impermeable treatment ground, and a threading steel wire is reserved in the threading pipe; a cement or stainless steel well platform with a height of not less than 50cm is built at the well mouth, a lockable well cover is arranged, and the drilling hole and instrument information are marked on the lockable well cover.

[0005] Further, in step S200, when a formation affecting the sealing property of the well mouth is encountered during drilling, the depth is recorded, and after the casing is installed, the well wall sealing property treatment is performed.

[0006] Further, in step S300, when the casing is installed after the variable diameter treatment, the geological seamless steel casing is installed in the center after the variable diameter treatment is completed, after the cement of the pressure grouting treatment is consolidated, a diamond drill with a diameter of 130mm is used to drill at a uniform speed and slowly for not less than 6m of complete bedrock section, the drilling depth is determined by the bedrock thickness and the standby layer requirement, and it is ensured that the well wall below the casing is complete and smooth.

[0007] Further, in step S300, when the casing is installed after the final hole, the geological seamless steel casing is installed in the center after the final hole, after the cement of the pressure grouting treatment is consolidated, the diamond drill with a diameter of 130mm is used to continue drilling at a uniform speed and slowly, and the cement falling off from the inner wall of the casing, the well wall of the bedrock section and the bottom of the well hole is removed.

[0008] Further, in step S300, a sealing gasket ring is arranged at the joint of the casings, the end of the casing is provided with a chamfer, and the outside of the joint of the casings is formed into a recessed notch by the chamfer; after the casings are screwed into place, the edge of the sealing gasket ring is ablated and deformed, and is pressed into the notch, and then waterproof paint is sprayed in the notch.

[0009] Further, the cement slurry in step S300 adopts a modified formula of nanoscale calcium carbonate, the mass ratio of cement, water and nanoscale calcium carbonate is 1:0.4:0.05, the grouting pressure is adjusted according to the hardness of the stratum, the soft soil layer is controlled at 1.2-1.5 MPa, and the bedrock layer is improved to 2.0-2.5 MPa; the grouting rate is monitored in real time by a flow sensor during the grouting process, and when the rate drops by more than 30%, the automatic pause and switching to the pulse grouting mode are realized, and the pore blockage is broken by a pressure pulse of 0.5 MPa, so that the slurry is uniformly dispersed.

[0010] Further, in step S400, a double-channel well washing system is adopted, the main channel injects clean water through a high-pressure water pump, the pressure is maintained at 3.0-4.0 MPa, and the dynamic balance of 1:1.2 is maintained between the pumping rate and the injection rate; the laser particle size instrument is connected in the later stage of well washing to monitor the particle diameter in water, and the well washing is stopped when more than 90% of the particles are less than 5 μm.

[0011] Further, in step S600, the detachable stainless steel well table is fixed to the water-impermeable treated ground by anchor bolts, and the contact gap between the well table and the water-impermeable treated ground is sealed with water-impermeable material.

[0012] Further, the length of the complete bedrock section below the casing is not less than 6 m, and the length of the complete bedrock section is not less than 3 m when the bedrock condition is poor; the whole hole coring rate is not less than 70%, the complete bedrock section coring rate is not less than 90%, the rock core of the complete bedrock section is preserved in a core box, and is numbered and photographed according to the coring sequence.

[0013] The present application has the following beneficial effects: 1. The observation accuracy is improved: by strictly controlling the drilling inclination (≤1°), the variable diameter concentricity and the concentric installation of the casing, the instrument probe is ensured to be in a stable working environment, and mechanical interference is reduced; 2. The anti-interference ability is enhanced: the pressure grouting and the casing sealing design realize the complete sealing of the well hole, avoid the interference of surface water, underground water and stratum vibration, and improve the data stability and the accuracy of observing the overall stress action of the stratum; 3. The reliability is improved: the high coring rate (complete bedrock section ≥90%) and the bedrock length control provide reliable geological basis for the observation horizon selection, and guarantee the effectiveness of long-term observation; 4. The safety is guaranteed: the casing cover, the well table with a lock and the threading pipe design effectively prevent foreign matter from falling into the well hole and human interference, improve the observation data quality and prolong the service life of the well hole; 5. Wide applicability: suitable for various types of complete bedrock sites, especially for deep adjustment schemes in complex terrains such as hillside, improving the flexibility of technical methods. BRIEF DESCRIPTION OF DRAWINGS

[0014] Fig. 1 is a schematic diagram of a well hole of the present application.

[0015] Fig. 2 is a schematic diagram of a lockable well cover of the present application.

[0016] Fig. 3 is a schematic diagram of a casing connection of the present application.

[0017] Wherein, 1 - lockable well cover; 2 - casing cover; 3 - well platform; 4 - impermeable treated ground; 5 - threading pipe; 6 - cement slurry; 7 - casing; 8 - variable diameter section; 9 - complete bedrock section; 10 - gasket ring; 11 - waterproof paint. DETAILED DESCRIPTION

[0018] To achieve the above-mentioned purposes and effects, the technical means and structure adopted by the present application are described in detail in combination with the preferred embodiments of the present application, features and functions.

[0019] As shown in the drawings, Figs. 1-3 The present application provides a seismic borehole strain observation hole forming method, which comprises the following steps: S100, drilling preparation stage: the area around the well hole is flattened; S200, hierarchical hole forming construction: a core drilling with a diameter not less than 160 mm is used to open a hole, and coring is started when drilling into the bedrock section and the core depth is marked in real time; after drilling not less than 1 m in the complete bedrock section 9, a conical drill is used for "bell mouth" variable diameter treatment to ensure the concentricity of the hole before and after variable diameter, and the hole diameter after variable diameter is 130 mm; a diamond drill with a diameter of 130 mm is used to drill at a constant speed and slowly for not less than 6 m in the complete bedrock section 9; the total depth of the well hole is controlled to be not less than 30 m, and the height difference is adjusted according to the special terrain such as hillside to ensure that the depth from the foot of the mountain to the bottom of the well is not less than 30 m; the inclination of the newly built well hole is not greater than 1°, and the rebuilt well hole maintains the same inclination as the original; S300, casing 7 installation and sealing treatment: install the casing 7 after variable diameter treatment or install the casing 7 after final hole, install the geological seamless casing 7 from the ground to the variable diameter section, the inner diameter of the casing 7 is not less than 136 mm, the overall top end is higher than the ground by not less than 30 cm and lower than the height of the well platform 3, a 3 cm x 8 cm notch is reserved at the top end of the casing 7 and a casing cover 2 is configured; the casing 7 adopts standard thread connection, the connection is sealed, and the casing 7 is installed centrally to ensure concentricity with the lower well hole; the cement slurry 6 is used to pressure grout between the outer wall of the casing 7 and the hole wall to consolidate the casing 7 and the formation, and after the cement is consolidated, the residual cement debris on the inner wall of the casing 7 and the bottom of the well hole is removed; S400, washing well: flushing the borehole with clean water until the rock debris, dust, cement slurry, etc. in the wellbore, well wall, casing 7 inner wall, etc. are washed clean, ensuring that the well wall, well bottom is smooth and clean, and all kinds of cleaning fluid is strictly prohibited.

[0020] S500, quality detection: fill the well with water for well leakage test, requiring water level to drop no more than 3 cm per hour; through downhole television inspection, confirm that the inner wall of the whole hole is smooth, the well wall below the casing is complete, and there is no debris and water accumulation at the well bottom; test the wellbore inclination, wellbore diameter of each section, lithology and rock integrity, and write large-scale columnar graph and construction log; S600, wellbore ground treatment: taking the casing 7 as the center, the area not less than 4m x 4m is cemented to form a water-impermeable treatment ground 4 with a thickness not less than 5 cm, ensuring that the ground is free of water, and the unattended site can be covered with original soil after hardening; the distance between the borehole and the recording room is controlled to be no more than 20 m, and the cable is connected to the recording room through the threading pipe 5 embedded under the water-impermeable treatment ground 4, and a threading steel wire is reserved in the threading pipe 5; the wellhead is built with a cement or stainless steel well platform 3 not less than 50 cm high, and a lockable well cover 1 is provided, on which the drilling and instrument information are marked.

[0021] In step S200, when the drilling process encounters formations such as rock broken section, fissure section, water gushing and leaking section, etc. affecting the wellhead airtightness, the depth is recorded, and after the casing 7 is installed, the well wall airtightness treatment is carried out.

[0022] In step S300, when the casing 7 is installed after the diameter change treatment, the geological seamless steel casing 7 is installed in the center after the diameter change treatment is completed, and after the cement of the grouting treatment is consolidated, a diamond drill with a diameter of 130 mm is used to drill at a uniform speed and slowly for not less than 6 m of complete bedrock section 9, and the drilling depth is determined by factors such as bedrock thickness, standby horizon demand, etc., and it is ensured that the well wall below the casing 7 is complete and smooth.

[0023] In step S300, when the casing 7 is installed after the final hole, the geological seamless steel casing 7 is installed in the center after the final hole, and after the cement of the grouting treatment is consolidated, the diamond drill with a diameter of 130 mm is used to drill at a uniform speed and slowly, and the cement falling off from the inner wall of the casing 7, the well wall of the bedrock section and the bottom of the wellbore due to the grouting treatment is removed.

[0024] In step S300, a rubber gasket ring 10 is provided at the connection between the casing 7 and the casing 7, the end of the casing 7 is provided with a chamfer, and the outside of the connection between the casing 7 and the casing 7 is recessed into a V-shaped notch formed by the chamfer, after the casing 7 and the casing 7 are screwed in place, the edge of the gasket ring 10 is ablated and deformed, and is pressed tightly in the notch, ensuring the edge airtightness, and then waterproof paint 11 is sprayed in the notch, further improving the waterproof effect.

[0025] In step S300, the cement grout 6 uses a nano-grade calcium carbonate modified formula, in which the mass ratio of cement, water, and nano-calcium carbonate is 1:0.4:0.05. The addition of nano-calcium carbonate can fill the micro-pores between cement particles, increasing the compressive strength of the consolidated body by 20-30% and reducing the permeability coefficient by 1-2 orders of magnitude. The grouting pressure is adjusted according to the hardness of the stratum, controlled at 1.2-1.5 MPa for soft soil layers and increased to 2.0-2.5 MPa for bedrock layers. During the grouting process, the grouting rate is monitored in real time by a flow sensor. When the rate drops by more than 30%, it is automatically paused and switched to pulse grouting mode. The 0.5 MPa pressure pulse breaks the pore blockage and ensures uniform diffusion of the grout.

[0026] In step S400, a dual-channel well-washing system is employed. The main channel injects clean water via a high-pressure pump, maintaining the pressure at 3.0-4.0 MPa to form a high-speed jet that peels away debris adhering to the borehole wall. The auxiliary channel simultaneously extracts turbid liquid, maintaining a dynamic balance between the pumping rate and the injection rate at a ratio of 1:1.2 to prevent excessive pressure within the borehole from causing well wall collapse. Later in the well-washing process, a laser particle size analyzer is connected to monitor the diameter of particles in the water. Well-washing is stopped when more than 90% of the particles are smaller than 5 μm. Compared to traditional visual judgment methods, the accuracy of well-washing cleanliness control is improved by 40%, effectively reducing interference factors in subsequent observations.

[0027] The detachable stainless steel well platform 3 is fixed to the impermeable ground 4 with anchor bolts, and the contact gap between the well platform 3 and the impermeable ground 4 is sealed with impermeable material.

[0028] The length of the intact bedrock section 9 below the control casing 7 shall not be less than 6m, and not less than 3m when the bedrock conditions are poor; the core recovery rate of the whole hole shall not be less than 70%, and the core recovery rate of the intact bedrock section shall not be less than 90%. The core of the intact bedrock section shall be stored in a core box, numbered according to the core recovery sequence, and photographed and recorded.

[0029] The above description is only a preferred embodiment of the present invention and not all embodiments. Anyone should know that structural changes made under the guidance of the present invention, and any technical solutions that are the same as or similar to the present invention, are within the protection scope of the present invention.

Claims

1. A method of hole formation for a seismic borehole strain observation, characterized by, The method comprises the following steps: S100, drilling preparation stage: the area around the well hole is flattened; S200, hierarchical hole forming construction: a core drilling with a diameter not less than 160 mm is used to drill a hole, and coring is started when drilling into the bedrock section and the core depth is marked in real time; after drilling not less than 1 m in the complete bedrock section, a tapered drill is used for "horn mouth" diameter change processing to ensure the concentricity of the hole before and after the diameter change, the diameter after the diameter change is 130 mm, and a diamond drill with a diameter of 130 mm is used to drill at a constant speed and slowly for not less than 6 m of the complete bedrock section; the total drilling depth is controlled to be not less than 30 m; the inclination of the newly built well hole is not greater than 1°, and the inclination of the rebuilt well hole is kept consistent with the original inclination; S300, casing installation and sealing treatment: install the casing after the diameter change processing or install the casing after the final hole, install the geological seamless casing from the ground to the diameter change position, the inner diameter of the casing is not less than 136 mm, the top end is higher than the ground by not less than 30 cm and lower than the well platform height, a 3 cm x 8 cm opening is reserved at the top end of the casing and a casing cover is arranged; the casing uses standard thread connection, the connection is sealed, and the casing is installed centrally to ensure concentricity with the lower well hole; cement slurry pressure grouting is used between the outer wall of the casing and the hole wall to consolidate the casing and the formation, and after the cement is consolidated, the residual cement debris on the inner wall of the casing and the bottom of the well hole is removed; S400, well washing: the drilling hole is washed with clean water until the rock debris, dust and cement slurry in the well hole are washed clean to ensure that the well wall and the well bottom are smooth and clean; S500, quality detection: fill the well hole with water to test the water leakage, and the water level is required to drop not more than 3 cm per hour; through the downhole television inspection, it is confirmed that the inner wall of the whole hole is smooth, the well wall below the casing is complete, and there is no debris and water accumulation at the well bottom; the well hole inclination, well diameter of each section, lithology and rock integrity are tested, and large-scale columnar graph and construction log are prepared; S600, well hole ground treatment: taking the casing as the center, a not less than 4 m x 4 m area is treated with cement hardening to form a water impermeable treatment ground with a thickness not less than 5 cm to ensure that the ground is free of water, and the unattended site can be covered with original soil after hardening; the drilling distance from the recording room is controlled to be not more than 20 m, and the cable is connected to the recording room through the threading pipe embedded under the water impermeable treatment ground, and a threading steel wire is reserved in the threading pipe; a cement or stainless steel well platform with a height not less than 50 cm is built at the well mouth, a lockable well cover is arranged, and the drilling and instrument information is marked on the lockable well cover.

2. The method of claim 1, wherein, In step S200, when a formation affecting the well mouth sealing property is encountered during drilling, the depth is recorded, and after the casing is installed, the well wall sealing property treatment is performed.

3. A method of hole making for seismic borehole strain observation according to claim 1 or 2, characterized in that, In step S300, when the casing is installed after the diameter change processing, the geological seamless steel casing is installed centrally after the diameter change processing, and after the cement consolidation of the grouting treatment, a diamond drill with a diameter of 130 mm is used to drill at a constant speed and slowly for not less than 6 m of the complete bedrock section, the drilling depth is determined by the bedrock thickness and the standby layer requirement, and it is ensured that the well wall below the casing is complete and smooth.

4. The method of claim 1 or 2, wherein, In step S300, after the final hole is drilled, the geological seamless steel casing is installed in the middle, and after the cement consolidation of the grouting treatment, the drilling is continued at a uniform speed and slow speed with a diamond bit with a diameter of 130 mm to remove the cement that falls on the inner wall of the casing, the well wall of the bedrock section, and the bottom of the well hole due to the grouting treatment.

5. The method of claim 1, wherein, In step S300, a sealing gasket ring is arranged at the connection between the casings, the end of the casing is chamfered, the outside of the connection between the casings is recessed into a notch formed by the chamfer, and after the casing is screwed into place, the edge of the sealing gasket ring is ablated and deformed, and is pressed tightly in the notch, and then waterproof paint is sprayed in the notch.

6. The method of claim 1, wherein, The cement slurry in step S300 uses a modified formula of nanoscale calcium carbonate, in which the mass ratio of cement, water, and nanoscale calcium carbonate is 1:0.4:0.05, the grouting pressure is adjusted according to the hardness of the stratum, the soft soil layer is controlled at 1.2-1.5 MPa, and the bedrock layer is increased to 2.0-2.5 MPa. During the grouting process, the grouting rate is monitored in real time by a flow sensor, and when the rate drops by more than 30%, the pulse grouting mode is automatically paused and switched to the pulse grouting mode, and the pore blockage is broken by a pressure pulse of 0.5 MPa to ensure uniform diffusion of the slurry.

7. The method of claim 1, wherein, In step S400, a double-channel well washing system is used, the main channel injects clean water through a high-pressure water pump, the pressure is maintained at 3.0-4.0 MPa, and the extraction rate and injection rate are kept in dynamic balance at 1:1.2; a laser particle size instrument is connected during the later stage of well washing to monitor the diameter of particles in water, and when more than 90% of the particles are less than 5 μm, well washing is stopped.

8. The method of claim 1, wherein, In step S600, the detachable stainless steel well platform is fixed to the water-impermeable ground with anchor bolts, and the contact gap between the well platform and the water-impermeable ground is sealed with water-impermeable material.

9. The method of claim 1, wherein, The length of the complete bedrock section below the casing is not less than 6 m, and when the bedrock conditions are poor, it is not less than 3 m; the core recovery rate of the whole hole is not less than 70%, and the core recovery rate of the complete bedrock section is not less than 90%; the rock core of the complete bedrock section is stored in a core box, numbered according to the core sequence, and photographed and recorded.

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