Water exploring and grouting method for lower bedrock section in shaft construction

Abstract

The invention discloses a water exploring and grouting method for a lower bedrock section in shaft construction. The water exploring and grouting method comprises the following steps that S1, a project summary and geological and hydrological conditions are obtained; s2, determining the necessity of advanced water detection and grouting; s3, working face advanced water detection, wherein according to the advanced water detection grouting depth of the water detection section, water detection holes are formed, and segmented advanced water detection is conducted; s4, grouting design and grouting construction are conducted, specifically, in the segmented grouting process, the grouting range is determined through grouting pad design, grouting hole arrangement, grouting pressure determination and grout preparation, and segmented grouting is conducted according to the segmented mode in the S3; and S5, grouting construction is conducted. The method can effectively detect and block rock stratum crack water, reduce water consumption and effectively guarantee safe and smooth operation of shaft digging and building construction.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of mine construction, and particularly relates to a method for water exploration and grouting in a lower bedrock section of a shaft construction. BACKGROUND

[0002] In the process of shaft construction, the upper soil section of the shaft excavation construction is often constructed using the freezing method to form a closed freezing curtain, which can effectively isolate the connection between groundwater and the shaft construction area, and can effectively avoid the occurrence of water inrush accidents at the working face and ensure normal shaft excavation construction. However, for shaft excavation construction in the lower complex bedrock section of the freezing section, the position of the aquifer and the hydrological characteristics need to be predicted based on the geological exploration data formed by the "drilling method", and the hydrological parameters obtained by drilling are used to determine whether further grouting is needed to avoid water inrush and water inrush accidents. The existing geological exploration data mainly has the following problems when dealing with complex bedrock sections and water exploration and grouting: (1) Traditional geological exploration mainly relies on a small amount of point drilling data, which is difficult to fully depict the three-dimensional spatial distribution of hidden aquifers in complex bedrock sections, especially in thick sandstone and non-uniformly developed fractured strata, which is prone to misjudgment or misjudgment of aquifers. (2) Conventional drilling can only obtain local hydrological parameters, and cannot systematically evaluate the spatial distribution, fracture connectivity and hydraulic characteristics of the aquifer, resulting in a lack of reliable basis for subsequent grouting design. In addition, the existing water exploration method mainly uses dense point drilling, which has a long construction period and high cost, and is difficult to match the progress requirements of shaft rapid excavation. (3) The existing water exploration and grouting operations are often independent of each other, lack real-time linkage and dynamic control mechanisms, and the adjustment of key parameters such as grouting range, pressure and slurry ratio is lagging behind, which can cause incomplete grouting or waste of materials. SUMMARY

[0003] The purpose of the present application is to provide a method for water exploration and grouting in the lower bedrock section of a shaft construction, which can effectively explore and block fissure water in the rock layer, reduce water consumption, and effectively ensure the safety and smooth progress of shaft excavation construction.

[0004] To achieve the above-mentioned purpose, the present application provides a method for water exploration and grouting in the lower bedrock section of a shaft construction, comprising the following steps: S1, obtaining the engineering summary and geological and hydrological conditions; S2, determining the necessity of advanced water exploration and grouting; S3, advanced water exploration at the working face: according to the advanced water exploration and grouting depth of the water exploration section, the water exploration holes are arranged and the advanced water exploration is carried out in sections; S4, grouting design: integrated design of water exploration and grouting, determination of grouting range and design of grouting pad, grouting hole arrangement, grouting pressure and slurry preparation amount, and sectional grouting according to the sectional method of S3; S5, grouting construction: according to real-time hydrological monitoring data dynamic adjustment grouting slurry concentration and grouting pressure, realize fine construction management.

[0005] As a further scheme of the present application: the water exploration hole in S3 is uniformly arranged in different directions in the wellbore, and after drilling by the drilling machine, the seamless steel pipe is pre-buried, the pipe is fixed, and the high-pressure valve is installed, then the hole is scanned and pressure tested.

[0006] As a further scheme of the present application: the number of grouting holes in S4 is calculated according to the following formula: ; In the formula, D is the net diameter of the wellbore; A is the distance between the grouting hole and the well wall; L is the grouting hole spacing; The radial inclination angle of the grouting hole is calculated according to the following formula: ; ; In the formula: is the angle between the grouting hole in the radial direction and the vertical axis; S is the distance of the final hole position exceeding the net diameter in the radial direction; E is the permanent well wall thickness; m is the distance of the final hole position exceeding the net diameter in the radial direction; A is the distance between the grouting hole and the well wall; H is the grouting section height.

[0007] As a further scheme of the present application: the slurry configuration calculation formula in S4 is as follows: ; In the formula: N is the number of grouting holes; a is the slurry consumption coefficient; H is the grouting section height; R is the effective diffusion radius of the slurry; β is the liquid filling coefficient; M is the stone rate; η is the fissure rate.

[0008] As a further scheme of the present application: in S5 grouting construction: Each grouting hole is grouted one by one; Before the current grouting hole grouting, water pressure test is carried out and the grouting hole water absorption is calculated: ; In the formula, q is the unit grouting hole water absorption, ; Q is the flow at the maximum water pressure, ; H is the grouting section height, m; During the grouting process of the current grouting hole, the grouting amount is adjusted in real time according to the grouting pressure, and 80% of the clear water in the grouting pipe and the grouting hole volume is injected before the grouting of the current grouting hole is completed; After the grouting of the current grouting hole is completed, the hole is swept and a water pressure test is carried out at the grouting section. When the water inflow of a single hole is less than 1.0 m³ / h, grouting is stopped and the grouting of the next hole is carried out. After grouting of all grouting holes was completed, the holes were cleaned and a water pressure test was conducted. The water inflow of each hole was less than 1.0 m³ / h, and the grouting was completed.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: By combining geological exploration data, the location and hydrological characteristics of aquifers can be predicted. Then, by drilling to obtain hydrological parameters, it can be determined whether further grouting is needed to avoid water inrush and gushing accidents. Advance water exploration and grouting at the working face can be carried out as needed, which can effectively identify and seal water in rock fissures, reduce water consumption, and effectively ensure the safety and smooth progress of well excavation and lining construction.

[0010] A closed-loop mechanism of "segmented water exploration, segmented grouting, and dynamic control within each segment" was established to achieve precise control of the treatment process: the bedrock section was divided into several sub-segments for sequential operation, and the grouting slurry concentration and grouting pressure were dynamically adjusted for each segment based on real-time hydrological monitoring data; at the same time, the integrated design of water exploration and grouting (using water exploration holes directly as grouting holes) reduced repeated drilling and improved construction efficiency. Attached Figure Description

[0011] Figure 1 A schematic diagram of the wellbore grouting hole arrangement in an embodiment of the present invention is shown; In the diagram, holes #2, #4, #6, and #8 are the original water exploration holes; holes #1, #3, #5, and #7 are grouting holes added according to the design. Detailed Implementation

[0012] The invention will now be further described with reference to the accompanying drawings.

[0013] A method for water exploration grouting in the lower bedrock section of a well shaft construction includes the following steps: S1. Obtain an overview of the project and information on its geology and hydrology.

[0014] S2. Clearly define the necessity of advanced water exploration and grouting.

[0015] S3. Advance water exploration at the working face: Based on the depth of the advance water exploration grouting in the exploration section, water exploration holes are set up and segmented advance water exploration is carried out.

[0016] Furthermore, several water exploration holes are evenly distributed in different directions inside the well. After drilling with a drilling rig, seamless steel pipes are pre-embedded, the pipes are fixed, and high-pressure valves are installed. Then, the holes are cleaned and pressure tested.

[0017] S4. Grouting Design: Integrated design of water exploration and grouting (using water exploration holes directly as grouting holes), determining the grouting range and designing grout stop pads, grouting hole layout, grouting pressure and grout preparation volume, and performing segmented grouting according to the segmented method of S3.

[0018] Specifically, the formula for calculating the number of grouting holes during the grouting hole arrangement is as follows: ; In the formula, D is the net diameter of the wellbore; A is the distance between the grouting hole and the well wall; L is the spacing between the grouting holes; The formula for calculating the radial inclination angle of the grouting hole is as follows: ; ; In the formula: The angle between the grouting hole and the vertical axis in the radial direction is denoted as ; S is the distance in the radial direction from the final hole position to the net diameter; E is the permanent well wall thickness; m is the distance in the radial direction from the final hole position to the rough diameter; A is the distance between the grouting hole and the well wall. H The height is for the grouting section.

[0019] The formula for calculating slurry preparation is as follows: ; In the formula: N is the number of grouting holes; a is the grout consumption coefficient; H is the height of the grouting section; R is the effective diffusion radius of the grout; β M is the liquid filling coefficient; M is the stone rate; η This represents the porosity.

[0020] S5. Grouting construction: The grouting slurry mix ratio and grouting pressure are dynamically adjusted based on real-time hydrological monitoring data to achieve refined construction management.

[0021] Furthermore, during the S5 grouting construction: Grout each grouting hole one by one; Before grouting, a water pressure test is conducted at the grouting hole, and the water absorption of the grouting hole is calculated: ; In the formula, q This refers to the water absorption per unit grouting hole. ; Q This is the flow rate at the maximum pressure of the pressurized water. ; H The height of the grouting section is in meters (m). During the grouting process of the current grouting hole, the grouting volume is adjusted in real time according to the grouting pressure. Before the grouting of the current grouting hole is completed, 80% of the volume of clean water in the grout delivery pipeline and the grouting hole is injected. After the grouting of the current grouting hole is completed, the hole is swept and a water pressure test is carried out at the grouting section. When the water inflow of a single hole is less than 1.0 m³ / h, grouting is stopped and the grouting of the next hole is carried out. After grouting of all grouting holes was completed, the holes were cleaned and a water pressure test was conducted. The water inflow of each hole was less than 1.0 m³ / h, and the grouting was completed.

[0022] The following is an example: S1. Project Overview and Geological and Hydrological Overview: The upper section of a coal mine shaft was constructed using the freezing method, while the lower bedrock section was constructed using the conventional method. The shaft has a net diameter of 5.0m, a freezing depth of 428m, and a lining depth of 416m in the frozen section (including a 10m wall support section); the lining depth in the conventional bedrock section is 272m. Currently, the lining construction of the main shaft in the frozen section has been completed. To ensure the safety of the next phase of construction through the aquifer in the bedrock section, water exploration needs to be conducted at the working face in the -416 to -516m section (conventional bedrock section), and grouting will be used at the working face to ensure normal shaft lining construction.

[0023] All wellbore inspection boreholes are located in the northern part of the coal mine, north of the Wanfu River, between Xinzhanglou Village and Qiujing Village. The water exploration section is located in the Permian Shihezi Formation, whose main rock strata are mudstone, sandy mudstone, fine sandstone, and siltstone. The mudstone is prone to cracking when exposed to wind and water, while the sandstone has relatively good lithology. For details, please refer to Table 1.

[0024] Table 1. Summary of stratigraphic properties of the Permian Shihezi Formation through wind inspection wells

[0025] The main surface rivers in the coal mining area are the Xin and Lao Wanfu Rivers and their tributaries, the Dasha River and the Jinji River. These rivers have the highest flow during the rainy season and lower flow during the dry season, drying up during droughts. Surface water has no impact on mine operations.

[0026] According to the geological report, the expected water inflow of the Kuishan sandstone aquifer in the Shihezi Formation (-349.68 to -409.90 m) is 78 m³ / h, and the expected water inflow of the sandstone aquifer at the bottom of Shihezi and the sandstone aquifer at the top of the No. 3 coal seam in the Shanxi Formation (-591.50 to -662.40 m) is 4.15 m³ / h. The water exploration location is between the two aquifers and there are four sandstone layers, namely fine sandstone and siltstone, with a cumulative thickness of 36.02 m and a maximum thickness of 23.62 m. There is mudstone above and below the sandstone layer, which has good water-blocking properties and good permeability. Although the geological survey report shows that there is no water at this water exploration location, the sandstone thickness is relatively large, and it is preliminarily predicted that there is a suspected aquifer in this section. The expected aquifer situation is shown in Table 2.

[0027] Table 2. Expected Aquifer Results for the Water Exploration Section of the Main Wellbore

[0028] Mudstone and sandy mudstone have poor water conductivity but good water-tightening properties, and can form a very good water-tight layer. The expected water-tight layer is shown in Table 3.

[0029] Table 3 Expected Results of Aquitard in the Water Exploration Section of the Main Wellbore

[0030] S2. Clarify the necessity of advance water exploration and grouting: The geological survey report indicates that there is no water in the exploration section (-416 to -516m), but the presence of a thick sandstone layer suggests the possibility of an aquifer. Therefore, the necessity of conducting advance water exploration in this section is analyzed below: (1) Limitations of geological exploration reports: Conventional geological exploration relies on a limited number of boreholes, which provide only a "hole view" of that point (a cylinder). If the aquifer is discontinuous in the lateral (plane) direction, or if the aquifer channel (such as a fissure or cave) happens to avoid the borehole location, the geological exploration report may not be able to capture it.

[0031] (2) Water-bearing potential due to the thickness of sandstone: Thick sandstone layers are usually good porosity-fracture aquifers. Even if the rock itself appears intact, it may contain a large number of microfractures, bedding, and joints, which can store and conduct water. During the deposition process, the composition, cementation degree, and fracture development degree of thick sandstone layers may change both vertically and horizontally. Geological exploration boreholes may only pass through well-cemented, fracture-free sections, while adjacent areas may contain water-rich sections with well-developed fractures. This exploration section contains a 23.62m thick siltstone layer and a continuous 6.1m thick siltstone and 4m thick fine sandstone layer, all of which may be aquifers.

[0032] S3. Advance water exploration at the working face: The water exploration depth for this section is 100m, with a borehole drilled 500mm from the well wall. First, water exploration is conducted on the upper 50m section. Based on the actual water output, grouting is performed on this upper 50m section until the grouting is completed. Then, water exploration is conducted on the lower 50m section, and grouting is performed again based on the actual water output until the entire section reaches the grouting completion standard. Afterward, well casing excavation and lining construction resumes.

[0033] Four boreholes were designed as water exploration holes, evenly distributed in four directions within the wellbore. The four exploration holes were constructed first. Two ZDY-1900S drilling rigs were used to drill Φ133mm boreholes, followed by the installation of Φ108×6mm seamless steel pipes, securing the pipes, and installing high-pressure valves. After the boreholes were cleaned and pressure tested to meet design requirements, normal drilling for water exploration could begin. Water exploration was then continued by drilling boreholes from inside the pipe at the borehole opening using φ75mm drill bits.

[0034] When water exploration was carried out on the upper 50m and lower 50m sections respectively, the water flow of no single hole in the four exploration holes exceeded 5m³ / h, but the total water flow of the exploration hole shafts all exceeded 10m³ / h. Therefore, it is necessary to start pre-grouting of the working face to seal the water in this section of the stratum to ensure the normal excavation and masonry construction of the subsequent working face. After the grouting was started, the four exploration holes also served as grouting holes.

[0035] S4. Grouting Design: Water exploration grouting involves drilling ahead of the wellhead to explore for water and then injecting grout to seal fissures in the rock strata. In this case, the grouting depth was 100m, with the borehole drilled 500mm from the well wall. The grouting was performed in two stages, a downward-pressurized approach, to control the grouting area after exploration. The first stage of the staged grouting covered -416m to -466m, and the second stage covered -466m to -516m. Grouting was first performed on the upper 50m stage, and after reaching the completion standard, the lower 50m stage was then grouted until the entire stage reached the completion standard, at which point wellhead excavation and lining work resumed. During the staged grouting process, the grouting parameters (such as grouting pressure and grout volume) could be dynamically adjusted to optimize the grouting effect. The grouting range was determined by designing the grout stop thickness, the pre-grouting hole layout, the grouting pressure, and the grout type to ensure the effectiveness of the water exploration grouting.

[0036] S4.1, Grout stop gasket design: The main shaft is frozen at a depth of 428m. The water exploration and grouting in this working face started at -416m. Because the reserved rock cap thickness could not meet the specifications, concrete grout stop pads were used for the first section of the exploration and grouting to resist the grouting pressure. The grout stop pads can also be used to control the grouting range and prevent grout from flowing across the surface.

[0037] This water exploration grouting project used a single-stage flat-bottomed concrete grout stop pad. The concrete design grade was C40, prepared with P.O42.5R ordinary Portland cement, plus 13% water-reducing agent by weight of cement. The type of water-reducing agent was selected based on the concrete mix proportions. According to the formula for a flat-bottomed grout stop pad: ; ; In the formula: P0 is the final grouting pressure of 16.2 MPa; r is the wellbore excavation radius of 3.2 m; This refers to the allowable compressive strength of concrete. The first segment represents the strength at the same age, taken as 44.2 MPa; K is the safety factor, taken as 2.0. The effective thickness of the grout stop is calculated to be 2.72 m using the formula.

[0038] S4.2 Grouting Hole Design: Based on relevant hydrogeological conditions, well characteristics, and construction experience from similar projects, the number of grouting holes and the radial inclination angle of the boreholes for this water exploration grouting were calculated. The number of grouting holes was calculated using the following formula: ;

[0039] In the formula: D is the net diameter of the wellbore, taken as 5.0m; A is the distance between the grouting hole and the well wall, taken as 0.5m; L is the spacing between grouting holes, taken as 1.6m. According to the formula, N=7.85, taking 8 holes, then numbering the boreholes clockwise, with the boreholes evenly arranged around the perimeter of the wellbore cross-section. The original water exploration holes also serve as grouting holes (2#, 4#, 6#, 8#), as shown... Figure 1 As shown.

[0040] The radial inclination angle of the water exploration grouting borehole is calculated using the following formula: ; ;

[0041] In the formula: S is the radial angle between the borehole and the vertical axis; S is the radial distance beyond the net diameter of the final borehole position; E is the permanent well wall thickness, taken as 0.45m; m is the radial distance beyond the rough diameter of the final borehole position, taken as 5.0m; A is the distance between the grouting hole and the well wall, which is 0.5m. H For the grouting section height, According to the formula, we can calculate: In practice, the drilling inclination angle is generally determined according to the actual situation. They came to drill holes for construction.

[0042] S4.3 Determine the grouting pressure: Grouting pressure drives the grout to flow, diffuse, fill, and compact within the fissures, and is one of the key factors controlling the grouting distance. According to the "Code for Construction of Coal Mine Shafts and Roadways," the final grouting pressure should be greater than or equal to 2 to 4 times the hydrostatic pressure. In this water exploration grouting, the grouting pressure was controlled in stages. Initially, it was controlled at 2 times the hydrostatic pressure, and later at 3 times the hydrostatic pressure. Simultaneously, the grouting pressure was adjusted reasonably based on the grouting effect. Dynamic adjustment of the grouting pressure can optimize the grouting effect.

[0043] S4.4 Preparation of slurry: This grouting primarily uses single-component cement grout, specifically P.O42.5 ordinary Portland cement, with 0.5% salt and 0.05% triethanolamine added by weight of the cement as admixtures to accelerate setting and early strength. The expected injection volume of the grout is calculated using the following formula: ;

[0044] In the formula: N is the number of grouting holes, taken as 8; a is the grout consumption coefficient, taken as 1.5; H is the height of the grouting section, H=100m; R is the effective diffusion radius of the grout, taken as 4m; β The liquid filling coefficient is taken as 0.9; M is the stone rate, taken as 0.85. η The fracture ratio is taken as 3% on average. The cement grout volume Q can be calculated using the formula as approximately 1916 m³. 3 .

[0045] Five cement grout concentrations are available: 2:1, 1.5:1, 1.25:1, 1:1, and 0.75:1. The appropriate concentration is selected based on the grout diffusion. The grouting effect can be optimized by dynamically adjusting the grouting volume.

[0046] S5. Grouting construction: To ensure grouting safety, a C40 concrete grout-stopping pad (2.72m) is constructed before the inner wall of the casing. After the casing is completed, water exploration is conducted in sections from -416m to -516m. Two grouting stations are required for water exploration grouting. One station is located on the ground, where a ground-based grouting pump and a high-pressure hose suspended from the well wall pump the mixed cement slurry into the aquifer fissures of the grouting hole to seal the fissure water. The other station is located on the working platform at the working face, used for grouting to reinforce the grout-stopping pad and the wellhead pipe. If, after joint water measurement at the exploration holes, the wellbore inflow exceeds 10m³ / h, pre-grouting at the working face should be implemented, utilizing the original exploration holes (2#, 4#, 6#, 8#) and the additional grouting holes (1#, 3#, 5#, 7#) added according to the design to complete the construction. Figure 1 As shown. The entire grouting process requires the installation of borehole pipes, the erection of a drilling platform, the construction of water exploration grouting holes, and finally, the grouting operation to seal the water guiding channels and reinforce the grouting holes.

[0047] S5.1, Installation of the borehole pipe: The length of the grout-stopping gasket orifice pipe in this section is 6.0m; the orifice pipe specification is Φ108×6mm seamless steel pipe, and a flange is welded to the upper part of the orifice for connection to the grouting valve. When the total water inflow of the water exploration verification hole exceeds 10m³ / h and pre-grouting of the working face is required, the orifice pipes of the remaining 4 grouting holes are installed. The drilling rig is fixed on the large template of the bedrock section according to the designed orientation, hole diameter, and inclination angle. Drilling is carried out with a Φ133mm impact drill bit to a drilling depth of 6.5m. The rock powder in the hole is blown out with compressed air, and the hole is filled with cement mortar. Then, the orifice pipes with a length of 6.0m are lowered in. One day later, the cement mortar in the orifice pipe is swept out with the drilling rig, and a double hydrostatic pressure test is carried out. The orifice pipe is reinforced with double-liquid grout until its pressure remains unchanged within the specified time to be considered qualified.

[0048] S5.2 Erecting the drilling rig platform: Before erecting the drilling platform, four brackets are installed on the wall base to secure the platform. Steel pipe supports are used to anchor the platform, ensuring a minimum height of 2 meters above the platform. The working platform is constructed from 16# channel steel and 4mm thick checkered steel plate. The platform is fixed to the brackets on the wall base and secured with safety ropes. One or two additional support columns are added to the middle of the main beam. The drilling rig is fixed to the platform using U-shaped clamps. Before fixing, technicians lay out the lines according to the drilling layout plan, avoiding the bucket lifting area as much as possible. After installation, the position, angle, and elevation of the drilling rig are checked to ensure they meet design requirements.

[0049] S5.3 Construction water exploration grouting holes: Grouting drilling uses one ZDY-1900s hydraulic drilling rig, equipped with a Ф63.5mm drill rod and a Ф75mm three-core drill bit, with clean water as the circulating fluid. Before drilling, a Ф100mm high-pressure ball valve must be installed on the Ф108mm borehole pipe to prevent well flooding caused by sudden water inrush from the aquifer during drilling.

[0050] After grouting is initiated, grouting will be carried out alternately in two groups. Holes #2 and #6 will be in the first group and will be constructed first. The second group will consist of holes #4 and #8, the third group will consist of holes #1 and #5, and the fourth group will consist of holes #3 and #7. If the water volume is large during construction, the number of grouting holes will be increased as appropriate based on the grouting effect.

[0051] Drilling is carried out on a drilling platform. During drilling, if the hole collapses due to rock breakage and cannot be drilled further, drilling is stopped and grouting is performed; otherwise, drilling continues until the designed depth is reached. At the end of the drilling, the drill string length must be verified to ensure that the drilling depth meets the design requirements.

[0052] S5.4 Drilling and Grouting: For each borehole grouting, a concentrated grout is used initially, with the concentration gradually decreasing during subsequent grouting. However, each grouting session generally starts with a thinner grout and progresses to a thicker one. If, during the fracture sedimentation and filling stages, the pressure does not increase and the grout volume does not decrease, the concentration should be gradually increased. Conversely, if the pressure rises rapidly and the volume decreases rapidly, the grout concentration should be gradually reduced to ensure a sufficient injection volume.

[0053] Each time the slurry concentration is changed, the duration should generally not be less than 20 minutes.

[0054] After being mixed by the mixing system, the grout enters the rock stratum to be injected via the grouting pump, grout delivery pipe, and grouting pipe. Once the grouting hole has been drilled to the predetermined depth, it is flushed with clean water (except for fractured zones) until clean water returns.

[0055] Before grouting, a water pressure test is conducted to flush the filling material in the rock fissures, improving the bond strength and impermeability between the grout-bound rock mass and the rock fissure surface. Based on the pump pressure and injection volume, the borehole water absorption is measured. The formula for calculating the water absorption is: ;

[0056] In the formula: q This refers to the water absorption per unit borehole. ; Q This is the flow rate at the maximum pressure of the pressurized water. H represents the height of the grouting section, in meters (m).

[0057] During the water pressure test, use the largest possible pump volume, and control the pressure value to the final pressure of the grouting section. The water pressure test typically lasts 20 minutes. Accurately measure and record the height, flow rate, and pressure of the water pressure test section. In fractured zones, shorten the water pressure test time or eliminate it altogether. Based on the water absorption per unit borehole measured in the water pressure test, determine the initial grout concentration during grouting, which will serve as one of the criteria for evaluating the grouting effect.

[0058] During the grouting process, the grouting pressure can be divided into three stages: initial, normal, and final pressure. Once the initial concentration is determined, the pump volume should be controlled in a timely manner according to the changes in grouting pressure, and the grout concentration and gel time should be adjusted to ensure that the grouting pressure increases gradually and avoids large fluctuations until the final grouting pressure and volume are reached and stabilized for more than 20 minutes.

[0059] When the drilling grouting reaches the completion standard, or when the crack is large and the completion standard has not been reached, but the grout has spread too far and the required injection volume for this grouting has been achieved, a certain amount of clean water should be injected before the grouting is terminated to flush the grout in the pipeline. The injection volume should be 80% of the volume of the grout delivery pipeline and the grouting hole. Then, close the ball valve at the borehole opening and disassemble the grout delivery pipeline for flushing.

[0060] After grouting is completed, the boreholes are swept at the grouting section, typically for 4-6 hours. Following sweeping, a water pressure test is conducted. If the water inflow from a single borehole is less than 1.0 m³ / h, grouting can cease, and grouting can proceed to the next borehole. Once all boreholes have been grouted, they are swept and a water pressure test is performed. If the water inflow from each borehole is less than 1.0 m³ / h, the grouting has successfully sealed the fissure water in the rock strata, ensuring normal excavation and lining construction of the subsequent working face.

[0061] Although the geological survey report for the -416 to -516m section of the main shaft of the coal mine indicated no water in this area, the complex geological conditions and thick sandstone suggested the presence of an aquifer, necessitating advanced water exploration. The results revealed that the total water inflow of the exploration boreholes in this section actually exceeded 10 m³ / h. Subsequent grouting operations reduced the water inflow of each borehole in this section to less than 1.0 m³ / h, effectively sealing the fissure water in the rock strata and ensuring the safe and normal excavation and lining of the shaft.

Claims

1. A method for water detection and grouting in the lower bedrock section of a wellbore construction, characterized by, Comprising the following steps: S1, obtaining engineering summary and geological and hydrological conditions; S2, determining the necessity of advanced water exploration and grouting; S3, advanced water exploration in working face: according to the advanced water exploration and grouting depth of water exploration section, water exploration holes are arranged and sectional advanced water exploration is carried out; S4, grouting design: integrated design of water exploration and grouting, determining the grouting range and designing grouting pad, grouting hole arrangement, grouting pressure and slurry preparation amount, sectional grouting according to the sectional mode of S3; S5, grouting construction, dynamically adjusting the slurry concentration and grouting pressure according to real-time hydrological monitoring data to realize fine construction management.

2. The method according to claim 1, wherein the method is characterized by, In S3, the water exploration holes are uniformly arranged in different directions in the shaft, after drilling by the drilling machine, pre-burying seamless steel pipes, fixing the pipes and installing high-pressure valves, the holes are scanned and pressure tested.

3. The method according to claim 1, wherein the method is characterized by, In S4, the number of grouting holes is calculated as follows: ； In the formula, D is the net diameter of the shaft, A is the distance between the grouting hole and the shaft wall, and L is the grouting hole spacing; The radial inclination angle of the grouting hole is calculated as follows: ； ； wherein: is the angle of the grouting hole with the vertical axis in the radial direction; S is the distance of the final hole position beyond the net diameter in the radial direction; E is the permanent well wall thickness; m is the distance of the final hole position beyond the raw diameter in the radial direction; A is the distance of the grouting hole from the well wall; H is the grouting section height.

4. The method according to claim 1, wherein the method is characterized by, In S4, the slurry preparation calculation formula is as follows: ； In the formula: N is the number of grouting holes; a is the slurry consumption coefficient; H is the height of the grouting section; R is the effective diffusion radius of the slurry; β is the liquid filling coefficient; M is the stone rate; η is the fissure rate.

5. The method according to claim 1, wherein the method is characterized by the steps of: In S5 grouting construction: Each grouting hole is grouted one by one; Before grouting the current grouting hole, water pressure test is carried out and the water absorption of the grouting hole is calculated: ； In the formula, q The water absorption of the unit grouting hole, ; Q The flow rate at the maximum pressure of the water pressure, ; H The grouting section height, m; During the grouting process of the current grouting hole, the grouting amount is adjusted in real time according to the grouting pressure, and 80% of the volume of the grouting pipe and the grouting hole is injected with clean water before the grouting of the current grouting hole is completed; After the grouting of the current grouting hole is completed, the hole is scanned and water pressure test is carried out at the grouting section position, when the single-hole water inflow is less than 1.0m³ / h, no more grouting is carried out, and the grouting of the next drilling hole is carried out; After the grouting of all grouting holes is completed, the hole is scanned and water pressure test is carried out, and the single-hole water inflow of each drilling hole is less than 1.0m³ / h, and the grouting is completed.

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