A method for small-section multi-angle hole curtain grouting

Abstract

The application discloses a kind of small section multi-angle hole curtain grouting methods, comprising the following steps: (1) in the inclined drift working section bottom plate, inclined drift working section contour line evenly into grouting pipe, different inclination angle is set to each grouting pipe, so that it is diffused in the outside of roadway contour line;The inclination angle of the grouting pipe is set so that the final hole of the grouting pipe is distributed at different distances outside the roadway contour line;(2) using grouting material, inject from grouting pipe, form water curtain outside the roadway contour line in a diffused manner.The small section multi-angle hole curtain grouting method has the advantages of simple operation, high construction efficiency, etc., and the hole arrangement mode of the final hole tangential intersection of drilling realizes the purpose of grouting and water plugging in the sandstone section of the main inclined shaft.

Description

Technical Field

[0001] This invention belongs to the field of mining construction technology, and in particular relates to a method for perforated curtain grouting. Background Technology

[0002] As coal mining depths increase, a large number of deep shafts are under construction or about to be put into operation. The hydrogeological conditions after mining into the deep layers are very complex, with many bedrock aquifers, abundant water in pores (fractures), and poor strata stability, which increases the risk of water inrush in the shafts. A large amount of groundwater suddenly gushes out, forming interconnected fissures and channels in the rock mass, creating underground rivers or underground lakes, which seriously threaten the safety of construction.

[0003] Pre-grouting at the main inclined shaft working face is a relatively mature water control method in China. Grouting for water control at the working face involves drilling holes and injecting grout into the rock strata. The grouting pressure forces the grout to diffuse into the fissures of the surrounding rock, sealing water outside the grouting area and forming a reinforced zone, or grouting curtain, thereby improving the integrity of the rock mass and enhancing the strength of the surrounding rock. However, traditional grouting hole layout methods have limited grouting effectiveness, insufficient grout diffusion, and poor water-blocking effect in complex strata. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above and to provide a method for small cross-section multi-angle perforated curtain grouting with good water-blocking effect.

[0005] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0006] A method for small-section, multi-angle perforated curtain grouting includes the following steps:

[0007] (1) Grouting pipes are uniformly driven into the bottom plate of the inclined roadway working section and within the outline of the inclined roadway working section. Each grouting pipe is set with a different inclination angle so that it diffuses outside the roadway outline. The inclination angle of the grouting pipes is set so that the final holes of the grouting pipes are distributed at different distances outside the roadway outline. Even if it diffuses in a diffuse manner on the outer tangent line within 5 meters outside the roadway outline, it forms a multi-point grouting and water blocking curtain to achieve the grouting and water blocking effect.

[0008] (2) Grouting material is used and injected from the grouting pipe to form a water-stop curtain outside the roadway outline in a diffused manner.

[0009] In the above-mentioned method of multi-angle perforated curtain grouting in small cross-sections, preferably, multiple grouting pipes are evenly arranged under the bottom plate of the working section of the inclined roadway, and each grouting pipe is set at an angle downward, to the left or to the right, so that the final hole is controlled at a different distance outside the roadway outline, and grouting pipes at different distances are alternately arranged.

[0010] In the above-mentioned method of multi-angle perforated curtain grouting with small cross-sections, preferably, a ring of grouting pipes is evenly arranged inside the outline of the inclined roadway working section and close to the outline of the inclined roadway working section. Each grouting pipe is set at an angle downward, to the left, or to the right, so that the final hole is controlled at a different distance outside the roadway outline. Grouting pipes at different distances are alternately arranged.

[0011] In the above-mentioned method of multi-angle perforated curtain grouting with small cross-sections, preferably, grouting pipes #1, #2, #3, #4, #5, and #6 are evenly arranged 1m below the bottom plate of the inclined tunnel working section, such that the final holes of grouting pipes #1, #3, and #5 are 5m outside the tunnel outline, and the final holes of grouting pipes #2, #4, and #6 are 4m outside the tunnel outline; grouting pipes #7, #8, #9, #10, #11, #12, #13, #14, #15, #16, #17, and #18 are evenly arranged inside and close to the outline of the inclined tunnel working section, such that grouting pipes #7, #2, #3, and #5 are 5m outside the tunnel outline, and the final holes of grouting pipes #2, #4, and #6 are 4m outside the tunnel outline. The final holes of grouting pipes #15 and #17 are located 1m outside the roadway outline, while the final holes of grouting pipes #16 and #18 are located 0m outside the roadway outline. Grouting pipes #19, #20, #21, #22, and #23 are evenly arranged within grouting pipes #7, #8, #9, #10, #11, #12, #13, #14, #15, #16, #17, and #18, at a distance of 0.5m from the outline of the inclined roadway working section. The final holes of grouting pipes #19 and #23 are located 5m outside the roadway outline, while the final holes of grouting pipes #20, #21, and #22 are located 4m outside the roadway outline. This method of grouting hole arrangement, by using multiple evenly arranged grouting pipes, achieves better water-blocking effect. This specific method is more suitable for situations where water seeps out at the roadway floor.

[0012] In the above-mentioned method of curtain grouting with multiple holes in a small cross section, preferably, an inspection hole is arranged in the middle of the working cross section of the inclined tunnel, and the inclination angle of the inspection hole is the same as that of the inclined tunnel.

[0013] The preferred method for small-section, multi-angle perforated curtain grouting includes the following steps:

[0014] S1. Drilling: Drill holes in the working section of the inclined tunnel according to the design. After drilling, install the telescopic grouting sealing device and connect the grouting pipe in a timely manner.

[0015] S2. Install ball valve and grouting pipeline: First install the ball valve, then connect the high-pressure grout inlet pipe, high-pressure grouting pipe and grouting pump outlet valve;

[0016] S3. Water pressure test: After connecting the pipeline, start the pump to inject clean water to test the pipeline performance and effectively flush the cracks to facilitate the flow of grout.

[0017] S4. Grouting: First inject thin grout, then thick grout to increase the grout absorption of a single hole. The sealing grouting uses a two-component grout. After the water blocking effect is achieved, switch holes for grouting.

[0018] In the above-mentioned method of small-section multi-angle perforated curtain grouting, preferably, the water absorption per unit borehole is calculated based on the water pressure test results in step S3, and the type and initial concentration of grout are selected accordingly. When the water absorption rate is >10 L / min -1 m -1 At that time, the grout used was a cement-water glass two-component grout, with an initial cement grout concentration of 1:1, and the water absorption rate was 7-10 L / min. -1 m -1 At that time, a single-component cement grout was used, with an initial cement grout concentration of 1:1, and the water absorption rate was 5-7 L / min. -1 m -1 At that time, a single-component cement grout was used, with an initial cement grout concentration of 2:1, and the water absorption rate was 3-5 L / min. -1 m -1 At that time, the grout used is single-component cement grout or ultrafine cement grout, and the initial concentration of cement grout is 3:1.

[0019] In the aforementioned method of small-section, multi-angle perforated curtain grouting, preferably, the grouting material includes cement grout and Baiyin brand grouting material. The Baiyin brand grouting material is prepared by mixing any one of the following: Baiyin brand BY12-VI type water-non-dispersible grout, BY12-IA type early-setting, early-strength, high-strength grout, BY12-I type high-performance non-shrink grout, and BY12-7 type gas sealing hole special grout with water. This material exhibits micro-expansion, high early strength, and strong impermeability. After grouting, the water inflow at the working face is not easily rebounded, making it particularly effective for open water holes with large water outflow.

[0020] In the above-mentioned method of multi-angle perforated curtain grouting with small cross-section, preferably, the weight water-cement ratio of the cement grout is 1:0.8-1:1, the weight water-cement ratio of the Baiyin brand grouting material grout is 0.27:1, and the volume ratio of cement grout to Baiyin brand grouting material grout is 1:0.8-1:1.

[0021] In the above-mentioned method of grouting curtains with multiple perforations in small cross sections, preferably, in step S4, the thin grout is injected first, followed by the thick grout. In practice, when grouting begins, 10-15Be′ water glass grout is used; during normal grouting, 20-25Be′ water glass grout is used; and when grouting the final hole, 36-40Be′ water glass grout or undiluted grout is used for sealing the hole.

[0022] In the above-mentioned method of multi-angle perforated curtain grouting with small cross-section, preferably, the grouting pressure is 2-4 times the hydrostatic pressure at the grouting point, and the grouting is stopped after stabilizing for 15 minutes. This process is repeated until there is no obvious water discharge from the working face.

[0023] In the above-mentioned method of multi-angle perforated curtain grouting with small cross-sections, preferably, the injection volume of pre-grouting slurry in the inclined tunnel working section is calculated according to the following formula:

[0024] ;

[0025] In the formula: Q The total amount of grout injected into the wellbore, in meters. 3 ; B The number of grouting holes in the wellbore; R The effective diffusion radius of the slurry is given in meters (m), and is typically 2-3 m. H The length of the grouting section is in meters (m). n denoted as the fracture ratio of the water-bearing rock strata, %; λ is the slurry loss coefficient, taken as 1.1-1.4. N The slurry stone-forming coefficient is taken as 0.75-0.85.

[0026] The present invention relates to a method for multi-angle perforated curtain grouting in a small cross-section of a water-rich inclined shaft working face. This method employs a novel perforation pattern, using multi-angle perforation. The final positions of the deep and shallow holes are located within the outer tangent of the roadway outline within a range of 5 meters, forming a multi-point grouting and water-blocking curtain to achieve the grouting and water-blocking effect. While ensuring that the grouting effect remains unchanged, the effective grouting length is increased and the grouting time is reduced.

[0027] The multi-angle hole arrangement method of the present invention can have grouting holes at 5m, 4m, 1m and 0m on the outer contour of the roadway, which ensures that the grout diffuses at more angles, can better reinforce and block water, and has a better water blocking effect.

[0028] Compared with the prior art, the advantages of the present invention are as follows:

[0029] The method of small-section multi-angle perforation curtain grouting of the present invention has the advantages of simple operation and high construction efficiency. The perforation arrangement of the final hole tangents achieves the purpose of grouting and water plugging in the sandstone section of the main inclined shaft. The new perforation arrangement achieves the purpose of saving costs and reducing engineering expenses. Under the influence of actual construction conditions, it realizes the engineering innovation of controlling large-section tunneling with small-section perforation grouting. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the borehole planar arrangement in the embodiment.

[0032] Figure 2 This is a three-dimensional view of the main inclined shaft and grouting holes in the embodiment. Detailed Implementation

[0033] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0034] It should be noted that when a component is described as being "fixed to, attached to, connected to or connected to" another component, it can be directly fixed to, attached to, connected to or connected to the other component, or it can be indirectly fixed to, attached to, connected to or connected to the other component through other intermediate connectors.

[0035] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0037] Example:

[0038] A method for small-section, multi-angle perforated curtain grouting includes the following steps:

[0039] (1) Grouting pipes are uniformly driven into the bottom plate of the inclined roadway working section and within the outline of the inclined roadway working section. Each grouting pipe is set with a different inclination angle so that it diffuses outside the roadway outline. The inclination angle of the grouting pipe is set so that the final hole of the grouting pipe is distributed at different distances outside the roadway outline.

[0040] (2) Grouting material is used and injected from the grouting pipe to form a water-stop curtain outside the roadway outline in a diffused manner.

[0041] In this embodiment, multiple grouting pipes are evenly arranged below the bottom plate of the inclined roadway working section. Each grouting pipe is set at an angle downward, to the left, or to the right, so that the final hole is controlled at a different distance outside the roadway outline. Grouting pipes at different distances are alternately arranged.

[0042] In this embodiment, a ring of grouting pipes is evenly arranged inside the working section outline of the inclined roadway and close to the working section outline. Each grouting pipe is set at an angle downward, to the left, or to the right, so that the final hole is controlled at a different distance outside the roadway outline. Grouting pipes at different distances are alternately arranged.

[0043] In this embodiment, an inspection hole is arranged in the middle of the working section of the inclined tunnel, and the inclination angle of the inspection hole is the same as that of the inclined tunnel.

[0044] The method for small-section, multi-angle perforated curtain grouting in this embodiment specifically includes the following steps:

[0045] S1. Drilling: Drill holes in the working section of the inclined tunnel according to the design. After drilling, install the telescopic grouting sealing device and connect the grouting pipe in a timely manner.

[0046] S2. Install ball valve and grouting pipeline: First install the ball valve, then connect the high-pressure grout inlet pipe, high-pressure grouting pipe and grouting pump outlet valve;

[0047] S3. Water pressure test: After connecting the pipeline, start the pump to inject clean water to test the pipeline performance and effectively flush the cracks to facilitate the flow of grout.

[0048] S4. Grouting: First inject thin grout, then thick grout to increase the grout absorption of a single hole. The sealing grouting uses a two-component grout. After the water blocking effect is achieved, switch holes for grouting.

[0049] In this embodiment, based on the water pressure test results in step S3, the water absorption per unit borehole is calculated, and the type and initial concentration of the slurry are selected accordingly. When the water absorption rate is >10 L / min -1 m -1 At that time, the grout used was a cement-water glass two-component grout, with a water absorption rate of 7-10 L / min. -1 m -1 At that time, single-component cement grout was used, and the water absorption rate was 5-7 L / min. -1 m -1 At that time, single-component cement grout was used, and the water absorption rate was 3-5 L / min. -1 m -1 At that time, the grout used is either single-component cement grout or ultrafine cement grout.

[0050] In this embodiment, the grouting material includes cement grout and Baiyin brand grouting material grout. The Baiyin brand grouting material grout is obtained by mixing any one of Baiyin brand BY12-VI type water-non-dispersible grout, BY12-IA type early-setting and high-strength grout, BY12-I type high-performance non-shrink grout, and BY12-7 type gas sealing hole special grout with water.

[0051] In this embodiment, the weight water-cement ratio of the cement grout is 1:0.8-1:1, the weight water-cement ratio of the Baiyin brand grouting material grout is 0.27:1, and the volume ratio of the cement grout to the Baiyin brand grouting material grout is 1:0.8-1:1.

[0052] In this embodiment, the amount of grout injected into the pre-grouting section of the inclined tunnel is calculated using the following formula:

[0053] ;

[0054] In the formula: Q The total amount of grout injected into the wellbore, in meters. 3 ; B The number of grouting holes in the wellbore; R The effective diffusion radius of the slurry is given in meters (m), and is typically 2-3 m. H The length of the grouting section is in meters (m). n denoted as the fracture ratio of the water-bearing rock strata, %; λ is the slurry loss coefficient, taken as 1.1-1.4. N The slurry stone-forming coefficient is taken as 0.75-0.85.

[0055] More specifically, a specific construction method is provided as follows:

[0056] During the grouting construction of a main inclined shaft in a mine, due to limitations in on-site construction conditions, a short-injection, short-excavation grouting method was adopted to safely pass through the sandstone aquifer. The inclined shaft was designed with a 19.8° downhill slope, and the actual construction floor was located 2.4 meters below the tunnel roof, with a straight-walled semi-circular arch cross-section. To promptly assess the water content of the rock within 20 meters in front of the working face and to perform grouting and water plugging, a grouting scheme combining the novel hole layout method of this invention with dual-liquid grouting was adopted.

[0057] Specifically, such as Figure 1 , Figure 2 As shown, grouting pipes #1, #2, #3, #4, #5, and #6 are evenly arranged 1m below the bottom plate of the inclined tunnel working section, with the final holes of grouting pipes #1, #3, and #5 located 5m outside the tunnel outline, and the final holes of grouting pipes #2, #4, and #6 located 4m outside the tunnel outline. Grouting pipes #7, #8, #9, #10, #11, #12, #13, #14, #15, #16, #17, and #18 are evenly arranged inside and close to the inclined tunnel working section outline, with the final holes of grouting pipes #7, #15, and #17 located... The final hole is 1m outside the roadway outline; the final holes of grouting pipes #16 and #18 are 0m outside the roadway outline. Grouting pipes #7, #8, #9, #10, #11, #12, #13, #14, #15, #16, #17, and #18 are evenly arranged inside the grouting pipes and at a distance of 0.5m from the outline of the inclined roadway working section. The final holes of grouting pipes #19 and #23 are 5m outside the roadway outline, and the final holes of grouting pipes #20, #21, and #22 are 4m outside the roadway outline.

[0058] When designing the drilling locations, six grouting holes were arranged 1 meter back from the bottom plate of the working face, with a center-to-center distance of 1.28m, named Holes 1#-6#. Nine grouting holes were evenly arranged along the roadway outline, with a center-to-center distance of 1.06m, named Holes 7#-15#. Three holes were arranged at a distance of 1.375m from the lower outline of the roadway, named Holes 16#-18#. Five holes were arranged 0.5 meters inside the working face outline of the roadway, with a center-to-center distance of 1.48m, named Holes 19#-23#. Two holes were arranged at appropriate locations within the roadway cross-section, constructed along the roadway, named Holes 24# and 25#. A total of 25 grouting holes were made in this operation (of which grouting holes 24# and 25# also served as inspection holes).

[0059] The detailed parameters for the drilling angle and hole depth are shown in Table 1 below.

[0060] Table 1: Detailed parameters of drilling angle and hole depth

[0061]

[0062] Among them, holes 1#, 3#, 5#, 9#, 11#, 13#, 19#, and 23# terminate at 5m from the outer contour line of the tunnel; holes 2#, 4#, 6#, 8#, 10#, 12#, 14#, 20#, 21#, and 22# terminate at 4m from the outer contour line of the tunnel; holes 7#, 15#, and 17# terminate at 1m from the outer contour line of the tunnel; and holes 16# and 18# terminate at 0m from the outer contour line of the tunnel.

[0063] The grouting slurry is prepared as follows:

[0064] 1. Preparation of cement grout: The water-cement ratio of cement grout is 1:0.8-1 (by weight).

[0065] 2. Preparation of grout for Baiyin brand BY12 grouting material: The water-cement ratio of the grout is 0.27:1 (by weight).

[0066] 3. Preparation of water glass slurry: The ratio of slurry to water glass slurry is 1:0.8-1 (volume ratio).

[0067] To increase the stone-setting rate of the grout, use fresh bagged P·O42.5 grade ordinary Portland cement; when the temperature of the main inclined shaft water inflow is too high and the ordinary Portland cement does not set well, use fresh bagged BY12-IA type early-setting and early-strength high-strength grout or BY12-I type high-performance non-shrink grout.

[0068] Based on the measured hydrostatic pressure, the final grouting pressure at this working face is determined to be 10MPa-20MPa.

[0069] The calculated grout injection volume at the working face is Q = 366.25 m. 3 .

[0070] The grouting equipment selected is a 2TGZ-130 / 130 type dual-liquid speed-regulating high-pressure grouting pump and a GS-700 type vertical high-speed grouting machine matched with the pump.

[0071] Grouting construction

[0072] 1. Drilling: First, drill holes on the working face according to the design. After drilling, promptly install the telescopic grouting sealing device and connect the grouting tail pipe.

[0073] 2. Installation of ball valve and grouting pipeline: First install the ball valve, then connect the high-pressure grout inlet pipe, high-pressure grouting pipe and grouting pump outlet valve, etc.

[0074] 3. Water pressure test: After connecting the pipeline, turn on the pump to inject clean water and test the pipeline performance and effectively flush the cracks (voids) to facilitate the flow of slurry.

[0075] 4. Grouting: First inject thin grout, then thick grout to increase the grout absorption capacity of a single hole. Two-component grouting is used for sealing; after achieving the water-blocking effect, switch holes for grouting. At the beginning of grouting, use 10-15Be′ water glass grout; during normal grouting, use 20-25Be′ water glass grout; and at the end of the hole grouting, use 36-40Be′ water glass grout or undiluted grout for sealing.

[0076] After each grouting session, a certain amount of clean water should be injected to flush the grout in the pump and pipelines. Any remaining grout in the pipes should be placed in a mine car and transported to the surface for discharge. After each grouting session, the equipment and pipelines must be cleaned, inspected, and test-run to prepare for the next grouting session.

[0077] By adopting the above-mentioned grouting pipe structure and grout, a good waterproofing effect can be achieved during the grouting construction process of the main inclined shaft of the mine.

Claims

1. A method for small-section, multi-angle perforated curtain grouting, characterized in that, Includes the following steps: (1) Grouting pipes are uniformly driven into the bottom plate of the inclined roadway working section and within the outline of the inclined roadway working section. Each grouting pipe is set with a different inclination angle so that it diffuses outside the roadway outline. The inclination angle of the grouting pipe is set so that the final hole of the grouting pipe is distributed at different distances outside the roadway outline. (2) Grouting material is used and injected from the grouting pipe to form a water-stop curtain outside the roadway outline in a diffused manner; Multiple grouting pipes are evenly arranged under the bottom plate of the inclined roadway working section. Each grouting pipe is set at an angle downward, to the left, or to the right, so that the final hole is controlled at a different distance outside the roadway outline. Grouting pipes at different distances are alternately arranged. A ring of grouting pipes is evenly arranged inside the working section outline of the inclined roadway and close to the working section outline of the inclined roadway. Each grouting pipe is set at an angle downward, to the left or to the right, so that the final hole is controlled at a different distance outside the roadway outline. Grouting pipes at different distances are alternately arranged. Grouting pipes #1, #2, #3, #4, #5, and #6 are evenly arranged 1m below the bottom plate of the inclined tunnel working section, with the final holes of grouting pipes #1, #3, and #5 located 5m outside the tunnel outline, and grouting pipes #2, #4, and #6 located 4m outside the tunnel outline. Grouting pipes #7, #8, #9, #10, #11, #12, #13, #14, #15, #16, #17, and #18 are evenly arranged inside and close to the inclined tunnel working section outline, with grouting pipes #7, #15, and #17 located... The final hole is 1m outside the roadway outline; the final holes of grouting pipes #16 and #18 are at the roadway outline. Grouting pipes #7, #8, #9, #10, #11, #12, #13, #14, #15, #16, #17, and #18 are evenly arranged inside the grouting pipes and at a distance of 0.5m from the outline of the inclined roadway working section. The final holes of grouting pipes #19 and #23 are 5m outside the roadway outline; the final holes of grouting pipes #20, #21, and #22 are 4m outside the roadway outline. Inspection holes are arranged in the middle of the working section of the inclined tunnel, and the inclination angle of the inspection holes is the same as that of the inclined tunnel. The method of small-section, multi-angle perforated curtain grouting specifically includes the following steps: S1. Drilling: Drill holes in the working section of the inclined tunnel according to the design. After drilling, install the telescopic grouting sealing device and connect the grouting pipe in a timely manner. S2. Install ball valve and grouting pipeline: First install the ball valve, then connect the high-pressure grout inlet pipe, high-pressure grouting pipe and grouting pump outlet valve; S3. Pressure test: After connecting the pipeline, start the pump to inject clean water to test the pipeline performance and effectively flush the cracks to facilitate the flow of grout. S4. Grouting: First inject thin grout, then thick grout to increase the grout absorption of a single hole. The sealing grouting uses a two-component grout. After the water blocking effect is achieved, switch holes for grouting.

2. The method for small-section multi-angle perforated curtain grouting according to claim 1, characterized in that, Based on the water pressure test results in step S3, calculate the water absorption per unit borehole, and select the type and initial concentration of grout accordingly. When the water absorption rate is >10 L·min -1 ·m -1 At that time, the grout used was a cement-water glass two-component grout, with a water absorption rate of 7-10 L / min. -1 ·m -1 At that time, single-component cement grout was used, and the water absorption rate was 5-7 L / min. -1 ·m -1 At that time, single-component cement grout was used, and the water absorption rate was 3-5 L / min. -1 ·m -1 At that time, the grout used is either single-component cement grout or ultrafine cement grout.

3. The method for small-section multi-angle perforated curtain grouting according to claim 1, characterized in that, The grout injection volume for the pre-grouting section of the inclined tunnel is calculated using the following formula: ； In the formula: Q The total amount of grout injected into the wellbore, in meters. 3 ; B The number of grouting holes in the wellbore; R The effective diffusion radius of the slurry is given in meters (m), and is typically 2-3 m. H The length of the grouting section is in meters (m). n The fracture rate of the water-bearing rock strata is %; λ is the slurry loss coefficient, which is taken as 1.1-1.4; N The slurry stone-forming coefficient is taken as 0.75-0.85.

Images