A method for hydraulic fracturing and grouting to plug water in karst fissure tunnels

Abstract

This invention discloses a method for hydraulic fracturing and grouting to plug water in karst fissure tunnels, relating to the field of underground mine construction technology. Test boreholes in different directions are drilled in the surrounding rock of the tunnel to determine the minimum diffusion radius of the grout under the design pressure and flow rate. Loosening zone boreholes are drilled at intervals around the tunnel perimeter, and the thickness of the loosening zone is determined using borehole television. Grouting boreholes are uniformly drilled in the surrounding rock of the tunnel in the water-bearing area. A hydraulic fracturing and grouting system is assembled, with the delivery pump connected to the grout tank and the grouting pipe placed at the bottom of the grouting boreholes. The hydraulic fracturing and grouting system is first flushed with water and adjusted. Then, the hydraulic fracturing and grouting pressure and flow rate are set, and hydraulic fracturing and grouting is performed hole by hole from the tunnel floor to the roof until the flow rate suddenly decreases and grout emerges from adjacent grouting boreholes. After the grout diffused around each grouting borehole solidifies, an artificial annular closed ring with water-proof properties is formed around the loosening zone of the tunnel. This method achieves directional long-distance diffusion of the grout, effectively cutting off the water-filling channel.

Description

Technical Field

[0001] This invention relates to the field of underground mine construction technology, specifically to a method for hydraulic fracturing and grouting to plug water in karst fissure tunnels. Background Technology

[0002] Currently, the main principles of mine water hazard prevention and control technology are sealing water-filling channels and / or draining water sources. For water sources with small volumes and low pressure, drainage is easy to achieve, and forced drainage can solve the mine water inrush problem. However, if the water source is abundant and the volume and pressure are large, causing the inrush to exceed the mine drainage system's capacity, forced drainage not only incurs high drainage costs and fails to adequately solve the mine water inrush problem, but also causes groundwater imbalance. For example, in southwestern my country, the rock strata are mostly carbonate rocks with well-developed karst fissures and strong water-bearing capacity. When the mine tunnels are exposed, the water sources are relatively scattered and the hydraulic connections are complex. The water inrush in the tunnels exhibits a full-section linear water-sprinkling state with a large outflow. In this case, the scattered karst water is difficult to accurately detect and drain, and sealing water-filling channels is the key to effectively preventing this type of water. Currently, the main engineering method is to seal the fissures in the surrounding rock of the mine tunnels using grouting technology, such as single-liquid cement grouting, cement-water glass double-liquid grouting, and chemical grouting. Current grouting methods face the challenge of achieving precise, directional sealing of water-filled channels in surrounding rock fissures. Influenced by random fissures, ground stress, and grout materials, grout diffusion is uneven, leading to grout leakage, runoff, and cross-contamination. Grouting has become a "black box" problem, making it difficult to visually assess its effectiveness on-site, often resulting in suboptimal grouting outcomes and high costs. Therefore, there is an urgent need to develop a grouting method for water sealing in karst fissure tunnels, achieving low-cost, high-efficiency grouting for water sealing. Summary of the Invention

[0003] The purpose of this invention is to provide a method for hydraulic fracturing and grouting to plug water in karst fissure tunnels, solving the problems of existing grouting methods which are difficult to perform in a precise direction and have unsatisfactory grouting effects.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for hydraulic fracturing and grouting to plug water in karst fissure tunnels, characterized in that: the method steps are as follows:

[0005] S1. Determine the minimum diffusion radius of the grout: Drill test boreholes in different directions in the downhole rock mass, and conduct rock mass grouting diffusion radius experiments using a fracturing grouting system. After grouting, use ground-penetrating radar and borehole television to determine the minimum diffusion radius of the grout under the design pressure and flow rate.

[0006] S2. Determine the thickness of the loosened zone of the surrounding rock in the roadway: Drill several loosened zone holes at intervals around the roadway, and use borehole television to determine the range of the loosened zone of the surrounding rock in the roadway and determine the thickness of the loosened zone of the surrounding rock in the roadway;

[0007] S3. Construction grouting boreholes: uniformly drill grouting boreholes in the surrounding rock of the roadway in the water inrush area, with a depth greater than the thickness of the loosened zone and a hole bottom distance less than the grout diffusion diameter.

[0008] S4. Install the fracturing grouting system: Connect the outlet of the grout pump to the control valve and the grouting steel pipe in sequence through the grouting hose. The end of the grouting steel pipe is connected to the grouting perforated pipe. The two ends of the grouting perforated pipe are fixed with sealing devices. The grout pump is connected to the grout tank. The grouting perforated pipe is placed at the bottom of the grouting borehole.

[0009] S5. Constructing a closed ring through fracturing grouting: First, flush the fracturing grouting system with water and make adjustments. Then, set the fracturing grouting pressure and flow rate and carry out fracturing grouting hole by hole from the bottom plate to the top plate of the roadway until the flow rate drops sharply and grout comes out of the adjacent grouting hole. After the grout that spreads around each grouting hole solidifies, an artificial ring with water-proof properties is constructed around the loosening zone of the roadway.

[0010] S6. Equipment removal and borehole sealing: After fracturing and grouting are completed, shut down the grout pump, remove the fracturing and grouting equipment, and seal the grouting boreholes in a timely manner.

[0011] A further technical solution is that in step S1, the test borehole diameter is 40-90mm, the borehole depth is 5-10m, the designed grouting pressure is 10-30MPa, the designed grouting flow rate is 200-400L / min, and the grout composition is cement grout, cement-water glass dual-liquid grout, or chemical grout.

[0012] A further technical solution is that in step S2, the diameter of the loosening ring drill hole is 30-60mm, the depth of the drill hole is 3-5m, and the number of holes is 5-8.

[0013] A further technical solution is that in step S5, the slurry pump pressurizes the slurry transported from the slurry tank, and the slurry is transported through the slurry delivery hose and control valve to the slurry delivery steel pipe in the grouting borehole, and then to the grouting perforated pipe between the two sealing devices at the bottom of the hole. The slurry is sprayed out from the nozzle of the grouting perforated pipe. With the sealing and sealing at both ends of the sealing device, the slurry is fracturing the surrounding rock under high pressure and spreading. Through the combined fracturing and grouting of multiple grouting boreholes around the roadway, an artificial annular closed ring with water-proof properties is finally formed around the loosened zone of the roadway.

[0014] A further technical solution is that the grouting steel pipe is composed of 1-2m long high-pressure resistant seamless steel pipes connected by threads, with a diameter of 40-60mm. The head of the grouting steel pipe is connected to the grouting perforated pipe of the same diameter by a sealing device, and the tail is connected to the grouting hose by a control valve.

[0015] A further technical solution is that the grouting pipe is made of high-pressure resistant seamless steel pipe, which is located at the bottom of the grouting borehole during fracturing grouting. The length of the grouting pipe is 0.5 to 1.5 m, and the diameter does not exceed that of the grouting steel pipe. The nozzles are arranged in rows evenly along the radial direction of the pipe, with 3 to 6 nozzles arranged in each row, a row spacing of 20 to 30 cm, and a nozzle diameter of 1 to 3 cm.

[0016] A further technical solution is that the sealing device is installed at both ends of the grouting pipe, and the sealing method is double sealing at both ends. When the high-pressure grout is delivered, the sealing device will quickly expand to seal the grouting borehole and create a closed space, which will cause the grout sprayed from the grouting pipe to maintain pressure, fracture the surrounding rock, and diffuse. The sealing device is made of rubber, with a length of 0.5 to 1.5 m, a diameter 1 to 3 cm larger than the grouting steel pipe, a radial expansion of 2 to 3 cm, and a high pressure resistance of over 70 MPa.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] (1) Through the preliminary test drilling and loosening zone drilling, combined with ground radar and borehole television, the minimum diffusion radius of the rock mass and the thickness of the loosening zone are determined, which provides a basis for the subsequent grouting drilling depth and hole spacing, high-pressure grouting, etc., so as to make the grouting sealing direction more accurate and effective.

[0019] (2) By using fracturing grouting, a closed ring with full-section water-proof performance is artificially constructed outside the loosened zone of the surrounding rock in the water-bearing roadway. This can effectively cut off the water-filling channel in the far field, and is not affected by the complex mining fractures in the near field, thus avoiding the leakage, cross-flow and run-out of grout that occur in the traditional grouting process.

[0020] (3) By arranging two plugs in the grouting borehole for double sealing and fracturing, the directional and orderly diffusion of grout was achieved. The fracturing method improved the diffusion speed and diffusion distance of grout, which greatly reduced the amount of grout used and the waste caused by near-field mining fractures compared with the previous free grouting method of blind diffusion of grout.

[0021] (4) This method is well adaptable to single-liquid grout, two-liquid grout and chemical grout. Whether the grout is discharged from adjacent grouting holes can be directly judged to determine whether the grout diffusion is in place, which overcomes the previous defect that the grouting effect is difficult to be directly detected on site. Attached Figure Description

[0022] Figure 1 A schematic diagram of fracturing and grouting for water plugging in karst fissure tunnels;

[0023] Figure 2 This is a schematic diagram of a fracturing grouting system.

[0024] Figure 3 This is a schematic diagram of the flower tube structure;

[0025] In the diagram: 1-Water inrush tunnel, 2-Loosening ring, 3-Closed ring, 4-Surrounding rock, 5-Water source, 6-Grouting borehole, 7-Fracturing grouting system, 701-Grouting tank, 702-Grouting pump, 703-Grouting hose, 704-Control valve, 705-Grouting steel pipe, 706-Sealing device, 707-Grouting perforated pipe, 7071-Nozzle. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0027] Figure 1 This is a schematic diagram of the grouting and water-blocking method for fracturing surrounding rock in karst fissure tunnels according to the present invention. If, after tunnel 1 is excavated, a loosening zone 2 of a certain thickness appears in the surrounding rock 4 of tunnel 1 under the action of mining stress, the thickness of the loosening zone 2 can be visually measured using borehole television. To prevent the karst fissure water source 5 hidden in the surrounding rock 4 from flowing into the tunnel 1, the main principle of this invention is as follows: First, a grout diffusion experiment is conducted on-site at the design pressure and flow rate using a fracturing grouting system 7 (without the sealing device 706) to determine the minimum grout diffusion radius; then, a certain number of grouting boreholes 6 with a depth greater than the thickness of the loosened ring 2 and a diameter are drilled at even intervals in the surrounding rock 4 around the tunnel 1, with the bottom distance of the boreholes less than the minimum grout diffusion radius; second, the fracturing grouting system 7 is formed by assembling the grout tank 701, grout pump 702, grout delivery hose 703, control valve 704, grout delivery steel pipe 705, two sealing devices 706, and grouting perforated pipe 707 with nozzle 7071. Figure 2 (As shown) and installed on site. During the fracturing grouting process at the designed pressure and flow rate, the grout in the grout tank 701 is transported to the grout pump 702 for pressurization, and then transported through the grout delivery hose 703 to the grout delivery steel pipe 705 in the grouting borehole 6, and then to the grouting perforated pipe 707 at the bottom of the grouting borehole 6. Each end of the grouting perforated pipe 707 is threaded with a sealing device 706. Under the action of high-pressure grout, the sealing device 706 expands rapidly, thereby forming a sealed space at the bottom of the hole. The grout ejected from the nozzle 7071 of the grouting perforated pipe 707 is pressurized and fracturing the surrounding rock in the sealed space at a higher pressure, realizing the directional diffusion of the grout. The adjacent holes of the grouting borehole 6 can be used as observation holes. When grout is discharged from the adjacent hole, the fracturing grouting is stopped, indicating that the rock mass between the two holes has been covered by the diffused grout. The fracturing grouting is carried out from the bottom plate of the roadway to the top plate one hole at a time. After all the grouting holes 6 are completed, a closed ring 3 with a certain thickness and water-proof performance is formed outside the loosening ring 2 of the roadway.

[0028] The steps of the present invention are described below with reference to an embodiment:

[0029] The tunnel project in a phosphate mine is mainly located in the upper (∈1z+∈1y) carbonate karst fissure aquifer of the Zhongyicun Formation and Yuhucun Formation of the Lower Cambrian System. The tunnel is buried at a depth of 240m, with a net width of 4.5m, a wall height of 2.0m, and an arch height of 1.5m. The surrounding rock lithology is mainly dolomite and phosphorite. The project revealed well-developed karst fissure water in the surrounding rock, with large-scale water seepage occurring throughout the entire cross-section of the tunnel, and a maximum water inflow of 200m³. 3 / h, tunnel construction and drainage are quite difficult. This embodiment uses Maris grout for fracturing and grouting the surrounding rock of the tunnel as follows:

[0030] (S1) Determine the minimum diffusion radius of the grout: In the working face of the underground roadway 1, a rock drilling rig was used to drill test holes with a depth of 15m and a diameter of 42mm in three directions: directly in front, to the right and above the surrounding rock 4. The rock mass grouting diffusion radius test was carried out using the fracturing grouting system 7. After the grouting was completed, the minimum diffusion radius of the Marisan grout under a grouting pressure of 20MPa and a flow rate of 200L / min was determined to be approximately 1.5m by using geophysical exploration and drilling methods such as SIR-4000 ground radar and GD3Q-GA borehole television.

[0031] (S2) Determine the thickness of the loosened zone of the surrounding rock in the roadway: Seven loosened zone holes with a depth of 3.5m and a diameter of 42mm were drilled at even intervals along the two sides and the roof of roadway 1 using a rock drilling rig. The range of the loosened zone of the surrounding rock in each hole was measured using a GD3Q-GA borehole television. The maximum thickness of the loosened zone 2 of the surrounding rock in the roadway was determined to be 1.8m.

[0032] (S3) Construction grouting boreholes: Ten grouting boreholes with a depth of 5m and a diameter of 42mm are uniformly drilled in the surrounding rock of the roadway in the water inrush area using a rock drilling rig. The bottom distance of the boreholes is required to be less than the grout diffusion radius.

[0033] (S4) Install the fracturing grouting system: Assemble the sealing device 706, grouting perforated pipe 707, grout delivery steel pipe 705, control valve 704, grout delivery hose 703, grout pump 702, and grout tank 701 on site to form a complete fracturing grouting system and install it. The sealing device 706 is 1.0m long and 38mm in diameter, made of rubber with a pressure resistance of 70MPa; the grouting perforated pipe 707 is a high-pressure resistant seamless steel pipe, 1.0m long and 32mm in diameter, with nozzles 7071 evenly arranged in rows along the radial direction of the pipe, 3 nozzles per row, 25cm apart, and 1cm in diameter. Each section of the grout delivery steel pipe 705 is 1.0m long and 38mm in diameter, consisting of two threaded sections. The control valve 704 is an on / off valve, connected to the grout delivery steel pipe 705 and the grout delivery hose 703 via a U-shaped clamp. The grout delivery hose 703 is made of rubber, 30mm in diameter, and withstands a high pressure of 70MPa. The grout pump 702 has a maximum flow rate of 400L / min and a pump pressure of 50MPa. The grout tank 701, with a volume of 1m³, is used for mixing and stirring the grout.3 .

[0034] (S5) Constructing a closed ring by fracturing grouting: First, flush the fracturing grouting system 7 with water and debug the system. Then, set the fracturing grouting pressure and flow rate to 20MPa and 200L / min respectively. Perform fracturing grouting from the bottom plate to the top plate of the roadway 1 hole by hole until the flow rate drops sharply and grout comes out of the adjacent grouting borehole 6. After the grout diffused around each grouting borehole 6 solidifies, construct an artificial annular closed ring 3 with a thickness of 1.0m with water-proof performance around the loosening ring 2 of the roadway 1.

[0035] (S6) Equipment removal and borehole sealing: After the fracturing grouting is completed, shut down the grout pump 702, remove the fracturing grouting system equipment and seal the borehole in a timely manner.

[0036] After using the above-mentioned fracturing and grouting method for water plugging, the total water inflow in the roadway is less than 10m³. 3 / h, achieving good grouting and water plugging results.

[0037] Although the invention has been described herein with reference to several illustrative embodiments, it should be understood that many other modifications and implementations can be devised by those skilled in the art, which will fall within the scope and spirit of this application. More specifically, various modifications and improvements can be made to the components or layouts within the scope of this application disclosure, drawings, and claims. Besides modifications and improvements to the components or layouts, other uses will be apparent to those skilled in the art.

Claims

1. A method for hydraulic fracturing and grouting to plug water in karst fissure tunnels, characterized in that: The method steps are as follows: S1. Determine the minimum diffusion radius of the grout: Drill test boreholes in different directions in the downhole rock mass, and conduct rock mass grouting diffusion radius experiments using a fracturing grouting system. After grouting, use ground-penetrating radar and borehole television to determine the minimum diffusion radius of the grout under the design pressure and flow rate. S2. Determine the thickness of the loosened zone of the surrounding rock in the roadway: Drill several loosened zone holes at intervals around the roadway, and use borehole television to determine the range of the loosened zone of the surrounding rock in the roadway and determine the thickness of the loosened zone of the surrounding rock in the roadway; S3. Construction grouting boreholes: uniformly drill grouting boreholes in the surrounding rock of the roadway in the water inrush area, with a depth greater than the thickness of the loosened zone and a hole bottom distance less than the grout diffusion diameter. S4. Install the fracturing grouting system: Connect the outlet of the grout pump to the control valve and the grouting steel pipe in sequence through the grouting hose. The end of the grouting steel pipe is connected to the grouting perforated pipe. The two ends of the grouting perforated pipe are fixed with sealing devices. The grout pump is connected to the grout tank. The grouting perforated pipe is placed at the bottom of the grouting borehole. S5. Constructing a closed ring through fracturing grouting: First, flush the fracturing grouting system with water and make adjustments. Then, set the fracturing grouting pressure and flow rate and carry out fracturing grouting hole by hole from the bottom plate to the top plate of the roadway until the flow rate drops sharply and grout comes out of the adjacent grouting hole. After the grout that spreads around each grouting hole solidifies, an artificial ring with water-proof properties is constructed around the loosening zone of the roadway. S6. Equipment removal and borehole sealing: After fracturing and grouting are completed, shut down the grout pump, remove the fracturing and grouting equipment, and seal the grouting boreholes in a timely manner.

2. The method for hydraulic fracturing and grouting to plug water in karst fissure tunnels according to claim 1, characterized in that: In step S1, the test borehole diameter is 40-90 mm and the depth is 5-10 m; the designed grouting pressure is 10-30 MPa and the designed grouting flow rate is 200-400 L / min; the grout composition is cement grout, cement-water glass two-component grout or chemical grout.

3. The method for hydraulic fracturing and grouting to plug water in karst fissure tunnels according to claim 1, characterized in that: In step S2, the diameter of the loosening ring drilled is 30-60mm, the depth of the drilled hole is 3-5m, and the number of holes is 5-8.

4. The method for hydraulic fracturing and grouting to plug water in karst fissure tunnels according to claim 1, characterized in that: In step S5, the slurry pump pressurizes the slurry transported from the slurry tank, which is then delivered to the slurry delivery steel pipe in the grouting borehole via the slurry delivery hose and control valve. The slurry is then delivered to the grouting perforated pipe between the two sealing devices at the bottom of the borehole, where it is ejected from the nozzle. With the sealing devices at both ends, the slurry is subjected to high pressure to fracturing the surrounding rock and diffuse. Through the combined fracturing and grouting of multiple grouting boreholes around the tunnel, an artificial annular closed ring with water-proof properties is finally formed around the loosened zone of the tunnel.

5. The method for hydraulic fracturing and grouting to plug water in karst fissure tunnels according to claim 1, characterized in that: The grouting steel pipe is composed of 1-2m long high-pressure resistant seamless steel pipes connected by threads, with a diameter of 40-60mm. The head of the grouting steel pipe is connected to the grouting perforated pipe of the same diameter by a sealing device, and the tail is connected to the grouting hose by a control valve.

6. The method for hydraulic fracturing and grouting to plug water in karst fissure tunnels according to claim 1, characterized in that: The grouting pipe is made of high-pressure resistant seamless steel pipe. During fracturing grouting, it is located at the bottom of the grouting borehole. The length of the grouting pipe is 0.5 to 1.5 m, and the diameter does not exceed that of the grouting steel pipe. The nozzles are arranged in rows evenly along the radial direction of the pipe, with 3 to 6 nozzles in each row, a row spacing of 20 to 30 cm, and a nozzle diameter of 1 to 3 cm.

7. The method for hydraulic fracturing and grouting to plug water in karst fissure tunnels according to claim 1, characterized in that: The sealing device is installed at both ends of the grouting pipe, and the sealing method is double sealing at both ends. When the high-pressure grout is delivered, the sealing device will quickly expand to seal the grouting borehole and create a closed space, which will cause the grout sprayed from the grouting pipe to maintain pressure, fracture the surrounding rock, and diffuse. The sealing device is made of rubber, with a length of 0.5 to 1.5 m, a diameter 1 to 3 cm larger than the grouting steel pipe, a radial expansion of 2 to 3 cm, and a high pressure resistance of over 70 MPa.

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