Tunnel long-distance high-pressure advance grouting construction method

Abstract

The invention discloses a long-distance high-pressure advance grouting construction method for a tunnel, and aims to solve the problems of short reinforcement length, long construction period, more holes, high slurry mixing risk and poor water blocking effect of pressure holes in the conventional advance grouting technology. Comprising the five steps of stable rock disc forming, hole site optimization design, segmented drilling and orifice sealing, high-pressure grouting construction and post-grouting quality inspection. The hole position is optimized based on the effective diffusion radius of 3.5 m grout, the hole opening shrinks inwards by 1.0 m to 1.3 m, the hole bottom expands outwards by 1.0 m to 1.5 m, and the total length of single-circulation grouting reaches 100 m; a bag type sealing device is adopted to realize quick high-pressure sealing of an orifice, and a sealing ring which resists pressure not less than 10MPa is formed within 12 hours; during grouting, a two-sequence hole jumping process is implemented, and the pressure and the injection rate are dynamically matched and controlled. The number of grouting holes is greatly reduced, the construction period is shortened, high-pressure grouting is matched with a pressurized water stratum, the water blocking and reinforcing effect is remarkable, the process flexibility is high, the engineering accident risk can be effectively avoided, and the method is suitable for tunnel construction with large burial depth, high water yield and complex geological conditions.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering construction technology, and in particular to a method for long-distance high-pressure advanced grouting construction in tunnels. Background Technology

[0002] In tunnel excavation, pre-grouting is a key technology for ensuring the stability of the surrounding rock and blocking groundwater inflow. For tunnels with great burial depth, high water content, and complex geological conditions (such as fault zones and areas with developed karst fissures), conventional pre-grouting technology has many drawbacks: First, the horizontal reinforcement length is relatively short (usually within 30m), requiring frequent cyclic construction, which leads to extended construction period; second, the number of grouting holes is large (usually more than 60 holes), and the segmentation and sequence are complex, making it easy for grout cross-contamination to occur, affecting the reinforcement effect; third, the grouting pressure is low (4~6MPa), and for pressurized holes with hydrostatic pressure >1.2MPa, the water-blocking reinforcement effect is not good; fourth, the construction of grout-stopping walls and grout-stopping pads takes a long time (about 10 days), further restricting the construction progress. Summary of the Invention

[0003] This invention aims to solve the problems of short reinforcement length, long construction period, large number of holes, and high risk of grout cross-contamination in existing conventional advanced grouting technology, and provides a method for long-distance high-pressure advanced grouting construction in tunnels.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for long-distance high-pressure advance grouting construction in tunnels, comprising the following steps: Step 1: Formation of a stable rock mass. In front of the tunnel section to be grouted, the working face and the surrounding rock behind it are reinforced to form a stable rock mass structure with a length of not less than 5 meters. Step 2: Hole location optimization design. Based on the effective diffusion radius of the high-pressure grout, the grout hole locations are optimized along the tunnel excavation outline, so that the hole opening is located at the working face and shrinks inward towards the outline, while the bottom of the hole extends outward from the outline. Step 3: Segmented drilling and borehole sealing. Using graded borehole diameter drilling, the borehole openings are quickly and under high pressure using a grouting device for each grouting segment, and the total length of a single-cycle grouting is divided into multiple grouting segments. Step 4: High-pressure grouting construction, using in-hole circulation method or pure pressure grouting, implementing two-sequence skip-hole process, controlling grouting pressure in stages and dynamically matching grout injection rate, and changing the water-cement ratio of grout from thin to thick in multiple stages. Step 5: Post-grouting quality inspection. After the grouting is completed and has set, drill inspection holes to conduct a water pressure test. The preset permeability and seepage per unit length are used as the criteria for judging whether the reinforcement is qualified.

[0005] Preferably, in step two, the inward contraction distance of the orifice from the contour line is 1.0 to 1.3 meters, the outward expansion distance of the bottom of the orifice from the contour line is 1.0 to 1.5 meters, and the effective diffusion radius of the grout is determined to be 3.5 meters based on the grouting pressure.

[0006] Preferably, in step three, the orifice diameter of the graded orifice section is ≥180mm, the total length of a single-cycle grouting is 80 meters or 100 meters, and the length of each grouting segment is 20 to 40 meters.

[0007] Preferably, the grouting device includes an in-hole grouting pipe, an in-hole return grouting pipe, an expandable seal, and a grout circulation pipeline inside the seal. The in-hole grouting pipe and the in-hole return grouting pipe are arranged in parallel. The seal is sleeved outside the orifice section of the in-hole grouting pipe and the in-hole return grouting pipe. One end of the grout circulation pipeline inside the seal is connected to the seal, and the other end extends outside the orifice. The in-hole grouting pipe and the in-hole return grouting pipe are respectively connected to an in-hole grouting ball valve and an in-hole return grouting ball valve at their ports outside the orifice.

[0008] Preferably, the grout injected into the seal is cement mortar with a water-cement ratio of 1:1 to 0.5:1, and after the grout sets, the seal forms a high-strength sealing ring that can withstand a grouting pressure of not less than 10 MPa within 12 hours.

[0009] Preferably, the sealing element is a bag made of industrial filter cloth, the bag is 3.5 to 4 meters long, and the bag can fit into the corresponding borehole wall after expansion.

[0010] Preferably, the internal slurry circulation pipeline of the seal includes a slurry injection pipe, a slurry return pipe, and a slurry injection ball valve connected to the movable end of the slurry injection pipe.

[0011] Preferably, when grouting the sealant, after the sealant is fully filled with cement mortar, the return grout pipe of the sealant is shielded from grout for 20 minutes, and grouting is carried out after 4 hours of setting.

[0012] Preferably, the two-sequence skip-hole process in step four is to number the drilled holes sequentially, implement the odd-numbered holes first, and after the adjacent odd-numbered holes are completed, implement the corresponding even-numbered holes. The dynamic matching control of grouting pressure and injection rate follows the following relationship: When the injection rate is greater than 200 L / min, the control pressure is less than 0.3 P; When the injection rate is 200 to 120 L / min, the control pressure is 0.3 P to 0.5 P; When the injection rate is 120 to 60 L / min, the control pressure is 0.5 P to 0.8 P; When the injection rate is less than 60 L / min, the control pressure is 0.8 P to 1.0 P; Where P is the design grouting pressure.

[0013] Preferably, in step four, pure cement grout is used for grouting, with a water-cement ratio of 2:1, 1:1, 0.7:1, and 0.5:1, gradually changing from thin to thick. The grouting volume for each water-cement ratio level meets the following requirements: ≥900L for a section length of 15m, ≥1200L for 20m, ≥1500L for 25m, and ≥1800L for 30m. The thickening level can be changed when there is no significant change in pressure and flow rate. The water-cement ratio is not changed when the grouting pressure remains constant and the injection rate continues to decrease, or when the injection rate remains constant and the pressure continues to increase.

[0014] This invention provides a method for long-distance high-pressure advanced grouting construction in tunnels, which has the following beneficial effects.

[0015] 1. Based on the 3.5-meter effective diffusion radius of the grout, the borehole design is optimized. The borehole opening is reduced by 1.0 to 1.3 meters inward from the outline, and the bottom of the borehole is expanded by 1.0 to 1.5 meters outward. This significantly increases the grouting coverage area of ​​a single hole. Moreover, the outward expansion of the bottom of the hole can effectively cover the outer side of the tunnel face. Expanding the grouting area can reduce the amount of water flowing out of the tunnel during subsequent construction and improve the stability of the surrounding rock. The number of grouting holes is greatly reduced. At the same time, a two-sequence skip-hole construction process is adopted, with odd-numbered holes constructed first and even-numbered holes constructed later. This process avoids the problem of grout cross-contamination between adjacent holes and ensures the uniformity of the reinforcement effect.

[0016] 2. By combining optimized borehole design with high-pressure grouting technology, the total length of a single-cycle grouting can reach 80 meters or 100 meters, which is 2.7 to 3.3 times that of conventional technology, eliminating the need for frequent cycle construction; at the same time, the time-consuming construction of grout-stopping walls and grout-stopping pads is eliminated, and with the rapid borehole sealing technology, the construction cycle is further compressed and the overall progress of tunnel excavation is improved.

[0017] 3. The grouting pressure is controlled in stages and can reach the design pressure P, which can effectively cope with pressurized pore formations with hydrostatic pressure >1.2MPa; a high-strength sealing ring with a pressure of ≥10MPa is formed by a bag-type sealing device, which provides reliable wellhead sealing conditions for high-pressure grouting and avoids grout leakage; the water-cement ratio of the grout is gradually changed from thin to thick and matched with a fixed injection volume to ensure that the surrounding rock fissures are fully filled, and the permeability and seepage volume after grouting meet the design standards. The water-blocking reinforcement effect is far superior to conventional low-pressure grouting.

[0018] 4. The grouting pressure and grout injection rate are dynamically linked and controlled. The pressure level is adjusted in real time according to the injection rate to avoid the problem of excessive pressure causing hole wall collapse and insufficient pressure failing to fill deep cracks. At the same time, the judgment conditions for the change of grout water-cement ratio are clearly defined. The grout is gradually thickened only when there is no significant change in pressure and flow rate, so as to ensure the controllability of the grouting process and the density of grout filling.

[0019] 5. The grouting section length can be flexibly divided into 20 to 40 meters, the hole spacing can be adjusted according to the surrounding rock grade, and the water-cement ratio and grouting volume can be adapted according to the section length. At the same time, it supports two grouting methods: in-hole circulation method or pure pressure method. It can meet the advanced grouting needs of tunnels with complex geological conditions such as large burial depth, strong water content, fracture zone and solution development zone, and has a wide range of applications.

[0020] 6. Before construction, a stable rock mass of no less than 5 meters should be formed to prevent the surrounding rock from collapsing during drilling and grouting. After grouting, inspection holes should be drilled and water pressure tests should be carried out. The permeability and seepage per unit length should be used as the criteria for qualification. Unqualified sections can be re-grouted in time to avoid the risks of engineering accidents such as water inrush and surrounding rock instability from the source and ensure the safety of tunnel construction. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the diffusion radius of the grout in the tunnel according to an embodiment of the present invention.

[0022] Figure 2 This is a diagram showing the starting point layout of the grouting holes in an embodiment of the present invention.

[0023] Figure 3 This is a diagram showing the final hole layout of the grouting holes in an embodiment of the present invention.

[0024] Figure 4 This is a schematic diagram of the closed opening of the bag in an embodiment of the present invention.

[0025] Figure 5 This is a comparison diagram of the grouting state in an embodiment of the present invention and the conventional advanced grouting state.

[0026] In the diagram: 1. Grouting pipe inside the borehole; 2. Grouting return pipe inside the borehole; 3. Grouting ball valve inside the borehole; 4. Grouting return ball valve inside the borehole; 5. Grouting pipe for the bladder bag; 6. Grouting return pipe for the bladder bag; 7. Grouting ball valve for the bladder bag; 8. Bladder bag. Detailed Implementation

[0027] like Figures 1 to 4 As shown, the present invention provides a method for long-distance high-pressure pre-grouting construction in tunnels, comprising the following steps: Step 1: Formation of a stable rock mass. In front of the tunnel section to be grouted, the working face and the surrounding rock behind it are reinforced to form a stable rock mass structure with a length of not less than 5 meters. Step 2: Hole location optimization design. Based on the effective diffusion radius of the high-pressure grout, the grout hole locations are optimized along the tunnel excavation outline, so that the hole opening is located at the working face and shrinks inward towards the outline, while the bottom of the hole extends outward from the outline. Step 3: Segmented drilling and borehole sealing. Using graded borehole diameter drilling, the borehole openings are quickly and under high pressure using a grouting device for each grouting segment, and the total length of a single-cycle grouting is divided into multiple grouting segments. Step 4: High-pressure grouting construction, using in-hole circulation method or pure pressure grouting, implementing two-sequence skip-hole process, controlling grouting pressure in stages and dynamically matching grout injection rate, and changing the water-cement ratio of grout from thin to thick in multiple stages. Step 5: Post-grouting quality inspection. After the grouting is completed and has set, drill inspection holes to conduct a water pressure test. The preset permeability and seepage per unit length are used as the criteria for judging whether the reinforcement is qualified.

[0028] In a preferred embodiment of the present invention, in step two, the inward contraction distance of the orifice from the contour line is 1.0 to 1.3 meters, the outward expansion distance of the bottom of the orifice from the contour line is 1.0 to 1.5 meters, and the effective diffusion radius of the grout is determined to be 3.5 meters based on the grouting pressure.

[0029] In a preferred embodiment of the present invention, in step three, the orifice diameter of the graded orifice section is ≥180mm, the total length of a single-cycle grouting is 80 meters or 100 meters, and the length of each grouting segment is 20 to 40 meters.

[0030] like Figure 4 As shown, the grouting device includes an in-hole grouting pipe 1, an in-hole return grouting pipe 2, an expandable seal, and a grout circulation pipeline inside the seal. The in-hole grouting pipe 1 and the in-hole return grouting pipe 2 are arranged in parallel. The seal is sleeved outside the orifice section of the in-hole grouting pipe 1 and the in-hole return grouting pipe 2. One end of the grout circulation pipeline inside the seal is connected to the seal, and the other end extends outside the orifice. The in-hole grouting ball valve 3 and the in-hole return grouting ball valve 4 are respectively connected to the ports of the in-hole grouting pipe 1 and the in-hole return grouting pipe 2 located outside the orifice.

[0031] When using the grouting device, first drill to the designed depth and clean the hole wall. Then, tie the grouting pipe 1 and the return grout pipe 2 in parallel, ensuring that the spacing between them is uniform and fixed. Place the bag 8 on the outside of the hole opening section of the two pipes and adjust the position of the bag 8 to make it centered to avoid displacement that would affect the sealing effect. Insert one end of the bag grouting pipe 5 and the bag return grout pipe 6 through the bag 8 and fix them to ensure that the grout does not leak. Extend the other end to the outside of the hole and fix it to complete the pre-assembly of the device. Finally, send the entire device into the hole opening section, adjust it to the preset position, and prepare for grouting and sealing of the bag 8.

[0032] In a preferred embodiment of the present invention, the grout injected into the sealing element is cement mortar with a water-cement ratio of 1:1 to 0.5:1, and after the grout sets, the sealing element forms a high-strength sealing ring that can withstand a grouting pressure of not less than 10 MPa within 12 hours.

[0033] In a preferred embodiment of the present invention, the sealing element is a bag 8, which is made of industrial filter cloth and has a length of 3.5 to 4 meters. After expansion, the bag 8 can fit against the wall of the corresponding drill hole.

[0034] In a preferred embodiment of the present invention, the internal slurry circulation pipeline of the sealing element includes a slurry injection pipe 5, a slurry return pipe 6, and a slurry injection ball valve 7 connected to the movable end of the slurry injection pipe 5.

[0035] When grouting the seal, after the seal is fully filled with cement mortar, the return grout pipe of the seal is shielded for 20 minutes, and grouting is carried out after 4 hours of setting.

[0036] The two-sequence skip-hole process described in step four involves sequentially numbering the drilled holes, implementing the odd-numbered holes first, and then implementing the corresponding even-numbered holes after the adjacent odd-numbered holes have been completed. The dynamic matching control of grouting pressure and injection rate follows the following relationship: When the injection rate is greater than 200 L / min, the control pressure is less than 0.3 P; When the injection rate is 200 to 120 L / min, the control pressure is 0.3 P to 0.5 P; When the injection rate is 120 to 60 L / min, the control pressure is 0.5 P to 0.8 P; When the injection rate is less than 60 L / min, the control pressure is 0.8 P to 1.0 P; Where P is the design grouting pressure.

[0037] In step four, pure cement grout is used for grouting, with water-cement ratios of 2:1, 1:1, 0.7:1, and 0.5:1, gradually increasing from thin to thick. The grouting volume for each water-cement ratio level must meet the following requirements: ≥900L for a section length of 15m, ≥1200L for 20m, ≥1500L for 25m, and ≥1800L for 30m. The thickening level can be increased if there are no significant changes in pressure and flow rate. The water-cement ratio should not be changed if the grouting pressure remains constant while the injection rate continuously decreases, or if the injection rate remains constant while the pressure continuously increases. I. Project Overview This water-rich tunnel section is a medium to strong water-rich tunnel within the Qingfeng fault zone. The surrounding rock types are Class III (56%), Class IV (33%), and Class V (11%), with the main lithology being dolomite and siliceous dolomite. The predicted maximum water inflow is 1000~10000 m³ / h. The tunnel adopts an 8.5m×7.0m horseshoe-shaped cross-section with an average slope of 8.17%.

[0038] II. Construction Implementation like Figure 5 As shown. The long-distance high-pressure pre-grouting construction method for tunnels of the present invention was used in four tests, with specific parameters as follows: First test (K0+383~K0+463 tunnel section): Reinforcement length: 80m (D-type hole: 20m+30m+30m); Number of grouting holes: 7 holes, with the hole positions 1.0m inward from the edge arch excavation outline and 1.2m outward from the end point; Drilling parameters: the diameter of the pipe section at the borehole opening is 180mm, and the diameter of the remaining section is 110mm; the borehole opening is sealed with a galvanized bag, and grouting is performed after 4 hours of curing. Grouting parameters: The in-hole circulation method is adopted, and the PE grouting pipe is lowered to the bottom of the hole; the construction is carried out in two sequences of skip holes, with odd-numbered holes being constructed first; the grouting pressure is 5.36~10.53MPa, and the water-cement ratio of the grout is changed step by step from 2:1 to 1:1 to 0.7:1 to 0.5:1. Post-grouting quality inspection: After 12 hours of setting, a water pressure test was conducted. The permeability of the first section was 5.17 Lu, the permeability of the second section was 3.53 Lu, and the total seepage rate of the entire borehole section was 1.8 L / (min). m), meeting the qualification standards; Construction period: 30 days, cement consumption: 356.8954t.

[0039] Second test (K0+455.5~K0+495.5 tunnel section): Reinforcement length: 40m (B-type hole adjustment: 20m + 20m); Number of grouting holes: 10 holes, with the hole positions 1.2m inward from the edge arch excavation outline and 1.0m outward from the end point; Grouting pressure: 4.57~8.47MPa, other parameters are the same as in the first test; Post-grouting quality inspection: the permeability of the first section was 2.12 Lu, the permeability of the second section was 1.76 Lu, and the total seepage rate was 1.2 L / (min). m); Construction period: 8 days, cement consumption: 196.21t.

[0040] Third test (K0+490.1~K0+535.1 tunnel section): Reinforcement length: 45m (Type B hole: 20m + 25m); Number of grouting holes: 10 holes, with the hole positions 1.3m inward from the edge arch excavation outline and 1.5m outward from the end point; Grouting pressure: 4.52~8.56MPa, other parameters are the same as in the first test; Post-grouting quality inspection: the permeability of the first section is 0.26 Lu, the permeability of the second section is 0.97 Lu, and the total seepage rate of the entire borehole is 0.8 L / (min). m); Construction period: 7 days, cement consumption: 159.375t.

[0041] Fourth test (K0+671-K0+771 tunnel section): Reinforcement length: 100m (Type B hole: 20m+30m+50m); Number of grouting holes: 10 holes + 1 pilot hole (76m) + 2 advance exploration holes (2×50m), with the hole positions 1.3m inward from the edge arch excavation outline and 1.5m outward from the end point; Grouting pressure: 4.49-10.26 MPa, other parameters are the same as in the first test; Post-grouting quality inspection: the permeability of the first section is 1.82 Lu, the permeability of the second section is 1.01 Lu, and the total seepage of the entire borehole is 1.07 Lu; Construction period: 15 days, cement consumption: 381.51t.

[0042] Conventional advanced grouting: Reinforcement length: 30m Number of grouting holes: 63 Grouting pressure: 1.53~6.10MPa Construction period: 30 days; cement consumption: 210.708 tons III. Implementation Results All four tests met the qualification standards, the tunnel water output was significantly reduced (daily drainage from 3000 m³ / d to below 500 m³ / d), the surrounding rock stability was significantly improved, and the construction period was shortened by more than 60% compared with the conventional method. No construction risks such as grout leakage or borehole wall collapse occurred, which verified the feasibility and superiority of the method of the present invention.

Claims

1. A method for long-distance high-pressure pre-grouting construction in tunnels, characterized in that, Includes the following steps: Step 1: Formation of a stable rock mass. In front of the tunnel section to be grouted, the working face and the surrounding rock behind it are reinforced to form a stable rock mass structure with a length of not less than 5 meters. Step 2: Hole location optimization design. Based on the effective diffusion radius of the high-pressure grout, the grout hole locations are optimized along the tunnel excavation outline, so that the hole opening is located at the working face and shrinks inward towards the outline, while the bottom of the hole extends outward from the outline. Step 3: Segmented drilling and borehole sealing. Using graded borehole diameter drilling, the borehole openings are quickly and under high pressure using a grouting device for each grouting segment, and the total length of a single-cycle grouting is divided into multiple grouting segments. Step 4: High-pressure grouting construction, using in-hole circulation method or pure pressure grouting, implementing two-sequence skip-hole process, controlling grouting pressure in stages and dynamically matching grout injection rate, and changing the water-cement ratio of grout from thin to thick in multiple stages. Step 5: Post-grouting quality inspection. After the grouting is completed and has set, drill inspection holes to conduct a water pressure test. The preset permeability and seepage per unit length are used as the criteria for judging whether the reinforcement is qualified.

2. The method for long-distance high-pressure advance grouting construction in tunnels as described in claim 1, characterized in that: In step two, the inward contraction distance of the borehole opening is 1.0 to 1.3 meters, the outward expansion distance of the borehole bottom is 1.0 to 1.5 meters, and the effective diffusion radius of the grout is determined to be 3.5 meters based on the grouting pressure.

3. The method for long-distance high-pressure advance grouting construction in tunnels as described in claim 1, characterized in that: In step three, the orifice diameter of the graded orifice section is ≥180mm, the total length of a single-cycle grouting is 80 meters or 100 meters, and the length of each grouting segment is 20 to 40 meters.

4. The method for long-distance high-pressure advance grouting construction in tunnels as described in claim 1, characterized in that: The grouting device includes an in-hole grouting pipe (1), an in-hole return grouting pipe (2), an expandable seal, and a grout circulation pipeline inside the seal. The in-hole grouting pipe (1) and the in-hole return grouting pipe (2) are arranged in parallel. The seal is sleeved outside the orifice section of the in-hole grouting pipe (1) and the in-hole return grouting pipe (2). One end of the grout circulation pipeline inside the seal is connected to the seal, and the other end extends to the outside. The in-hole grouting pipe (1) and the in-hole return grouting pipe (2) are respectively connected to an in-hole grouting ball valve (3) and an in-hole return grouting ball valve (4) at the port of the in-hole grouting pipe (1) and the in-hole return grouting pipe (2) located outside the hole.

5. The method for long-distance high-pressure advance grouting construction in tunnels as described in claim 4, characterized in that: The grout injected into the seal is cement mortar with a water-cement ratio of 1:1 to 0.5:1, and after the grout sets, the seal forms a high-strength sealing ring that can withstand a grouting pressure of not less than 10 MPa within 12 hours.

6. The method for long-distance high-pressure advance grouting construction in tunnels as described in claim 5, characterized in that: The sealing element is a bag (8), which is made of industrial filter cloth. The bag (8) is 3.5 to 4 meters long and can fit into the corresponding borehole wall after expansion.

7. The method for long-distance high-pressure advance grouting construction in tunnels as described in claim 4, characterized in that: The internal slurry circulation pipeline of the seal includes a slurry injection pipe (5), a slurry return pipe (6), and a slurry injection ball valve (7) connected to the movable end of the slurry injection pipe (5).

8. The method for long-distance high-pressure advance grouting construction in tunnels as described in claim 4, characterized in that: When grouting the seal, after the seal is fully filled with cement mortar, the return grout pipe of the seal is shielded for 20 minutes, and grouting is carried out after 4 hours of setting.

9. The method for long-distance high-pressure advance grouting construction in tunnels as described in claim 1, characterized in that: The two-sequence skip-hole process described in step four involves sequentially numbering the drilled holes, implementing the odd-numbered holes first, and then implementing the corresponding even-numbered holes after the adjacent odd-numbered holes have been completed. The dynamic matching control of grouting pressure and injection rate follows the following relationship: When the injection rate is greater than 200 L / min, the control pressure is less than 0.3 P; When the injection rate is 200 to 120 L / min, the control pressure is 0.3 P to 0.5 P; When the injection rate is 120 to 60 L / min, the control pressure is 0.5 P to 0.8 P; When the injection rate is less than 60 L / min, the control pressure is 0.8 P to 1.0 P; Where P is the design grouting pressure.

10. The method for long-distance high-pressure advance grouting construction in tunnels as described in claim 1, characterized in that: In step four, pure cement grout is used for grouting, with water-cement ratios of 2:1, 1:1, 0.7:1, and 0.5:1, gradually increasing from thin to thick. The grouting volume for each water-cement ratio level meets the following requirements: ≥900L for a section length of 15m, ≥1200L for 20m, ≥1500L for 25m, and ≥1800L for 30m. The thickening level can be changed if there is no significant change in pressure and flow rate. The water-cement ratio is not changed if the grouting pressure remains constant while the injection rate continues to decrease, or if the injection rate remains constant while the pressure continues to increase.

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