A grouting process for breaking surrounding rock in a cross-passage tunnel

Abstract

The application discloses a kind of grouting processes of broken surrounding rock of passing through roadway, belong to grouting construction technical field, comprising the following steps: S1, determine the construction range of grouting roadway, the construction range is divided into passing through area and construction area, and safety distance is reserved between passing through area and construction area;S2, grouting hole is drilled to the top, side and side bottom of grouting roadway, the grouting hole in construction area adopts the way of combined grouting of shallow hole and deep hole, and the end of grouting hole in passing through area needs to keep a safe distance from the floor of upper roadway;S3, grouting is carried out to grouting hole;S4, the acceptance of grouting effect is carried out, and unqualified acceptance continues to be re-injected until acceptance is passed.The application provides a set of clear process, construction method of passing through roadway, which can effectively reduce the disturbance to the upper roadway, improve the grouting reinforcement effect, overcome the limitations of construction by experience, facilitate the management and technical application of grouting construction process.

Description

Technical Field

[0001] This invention relates to the field of grouting construction technology, and in particular to a grouting process for fractured surrounding rock in tunnels. Background Technology

[0002] In underground mine tunnel engineering, grouting is used to reinforce the surrounding rock of coal mine tunnels to prevent the infiltration of the upper aquifer into the tunnel or to strengthen the fractured surrounding rock inside the tunnel. This improves the strength and integrity of the fractured surrounding rock, enhances its mechanical properties, increases the stability of the fractured coal and rock mass during mining, controls deformation and damage of the surrounding rock, and avoids or reduces roof falls and spalling accidents caused by the fractured surrounding rock. Because rock fissures exist within the surrounding rock and are highly concealed, grouting construction is more difficult. Furthermore, factors such as grouting pressure, grouting volume, grouting time, grout diffusion radius, and grout hole layout parameters also affect the grouting effect to varying degrees. Currently, there is no mature and standardized grouting construction process for tunnels. On-site workers mostly rely on their own work experience, lacking scientific construction techniques, which hinders construction management and impedes the promotion of safe and efficient coal mine production.

[0003] Therefore, patent application number "202010234935.1", entitled "A Repair Process for Improving the Compressive Strength of the Loosening Zone of Surrounding Rock in Underground Coal Mine Roadways", discloses a grouting process for fractured surrounding rock in roadways. As a guiding process for roadway grouting, it includes the following steps: S1: Determine the location of the deformed roadway; S2: Perform bottoming, side widening, roof lifting, and re-supporting on the deformed roadway; S3: Divide the deformed roadway into several sections along its length, and drill a pair of grouting holes on both sides of the roadway, the roadway roof, and the roadway bottom of each section according to the arranged repair sequence. Each pair of grouting holes consists of one shallow grouting hole and one deep grouting hole; S4: The shallow grouting holes drilled in step 3 and... Insert a shallow grouting pipe and a deep grouting pipe into the deep grouting hole respectively. Seal the gap between the pipe walls of the shallow and deep grouting pipes and the corresponding shallow and deep grouting hole openings with anchoring agent. S5: Cover the area completed in step 4 with cement grout. S6: Inject clean water into the shallow and deep grouting pipes. Stop water injection when the pressure exceeds 6 MPa. S7: Prepare cement grout. S8: Inject the prepared cement grout into the shallow grouting pipe at a pressure of ≤1 MPa. Stop grouting when water or grout returns to the deep grouting pipe. After 8 hours, inject the prepared cement grout into the deep grouting pipe at a pressure of ≤4 MPa. End grouting when the grouting pressure is greater than 4 MPa. S9: Finally, seal the grouting pipes with cement grout. However, the grouting process described in the patent is only applicable to grouting of grouting roadways without overhead tunnels. In actual construction, as coal mines are mined, mine roadways are often crisscrossed in vertical space. Sometimes, there is more than one roadway above a roadway. When grouting is carried out in the roadway below, improper construction can easily disturb the roadway above, or even cause deformation or collapse. Therefore, there is an urgent need in the market for a mature and complete grouting construction process with a clear process for roadways with overhead tunnels. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned technical problems and provide a grouting process for fractured surrounding rock in tunnels. It mainly provides construction personnel with a clear and systematic construction method for tunnels, which can reduce the disturbance to the tunnel above the grouting tunnel while improving the grouting reinforcement effect of fractured surrounding rock in shaft engineering. It overcomes the limitations of relying on experience for construction and facilitates the management of the grouting construction process and the promotion and application of the technology.

[0005] To achieve the above objectives, the present invention provides the following solution: The present invention discloses a grouting process for fractured surrounding rock in a tunnel, comprising the following steps:

[0006] S1. Determine the construction scope of the grouting tunnel. Based on the passage position of the tunnel above the grouting tunnel, divide the construction scope into the passage area and the construction area. A safety distance is reserved between the passage area and the construction area. The safety distance is determined according to the grouting diffusion radius.

[0007] S2. Grouting holes are drilled at a preset spacing on the top, sides and bottom of the sides in the construction area and the tunnel area. The grouting holes in the construction area adopt a combination of shallow and deep hole grouting. When grouting, the shallow holes are injected first, followed by the deep holes. The ends of the grouting holes in the tunnel area must maintain a safe distance from the bottom plate of the upper tunnel. The safe distance is determined according to the layer spacing between the tunnel area and the upper tunnel.

[0008] S3. Grout the grouting hole;

[0009] S4. The grouting effect is inspected. If the inspection fails, the grouting is repeated until the inspection is passed.

[0010] Preferably, the safety distance is not less than 5m.

[0011] Preferably, in step S3, during grouting, the spacing and number of grouting holes are increased or decreased according to the development of surrounding rock fissures, the amount of grouting, and the leakage of grout within the construction area.

[0012] Preferably, in step S3, when injecting the shallow hole, first inject clean water for pressure testing, and then gradually increase the grout concentration. Each increase in grout concentration requires continuous grouting for 3-5 minutes. The grouting pressure of the shallow hole does not exceed 2 MPa, and the grouting pressure of the deep hole does not exceed 4 MPa.

[0013] Preferably, in step S2, the shallow holes and deep holes in the construction area are arranged alternately and at equal intervals, or the shallow holes and deep holes are arranged in equal rows and at equal intervals.

[0014] Preferably, in step S2, the grouting hole located at the top is adjusted to the shoulder position, and the opening angle is inclined upward at 70°-90°.

[0015] Preferably, the grouting holes of the sidewall are located at a height of 1.2m above the roadway floor, and the opening angle is inclined upward at 30°-60°.

[0016] Preferably, the grouting hole of the bottom of the sidewall is located 0.2-0.5mm above the bottom plate of the roadway, and is constructed at an angle of -60° to -75° downwards, with the shallow hole depth not less than 3m.

[0017] Preferably, in step S4, the water injection pressure test method is used for acceptance. Multiple sets of acceptance sections are set within the construction area, and each set of acceptance sections is equipped with no less than 3 acceptance holes. The acceptance holes are arranged at the top of the construction area and the tunnel area. The final pressure of the acceptance hole reaches 3MPa and can maintain the pressure stability for more than 2 minutes, which is considered as the grouting acceptance is qualified.

[0018] Preferably, in step S4, multiple sets of roadway cross displacement observation stations are arranged within the construction area to periodically measure the top subsidence and the mutual convergence of the two side walls in the construction area and the roadway area. If the top subsidence and the mutual convergence of the two side walls are within the allowable deformation range, the grouting is considered to be qualified.

[0019] The present invention achieves the following technical effects compared to the prior art:

[0020] 1. The present invention provides a grouting process for reinforcing fractured surrounding rock in roadways. It mainly provides construction personnel with a clear and systematic construction method for roadways, which can reduce disturbance to the roadway above the grouting roadway while improving the grouting reinforcement effect of fractured surrounding rock in shaft engineering. It overcomes the limitations of relying on experience for construction, facilitates the management of the grouting construction process and the promotion and application of the technology. By setting a safe distance between the grouting hole in the roadway area and the roadway above, and by setting a safe distance between the roadway area and the construction area, the disturbance to the roadway above the grouting roadway can be effectively reduced. At the same time, setting deep holes only in the construction area can prevent grout from seeping into the roadway above during grouting.

[0021] 2. The selection of the safety distance parameter in this invention is based on the grouting diffusion radius. Based on experience, the value is 3.5-5m. In order to minimize the disturbance to the roadway above, the maximum value of 5m is selected to minimize the disturbance to the roadway above. The same applies to selecting a safety distance of at least 5m.

[0022] 3. In this invention, when injecting the shallow hole, first inject clean water for pressure testing. The clean water pressure test can flush out small particles in the grouting pipe and surrounding rock fissures, open up the fissures, improve the grouting effect, and at the same time, directly observe the leakage on the roadway surface and take timely sealing measures.

[0023] 4. This invention also discloses two acceptance methods to make the process flow of this grouting process more complete, with a clear process and rules to follow, overcoming the limitations of construction based on experience. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the construction area for the alleyway.

[0026] Figure 2 This is a schematic diagram of the cross-section construction of the tunnel.

[0027] Figure 3 This diagram shows an alternating, equidistant arrangement of deep and shallow holes.

[0028] Figure 4 This is a diagram showing another arrangement of deep and shallow holes.

[0029] Explanation of reference numerals in the attached diagram: 1. Grouting tunnel; 2. First upper tunnel; 3. Second upper tunnel; 4. Third upper tunnel; 5. Grouting hole; 6. Shallow hole; 7. Deep hole. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] This embodiment provides a grouting process for fractured surrounding rock in a tunnel, such as... Figures 1 to 4 As shown, it includes the following steps:

[0032] S1. Determine the construction scope of grouting tunnel 1. Based on the passage position of the upper tunnel of grouting tunnel 1, divide the construction scope into the passage area and the construction area. A safety distance is reserved between the passage area and the construction area. The safety distance is determined according to the grouting diffusion radius. Preferably, the passage position of the upper tunnel and the layer spacing between grouting tunnel 1 and the upper tunnel can be marked on the side of the construction scope. A safety distance is reserved from the passage area to the extension direction of grouting tunnel 1. The construction scope outside the safety distance is the construction area.

[0033] S2. Grouting holes 5 are drilled at a preset spacing on the top, sides, and bottom of the sides in the construction area and the tunnel area. The grouting holes 5 in the construction area adopt a combined grouting method of shallow holes 6 and deep holes 7. When grouting, shallow holes 6 are injected first, followed by deep holes 7. Grouting shallow holes 6 first can form a sealing layer in the shallow part of the surrounding rock. When grouting deep holes 7 is performed, even if the grout in the deep part flows back to the shallow part, there will be no grout leakage, or the grout leakage will be within a controllable range. The end of the grouting hole 5 in the tunnel area must maintain a safe distance from the bottom plate of the roadway above. The safe distance is determined according to the layer spacing between the tunnel area and the roadway above (the vertical distance from the bottom plate of the roadway above to the top plate of the grouting tunnel 1).

[0034] S3. Grouting is performed on grouting holes 5 in the construction area and the tunnel area;

[0035] S4. Inspect the grouting effect within the construction area. If the inspection fails, continue grouting until the inspection is passed.

[0036] The following is based on an actual tunnel project:

[0037] like Figure 1 As shown, construction proceeds from east to west within grouting tunnel 1, as indicated by the arrow, with a total length of 162m. Three tunnels pass above the construction area of ​​grouting tunnel 1: the first upper tunnel 2, the second upper tunnel 3, and the third upper tunnel 4.

[0038] A set of deep holes 7 and a set of shallow holes 6 are arranged at the top, sidewall, and bottom of the sidewall of the grouting tunnel 1 within the construction area, such as... Figure 3 As shown. Based on the strata exposed during the excavation of grouting tunnel 1, the area within 15m above grouting tunnel 1 is sandstone, with some sections containing tunnel passages, faults, and geological boreholes. Shallow borehole 6 is designed with a depth of 3m to reinforce the fractured surrounding rock in the shallow part of the tunnel. After the grout solidifies, it will form a sealing layer in the shallow part of the tunnel to prevent grout leakage during deep borehole grouting. Deep borehole 7 has a depth of 10-15m, and the end of deep borehole 7 is rooted in the sandstone layer.

[0039] Furthermore, in this embodiment, as Figures 1 to 4 As shown, the safety distance is not less than 5m. The selection of the "not less than 5m" safety distance parameter depends on the grouting diffusion radius, and is empirically taken as 3.5-5m. To minimize disturbance to the roadway above, this embodiment selects the maximum value of 5m. However, due to different geological conditions of the surrounding rock in different mining areas, the grouting diffusion radius of the roadway needs to be calculated and measured when selecting the value. Therefore, the safety distance can also be adjusted according to the actual situation during actual construction and is not limited to the parameter of "not less than 5m". Similarly, the "not less than 5m" safety distance is not limited to this parameter.

[0040] The above-mentioned actual tunnel engineering is still used as a reference:

[0041] like Figure 1 As shown, the layer spacing between the first upper roadway 2 and the grouting roadway 1 is 9.6m. To prevent grout from being injected into the first upper roadway 2 during grouting in the roadway area, the drilling depth of the shallow hole 6 can be adjusted to 4m, maintaining a safe distance of 5.6m from the bottom plate of the first upper roadway 2.

[0042] Furthermore, in this embodiment, as Figures 1 to 4 As shown, in step S3, during grouting, the spacing and number of grouting holes 5 are increased or decreased according to the development of surrounding rock fissures, the amount of grouting, and the leakage of grout within the construction area.

[0043] Based on the above-mentioned actual tunnel engineering:

[0044] Grouting holes 5 are arranged at a spacing of 10-15m. If the grout intake of two adjacent rows of grouting holes 5 is large or the grout leakage on the roadway surface is serious, a new hole is opened in the middle position of the two rows of grouting holes 5 for grouting. At the same time, additional grouting holes 5 can be added in the grouting section. If the grout intake is small, no hole is opened in the middle position, but shallow hole 6 grouting is required for auxiliary grouting.

[0045] Furthermore, in this embodiment, as Figures 1 to 4 As shown, in step S3, when injecting grout into shallow hole 6, first inject clean water for pressure testing, and then gradually increase the grout concentration. Each increase in grout concentration requires continuous grouting for 3-5 minutes. The grouting pressure of shallow hole 6 should not exceed 2 MPa, and the grouting pressure of deep hole 7 should not exceed 4 MPa. Water pressure testing can flush out small particles in the grouting pipe and surrounding rock fissures, opening up the fissures and improving the grouting effect. It also allows for direct observation of surface leakage in the tunnel, enabling timely sealing measures. Generally, if the sealing effect of shallow hole 6 is good, the leakage in deep hole 7 will decrease even if clean water is injected. Therefore, this embodiment does not perform water pressure testing on deep hole 7. However, in actual engineering, deep hole 7 can also be tested with clean water, which does not mean that deep hole 7 cannot be tested with clean water.

[0046] Furthermore, in this embodiment, as Figures 1 to 4 As shown, when injecting shallow holes 6, cement grout is preferred. In areas with severe grout leakage, it is necessary to switch to "cement + water glass" two-component grouting in a timely manner. Other chemical grouts can also be selected.

[0047] ① The following construction process can be adopted for two-component grouting: Two grouting machines are used, one to draw cement grout (1#) and the other to draw water glass (2#). To control the mixing ratio, the two suction ports of grouting machine 1# simultaneously draw grout, and all the grout enters the grouting pipe; the two suction ports of grouting machine 2# draw water glass diluent and clean water respectively, with the water glass entering the grouting pipe and the clean water being discharged. The cement grout is mixed at a water-cement ratio of 1.2:1, and the water glass is diluted (water:water glass = 1:1). The two grouting machines are adjusted to operate at a frequency of 8 times for grouting machine 1# and 1 time for grouting machine 2#. The water glass diluent and cement grout are respectively connected to the tee of the anchor pipe head through a φ25mm high-pressure hose and mixed and injected into the anchor pipe.

[0048] ② The following switching methods can be used when switching between two-component slurry and single-component slurry:

[0049] When single-component grout leakage is significant and the grouting effect is poor, switch to double-component grouting. In this case, do not stop the cement grouting machine; directly start the water glass grouting machine to begin double-component grouting. After the double-component grouting is pressurized, when preparing to switch to single-component grouting, do not stop the cement grouting machine. Directly stop the water glass grouting machine or place the suction port in clean water. Then, inject cement grout for at least 2-3 minutes before stopping the machine to address grout leakage and prevent the grouting holes from becoming clogged. After stopping the machine, clean the holes with water.

[0050] ③ Grouting materials and technical requirements:

[0051] Grouting pipes: Made of seamless steel pipes with a diameter of Ф20mm and a wall thickness of 2.5mm, with lengths of L=1000mm, L=2000mm, and L=3000mm used in combination. Both ends are threaded with M20 threads, and the grouting pipes are connected using matching clamps. Anchor pipes use 60mm long M20 threads to connect with other rods. Care must be taken to protect the rod threads during the driving, transportation, installation, and use of the anchor pipes. Of course, the above is only a preferred method and does not mean that this is the only option.

[0052] Grouting cement and mix proportions: Single-component cement grout is used, with PO42.5 cement selected, and water-cement ratios of 0.7:1 and 1:1. When the water-cement ratio is 1:1, the mixing tank volume is 0.28 m³. 3 When the bucket is full: 215L of water and 4.3 bags of cement; when the bucket is 2 / 3 full: 150L of water and 3 bags of cement; when the water-cement ratio is 0.7:1, the mixing bucket volume is 0.28m³. 3 When the bucket is full: 180L of water and 5.3 bags of cement; when the bucket is 2 / 3 full: 120L of water and 3.5 bags of cement. Of course, the above is only a preferred method and does not mean that this is the only option. When using two-component grouting, the ratio of cement grout to water glass diluent is 8:1. The water glass diluent is mixed at a ratio of water to water glass of 1:1. The volume of the container is 0.224m³. 3 The tank contains 100L of water and 100L of water glass. Of course, the above is just a preferred method and does not mean that this is the only option.

[0053] In this embodiment, as Figures 1 to 4 As shown, in step S2, the shallow holes 6 and deep holes 7 in the construction area can be arranged alternately and at equal intervals, or the shallow holes and deep holes can be arranged in equal rows and at equal intervals.

[0054] staggered and equidistant arrangement, such as Figure 3 As shown, shallow holes 6 are arranged in one row, and deep holes 7 are arranged in another row, with the positions of the shallow holes 6 and deep holes 7 differing by a grouting row spacing. Equal rows and equal spacing mean that the shallow holes 6 and deep holes 7 are in the same position. This is achieved by first drilling the larger diameter shallow holes 6, and then drilling the smaller diameter deep holes 7 inside the shallow holes 6. Of course, there is another method in practice, such as... Figure 4 As shown, shallow hole 6 is arranged near deep hole 7, generally within a range of 10cm. First, shallow hole 6 is drilled, and then deep hole 7 is re-drilled within a range of 10cm.

[0055] In this embodiment, as Figures 1 to 4As shown, in step S2, if the top of the roadway is not convenient for grouting due to on-site construction conditions, the grouting holes 5 originally located at the top (the construction area is the shallow holes 6 and deep holes 7, and the area passing through the roadway is the grouting hole 5) can be adjusted to the shoulder socket position, and the opening angle is constructed obliquely upward at 70°-90°. It is necessary to ensure that the position of the end hole falls within the fracture development zone at the top of the roadway.

[0056] Further, in this embodiment, as Figures 1 to 4 shown, the arrangement position of the grouting holes 5 on the rib (the construction area is the shallow holes 6 and deep holes 7, and the area passing through the roadway is the grouting hole 5) is more than 1.2 m above the floor of the roadway. This height is convenient for workers to construct. The opening angle is constructed obliquely upward at 30°-60°, and preferably at 45° obliquely upward.

[0057] Further, in this embodiment, as Figures 1 to 4 shown, the position of the grouting holes 5 at the bottom of the rib (the construction area is the shallow holes 6 and deep holes 7, and the area passing through the roadway is the grouting hole 5) is more than 0.2-0.5 mm above the floor of the roadway, and is constructed obliquely downward at -60° to -75°. The depth of the shallow holes 6 (the area passing through the roadway is the grouting hole 5) is not less than 3 m.

[0058] In this embodiment, as Figures 1 to 4 shown, in step S4, the water injection pressure test method is used for acceptance. Multiple groups of acceptance sections are set within the construction range. Each group of acceptance sections has no less than 3 acceptance holes. The acceptance holes are arranged at the top of the construction area and the area passing through the roadway. When the final pressure of the acceptance holes reaches 3 MPa and the pressure can be maintained stably for more than 2 min, it is considered that the grouting acceptance is qualified.

[0059] Specifically, taking the above actual roadway project as a reference:

[0060] Using the water injection pressure test method, each 20 meters is a group of acceptance sections. The acceptance sections are preferably set in the middle of two rows of grouting holes 1 to check the slurry diffusion reinforcement effect. Each group of acceptance sections has no less than 3 acceptance holes, and 1 is arranged at the top of the roadway and on each side of the two ribs. When injecting clear water, when the final pressure of the acceptance holes reaches 3.0 MPa, stop the machine and close the ball valve on the grouting pipe. If the pressure does not decrease significantly and there is no water seepage around the roadway, and the stable time is more than 2 min, it is considered a qualified product.

[0061] In this embodiment, as Figures 1 to 4 shown, in step S4, another acceptance method is used for acceptance. Multiple groups of roadway cross displacement observation stations are arranged within the construction range. The top subsidence amount and the mutual approach amount of the two side ribs in the construction area and the area passing through the roadway are measured regularly. When the top subsidence amount and the mutual approach amount of the two side ribs are within the allowable deformation range, it is considered that the grouting acceptance is qualified. It should be noted that the "allowable deformation range" here is generally set according to engineering experience and can be set to not exceed 5%-10% of the roadway deformation amount.

[0062] In this embodiment, a method for treating grout leakage is also provided:

[0063] ① Before grouting, the cracks on the surface of the tunnel should be excavated and re-sprayed in a targeted manner;

[0064] ② Implement staggered grouting, increase the spacing between grouting rows, and only after each row of grouting is completed can the required grouting holes for the next row be drilled to prevent cross-grouting caused by drilling holes in advance;

[0065] ③Increase the grout concentration and perform intermittent grouting;

[0066] ④ For areas where grout is leaking, depending on the specific situation, use cotton yarn to plug the cracks, or use cement with added quick-setting agent to seal them. Use yellow mud to seal the areas in some places. If there is a large area of ​​grout leakage, excavate and repair the area. After curing and solidification, and after it has a certain strength, drill holes nearby and inject grout.

[0067] In this embodiment, a safety technical measure for grouting in the tunnel section is also provided:

[0068] ① The depth of grouting hole 5 in the tunnel area is specified as follows: the end of grouting hole 5 shall maintain a safe distance of not less than 5m from the bottom plate of the tunnel above.

[0069] ② During the grouting process, the grouting personnel should inspect the overhead tunnel and stop the machine immediately if any grout leakage is found.

[0070] ③ If the pressure suddenly decreases during grouting, stop the machine immediately and have the grouting personnel enter the upper tunnel section to check for grout leakage.

[0071] ④ During grouting, it is strictly forbidden to grout under excessive pressure.

[0072] ⑤ Before grouting, clearly mark the passing points and layer spacing parameters in this roadway.

[0073] ⑥ When the grouting volume of a single hole exceeds 100 bags, stop grouting for one shift and wait for the cement grout to solidify before continuing grouting.

[0074] In this embodiment, as Figures 1 to 4 As shown, a grouting construction process is also provided:

[0075] ① Grouting process: Single-component cement undergoes secondary mixing → grouting pump → control valve → orifice pipe → rock fissure.

[0076] ② Grouting system preparation: Install and position the grouting pump, mixing drum, clean water tank, grout tank, and all connecting pipes, valves, and equipment to form the grouting system.

[0077] ③ Grouting fluid preparation: Grouting fluid is prepared on site using a grout mixing tank. Cement is first coarsely screened to remove impurities, and then put into the mixing container, mixed evenly, and grouting begins.

[0078] ④ Pressure test before initial grouting: Use clean water for pressure testing. The test pressure must be greater than 1.5 times the maximum grouting pressure and the duration must not be less than 15 minutes to check the connectivity and pressure resistance of the grouting pipeline system. Any problems found should be dealt with in a timely manner.

[0079] ⑤ Before each grouting of a new hole, the roadway should be injected with clean water at low pressure to flush and clear the cracks in the loose zone of the roadway, so as to ensure the grouting effect in the later stage.

[0080] ⑥ When grouting, first use thin grout to grout shallow hole 6. The final grouting pressure of shallow hole 6 should be controlled within 1.0MPa. The low-pressure grouting of shallow hole 6 should be repeatedly injected. Stop the shallow hole grouting when the long pipe returns water and grout. After one shift, carry out high-pressure grouting of deep hole 7. When grouting deep hole 7, the pressure should be gradually increased. The final grouting pressure is 4MPa.

[0081] ⑦ Pressure adjustment: The pressure adjustment should be closely coordinated with the conditions inside the hole and the grout concentration. Once the grout concentration is determined, the pump flow rate should be manually controlled to bring the grouting working pressure to the final pressure.

[0082] ⑧ Grout adjustment: If the pressure and grouting volume remain stable in the rock fissures and during the filling stage, the grout concentration should be increased step by step. If the pressure rises rapidly and the grouting volume decreases rapidly, the grout concentration should be decreased step by step. Each change in grout concentration should last for 3-5 minutes.

[0083] ⑨ For initial grouting, slowly open the air supply valve of the grouting pump in ascending order of pressure. During grouting, pay close attention to the pressure gauge readings. When the pressure gauge reaches the design value and stabilizes for 5 minutes, first shut off the grouting pump, then close the orifice valve at the grouting pipe. Next, open the pressure relief valve below the pressure gauge to release pressure, allowing any remaining grout in the pipeline to flow back into the storage tank. Then, remove the U-pin and disconnect the grouting pipeline. The orifice valve should only be disassembled after the grout in the grouting pipe has initially set.

[0084] The grouting construction technical requirements provided in this embodiment are as follows:

[0085] ① The main body of the grouting pipe is made of steel pipe with threaded ends, and the grouting pipes are mechanically connected by clamps (connecting sleeves).

[0086] ② Grouting pipe: The grouting pipe should be exposed 50-100mm, with a depth tolerance of ±100mm and an angle ≥75°. The threaded portion of the grouting pipe should be covered with a special protective cover, and the hole should be sealed with resin anchoring agent. To prevent the anchor bolt from slipping due to a large tilt angle at the top anchor bolt hole, after inserting the grouting pipe, it can be connected to nearby support anchor bolts (mesh) or permanent pipelines using #12 iron wire for secondary protection.

[0087] ③ During dual-liquid grouting, grout adjustment: If the pressure and grouting volume remain stable in the rock fissures and during the filling stage, the grout concentration should be increased step by step. If the pressure rises rapidly and the grouting volume decreases quickly, the grout concentration should be decreased sequentially. Each change in grout concentration should last for 2 minutes.

[0088] ④ During dual-liquid grouting, the initial grouting should be carried out by slowly opening the valve of the grouting pump in order from small to large. During the grouting process, pay attention to the changes in the pressure gauge. The pressure should be gradually increased. When the stabilization time reaches 5 minutes, first turn off the grouting pump, then close the orifice valve at the grouting pipe, and then open the pressure relief valve to release the pressure.

[0089] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A grouting process for fractured surrounding rock in a tunnel, characterized in that, Includes the following steps: S1. Determine the construction scope of the grouting tunnel. Based on the passage position of the tunnel above the grouting tunnel, divide the construction scope into a passage area and a construction area. A safety distance is reserved between the passage area and the construction area. The safety distance is determined according to the grouting diffusion radius and is reserved from the passage area to the extension direction of the grouting tunnel. S2. Grouting holes are drilled at a preset spacing on the top, sides and bottom of the sides in the construction area and the tunnel area. The grouting holes in the construction area adopt a combination of shallow and deep hole grouting. When grouting, the shallow holes are injected first, followed by the deep holes. The ends of the grouting holes in the tunnel area must maintain a safe distance from the bottom plate of the upper tunnel. The safe distance is determined according to the layer spacing between the tunnel area and the upper tunnel. The grouting holes located at the top are adjusted to the shoulder recess position, with the opening angle inclined upwards at 70°-90°; the grouting holes on the sidewall are located at a position above 1.2m above the roadway floor, with the opening angle inclined upwards at 30°-60°; the grouting holes at the bottom of the sidewall are located at a position above 0.2mm above the roadway floor, with the opening angle inclined downwards at -60° to -75°; shallow holes and deep holes are arranged alternately and equidistantly within the construction area, or shallow holes and deep holes are arranged in equal rows and equidistantly. S3. Grout the grouting holes. When grouting shallow holes, use cement grout. In areas with serious grout leakage, switch to cement + water glass dual-liquid grouting in time. S4. Accept the grouting effect. If the acceptance is not satisfactory, continue grouting until the acceptance is satisfactory.

2. The grouting process for fractured surrounding rock in a tunnel according to claim 1, characterized in that, The safety distance is not less than 5m.

3. The grouting process for fractured surrounding rock in a tunnel according to claim 2, characterized in that, In step S3, during grouting, the spacing and number of grouting holes are increased or decreased according to the development of surrounding rock fissures, the amount of grouting, and the leakage of grout within the construction area.

4. The grouting process for fractured surrounding rock in a tunnel according to claim 3, characterized in that, In step S3, when injecting the shallow hole, first inject clean water for pressure testing, and then gradually increase the grout concentration. Each time the grout concentration is increased, grouting should continue for 3-5 minutes. The grouting pressure of the shallow hole should not exceed 2 MPa, and the grouting pressure of the deep hole should not exceed 4 MPa.

5. The grouting process for fractured surrounding rock in a tunnel according to claim 1, characterized in that, The depth of the shallow hole is not less than 3m.

6. The grouting process for fractured surrounding rock in a tunnel according to claim 1, characterized in that, In step S4, the water injection pressure test method is used for acceptance. Multiple sets of acceptance sections are set within the construction area, and each set of acceptance sections has no less than 3 acceptance holes. The acceptance holes are arranged at the top of the construction area and the tunnel area. The final pressure of the acceptance hole reaches 3MPa and can maintain the pressure stability for more than 2 minutes, which is considered as the grouting acceptance is qualified.

7. The grouting process for fractured surrounding rock in a tunnel according to claim 1, characterized in that, In step S4, multiple sets of roadway cross displacement observation stations are set up within the construction area to periodically measure the top subsidence and the mutual convergence of the two side walls in the construction area and the roadway area. If the top subsidence and the mutual convergence of the two side walls are within the allowable deformation range, the grouting is considered to be qualified.

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