Drilling directional grouting method and advance grouting excavation method for small cross-section tunnels

Abstract

This invention discloses a borehole directional grouting method, a method for advanced grouting excavation of small-section tunnels, and an advanced support structure for small-section tunnels, relating to the field of tunnel engineering. It solves the problem that existing directional grouting methods cannot effectively control the direction of grout diffusion. The technical solution adopted in this invention is as follows: For the borehole directional grouting method, after drilling is completed, a grouting pipe is inserted into the borehole. The area between the outer wall of the grouting pipe and the borehole wall is divided into a first grouting zone and a second grouting zone. Mortar is injected into the first grouting zone, and then grout is injected into the second grouting zone through the grouting pipe, achieving directional grouting. For the advanced grouting excavation method for small-section tunnels, steel supports are installed near the tunnel face. Borehole positions are marked outside the arching line and along the arching line direction, and boreholes are drilled. Support is provided according to the above-described borehole directional grouting method to form an arched consolidated shell. Then, the tunnel is excavated, slag removed, and supported. This invention is used for directional grouting of boreholes and the construction of small-section tunnels.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering, specifically to a borehole directional grouting method, a method for advanced grouting excavation of small-section tunnels, and an advanced support structure for small-section tunnels. Background Technology

[0002] Currently, the excavation and construction of small-section tunnels in weak and fractured sections with groundwater mainly adopts the advanced small-pipe grouting method. By grouting through advanced small pipes, the rock and soil mass after advanced drainage is pre-consolidated, forming an arched shell above the excavation section, which enhances the ability to resist the load at the top of the tunnel.

[0003] Conventional advanced small-diameter pipe grouting method has shortcomings. In weak and fractured tunnel sections with groundwater, there are many pores in the rock and soil. When grouting with small pipes, the grout can more easily penetrate downward into the rock and soil within the excavation area, causing the rock and soil within the excavation area to consolidate and harden. However, the actual amount of grout injected into the rock and soil outside the excavation area is insufficient, which not only wastes grout but also increases the excavation difficulty and construction risk.

[0004] Patent CN 112538850 A discloses a device and method for pre-grouting of underground utility tunnels to protect trees. This method solves the problem of protecting trees during the construction of underground utility tunnels through directional grouting. The device includes a directional grouting pipe with a grouting directional plate on it. The directional grouting plate is located on the longitudinal outer wall of one side of the grouting pipe. A grout outlet is located on the grouting pipe inside the directional grouting plate. The width of the directional grouting plate is greater than or equal to the diameter of the grouting pipe, and the length of the directional grouting plate is greater than or equal to the designed length that restricts the diffusion of grout from the outlet to the structure on one side of the grouting pipe. Directional grouting pipes use grouting directional plates to block the diffusion direction of grouting fluid. However, since there are unavoidable gaps between the borehole wall and the grouting directional plate, as well as gaps in the rock and soil of the borehole wall, and since grouting is completed in one go, the grouting directional plate has a very weak blocking effect on the diffusion of grouting fluid. It can only block the upward diffusion of grouting fluid when the grouting pressure is low enough, and cannot be used to block the downward diffusion of grouting fluid. Summary of the Invention

[0005] This invention first provides a borehole directional grouting method, which solves the problem that existing directional grouting methods cannot effectively control the direction of grout diffusion.

[0006] The technical solution adopted in this invention is: a borehole directional grouting method, comprising the following steps:

[0007] S1. After drilling is completed, the grouting pipe is inserted into the borehole, with the front end of the grouting pipe inserted to the bottom of the borehole or deeper than the bottom of the borehole. The two sides of the borehole are the control grouting side and the directional grouting side, respectively. On the cross-section perpendicular to the drilling direction, the outer wall of the grouting pipe has at least two contact points or contact arcs with the borehole wall. The area between the outer wall of the grouting pipe and the borehole wall is divided into at least two small areas. The small area on the control grouting side of the borehole is the first grouting area, and the small area on the directional grouting side of the borehole is the second grouting area. The inner cavity of the grouting pipe is separated from the first grouting area by a solid pipe wall. Grouting holes are provided in the pipe wall between the inner cavity of the grouting pipe and the second grouting area. A grout stop section is provided at the rear end of the grouting pipe.

[0008] To facilitate the insertion of the grouting pipe into the borehole, the front end of the grouting pipe is further shaped into a pointed cone and inserted into the rock and soil at the bottom of the borehole.

[0009] To facilitate the processing of the grouting pipe and to improve its strength, the grouting pipe is further designed as a concave steel pipe with at least two arc-shaped grooves protruding towards the center line of the grouting pipe on its wall. These arc-shaped grooves are arranged along the length of the grouting pipe.

[0010] Specifically: The grouting pipe has three arc-shaped grooves evenly arranged on its wall, protruding towards the center line of the grouting pipe. The area between the outer wall of the grouting pipe and the borehole wall is divided into three small areas of the same shape. One of these small areas is the first grouting area, and the other two are the second grouting areas.

[0011] Grouting pipes are typically inserted into boreholes by driving or jacking. To prevent damage to the rear end of the grouting pipe and to facilitate grouting, a stiffening hoop is installed at the rear end of the grouting pipe.

[0012] Specifically: the diameter of the grouting hole in the grouting pipe is... The grouting holes are spaced 10cm apart and arranged in a quincunx pattern. The length of the grout-stopping section of the grouting pipe is not less than 30cm, and the rear end of the grouting pipe is welded. The stiffening hoop.

[0013] S2. Prepare the mortar and inject it into the first grouting area. After the mortar is injected, seal the opening of the first grouting area. To further accelerate the setting speed of the mortar, a quick-setting agent is added when preparing the mortar.

[0014] S3. Prepare the grout and inject it into the second grouting zone through the grouting pipe. To ensure the quality of grouting, the second grouting zone is further cleaned before grouting.

[0015] The beneficial effects of the directional grouting method of the present invention are as follows: After the grouting pipe is inserted into the borehole, the grouting pipe divides the borehole into a first grouting zone and a second grouting zone. First, mortar is injected into the first grouting zone to seal the pores and fissures of the rock and soil on the grouting side. Then, grout is injected into the second grouting zone through the grouting pipe. Since the fissures and fissures of the rock and soil on the grouting side have been sealed, most of the grout can only diffuse into the rock and soil on the directional grouting side, thereby effectively realizing directional grouting.

[0016] This invention also provides a method for advanced grouting excavation of small-section tunnels, solving the problem that existing advanced small-diameter pipe grouting methods cause consolidation and hardening of the soil and rock within the excavation area, which wastes grout and increases excavation difficulty and construction risk. The technical solution adopted is: a method for advanced grouting excavation of small-section tunnels, including the following steps:

[0017] A. Near the working face, first remove the loose slag at the bottom, install steel supports, and carry out the support construction of the steel supports.

[0018] B. Draw the excavation outline on the tunnel face, mark the drilling positions outside the arching line and along the direction of the arching line, and drill holes in an upward direction. For example, the spacing between adjacent holes should be 20-40 cm, and the elevation angle of each hole should not exceed 5°.

[0019] C. Following step S1 of the above-mentioned directional grouting method, insert grouting pipes into each borehole. The first grouting zone of the grouting pipe is located on the side closer to the tunnel that needs to be excavated, and the second grouting zone of the grouting pipe is located on the side farther away from the tunnel that needs to be excavated. The rear end of the grouting pipe is fixedly connected to the steel support.

[0020] D. Following step S2 of the above-mentioned borehole directional grouting method, mortar is injected into the first grouting zone of each borehole.

[0021] E. Following step S3 of the above-described borehole directional grouting method, grout is injected into the second grouting zone of each borehole to form an arched consolidation shell.

[0022] F. Excavation, muck removal, and support of the tunnel.

[0023] This invention also provides a pre-support structure for small-section tunnels, which is a structure constructed according to steps A to E of the aforementioned pre-grouting excavation method for small-section tunnels. In this pre-support structure, steel supports are installed near the tunnel face. Holes are spaced along the outer side of the tunnel's arching line. The side of the hole closest to the tunnel to be excavated is the control grouting side, and the side facing away from the tunnel to be excavated is the directional grouting side. The centerline of the hole is angled upwards. A grouting pipe is inserted into the hole, with its front end located at the bottom of the hole or deeper. The rear end of the grouting pipe is fixedly connected to the steel supports, and a grout-stop section is provided at the rear of the grouting pipe. In a cross-section perpendicular to the drilling direction, the outer wall of the grouting pipe has at least two contact points with the hole wall. The area between the outer wall of the grouting pipe and the borehole wall is divided into at least two small areas. The small area on the control grouting side of the borehole is the first grouting area, and the small area on the directional grouting side of the borehole is the second grouting area. The inner cavity of the grouting pipe is separated from the first grouting area by a solid pipe wall, and grouting holes are provided in the pipe wall between the inner cavity of the grouting pipe and the second grouting area. The first grouting area of ​​the borehole contains grout, and the second grouting area of ​​the borehole and the inner cavity of the grouting pipe contain slurry. The solidified and hardened grout, slurry, and the surrounding soil and rock mass, together with the grouting pipe, form an integral arched solidified shell.

[0024] To facilitate the insertion of the grouting pipe into the borehole, the front end of the grouting pipe is further designed to be conical, and the front end of the grouting pipe is located in the rock and soil at the bottom of the borehole.

[0025] Specifically: On the cross-section of the grouting pipe, the outer contour of the grouting pipe can be polygonal, with all vertices of the polygon in contact with the borehole wall. Alternatively, on the cross-section of the grouting pipe, the outer contour of the grouting pipe can be spindle-shaped, or it can be rectangular in the middle with the opposite sides of the rectangle forming a minor arc.

[0026] To facilitate the processing of the grouting pipe and to improve its strength, the grouting pipe is further designed as a concave steel pipe with at least two arc-shaped grooves protruding towards the center line of the grouting pipe on its wall. These arc-shaped grooves are arranged along the length of the grouting pipe.

[0027] Specifically: The grouting pipe has three arc-shaped grooves evenly arranged on its wall, protruding towards the center line of the grouting pipe. The area between the outer wall of the grouting pipe and the borehole wall is divided into three small areas of the same shape. One of these small areas is the first grouting area, and the other two are the second grouting areas.

[0028] Grouting pipes are typically inserted into boreholes by driving or jacking. To prevent damage to the rear end of the grouting pipe and to facilitate grouting, a stiffening hoop is installed at the rear end of the grouting pipe.

[0029] Specifically: the diameter of the grouting hole in the grouting pipe is... The grouting holes are spaced 10cm apart and arranged in a quincunx pattern. The length of the grout-stopping section of the grouting pipe is not less than 30cm, and the rear end of the grouting pipe is welded. The stiffening hoop.

[0030] Specifically: the spacing between adjacent boreholes is 30-40cm, and the borehole elevation angle is no more than 5°.

[0031] The beneficial effects of the pre-grouting excavation method and pre-support structure for small-section tunnels of this invention are as follows: By first injecting mortar into the first grouting zone on the control grouting side, the pores and fissures of the soil and rock near the tunnel are sealed. Subsequently, during grouting through small guide pipes, the grout diffuses as much as possible into the soil and rock outside the tunnel excavation area, saving grout volume and facilitating excavation. The consolidated and hardened mortar, grout, and the surrounding soil and rock, along with the grouting pipe, form an integral arched consolidated shell. This arched shell has high strength and provides stable support to the soil and rock above the tunnel during excavation, preventing collapse accidents and reducing safety risks during construction. The soil and rock below the arched shell requires little or no grouting or mortar, reducing excavation difficulty. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the small-section tunnel advance support structure of the present invention.

[0033] Figure 2 yes Figure 1 A magnified view of the highest borehole in the center.

[0034] Attached reference numerals: 1. Drill hole; 2. Grouting pipe; 3. First grouting zone; 4. Second grouting zone; 5. Steel support. Detailed Implementation

[0035] The invention will now be further described with reference to the accompanying drawings.

[0036] The first subject of this invention is a borehole directional grouting method. See also Figure 2 The borehole directional grouting method includes the following steps S1 to S3.

[0037] S1. After drilling hole 1 is completed, grouting pipe 2 is inserted into drilling hole 1, with the front end of grouting pipe 2 inserted to the bottom of drilling hole 1 or deeper than the bottom of the hole.

[0038] The two sides of borehole 1 are the control grouting side and the directional grouting side, respectively. The control grouting side is the side of borehole 1 that does not require or only requires a small amount of grouting, while the directional grouting side is the side of borehole 1 that requires grouting. The central angle corresponding to the control grouting side is generally equal to the central angle corresponding to the directional grouting side, but they may also be unequal. The sum of the two is 360°.

[0039] When inserting the grouting pipe 2 into borehole 1, attention should be paid to the orientation of the grouting pipe 2 relative to the control grouting side and the directional grouting side. See [link / reference] Figure 2 In a cross-section perpendicular to borehole 1, the outer wall of the grouting pipe 2 has at least two contact points with the borehole wall of borehole 1. These contact points are either contact points or contact arcs. The area between the outer wall of the grouting pipe 2 and the borehole wall of borehole 1 is divided into at least two smaller areas, the number of which matches the number of contact points. All smaller areas are divided into two categories: one category consists of smaller areas located on the control grouting side of borehole 1, which are all first grouting areas 3; the other category consists of smaller areas located on the directional grouting side of borehole 1, which are all second grouting areas 4. The inner cavity of the grouting pipe 2 is separated from the first grouting area 3 by a solid pipe wall; that is, the inner cavity of the grouting pipe 2 is not connected to the first grouting area 3. Grouting holes are provided in the pipe wall between the inner cavity of the grouting pipe 2 and the second grouting area 4, meaning the inner cavity of the grouting pipe 2 is connected to the second grouting area 4. The inner cavity of the grouting pipe 2 is used for grouting into the second grouting area 4; therefore, a grout-stopping section is provided at the rear of the grouting pipe 2. Grouting pipe 2 is generally made of steel pipe. For example, grouting pipe 2 is made of hot-rolled seamless steel pipe with a wall thickness of 3.5mm and an outer diameter of 42mm. The diameter of the grouting hole is... The grouting holes are spaced 10cm apart and arranged in a quincunx pattern. The length of the grout-stopping section of the grouting pipe 2 is not less than 30cm.

[0040] The grouting pipe 2 can be inserted into the borehole 1 by hammering, pressing, or jacking. To facilitate insertion, the front end of the grouting pipe 2 is tapered. The insertion of the front end of the grouting pipe 2 into the rock and soil at the bottom of the borehole 1 not only serves to separate the first grouting zone 3 and the second grouting zone 4, but also to fix the grouting pipe 2 and prevent it from slipping out of the borehole 1. To prevent damage to the rear end of the grouting pipe 2 during construction and to facilitate grouting, a stiffening hoop is installed at the rear end of the grouting pipe 2. For example, the rear end of the grouting pipe 2 is welded... The stiffening hoop.

[0041] The shape of the grouting pipe 2 is illustrated below. In the cross-section of the grouting pipe 2 and the borehole, the outer contour of the grouting pipe 2 can be a regular polygon, such as a triangle or quadrilateral, with the diameter of the circumcircle of the polygon matching the diameter of the borehole 1. Alternatively, in the cross-section of the grouting pipe 2 and the borehole, the outer contour of the grouting pipe 2 can also be an irregular shape, such as a spindle shape, or a shape with a rectangular center and opposite sides forming a minor arc.

[0042] See Figure 1 and 2To facilitate the processing of grouting pipe 2 and to improve its strength, grouting pipe 2 is a concave steel pipe. The pipe wall of grouting pipe 2 is provided with at least two arc-shaped grooves convex towards the center line of grouting pipe 2. These arc-shaped grooves are arranged along the length of grouting pipe 2; that is, on the cross-section of grouting pipe 2, the sidewalls and bottoms of the arc-shaped grooves are continuous arcs, convex towards the center of grouting pipe 2, and the center line of the arc-shaped grooves is parallel to the center line of grouting pipe 2. (See also...) Figure 1 and 2 The grouting pipe 2 has three evenly spaced arc-shaped grooves protruding towards its center line. The area between the outer wall of the grouting pipe 2 and the borehole wall of the borehole 1 is divided into three small areas of the same shape. One of these small areas is the first grouting area 3, and the other two are the second grouting areas 4. The two small areas corresponding to the second grouting area 4 can be isolated from each other, or a notch can be provided on the outer wall of the grouting pipe to connect the two small areas corresponding to the second grouting area 4.

[0043] S2. Prepare mortar and inject it into the first grouting zone 3. After the mortar is injected, seal the opening of the first grouting zone 3.

[0044] The mortar is used to seal the side of borehole 1 that requires little or no grouting; therefore, the mortar is a dense cement mortar. To accelerate the setting speed of the mortar, a quick-setting agent can be added during preparation. During mortar injection, the injection pipe should be inserted into the bottom of the hole first, and then slowly and evenly pulled out as the mortar is injected. The mortar should be thoroughly mixed and used immediately after mixing, and the mortar mix ratio should conform to the design. The mortar in the first grouting zone 3 should be dense and full. After the mortar injection is completed, the borehole opening in the first grouting zone 3 should be sealed with a sealing material to prevent mortar leakage.

[0045] If the first grouting zone 3 and the second grouting zone 4 are interconnected, the grout will enter the second grouting zone 4 during grouting, thus affecting the subsequent grouting step S3. Therefore, the grouting pipe 2 needs to completely separate the first grouting zone 3 and the second grouting zone 4. When there are two or more small areas corresponding to the first grouting zone 3, grout can be injected into each small area separately, and grout can be injected into the entire first grouting zone 3, thereby sealing the pores and fissures of the rock and soil on the grouting side of the borehole 1; or, the grouting pipe 2 can be provided with channels or gaps that connect the various small areas of the first grouting zone 3 but do not connect to the second grouting zone 4, so that the grout can flow between the small areas of the first grouting zone 3.

[0046] S3. Prepare the grout and inject it into the second grouting zone 4 through the grouting pipe 2. To ensure the quality of grouting, the second grouting zone 4 is cleaned before grouting. For example, high-pressure air is used to blow away the sand and gravel in the second grouting zone 4, and the hole opening and surrounding cracks are sealed with plastic materials such as hemp fiber or anchoring agent.

[0047] The second subject of this invention is a method for pre-grouting excavation of small-section tunnels. See also... Figure 1The method for pre-grouting excavation of small-section tunnels includes the following steps A to F.

[0048] A. Near the working face, first remove the loose slag at the bottom, install steel support 5 and carry out the support construction of steel support 5, where steel support 5 is a steel arch frame.

[0049] B. Draw the excavation outline on the tunnel face. Mark the drilling positions outside the arching line and along its direction, and drill holes. Drill hole 1 should be angled upwards. There can be one or two layers of drilling positions. The angles between each layer of drilling hole 1 and the longitudinal centerline of the tunnel can be equal or different. Drill hole 1 is located outside the tunnel excavation area and extends longitudinally into the tunnel. For example, using a Φ150mm drill bit, the spacing between adjacent drilling holes 1 is 20–40cm, and the elevation angle of drilling hole 1 should not exceed 5°. An elevation angle of drilling hole 1 not exceeding 5° means that the angle between drilling hole 1 and the horizontal plane should not exceed 5°. Drilling should be strictly carried out according to the determined drilling positions to ensure the accuracy of drilling hole 1's location. During drilling, observe the drill rod direction and insertion angle regularly. Adjustments should be made if significant deviations in direction or insertion angle are found.

[0050] C. Following step S1 of the above-described directional grouting method, insert grouting pipes 2 into each borehole 1. The first grouting zone 3 of the grouting pipe 2 is located on the side closer to the tunnel that needs to be excavated, and the second grouting zone 4 of the grouting pipe 2 is located on the side opposite to the tunnel that needs to be excavated. That is, the interface between the first grouting zone 3 and the second grouting zone 4 is perpendicular to the radial direction of the arching line, and the first grouting zone 3 is located on the side closer to the tunnel that needs to be excavated. After the grouting pipe 2 is inserted into the borehole 1, fix the rear end of the grouting pipe 2 to the steel support 5.

[0051] D. Following step S2 of the above-described directional grouting method, mortar is injected into the first grouting zone 3 of each borehole 1. The mortar seeps into the rock and soil body on the side of borehole 1 closest to the tunnel that needs to be excavated, and the first grouting zone 3 is completely filled with mortar.

[0052] E. Following step S3 of the above-mentioned borehole directional grouting method, grout is injected into the second grouting zone 4 of each borehole 1 to form an arched consolidation shell.

[0053] Grouting equipment with good performance and working pressure meeting grouting requirements should be selected, and on-site test runs should be conducted. The maximum pressure at the borehole opening during grouting should be strictly controlled within the allowable range. Even if grout from a single pipe can diffuse into the soil and rock mass within a radius of 0.5–1.0 m around borehole 1, the grouting pressure should generally be 0.5–1.0 MPa to avoid fracturing the excavation face. Care should be taken to control the grouting volume; grouting should be stopped when the specified injection volume is reached for each grouting pipe 2. Grouting should also be stopped if the borehole pressure has reached the specified pressure value but the injection volume is still insufficient.

[0054] F. Excavation, muck removal, and support of the tunnel.

[0055] After the grout has solidified and reached its predetermined strength, excavation of the soil and rock mass begins. Excavation should employ a "weak blasting, short advance" method, with mechanical excavation used when necessary. After excavation, muck removal is carried out. Following muck removal, anchor bolts are installed inside the tunnel, steel mesh is hung, and shotcrete is applied. The shotcrete thickness is generally 8-10 cm to form a protective layer. If, after multiple excavations, the reinforced area no longer meets the requirements for continued excavation, the above steps are repeated.

[0056] The third subject of this invention is a pre-support structure for small-section tunnels, which is a structure constructed according to steps A to E of the pre-grouting excavation method for small-section tunnels described in the second subject above. For example... Figure 1 As shown, in the pre-support structure of the small-section tunnel, steel supports 5 are installed near the tunnel face, and the steel supports 5 are steel arch frames. Drill holes 1 are spaced apart along the outer side of the tunnel's arching line. The side of drill hole 1 closest to the tunnel that needs excavation is the control grouting side, and the side of drill hole 1 opposite to the tunnel that needs excavation is the directional grouting side. The spacing between adjacent drill holes 1 is determined according to actual conditions, and is generally 30–40 cm. The centerline of drill hole 1 is angled upwards, and the elevation angle of drill hole 1 is generally no greater than 5°.

[0057] A grouting pipe 2 is inserted into borehole 1. The front end of the grouting pipe 2 is located at the bottom of borehole 1 or deeper than the bottom, ensuring that the first grouting zone 3 and the second grouting zone 4 separated by the grouting pipe 2 are not connected. The rear end of the grouting pipe 2 is fixedly connected to a steel support 5 to ensure the stability of the grouting pipe 2. The grouting pipe 2 is generally inserted into borehole 1 by driving or jacking. To facilitate the insertion of the grouting pipe 2 into borehole 1, the front end of the grouting pipe 2 is tapered and located in the rock and soil mass at the bottom of borehole 1. To prevent damage to the rear end of the grouting pipe 2 during construction and to facilitate grouting through the grouting pipe 2, a stiffening hoop is installed at the rear end of the grouting pipe 2. For example, the tail of the grouting pipe 2 is welded... The stiffening hoop.

[0058] The grouting pipe 2 serves two purposes: grouting and separation. In a cross-section perpendicular to the borehole 1, the outer wall of the grouting pipe 2 has at least two contact points or contact arcs with the borehole wall of the borehole 1. The area between the outer wall of the grouting pipe 2 and the borehole wall of the borehole 1 is divided into at least two smaller areas. The smaller area on the control grouting side of the borehole 1 is the first grouting area 3, and the smaller area on the directional grouting side of the borehole 1 is the second grouting area 4. To facilitate the processing and construction of the grouting pipe 2, the number of contact points and contact arcs between the outer wall of the grouting pipe 2 and the borehole wall of the borehole 1 should be minimized. For example, in the cross-section of the grouting pipe 2, the outer contour of the grouting pipe 2 is polygonal, with all vertices of the polygon contacting the borehole wall of the borehole 1. The polygon can be a triangle, quadrilateral, etc. For example, in the cross-section of the grouting pipe 2, the outer contour of the grouting pipe 2 is spindle-shaped, in which case the outer wall of the grouting pipe 2 has only two contact points with the borehole wall of the drill hole 1; or, the outer contour of the grouting pipe 2 is rectangular in the middle and the opposite sides of the rectangle are curved, in which case the outer wall of the grouting pipe 2 has only two contact arcs with the borehole wall of the drill hole 1. Furthermore, to facilitate the processing of the grouting pipe 2 and to improve its strength, the grouting pipe 2 can be a concave steel pipe, with at least two arc-shaped grooves convex towards the center line of the grouting pipe 2 on its wall. These arc-shaped grooves are arranged along the length of the grouting pipe 2, meaning that in the cross-section of the grouting pipe 2, the sidewalls and bottom of the arc-shaped grooves are continuous arcs, convex towards the center of the grouting pipe 2, and the center line of the arc-shaped grooves is parallel to the center line of the grouting pipe 2. See also Figure 1 and Figure 2 The grouting pipe 2 has three evenly spaced arc-shaped grooves protruding towards its centerline. The small area between the outer wall of the grouting pipe 2 and the borehole wall of the borehole 1 is divided into three identical small areas. One of these small areas is the first grouting area 3, and the other two are the second grouting areas 4. The two small areas corresponding to the second grouting area 4 can be isolated from each other, or a notch can be provided on the outer wall of the grouting pipe to connect the two small areas corresponding to the second grouting area 4.

[0059] The inner cavity of grouting pipe 2 and the first grouting zone 3 are separated by a solid pipe wall; that is, the inner cavity of grouting pipe 2 and the first grouting zone 3 are not connected. Grouting holes are provided in the pipe wall between the inner cavity of grouting pipe 2 and the second grouting zone 4. For example, the diameter of the grouting holes in grouting pipe 2 is... The grouting holes are spaced 10cm apart and arranged in a quincunx pattern. A grout-stop section is provided at the rear of the grouting pipe 2, for example, the length of the grout-stop section of the grouting pipe 2 is not less than 30cm.

[0060] For information on the shape of the single grouting pipe 2 and its relationship with the borehole 1, please refer to the relevant descriptions of steps S1 and S2 of the first topic of the borehole directional grouting method.

[0061] The first grouting zone 3 of borehole 1 contains injected mortar. The first grouting zone 3 is surrounded by the grouting pipe 2 and the borehole wall of borehole 1. The borehole wall corresponding to the first grouting zone 3 is rock and soil filled with mortar. The second grouting zone 4 of borehole 1 and the inner cavity of the grouting pipe 2 contain injected grout. The solidified and hardened mortar, grout, rock and soil surrounding borehole 1, and grouting pipe 2 together form an integral arched solidified shell.

Claims

1. A borehole directional grouting method, characterized in that: Includes the following steps: S1. After the drilling (1) is completed, the grouting pipe (2) is inserted into the drilling (1). The front end of the grouting pipe (2) is inserted to the bottom of the drilling (1) or deeper than the bottom of the hole. The two sides of the drilling (1) are the control grouting side and the directional grouting side, respectively. On the cross section perpendicular to the drilling (1), the outer wall of the grouting pipe (2) and the hole wall of the drilling (1) have at least two contact points or contact arcs. The area between the outer wall of the grouting pipe (2) and the hole wall of the drilling (1) is divided into at least two small areas. The small area on the control grouting side of the drilling (1) is the first grouting area (3), and the small area on the directional grouting side of the drilling (1) is the second grouting area (4). The inner cavity of the grouting pipe (2) and the first grouting area (3) are solid pipe walls. The pipe wall between the inner cavity of the grouting pipe (2) and the second grouting area (4) is provided with grouting holes. The rear section of the grouting pipe (2) is provided with a grout-stopping section. S2. Prepare mortar and inject mortar into the first grouting area (3). After the mortar is injected, seal the opening of the first grouting area (3). S3. Prepare the grout and inject it into the second grouting zone (4) through the grouting pipe (2).

2. The borehole directional grouting method as described in claim 1, characterized in that: In step S1, the front end of the grouting pipe (2) is cone-shaped and is inserted into the rock and soil body at the bottom of the borehole (1).

3. The borehole directional grouting method as described in claim 1, characterized in that: In step S1, the grouting pipe (2) is a concave steel pipe. The pipe wall of the grouting pipe (2) is provided with at least two arc-shaped grooves protruding towards the center line of the grouting pipe (2). The arc-shaped grooves are arranged along the length direction of the grouting pipe (2).

4. The borehole directional grouting method as described in claim 3, characterized in that: In step S1, three arc-shaped grooves protruding towards the center line of the grouting pipe (2) are evenly arranged on the pipe wall. The area between the outer wall of the grouting pipe (2) and the hole wall of the borehole (1) is divided into three small areas with the same shape. One of the small areas is the first grouting area (3), and the other two small areas are the second grouting area (4).

5. The borehole directional grouting method according to any one of claims 1 to 4, characterized in that: In step S1, a stiffening hoop is installed at the rear end of the grouting pipe (2).

6. The borehole directional grouting method as described in claim 5, characterized in that: In step S1, the diameter of the grouting hole of the grouting pipe (2) is φ8mm, the hole spacing of the grouting holes is 10cm and arranged in a plum blossom pattern, the length of the grout-stopping section of the grouting pipe (2) is not less than 30cm, and a φ6.5mm stiffening hoop is welded to the rear end of the grouting pipe (2).

7. The borehole directional grouting method according to any one of claims 1 to 4, characterized in that: In step S2, an accelerator is added when preparing the mortar.

8. The borehole directional grouting method according to any one of claims 1 to 4, characterized in that: In step S3, after cleaning the holes in the second grouting zone (4), grouting is then performed.

9. A method for pre-grouting excavation of small-section tunnels, comprising directional grouting using the borehole directional grouting method described in any one of claims 1 to 8, characterized in that, Includes the following steps: A. At the location near the working face, first remove the floating slag at the bottom, install steel support (5) and carry out the support construction of steel support (5); B. Draw the excavation outline on the tunnel face, mark the drilling positions outside the arching line and along the direction of the arching line, and drill holes in the direction of the drilling diagonally upward. C. Insert grouting pipes (2) into each borehole (1). The first grouting zone (3) of the grouting pipe (2) is located on the side close to the tunnel that needs to be excavated, and the second grouting zone (4) of the grouting pipe (2) is located on the side away from the tunnel that needs to be excavated. The rear end of the grouting pipe (2) is fixedly connected to the steel support (5). D. Grouting is injected into the first grouting zone (3) of each borehole (1); E. Grouting is performed into the second grouting zone (4) of each borehole (1) to form an arched solidified shell; F. Excavation, muck removal, and support of the tunnel.

10. The method for advance grouting excavation of small-section tunnels as described in claim 9, characterized in that: In step B, the distance between adjacent boreholes (1) is 20-40cm, and the elevation angle of each borehole (1) is no greater than 5°.

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