A construction method for magnetic slurry grouting of initial support in tunnels

Abstract

The present invention provides a construction method for magnetic slurry grouting in the initial support of a tunnel. After the tunnel is excavated for a set distance, shotcrete mortar is sprayed on the crown and side walls of the newly excavated section of the tunnel; holes are drilled from the crown to the side walls of the tunnel from top to bottom to form bolt holes; magnetic concrete slurry is prepared; outside the bolt, a galvanized copper coil is wound tightly around the outer wall of the bolt from the top end of the bolt to the anchor head, and then the bolt is inserted into the bolt hole; the galvanized copper coil is connected to an external power supply through a wire, and the magnitude of the magnetic field around the bolt is controlled by regulating the magnitude of the current of the external power supply; construction of the magnetic concrete slurry anchor solid; the magnetic metal mesh is fixed and laid on the surrounding rock of the crown and side walls of the tunnel through bolts; magnetic concrete slurry is sprayed on the surrounding rock in the area where the magnetic metal mesh and bolts are installed.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel engineering, and in particular relates to a construction method for magnetic slurry grouting of initial tunnel support. Background Art

[0002] In recent years, my country's infrastructure has developed rapidly. As a pillar industry that benefits the country and the people, the transportation industry plays a pivotal role in infrastructure construction. However, my country's terrain is complex, especially in the southwest region where there are mountains crisscrossing. Tunnel construction has become the biggest challenge in opening up the national transportation network. Generally, after tunnel excavation, initial support should be carried out immediately. The usual practice is to erect arch frames and steel mesh and carry out spray anchor protection.

[0003] At present, the initial support of railway tunnels is basically arranged by hollow anchors in the vault and mortar anchors in the side walls. The hollow anchors in the vault are used after the slurry solidifies to prevent the surrounding rock from sliding, dislocation and plastic deformation. The prestressed anchor support, which should enable the loose circle to form self-stabilizing ability as soon as possible, is increasingly valued and used.

[0004] At present, when grouting anchor rods, the filling density of cement slurry in the flower tube is not enough, the slurry adsorbed around the tube body is not easily dispersed by water flow, the grouting amount cannot be effectively controlled when the gap in the surrounding rock is large, and the anchor head cannot be quickly solidified, which makes the initial support of the tunnel extremely difficult. Therefore, in order to solve such problems, it is urgent to develop a method for initial support of the tunnel using magnetic concrete slurry. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a construction method for magnetic slurry grouting of initial tunnel support. Through this construction method, the slurry can quickly fill the interior of the anchor rod, and the gas in the grouting pipe can be better discharged. Under the action of the magnetic field, it can well solve the problem of unlimited increase in grouting volume due to large voids in the rock mass, and can also avoid the problem of no grouting at the anchor head, thereby increasing the anchoring force; and it can also effectively prevent the surrounding rock from entering a plastic state due to the disturbance caused by excavation, and can limit harmful deformation of the surrounding rock, further ensuring the stability and safety of the initial tunnel support.

[0006] In order to realize the above technical features, the object of the present invention is achieved as follows: A construction method for magnetic slurry grouting for initial support of a tunnel, characterized in that it comprises the following steps:

[0007] Step 1: After each tunnel excavation of a set distance, quick-setting cement mortar is sprayed on the vault and side walls of the newly excavated section of the tunnel;

[0008] Step 2: drilling from the top to the side wall of the tunnel to form anchor holes;

[0009] Step 3: Prepare the magnetic concrete slurry;

[0010] Step 4: Outside the anchor rod, tightly wind a galvanized copper coil around the outer wall of the anchor rod from the top end of the anchor rod to the anchor head, and then insert the anchor rod into the anchor rod hole;

[0011] Step 5: Connect the galvanized copper coil to an external power supply through a wire, and control the magnitude of the magnetic field around the anchor rod by regulating the magnitude of the current of the external power supply;

[0012] Step 6: When injecting the prepared magnetic concrete slurry into the anchor rod hole, turn on the external power supply, gradually increase the current magnetic field intensity, and through the electromagnetic field suction force formed by the magnetic particles in the magnetic concrete slurry and the galvanized copper coil, the concrete at the anchor head of the anchor rod converges and solidifies, increasing the density of the concrete slurry at the anchor head and improving the anchoring force, thus completing the construction of the magnetic concrete slurry anchor body;

[0013] Step 7: Fix and lay the magnetic metal mesh on the surrounding rock of the top arch and side walls of the tunnel through the anchor rod;

[0014] Step 8: Spray the magnetic concrete slurry on the surrounding rock in the area where the magnetic metal mesh and the anchor rod are installed. The electromagnetic field suction force formed by the magnetic particles in the magnetic concrete slurry and the magnetic metal mesh makes the magnetic concrete slurry more densely adsorbed on the surrounding rock, and the concrete layer formed after solidification and the anchor rod and the magnetic metal mesh form a surrounding rock support structure that jointly bears the load.

[0015] During the formation process of the anchor rod hole in Step 2, the drill pipe is repeatedly inserted and withdrawn, water is injected, or a high-pressure air blower is used to clean the hole.

[0016] The magnetic concrete slurry in Step 3 is prepared by adding magnetic materials, gelling agents, and accelerating agents to the concrete slurry and mixing them evenly.

[0017] The number of turns of the galvanized copper coil wound around the outside of the anchor rod in Step 4 is determined according to the actual engineering situation.

[0018] During the installation of the anchor rod in Step 4, an anchor backing plate is installed at the end of the anchor rod and fixed by a nut fixed to the end of the rod body.

[0019] During the grouting of the anchor rod in Step 6, the grouting pipe should be inserted to a distance of 50 - 100 mm from the bottom of the hole, the grouting pressure is controlled between 0.5 - 2.0 MPa, slowly open the grouting valve to start grouting. Under the push of the grouting air pressure, the magnetic concrete slurry is pumped into the anchor rod hole. As the magnetic concrete slurry in the hole increases, the grouting pipe slowly withdraws outward, and the grouting pipe orifice is always kept buried in the magnetic concrete slurry; after grouting, the grouting orifice needs to be blocked with an anchoring agent or a wooden plug to prevent the magnetic concrete slurry from flowing out and affecting the grouting quality.

[0020] The magnetic material is nano magnetic powder or iron powder.

[0021] The particle size of the nano magnetic powder is 100nm - 200nm, and the addition amount is 25 - 35% of the cement mass content in the magnetic concrete slurry; the particle size of the iron powder is 150 - 500μm, and the addition amount is 10 - 50% of the cement mass content in the magnetic concrete slurry.

[0022] The present invention has the following beneficial effects:

[0023] 1. The production process of the magnetic concrete slurry in the present invention is simple and low - cost. It only needs to add the magnetic material into the concrete slurry.

[0024] 2. The shape of the tin - plated copper coil can be changed arbitrarily, and the magnetic force can be controlled by the magnitude of the external power supply current, enabling the bolt to be in an electromagnetic field environment. When used in combination with the magnetic concrete slurry, compared with the traditional grouting process, the slurry quickly fills the inside of the bolt, and the magnetic slurry tightly wraps the bolt, avoiding the loss of slurry. At the same time, it also makes the slurry at the anchor head fill from the anchor head to the surrounding, increasing the compactness at the anchor head and also increasing the anchoring force.

[0025] 3. When spraying concrete, the magnetic metal mesh is laid on the surrounding rock of the tunnel arch top and side walls. Due to the magnetism of the magnetic metal mesh, a stable magnetic field effect is formed on the outer surface of the surrounding rock. When used in combination with the magnetic concrete slurry, it can make the slurry overcome gravity and is not easy to separate and fall off.

[0026] 4. Since its bolt outer wall is wound with a tin - plated copper coil, the use of magnetic material for the whole bolt is avoided, which not only simplifies the manufacturing difficulty and process of the bolt, but also can greatly reduce the cost, and can be widely applied in engineering practice.

[0027] 5. The magnetic field effect around the bolt can avoid the loss of slurry, and can also solve the problems of large voids in the rock mass leading to an infinite increase in the grouting volume and no slurry filling at the anchor head. The construction plan is simple, the operation is convenient, and it can greatly improve the bonding force, thus increasing the anchoring force of the whole anchoring system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below with reference to the drawings and embodiments.

[0029] Figure 1 It is the front view of the initial support of the tunnel of the present invention.

[0030] Figure 2 It is the structural schematic diagram of the bolt with an internal galvanized copper coil.

[0031] Figure 3 After the initial support of the tunnel is completed Figure 1 The enlarged schematic diagram of part A in it.

[0032] In the figure: anchor bolt 1, magnetic metal mesh 2, rock surface 3, external power supply 4, galvanized copper coil 5, anchor plate 6, nut 7, anchor bolt hole 8, concrete layer 9. Specific implementation mode

[0033] The following further describes the implementation mode of the present invention in conjunction with the accompanying drawings.

[0034] Embodiment 1:

[0035] See Figures 1-3 , a construction method for magnetic slurry grouting in the initial support of a tunnel, characterized by including the following steps:

[0036] Step 1, after the tunnel 10 is excavated for a set distance each time, spray quick-setting cement mortar on the crown and side walls of the newly excavated section of the tunnel 10;

[0037] Step 2, drill holes from the crown to the side walls of the tunnel 10 from top to bottom to form anchor bolt holes 8;

[0038] Step 3, prepare magnetic concrete slurry;

[0039] Step 4, outside the anchor bolt 1, and tightly wind the galvanized copper coil 5 around the outer wall of the anchor bolt from the top end of the anchor bolt to the anchor head, and then insert the anchor bolt 1 into the anchor bolt hole 8;

[0040] Step 5, connect the galvanized copper coil 5 to the external power supply 4 through a wire, and control the magnitude of the magnetic field around the anchor bolt 1 by adjusting the magnitude of the current of the external power supply 4;

[0041] Step 6, when injecting the prepared magnetic concrete slurry into the anchor bolt hole 8, turn on the external power supply 4, gradually increase the current magnetic field intensity, and through the electromagnetic field suction force formed by the magnetic particles in the magnetic concrete slurry and the galvanized copper coil 5, make the concrete at the anchor head of the anchor bolt 1 gather and solidify, increasing the density of the concrete slurry at the anchor head, improving the anchoring force, and completing the construction of the magnetic concrete slurry anchor solid;

[0042] Step 7, fix and lay the magnetic metal mesh 2 on the surrounding rocks at the crown and side walls of the tunnel through the anchor bolt 1;

[0043] Step 8, spray magnetic concrete slurry on the surrounding rocks in the area where the magnetic metal mesh 2 and the anchor bolt 1 are installed. The electromagnetic field suction force formed by the magnetic particles in the magnetic concrete slurry and the magnetic metal mesh 2 makes the magnetic concrete slurry more densely adsorbed on the surrounding rocks. After solidification, the formed concrete layer 9, the anchor bolt 1, and the magnetic metal mesh 2 form a surrounding rock support structure that jointly bears the load.

[0044] Further, during the formation process of the anchor rod hole 8 in Step 2, the drill pipe is repeatedly inserted and withdrawn, water is injected, or a high-pressure air blower is used to clean the hole. By adopting the above-mentioned formation process of the anchor rod hole 8, the formation quality of the anchor rod hole is ensured to enhance the anchoring force of the subsequent anchor rod.

[0045] Further, the magnetic concrete slurry in Step 3 is prepared by adding magnetic materials, gelling agents, and accelerating agents to the concrete slurry and mixing them evenly. Through the above-mentioned magnetic concrete slurry, it can cooperate with the anchor rod 1 with a magnetic field and the magnetic metal mesh 2 during the subsequent grouting process, thereby enhancing the adsorption effect of the magnetic concrete slurry.

[0046] Further, the number of turns of the galvanized copper coil 5 wound around the outside of the anchor rod 1 in Step 4 is determined according to the actual engineering situation. Through the above-mentioned winding design, the magnitude of the electromagnetic force can be conveniently adjusted to ensure the best electromagnetic adsorption effect, thereby ensuring the subsequent grouting quality, increasing the density of the concrete slurry at the anchor head, and improving the anchoring force.

[0047] Further, during the installation process of the anchor rod 1 in Step 4, an anchor plate 6 is installed at the end of the anchor rod 1 and fixed by a nut 7 fixed to the end of the rod body. Through the cooperation of the above-mentioned anchor plate 6 and nut 7, the fixing effect of the anchor rod 1 is enhanced.

[0048] Further, when grouting the anchor rod 1 in Step 6, the grouting pipe should be inserted to a distance of 50 - 100 mm from the bottom of the hole, the grouting pressure is controlled between 0.5 - 2.0 MPa, the grouting valve is slowly opened to start grouting. Under the push of the grouting air pressure, the magnetic concrete slurry is pumped into the anchor rod hole. As the magnetic concrete slurry in the hole increases, the grouting pipe slowly withdraws outward and always keeps the grouting pipe orifice buried in the magnetic concrete slurry; after grouting, the grouting orifice needs to be blocked with an anchoring agent or a wooden plug to prevent the magnetic concrete slurry from flowing out and affecting the grouting quality. By adopting the above-mentioned grouting process, the quality and effect of grouting the anchor rod 1 are effectively ensured, thereby ensuring the anchoring force after grouting.

[0049] Further, the magnetic material is nano magnetic powder or iron powder. By using magnetic materials, the magnetic property of the magnetic concrete slurry can be increased, so that it can generate a certain adsorption force under the action of a magnetic field, and then it can be adsorbed on the periphery of the anchor rod 1, increasing the density of the concrete slurry at the anchor head and improving the anchoring force.

[0050] Further, the particle size of the nano magnetic powder is 100 nm - 200 nm, and the addition amount is 25 - 35% of the cement mass content in the magnetic concrete slurry; the particle size of the iron powder is 150 - 500 μm, and the addition amount is 10 - 50% of the cement mass content in the magnetic concrete slurry.

Claims

1. A construction method for magnetic slurry grouting in the initial support of a tunnel, characterized in that, It includes the following steps: Step 1: After the tunnel (10) is excavated for a set distance, spray quick-setting cement mortar on the crown and side walls of the newly excavated section of the tunnel (10). Step 2: Drill holes from the crown to the side walls of the tunnel (10) from top to bottom to form bolt holes (8). Step 3: Prepare magnetic concrete slurry. Step 4: Outside the bolt (1), tightly wind a galvanized copper coil (5) around the outer wall of the bolt from the top end of the bolt to the anchor head, and then insert the bolt (1) into the bolt hole (8). Step 5: Connect the galvanized copper coil (5) to an external power supply (4) through a wire, and control the magnitude of the magnetic field around the bolt (1) by regulating the magnitude of the current of the external power supply (4). Step 6: When injecting the prepared magnetic concrete slurry into the bolt hole (8), turn on the external power supply (4), gradually increase the current magnetic field strength. Through the electromagnetic field suction formed by the magnetic particles in the magnetic concrete slurry and the galvanized copper coil (5), the concrete at the anchor head of the bolt (1) converges and solidifies, increasing the density of the concrete slurry at the anchor head and improving the anchoring force, and completing the construction of the magnetic concrete slurry anchor solid. Step 7: Fix and lay the magnetic metal mesh (2) on the surrounding rocks of the tunnel crown and side walls through the bolt (1). Step 8: Spray magnetic concrete slurry on the surrounding rocks in the area where the magnetic metal mesh (2) and the bolt (1) are installed. The electromagnetic field suction formed by the magnetic particles in the magnetic concrete slurry and the magnetic metal mesh (2) makes the magnetic concrete slurry more densely adsorbed on the surrounding rocks. After solidification, the formed concrete layer (9) and the bolt (1) and the magnetic metal mesh (2) form a surrounding rock support structure with common bearing capacity.

2. The construction method of magnetic slurry grouting for initial support of tunnels according to claim 1, characterized in that: During the forming process of the bolt hole (8) in Step 2, the drill rod is repeatedly inserted and withdrawn, water is injected, or a high-pressure air blower is used to clean the hole.

3. The construction method of magnetic slurry grouting for the initial support of a tunnel according to claim 1, characterized in that: In Step 3, the magnetic concrete slurry is prepared by adding magnetic materials, gelling agents, and quick-setting agents to the concrete slurry and mixing them evenly.

4. The construction method of magnetic slurry grouting for initial support of a tunnel according to claim 1, characterized in that: The number of turns of the galvanized copper coil (5) wound around the outside of the bolt (1) in Step 4 is determined according to the actual engineering situation.

5. The construction method of magnetic slurry grouting for the initial support of a tunnel according to claim 1, characterized in that: During the installation process of the bolt (1) in Step 4, an anchor plate (6) is installed at the end of the bolt (1) and fixed by a nut (7) fixed to the end of the rod body.

6. The construction method of magnetic slurry grouting for initial support of tunnels according to claim 1, characterized in that: In Step 6, when grouting the bolt (1), the grouting pipe should be inserted to a distance of 50 - 100 mm from the bottom of the hole, the grouting pressure is controlled between 0.5 - 2.0 MPa, slowly open the grouting valve to start grouting. Under the push of the grouting air pressure, the magnetic concrete slurry is pumped into the bolt hole. As the magnetic concrete slurry in the hole increases, the grouting pipe slowly withdraws outward, and the grouting pipe orifice is always kept buried in the magnetic concrete slurry. After grouting, the grouting orifice needs to be blocked with an anchoring agent or a wooden plug to avoid the outflow of the magnetic concrete slurry affecting the grouting quality.

7. The construction method of magnetic slurry grouting for initial support of a tunnel according to claim 3, characterized in that: The magnetic material is nano magnetic powder or iron powder.

8. The construction method of magnetic slurry grouting for initial support of tunnels according to claim 7, characterized in that: The particle size of the nano magnetic powder is 100nm - 200nm, and the addition amount is 25 - 35% of the cement mass content in the magnetic concrete slurry; the particle size of the iron powder is 150 - 500μm, and the addition amount is 10 - 50% of the cement mass content in the magnetic concrete slurry.

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