A U-shaped double-layer fully enclosed grouting water-stop device and method for tunnel construction in water-rich sand strata

Abstract

A U-shaped double-layer fully enclosed grouting water-stop device and method for tunnel construction in water-rich sand strata, belonging to the field of underground engineering and geotechnical engineering construction. The device includes a U-shaped double-layer fully enclosed structure drilling casing (1), a flexible drill tool (2), and an orientation bit (3); during use, a drill rig and construction grouting holes are respectively installed outside the planned excavation boundary of the tunnel in sequence, and grouting is carried out in the holes in sequence to achieve U-shaped double-layer fully enclosed grouting of the water-rich sand strata at the top, bottom, and both side walls of the tunnel in front of the tunnel face.

Description

Technical Field

[0001] The present invention relates to a U-shaped double-layer fully enclosed grouting water-stop device and method for tunnel construction in water-rich sand strata, belonging to the field of construction methods for underground engineering and geotechnical engineering. Background Art

[0002] When constructing an underground tunnel project in water-rich sand strata, it is necessary to carry out water-stop and pre-reinforcement treatment on the front and periphery of the tunnel face to prevent engineering safety accidents such as sand and water gushing from the tunnel face caused by groundwater and prevent surrounding rock collapse and deformation. Usually, the method of drilling and high-pressure grouting reinforcement is adopted. However, due to the extremely poor permeability of cement slurry in water-rich sandy soil strata, the grouting range and grouting quality are extremely poor, and cannot meet the requirements of engineering construction.

[0003] The present invention is a U-shaped double-layer fully enclosed grouting water-stop device and method for tunnel construction in water-rich sand strata, which performs full-section grouting and sealing on the tunnel to prevent formation loss, effectively control construction risks and improve project quality. Summary of the Invention

[0004] The structure of a U-shaped double-layer fully enclosed grouting water-stop device for tunnel construction in water-rich sand strata according to the present invention is characterized by comprising a U-shaped double-layer fully enclosed structure drilling hole (1), a flexible drill tool (2), and an orientation bit (3); the structure of the U-shaped double-layer fully enclosed structure drilling hole (1) is specifically: comprising a left upper vertical drilling hole (1.1), a right upper vertical drilling hole (1.3), a right-opening horizontal U-shaped drilling hole (1.2), and a left-opening horizontal U-shaped drilling hole (1.4). The structure of the horizontal U-shaped drilling hole: comprises two horizontal drilling holes that are parallel up and down, and the two horizontal drilling holes are connected and communicated through a vertical drilling hole to form a horizontally U-shaped communicating drilling hole; the left upper vertical drilling hole (1.1) is linearly connected and communicated with the vertical drilling hole on the left side of the right-opening horizontal U-shaped drilling hole (1.2); the right upper vertical drilling hole (1.3) is linearly connected and communicated with the vertical drilling hole on the right side of the left-opening horizontal U-shaped drilling hole (1.4).

[0005] The right-opening horizontal U-shaped borehole (1.2) and the left-opening horizontal U-shaped borehole (1.4) relatively enclose a closed rectangular structure, and this closed rectangular structure corresponds to the rectangular structure of the tunnel cross-section; the upper horizontal boreholes of the right-opening horizontal U-shaped borehole (1.2) and the left-opening horizontal U-shaped borehole (1.4) are stacked in parallel up and down, and the corresponding positions after stacking are located at the grouting area position at the top of the tunnel; the lower horizontal boreholes of the right-opening horizontal U-shaped borehole (1.2) and the left-opening horizontal U-shaped borehole (1.4) are stacked in parallel up and down, and the corresponding positions after stacking are located at the grouting area position at the bottom of the tunnel; the left vertical borehole of the right-opening horizontal U-shaped borehole (1.2) and the right vertical borehole of the left-opening horizontal U-shaped borehole (1.4) are respectively located at the grouting area positions on both sides of the tunnel; the upper left vertical borehole (1.1) and the upper right vertical borehole (1.3) respectively extend upward out of the ground;

[0006] One end of the flexible drill tool (2) extends into the borehole for drilling and grouting, and the other end is located outside the borehole for connecting with the grouting pump; the end of the one extending into the borehole is a directional drill bit (3).

[0007] The flexible drill tool (2) includes a connecting thread (2.1), a connecting body (2.2), an ear piece (2.3), a pin / hole (2.4) and an outer wall rubber high-pressure protection structure (2.5); one end of the connecting body (2.2) is a connecting thread (2.1), and the other end is an ear piece (2.3), and a pin / hole (2.4) is provided on the ear piece (2.3). Multiple connecting bodies (2.2) are connected end to end, and the connection part is: the connection between the connecting thread (2.1) and the ear piece (2.3) is fixed by the pin / hole (2.4) to form a flexible long connecting body, and the outer periphery of the flexible long connecting body is an outer wall rubber high-pressure protection structure (2.5).

[0008] The said connecting body (2.2) is placed inside the flexible drill tool and is the main part of the drill tool, which plays the role of transmitting pressure and torque;

[0009] The said pin / hole (2.4) is placed inside the flexible drill tool and is the main part of the drill tool to connect and fix the connecting body (2.2);

[0010] The said outer wall rubber high-pressure protection structure (2.5) limits the drill tool connecting body, injects circulating mud and cement slurry, and its pressure resistance level is greater than the grouting pressure;

[0011] The inner walls of the upper left vertical borehole (1.1) and the upper right vertical borehole (1.3) are provided with casing pipes. The borehole refers to the borehole pre-drilled by the drilling rig, and a steel casing pipe for protecting the well wall can be lowered into the borehole; the diameter of the borehole is larger than the outer diameter of the steel casing pipe; the outer diameter of the casing pipe is larger than the outer diameter of the directional drill bit.

[0012] The said flexible drill tool (2) can bend and rotate along with the drilling track of the directional drill bit (3);

[0013] The directional drill bit (3) includes a drill bit body and a drill bit guiding controller (9). The guiding controller (9) is controlled by a ground control system to measure the position of the drill bit and control the drilling direction of the drill bit.

[0014] The present invention is applicable to a double-layer structure with cohesive soil (8) in the upper formation and water-rich sand layer (7) in the lower formation. When the tunnel support structure (5) is constructed to the tunnel face (4), grouting pre-reinforcement is carried out on the formation in front of the tunnel face, namely the tunnel grouting reinforcement area (6). The tunnel grouting reinforcement area (6) is a U-shaped double-layer fully enclosed area, that is, the position where the U-shaped double-layer fully enclosed structure drilling of the present device is located.

[0015] To prevent engineering safety accidents such as sand and water gushing from the tunnel face and surrounding rock collapse and deformation in the water-rich sand and soil formation during tunnel construction, the above device is used for the U-shaped double-layer fully enclosed grouting and water stop method for water-rich sand layer tunnels, which is characterized by including the following steps:

[0016] The first step: On-site lofting to determine the positions of the grouting holes and install the drilling rig equipment;

[0017] The second step: Use the directional drill bit to construct vertical holes and insert the holes according to the positions of the left upper vertical hole (1.1) and the right upper vertical hole (1.3) until the depth reaches the tunnel top grouting layer, obtaining the left upper vertical hole (1.1) and the right upper vertical hole (1.3). At the same time, install casing on the inner walls of the left upper vertical hole (1.1) and the right upper vertical hole (1.3);

[0018] The third step: Simultaneously or successively, insert the flexible drill tool (2) and the directional drill bit (3) into the left upper vertical hole (1.1) and the right upper vertical hole (1.3) respectively. Use the drill bit guiding controller (9) to control the position and direction of the drill bit, and carry out directional drilling along the tunnel top grouting layer until the predetermined grouting position on the opposite side of the tunnel, forming the upper horizontal holes of the right-opening horizontal U-shaped hole (1.2) and the left-opening horizontal U-shaped hole (1.4); Connect a grouting pump to the other end of the drill tool, and pump cement slurry through the flexible drill tool along the upper horizontal holes of the right-opening horizontal U-shaped hole (1.2) and the left-opening horizontal U-shaped hole (1.4) to seal and reinforce the aquifer at the tunnel top;

[0019] The fourth step: Use the same method as the second step to prepare the left vertical hole of the right-opening horizontal U-shaped hole (1.2) and the right vertical hole of the left-opening horizontal U-shaped hole (1.4);

[0020] Step 5: Prepare the lower horizontal boreholes of the right-opening horizontal U-shaped borehole (1.2) and the left-opening horizontal U-shaped borehole (1.4) by the same method as in Step 3; Connect a grouting pump to the other end of the drill string, and pump cement slurry along the lower horizontal boreholes of the right-opening horizontal U-shaped borehole (1.2) and the left-opening horizontal U-shaped borehole (1.4) through the flexible drill string to seal and reinforce the aquifer at the bottom of the tunnel.

[0021] Step 6: Pump cement slurry along the left vertical borehole of the right-opening horizontal U-shaped borehole (1.2) and the right vertical borehole of the left-opening horizontal U-shaped borehole (1.4) through the flexible drill string to seal and reinforce the aquifer on the side of the tunnel; Finally, realize the U-shaped double-layer full-closure grouting for the water-rich sandy soil strata at the top, bottom and both side walls in front of the tunnel face of the tunnel.

[0022] Furthermore, the specific operations of Step 3, Step 5 and Step 6 for pumping cement slurry into the boreholes to seal and reinforce the aquifer on the side of the tunnel are as follows: Carry out high-pressure jet grouting for the first grouting section at the end, stop after reaching the grouting time under the designed grouting pressure, then pull the flexible drill string backward until the directional drill bit reaches the second predetermined grouting section for high-pressure jet grouting, stop after reaching the grouting time under the designed grouting pressure, and so on, pulling back the drill string and carrying out high-pressure jet grouting.

[0023] The grouting and water-stop method is applicable to water-rich sandy soil strata (7), and generally the overlying strata are water-proof clay strata (8); The grouting layer at the top of the tunnel refers to the water-rich sandy layer above the tunnel arch crown; The grouting layer at the bottom of the tunnel refers to the water-rich sandy layer above the tunnel arch crown; The grouting layers on both sides of the tunnel refer to the water-rich sandy layers on both inner sides of the tunnel; The tunnel includes the tunnel face (4) and the tunnel support structure (5); The grouting holes are symmetrically arranged outside the construction area of the grouting tunnel on both sides along the cross-sectional line direction of the tunnel, and are arranged sequentially outside the construction area of the grouting tunnel on both sides along the tunnel axis direction, and are constructed at intervals of skip holes.

[0024] Advantages of the present invention:

[0025] Advantages of the U-shaped double-layer full-closure grouting and water-stop method for the construction of water-rich sandy layer tunnels of the present invention:

[0026] (1) Make full use of the limited ground space, construct the least number of grouting holes, and carry out full-section closure grouting for the water-rich sandy layers at the top, bottom and sides of the tunnel;

[0027] (2) The present invention adopts a flexible drill string and a directional drill bit, and can control the direction and position of the grouting holes through the ground control system to accurately position and grout at any position for the water-rich sandy layer;

[0028] (3) The present invention is applicable to directional grouting in any direction and directional grouting along the bedding plane.

[0029] (4) The present invention realizes positioning and directional grouting, which can save a large amount of grouting materials and construction workload, effectively improve economic and social benefits, and achieve green construction.

[0030] (5) The present invention has theoretical value and application value, and has replicability and popularizability. Description of the Drawings

[0031] Figure 1 Structural diagram of U-shaped double-layer fully enclosed grouting and water stop for construction of tunnel in water-rich sand layer

[0032] Figure 2 Structural diagram of tunnel and stratum

[0033] Figure 3 Relationship diagram of flexible drill tool and drill bit

[0034] Figure 4 Tunnel grouting zoning diagram

[0035] Figure 5 Tunnel grouting sectional diagram

[0036] Figure 6 Structural diagram of flexible drill tool

[0037] Figure 7 Drilling hole

[0038] In the figure: 1 is the drilling hole of U-shaped double-layer fully enclosed structure, 1.1 is the vertical drilling hole in the upper left part, 1.2 is the horizontal U-shaped drilling hole with right opening, 1.3 is the vertical drilling hole in the upper right part, 1.4 is the horizontal U-shaped drilling hole with left opening, 2 is the flexible drill tool, 2.1 is the connecting screw thread, 2.2 is the connecting body, 2.3 is the connecting ear piece, 2.4 is the pin / hole, 3 is the directional drill bit, 4 is the tunnel face, 5 is the tunnel support structure, 6 is the tunnel grouting reinforcement area, 7 is the water-rich sand layer, 8 is the clay layer, and 9 is the drill bit guiding controller. Detailed implementation manners

[0039] The present invention will be further described below in combination with an example of a subway tunnel in Beijing, but the present invention is not limited to the following embodiments.

[0040] Specific structural diagram of the U-shaped double-layer fully enclosed grouting and water stop device for construction of tunnel in water-rich sand layer.

[0041] The first step: Determine the positions of grouting holes by on-site lofting and install drilling rig equipment;

[0042] The second step: Use a directional drilling rig to construct vertical drilling holes and lower them until the depth reaches the grouting layer at the top of the tunnel;

[0043] Step 3: Lower a flexible drill tool (2) and a directional drill bit (3) into the vertically drilled holes (1.1) in the upper left and (1.3) in the upper right (both with casing on their inner walls). Use a drill bit orientation controller (9) to control the position and direction of the drill bit, and conduct directional drilling along the grouting layer at the top of the tunnel until the predetermined grouting position on the opposite side of the tunnel is reached.

[0044] Step 4: Connect a grouting pump to the end of the drill tool and pump cement slurry through the flexible drill tool to conduct high-pressure jet grouting on the first grouting section (at the top of the tunnel) (A) at the end of the drill bit. Stop after reaching the grouting time under the designed grouting pressure.

[0045] Step 5: Lift the drill tool until the drill bit reaches the second predetermined grouting section (at the top of the tunnel). Pump cement slurry through the flexible drill tool to conduct high-pressure jet grouting on the second grouting section (B) at the end of the drill bit. Stop after reaching the grouting time under the designed grouting pressure. Then, successively retract the drill tool and conduct grouting until the grouting tasks for all predetermined sections (at the top of the tunnel) (A, B, C, D,...) of this grouting hole are completed, to seal and reinforce the water-bearing layer at the top of the tunnel.

[0046] Step 6: Continue to vertically drill and lower a hole at the hole position until the depth reaches the grouting layer at the bottom of the tunnel.

[0047] Step 7: Lower a flexible drill tool (2) and a directional drill bit (3) into it. Use a drill bit orientation controller (9) to control the position and direction of the drill bit, and conduct directional drilling along the grouting layer at the bottom of the tunnel until the predetermined grouting position on the opposite side of the tunnel is reached.

[0048] Step 8: Connect a grouting pump to the end of the drill tool and pump cement slurry through the flexible drill tool to conduct high-pressure jet grouting on the first grouting section (at the bottom of the tunnel) (A) at the end of the drill bit. Stop after reaching the grouting time under the designed grouting pressure.

[0049] Step 9: Lift the drill tool until the drill bit reaches the second predetermined grouting section (at the bottom of the tunnel). Pump cement slurry through the flexible drill tool to conduct high-pressure jet grouting on the second grouting section (B) at the end of the drill bit. Stop after reaching the grouting time under the designed grouting pressure. Then, successively retract the drill tool and conduct grouting until the grouting tasks for all predetermined sections (at the bottom of the tunnel) (A, B, C, D,...) of this grouting hole are completed, to seal and reinforce the water-bearing layer at the bottom of the tunnel and the water-rich sand layer on the sidewalls of the tunnel.

[0050] Install drilling rigs and construct grouting holes outside the proposed excavation boundary of the tunnel in sequence, and conduct sequential grouting in the holes to achieve U-shaped double-layer full-closure grouting for the water-rich sandy soil layers at the top, bottom, and both sidewalls in front of the tunnel face of the tunnel.

[0051] Example 1

[0052] In a certain subway tunnel in Beijing, the ground layer from 0 to 15 meters below the ground is mainly composed of silty clay stratum 8, and below it is a water-rich medium-fine sand layer 7.

[0053] The type of groundwater is a mixed form of phreatic water and confined water. There is a river flowing on the ground. The cross-section of the subway tunnel is about 100m 2 or so, and the tunnel construction method is the CRD method. When the tunnel construction reaches the heading face 4) ahead, grouting pre-reinforcement is carried out on the surrounding rock of the tunnel ahead of the heading face (4). The specific implementation steps are as follows:

[0054] The first step of the implementation of the present invention is the positioning of the drill rig. Construction lofting is carried out according to the tunnel design drawing to determine the positions of the grouting holes; the depths of the grouting layers at the top and bottom of the tunnel and the lithology of the strata are determined according to the geological section diagram;

[0055] The second step is to construct the grouting holes. Drill to a depth of 17 meters (the grouting reinforcement area (6) at the top of the tunnel) according to the designed depth. Lower the drilling steel, and the diameter of the steel is larger than the outer diameter of the drill bit;

[0056] The third step is to lower the flexible drill tool (2) and the directional drill bit (3) into the vertical drill hole (1.1) in the upper left and the vertical drill hole (1.3) in the upper right. At the bottom of the hole, use the drill bit orientation controller (9) to control the position and direction of the drill bit to carry out directional deviation correction according to the designed direction, and carry out directional control in the ground control room. Construct the horizontal fixed drill hole to the designed position on the opposite side of the tunnel, and wash the drill hole;

[0057] The fourth step is to connect the grouting pump and carry out high-pressure grouting on the grouting section A of the grouting reinforcement area (6) at the top of the tunnel through the flexible drill tool and the drill bit. The grouting pressure is about 0.5, and the stable grouting time is 1 hour;

[0058] The fifth step is to lift the drill tool about 0.5 meters and carry out high-pressure grouting on the grouting section B of the grouting reinforcement area (6) at the top of the tunnel. The grouting pressure is about 0.5, and the stable grouting time is 1 hour;

[0059] The seventh step is to lift the drill tool in turn, about 0.5 meters each time, and carry out high-pressure grouting on each grouting section of the grouting reinforcement area (6) at the top of the tunnel to complete the grouting reinforcement of the grouting area (6) at the top of the tunnel;

[0060] The eighth step is to continue to construct the vertical drill hole in the vertical drill hole to a depth of 30 meters (the grouting reinforcement area (6) at the bottom of the tunnel), and lower the drill hole (1.2);

[0061] The ninth step is to lower the flexible drill tool (2) and the directional drill bit (3) into it. Use the drill bit orientation controller (9) to control the position and direction of the drill bit, carry out directional deviation correction at the bottom of the hole according to the designed direction, and carry out directional control in the ground control room. Construct the horizontal fixed drill hole to the designed position on the opposite side of the tunnel, and wash the drill hole;

[0062] Step 10: Connect the grouting pump and conduct high-pressure grouting on grouting section A of the tunnel bottom grouting reinforcement area (6) through a flexible drill tool and a drill bit. The grouting pressure is about 0.5, and the stable grouting time is 1 hour;

[0063] Step 11: Lift the drill tool by about 0.5 m and conduct high-pressure grouting on grouting section B of the tunnel bottom grouting reinforcement area. The grouting pressure is about 0.5, and the stable grouting time is 1 hour;

[0064] Step 12: Lift the drill tool successively, about 0.5 m each time, and conduct high-pressure grouting on each grouting section of the tunnel bottom grouting reinforcement area and the tunnel side respectively to complete the grouting reinforcement of the tunnel bottom grouting area (6) and the tunnel side grouting area (6);

[0065] Step 13: Move the drill rig 1 m along the tunnel axis direction and successively complete the above-mentioned drilling and grouting operations;

[0066] Step 14: 48 hours after the grouting of the grouting holes in Step 13 is completed, punch plum blossom-shaped grouting holes at the middle positions between adjacent two grouting holes. The specific method is the same as before;

[0067] Step 15: On the symmetric side of the tunnel axis, gradually complete the grouting work according to the same construction process;

[0068] Gradually construct and complete the grouting of all designed sections as above to form a U-shaped double-layer fully enclosed water-stop reinforcement structure in the tunnel heading excavation area, and then carry out the excavation work of the tunnel heading.

[0069] The U-shaped double-layer fully enclosed grouting water-stop method for the construction of a water-rich sand layer tunnel in the present invention includes but is not limited to the above content, and is also applicable to related methods such as horizontal drilling directional grouting.

Claims

1. A U-shaped double-layer fully enclosed grouting water-stop device for tunnel construction in water-rich sand strata, characterized in that, It includes a U-shaped double-layer fully enclosed structure drilling hole (1), a flexible drill tool (2), and a directional drill bit (3); The specific structure of the U-shaped double-layer fully enclosed structure drilling hole (1) is as follows: it includes a left upper vertical drilling hole (1.1), a right upper vertical drilling hole (1.3), a right-opening horizontal U-shaped drilling hole (1.2), and a left-opening horizontal U-shaped drilling hole (1.4). The structure of the horizontal U-shaped drilling hole: it includes two horizontal drilling holes that are parallel up and down, and the two horizontal drilling holes are connected and communicated through a vertical drilling hole to form a horizontal U-shaped connected drilling hole; The left upper vertical drilling hole (1.1) is linearly connected and communicated with the vertical drilling hole on the left side of the right-opening horizontal U-shaped drilling hole (1.2); The right upper vertical drilling hole (1.3) is linearly connected and communicated with the vertical drilling hole on the right side of the left-opening horizontal U-shaped drilling hole (1.4). The right-opening horizontal U-shaped drilling hole (1.2) and the left-opening horizontal U-shaped drilling hole (1.4) relatively enclose a closed rectangular structure, and this closed rectangular structure corresponds to the rectangular structure of the tunnel cross-section; The upper horizontal drilling hole of the right-opening horizontal U-shaped drilling hole (1.2) and the upper horizontal drilling hole of the left-opening horizontal U-shaped drilling hole (1.4) are parallel and stacked up and down, and the positions after stacking correspond to the position of the grouting area at the top of the tunnel; The lower horizontal drilling hole of the right-opening horizontal U-shaped drilling hole (1.2) and the lower horizontal drilling hole of the left-opening horizontal U-shaped drilling hole (1.4) are parallel and stacked up and down, and the positions after stacking correspond to the position of the grouting area at the bottom of the tunnel; The vertical drilling hole on the left side of the right-opening horizontal U-shaped drilling hole (1.2) and the vertical drilling hole on the right side of the left-opening horizontal U-shaped drilling hole (1.4) are respectively located at the positions of the grouting areas on both sides of the tunnel; The left upper vertical drilling hole (1.1) and the right upper vertical drilling hole (1.3) respectively extend upward out of the ground. One end of the flexible drill tool (2) extends into the drilling hole for drilling and grouting, and the other end is located outside the drilling hole for connecting with the grouting pump; The end of the one extending into the drilling hole is the directional drill bit (3). The flexible drill tool (2) includes a connecting thread (2.1), a connecting body (2.2), an ear piece (2.3), a pin / hole (2.4), and an outer wall rubber high-pressure protection structure (2.5); One end of the connecting body (2.2) is the connecting thread (2.1), and the other end is the ear piece (2.3). The ear piece (2.3) is provided with a pin / hole (2.4). A plurality of connecting bodies (2.2) are connected end to end. The connection part is: the connection between the connecting thread (2.1) and the ear piece (2.3) is fixed by the pin / hole (2.4) to form a flexible long connecting body, and the outer periphery of the flexible long connecting body is the outer wall rubber high-pressure protection structure (2.5). The said connecting body (2.2) plays the role of transmitting pressure and torque; The flexible drill tool (2) can bend and rotate along with the drilling track of the directional drill bit (3). The drilling hole refers to the drilling hole pre-drilled by the drill rig; The diameter of the drilling hole is larger than the outer diameter of the casing; The outer diameter of the casing is larger than the outer diameter of the directional drill bit. The inner walls of the left upper vertical drilling hole (1.1) and the right upper vertical drilling hole (1.3) are provided with casings. The said directional drill bit (3) includes a drill bit body and a drill bit guiding controller (9). The guiding controller (9) is controlled by a ground control system to measure the position of the drill bit and control the drilling direction of the drill bit.

2. The U-shaped double-layer fully enclosed grouting water-stop device for the construction of a tunnel in a water-rich sand layer according to claim 1, characterized in that, For a double-layer structure with cohesive soil (8) in the upper formation and water-rich sand layer (7) in the lower formation, when the tunnel support structure (5) is constructed to the tunnel face (4), grouting pre-reinforcement is carried out on the formation in front of the face, namely the tunnel grouting reinforcement area (6). The tunnel grouting reinforcement area (6) is a U-shaped double-layer fully enclosed area, that is, the position where the drilling of the U-shaped double-layer fully enclosed structure described in this device is located.

3. The U-shaped double-layer fully enclosed grouting water-stop method for the construction of a tunnel in a water-rich sand layer using the device according to any one of claims 1-2, characterized in that, It includes the following steps: The first step: Conduct on-site lofting to determine the positions of grouting holes and install drilling equipment; The second step: Use a directional drill bit to construct vertical holes and lower the holes according to the positions of the left upper vertical hole (1.1) and the right upper vertical hole (1.3) until the depth reaches the tunnel top grouting layer, obtaining the left upper vertical hole (1.1) and the right upper vertical hole (1.3); at the same time, install casing tubes on the inner walls of the left upper vertical hole (1.1) and the right upper vertical hole (1.3); The third step: Respectively, simultaneously or successively, lower flexible drilling tools (2) and directional drill bits (3) into the left upper vertical hole (1.1) and the right upper vertical hole (1.3), use the drill bit orientation controller (9) to control the position and direction of the drill bit, and conduct directional drilling along the tunnel top grouting layer until the predetermined grouting position on the opposite side of the tunnel is reached, forming the upper horizontal holes of the right-opening horizontal U-shaped hole (1.2) and the upper horizontal holes of the left-opening horizontal U-shaped hole (1.4); connect a grouting pump to the other end of the drilling tool, and pump cement slurry through the flexible drilling tool along the upper horizontal holes of the right-opening horizontal U-shaped hole (1.2) and the upper horizontal holes of the left-opening horizontal U-shaped hole (1.4) to seal and reinforce the aquifer at the tunnel top; The fourth step: Use the same method as the second step to prepare the left vertical hole of the right-opening horizontal U-shaped hole (1.2) and the right vertical hole of the left-opening horizontal U-shaped hole (1.4); The fifth step: Use the same method as the third step to prepare the lower horizontal holes of the right-opening horizontal U-shaped hole (1.2) and the lower horizontal holes of the left-opening horizontal U-shaped hole (1.4); connect a grouting pump to the other end of the drilling tool, and pump cement slurry through the flexible drilling tool along the lower horizontal holes of the right-opening horizontal U-shaped hole (1.2) and the lower horizontal holes of the left-opening horizontal U-shaped hole (1.4) to seal and reinforce the aquifer at the tunnel bottom; The sixth step: Pump cement slurry through the flexible drilling tool along the left vertical hole of the right-opening horizontal U-shaped hole (1.2) and the right vertical hole of the left-opening horizontal U-shaped hole (1.4) to seal and reinforce the aquifer at the tunnel side; finally, realize U-shaped double-layer full-enclosed grouting for the water-rich sandy soil strata at the tunnel top, tunnel bottom, and both side walls in front of the tunnel face.

4. The method according to claim 3, characterized in that For the specific operations of the third step, fifth step, and sixth step of pumping cement slurry into the holes to seal and reinforce the aquifer at the tunnel side, they are all the following steps: Conduct high-pressure jet grouting for the first grouting section at the end, stop after reaching the grouting time under the designed grouting pressure, then pull the flexible drilling tool backward until the directional drill bit reaches the second predetermined grouting section for high-pressure jet grouting, stop after reaching the grouting time under the designed grouting pressure, and so on, pulling back the drilling tool and conducting high-pressure jet grouting.

5. The method according to claim 3, wherein The grouting water-stop method is applicable to water-rich sand layers (7) with overlying strata being cohesive soil (8); the grouting layer at the top of the tunnel refers to the water-rich sand layer stratum above the tunnel vault; the grouting layer at the bottom of the tunnel refers to the water-rich sand layer stratum at the bottom of the tunnel; the grouting layers on both sides of the tunnel refer to the water-rich sand layer strata on the two inner sides of the tunnel; the tunnel includes a tunnel face (4) and a tunnel support structure (5); the grouting holes are arranged symmetrically along the cross-sectional line of the tunnel outside the construction area of the grouting tunnels on both sides and are arranged sequentially along the tunnel axis direction outside the construction area of the grouting tunnels on both sides, and construction is carried out at intervals of skipping holes.

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