A temporary support method for the arch feet of a steel arch in tunnel construction

Abstract

The present invention discloses a temporary support method for the arch feet of a steel arch in tunnel construction. The precast concrete cushion blocks can be used for supporting the arch feet of the steel arch. Before the arch feet of the steel arch accurately fall onto the measuring points, anti-reinforcement mesh sheets are placed on the lower surface and the upper surface of the concrete cushion blocks to reduce the pressure of the concrete cushion blocks on the ground foundation and the pressure of the arch feet on the concrete cushion blocks. At the same time, C25 shotcrete is used to densely fill the area between the two layers of reinforcement mesh sheets and the area between the upper layer of reinforcement mesh sheets and the arch feet of the steel arch. After the C25 shotcrete solidifies, confinement is achieved. The built-in reinforcement mesh sheets and C25 shotcrete become reinforced concrete to increase strength, and can be combined with confinement on the ground foundation of the tunnel. Finally, it is ensured that the arch feet rest on a firm foundation and the stress is uniform, effectively reducing the disturbance to the arch during later construction and avoiding situations such as abnormal settlement.

Description

Technical Field

[0001] The present invention relates to the field of construction, and particularly to a temporary support method for the arch feet of steel arch frames in tunnel construction. Background Art

[0002] Steel arch frames are used in the initial support of tunnels to prevent excessive deformation of soft surrounding rock tunnels. Especially when the surrounding rock conditions are poor, due to the factors of the surrounding rock itself and the on-site construction conditions, the effect of radial system bolts is often not obvious, and it increases the tunnel construction cost and prolongs the construction period. At this time, adding steel arch frames in the initial support can quickly provide sufficient support resistance, meet the main stiffness required for the initial support, and quickly control the continuous relaxation of the surrounding rock and the continuous expansion of the plastic zone; limit the excessive deformation of the surrounding rock and ensure the stability of the tunnel support structure system.

[0003] The arch feet of the steel arch frame need to be placed on a firm foundation. During the construction process, steel plates or sleepers are usually laid under the arch feet to increase the bearing area and ensure that the steel arch frame does not sink. However, the shape of the steel arch frame is usually larger than a semi-circle. At this time, the lower surface of the arch foot is inclined. After laying steel plates and sleepers for the arch foot to support, there is a gap between the steel plate or sleeper and the arch foot, resulting in the arch foot not being stably placed on a firm foundation, and it is easy to have abnormal settlement, initial support cracking, intrusion and other phenomena in the later stage. Summary of the Invention

[0004] The purpose of the present invention is to provide a temporary support method for the arch feet of steel arch frames in tunnel construction. By adopting the method of precast concrete pads combined with shotcrete confinement, it is ensured that the arch feet fall on a firm foundation and the force is evenly distributed.

[0005] The above technical purpose of the present invention is achieved through the following technical solutions: A temporary support method for the arch feet of steel arch frames in tunnel construction, including the following steps:

[0006] S1 Precast Concrete Pads

[0007] Use C30 concrete to precast multiple concrete pads. The upper surfaces of the multiple concrete pads are inclined. The length and width of the multiple concrete pads are both 50 cm. The height of one end of the multiple concrete pads is 10 cm and the height of the other end is 5 - 8 cm and varies.

[0008] S2 Ground Foundation Cleaning

[0009] After the initial spraying in tunnel excavation and before the installation of the steel arch frame, through measurement and lofting, manually clean the loose slag near the arch feet of the steel arch frame to ensure that the concrete pads are placed on a solid and flat ground foundation;

[0010] S3 Installation of Precast Concrete Pads

[0011] S31: After the steel arch frame is assembled and not accurately placed at the measuring point, a layer of steel mesh is placed on the ground foundation at the arch foot of the corresponding steel arch frame, and then a concrete pad is placed above the middle of the steel mesh;

[0012] S32: Place the steel arch frame precisely at the measuring point, lift the steel arch frame by 2 to 3 centimeters, adjust the position of the concrete pad so that the arch foot is aligned with the middle of the concrete pad, and place a layer of steel mesh on the upper surface of the concrete pad;

[0013] S33: Place the steel arch frame precisely at the measuring point so that the arch foot of the steel arch frame is placed on the upper steel mesh. When the anchor rods and small conduits are completed and inspected and qualified, use C25 sprayed concrete to fill the area between the two layers of steel mesh and the area between the upper steel mesh and the arch foot of the steel arch frame densely, and the C25 sprayed concrete will be solidified before it is confined.

[0014] The present invention is further configured as follows: in step S31 of step S3, the end of the concrete pad with a smaller height faces the inner wall of the tunnel, and a concrete pad with an upper surface inclination angle not less than the lower surface inclination angle of the arch foot of the steel arch frame is selected.

[0015] The present invention is further configured as follows: when prefabricating the concrete pad in step S1, a limiting groove is provided on the upper surface of the concrete pad, and the limiting grooves of the concrete pad are arranged and distributed along its inclined surface; in S31 of step S3, the steel bars of the steel mesh in contact with the concrete pad are respectively embedded in the limiting grooves of the concrete pad.

[0016] The present invention is further configured as follows: before using C25 sprayed concrete in step S3, a plurality of wedge-shaped blocks are hammered in between the upper surface of the concrete pad and one end of the arch foot of the steel arch frame close to the inner wall of the tunnel.

[0017] The present invention is further configured as follows: when prefabricating a concrete pad in step S1, a groove is provided in the middle of the upper surface of the concrete pad, and an "L"-shaped injection pipe is pre-buried between the higher end side of the concrete pad and the groove; when filling with C25 sprayed concrete in step S3, the spraying pipe is first connected to one end of the injection pipe on the higher end side of the concrete pad, so that the C25 sprayed concrete fills the gap between the upper steel mesh and the arch foot of the steel arch frame.

[0018] A further setting of the present invention is that before filling with C25 shotcrete in step S3, the two side edges of the upper steel mesh and the corners of the lower steel mesh are reinforced by a reinforcing mechanism respectively; the reinforcing mechanism includes two connecting sleeves with regular polygon-shaped inserting columns, a two-way threaded pipe with internal threads having opposite thread directions at both ends, a first screw rod with one end threadedly connected to one end of the two-way threaded pipe and the other end having an inserting groove matching the inserting column, and a second screw rod with one end threadedly connected to the other end of the two-way threaded pipe and the other end having an inserting groove matching the inserting column. The two connecting sleeves are respectively pre-installed on the steel bars of the upper steel mesh close to the concrete cushion block and the steel bars of the lower steel mesh close to the concrete cushion block, and the connecting sleeves are sleeved on the corresponding steel bars during the production of the steel mesh.

[0019] A further setting of the present invention is that the reinforcing mechanism further includes a rotating rod, a spherical head provided at one end of the rotating rod, and a spherical seat provided on the circumferential side of the middle part of the two-way threaded pipe and having a spherical groove for the spherical head to be embedded and movably connected.

[0020] A further setting of the present invention is that before filling with C25 shotcrete in step S3, a formwork mechanism is arranged on the circumferences of the upper steel mesh and the lower steel mesh to prevent the C25 shotcrete from overflowing; the formwork mechanism includes two corner seats in an "L" shape and having inserting grooves at both ends, a first formwork with both ends for inserting between the inserting grooves of the two corner seats and close to the higher end of the concrete cushion block, and two second formworks with one end inserted on the corner seats and arranged in parallel on both sides. A waist-shaped groove close to the reinforcing mechanism is arranged at the end of the second formwork away from the corner seat, the waist-shaped groove extends along the vertical direction, the rotating rod passes through the waist-shaped groove, the circumferential side of the rotating rod has threads, and a locking nut for abutting against the second formwork is threadedly connected to the end of the rotating rod passing through the waist-shaped groove.

[0021] In summary, the present invention has the following beneficial effects:

[0022] 1. The prefabricated concrete cushion blocks can support the arch feet of the steel arch frame. Before the arch feet of the steel arch frame accurately fall on the measuring points, anti-reinforcing mesh sheets are placed on the lower surface and the upper surface of the concrete cushion blocks to reduce the pressure of the concrete cushion blocks on the ground foundation and the pressure of the arch feet on the concrete cushion blocks; at the same time, C25 shotcrete is used to densely fill the range between the two layers of steel mesh sheets and the range between the upper steel mesh sheet and the arch feet of the steel arch frame. After the C25 shotcrete solidifies, it is imprisoned. The internal steel mesh sheets and C25 shotcrete become reinforced concrete to increase strength, and can be combined with the ground foundation of the tunnel for imprisonment; finally, it is ensured that the arch feet fall on a firm foundation and the force is uniform, effectively reducing the disturbance to the arch frame during later construction and avoiding situations such as abnormal settlement.

[0023] 2. Since the shape of the steel arch frame is usually larger than a semicircle, the lower surface of the arch foot is inclined and extends downward toward the direction close to the random inner wall. At this time, in S32 of step S3, the end of the concrete pad with a smaller height is directed toward the inner wall of the tunnel, and a concrete pad with an upper surface inclination angle not less than the lower surface inclination angle of the arch foot of the steel arch frame is selected; at this time, the arch foot is placed on the steel mesh above the middle of the concrete pad, and the problem of lifting the arch foot upward will not occur, so as to ensure that the steel arch frame falls accurately into the measuring point; in addition, if only a concrete pad with an upper surface inclination angle greater than the lower surface inclination angle of the arch foot of the steel arch frame can be selected, the problem of one end of the arch foot close to the inner wall of the tunnel is likely to be suspended, and the gap can be filled by using C25 spraying concrete in step S3 at a later stage;

[0024] 3. Grooving is made on the surface of the concrete pad, and the steel bars in contact with the concrete pad are respectively embedded in the grooves of the concrete pad. At this time, on the one hand, the steel mesh on the concrete pad can be prevented from slipping, and on the other hand, the end of the arch foot away from the inner wall of the tunnel is supported on the steel mesh. At this time, the contact line between the arch foot and the steel mesh, and the extension square of the steel bars in contact with the steel mesh and the arch foot are perpendicular, so that the end of the arch foot away from the inner wall of the tunnel can be stably supported;

[0025] 4. If you can only choose a concrete pad with an upper surface inclination angle greater than the lower surface inclination angle of the arch foot of the steel arch frame, it is easy to cause the end of the arch foot close to the inner wall of the tunnel to be suspended. In this case, multiple wedge-shaped blocks embedded by a hammer can improve the support stability of the arch foot;

[0026] 5. Since the arch foot is placed on the steel mesh on the upper surface of the concrete pad, it is difficult to densely fill the area between the concrete pad and the arch foot when C25 spraying concrete is used in step S3. At this time, by grooving the upper surface of the concrete pad and pre-embedded injection pipes, concrete can enter the gap between the concrete pad and the arch foot and solidify, thereby improving the support effect on the arch foot;

[0027] 6. The setting of the reinforcement mechanism can realize the connection of the two steel meshes at the corners to improve the overall structural strength and prevent the upper steel mesh from sliding on the concrete pad; at the same time, when the reinforcement mechanism is used: the notch of the connecting sleeve can be inserted from the annular groove of the steel bar of the steel mesh, and after the length of the first screw and the second screw is adjusted, the first screw below is first connected to the plug-in column of the connecting sleeve below, and then the position of the second screw is adjusted, so that the first screw, the two-way threaded tube and the second screw are moved up as a whole, so that the plug-in columns of the two connecting sleeves of the first screw and the second screw are connected, and then the spacing between the two layers of steel mesh is adjusted by rotating the two-way threaded tube to achieve connection support; at the same time, the setting of the rotating rod, the spherical head and the spherical seat facilitates the rotation of the two-way threaded tube;

[0028] 7. Because the lower end of the concrete pad is close to the inner wall of the tunnel, when C25 sprayed concrete is used for filling, the formwork mechanism does not need to protect the lower end of the concrete pad; at this time, the formwork mechanism includes two corner seats, a first formwork and two second formworks, which can form a "凵"-shaped formwork mechanism. After the formwork mechanism is placed, the rotating rod can pass through the waist groove of the second formwork and be fixed by a locking nut, which can prevent the second formwork from being displaced during C25 sprayed concrete filling. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a reference structural schematic diagram of Example 1;

[0030] Figure 2 is a side view of Example 1;

[0031] Figure 3 is a side view of the reference structure of Example 2;

[0032] Figure 4 yes Figure 3 A local enlarged view at A in the figure;

[0033] Figure 5 is a structural cross-sectional view of the concrete pad in Example 2;

[0034] Figure 6 is a reference structural diagram of Example 3;

[0035] Figure 7 yes Figure 6 A partial enlarged view at B in the figure;

[0036] Figure 8 is a reference structural diagram of Example 4;

[0037] Figure 9 It is a structural schematic diagram of the template mechanism in Example 4.

[0038] Figure numerals: 1. Concrete pad; 11. Limiting groove; 12. Groove; 13. Injection pipe; 2. Steel mesh; 21. Steel bar; 3. Wedge block; 4. Reinforcement mechanism; 41. Connecting sleeve; 411. Plug-in column; 42. Bidirectional threaded pipe; 43. First screw; 44. Second screw; 46. Rotating rod; 47. Spherical head; 48. Spherical seat; 5. Formwork mechanism; 51. Corner seat; 511. Plug-in groove; 52. First formwork; 53. Second formwork; 531. Waist-shaped groove; 532. Locking nut; 6. Steel arch frame; 61. Arch foot. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0040] Embodiment 1: A method for temporarily supporting the arch foot of a steel arch frame in tunnel construction, such asFigure 1 and Figure 2 As shown in Figure 2 , it includes the following steps: S1 precast concrete cushion blocks 1; S2 ground foundation cleaning; S3 installation of precast concrete cushion blocks 1.

[0041] In step S1 of precasting the concrete cushion blocks 1, multiple concrete cushion blocks 1 are precast using C30 concrete. The upper surfaces of the multiple concrete cushion blocks 1 are inclined. The lengths and widths of the multiple concrete cushion blocks 1 are both 50 cm. One end of the multiple concrete cushion blocks 1 has a height of 10 cm and the other end has a height ranging from 5 to 8 cm.

[0042] In step S2 of ground foundation cleaning, after the initial spraying in tunnel excavation and before the installation of the steel arch 6, after measurement and lofting, the loose slag near the arch feet 61 of the steel arch 6 is manually cleaned up to ensure that the concrete cushion blocks 1 are placed on a solid and flat ground foundation.

[0043] In step S3 of installing the precast concrete cushion blocks 1, it includes the following steps: S31: Before the steel arch 6 is assembled and accurately placed on the measurement point, first place a layer of steel mesh 2 on the ground foundation at the corresponding arch feet 61 of the steel arch 6, and then place the concrete cushion blocks 1 above the middle of the steel mesh 2; S32: Accurately place the steel arch 6 on the measurement point, lift the steel arch 6 by 2 - 3 cm, adjust the position of the concrete cushion blocks 1 so that the arch feet 61 are aligned with the middle of the concrete cushion blocks 1, and place a layer of steel mesh 2 on the upper surface of the concrete cushion blocks 1; S33: Accurately place the steel arch 6 on the measurement point so that the arch feet 61 of the steel arch 6 are placed on the upper layer of steel mesh 2. When re - spraying after the construction of bolts and small ducts is completed and passes the inspection, use C25 sprayed concrete to densely fill the area between the two layers of steel mesh 2 and the area between the upper layer of steel mesh 2 and the arch feet 61 of the steel arch 6. After the C25 sprayed concrete solidifies, confinement is achieved.

[0044] And in S31 of step S3, the end of the concrete cushion block 1 with a smaller height faces the inner wall of the tunnel, and a concrete cushion block 1 with an upper surface inclination angle not less than the inclination angle of the lower surface of the arch feet 61 of the steel arch 6 is selected.

[0045] Implementation effect: The precast concrete cushion blocks 1 can support the arch feet 61 of the steel arch 6. Before the arch feet 61 of the steel arch 6 accurately fall on the measurement point, steel mesh 2 is placed on the lower and upper surfaces of the concrete cushion blocks 1 to reduce the pressure of the concrete cushion blocks 1 on the ground foundation and the pressure of the arch feet 61 on the concrete cushion blocks 1; at the same time, use C25 sprayed concrete to densely fill the area between the two layers of steel mesh 2 and the area between the upper layer of steel mesh 2 and the arch feet 61 of the steel arch 6. After the C25 sprayed concrete solidifies, confinement is achieved. The internal steel mesh 2 and C25 sprayed concrete form reinforced concrete 21 to increase the strength and can be combined with the ground foundation of the tunnel for confinement; ultimately, ensure that the arch feet 61 fall on a firm foundation and the stress is uniform, effectively reducing the disturbance to the arch during later construction and avoiding situations such as abnormal settlement.

[0046] Because the shape of the steel arch frame 6 is usually larger than a semicircle, the lower surface of the arch foot 61 is inclined and extends downward in the direction close to any inner wall. At this time, in S32 of step S3, the end of the concrete pad 1 with a smaller height is made to face the inner wall of the tunnel, and a concrete pad 1 with an upper surface inclination angle not less than the lower surface inclination angle of the arch foot 61 of the steel arch frame 6 is selected; at this time, the arch foot 61 is placed on the steel mesh 2 above the middle of the concrete pad 1, and the problem of lifting the arch foot 61 upward will not occur, so as to ensure that the steel arch frame 6 falls accurately into the measuring point; in addition, if only a concrete pad 1 with an upper surface inclination angle greater than the lower surface inclination angle of the arch foot 61 of the steel arch frame 6 can be selected, the problem of one end of the arch foot 61 close to the inner wall of the tunnel is likely to be suspended, and the gap can be filled in the later stage by using C25 spraying concrete in step S3.

[0047] Embodiment 2: A method for temporarily supporting the arch foot of a steel arch frame in tunnel construction, such as Figures 3 to 5 As shown, the difference from Example 1 is that: when the concrete pad 1 is prefabricated in step S1, a limit groove 11 is provided on the upper surface of the concrete pad 1, and the limit grooves 11 of the concrete pad 1 are arranged and distributed along its inclined surface; in step S31 of step S3, the steel bars 21 of the steel mesh 2 in contact with the concrete pad 1 are respectively embedded in the limit grooves 11 of the concrete pad 1. Before using C25 spraying concrete in step S3, a plurality of wedge blocks 3 are hammered in between the upper surface of the concrete pad 1 and the end of the arch foot 61 of the steel arch frame 6 close to the inner wall of the tunnel.

[0048] At the same time, when prefabricating the concrete pad 1 in step S1, a groove 12 is set in the middle of the upper surface of the concrete pad 1, and an "L"-shaped injection pipe 13 is pre-buried between the higher end side of the concrete pad 1 and the groove 12; when using C25 sprayed concrete for filling in step S3, the spray pipe is first connected to one end of the injection pipe 13 on the higher end side of the concrete pad 1, so that the C25 sprayed concrete fills the gap between the upper steel mesh 2 and the arch foot 61 of the steel arch frame 6.

[0049] Implementation effect: by making grooves on the surface of the concrete pad 1, and making the steel mesh 2 and the steel bars 21 in contact with the concrete pad 1 respectively embedded in the grooves of the concrete pad 1, on the one hand, the steel mesh 2 on the concrete pad 1 can be prevented from slipping, and on the other hand, the end of the arch foot 61 away from the inner wall of the tunnel is supported on the steel mesh 2. At this time, the contact line between the arch foot 61 and the steel mesh 2, and the extension square of the steel mesh 2 and the steel bars 21 in contact with the arch foot 61 are perpendicular, so that the end of the arch foot 61 away from the inner wall of the tunnel can be stably supported. If only the concrete pad 1 with an upper surface inclination angle greater than the lower surface inclination angle of the arch foot 61 of the steel arch frame 6 can be selected, the problem of the end of the arch foot 61 close to the inner wall of the tunnel is likely to be suspended. At this time, the multiple wedge-shaped blocks 3 embedded by the hammer can improve the support stability of the arch foot 61.

[0050] Since the arch feet 61 are placed on the steel mesh 2 on the upper surface of the concrete cushion block 1, it is difficult to densely fill the range between the concrete cushion block 1 and the arch feet 61 when spraying C25 sprayed concrete in step S3. At this time, by grooving the upper surface of the concrete cushion block 1 and setting the embedded injection pipe 13, the concrete can enter the gap between the concrete cushion block 1 and the arch feet 61 and solidify, improving the support effect on the arch feet 61;

[0051] Example 3: A method for temporarily supporting the arch feet of a steel arch in tunnel construction, as Figure 6 and Figure 7 shown. The difference from Example 2 is that before filling with C25 sprayed concrete in step S3, the two side edges of the upper steel mesh 2 and the corners of the lower steel mesh 2 are respectively reinforced by the reinforcement mechanism 4.

[0052] The reinforcement mechanism 4 includes two connecting sleeves 41 with regular polygon plug-in columns 411, a two-way threaded pipe 42 with internally threaded ends having opposite thread directions, a first screw 43 with one end threadedly connected to one end of the two-way threaded pipe 42 and the other end having a plug-in groove 511 matching the plug-in column 411, and a second screw 44 with one end threadedly connected to the other end of the two-way threaded pipe 42 and the other end having a plug-in groove 511 matching the plug-in column 411. The two connecting sleeves 41 are respectively pre-installed on the steel bars 21 of the upper steel mesh 2 close to the concrete cushion block 1 and the steel bars 21 of the lower steel mesh 2 close to the concrete cushion block 1. The connecting sleeve 41 is sleeved on the steel bar 21 at the corresponding position during the production of the steel mesh 2. At the same time, the reinforcement mechanism 4 also includes a rotating rod 46, a spherical head 47 provided at one end of the rotating rod 46, and a spherical seat 48 provided on the circumferential side of the middle of the two-way threaded pipe 42 and having a spherical groove for the spherical head 47 to be embedded and movably connected.

[0053] Implementation effect: The setting of the reinforcement mechanism 4 can connect the corners of the two steel meshes 2 to improve the overall structural strength and prevent the upper steel mesh 2 from sliding on the concrete cushion block 1; at the same time, when the reinforcement mechanism 4 is used: the notch of the connecting sleeve 41 can be sleeved from the annular groove of the steel bar 21 of the steel mesh 2. After adjusting the length of the first screw 43 and the second screw 44, the lower first screw 43 is first connected to the plug-in column 411 of the lower connecting sleeve 41, and then the position of the second screw 44 is adjusted so that the first screw 43, the two-way threaded pipe 42 and the second screw 44 are moved upward as a whole, so that after the first screw 43 and the second screw 44 are connected to the plug-in columns 411 of the two connecting sleeves 41, the distance between the two layers of steel meshes 2 is adjusted by rotating the two-way threaded pipe 42 to achieve connection and support; at the same time, the setting of the rotating rod 46, the spherical head 47 and the spherical seat 48 facilitates the rotation of the two-way threaded pipe 42.

[0054] Example 4: A method for temporarily supporting the arch feet of a steel arch in tunnel construction, as Figure 8and Figure 9 As shown in Figure 9 , the difference from Embodiment 3 is that before filling with C25 shotcrete in step S3, a formwork mechanism 5 is arranged on the peripheral sides of the upper steel mesh 2 and the lower steel mesh 2 to prevent the C25 shotcrete from overflowing; the formwork mechanism 5 includes two corner seats 51 in an "L" shape with plug-in slots 511 at both ends, a first formwork 52 with both ends for plugging between the plug-in slots 511 of the two corner seats 51 and close to the higher end of the concrete cushion block 1, and two second formworks 53 with one end plugged on the corner seats 51 and arranged in parallel on both sides. A waist-shaped slot 531 close to the reinforcement mechanism 4 is arranged at the end of the second formwork 53 away from the corner seat 51. The waist-shaped slot 531 extends along the vertical direction. A rotating rod 46 passes through the waist-shaped slot 531. The peripheral side of the rotating rod 46 has threads, and a locking nut 532 for abutting against the second formwork 53 is threadedly connected to the end of the rotating rod 46 passing through the waist-shaped slot 531.

[0055] Implementation effect: Since the lower end of the concrete cushion block 1 is close to the inner wall of the tunnel, when filling with C25 shotcrete at this time, the formwork mechanism 5 does not need to protect the lower end of the concrete cushion block 1; at this time, the formwork mechanism 5 includes two corner seats 51, a first formwork 52 and two second formworks 53, and can form a formwork mechanism 5 in a "U" shape. After the formwork mechanism 5 is placed, the rotating rod 46 can pass through the waist-shaped slot 531 of the second formwork 53 and be fixed by the locking nut 532, which can prevent the second formwork 53 from displacing during the filling of C25 shotcrete.

[0056] This specific embodiment is only an interpretation of the present invention, and it is not a limitation of the present invention. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

Claims

1. A temporary support method for the arch feet of a steel arch in tunnel construction, characterized in that: The steps include: S1 Precast Concrete Pad (1) A plurality of concrete pads (1) are prefabricated using C30 concrete, the upper surfaces of the plurality of concrete pads (1) are arranged in an inclined plane, the length and width of the plurality of concrete pads (1) are both 50 cm, the height of one end of the plurality of concrete pads (1) is 10 cm and the height of the other end varies from 5 to 8 cm; S2 Ground Foundation Cleaning After the initial spraying of the tunnel excavation, the steel arch frame (6) is measured and laid out before installation, and the slag near the arch foot (61) of the steel arch frame (6) is manually cleaned to ensure that the concrete pad (1) is placed on a solid and flat ground foundation; S3 precast concrete pad (1) installation S31: After the steel arch frame (6) is assembled but not yet accurately placed at the measuring point, a layer of steel mesh (2) is placed on the ground foundation at the arch foot (61) of the corresponding steel arch frame (6), and then a concrete pad (1) is placed above the middle of the steel mesh (2); S32: accurately place the steel arch frame (6) at the measuring point, lift the steel arch frame (6) by 2 to 3 centimeters, adjust the position of the concrete pad (1) so that the arch foot (61) is aligned with the middle of the concrete pad (1), and place a layer of steel mesh (2) on the upper surface of the concrete pad (1); S33: The steel arch frame (6) is precisely placed at the measuring point so that the arch foot (61) of the steel arch frame (6) is placed on the upper steel mesh (2). When the anchor rods and small conduits are completed and inspected and qualified, the area between the two layers of steel mesh (2) and the area between the upper steel mesh (2) and the arch foot (61) of the steel arch frame (6) are filled and compacted with C25 shotcrete during the re-spraying. After the C25 shotcrete solidifies, the area is locked.

2. A temporary support method for the arch feet of a steel arch frame in tunnel construction according to claim 1, characterized in that: In step S31 of step S3, the end of the concrete pad (1) with a smaller height is directed toward the inner wall of the tunnel, and a concrete pad (1) is selected whose upper surface inclination angle is not less than the lower surface inclination angle of the arch foot (61) of the steel arch frame (6).

3. A temporary support method for the arch feet of a steel arch in tunnel construction according to claim 2, characterized in that: When the concrete pad (1) is prefabricated in step S1, a limiting groove (11) is provided on the upper surface of the concrete pad (1), and the limiting grooves (11) of the concrete pad (1) are arranged and distributed along the inclined surface thereof; in step S31 of step S3, the steel bars (21) of the steel mesh (2) in contact with the concrete pad (1) are respectively embedded in the limiting grooves (11) of the concrete pad (1).

4. A temporary support method for the arch feet of a steel arch in tunnel construction according to claim 2, characterized in that: Before using C25 sprayed concrete in step S3, a plurality of wedge-shaped blocks (3) are hammered in between the upper surface of the concrete pad (1) and the end of the arch foot (61) of the steel arch frame (6) close to the inner wall of the tunnel.

5. A temporary support method for the arch feet of a steel arch in tunnel construction according to claim 2, characterized in that: When the concrete pad (1) is prefabricated in step S1, a groove (12) is provided in the middle of the upper surface of the concrete pad (1), and an L-shaped injection pipe (13) is pre-buried between the higher end side of the concrete pad (1) and the groove (12); when C25 sprayed concrete is used for filling in step S3, the spray pipe is first connected to the end of the injection pipe (13) located on the higher end side of the concrete pad (1), so that the C25 sprayed concrete can fill the gap between the upper steel mesh (2) and the arch foot (61) of the steel arch frame (6).

6. A temporary support method for the arch feet of a steel arch in tunnel construction according to claim 2, characterized in that: Before filling with C25 shotcrete in step S3, the two side edges of the upper steel mesh (2) and the corners of the lower steel mesh (2) are reinforced by a reinforcing mechanism (4) respectively; the reinforcing mechanism (4) includes two connecting sleeves (41) each having a regular polygon-shaped inserting column (411), a two-way threaded pipe (42) with internal threads of opposite thread directions at both ends, a first screw rod (43) with one end threadedly connected to one end of the two-way threaded pipe (42) and the other end having an inserting groove (511) matching the inserting column (411), and a second screw rod (44) with one end threadedly connected to the other end of the two-way threaded pipe (42) and the other end having an inserting groove (511) matching the inserting column (411). The two connecting sleeves (41) are respectively pre-installed on the steel bars (21) of the upper steel mesh (2) close to the concrete cushion block (1) and the steel bars (21) of the lower steel mesh (2) close to the concrete cushion block (1), and the connecting sleeves (41) are sleeved on the steel bars (21) at corresponding positions when the steel mesh (2) is fabricated.

7. A temporary support method for the arch feet of a steel arch in tunnel construction according to claim 6, characterized in that: The reinforcing mechanism (4) further includes a rotating rod (46), a spherical head (47) provided at one end of the rotating rod (46), and a spherical seat (48) provided on the circumferential side of the middle part of the two-way threaded pipe (42) and having a spherical groove for the spherical head (47) to be embedded and movably connected.

8. A temporary support method for the arch feet of a steel arch in tunnel construction according to claim 7, characterized in that: Before filling with C25 shotcrete in step S3, a formwork mechanism (5) is arranged on the circumferential sides of the upper steel mesh (2) and the lower steel mesh (2) to prevent the C25 shotcrete from overflowing; the formwork mechanism (5) includes two corner seats (51) in an "L" shape and having inserting grooves (511) at both ends, a first formwork (52) with both ends for inserting between the inserting grooves (511) of the two corner seats (51) and close to the higher end of the concrete cushion block (1), and two second formworks (53) with one end inserted on the corner seats (51) and arranged in parallel on both sides. A waist-shaped groove (531) close to the reinforcing mechanism (4) is arranged at the end of the second formwork (53) away from the corner seat (51). The waist-shaped groove (531) extends along the vertical direction. The rotating rod (46) passes through the waist-shaped groove (531). The circumferential side of the rotating rod (46) has threads, and a locking nut (532) for abutting against the second formwork (53) is threadedly connected to the end of the rotating rod (46) passing through the waist-shaped groove (531).

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