A cold excavation construction method for tunnels passing under densely populated residential areas

Abstract

The invention discloses a cold excavation construction method for a tunnel passing under densely populated residential areas, comprising the following steps: 1. before excavation, performing advanced support construction on the tunnel; 2. after completing the advanced support, using a cantilever tunnel boring machine to circumferentially excavate a contour line; 3. after completing the excavation of the tunnel face, cleaning up the excavated rock waste; 4. setting up a support trolley and taking support measures for the tunnel; 5. using the cantilever tunnel boring machine to excavate a reserved core soil portion and excavate the core soil portion; 6. after completing the excavation of the core soil, cleaning up the excavated rock waste; and 7. starting the next cycle. The method adopts a cantilever tunnel boring machine to first excavate the outer edge contour of the tunnel face, and after completing the cleaning of the waste waste, initial support and other steps can be performed. During the support, the cantilever tunnel boring machine can simultaneously excavate the core soil. The excavation method can greatly improve the excavation efficiency of the tunnel, save time and cost, and has the characteristics of high safety and construction efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction, and in particular to a cold excavation construction method for a tunnel passing under densely populated residential areas. Background Art

[0002] Tunnel excavation refers to a construction method that uses open-cut or underground excavation to dig holes in the mountain to guide roads. In recent years, with the continuous development of urban transportation, in order to alleviate the traffic pressure in the city, this form of transportation has gradually appeared in people's vision and has been widely used in recent years. During the construction of the subway, it is necessary to construct a tunnel under the existing building complex. Under different geological conditions, this has caused great interference to the tunnel construction. For example, the karst landform in southwest my country is often accompanied by many underground caves. During the construction of the tunnel, disasters such as roof collapse and surface subsidence are prone to occur; when constructing tunnels in water-rich strata, water and mud bursts are very likely to occur, affecting construction safety and structural safety, and easily leading to tunnel collapse, thereby affecting the safety of surrounding existing structures;

[0003] At the same time, in the construction process of some mountain tunnels, most of the excavation methods in China are currently carried out by controlled blasting. Tunnels passing under densely populated residential areas have strict requirements on ground vibration and settlement. If traditional controlled blasting is still used for construction, it will not only have a significant impact on nearby residents, but also pose serious safety hazards. Therefore, higher requirements are placed on the construction process of tunnels passing under densely populated residential areas.

[0004] Based on this, it is urgent to design a tunnel excavation construction method for passing through densely populated residential areas to solve the problems existing in the above-mentioned existing technologies. Summary of the Invention

[0005] In response to the above-mentioned problems, the present invention aims to provide a cold excavation construction method for tunnels passing under densely populated residential areas. This method uses a cantilever tunnel boring machine to first excavate the outer edge contour of the tunnel face. After completing the cleaning of waste slag, initial support and other steps can be carried out. While supporting, the cantilever tunnel boring machine can also excavate the core soil. This excavation method can greatly improve the tunnel excavation efficiency, save time and cost, and has the characteristics of safety and high construction efficiency.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A cold excavation construction method for a tunnel passing under densely populated residential areas, comprising:

[0008] Step 1. Advanced support construction: Before excavation, advanced support construction of the tunnel is carried out according to the design requirements;

[0009] Step 2. After completing the advance support, use a boom tunnel boring machine to circumferentially excavate the contour line;

[0010] Step 3. Mechanical slag removal and transportation: After the excavation of the outer edge of the tunnel face is completed, the excavator enters the site to clean up the excavated rock slag and transport it using a transport vehicle;

[0011] Step 4. Set up a support trolley and implement initial support measures for the tunnel to reduce the deformation time of the surrounding rock;

[0012] Step 5. The cantilever tunnel boring machine excavates the reserved core soil part, and excavates the core soil part while providing support;

[0013] Step 6. Mechanical slag removal and transportation: After the core soil excavation is completed, the excavator enters the site to clean up the excavated rock slag and use the loader to transport it;

[0014] Step 7. Start the next cycle.

[0015] Preferably, the advanced support construction described in step 1 includes

[0016] Step 1.1 Middle pipe roof support

[0017] The middle pipe shed support is made of hot-rolled seamless steel flower pipes. Grouting holes are drilled in the pipe wall in a plum blossom pattern. The front end is processed into a cone. The circumferential spacing is 0.4m. There are 50 pipes in each ring, each 8m long, and a longitudinal ring of 4.8m. The external insertion angle is 10° to 15°. Cement slurry is used for grouting. The water-binder ratio of the cement slurry is 0.5:1 to 0.8:1. At the same time, the single-hole grouting completion standard is adopted: the grouting pressure is gradually increased. When it reaches the designed final pressure and stabilizes for 10 minutes, the middle pipe shed support construction is completed.

[0018] Step 1.2 Small catheter support

[0019] (1) The small conduit is installed by drilling method, and the diameter of the drill hole is 3 to 5 mm larger than the diameter of the steel pipe;

[0020] (2) Then, the small conduit is passed through the steel arch frame and pushed in by hammering, with the insertion length not less than 90% of the length of the steel pipe, and the sand and gravel in the steel pipe are blown out by high-pressure air;

[0021] (3) After the small tube is installed, use plastic mud to seal the hole and surrounding cracks, and spray concrete near the small tube and on the working surface.

[0022] Preferably, during the small conduit support process, the excavation length of the tunnel is less than the grouting length of the small conduit, and the length of the reserved part of the excavation depth does not exceed 10% of the length of the leading small conduit; and the small conduit and the pipe-roof steel pipe segments are connected with threads, and the number of joints in the same section shall not exceed 50% of the number of conduits on the end face; the radial construction error shall not exceed 15 cm, and the adjacent circumferential distance shall not be greater than 5 cm.

[0023] Preferably, the process of using a boom tunnel boring machine to circumferentially excavate the contour line in step 2 includes:

[0024] Step 2.1. After the boom tunnel boring machine arrives on site, first adjust the boom tunnel boring machine body to the center of the tunnel face. Adjust the machine body so that the excavation area is within its own excavation range. Then, excavate circumferentially along the contour line until the specified core soil size contour is reached. The contour line is trimmed to the design requirements.

[0025] During excavation, the contour line is excavated from left to right in a clockwise direction, and then from right to left in a counterclockwise direction. This cycle is repeated until the core soil size is reached. The width of each excavation is 1m, which is the size of the cantilever tunnel boring machine cutting head.

[0026] Step 2.2. Clean the waste residue from the outer edge of the tunnel face.

[0027] Preferably, the process of performing initial support on the tunnel described in step 4 includes:

[0028] Step 4.1 Before spraying, clean the pumice on the excavation surface and the rock debris and accumulation at the foot of the wall, and check the clearance size of the excavation section;

[0029] Step 4.2: Rinse the sprayed surface and set the mark to control the thickness of the sprayed concrete. If there are any depressions, spray them to fill them first.

[0030] During step 4.3, the nozzle is perpendicular to the rock surface, 0.6m to 1.8m away from the target, and moves in a spiral motion. The wind pressure is 0.5 to 0.7 MPa. The liquid accelerating agent is added near the outlet of the spray gun using an accelerating agent pump.

[0031] Step 4.4: Spraying is carried out continuously in sections, slices, and layers from bottom to top, with the length of each section not exceeding 6 cm.

[0032] Among them, when spraying in layers, the thickness of the initial sprayed concrete shall not be less than 40mm, and the latter layer shall be sprayed after the previous layer of concrete has completely set.

[0033] Preferably, the steel arch support process described in step 5 includes:

[0034] Step 5.1: First, place the lower end of the steel arch frame on a stable stratum. The arch foot should be 15 to 20 cm below the excavation bottom line. If the arch foot is too deep, add steel plates or concrete pads. After installation, use the locking anchor device to position the steel arch frame.

[0035] Step 5.2 When the arch foot is too deep, spray the same grade of concrete on the back of the steel arch frame to make the steel arch frame support closely attached to the surrounding rock.

[0036] Preferably, the foot locking anchor device described in step 5.1 includes a connecting rod, an anchor positioning mechanism and an anchor.

[0037] The connecting rod is arranged at the lower end foot arch of the steel arch frame through a connecting rod mounting piece;

[0038] The anchor rod positioning mechanism is arranged on the connecting rod, and includes a first arc-shaped positioning block, a first positioning member, a second positioning member and a rotating positioning member. The first arc-shaped positioning block is arranged on the upper side of the first positioning member and is used in conjunction with the connecting rod. The first positioning member is arranged on the upper side of the second positioning member and is connected to the second positioning member through a horizontal positioning assembly. The rotating positioning member is arranged at the lower end of the second positioning member and is used in conjunction with the anchor rod.

[0039] The anchor rod is arranged on the connecting rod through an anchor rod positioning mechanism and is used in conjunction with the tunnel arch foot.

[0040] Preferably, the first positioning member includes a threaded connecting rod and an adjusting nut, the threaded connecting rod passes through the adjusting slot and is arranged in the tail rod threaded hole of the second positioning member, and the adjusting nut is arranged at the outer end of the threaded connecting rod; the rotating positioning member is arranged at the lower end of the second positioning member through the U-shaped mounting member, and includes a positioning sleeve and a positioning nut, the positioning sleeve is arranged in the mounting slot of the U-shaped mounting member, and a positioning bolt is arranged on the lower side of the positioning sleeve, and the positioning bolt is used in conjunction with the anchor rod; the positioning nuts are arranged on both sides of the positioning sleeve, and are used in conjunction with the positioning columns arranged on both sides of the positioning sleeve.

[0041] Preferably, the anchor rod comprises an outer steel tube, an inner steel core anchor rod, an adjusting core, a first bevel gear, a second bevel gear and an adjusting handle;

[0042] The outer steel cylinder is arranged at the tail end of the inner steel core anchor rod, and mutually communicating steel cylinder cavities are arranged in the outer steel cylinder;

[0043] The inner steel core anchor rod is movably arranged in the steel cylinder cavity, and a limiting ring is arranged at the tail of the inner steel core anchor rod to match the limiting cavity arranged in the outer steel cylinder;

[0044] The adjusting core is installed in the steel cylinder cavity through the first bearing, and the adjusting core is provided with an external thread adapted to the internal thread provided in the inner cavity of the inner steel core anchor rod;

[0045] The first helical gear is arranged at the outer end of the adjusting core and meshes with the second helical gear;

[0046] The second bevel gear is arranged at the end of the adjustment handle;

[0047] The adjusting handle is arranged on the outer steel cylinder through a second bearing.

[0048] Preferably, the limiting ring is a prismatic limiting ring, the limiting cavity is adapted to the limiting ring, and a screw thread is further provided at the front end of the inner steel core anchor rod.

[0049] The beneficial effects of the present invention are as follows: the present invention discloses a cold excavation construction method for a tunnel passing under densely populated residential areas. Compared with the prior art, the present invention has the following improvements:

[0050] 1. This invention designs a cold excavation construction method for tunnels passing under densely populated residential areas. Compared with existing technologies, this construction method ensures both construction safety and the normal lives of residents at the top of the tunnel. A cantilevered tunnel boring machine first excavates the outer edge contour of the tunnel face. After the waste residue is cleared, initial support and other steps can be carried out. While supporting, the cantilevered tunnel boring machine can also excavate the core soil. This excavation method greatly improves tunnel excavation efficiency and saves time and costs.

[0051] 2. The method of the present invention takes into account the safety of tunnel construction while also taking into account the safety of residential areas. The construction method is safe, reasonable, economical and efficient.

[0052] 3. The present invention adopts steel arches and steel mesh for support after excavation is completed, which can reduce the deformation time of surrounding rock without support after excavation, thereby effectively controlling the deformation of surrounding rock;

[0053] 4. The present invention designs a locking foot anchor rod device, which can adjust the anchoring position and anchoring point of the anchor rod during use, so that its anchoring effect is better, and can effectively fix the position of the steel arch frame in the tunnel. It has the advantages of simple structure and easy use. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 The present invention is a construction flow chart of the cold excavation construction method of a tunnel passing under densely populated residential areas.

[0055] Figure 2 Schematic diagram of the excavation sequence of the cantilever tunnel boring machine of the present invention.

[0056] Figure 3 It is a schematic diagram of the support stand structure of the present invention.

[0057] Figure 4 This is the longitudinal layout diagram of the pipe rack in the present invention.

[0058] Figure 5 This is a flow chart of the steel frame and steel mesh support of the present invention.

[0059] Figure 6 This is a diagram of the longitudinal layout of the small catheters of the present invention.

[0060] Figure 7 This is a layout diagram of the locking foot anchor device of the present invention.

[0061] Figure 8 It is a schematic diagram of the steel arch frame of the present invention.

[0062] Figure 9This is an installation effect diagram of the locking foot anchor device of the present invention.

[0063] Figure 10 It is a structural schematic diagram of the anchor rod positioning mechanism of the present invention.

[0064] Figure 11 It is a partial enlarged view of the anchor rod positioning mechanism A of the present invention.

[0065] Figure 12 This is a front view of the second positioning member of the present invention.

[0066] Figure 13 This is a diagram showing the installation effect of the anchor rod of the present invention.

[0067] Figure 14 It is a cross-sectional view of the anchor rod of the present invention.

[0068] Figure 15 It is a structural schematic diagram of the inner steel core anchor rod of the present invention.

[0069] 1. Steel arch frame, 2. Connecting rod, 3. Anchor rod positioning mechanism, 31. First arc-shaped positioning block, 32. First positioning member, 321. Adjusting slot, 33. Second positioning member, 331. Tail rod screw hole, 332. U-shaped mounting member, 34. Adjusting nut, 35. Rotating positioning member, 351. Positioning sleeve, 352. Positioning column, 353. Positioning nut, 354. Positioning bolt, 36. Screw-on connecting rod, 4. Anchor rod, 41. Outer steel tube, 411. Limiting cavity, 42. Inner steel core anchor rod, 421. Inner cavity, 422. Limiting ring, 43. Adjusting core, 44. First bearing, 45. First bevel gear, 46. Second bevel gear, 47. Second bearing, 48. Adjusting handle, 5. Connecting rod mounting member. DETAILED DESCRIPTION

[0070] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0071] Example 1: Refer to the attached Figure 1-15 A cold excavation construction method for a tunnel passing under densely populated residential areas is shown, comprising

[0072] Step 1. Advance support construction: Before excavation, advance support construction of the tunnel shall be carried out according to the design requirements.

[0073] Among them: the advanced support includes the middle pipe shed support and the advanced small pipe support, the middle pipe shed support is in front and the small pipe support is in the back;

[0074] Step 1.1 Middle pipe roof support

[0075] The middle pipe shed support adopts hot-rolled seamless steel flower pipe. Grouting holes must be drilled in the pipe wall in a plum blossom-shaped arrangement. The front end is processed into a cone. The circumferential spacing is 0.4m. There are 50 pipes in each ring. Each pipe is 8m long. The longitudinal ring is 4.8m. The external insertion angle is 10° to 15°. Cement slurry is generally used for grouting. The water-binder ratio of the cement slurry is 0.5:1 to 0.8:1. At the same time, the single-hole grouting completion standard is adopted: the grouting pressure is gradually increased. When it reaches the designed final pressure and stabilizes for 10 minutes, the middle pipe shed support construction is completed.

[0076] Step 1.2 Small catheter support

[0077] The installation of small conduits adopts the drilling method, that is, first drill a hole according to the design requirements, and the diameter of the hole is 3 to 5 mm larger than the diameter of the steel pipe. Then the small conduit is passed through the steel arch frame and pushed in by hammering. The pushing length should not be less than 90% of the length of the steel pipe, and the sand and gravel in the steel pipe should be blown out with high-pressure air. After the small conduit is installed, the hole and the surrounding cracks are sealed with plastic mud. If necessary, concrete is sprayed near the small conduit and on the working surface to prevent the working surface from collapsing. The excavation length of the tunnel should be less than the grouting length of the small conduit, and the excavation length of the tunnel should be less than the grouting length of the small conduit. The reserved part that does not exceed 10% of the length of the small conduit in advance is used as the grouting wall for the next cycle. During the grouting process, the changes in the grouting pressure and the discharge volume of the grouting pump should be observed at any time, and the grouting situation should be analyzed to prevent pipe blockage, slurry leakage, and slurry leakage.

[0078] Before construction, hole locations are determined and marked according to design requirements and the surrounding rock conditions of the face. A pipe-roof drilling rig is used to drill holes, using a guide frame with an external insertion angle of 10° to 15°. Geological records of each hole are kept. Steel pipes are pushed in by the drilling rig, and sections are connected with threads. The number of joints on the same section must not exceed 50% of the number of pipes on that end face. The radial construction error must not exceed 15 cm, and the circumferential distance between adjacent sections must not exceed 5 cm. Once the pipe-roof is in place, the gap between the steel pipe and the guide pipe must be tightly sealed with quick-setting cement or other materials to prevent slurry from escaping. Slurry inlet and exhaust holes must be provided when blocking.

[0079] Step 2. After completing the advance support, use the cantilever tunnel boring machine to circumvent the contour line

[0080] Step 2.1. The boom tunnel boring machine enters the site. First, adjust the boom tunnel boring machine body to the center of the tunnel face. Adjust the machine body so that the excavation area is within its own excavation range. Then, excavate circumferentially along the contour line until the specified core soil size contour is excavated. The contour line is trimmed to the design requirements.

[0081] Specifically, during excavation, first excavate the contour line from left to right in a clockwise direction, then excavate from right to left in a counterclockwise direction, and repeat the cycle until the core soil size is excavated. The width of each excavation is 1m, which is the size of the cantilever tunnel boring machine cutting head.

[0082] Step 2.2. Clean the waste residue on the outer edge of the tunnel face;

[0083] Step 3. Mechanical slag removal and transportation: After the excavation of the outer edge of the tunnel face is completed, the excavator enters the site to clean up the excavated rock waste, and transports it by transport vehicle to the designated location for treatment;

[0084] Step 4. Set up the support trolley, carry out initial support measures such as concrete pouring, steel frame, steel mesh, etc. to reduce the deformation time of the surrounding rock.

[0085] Step 4.1 Before spraying, clean up the pumice on the excavation surface and the rock debris and accumulation at the foot of the wall. Check the clearance size of the excavation section. If there is water gushing, dripping and concentrated water outlet on the sprayed surface, divert the water first.

[0086] Step 4.2: Use high-pressure water to flush the sprayed surface, set the mark to control the thickness of the sprayed concrete, and fill the larger depressions with spray first;

[0087] Step 4.3: Use a concrete mixer truck to transport concrete and unload it into the wet spraying machine. The nozzle should be perpendicular to the rock surface and 0.6m to 1.8m away from the target area. The nozzle should move in a spiral motion. The wind pressure should be 0.5 to 0.7 MPa. Liquid accelerator should be added near the spray gun outlet using an accelerator pump.

[0088] Step 4.4: Spraying should be done continuously. Spraying should be done in sections, slices, and layers from bottom to top. The length of each section should not be greater than 6 cm.

[0089] Among them, when spraying in layers, the thickness of the initial sprayed concrete shall not be less than 40mm, and the next layer of spraying shall be carried out after the previous layer of concrete has finally set;

[0090] Step 5. The cantilever tunnel boring machine excavates the reserved core soil. While providing support, the core soil is excavated simultaneously to improve tunnel excavation efficiency and save time and costs.

[0091] Step 5.1: First, place the lower end of the steel arch frame on a stable stratum. The arch foot should be 15 to 20 cm below the excavation bottom line. If the arch foot is too deep, add steel plates or concrete pads. After installation, use the locking anchor device to position it.

[0092] Step 5.2: If the arch foot is too deep, spray-fill the steel arch back with concrete of the same grade to ensure that the steel arch support is in close contact with the surrounding rock.

[0093] Because the tunnel is shallow and excavated using a cantilevered tunnel boring machine (TBM) that minimally disturbs the surrounding rock, the project has a high safety factor, so accelerating excavation progress is crucial. The TBM first excavates the contour line, then excavates from the outside inward until the core soil is reached. A support gantry is then set up. While the TBM excavates the core soil, operators perform initial support operations on the gantry. This shortens the time between the previous and subsequent steps and accelerates tunnel excavation progress.

[0094] Step 6. Mechanical slag removal and transportation: After the core soil excavation is completed, the excavator enters the site to clean up the excavated rock waste, and the loader is used to transport it to the designated location for treatment;

[0095] Step 7. Start the next cycle.

[0096] Preferably, the steel mesh described in step 4 is centrally processed using CNC welded mesh and transported to the construction site, with the overlap length between mesh pieces being no less than one grid; when spraying concrete, the distance from the nozzle to the sprayed surface is reduced and the wind pressure is controlled to reduce the vibration of the steel mesh and reduce rebound.

[0097] Preferably, the steel arch frame is installed according to the design requirements, and the allowable deviation of the installation dimensions is: longitudinal spacing ±100mm, lateral position ±20mm, verticality ±1°, the lower end of the steel arch frame is set on a stable stratum, and the arch foot height is 15 to 20cm lower than the upper excavation bottom line. When the arch foot excavation is too deep, a steel plate or concrete pad is added, and after installation, it is positioned using a locking anchor device. When the over-excavation is too large, the arch back is sprayed with concrete of the same grade to make the support close to the surrounding rock and control deformation. The two rows of steel frames are firmly connected longitudinally with connecting steel bars to form an overall force-bearing structure.

[0098] Preferably, the mortar anchor rods are drilled using a pneumatic anchor rod hole. The anchor rod holes are drilled using a rig and driven as vertically as possible to the structural surface according to the designed spacing. High-pressure air is used to blow the hole, and then the anchor rod is sent into the hole with an air gun, with the rod body located in the center of the hole. A grouting pump is used to fill the hole with early-strength mortar, and then a pad is installed. The pad must be fastened to the rock surface with a nut to enhance the comprehensive support effect of the anchor rod and sprayed concrete. The tail end of the anchor rod should be welded to the arch frame as much as possible so that they can bear the force together.

[0099] Preferably, Figure 2In the tunnel, the tunnel face is divided into two areas, Zone I and Zone II, of which Zone I is the circular excavation area and Zone II is the core soil part; the tunnel face first excavates Zone I of the circular excavation area, and this part is excavated from the outside to the inside in sequence, alternating between clockwise and counterclockwise directions. The size of each excavation is the size of the cantilever tunnel boring machine's milling head itself, until the reserved core soil part is excavated, and the excavation of this area is stopped; after the support platform is set up, the cantilever tunnel boring machine excavates the core soil Zone II part, and the excavation order is also from the outside of the core soil to the inside, alternating between clockwise and counterclockwise, until the excavation of the current tunnel face is completed.

[0100] Example 2: Different from the above-mentioned Example 1, in order to lock the steel arch frame 1 and fix the steel arch frame 1 in the tunnel, the locking foot anchor device is designed to include a connecting rod 2, an anchor positioning mechanism 3 and an anchor 4, wherein

[0101] The connecting rod 2 is detachably mounted on the lower end of the steel arch frame 1 through the connecting rod mounting member 5;

[0102] The anchor rod positioning mechanism 3 is detachably mounted on the connecting rod 2 and is used in conjunction with the anchor rod 4;

[0103] The anchor rod 4 is installed on the connecting rod 2 through the anchor rod positioning mechanism 3 and is used in conjunction with the tunnel arch foot to fix the steel arch frame 1 in the tunnel.

[0104] Preferably, since the anchoring direction of the anchor rod 4 needs to be adjusted according to the rock formation conditions when the steel arch frame 1 is positioned using the anchor rod 4, the anchor rod positioning mechanism 3 is designed to include a first arc-shaped positioning block 31, a first positioning member 32, a second positioning member 33 and a rotating positioning member 35, wherein

[0105] The first arc-shaped positioning block 31 is arranged on the upper side of the first positioning member 32 and is used in conjunction with the connecting rod 2;

[0106] The first positioning member 32 is disposed on the upper side of the second positioning member 33 and is rotatably connected to the second positioning member 33 via a horizontal positioning assembly;

[0107] The rotation positioning member 35 is provided at the lower end of the second positioning member 33 and is used in conjunction with the anchor rod 4 to adjust the anchoring direction of the anchor rod 4 .

[0108] Preferably, a second arc-shaped positioning block is provided at the top end of the sleeve of the first positioning member 32, and the second arc-shaped positioning block is used in conjunction with the first positioning member 32. When in use, the first arc-shaped positioning block 31 is connected to the second arc-shaped positioning block by a bolt member, so that the anchor rod positioning mechanism 3 is installed on the connecting rod 2; and in order to be used in conjunction with the horizontal positioning assembly, an adjustment groove 321 is also provided on the sleeve of the first positioning member 32.

[0109] Preferably, the first positioning member 32 includes a threaded connecting rod 36 and an adjusting nut 34, wherein the threaded connecting rod 36 passes through the adjusting groove 321 and is threadedly arranged in the tail rod threaded hole 331 of the second positioning member 33, and can move along the tail rod threaded hole 331 when in use, and the adjusting nut 34 is threadedly installed on the outer end of the threaded connecting rod 36, and is used to fix the position of the second positioning member 33 after adjustment by rotating the adjusting nut 34 when in use, so as to adjust the horizontal direction position of the second positioning member 33.

[0110] Preferably, the rotating positioning member 35 is rotatably mounted on the lower end of the second positioning member 33 through a U-shaped mounting member 332, and includes a positioning sleeve 351 and a positioning nut 353, wherein

[0111] The positioning sleeve 351 is rotatably mounted in the mounting slot of the U-shaped mounting member 332, and a positioning bolt 354 is screwed and mounted on the lower side of the positioning sleeve 351. The positioning bolt 354 cooperates with the anchor rod 4 to fix the position of the anchor rod 4 in the positioning sleeve 351.

[0112] The positioning nuts 353 are installed on both sides of the positioning sleeve 351 and are used in conjunction with the positioning columns 352 provided on both sides of the positioning sleeve 351. When in use, the position of the positioning sleeve 351 in the U-shaped mounting member 332 is fixed by adjusting the positioning nuts 353.

[0113] Preferably, in order to facilitate the use with the tunnel arch foot rock formation, the steel arch frame 1 is fixed in the tunnel, and the anchor rod 4 is designed to include an outer steel cylinder 41, an inner steel core anchor rod 42, an adjustment core 43, a first bevel gear 45, a second bevel gear 46 and an adjustment handle 48;

[0114] The outer steel cylinder 41 is arranged at the tail end of the inner steel core anchor rod 42, and interconnected steel cylinder cavities are arranged in the outer steel cylinder 41;

[0115] The tail end of the inner steel core anchor rod 42 is movably installed in the steel cylinder cavity, and a limiting ring 422 is provided at the tail end of the inner steel core anchor rod 42 to cooperate with the limiting cavity 411 provided in the outer steel cylinder 41;

[0116] The adjusting core 43 is rotatably mounted in the steel cylinder cavity via a first bearing 44, and an external thread is provided on the adjusting core 43 to cooperate with an internal thread provided in the inner cavity 421 of the inner steel core anchor rod 42, that is, when the adjusting core 43 rotates, the inner steel core anchor rod 42 is driven to move along the length direction of the steel cylinder cavity;

[0117] The first bevel gear 45 is provided at the outer end of the adjustment core 43 and meshes with the second bevel gear 46;

[0118] The second bevel gear 46 is provided at the end of the adjustment handle 48;

[0119] The adjusting handle 48 is mounted on the outer steel cylinder 41 via the second bearing 47 , that is, when in use, the adjusting core 43 is driven to rotate by rotating the adjusting handle 48 .

[0120] Preferably, in order to prevent the adjusting core 43 from driving the inner steel core anchor rod 42 to rotate when rotating, the limiting ring 422 is designed to be a prismatic limiting ring, and the limiting cavity 411 is adapted to the limiting ring 422. At the same time, in order to facilitate screwing into the rock formation, a screw-in pattern is also provided at the front end of the inner steel core anchor rod 42.

[0121] The use process and principle of the locking foot anchor device of this embodiment include:

[0122] During use, after the lower end of the steel arch frame is placed on a stable stratum, the connecting rod 2 is first installed to connect the steel arch frame 1 to form a whole; then the anchor rod positioning mechanism 3 is used to adjust it according to the anchoring position and anchoring direction of the anchor rod required by the design, and the anchor rod 4 is installed after the adjustment is completed; the adjusting core 43 is driven to rotate by rotating the adjusting handle 48, and when the adjusting core 43 rotates, the inner steel core anchor rod 42 is driven to move along the length direction of the steel cylinder cavity, so that the front end of the inner steel core anchor rod 42 is anchored in the rock formation of the tunnel arch foot, and the steel arch frame 1 is fixed in the tunnel.

[0123] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A cold excavation construction method for a tunnel passing under densely populated residential areas, characterized by: include Step 1. Advanced support construction: Before excavation, advanced support construction of the tunnel is carried out according to the design requirements; Step 2. After completing the advance support, use a boom tunnel boring machine to circumferentially excavate the contour line; Step 3. Mechanical slag removal and transportation: After the excavation of the outer edge of the tunnel face is completed, the excavator enters the site to clean up the excavated rock slag and transport it using a transport vehicle; Step 4. Set up a support trolley and implement initial support measures for the tunnel to reduce the deformation time of the surrounding rock; Step 5. The cantilever tunnel boring machine excavates the reserved core soil part, and excavates the core soil part while providing support; Step 6. Mechanical slag removal and transportation: After the core soil excavation is completed, the excavator enters the site to clean up the excavated rock slag and use the loader to transport it; Step 7. Start the next cycle; The support process described in step 5 includes using steel arch support, and the specific support steps are: Step 5.1: First, place the lower end of the steel arch frame on a stable stratum. The arch foot should be 15 to 20 cm below the excavation bottom line. If the arch foot is too deep, add steel plates or concrete pads. After installation, use the locking anchor device to position the steel arch frame. Step 5.2: If the arch foot is too deep, spray-fill the steel arch frame with concrete of the same grade to ensure that the steel arch frame is in close contact with the surrounding rock. The foot locking anchor device described in step 5.1 includes a connecting rod, an anchor positioning mechanism and an anchor. The connecting rod is arranged at the lower end foot arch of the steel arch frame through a connecting rod mounting piece; The anchor rod positioning mechanism is arranged on the connecting rod, and includes a first arc-shaped positioning block, a first positioning member, a second positioning member and a rotating positioning member. The first arc-shaped positioning block is arranged on the upper side of the first positioning member and is used in conjunction with the connecting rod. The first positioning member is arranged on the upper side of the second positioning member and is connected to the second positioning member through a horizontal positioning assembly. The rotating positioning member is arranged at the lower end of the second positioning member and is used in conjunction with the anchor rod. The anchor rod is arranged on the connecting rod through the anchor rod positioning mechanism and is used in conjunction with the tunnel arch foot; The first positioning member includes a threaded connecting rod and an adjusting nut, the threaded connecting rod passes through the adjusting slot and is arranged in the tail rod threaded hole of the second positioning member, and the adjusting nut is arranged at the outer end of the threaded connecting rod; the rotating positioning member is arranged at the lower end of the second positioning member through the U-shaped mounting member, and includes a positioning sleeve and a positioning nut, the positioning sleeve is arranged in the mounting groove of the U-shaped mounting member, and a positioning bolt is arranged on the lower side of the positioning sleeve, and the positioning bolt is used in conjunction with the anchor rod; the positioning nuts are arranged on both sides of the positioning sleeve and are used in conjunction with the positioning columns arranged on both sides of the positioning sleeve; The anchor rod comprises an outer steel cylinder, an inner steel core anchor rod, an adjusting core, a first bevel gear, a second bevel gear and an adjusting handle; The outer steel cylinder is arranged at the tail end of the inner steel core anchor rod, and mutually communicating steel cylinder cavities are arranged in the outer steel cylinder; The inner steel core anchor rod is movably arranged in the steel cylinder cavity, and a limiting ring is arranged at the tail of the inner steel core anchor rod to match the limiting cavity arranged in the outer steel cylinder; The adjusting core is installed in the steel cylinder cavity through the first bearing, and the adjusting core is provided with an external thread adapted to the internal thread provided in the inner cavity of the inner steel core anchor rod; The first helical gear is arranged at the outer end of the adjusting core and meshes with the second helical gear; The second bevel gear is arranged at the end of the adjustment handle; The adjusting handle is arranged on the outer steel cylinder through a second bearing.

2. The cold excavation construction method for a tunnel under densely populated residential areas according to claim 1 is characterized by: The advanced support construction described in step 1 includes Step 1.1 Middle pipe roof support The middle pipe shed support is made of hot-rolled seamless steel flower pipes. Grouting holes are drilled in the pipe wall in a plum blossom pattern. The front end is processed into a cone. The circumferential spacing is 0.4m. There are 50 pipes in each ring, each 8m long, and a longitudinal ring of 4.8m. The external insertion angle is 10° to 15°. Cement slurry is used for grouting. The water-binder ratio of the cement slurry is 0.5:1 to 0.8:

1. At the same time, the single-hole grouting completion standard is adopted: the grouting pressure is gradually increased. When it reaches the designed final pressure and stabilizes for 10 minutes, the middle pipe shed support construction is completed. Step 1.2 Small catheter support (1) The small conduit is installed by drilling method, and the diameter of the drill hole is 3 to 5 mm larger than the diameter of the steel pipe; (2) Then, the small conduit is passed through the steel arch frame and pushed in by hammering, with the insertion length not less than 90% of the length of the steel pipe, and the sand and gravel in the steel pipe are blown out by high-pressure air; (3) After the small tube is installed, use plastic mud to seal the hole and surrounding cracks, and spray concrete near the small tube and on the working surface.

3. The cold excavation construction method for a tunnel passing under densely populated residential areas according to claim 2, characterized in that: During the small-conductor support process, the excavation length of the tunnel is less than the grouting length of the small-conductor, and the length of the reserved part of the excavation depth does not exceed 10% of the length of the small-conductor in advance; and the small-conductor and the pipe-roof steel pipe segments are connected with threads, and the number of joints in the same section shall not exceed 50% of the number of conduits in the section; the radial construction error shall not exceed 15 cm, and the adjacent circumferential distance shall not be greater than 5 cm.

4. The cold excavation construction method for a tunnel passing under densely populated residential areas according to claim 1 is characterized in that: The process of using a boom tunnel boring machine to excavate the contour line in a circular direction as described in step 2 includes: Step 2.

1. After the boom tunnel boring machine arrives on site, first adjust the boom tunnel boring machine body to the center of the tunnel face. Adjust the machine body so that the excavation area is within its own excavation range. Then, excavate circumferentially along the contour line until the specified core soil size contour is excavated. The contour line is trimmed to the design requirements. During excavation, the contour line is excavated from left to right in a clockwise direction, and then from right to left in a counterclockwise direction. This cycle is repeated until the core soil size is reached. The width of each excavation is 1m, which is the size of the cantilever tunnel boring machine cutting head. Step 2.

2. Clean the waste residue from the outer edge of the tunnel face.

5. The cold excavation construction method for a tunnel passing under densely populated residential areas according to claim 1 is characterized in that: The process of initial tunnel support described in step 4 includes: Step 4.1 Before spraying, clean the pumice on the excavation surface and the rock debris and accumulation at the foot of the wall, and check the clearance size of the excavation section; Step 4.2: Rinse the sprayed surface and set the mark to control the thickness of the sprayed concrete. If there are any depressions, spray them to fill them first. During step 4.3, the nozzle is perpendicular to the rock surface, 0.6m to 1.8m away from the target, and moves in a spiral motion. The wind pressure is 0.5 to 0.7 MPa. The liquid accelerating agent is added near the outlet of the spray gun using an accelerating agent pump. Step 4.4: Spraying is carried out continuously in sections, slices, and layers from bottom to top, with the length of each section not exceeding 6 cm. Among them, when spraying in layers, the thickness of the initial sprayed concrete shall not be less than 40mm, and the next layer of spraying shall be carried out after the previous layer of concrete has finally set.

6. The cold excavation construction method for a tunnel passing under densely populated residential areas according to claim 1, characterized in that: The limiting ring is a prismatic limiting ring, the limiting cavity is adapted to the limiting ring, and a screw thread is further provided at the front end of the inner steel core anchor rod.

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