Hole-out through construction method for weathered silty mudstone tunnel at broken shallow-buried section

Abstract

The invention provides an out-hole through construction method for a weathered silty mudstone tunnel at a broken shallow-buried section, which comprises the following steps of: grouting and reinforcing into a whole by adopting an earth surface steel floral tube at the earth surface position of a tunnel vault of weak surrounding rock according to field topography and geology; at the small pile number inlet section, n rows of steel pipes internally provided with reinforcing reinforcement cages are adopted as advanced pipe sheds to penetrate through the upper portion of the tunnel face of the large pile number outlet section, double-layer advanced small guide pipes are combined to serve as advanced supports, and system anchor rods and double rows of feet-lock anchor rods are adopted in a tunnel body to reinforce a profile steel arch frame, so that the overall stability of the supports is improved; during penetration, the support is closed into a ring in time by utilizing three-step footage construction, so that the overall stress of the support is improved, and the technical problems of large tunnel settlement, even possible roof fall and large safety risk during penetration construction of the weathered silty mudstone tunnel at the shallowly buried broken section are solved; and compared with the mode that manual excavation is combined with mechanical excavation is generally adopted in the shallowly-buried section of the tunnel in the prior art, the construction efficiency of tunnel penetration is improved.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel penetration construction, in particular to a tunnel penetration construction method for a weathered silty mudstone tunnel in a broken shallow buried section. Background Art

[0002] At present, in order to complete the tunneling construction under the conditions of weathered silty mudstone tunnels, the conventional construction method is generally to use the three-step method and the double-side wall pilot pit method to carry out excavation and support construction while ensuring the tunneling footage and support strength. The excavation mainly adopts manual excavation to reduce the disturbance to the surrounding rock to ensure safety, and the support form only adopts "single-layer advanced small guide tube + system anchor" support. Since the weathered silty mudstone will further reduce its strength when it encounters water after excavation, the upper surrounding rock of the broken shallow buried section of the tunnel cannot be well combined due to the broken rock mass, the upper surrounding rock cannot be self-stabilized and the load on the upper part is increased. The support method using the above conventional construction method cannot ensure the construction safety during the penetration process, and then its excavation generally can only use weak blasting or manual excavation, resulting in a long tunnel penetration construction period. Summary of the invention

[0003] The present invention aims to provide a construction method for a weathered siltstone tunnel to penetrate a broken shallow buried section, so as to solve the technical problem that the prior art cannot ensure the tunnel penetration under safe, stable and efficient conditions when encountering unfavorable conditions such as the penetration of a weathered siltstone tunnel in a broken shallow buried section.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A construction method for a weathered silty mudstone tunnel in a broken shallow buried section, comprising the following steps:

[0006] S1, single hole advance: During tunnel construction, excavation is carried out inward from both ends of the tunnel in a step-by-step manner to form a small-pile entrance section and a large-pile exit section. The section between the small-pile entrance section and the large-pile exit section is the section to be penetrated. When the excavation of the small-pile entrance section and the large-pile exit section makes the section to be penetrated reach a preset length, excavation is stopped on the side of the large-pile exit section, and the single-hole three-step method is adopted to enter the tunnel from the small-pile entrance section;

[0007] S2, grouting reinforcement of the surface steel pipe on the vault: During the tunneling process, a surface steel pipe is installed on the surface of the tunnel vault to reinforce the surface of the tunnel vault by grouting;

[0008] S3, constructing the nth row of advanced pipe sheds: the advanced pipe shed is used for advanced support of the current tunnel face at the entrance, the advanced pipe shed comprises a steel pipe and a reinforcement steel cage built in the steel pipe, and the pipe wall of the steel pipe is provided with a slurry outlet hole; the construction of the advanced pipe shed comprises the following steps:

[0009] S31, driving one end of the steel pipe into the rock and soil of the current tunnel face, and making the steel pipe gradually tilt upward toward the direction close to the exit section with a large pile number;

[0010] S32, after grouting in the steel pipe, replenish slurry through the slurry outlet hole to the surrounding broken loose rock and soil;

[0011] S4, after the current tunnel face is further advanced, concrete is first sprayed on the tunnel face after the advancement and the steel arch frame is supported. Subsequently, holes are opened on the steel arch frame within a 120° circumferential range on both sides of the center line of the steel arch frame arch top, and double-layer advance small conduit support is adopted. The double-layer advance small conduit includes a plurality of pairs of grouting steel flower pipes, and the plurality of pairs of grouting steel flower pipes are spaced along the length direction of the steel arch frame. A pair of grouting steel flower pipes are driven into the rock and soil of the corresponding tunnel face at two angles, and one end is fixed in the opening of the steel arch frame. The rock and soil of the tunnel face is grout-reinforced by the grouting steel flower pipes to complete the advance support;

[0012] S5: After advance support, the surrounding rock is reinforced by laying system anchors in a plum blossom pattern with a spacing of 100×100 cm on both sides of the center line of the steel arch in a circumferential range of 180° on the steel arch frame, and double-row locking anchors are set at the arch waist and arch foot of the steel arch frame to embed into the surrounding rock. After the double-row locking anchors are driven into the tunnel rock mass, they are welded to the steel arch frame with U-shaped connecting bars, and finally the gaps between the double-row locking anchors and the tunnel rock mass are filled and compacted with cement rolls;

[0013] S6, determine whether the distance between one end of the advance pipe shed near the large pile number exit section and one end of the section to be penetrated near the large pile number exit section exceeds 3 meters: if so, excavate the upper step and cooperate with the advance small pipe support until the section to be penetrated is penetrated, thereby realizing the penetration of the tunnel, and finally carry out the construction of secondary lining and lining invert to make the support closed in a ring; if not, enter step S2 again.

[0014] Furthermore, the preset length of the section to be penetrated is 28 meters. When the length of the advanced pipe shed used is 12 meters, the spacing between two adjacent rows of advanced pipe sheds is 2 sheds, and the lap length of the tail end of the previous row of advanced pipe sheds of the rear row is 2m, a total of 3 rows of advanced pipe sheds are constructed along the length direction of the tunnel so that the distance between the end of the advanced pipe shed close to the exit section with a large pile number and the end of the section to be penetrated close to the exit section with a large pile number exceeds 3 meters.

[0015] Furthermore, one end of the steel pipe is a grout inlet, and the other end of the steel pipe is a conical head. In step S31, the steel pipe is drilled through the conical head until the steel pipe is driven into the rock and soil of the current face. In step S32, grout is injected into the steel pipe from the grout inlet.

[0016] Furthermore, a reinforcement hoop is welded and fixed at the slurry inlet, and the reinforcement hoop is arranged around the slurry inlet.

[0017] Furthermore, the reinforcement steel cage includes a plurality of fixing rings and a plurality of threaded steel bars, the plurality of fixing rings are arranged at intervals along the axial direction of the steel pipe, the plurality of threaded steel bars are evenly arranged around the outer circumference of the fixing rings, and each of the threaded steel bars is fixedly connected to the plurality of fixing rings.

[0018] Furthermore, in step S2, the surface grouting from the entrance of the small pile number section to the top of the tunnel vault to be penetrated is constructed, and 1.5m plum blossom-shaped grouting reinforcement holes are opened on the surface of the tunnel vault, and then the surface steel flower pipes are driven into the corresponding grouting reinforcement holes for grouting reinforcement.

[0019] Furthermore, in step S4, one end of each pair of grouting steel flower tubes is respectively fixed in the openings of two adjacent steel arch frames, and the angles between the extension directions of the two grouting steel flower tubes in each pair and the horizontal plane are different.

[0020] Furthermore, the double-row locking foot anchor rods are respectively arranged at the front and rear sides of the steel arch frame at corresponding positions, and the inclination angles of the double-row locking foot anchor rods relative to the horizontal plane are different.

[0021] Furthermore, the U-shaped connecting rib includes a first fixing portion, a second fixing portion and a connecting portion fixedly connecting the same end of the first fixing portion and the second fixing portion, the first fixing portion, the second fixing portion and the connecting portion are arranged to form a receiving cavity, the U-shaped connecting rib is sleeved on the steel arch frame through the receiving cavity, the top surface of the steel arch frame is welded and fixed to the inner side surface of the connecting portion; the double-row locking foot anchor rods are respectively arranged on opposite sides of the U-shaped connecting rib, and are respectively welded and fixed to the outer side surfaces of the first fixing portion and the second fixing portion.

[0022] Furthermore, during the through-construction process, monitoring and measurement measures are used to assist. By continuously monitoring the settlement of the arch surrounding rock at the left measuring point, the middle measuring point and the right measuring point of the arch, and conducting peripheral displacement and settlement observations on the convergence measuring lines around the upper step, the middle step and the lower step, the on-site support construction is guided in a timely manner.

[0023] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0024] The invention discloses a construction method for a weathered silty mudstone tunnel through a broken shallow buried section. The construction tunnel is silty mudstone with a broken shallow buried section above. The method adopts surface steel flower pipes for grouting reinforcement as a whole at the surface position of the tunnel vault of the weak surrounding rock according to the on-site topography and geology. At the entrance section of the small pile number, n rows of steel pipes with built-in reinforced steel cages are adopted as an advance pipe shed to penetrate above the heading face of the exit section of the large pile number and are combined with double-layer advance small guide tubes as advance support. The tunnel body adopts a system anchor rod + double-row locking foot anchor rod to reinforce the steel arch frame to improve the overall stability of the support. When penetrating, the three-step advance construction is used to close the support into a ring in time to improve the overall stress of the support. By using the "multi-layer overlapped advanced large pipe shed (with built-in steel cage to increase strength) + double-layer advanced small guide tube + surface grouting above the through section" measures in the weathered silty mudstone tunnel exit and through construction method in the broken shallow buried section of the present invention, the integrity and self-stabilization ability of the tunnel rock mass are further enhanced, and the technical problem that the weathered silty mudstone tunnel exit and through construction in the broken shallow buried section may have large tunnel settlement or even roof collapse and high safety risks is solved, so that the excavation can be carried out by weak blasting using the drilling and blasting method. Compared with the prior art method of using manual combined with mechanical excavation, the construction efficiency of the tunnel penetration is improved, and the construction method is easy to operate, the materials are easy to obtain, and the safety and economy are good, ensuring that the tunnel is smoothly penetrated under safe, stable and efficient conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic flow chart of a construction method for a weathered silty mudstone tunnel in a broken shallow buried section according to a preferred embodiment of the present invention;

[0026] Figure 2 It is a schematic diagram of the state of the weathered silty mudstone tunnel during construction of the method for exiting and penetrating the broken shallow buried section according to the preferred embodiment of the present invention;

[0027] Figure 3 Schematic diagram of the structure for opening grouting reinforcement holes on the surface of the vault;

[0028] Figure 4 It is a structural schematic diagram of an advanced pipe rack according to a preferred embodiment of the present invention;

[0029] Figure 5 It is a structural schematic diagram of a reinforced steel cage according to a preferred embodiment of the present invention;

[0030] Figure 6 for Figure 5 Schematic diagram of the cross-sectional structure;

[0031] Figure 7 This is a schematic diagram of the structure of a double-layer advanced small conduit support according to a preferred embodiment of the present invention;

[0032] Figure 8It is a schematic diagram of the cross-sectional structure of a weathered silty mudstone tunnel during construction of a method for exiting and penetrating a broken shallow buried section according to a preferred embodiment of the present invention;

[0033] Fig. 9 It is a schematic diagram of the structure of the connection between the double-row locking foot anchor rods and the steel arch frame in a preferred embodiment of the present invention;

[0034] Fig.10 for Fig. 9 A magnified view of the structure in the middle;

[0035] Fig.11 Schematic diagram of the locations of various monitoring points of the monitoring and measurement measures adopted in a preferred embodiment of the present invention.

[0036] Main component symbols

[0037] 1. Surface steel flower pipe; 2. Advance pipe shed; 3. Double-layer advance small guide tube; 4. Small pile entrance section; 5. Large pile exit section; 6. Section to be penetrated; 7. Soil; 11. Tunnel vault surface; 12. Grouting reinforcement hole; 21. Steel pipe; 22. Reinforcement hoop; 23. Grouting hole; 24. Conical head; 25. Reserved grouting section; 26. Reinforced steel cage; 27. Threaded steel bar; 28. Fixed ring; 31. Grouting steel flower pipe; 32. Steel arch frame; 34. Secondary lining; 41. System Anchor rod; 42, double-row locking anchor rod; 43, lining invert; 421, cement roll; 422, welding connection; 423, U-shaped connecting reinforcement; 4231, first fixing part; 4232, second fixing part; 4233, connecting part; 4234, receiving cavity; 424, tunnel rock mass; 81, left measuring point of arch crown; 82, middle measuring point of arch crown; 83, right measuring point of arch crown; 84, convergence measuring line around upper step; 85, convergence measuring line around middle step; 86, convergence measuring line around lower step. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may also be a component centered. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may also be a component centered. When a component is considered to be "set on" another component, it may be directly set on the other component or there may also be a component centered. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0041] Please also see Figures 1 to 11 A preferred embodiment of the present invention provides a method for constructing a weathered silty mudstone tunnel in a broken shallow buried section, comprising the following steps:

[0042] S1, single hole advance: during tunnel construction, excavation is carried out inward from both ends of the tunnel in a step construction manner to form a small pile entrance section 4 and a large pile exit section 5. The section 6 to be penetrated is between the small pile entrance section 4 and the large pile exit section 5. When the excavation of the small pile entrance section 4 and the large pile exit section 5 makes the section 6 to be penetrated reach a preset length, excavation is stopped on one side of the large pile exit section 5, and the single hole three-step method is adopted to enter the tunnel from the small pile entrance section 4 to excavate the soil 7 of the section 6 to be penetrated, thereby achieving tunnel penetration.

[0043] Preferably, in this embodiment, the position of the through hole is ensured to be located 22 m inward from the hole opening of the large pile number exit section 5 .

[0044] S2, grouting reinforcement of the arch surface steel pipe: during the tunnel entry process, a surface steel pipe 1 is installed on the tunnel arch surface 11 to perform grouting reinforcement on the tunnel arch surface 11.

[0045] In step S2, grouting is performed from the opening of the small pile entrance section 4 to the tunnel vault surface 11 above the tunnel vault section 6 to be penetrated. Specifically, grouting reinforcement holes 12 are opened on the tunnel vault surface 11 in a plum blossom shape with a spacing of a=1.5m, and then the surface steel pipe 1 is driven into the corresponding grouting reinforcement hole 12 for grouting reinforcement.

[0046] S3, constructing the nth row of advanced pipe shed 2: the advanced pipe shed 2 is used for advanced support of the current tunnel face at the entrance, the advanced pipe shed 2 comprises a steel pipe 21 and a reinforcement steel cage 26 built in the steel pipe 21, and the pipe wall of the steel pipe 21 is provided with a slurry outlet hole 23; the construction of the advanced pipe shed 2 comprises the following steps:

[0047] S31, driving one end of the steel pipe 21 into the rock and soil of the current tunnel face, and making the steel pipe 21 gradually tilt upward toward the direction close to the large pile exit section 5;

[0048] S32, after grouting in the steel pipe 21, slurry is added to the surrounding broken loose rock and soil through the slurry outlet hole 23, which plays a role in reinforcing the surrounding rock and enhancing the integrity of the surrounding rock.

[0049] In this embodiment, the length of the advanced pipe rack 2 used is 12 meters, the spacing between two adjacent rows of advanced pipe racks 2 is 2 racks, and the lap length of the tail end of the previous row of advanced pipe racks 2 of the next row of advanced pipe racks 2 is 2m, that is, the overlapping part of the previous row of advanced pipe racks 2 of the next row of advanced pipe racks 2 has a projection length of 2 meters in the horizontal plane.

[0050] One end of the steel pipe 21 is a grout inlet (not shown), and a preset length is reserved inward from the grout inlet of the steel pipe 21 as a reserved grouting stop section 25; the other end of the steel pipe 21 is a conical head 24, and in step S31, the steel pipe 21 is drilled through the conical head 24 until the steel pipe 24 is driven into the rock and soil of the current tunnel face; in step S32, grouting is injected into the steel pipe 21 from the grout inlet. In addition, a reinforcing hoop 22 is welded and fixed at the grout inlet, and the reinforcing hoop 22 is arranged around the grout inlet to prevent the grout inlet from deforming during the grouting process.

[0051] The reinforcing steel cage 26 includes a plurality of fixing rings 28 and a plurality of threaded steel bars 27. The plurality of fixing rings 28 are arranged at intervals along the axial direction of the steel pipe 21. The plurality of threaded steel bars 27 are evenly arranged around the outer circumference of the fixing rings 28. Each threaded steel bar 27 is fixedly connected to a plurality of fixing rings 28. The arrangement of the reinforcing steel bars 26 can greatly enhance the strength of the advanced pipe rack 2.

[0052] S4, after the current face is further advanced, concrete is sprayed on the face after the advancement and the steel arch frame 32 is supported. Subsequently, holes are opened on the steel arch frame 32 within a 120° circumferential range on both sides of the center line of the arch top of the steel arch frame 32, and then a double-layer advanced small duct 3 is used for support. The double-layer advanced small duct 3 includes a plurality of pairs of grouting steel flower pipes 31, and the plurality of pairs of grouting steel flower pipes 31 are spaced apart along the length direction of the steel arch frame 32. A pair of grouting steel flower pipes 31 are driven into the rock and soil of the corresponding face at two angles, and one end is fixed to the opening of the steel arch frame 32. The grouting steel flower pipes 31 are used to grout and reinforce the rock and soil of the face to complete the advanced support.

[0053] In the present embodiment, specifically, the double-layer advance small duct 3 is arranged within a circumferential range of 120° on both sides of the center line of the arch of the steel arch frame 32, and one end of each pair of grouting steel flower pipes 31 is respectively fixed in the openings of two adjacent steel arch frames 32, and the extension directions of the two grouting steel flower pipes 31 in each pair have different angles with the horizontal plane, wherein the angle α1 between the grouting steel flower pipes 31 near the small pile number inlet section 4 and the horizontal plane is greater than the angle α2 between the grouting steel flower pipes 31 near the large pile number outlet section 5 and the horizontal plane.

[0054] S5, after the advance support, on the steel arch frame 32, system anchor rods 41 are arranged in a plum blossom shape with a spacing of 100×100 cm within a circumferential range of 180° on both sides of the center line of the arch top of the steel arch frame 32 to reinforce the surrounding rock, and double-row locking foot anchor rods 42 are arranged at the arch waist and arch foot of the steel arch frame 32 to embed into the surrounding rock. After the double-row locking foot anchor rods 42 are driven into the tunnel rock mass 424, they are welded to the steel arch frame 32 with U-shaped connecting bars 423, and finally the gap between the double-row locking foot anchor rods 42 and the tunnel rock mass 423 is filled and compacted with cement rolls 421.

[0055] Specifically, the system anchor rod 41 is arranged within a 180° circumferential range on both sides of the arch centerline of the steel arch frame, and one end of the system anchor rod 41 is welded and fixed to the steel arch frame 32. The double-row locking foot anchor rods 42 are respectively arranged on the front and rear sides of the steel arch frame 32 at corresponding positions, and the double-row locking foot anchor rods 32 have different inclination angles relative to the horizontal plane. The U-shaped connecting rib 423 includes a first fixing portion 4231 and a second fixing portion 4232 which are arranged opposite to each other, and a connecting portion 4233 which is fixedly connected to the same end of the first fixing portion 4231 and the second fixing portion 4232. The first fixing portion 4231, the second fixing portion 4232 and the connecting portion 4233 are arranged to form a receiving cavity 4234. The U-shaped connecting rib 423 is sleeved on the steel arch frame 32 through the receiving cavity 4233. The top surface of the steel arch frame 32 is welded and fixed to the inner side surface of the connecting portion 4233. The double-row locking foot anchor rods 42 are respectively arranged on the opposite sides of the U-shaped connecting rib 423, and are respectively welded and fixed to the outer side surfaces of the first fixing portion 4231 and the second fixing portion 4232.

[0056] S6, determine whether the distance L between one end of the advance pipe shelf 2 close to the large pile number exit section 5 and one end of the section to be penetrated 6 close to the large pile number exit section 5 exceeds 3 meters, that is, whether the end of the projection length of the advance pipe shelf 2 is 3 meters longer than the surface to be penetrated: if so, excavate the upper step and cooperate with the advance small pipe support until the section to be penetrated 6 is penetrated, thereby realizing the penetration of the tunnel, and finally carry out the construction of the secondary lining 34 and the lining arch 43 to make the support closed in a ring; if not, enter step S2 again.

[0057] Specifically, the surface to be penetrated is the top surface of the section to be penetrated 6. In the present embodiment, the preset length of the surface to be penetrated of the section to be penetrated 6 is approximately 28 meters. When the length of the adopted advance pipe shed 2 is 12 meters, the spacing between two adjacent rows of advance pipe sheds 2 is 2 frames, and the lap length between the tail ends of the rear row of advance pipe sheds 2 and the front row of advance pipe sheds 2 is 2m, a total of 3 rows of advance pipe sheds 2 are constructed along the length direction of the tunnel, which can make the projection length of the advance pipe shed 2 along the longitudinal section of the tunnel exceed the length of the section to be penetrated 6 by more than 3 meters, so that the advance pipe shed 2 passes through the vault of the section to be penetrated 6 to pass through above the heading face of the large pile number exit section.

[0058] In this embodiment, monitoring and measurement measures are also used during the through-construction process. By continuously monitoring the settlement of the arch surrounding rock at the left measuring point 81, the middle measuring point 82 and the right measuring point 83 of the arch, and observing the peripheral displacement and settlement of the upper step perimeter convergence measuring line 84, the middle step perimeter convergence measuring line 85 and the lower step perimeter convergence measuring line 86, the on-site support construction is timely guided.

[0059] The invention discloses a construction method for a weathered silty mudstone tunnel in a broken shallow buried section. The construction tunnel is silty mudstone with a broken shallow buried section above. The method adopts a surface steel flower pipe 1 for grouting reinforcement as a whole at the surface position of the tunnel vault of the weak surrounding rock according to the on-site topography and geology. At the small pile entrance section 4, n rows of steel pipes with built-in reinforced steel cages 26 are adopted as an advance pipe shed 2 to penetrate above the heading of the large pile exit section 5 and combined with a double-layer advance small guide tube 3 as an advance support. The tunnel body adopts a system anchor rod 41 + a double-row locking foot anchor rod 42 to strengthen the steel arch frame 32 to improve the overall stability of the support. When penetrating, the three-step advance construction is used to close the support into a ring in time to improve the overall stress of the support. By using the "multi-layer overlapped advanced large pipe shed (with built-in steel cage to increase strength) + double-layer advanced small guide tube + surface grouting above the through section" measures in the weathered silty mudstone tunnel exit and through construction method in the broken shallow buried section of the present invention, the integrity and self-stabilization ability of the tunnel rock mass are further enhanced, and the technical problem that the weathered silty mudstone tunnel may have large tunnel settlement or even roof collapse and high safety risks in the through construction of the broken shallow buried section is solved, so that the excavation in the broken shallow buried section can still be carried out by the weak blasting method of drilling and blasting. Compared with the prior art method of using manual combined with mechanical excavation, the construction efficiency of the tunnel penetration is improved, and the construction method is easy to operate, the materials are easy to obtain, and the safety and economy are good, ensuring the smooth penetration of the tunnel under safe, stable and efficient conditions.

[0060] The above description is a detailed description of the preferred feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modified changes completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A construction method for a weathered silty mudstone tunnel in a broken shallow buried section, characterized in that: The following steps are involved: S1, single hole advance: During tunnel construction, excavation is carried out inward from both ends of the tunnel in a step-by-step manner to form a small-pile entrance section and a large-pile exit section. The section between the small-pile entrance section and the large-pile exit section is the section to be penetrated. When the excavation of the small-pile entrance section and the large-pile exit section makes the section to be penetrated reach a preset length, excavation is stopped on the side of the large-pile exit section, and the single-hole three-step method is adopted to enter the tunnel from the small-pile entrance section; S2, grouting reinforcement of the surface steel pipe on the vault: During the tunneling process, a surface steel pipe is installed on the surface of the tunnel vault to reinforce the surface of the tunnel vault by grouting; S3, constructing the nth row of advanced pipe sheds: the advanced pipe shed is used for advanced support of the current tunnel face at the entrance, the advanced pipe shed includes a steel pipe and a reinforced steel cage built in the steel pipe, and the pipe wall of the steel pipe is provided with a slurry outlet hole; during the construction of the advanced pipe shed, The following steps are involved: S31, driving one end of the steel pipe into the rock and soil of the current tunnel face, and making the steel pipe gradually tilt upward toward the direction close to the exit section with a large pile number; S32, after grouting in the steel pipe, replenish slurry through the slurry outlet hole to the surrounding broken loose rock and soil; S4, after the current tunnel face is further advanced, concrete is first sprayed on the tunnel face after the advancement and the steel arch frame is supported. Subsequently, holes are opened on the steel arch frame within a 120° circumferential range on both sides of the center line of the steel arch frame arch top, and double-layer advance small conduit support is adopted. The double-layer advance small conduit includes a plurality of pairs of grouting steel flower pipes, and the plurality of pairs of grouting steel flower pipes are spaced along the length direction of the steel arch frame. A pair of grouting steel flower pipes are driven into the rock and soil of the corresponding tunnel face at two angles, and one end is fixed in the opening of the steel arch frame. The rock and soil of the tunnel face is grout-reinforced by the grouting steel flower pipes to complete the advance support; S5: After advance support, the surrounding rock is reinforced by laying system anchors in a plum blossom pattern with a spacing of 100×100 cm on both sides of the center line of the steel arch in a circumferential range of 180° on the steel arch frame, and double-row locking anchors are set at the arch waist and arch foot of the steel arch frame to embed into the surrounding rock. After the double-row locking anchors are driven into the tunnel rock mass, they are welded to the steel arch frame with U-shaped connecting bars, and finally the gaps between the double-row locking anchors and the tunnel rock mass are filled and compacted with cement rolls; S6, determine whether the distance between one end of the advance pipe shed near the large pile number exit section and one end of the section to be penetrated near the large pile number exit section exceeds 3 meters: if so, excavate the upper step and cooperate with the advance small pipe support until the section to be penetrated is penetrated, thereby realizing the penetration of the tunnel, and finally carry out the construction of secondary lining and lining invert to make the support closed in a ring; if not, enter step S2 again.

2. The weathered silty mudstone tunnel construction method in the broken shallow buried section as claimed in claim 1 is characterized in that: The preset length of the section to be penetrated is 28 meters. When the length of the advanced pipe shed used is 12 meters, the spacing between two adjacent rows of advanced pipe sheds is 2 sheds, and the lap length of the tail end of the previous row of advanced pipe sheds of the rear row is 2m, a total of 3 rows of advanced pipe sheds are constructed along the length direction of the tunnel so that the distance between the end of the advanced pipe shed close to the exit section with a large pile number and the end of the section to be penetrated close to the exit section with a large pile number exceeds 3 meters.

3. The weathered silty mudstone tunnel construction method in a broken shallow buried section as claimed in claim 1 is characterized in that: One end of the steel pipe is a grout inlet, and the other end of the steel pipe is a conical head. In step S31, the steel pipe is drilled through the conical head until the steel pipe is driven into the rock and soil of the current face. In step S32, grout is injected into the steel pipe from the grout inlet.

4. The weathered silty mudstone tunnel construction method in a broken shallow buried section as claimed in claim 3 is characterized in that: A reinforcement hoop is welded and fixed at the slurry inlet, and the reinforcement hoop is arranged around the slurry inlet.

5. The weathered silty mudstone tunnel construction method in a broken shallow buried section as claimed in claim 1 is characterized in that: The reinforcement steel cage includes a plurality of fixing rings and a plurality of threaded steel bars. The plurality of fixing rings are arranged at intervals along the axial direction of the steel pipe, and the plurality of threaded steel bars are evenly arranged around the outer circumference of the fixing rings. Each of the threaded steel bars is fixedly connected to the plurality of fixing rings.

6. The weathered silty mudstone tunnel construction method in a broken shallow buried section as claimed in claim 1 is characterized in that: In step S2, the surface grouting from the entrance of the small pile number section to the top of the tunnel vault to be penetrated is completed, and 1.5m plum blossom-shaped grouting reinforcement holes are opened on the surface of the tunnel vault, and then the surface steel flower pipes are driven into the corresponding grouting reinforcement holes for grouting reinforcement.

7. The weathered silty mudstone tunnel construction method in a broken shallow buried section as claimed in claim 1 is characterized in that: In step S4, one end of each pair of grouting steel flower pipes is respectively fixed in the openings of two adjacent steel arch frames, and the angles between the extension directions of the two grouting steel flower pipes in each pair and the horizontal plane are different.

8. The weathered silty mudstone tunnel construction method in a broken shallow buried section as claimed in claim 1 is characterized in that: The double-row locking foot anchor rods are respectively arranged at the front and rear sides of the steel arch frame at corresponding positions, and the inclination angles of the double-row locking foot anchor rods relative to the horizontal plane are different.

9. The weathered silty mudstone tunnel construction method in a broken shallow buried section as claimed in claim 8, characterized in that: The U-shaped connecting rib includes a first fixing portion, a second fixing portion and a connecting portion fixedly connected to the same end of the first fixing portion and the second fixing portion, the first fixing portion, the second fixing portion and the connecting portion are arranged to form a receiving cavity, the U-shaped connecting rib is sleeved on the steel arch frame through the receiving cavity, the top surface of the steel arch frame is welded and fixed to the inner side surface of the connecting portion; the double-row locking foot anchor rods are respectively arranged on the opposite sides of the U-shaped connecting rib, and are respectively welded and fixed to the outer side surfaces of the first fixing portion and the second fixing portion.

10. The weathered silty mudstone tunnel construction method in a broken shallow buried section as claimed in claim 1, characterized in that: During the through-construction process, monitoring and measurement measures are used to assist. By continuously monitoring the settlement of the arch surrounding rock at the left measuring point, the middle measuring point and the right measuring point of the arch, and conducting peripheral displacement and settlement observations on the convergence measuring lines around the upper step, the middle step and the lower step, the on-site support construction is guided in a timely manner.

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