A tunnel support method suitable for expansive soft rock formations

Abstract

The present invention discloses a tunnel support method suitable for use in expansive soft rock formations, which relates to the technical field of tunnel reinforcement and support, including S1, construction preparation; S2, installation of an advance small guide tube; S3, filling and grouting the advance small guide tube; S4, tunnel excavation upon reaching the slurry age; S5, surrounding rock grouting and sealing; S6, off-wall support construction of steel brackets; S7, spraying net support construction; S8, anchor support construction; S9, full-section re-spraying construction; S10, static pressure deformation; S11, roof anchor cable support construction; S12, off-wall support of steel brackets; S13, back-up filling construction; S14, bottom plate anti-bottom arch construction, a total of fourteen construction steps. The present invention can effectively control expansive soft surrounding rocks, ensure excavation safety, and improve tunnel excavation construction efficiency. It not only solves the shortcomings of the existing technology, but also provides a new method and idea for tunnel support reinforcement in expansive soft rock formations in metal mines.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel reinforcement and support, and in particular to a tunnel support method suitable for use in expansive soft rock formations. Background Art

[0002] Underground mining of metal ore deposits is mainly limited by geological conditions. Complex strata and widely varying rock types increase the difficulty of mining metal ore deposits. Many metal mines have complex occurrence conditions, developed faults, joints and fissures, weak and broken surrounding rocks, and even some surrounding rocks undergo montmorillonization or kaolinization, which are expansive. Excavating tunnels in such weak and complex surrounding rocks can easily cause accidents such as roof falls and rock spalling. In the existing technology, there are many grouting reinforcement and support technologies for tunnel engineering, but there are few grouting reinforcement and support technologies for tunnels under weak and complex surrounding rock conditions. Moreover, in metal mines, it is difficult to ensure safety by relying solely on ordinary grouting support technology.

[0003] Therefore, in view of the engineering characteristics of tunnel excavation in expansive soft rock formations, how to develop a tunnel support method suitable for tunnel expansive soft rock formations to effectively control the expansive soft surrounding rock, ensure excavation safety, and improve the construction efficiency and safety of tunnel excavation has become a technical problem that technical personnel in this field urgently need to solve. Summary of the Invention

[0004] The purpose of the present invention is to provide a tunnel support method suitable for use in expansive soft rock formations, which can effectively control the expansive soft surrounding rock, ensure tunneling safety, and improve tunneling construction efficiency.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The present invention provides a tunnel support method applicable to expansive weak rock formations, comprising the following steps:

[0007] S1. Construction preparation;

[0008] S2. Installing a small advance guide tube, which is arranged at an angle in a radial shape on the top of the tunnel;

[0009] S3: Grouting is performed by filling the small lead pipe in advance. Grouting is performed into the surrounding rock of the roadway through the inner hole of the small lead pipe and the grouting holes on the side wall. The slurry penetrates into the surrounding rock.

[0010] S4, when the slurry age is reached, the tunnel is excavated;

[0011] S5. Shotcrete sealing of surrounding rock: Shotcrete sealing is carried out promptly after tunnel excavation to form a protective layer on the surrounding rock surface;

[0012] S6. Construction of steel support from the wall. The steel support is supported at a set distance and forms a U-shaped frame. Space is reserved between the steel support and the side wall of the roadway for deformation.

[0013] S7, spray mesh support construction, laying a layer of steel mesh in front and behind the steel support, and spraying and sealing, and connecting adjacent steel supports with tie rods;

[0014] S8. Anchor support construction, including roof anchors and side anchors. The roof anchors are radially located on the curved top of the tunnel, and the side anchors are evenly spaced on the two vertical side walls.

[0015] S9, full section re-spraying construction, after the construction is completed, the spray layer covers the anchor tray;

[0016] S10, let it stand for a specified time after the full section spraying is completed to allow the pressure to deform;

[0017] S11, roof anchor support construction, multiple anchor cables are set in a radial shape on the top of the tunnel to form secondary reinforcement support;

[0018] S12, steel support off-wall support: first expand the side and roof of the tunnel, then carry out steel support off-wall support, use pit wood backfill between the arch and roof of the steel support, and use I-beam support at the bottom;

[0019] S13, post-support filling construction, filling the space between the steel support and the surrounding rock with polyurethane foam material;

[0020] S14, bottom plate anti-bottom arch construction, the I-beam set in the middle is the anti-bottom arch body, a foam board cushion layer is set between the bottom of the anti-bottom arch body and the tunnel bottom plate, and a pit wood cushion layer is set above the anti-bottom arch body.

[0021] Preferably, in S3, the advance small conduit is made of a hot-rolled seamless steel pipe, and a plurality of overflow holes are opened on the pipe body, and the overflow holes are arranged in a plum blossom shape; there are no overflow holes within the front 0.2m range of the advance small conduit, and it is processed into a pointed cone shape and sealed tightly; there are no overflow holes within the rear 1.0m range, and the tail end of the advance small conduit is exposed during installation, and the exposed length is set to 30±5cm.

[0022] Preferably, in S3, the pressure during grouting does not exceed 2 MPa.

[0023] Preferably, in S4, a certain grouting reinforcement distance is reserved during tunnel excavation as a grouting stop pad for the next grouting cycle construction, and the grouting reinforcement distance is set to 2 to 4 meters.

[0024] Preferably, in S6, the steel section adopts a fully enclosed structure, and a layer of steel mesh is laid in front and behind the steel section bracket. The mesh specification is 2100mm×1050mm, the mesh specification is 100mm×100mm, the mesh overlap length is 100mm, and it is sprayed and sealed, and the steel frames are connected by tie rods.

[0025] Preferably, in S8, the specific operations of the anchor support construction are:

[0026] The construction steps of roof anchor are as follows: excavate gangue and ore → knock the roof and remove dangerous rocks → lay steel mesh → install steel support beams → use anchor drill to drill the anchor hole in the middle of the roof → clean the hole → put resin roll into the hole → use the anchor head to support the resin roll and send it to the bottom of the hole → raise the anchor drill and connect the anchor drill to the anchor tail with a stirrer → rotate the anchor drill to stir the resin roll for a specified time → stop stirring and wait for a specified time → use the installer to connect the anchor drill to the anchor tail → rotate the anchor drill to tighten the nut → install other roof anchors;

[0027] The construction steps of the two-side anchor rods are as follows: connect the metal mesh → drill the two-side anchor rod holes with an anchor drill → clean the holes → put the resin roll into the holes → use the anchor rod head to support the roll and send it to the bottom of the hole → use a stirrer to connect the drill rig and the anchor rod tail → turn the drill rig to stir the resin roll for the specified time → stop stirring and wait for the specified time → tighten the nut with a wrench → install the other two-side anchor rods.

[0028] Preferably, in S11, the specific operations of the top plate anchor cable support construction are:

[0029] Determine the anchor hole position → Use the anchor drill to drill the anchor hole in the middle of the roof → Clean the hole → Put the resin roll into the hole → Use the anchor head to support the resin roll and send it to the bottom of the hole → Raise the drill and connect the anchor drill and the anchor tail with a stirrer → Turn the drill to stir the resin roll for the specified time → Stop stirring and wait for the specified time, then retract the anchor machine and remove the stirrer → Wait for 15 minutes → Put on the support plate to install the anchor → Use the tensioning equipment to tension the anchor until the designed preload force → Then install other roof anchors in sequence from the middle to the outside.

[0030] Preferably, in S14, the anti-bottom arch body is formed by tying steel beams, with the bottoms of the two sides gradually transitioning to the center of the bottom plate in an arc shape, the foam board cushion layer is formed by filling foam, and the pit wood cushion layer is formed by filling pit wood.

[0031] Preferably, a drainage ditch is provided in the middle of the pit wooden cushion layer.

[0032] Compared with the prior art, the present invention has the following beneficial technical effects:

[0033] The present invention provides a tunnel support method suitable for use in expansive soft rock formations, comprising S1, construction preparation; S2, installation of an advance small guide tube; S3, filling and grouting of the advance small guide tube; S4, tunnel excavation upon reaching the slurry age; S5, surrounding rock grouting and sealing; S6, off-wall support construction of steel brackets; S7, spraying net support construction; S8, anchor rod support construction; S9, full-section re-spraying construction; S10, static deformation by pressure; S11, top plate anchor cable support construction; S12, off-wall support of steel brackets; S13, back-up filling construction; S14, bottom plate anti-bottom arch construction, with a total of fourteen construction steps.

[0034] First, advance curtain grouting is performed in small guide tubes S1-S4 to form advance support in the roadway, providing improved surrounding rock conditions for roadway excavation.

[0035] Secondly, S5 is used to promptly seal the tunnel after excavation to prevent further weathering and expansion of the surrounding rock.

[0036] Furthermore, by using the steel support off-wall support, the deformation capacity of the tunnel surrounding rock is reserved;

[0037] Afterwards, the weathered surface surrounding rock is allowed to fully deform by allowing it to rest and release pressure, thus reducing the impact of the weathered surrounding rock expansion on the long-term stability of the roadway.

[0038] Then, polyurethane foam material is filled between the steel support and the surrounding rock to prevent the surface surrounding rock from further weathering;

[0039] Finally, by adding an anti-bottom arch and filling a foam pad at the bottom plate, the bearing capacity of the bottom plate is enhanced, and at the same time a certain buffer space is provided for the deformation of the bottom plate.

[0040] In general, the construction steps of the present invention are orderly and reasonable, which can effectively control the expansive weak surrounding rock, ensure the safety of excavation, and improve the excavation construction efficiency of the tunnel. It not only solves the shortcomings of the existing technology, but also provides new methods and ideas for the support and reinforcement of tunnels in expansive weak rock formations in metal mines. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention will be further described below with reference to the accompanying drawings.

[0042] Figure 1 This is a flow chart of the tunnel support method applicable to expansive weak rock formations of the present invention;

[0043] Figure 2 This is a schematic cross-sectional diagram of the advanced small-duct grouting process of the present invention;

[0044] Figure 3 This is a side view schematic diagram of the advanced small-duct grouting of the present invention;

[0045] Figure 4This is a schematic cross-sectional view of the wall support construction of the steel support of the present invention;

[0046] Figure 5 This is a schematic diagram of the anchor support of the present invention;

[0047] Figure 6 Schematic diagram of anchor cable reinforcement support of the present invention Figure 1 ;

[0048] Figure 7 Schematic diagram of anchor cable reinforcement support of the present invention Figure 2 ;

[0049] Figure 8 This is a schematic diagram of the construction of the steel support and base plate of the present invention.

[0050] Explanation of reference numerals: 1. small advance guide tube; 2. steel support; 3. tunnel sidewall; 4. anchor rod; 5. anchor cable; 6. filling layer; 7. anti-bottom arch body; 8. foam board cushion layer; 9. pit wood cushion layer; 10. drainage ditch; 11. pit wood;

[0051] 201. Bottom bracket; 202. Top arch; 203. Connector. DETAILED DESCRIPTION

[0052] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0053] like Figure 1-8 As shown, a tunnel support method suitable for use in expansive soft rock formations includes the following steps: S1, construction preparation;

[0054] S2, installing the advance small conduit 1, which is arranged at an angle in a radial shape on the top of the tunnel;

[0055] S3: Grouting is performed by filling the small lead pipe in advance. Grouting is performed into the surrounding rock of the roadway through the inner hole of the small lead pipe and the grouting holes on the side wall. The slurry penetrates into the surrounding rock.

[0056] S4, when the slurry age is reached, the tunnel is excavated; the specific judgment of whether the grouting standard is met is: (1) the grouting volume per meter exceeds 10-15m 3 (2) When the grouting pressure of each grouting hole reaches the designed final pressure value, and the injection volume is less than 10-20L / min and remains stable for more than 10 minutes, grouting can be stopped;

[0057] like Figure 2-3As shown in the figure, through the above S1-S4 small-duct advance curtain grouting operation, advance support is formed in the tunnel, providing improved surrounding rock conditions for tunnel excavation;

[0058] S5. Shotcrete sealing of surrounding rock: Shotcrete sealing is carried out promptly after tunnel excavation to form a protective layer on the surrounding rock surface. Specifically, the shotcrete strength grade is C20, the mix ratio is 1:2:2, 3% to 5% accelerator is added, and the shotcrete thickness is set to 60 to 80 mm.

[0059] S6, Steel support 2 off-wall support construction, such as Figure 3 As shown, the steel support 2 is supported according to the set distance and forms a U-shaped frame; there is a space reserved for deformation between the steel support and the tunnel side wall 3;

[0060] S7, sprayed mesh support construction, a layer of steel mesh is laid in front and behind the steel support, and sprayed to create conditions for the implementation of anchor mesh spray support. Adjacent steel supports are connected by tie rods; the sprayed concrete strength grade is C20, the mix ratio is 1:2:2, 3% to 5% of accelerating agent is added, and the spray thickness is 60 to 80 mm;

[0061] S8, anchor bolt 4 support construction, including roof anchor bolts and side anchor bolts, the roof anchor bolts are located on the curved top of the tunnel in a radial shape, and the side anchor bolts are located on the two vertical side walls at equal intervals;

[0062] S9, full section re-spraying construction, after the construction is completed, the sprayed layer covers the anchor tray; specifically, the sprayed concrete strength grade is C20, the thickness is 40-60mm, and the sprayed layer is guaranteed to cover the anchor tray. The total thickness of the sprayed layer is 100-120mm;

[0063] S10, static deformation, after the full section of the spraying is completed, the tunnel is left to stand for a specified time to allow deformation. Specifically, the tunnel is left to stand for 15 days to allow the weathered surface surrounding rock to fully deform and reduce the impact of the weathered surrounding rock expansion on the long-term stability of the tunnel.

[0064] S11, top plate anchor cable 5 support construction, such as Figure 6-7 As shown, multiple anchor cables are arranged in a radial shape at the top of the tunnel to form secondary reinforcement support. Specifically, end anchor cables with a diameter of Φ18.9mm×8000mm are used, with a hole diameter of Φ32mm and a spacing of 1000mm×800mm, and a 4-3-4 arrangement. One roll of fast-speed 2350 type and three rolls of medium-speed 2350 type resin drug rolls are used for extended anchoring. The anchor cables are tensioned by about 20%, leaving sufficient space for subsequent deformation of the anchor cables. High spherical trays (300mm×300mm×15mm) and special anchors and equipment are used for tensioning, fixing and cutting, and a high-strength anchor is equipped at the tail.

[0065] S12, steel support 2 off-wall support, first expand the side and top plate of the tunnel, then carry out steel support off-wall support, use pit wood 11 to backfill between the arch and top plate of the steel support, and use I-beam support at the bottom; this off-wall support operation is a secondary support method after pressure unloading, the rock mass has completed pressure release, and the placement of pit wood is to reserve buffer space for its subsequent long-term creep.

[0066] Specifically, the steel support 2 includes a bottom support 201 and an arc-shaped top arch 202, and the connecting ends of the two are fastened together by a connector 203. The reserved deformation amount of the two side parts is 500mm (can also be adjusted according to actual needs, the adjustment range is 200-600mm), the reserved deformation amount of the tunnel roof is 200mm, and pit wood is used for support between the tunnel roof and the steel support 2; the fully enclosed steel support 2 is made of 36U steel, a fully enclosed structure, and a row spacing of 800mm. The 36U steel has better strength to ensure the safety of permanent support. Channel steel is used to connect the steel frames, and every three supports are connected into a whole to improve the overall stability of the support. The bottom of each steel support is supported by I-beams to improve the bearing capacity of the support foot. Metal mesh is laid on the inner and outer layers of the steel support. The metal mesh is welded with φ6mm steel bars. The mesh size is 2100mm×1050mm, the mesh size is 100mm×100mm, and the mesh overlap length is 100mm. The sprayed concrete strength grade is C20, the mix ratio is 1:2:2, 3% to 5% of accelerator is added, and the spray thickness is 60 to 80mm.

[0067] S13, backfill construction, such as Figure 8 As shown, a polyurethane foam material is filled between the steel support and the surrounding rock to form a filling layer 6, which can prevent the surrounding rock from further weathering and expansion;

[0068] S14, bottom plate anti-bottom arch construction, the I-beam arranged in the middle is the anti-bottom arch body 7, a foam board cushion layer 8 is arranged between the bottom of the anti-bottom arch body 7 and the tunnel bottom plate, and a pit wood cushion layer 9 is arranged above the anti-bottom arch body.

[0069] like Figure 8 As shown, specifically, first clear the original floor to the design elevation, then construct a 600mm thick underlayment (excluding the reserved 100mm surface layer), with the bottoms of both sides (excluding the surface layer thickness of at least 300mm) transitioning gradually to the center of the floor in an arc shape. A 300mm×300mm×5000mm steel bar tie beam can be pre-tied on the ground (longitudinal bars are HRB335 steel bars, 3 each on the top and bottom, and 2 waist bars, with a diameter of 16mm; stirrups are HPB300, with a diameter of 8mm, and stirrup spacing of 200mm, with spacing of 100mm at bends).

[0070] The bottom plate is paved with foam board to form a foam board cushion layer 8 with a thickness of 300mm. Then pit wood is used for backfilling to form a pit wood cushion layer 9 with a maximum backfill thickness of 300mm to ensure normal traffic in the tunnel. A drainage ditch 10 is provided in the middle of the pit wood cushion layer.

[0071] Specifically, in S3, the advance small conduit is made of a hot-rolled seamless steel pipe with a diameter of φ50~60mm. A number of overflow holes are opened on the pipe body with a hole diameter of φ8mm, and the overflow holes are arranged in a plum blossom shape; there is no overflow hole within the front end 0.2m of the advance small conduit, and it is processed into a pointed cone shape and sealed tightly; there is no overflow hole within the rear end 1.0m. During installation, the tail end of the advance small conduit is exposed, and the exposed length is set to 30±5cm.

[0072] In S3, the pressure during grouting does not exceed 2MPa to ensure that the sprayed layer does not crack.

[0073] In S4, a certain grouting reinforcement distance is retained during tunnel excavation as a grouting pad for the next grouting cycle construction. The grouting reinforcement distance is set to 2 to 4 meters, preferably 3 meters. It can also be set to other sizes as needed, such as 2 meters, 2.5 meters, 3.5 meters or 4 meters.

[0074] In S6, the steel section adopts a fully enclosed structure. A layer of steel mesh is laid in front and behind the steel section support. The mesh size is 2100mm × 1050mm, the mesh size is 100mm × 100mm, and the mesh overlap length is 100mm. The mesh is sealed with spray grout. The steel frames are connected with tie rods to improve the stability of the support. Specifically, the steel section support 2 is made of 29U steel and has a fully enclosed structure with a row spacing of 750mm.

[0075] like Figure 4 As shown in S8, the specific operations of anchor support construction are:

[0076] The construction steps of roof anchor are as follows: excavate gangue and ore → knock the roof and remove dangerous rocks → lay steel mesh → install steel support beams → use anchor drill to drill the anchor hole in the middle of the roof → clean the hole → put resin roll into the hole → use the anchor head to support the resin roll and send it to the bottom of the hole → raise the anchor drill and connect the anchor drill to the anchor tail with a stirrer → rotate the anchor drill to stir the resin roll for the specified time → stop stirring and wait for the specified time → use the installer to connect the anchor drill to the anchor tail → rotate the anchor drill to tighten the nut → install other roof anchors;

[0077] The construction steps of the two-side anchor rods are as follows: connect the metal mesh → drill the two-side anchor rod holes with an anchor drill → clean the holes → put the resin roll into the holes → use the anchor rod head to support the roll and send it to the bottom of the hole → use a stirrer to connect the drill rig and the anchor rod tail → turn the drill rig to stir the resin roll for the specified time → stop stirring and wait for the specified time → tighten the nut with a wrench → install the other two-side anchor rods.

[0078] Specifically, the anchor rods are high-performance threaded steel anchor rods with specifications of Φ20mm × 2400mm and a spacing of 750mm × 750mm. The rod body is made of left-handed unreinforced threaded steel bar, the anchor hole diameter is Φ32mm, and two slow-speed 2335 resin coils are used for extended anchoring. The anchor length is no less than 1000mm, the anchoring force is no less than 100kN, and the preload force is no less than 40kN.

[0079] In S11, the specific operations of the roof anchor cable support construction are:

[0080] Determine the anchor hole position → Use the anchor drill to drill the anchor hole in the middle of the roof → Clean the hole → Put the resin roll into the hole → Use the anchor head to support the resin roll and send it to the bottom of the hole → Raise the drill and connect the anchor drill and the anchor tail with a stirrer → Turn the drill to stir the resin roll for the specified time → Stop stirring and wait for the specified time, then retract the anchor machine and remove the stirrer → Wait for 15 minutes → Put on the support plate to install the anchor → Use the tensioning equipment to tension the anchor until the designed preload force → Then install other roof anchors in sequence from the middle to the outside.

[0081] In S14, the anti-bottom arch body is formed by tying steel beams, and the bottoms of the two sides are gradually transitioned to the center of the bottom plate in an arc shape. The foam board cushion layer is formed by filling foam, and the pit wood cushion layer is formed by filling pit wood.

[0082] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0083] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A tunnel support method suitable for use in expansive soft rock formations, characterized by: The following steps are involved: S1. Construction preparation; S2. Installing a small advance guide tube, which is arranged at an angle in a radial shape on the top of the tunnel; S3: Grouting is performed by filling the small lead pipe in advance. Grouting is performed into the surrounding rock of the roadway through the inner hole of the small lead pipe and the grouting holes on the side wall. The slurry penetrates into the surrounding rock. S4, when the slurry age is reached, the tunnel is excavated; S5. Shotcrete sealing of surrounding rock: Shotcrete sealing is carried out promptly after tunnel excavation to form a protective layer on the surrounding rock surface; S6. Construction of steel support from the wall. The steel support is supported at a set distance and forms a U-shaped frame. Space is reserved between the steel support and the side wall of the roadway for deformation. S7, spray mesh support construction, laying a layer of steel mesh in front and behind the steel support, and spraying and sealing, and connecting adjacent steel supports with tie rods; S8. Anchor support construction, including roof anchors and side anchors. The roof anchors are radially located on the curved top of the tunnel, and the side anchors are evenly spaced on the two vertical side walls. S9, full section re-spraying construction, after the construction is completed, the spray layer covers the anchor tray; S10, let it stand for a specified time after the full section spraying is completed to allow the pressure to deform; S11, roof anchor support construction, multiple anchor cables are set in a radial shape on the top of the tunnel to form secondary reinforcement support; S12, steel support off-wall support: first expand the side and roof of the tunnel, then carry out steel support off-wall support, use pit wood backfill between the arch and roof of the steel support, and use I-beam support at the bottom; S13, post-support filling construction, filling the space between the steel support and the surrounding rock with polyurethane foam material; S14, bottom plate anti-bottom arch construction, the I-beam set in the middle is the anti-bottom arch body, a foam board cushion layer is set between the bottom of the anti-bottom arch body and the tunnel bottom plate, and a pit wood cushion layer is set above the anti-bottom arch body.

2. The tunnel support method for expansive soft rock formations according to claim 1 is characterized in that: In S3, the advance small conduit is made of hot-rolled seamless steel pipe, and a number of overflow holes are opened on the pipe body, and the overflow holes are arranged in a plum blossom shape; there are no overflow holes within the front 0.2m range of the advance small conduit, and it is processed into a pointed cone shape and sealed tightly; there are no overflow holes within the rear 1.0m range, and the tail end of the advance small conduit is exposed during installation, and the exposed length is set to 30±5cm.

3. The tunnel support method for expansive weak rock formations according to claim 1 is characterized in that: In S3, the pressure during grouting does not exceed 2 MPa.

4. The tunnel support method for expansive weak rock formations according to claim 1 is characterized in that: In S4, a certain grouting reinforcement distance is retained during tunnel excavation as a grouting pad for the next grouting cycle construction, and the grouting reinforcement distance is set to 2 to 4 meters.

5. The tunnel support method for expansive weak rock formations according to claim 1 is characterized in that: In S6, the steel section adopts a fully enclosed structure, and a layer of steel mesh is laid in front and behind the steel section support. The mesh specification is 2100mm×1050mm, the mesh specification is 100mm×100mm, the mesh overlap length is 100mm, and it is sprayed and sealed. The steel frames are connected with tie rods.

6. The tunnel support method for expansive weak rock formations according to claim 1 is characterized in that: In S8, the specific operations of anchor support construction are: The construction steps of roof anchor are as follows: excavate gangue and ore → knock the roof and remove dangerous rocks → lay steel mesh → install steel support beams → use anchor drill to drill the anchor hole in the middle of the roof → clean the hole → put resin roll into the hole → use the anchor head to support the resin roll and send it to the bottom of the hole → raise the anchor drill and connect the anchor drill to the anchor tail with a stirrer → rotate the anchor drill to stir the resin roll for the specified time → stop stirring and wait for the specified time → use the installer to connect the anchor drill to the anchor tail → rotate the anchor drill to tighten the nut → install other roof anchors; The construction steps of the two-side anchor rods are as follows: connect the metal mesh → drill the two-side anchor rod holes with an anchor drill → clean the holes → put the resin roll into the holes → use the anchor rod head to support the roll and send it to the bottom of the hole → use a stirrer to connect the drill rig and the anchor rod tail → turn the drill rig to stir the resin roll for the specified time → stop stirring and wait for the specified time → tighten the nut with a wrench → install the other two-side anchor rods.

7. The tunnel support method for expansive weak rock formations according to claim 1 is characterized in that: In S11, the specific operations of the roof anchor cable support construction are: Determine the anchor hole position → Use the anchor drill to drill the anchor hole in the middle of the roof → Clean the hole → Put the resin roll into the hole → Use the anchor head to support the resin roll and send it to the bottom of the hole → Raise the drill and connect the anchor drill and the anchor tail with a stirrer → Turn the drill to stir the resin roll for the specified time → Stop stirring and wait for the specified time, then retract the anchor machine and remove the stirrer → Wait for 15 minutes → Put on the support plate to install the anchor → Use the tensioning equipment to tension the anchor until the designed preload force → Then install other roof anchors in sequence from the middle to the outside.

8. The tunnel support method for expansive weak rock formations according to claim 1 is characterized in that: In S14, the anti-bottom arch body is formed by tying steel beams, and the bottoms of the two sides are gradually transitioned to the center of the bottom plate in an arc shape. The foam board cushion layer is formed by filling foam, and the pit wood cushion layer is formed by filling pit wood.

9. The tunnel support method for expansive weak rock formations according to claim 8, characterized in that: A drainage ditch is provided in the middle of the pit wooden cushion layer.

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