Roadway supporting method suitable for expansive soft rock stratum

Abstract

The invention discloses a roadway supporting method suitable for an expansive soft rock stratum, and relates to the technical field of roadway reinforcing and supporting. S2, an advanced small guide pipe is installed; s3, the advanced small guide pipe is filled and grouted; s4, when the slurry age is reached, roadway tunneling is carried out; s5, surrounding rock guniting sealing is conducted; s6, profile steel support off-wall supporting construction is conducted; s7, net spraying support construction; s8, anchor rod supporting construction; s9, performing full-section re-spraying construction; s10, standing for yielding deformation; s11, roof anchor cable support construction is conducted; s12, supporting the section steel bracket away from the wall; s13, filling construction is carried out after erection; and S14, bottom plate inverted arch construction is carried out, and 14 construction steps are carried out in total. According to the method, the expansible weak surrounding rock can be effectively treated, the tunneling safety is guaranteed, the tunneling construction efficiency of the roadway is improved, the defects in the prior art are overcome, and a new method and thought are provided for supporting and reinforcing the roadway in the expansible weak rock stratum of the metal mine.

Description

Technical Field

[0001] The 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 different rock properties 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 have become montmorillonized or kaolinized, which are expansive. Excavating tunnels in such weak and complex surrounding rocks can easily cause accidents such as roof falls and spalling. In the prior art, 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 strata, how to develop a tunnel support method suitable for tunnel expansive soft rock strata 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 expansive soft rock strata, which can effectively control the expansive soft surrounding rock, ensure the safety of tunneling, and improve the construction efficiency of tunneling.

[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 suitable for use in expansive soft rock formations, comprising the following steps:

[0007] S1. Construction preparation;

[0008] S2, installing a small advance conduit, wherein the small advance conduit is arranged at an angle on the top of the tunnel in a radial shape;

[0009] S3, grouting of the small advance pipe, grouting operation is carried out into the surrounding rock of the tunnel through the inner hole of the small advance pipe and the grouting holes on the side wall, and the slurry penetrates into the surrounding rock;

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

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

[0012] S6, construction of steel support away from the wall, the steel support is supported at a set distance and forms a U-shaped frame; there is a space reserved for deformation between the steel support and the side wall of the tunnel;

[0013] S7, spray mesh support construction, a layer of steel mesh is laid before and after the steel support, and spray grouting is performed to seal it, and adjacent steel supports are connected by tie rods;

[0014] S8, anchor support construction, including roof anchors and side anchors, the roof anchors are located on the arc top of the tunnel in a radial shape, and the side anchors are located on the two vertical side walls at equal intervals;

[0015] S9, full section re-spraying construction, after the construction is completed, the spraying 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 cable 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 top plate of the tunnel, then carry out steel support off-wall support, use pit wood to backfill between the arch and top plate of the steel support, and use I-beam support at the bottom;

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

[0020] S14, bottom plate anti-bottom arch construction, the I-beam arranged in the middle is the anti-bottom arch body, a foam board cushion layer is arranged between the bottom of the anti-bottom arch body and the bottom plate of the tunnel, and a pit wood cushion layer is arranged 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; no overflow holes are arranged within the front 0.2m range of the advance small conduit, and it is processed into a pointed cone shape and sealed tightly; no overflow holes are arranged 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 m.

[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 the roof anchor are as follows: excavate the gangue and ore → knock the top to find out the dangerous rock → lay the steel mesh → install the steel support beam → 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 anchor drill and connect the anchor drill and the anchor tail with a stirrer → turn 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 and the anchor tail → turn 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 holes for the two-side anchor rods with an anchor drill → clean the holes → put the resin roll into the holes → hold the roll with the head of the anchor rod and send it to the bottom of the hole → connect the drill rig and the tail of the anchor rod with a stirrer → 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 → then install other roof anchors from the middle to the outside.

[0030] Preferably, 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.

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

[0032] Compared with the prior art, the beneficial technical effects of the present invention are:

[0033] The invention discloses 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 when the slurry age is reached; 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 deformation by pressure; S11, top plate anchor cable support construction; S12, off-wall support of steel brackets; S13, back-end filling construction; S14, bottom plate anti-bottom arch construction, with a total of fourteen construction steps.

[0034] First, advance support is formed in the tunnel through advance curtain grouting of small guide tubes S1-S4, providing improved surrounding rock conditions for tunnel excavation;

[0035] Secondly, S5 was used to promptly carry out shotcrete sealing after tunnel excavation to prevent further weathering and expansion of the surrounding rock;

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

[0037] Afterwards, the weathered surface surrounding rock is allowed to fully deform by statically allowing the pressure to be released, thus reducing the impact of the expansion of the weathered surrounding rock on the long-term stability of the tunnel;

[0038] Then, the surface surrounding rock is prevented from further weathering by filling the space between the steel support and the surrounding rock with polyurethane foam material;

[0039] Finally, by adding an anti-bottom arch and filling a foam cushion layer 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 soft surrounding rock, ensure the safety of excavation, and improve the excavation construction efficiency of the tunnel. It not only solves the shortcomings of the prior art, but also provides new methods and ideas for the support and reinforcement of tunnels in expansive soft rock strata in metal mines. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0044] Figure 3 It is a side view schematic diagram of the advanced small conduit grouting of the present invention;

[0045] Figure 4It is a schematic diagram of the cross section of the off-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 The anchor cable reinforcement support of the present invention is shown in FIG. Figure 1 ;

[0048] Figure 7 The anchor cable reinforcement support of the present invention is shown in FIG. Figure 2 ;

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

[0050] Description of reference numerals: 1. small advance guide tube; 2. steel support; 3. tunnel side wall; 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 bracket; 203, connecting piece. 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 in conjunction with 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 used to limit the present invention.

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

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

[0055] S3, grouting of the small advance pipe, grouting operation is carried out into the surrounding rock of the tunnel through the inner hole of the small advance pipe and the grouting holes on the side wall, and the slurry penetrates into the surrounding rock;

[0056] S4: When the slurry age is reached, the tunnel is excavated; the specific judgment on 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, the grouting can be stopped;

[0057] like Figure 2-3As shown, 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 in time after tunnel excavation to form a protective layer on the surface of surrounding rock; specifically, the strength grade of shotcrete is C20, the mix ratio is 1:2:2, 3% to 5% of accelerating agent 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 deformation reserved space between the steel support and the tunnel side wall 3;

[0060] S7, spraying support construction, a layer of steel mesh is laid before and after the steel support, and spraying is carried out to create conditions for the implementation of anchor mesh spraying support, and 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 spraying thickness is 60 to 80 mm;

[0061] S8, anchor rod 4 support construction, including top plate anchor rods and two side anchor rods, the top plate anchor rods are located on the arc top of the tunnel in a radial shape, and the two side anchor rods 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, to ensure that the sprayed layer can cover the anchor tray, the total thickness of the sprayed layer is 100-120mm;

[0063] S10, let it stand for a specified time after the full section re-spraying is completed, and the deformation is completed by standing still; 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 expansion of the weathered surrounding rock 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, an end anchor cable of Φ18.9mm×8000mm is used, with a hole diameter of Φ32mm, a spacing of 1000mm×800mm, and a 4-3-4 arrangement; 1 roll of fast 2350 type and 3 rolls of medium-speed 2350 type resin drug rolls are used for lengthened anchoring; the anchor cable is tensioned by about 20%, leaving sufficient space for subsequent deformation of the anchor cable; a high spherical tray (300mm×300mm×15mm) and special anchors and equipment are used for tensioning, fixing and cutting, and a high-strength anchor is provided 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 relief, the rock mass has completed pressure release, and the pit wood is placed 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, the connecting ends of the two are fastened together by a connector 203, the reserved deformation of the two sides is 500mm (can also be adjusted according to actual needs, the adjustment range is 200-600mm), the reserved deformation of the tunnel roof is 200mm, and pit wood is used 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 strength of 36U steel is better to ensure the safety of permanent support. Channel steel is used to connect the steel frames, connecting every three supports 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, the mesh overlap length is 100mm, the strength grade of shotcrete is C20, the mix ratio is 1:2:2, 3% to 5% of accelerating agent is added, and the spraying thickness is 60 to 80mm.

[0067] S13, backfilling 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, and the filling layer 6 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 bottom plate of the tunnel, and a pit wood cushion layer 9 is arranged above the anti-bottom arch body.

[0069] like Figure 8 As shown, first clear the original floor to the design elevation, then make the tunnel floor 600mm thick (excluding the reserved 100mm surface layer), the bottom of the two sides (excluding the surface layer thickness of not less than 300mm) gradually transition to the center of the floor in an arc shape. 300mm×300mm×5000mm tied steel beams can be pre-tied on the ground (longitudinal reinforcement is HRB335 steel bars, 3 each on the top and bottom, 2 waist reinforcements, with a diameter of 16mm; stirrups are HPB300, with a diameter of 8mm, stirrup spacing is 200mm, and spacing at bends is 100mm).

[0070] The bottom plate is paved with foam board to form a foam board cushion layer 8 with a thickness of 300mm, and then pit wood is backfilled to form a pit wood cushion layer 9 with a maximum backfill thickness of 300mm to ensure normal traffic in the tunnel; and a drainage ditch 10 is opened in the middle of the pit wood cushion layer.

[0071] Specifically, in S3, the advance small conduit is made of 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; no overflow holes are set within the front end 0.2m of the advance small conduit, and it is processed into a pointed cone and sealed tightly; no overflow holes are set within the rear end 1.0m, and the tail end of the advance small conduit is exposed during installation, 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 reserved during tunnel excavation as a grouting pad for the next grouting cycle construction. The grouting reinforcement distance is set to 2 to 4m, preferably 3m, and can also be set to other sizes as needed, such as 2m, 2.5m, 3.5m or 4m.

[0074] In S6, the steel section adopts a fully enclosed structure, and a layer of steel mesh is laid before and after the steel section bracket, the mesh size is 2100mm×1050mm, the mesh size is 100mm×100mm, the mesh overlap length is 100mm, and the mesh is sprayed and sealed, and the steel frames are connected by tie rods to improve the stability of the bracket. Specifically, the steel section bracket 2 is made of 29U steel, which is a fully enclosed structure, and the row spacing is set to 750mm.

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

[0076] The construction steps of the roof anchor are as follows: excavate the gangue and ore → knock the top to find out the dangerous rock → lay the steel mesh → install the steel support beam → 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 anchor drill and connect the anchor drill and the anchor tail with a stirrer → turn 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 and the anchor tail → turn 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 holes for the two-side anchor rods with an anchor drill → clean the holes → put the resin roll into the holes → hold the roll with the head of the anchor rod and send it to the bottom of the hole → connect the drill rig and the tail of the anchor rod with a stirrer → 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 rod adopts high-performance threaded steel anchor rod with specifications of Φ20mm×2400mm and spacing of 750mm×750mm. The rod body adopts left-handed threaded steel bar without longitudinal reinforcement, the diameter of the anchor hole is Φ32mm, and two slow-speed 2335 resin drug rolls are used for extended anchoring. The anchoring length is not less than 1000mm, the anchoring force is not less than 100KN, and the preload force is not less than 40KN.

[0079] In S11, the specific operations of the top plate 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 → then install other roof anchors from the middle to the outside.

[0081] In S14, the anti-bottom arch body is formed by tying steel beams, and the bottom 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 article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0083] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A tunnel support method suitable for use in expansive soft rock formations, characterized in that: The following steps are involved: S1. Construction preparation; S2, installing a small advance conduit, wherein the small advance conduit is arranged at an angle on the top of the tunnel in a radial shape; S3, grouting of the small advance pipe, grouting operation is carried out into the surrounding rock of the tunnel through the inner hole of the small advance pipe and the grouting holes on the side wall, and the slurry penetrates into the surrounding rock; S4, when the slurry age is reached, tunnel excavation begins; S5. Shotcrete sealing of surrounding rock: Shotcrete sealing is carried out in time after tunnel excavation to form a protective layer on the surface of surrounding rock; S6, construction of steel support away from the wall, the steel support is supported at a set distance and forms a U-shaped frame; there is a space reserved for deformation between the steel support and the side wall of the tunnel; S7, sprayed mesh support construction, a layer of steel mesh is laid before and after the steel support, and sprayed and sealed, and adjacent steel supports are connected by tie rods; S8, anchor support construction, including roof anchors and side anchors, the roof anchors are located on the arc top of the tunnel in a radial shape, and the side anchors are located on the two vertical side walls at equal intervals; S9, full section re-spraying construction, after the construction is completed, the spraying 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 cable 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 top plate of the tunnel, then carry out steel support off-wall support, use pit wood to backfill between the arch and top plate of the steel support, and use I-beam support at the bottom; S13, post-support filling construction, filling polyurethane foam material between the steel support and the surrounding rock; S14, bottom plate anti-bottom arch construction, the I-beam arranged in the middle is the anti-bottom arch body, a foam board cushion layer is arranged between the bottom of the anti-bottom arch body and the bottom plate of the tunnel, and a pit wood cushion layer is arranged above the anti-bottom arch body.

2. The tunnel support method applicable to 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 is no overflow hole within the front 0.2m range of the advance small conduit, and it is processed into a pointed cone and sealed tightly; there is no overflow hole 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 applicable to expansive soft rock formations according to claim 1 is characterized in that: In S3, the pressure during grouting does not exceed 2MPa.

4. The tunnel support method applicable to expansive soft 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 stop pad for the next grouting cycle construction, and the grouting reinforcement distance is set to 2 to 4 meters.

5. The tunnel support method applicable to expansive soft 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 by tie rods.

6. The tunnel support method applicable to expansive soft rock formations according to claim 1 is characterized in that: In S8, the specific operations of anchor support construction are: The construction steps of the roof anchor are as follows: excavate the gangue and ore → knock the top to find out the dangerous rock → lay the steel mesh → install the steel support beam → 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 anchor drill and connect the anchor drill and the anchor tail with a stirrer → turn 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 and the anchor tail → turn 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 holes for the two-side anchor rods with an anchor drill → clean the holes → put the resin roll into the holes → hold the roll with the head of the anchor rod and send it to the bottom of the hole → connect the drill rig and the tail of the anchor rod with a stirrer → 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 applicable to expansive soft rock formations according to claim 1 is characterized in that: In S11, the specific operations of the top plate 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 → then install other roof anchors from the middle to the outside.

8. The tunnel support method applicable to expansive soft 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 bottom 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 applicable to expansive soft 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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