Exterior and interior co-treatment supporting system suitable for extremely soft coal roadway and construction method

Abstract

The invention relates to an exterior and interior co-treatment supporting system suitable for an extremely-soft coal roadway and a construction method. The exterior and interior co-treatment support system comprises drilling and grouting integrated advanced small guide pipes, the drilling and grouting integrated advanced small guide pipes are fully distributed on the section of a roadway and driven into surrounding rock by a certain depth in the excavation direction, and advanced temporary support is formed through grouting; the net surface layer is laid along the inner wall of the roadway and is fixed on the surface of the surrounding rock after the roadway is excavated; the post-net filling layer is formed by grouting between the net surface layer and the surrounding rock; the anchor rod cable supporting structure is installed in the surrounding rock according to the design requirement after the grouting material reaches the target strength, and proper pre-tightening force is applied to the anchor rod cable supporting structure. In order to solve the excavation supporting problem of the extremely soft coal roadway, passive surface layer protection (surface) is provided by means of the net surface layer and the filling layer behind the net, active deep supporting (inner) is provided by means of the anchor rod and anchor cable supporting structure, a powerful supporting structure is formed through common treatment of the surface and the inner, and the overall stability of the roadway is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of roadway excavation, especially extremely soft coal roadways, and specifically relates to a support system and construction method for treating both the inside and outside of extremely soft coal roadways. Background Art

[0002] Currently, in the excavation support of surrounding rock roadways, the combined support of bolt support and shotcrete is the most commonly used support method.

[0003] Bolt support mainly controls the displacement and deformation of the surrounding rock by embedding bolts into the rock mass and using the friction and bonding force between the bolts and the surrounding rock, thereby forming a stable support structure. In soft and broken surrounding rock, bolts are prone to a decrease in anchoring force and loosening. If the anchoring force of the bolts is insufficient, their mechanical properties cannot be fully exerted to ensure the stability of the surrounding rock.

[0004] Shotcrete support technology forms a solid support layer by spraying concrete on the roadway surface. The construction process is relatively complex and requires a large investment in construction equipment and materials. It has high requirements for the construction environment, requiring good ventilation conditions and humidity control, which will increase the construction difficulty and cost. The shotcrete layer has high rigidity but greatly reduced flexibility. Due to the large deformability of soft rock, the shotcrete support is prone to peeling off in soft rock roadways, affecting the support effect.

[0005] In soft rock and broken surrounding rock roadways, due to the low self-bearing capacity of soft rock, the surrounding rock will quickly become unstable after exposure, usually showing deformation and damage within dozens of minutes to several hours. After the excavation of soft and broken surrounding rock, it is easy to loosen and break, resulting in serious roof subsidence and mesh pocket phenomena. Due to the poor self-stabilization ability of soft and broken surrounding rock, the lack of timely support measures will lead to the instability of the surrounding rock, and then collapse or roof fall accidents will occur, which will seriously affect construction safety and engineering quality. Due to the low strength and broken structure of the surrounding rock, traditional support measures such as bolts and cable bolts are difficult to be stably anchored to the surrounding rock, resulting in a decrease in anchoring force and the inability to fully exert their mechanical properties, leading to support failure. In addition, soft and broken surrounding rock often contains a high proportion of clay minerals, which are prone to slaking and swelling when encountering water, resulting in an increase in the instability of the surrounding rock. Especially under the aquifer, seepage water enters the roadway along the cracks, further deteriorating the stability of the surrounding rock. Due to the complexity and instability of soft and broken surrounding rock, the support construction process is restricted in many ways. The construction period is long, the efficiency is low, and the engineering cost is high, bringing certain pressure to the construction progress and economic benefits.

[0006] Therefore, it is very necessary to design a support scheme that can effectively prevent safety risks during the excavation of extremely soft coal roadways, give full play to the role of bolt support, prevent the infiltration of water, mud, etc. and the caving of rocks, and construct in a complex engineering environment to improve construction efficiency. Summary of the Invention

[0007] In view of the deficiencies of the prior art, the main object of the present invention is to provide a support system and construction method for treating both the surface and the interior applicable to extremely soft coal roadways, so as to solve the problems encountered in the excavation and support process of extremely soft coal roadways.

[0008] The technical solution of the present invention is as follows:

[0009] The present invention first provides a support system for treating both the surface and the interior applicable to extremely soft coal roadways, including:

[0010] Integrated drilling and grouting advanced small pipes, the integrated drilling and grouting advanced small pipes are densely arranged in the roadway section and drilled into the surrounding rock to a certain depth along the excavation direction, and grouted to form an advanced temporary support for roadway excavation;

[0011] Mesh surface layer, the mesh surface layer is laid along the inner wall of the roadway after excavation and fixed on the surface of the surrounding rock, and there is a small gap between the mesh surface layer and the surrounding rock;

[0012] Backfill layer behind the mesh, the backfill layer behind the mesh is formed by grouting between the mesh surface layer and the surrounding rock, and the grouting material fills the gaps and cracks between the mesh surface layer and the surrounding rock, forming a passive surface protection for the roadway surrounding rock, that is, the "surface" of the surface and interior treatment system;

[0013] Bolt and cable support structure, after the grouting material reaches the target strength, the bolt and cable support structure is installed in the surrounding rock according to the design requirements and appropriate pre-tightening force is applied, forming an active deep support for the roadway surrounding rock, that is, the "interior" of the surface and interior treatment system.

[0014] In some embodiments, the integrated drilling and grouting advanced small pipes include:

[0015] Front section, the tail end of the front section is provided with an internal thread connection section, the front end is provided with a conical drill bit, and grouting holes are evenly opened on the pipe wall;

[0016] Tail section, the tail end of the tail section is provided with an internal thread connection section, a grouting port is arranged near the internal thread connection section, the front end is provided with an external thread reduced diameter connection section, and grouting holes are evenly opened on the pipe wall;

[0017] Standard section, the tail end of the standard section is provided with an internal thread connection section, the front end is provided with an external thread reduced diameter connection section, and grouting holes are evenly opened on the pipe wall.

[0018] In some embodiments, the pipe body of the integrated drilling and grouting advanced small pipes is made of high-strength seamless steel pipe, the aperture of the grouting holes on the pipe wall is 6-10 mm, the hole spacing is 15-20 cm, and in severely broken areas, the hole spacing is reduced to 10-15 cm.

[0019] In some embodiments, a scale ruler is laser-engraved on the surface of the pipe body of the integrated drilling and grouting advanced small pipe to accurately control the drilling depth during construction.

[0020] In some embodiments, the mesh layer includes:

[0021] A first soft and dense mesh layer;

[0022] A second hard and sparse mesh layer; and

[0023] The first soft and dense mesh layer and the second hard and sparse mesh layer are pre-combined to form a whole, which is laid along the inner wall of the roadway and fixed on the surface of the surrounding rock after the roadway excavation is completed. The first soft and dense mesh layer is located on the inner side, and the second hard and sparse mesh layer is located on the outer side.

[0024] In some embodiments, the mesh layer includes:

[0025] A first soft and dense mesh layer, which is laid along the inner wall of the roadway and fixed on the surface of the surrounding rock after the roadway excavation is completed;

[0026] A second hard and sparse mesh layer, which is laid and fixed on the outer side of the first soft and dense mesh layer.

[0027] In some embodiments, the first soft and dense mesh layer is a woven mesh or a woven bag, and the second hard and sparse mesh layer is a metal mesh.

[0028] In some embodiments, the bolt and cable support structure uses a combination of relatively short bolts and relatively long cables, and appropriate pre-tightening forces are applied to the bolts and cables.

[0029] The present invention also provides a construction method according to the internal and external co-governance support system, including the following steps:

[0030] S10, constructing the integrated drilling and grouting advanced small pipe and grouting:

[0031] Before the roadway excavation, construct the integrated drilling and grouting advanced small pipe along the excavation direction in the roadway section according to the design requirements. Use a drill rig to drill the integrated drilling and grouting advanced small pipe into the surrounding rock to a certain depth along the excavation direction. Install one section for each excavation step, install it as the excavation progresses, and grout through the small pipe. The grout fills the gap between the small pipe and the hole wall. After the grout solidifies, the small pipe is tightly bonded to the surrounding rock, and the small pipe is fixed in the surrounding rock to form an advanced temporary support;

[0032] S20, excavating the roadway:

[0033] Carry out the excavation work of the roadway according to the design requirements and the situation of the advanced temporary support;

[0034] S30, laying the mesh layer:

[0035] After the roadway excavation is completed, a mesh layer is laid along the roadway surface and fixed on the inner wall of the roadway to form a uniform support layer.

[0036] S40, grouting and filling:

[0037] Grouting is carried out between the mesh layer and the surrounding rock, and the voids and cracks between the mesh layer and the surrounding rock are filled with grouting material, and the grouting material fully and evenly fills the entire support layer.

[0038] S50, installing bolt cables:

[0039] After the grouting material reaches the target strength, bolts and cable bolts are installed in the surrounding rock according to the design requirements, and appropriate pre-tightening force is applied.

[0040] In some embodiments, the excavated roadway includes:

[0041] Strengthening the advanced support: During excavation, if a severely soft and broken surrounding rock area is encountered, the layout spacing of the integrated drilling and grouting advanced small pipes is densified, or the driving depth is increased to more effectively reinforce the surrounding rock, control the deformation and loosening of the surrounding rock in advance, and reduce the risk of collapse.

[0042] In some embodiments, the laying of the mesh layer includes:

[0043] Timely closing the surrounding rock: If a severely soft and broken surrounding rock area is encountered, the speed of laying the mesh layer and grouting and filling is increased to reduce the exposure time of the surrounding rock.

[0044] In some embodiments, the installation of bolt cables includes:

[0045] Strengthening the subsequent support: In a severely soft and broken surrounding rock area, the layout spacing of bolts and cable bolts is appropriately reduced to increase the number of bolts and cable bolts, or the pre-tightening force is increased to enhance the stability and bearing capacity of the surrounding rock.

[0046] The beneficial effects of the present invention compared with the prior art are: The present invention proposes a surface and interior co-governance support system and construction method applicable to extremely soft coal roadways, which can effectively solve the problems encountered in the excavation and support process of extremely soft coal roadways. Specifically, at least one or more of the following beneficial effects can be achieved:

[0047] (1) Reinforce and strengthen the surrounding rock by using an integrated drilling and grouting advanced small duct. For traditional small ducts, the procedures are cumbersome, involving drilling first → withdrawing the drill rod → inserting the duct → grouting. It is prone to borehole collapse in soft and fractured surrounding rock, making it impossible to carry out the support construction smoothly. The present invention adopts an integrated drilling and grouting advanced small duct construction process to achieve integrated drilling and grouting, avoiding the risk of borehole collapse during drill withdrawal in the traditional method, improving the hole-forming rate. Moreover, this support method can detect and handle problems of soft and fractured surrounding rock early, perform advanced grouting on the heading face before excavation, improve the cohesion of extremely soft coal at the roadway heading face, enhance the stability of the roadway heading face, effectively control the deformation and collapse of the roadway, and improve the stability of the roadway.

[0048] (2) Lay a mesh layer, and then grout and fill behind the mesh layer. The grouting material can penetrate into the gap between the mesh and the surrounding rock, forming an integral arch between the support structure and the surrounding rock, enhancing the integrity of the support system. At the same time, grouting can also form a uniform anti-seepage layer to prevent water, mud, etc. from seeping into the roadway interior, keeping the roadway dry and clean. Thus, passive surface protection ("surface") is provided for the soft and fractured surrounding rock.

[0049] (3) The combined structure of the metal mesh and the woven mesh can also effectively limit the fragmentation and spalling of the rock mass. The woven mesh with a soft structure can avoid contact damage to the surface of the soft and fractured surrounding rock.

[0050] (4) After the filling layer behind the mesh solidifies to form an arch, install anchor bolts and cable bolts. The filling layer behind the mesh formed by grouting not only provides the condition for the anchor bolts to apply pre-tightening force in soft rock, prevents the anchor bolts from becoming unstable, and gives full play to the support performance of the anchor bolts, but also forms a strong surface protection support structure by forming a complete arched structure. The anchor bolt and cable bolt support structure provides active deep support ("inside") for the soft and fractured surrounding rock. Acting together with the passive surface protection ("surface") of the metal mesh and woven mesh, it forms a coordinated treatment of the surface and inside, effectively enhancing the overall stability of the roadway.

[0051] (5) The laying of the metal mesh and the woven mesh is relatively simple, and the structure after grouting is also easy to construct. The grouting material can quickly fill the gaps in the structure and solidify within a short time. This can accelerate the roadway support construction progress and improve the construction efficiency. It is suitable for roadway support applications under complex geological conditions.

[0052] It should be understood that the implementation of any embodiment of the present invention does not mean that multiple or all of the above beneficial effects need to be achieved simultaneously. Description of the Drawings

[0053] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary. For those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained by extending the provided drawings.

[0054] The structures, ratios, sizes, etc. shown in this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they do not have technical substance. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in the present invention.

[0055] Figure 1 Overall schematic diagram of the internal and external co-governance support system for the embodiments of the present invention;

[0056] Figure 2 Schematic diagram of the layout of the integrated drilling and grouting advanced small ducts for the embodiments of the present invention;

[0057] Figure 3 Schematic diagram of the integrated drilling and grouting advanced small ducts and combined net structure for the embodiments of the present invention;

[0058] Figure 4 Schematic diagram of the integrated drilling and grouting advanced small duct structure for the embodiments of the present invention, where (a) is the tail section, (b) is the standard section, and (c) is the front section;

[0059] Figure 5 For the embodiments of the present invention Figure 1 Detail structure schematic diagram of area A;

[0060] Figure 6 Schematic diagram of the combined net and the filling layer behind the net for the embodiments of the present invention;

[0061] Figure 7 Schematic diagram of the construction method flow of the internal and external co-governance support system for the embodiments of the present invention.

[0062] Markings in the figure:

[0063] Internal and external co-governance support system 100;

[0064] Integrated drilling and grouting advanced small duct 1, internal thread connection section 11, conical drill bit 12, grouting port 13, external thread reduced diameter connection section 14, net surface layer 2, first soft and dense net layer 21, second hard and sparse net layer 22, filling layer 3 behind the net, anchor cable support structure 4, anchor cable 41, anchor bolt 42;

[0065] Construction method 200.

[0066] The same or corresponding reference numerals in the drawings denote the same or corresponding parts. Specific embodiments

[0067] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer and more understandable, the embodiments of the present invention will be further described in detail below with reference to the embodiments and the drawings. Herein, the illustrative embodiments of the present invention and the descriptions thereof are used to explain the present invention, but are not intended to limit the present invention.

[0068] In the present invention, unless otherwise clearly specified and limited, terms such as "installation", "connection", "coupling", "fixing" and the like shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral body; it may be a mechanical connection or an electrical connection; it may be a direct connection or an indirect connection through an intermediate medium, and may be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0069] It should be understood that the terms "including / comprising", "consisting of" or any other variants are intended to cover non-exclusive inclusion, so that a product, device, process or method including a series of elements not only includes those elements, but also includes other elements that are not clearly listed when needed, or further includes elements inherent to such product, device, process or method. Without further limitation, the elements defined by the statements "including / comprising...", "consisting of..." do not exclude the existence of additional identical elements in the product, device, process or method including the said elements.

[0070] It should also be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer" and the like indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated device, component or structure must have a specific orientation, be constructed or operated in a specific orientation, and cannot be construed as a limitation to the present invention.

[0071] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined by "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0072] The extremely soft coal roadway has the following characteristics:

[0073] (1) Extremely low strength: The coal body is as soft as wet sawdust, and its uniaxial compressive strength is much lower than that of ordinary rock (<2MPa is a typical value), and it can be easily destroyed by machinery or manpower;

[0074] (2) Instantaneous instability: Excavation disturbance breaks the original stress balance, and the exposed coal wall and roof will begin to spall, peel off, and collapse in a very short time (excavation means exposure), and the self-stabilization time is almost negligible;

[0075] (3) No self-supporting arch: It is impossible to form a bearing pressure arch like harder rock formations, and the coal body near the excavation face is in a completely loose and broken state.

[0076] It is precisely because of the fatal weakness of extremely soft coal tunnels that "instability will occur as soon as excavation is started and collapse will occur without support" that the fragile coal body in front of the working face and outside the contour line must be actively reinforced and pre-supported before the excavation disturbance occurs. Without advance support to actively reinforce the broken coal body in front, the excavation operation will fall into the dilemma of "the more you dig, the more you collapse", facing frequent and uncontrollable roof falls and slabs, which will seriously endanger personnel safety, hinder construction progress, and greatly increase costs.

[0077] For this reason, the present invention designs an internal and external co-control support system and a construction method suitable for extremely soft coal tunnels to solve the excavation problem of extremely soft coal tunnels.

[0078] The implementation of the present invention is described in detail below in conjunction with preferred embodiments.

[0079] See also Figure 1 , 2 3 shows a schematic diagram of the specific layout of an internal and external co-control support system suitable for extremely soft coal roadways. The internal and external co-control support system 100 includes an integrated drilling and injection leading small guide tube 1, a mesh surface layer 2, a backfill layer 3, and an anchor cable support structure 4.

[0080] Specifically, before excavation, the integrated drilling and injection small advance conduit 1 is laid out in the tunnel section and driven into the surrounding rock to a certain depth along the excavation direction. The integrated drilling and injection small advance conduit 1 is installed for each excavation step and installed as the excavation progresses. The layout spacing and driving depth of the integrated drilling and injection small advance conduit 1 in the tunnel section are determined according to the design requirements. After the installation of the integrated drilling and injection small advance conduit 1, grouting is performed to form an advance temporary support for tunnel excavation. By pre-burying small conduits in advance to reinforce and strengthen the surrounding rock, the problem of weak and broken surrounding rock can be discovered and dealt with early, the deformation and collapse of the tunnel can be effectively controlled, and the stability of the tunnel can be improved.

[0081] like Figure 4 As shown, the integrated drilling and injection leading small catheter 1 may include a front section, a tail section and a standard section; see Figure 4In (c), the tail end of the front section is provided with an internal thread connection section 11, the front end is provided with a conical drill bit 12, and grouting holes are evenly arranged on the pipe wall; see Figure 4 In (a), the tail end of the tail section is provided with an internal thread connection section 11, a grouting port 13 is arranged near the internal thread connection section 11, the grouting port 13 may be provided with a rubber grout stopper, the front end is provided with an external thread reduced diameter connection section 14, and grouting holes are evenly arranged on the pipe wall; see Figure 4 In (b), the tail end of the standard section is provided with an internal thread connection section 11, the front end is provided with an external thread reduced diameter connection section 14, and grouting holes are evenly arranged on the pipe wall.

[0082] It should be noted that in actual use, according to the specific drilling and grouting depth, when it is relatively shallow, the tail section + front section can be used alone. The internal thread connection section 11 at the tail end of the tail section is threadedly connected to the drill pipe of the drill rig, and the external thread reduced diameter connection section 14 at the front end of the tail section is connected to the internal thread connection section 11 at the tail end of the front section, and the drill rig drives the conical drill bit 12 at the front end of the front section to drill. When a deeper one-time advanced support depth is required, standard sections can be continuously connected between the tail section and the front section. The present invention designs an integrated drilling and grouting advanced small pipe, which does not require drilling and retracting the drill rod, avoids the risk of hole collapse during retraction in the traditional method, improves the hole formation rate, and effectively controls the deformation and collapse of the roadway.

[0083] The following requirements should be noted when selecting the integrated drilling and grouting advanced small pipe:

[0084] (1) Pipe body material: High-strength seamless steel pipes (such as Q235 or Q345 steel) are selected. The steel pipe has high strength and stiffness, can maintain the structural integrity during the process of inserting into the surrounding rock, is not easy to bend or break, and ensures stable advanced support force in soft and broken surrounding rock.

[0085] Pretreatment: The inner and outer surfaces of the steel pipe are derusted, polished, and sprayed with an anti-rust coating (such as epoxy resin) to improve corrosion resistance.

[0086] (2) Grouting hole design: Grouting holes are evenly arranged on the pipe wall, and the hole diameter is usually 6 - 10 mm. These holes can make the injected grout diffuse into the cracks and cavities of the surrounding rock, fill and reinforce the surrounding rock, and enhance its stability. In severely broken areas, the spacing of the grouting holes is reduced, such as from the conventional 15 - 20 cm to 10 - 15 cm, to ensure that the grout can fully penetrate into the broken surrounding rock.

[0087] (3) Front end shape: The front end is designed as a sharp cone, which is convenient for smoothly inserting into the surrounding rock after drilling, reduces the insertion resistance, enables the small pipe to better contact with the surrounding rock tightly, and improves the support effect.

[0088] (4) Rear end structure: An interface for connecting with the grouting equipment is provided at the rear end, which can be a standard thread interface or a quick connector, ensuring stable connection during grouting, preventing grout leakage, and ensuring the smooth progress of the grouting operation.

[0089] (5)Improvement of the tail grouting plug: Select a high-pressure and wear-resistant ethylene propylene diene monomer (EPDM) grouting plug to adapt to complex geological conditions.

[0090] (6)Modularization of the front drill bit interface: Machine short threads on the shank of the drill bit, and at the same time, design a locking nut at the front end of the conduit. The drill bit can be quickly locked by rotating the nut, reducing the number of screwing times. It supports the quick replacement of different drill bits (such as alloy drill bits and diamond drill bits).

[0091] (7)Surface marking and function zoning: Laser engrave a scale ruler (one grid per 10 cm) on the surface of the conduit to facilitate precise control of the drilling depth during construction.

[0092] After the installation of the integrated drilling and grouting advanced small conduit 1 is completed, the roadway section excavation can be carried out to form the roadway contour. The mesh layer 2 is laid along the inner wall of the roadway and fixed on the surface of the surrounding rock after the roadway excavation is completed, and there is a small gap between the mesh layer 2 and the surrounding rock. The mesh layer 2 should be correctly laid and fixed on the roadway wall to form a uniform support layer, which can effectively limit the fragmentation and caving of the rock mass, which is particularly important for the support of soft and broken surrounding rock.

[0093] By reserving a small gap between the mesh layer 2 and the surrounding rock, the purposes are as follows:

[0094] (1)Facilitate grouting operation and slurry diffusion: The reserved gap provides space for grouting, enabling the grouting material to smoothly fill the voids and cracks between the mesh layer and the surrounding rock. If the two are in close contact without a gap, it is difficult for the slurry to flow and diffuse during grouting, and it is impossible to effectively fill the fine cracks in the surrounding rock, making it difficult to form a uniform anti-seepage layer, and it is also not conducive to forming an integral arch between the support structure and the surrounding rock, thereby affecting the integrity and stability of the support system.

[0095] (2)Adapt to the deformation of the surrounding rock: The soft and broken surrounding rock will produce certain deformation after the roadway excavation. The small gap can buffer the deformation of the surrounding rock to a certain extent, avoiding the damage of the mesh layer caused by the extrusion of the surrounding rock deformation or the loss of the support effect. There is a gap between the mesh layer and the surrounding rock. When the surrounding rock undergoes slight deformation, the mesh layer can have a certain movement space and will not be damaged due to the concentration of deformation stress, ensuring its continuous role in restricting the fragmentation and caving of the rock mass.

[0096] (3)Improve construction convenience: During the construction process, the reserved gap facilitates the laying and fixing of the mesh layer. If it is required that the mesh layer is completely attached to the surrounding rock, the construction difficulty will increase significantly in the case of uneven inner wall of the roadway, consuming more time and labor costs. With the gap set, the construction personnel can more conveniently lay the mesh layer on the inner wall of the roadway and carry out the fixing operation, improving the construction efficiency.

[0097] After the mesh surface layer 2 is laid, grouting is performed between the mesh surface layer 2 and the surrounding rock. The grouting material can be injected concrete. After the concrete is finally set, a backfilling layer 3 is formed. Figure 3 , 5 6, and the grouting material fills the gaps and cracks between the mesh layer 2 and the surrounding rock, forming an integral arch between the support layer and the surrounding rock, and improving the integrity of the support system. The grouting should evenly and fully fill the entire support layer to ensure a tight connection between the support layer and the surrounding rock. With the solidification of the grouting material, a uniform impermeable layer can also be formed to prevent water, mud, etc. from penetrating into the interior of the tunnel, keeping the tunnel dry and clean.

[0098] The mesh surface layer 2 combined with the backfill layer 3 forms a passive surface protection for the tunnel surrounding rock, which is the "surface" in the surface-inside co-control system. The mesh surface layer 2 and the backfill layer 3 play their due roles individually and in combination, specifically:

[0099] The mesh surface layer 2 provides a basic function: after the tunnel excavation is completed, the mesh surface layer 2 is laid along the inner wall of the tunnel and fixed to the surface of the surrounding rock. Its double-layer structure (the first soft dense mesh layer 21 and the second hard sparse mesh layer 22) can effectively limit the breakage and falling of the rock mass. The first soft dense mesh layer 21 is soft in texture and dense in mesh. It is in direct contact with the surrounding rock, which can avoid contact damage to the surface of the weak and broken surrounding rock and initially restrict the breakage of the surrounding rock; the second hard sparse mesh layer 22 is hard in texture and sparse in mesh. It is laid on the outside of the first soft dense mesh layer 21, which can protect and carry the first soft dense mesh layer 21 and the rock fragments that may fall from it, preventing them from falling off from the inner wall of the tunnel, and providing basic support for passive surface protection.

[0100] The backfill layer 3 provides a strengthening effect: after the mesh surface layer 2 is laid, grouting is performed between it and the surrounding rock to form the backfill layer 3. The grouting material fills the gaps and cracks between the mesh surface layer 2 and the surrounding rock, forming an integral arch between the support layer and the surrounding rock, greatly improving the integrity of the support system. At the same time, the uniform impermeable layer formed by grouting can prevent water, mud, etc. from penetrating into the tunnel, keeping the tunnel dry and clean, and further enhancing the protection effect on the weak and broken surrounding rock.

[0101] The mesh surface layer 2 and the backfill layer 3 work together to form a "surface": the mesh surface layer 2 and the backfill layer 3 cooperate with each other, the mesh surface layer 2 provides preliminary protection and limits the function of rock mass crushing, and the backfill layer 3 is strengthened in terms of integrity and impermeability. The two together form a passive surface protection for the tunnel surrounding rock, that is, the "surface" in the surface-inside co-governance system. It can not only effectively limit the crushing and falling of the surface rock of the weak and broken surrounding rock, but also form an integral arch with the surrounding rock, and form a uniform impermeability layer.

[0102] Create conditions for subsequent support: After the filling layer 3 behind the mesh solidifies, it provides a stable foundation for the installation of the bolt and cable support structure. In soft rock, it is difficult to directly and effectively anchor bolts and cables. The existence of the filling layer 3 behind the mesh increases the stability of the anchoring area, prevents the instability of the cable bolts, enables them to apply pre-tightening force better, gives full play to the support performance, and enhances the stability of the entire support system.

[0103] Buffer the deformation stress of the surrounding rock: The soft and broken surrounding rock has large deformation. The mesh layer 2 and the filling layer 3 behind the mesh have certain flexibility and elasticity. When the surrounding rock deforms, they can absorb and disperse part of the stress, avoiding roadway damage caused by stress concentration. For example, when the surrounding rock slightly expands or displaces, the mesh layer 2 can deform with it, and the filling layer 3 behind the mesh can also adjust the stress state to protect the roadway structure.

[0104] Facilitate construction inspection and maintenance: The construction process of the mesh layer 2 and the filling layer 3 behind the mesh is relatively intuitive. Construction workers can observe the laying situation of the mesh layer 2 and the grouting effect in a timely manner to discover problems and make adjustments. During later maintenance, if abnormalities occur locally in the roadway, the condition of the surrounding rock can be initially judged through the mesh layer 2 and the filling layer 3 behind the mesh, and the maintenance plan can be determined to improve the construction and maintenance efficiency.

[0105] After the construction of the filling layer 3 behind the mesh is completed and the grouting material reaches the target strength after final setting, the bolt and cable support structure 4 is constructed into the surrounding rock. The bolt and cable support structure 4 is composed of relatively long cables 41 and relatively short bolts 42 used in combination. The driving lengths, spacings, etc. of the cables 41 and bolts 42 are determined according to the design requirements, and appropriate pre-tightening force is applied to increase the stability and bearing capacity of the surrounding rock.

[0106] The bolt and cable support structure 4 forms an active deep support for the roadway surrounding rock, that is, the "inside" in the system of treating both the surface and the inside. Under the combined action of the surface and the inside, the treatment of both the surface and the inside is formed, effectively improving the overall stability of the roadway. And the previously formed filling layer 3 behind the mesh provides conditions for the cables and bolts to apply pre-tightening force in soft rock, prevents the instability of the cables and bolts, gives full play to the support performance of the cables and bolts, and the cables and bolts can in turn form a strong pulling and pre-tightening effect on the arched support structure, making the surface protection support structure more stable, the integrity of the entire support system better, and the overall performance stronger, truly realizing the "treatment of both the surface and the inside".

[0107] Continue to refer to Figure 6 This embodiment of the present invention provides a specific mesh layer structure. The mesh layer 2 is a double-layer mesh structure, including a first soft and dense mesh layer 21 and a second hard and sparse mesh layer 22. It is easy to understand that, relatively speaking, the texture of the first soft and dense mesh layer 21 is softer and the mesh is denser. The soft mesh body is not easy to damage the soft and broken surrounding rock mass. The first soft and dense mesh layer 21 is used to directly contact the surrounding rock and restrict the fragmentation and falling blocks of the soft and broken surrounding rock mass.

[0108] The second hard sparse mesh layer 22 is harder in texture and relatively sparse in mesh. The second hard sparse mesh layer 22 is laid on the outside of the first soft dense mesh layer 21 and has higher strength, which is used to protect and support the first soft dense mesh layer 21, ensuring that the first soft dense mesh layer 21 and the possible falling rock fragments it undertakes will not fall off from the inner wall of the roadway, and ensuring that the entire support structure can effectively play its role.

[0109] Specifically, the first soft dense mesh layer 21 is made of a woven mesh or a woven bag. Ordinary woven bags are mostly made of polypropylene (PP) or polyethylene (PE) materials and are used for packaging daily necessities or agricultural products, etc., with relatively low strength and durability. For the woven bags applied to the support of extremely soft coal roadways, in order to effectively limit rock fragmentation and block falling, high-strength and wear-resistant fiber materials need to be used for production, such as high-strength synthetic fibers, such as aramid fibers, or polypropylene fibers treated specially. The woven bags made of these materials have higher tensile strength and tear resistance while ensuring a soft texture, and can withstand the pressure and friction of the rock mass. The second hard sparse mesh layer 22 is a metal mesh, such as a wire mesh.

[0110] When installing and laying the mesh surface layer 2, one way is the integral installation, that is, the first soft dense mesh layer 21 and the second hard sparse mesh layer 22 are pre-combined to form a combined body. After the roadway excavation is completed, the combined body is integrally laid along the inner wall of the roadway and fixed on the surface of the surrounding rock, and the first soft dense mesh layer 21 is located on the inner side and the second hard sparse mesh layer 22 is located on the outer side. For the roadway roof, the inner side means the upper part and the outer side means the lower part. Then, concrete is poured onto the first soft dense mesh layer 21 to form the post-mesh filling layer 3, as Figure 6 shown.

[0111] Another installation method is the distributed installation. First, after the roadway excavation is completed, the first soft dense mesh layer 21 is laid along the inner wall of the roadway and fixed on the surface of the surrounding rock, and then the second hard sparse mesh layer 22 is continuously laid and fixed on the outside of the first soft dense mesh layer 21.

[0112] When fixing the mesh surface layer 2, traditional fixing methods include bolt fixing, welding fixing, etc. However, in soft and broken surrounding rocks, these methods have certain limitations. For bolt fixing, due to the broken surrounding rock, the anchoring force of the bolt may be insufficient. For welding fixing, if the surface of the surrounding rock is uneven, the welding is difficult and the welding quality is difficult to guarantee. The tail of the small duct can be modified to leave a position for the clamping groove, and then the metal mesh is connected to the tail of the small duct through a clamp to realize the fixing of the metal mesh. In this way, rapid installation can be achieved: the single-point connection takes ≤ 30 seconds, and the efficiency is increased by more than 50% compared with traditional welding / binding; it does not require special tools: it has a pure mechanical structure and does not require the assistance of electric or hydraulic equipment; it can be repeatedly adjusted: if the position of the mesh needs to be corrected, the buckle can be unlocked by rotating counterclockwise, and after repositioning, it can be locked again.

[0113] The present invention further provides a construction method for such a support system for treating both the exterior and interior, as shown in Figure 7 the following flow block diagram. The construction method 200 is as follows:

[0114] S10. Install the integrated drilling and grouting advanced small ducts: Before the roadway excavation, construct the integrated drilling and grouting advanced small ducts 1 along the excavation direction in the roadway section according to the design requirements, and fix the small ducts in the surrounding rock to form an advanced temporary support, as shown in Figure 2 ;

[0115] Specifically, the integrated drilling and grouting advanced small ducts 1 are densely arranged in the roadway section, drilled into the surrounding rock to a certain depth along the excavation direction, and one section is installed for each excavation step, and installed as the excavation progresses. Their layout spacing and drilling depth are determined according to the design requirements, and reasonable layout can ensure the effective reinforcement range of the surrounding rock. For example, in areas where the surrounding rock is severely broken, the spacing of the small ducts needs to be reduced and the drilling depth increased. The spacing is reduced from the conventional 1.0 - 1.5 meters to 0.5 - 0.8 meters, and the drilling depth is increased from 3 - 5 meters to 5 - 8 meters, so as to enhance the pre - support effect on the surrounding rock and better control the deformation and collapse of the roadway. The installation of the small ducts requires precise operation to ensure their stable position in the surrounding rock, laying a foundation for subsequent grouting and support.

[0116] After installation, post - grouting is carried out to form an advanced temporary support. The grouting material fills the gaps and cavities in the surrounding rock, making the small ducts and the surrounding rock closely integrated into a whole, improving the stability of the surrounding rock. The grouting should be uniform and sufficient to ensure that the slurry diffuses to the effective range. If the grouting is not sufficient, local weak reinforcement areas will appear, affecting the support effect. The performance of the grouting material is also crucial. High - adhesion and early - strength slurries need to be selected, which can quickly improve the strength of the surrounding rock and provide reliable support for the roadway excavation.

[0117] Connection with the subsequent support: The advanced temporary support is the starting part of the whole support system and needs to be effectively connected with the subsequent mesh layer, cable bolt and bolt support structures. The support body formed by grouting the integrated drilling and grouting advanced small ducts should create stable conditions for the laying of the mesh layer. The construction of the mesh layer should not damage the advanced temporary support structure. The advanced temporary support also needs to provide a suitable foundation for the installation of the cable bolts and bolts to ensure that the subsequent support can play its role smoothly and jointly improve the overall stability of the roadway.

[0118] S20. Excavate the roadway: According to the design requirements and the situation of the advanced temporary support, carry out the excavation work of the roadway, as shown in Figure 3 ; During the excavation process, attention should be paid to promptly dealing with the problems of soft and broken surrounding rock encountered to avoid the collapse and deformation of the roadway;

[0119] S30. Lay the mesh layer: After the roadway excavation is completed, lay the mesh layer 2 along the roadway surface and fix it on the inner wall of the roadway. The metal mesh and the woven mesh should be correctly laid and fixed on the roadway wall to form a uniform support layer, as shown in Figure 3 、5 as shown;

[0120] Timely enclosing of surrounding rock: After the roadway excavation is completed, a mesh layer should be laid along the inner wall of the roadway as soon as possible and fixed on the surface of the surrounding rock. Although there is a small gap between the mesh layer and the surrounding rock, it can restrict the fragmentation and caving of the rock mass.

[0121] S40, Grouting and filling: Grout between the mesh layer 2 and the surrounding rock, and use the grouting material to fill the voids and cracks between the mesh layer 2 and the surrounding rock. The grouting material fills the entire support layer fully and evenly to ensure the tight connection between the support structure and the surrounding rock, forming a post-mesh filling layer 3, as Figure 3 、 5 shown;

[0122] The grouting material fills the voids and cracks, not only forming an integral arch between the support layer and the surrounding rock to enhance the integrity of the support system, but also forming an anti-seepage layer to prevent the infiltration of water, slurry, etc. When encountering soft and broken surrounding rock, the speed of laying the mesh layer and grouting and filling should be accelerated to reduce the exposure time of the surrounding rock. In some areas of soft and broken surrounding rock that are prone to weathering and soften when exposed to water, shotcrete can be used to temporarily seal the exposed surrounding rock to gain time for subsequent support.

[0123] S50, Installing bolts and cables: After the grouted concrete has reached the final setting and the target strength, install cables 41 and bolts 42 in the surrounding rock according to the design requirements, and apply an appropriate pre-tightening force to increase the stability and bearing capacity of the surrounding rock, as Figure 1 shown.

[0124] Strengthening subsequent support: When the grouting material reaches the target strength, install the cable and bolt support structure according to the design requirements and apply a pre-tightening force. In areas of soft and broken surrounding rock, the number of cables and bolts can be appropriately increased, or their pre-tightening force can be increased. For example, if the original design cable spacing is 3 meters, it can be reduced to 2 meters in this area; if the original bolt pre-tightening force is 100 kN, it can be increased to 120 kN to increase the stability and bearing capacity of the surrounding rock and further ensure the stability of the roadway.

[0125] S60, Subsequent roadway support: According to the specific situation of the roadway and the project requirements, further support work can be carried out as needed. This includes the reinforcement and adjustment of the support structure, further filling of the grouting material, etc.

[0126] In summary, a surface and interior co-governance support system and construction method for extremely soft coal roadways provided by the present invention, aiming at the excavation and support problems of extremely soft coal roadways, provides passive surface protection ("surface") for soft and broken surrounding rock with the help of the mesh layer and the post-mesh filling layer, and provides active deep support ("interior") for soft and broken surrounding rock with the help of the bolt and cable support structure. Under the combined action of the surface and interior, surface and interior co-governance is formed, a strong support structure is formed, and the overall stability of the roadway is effectively improved.

[0127] The embodiments of the present invention have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

[0128] Although several specific implementation details are included in the above discussion, these should not be construed as limiting the scope of the present invention. Certain features described in the context of separate embodiments can also be implemented in combination in a single implementation. Conversely, the various features described in the context of a single implementation can also be implemented separately or in any suitable sub-combination in multiple implementations.

Claims

1. A support system for co-governance of the surface and interior applicable to extremely soft coal roadways, characterized in that, Including: An integrated drilling and grouting advanced small duct, which is densely arranged in the roadway section and drilled into the surrounding rock to a certain depth along the excavation direction, and grouted to form an advanced temporary support for roadway excavation; A mesh layer, which is laid along the inner wall of the roadway and fixed on the surface of the surrounding rock after the roadway excavation is completed, and there is a small gap between the mesh layer and the surrounding rock; A post-mesh filling layer, which is formed by grouting between the mesh layer and the surrounding rock, and the grouting material fills the gaps and cracks between the mesh layer and the surrounding rock to form a passive surface protection for the roadway surrounding rock, that is, the "surface" of the internal and external co-governance system; An anchor cable support structure, which is installed in the surrounding rock and applied with appropriate pre-tightening force according to the design requirements after the grouting material reaches the target strength, to form an active deep support for the roadway surrounding rock, that is, the "inside" of the internal and external co-governance system.

2. The internal and external co-governance support system according to claim 1, wherein The integrated drilling and grouting advanced small duct includes: The front section, the tail end of the front section is provided with an internal thread connection section, the front end is provided with a conical drill bit, and grouting holes are evenly arranged on the pipe wall; The tail section, the tail end of the tail section is provided with an internal thread connection section, a grouting port is arranged near the internal thread connection section, the front end is provided with an external thread reduced-diameter connection section, and grouting holes are evenly arranged on the pipe wall; The standard section, the tail end of the standard section is provided with an internal thread connection section, the front end is provided with an external thread reduced-diameter connection section, and grouting holes are evenly arranged on the pipe wall.

3. The internal and external combined support system according to claim 2, characterized in that The pipe body of the integrated drilling and grouting advanced small duct is made of high-strength seamless steel pipe, the aperture of the grouting holes on the pipe wall is 6-10mm, the hole spacing is 15-20cm, and in the severely fractured area, the hole spacing is reduced to 10-15cm.

4. The inside-outside co-governance support system according to claim 2, wherein The surface of the pipe body of the integrated drilling and grouting advanced small duct is laser-printed with a scale ruler to accurately control the drilling depth during construction.

5. The internal and external collaborative support system according to claim 1, wherein The mesh layer includes: The first soft and dense mesh layer; The second hard and sparse mesh layer; and The first soft and dense mesh layer and the second hard and sparse mesh layer are pre-combined to form an integral body, which is laid along the inner wall of the roadway and fixed on the surface of the surrounding rock after the roadway excavation is completed, and the first soft and dense mesh layer is located on the inner side and the second hard and sparse mesh layer is located on the outer side.

6. The internal and external combined support system according to claim 1, wherein, The mesh layer includes: The first soft and dense mesh layer, which is laid along the inner wall of the roadway and fixed on the surface of the surrounding rock after the roadway excavation is completed; The second hard and sparse mesh layer, which is laid and fixed on the outer side of the first soft and dense mesh layer.

7. The inside-outside collaborative support system according to claim 5 or 6, characterized in that The first soft and dense mesh layer is a woven mesh or a woven bag, and the second hard and sparse mesh layer is a metal mesh.

8. The internal and external combined support system according to claim 1, characterized in that, The anchor cable support structure is composed of relatively short anchor bolts and relatively long anchor cables used in combination, and appropriate pre-tightening force is applied to the anchor bolts and anchor cables.

9. A construction method of the internal and external co-governance support system according to any one of claims 1 to 8, characterized in that, Including the following steps: S10, constructing the integrated drilling and grouting advanced small duct and grouting: Before roadway excavation, construct the integrated drilling and grouting advanced small duct along the excavation direction in the roadway section according to the design requirements, drill the integrated drilling and grouting advanced small duct into the surrounding rock to a certain depth along the excavation direction through a drill rig, install one section for each excavation step, install it as excavation progresses, and grout through the small duct. The slurry fills the gap between the small duct and the hole wall. After the slurry solidifies, the small duct is tightly bonded to the surrounding rock, and the small duct is fixed in the surrounding rock to form an advanced temporary support; S20, excavating the roadway: According to the design requirements and the situation of the advanced temporary support, the roadway excavation work is carried out; S30, laying the mesh layer: After the roadway excavation is completed, the mesh layer is laid along the roadway surface and fixed on the inner wall of the roadway to form a uniform support layer; S40, grouting and filling: Grouting is carried out between the mesh layer and the surrounding rock, and the voids and cracks between the mesh layer and the surrounding rock are filled with grouting material. The grouting material fully and evenly fills the entire support layer; S50, installing anchor bolts and cables: After the grouting material reaches the target strength, according to the design requirements, anchor bolts and cables are installed in the surrounding rock and appropriate pre-tightening force is applied.

10. The construction method according to claim 9, characterized in that, It also includes one or more of the following steps: Strengthening the advanced support: During excavation, if a severely weak and fractured surrounding rock area is encountered, the layout spacing of the integrated drilling and grouting advanced small pipes is encrypted, or the driving depth is increased to more effectively reinforce the surrounding rock, control the deformation and loosening of the surrounding rock in advance, and reduce the risk of collapse; Promptly closing the surrounding rock: If a severely weak and fractured surrounding rock area is encountered, the speed of laying the mesh layer and grouting and filling is increased to reduce the exposure time of the surrounding rock; Strengthening the subsequent support: In a severely weak and fractured surrounding rock area, the layout spacing of the anchor bolts and cables is appropriately reduced to increase the number of anchor bolts and cables, or the pre-tightening force is increased to enhance the stability and bearing capacity of the surrounding rock.

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