Method for supporting three-soft coal seam large-deformation roadway under complex geological conditions

Abstract

The invention relates to the technical field of roadway surrounding rock control under complex geological conditions of a coal mine, in particular to a method for supporting a large-deformation roadway of a three-soft coal seam under complex geological conditions, which combines three procedures of surrounding rock grouting modification, anchor net cable supporting and thin spraying reinforcement to form a cooperative surrounding rock control system. According to the method, firstly, a grouting material is pumped into roadway surrounding rock to form a deep reinforcing structure, after grouting slurry permeates into surrounding rock cracks to be solidified, a network framework structure is formed, the strength of the surrounding rock is improved, and damage expansion is limited. Then, anchor net cable supporting is conducted on the two sides and the top plate of the roadway through a supporting structure, grouting anchor cables and anchor net cables are combined for supporting, and the stability of the roadway is improved. And finally, a spraying material is thinly sprayed on the surface of the roadway coal rock mass to form a reinforced surface layer, and surrounding rock and supporting components are protected from being affected by weathering and hydration. The roadway surrounding rock control effect can be improved, the roadway maintenance work amount is reduced, the roadway maintenance cost is reduced, and the construction efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of surrounding rock control of coal mine tunnels with complex geological conditions, and in particular to a method for supporting large deformation tunnels in three-soft coal seams with complex geological conditions. Background Art

[0002] "Three soft coal seams" refers to coal mines where the coal seams and roof and floor plates are both weak rock formations. This type of surrounding rock generally has low strength, developed cracks, poor occurrence conditions, and significant rheological properties. The tunnels excavated and maintained in the "three soft coal seams" have a long continuous deformation time, fast deformation speed, and large deformation amount. Although they can be short-term stable under the support, the rheological properties of the soft rock cause it to gradually produce huge deformation over time. For a long time, the support problem of the "three soft coal seam" tunnel has been a difficult problem that has plagued production. Due to the great differences in the types and lithology of soft rocks, the ground stress and tectonic stress of the tunnels are also very different. For the "three soft coal seam" tunnels, as the mechanical properties of the surrounding rock change and the depth of the tunnel increases, the support parameters must also change accordingly. However, there is currently a lack of systematic and quantitative research.

[0003] Traditional tunnel surrounding rock support has formed a combined support system of U-shaped sheds, anchor nets, anchor cables, anchor rods and pipe sheds. According to the different surrounding rock properties and the position relationship between the adjacent layers and the goaf (dynamic pressure disturbance zone), strengthening and encrypting the surrounding rock support can effectively control the stability of the surrounding rock, but it also increases the difficulty of construction and affects the excavation efficiency.

[0004] The support of the tunnels in the "three soft" coal seams has always been a difficult point. The support technology in shallow mines cannot solve the problem of surrounding rock control in deep soft rock tunnels. Under the superposition of high ground stress and strong mining, the deep fractures in the soft rock tunnels with large mining depths and large sections undergo continuous rheology, the surrounding rock moves as a whole, the tunnels are severely deformed, the coal and rock soften, the fractures close, and the surrounding rock has poor permeability. After the tunnels are greatly deformed, the inside of the tunnels often have problems such as broken anchor rods and cables, damaged and ineffective support components, and large-scale bulging on the tunnel surface. Therefore, studying the technical issues such as the stability and support countermeasures of the "three soft coal seams" tunnels in coal mine production is a major and urgent problem in the research of soft rock tunnel support. Summary of the invention

[0005] The invention provides a method for supporting a large deformation tunnel under complex geological conditions to solve the problem of surrounding rock control in deep soft rock tunnels.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention proposes a method for supporting a large deformation roadway in a three-soft coal seam under complex geological conditions, comprising the following steps: Step 1: During mining, grouting material is pumped into the tunnel surrounding rock to form a deep reinforcement structure of the tunnel surrounding rock; Step 2: Use a supporting structure to implement anchor wire support on the sides and top of the tunnel; Step 3, spraying the material thinly on the surface of the coal rock mass in the roadway to form a reinforced surface layer.

[0007] Preferably, in step 1, the construction sequence of pumping grouting material into the surrounding rock of the tunnel is: S1, drilling grouting holes arranged at intervals on the coal rock wall of the tunnel surrounding rock; S2, mixing two-component reinforcement material raw materials in a slurry bucket to form grouting slurry, and connecting the slurry bucket and the grouting pump with a grouting pipe; S3, grouting each grouting hole in turn, inserting the grouting pipe head into the grouting hole to the bottom of the hole, starting the grouting pump to grout, and ending the grouting after the grouting pressure gradually rises to a stable level, and shutting down the grouting pump.

[0008] Further preferably, the depth L of the grouting hole is greater than or equal to max{ P 理论 , P 模拟 , P 钻孔窥视},in P 理论 The maximum damage depth determined by theoretical formula calculation is: P 模拟 The maximum damage depth determined by numerical simulation, P 钻孔窥视 In order to determine the maximum failure depth by drilling observation, the depth L of the grouting hole is greater than the failure depth of the plastic zone of the tunnel surrounding rock.

[0009] Further preferably, the diameter of the grouting hole is 30~42mm.

[0010] Further preferably, the hole spacing of the grouting holes is a ≤ 2 r ,in r is the grouting diffusion radius.

[0011] Further preferably, the low-pressure grouting is adopted in S3, and the grouting pressure is 0.3 MPa~2.0 MPa.

[0012] Further preferably, the grouting pressure in S3 gradually rises and stabilizes at 20 MPa and is maintained for 9 to 11 minutes, or the grouting pressure rises and stabilizes at above 25 MPa, and the grouting is completed.

[0013] Further preferably, in step 3, at least two layers of thin spraying material are applied on the surface of the coal rock mass in the roadway, and the time interval between applying different layers of thin spraying material is no more than 2 hours.

[0014] Preferably, the thickness of the reinforced surface layer in step 3 is not less than 20 mm.

[0015] Preferably, the grouting material is a two-component inorganic material plus mineral powder, and the thin spraying material is a two-component composite spraying material.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention proposes a surrounding rock grouting modification-support-thin shotcrete coordinated surrounding rock control system for providing support for large deformation tunnels in three soft coal seams under complex geological conditions. First, grouting is performed in the broken area of ​​the tunnel to improve the bearing capacity of the tunnel, then anchor mesh cable support is performed, and finally thin shotcrete is performed. The three processes form a coordinated surrounding rock control system. When grouting is performed in the broken area of ​​the tunnel, the grouting slurry penetrates into the cracks of the surrounding rock and solidifies to form a network skeleton structure. When the stress of the coal body exceeds the strength of the coal body and a large deformation occurs, the network of the consolidation material plays a skeleton role with its good toughness and bonding strength, improves the residual strength of the surrounding rock, and limits the expansion of surrounding rock damage. The solidification of the slurry greatly weakens the stress concentration at the end of the surrounding rock crack. In addition, the crack is filled with solidified materials, and the coal rock mass near the crack changes from biaxial stress to triaxial stress, the strength of the coal rock mass is greatly enhanced, and the brittleness is weakened and the plasticity is enhanced. From the perspective of the stress state, grouting solidification also plays a role in transforming the rock mass failure mechanism and improving the strength of the surrounding rock. In addition, grouting reinforcement can effectively fill the micropores or microcracks on the surface of the cracks, and can fill, cement and bond the upper and lower crack surfaces, so that the broken coal and rock become an integral structure, thereby significantly improving its compressive, tensile and shear strengths, cohesive force and internal friction angle. Grouting transforms the end-anchored bolt into a full-length anchor or extended anchor through the penetration and pressure of slurry, and the grouting material consolidation body in the bolt hole reacts to the surrounding rock to prevent its deformation, thereby generating shear stress that limits the deformation of the surrounding rock on the contact surface between the anchoring agent, grouting material and the surrounding rock, so that the bolt and the surrounding rock form a whole, giving full play to the bolt support function.

[0017] After the surrounding rock is modified by grouting, the grouting anchor cable is constructed to bond the loose rock mass into a whole at multiple levels to form a bearing structure. The grouting anchor cable also improves the stress state and controls the deformation of the surrounding rock. The grouting anchor cable and the anchor net cable are jointly supported to improve the stability of the roadway.

[0018] Thin-shot support is carried out on the basis of surrounding rock modification and support. The thin-shot material itself deforms without cracking, protecting the surrounding rock, metal mesh and support components from weathering and hydration, and indirectly controlling the deformation of the surrounding rock. Compared with traditional concrete spraying, it has high toughness, good flexibility, and is not easy to crack, deform or fall off under pressure. The material consumption is only one-tenth of that of shotcrete, which greatly reduces the workload of mine transportation. The construction process is simple, and the construction speed is more than 5 times that of ordinary shotcrete. The general rebound rate is below 5%, which is much lower than the rebound rate of concrete.

[0019] The invention aims to solve the problem of large deformation of the roadway in the three soft coal seams under complex geological conditions in coal mines. Due to the poor self-stabilization ability of the surrounding rock in the three soft coal seams, the support effect of the traditional anchor net cable support technology is not ideal. It is difficult to cope with the significant deformation of the surrounding rock after the plastic zone of the roadway deteriorates by using a single anchor net support. The surrounding rock near the surface of the roadway still shows strong continuous deformation, large deformation, and serious damage. A large deformation roadway surrounding rock grouting modification technology is provided to solve the problem of surrounding rock control, reduce the roadway maintenance project, reduce the roadway maintenance cost, reduce the labor intensity, and greatly improve the roadway surrounding rock Compared with traditional support methods such as grouting reinforcement, single anchor mesh (grouting anchor) support or concrete shotcrete technology, coordinated surrounding rock control technology integrates their advantages. After multi-dimensional modification of the surrounding rock of large deformation tunnels with complex geological conditions, it greatly improves the surrounding rock bearing capacity and creates a stronger surrounding rock bearing structure. It avoids the corrosion and damage of mesh and supporting components after long-term weathering and hydration, greatly improves the effect of tunnel surrounding rock control, reduces the amount of tunnel maintenance work, greatly reduces the use of anchor mesh support materials, and reduces the tunnel maintenance cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the distribution position and shape of the surrounding rock crushing area after the tunnel is excavated and supported; Figure 2 Yes Figure 1 The schematic diagram of grouting modification and reinforcement of the surrounding rock fracture area is shown; Figure 3 is Figure 2 Schematic diagram of anchor cable (grouting anchor cable) support based on grouting modification reinforcement; Figure 4 is Figure 3 The schematic diagram of thin shotcrete sealing based on grouting modification and support is shown; Figure 5 It is a schematic diagram of three calculation methods of grouting hole depth L; In the figure: 1 surrounding rock, 2 tunnel, 3 surrounding rock crushing area, 4 anchor rod, 5 anchor cable, 6 grouting hole, 7 grouting anchor cable, 8 thin shotcrete consolidation body. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0022] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings: The present invention proposes a method for supporting a large deformation roadway in a three-soft coal seam under complex geological conditions, comprising the following steps: Step 1, please refer to Figure 1 During mining or excavation, grouting materials are pumped into the surrounding rock crushing area 3 inside the surrounding rock 1 of the tunnel 2 to form a deep reinforcement structure of the tunnel surrounding rock. The specific construction sequence is: 1) First, grouting holes 6 arranged at intervals are drilled on the coal rock wall of the tunnel surrounding rock, such as Figure 2 shown.

[0024] Before drilling the grouting holes arranged at intervals, it is necessary to determine the parameters of the grouting holes according to the specific construction tunnel construction scene and the surrounding rock conditions, including the depth of the grouting holes, the diameter of the grouting holes, the hole spacing between adjacent grouting holes, and the sealing depth. The determination method of each parameter is as follows: For the application scenario of two-component inorganic reinforcement shallow hole grouting, the depth of the grouting hole L ≥max{ P 1, P 2, P 3}, where P 1 is the maximum damage depth calculated by theoretical formula, see Figure 5 (a) P 2 is the maximum damage depth determined by numerical simulation, see Figure 5 b), P 3. Determine the maximum damage depth for drilling observation, see Figure 5 (c) Design drilling depth L Should be greater than the failure depth of the plastic zone of the tunnel surrounding rock P , but the drilling depth LIt should not be too deep, because the deep surrounding rock fissures are primary fissures inside the coal (rock) body, the fissures are not developed, and the slurry is not easy to penetrate, so too deep drilling has little effect. For the application scenarios of single-component inorganic reinforcement deep hole grouting, including grouting in special geological structure areas with large scale in the excavation working face, and pre-grouting in two chute advances in special geological areas with large scale in the comprehensive mining working face, the drilling holes are mainly long holes, and the grouting treatment objects are mainly geological structure fracture zones, requiring the drilling length to reach the boundary of the geological structure fracture zone.

[0025] Drill hole to confirm P The implementation steps of 3 include drilling construction, installation of peep instruments, and observation and analysis. Drilling construction is to drill a certain number and depth of boreholes in the target area based on geological survey results and engineering requirements. The diameter and depth of the borehole should be determined according to the specific situation to ensure that the peep instrument can enter smoothly and observe to a sufficient depth. Install the peep instrument (such as a borehole peep instrument) into the borehole, and adjust its position and angle so that the damage inside the borehole can be clearly observed. Start the peep instrument to observe and record the inside of the borehole. Focus on observing the location and form of damage features such as cracks, broken zones, and abscission layers, as well as their degree of development and extension direction. Based on the observation results, conduct a comprehensive analysis of the damage to the geological structure to determine the maximum damage depth P 3.

[0026] The borehole diameter is related to the type of drilling rig and the size of the drill bit. The basic requirement for the borehole diameter is that it should be larger than the outer diameter of the grouting iron pipe and the outer diameter of the hole sealer. For two-component inorganic reinforcement materials, the main application scenario is shallow hole grouting in tunnels (mines). Single-body pneumatic rotary roof anchor drills, single-body hydraulic rotary roof anchor drills, handheld pneumatic auxiliary anchor drills, and leg-type pneumatic auxiliary anchor drills are commonly used. At this time, the borehole diameter is required to be larger than the outer diameter of the hole sealer. Combined with the field test results of two-component inorganic reinforcement, the grouting hole diameter can be selected from 30 to 42 mm.

[0027] The selection of the spacing between grouting holes is closely related to the diffusion radius. The spacing between the grouting holes should make the diffusion ranges of the two grouting holes overlap to a certain extent and should be smaller than twice the diffusion radius. a ≤2 r ,in r is the grouting diffusion radius.

[0028] The sealing depth can change the trajectory of the slurry diffusion to the shallow part. The slurry diffusion to the shallow part is roughly umbrella-shaped. The longer the sealing hole, the longer the slurry diffusion trace, the faster the solidification speed when it reaches the tunnel surface, the less leakage, but the shallow grouting effect is worse. On the contrary, the leakage will be serious, but the shallow grouting effect is good. For the application scenario of two-component inorganic reinforcement shallow hole grouting, the grouting reinforcement treatment object is the shallow broken surrounding rock of the tunnel. The position of the sealer should be moderate. The surrounding rock in the area where the sealer is placed should not be extremely broken to avoid damage to the surrounding rock of the borehole after the sealer expands, resulting in sealing failure. It should not be placed too deep to avoid fewer cracks in the deep grouting, which will lead to the grouting pump being blocked and the sealer retreating, resulting in sealing failure.

[0029] 2) Then mix the two-component reinforcement material raw materials in the slurry bucket to form grouting slurry, and connect the slurry bucket and the grouting pump with a grouting pipe.

[0030] The grouting pump is used to pump the grouting material into the surrounding rock of the tunnel, including a double-liquid pneumatic grouting pump and 2 starting mixing barrels.

[0031] The grouting material used in the embodiment of the present invention is prepared by mixing A / B two-component inorganic and mineral powder materials, has a nanometer-level particle size, has good permeability to small rock cracks, can be quickly consolidated within a few seconds to tens of seconds, and can reach sufficient strength in a short time.

[0032] Component A and component B materials are selected from materials with similar properties in terms of curing speed, strength, reaction temperature, etc. to ensure that the grouting materials are non-spontaneous, non-toxic, non-corrosive, and non-polluting. Component A and component B materials are mixed evenly in a water-cement ratio of 0.4, and then the mixture is pumped into the surrounding rock in a 1:1 ratio using a double-liquid grouting pump.

[0033] 3) Finally, grout each grouting hole in turn, insert the grouting pipe head into the grouting hole to the bottom of the hole, start the grouting pump to grout, and end the grouting after the grouting pressure gradually rises to a stable level, and turn off the grouting pump.

[0034] The basic principle of grouting technology is to inject flowing grout into the broken surrounding rock, and bond it with the traditional anchor net (cable) support to form an organic whole to jointly maintain the stability of the surrounding rock. By improving the physical and mechanical properties of the rock mass, the loose, low-strength rock mass is transformed into a structure with high strength, excellent stability and sufficient bearing capacity. The grouting technology of the present invention mainly plays the following roles in the specific embodiment: 1) Constructing a network skeleton. After the slurry enters the cracks of the broken rock mass and solidifies through reaction, it fills the cracks in the form of solid, forming a new grid skeleton system. When the load is greater than the bearing capacity of the surrounding rock and causes the surrounding rock to deform violently, the consolidation grid skeleton plays a supporting role with its excellent bonding ability and toughness, mobilizing the residual strength of the surrounding rock mass, inhibiting the development of damage, and controlling the deformation of the surrounding rock.

[0035] 2) Improve rock mass strength and stability. Grouting has a compaction effect, which can improve various mechanical parameters of the rock mass, improve bearing strength, and increase the overall anti-deformation stiffness of the surrounding rock, thereby achieving a reinforcement effect.

[0036] 3) Grouting filling and compaction. Grouting materials can fill the cracks with high density and achieve a tight sealing effect. At the same time, when the cracks are filled with slurry, the unit stress near the crack surface in the surrounding rock will be adjusted from the initial biaxial stress state to a triaxial stress state.

[0037] Step 2: Use support structures to implement anchor wire support on the sides and top of the tunnel. Figure 3 , the broken surrounding rock 3 treated in step 1 is consolidated by the grouting slurry, which is more conducive to the formation and application of the active support force of the grouting anchor cable 7. The anchor mesh cable support structure is adopted, such as the grouting anchor cable 7, to provide active support force in the broken surrounding rock 3 area after deep reinforcement in step 1. After the broken loose rock mass of the tunnel surrounding rock is reinforced, the loose rock mass can be re-cemented to shape a new bearing structure. Combined with the support of the original anchor rod 4 and anchor cable 5 of the surrounding rock 1 of the tunnel 2, the integrity and self-stabilization capacity of the surrounding rock mass of the tunnel 2 are enhanced. Since the gap between the grouting body and the anchor rod (cable) is filled, the anchor rod (cable) obtains a stable force foundation, and the anchoring length is also increased, which ensures the continuity and reliability of force transmission, reduces the load acting on the anchor rod (cable), improves the stress distribution of the surrounding rock, and the rock mass can always maintain a certain support reaction force, inhibits the surrounding rock from producing a large deformation, significantly reduces the movement of the tunnel, and achieves relative stability of the surrounding rock.

[0038] Step 3, spraying the material thinly on the surface of the coal rock mass in the roadway to form a thin spray consolidation body 8 to form a reinforced surface layer, see Figure 4 , which increases the adhesion strength of the overall structure and at the same time achieves grouting slurry sealing to avoid corrosion.

[0039] In some embodiments of the present invention, the thin-film spraying material is a two-component composite spraying material, and the thin-film spraying composite material includes a polymer emulsion M material and a solid powder N material. After the two components of M material and N material are evenly mixed in a ratio of M:N=1:1, they are sprayed onto the surface of the coal rock through a special pneumatic spray pump, and the thickness of the reinforced surface layer is not less than 20 mm.

[0040] In some preferred embodiments, at least two layers of thin spraying materials are applied on the surface of the coal and rock mass in the roadway, and the time interval between applying different layers of thin spraying materials is no more than 2 hours.

[0041] The thin shotcrete step seals the water source and air channel. The intervention of water will cause the strength of the tunnel surrounding rock to decrease rapidly, especially the mudstone that expands when it encounters water. The properties of the rock will be reversed due to the dissolution and softening of water, which is significantly reflected in the strength and deformation characteristics. Grouting solidification can reduce the impact of water on the surrounding rock and delay the occurrence of rheology. Grouting can interrupt the connection between air, water and internal rock mass, reduce weathering and water damage, and prevent the anchor (cable) from rusting, which is very critical to maintaining the mechanical indicators of the surrounding rock and the stability of the support system.

[0042] The present invention combines the thin spraying technology with the surrounding rock grouting technology, and sprays the thin spraying material for mining with the function of bonding and quickly blocking air leakage onto the surface of the coal rock mass, so as to quickly solve the problems of air leakage, weathering, and harmful gas outflow on the surface of the coal rock mass in the coal mine, and can play a role in quickly closing the roadway, preventing the weathering of the surrounding rock of the roadway, avoiding oxidation and rusting of the supporting structure, preventing coal gas from overflowing, and extending the service life of the roadway. This technology uses a special spraying equipment to mix the two materials and then spray them out, forming a high-toughness, large-deformation-adaptive, airtight film on the surface of the roadway, which is tightly attached to the surface of the coal rock mass and the supporting structure of the roadway, isolating the humid air and moisture in the roadway, and achieving the purpose of indirectly controlling the deformation of the surrounding rock.

[0043] The surrounding rock grouting modification-support-thin shotcrete coordinated surrounding rock control system first injects grout into the broken area of ​​the tunnel to improve the bearing capacity of the tunnel, then carries out anchor mesh support, and finally carries out thin shotcrete. The three processes form a coordinated surrounding rock control system.

[0044] The following is further described in conjunction with specific embodiments: The method for supporting large deformation roadways in three soft coal seams under complex geological conditions adopted in this embodiment includes the following steps: Step 1: Preparation work before grouting: Before grouting, the grouting equipment and grouting materials must be transported to the designated location, and then the grouting equipment must be placed horizontally to ensure that the working cylinder is vertical to the ground, otherwise it will affect the normal operation of the working cylinder. The grouting pump and mixing barrel need to be connected to the power by a professional electrician. After the test run is normal, the grouting system can be connected. After the grouting equipment is operating normally, connect the grouting pump and the grouting casing to conduct a pressure test. Grouting can only be carried out after the pressure test is passed.

[0045] Batching and debugging ratio: transport the grouting material to the vicinity of the grouting pump. The water-cement ratio of reinforcement materials A and B is 0.4:1, and the ratio of A and B slurry is controlled at 1:1. Inorganic reinforcement materials A and B are placed in a mixing bucket. After the slurry is fully mixed for 1-2 minutes, stir evenly, and place the slurry suction pipe into the slurry for grouting. After the configuration is completed, insert the suction pipe into the bottom of the bucket.

[0046] Grouting: Connect the grouting pipeline to the orifice pipe. During the grouting process, proceed step by step to avoid too fast pressure rise, which may cause abnormal operation of the equipment. When the grouting pressure stabilizes at 20MPa for more than 10 minutes, or reaches 25MPa, the grouting of the grouting hole is completed, and the next hole is switched to grouting, or the grouting is ended.

[0047] Step 2: Reference Figure 3 , use pre-tightened grouting anchor cables 7 that meet the original support design of the tunnel to support the crushed rock area 3 reinforced in step 1.

[0048] Step 3: Use ZZQ-0.9 / 5 grouting device for spraying, spray a thin layer of spray material with a thickness of 10~20mm at a time, and spray again in time. The interval between spraying should not exceed 2 hours. Otherwise, flush the sprayed surface with high-pressure water and then spray again to form a thin spray consolidation body 8.

[0049] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for supporting large deformation tunnels in three-soft coal seams under complex geological conditions, characterized in that: The following steps are involved: Step 1, pumping grouting material into the deep part of the tunnel surrounding rock to form a deep reinforcement structure of the tunnel surrounding rock; Step 2: Use a supporting structure to implement anchor wire support on the sides and top of the tunnel; Step 3, spraying the material thinly on the surface of the coal rock mass in the roadway to form a reinforced surface layer.

2. The method for supporting large deformation tunnels in three-soft coal seams under complex geological conditions according to claim 1 is characterized in that: In step 1, the construction sequence of pumping grouting materials into the surrounding rock of the tunnel is: S1, drilling grouting holes arranged at intervals on the coal rock wall of the tunnel surrounding rock; S2, mixing two-component reinforcement material raw materials in a slurry bucket to form grouting slurry, and connecting the slurry bucket and the grouting pump with a grouting pipe; S3, grouting each grouting hole in turn, inserting the grouting pipe head into the grouting hole to the bottom of the hole, starting the grouting pump to grout, and ending the grouting after the grouting pressure gradually rises to a stable level, and shutting down the grouting pump.

3. The method for supporting large deformation tunnels in three-soft coal seams with complex geological conditions according to claim 2, characterized in that: The depth of the grouting hole L ≥max{ P 理论 , P 模拟 , P 钻孔窥视 } and is greater than the failure depth of the plastic zone of the tunnel surrounding rock.

4. The method for supporting large deformation tunnels in three-soft coal seams under complex geological conditions according to claim 2 is characterized in that: The diameter of the grouting hole is 30-42 mm.

5. The method for supporting large deformation tunnels in three-soft coal seams under complex geological conditions according to claim 2 is characterized in that: The hole spacing of the grouting holes a ≤2 r ,in r is the grouting diffusion radius.

6. The method for supporting large deformation tunnels in three-soft coal seams with complex geological conditions according to claim 2, characterized in that: S3 describes the use of low-pressure grouting, where the grouting pressure is 0.3 MPa~2.0 MPa.

7. The method for supporting large deformation tunnels in three-soft coal seams under complex geological conditions according to claim 2 is characterized in that: The grouting pressure in S3 gradually rises and stabilizes at 20 MPa and is maintained for 9 to 11 minutes, or when the grouting pressure rises and stabilizes at above 25 MPa, the grouting is completed.

8. The method for supporting large deformation tunnels in three-soft coal seams under complex geological conditions according to claim 1 is characterized in that: In the step 3, at least two layers of thin spraying materials are applied on the surface of the coal rock mass in the roadway, and the time interval between applying different layers of thin spraying materials is no more than 2 hours.

9. The method for supporting large deformation tunnels in three-soft coal seams under complex geological conditions according to claim 1 is characterized in that: The thickness of the reinforced surface layer in step 3 is not less than 20 mm.

10. The method for supporting large deformation tunnels in three-soft coal seams under complex geological conditions according to claim 1, characterized in that: The grouting material is a two-component inorganic material plus mineral powder, and the thin spraying material is a two-component composite spraying material.

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