Roadway support construction method and material based on high-stress soft rock and broken surrounding rock

Abstract

The invention discloses a roadway supporting construction method and material based on high-stress soft rock and broken surrounding rock, and the supporting construction method comprises the following steps: constructing an anchor rod on the surface of a roadway to be supported, and installing a first reinforcing mesh and a second reinforcing mesh on the constructed anchor rod; reinforcing ribs are arranged on the first reinforcing mesh at intervals; the grid size of the second reinforcing mesh is smaller than that of the first reinforcing mesh, the second reinforcing mesh comprises a layer of reinforcing mesh piece and a layer of mining flame-retardant plastic mesh, and the mining flame-retardant plastic mesh is located between the first reinforcing mesh and the reinforcing mesh piece; a first material is sprayed on the surface of the second reinforcing mesh to construct a supporting layer, and grouting holes are reserved in the supporting layer; and after the supporting layer is initially set, grouting of a second material is conducted between the supporting layer and the surface of the roadway to be supported through the grouting holes, so that a buffer layer is constructed. In the supporting process of large-deformation soft rocks and surrounding rocks, rapid supporting can be achieved, and meanwhile good supporting stability is achieved.

Description

Technical Field

[0001] The present invention relates to the field of support technology, and in particular to a tunnel support method and material based on high-stress soft rock and broken surrounding rock. Background Art

[0002] At present, support forms such as anchor spraying, anchor cable spraying, masonry support or cast-in-place concrete are widely used in water conservancy, railways, mine shafts, roads, and tunnel projects. Among them, the main obstacles and threats in the rapid construction of shafts and tunnels are high-stress soft rocks and broken surrounding rocks. In the process of tunnel excavation, the construction progress is restricted by the soft and broken surrounding rock surface soil layer, poor firmness, poor integrity, and poor safety and reliability. Especially in the construction process of coal mine tunnels, this problem is very obvious and has a serious impact on the safety of tunnel support.

[0003] In the related technology, various forms of combined support such as metal arch, anchor mesh spraying, anchor cable and reinforced concrete pouring support are adopted. However, with the increase of the mining depth of the tunnel, especially in the tunnels with high-stress soft rock and broken surrounding rock, it is easy to cause the concentrated stress and deviator stress in the tunnel soft rock and surrounding rock to increase, causing significant changes in the deformation characteristics of the soft rock and surrounding rock. In addition, the propagation of deep ground stress in the tunnel can easily make the soft rock and surrounding rock in the deep tunnel unstable. In a short period of time, the tunnel surrounding rock will show large deformation, which significantly increases the difficulty of tunnel support. Therefore, how to balance the stability and construction efficiency of tunnel support has become a technical problem that technicians in this field need to solve urgently. Summary of the invention

[0004] In order to solve the above problems, an embodiment of the present application provides a tunnel support method and material based on high-stress soft rock and broken surrounding rock, which can achieve rapid support and have better support stability during the support process of soft rock and surrounding rock with large deformation.

[0005] To this end, the following technical solutions are adopted in the embodiments of the present application: In a first aspect, the present application provides a tunnel support method and material based on high-stress soft rock and broken surrounding rock, comprising the following steps: Anchor rods are constructed on the surface of the tunnel to be supported, and a first steel mesh and a second steel mesh are installed on the constructed anchor rods; wherein reinforcing ribs are arranged at intervals on the first steel mesh; the mesh size of the second steel mesh is smaller than the mesh size of the first steel mesh, and the second steel mesh includes a layer of steel mesh and a layer of anti-flame retardant plastic mesh for mining, and the anti-flame retardant plastic mesh for mining is located between the first steel mesh and the steel mesh; The first material is sprayed on the surface of the second steel mesh to construct a support layer, and grouting holes are reserved on the support layer, wherein the support layer is used to provide high-strength and stable support for the tunnel; After the supporting layer is finally set, grouting of a second material is performed between the supporting layer and the surface of the roadway to be supported through the grouting hole to construct a buffer layer, wherein the buffer layer is used to provide a buffer for the deformation and movement of the roadway; Among them, the first material includes the following components in parts by weight: 20-60 parts of cement, 20-40 parts of admixture, 5-15 parts of reinforcing fiber, 0.5-1.5 parts of water reducer, 1-5 parts of early strength agent, 2-4 parts of thixotropic agent, 80-120 parts of high-strength aggregate, 3-6 parts of accelerator and 10-30 parts of water; the accelerator includes polyaluminum sulfate, polyethyleneimine, diethanol monoisopropanolamine and modified nano-silica in a weight ratio of 50-55:4-6:2-5:1-3.

[0006] In this embodiment, the present application can effectively improve the stability of the support and enhance the bearing capacity of the surrounding rock by setting a double-layer steel mesh structure. Among them, a combination of the first and second steel meshes is used, wherein the first steel mesh provides basic support, and the second steel mesh improves the overall strength and crack resistance of the support layer by adding a smaller mesh size and a flame-retardant plastic mesh for mining. The design of the reinforcing rib further improves the rigidity of the structure and can better disperse the concentrated stress. In this embodiment, the first material is first sprayed to form a support layer, and the material is provided with a grouting hole after initial setting. Then the second material is injected through the grouting hole to form a buffer layer. In this construction method, in the case of constructing a buffer layer, the second steel mesh and the flame-retardant plastic mesh for mining are configured to form a pre-preparation for the spraying construction of the support layer, and then the support layer is quickly sprayed to construct the support layer. Moreover, the addition of an early strength agent and a quick setting agent can improve the construction rate of the support layer, and at the same time, the support layer can have a better early strength, especially in the face of soft surrounding rock, and can provide support in time to avoid further damage to the surrounding rock caused by long-term exposure. At the same time, the higher-strength support layer also facilitates the subsequent grouting construction of the buffer layer.

[0007] In addition, the double-layer steel mesh and anchor structure provide base support for the buffer layer and the support layer. The buffer layer composed of the second material has sufficient flexibility to withstand the large deformation caused by the expansion type soft rock and the high ground stress soft rock to transform its expansion energy and deformation energy, and has sufficient strength in a specific time period to control the destructive deformation of the expansion type soft rock and the high ground stress soft rock to meet the safety and reliability of the support, and has economic benefits. The buffer layer cooperates with the support layer composed of the first material to form a joint support. The buffer layer can well release the deformation energy and expansion pressure of the surrounding rock, greatly reducing the stress on the support layer and improving the reliability of the support structure.

[0008] It is understandable that the second material of the above-mentioned structural buffer layer can be a material with good elasticity and compressive strength, which can effectively absorb and disperse stress, such as lightweight foam concrete prepared with lightweight aggregate (such as expanded perlite, ceramsite or rubber particles), which can reduce the weight of the overall structure while providing good buffering effect.

[0009] Furthermore, the support layer constructed with the second concrete material uses components such as high-strength aggregate and reinforcing fiber, and the support layer can significantly enhance the force-bearing capacity and bearing capacity of the structure to be supported, and improve the overall strength. The support layer can suppress the deformation or cracking of the surrounding rock with its own strength and stiffness. On the other hand, in addition to being able to withstand higher pressures, the support layer has good crack resistance due to the addition of a high amount of reinforcing fiber, so that the support layer can remain unbroken after bearing a pressure exceeding its own compressive strength, and can also effectively prevent the generation and expansion of cracks, thereby improving the support capacity. Admixtures play the role of filling and refining particles in concrete, increasing the density and strength of the material. Thixotropic agents can increase the viscosity and plasticity of concrete, so that the second concrete material can achieve good slurry hanging with the matrix, and improve the spraying construction performance of the second concrete material. The addition of accelerators and early strength agents enables this method to achieve rapid connection of construction processes, improve construction efficiency, shorten construction period, and take into account both construction efficiency and support stability. In particular, the quick-setting agent adopts polyaluminum sulfate, polyethyleneimine, diethanol monoisopropanolamine and modified nano-silica in a weight ratio of 50-55:4-6:2-5:1-3, so that the support layer constructed with the first material can achieve initial setting in 80s-90s and final setting in 200s-210s, and the early strength of the support layer after final setting has a 1h compressive strength of 5Mpa, a 2h compressive strength of 10Mpa, a medium-term 4h compressive strength of 20-30Mpa, a 1d compressive strength of 50Mpa, and a 28d compressive strength of 140Mpa. This shows that the quick-setting agent and early-strength agent added in this embodiment not only promote the early strength of the support layer, but also have a certain promoting effect on the improvement of the later strength of the support layer, so that the support layer composed of the first material not only has a high compressive strength grade but also has good toughness and shear resistance, and can quickly provide continuous support for rapid support or emergency projects.

[0010] Specifically, the polyaluminium sulfate in the above-mentioned accelerator component can accelerate cement hydration, promote the shortening of initial setting time, and improve early strength by enhancing the interaction between cement particles. The high molecular structure of polyethyleneimine can be effectively adsorbed on the surface of cement particles to accelerate the hydration reaction of cement; and polyethyleneimine can improve the microstructure of concrete, enhance adhesion, and thus improve compressive strength and toughness. Diethanol monoisopropanolamine is used as an auxiliary agent, which can reduce the viscosity of concrete, promote the reaction between water and cement, and improve the overall strength of concrete by improving the fluidity of cement paste. The small size and high specific surface area of ​​modified nano-silica enable it to fill the gaps between cement particles, promote cement hydration, and form a denser microstructure, significantly improving the compressive strength and durability of concrete. The synergistic effect of these components in the accelerator enables concrete to obtain good strength performance in both the early and late stages. For example, the combination of polyaluminium sulfate and polyethyleneimine accelerates the hydration reaction, diethanol monoisopropanolamine further optimizes the fluidity of the mixture, and modified nano-silica improves the final strength by filling and enhancing the microstructure. At the same time, this diverse combination not only ensures the requirements of rapid construction, but also lays the foundation for long-term durability.

[0011] As mentioned above, the anchor rods are connected to the concrete masonry, which enhances the support stability of the buffer layer and the supporting layer. The buffer layer can effectively unload the deformation energy and expansion pressure of the surrounding rock, while reducing the mechanical state of the surrounding rock to a certain extent. Combined with the high-strength supporting layer, the supporting structure is more reliable.

[0012] As an achievable implementation method, the preparation method of the modified nano-silicon dioxide is as follows: Ultrasonic dispersion of 0.5 g of nano-silicon dioxide particles with a particle size of 1-15 nm in an aqueous solution of hexadecyltrimethylammonium bromide was performed for at least 30 minutes to obtain a nano-material dispersion; After adding alkali to the nanomaterial dispersion, tetraethyl silicate is slowly added dropwise, and the ratio of the added tetraethyl silicate to hexadecyltrimethylammonium bromide is 4ml-5ml:0.1g; ultrasonic reaction is carried out at 45 degrees for 24 hours to obtain a nano-silicon dioxide material suspension; Add silane coupling agent and polyvinyl alcohol to the nano-silicon dioxide material suspension, carry out ultrasonic reaction at 60-68°C for 1-2h, and centrifuge to obtain the solid phase to obtain modified nano-silicon dioxide; the weight ratio of the nano-silicon dioxide, silane coupling agent and polyvinyl alcohol is 1:5-8:3-6.

[0013] In this embodiment, an aqueous solution of hexadecyltrimethylammonium bromide (CTAB) is used as a surfactant, which can help form a uniform mesoporous silica (mSiO2) film, so that tetraethyl silicate can coat a layer of mesoporous silica with multiple silanol groups on the surface of nano-silica, and then further modify it by adding silane coupling agent and polyvinyl alcohol to obtain modified nano-silica. The modified nano-silica has smaller particles and a higher specific surface area, which can effectively fill the gaps between cement particles and increase the interface contact area, thereby improving the compactness and strength of concrete. The modified nano-silica can react with calcium hydroxide in cement to generate more hydrated silicate (CSH), which is a hydration product that is crucial to strength improvement. Through this reaction, the early strength is improved. The presence of silanol groups enhances the bonding force between the modified nano-silica and the cement matrix, improves the interfacial bonding performance, and thus improves the overall strength of the concrete. In addition, by combining nano-silica with other modifiers (such as silane coupling agents and polyvinyl alcohol), multiple modification effects can be achieved. The synergistic effect of these ingredients not only accelerates the hydration reaction, but also improves the mechanical properties and durability of concrete. For example, by combining with silane coupling agents and polyvinyl alcohol, modified nano-silica can improve the fluidity of concrete, making the concrete more uniform during mixing and pouring, and facilitating construction. The improvement in fluidity also helps to reduce pores or cracks that may appear during construction, thereby improving the overall quality. Moreover, polyvinyl alcohol can form a flexible network structure in concrete, and use modified nano-silica as a connecting node to enhance the toughness and crack resistance of concrete, reduce the development of microcracks, and promote the improvement of later strength. This also enables the interaction between modified nano-silica and cement and aggregate to enhance the bonding between them, thereby improving the tensile and shear strength of concrete. This enhanced bonding makes concrete perform better under stress.

[0014] As a feasible implementation method, the particle size of the modified nano-silica is 10-25nm. Within this particle size range, the nano-silica has a very strong hydration activity, reacts with Ca(OH)2 in concrete to form hydrated calcium silicate gel, thereby improving the early strength of the concrete. At the same time, there are a large number of pores in the shotcrete, especially the spatial network structure of ettringite. Due to its extremely small particle size, the nano-silica can be well filled in the pores, thereby improving the density of the shotcrete and improving its mechanical properties.

[0015] As a feasible implementation method, the concentration of the aqueous solution of hexadecyltrimethylammonium bromide is 0.01% to 1%.

[0016] As an achievable implementation manner, the ratio of tetraethyl silicate to hexadecyltrimethylammonium bromide is 4 ml:0.1 g.

[0017] In this embodiment, CTAB forms micelles in the reaction system, and these micelles, in the presence of a silicon source (such as silicon tetrachloride), cause silicon dioxide to be deposited on its surface to form an ordered mesoporous structure. By adjusting the ratio of CTAB to tetraethyl silicate and controlling the concentration of the CTAB aqueous solution, the size and distribution of the mesopores can be controlled. Specifically, tetraethyl silicate (TEOS) undergoes a hydrolysis reaction in the presence of water to form siloxane (Si-O-Si) chains. In this process, the reaction of TEOS with water generates silicic acid, which further undergoes a polycondensation reaction to form a silicon oxide with a three-dimensional network structure. Hexadecyltrimethylammonium bromide (CTAB), as a cationic surfactant, can self-assemble in the aqueous phase to form micelles. CTAB micelles can encapsulate water-soluble substances and change the interfacial properties of the mixed system, thereby promoting the uniform dispersion and reaction of TEOS, and CTAB can guide TEOS to form an ordered nanostructure, such as a mesoporous silica layer, on the surface of nano-silica. By adjusting the ratio of TEOS and CTAB, the pore size, specific surface area and other properties of the mesoporous silica layer of the modified nano-silica can be controlled, thereby affecting the role of the modified nano-silica in concrete, and then affecting the early and late strength of the support layer. It has been verified that the above ratio of tetraethyl silicate and hexadecyltrimethylammonium bromide can significantly improve the early and late strength of the first material and improve the support performance of the support layer.

[0018] As an achievable implementation manner, the weight ratio of the nano-silicon dioxide, the silane coupling agent and the polyvinyl alcohol is 1:5-6:5-6.

[0019] As an achievable implementation manner, the weight ratio of the nano-silicon dioxide, the silane coupling agent and the polyvinyl alcohol is 1:5:5.

[0020] In this embodiment, at this ratio, the modified nano-silica reacts more efficiently with cement, which can significantly improve the early strength of concrete, allowing the project to be put into use quickly. In addition, the fluidity and adhesion of concrete can be optimized, making it easier to spray and form a thin layer of the first material, thereby improving construction efficiency. At the same time, it also has a certain effect on improving the later strength of the support layer and improving the support stability.

[0021] As an achievable embodiment, the base includes any one of triethylamine and triethanolamine.

[0022] In this embodiment, the pH value of the reaction can be adjusted by using an alkaline solution (such as triethylamine, triethanolamine, sodium hydroxide, etc.), thereby controlling the gelation rate and structure of the silica. Different concentrations of alkali will affect the formation rate of silica and the thickness of the film.

[0023] As an achievable implementation, the early strength agent includes acyloxysilane, sodium thiosulfate and triethanolamine in a weight ratio of 2-4:3-4:2-4.

[0024] In this embodiment, acyloxysilane is used as a chemical modifier, and acyloxysilane can improve the bonding between cement paste and aggregate, improve the overall strength of concrete, and it can form a silicon oxide structure during cement hydration, further enhancing the durability of concrete. Sodium thiosulfate is usually used as an accelerator, which can promote the hydration reaction of cement, and then improve early strength. It can react with calcium ions in cement, increase the activity of cement particles, and thus accelerate the hardening process. As an organic base, triethanolamine can increase the rate of cement hydration reaction, improve the fluidity and workability of concrete, and it can effectively reduce the initial viscosity of concrete, so that the improvement of early strength is more obvious. The early strength agent significantly improves the early strength of concrete and improves its physical and mechanical properties through the synergistic effect of its components. This makes it more efficient to meet construction requirements in projects that require rapid prototyping.

[0025] As an achievable implementation, the early strength agent includes acyloxysilane, sodium thiosulfate and triethanolamine in a weight ratio of 3:4:2.

[0026] In this embodiment, it has been verified that the early strength agent in the above ratio can promote the hydration reaction of cement, resulting in more hydration products (such as CSH gel) in the early stage, thereby improving the early strength. At the same time, it makes the microstructure of concrete denser, reduces porosity, and enhances compressive strength.

[0027] As an achievable implementation, the method of spraying the first material on the surface of the second steel mesh to construct the support layer includes: According to the preset weight proportions, 20-60 parts of cement, 20-40 parts of admixture, 5-15 parts of reinforcing fiber, 0.5-1.5 parts of water reducer, 2-4 parts of thixotropic agent, 80-120 parts of high-strength aggregate and 10-30 parts of water are mixed evenly to obtain the first concrete primary mix; subsequently, when pumping the first concrete primary mix, 3-6 parts of the accelerator and 1-5 parts of the early strength agent are pumped into the pipeline 1-3m in front of the concrete spray gun; after being evenly mixed in the pipeline mixer, they are sprayed on the surface of the second steel mesh through the concrete spray gun to construct a support layer.

[0028] In this embodiment, the first concrete primary mix, the accelerating setting agent and the early strength agent are pumped at different positions of the pipeline respectively, and are fully mixed by the mixer before spraying. In this way, the mixed materials of different components are mixed in layers during the spraying process through the double-wrapped parallel method, which can not only accurately control the dosage of different components, but also reduce the influence of the accelerating setting agent and the early strength agent on the first concrete primary mix. It is suitable for the tunnel support construction environment that requires higher strength and fast hardening, and can meet the demanding construction requirements.

[0029] In a second aspect, the present application also provides a tunnel support method based on high-stress soft rock and broken surrounding rock, comprising the following steps: Anchor rods are constructed on the surface of the tunnel to be supported and a second steel mesh is installed on the constructed anchor rods; wherein the second steel mesh comprises a layer of steel mesh and a layer of anti-flame retardant plastic mesh for mining, and the anti-flame retardant plastic mesh for mining is located between the first steel mesh and the surface of the tunnel to be supported; A first material is sprayed on the surface of the second steel mesh to construct a support layer, which is used to provide high-strength and stable support for the tunnel; wherein the first material includes the following components in parts by weight: 20-60 parts of cement, 20-40 parts of admixture, 5-15 parts of reinforcing fiber, 0.5-1.5 parts of water reducer, 1-5 parts of early strength agent, 2-4 parts of thixotropic agent, 80-120 parts of high-strength aggregate, 3-6 parts of accelerator and 10-30 parts of water; the accelerator includes polyaluminum sulfate, polyethyleneimine, diethanol monoisopropanolamine and modified nano-silica in a weight ratio of 50-55:4-6:2-5:1-3.

[0030] In this way, a supporting layer for the underground tunnel can be quickly formed in an underground tunnel that does not require a buffer layer.

[0031] In the third aspect, the embodiment of the present application also provides a tunnel support material based on high-stress soft rock and broken surrounding rock, including a first material, which includes the following components in parts by weight: 20-60 parts of cement, 20-40 parts of admixture, 5-15 parts of reinforcing fiber, 0.5-1.5 parts of water reducer, 1-5 parts of early strength agent, 2-4 parts of thixotropic agent, 80-120 parts of high-strength aggregate, 3-6 parts of accelerator and 10-30 parts of water; the accelerator includes polyaluminum sulfate, polyethyleneimine, diethanol monoisopropanolamine and modified nano-silica in a weight ratio of 50-55:4-6:2-5:1-3.

[0032] As a feasible implementation mode, the cement is P.O42.5 cement.

[0033] As a feasible implementation manner, the admixture is zeolite powder.

[0034] As an achievable implementation method, the reinforcing fibers include organic fibers and inorganic fibers; wherein the organic fibers include polypropylene fibers, polyvinyl alcohol fibers, and polyoxymethylene fibers; and the inorganic fibers include basalt fibers, sepiolite fibers, and steel fibers.

[0035] As an achievable implementation manner, the reinforcing fiber is composed of polyoxymethylene fiber and steel fiber in a weight ratio of 3:5.

[0036] As a feasible implementation, the water reducer is a polycarboxylate water reducer.

[0037] As an achievable implementation, the thixotropic agent comprises nano-aluminum oxide fibers, nano-silicon oxide fibers and nano-carbon fibers in a weight ratio of 0.5:3:4.

[0038] As a feasible implementation method, the high-strength aggregate is quartz sand, and the particle size of the quartz sand is 1.0-1.8 mm.

[0039] On the fourth aspect, the embodiment of the present application also provides an application of a tunnel support method based on high-stress soft rock and broken surrounding rock. The support method can be applied to any one of the support of coal mine tunnels, deep foundation engineering foundation pit support, subway tunnel wall support, foundation support of large or high-rise buildings, highway tunnels and hydraulic tunnel support. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic diagram of a support structure of a first tunnel support method based on high-stress soft rock and broken surrounding rock provided in Example 1 of the present application is shown; Figure 2 A schematic diagram of the support structure of the second tunnel support method based on high-stress soft rock and broken surrounding rock provided in Example 1 of the present application is shown. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application are described below.

[0042] It is particularly noted that, unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the raw materials, instruments and equipment used in the following examples, etc., can all be purchased on the market or can be obtained by existing methods; the amounts of the experimental reagents used, unless otherwise specified, are the amounts of reagents used in conventional experimental operations; the experimental methods, unless otherwise specified, are all conventional methods.

[0043] The cement in the first material in the embodiment of the present application is P.O42.5 cement; the admixture is zeolite powder; the reinforcing fiber is composed of polyoxymethylene fiber and steel fiber in a weight ratio of 3:5, the length of polyoxymethylene fiber and steel fiber is 7-8mm, and the diameter is 30-60μm; the thixotropic agent includes nano-alumina fiber, nano-silicon oxide fiber and nano-carbon fiber in a weight ratio of 0.5:3:4; the silane coupling agent is aminopropyltriethoxysilane; the water reducer is a polycarboxylic acid high-performance water reducer with a water reduction rate of 26.8%; the high-strength aggregate is quartz sand with a particle size of 1.0-1.8mm; the rubber particles are crushed from waste natural rubber with a crushing particle size of 35-40 mesh; the foaming agent is sodium dodecyl sulfate, and the foaming agent is prepared by a nano-foam generator to obtain nano-foam.

[0044] It should be noted that the excavation of coal mine tunnels will inevitably lead to the redistribution of the original stress of the surrounding rock. The mechanical behavior of the entire surrounding rock stress redistribution can be summarized as the following process: after the three stages of "balance", "relaxation" and "looseness and collapse", a new balance is reached. "Balance" stage: before the tunnel excavation, the surrounding rock is in a relatively balanced state, and the internal stress distribution is relatively stable. During the excavation process, the original stress of the surrounding rock will be affected by destruction and redistribution. "Relaxation" stage: when the tunnel begins to be excavated, the surrounding rock is affected by the stress release of the excavation surface, and the original stress will gradually decrease, thereby generating a deformation pressure. At this stage, the surrounding rock will deform to a certain extent, but the surrounding rock can still be considered as a continuous medium or a quasi-continuous medium as a whole. "Looseness and collapse" stage: when the tunnel excavation goes deeper, the deformation growth of the surrounding rock reaches a certain extent, and the rock block may separate from the original rock, resulting in collapse or pressure caused by the deadweight of the rock block. The load generated at this stage is called loose pressure, which has a certain impact on the support structure. That is to say, during the tunnel excavation process, the surrounding rock undergoes a stress redistribution process in three stages: balance, relaxation, and loosening and collapse. Before the balance stage, the surrounding rock is in a relatively stable state; in the relaxation stage, the deformation pressure mainly affects the stress distribution of the surrounding rock; in the loosening and collapse stage, the loosening pressure is mainly caused by deformation and separation, which affects the support structure.

[0045] In particular, the probability of plastic deformation of soft rock (i.e. weak surrounding rock) is very high, which often causes the clearance of the tunnel to become smaller, affecting the normal construction and use of the tunnel. Due to the loose geological structure of the weak surrounding rock itself and its extremely poor stability, it is determined that it will inevitably produce a certain degree of deformation during tunnel construction. Due to the poor stability of the weak surrounding rock, the original ground stress balance is destroyed after the tunnel is excavated, resulting in deformation of the surrounding rock. In other words, the difficulty in supporting soft rock and large deformation of surrounding rock caused by high ground stress is that the surrounding rock stress is huge after excavation, and the strength and stiffness requirements of the support system are extremely high. In addition, the deformation of soft rock with high ground stress is large, develops rapidly and continues to not converge. It is very common for the constructed support system to cause erosion due to poor control of deformation. To this end, the present application is specially proposed. The support method of the present application has simple steps, reasonable design, convenient construction, and good use effect. It can easily and quickly complete the support construction of high-stress soft surrounding rock and broken surrounding rock tunnels, and the construction process is safe and reliable, and can effectively control the large deformation of soft rock.

[0046] The first material provided in the embodiments of the present application is introduced in detail below.

[0047] Preparation Example Preparation Example 1 Preparation of the first material: take 20 parts of cement, 20 parts of admixture, 5 parts of reinforcing fiber, 0.5 parts of water reducer, 1 part of early strength agent, 2 parts of thixotropic agent, 80 parts of high-strength aggregate, 3 parts of accelerating agent and 10 parts of water.

[0048] The quick-setting agent includes polyaluminium sulfate, polyethyleneimine, diethanol monoisopropanolamine and modified nano-silica in a weight ratio of 50:4:2:1.

[0049] The preparation method of modified nano-silicon dioxide is as follows: 0.5 g of nano-silicon dioxide particles with a particle size of 10 nm were ultrasonically dispersed in 100 ml of a 1% hexadecyltrimethylammonium bromide aqueous solution, and ultrasonically treated for 30 min to obtain a nano-material dispersion; After adding 10 ml of triethylamine to the nanomaterial dispersion, 4 ml of tetraethyl silicate was slowly added dropwise, and the ratio of the added tetraethyl silicate to hexadecyltrimethylammonium bromide was 4 ml:0.1 g; ultrasonic reaction was performed at 45 degrees for 24 hours to obtain a nano-silicon dioxide material suspension; Add silane coupling agent and polyvinyl alcohol to the nano-silica material suspension, carry out ultrasonic reaction at 60° C. for 1 hour, and centrifuge to obtain the solid phase to obtain modified nano-silica; the weight ratio of the nano-silica, silane coupling agent and polyvinyl alcohol is 1:5:3.

[0050] The early strength agent includes acyloxysilane, sodium thiosulfate and triethanolamine in a weight ratio of 4:3:4.

[0051] Preparation Example 2 Preparation of the first material: take 40 parts of cement, 30 parts of admixture, 10 parts of reinforcing fiber, 1 part of water reducing agent, 3 parts of early strength agent, 3 parts of thixotropic agent, 10 parts of high-strength aggregate, 4 parts of accelerating setting agent and 20 parts of water.

[0052] The quick-setting agent includes polyaluminium sulfate, polyethyleneimine, diethanol monoisopropanolamine and modified nano-silica in a weight ratio of 50:4:2:1.

[0053] The preparation method of modified nano-silicon dioxide is as follows: 0.5 g of nano-silicon dioxide particles with a particle size of 10 nm were ultrasonically dispersed in 100 ml of a 1% hexadecyltrimethylammonium bromide aqueous solution, and ultrasonically treated for 30 min to obtain a nano-material dispersion; After adding 10 ml of triethylamine to the nanomaterial dispersion, 4 ml of tetraethyl silicate was slowly added dropwise, and the ratio of the added tetraethyl silicate to hexadecyltrimethylammonium bromide was 4 ml:0.1 g; ultrasonic reaction was performed at 45 degrees for 24 hours to obtain a nano-silicon dioxide material suspension; Add silane coupling agent and polyvinyl alcohol to the nano-silica material suspension, carry out ultrasonic reaction at 60° C. for 1 hour, and centrifuge to obtain the solid phase to obtain modified nano-silica; the weight ratio of the nano-silica, silane coupling agent and polyvinyl alcohol is 1:5:3.

[0054] The early strength agent includes acyloxysilane, sodium thiosulfate and triethanolamine in a weight ratio of 4:3:4.

[0055] Preparation Example 3 Preparation of the first material: take 60 parts of cement, 40 parts of admixture, 15 parts of reinforcing fiber, 1.5 parts of water reducer, 5 parts of early strength agent, 4 parts of thixotropic agent, 120 parts of high-strength aggregate, 6 parts of accelerating agent and 30 parts of water.

[0056] The quick-setting agent includes polyaluminium sulfate, polyethyleneimine, diethanol monoisopropanolamine and modified nano-silica in a weight ratio of 50:4:2:1.

[0057] The preparation method of modified nano-silicon dioxide is as follows: 0.5 g of nano-silicon dioxide particles with a particle size of 10 nm were ultrasonically dispersed in 100 ml of a 1% hexadecyltrimethylammonium bromide aqueous solution, and ultrasonically treated for 30 min to obtain a nano-material dispersion; After adding 10 ml of triethylamine to the nanomaterial dispersion, 4 ml of tetraethyl silicate was slowly added dropwise, and the ratio of the added tetraethyl silicate to hexadecyltrimethylammonium bromide was 4 ml:0.1 g; ultrasonic reaction was performed at 45 degrees for 24 hours to obtain a nano-silicon dioxide material suspension; Add silane coupling agent and polyvinyl alcohol to the nano-silica material suspension, carry out ultrasonic reaction at 60° C. for 1 hour, and centrifuge to obtain the solid phase to obtain modified nano-silica; the weight ratio of the nano-silica, silane coupling agent and polyvinyl alcohol is 1:5:3.

[0058] The early strength agent includes acyloxysilane, sodium thiosulfate and triethanolamine in a weight ratio of 4:3:4.

[0059] Preparation Example 4 Preparation Example 4 also provides a first material. Unlike Preparation Example 2, the accelerating setting agent includes polyaluminum sulfate, polyethyleneimine, diethanol monoisopropanolamine and modified nano-silica in a weight ratio of 52:6:3:2.

[0060] Preparation Example 5 Preparation Example 5 also provides a first material. Different from Preparation Example 2, the accelerating setting agent includes polyaluminum sulfate, polyethyleneimine, diethanol monoisopropanolamine and modified nano-silica in a weight ratio of 55:5:5:3.

[0061] Preparation Example 6 Preparation Example 6 also provides a first material. The difference from Preparation Example 2 is that the weight ratio of nano-silicon dioxide, silane coupling agent and polyvinyl alcohol is 1:6:4. Preparation Example 7 Preparation Example 7 also provides a first material. The difference from Preparation Example 2 is that the weight ratio of nano-silicon dioxide, silane coupling agent and polyvinyl alcohol is 1:8:6.

[0062] Preparation Example 8 Preparation Example 8 also provides a first material. Different from Preparation Example 2, the early strength agent includes acyloxysilane, sodium thiosulfate and triethanolamine in a weight ratio of 2:4:3.

[0063] Preparation Example 9 Preparation Example 8 also provides a first material. Different from Preparation Example 2, the early strength agent includes acyloxysilane, sodium thiosulfate and triethanolamine in a weight ratio of 3:4:2. Comparative Example 1 Comparative Example 1 also provides a first material. The difference from Preparation Example 1 is that the modified nano-silicon dioxide in the accelerating agent is replaced by ordinary nano-silicon dioxide.

[0064] Comparative Example 2 Comparative Example 1 also provides a first material. The difference from Preparation Example 1 is that the accelerating setting agent is JYS154 accelerating setting agent produced by Wuhan Jiyesheng Chemical Co., Ltd.

[0065] The mechanical properties of the first material in Preparation Examples 1-9 and Comparative Examples 1-2 were tested according to GB / T 50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete" to test the initial and final setting time, 1h, 2h, 4h, 1d, and 28d compressive strength of the hardened concrete cube. The test results are shown in Table 1.

[0066] Table 1 Test results of the second concrete materials obtained in Preparation Examples 1-9 and Comparative Example 8 project Initial setting time (s) Final setting time (s) 1h compressive strength (Mpa) 2h compressive strength (Mpa) 4h compressive strength (Mpa) 1d compressive strength (Mpa) 28d compressive strength (Mpa) Preparation Example 1 90 210 5 10 20 50 140 Preparation Example 2 88 208 7 14 28 55 151 Preparation Example 3 80 200 6 12 25 52 144 Preparation Example 4 85 206 9 16 30 55 155 Preparation Example 5 81 202 8 15 29 54 153 Preparation Example 6 88 208 11 18 33 58 158 Preparation Example 7 88 208 10 16 31 56 155 Preparation Example 8 88 208 12 16 30 57 152 Preparation Example 9 88 208 14 18 33 57 153 Comparative Example 1 120 310 4 8 18 45 135 Comparative Example 2 170 330 3 7 16 42 128 It can be seen from Table 1 that the first material in Preparation Example 1-9 has an early strength of 5 MPa in 1h and 10 MPa in 2h after final setting, a medium-term 4h compressive strength of 20-30 MPa, a 1d compressive strength of 50 MPa, and a 28d compressive strength of 140 MPa, which indicates that the quick-setting agent and early-strength agent added in this embodiment not only promote the early strength of the first material, but also promote the improvement of the later strength of the first material to a certain extent, so that the support layer composed of the first material not only has a high compressive strength grade but also has good toughness and shear resistance, and can quickly provide continuous support for rapid support or emergency projects.

[0067] It can be seen from Preparation Examples 2 and 4-5 that the ratio of polyaluminum sulfate, polyethyleneimine, diethanol monoisopropanolamine and modified nano-silica in the accelerator can affect the mechanical properties of the first material. Among them, when the ratio of polyaluminum sulfate, polyethyleneimine, diethanol monoisopropanolamine and modified nano-silica is 52:6:3:2, the 1h compressive strength of the first material reaches 9Mpa, the 2h compressive strength reaches 16Mpa, the medium-term 4h compressive strength reaches 30Mpa, the 1d compressive strength reaches 55Mpa, and the 28d compressive strength reaches 155Mpa.

[0068] It can be seen from Preparation Examples 2 and 6-7 that the weight ratio of nano-silica, silane coupling agent and polyvinyl alcohol in the preparation of modified nano-silica in the accelerator will also affect the mechanical properties of the first material to a certain extent. Among them, when the weight ratio of nano-silica, silane coupling agent and polyvinyl alcohol is 1:6:4, the 1h compressive strength of the first material reaches 11Mpa, the 2h compressive strength reaches 18Mpa, the medium-term 4h compressive strength reaches 33Mpa, the 1d compressive strength reaches 58Mpa, and the 28d compressive strength reaches 158Mpa.

[0069] It can be seen from Preparation Examples 2 and 8-9 that the weight ratio of acyloxysilane, sodium thiosulfate and triethanolamine in the early strength agent will also affect the mechanical properties of the first material. Among them, when the weight ratio of acyloxysilane, sodium thiosulfate and triethanolamine is 3:4:2, the 1h compressive strength of the first material reaches 14Mpa, the 2h compressive strength reaches 18Mpa, the medium-term 4h compressive strength reaches 33Mpa, the 1d compressive strength reaches 57Mpa, and the 28d compressive strength reaches 153Mpa.

[0070] It can be seen from Preparation Example 1 and Comparative Examples 1-2 that the mechanical properties of the first material prepared by using modified nano-silicon dioxide are greatly improved compared to the ordinary nano-silicon dioxide in Comparative Example 1 and the ordinary commercially available accelerating agent in Comparative Example 2, and the initial setting and final setting times are further shortened. It shows that the presence of silanol groups enhances the binding force between modified nano-silicon dioxide and cement matrix, improves the interfacial bonding performance, and thus improves the overall strength of concrete. In addition, by combining nano-silicon dioxide with other modifiers (such as silane coupling agents, polyvinyl alcohol), the overall mechanical properties of the first material are further improved. Among them, the 1h compressive strength of the first material in Preparation Example 2 reaches 7Mpa, the 2h compressive strength reaches 14Mpa, the mid-term 4h compressive strength reaches 28Mpa, the 1d compressive strength reaches 55Mpa, and the 28d compressive strength reaches 151Mpa.

[0071] In this way, the first material is applied to the support system through spraying construction, which makes the construction quick and efficient. Because the first material has a high early strength (2h compressive strength greater than or equal to 10MPa), the support strength can be quickly established.

[0072] Preparation Example 10 Preparation of the second material: take 100 parts of cement, 210 parts of rubber particles, 60 parts of admixture, 10 parts of anti-seepage fiber, 3 parts of foaming agent, 3 parts of water reducer, 50 parts of water and 15 parts of early strength agent; mix the above raw materials evenly to obtain the first material mortar; wherein the anti-seepage fiber is composed of polyester fiber; the length of the polyester fiber is 5-7mm and the diameter is 15-20μm; the early strength agent includes acyloxysilane, sodium thiosulfate and triethanolamine in a weight ratio of 3:4:2. Example Example

[0073] Figure 1 The schematic diagram of the support structure of the first tunnel support method based on high-stress soft rock and broken surrounding rock provided in Example 1 of the present application is shown. Figure 1 , a tunnel support method based on high-stress soft rock and broken surrounding rock, including the following steps: S1. After constructing anchor holes on the surface 1 of the structure to be supported and installing anchors 2, the first steel mesh 3 and the second steel mesh 4 are installed on the anchors 2. In other words, the first steel mesh 3 and the second steel mesh 4 are fixed by using the anchors 2.

[0074] For example, the surface of the structure 1 to be supported can be any one of a coal mine tunnel surface, a foundation pit surface, a highway tunnel, and a hydraulic tunnel. The following is an exemplary description using the coal mine tunnel surface as an example, but it should be understood that the present application is not limited thereto.

[0075] Exemplarily, the anchor rod 2 is a threaded steel anchor rod with a specification of Φ0.02×2.00m; one end of the anchor rod is threaded, the thread length is 30cm, the anchor rod hole depth is 170cm, the anchoring length is 120cm, and the exposed length is 80cm. It is used as a temporary support and can also be used to hang the first steel mesh.

[0076] For example, the main supporting reinforcement of the first steel mesh 3 is made of Φ22 threaded steel with a longitudinal spacing of 20 cm, the distribution reinforcement is made of Φ14 threaded steel with a circumferential spacing of 25 cm, and the stirrups are made of φ8 round steel with a spacing of 25 cm.

[0077] In an optional implementation, reinforcing ribs (not shown) are provided on the first steel mesh 3. The reinforcing ribs are made of Φ14 threaded steel bars and are spaced apart relative to the supporting main bars of the first steel mesh.

[0078] It should be noted that the second steel mesh 4 includes a layer of steel mesh and a layer of anti-flame retardant plastic mesh for mining, and the anti-flame retardant plastic mesh for mining is located between the first steel mesh and the steel mesh. Exemplarily, the mesh size of the second steel mesh 4 is smaller than the mesh size of the first steel mesh 3. For example, the second steel mesh 4 uses Φ12 threaded steel with a longitudinal spacing of 10 cm, the distribution bars use Φ10 threaded steel with a circumferential spacing of 12 cm, and the stirrups use φ8 round steel with a spacing of 25 cm. Optionally, the anti-flame retardant plastic mesh for mining can be double-layered to reduce slurry leakage when spraying the first material.

[0079] S2. Spray the first material on the surface of the second steel mesh 4 to construct a support layer 5, and reserve grouting holes (not shown) on the support layer 5. The support layer 5 is used to provide high-strength and stable support for the tunnel.

[0080] Exemplarily, spraying the first material on the surface of the second steel mesh 4 to construct the support layer 5 includes: according to the preset weight proportions, for example, the first material in Preparation Example 1, taking 20 parts of cement, 20 parts of admixture, 5 parts of reinforcing fiber, 0.5 parts of water reducer, 2 parts of thixotropic agent, 80 parts of high-strength aggregate and 10 parts of water, and mixing them evenly to obtain a first concrete primary mix; then, when pumping the first concrete primary mix, pumping 3 parts of the accelerator and 1 part of the early strength agent into the pipeline 1-3m in front of the concrete spray gun; after being evenly mixed in the pipeline mixer, spraying them on the surface of the second steel mesh through the concrete spray gun to construct the support layer.

[0081] S3. After the supporting layer 5 is finally set, a second material is injected into the space between the supporting layer and the surface of the tunnel to be supported through the injection holes to construct a buffer layer 6, which is used to provide a buffer for the deformation and movement of the tunnel.

[0082] Optionally, the second material for constructing the buffer layer 6 can be a material with good elasticity and compressive strength, which can effectively absorb and disperse stress, such as lightweight foam concrete prepared with lightweight aggregate (such as expanded perlite, ceramsite or rubber particles), which can reduce the weight of the overall structure while providing a good buffering effect. Exemplarily, the second material is the second material provided in Preparation Example 10.

[0083] In this embodiment, the first material is first sprayed to form a support layer 5, and the material is provided with grouting holes after initial setting. Then, the second material is injected through the grouting holes to form a buffer layer 6. In this construction method, in the case of no buffer layer, the steel mesh in the second steel mesh 4 and the anti-flame retardant plastic mesh for mining are configured to form the pre-preparation for the spraying construction of the support layer 5, and then the support layer 5 is quickly sprayed to construct the support layer 5. Since the support layer 5 has a certain distance from the tunnel surface, the initial deformation of the tunnel will not produce excessive pressure on the support layer 5. Then, the buffer layer 6 is grouted, and the initial pressure-yielding support that effectively connects the anchor rod 2 and the buffer layer 6 is used to effectively utilize the bearing capacity of the surrounding rock, significantly improve the bearing capacity of the initial support, control the large deformation of the surrounding rock, and more effectively deal with the large deformation of the high-stress soft rock tunnel, ensure construction safety, and wet spraying construction can effectively improve construction efficiency compared to casting construction. At the same time, the buffer layer 6 constructed by the second material in Preparation Example 10 has high compressibility, high ductility and a certain bearing capacity. It can absorb the deformation energy generated by the surrounding rock after the support layer is applied under the reaction force provided by the support layer 5, and can produce a yield deformation of 100-150cm. In view of the unpredictable deformation load of high-stress soft rock formations, when the initial yield support produces a large deformation, the rubber particles of the buffer layer 6 can produce compression deformation under the support of the support layer 5. Under the combined effect of the bonding and connection of cement and anti-seepage fibers, the buffer layer can produce a certain compression deformation without cracking, absorbing the energy generated by the large deformation load of the surrounding rock without affecting its support performance. Similarly, the supporting layer constructed by the first material in Preparation Example 2 has excellent stress-strain capacity, that is, the second concrete material can support a large initial stress and has excellent deformation capacity; on the other hand, in addition to being able to withstand a relatively high pressure ≥120 MPa, the supporting layer 5 has good crack resistance due to the addition of a high amount of reinforcing fibers, so that the supporting layer 5 can remain in an unbroken state after being subjected to a pressure exceeding its own compressive strength, and can also effectively prevent the generation and expansion of cracks, thereby improving the support capacity.

[0084] In this implementation plan, a combination of "deformation reserve, first flexible then rigid, and support reinforcement" is used to effectively control the large deformation of soft rock, ensure the safety of tunnel construction, and significantly reduce construction risks. At the same time, wet spraying concrete is used to construct the support layer and grouting is used to form the buffer layer. While ensuring construction efficiency, the buffer layer can fill the gap between the support layer and the tunnel to resist part of the deformation pressure, and the support layer can achieve its reinforcement role, together forming a systematic support system for controlling the large deformation of the tunnel, so as to further effectively control the large deformation of soft rock. Example

[0085] Figure 2The schematic diagram of the support structure of the second tunnel support method based on high-stress soft rock and broken surrounding rock provided in Example 2 of the present application is shown. Figure 2 , a tunnel support method based on high-stress soft rock and broken surrounding rock, including the following steps: S1. After constructing anchor holes on the surface of the structure 1 to be supported and installing the anchors 2, a second steel mesh 4 is placed on the anchors 2. In other words, the second steel mesh 4 is fixed using the anchors 2.

[0086] For example, the surface of the structure 1 to be supported can be any one of a coal mine tunnel surface, a foundation pit surface, a highway tunnel, and a hydraulic tunnel. The following is an exemplary description using the coal mine tunnel surface as an example, but it should be understood that the present application is not limited thereto.

[0087] Exemplarily, the anchor rod 2 is a threaded steel anchor rod with a specification of Φ0.02×2.00m; one end of the anchor rod is threaded, the thread length is 30cm, the anchor rod hole depth is 170cm, the anchoring length is 120cm, and the exposed length is 80cm. It is used as a temporary support and can also be used to hang the first steel mesh.

[0088] It should be noted that the second steel mesh 4 includes a layer of steel mesh and a layer of anti-flame retardant plastic mesh for mining, and the anti-flame retardant plastic mesh for mining is located between the first steel mesh and the surface of the structure to be supported 1. Exemplarily, the second steel mesh 4 uses Φ12 threaded steel with a longitudinal spacing of 10 cm, the distribution bars use Φ10 threaded steel with a circumferential spacing of 12 cm, and the stirrups use φ8 round steel with a spacing of 25 cm. Optionally, the anti-flame retardant plastic mesh for mining can be double-layered to reduce slurry leakage when spraying the first material.

[0089] S2. Spray the first material on the surface of the second steel mesh 4 to construct a supporting layer 5, which is used to provide high-strength and stable support for the tunnel.

[0090] Exemplarily, spraying the first material on the surface of the second steel mesh 4 to construct the support layer 5 includes: according to preset weight proportions, for example, the first material in Preparation Example 1, taking 20 parts of cement, 20 parts of admixture, 5 parts of reinforcing fiber, 0.5 parts of water reducer, 2 parts of thixotropic agent, 80 parts of high-strength aggregate and 10 parts of water, and mixing them evenly to obtain a first concrete primary mix; then, when pumping the first concrete primary mix, pumping 3 parts of the accelerator and 1 part of the early strength agent into the pipeline 1-3m in front of the concrete spray gun; after being evenly mixed in the pipeline mixer, spraying them on the surface of the second steel mesh through the concrete spray gun to construct the support layer 5.

[0091] In this embodiment, compared with Example 1, the steps of constructing the first steel mesh 3 and the buffer layer 6 are missing. Therefore, for the tunnel support with small deformation, rapid support can be achieved while having better support stability. Construction personnel can flexibly choose the support method according to the deformation of the underground tunnel, which improves the applicability of the support method of this application. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application. Those of ordinary skill in the art should understand that although the present application is described in detail with reference to the aforementioned embodiments, it is still possible to modify the technical solutions described in the aforementioned embodiments, or to replace some of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions in the embodiments of this application.

Claims

1. A tunnel support method based on high-stress soft rock and broken surrounding rock, characterized in that: The following steps are involved: Anchor rods are constructed on the surface of the tunnel to be supported, and a first steel mesh and a second steel mesh are installed on the constructed anchor rods; wherein reinforcing ribs are arranged at intervals on the first steel mesh; the mesh size of the second steel mesh is smaller than the mesh size of the first steel mesh, and the second steel mesh includes a layer of steel mesh and a layer of anti-flame retardant plastic mesh for mining, and the anti-flame retardant plastic mesh for mining is located between the first steel mesh and the steel mesh; The first material is sprayed on the surface of the second steel mesh to construct a support layer, and grouting holes are reserved on the support layer, wherein the support layer is used to provide high-strength and stable support for the tunnel; After the supporting layer is finally set, grouting of a second material is performed between the supporting layer and the surface of the roadway to be supported through the grouting hole to construct a buffer layer, wherein the buffer layer is used to provide a buffer for the deformation and movement of the roadway; Among them, the first material includes the following components in parts by weight: 20-60 parts of cement, 20-40 parts of admixture, 5-15 parts of reinforcing fiber, 0.5-1.5 parts of water reducer, 1-5 parts of early strength agent, 2-4 parts of thixotropic agent, 80-120 parts of high-strength aggregate, 3-6 parts of accelerator and 10-30 parts of water; the accelerator includes polyaluminum sulfate, polyethyleneimine, diethanol monoisopropanolamine and modified nano-silica in a weight ratio of 50-55:4-6:2-5:1-3.

2. The support method according to claim 1, characterized in that: The preparation method of the modified nano silicon dioxide is as follows: Ultrasonic dispersion of 0.5 g of nano-silicon dioxide particles with a particle size of 1-20 nm in an aqueous solution of hexadecyltrimethylammonium bromide was performed for at least 30 minutes to obtain a nano-material dispersion; After adding alkali to the nanomaterial dispersion, tetraethyl silicate is slowly added dropwise, and the ratio of the added tetraethyl silicate to hexadecyltrimethylammonium bromide is 4ml-5ml:0.1g; ultrasonic reaction is carried out at 45 degrees for 24 hours to obtain a nano-silicon dioxide material suspension; Add silane coupling agent and polyvinyl alcohol to the nano-silicon dioxide material suspension, carry out ultrasonic reaction at 60-68°C for 1-2h, and centrifuge to obtain the solid phase to obtain modified nano-silicon dioxide; the weight ratio of the nano-silicon dioxide, silane coupling agent and polyvinyl alcohol is 1:5-8:3-6.

3. The support method according to claim 2, characterized in that: The ratio of tetraethyl silicate to hexadecyltrimethylammonium bromide is 4ml:0.1g.

4. The support method according to claim 2, characterized in that: The weight ratio of the nano silicon dioxide, the silane coupling agent and the polyvinyl alcohol is 1:5-6:5-6.

5. The support method according to claim 4, characterized in that: The weight ratio of the nano silicon dioxide, the silane coupling agent and the polyvinyl alcohol is 1:5:

5.

6. The support method according to claim 2, characterized in that: The base includes any one of triethylamine and triethanolamine.

7. The support method according to claim 1, characterized in that: The early strength agent comprises acyloxysilane, sodium thiosulfate and triethanolamine in a weight ratio of 2-4:3-4:2-4.

8. The support method according to claim 1, characterized in that: The method of spraying the first material on the surface of the second steel mesh to construct a supporting layer includes: According to the preset weight proportions, 20-60 parts of cement, 20-40 parts of admixture, 5-15 parts of reinforcing fiber, 0.5-1.5 parts of water reducer, 2-4 parts of thixotropic agent, 80-120 parts of high-strength aggregate and 10-30 parts of water are mixed evenly to obtain the first concrete primary mix; subsequently, when pumping the first concrete primary mix, 3-6 parts of the accelerator and 1-5 parts of the early strength agent are pumped into the pipeline 1-3m in front of the concrete spray gun; after being evenly mixed in the pipeline mixer, they are sprayed on the surface of the second steel mesh through the concrete spray gun to construct a support layer.

9. A tunnel support method based on high-stress soft rock and broken surrounding rock, characterized in that: The following steps are involved: Anchor rods are constructed on the surface of the tunnel to be supported and a second steel mesh is installed on the constructed anchor rods; wherein the second steel mesh comprises a layer of steel mesh and a layer of anti-flame retardant plastic mesh for mining, and the anti-flame retardant plastic mesh for mining is located between the first steel mesh and the surface of the tunnel to be supported; A first material is sprayed on the surface of the second steel mesh to construct a support layer, which is used to provide high-strength and stable support for the tunnel; wherein the first material includes the following components in parts by weight: 20-60 parts of cement, 20-40 parts of admixture, 5-15 parts of reinforcing fiber, 0.5-1.5 parts of water reducer, 1-5 parts of early strength agent, 2-4 parts of thixotropic agent, 80-120 parts of high-strength aggregate, 3-6 parts of accelerator and 10-30 parts of water; the accelerator includes polyaluminum sulfate, polyethyleneimine, diethanol monoisopropanolamine and modified nano-silica in a weight ratio of 50-55:4-6:2-5:1-3.

10. A tunnel support material based on high-stress soft rock and broken surrounding rock, characterized in that: The invention comprises a first material, which comprises the following components in parts by weight: 20-60 parts of cement, 20-40 parts of admixture, 5-15 parts of reinforcing fiber, 0.5-1.5 parts of water reducer, 1-5 parts of early strength agent, 2-4 parts of thixotropic agent, 80-120 parts of high-strength aggregate, 3-6 parts of accelerating agent and 10-30 parts of water; the accelerating agent comprises polyaluminium sulfate, polyethyleneimine, diethanol monoisopropanolamine and modified nano-silica in a weight ratio of 50-55:4-6:2-5:1-3.

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