Water-rich tunnel shotcrete and preparation method and application thereof

Abstract

This invention relates to the field of shotcrete preparation, specifically to a water-rich tunnel shotcrete, its preparation method, and its application. The water-rich tunnel shotcrete is mainly prepared from cement, fly ash, nano-silica powder, sand, small stones, modified polypropylene multi-anchor fiber, accelerator, water-reducing agent, and water. By adding specific accelerators, nano-silica powder, and modified polypropylene multi-anchor fiber to the raw materials and adjusting the raw material ratio accordingly, the concrete provided by this invention can still achieve a smooth and flat surface, rapid strength development, good integrity, and no spalling issues even when facing a large flow of flowing water on the rock surface, making it easy to promote and apply.

Description

Technical Field

[0001] This invention relates to the technical field of shotcrete, specifically to a shotcrete method for preparing water-rich tunnels and its application. Background Technology

[0002] The geological conditions of a certain highway tunnel are complex, with high-grade surrounding rock. During the tunnel excavation, a large water flow occurred at the excavation section, and the diversion was difficult. When shotcreting the tunnel rock surface, conventional shotcreting was used. However, under the action of water erosion (the rock mass has well-developed joints and fissures, and the diameter of the water flow is ≤3cm), the shotcreting had poor adhesion to the rock mass, a large rebound, and severe spalling after the first shotcreting. The integrity of the initial shotcreting was poor, and even after multiple re-sprayings, there was still severe local spalling. This not only affected the appearance of the tunnel concrete but also the quality of the tunnel.

[0003] Therefore, when applying shotcrete to rock surfaces eroded by a large amount of flowing water, it is of great significance to develop a shotcrete that can stably adhere to the rock surface and reduce or avoid the need for re-spraying. Summary of the Invention

[0004] The purpose of this invention is to address the problem of poor spraying effect and severe spalling when applying shotcrete to rock surfaces eroded by large volumes of flowing water in existing technologies. This invention provides a water-rich tunnel shotcrete, its preparation method, and its application. The concrete provided by this invention can still achieve a smooth and flat shotcrete surface without spalling even when facing rock surfaces with large volumes of flowing water.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A water-rich tunnel shotcrete, comprising the following raw materials by weight: 380-409 parts cement, 46-60 parts fly ash, 18-22 parts nano-silica powder, 910-920 parts sand, 740-750 parts aggregate, 38-42 parts modified polypropylene multi-anchor fiber, 26-30 parts quick-setting agent, 6-8 parts water-reducing agent, and 180-190 parts water.

[0007] The quick-setting agent comprises, by weight, the following raw materials: 40-50 parts aluminum sulfate octadechydrate, 5-10 parts amorphous nano alumina, 1-3 parts calcium sulfate, 0.5-1 part EDTA, 1-5 parts triethanolamine, 10-15 parts sulfuric acid solution, 5-10 parts nitric acid solution, 3-5 parts formic acid, 5-10 parts aluminum nitrate, and 20-50 parts water.

[0008] The initial setting time of the accelerator is ≤4 min, and the final setting time is ≤7 min;

[0009] The nano-silicon powder contains ≥95% SiO2, has an average particle size ≤0.1μm, and a specific surface area ≥18000m². 2 / kg, water requirement ratio ≤105%;

[0010] The modified polypropylene multi-anchor fiber is a modified polypropylene (PP) fiber with indentations on its surface, with a specific gravity of 0.90-0.98 g / cm³. 3 Length: 20-30mm; Diameter ≥ 0.15mm; Tensile strength ≥ 450MPa; Alkali resistance ≥ 96%.

[0011] The water-rich tunnel shotcrete provided by this invention is mainly prepared from cement, fly ash, nano-silica powder, sand, small stones, modified polypropylene multi-anchor fiber, accelerator, water-reducing agent and water. By adding specific accelerator, nano-silica powder of specific specifications and modified polypropylene multi-anchor fiber of specific specifications to the raw materials and by specifically adjusting the raw material ratio, the concrete provided by this invention can still achieve a relatively smooth and flat shotcrete surface, rapid strength development, good integrity and no problem of sharding when facing a large flow of water on the rock surface, which is convenient for promotion and application.

[0012] Experimental investigations revealed that altering the properties of the quick-setting agent, the specifications of the nano-silica powder, and the specific specifications of the modified polypropylene multi-anchor fiber all resulted in concrete that could not meet the spraying effect required for rock surfaces subjected to large volumes of flowing water.

[0013] The quick-setting agent provided in this application is mainly prepared from aluminum sulfate octadecahydrate, amorphous nano alumina, calcium sulfate, EDTA, triethanolamine, sulfuric acid, nitric acid, formic acid, aluminum nitrate and water. The prepared quick-setting agent has the effects of rapid setting, early strength and toughening, which can reduce the setting time of concrete, increase the bridging between hydration products and promote early strength development.

[0014] The nano-silica powder added to the raw materials of this application can increase the viscosity and microstructure density of concrete, and enhance its bonding performance with rock mass.

[0015] The modified polypropylene multi-anchor fiber added to the raw materials of this application can improve the tensile strength and toughness of concrete, enhance the integrity of concrete, and prevent local water flow from eroding and collapsing into pieces.

[0016] Furthermore, the concrete, by weight, comprises the following raw materials: 395-409 parts cement, 55-60 parts fly ash, 20-22 parts nano-silica powder, 915-920 parts sand, 745-750 parts aggregate, 40-42 parts modified polypropylene multi-anchor fiber, 27-30 parts accelerator, 6-8 parts water-reducing agent, and 180-185 parts water. Research has found that when the specific accelerator, nano-silica powder, and modified polypropylene multi-anchor fiber exceed the formulation range provided in this application, the concrete quality significantly decreases. Only through the synergistic interaction of the various raw materials can the water-rich tunnel shotcrete effect of this application be achieved.

[0017] Furthermore, the quick-setting agent comprises, by weight, the following raw materials: 44-48 parts aluminum sulfate octadechydrate, 6-8 parts amorphous nano alumina, 2-3 parts calcium sulfate, 0.8-1 parts EDTA, 2-4 parts triethanolamine, 12-15 parts sulfuric acid solution, 6-8 parts nitric acid solution, 3-5 parts formic acid, 6-8 parts aluminum nitrate, and 30-45 parts water.

[0018] Furthermore, the sulfuric acid solution is an aqueous solution with a concentration of 0.15–0.3 mol / L; the nitric acid solution is an aqueous solution with a concentration of 0.8–1.5 mol / L.

[0019] Furthermore, the accelerator is prepared using the following steps:

[0020] S1. Mix sulfuric acid, nitric acid and formic acid, stir evenly, heat in a water bath to 75℃~85℃, add amorphous nano alumina and aluminum nitrate, stir for 30~60min, filter to remove residue, cool to room temperature to obtain sulfoaluminate complex.

[0021] S2. Heat water to 75℃~85℃, and slowly add aluminum sulfate octadecahydrate and the sulfoaluminate complex obtained in S1 under stirring, stirring until the solution is basically clear;

[0022] S3. Under stirring conditions, calcium sulfate and EDTA are slowly added to the material obtained in S2, and stirring is continued for 30 to 60 minutes.

[0023] S4. Add triethanolamine to the material obtained in S3, stir for 10-20 minutes, and let it stand and cool to room temperature to obtain the quick-setting agent.

[0024] Furthermore, the fineness modulus of the sand is 2.7-3.1, and the stone powder content is ≤7%; the particle size of the small stones is 5-10 cm; and the water-reducing agent is a high-performance polycarboxylate water-reducing agent. Preferably, the sand is manufactured sand.

[0025] Another object of the present invention is to provide a method for preparing the above-mentioned water-rich tunnel shotcrete.

[0026] The preparation method of shotcrete for water-rich tunnels as described above includes the following steps:

[0027] Step 1: Mix sand, small stones, cement, fly ash, modified polypropylene multi-anchor fiber and nano-micro silica powder evenly to obtain the first material;

[0028] Step 2: Add water and water-reducing agent to the first material, stir and mix evenly to obtain the second material;

[0029] Step 3: Before spraying, add an accelerator to the second material to obtain water-rich tunnel sprayed concrete.

[0030] This application provides a method for preparing water-rich shotcrete, which mainly includes step 1: mixing sand, small stones, cement, fly ash, modified polypropylene multi-anchor fiber and nano-microsilica powder evenly to obtain a first material; step 2: adding water and water-reducing agent to the first material and mixing evenly to obtain a second material; step 3: adding an accelerator to the second material before spraying to obtain water-rich tunnel shotcrete; the preparation process is simple and the cost is low.

[0031] Another objective of this invention is to improve the application of shotcrete in water-rich tunnels.

[0032] The application of the above-mentioned water-rich tunnel shotcrete on the surface of rock mass eroded by jet water flow.

[0033] Furthermore, the diameter of the streams of water on the rock surface is ≤3cm. Even further, the diameter of the streams of water on the rock surface is 1–3cm.

[0034] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0035] 1. The water-rich tunnel shotcrete provided by this invention is mainly prepared from cement, fly ash, nano-silica powder, sand, small stones, modified polypropylene multi-anchor fiber, accelerator, water-reducing agent and water. By adding specific accelerator, specific specifications of nano-silica powder and specific specifications of modified polypropylene multi-anchor fiber to the raw materials and adjusting the raw material ratio accordingly, the concrete provided by this invention can still achieve a relatively smooth and flat shotcrete surface, fast strength development, good integrity and no problem of sharding when facing a large flow of water on the rock surface, which is convenient for promotion and application.

[0036] 2. The accelerator provided in this application is mainly prepared from aluminum sulfate octadecahydrate, amorphous nano-alumina, calcium sulfate, EDTA, triethanolamine, sulfuric acid, nitric acid, formic acid, aluminum nitrate, and water. The prepared accelerator has the effects of rapid setting, early strength, and toughening, reducing concrete setting time, increasing the bridging between hydration products, and promoting early strength development. Nano-silica powder can increase the viscosity and microstructure density of concrete, enhancing its bonding performance with rock mass. Modified polypropylene multi-anchor fiber can improve the tensile strength and toughness of concrete, enhance the integrity of concrete, and prevent localized water erosion and spalling.

[0037] 3. This application provides a method for preparing water-rich shotcrete, which mainly includes step 1: mixing sand, small stones, cement, fly ash, modified polypropylene multi-anchor fiber and nano-microsilica powder evenly to obtain a first material; step 2: adding water and water-reducing agent to the first material and mixing evenly to obtain a second material; step 3: adding an accelerator to the second material before spraying to obtain water-rich tunnel shotcrete; the preparation process is simple and the cost is low.

[0038] 4. The present invention also provides the application of water-rich tunnel shotcrete on the surface of rock mass under the scouring of jet water flow. Attached Figure Description

[0039] Figure 1 This is a diagram showing the state of the concrete prepared in Example 1 after spraying rock.

[0040] Figure 2 This is a diagram showing the state of the concrete prepared in Example 2 after spraying rock.

[0041] Figure 3 This is a state diagram of the test spraying of water-bearing rock with concrete prepared in Example 3. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings.

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0044] In the following examples, the specifications and sources of each raw material are as follows:

[0045] Nano-silica powder: SiO2 content ≥95%, average particle size ≤0.1μm, specific surface area ≥18000m² 2 / kg, water requirement ratio ≤105%; Purchaser: Chengdu Donglanxing New Materials Co., Ltd.

[0046] Modified polypropylene multi-anchor fiber is a modified polypropylene (PP) fiber with indentations on its surface, with a specific gravity of 0.90-0.98 g / cm³. 3 Length: 20-30mm; Diameter ≥ 0.15mm; Tensile strength ≥ 450MPa; Alkali resistance ≥ 96%. Shiweike PPD12.

[0047] The fineness modulus of the sand is 2.7-3.1, and the stone powder content is ≤7%; the particle size of the small stones is 5-10cm; the water-reducing agent is a high-performance polycarboxylate water-reducing agent.

[0048] Example 1

[0049] quick-setting agent

[0050] 44 parts aluminum sulfate octadechydrate, 8 parts amorphous nano alumina, 3 parts calcium sulfate, 1 part EDTA, 4 parts triethanolamine, 15 parts sulfuric acid solution with a concentration of 0.2 mol / L, 8 parts nitric acid solution with a concentration of 1.2 mol / L, 5 parts formic acid, 8 parts aluminum nitrate, and 30 parts water.

[0051] S1. Mix sulfuric acid, nitric acid and formic acid, stir evenly, heat in a water bath to 80°C, add amorphous nano alumina and aluminum nitrate, stir for 45 min, filter to remove residue, cool to room temperature, and obtain sulfoaluminate complex.

[0052] S2. Heat water to 80°C, and slowly add aluminum sulfate octadecahydrate and the sulfoaluminate complex obtained in S1 under stirring, stirring until the solution is basically clear;

[0053] S3. Under stirring conditions, calcium sulfate and EDTA are slowly added to the material obtained in S2, and stirring is continued for 45 minutes.

[0054] S4. Add triethanolamine to the material obtained in S3, stir for 15 minutes, and let it stand and cool to room temperature to obtain the quick-setting agent.

[0055] Shotcrete for water-rich tunnels

[0056] 400 parts cement, 58 parts fly ash, 21 parts nano-silica powder, 918 parts sand, 748 parts small stones, 41 parts modified polypropylene multi-anchor fiber, 28 parts quick-setting agent, 7 parts water-reducing agent, and 182 parts water.

[0057] Step 1: Mix sand, small stones, cement, fly ash, modified polypropylene multi-anchor fiber and nano-micro silica powder evenly to obtain the first material;

[0058] Step 2: Add water and water-reducing agent to the first material, stir and mix evenly to obtain the second material;

[0059] Step 3: Before spraying, add an accelerator to the second material to obtain water-rich tunnel sprayed concrete.

[0060] The trial-mixed concrete was molded into a large slab and cut into 100mm cube specimens to test its early strength. The test results were as follows: the compressive strength at 1 day was 13.5 MPa, the compressive strength at 3 days was 26.7 MPa, and the compressive strength at 7 days was 39.2 MPa.

[0061] Example 2

[0062] quick-setting agent

[0063] 48 parts aluminum sulfate octadechydrate, 6 parts amorphous nano alumina, 2 parts calcium sulfate, 0.8 parts EDTA, 2 parts triethanolamine, 12 parts sulfuric acid solution with a concentration of 0.25 mol / L, 6 parts nitric acid solution with a concentration of 1.0 mol / L, 3 parts formic acid, 6 parts aluminum nitrate, and 45 parts water.

[0064] S1. Mix sulfuric acid, nitric acid and formic acid, stir evenly, heat in a water bath to 85°C, add amorphous nano alumina and aluminum nitrate, stir for 30 min, filter to remove residue, cool to room temperature, and obtain sulfoaluminate complex.

[0065] S2. Heat water to 85°C, and slowly add aluminum sulfate octadecahydrate and the sulfoaluminate complex obtained in S1 under stirring, stirring until the solution is basically clear;

[0066] S3. Under stirring conditions, calcium sulfate and EDTA are slowly added to the material obtained in S2, and stirring is continued for 30 minutes.

[0067] S4. Add triethanolamine to the material obtained in S3, stir for 10 minutes, and let it stand and cool to room temperature to obtain the quick-setting agent.

[0068] Shotcrete for water-rich tunnels

[0069] 402 parts cement, 57 parts fly ash, 21 parts nano-silica powder, 916 parts sand, 747 parts small stones, 41 parts modified polypropylene multi-anchor fiber, 28 parts quick-setting agent, 7 parts water-reducing agent, and 184 parts water.

[0070] Step 1: Mix sand, small stones, cement, fly ash, modified polypropylene multi-anchor fiber and nano-micro silica powder evenly to obtain the first material;

[0071] Step 2: Add water and water-reducing agent to the first material, stir and mix evenly to obtain the second material;

[0072] Step 3: Before spraying, add an accelerator to the second material to obtain water-rich tunnel sprayed concrete.

[0073] The trial-mixed concrete was molded into a large slab and cut into 100mm cube specimens to test its early strength. The test results were as follows: the compressive strength at 1 day was 13.1 MPa, the compressive strength at 3 days was 25.4 MPa, and the compressive strength at 7 days was 37.4 MPa.

[0074] Example 3

[0075] quick-setting agent

[0076] 40 parts aluminum sulfate octadechydrate, 10 parts amorphous nano alumina, 3 parts calcium sulfate, 1 part EDTA, 5 parts triethanolamine, 15 parts sulfuric acid solution with a concentration of 0.15 mol / L, 10 parts nitric acid solution with a concentration of 0.8 mol / L, 5 parts formic acid, 10 parts aluminum nitrate, and 50 parts water.

[0077] S1. Mix sulfuric acid, nitric acid and formic acid, stir evenly, heat in a water bath to 75°C, add amorphous nano alumina and aluminum nitrate, stir for 60 min, filter to remove residue, cool to room temperature, and obtain sulfoaluminate complex.

[0078] S2. Heat water to 75°C, and slowly add aluminum sulfate octadecahydrate and the sulfoaluminate complex obtained in S1 under stirring, stirring until the solution is basically clear;

[0079] S3. Under stirring conditions, calcium sulfate and EDTA are slowly added to the material obtained in S2, and stirring is continued for 60 minutes.

[0080] S4. Add triethanolamine to the material obtained in S3, stir for 20 minutes, and let it stand and cool to room temperature to obtain the quick-setting agent.

[0081] Shotcrete for water-rich tunnels

[0082] 380 parts cement, 60 parts fly ash, 22 parts nano-silica powder, 920 parts sand, 750 parts small stones, 42 parts modified polypropylene multi-anchor fiber, 30 parts quick-setting agent, 8 parts water-reducing agent; 190 parts water.

[0083] Step 1: Mix sand, small stones, cement, fly ash, modified polypropylene multi-anchor fiber and nano-micro silica powder evenly to obtain the first material;

[0084] Step 2: Add water and water-reducing agent to the first material, stir and mix evenly to obtain the second material;

[0085] Step 3: Before spraying, add an accelerator to the second material to obtain water-rich tunnel sprayed concrete.

[0086] The trial-mixed concrete was molded into a large slab and cut into 100mm cube specimens to test its early strength. The test results were as follows: the compressive strength at 1 day was 12.3 MPa, the compressive strength at 3 days was 29.1 MPa, and the compressive strength at 7 days was 36.9 MPa.

[0087] Example 4

[0088] quick-setting agent

[0089] 50 parts aluminum sulfate octadechydrate, 5 parts amorphous nano alumina, 1 part calcium sulfate, 0.5 parts EDTA, 1 part triethanolamine, 10 parts sulfuric acid solution with a concentration of 0.3 mol / L, 5 parts nitric acid solution with a concentration of 1.5 mol / L, 3 parts formic acid, 5 parts aluminum nitrate, and 20 parts water.

[0090] S1. Mix sulfuric acid, nitric acid and formic acid, stir evenly, heat in a water bath to 85°C, add amorphous nano alumina and aluminum nitrate, stir for 50 min, filter to remove residue, cool to room temperature, and obtain sulfoaluminate complex.

[0091] S2. Heat water to 80°C, and slowly add aluminum sulfate octadecahydrate and the sulfoaluminate complex obtained in S1 under stirring, stirring until the solution is basically clear;

[0092] S3. Under stirring conditions, calcium sulfate and EDTA are slowly added to the material obtained in S2, and stirring is continued for 45 minutes.

[0093] S4. Add triethanolamine to the material obtained in S3, stir for 15 minutes, and let it stand and cool to room temperature to obtain the quick-setting agent.

[0094] Shotcrete for water-rich tunnels

[0095] 409 parts cement, 46 parts fly ash, 18 parts nano-silica powder, 910 parts sand, 740 parts small stones, 38 parts modified polypropylene multi-anchor fiber, 26 parts quick-setting agent, 6 parts water-reducing agent; 180 parts water.

[0096] Step 1: Mix sand, small stones, cement, fly ash, modified polypropylene multi-anchor fiber and nano-micro silica powder evenly to obtain the first material;

[0097] Step 2: Add water and water-reducing agent to the first material, stir and mix evenly to obtain the second material;

[0098] Step 3: Before spraying, add an accelerator to the second material to obtain water-rich tunnel sprayed concrete.

[0099] The trial-mixed concrete was molded into a large slab and cut into 100mm cube specimens to test its early strength. The test results were as follows: the compressive strength at 1 day was 12.8 MPa, the compressive strength at 3 days was 31.8 MPa, and the compressive strength at 7 days was 37.5 MPa.

[0100] Comparative Example 1

[0101] Comparative Example 1 improved the concrete properties compared to Example 1, which replaced the ordinary quick-setting agent. All other concrete materials, additive ratios, and preparation processes were the same as in Example 1, as detailed below:

[0102] The common quick-setting agent used is the commercially available ZY98 type quick-setting agent.

[0103] Shotcrete for water-rich tunnels

[0104] 400 parts cement, 58 parts fly ash, 21 parts nano-silica powder, 918 parts sand, 748 parts small stones, 41 parts modified polypropylene multi-anchor fiber, 28 parts ordinary quick-setting agent, 7 parts water-reducing agent, and 182 parts water.

[0105] Step 1: Mix sand, small stones, cement, fly ash, modified polypropylene multi-anchor fiber and nano-micro silica powder evenly to obtain the first material;

[0106] Step 2: Add water and water-reducing agent to the first material, stir and mix evenly to obtain the second material;

[0107] Step 3: Before spraying, add an accelerator to the second material to obtain water-rich tunnel sprayed concrete.

[0108] Comparative Example 2

[0109] The concrete provided in Comparative Example 2 did not contain the accelerator provided in this application, unlike that in Example 1.

[0110] Shotcrete for water-rich tunnels

[0111] 400 parts cement, 58 parts fly ash, 21 parts nano-silica powder, 918 parts sand, 748 parts small stones, 41 parts modified polypropylene multi-anchor fiber, 7 parts water-reducing agent, and 182 parts water.

[0112] Step 1: Mix sand, gravel, cement, fly ash, modified polypropylene multi-anchor fiber and nano-silica powder evenly to obtain the first material.

[0113] Step 2: Add water and water-reducing agent to the first material, stir and mix evenly to obtain water-rich tunnel shotcrete.

[0114] Comparative Example 3

[0115] The concrete provided in Comparative Example 3 did not contain nano-silica powder, unlike that provided in Example 1.

[0116] quick-setting agent

[0117] 44 parts aluminum sulfate octadechydrate, 8 parts amorphous nano alumina, 3 parts calcium sulfate, 1 part EDTA, 4 parts triethanolamine, 15 parts sulfuric acid solution with a concentration of 0.2 mol / L, 8 parts nitric acid solution with a concentration of 1.2 mol / L, 5 parts formic acid, 8 parts aluminum nitrate, and 30 parts water.

[0118] S1. Mix sulfuric acid, nitric acid and formic acid, stir evenly, heat in a water bath to 80°C, add amorphous nano alumina and aluminum nitrate, stir for 45 min, filter to remove residue, cool to room temperature, and obtain sulfoaluminate complex.

[0119] S2. Heat water to 80°C, and slowly add aluminum sulfate octadecahydrate and the sulfoaluminate complex obtained in S1 under stirring, stirring until the solution is basically clear;

[0120] S3. Under stirring conditions, calcium sulfate and EDTA are slowly added to the material obtained in S2, and stirring is continued for 45 minutes.

[0121] S4. Add triethanolamine to the material obtained in S3, stir for 15 minutes, and let it stand and cool to room temperature to obtain the quick-setting agent.

[0122] Shotcrete for water-rich tunnels

[0123] 400 parts cement, 58 parts fly ash, 918 parts sand, 748 parts small stones, 41 parts modified polypropylene multi-anchor fiber, 28 parts quick-setting agent, 7 parts water-reducing agent, and 182 parts water.

[0124] Step 1: Mix sand, gravel, cement, fly ash, and modified polypropylene multi-anchor fiber evenly to obtain the first material.

[0125] Step 2: Add water and water-reducing agent to the first material, stir and mix evenly to obtain the second material;

[0126] Step 3: Before spraying, add an accelerator to the second material to obtain water-rich tunnel sprayed concrete.

[0127] Comparative Example 4

[0128] The concrete provided in Comparative Example 4 did not contain modified polypropylene multi-anchor fiber as in Example 1.

[0129] quick-setting agent

[0130] 44 parts aluminum sulfate octadechydrate, 8 parts amorphous nano alumina, 3 parts calcium sulfate, 1 part EDTA, 4 parts triethanolamine, 15 parts sulfuric acid solution with a concentration of 0.2 mol / L, 8 parts nitric acid solution with a concentration of 1.2 mol / L, 5 parts formic acid, 8 parts aluminum nitrate, and 30 parts water.

[0131] S1. Mix sulfuric acid, nitric acid and formic acid, stir evenly, heat in a water bath to 80°C, add amorphous nano alumina and aluminum nitrate, stir for 45 min, filter to remove residue, cool to room temperature, and obtain sulfoaluminate complex.

[0132] S2. Heat water to 80°C, and slowly add aluminum sulfate octadecahydrate and the sulfoaluminate complex obtained in S1 under stirring, stirring until the solution is basically clear;

[0133] S3. Under stirring conditions, calcium sulfate and EDTA are slowly added to the material obtained in S2, and stirring is continued for 45 minutes.

[0134] S4. Add triethanolamine to the material obtained in S3, stir for 15 minutes, and let it stand and cool to room temperature to obtain the quick-setting agent.

[0135] Shotcrete for water-rich tunnels

[0136] 400 parts cement, 58 parts fly ash, 21 parts nano-silica powder, 918 parts sand, 748 parts small stones, 28 parts quick-setting agent, 7 parts water-reducing agent, and 182 parts water.

[0137] Step 1: Mix sand, gravel, cement, fly ash and nano-silica powder evenly to obtain the first material;

[0138] Step 2: Add water and water-reducing agent to the first material, stir and mix evenly to obtain the second material;

[0139] Step 3: Before spraying, add an accelerator to the second material to obtain water-rich tunnel sprayed concrete.

[0140] test

[0141] Select multiple 1m blocks 2 The surface of the rock mass was washed by water of different sizes, with the diameter of the water stream on the rock mass surface being 2.5 cm. The same volume of concrete prepared in Examples 1-4 and Comparative Examples 1-4 (test volume of 1 cm thickness) was sprayed onto the surface of the rock mass.

[0142] Table 1. Rock Mass Shotcrete Test

[0143] Example 1 The sprayed concrete surface is relatively smooth and flat, without any loose pieces. Example 2 The sprayed concrete surface is relatively smooth and flat, without any loose pieces. Example 3 The sprayed concrete surface is relatively smooth and flat, without any loose pieces. Example 4 The sprayed concrete surface is relatively smooth and flat, without any loose pieces. Comparative Example 1 The concrete surface has poor smoothness, with obvious spalling. Comparative Example 2 The concrete surface has poor smoothness, with obvious spalling. Comparative Example 3 The concrete surface has poor smoothness, with obvious spalling. Comparative Example 4 The concrete surface has poor smoothness, with obvious spalling.

[0144] The test results from Examples 1-4 show that the shotcrete for water-rich tunnels exhibits good workability and cohesiveness. Compared with ordinary shotcrete, the shotcrete for water-rich tunnels effectively reduces the rebound of the slurry during construction, which not only improves the working environment but also increases the economic efficiency of the material. Furthermore, due to its excellent bonding properties, the shotcrete for water-rich tunnels can achieve a higher single-layer spraying thickness, thereby improving production efficiency. After spraying, the shotcrete for water-rich tunnels is evenly distributed on the tunnel surface, dense, with a clear and straight appearance, a smooth and clean surface, and a consistent color, without any spalling, cracks, peeling, hollow areas, or leakage.

[0145] Tests conducted in Examples 1-4 revealed that ordinary shotcrete exhibits problems during construction, including spalling, grout leakage, bleeding, and a high rebound rate. After spraying, the tunnel surface is relatively rough and uneven, with some areas showing exposed rebar, hollow areas, and water leakage. These problems not only affect construction quality but may also impact the tunnel's usability and safety.

[0146] As can be seen from the test results in Table 1, the water-rich tunnel shotcrete provided by this invention in Examples 1-4 still achieves a relatively smooth and flat shotcrete surface without spalling, even when facing a large flow of flowing water on the rock surface. Changing the formula provided by this invention will significantly reduce the technical effect of the concrete.

[0147] Among them, such as Figure 1 and Figure 2 As shown, areas with severe local spalling, exposed rebar, and water seepage were selected for re-spraying. After re-spraying with concrete prepared in Examples 1 and 2 respectively, the exposed rebar areas were filled densely and the surface was smooth.

[0148] like Figure 3 As shown, a representative water-rushing stage was selected for test spraying. The dark area represents the effect of the previous stage of shotcrete construction, with poor surface smoothness and obvious local defects such as spalling and exposed reinforcement at the arch. The light area represents the test section, where the surface is relatively smooth and flat, and there is no obvious spalling at the arch except for the local areas of gushing water.

[0149] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A type of shotcrete for water-rich tunnels, characterized in that, It is prepared from the following raw materials in parts by weight. 395-409 parts cement, 55-60 parts fly ash, 20-22 parts nano-silica powder, 915-920 parts sand, 745-750 parts small stone, 40-42 parts modified polypropylene multi-anchor fiber, 27-30 parts quick-setting agent, 6-8 parts water-reducing agent, and 180-185 parts water. The quick-setting agent comprises, by weight, the following raw materials: 44-48 parts aluminum sulfate octadechydrate, 6-8 parts amorphous nano alumina, 2-3 parts calcium sulfate, 0.8-1 parts EDTA, 2-4 parts triethanolamine, 12-15 parts sulfuric acid solution, 6-8 parts nitric acid solution, 3-5 parts formic acid, 6-8 parts aluminum nitrate, and 30-45 parts water. The quick-setting agent is prepared by the following steps: S1. Mix sulfuric acid solution, nitric acid solution and formic acid, stir evenly, heat in a water bath to 75℃~85℃, add amorphous nano alumina and aluminum nitrate, stir for 30~60min, filter to remove residue, cool to room temperature to obtain sulfoaluminate complex. S2. Heat water to 75℃~85℃, and slowly add aluminum sulfate octadecahydrate and the sulfoaluminate complex obtained in S1 under stirring, stirring until the solution is basically clear; S3. Under stirring conditions, calcium sulfate and EDTA are slowly added to the material obtained in S2, and stirring is continued for 30 to 60 minutes. S4. Add triethanolamine to the material obtained in S3, stir for 10-20 minutes, and let stand and cool to room temperature to obtain the quick-setting agent. The initial setting time of the accelerator is ≤4 min, and the final setting time is ≤7 min; The nano-silicon powder contains ≥95% SiO2, has an average particle size ≤0.1μm, and a specific surface area ≥18000m². 2 / kg, water requirement ratio ≤105%; The modified polypropylene multi-anchor fiber is a modified polypropylene (PP) fiber with indentations on its surface, with a specific gravity of 0.90-0.98 g / cm³. 3 Length: 20-30mm; Diameter ≥ 0.15mm; Tensile strength ≥ 450MPa; Alkali resistance ≥ 96%.

2. The water-rich tunnel shotcrete according to claim 1, characterized in that, The sulfuric acid solution is an aqueous solution with a concentration of 0.15–0.3 mol / L; the nitric acid solution is an aqueous solution with a concentration of 0.8–1.5 mol / L.

3. The water-rich tunnel shotcrete according to any one of claims 1-2, characterized in that: The fineness modulus of the sand is 2.7-3.1, and the stone powder content is ≤7%; the particle size of the small stones is 5-10cm; the water-reducing agent is a high-performance polycarboxylate water-reducing agent.

4. The method for preparing shotcrete for water-rich tunnels as described in any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Mix sand, small stones, cement, fly ash, modified polypropylene multi-anchor fiber and nano-micro silica powder evenly to obtain the first material; Step 2: Add water and water-reducing agent to the first material, stir and mix evenly to obtain the second material; Step 3: Before spraying, add an accelerator to the second material to obtain water-rich tunnel sprayed concrete.

5. The application of water-rich tunnel shotcrete as described in any one of claims 1-4 on the surface of rock mass eroded by jet water flow.

6. The application according to claim 5, characterized in that, The diameter of the streams of water on the rock surface is ≤3cm.

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