A synchronous grouting material for a coastal area shield tunnel and a preparation method thereof

Abstract

This invention discloses a synchronous grouting material for shield tunnels in coastal areas and its preparation method. The synchronous grouting material for shield tunnels in coastal areas comprises the following raw materials in parts by weight: 20-40 parts cement, 10-25 parts steel slag powder, 80-120 parts shield excavated soil, 15-35 parts phosphogypsum, 120-150 parts unpurified sea sand, 4-6 parts early-strength agent, 1-3 parts conditioning agent, and 100-125 parts mixing water. The amount of shield excavated soil is based on its weight excluding water, and the amount of mixing water includes the water content of the shield excavated soil. This invention makes full use of coastal resources and the excavated soil generated during shield tunneling as raw materials. With the use of other raw materials, it significantly reduces the amount of cement and river sand used, disposes of construction waste, thereby reducing costs and realizing the green and low-carbon production of synchronous grouting materials.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of grouting materials, and particularly relates to a synchronous grouting material for a coastal area shield tunnel and a preparation method thereof. BACKGROUND

[0002] With the continuous rise of the total economy of coastal cities and the continuous expansion of the built-up area, rail transit has become an important means to optimize the layout of urban structure and relieve traffic congestion. At present, the fifth phase of Shenzhen rail transit, the fourth phase of Guangzhou subway and the fourth phase of Shanghai subway have been approved for planning and will soon start construction.

[0003] The shield method is a fully mechanized construction method in which the surrounding rock is supported by a shield shell, the soil is excavated in front of the excavation face by a cutting device, the jacks are pressed in the rear part, and the prefabricated concrete segments are assembled to form a tunnel structure. With its safety and high efficiency, the shield method has become the main method for urban subway construction. During the tunneling process of the shield machine, the segment assembly is carried out in the shield shell. After the segment is out of the shield tail, there is a certain gap between the segment and the stratum. If synchronous grouting is not carried out in time, problems such as segment floating, segment misalignment and tunnel top stratum subsidence will occur. At present, the synchronous grouting material mostly uses conventional cement mortar, which uses a large amount of cement and river sand, which are non-renewable resources. The carbon emissions during the production of cement are huge, and the resources of river sand in some areas have been greatly reduced or close to exhaustion after decades of exploitation. Therefore, it is of great significance and application value to reduce the amount of cement and river sand in the synchronous grouting material to reduce the cost.

[0004] Before the shield starts, a super-deep and super-large working well will be excavated, producing a large amount of muck. The disposal of construction muck by landfill and storage will cause safety hazards and environmental pollution, and the resource utilization of muck is urgent. In addition, the southeast coastal area is rich in sea sand resources, but due to the prohibition of using sea sand in structural concrete by relevant departments, the application range of sea sand resources is limited. Considering that the synchronous grouting material of the shield is only used to fill the gap and has low strength requirements, it is theoretically feasible to mix muck and reduce the amount of cement, and to use sea sand to replace river sand to prepare the synchronous grouting material.

[0005] Chinese patent CN 112723823 A discloses a synchronous mortar prepared from shield slag slurry and a preparation method thereof, and specifically discloses that the synchronous mortar comprises the following raw materials in parts by weight: shield slag slurry 40-60 parts, defoaming agent 0.02-0.07 parts, tackifier 0.5-1 part, foam inhibitor 0.03-0.05 part, fast swelling bentonite 2-6 parts, cement 5-15 parts, fly ash 5-15 parts, medium-fine sand 10-20 parts, adsorption sacrifice agent 0.02-0.05 part, early strength agent 0.2-0.5 part, and water 3-10 parts. Although the patent reduces the use amount of natural river sand and fly ash, it still needs to use a certain amount of medium-fine sand and fly ash, and the cost is relatively high. SUMMARY

[0006] To solve the above technical problems, the present application provides a synchronous grouting material for shield tunnel in coastal areas and a preparation method thereof, which fully utilizes the resources in coastal areas and the slag produced by shield construction as raw materials, cooperates with the use of other raw materials, greatly reduces the use amount of cement and river sand, absorbs construction slag, thereby reducing the cost and realizing the green and low-carbon production of the synchronous grouting material.

[0007] The technical scheme adopted by the present application is as follows:

[0008] A synchronous grouting material for shield tunnel in coastal areas, which comprises the following raw materials in parts by weight: cement 20-40 parts, steel slag powder 10-25 parts, shield slag 80-120 parts, phosphogypsum 15-35 parts, unrefined sea sand 120-150 parts, early strength agent 4-6 parts, conditioning agent 1-3 parts, and mixing water 100-125 parts, wherein the amount of shield slag is calculated without water, and the amount of mixing water includes the water content in shield slag.

[0009] The cement is a commercially available ordinary portland cement with a strength not less than 42.5 grade.

[0010] The mass percentage of free CaO in the steel slag powder is 6%-8%, and the specific surface area is greater than 350 m 2 / kg g.

[0011] The shield slag is the slag produced by the excavation of a shield working well, and the water content ω1 of the slag is measured, so the actual amount of the slag should be (80-120) x (1+ω1) parts.

[0012] The phosphogypsum is an industrial by-product in the production process of phosphoric acid, which is dried, heat-activated at high temperature, and then ground into a powder with a particle size range of 20-50 μm.

[0013] The drying condition is 50-60 DEG C for 4h, and the heat activation condition is 80-120 DEG C for 45-90min, and then reduced to normal temperature.

[0014] The unrefined sea sand is natural sea sand with a particle size range of 0.5-2mm after shell screening, and the spherical particle content is 50%-75%.

[0015] The early strength agent is polyaluminum sulfate, and the mass percentage of aluminum oxide is >12%.

[0016] The conditioner is compounded by inorganic components and organic components according to a mass ratio of 10:(0.6-1.2), wherein the inorganic components are composed of one or more of sepiolite powder and attapulgite powder; and the organic components are composed of one or more of hydroxypropyl methyl cellulose and anionic polyacrylamide.

[0017] The average particle size of the sepiolite powder and the attapulgite powder is 10-75mu, and the sepiolite powder and the attapulgite powder are subjected to acid treatment before use; the hydroxypropyl methyl cellulose is of medium viscosity, and the viscosity range is 4000-8000mPa·s; and the molecular weight of the anionic polyacrylamide is 2-4 million.

[0018] The acid treatment step is that one or more of sepiolite powder and attapulgite powder is subjected to ultrasonic acid treatment in a mass concentration of 15-30% hydrochloric acid solution according to a solid-liquid ratio of 1:(4-10) at a temperature of 45-80 DEG C for 24h, and then filtered and dried after acid treatment.

[0019] The application further provides a preparation method of the synchronous grouting material for the coastal area shield tunnel, and the preparation method comprises the following steps: uniformly mixing cement, steel slag powder and phosphogypsum according to a formula amount to obtain component A; dissolving the conditioner in mixed water to obtain solution B; putting shield muck into a stirring device, and adding part of the solution B while stirring until the muck is in a flow state, and continuously stirring for 8-10min after flow state to obtain component C; putting component A, unrefined sea sand, residual solution B and early strength agent into the stirring device, and stirring for 30-60s to obtain the synchronous grouting material.

[0020] The raw material of the synchronous grouting material for the coastal area shield tunnel provided by the application uses steel slag powder, which has weak water hardness and can generate hydration products such as hydrated calcium silicate to contribute to the strength. In addition, the steel slag powder contains free CaO, which can generate swelling substances in cooperation with cement hydration to improve the stone rate of the grouting material. The national standard "Steel slag powder for cement and concrete" stipulates that the content of free CaO in the steel slag powder should not be greater than 4% to avoid excessive expansion leading to structural cracking. In the application, the content of free CaO in the steel slag powder is 6%-8% because the synchronous grouting material after hardening is in a strong constraint state, and excessive expansion is beneficial to fully filling the voids, and on the other hand, it can also consume the steel slag powder that cannot be used in cement concrete due to poor stability.

[0021] The purpose of the thermal activation of phosphogypsum is that the main component of phosphogypsum is dihydrate gypsum, and the original phosphogypsum has a high water content and is in a muddy state. The free water in the original phosphogypsum can be removed by baking at 50-60°C for 4h, and the dihydrate gypsum will partially change its crystal form into a mixture of dihydrate gypsum, hemihydrate gypsum and anhydrite by keeping warm at 80-120°C for 45-90min.

[0022] The purpose of using the thermal activation of phosphogypsum is that gypsum can react with cement and steel slag powder to generate ettringite to form a network skeleton, and the generation process of ettringite is swelling, which can improve the stone rate of the grouting material, and the excess unreacted phosphogypsum acts as an inert filler to fill the skeleton to form a dense skeleton interstitial structure. In addition, the activation of phosphogypsum can further improve the hydration degree of steel slag powder and improve the strength of the hardened body. The hydration process of hemihydrate gypsum and anhydrite to dihydrate gypsum is relatively fast, which can shorten the setting time and provide part of the early strength.

[0023] The purpose of using sea sand with a particle size range of 0.5-2mm and a spherical particle content of 50%-75% is to reduce the particle size range of sand to increase the water retention of the slurry and reduce segregation and bleeding. In the application, the spherical particle content in the sand is greater than 50% to improve the fluidity of the slurry to meet the pumping construction performance requirements of the grouting material, and the spherical particle content is not greater than 75% to ensure that there is still a certain interlocking and occlusion force between the angular sand particles to improve the strength of the hardened slurry.

[0024] The purpose of using early strength agent is that the low dosage of cement and the high dosage of slag and phosphogypsum make the grouting material have a long setting time and slow early strength development, and the use of early strength agent can shorten the setting time and promote the development of early strength. The polyaluminum sulfate can also increase the content of aluminum phase in the system, and in the system containing persulfate ions, it can promote the generation of ettringite.

[0025] The purpose of using the conditioner is that: low-dose glue material makes the grouting material poor in cohesiveness, easy to block the pipe in the pumping process, the incorporation of the conditioner can improve the stability of the slurry, and the conditioner can also play a role in resisting erosion in the underground water-rich environment. The meerschaum and the attapulgite are in the form of microfibers, and can form a nearly network structure in the slurry, and can play a good viscosity increasing effect, and the specific interlayer structure makes the specific surface area and interlayer porosity of the meerschaum and the attapulgite after acidification treatment be very large, and the viscosity increasing effect is further strengthened. The hydroxymethyl cellulose and the anionic polyacrylamide have excellent thickening effect, and the thickening effect is related to the viscosity and the molecular weight, and the effect is not good if the viscosity and the molecular weight are too low, and the strength of the hardened slurry is affected if the viscosity and the molecular weight are too high.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] The synchronous grouting material for the coastal area shield tunnel provided by the present application is prepared by uniformly mixing cement, steel slag powder, shield slag, phosphogypsum, unrefined sea sand, early strength agent and conditioner with water, the present application makes full use of the resources in the coastal area and the slag produced by the shield, greatly reduces the use amount of cement and river sand, absorbs construction slag, thereby reducing the cost and realizing the green and low-carbon production of the synchronous grouting material. DETAILED DESCRIPTION

[0028] The synchronous grouting material for the coastal area shield tunnel provided by the present application comprises the following raw materials in parts by weight: cement 20-40 parts, steel slag powder 10-25 parts, shield slag 80-120 parts, phosphogypsum 15-35 parts, unrefined sea sand 120-150 parts, early strength agent 4-6 parts, conditioner 1-3 parts, and mixing water 100-125 parts, wherein the amount of the shield slag is calculated based on the water-free mass, and the amount of the mixing water includes the water content in the shield slag.

[0029] The cement is commercially available ordinary portland cement with a strength not less than 42.5 grade.

[0030] The mass percentage of free CaO in the steel slag powder is 6%-8%, and the specific surface area is greater than 350 m 2 / kg g.

[0031] The shield slag is the slag produced by the shield working well excavation, the water content ω1 of the slag is measured, and then the actual amount of the slag is (80-120) x (1+ω1) parts.

[0032] The phosphogypsum is an industrial by-product in the production process of phosphoric acid, is dried, is heat-activated at high temperature, and is ground into a powder with a particle size range of 20-50 μm for use.

[0033] The drying condition is 50-60 DEG C for 4 h, and the heat-activation condition is 80-120 DEG C for 45-90 min, and then the temperature is reduced to room temperature.

[0034] The unrefined sea sand is natural sea sand with a particle size range of 0.5-2 mm after shell screening, and a spherical particle content of 50%-75%.

[0035] The early strength agent is polyaluminum sulfate, and the mass percentage of aluminum oxide is >12%.

[0036] The conditioner is compounded from inorganic components and organic components according to a mass ratio of 10:(0.6-1.2), wherein the inorganic components are composed of one or more of sepiolite powder and attapulgite powder; and the organic components are composed of one or more of hydroxypropyl methyl cellulose and anionic polyacrylamide.

[0037] The average particle size of the sepiolite powder and the attapulgite powder is 10-75 μm, and the sepiolite powder and the attapulgite powder are subjected to acid treatment before use; the hydroxypropyl methyl cellulose is of medium viscosity, and the viscosity range is 4000-8000 mPa·s; and the molecular weight of the anionic polyacrylamide is 2-4 million.

[0038] The acid treatment step is as follows: one or more of sepiolite powder and attapulgite powder is subjected to ultrasonic acid treatment in a hydrochloric acid solution with a mass concentration of 15-30% under the condition of a solid-liquid ratio of 1:(4-10) and a temperature of 45-80 ℃ for 24 h, and then filtered and dried after the acid treatment is completed.

[0039] The application will be described in detail below in conjunction with examples, and the same raw materials are used in the examples and comparative examples.

[0040] The amount and weight parts of the synchronous grouting material in each example are shown in Table 1.

[0041] Table 1

[0042]

[0043] In Table 1, the conditioner in Example 1 is compounded from acidized sepiolite powder and hydroxypropyl methyl cellulose according to a mass ratio of 10:1; the conditioner in Example 2 is compounded from acidized attapulgite powder and anionic polyacrylamide according to a mass ratio of 10:0.8; the conditioner in Example 3 is compounded from acidized sepiolite powder, acidized attapulgite powder and hydroxypropyl methyl cellulose according to a mass ratio of 7:3:1.2; and the conditioner in Example 4 is compounded from acidized attapulgite powder and hydroxypropyl methyl cellulose according to a mass ratio of 10:1.

[0044] Comparative Example 1

[0045] The other conditions are the same as in Example 1, except that the phosphogypsum is not subjected to drying and high-temperature heat activation treatment, but is directly used after being ground into a powder with a particle size range of 20-50 μm.

[0046] Comparative Example 2

[0047] Other than Example 1, only the particle size range of sea sand is 3-5mm, and the spherical particle content is 45%.

[0048] Comparative Example 3

[0049] Other than Example 1, only the conditioner is compounded by un-acidified sepiolite powder and hydroxypropyl methyl cellulose according to the mass ratio of 10:1.

[0050] Comparative Example 4

[0051] Other than Example 1, only the steel slag powder is not used in the raw material of the simultaneous grouting material.

[0052] According to JGJ / T 70-2009 "Building mortar basic performance test method", the flowability, setting time, bleeding rate, strength and other performances of the simultaneous grouting material are as follows:

[0053] Table 2 Strength simultaneous grouting material performance

[0054]

[0055] As shown in Table 2, the simultaneous grouting material prepared according to the ratio of each example has a flowability greater than 350mm, a stone formation rate greater than 95%, a bleeding rate less than 3.0%, a 3d strength greater than 1.5MPa, and a 28d strength greater than 2.5MPa, meeting the performance requirements of simultaneous grouting of shield segments.

[0056] Comparative Example 1 relative to Example 1, because the phosphogypsum is not dried and high-temperature activated, the final setting time of the simultaneous grouting material is longer, and the early strength is poor. It can be seen that the hydration process of the phosphogypsum after drying and high-temperature activation into semi-hydrated gypsum and anhydrite to dihydrate gypsum is faster, which can shorten the setting time and provide part of the early strength.

[0057] Comparative Example 2 relative to Example 1, because the particle size of the sea sand is too large and the spherical particle content is less, the flowability of the simultaneous grouting material is poor and the bleeding is serious. It can be seen that reducing the particle size range of the sand can increase the water retention of the slurry and reduce the segregation bleeding; the spherical particle content greater than 50% can improve the flowability of the slurry, meeting the pumping construction performance requirements of the grouting material.

[0058] Comparative Example 3 relative to Example 1, because the sepiolite powder in the conditioner is not acidified, the viscosity of the simultaneous grouting material is not enough, and the bleeding is serious.

[0059] Comparative Example 4, relative to Example 1, has lower strength and lower stone rate of the simultaneous grouting material due to the absence of steel slag powder. The steel slag powder has weak hydraulicity and can generate products such as hydrated calcium silicate by hydration, contributing to the strength. In addition, the steel slag powder contains free CaO, and the cement can generate expansive substances by synergistic hydration, improving the stone rate of the grouting material.

[0060] The above detailed description of the simultaneous grouting material for a coastal shield tunnel and the preparation method thereof according to the reference examples is illustrative rather than limiting, and a number of examples can be listed within the defined range, and thus variations and modifications without departing from the general concept of the present application shall fall within the scope of the present application.

Claims

1. A synchronous grouting material for shield tunnels in coastal areas, characterized in that, The synchronous grouting material for shield tunnels in coastal areas includes the following raw materials in parts by weight: 20-40 parts cement, 10-25 parts steel slag powder, 80-120 parts shield excavated soil, 15-35 parts phosphogypsum, 120-150 parts unpurified sea sand, 4-6 parts early strength agent, 1-3 parts conditioning agent, and 100-125 parts mixing water. The amount of shield excavated soil is based on its weight without water, and the amount of mixing water includes the water content in the shield excavated soil. The mass percentage of free CaO in the steel slag powder is 6%-8%; The phosphogypsum is an industrial byproduct of phosphoric acid production. After drying and thermal activation at high temperature, it is ground into powder with a particle size range of 20~50μm for use. The unpurified sea sand is natural sea sand with a particle size range of 0.5~2mm after sieving out shells, and its spherical particle content is 50%-75%. The conditioning agent is composed of inorganic and organic components in a mass ratio of 10:(0.6~1.2), wherein the inorganic component consists of one or more of sepiolite powder and attapulgite powder; and the organic component consists of one or more of hydroxypropyl methylcellulose and anionic polyacrylamide. The sepiolite powder and attapulgite powder have an average particle size of 10~75μm and are acidified before use.

2. The synchronous grouting material for shield tunnels in coastal areas according to claim 1, characterized in that, The cement is commercially available ordinary Portland cement with a strength of not less than 42.

5.

3. The synchronous grouting material for shield tunnels in coastal areas according to claim 1, characterized in that, The specific surface area of ​​the steel slag powder is greater than 350m². 2 / kg.

4. The synchronous grouting material for shield tunnels in coastal areas according to claim 1, characterized in that, The drying conditions are: drying at 50-60℃ for 4 hours; the thermal activation conditions are: holding at 80-120℃ for 45-90 minutes, and then cooling to room temperature.

5. The synchronous grouting material for shield tunnels in coastal areas according to claim 1, characterized in that, The early strength agent is polyaluminum sulfate, with an alumina mass percentage >12%.

6. The synchronous grouting material for shield tunnels in coastal areas according to claim 1, characterized in that, The hydroxypropyl methylcellulose is of medium viscosity, with a viscosity range of 4000~8000 mPa·s; the anionic polyacrylamide has a molecular weight of 2 million to 4 million.

7. The method for preparing synchronous grouting material for shield tunnels in coastal areas as described in any one of claims 1-6, characterized in that, The preparation method includes the following steps: mixing cement, steel slag powder, and phosphogypsum in the specified amounts to obtain component A; dissolving the conditioner in the mixing water to obtain solution B; adding shield tunnel slag to a mixing device, adding part of solution B while stirring, until the slag becomes fluid, and continuing to stir for 8-10 minutes after fluidization to obtain component C; adding component A, unpurified sea sand, the remaining solution B, and early strength agent to the mixing device, and stirring for 30-60 seconds to obtain the synchronous grouting material.

Images