A clay stratum slurry shield mud material and a preparation method thereof

Abstract

The present application belongs to the technical field of mortar composition, and particularly relates to a clay stratum slurry shield mortar material and a preparation method thereof. The mortar material is prepared from the following components: 200 parts of water, 3-6 parts of bentonite, 0.06-0.15 parts of polyacrylamide, 0.04-0.08 parts of polyethylene glycol-b-poly caprolactone, 0.03-0.06 parts of PHBV, 0.15-0.3 parts of attapulgite, 0.15-0.3 parts of sodium carbonate, 0.01-0.02 parts of adipic acid dihydrazide, 0.015-0.03 parts of aluminum sulfate and 0.01-0.03 parts of sodium sulfate. The preparation method is to blend hydrolyzed polyacrylamide solution, aluminum sulfate solution, sodium sulfate solution and matrix suspension liquid, homogenize and maintain to obtain the mortar material. The improved mortar material is used in clay stratum slurry shield, and has superior performance in the aspects of excavation face support, stratum permeation control and environmental protection.

Description

Technical Field

[0001] This invention belongs to the technical field of mortar composition, specifically relating to a slurry material for clay strata in slurry shield tunneling and its preparation method. Background Technology

[0002] With the rapid development of transportation infrastructure construction, underwater tunnels and cross-river / sea tunnels are becoming increasingly common. Slurry shield tunneling, due to its minimal environmental disturbance and high excavation efficiency, has become one of the core technologies for tunnel construction in clay strata. Slurry, as a key material in slurry shield tunneling, must simultaneously meet multiple requirements, including stable support at the excavation face, control of ground seepage, and good environmental performance. Clay strata are characterized by low porosity, weak permeability, but high plasticity. While traditional bentonite-based slurry materials can achieve film-forming support to some extent, they generally have many drawbacks: First, the filtration loss control effect of traditional bentonite-based slurry materials is poor, and slurry splitting is prone to occur under high water pressure and shallow overburden conditions, leading to ground instability or slurry leakage; second, some additives in traditional slurry materials have potential pollution, and waste slurry treatment is difficult, costly, and lacks environmental friendliness; finally, during long-distance excavation in clay strata, traditional bentonite-based slurry materials are prone to problems such as incomplete film formation and rapid viscosity decay, resulting in reduced pressure transmission efficiency at the excavation face. Therefore, developing a new type of mud material that combines environmental friendliness, stability, and compatibility with clay strata to solve the problems of high pollution risk, poor film formation effect, and insufficient support capacity of traditional mud in clay strata construction has become a technical challenge that urgently needs to be overcome in the field of slurry shield tunneling.

[0003] Chinese patent CN106675538A discloses a leak-sealing shield tunneling mud, comprising the following components: 1.0-5.0% clay minerals, 0.01%-0.2% thickener, 0.5-7% inert leak-sealing material, and the balance being water; the clay minerals are one or a mixture of several of calcium-based bentonite, sodium-based bentonite, kaolin, and sepiolite powder; the thickener is one or a mixture of several of polyacrylamide, carboxymethyl cellulose, xanthan gum, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose; the inert leak-sealing material is a mixture of two or more of sawdust, crushed walnut shells, crushed cottonseed hulls, vermiculite, diatomaceous earth, crushed plastic particles, asbestos fiber, glass fiber, crushed sugarcane, hay fiber, mica flakes, and plastic flakes of different particle sizes.

[0004] Mud materials should have a relatively balanced performance in at least three aspects: stable support of the excavation face, anti-seepage sealing, and environmental protection, in order to meet construction requirements. This patent only specifically improves the anti-seepage sealing performance of mud materials during shield tunneling. Therefore, it uses a variety of high-content, high-rigidity solid components and clay minerals and thickeners in combination, which can easily increase the apparent viscosity of the mud and lead to an excessively thick mud film. An excessively thick mud film will isolate the mud from the contact between the mud and the excavation face. When used in slurry shield tunneling in clay strata, there is a risk that the pressure cannot be effectively transmitted to the excavation face, causing local stress imbalance at the excavation face, which in turn affects the stability of the excavation face support.

[0005] Chinese patent CN102250597A discloses a grouting mud for loose formations, which comprises the following components: bentonite 10.8~66 kg / m³ 3 Soda ash 3~6kg / m 3 Cement 27~28kg / m 3 Water glass 17~39kg / m 3 Fly ash 30~38kg / m³ 3 Fine sand 100~161kg / m 3 Water-reducing agent iron-chromium lignin sulfonate 6.5~12kg / m 3 Crosslinking agent: aluminum sulfate or sodium sulfate 2.5~4 kg / m 3 Hydrolyzed polyacrylamide 0.15~0.24kg / m 3 Hydrolyzed polyacrylonitrile 1.4~3.2 kg / m³ 3 And the balance of water.

[0006] The patent incorporates a large amount of alkaline substances, such as soda ash, water glass, fly ash, and cement, causing the pH of the grouting slurry to reach 11. In a strongly alkaline environment, aluminum ions in aluminum sulfate are more likely to be further hydrated and precipitated, affecting their cross-linking activity with hydrolyzed polyacrylamide and hydrolyzed polyacrylonitrile. In addition, a strongly alkaline environment can easily corrode the metal components in the grouting pipeline, shortening the service life of the equipment. Summary of the Invention

[0007] The purpose of this invention is to provide a slurry material for slurry shield tunneling in clay strata. When this slurry material is used in slurry shield tunneling in clay strata, it exhibits superior performance in terms of excavation face support, stratum seepage control, and environmental friendliness. This invention also provides a method for preparing this slurry material.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The mud material for slurry shield tunneling in clay soil strata according to the present invention is made of the following components by weight: 200 parts water, 3-6 parts bentonite, 0.06-0.15 parts polyacrylamide, 0.04-0.08 parts polyethylene glycol-b-polycaprolactone, 0.03-0.06 parts poly(3-hydroxybutyrate-co-3-hydroxyvalerate), 0.15-0.3 parts attapulgite, 0.15-0.3 parts sodium carbonate, 0.01-0.02 parts adipic acid dihydrazide, 0.015-0.03 parts aluminum sulfate, and 0.01-0.03 parts sodium sulfate.

[0009] The polyacrylamide has a weight-average molecular weight of 8 million to 12 million and a degree of hydrolysis of 15% to 35%; sodium-based bentonite is preferred.

[0010] The preparation method of the slurry material for clay strata in this invention includes the following steps: S1. Pre-treat bentonite; S2. Prepare a hydrolyzed polyacrylamide solution by mixing polyacrylamide, sodium carbonate, polyethylene glycol-b-polycaprolactone and adipate dihydrazide. S3. Prepare aluminum sulfate solution; S4. Prepare sodium sulfate solution; S5. Pretreated bentonite, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and attapulgite are formulated into a matrix suspension. S6. Mix the matrix suspension, hydrolyzed polyacrylamide solution, aluminum sulfate solution and sodium sulfate solution to obtain a mud precursor suspension; S7. The mud precursor suspension is homogenized and cured to obtain mud material for clay strata slurry shield tunneling.

[0011] in: In S1, the pretreatment includes drying, pulverizing, and sealed storage. The drying temperature is 60~70℃ and the drying time is 2~3h. The pulverizing pressure is 0.6~0.9MPa. The relative humidity of the sealed storage environment is 30~40%RH.

[0012] In S2, the preparation process is as follows: set the stirring speed to 400~450 r / min, add polyacrylamide and sodium carbonate to water and mix well, then add polyethylene glycol-b-polycaprolactone and adipate dihydrazide, mix well, and keep it at 50~60℃ for 3.5~5 h to obtain a hydrolyzed polyacrylamide solution; wherein the mass ratio of polyacrylamide to water is (0.06~0.15):(80~100).

[0013] In S3, the preparation process is as follows: set the stirring speed to 150~200r / min, mix aluminum sulfate and water at a mass ratio of (0.15~0.3):(50~150) for 1~3min, let stand for 3~5min, and obtain aluminum sulfate solution.

[0014] In S4, the preparation process is as follows: set the stirring speed to 150~200 r / min, stir and mix sodium sulfate and water at a mass ratio of (0.1~0.3):(50~150) for 1~3 min, let stand for 3~5 min, and obtain sodium sulfate solution.

[0015] In S5, the preparation process is as follows: the pretreated bentonite and the remaining water are stirred at a speed of 600~800 r / min for 12~20 min, then poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and attapulgite are added, and stirred at a speed of 300~500 r / min for 15~30 min. Finally, it is allowed to stand at 20~30℃ for 24 h. During the standing period, it is stirred at 200 r / min for 5 min every 8 h. After 8 h, when there is no obvious sedimentation, the matrix suspension is obtained.

[0016] In S6, the blending process is as follows: hydrolyzed polyacrylamide solution is added to the matrix suspension at 20~30℃ and stirred for 25~35 min; aluminum sulfate solution is added and stirred for 20~30 min; finally, sodium sulfate solution is added and stirred for 35~40 min to obtain mud precursor suspension.

[0017] In S7, gradient stirring is used during homogenization, that is, stirring at 300~350r / min for 25~30min, 200~250r / min for 20~30min, and 100~150r / min for 15~30min in sequence.

[0018] In the S7 process, during curing, the mixture is left to stand for 24-40 hours at 25-30℃ and 40-50%RH relative humidity, and stirred for 10-15 minutes at a speed of 200-300r / min every 8-12 hours.

[0019] It is known that existing bentonite-based mud systems have significant shortcomings in three main aspects during slurry shield tunneling in clay strata: face stabilization, seepage prevention, and environmental friendliness. The core functional phase of bentonite-based mud is montmorillonite. After hydration, montmorillonite particles form flaky colloidal particles, which then spontaneously and randomly grow. This random growth results in the formation of a thick, loose, and highly porosity mud film at the excavation face, which is difficult to embed into the micropores of the clay strata to form an internal seal. The mud film is easily punctured by water pressure, and its pressure-bearing capacity and erosion resistance are insufficient. Ultimately, these factors lead to poor support stability at the excavation face.

[0020] Furthermore, bentonite-based drilling mud cannot embed itself into the pores of clay formations to form internal seals. It can only float on the surface to form a filter cake with high porosity. Free water can continuously penetrate through the pores of the filter cake into the formation. During shield tunneling in clay formations, the bentonite-based drilling mud structure is sheared and degraded under high water pressure conditions. Microscopically, this manifests as the irreversible curling of the molecular chains of high-molecular-weight materials (such as polyacrylamide) within the bentonite-based drilling mud, which cannot form a network-like water-blocking structure and cannot stabilize the bentonite particles. Ultimately, this results in insufficient anti-seepage sealing capacity of the bentonite-based drilling mud and a large filtration loss.

[0021] Finally, anionic surfactants are sometimes used in mud, causing eutrophication of water bodies; in addition, in order to meet the requirements of excavation face support stability and low filtration loss, it is sometimes necessary to significantly increase the amount of bentonite and flocculants, which in turn leads to low mud-water separation efficiency, long treatment cycle and insufficient environmental protection.

[0022] The beneficial effects of this invention are as follows: Polyacrylamide undergoes further hydrolysis in an alkaline environment to generate carboxylate ions. Through electrostatic repulsion, the molecular chains further extend, and aluminum ions provided by aluminum sulfate combine with the carboxylate ions on the side chains of polyacrylamide. Simultaneously, adipic acid dihydrazide forms covalent crosslinks with the polyacrylamide. During this process, the hydrophilic segments of polyethylene glycol-β-polycaprolactone react with the -CONH2 and -COO groups in the hydrolyzed polyacrylamide via ether oxygen. - A hydrogen-bonded network is formed, and the hydrophobic segments in polyethylene glycol-β-polycaprolactone (PEG-β-polycaprolactone) can serve as an internal support framework to further promote the extension of polyacrylamide segments. Through this hydrogen-bonded network, on the one hand, PEG-β-polycaprolactone and polyacrylamide coat aluminum ions, inhibiting premature hydration and precipitation of aluminum ions, thus preventing loss of crosslinking activity; on the other hand, it can reduce the local supersaturation of aluminum ions, promoting the formation of a unified whole among the hydrolyzed polyacrylamide molecular chains and preventing excessive local crosslinking. Simultaneously, the hydrophobic segments aggregate and intertwine due to hydrophobic interactions, forming a semi-interpenetrating network with the crosslinked molecular chains during the coordination and covalent crosslinking of the hydrolyzed polyacrylamide. After hydrolysis, polyacrylamide, PEG-β-polycaprolactone, adipic acid dihydrazide, and aluminum ions, through two-stage crosslinking, further promote the formation of a semi-interpenetrating network, making the four components form a unified whole, effectively improving the load-bearing capacity and toughness of the polyacrylamide-based network structure.

[0023] Meanwhile, attapulgite and sodium bentonite are introduced into the three-dimensional network structure. Attapulgite, a needle-like / fibrous silicate, forms a three-dimensional interpenetrating overlapping structure with the montmorillonite flake particles and the three-dimensional network structure in the sodium bentonite. This overlapping structure allows for dynamic adjustment of surface tension. When stationary, it provides stable support for the three-dimensional network structure, achieves water and soil pressure balance, and facilitates the post-treatment of waste mud. During shearing, it prevents irreversible shrinkage of the molecular chain conformation in the three-dimensional network structure while achieving dynamic adjustment of density and viscosity, effectively improving the pressure-bearing capacity and erosion resistance of the mud film. This three-dimensional interpenetrating overlapping structure provides elastic support for the entire mud film, solving the problem of degradation of traditional mud films under high water pressure during shield tunneling in clay strata, which leads to poor mud film quality and excavation face instability. It also meets the requirement of rapid mud film formation under high water pressure in the solution.

[0024] Furthermore, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a semi-crystalline aliphatic polyester. During the preparation of the matrix suspension, sodium bentonite and attapulgite particles are used as templates to promote the embedding of PHBV into the three-dimensional interpenetrating overlap structure, thereby improving the hydrophobicity of the three-dimensional interpenetrating overlap structure and forming a hydrophobic lubricating film. During high-pressure construction, the hydrophobic lubricating film acts like a ball bearing, which can significantly reduce the friction between clay particles in the clay layer and the three-dimensional interpenetrating overlap structure, reduce the resistance embedded in the pores of the clay layer, promote the tightness of the internal sealing, and greatly improve the pressure resistance, erosion resistance and seepage prevention and sealing performance of the mud film. In addition, when in a static state, the hydrophobic lubricating film shrinks under the tendency of minimizing surface energy, which facilitates the separation of mud and water from waste mud and improves environmental protection.

[0025] Finally, the raw materials selected in this invention do not contain heavy metals, toxic polymers, or harmful volatiles, and PHBV is a biodegradable material; the mud material is not prone to degradation, shrinkage, or metal ion desorption during use; a small amount of aluminum sulfate undergoes hydration in an alkaline environment and can further interact with sodium bentonite and attapulgite to promote aluminum ion flocculation; in addition, this invention uses a small amount of bentonite and attapulgite, the waste mud is easy to separate from water and dehydrate, the waste residue is easy to dispose of in compliance with regulations, and the slurry can be recycled, thus meeting environmental protection requirements. Attached Figure Description

[0026] Figure 1 The image shown is a SEM image of the mud material prepared in Example 1, with a magnification of 2000. Figure 2 The image shown is a SEM image of the mud material prepared in Example 1, magnified to 200. Detailed Implementation

[0027] The present invention will now be described and illustrated in detail with reference to the embodiments.

[0028] The raw materials used in the following examples and comparative examples are all commercially available products. Among them, poly(3-hydroxybutyrate-co-3-hydroxyvalerate), abbreviated as PHBV, was provided by Ningbo Tianan Biomaterials Co., Ltd.; polyethylene glycol-b-polycaprolactone, with an average molecular weight of 5000 for polyethylene glycol and an average molecular weight of 2000 for polycaprolactone, was provided by Shanghai Yubo Biotechnology Co., Ltd.; and polyacrylamide, with a weight-average molecular weight of 8 million to 12 million and a degree of hydrolysis of 15% to 35%, was provided by Henan Guohong Water Treatment Materials Co., Ltd. Example 1

[0029] This embodiment provides a mud material for slurry shield tunneling in clay strata and its preparation method. The mud material is made from the following components: 200 parts water, 3 parts sodium bentonite, 0.06 parts polyacrylamide (weight average molecular weight of 10 million, degree of hydrolysis of 35%), 0.08 parts polyethylene glycol-b-polycaprolactone, 0.03 parts poly(3-hydroxybutyrate-co-3-hydroxyvalerate), 0.3 parts attapulgite, 0.15 parts sodium carbonate, 0.015 parts adipic acid dihydrazide, 0.015 parts aluminum sulfate, and 0.01 parts sodium sulfate.

[0030] The preparation method comprises the following specific steps: S1: Place 3 parts of sodium-based bentonite in a 65℃ oven and dry for 2.5 hours. After pulverizing using an airflow pulverizer with a wind pressure of 0.7MPa, store it in a sealed container in an environment with a relative humidity of 35%RH. One hour before use, allow the sodium-based bentonite to warm up to room temperature.

[0031] S2: Measure 80 parts of water and pour them into a container. Turn on the stirrer and set the speed to 420 r / min. At the same time, slowly add polyacrylamide and sodium carbonate; continue to add polyethylene glycol-b-polycaprolactone and adipate dihydrazide, mix well, and then place the solution in a constant temperature environment of 50℃ for 4 hours to obtain a hydrolyzed polyacrylamide solution. The viscosity was measured by a rotational viscometer and was 28 mPa·s, which meets the characteristics of a non-Newtonian pseudoplastic fluid, ensuring its bridging effect.

[0032] S3: Measure 15 parts of deionized water, add 0.015 parts of aluminum sulfate, stir at 180 r / min for 1.5 min, let stand for 5 min, and check that there are no undissolved particles in the solution. The aluminum sulfate solution is then ready for use.

[0033] S4: Measure 15 parts of deionized water, add 0.01 parts of sodium sulfate, stir at 170 r / min for 1 min, let stand for 5 min, and check that there are no undissolved particles in the solution. The sodium sulfate solution is then ready for use.

[0034] S5: Add 3 parts of sodium bentonite and the remaining water after the temperature has stabilized to a stirred tank, stir at 600 r / min for 20 min, then reduce to 300 r / min, add 0.03 parts of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and 0.3 parts of attapulgite, stir for 25 min, and remove any residual lumps from the side wall of the container during stirring using a scraper. After stirring, place the container in a constant temperature environment of 23℃ for 24 h, and stir at 200 r / min for 5 min every 8 h during the standing period. After 8 h, if there is no obvious sedimentation, a matrix suspension is obtained.

[0035] S6: At 30°C, add hydrolyzed polyacrylamide solution to the matrix suspension and stir for 32 min; after a 10 min interval, add aluminum sulfate solution and stir for 28 min; after another 10 min interval, add sodium sulfate solution and stir for 38 min to obtain mud precursor suspension.

[0036] S7: The mud precursor suspension was homogenized by stirring at 350 r / min for 30 min, 250 r / min for 30 min, and 150 r / min for 20 min in sequence. After homogenization, it was placed in a constant temperature and humidity curing chamber at 26℃ and 45% RH for 24 h using a double-layer sealing and light-proof wrapping method. During the curing period, it was stirred at 250 r / min for 13 min every 8 h. After curing, the mud material (i.e., clay stratum slurry shield tunneling mud material) was obtained. Example 2

[0037] This embodiment provides a slurry material for slurry shield tunneling in clay strata and its preparation method. The slurry material is made from the following components: 200 parts water, 4.5 parts sodium bentonite, 0.14 parts polyacrylamide (weight average molecular weight of 8 million, degree of hydrolysis of 15%), 0.05 parts polyethylene glycol-b-polycaprolactone, 0.04 parts poly(3-hydroxybutyrate-co-3-hydroxyvalerate), 0.15 parts attapulgite, 0.28 parts sodium carbonate, 0.01 parts adipic acid dihydrazide, 0.028 parts aluminum sulfate, and 0.025 parts sodium sulfate.

[0038] The preparation method comprises the following specific steps: S1: Place 4.5 parts of sodium-based bentonite in a 60℃ oven and dry for 3 hours. After pulverizing using an airflow pulverizer with a wind pressure of 0.6MPa, store it in a sealed container in an environment with a relative humidity of 40%RH. One hour before use, allow the sodium-based bentonite to warm up to room temperature.

[0039] S2: Measure 100 parts of water and pour them into a container. Turn on the stirrer and set the speed to 450 r / min. At the same time, slowly add polyacrylamide and sodium carbonate and stir until uniform. Continue to add polyethylene glycol-b-polycaprolactone and adipate dihydrazide, mix well, and then place the solution in a constant temperature environment of 55℃ for 3.5 h to obtain a hydrolyzed polyacrylamide solution. The viscosity was measured by a rotational viscometer to be 34 mPa·s, which meets the characteristics of a non-Newtonian pseudoplastic fluid, ensuring its bridging effect.

[0040] S3: Measure 10 parts of deionized water, add 0.028 parts of aluminum sulfate, stir at 150 r / min for 1 min, let stand for 4 min, and check that there are no undissolved particles in the solution. The aluminum sulfate solution is then ready for use.

[0041] S4: Measure 10 parts of deionized water, add 0.025 parts of sodium sulfate, stir at 200 r / min for 1.5 min, let stand for 4 min, and check that there are no undissolved particles in the solution. The sodium sulfate solution is then ready for use.

[0042] S5: Add 4.5 parts of sodium bentonite and the remaining water to a stirred tank after the temperature has stabilized. Stir at 800 r / min for 15 min, then reduce the speed to 400 r / min. Add 0.04 parts of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and 0.15 parts of attapulgite. Stir for 30 min, and remove any remaining clumps from the sidewall of the container using a scraper. After stirring, place the container in a constant temperature environment of 25℃ for 24 h. During the standing period, stir at 200 r / min for 5 min every 8 h. After 8 h, if there is no obvious sedimentation, a matrix suspension is obtained.

[0043] S6: At 25°C, add hydrolyzed polyacrylamide solution to the matrix suspension and stir for 25 min; after a 15 min interval, add aluminum sulfate solution and stir for 30 min; after another 15 min interval, add sodium sulfate solution and stir for 40 min to obtain mud precursor suspension.

[0044] S7: The mud precursor suspension was homogenized by stirring at 300 r / min for 25 min, 200 r / min for 25 min, and 100 r / min for 15 min in sequence. After homogenization, it was placed in a constant temperature and humidity curing chamber at 25℃ and 40% RH for 40 h using a double-layer sealing and light-proof wrapping method. During this period, it was stirred at 200 r / min for 15 min every 8 h. After curing, the mud material (i.e., mud-water shield tunneling mud material for clay strata) was obtained. Example 3

[0045] This embodiment provides a slurry material for slurry shield tunneling in clay strata and its preparation method. The slurry material is made from the following components: 200 parts water, 6 parts sodium bentonite, 0.15 parts polyacrylamide (weight average molecular weight of 12 million, degree of hydrolysis of 25%), 0.04 parts polyethylene glycol-b-polycaprolactone, 0.06 parts poly(3-hydroxybutyrate-co-3-hydroxyvalerate), 0.2 parts attapulgite, 0.3 parts sodium carbonate, 0.02 parts adipic acid dihydrazide, 0.03 parts aluminum sulfate, and 0.03 parts sodium sulfate.

[0046] The preparation method comprises the following specific steps: S1: Place 6 parts of sodium-based bentonite in a 70℃ oven and dry for 2 hours. After pulverizing using an airflow pulverizer with a wind pressure of 0.9MPa, seal and store in an environment with a relative humidity of 30%RH. One hour before use, allow the sodium-based bentonite to warm up to room temperature.

[0047] S2: Measure 90 parts of water and pour them into a container. Turn on the stirrer and set the speed to 400 r / min. At the same time, slowly add polyacrylamide and sodium carbonate and stir until uniform. Continue to add polyethylene glycol-b-polycaprolactone and adipate dihydrazide, mix well, and then place the solution in a constant temperature environment of 60℃ for 5 hours to obtain a hydrolyzed polyacrylamide solution. The viscosity was measured by a rotational viscometer to be 36 mPa·s, which meets the characteristics of a non-Newtonian pseudoplastic fluid and improves the mud's resistance to splitting.

[0048] S3: Measure 5 parts of deionized water, add 0.03 parts of aluminum sulfate, stir at 200 r / min for 3 min, let stand for 3 min, and check that there are no undissolved particles in the solution. The aluminum sulfate solution is then ready for use.

[0049] S4: Measure 5 parts of deionized water, add 0.03 parts of sodium sulfate, stir at 150 r / min for 3 min, let stand for 3 min, and check that there are no undissolved particles in the solution. The sodium sulfate solution is then ready for use.

[0050] S5: Add 6 parts of sodium bentonite and the remaining water after the temperature has stabilized to a stirred tank, stir at 730 r / min for 12 min, then reduce to 500 r / min, add 0.06 parts of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and 0.2 parts of attapulgite, stir for 15 min, and remove any residual clumps from the side wall of the container using a scraper during the stirring process; after stirring, place in a constant temperature environment of 20℃ for 24 h, stirring at 200 r / min for 5 min every 8 h during the standing period, until there is no obvious sedimentation after 8 h, and obtain the matrix suspension.

[0051] S6: At 20°C, add hydrolyzed polyacrylamide solution to the matrix suspension and stir for 35 min; after a 15 min interval, add aluminum sulfate solution and stir for 20 min; after another 15 min interval, add sodium sulfate solution and stir for 35 min to obtain mud precursor suspension.

[0052] S7: The mud precursor suspension was homogenized by stirring at 320 r / min for 28 min, 230 r / min for 20 min, and 120 r / min for 30 min in sequence. After homogenization, it was placed in a constant temperature and humidity curing chamber at 30℃ and 50% RH for 36 h using a double-layer sealing and light-proof wrapping method. During the curing period, it was stirred at 300 r / min for 10 min every 12 h. After curing, the mud material (i.e., clay stratum slurry shield tunneling mud material) was obtained.

[0053] Comparative Example 1 Without adding polyethylene glycol-b-polycaprolactone, the remaining steps are the same as in Example 1 to obtain the mud material.

[0054] Comparative Example 2 Without adding poly(3-hydroxybutyrate-co-3-hydroxyvalerate), the remaining steps are the same as in Example 1 to obtain the mud material.

[0055] Comparative Example 3 Without adding attapulgite, the remaining steps are the same as in Example 1 to obtain the mud material.

[0056] Comparative Example 4 Without adding adipic acid dihydrazide, the remaining steps are the same as in Example 1 to obtain the mud material.

[0057] Implementation effect evaluation

[0058] Funnel viscosity test procedure: A standard Souwer funnel viscometer was selected. Before the test, the outflow time was calibrated with 946 mL of clean water at 20±0.5℃. The mud material prepared in Example 1 was taken, stirred thoroughly, and sieved to remove large particles of impurities. The outflow nozzle of the funnel was blocked with a finger, and the mud was poured into the funnel to the lower edge of the sieve. The measuring cup was placed directly below the nozzle. The stopwatch was started at the same time as the finger was released, and the time it took for the mud to flow into the 946 mL measuring cup was recorded in seconds (s), which is the Souwer funnel viscosity. The test was performed in parallel for 3 times, and the arithmetic mean was taken as the final result.

[0059] Filtration loss test procedure: A standard medium-pressure filtration loss tester was selected. The mud material prepared in Example 1 was taken, stirred thoroughly, and the temperature was adjusted to 25°C. 350 mL of mud material was poured into the filtration loss tester, and the pressure was stabilized at 120 psi. The stopwatch was started and the pressure was continuously increased for 30 min. After the timing was completed, the air source was turned off and the pressure was released. The volume of filtrate collected in the graduated cylinder (mL) was read, which is the filtration loss.

[0060] Dynamic shear force test procedure: A rotational viscometer was used to measure the dynamic shear force of the mud material prepared in Example 1, in accordance with GB / T22235-2008 "Determination of viscosity of liquids - Rotational viscometer method".

[0061] Gel strength test procedure: A rotational viscometer was used. The slurry material prepared in Example 1 was poured into a sample cup and stirred at 600 r / min for 10 s. Stirring was stopped, and the mixture was allowed to stand for 15 s. The viscometer was then turned on and adjusted to 3 r / min. The maximum deflection value Φ on the scale was read. max Calculate the gel strength according to the standard formula, in Pa: gel strength = 0.511 × Φ max .

[0062] Environmental testing: In accordance with the requirements of Class II water areas in GB3838-2002 Surface Water Environmental Quality Standard, the content of heavy metals such as copper, zinc, and chromium, as well as anionic surfactants, is tested to determine whether it meets the requirements.

[0063] The testing process for other embodiments and comparative examples is the same as that for Example 1. The test results of the mud material performance are shown in Table 1.

[0064] Table 1 Test results of mud material properties

[0065] Dynamic shear force refers to the minimum shear stress that mud needs to overcome to start flowing in a laminar state. It can be used to characterize the strength of the network structure formed by mud material and clay particles. It is a core indicator of mud shear dilution, suspension stability and excavation face adhesion.

[0066] Souwert funnel viscosity is a core parameter used to characterize the apparent viscosity and flow resistance of mud materials. A reasonable Souwert funnel viscosity reflects smooth mud pressure transmission at the excavation face and excellent excavation face stability.

[0067] Gel strength can be used to characterize the thixotropic properties and static structural stability of mud. Reasonable gel strength reflects that the mud material can quickly form a high-strength gel structure when static, which can form stable suspended slag particles, maintain the stability of the mud morphology at the excavation face, and avoid instability of the excavation face and surface subsidence caused by a sudden drop in pressure in shallow overburden strata.

[0068] Filtration loss is the filtration volume of mud material, which directly characterizes the filtration loss control ability and wall-building performance of mud material. That is, the ability of mud material to control water loss into the formation under the high pressure requirements of mud-water shield tunneling in clay formations, as well as the quality of mud film formed.

[0069] The test results of heavy metals and anionic surfactants characterize the environmental toxicity and eco-friendliness of mud, which directly determines the environmental compliance of the project and the difficulty of waste mud disposal.

[0070] Dynamic shear force, Souvlet funnel viscosity, and gel strength mainly reflect the excavation face support stability of the mud material; 120psi filtration loss reflects the formation permeability control of the mud material; and the test results of heavy metals and anionic surfactants mainly reflect the environmental friendliness. As shown in Table 1, the mud material prepared by this invention has superior performance in excavation face support, formation permeability control, and environmental friendliness, and can cope with the slurry shield tunneling situation characterized by medium and high water pressure and shallow overburden clay strata.

Claims

1. A slurry material for slurry shield tunneling in clay soil strata, characterized in that, The product is composed of the following components in parts by weight: 200 parts water, 3-6 parts bentonite, 0.06-0.15 parts polyacrylamide, 0.04-0.08 parts polyethylene glycol-b-polycaprolactone, 0.03-0.06 parts poly(3-hydroxybutyrate-co-3-hydroxyvalerate), 0.15-0.3 parts attapulgite, 0.15-0.3 parts sodium carbonate, 0.01-0.02 parts adipic acid dihydrazide, 0.015-0.03 parts aluminum sulfate, and 0.01-0.03 parts sodium sulfate. Polyacrylamide has a weight-average molecular weight of 8 million to 12 million and a degree of hydrolysis of 15 to 35%.

2. A method for preparing the slurry material for clayey shield tunneling as described in claim 1, characterized in that, Includes the following steps: S1. Pre-treat bentonite; S2. Prepare a hydrolyzed polyacrylamide solution by mixing polyacrylamide, sodium carbonate, polyethylene glycol-b-polycaprolactone and adipate dihydrazide. S3. Prepare aluminum sulfate solution; S4. Prepare sodium sulfate solution; S5. Pretreated bentonite, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and attapulgite are formulated into a matrix suspension. S6. Mix the matrix suspension, hydrolyzed polyacrylamide solution, aluminum sulfate solution and sodium sulfate solution to obtain a mud precursor suspension; S7. The mud precursor suspension is homogenized and cured to obtain mud material for clay strata slurry shield tunneling.

3. The method for preparing slurry material for clayey strata in tunnel boring machines according to claim 2, characterized in that, In S1, the pretreatment includes drying, pulverizing, and sealed storage. The drying temperature is 60~70℃ and the drying time is 2~3h. The pulverizing pressure is 0.6~0.9MPa. The relative humidity of the environment during sealed storage is 30~40%RH.

4. The method for preparing slurry material for clayey strata in tunnel boring machines according to claim 2, characterized in that, In S2, the preparation process is as follows: Set the stirring speed to 400~450r / min, add polyacrylamide and sodium carbonate to water and mix well, then add polyethylene glycol-b-polycaprolactone and adipate dihydrazide, mix well, and keep it at 50~60℃ for 3.5~5h to obtain a hydrolyzed polyacrylamide solution; wherein the mass ratio of polyacrylamide to water is (0.06~0.15):(80~100).

5. The method for preparing slurry material for clayey strata in shield tunneling according to claim 4, characterized in that, In S3, the preparation process is as follows: Set the stirring speed to 150~200r / min, mix aluminum sulfate and water at a mass ratio of (0.15~0.3):(50~150) for 1~3min, let stand for 3~5min, and obtain aluminum sulfate solution.

6. The method for preparing slurry material for clayey shield tunneling according to claim 5, characterized in that, In S4, the preparation process is as follows: Set the stirring speed to 150~200r / min, mix sodium sulfate and water at a mass ratio of (0.1~0.3):(50~150) for 1~3min, let stand for 3~5min, and obtain sodium sulfate solution.

7. The method for preparing slurry material for clayey strata in tunnel boring machines according to claim 6, characterized in that, In S5, the preparation process is as follows: the pretreated bentonite and the remaining water are stirred at a speed of 600~800 r / min for 12~20 min, then poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and attapulgite are added, and stirred at a speed of 300~500 r / min for 15~30 min to obtain the matrix suspension.

8. The method for preparing slurry material for clayey shield tunneling according to claim 2, characterized in that, In S6, the blending process is as follows: add hydrolyzed polyacrylamide solution to the matrix suspension at 20~30℃ and stir for 25~35min; continue to add aluminum sulfate solution and stir for 20~30min; finally add sodium sulfate solution and stir for 35~40min to obtain mud precursor suspension.

9. The method for preparing slurry material for clayey shield tunneling according to claim 2, characterized in that, In S7, gradient stirring is used during homogenization, that is, stirring at 300~350r / min for 25~30min, 200~250r / min for 20~30min, and 100~150r / min for 15~30min in sequence.

10. The method for preparing slurry material for clayey shield tunneling according to claim 2, characterized in that, In S7, during curing, store at 25~30℃ and 40~50%RH for 24~40h, stirring at 200~300r / min for 10~15min every 8~12h.

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