Method for forming plastic diaphragm wall based on in-situ slurry solidification and diaphragm wall

Abstract

The invention discloses a method for forming a plastic diaphragm wall based on in-situ slurry solidification. The method comprises the following steps that S1, the specific gravity and the particle activity of wall protection slurry are determined; determining the mixing amount of the mineral-based cementing material (1) according to the specific gravity of the wall protection slurry and the particle activity; s2, foundation trench excavation is conducted, undisturbed soil is used for making mud, dry soil is added into the mud made of the undisturbed soil, the specific gravity of the mud made of the undisturbed soil is adjusted to the specific gravity of wall protection mud, and in-situ wall protection mud (3) is obtained; s3, mixing the mineral-based cementing material (1) with the in-situ wall protection slurry (3) by adopting a bipolar mixing process, and filling the groove section (2) with the mixture; and S4, in-situ curing is conducted, and the plastic diaphragm wall is formed. The invention further discloses the diaphragm wall which is formed based on the method, the construction period is shortened, the problem that the plastic diaphragm wall is prone to cracks and cavities is effectively solved, the integrity of the diaphragm wall structure is guaranteed, meanwhile, construction waste is reduced, the ecological environment is protected, and the construction quality of the diaphragm wall is guaranteed.

Description

Technical Field

[0001] The present invention relates to the fields of water conservancy and hydropower projects, landfills, tailing dams, etc. that require continuous cut-off walls, and specifically relates to a method for forming a plastic cut-off wall by in-situ mud curing and the cut-off wall. Background Art

[0002] Due to its relatively low deformation modulus compared to conventional concrete, the plastic cut-off wall can withstand large deformations in its wall body and can coordinate with the surrounding undisturbed soil to deform together. Therefore, the plastic cut-off wall is the main anti-seepage measure in water conservancy and hydropower projects, and is also a commonly used anti-seepage method in landfills and various tailing dams. It has been widely applied and achieved good benefits.

[0003] Chinese Patent CN116514482A discloses a method for preparing concrete for a cut-off wall in a water conservancy project and a construction process. By scientifically regulating the proportion of coarse aggregate, fine aggregate, fly ash, and clay, the permeability coefficient of the plastic concrete is reduced while the overall strength is improved. Fly ash and clay have excellent viscosity, which helps to prevent the settlement of the reconstituted raw materials and helps the raw materials of each component to be evenly dispersed in the concrete product, improving the mechanical properties of the product and enhancing the crack resistance of the product.

[0004] Chinese Patent CN115434282A discloses a composite cut-off wall for a water conservancy project and its construction method, including an anti-seepage wall body and a pre-embedded steel bar frame arranged in the anti-seepage wall body. The anti-seepage wall body is obtained by curing and forming anti-seepage concrete; the anti-seepage concrete includes the following raw materials: 80-115 parts of cement, 155-185 parts of crushed stone, 210-240 parts of sand, 65-85 parts of bentonite, 15-30 parts of fly ash, 130-160 parts of water, 1.5-4.5 parts of water reducer, and 3.5-6.6 parts of glycidyl ester type epoxy resin-coated SAP. Construction method of the cut-off wall: S1. Excavate a trench in the excavation area to form a construction trench; S2. Place and install the pre-embedded steel bar frame in the construction trench, then inject anti-seepage concrete and cure to form an anti-seepage wall body, completing the construction of the composite cut-off wall. This application has the effect of improving the anti-seepage performance of the cut-off wall.

[0005] However, the existing plastic cut-off walls have the following problems: 1) The commonly used curing material for plastic cut-off walls is cement. Due to the reaction characteristics of heat release and shrinkage of cement, it will cause shrinkage cracks during the curing process of plastic concrete, resulting in an increase in the permeability coefficient (k≥1×10 -6cm / s), the anti-seepage effect is greatly reduced. 2) In the construction of plastic cut-off walls, underwater pouring is generally used to replace bentonite or clay slurry to form a wall, and the replaced slurry is generally treated as solid waste, which not only causes waste of resources, but also has an adverse impact on the surrounding ecological environment. 3) The quality of the formed wall is closely related to the slurry replacement effect. If there are slight mistakes in the construction process, at key parts such as the wall segment joints and the bottom of the wall, it is very easy to leave potential safety hazards due to problems such as slurry residue and incomplete replacement, threatening the anti-seepage performance of the cut-off wall. 4) The traditional process requires multiple replacements of the slurry, and the construction period is long.

[0006] Therefore, how to reasonably solve the problem of cracks in the existing plastic cut-off walls, while ensuring the avoidance of resource waste and environmental pollution during construction, ensuring the construction quality of the cut-off wall, and shortening the construction period, has become an urgent problem to be solved. Summary of the Invention

[0007] In order to solve the natural defects of the existing solidifying materials for plastic cut-off walls and avoid problems such as quality hazards during construction, the present invention provides a method for forming a plastic cut-off wall based on in-situ slurry solidification and a cut-off wall, which can effectively solve the problem of cracks in the cut-off wall.

[0008] The technical solution adopted by the present invention to solve its technical problems is:

[0009] A method for forming a plastic cut-off wall based on in-situ slurry solidification, comprising the following steps:

[0010] S1. Determine the specific gravity of the slurry for protecting the wall and the particle activity; determine the dosage of the mineral-based cementitious material according to the specific gravity of the slurry for protecting the wall and the particle activity;

[0011] S2. Excavate the foundation trench, and use the undisturbed soil to make slurry. Add dry soil to the slurry made from the undisturbed soil to adjust the specific gravity of the slurry made from the undisturbed soil to the specific gravity of the slurry for protecting the wall, and obtain the in-situ slurry for protecting the wall;

[0012] S3. Adopt a bipolar mixing process to mix the mineral-based cementitious material with the in-situ slurry for protecting the wall and fill it in the trench section;

[0013] S4. Cure in-situ to form a plastic cut-off wall.

[0014] Preferably, the preliminary determination method of the specific gravity of the slurry for protecting the wall in S1 is: ρ = ρ 水 +(ρ 土 -ρ 水 )K a , usually the specific gravity of the slurry for protecting the wall is 1.15 - 1.25 g / cm 3 ;

[0015] In the formula, ρ is the specific gravity of the slurry for protecting the wall, ρ 水 is the specific gravity of water, ρ 土is the true density of undisturbed soil, K a is the coefficient of active earth pressure;

[0016] The method for determining the particle activity in S1 is as follows: Use a laser particle size analyzer to measure the particle size of the slurry. Particles with a diameter less than 0.002 mm are active particles.

[0017] Preferably, the mineral-based cementitious material in S1 includes an activator, cement, and slag powder; the mass ratio of the activator, cement, and slag powder is 1:1:3;

[0018] The activator is a calcium-based alkali activator, the cement is PO 42.5 cement, and the slag powder is S95-grade slag micro-powder;

[0019] The preparation method is as follows: At an ambient temperature of 5 - 22 °C, fully mix the slag powder and cement for 5 - 10 minutes to obtain mixture A; remix the calcium-based alkali activator with mixture A for 5 - 10 minutes to obtain a high-performance mineral-based cementitious material.

[0020] Preferably, the method for determining the dosage of the mineral-based cementitious material in S1 is as follows: The method for determining the dosage of the mineral-based cementitious material in S1 is as follows: According to the characteristics of the mineral-based cementitious material, when the volume fraction of active particles in the in-situ retaining wall slurry is 20%, the mass dosage of the mineral-based cementitious material is 15%; when the volume fraction of active particles in the in-situ retaining wall slurry is 40%, the mass dosage of the mineral-based cementitious material is 10%. When the volume fraction of active particles in the in-situ retaining wall slurry is 20 - 40%, the mass dosage of the mineral-based cementitious material is calculated by the interpolation method.

[0021] Preferably, the method for adjusting the specific gravity of the slurry made from undisturbed soil to the specific gravity of the retaining wall slurry in S2 is as follows: From the mass identity before and after mixing the slurry and dry soil, we can get: Obtained from the mass identity before and after

[0022] In the formula, ρ is the specific gravity of the retaining wall slurry determined in S1, ρ1 is the specific gravity of the retaining wall slurry at the bottom of the excavation, v1 is the volume of the slurry in the trench, ρ2 is the true density of the dry soil, and m2 is the mass of the required dry soil.

[0023] Preferably, in S3, the mineral-based cementitious material and the in-situ retaining wall slurry are mixed using a mixer, and the mixer speed is set at 20 - 40 revolutions per minute, and the mixing time is 5 - 10 minutes.

[0024] Preferably, the bipolar mixing process steps in S3 are as follows: Pump out the in-situ retaining wall slurry in the trench section and fully stir and mix it with the mineral-based cementitious material, and then pump the mixed solidified slurry to the bottom of the trench section to completely replace all the in-situ retaining wall slurry in the trench section.

[0025] Preferably, the specific steps of the bipolar mixing process in S3 are as follows:

[0026] S31. Place a slurry pumping conduit above the liquid level of the in-situ slurry for protecting the wall in the trench section to make preparations for slurry pumping. The slurry pumping conduit uses a PE pipe with a diameter of 100 mm.

[0027] S32. Pump the upper in-situ slurry for protecting the wall in the trench section into the mixing barrel, and at the same time inject the mineral-based cementitious material in the storage tank into the mixing barrel through the conveying pipeline. The mineral-based cementitious material and the in-situ slurry for protecting the wall are mixed for the first time in the mixing barrel. The mixing rotation speed is set at 20 - 30 revolutions per minute, the mixing time is not less than 3 minutes, and the mixing revolutions are not less than 180 times. The conveying pipeline uses a PE pipe with a diameter of 50 mm.

[0028] S33. The well-mixed solidified slurry enters the static mixer through the slurry conveying pipe for secondary mixing. The slurry conveying pipe uses a PE pipe with a diameter of 100 mm. The unit type of the static mixer is SK + SX mixer, the pipe diameter is 100 mm, the length is 1200 mm, and it is made of stainless steel with a design pressure of 1.6 MP.

[0029] S34. Pump the well-mixed solidified slurry to the bottom of the trench section through the guide slurry pipe until all the slurry in the trench section is replaced by the solidified slurry added with the high-performance mineral-based cementitious material. The guide slurry pipe uses a PE pipe with a diameter of 100 mm.

[0030] S35. Move to the next trench section and repeat steps S31 - S35 until all the in-situ slurry for protecting the wall in all trench sections is replaced by the solidified slurry.

[0031] Preferably, 5 hours after the construction of the plastic impervious wall is completed in S4, water is covered on its top surface with a thickness of not less than 0.1 m, and the impervious wall is cured in-situ underwater for 7 days. The wall quality inspection of the cured plastic impervious wall is carried out according to the current specifications and standards.

[0032] Preferably, an impervious wall includes a trench section. Initially, the in-situ slurry for protecting the wall is in the trench section. A guide slurry pipe is arranged in the in-situ slurry for protecting the wall. The top end of the guide slurry pipe is connected to a static mixer. The static mixer is connected to two slurry conveying pipes. The two slurry conveying pipes are respectively communicated with two mixing barrels. The mixing barrels are also communicated with the in-situ slurry for protecting the wall through the slurry pumping conduit. Conveying pipelines are respectively arranged at the upper ends of the two mixing barrels. The two conveying pipelines are both connected to the storage tank. Through in-situ mixing and replacement, the final in the trench section is the solidified slurry.

[0033] The beneficial effects of the present invention are:

[0034] By optimizing the material ratio and construction technology, the anti-seepage wall has better anti-seepage performance; the construction is simple, significantly shortening the construction period and reducing the labor cost; the in-situ mud solidification technology avoids the situation of a large amount of mud being treated as solid waste, reducing environmental pollution and resource waste, realizing the coordinated development of engineering construction and environmental protection, and ensuring the construction quality and long-term stable operation of the anti-seepage wall.

[0035] The construction period of the present invention is shorter than that of the traditional construction technology, effectively solving the problems of cracks and cavities easily appearing in the plastic anti-seepage wall, ensuring the integrity of the anti-seepage wall structure. At the same time, the construction waste is reduced, avoiding resource waste, protecting the ecological environment, and ensuring the construction quality of the anti-seepage wall. The method of the present invention has the advantages of good anti-seepage performance, simple construction, short construction period, environmental friendliness and reliable quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the initial construction of the in-situ mud solidification anti-seepage wall described in the present invention.

[0037] Figure 2 It is a schematic diagram of the intermediate construction of the in-situ mud solidification anti-seepage wall described in the present invention.

[0038] Figure 3 It is a schematic diagram of the final construction of the in-situ mud solidification anti-seepage wall described in the present invention.

[0039] Reference numerals: 1 - high-performance mineral-based cementitious material, 2 - groove section, 3 - in-situ retaining mud, 4 - solidification slurry, 5 - slurry extraction conduit, 6 - mixing barrel, 7 - storage tank, 8 - conveying pipeline, 9 - slurry delivery pipe, 10 - static mixer, 11 - slurry guiding pipe. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description progresses. However, the embodiments are only exemplary and do not constitute any limitation to the scope of the present invention. Those skilled in the art should understand that without departing from the spirit and scope of the present invention, the details and forms of the technical solutions of the present invention can be modified or replaced, but these modifications and replacements all fall within the protection scope of the present invention.

[0041] A method for forming a plastic anti-seepage wall based on in-situ mud solidification, specifically including the following steps:

[0042] (1) First, according to the physical and mechanical properties of the soil mass at the foundation trench position and the groundwater level, calculate and determine the specific gravity of the in-situ retaining mud.

[0043] Determine the particle activity of the in-situ retaining mud and the dosage of the high-performance mineral-based cementitious material through experiments.

[0044] (2) Use the conventional trench excavation process to excavate the foundation trench, make slurry for wall protection, add dry soil, and adjust the specific gravity of the slurry for wall protection to the value determined in the early stage.

[0045] (3) Adopt the bipolar mixing process to mix the high-performance mineral-based gelling material with the in-situ slurry for wall protection and fill it in the trench section.

[0046] (4) Cure in-situ to form a plastic impervious wall.

[0047] Example 1

[0048] The following only takes a certain river dike as an example to specifically illustrate the features of the present invention. However, all descriptions are only for illustration and should not be construed as any limitation to the present invention.

[0049] The lithology of the soil stratum of the foundation of a certain river dike is mainly sandy loam, loam, silty sand and fine sand formed by the alluvial (Q4 alp ) origin, and the bottom layer is gravel layer, etc. The main types of foundation geological structures are single-layer structure, double-layer structure and multi-layer structure. After the seepage stability calculation, the exit gradient behind the dike at some double-layer and multi-layer foundation parts is higher than the allowable gradient and does not meet the requirements. In order to reduce the seepage around the sand foundation and cause downstream seepage damage, the plastic impervious wall is used for foundation treatment at the parts of the foundation containing silty sand, fine sand and silty fine sand. The specific implementation steps are as follows.

[0050] (1) First, according to the physical and mechanical properties of the soil and the groundwater level at the foundation trench location, calculate to determine the specific gravity of the in-situ slurry for wall protection. The true density of the undisturbed soil is 1.5 g / cm 3 , the coefficient of active earth pressure is 0.271, considering a safety factor of 1.1, calculate the specific gravity of the slurry for wall protection to be 1.25 g / cm 3 .

[0051] Use a laser particle size analyzer to test the particle size of the slurry, determine that the particle active volume content of the slurry for wall protection is 30%, and formulate the mass dosage of the high-performance mineral-based gelling material to be 10%. The mineral-based gelling material includes an activator, cement and slag powder; the mass ratio of the activator, cement and slag powder is 1:1:3;

[0052] The activator is a calcium-based alkali activator, the cement is PO 42.5 cement, and the slag powder is S95-grade slag micro-powder;

[0053] The preparation method is: at an ambient temperature of 5-22 °C, fully mix the slag powder and cement for 8 minutes to obtain mixture A; remix the calcium-based activator with mixture A for 8 minutes to obtain the high-performance mineral-based gelling material.

[0054] (2) Excavate the impervious wall foundation trench according to the designed depth of 18.75 m and thickness of 0.8 m, and use the undisturbed soil to make slurry for wall protection.

[0055] The current mud specific gravity is 1.18 g / cm 3 , and the required mud specific gravity for shaft protection is 1.25 g / cm 3 , the true density of dry soil is 1.6 g / cm 3 , the volume of mud in the trench is 150 m 3 . It is calculated that the weight of dry soil to be added is 225 tons.

[0056] Add 225 tons of dry soil in batches. The mixer runs at 30 revolutions per minute for 8 minutes, and the mud specific gravity is adjusted to 1.25 g / cm 3 .

[0057] (3) Pump the in-situ shaft protection mud in the trench section into the mixing barrel, and at the same time inject the high-performance mineral-based cementitious material into the mixing barrel through the conveying pipeline. Conduct the first mixing in the mixing barrel, with the mixing speed set at 25 revolutions per minute and the mixing time of 8 minutes.

[0058] After secondary mixing through the static mixer, inject the solidified slurry into the bottom of the trench at a pump speed of 4 m 3 / min for continuous replacement.

[0059] Shift to the next trench section and repeat the above steps until all the in-situ shaft protection mud in all trench sections is replaced with the solidified slurry.

[0060] As Figures 1 to 3 shown, the specific steps are as follows:

[0061] S31. Place the slurry pumping conduit 5 above the liquid level of the in-situ shaft protection mud 3 in the trench section 2, make preparations for slurry pumping. The slurry pumping conduit 5 uses a PE pipe with a diameter of 100 mm;

[0062] S32. Pump the upper in-situ shaft protection mud 3 in the trench section 2 into the mixing barrel 6, and at the same time inject the mineral-based cementitious material 1 in the storage tank 7 into the mixing barrel 6 through the conveying pipeline 8. The mineral-based cementitious material 1 and the in-situ shaft protection mud 3 are subjected to the first mixing in the mixing barrel 6. The mixing speed is set at 20 - 30 revolutions per minute, the mixing time is not less than 3 minutes, or the mixing times are not less than 180 times. The conveying pipeline 8 uses a PE pipe with a diameter of 50 mm;

[0063] S33. The mixed solidified slurry 4 enters the static mixer 10 through the slurry conveying pipe 9 for secondary mixing. The slurry conveying pipe 9 uses a PE pipe with a diameter of 100 mm. The unit type of the static mixer 10 is the SK + SX mixer, the pipe diameter is 100 mm, the length is 1200 mm, and the design pressure is 1.6 MP of stainless steel material;

[0064] S34. Pump the well - stirred solidified slurry 4 through the slurry guide pipe 11 to the bottom of the trench section 2 until all the slurry in the trench section 2 is replaced by the solidified slurry 4 added with the high - performance mineral - based cementitious material 1. The slurry guide pipe 11 is a PE pipe with a diameter of 100 mm;

[0065] S35. Move to the next trench section 2 and repeat steps S31 - S35 until all the in - situ retaining slurry 3 in all trench sections 2 is replaced by the solidified slurry 4.

[0066] (4) Five hours after the construction of the plastic impervious wall is completed, cover it with water on its top surface with a thickness of 0.1 m, and the impervious wall is cured in - situ underwater for 7 days. After 7 - day curing, conduct the quality inspection of the formed wall of the plastic impervious wall according to the current specifications and standards. The test results show that the permeability coefficient k = 8×10 -9 cm / s and the compressive strength is 3.51 MPa.

[0067] The structure of the plastic impervious wall includes: a trench section 2, initially filled with in - situ retaining slurry 3 inside the trench section 2. A slurry guide pipe 11 is arranged in the in - situ retaining slurry 3. The top end of the slurry guide pipe 11 is connected to a static mixer 10. The static mixer 10 is connected to two slurry delivery pipes 9. The two slurry delivery pipes 9 are respectively connected to the mixing barrels 6. The mixing barrels 6 are also connected to the in - situ retaining slurry 3 through the slurry suction conduits 5. Delivery pipes 8 are respectively arranged at the upper ends of the two mixing barrels 6, and the two delivery pipes 8 are both connected to the storage tank 7. Through in - situ stirring and replacement, the inside of the section 2 finally becomes the solidified slurry 4.

[0068] Example Two

[0069] In a pneumatic shield dam project, the water - retaining height is 4.5 m. To reduce the uplift pressure at the gate chamber position and the seepage around both sides, and at the same time improve the anti - sliding stability of the gate chamber, impervious walls are set at the front edge of the pneumatic shield dam bottom slab and on both banks. The specific implementation steps are as follows.

[0070] (1) First, according to the formation and groundwater level conditions at the position of the pneumatic shield dam, calculate and determine the specific gravity of the in - situ retaining slurry. The true density of the undisturbed soil is 1.13 g / cm 3 , the coefficient of active earth pressure is 0.349. Considering a safety factor of 1.1, calculate the specific gravity of the retaining slurry to be 1.15 g / cm 3 .

[0071] Use a laser particle size analyzer to test the particle size of the slurry, determine that the particle active volume content of the retaining slurry is 40%, and formulate the mass admixture of the high - performance mineral - based cementitious material to be 10%. The mineral - based cementitious material includes an activator, cement, and slag powder; the mass ratio of the activator, cement, and slag powder is 1:1:3;

[0072] The activator is a calcium - based alkali activator, the cement is PO 42.5 cement, and the slag powder is S95 - grade slag micro - powder;

[0073] The preparation method is as follows: at an ambient temperature of 5 - 22°C, the mineral powder and cement are fully mixed for 5 minutes to obtain mixture A; the calcium-based activator is mixed with the mixture A again for 10 minutes to obtain a high-performance mineral-based cementitious material.

[0074] (2) Excavate the cut-off wall foundation trench to a depth of 10 m and a thickness of 0.5 m according to the design requirements, and use the in-situ soil to make slurry for wall protection.

[0075] The current slurry specific gravity is 1.13 g / cm 3 , and the slurry specific gravity required for wall protection is 1.15 g / cm 3 , the true density of dry soil is 1.61 g / cm 3 , the volume of slurry in the trench is 50 m 3 , and it is calculated that the weight of dry soil to be added is 60.0 tons.

[0076] Add 60.0 tons of dry soil in batches, and the mixer runs at 20 revolutions per minute for 8 minutes to adjust the slurry specific gravity to 1.15 g / cm 3 .

[0077] (3) Pump the in-situ wall protection slurry in the trench section into the mixing barrel, and at the same time inject the high-performance mineral-based cementitious material into the mixing barrel through the conveying pipeline. Conduct the first stirring in the mixing barrel, set the stirring speed at 20 revolutions per minute, and the stirring time is 10 minutes.

[0078] After secondary stirring through the static mixer, inject the solidified slurry into the bottom of the trench at a pump speed of 4 m 3 / min for continuous replacement.

[0079] Shift to the next trench section and repeat the above steps until all the in-situ wall protection slurry in all trench sections is replaced with the solidified slurry.

[0080] As Figures 1 to 3 shown, the specific steps are as follows:

[0081] S31. Place the slurry pumping conduit 5 above the liquid level of the in-situ wall protection slurry 3 in trench section 2 to make preparations for slurry pumping. The slurry pumping conduit 5 uses a PE pipe with a diameter of 100 mm;

[0082] S32. Pump the upper in-situ wall protection slurry 3 in trench section 2 into the mixing barrel 6, and at the same time inject the mineral-based cementitious material 1 in the storage tank 7 into the mixing barrel 6 through the conveying pipeline 8. The mineral-based cementitious material 1 and the in-situ wall protection slurry 3 are subjected to the first stirring in the mixing barrel 6. Set the stirring speed at 20 - 30 revolutions per minute, the stirring time is not less than 3 minutes, or the number of stirring times is not less than 180 times. The conveying pipeline 8 uses a PE pipe with a diameter of 50 mm;

[0083] S33. The well-stirred solidified slurry 4 enters the static mixer 10 through the slurry delivery pipe 9 for secondary stirring. The slurry delivery pipe 9 is a PE pipe with a diameter of 100 mm. The static mixer 10 is of the SK+SX mixer type, with a pipe diameter of 100 mm, a length of 1200 mm, and is made of stainless steel with a design pressure of 1.6 MP.

[0084] S34. Pump the well-stirred solidified slurry 4 to the bottom of the trench section 2 through the guide slurry pipe 11 until all the slurry in the trench section 2 is replaced by the solidified slurry 4 added with the high-performance mineral-based cementitious material 1. The guide slurry pipe 11 is a PE pipe with a diameter of 100 mm.

[0085] S35. Move to the next trench section 2 and repeat steps S31 - S35 until all the in-situ retaining slurry 3 in all trench sections 2 is replaced by the solidified slurry 4.

[0086] (5) Five hours after the construction of the plastic impervious wall is completed, cover it with water on its top surface with a thickness of 0.1 m, and the impervious wall is cured in-situ underwater for 7 days. After 7 days of curing, conduct the quality inspection of the formed wall of the plastic impervious wall according to the current specifications and standards. The test results show that the permeability coefficient k = 2.1×10 -8 cm / s and the compressive strength is 3.42 MPa.

[0087] The structure of the plastic impervious wall includes: the trench section 2, initially filled with in-situ retaining slurry 3 inside the trench section 2. A guide slurry pipe 11 is arranged inside the in-situ retaining slurry 3. The top end of the guide slurry pipe 11 is connected to the static mixer 10. The static mixer 10 is connected to two slurry delivery pipes 9. The two slurry delivery pipes 9 are respectively connected to the mixing barrels 6. The mixing barrels 6 are also connected to the in-situ retaining slurry 3 through the slurry suction conduits 5. Conveying pipes 8 are respectively arranged at the upper ends of the two mixing barrels 6, and the two conveying pipes 8 are both connected to the storage tank 7. Through in-situ stirring and replacement, the inside of the section 2 finally becomes the solidified slurry 4.

[0088] Example 3

[0089] In a hinge dam project, there is a fine sand layer in the strata under the dam, with a buried depth of about 16 m and a thickness of about 5 m. The standard penetration test hammer blow number of this layer is 11. According to the geological exploration report, the liquefaction grade is severe. It is designed to use a concrete diaphragm wall for enclosure to eliminate liquefaction and settlement. The specific implementation steps are as follows.

[0090] (1) First, according to the strata and groundwater level conditions at the hinge dam location, calculate and determine the specific gravity of the in-situ retaining slurry. The true density of the undisturbed soil is 1.30 g / cm 3 , the coefficient of active earth pressure is 0.302. Considering a safety factor of 1.1, calculate the specific gravity of the retaining slurry to be 1.20 g / cm 3 .

[0091] The particle size of the mud is measured by a laser particle size analyzer, and the particle active volume content of the hole-protecting mud is determined to be 30%, and the mass dosage of the high-performance mineral-based cementitious material is formulated to be 12.5%. The mineral-based cementitious material includes an activator, cement, and slag powder; the mass ratio of the activator, cement, and slag powder is 1:1:3;

[0092] The interpolation formula is: Y = Y1 + (Y2 - Y1) × (X - X1) / (X2 - X1).

[0093] 12.5% = 15% + (10% - 15%) × (30% - 20%) / (40% - 20%)

[0094] The activator is a calcium-based alkali activator, the cement is PO 42.5 cement, and the slag powder is S95-grade granulated blast-furnace slag powder;

[0095] The preparation method is as follows: at an ambient temperature of 5 - 22 °C, the slag powder and cement are fully mixed for 10 minutes to obtain mixture A; the calcium-based activator is mixed with mixture A again for 5 minutes to obtain the high-performance mineral-based cementitious material.

[0096] (2) Excavate the cutoff wall foundation trench according to the designed depth of 17.0 m and thickness of 0.4 m, and use the in-situ soil to make mud for hole protection.

[0097] The specific gravity of the current mud is 1.15 g / cm 3 , and the specific gravity of the hole-protecting mud required is 1.20 g / cm 3 , the true density of the dry soil is 1.61 g / cm 3 , the volume of the mud in the trench is 54.4 m 3 , and it is calculated that the weight of the dry soil to be added is 73.2 tons.

[0098] Add 73.2 tons of dry soil in batches, and the mixer runs at 25 revolutions per minute for 8 minutes to adjust the specific gravity of the mud to 1.20 g / cm 3 .

[0099] (3) Pump the in-situ hole-protecting mud in the trench section into the mixing barrel, and at the same time inject the high-performance mineral-based cementitious material into the mixing barrel through a conveying pipeline, and conduct the first mixing in the mixing barrel, with the mixing speed set at 40 revolutions per minute and the mixing time of 5 minutes.

[0100] After secondary mixing through a static mixer, inject the solidified slurry into the bottom of the trench at a pump speed of 4 m 3 / min for continuous replacement.

[0101] Shift to the next trench section and repeat the above steps until all the in-situ hole-protecting mud in all trench sections is replaced with the solidified slurry.

[0102] Such as Figures 1 to 3As shown in the figure, the specific steps are as follows:

[0103] S31. Place the slurry pumping conduit 5 above the liquid level of the in-situ slurry support 3 in the trench section 2 to prepare for slurry pumping. The slurry pumping conduit 5 is a PE pipe with a diameter of 100 mm.

[0104] S32. Pump the upper part of the in-situ slurry support 3 in the trench section 2 into the mixing barrel 6. At the same time, inject the mineral-based cementitious material 1 in the storage tank 7 into the mixing barrel 6 through the conveying pipeline 8. The mineral-based cementitious material 1 and the in-situ slurry support 3 are stirred for the first time in the mixing barrel 6. The stirring speed is set at 20 - 30 revolutions per minute, and the stirring time is not less than 3 minutes, or the number of stirrings is not less than 180 times. The conveying pipeline 8 is a PE pipe with a diameter of 50 mm.

[0105] S33. The well-stirred solidified slurry 4 enters the static mixer 10 through the slurry conveying pipe 9 for secondary stirring. The slurry conveying pipe 9 is a PE pipe with a diameter of 100 mm. The unit type of the static mixer 10 is SK + SX mixer, with a pipe diameter of 100 mm and a length of 1200 mm, and it is made of stainless steel with a design pressure of 1.6 MP.

[0106] S34. Pump the well-stirred solidified slurry 4 to the bottom of the trench section 2 through the guide slurry pipe 11 until all the slurry in the trench section 2 is replaced with the solidified slurry 4 added with the high-performance mineral-based cementitious material 1. The guide slurry pipe 11 is a PE pipe with a diameter of 100 mm.

[0107] S35. Move to the next trench section 2 and repeat steps S31 - S35 until all the in-situ slurry support 3 in all trench sections 2 is replaced with the solidified slurry 4.

[0108] (6) Five hours after the construction of the plastic impervious wall is completed, cover it with water on its top surface with a thickness of 0.1 m, and the impervious wall is cured in-situ underwater for 7 days. After 7 days of curing, conduct the wall-forming quality inspection of the plastic impervious wall according to the current specifications and standards. The inspection results show that the permeability coefficient k = 1.15×10 -7 cm / s and the compressive strength is 3.45 MPa.

[0109] The structure of the plastic impervious wall includes: the trench section 2, initially filled with the in-situ slurry support 3 inside the trench section 2. A guide slurry pipe 11 is arranged in the in-situ slurry support 3. The top end of the guide slurry pipe 11 is connected to the static mixer 10. The static mixer 10 is connected to two slurry conveying pipes 9. The two slurry conveying pipes 9 are respectively communicated with the mixing barrel 6. The mixing barrel 6 is also communicated with the in-situ slurry support 3 through the slurry pumping conduit 5. The upper ends of the two mixing barrels 6 are respectively provided with conveying pipelines 8, and the two conveying pipelines 8 are both connected to the storage tank 7. Through in-situ stirring and replacement, the trench section 2 finally contains the solidified slurry 4.

[0110] Comparative Example 1

[0111] The riverbed strata where the dam foundation of a certain rubber dam project is located basically belong to a double-layer structure of rock and soil. The lithology of the soil layer is mainly gravel, loam or gravelly soil, with a layer thickness of 1.0 - 7.0 m, and the rock layer is granite gneiss. The gravelly soil belongs to a strongly permeable layer with a permeability coefficient of 3.6×10 -2 cm / s. The permeability coefficient of the completely weathered zone of granite gneiss is 2.7×10 -4 ~3.3×10 -6 cm / s, with an average value of 5.6×10 -5 cm / s, belonging to weak water permeability. The construction adopts the traditional cement solidification process and uses cement-bentonite slurry (cement content 20%). The specific implementation steps are as follows.

[0112] (1) First, conduct the mix ratio and performance test of the slurry for shaft protection, and determine that the specific gravity of the slurry for shaft protection is 1.26 g / cm 3 .

[0113] (2) Establish a construction survey control network, conduct construction layout, and accurately determine the position of the cut-off wall.

[0114] (3) According to the hole-making method, machine performance, hole-making duration, concrete supply intensity, and the layout principle of the pouring conduit, determine that the sectional length of the trench is 8.0 m.

[0115] (4) Use a hydraulic grab to form the trench, and the wall thickness is 0.6 m.

[0116] (5) Ensure the supply of slurry during the trench formation process to maintain the stability of the hole wall. A drainage ditch is set up at the construction site to timely drain the waste water, waste slurry, and waste residue around the trench.

[0117] (6) After the trench formation is completed, conduct a comprehensive inspection of the width, depth, and verticality of the formed trench.

[0118] (7) Three hours after the trench formation acceptance, conduct the operation of cleaning the trench and removing the sediment. Wait for the floating sediment to settle, and use the grab to directly lower it into the trench to grab the sediment and fish out the sediment. Avoid the incomplete replacement at the bottom of the cut-off wall caused by the residual sediment, which affects the anti-seepage performance.

[0119] (8) Conduct the cement pouring within 4 hours after the trench cleaning. Adopt the direct-pouring conduit method, and the inner diameter of the conduit is 25 cm.

[0120] (9) Control the distance between the bottom of the conduit and the trench bottom within the range of 15 - 25 cm. Control the depth of the conduit buried in the concrete to be 2.0 m. The rising speed of the poured cement surface is 2.5 m / h.

[0121] (10) Eliminate the pouring height error caused by the influence of the slurry, ensure that the top of the cut-off wall reaches the designed height requirement, and the final pouring top surface should be 50 cm higher than the designed elevation.

[0122] (11) Curing shall start 6 hours after the diaphragm wall is poured to prevent cracks caused by excessive evaporation of moisture on the concrete surface. Geotextiles shall be laid on its top surface and watered for curing for 14 days. During this period, water shall be sprinkled regularly according to the evaporation of moisture to keep it moist.

[0123] (12) Quality inspection of the wall body shall be carried out 28 days after the wall is formed. On-site drilling and coring and water pressure tests shall be used to check the uniformity and possible defects of the wall. After testing, the permeability coefficient is k = 1.5×10 -6 cm / s and the compressive strength is 1.92 MPa.

[0124] Comparative analysis of the examples and comparative examples shows that:

[0125] (1) The plastic diaphragm wall constructed by the present invention shows significant advantages in many performance indicators compared with the traditional cement-solidified diaphragm wall.

[0126] (2) The present invention adopts in-situ mixing and replacement, avoiding the incomplete replacement at the bottom of the diaphragm wall caused by the residue of sediment in the existing process.

[0127] (3) After the slurry with high-performance mineral-based cementitious materials is solidified, it effectively avoids the occurrence of dry shrinkage cracks and effectively improves the anti-seepage ability of the diaphragm wall.

[0128] (4) No waste slurry is generated during the construction of the present invention, reducing the pollution pressure on the surrounding environment and realizing the coordinated development of engineering construction and environmental protection.

[0129] (5) The construction period is generally shortened, significantly improving the construction efficiency and reducing the labor cost and equipment rental cost.

[0130] (6) It avoids the situation of treating the slurry for retaining wall as solid waste in the prior art, effectively reducing the pollution pressure on the surrounding environment and realizing the coordinated development of engineering construction and environmental protection.

[0131] In the embodiment, in-situ soil is innovatively used to make slurry for shaft protection, and a high-performance mineral-based cementitious material is added. After the two are fully stirred and mixed, a solidified slurry is formed, avoiding the situation of treating the shaft protection slurry in the prior art as solid waste, which causes waste of resources and environmental pollution. After the slurry with the high-performance mineral-based cementitious material is solidified, no dry shrinkage cracks will occur, fundamentally ensuring the anti-seepage performance of the cut-off wall. The in-situ stirring process is adopted to effectively avoid many drawbacks existing in the traditional process. In traditional construction, key parts such as joints and the bottom of the wall often have problems such as residual slurry and incomplete replacement, resulting in cavities and incomplete structures in the cut-off wall, which seriously affect the anti-seepage performance. At the same time, the traditional cut-off wall construction process also has problems such as complex construction processes and high failure rates. The in-situ stirring process, relying on its own advantages, not only simplifies the construction process, ensures the integrity of the cut-off wall structure, but also greatly improves the anti-seepage performance, providing more reliable technical support for related engineering construction.

[0132] The above is only used to introduce the specific implementation manners of the present invention in detail, but the technical solutions proposed by the present invention are not limited to the above methods. Without departing from the basic principles of the present technology, equivalent modifications and changes made by those skilled in the art to the technology proposed by the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for forming a plastic anti-seepage wall based on in-situ slurry solidification, characterized in that: The following steps are involved: S1, determining the specific gravity and particle activity of the wall protection slurry; determining the dosage of the mineral-based cementitious material (1) according to the specific gravity and particle activity of the wall protection slurry; S2, excavating the foundation trench, and making mud with the original soil, adding dry soil to the mud made with the original soil, adjusting the specific gravity of the mud made with the original soil to the specific gravity of the wall protection mud, and obtaining the in-situ wall protection mud (3); S3, using a bipolar mixing process, mixing the mineral-based cementitious material (1) with the in-situ wall protection slurry (3), and filling the mixture into the trench section (2); S4. In-situ maintenance to form a plastic anti-seepage wall.

2. A method for forming a plastic anti-seepage wall based on in-situ slurry solidification according to claim 1, characterized in that: The preliminary method for determining the specific gravity of the wall protection mud in S1 is: ρ=ρ 水 +(ρ 土 -ρ 水 )K a The specific gravity of the wall protection mud is 1.15~1.25g / cm 3 ; Where ρ is the specific gravity of the wall protection mud, ρ 水 is the specific gravity of water, ρ 土 is the true density of the original soil, K a is the active earth pressure coefficient; The method for determining the activity of particles in S1 is: using a laser particle size analyzer to test the size of mud particles, and particles with a diameter less than 0.002 mm are active particles.

3. The method for forming a plastic anti-seepage wall based on in-situ slurry solidification according to claim 1, characterized in that: The mineral-based cementitious material in S1 includes an activator, cement and mineral powder; the mass ratio of the activator, cement and mineral powder is 1:1:3; The activator is a calcium-based alkali activator, the cement is PO 42.5 cement, and the mineral powder is S95 grade slag powder; The preparation method is as follows: at an ambient temperature of 5-22°C, fully mix the mineral powder and cement for 5-10 minutes to obtain a mixture A; and mix the calcium-based alkali activator with the mixture A again for 5-10 minutes to obtain a high-performance mineral-based cementitious material.

4. A method for forming a plastic anti-seepage wall based on in-situ slurry solidification according to claim 2, characterized in that: The method for determining the amount of mineral-based cementitious material (1) in S1 is as follows: according to the characteristics of the mineral-based cementitious material (1), when the volume proportion of active particles in the in-situ wall protection mud is 20%, the mass proportion of the mineral-based cementitious material (1) is 15%; when the volume proportion of active particles in the in-situ wall protection mud is 40%, the mass proportion of the mineral-based cementitious material (1) is 10%; when the volume proportion of active particles in the in-situ wall protection mud is 20-40%, the mass proportion of the mineral-based cementitious material (1) is calculated according to the interpolation method.

5. The method for forming a plastic anti-seepage wall based on in-situ slurry solidification according to claim 1, characterized in that: The method for adjusting the mud density of the original soil to the mud density of the wall protection in S2 is: by mixing the mud with dry soil, the mass identity before and after can be obtained: From the front and rear mass identities, we can find In the formula, ρ is the specific gravity of the wall protection mud determined by S1, ρ1 is the specific gravity of the wall protection mud when excavating to the bottom, v1 is the volume of mud in the trench, ρ2 is the true density of dry soil, and m2 is the mass of dry soil required.

6. The method for forming a plastic anti-seepage wall based on in-situ slurry solidification according to claim 1, characterized in that: The mineral-based cementitious material (1) in S3 and the in-situ wall protection mud (3) are mixed by a stirrer, the speed of the stirrer is set at 20 to 40 revolutions per minute, and the stirring time is 5 to 10 minutes.

7. A method for forming a plastic anti-seepage wall based on in-situ slurry solidification according to claim 1, characterized in that: The bipolar mixing process steps in S3 are as follows: extract the in-situ wall protection mud (3) in the tank section (2) and fully stir and mix it with the mineral-based cementitious material (1), and then pump the mixed solidified slurry (4) to the bottom of the tank section (2), so as to completely replace the in-situ wall protection mud (3) in the tank section (2).

8. A method for forming a plastic anti-seepage wall based on in-situ slurry solidification according to claim 7, characterized in that: The specific steps of the bipolar mixing process in S3 are as follows: S31, placing a slurry extraction conduit (5) above the liquid level of the in-situ wall protection slurry (3) in the trough section (2), and making preparations for slurry extraction, wherein the slurry extraction conduit (5) is a PE pipe with a diameter of 100 mm; S32, extracting the in-situ wall protection slurry (3) from the upper part of the tank section (2) into the mixing barrel (6), and at the same time injecting the mineral-based cementitious material (1) in the storage tank (7) into the mixing barrel (6) through the delivery pipe (8), the mineral-based cementitious material (1) and the in-situ wall protection slurry (3) are stirred for the first time in the mixing barrel (6), the stirring speed is set at 20 to 30 rpm, the stirring time is not less than 3 minutes, the stirring number of revolutions is not less than 180 times, and the delivery pipe (8) adopts a PE pipe with a diameter of 50 mm; S33, the stirred solidified slurry (4) enters the static mixer (10) through the slurry delivery pipe (9) for secondary stirring, the slurry delivery pipe (9) adopts a PE pipe with a diameter of 100 mm, and the static mixer (10) unit type is a SK+SX mixer, the pipe diameter is 100 mm, the length is 1200 mm, and the design pressure is 1.6 MPa of stainless steel; S34, pumping the stirred solidified slurry (4) to the bottom of the tank section (2) through the slurry guide pipe (11), until the mud in the tank section (2) is completely replaced by the solidified slurry (4) added with the high-performance mineral-based cementitious material (1), and the slurry guide pipe (11) is a PE pipe with a diameter of 100 mm; S35, shift to the next slot section (2), and repeat steps S31 to S35 until the in-situ wall protection slurry (3) in all slot sections (2) is replaced with solidified slurry (4).

9. The method for forming a plastic anti-seepage wall based on in-situ slurry solidification according to claim 1, characterized in that: In S4, 5 hours after the construction of the plastic cut-off wall is completed, water is covered on its top surface with a thickness of not less than 0.1m. The cut-off wall is cured in situ underwater for 7 days. The quality inspection of the cured plastic cut-off wall is carried out in accordance with the current specifications and standards.

10. An anti-seepage wall, based on the method for forming a plastic anti-seepage wall based on in-situ slurry solidification according to any one of claims 1 to 9, characterized in that: The plastic anti-seepage wall comprises a trough section (2), wherein the trough section (2) initially contains in-situ wall protection slurry (3), wherein a slurry guide pipe (11) is arranged in the in-situ wall protection slurry (3), wherein the top end of the slurry guide pipe (11) is connected to a static mixer (10), wherein the static mixer (10) is connected to two slurry delivery pipes (9), wherein the two slurry delivery pipes (9) are respectively connected to two stirring barrels (6), wherein the stirring barrels (6) are also connected to the in-situ wall protection slurry (3) via a slurry extraction conduit (5), wherein conveying pipes (8) are respectively arranged at the upper ends of the two stirring barrels (6), wherein the two conveying pipes (8) are both connected to a storage tank (7), and wherein the trough section (2) finally contains solidified slurry (4) through in-situ stirring and displacement.

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