Method for constructing a concrete diaphragm wall

Abstract

The application relates to a construction method of a concrete cutoff wall, and the construction method of the concrete cutoff wall is applied to a reservoir dam body, the upper layer of the reservoir dam body is a covering layer, the lower layer is a bedrock layer, and the construction method of the concrete cutoff wall comprises the following steps: S1, using a hydraulic grab bucket trenching device to excavate a pouring groove which penetrates the covering layer from a construction operation platform of the reservoir dam body and adding mud with wall protection performance into the pouring groove; S2, when the bottom of the pouring groove is lowered to the upper surface of the bedrock layer, a double-wheel trenching device is used to continue excavating the pouring groove downward in the bedrock layer until the depth of the pouring groove reaches a set value. The construction method of the concrete cutoff wall adopts a combined trenching method of the upper covering layer hydraulic grab bucket trenching device and the lower bedrock layer double-wheel trenching device, is suitable for efficiently trenching in a soft and hard composite stratum, and has the advantages of high construction efficiency, short construction period, precise control, high trenching precision, small vibration noise, low dam body disturbance and the like.

Description

Technical Field

[0001] This application relates to the field of concrete cut-off walls, and in particular to a construction method for concrete cut-off walls. Background Technology

[0002] Seepage safety is a core control element for the safe operation of earth-rock dams. In domestic reservoir reinforcement and dam upgrading projects, vertical cutoff walls are the mainstream technology for controlling seepage hazards in dam bodies and improving overall seepage prevention capabilities. Low-modulus concrete cutoff walls exhibit excellent deformation coordination, allowing them to deform in tandem with the dam body and foundation soil. They demonstrate outstanding adaptability, durability, and seepage prevention stability, and have been widely applied in water conservancy seepage prevention projects. Concrete cutoff walls are typically constructed by trenching from top to bottom, penetrating the dam body and embedding into weakly weathered rock layers. The geological structure during construction generally features a composite stratum of soft upper layers and hard lower layers. Traditional construction methods often employ a combination of "grab bucket trenching + drilling and splitting," which has significant drawbacks. Firstly, it is inefficient, slow in construction period, has many uncontrollable factors, and is difficult to manage the construction schedule. Secondly, drilling is prone to deviation and trenching accuracy is low. Finally, it generates significant impact vibration and noise, which can disturb residents. More seriously, it can easily damage the original dam body and soil structure, resulting in the reservoir generally needing to be empty during construction. Summary of the Invention

[0003] To address the construction challenges of the traditional combined "grab bucket trenching + drilling and splitting" process, this application provides a novel construction method for concrete anti-seepage walls.

[0004] One aspect of this disclosure proposes a construction method for a concrete cutoff wall, applied to a reservoir dam body. During construction, the reservoir is allowed to maintain a normal water storage state, with the water level 5-6 meters below the construction platform of the dam body. The upper layer of the dam body is a cover layer, and the lower layer is a bedrock layer. The method includes the following construction steps: S1. Using a hydraulic grab trenching device, excavate a pouring trench from the reservoir dam construction platform downwards through the overburden layer, and add mud with wall-protecting properties into the pouring trench. S2. When the bottom of the trench to be poured descends to the upper surface of the bedrock layer, switch to a twin-wheel trenching machine to continue excavating the trench downwards in the bedrock layer until the depth of the trench reaches the set value. The ratio of the number of hydraulic grab troughing equipment to the number of twin wheel milling equipment is greater than or equal to 2:1. The twin wheel milling equipment operates continuously during construction, while the hydraulic grab troughing equipment performs construction of other pouring troughs during the construction of the twin wheel milling equipment. S3. After replacing the mud in the pouring trench, pour concrete below the mud in the pouring trench, and remove the excess mud in the pouring trench during the pouring process. S4. After the concrete has solidified, repeat S1-S3 to excavate the next pouring trench and pour concrete, ensuring that the poured concrete is sealed and fixedly connected to the concrete in the previous pouring trench.

[0005] Preferably, S1, using a hydraulic grab trenching device to excavate a pouring trench penetrating the overburden layer from the reservoir dam construction platform downwards, and adding mud with wall-protecting properties into the pouring trench includes: A guide wall is installed on the wall of the casting trough opening; The casting trench is divided into three sections along the width of the trench. The end sections are excavated first, and the middle section is excavated last. During the excavation process, mud was continuously added into the casting trench, and the mud level was kept 1.5m above the groundwater level. The width of the end casting groove is greater than the width of the middle casting groove.

[0006] Preferably, during the construction of the guide wall, the layout error of the guide wall axis is no more than 10mm, the flatness deviation of the inner wall surface of the guide wall is no more than 3mm, the verticality is no more than 0.5%, and the flatness of the top surface of the guide wall is 5mm.

[0007] Preferably, in step S2, when the bottom of the trench to be poured descends to the upper surface of the bedrock layer, a twin-wheel trenching machine is used to continue excavating the trench downwards in the bedrock layer until the depth of the trench reaches the set value, including: In the bedrock layer, the casting trench is divided into three milled sections along the width of the trench. The end milled trench is milled first, and the middle milled trench is milled last. During the process of continuing to excavate the casting trench downwards in the bedrock layer, the mud at the bottom of the casting trench is pumped out while new mud is added into the casting trench, and the mud level is kept 1.5m above the groundwater level. The depth of the casting trough is obtained by averaging measurements taken at multiple locations; The width of the end casting groove is greater than the width of the middle casting groove.

[0008] Preferably, the slurry pumped out from the bottom of the casting tank is filtered and then flows back into the casting tank; The new mud contains bentonite, soda ash, and CMC; The slurry in the casting tank meets the following requirements: concentration greater than 4.5%, density less than 1.1 g / cm3, funnel viscosity 30-90 s, plastic viscosity less than 20 cp, static shear force at 10 minutes 1.4-10 N / m2, and pH value 9.5-12.

[0009] Preferably, the distance between the mud slurry surface and the opening of the casting trench is 40-60cm.

[0010] Preferably, in step S3, after replacing the slurry in the pouring trench, concrete is poured below the slurry in the pouring trench. During the pouring process, removing excess slurry from the pouring trench includes: While pumping out the mud from the bottom of the casting trench, new mud is added into the casting trench, and the mud level is kept 1.5m above the groundwater level until all the mud in the casting trench is replaced. Concrete is poured below the slurry in the pouring trench using the tremie pipe method, while excess slurry in the pouring trench is removed at the same time. After the concrete has hardened, grooves are formed at both ends of the concrete.

[0011] Preferably, in S4, the concrete poured in the next section of the pouring trench enters the groove and is sealed and fixedly connected with the concrete in the previous section of the pouring trench.

[0012] Preferably, before pouring concrete in the next section of the pouring trench in S4, the trench wall is brushed and washed. During the brushing process, the mud near the trench is removed, and the mud level in the pouring trench is kept above the groundwater level by 1.5m.

[0013] Preferably, before pouring concrete, the concrete is subjected to slump, compressive strength and impermeability tests; the conduit is equipped with a water-proof bladder.

[0014] Beneficial technical effects: 1. The construction method of the concrete anti-seepage wall in this application adopts a combination of trenching with hydraulic grab bucket trenching equipment for the upper cover layer and rock breaking with double wheel milling equipment for the lower bedrock layer. It is suitable for efficient trenching in soft and hard composite strata and has the advantages of high construction efficiency, short construction period, precise control, high trenching accuracy, low vibration and noise, and low dam body disturbance. 2. During construction, the hydraulic grab trenching equipment for the upper overburden layer (three-stage grab trenching) and the double-wheel milling equipment for the lower bedrock layer (three-stage milling trenching) both adopt a three-stage construction method of first the two sides and then the middle. This effectively reduces the lateral pressure on the trench wall, prevents the trench from collapsing, ensures the stability of the trench, and results in high trenching quality. Moreover, the recovered mud can be treated and reused, reducing construction costs. 3. Since the rental price of the twin-wheel milling equipment per unit time is much higher than that of the hydraulic grab troughing equipment, the configuration ratio of the hydraulic grab troughing equipment to the twin-wheel milling equipment should be set to greater than or equal to 2:1. This way, the hydraulic grab troughing equipment can carry out the construction of other troughs while the twin-wheel milling equipment is constructing, thus ensuring that the hydraulic grab troughing equipment is not interrupted during construction, so as to make full use of the hydraulic grab troughing equipment during the construction period and avoid the waste of high rental prices. 4. The construction method for the concrete cutoff wall in this application has the advantages of minimal construction disturbance and the use of milling wheel flat... It features stable cutting and rock breaking without impact crushing, low construction vibration amplitude and low noise, and minimal disturbance to the existing dam body and surrounding rock and soil structure. Therefore, the reservoir can maintain normal water storage level during the implementation period, meeting the rigid water demand of downstream water supply, irrigation, and ecological flow. It is suitable for reservoir seepage prevention projects that undertake water supply tasks but do not have the conditions for emptying or have huge losses from emptying. At the same time, it can also reduce noise pollution and is suitable for environmentally sensitive conditions in nearby residential areas. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the casting trough in an embodiment of this application.

[0016] Figure 2 This is a schematic diagram of the three-segment gripping groove in the embodiment of this application.

[0017] Figure 3 This is a schematic diagram of the three-section milled groove in an embodiment of this application.

[0018] Figure 4 This is a flowchart of the mud recycling and filtration process in the embodiments of this application.

[0019] Figure 5 This is the mud quality control index table in the embodiments of this application.

[0020] Figure 6 This is a flowchart of the construction method for the concrete anti-seepage wall in the embodiments of this application.

[0021] Explanation of reference numerals in the attached diagram: 1. Guide wall; 2. Casting trench; 3. Mud; 4. Overburden layer; 5. Bedrock layer. Detailed Implementation

[0022] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore detailed descriptions of them will be omitted. Furthermore, the drawings are merely illustrative of this disclosure and are not necessarily drawn to scale.

[0023] Currently, in reservoir reinforcement and dam upgrading projects, vertical anti-seepage walls are the mainstream technology for controlling seepage hazards in dam bodies and improving overall anti-seepage capabilities.

[0024] Concrete cutoff walls are typically constructed by trenching from top to bottom, penetrating the dam body and embedding into weakly weathered rock layers. The geological structure during construction generally exhibits a composite stratum characteristic of soft upper layers and hard lower layers. Traditional construction methods often employ a combination of "grab bucket trenching + drilling and splitting," which has significant drawbacks. Firstly, there are many uncontrollable factors, making it difficult to manage the construction period. Secondly, drilling is prone to deviation and trenching accuracy is low. Finally, there is significant impact vibration and noise, which can disturb residents. More seriously, it can easily damage the original dam body and soil structure, resulting in the reservoir generally needing to be in an empty state during construction.

[0025] To address the aforementioned problems, this disclosure proposes a construction method for a concrete cutoff wall. Compared to the traditional combination or single construction process of "hydraulic grab trenching + drilling and splitting," this method offers the following advantages: 1. High trenching efficiency, significantly improving overall construction efficiency, especially suitable for reservoir renovation projects with deep walls, tight schedules, and the need to be completed before the flood season, with a significant effect on shortening the construction period; 2. Precisely adaptable to complex strata with upper loose soil, silty clay, and boulder cover layers; 4. Lower medium-hard rock and hard bedrock. The hydraulic grab trenching equipment is responsible for excavating the upper loose layer, while the double wheel trenching equipment specializes in milling hard rock. Layered adaptation and each performs its own function. 3. Excellent trenching quality: The dual-wheel trenching equipment comes with a guide and verticality online monitoring system, which mills the trench wall smoothly and evenly, and has high precision in controlling the verticality of the wall, effectively ensuring the tightness of the trench joints and improving the overall integrity and seepage prevention stability of the anti-seepage wall. 4. The process is smoothly connected. The hydraulic grab troughing equipment and the double wheel milling equipment work together to avoid the problem of frequent disassembly and assembly and repeated process switching of a single equipment due to sudden changes in the stratum. The construction process is compact and continuous, and the operation rhythm is stable. 5. Minimal construction disturbance: The use of milling wheels for smooth rock cutting and crushing results in low vibration amplitude and noise, minimizing disturbance to the existing dam body and surrounding soil and rock structures. Therefore, the reservoir can maintain normal water level operation during implementation, meeting the rigid water demand of downstream water supply, irrigation, and ecological flow. It is suitable for reservoir seepage prevention projects that undertake water supply tasks but do not have the conditions for emptying or have huge losses from emptying. At the same time, it can reduce noise pollution and is also suitable for environmentally sensitive conditions in nearby residential areas. 6. Because the rental price of a twin-wheel trenching machine per unit time is much higher than that of a hydraulic grab trenching machine (renting one month: a twin-wheel trenching machine costs 700,000-800,000 RMB per unit, while a hydraulic grab trenching machine costs less than 100,000 RMB per unit), and the total depth of the trench reaches about 65 meters, with the hydraulic grab trenching machine needing to work downwards for more than 60 meters, while the twin-wheel trenching machine needs to work downwards for 2-3 meters, the configuration ratio of hydraulic grab trenching machines to twin-wheel trenching machines should be set to greater than or equal to 2:1. This way, the hydraulic grab trenching machine can carry out the construction of other trenches while the twin-wheel trenching machine is working, thus ensuring uninterrupted construction by the hydraulic grab trenching machine. This achieves full utilization of the hydraulic grab trenching machine during the construction period, avoiding the waste of the high rental price of the twin-wheel trenching machine. Furthermore, the twin-wheel trenching machine and the hydraulic grab trenching machine maintain continuous and uninterrupted operation during the construction period. In addition, both have the characteristics of high-speed construction. Using the combination of the two for construction can shorten the construction period by three to four months compared with existing technologies.

[0026] Furthermore, the construction method for this concrete cutoff wall is highly versatile and can be applied to trenching construction of concrete cutoff walls in water conservancy and hydropower projects under most geological conditions, and is particularly suitable for the following construction scenarios: 1. Engineering of soft and hard composite strata: Dam foundation anti-seepage wall engineering with soft overburden layer on top and medium to hard bedrock below. 2. Projects with strict schedule control: Reservoir reinforcement and dam upgrading projects, seepage prevention projects that need to be completed before the flood season and have strict schedule requirements. 3. Environmentally sensitive control conditions: The construction site is adjacent to densely populated areas such as villages and residential areas, as well as ecologically sensitive areas.

[0027] The construction method of the concrete anti-seepage wall of this application will be described in detail below through a specific embodiment.

[0028] This disclosure discloses a construction method for a concrete cutoff wall, which is applied to a reservoir dam. During construction, the reservoir is allowed to maintain a normal water storage state, with the water level 5-6 meters below the construction platform of the dam. The upper layer of the dam is a cover layer 4, and the lower layer is a bedrock layer 5. Figure 6 As shown, the construction method of the concrete anti-seepage wall includes the following steps: S1. Using a hydraulic grab trenching device, excavate a pouring trench 2 that penetrates the overburden layer 4 from the reservoir dam construction platform downwards, and add mud slurry 3 with wall-protecting properties into the pouring trench 2.

[0029] The cover layer 4 is typically composed of loose fill, clay, sand and gravel, and boulders. Therefore, using a hydraulic grab trenching device, the double force of the hydraulic grab's own weight and hydraulic closing gripping can easily grab and excavate the casting trench 2 within the cover layer 4. The hydraulic grab is flexible and adaptable to changes in the strata, with fast hole-opening speed and regular trench opening formation, which can quickly form a stable casting trench 2 structure. At the same time, the static pressure of the mud slurry 3 inside the trench balances the soil pressure on the trench wall, inhibiting soil collapse, diameter reduction, and rockfall, thus achieving rapid, low-cost, and high-efficiency trenching of the cover layer 4.

[0030] In one example, S1 includes: S11. A guide wall 1 is installed on the groove wall of the casting trough 2.

[0031] like Figure 1 As shown, the guide wall 1 adopts a "┓┏" shaped cross section. This structural form can withstand repeated impacts from hydraulic grab grooving equipment and double wheel milling equipment. It generally will not break under conditions where the main hole is suspended within 3 meters of severe hole collapse without vertical pressure. Its rigidity and flexural strength are significantly improved compared to the cuboid structure. Specifically, during the construction of guide wall 1, the layout of the guide wall 1 axis must be accurate, with an error of no more than 10mm. The guide wall 1 must be straight, with a flatness deviation of no more than 3mm on the inner wall surface and a verticality deviation of no more than 0.5%. The flatness of the top surface of guide wall 1 is 5mm. The base of guide wall 1 must be in close contact with the soil surface to prevent deformation under stress.

[0032] S12. Divide the casting trench 2 into three sections along the width of the trench. First, excavate the end sections of the casting trench, and finally excavate the middle section.

[0033] Specifically, such as Figure 2 As shown, the casting trench 2 is divided into three sections along its width, each corresponding to a different coverage area, as follows: Figure 2 As shown in a, during excavation, it can be done as follows: Figure 2 b- Figure 2 As shown in diagram d, the first grab trench on the left is obtained by excavating the left cover area, followed by the right cover area to obtain the second grab trench on the right, and finally the middle cover area to obtain the third grab trench in the middle. Alternatively, the right grab trench can be excavated first, followed by the left grab trench, and finally the middle grab trench. This design ensures that the hydraulic grab bucket bears a balanced load during excavation, effectively correcting deviations, ensuring the verticality of the trench, reducing lateral pressure on the trench walls, preventing trench collapse, and guaranteeing trench stability.

[0034] Optionally, the width of the end grab groove is greater than the width of the middle grab groove. This design allows the hydraulic grab to excavate towards the middle coverage area, thus ensuring balanced force on the hydraulic grab, effectively correcting deviation, and guaranteeing the verticality of the groove. As an example, during the excavation of a section of casting trench 2, the section of casting trench 2 can be divided into multiple sections along its length based on the excavation length of the hydraulic grab bucket in one excavation. During excavation, one section of casting trench 2 is first excavated to the designed depth before excavating the next adjacent section. This facilitates timely correction of the orientation of each section of casting trench 2, thereby ensuring good straightness in the lateral direction of a section of casting trench 2. Because the verticality of the trench excavated by the hydraulic grab bucket is different during the excavation of each section of casting trench 2, excavating one section of casting trench 2 to the designed depth before excavating the next adjacent section can smooth out the uneven surfaces caused by the different verticality.

[0035] In one example, during the excavation of each pouring trench 2, three pouring trenches of equal height are first dug out, and then the next three pouring trenches of equal height are dug down until the overburden 4 is penetrated.

[0036] S13. During the excavation process, mud slurry 3 is continuously added to the casting trench 2, and the level of mud slurry 3 is kept above the groundwater level by 1.5m. In this way, the static pressure of the mud slurry 3 in the trench wall can be used to balance the soil pressure on the trench wall, inhibiting soil collapse, diameter reduction, and rockfall, and achieving rapid, low-cost, and high-efficiency trenching of the cover layer 4.

[0037] Furthermore, during the operation of the hydraulic grab bucket, grouting is carried out simultaneously with the grabbing operation, so that the slurry level 3 is maintained at 40-60cm from the opening of the casting trench 2, thereby ensuring that the static pressure of the wall-protecting slurry 3 can effectively balance the soil pressure on the trench wall.

[0038] Optionally, on-site construction personnel can control the grabbing speed according to the grout condition in the pouring trench 2. If the grout surface is relatively stable, the grabbing speed can be adjusted according to the normal grabbing speed of the hydraulic grab bucket, and continuous construction can be carried out for 24 hours. If the geological conditions are more complex and the grout leakage is serious, the grabbing speed can be slowed down or even stopped, the grout replenishment can be accelerated and an appropriate amount of yellow sand can be backfilled, and the grout can be stirred by the hydraulic grab bucket body to achieve the technical effect of sealing the grout leakage area. Optionally, during the construction of the hydraulic grab troughing equipment, the inclination meter built into the hydraulic grab troughing equipment can be used to observe and correct any deviations in a timely manner, thereby controlling the inclination of the holes in the casting trough 2.

[0039] In this embodiment, the mud 3 contains bentonite, soda ash, and CMC, such as Figure 5 As shown, the mud slurry 3 in the casting tank 2 meets the following requirements: concentration greater than 4.5%, density less than 1.1 g / cm3, funnel viscosity 30-90s, plastic viscosity less than 20cp, static shear force at 10 minutes 1.4-10 N / m2, and pH value 9.5-12. This design ensures that the mud slurry 3 has the ability to protect the wall.

[0040] S2. When the bottom of the pouring trench 2 descends to the upper surface of the bedrock layer 5, the double-wheel milling equipment is used to continue excavating the pouring trench 2 downward in the bedrock layer 5 until the depth of the pouring trench 2 reaches the set value.

[0041] The bedrock layer 5 is typically composed of medium-hard and hard rock. Therefore, after the overburden layer 4 of a section of the casting trench 2 is excavated, when excavating the bedrock layer 5 of that section of the casting trench 2, it is necessary to switch to a double-wheel trenching machine to continue the excavation. Thus, after the hydraulic grab trenching equipment excavates down into the casting trench 2 to the interface between the bedrock layer 5 and the overburden layer 4, the double-wheel trenching machine is used for construction. The two sets of hydraulically driven milling wheels at the bottom of the double-wheel trenching machine rotate synchronously in opposite directions. The carbide hobs and milling teeth on the milling wheels perform continuous static pressure cutting and progressive crushing of the bedrock without impact or strong vibration. This causes minimal disturbance to the existing dam body and surrounding soil and rock structures. Therefore, the reservoir is allowed to maintain a normal water storage state during construction. Construction operations can be carried out when the reservoir water level is 5-6 meters lower than the construction platform of the reservoir dam body. At the same time, the noise is low, it does not disturb the residents, and it is also suitable for environmentally sensitive conditions in nearby residential areas.

[0042] In addition, the twin-wheel milling equipment produces excellent trenching quality. It comes with a built-in guide and verticality online monitoring system, which mills the trench wall smoothly and evenly, and has high precision in controlling the verticality of the wall. This effectively ensures the tightness of the joints in the trench sections and improves the overall integrity and seepage prevention stability of the anti-seepage wall.

[0043] In this embodiment, the rock chips and rock powder generated by the twin-wheel milling equipment are mixed with the wall slurry 3 inside the trench and pumped away by the slurry 3 pump built into the upper part of the milling wheel. Therefore, during the process of continuing to excavate and pour the trench 2 downward in the bedrock layer 5, it is necessary to pump away the slurry 3 at the bottom of the trench 2 while adding new slurry 3 into the trench 2, and keep the slurry 3 level above the groundwater level by 1.5m to balance the soil pressure on the trench wall and ensure the long-term stability of the trench wall.

[0044] Optionally, the mud slurry 3 pumped out from the bottom of the casting tank 2 can be filtered and then flowed back into the casting tank 2. With this design, the recovered mud slurry 3 can be treated and reused, reducing construction costs.

[0045] Specifically, such as Figure 4 As shown, the mud slurry 3 pumped from the bottom of the casting tank 2 is transported to the ground and then purified by a vibrating screen, hydrocyclone, and centrifuge for slag removal. The qualified mud slurry 3 is returned to the casting tank 2 for recycling, and the slag is separated and transported away.

[0046] The construction method of the concrete cutoff wall in this embodiment adopts a combined trenching method of trenching with hydraulic grab trenching equipment in the upper overburden layer 4 and rock breaking with double wheel milling equipment in the lower bedrock layer. This method fully leverages the advantages of hydraulic grab trenching equipment in the overburden layer 4, which is characterized by high efficiency and low cost. At the same time, it utilizes the advantages of double wheel milling equipment in hard rock or dense strata, which is characterized by high trenching efficiency, regular hole shape, good verticality and low disturbance. This method achieves complementary advantages, improves the overall construction efficiency and quality, and is suitable for efficient trenching in soft and hard composite strata. It has the advantages of high construction efficiency, short construction period, precise control, high trenching accuracy, low vibration and noise and low dam body disturbance.

[0047] In one example, when the twin-wheel milling machine is working, it works similarly to the overburden layer 4, dividing the casting trench 2 into three sections along the width direction in the bedrock layer 5. The end sections are milled first, and the middle section is milled last. For example... Figure 3 As shown in Figure a, the three milled grooves correspond to three different rock strata, such as... Figure 3 As shown in b-3c, during operation, the left-side rock strata are milled away first to create the first milled trench, then the right-side rock strata are milled away to create the second milled trench, and finally the middle rock strata are milled away to create the third milled trench. Of course, in other embodiments, the right-side rock strata can be milled away first, followed by the left-side rock strata. This design reduces the lateral pressure on the trench walls, prevents trench collapse, and ensures trench stability.

[0048] Optionally, the width of the end milled groove is greater than the width of the middle milled groove. With this design, the dual-wheel milling machine can completely cover the middle rock layer, ensuring the quality of the groove. As an example, during construction in bedrock layer 5, a section of the casting trench 2 is divided into multiple segments. After the overburden layer 4 of a segment of the casting trench 2 is excavated, the bedrock layer 5 of that segment of the casting trench 2 is milled. After the segment of the casting trench 2 is milled to the design depth, the next adjacent segment of the casting trench 2 is excavated. This facilitates timely correction of the orientation of each segment of the casting trench 2, thereby ensuring good straightness in the transverse direction of a segment of the casting trench 2.

[0049] During the milling process of each section of the casting trough 2, three sections of milled grooves of equal height are milled out first, and then the next section of three sections of milled grooves of equal height is milled out downwards until the depth of the casting trough 2 reaches the design depth.

[0050] Optionally, the depth of the casting trough 2 is obtained by averaging measurements taken at multiple locations.

[0051] In this embodiment, the construction method for the concrete cutoff wall employs a three-stage pouring process: first pouring from both sides, then from the middle, using a hydraulic grab bucket trenching device for the upper cover layer and a double-wheel milling device for the lower bedrock. This effectively reduces lateral pressure on the trench walls, prevents trench collapse, ensures trench stability, and results in high-quality trenching. Furthermore, the recovered mud slurry 3 is treated and reused, reducing construction costs.

[0052] S3. After replacing the mud 3 in the pouring trench 2, pour concrete below the mud 3 in the pouring trench 2. During the pouring process, remove the excess mud 3 in the pouring trench 2.

[0053] Specifically, the method for replacing the mud slurry 3 in the casting trench 2 in S3 is to simultaneously pump out the mud slurry 3 from the bottom of the casting trench 2 and add new mud slurry 3 into the casting trench 2, ensuring that the mud slurry 3 level is 1.5m above the groundwater level, until all the mud slurry 3 in the casting trench 2 is replaced. The mud slurry 3 at the bottom of the casting trench 2 contains debris such as rock fragments, rock powder, silt, sand, pebbles, and boulder. These debris will affect the casting and forming quality of the concrete anti-seepage wall, so it needs to be cleaned before concrete casting can proceed.

[0054] After one section of the pouring trench 2 is excavated to the designed depth, the next adjacent section of the pouring trench 2 is excavated until the entire section of the pouring trench 2 is excavated. After the section of the pouring trench 2 is excavated, the mud slurry 3 in the pouring trench 2 is replaced and the rock chips, rock powder, silt, sand, gravel, boulders and other debris that affect the quality of the concrete anti-seepage wall are thoroughly removed from the bottom of the pouring trench 2. Then, the concrete is poured below the mud slurry 3 in this section of the pouring trench 2 using the tremie pipe construction method. At the same time, the excess mud slurry 3 in the pouring trench 2 is pumped out to prevent the mud slurry 3 from flowing out of the pouring trench 2.

[0055] Specifically, underwater concrete pouring adopts the tremie pipe method. The concrete tremie pipe is made of steel pipe with threaded joints. The tremie pipe can be hoisted into the specified position of the two sections of the pouring tank using a gantry. A funnel is installed at the top of the tremie pipe.

[0056] It should be noted that the slump of the concrete should be tested before pouring, and test blocks should be made. Concrete compressive strength and impermeability test blocks should be made according to the specifications. After the final hole acceptance is completed, concrete should be poured in a timely manner, and the guide pipe should be inserted to 300-500mm from the bottom of the pouring trench.

[0057] In addition, a bladder should be installed inside the guide pipe before pouring concrete to prevent water from entering, and the concrete mix proportions should be checked before pouring. The installation length of the guide pipe should also be checked and recorded, and a record should be made of the concrete rise height and guide pipe embedment depth for each truckload of concrete. After the concrete in S3 has solidified, grooves are constructed at both ends of the concrete in the length direction of the pouring trench 2. The purpose of setting the grooves is to facilitate the connection and sealing of the concrete in the adjacent pouring trench 2 with the concrete in this pouring trench 2, so as to finally form a complete concrete anti-seepage wall.

[0058] In one example, when pouring concrete, a mold, such as a hemisphere or a pipe, is set at the appropriate location to form a groove. When the concrete is about to solidify, the mold is removed, and grooves are formed at both ends of the concrete.

[0059] S4. After the concrete has solidified, repeat S1-S3 to excavate the next section of the pouring trench 2 and pour concrete, and seal and fix the poured concrete to the concrete in the previous section of the pouring trench 2.

[0060] After one section of the pouring trench 2 is excavated and concrete is poured, and the concrete has solidified, the next section of the adjacent pouring trench 2 is poured and the concrete is poured. The poured concrete penetrates into the groove of the concrete in the previous section of the pouring trench 2 and is sealed and fixed together, thus forming an integral and continuous concrete anti-seepage wall.

[0061] As an example, before pouring concrete into the next pouring trough 2, the grooves of the concrete in the previous pouring trough 2 are first scrubbed to remove silt and other debris from the groove walls that may affect the sealing and fixing of the concrete.

[0062] During the cleaning of the groove, mud slurry 3 near the groove is pumped out while new mud slurry 3 is added into the casting tank 2, and the mud slurry 3 in the casting tank 2 is kept above the groundwater level by 1.5m.

[0063] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," "third," and similar terms used in this application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising" or "including" and similar terms mean that the elements or objects preceding "comprising" or "including" encompass the elements or objects listed following "comprising" or "including" and their equivalents, and do not exclude other elements or objects. "Above," "below," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0064] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A construction method for a concrete anti-seepage wall, characterized in that... This method is applied to reservoir dams, where the reservoir is allowed to maintain a normal water storage state during construction, with the water level 5-6 meters lower than the construction platform of the dam. The upper layer of the dam is a cover layer, and the lower layer is a bedrock layer. The construction steps include the following: S1. Using a hydraulic grab trenching device, excavate a pouring trench from the reservoir dam construction platform downwards through the overburden layer, and add mud with wall-protecting properties into the pouring trench. S2. When the bottom of the trench to be poured descends to the upper surface of the bedrock layer, switch to a twin-wheel trenching machine to continue excavating the trench downwards in the bedrock layer until the depth of the trench reaches the set value. The ratio of the number of hydraulic grab troughing equipment to the number of twin wheel milling equipment is greater than or equal to 2:

1. The twin wheel milling equipment operates continuously during construction, while the hydraulic grab troughing equipment performs construction of other pouring troughs during the construction of the twin wheel milling equipment. S3. After replacing the mud in the pouring trench, pour concrete below the mud in the pouring trench, and remove the excess mud in the pouring trench during the pouring process. S4. After the concrete has solidified, repeat S1-S3 to excavate the next pouring trench and pour concrete, ensuring that the poured concrete is sealed and fixedly connected to the concrete in the previous pouring trench.

2. The construction method of the concrete anti-seepage wall according to claim 1, characterized in that: S1. Using a hydraulic grab trenching device, excavate a pouring trench from the reservoir dam construction platform downwards through the overburden layer, and add mud with wall-protecting properties into the pouring trench, including: A guide wall is installed on the wall of the casting trough opening; The casting trench is divided into three sections along the width of the trench. The end sections are excavated first, and the middle section is excavated last. During the excavation process, mud slurry was continuously added to the casting trench, and the mud slurry level was kept 1.5m above the groundwater level. The width of the casting groove at the end is greater than the width of the casting groove in the middle.

3. The construction method of the concrete anti-seepage wall according to claim 2, characterized in that: During the construction of the guide wall, the error in the layout of the guide wall axis shall not exceed 10mm, the flatness deviation of the inner wall surface of the guide wall shall not exceed 3mm, the verticality shall not exceed 0.5%, and the flatness of the top surface of the guide wall shall be 5mm.

4. The construction method of the concrete anti-seepage wall according to claim 1, characterized in that: S2. When the bottom of the trench to be poured descends to the upper surface of the bedrock layer, switch to a twin-wheel trenching machine to continue excavating the trench downwards in the bedrock layer until the depth of the trench reaches the set value, including: In the bedrock layer, the casting trench is divided into three milled sections along the width of the trench. The end milled trench is milled first, and the middle milled trench is milled last. During the process of continuing to excavate the casting trench downwards in the bedrock layer, the mud at the bottom of the casting trench is pumped out while new mud is added into the casting trench, and the mud level is kept 1.5m above the groundwater level. The depth of the casting trough is obtained by averaging measurements taken at multiple locations; The width of the casting groove at the end is greater than the width of the casting groove in the middle.

5. The construction method of the concrete anti-seepage wall according to claim 4, characterized in that: The mud pumped out from the bottom of the casting tank is filtered and then flows back into the casting tank. The new mud contains bentonite, soda ash, and CMC; The slurry in the casting tank must have a concentration greater than 4.5% and a density less than 1.1 g / cm³. 3 Funnel viscosity 30-90s, plastic viscosity less than 20cp, static shear force at 10 minutes 1.4-10N / m 2 pH value 9.5-12.

6. The construction method of the concrete anti-seepage wall according to claim 2 or 4, characterized in that: The distance between the mud slurry surface and the opening of the casting trench is 40-60cm.

7. The construction method of the concrete anti-seepage wall according to claim 1, characterized in that: S3. After replacing the slurry in the pouring trench, pour concrete below the slurry in the pouring trench. During the pouring process, remove excess slurry from the pouring trench, including: While pumping out the mud from the bottom of the casting trench, new mud is added into the casting trench, and the mud level is kept 1.5m above the groundwater level until all the mud in the casting trench is replaced. Concrete is poured below the slurry in the pouring trench using the tremie pipe method, while excess slurry in the pouring trench is removed at the same time. After the concrete has hardened, grooves are formed at both ends of the concrete.

8. The construction method of the concrete anti-seepage wall according to claim 7, characterized in that: The concrete poured in the next section of the S4 pouring trench enters the groove and is sealed and fixedly connected with the concrete in the previous section of the pouring trench.

9. The construction method of the concrete anti-seepage wall according to claim 7, characterized in that: Before pouring concrete into the next section of the S4 pouring trench, the trench walls are scrubbed. During the scrubbing process, the mud near the trench is removed, and the mud level in the pouring trench is kept 1.5m above the groundwater level.

10. The construction method of the concrete anti-seepage wall according to claim 7, characterized in that: Before pouring concrete, slump, compressive strength and impermeability tests are conducted on the concrete; the conduit is equipped with a water-proof bladder.

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