A method for treating a water permeable foundation pit

Abstract

The application discloses a treatment method for a water-permeable foundation pit, and solves the problems of complicated water gushing treatment, poor treatment effect and long construction period of the foundation pit. The treatment method comprises the following steps: S1, step construction on a stone slag water intercepting ridge on a water side of the foundation pit; S2, step construction under the stone slag water intercepting ridge on the water side of the foundation pit; and S3, foundation pit excavation.

Description

Technical Field

[0001] This invention relates to the field of foundation pit water inflow treatment technology, and in particular to a treatment method for permeable foundation pits. Background Technology

[0002] Groundwater inrush into building foundation pits is a common phenomenon, especially when the excavation depth is below the groundwater level. When a shallow confined aquifer exists below the pit bottom, the thickness and strength of the impermeable layer above the aquifer decrease as the excavation depth increases. When the aquifer head pressure exceeds the strength of the impermeable layer, the confined water breaches the pit bottom and rushes into the pit. This water inrush can sometimes cause slope instability, leading to a sudden surge of water that floods the pit, posing significant challenges to construction.

[0003] To avoid water inrush in the foundation pit and its associated construction difficulties, the potential water inrush volume is predicted before excavation. Based on local hydrogeological conditions and the predicted inrush volume, appropriate prevention and control measures are implemented. For foundation pits with large inrush volumes, seepage-proof curtains or pumping wells / holes are used. For foundation pits with small inrush volumes, pumps with appropriate drainage capacity are selected for dewatering. In construction on foundation pits in saturated sandy soil, artificial freezing methods can be used to seal the inrush.

[0004] The outlet pit of the diversion tunnel at the Jinping Hydropower Station in Sichuan Province is located on the excavation site for slope excavation and tunnel adit excavation. During construction of the diversion tunnel outlet, it was planned to utilize the excavated spoil heap to form the pit. However, the spoil heap is adjacent to the fast-flowing Yalong River. After the pit was excavated to the river's water level, river water seeped into the pit through loose rocks, exacerbating the drainage work at the diversion tunnel outlet and making dry-land operations impossible. To contain the water inflow, a 3-meter-wide clay sloping wall was backfilled on the three water-facing slopes of the pit as a seepage-proof structure for the water-facing side slope. As the excavation and drainage work of the foundation pit proceeded, the clay inclined wall collapsed automatically due to water immersion during the dewatering process, forming a layer of a certain thickness inside the foundation pit. After the water level difference between the inside and outside of the foundation pit appeared, the clay layer was penetrated by the seeping river water, and a large amount of river water gushed out from the penetrated holes, making it impossible to enter the foundation pit of the diversion tunnel outlet for the foundation excavation of the diversion tunnel outlet building.

[0005] Based on the current situation analysis of the diversion tunnel outlet pit, the pit not only suffers from the aforementioned problems, but also faces considerable construction difficulties due to constraints on the construction period and geological characteristics. 1. The foundation pit slope is composed of loose stone and is highly permeable. Water interception measures must be taken to ensure the working conditions of the foundation pit construction. Using dewatering wells (holes) is not only difficult to form a dewatering curtain, but also the drainage project is costly and risky. 2. The anti-seepage structure adopts the curtain grouting scheme, which not only presents great difficulties in drilling holes in loose large blocks, but also has uncontrollable problems in grouting. Loose stone and slag strata consume a large amount of grout, and the construction period does not allow for it. 3. The seepage prevention structure adopts a continuous wall structure, and the trench is formed by impact drilling according to the needs of the stratum structure. The work efficiency is low, and the quality and safety risks such as hole collapse during the trenching process are relatively high. 4. Other seepage prevention structures cannot be implemented due to the constraints of geological conditions, such as steel sheet pile seepage interception, high-pressure jet grouting wall, and mixing pile interlocking wall, which are also affected by the size and particle size of the stone slag. 5. After the clay inclined wall seepage prevention body failed to achieve the purpose of interception and seepage prevention, a trench was excavated outside the foundation pit and backfilled with clay in an attempt to intercept seepage in the form of a clay core wall. However, due to the large amount of seepage in the stone chips, the backfilled clay formed clay paste in the trench. With the entry of seepage water and the large pressure difference between the inside and outside caused by the drop in the water level in the foundation pit, the clay core wall was also breached.

[0006] 6. Even if the seepage prevention structure is successfully used to treat the water seepage in the foundation pit, the dredging of the approximately 1000m³ of silt that will form in the foundation pit will become another problem that restricts the construction period. Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, the present invention provides a method for treating permeable foundation pits, which effectively solves the problems of cumbersome, ineffective, and time-consuming treatment of foundation pit water inrush.

[0008] To achieve the above objectives, the technical solution of the present invention is: a method for treating permeable foundation pits, comprising the following steps: S1, Construction of the steps on the stone cutting embankment on the water-facing side of the foundation pit; S2, Construction of the step below the stone cutting embankment on the water-facing side of the foundation pit; S3, Excavation of the foundation pit.

[0009] Preferably, the construction of the steps on the stone cutting embankment on the water-facing side of the foundation pit includes the following steps: S11, the boundary line of the foundation pit excavation is measured and set out. For straight sections, a stake is set every 10m to 15m, and for horizontal curves, a stake is set every 5m to 10m for marking. S12, the width of the clay and stone slag mixing and consolidation is controlled according to the axial width of 3m, and the length of each working section is also controlled according to 3m; S13, according to the excavation boundary line and the layout range of the steps on the intercepting embankment, remove surface obstacles, set up access road for the backhoe to enter and exit the construction work face, and put the backhoe into position in the work face; S14. After mixing the buried clay core material with the surrounding stone chips by turning it up from the bottom with a backhoe 2-3 times, use the backhoe to lift it to a height of 3-4m and let it fall into the trench for mixing. For the parts where the clay core material is not buried or the parts where the filling is supplemented, put in clay and mix it evenly with a backhoe, then soak it in water in place for 24 hours to dissolve and expand the clay. S15, calculate the amount of cement and clay curing agent. The mixing ratio of the curing slurry is clay:cement:curing agent = 80%:20%:0.3~0.4%. The volume of cement slurry is not less than 30% of the volume of stone chips.

[0010] S16. Calculate the amount of cement used per square meter based on the depth of the mixing area and the predetermined cement dosage, and determine the longitudinal and transverse spacing of the cement placement. S17. Use a backhoe to spread the cement evenly on the ground, and make sure that the spreading area of ​​each bag of cement is equal. S18. After the cement is laid, there should be no blank areas or excessively concentrated spots on the surface. S19: Use a backhoe to turn the mixed stone and clay mixture up from the bottom and mix it with cement. Then lift the mixture to a height of 3-4m and let it fall freely into the trench. Repeat this operation 2-3 times. S100, after adding the clay solidifier, use a backhoe to repeatedly grab and stir it 2 to 3 times, and then impact it into the trench to press and mix it 2 to 3 times. S101, the connection between two adjacent working sections adopts an overlapping joint, and the overlapping length is controlled at 1.0m; S102, after each working section is mixed, it is initially shaped, leveled and compacted with a backhoe. S103, after compaction, enters the curing period, during which the surface after compaction is kept moist; S104: During the shaping and recovery period, all vehicles are strictly prohibited from passing through to ensure that the ground is not damaged.

[0011] Preferably, the construction of the lower step of the stone cutting embankment on the water-facing side of the foundation pit includes the following steps: S21, the width of the clay and stone slag mixing and consolidation is controlled at 2m according to the axis width, and the length of each working section is controlled at 3m. S22, excavate the construction access road, and the backhoe enters the work area and takes position; S23, after adding clay and mixing it evenly with a backhoe, soak it in water in situ for 24 hours to dissolve and expand the clay; S24, after using a backhoe to flip up and stir the mixture from the bottom 2-3 times, use the backhoe to lift it to a height of 3-4m and let it fall freely into the tank for mixing; S25, calculate the amount of cement and clay curing agent used. The mixing ratio of the curing slurry is clay:cement:curing agent = 80%:20%:0.3~0.4%, and the volume of cement slurry is not less than 30% of the volume of stone chips. S26. Calculate the amount of cement used per square meter based on the depth of the mixing area and the predetermined cement dosage, and determine the longitudinal and transverse spacing of the cement. S27. Use a backhoe to spread the cement evenly on the ground, and make sure that the spreading area of ​​each bag of cement is equal. S28. After the cement is laid, there should be no blank areas or excessively concentrated spots on the surface. S29. Use a backhoe to turn the mixed stone and clay mixture up from the bottom and mix it with cement. Then lift the mixture to a height of 3-4m and let it fall freely into the trench. Repeat this process 2-3 times. S200, after adding clay solidifier, use a backhoe to repeatedly grab and mix 2 to 3 times, and then impact and press the mixture into the trench 2 to 3 times. S201, the connection between two adjacent work sections adopts an overlapping joint, and the overlapping length is controlled at 1.0m; S202: After each working section is mixed, it is initially shaped, leveled and compacted using a backhoe.

[0012] Preferably, the excavation of the foundation pit includes the following steps: S31, After the construction of the stone cutting embankment on the water-facing side of the foundation pit is completed, water will be pumped out to remove the water accumulated in the foundation pit; S32, dump stone chips into the pit and use a backhoe to turn them over from the bottom and mix them 2-3 times; S33, calculate the amount of cement and clay curing agent used. The curing slurry mix ratio is clay:cement:curing agent = 80%:20%:0.3~0.4%.

[0013] S34. Calculate the amount of cement used per square meter based on the depth of the mixing area and the predetermined cement dosage, and determine the longitudinal and transverse spacing of the cement. S35: Use a backhoe to turn the mixed stone and clay mixture up from the bottom and mix it with cement. Then lift the mixture to a height of 3-4m and let it fall freely into the trench. Repeat this operation 2-3 times. S36, after adding the clay solidifier, use a backhoe to repeatedly grab and stir the mixture 2 to 3 times, and then impact and press the mixture into the trench 2 to 3 times. S37. After the clay, stone chips and cement mixture is mixed, wait for 4 hours before excavating the solidified stone chips and transferring them to the next working section. S38. Repeat steps S32 to S37 to complete the foundation pit excavation.

[0014] Compared with existing technologies, this invention has the following advantages: 1) After adding clay curing agent, the clay slurry can achieve a 100% colloid solidification rate, increasing the likelihood that the solidified clay will completely fill the voids in the stratum; 2) Adding clay curing agent can adjust and control the initial setting time and gelling time of the clay slurry, ensuring the mixing time between the clay slurry and the stone slag stratum, and accelerating the initial setting of the cement and clay slurry, preventing the slurry from being lost underwater; 3) Filling and blocking the seepage channels and voids in the stratum improves the foundation bearing capacity while reducing seepage into the foundation pit, saving on the cost of regular drainage of the foundation pit; 4) Excavating the clay slurry and silt in the foundation pit after solidification saves time and costs, and prevents the slurry from polluting the environment, soil, and water bodies; 5) Using local materials and existing excavation equipment, the excavation and cleaning of a foundation pit approximately 90m long and 10m wide was completed in just over 10 days, demonstrating "fast, efficient, and economical" technical and economic benefits compared to other construction techniques. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the solidification treatment of permeable foundation pits according to the present invention. Detailed Implementation

[0016] The present invention will now be described in further detail with reference to the accompanying drawings. The drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0017] The present invention has the following objectives: 1) To address the slope safety issues caused by the collapse of slopes due to severe water permeability after the foundation pit is excavated and formed by the formation of a stratum composed of stone slag; 2) To ensure normal dry-land operation conditions after the foundation pit is excavated, thus guaranteeing the construction conditions of the diversion tunnel outlet gate chamber and open channel; 3) To solidify 1000m³ of mud in the foundation pit, facilitating the excavation and forming of the foundation pit and preventing the mud from polluting the water body and the environment; 4) To facilitate rapid construction by using existing construction equipment and local materials, thereby aiming to complete the construction of the diversion tunnel outlet open channel and underwater structures before the flood season.

[0018] The working principle of this invention is as follows: Clay is mixed into the stone chips, and then cement and clay curing agent are added and stirred evenly to solidify it into a solid body of corresponding strength. The solidified cement-clay slurry is solidified with the stone chips to form a whole, and the pores between the blocks are filled and solidified to prevent water from flowing into the foundation pit, ensuring the stability of the seepage on the foundation pit slope after the stone chip stratum is excavated, controlling the flow of river water into the foundation pit, and reducing the amount of drainage in the foundation pit.

[0019] Before implementing this plan, the reduced bearing capacity and settlement of the foundation caused by the previous construction of clay inclined walls or clay core walls should be reinforced to ensure that the working face meets the conditions for the entry and operation of mechanical equipment.

[0020] As shown in the figure, a method for treating a permeable foundation pit includes the following steps: S1, Construction of the steps on the stone cutting embankment on the water-facing side of the foundation pit; S2, Construction of the step below the stone cutting embankment on the water-facing side of the foundation pit; S3, Excavation of the foundation pit.

[0021] Preferably, the construction of the steps on the stone cutting embankment on the water-facing side of the foundation pit includes the following steps: S11, the boundary line of the foundation pit excavation is measured and set out. For straight sections, a stake is set every 10m to 15m, and for horizontal curves, a stake is set every 5m to 10m for marking. S12, the width of the clay and stone slag mixing and consolidation is controlled according to the axial width of 3m, and the length of each working section is also controlled according to 3m; S13, according to the excavation boundary line and the layout range of the steps on the intercepting embankment, remove surface obstacles, set up access road for the backhoe to enter and exit the construction work face, and put the backhoe into position in the work face; S14. After mixing the buried clay core material with the surrounding stone chips by turning it up from the bottom with a backhoe 2-3 times, use the backhoe to lift it to a height of 3-4m and let it fall into the trench for mixing. For the parts where the clay core material is not buried or the parts where the filling is supplemented, put in clay and mix it evenly with a backhoe, then soak it in water in place for 24 hours to dissolve and expand the clay. S15, calculate the amount of cement and clay curing agent. The mixing ratio of the curing slurry is clay:cement:curing agent = 80%:20%:0.3~0.4%. The volume of cement slurry is not less than 30% of the volume of stone chips.

[0022] S16. Calculate the amount of cement used per square meter based on the depth of the mixing area and the predetermined cement dosage, and determine the longitudinal and transverse spacing of the cement placement. S17. Use a backhoe to spread the cement evenly on the ground, and make sure that the spreading area of ​​each bag of cement is equal. S18. After the cement is laid, there should be no blank areas or excessively concentrated spots on the surface. S19: Use a backhoe to turn the mixed stone and clay mixture up from the bottom and mix it with cement. Then lift the mixture to a height of 3-4m and let it fall freely into the trench. Repeat this operation 2-3 times. S100, after adding the clay solidifier, use a backhoe to repeatedly grab and stir it 2 to 3 times, and then impact it into the trench to press and mix it 2 to 3 times. S101, the connection between two adjacent working sections adopts an overlapping joint, and the overlapping length is controlled at 1.0m; S102, after each working section is mixed, it is initially shaped, leveled and compacted with a backhoe. S103, after compaction, enters the curing period, during which the surface after compaction is kept moist; S104: During the shaping and recovery period, all vehicles are strictly prohibited from passing through to ensure that the ground is not damaged.

[0023] Preferably, the construction of the lower step of the stone cutting embankment on the water-facing side of the foundation pit includes the following steps: S21, the width of the clay and stone slag mixing and consolidation is controlled at 2m according to the axis width, and the length of each working section is controlled at 3m. S22, excavate the construction access road, and the backhoe enters the work area and takes position; S23, after adding clay and mixing it evenly with a backhoe, soak it in water in situ for 24 hours to dissolve and expand the clay; S24, after using a backhoe to flip up and stir the mixture from the bottom 2-3 times, use the backhoe to lift it to a height of 3-4m and let it fall freely into the tank for mixing; S25, calculate the amount of cement and clay curing agent used. The mixing ratio of the curing slurry is clay:cement:curing agent = 80%:20%:0.3~0.4%, and the volume of cement slurry is not less than 30% of the volume of stone chips. S26. Calculate the amount of cement used per square meter based on the depth of the mixing area and the predetermined cement dosage, and determine the longitudinal and transverse spacing of the cement. S27. Use a backhoe to spread the cement evenly on the ground, and make sure that the spreading area of ​​each bag of cement is equal. S28. After the cement is laid, there should be no blank areas or excessively concentrated spots on the surface. S29. Use a backhoe to turn the mixed stone and clay mixture up from the bottom and mix it with cement. Then lift the mixture to a height of 3-4m and let it fall freely into the trench. Repeat this process 2-3 times. S200, after adding clay solidifier, use a backhoe to repeatedly grab and mix 2 to 3 times, and then impact and press the mixture into the trench 2 to 3 times. S201, the connection between two adjacent work sections adopts an overlapping joint, and the overlapping length is controlled at 1.0m; S202: After each working section is mixed, it is initially shaped, leveled and compacted using a backhoe.

[0024] Preferably, the excavation of the foundation pit includes the following steps: S31, After the construction of the stone cutting embankment on the water-facing side of the foundation pit is completed, water will be pumped out to remove the water accumulated in the foundation pit; S32, dump stone chips into the pit and use a backhoe to turn them over from the bottom and mix them 2-3 times; S33, calculate the amount of cement and clay curing agent used. The curing slurry mix ratio is clay:cement:curing agent = 80%:20%:0.3~0.4%.

[0025] S34. Calculate the amount of cement used per square meter based on the depth of the mixing area and the predetermined cement dosage, and determine the longitudinal and transverse spacing of the cement. S35: Use a backhoe to turn the mixed stone and clay mixture up from the bottom and mix it with cement. Then lift the mixture to a height of 3-4m and let it fall freely into the trench. Repeat this operation 2-3 times. S36, after adding the clay solidifier, use a backhoe to repeatedly grab and stir the mixture 2 to 3 times, and then impact and press the mixture into the trench 2 to 3 times. S37. After the clay, stone chips and cement mixture is mixed, wait for 4 hours before excavating the solidified stone chips and transferring them to the next working section. S38. Repeat steps S32 to S37 to complete the foundation pit excavation.

[0026] Specific project overview The left bank diversion tunnel of the Jinping I Hydropower Station has a gate-shaped cross-section, with dimensions of 15×19m (width×height) after lining. The tunnel length is 1214.359m, and the inlet and outlet bottom elevations are 1638.50m and 1634.00m, respectively. The entire diversion tunnel is arranged with a double bend, consisting of an inlet channel section, a gate chamber section, a transition section, a tunnel body section, a plug section, and an outlet channel section. The foundation on the river-facing side of the outlet channel section is a beach formed by slag excavation from the dam slope along the Yalong River channel, while the foundation on the other side is a rock excavation surface on the riverbank. After the foundation pit was excavated to the river water level, river water seeped into the foundation pit through loose rocks, increasing the drainage workload at the diversion tunnel outlet and making it impossible to excavate the foundation surface under dry-land conditions. In the early stage, a 3m wide clay sloping wall was backfilled on the water-facing slope of the foundation pit to intercept water. As the foundation pit was excavated and the drainage work was carried out, the clay sloping wall collapsed automatically due to water immersion, forming a certain thickness of cover inside the foundation pit. After the water level difference between the inside and outside of the foundation pit appeared, the clay cover was penetrated by the seeping river water, and a large amount of river water gushed out from the penetrated hole, making it impossible to enter the foundation pit of the diversion tunnel outlet for the foundation excavation of the diversion tunnel outlet building.

[0027] In order to cut off the channel for river water to enter the foundation pit, the research team compared and analyzed the drainage schemes and concluded that the existing technical solutions all had serious problems: 1. The foundation pit slope is composed of loose gravel and is highly permeable. Using drainage wells (holes) not only makes it difficult to form a rain curtain, but also results in high drainage costs and risks.

[0028] 2. Curtain grouting on loose, large blocks is not only difficult to drill, but also has uncontrollable grout consumption. Loose rock and gravel strata have high grout consumption, and the construction period does not allow for it.

[0029] 3. Using continuous wall for seepage prevention requires trenching with impact drilling, which is not only inefficient but also carries a high risk of quality and safety issues such as hole collapse during the trenching process.

[0030] 4. The methods of steel sheet pile seepage interception, high-pressure jet grouting wall seepage interception, and mixing pile interlocking wall seepage interception are not feasible due to the influence of stone chip size and particle size.

[0031] Overall Deployment of Foundation Pit Water Inrush Treatment To quickly resolve the impact of water inflow on foundation pit drainage and excavation, this patented solution was adopted to intercept the water inflow: clay was mixed into the stone slag, followed by cement and clay curing agent, and the mixture was stirred evenly to solidify it into a solidified body of appropriate strength. The solidified cement-clay slurry was then solidified with the stone slag to form a whole, and the pores between the blocks were filled and solidified to prevent water from entering the foundation pit. This ensured the stability of seepage on the foundation pit slope after the stone slag stratum was excavated, controlled the flow of river water into the foundation pit, and reduced the amount of foundation pit drainage.

[0032] Before implementing this plan, the foundation bearing capacity reduction and settlement caused by the previous clay inclined wall or clay core wall were reinforced in accordance with the patent plan, so that the working face meets the conditions for mechanical equipment to enter the site for operation.

[0033] Implementation effect This patented technology fills and seals seepage channels and pores in the strata, improving the foundation's bearing capacity while reducing seepage into the foundation pit and saving on regular drainage costs. Excavation of the clay slurry and silt within the pit after solidification saves time and costs, and prevents pollution of the environment, soil, and water bodies by the slurry.

[0034] This patented technology utilizes locally sourced, inexpensive clay materials and employs a combination of backhoe mixing and free-fall grouting. It completed the excavation and cleaning of a foundation pit approximately 90m long and 10m wide in just over 10 days. Compared to other construction techniques, it offers significant technical and economic benefits in terms of speed, efficiency, and cost-effectiveness.

[0035] The embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that various variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom remain within the scope of this invention.

Claims

1. A method for treating permeable foundation pits, characterized in that, Includes the following steps: S1, Construction of the steps on the stone cutting embankment on the water-facing side of the foundation pit; S2, Construction of the step below the stone cutting embankment on the water-facing side of the foundation pit; S3, Excavation of the foundation pit; The construction of the steps on the stone cutting embankment on the water-facing side of the foundation pit includes the following steps: S11, the boundary line of the foundation pit excavation is measured and set out. For straight sections, a stake is set every 10m to 15m, and for horizontal curves, a stake is set every 5m to 10m for marking. S12, the width of the clay and stone slag mixing and consolidation is controlled according to the axial width of 3m, and the length of each working section is also controlled according to 3m; S13, according to the excavation boundary line and the layout range of the steps on the intercepting embankment, remove surface obstacles, set up access road for the backhoe to enter and exit the construction work face, and put the backhoe into position in the work face; S14. After mixing the buried clay core material with the surrounding stone chips by turning it up from the bottom with a backhoe 2-3 times, use the backhoe to lift it to a height of 3-4m and let it fall into the trench for mixing. For the parts where the clay core material is not buried or the parts where the filling is supplemented, put in clay and mix it evenly with a backhoe, then soak it in water in place for 24 hours to dissolve and expand the clay. S15, calculate the amount of cement and clay curing agent used. The mixing ratio of the curing slurry is clay:cement:curing agent = 80%:20%:0.3~0.4%, and the volume of cement slurry is not less than 30% of the volume of stone chips. S16. Calculate the amount of cement used per square meter based on the depth of the mixing area and the predetermined cement dosage, and determine the longitudinal and transverse spacing of the cement placement. S17. Use a backhoe to spread the cement evenly on the ground, and make sure that the spreading area of ​​each bag of cement is equal. S18. After the cement is laid, there should be no blank areas or excessively concentrated spots on the surface. S19: Use a backhoe to turn the mixed stone and clay mixture up from the bottom and mix it with cement. Then lift the mixture to a height of 3-4m and let it fall freely into the trench. Repeat this operation 2-3 times. S100, after adding the clay solidifier, use a backhoe to repeatedly grab and stir the mixture 2 to 3 times, and then impact and press the mixture into the trench 2 to 3 times. S101, the connection between two adjacent working sections adopts an overlapping joint, and the overlapping length is controlled at 1.0m; S102, after each working section is mixed, it is initially shaped, leveled and compacted with a backhoe. S103, after compaction, enters the curing period, during which the surface after compaction is kept moist; S104: During the procedure and recovery period, all vehicles are strictly prohibited from passing through to ensure that the ground is not damaged. The construction of the lower step of the stone cutting embankment on the water-facing side of the foundation pit includes the following steps: S21, the width of the clay and stone slag mixing and consolidation is controlled at 2m according to the axis width, and the length of each working section is controlled at 3m. S22, excavate the construction access road, and the backhoe enters the work area and takes position; S23, after adding clay and mixing it evenly with a backhoe, soak it in water in situ for 24 hours to dissolve and expand the clay; S24, after using a backhoe to flip up and stir the mixture from the bottom 2-3 times, use the backhoe to lift it to a height of 3-4m and let it fall freely into the tank for mixing; S25, calculate the amount of cement and clay curing agent used. The mixing ratio of the curing slurry is clay:cement:curing agent = 80%:20%:0.3~0.4%, and the volume of cement slurry is not less than 30% of the volume of stone chips. S26. Calculate the amount of cement used per square meter based on the depth of the mixing area and the predetermined cement dosage, and determine the longitudinal and transverse spacing of the cement. S27. Use a backhoe to spread the cement evenly on the ground, and make sure that the spreading area of ​​each bag of cement is equal. S28. After the cement is laid, there should be no blank areas or excessively concentrated spots on the surface. S29. Use a backhoe to turn the mixed stone and clay mixture up from the bottom and mix it with cement. Then lift the mixture to a height of 3-4m and let it fall freely into the trench. Repeat this process 2-3 times. S200, after adding clay solidifier, use a backhoe to repeatedly grab and mix 2 to 3 times, and then impact and press the mixture into the trench 2 to 3 times. S201, the connection between two adjacent work sections adopts an overlapping joint, and the overlapping length is controlled at 1.0m; S202, after each working section is mixed, it is initially shaped, leveled and compacted with a backhoe. Excavation of the foundation pit includes the following steps: S31, After the construction of the stone cutting embankment on the water-facing side of the foundation pit is completed, water will be pumped out to remove the water accumulated in the foundation pit; S32, dump stone chips into the pit and use a backhoe to turn them over from the bottom and mix them 2-3 times; S33, calculate the dosage of cement and clay curing agent, and the mixing ratio of the curing slurry is clay:cement:curing agent = 80%:20%:0.3~0.4%; S34. Calculate the amount of cement used per square meter based on the depth of the mixing area and the predetermined cement dosage, and determine the longitudinal and transverse spacing of the cement. S35: Use a backhoe to turn the mixed stone and clay mixture up from the bottom and mix it with cement. Then lift the mixture to a height of 3-4m and let it fall freely into the trench. Repeat this operation 2-3 times. S36, after adding the clay solidifier, use a backhoe to repeatedly grab and stir the mixture 2 to 3 times, and then impact and press the mixture into the trench 2 to 3 times. S37. After the clay, stone chips and cement mixture is mixed, wait for 4 hours before excavating the consolidated stone chips and transferring them to the next working section. S38. Repeat steps S32 to S37 to complete the foundation pit excavation.

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