Construction method for preventing concentrated leakage of cofferdam

Abstract

The invention relates to the technical field of cofferdam construction, and provides a construction method for preventing concentrated leakage of a cofferdam, which comprises the following steps: S1, carrying out detailed geological survey on a construction area to obtain parameters such as soil layer distribution, underground water level and soil permeability coefficient; s2, designing a composite cofferdam structure according to a geological survey result; s3, cofferdam construction is conducted; s4, the cofferdam is monitored regularly, monitoring data are transmitted to a monitoring center in a wireless mode, and if abnormity is found, reinforcement measures are taken in time; and S5, when concentrated leakage is found, a double-liquid grouting method is adopted for blocking, grouting materials are cement paste and water glass, and the proportion of the cement paste and the water glass is determined according to a field test. The composite cofferdam structure is accurately designed through detailed geological survey and three-dimensional geological model analysis, the waterproof performance of the cofferdam is effectively improved, and the stability and the pressure resistance of the cofferdam are enhanced by adopting the mode of combining the high-strength concrete cast-in-place piles, the waterproof geotechnical cloth and the steel sheet piles.

Description

Technical Field

[0001] The present application relates to the field of cofferdam construction technology, and in particular to a construction method for preventing concentrated leakage of a cofferdam. Background Art

[0002] During the cofferdam construction process, concentrated leakage is a problem that needs to be focused on. It usually occurs during the cofferdam construction of water conservancy projects, bridge foundations, etc. It may be caused by inaccurate geological surveys, unreasonable cofferdam structure design, substandard construction quality, poor material performance, etc. Concentrated leakage will cause the construction area to be flooded, affect the progress of the project, increase costs, and even threaten the safety of construction workers.

[0003] Traditional cofferdam construction methods mostly use a single structural form, such as concrete walls, steel sheet piles, etc. These methods have certain limitations in preventing leakage. For example, concrete walls are prone to cracks when affected by uneven settlement or earthquakes, leading to leakage; and steel sheet piles may have problems such as loose locks and water leakage at joints. In addition, traditional methods cause great damage to the environment during construction, high energy consumption, and high maintenance costs in the later stage. Therefore, in response to these problems, the present invention proposes a safer, environmentally friendly, and economical construction method for preventing concentrated leakage of cofferdams. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present invention provides a construction method for cofferdams to prevent concentrated leakage, thereby solving the problems of cofferdam construction in the prior art.

[0005] To achieve the above purpose, the present invention is implemented by the following technical scheme: A construction method for preventing concentrated leakage of a cofferdam comprises the following steps: S1. Conduct detailed geological surveys of the construction area to obtain parameters such as soil layer distribution, groundwater level and soil permeability coefficient, and use GIS to establish a three-dimensional geological model to accurately analyze possible leakage paths; S2. Design a composite cofferdam structure based on the geological survey results. The bottom layer of the composite cofferdam structure uses high-strength concrete cast-in-place piles, the pile spacing is determined according to calculations, the middle layer is a waterproof geotextile, the top layer uses steel sheet piles, and adjacent steel sheet piles are connected by lock-mouth sealing; S3. Carry out cofferdam construction S31. Carry out cast-in-place pile construction. The concrete strength of the cast-in-place pile shall not be less than C30, the verticality deviation of the pile body shall not exceed 1%, and the pile position deviation shall not exceed 50mm; S32. Lay waterproof geotextile on the top of the cast-in-place pile. The overlap width of the geotextile should not be less than 50cm and it should be firmly bonded with special glue. S33. Install steel sheet piles using the vibration pile sinking method. During the pile sinking process, the verticality and horizontal displacement of the pile body are monitored in real time to ensure that the deviation is within the allowable range; S34. Multiple support structures are set up inside the cofferdam, with steel beams and steel columns used for support. The spacing is determined according to calculations and is firmly connected to the cofferdam wall; S35. Lay a layer of polymer waterproofing membrane on the water-facing surface of the cofferdam. The membrane is pasted by hot-melt method to ensure that there are no hollows and wrinkles; S36. Set up a drainage blind ditch at the bottom of the cofferdam, fill the blind ditch with graded crushed stone, and cover it with anti-filter geotextile. The drainage blind ditch is connected to the water collection well through a drainage pipe, and an automatic pumping device is installed in the water collection well; S4. Regularly monitor the cofferdam, including water level changes, wall deformation and water seepage, etc. The monitoring data is transmitted to the monitoring center via wireless. If any abnormality is found, reinforcement measures are taken in time; S5. When concentrated leakage is found, double-liquid grouting method is used for sealing. The grouting materials are cement slurry and water glass, and the ratio is determined based on field tests.

[0006] Preferably, the design of the composite cofferdam structure is simulated and calculated using finite element analysis software to determine the stress and deformation conditions of each layer of the structure.

[0007] Preferably, before the construction of the cast-in-place piles, the pile positions are accurately measured and located using a total station, with an error of no more than 10 mm.

[0008] Preferably, during the vibration pile driving process, the vibration frequency and amplitude are controlled to avoid excessive disturbance to the surrounding soil.

[0009] Preferably, the steel beams and steel columns of the support structure are pre-assembled before installation to ensure size and connection accuracy.

[0010] Preferably, before laying the polymer waterproof membrane, the base layer is cleaned and processed to ensure that the base layer is flat, dry and free of debris.

[0011] Preferably, the slope of the drainage blind ditch is not less than 0.5% to ensure smooth drainage.

[0012] Preferably, the monitoring equipment uses a high-precision sensor with a measurement accuracy of not less than 1 mm.

[0013] Preferably, the pressure and flow rate of the double-liquid grouting are adjusted according to the on-site conditions, and the grouting sequence is from bottom to top and performed at intervals.

[0014] Preferably, the construction method also includes operating in strict accordance with construction specifications and quality standards during the construction process, and conducting acceptance after each process is completed, and only proceeding to the next process after passing the acceptance.

[0015] In summary, the present application includes at least one of the following beneficial technical effects: The present invention accurately designs the composite cofferdam structure through detailed geological survey and three-dimensional geological model analysis, effectively improves the waterproof performance of the cofferdam, and adopts a combination of high-strength concrete bored piles, waterproof geotextiles and steel sheet piles to enhance the stability and compressive resistance of the cofferdam. At the same time, regular monitoring and double-liquid grouting method sealing are used to ensure the safety and reliability of the cofferdam during use. This method reduces construction costs while improving the waterproof performance of the cofferdam, and has good economic and social benefits.

[0016] The construction method for preventing concentrated leakage of the cofferdam of the present invention fully considers the requirements of environmental protection and resource conservation. The materials and technologies adopted, such as the polymer waterproof membrane and the double-liquid grouting method, all meet the environmental protection standards and reduce the pollution to the environment. At the same time, by optimizing the construction process and improving the construction efficiency, the energy consumption and material waste are reduced, and green construction is realized. At the same time, the service life of the cofferdam is increased, the frequency of repair and replacement is reduced, and the long-term maintenance cost is reduced. DETAILED DESCRIPTION

[0017] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0018] Embodiment 1: The embodiment of the present invention provides a construction method for preventing concentrated leakage of a cofferdam, comprising the following steps: S1. A detailed geological survey was conducted on the construction area, and the soil layer distribution was obtained. From top to bottom, it was found that there were 2 meters thick silty clay, 5 meters thick sand and 8 meters thick rock layers, the groundwater level was 3 meters below the surface, and the soil permeability coefficient was 0.005cm / s. A three-dimensional geological model was established using GIS, and accurate analysis showed that the possible leakage path was mainly concentrated at the junction of the sand and rock layers.

[0019] S2. Design a composite cofferdam structure based on the geological survey results. The bottom layer uses high-strength concrete piles with a pile spacing of 1.5 meters. The middle layer is a waterproof geotextile, and the top layer uses steel sheet piles. Adjacent steel sheet piles are connected by lock-type sealing.

[0020] S3. Carry out cofferdam construction: During cast-in-place pile construction, the concrete strength of the cast-in-place pile is C35, the verticality deviation of the pile body is controlled at 0.8%, and the pile position deviation is controlled at 40mm; waterproof geotextile is laid on the top of the cast-in-place pile, the overlap width of the geotextile is 60cm, and it is firmly bonded with special glue; when installing steel sheet piles, the vibration pile sinking method is adopted, the vibration frequency is 15Hz, the amplitude is 2cm, and the verticality and horizontal displacement of the pile body are monitored in real time during the pile sinking process to ensure that the verticality deviation of the pile body is within 0.5% and the horizontal displacement deviation is within 30mm; 5 support structures are set inside the cofferdam to support the construction of the steel sheet pile. Steel beams and steel columns are used. The steel beams and steel columns of the supporting structure are pre-assembled before installation to ensure the size and connection accuracy. The spacing is 3 meters and they are firmly connected to the cofferdam wall. A layer of polymer waterproof membrane is laid on the water-facing surface of the cofferdam. Before laying the polymer waterproof membrane, the base layer is cleaned and treated to ensure that the base layer is flat, dry and free of debris. The membrane is pasted by hot melt method to ensure that there are no hollows and wrinkles. A drainage blind ditch is set at the bottom of the cofferdam, filled with graded gravel, and covered with anti-filter geotextile. The slope of the drainage blind ditch is 0.8%, which is connected to the collection well through a drainage pipe. An automatic pumping device is installed in the collection well.

[0021] S4. Monitor the cofferdam regularly. The monitoring equipment uses high-precision sensors with a measurement accuracy of 0.5mm. The monitoring data is transmitted to the monitoring center via wireless, including water level changes, wall deformation, and water seepage. If abnormal conditions such as the water level rising by 50cm within 1 hour, the wall deformation exceeding 30mm, or the water seepage exceeding 10 cubic meters per hour are found, reinforcement measures should be taken in a timely manner.

[0022] S5. When concentrated leakage is found, double liquid grouting method is used for plugging. The grouting materials are cement slurry and water glass with a ratio of 1:0.5. The grouting pressure is 2MPa, the flow rate is 20L / min, and the grouting sequence is from bottom to top, with an interval of 2 meters.

[0023] During the construction process, we strictly follow the construction specifications and quality standards, and accept the inspection after each process is completed. The next process can only be carried out after it passes the inspection.

[0024] The design of the composite cofferdam structure is simulated and calculated by finite element analysis software to determine the stress and deformation of each layer of the structure. The simulation calculation method is: 1. Establish a geometric model. According to the actual construction area size and the design parameters of the composite cofferdam structure, create a three-dimensional geometric model in the finite element software, including the shape and size of the cast-in-place piles, waterproof geotextile, steel sheet piles, supporting structure, etc.; 2. Define material properties and assign corresponding material mechanical performance parameters, such as elastic modulus, Poisson's ratio, yield strength, etc., to each component (such as cast-in-place pile concrete, steel sheet pile material, etc.); 3. Mesh the geometric model and select the appropriate unit type and mesh size to ensure calculation accuracy and efficiency; 4. Apply boundary conditions and determine the boundary constraints of the model according to the actual situation, such as bottom fixation, side limit horizontal displacement, etc.; 5. Apply loads, taking into account soil pressure, water pressure, construction loads, etc., and load them onto the model in an appropriate manner. The soil pressure calculation formula is: Ea=1 / 2γH2Ka, where γ is the weight of the soil, H is the depth of the calculation point, Ka is the active soil pressure coefficient, and the hydrostatic pressure calculation formula is: P=ρgh, where ρ is the density of water, g is the acceleration of gravity, and h is the water depth; 6. Calculation and analysis: Run finite element analysis software to calculate and solve the stress and deformation of the structure; 7. Result evaluation: check the calculation results, including stress distribution and deformation of each part. Evaluate the stability and safety of the structure; 8. Optimize the design. If the result does not meet the requirements, adjust the design parameters (such as pile spacing, support spacing, etc.) and recalculate until the design requirements are met.

[0025] Before the construction of cast-in-place piles, the pile positions are accurately measured and located using a total station with an error of no more than 10 mm.

[0026] Embodiment 2: The embodiment of the present invention provides a construction method for preventing concentrated leakage of a cofferdam, comprising the following steps: S1. Conducting geological surveys in the construction area, the results show that the soil layers are 3 meters thick muddy soil, 4 meters thick silt soil and 6 meters thick strongly weathered rock, the groundwater level is 2.5 meters below the surface, and the soil permeability coefficient is 0.003cm / s. Using GIS to establish a three-dimensional geological model, the analysis shows that the possible leakage path is mainly at the junction of muddy soil and silt soil; S2. Design a composite cofferdam structure with a bottom pile spacing of 1.2 meters; S3. Carry out cofferdam construction: The concrete strength of the bored piles is selected as C40, the verticality deviation of the pile body is controlled within 0.5%, and the pile position deviation is controlled within 30mm; the waterproof geotextile laid on the top of the bored pile has an overlap width of 70cm and is bonded with special glue; the steel sheet piles are installed by vibration pile sinking method, with a vibration frequency of 12Hz and an amplitude of 1.5cm. During the pile sinking process, the verticality deviation of the pile body is ensured to be within 0.3%, and the horizontal displacement deviation is within 20mm; 4 support structures are set inside the cofferdam, and the supporting steel beams and steel columns are 2.5 meters apart and firmly connected to the cofferdam wall; polymer waterproof membrane is laid on the water-facing surface of the cofferdam, and the membrane is pasted by hot melt method to ensure that there are no hollows and wrinkles; a drainage blind ditch is set at the bottom of the cofferdam, filled with graded gravel, and covered with anti-filter geotextile. The slope of the drainage blind ditch is 1%, which is connected to the water collection well through a drainage pipe, and an automatic pumping device is set in the water collection well.

[0027] S4. Monitor the cofferdam regularly, with the monitoring equipment measuring with an accuracy of 0.3mm, and transmit the monitoring data wirelessly to the monitoring center. If the water level rises by 40cm within 30 minutes, the wall deformation exceeds 20mm, or the water seepage exceeds 8 cubic meters per hour, etc., take reinforcement measures in time.

[0028] S5. When concentrated leakage is found, double-liquid grouting method is used for sealing. The ratio of cement slurry and water glass is 1:0.3, the grouting pressure is 1.5MPa, the flow rate is 15L / min, and the grouting sequence is from bottom to top, with an interval of 1.5 meters.

[0029] The construction process is carried out strictly in accordance with specifications and quality standards. Each process is inspected after completion and the next process is carried out after passing the inspection.

[0030] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A construction method for preventing concentrated leakage by using a cofferdam, characterized in that: The following steps are involved: S1. Conduct detailed geological surveys of the construction area to obtain parameters such as soil layer distribution, groundwater level and soil permeability coefficient, and use GIS to establish a three-dimensional geological model to accurately analyze possible leakage paths; S2. Design a composite cofferdam structure based on the geological survey results. The bottom layer of the composite cofferdam structure uses high-strength concrete cast-in-place piles, the pile spacing is determined according to calculations, the middle layer is a waterproof geotextile, the top layer uses steel sheet piles, and adjacent steel sheet piles are connected by lock-mouth sealing; S3. Carry out cofferdam construction S31. Carry out cast-in-place pile construction. The concrete strength of the cast-in-place pile shall not be less than C30, the verticality deviation of the pile body shall not exceed 1%, and the pile position deviation shall not exceed 50mm; S32. Lay waterproof geotextile on the top of the cast-in-place pile. The overlap width of the geotextile should not be less than 50cm and it should be firmly bonded with special glue. S33. Install steel sheet piles using the vibration pile sinking method. During the pile sinking process, the verticality and horizontal displacement of the pile body are monitored in real time to ensure that the deviation is within the allowable range; S34. Multiple support structures are set up inside the cofferdam, with steel beams and steel columns used for support. The spacing is determined according to calculations and is firmly connected to the cofferdam wall; S35. Lay a layer of polymer waterproofing membrane on the water-facing surface of the cofferdam. The membrane is pasted by hot-melt method to ensure that there are no hollows and wrinkles; S36. Set up a drainage blind ditch at the bottom of the cofferdam, fill the blind ditch with graded crushed stone, and cover it with anti-filter geotextile. The drainage blind ditch is connected to the water collection well through a drainage pipe, and an automatic pumping device is installed in the water collection well; S4. Regularly monitor the cofferdam, including water level changes, wall deformation and water seepage, etc. The monitoring data is transmitted to the monitoring center via wireless. If any abnormality is found, reinforcement measures are taken in time; S5. When concentrated leakage is found, double-liquid grouting method is used for sealing. The grouting materials are cement slurry and water glass, and the ratio is determined based on field tests.

2. The construction method for preventing concentrated leakage of cofferdam according to claim 1 is characterized in that: The design of the composite cofferdam structure is simulated and calculated using finite element analysis software to determine the stress and deformation conditions of each layer of the structure.

3. The construction method for preventing concentrated leakage of cofferdam according to claim 1, characterized in that: Before the construction of the cast-in-place piles, the pile positions are accurately measured and located using a total station, with an error of no more than 10 mm.

4. The construction method for preventing concentrated leakage of cofferdam according to claim 1, characterized in that: During the vibration pile driving process, the vibration frequency and amplitude are controlled to avoid excessive disturbance to the surrounding soil.

5. The construction method for preventing concentrated leakage of cofferdam according to claim 1, characterized in that: The steel beams and steel columns of the supporting structure are pre-assembled before installation to ensure size and connection accuracy.

6. The construction method for preventing concentrated leakage of cofferdam according to claim 1, characterized in that: Before laying the polymer waterproofing membrane, the base layer is cleaned and processed to ensure that the base layer is flat, dry and free of debris.

7. The construction method for preventing concentrated leakage of cofferdam according to claim 1, characterized in that: The slope of the drainage blind ditch is not less than 0.5% to ensure smooth drainage.

8. The construction method for preventing concentrated leakage of cofferdam according to claim 1, characterized in that: The monitoring equipment adopts a high-precision sensor with a measurement accuracy of no less than 1 mm.

9. The construction method for preventing concentrated leakage of cofferdam according to claim 1, characterized in that: The pressure and flow rate of the double-liquid grouting are adjusted according to the on-site conditions, and the grouting sequence is from bottom to top and is carried out at intervals.

10. The construction method for preventing concentrated leakage of cofferdam according to claim 1, characterized in that: The construction method also includes strictly following the construction specifications and quality standards during the construction process, and conducting acceptance after each process is completed, and only proceeding to the next process after passing the acceptance.