What issues should be paid attention to during the construction of water conservancy pumping stations?

Construction cofferdam project, as a temporary structure for water conservancy construction, its smooth completion and safety guarantee often become the key to the success or failure of the entire project. The main function of the cofferdam project is to intercept and retain water, and create construction conditions for the construction of pump stations. Strictly preventing water inflow and preventing the collapse of weir embankments is the key to the success or failure of cofferdams. (1) The construction process of the cofferdam: Measure and set out → clear the foundation → fill the weir body → lay the composite geomembrane on the water surface → protect it with earth bags. (2) According to the results of the water surface line calculation, the water level at the location of the pumping station during the 20-year return period is 120.18 meters. Considering adding 0.5 meters of super height, the top elevation of the cofferdam is finally determined to be 120.68 meters, and the maximum cofferdam height is 3.68 meters. In order to ensure dry construction, a trapezoidal cross-section earth cofferdam is used, with a slope ratio of 1:2.5, a bottom width of 21 meters, and a top width of 3 meters. The construction of the cofferdam project, as a temporary building for water conservancy construction, requires its smooth completion and safety. Guarantee often becomes the key to the success or failure of the entire project. The cofferdam is filled with embankment soil materials to 120.68 meters, and bulldozed and rolled using bulldozers. According to the design requirements, the cofferdam compaction standard reaches more than 90%. In order to ensure the quality and stability of the cofferdam, a layer of composite geomembrane is laid on the water-facing side of the cofferdam and then protected with earth bags to prevent river water from scouring the cofferdam. (3) Weir body filling: 1) Before filling, the base should be cleared within the weir body and the base should be rolled. The underwater part should be dredged with an excavator according to the actual situation. 2) The cofferdam body is filled with bulldozers that are leveled and rolled in layers to ensure that the top width of the cofferdam is 3m. According to the design requirements, the cofferdam filling and compaction standard reaches more than 90%. 2. Foundation pit support Since the foundation of the drainage gate is a fine sand layer, a medium sand layer and a silty clay layer, to prevent the foundation pit from collapsing during excavation, steel sheet piles are used to protect the foundation pit on the inside of the cofferdam. 2.1 First, choose steel sheet piles based on the characteristics of the site where the project is located, combined with the characteristics of steel sheet piles, construction methods, etc., and select Larsen III steel sheet piles. Larsen III steel sheet piles have moderate width and good bending resistance. Its main technology The parameters are: W=1600cm3, g=60kg/m. According to the geological data and operating conditions, the steel sheet pile length is 6m, and the steel sheet pile penetration depth is required to be more than 0.5 times the pile length. 2.2 Single pile driving method one by one to drive steel sheet piles A. First, the surveyor determines the axis of the steel sheet pile cofferdam. Guide piles can be set at certain distances. The guide piles directly use steel sheet piles, and then hang ropes as conductors. When piling, wires are used to control the axis of the steel sheet pile. B. Prepare pile caps and deliver piles: the pile driver lifts the steel sheet piles and manually sets them in place. 2.3 Pulling out the piles. In principle, the piles can be pulled out after the construction of the culvert and outlet retaining wall is completed. After the wall is backfilled with earth to half its height, the piles are immediately pulled out, and the piles are repaired and reused. First, use a pile driver to clamp the head of the steel sheet pile and vibrate it for 1 to 2 minutes to loosen the soil around the steel sheet pile, produce "liquefaction" and reduce the frictional resistance of the soil to the pile, and then slowly pull it up. When pulling out piles, pay attention to the load of the pile driver. If it is difficult to pull out the pile or it cannot be pulled out, you should stop pulling out the pile. First vibrate for 1 to 2 minutes, then hammer down 0.5 to 1.0m and then vibrate upward. Repeat this to pull the pile up. Pull it out. 3. Construction diversion and precipitation 3.1 Brief description of hydrogeological conditions The foundation of the drainage gate of the pumping station is a fine sand layer, a medium sand layer and a silty clay layer. The groundwater level is 114m~115m deep, the aquifer is rich in water, and the foundation sand layer is thick, fully replenishing each other with the Songhua River water. 3.2 Selection of diversion method The pumping station is the Songbei District sewage and rainwater pumping station, with a forced discharge flow of 10m3/s and a diversion flow of 5m3/s. (1) Considering project investment, try to reduce the project cost as much as possible, use the actual existing drainage volume and peak drainage needs, combined with the water storage capacity of the water collection tank, and based on the drainage situation of the pumping station: 1) The maximum daily drainage volume in 2011 is 40,000m3 (divided into eight times) Discharge) uses 250KW each time, the flow is 5000m3/h, and the sewage pump discharges for one hour every two hours. 2) The existing daily drainage volume of 10,000m3-150,000m3 is discharged in two times, each time using a 250KW sewage pump with a flow rate of 5,000m3/h, and the water is discharged for one hour in the morning and evening. (2) Based on the above, the design basic displacement should be 30,000m3 per day. 1) Use 5 sewage pumps, 22KW, flow rate 300m3/h, lift 15m, and 2 standby sewage pumps. 2) Discharge to the Songhua River area through separate pipes.

3) For the water pipe outlet, use broken bricks to lay flat 1.2m3150# mortar for grouting. (3) After the start of construction, first conduct a pumping test to determine the drainage volume, and adjust the water pump and pipeline to meet the drainage needs. (4) The drainage pump must ensure day and night operation, and the power supply equipment should use dual lines to prevent midway power outages or other accidents that may affect drainage. The generator set shall meet the construction requirements when necessary. 24-hour on-duty inspections, equipped with electricians and mechanics. If the pump is found to be stopped, it should be dealt with immediately and the drainage should be restored as soon as possible to prevent overflow accidents caused by the stopped pump. 4. Earthwork construction 4.1 Earthwork excavation The earthwork excavation for the foundation of this drainage gate is 3000m3. It is planned to arrange a construction period of two days, using one excavation method, with a daily excavation intensity of 1500m3. It is excavated with a 2.0m3 excavator and transported by a 20T dump truck. It is transported to the spoil yard and storage yard for storage. 4.2 Earthwork backfill The earthwork backfill construction should meet the following requirements: before filling, the milk skin, dust and oil stains on the surface of the building should be removed; leaking iron parts on the surface (such as formwork dowel bolts, etc.) should be cut off, and if necessary, The remaining outcrops of iron parts need to be covered and protected with cement mortar. 5. Concrete construction The concrete building of the pumping station includes embankment culverts, reinforced concrete retaining walls, traffic bridge racks and plate girders, and the exit section stilling tank. Concrete pouring: (1) Commercial concrete is used for the supply of concrete. The mix ratio issued by the testing unit with corresponding water conservancy qualifications entrusted by the commercial concrete mixing station is used to guide the construction. The production capacity of commercial concrete mixing plants meets the concrete supply intensity required for project construction. When pouring concrete, a special person must be on duty at the mixing station to be responsible for the supply and demand of concrete. After the commercial concrete arrives at the site, the laboratory technician will test the slump of the concrete and the workability of the concrete, record it, organize and file it, and follow the construction instructions. The corresponding number of concrete test blocks shall be reserved according to the specifications. (2) Before pouring concrete, the debris in the formwork must be cleaned, rinsed with a water gun, and the formwork moistened, but there must be no accumulation of water. At the construction joints, 50-100mm thick cement mortar with the same strength grade as the concrete is first laid. (3) Concrete should be poured continuously in layers, using the long running water circle operation method to make the concrete rise evenly. The height difference should not exceed 1.5m, and the interval between layers should be ≯2h. (4) The vibrator should be "inserted quickly and unplugged slowly", and the points should be evenly arranged with a spacing of about 400mm, step by step, and no vibration should be leaked. If necessary, send someone to pound the formwork to prevent holes in the concrete. When vibrating the upper concrete, the vibrating rod should be inserted into the lower concrete by no less than 50mm. (5) When pouring concrete, you should always check whether the templates, steel bars, reserved holes, etc. have moved, and check whether the support system is firm. If problems are discovered, rectification must be carried out immediately and concrete construction must be suspended. (6) At the intersection of walls, beams, and column nodes, and where the steel bars are densely packed, the concrete must be carefully vibrated to ensure that the concrete is dense and has no holes, honeycomb pits, leaking bars, or other phenomena that affect the quality of the concrete. (7) When pouring concrete, send special personnel to guard the steel bars to ensure the correct position of the steel bars, and promptly clean the concrete lines on the steel bars. When pouring the slab, lay out the wooden boards in advance, and do not step on the steel bars at will. Pay special attention to the fact that the upper layer is strictly prohibited from negative bending. Rectangular steel bars will sink when stepped on, so pay attention to the setting of the protective layer of the steel bars. 6. Formwork production and installation 6.1 Formwork installation (1) The installation of formwork follows the principles of safety, convenience, speed and making the concrete surface beautiful. Different formwork installation methods are selected according to different concrete parts, and the order of formwork installation is arranged according to the overall construction progress plan and the layering and blocking of concrete pouring. (2) Before formwork construction, organize the study of drawings, conduct technical briefings, propose installation plans, and measure personnel to set out to ensure accurate positioning. Before installing the template, remove dirt from the template and apply release agent. The formwork installation must ensure that the joints of the formwork are straight, neat and tight, and the positions of embedded parts and reserved holes are accurate and without deviation. Reinforcement is safe and reliable, facilitates the installation of steel bars and concrete pouring and maintenance, and helps speed up the construction progress. During the formwork installation process, temporary tension and bracing reinforcement facilities must be installed to prevent overturning. 6.2 Formwork removal (1) In order to facilitate surface protection and avoid formwork removal at night, the formwork removal time shall be determined based on the weather, environment, structure type, characteristics and the strength of the concrete: non-load-bearing formwork, such as side formwork, side formwork, approx. The formwork is allowed to be removed only after the concrete strength reaches 3.5MPa; the load-bearing formwork can only be removed after the concrete strength reaches the requirements of the construction specifications.

(2) The formwork should be dismantled piece by piece from top to bottom; those supported first should be removed later, and those supported later should be removed first; non-load-bearing parts should be removed first, and then the load-bearing parts. During construction, first remove the supporting and pulling steel pipes and steel bars, loosen the bolts from top to bottom, take out the inner and outer corrugations, and take out the formwork. Pay attention to safety when removing formwork. Construction workers are not allowed to stand above or below the formwork being removed. Pay attention to the dismantling skills, and do not pry hard or use excessive force, thereby damaging the formwork and structure; when the formwork is removed from a high place, slowly lower it with a rope, and do not throw it randomly to damage the formwork.

For more information about engineering/service/purchasing tender document writing and production to improve the bid winning rate, you can click on the official website customer service at the bottom for free consultation: /#/?source=bdzd