1. Basis for compilation 2. Technical Specification for Building Foundation Pit Support JGJ12－993, Code for Acceptance of Construction Quality of Building Foundation Engineering GB522－22 2. General situation and characteristics of the project 2. The elevation difference between the fire pump house and the natural ground is 1.5m, the earthwork excavation depth is 5.4m, and the excavation depth of the local deepened part reaches 6.9m Considering the lateral pressure of the foundation pit and the safety requirements of earthwork excavation of the adjacent sales centers, Third, the main materials and appearance inspection of the supporting structure 1. Steel sheet piles are made of 4×1U steel sheet piles, with a length of 12m and a thickness of 1mm. 2. The supporting structure adopts Q235 grade B carbon structural steel. 3. The purlin of steel sheet pile adopts [1 channel steel. 3. Appearance inspection of steel sheet piles Visual inspection of steel sheet piles is carried out to correct the steel sheet piles that do not meet the shape requirements and reduce the difficulties in piling. Appearance inspection includes surface defects, length, width, thickness, end rectangle ratio, straightness and lock shape. Attention should be paid to the following aspects during inspection: ① Welded parts that have an influence on driving steel sheet piles should be cut off; (2), there are cut holes, section defects should be reinforced; (3), if the steel sheet pile has serious corrosion, should measure the actual section thickness, in order to decide whether to reduce in the calculation. In principle, all steel sheet piles should be visually inspected, and those that do not meet the requirements should be corrected. IV. Construction Steps of Foundation Pit Support 1. This foundation pit adopts 12m-long 4×1U steel sheet piles with a spacing of 4. It is forbidden to pile up heavy objects and additional loads at the top of foundation pit slope. 2. In order to make the steel sheet pile and the steel sheet pile form a whole, both sides of the steel sheet pile are connected by [1 channel steel welding. 3. Construction sequence: Axis positioning of pile position →U-shaped steel sheet pile → Installation of channel steel purlins on both sides of steel sheet pile → Earthwork excavation to the bottom of pit → Underground structure construction → Earthwork backfilling → Pulling out U-shaped steel sheet pile. 5, operation method (1), baseline determination: the builder's axis is set on the gantry beside the foundation pit, leaving the working face needed for future construction and determining the construction position of steel sheet piles. (2), pile location. Indicate the actual pile positions of steel sheet piles in sequence, and mark them with ash sprinkling lines. (3) Driving of steel sheet piles: Self-vibrating special machinery for steel sheet piles is used for driving. The first steel sheet pile is inserted and driven: the steel sheet pile is hoisted by the forearm of the pile driver, and the pile head is clamped by the splint of the pile head. After being vertical, the steel sheet pile is inserted to the design depth by the hydraulic vibration hammer of the pile driver. Subsequent steel sheet pile insertion: after the first pile is inserted, the subsequent steel sheet pile is inserted to the design depth along the buckle groove of the previous pile until the steel sheet pile enclosure system of the closed foundation pit is formed; The corners of the foundation pit are connected by big buckles to make the steel sheet piles continuous. In the construction of steel sheet pile, the allowable errors of driving are: the elevation deviation of pile top is 1 mm, the axis deviation of steel sheet pile is 1 mm, and the verticality deviation of steel sheet pile is 1%; In the process of setting, whether it is within the allowable error range should be monitored, and it should be corrected in time if it exceeds the allowable error range. When the steel sheet pile is driven, the actual length of the curtain cannot be guaranteed to be an integer multiple of the standard width of the steel sheet pile due to the errors in the production of the steel sheet pile, the deviation in piling and the limitation of construction conditions, so it is quite difficult to finally close the curtain of the steel sheet pile. Adjustment methods are usually closed by using special-shaped steel sheet piles or by adjusting the curtain axis with standard piles. Because the precision of the steel sheet pile wall in this project is not high, the latter method is adopted to close the corner, that is, the width of 1 steel sheet piles is used to adjust the axis on both sides of the corner to close it. If the length of some steel sheet piles is insufficient, it can be extended by welding, usually by fishplate welding. When extending, prevent two adjacent pile joints from being at the same depth. The joint positions should be staggered by more than 1M, and piling should be placed at intervals. (4) Purlins and tie rods In order to strengthen the overall rigidity of the steel sheet pile wall, purlins are set along the whole length of the steel sheet pile wall and welded on the steel sheet pile with [1 channel steel. There are two channels for purlin channel steel, one at the top of the steel sheet pile and one at the middle of the steel sheet pile for foundation pit support. See Attached Figure 2 for the actual location of purlin. The tie rods are made of φ48×3.5 steel pipes, which are connected by fasteners. One end is fixed on the purlin of the steel sheet pile channel steel, and the other end is fixed on the frame column of the sales center. The distance between the tie rods is 1m. See Attached Figure 2 for the actual practice. 5], steel sheet pile pull out. After the completion of civil engineering, the steel sheet pile will be pulled out. Considering the actual situation on site, the crane and the vibrating hammer are used to pull out the steel sheet pile, that is, the forced vibration generated by the vibrating hammer is used to disturb the soil quality and destroy the cohesion of the soil around the steel sheet pile to overcome the resistance of pile pulling out, and the pile is pulled out by adding the crane. The pile hole left after the steel sheet pile is pulled out should be backfilled immediately. Backfilling usually uses compaction method or filling method, and the material used is medium sand. Quality requirements 1. In the process of driving steel sheet piles, immediately check whether the plane position is correct and whether the pile body is vertical. If it is found to be inclined (whether it is inclined back and forth or inclined up and down), immediately correct it or pull it up again. Steel sheet piles are sunk by vibration and other methods. At the beginning of pile sinking, you should use self-weight to sink, and then use vibration to sink after the pile body is stable enough. 2. Construction of steel piles should be started after the site is leveled to the design elevation. 3. Allowable deviation of steel sheet pile construction: the verticality of H pile sinking is controlled at 1.5%. 4. When the steel sheet pile is pulled out, the gap should be filled with cement slurry or medium coarse sand in time. 5. Weld form: purlin and steel sheet pile are connected by welding. The weld quality grade is Grade III. Vi. Requirements of technical measures for foundation pit excavation construction 1. After the Larsen steel sheet pile is set, install the supporting device. Then carry out foundation pit excavation, which requires the following: (1) During mechanical excavation, dig to the bottom elevation of foundation quickly, and leave earthwork with a thickness of 3mm for manual repair and excavation. In order to reduce the deformation, concrete cushion should be laid as soon as possible after excavation, which can play the role of partial bottom support to reduce the deformation of steel sheet piles. (2) During mechanical excavation, attention should be paid to the fact that the bucket cannot collide with the steel sheet pile. 2. Considering the influence of rainfall, in order to better drain, 5*5*6 collecting wells are set in the northwest corner and northeast corner of the foundation pit, and the wall is protected by bricks. At the same time, drainage ditches are dug around the bottom of the pit, so that the water at the bottom of the pit is collected in the collecting wells through the drainage ditches, and the accumulated water in the pit is discharged out of the pit in time and effectively with submersible pumps. Vii. Safety and environmental protection measures 1. Establish and improve the safety and environmental protection system, institutionalize and regularize the work of safety production and environmental protection, and ensure that the work of safety and environmental protection at the construction site runs through the whole process of project construction. 2. Conscientiously and thoroughly implement the relevant safety policies, rules and regulations of Fujian Province and Fuzhou City, educate and train the employees involved in the project, firmly establish the idea of "safety first" and adhere to the policy of "safety in production and prevention first". 3. Do a good job in safety disclosure, and adhere to the "three-work system" activity of stressing safety before work, checking safety during work and evaluating safety after work. 4. The project leader shall take the leadership and management responsibility for the safety production and environmental protection in the whole construction process. 5, according to the characteristics of steel supporting engineering, the following main types of work should pay attention to safety matters; (1) Drivers and riggers Drivers and riggers should be assessed according to the relevant provisions of the labor and personnel departments and obtain certificates. Drivers should know the working principle of the crane they operate, be familiar with the structure of the crane, the functions of various safety devices and their adjustment methods, and master the operation methods of various performances of the crane and the maintenance technology of the crane. No articles are allowed to be hung obliquely, no articles are allowed to be squeezed in a staggered way, and no articles buried in the soil or frozen on the ground are allowed to be lifted. Drivers and riggers are not allowed to leave their jobs when things are hanging in the air. Drivers should carefully record the use, repair, maintenance and handover of cranes. Drivers are strictly forbidden to operate on the computer after drinking. (2) The shell of electric welder should be well grounded, and the power supply should be assembled and disassembled by an electrician. The electric welding machine shall be equipped with a separate switch, which shall be placed in a rain-proof brake box, and gloves shall be worn for lateral operation when it is closed. Electrode holder and handle wire should be well insulated and firmly connected, and gloves should be worn when replacing covered electrode. When working in wet places, you should stand on insulating rubber sheets or wooden boards. It is forbidden to weld vessels or pipelines under pressure, and the power supply should be cut off before welding live equipment. Welded containers or pipelines that have stored flammable, explosive and toxic substances shall be cleaned and all orifices shall be opened. When welding in a closed metal container, the container should be reliably grounded, well ventilated and supervised. It is forbidden to input oxygen into the container. When welding preheating workpieces, thermal insulation measures such as asbestos cloth or baffle should be taken. Do not touch the wire and ground wire, and do not use wire rope or mechanical and electrical equipment to replace the zero line. All ground connectors should be firmly connected. When changing the moving handle of the site, cut off the power supply, and do not climb the ladder with the handle. Wear protective glasses or a mask when removing welding slag and using arc gouging for root cleaning to prevent iron slag from splashing and hurting people. When multiple welders are welded together, the welding platform or weldment should be grounded and should have a light barrier. The shell of carbon dioxide gas preheater should be insulated, and the terminal voltage should not be greater than 36V. During thunderstorm, open-air welding operation should be stopped. Flammable and explosive articles should be removed around the welding site, or covered and isolated. . (3) When the vibrating pile driver vibrates to pull out the pile, it should be vertically upward and pull out while shaking. When vibrating pile sinking, no one is allowed to stay at the lower part of the frame. After adjusting the eccentric block, the residue in the box should be removed before commissioning. The vibration and noise of piling operation are large, so piling construction should be carried out within the time period stipulated by Anshan environmental protection, and the rest time such as lunch break and evening should be avoided.