What is a U-shaped steel sheet pile?
Larsen steel sheet piles are also called U-shaped steel sheet piles. As a new type of building material, it plays an important role in the construction of bridge cofferdams, large pipeline laying, temporary ditch excavation as earth, water and sand retaining walls; in docks, loading docks as retaining walls, retaining walls, embankment berms and other projects. Larsen sheet pile cofferdam is not only green, environmental protection and fast construction, low construction cost, has a very good waterproof function.
According to the production process, U-shaped steel sheet piles are divided into two types: cold-formed steel sheet piles and hot-rolled steel sheet piles. In engineering construction, cold-formed steel sheet piles are relatively cost-effective, and in engineering applications, the two types can be substituted for each other. So how are U-shaped steel sheet piles generally constructed?
Construction steps of U-shaped steel sheet pile:
1) Before piling, inspect the U-shaped steel sheet piles one by one, and remove the U-shaped steel sheet piles with corroded and severely deformed connection locks, and those unqualified can only be used after trimming. Apply grease to the lock of the U-shaped steel sheet pile to facilitate driving in and pulling out.
2) Measure and monitor the inclination of each pile at any time during the insertion and driving process, which does not exceed 2%. When the inclination is too large and cannot be adjusted by the method of pulling, pull it up and hit it again.
3) First, use a crane to hoist the U-shaped steel sheet pile to the point where the pile is inserted. When inserting the pile, the lock should be aligned. After each piece is inserted, put on the pile cap and lightly hammer it. In the process of piling, in order to ensure the verticality, two theodolites are used to control in two directions. In order to prevent the displacement of the center plane of the lock, a clamping plate is installed at the lock of the U-shaped steel sheet pile in the direction of piling to prevent the displacement of the sheet pile. At the same time, the position of each plate is pre-calculated on the purlin, so that it can be checked and corrected at any time.
4) The U-shaped steel sheet piles are driven in several times, the first time from 20m to 15m, the second time to 10m, the third time to the height of the guide beam, and the fourth time to the design after the guide frame is removed elevation. When piling, start to set the driving position and direction of the first and second steel plates to ensure the accuracy, and measure once every 1m of driving.
5) Use U-shaped steel piles to be placed vertically or the locks of steel sheet piles to be inserted into the locks of adjacent piles. After the piles are stable, in the correct position and vertical, they will vibrate and sink. Every time the U-shaped steel sheet pile sinks by about 1 to 2 mm, the verticality of the pile shall be stopped and detected, and the deviation shall be corrected in time.
6) In order to strengthen the overall rigidity of the U-shaped steel sheet pile wall, a surrounding purlin is set along the entire length of the U-shaped steel sheet pile wall. It is composed of two Φ25 steel bars, welded on the steel pipe anchor. For the sake of safety, use channel steel or angle steel as angle braces on the five corners of the U-shaped steel sheet pile wall.
7) After the foundation pit is backfilled, the U-shaped steel sheet pile should be pulled out for reuse. Before pulling out the U-shaped steel sheet pile, the sequence of the pulling method, the pulling time and the soil hole treatment should be carefully studied. Otherwise, ground settlement and displacement will be caused due to the impact of the vibration of the pulling piles and the excessive soil attached to the pulling piles, which will cause harm to the constructed underground structure and affect the safety of adjacent original buildings, structures or underground pipelines. It is very important to try to reduce the soil caused by pulling piles. At present, measures such as irrigation and sand filling are mainly adopted.
Firstly, use the pile extractor to clamp the head of U-shaped steel sheet pile and vibrate for 1min～2min to loosen the soil around the U-shaped steel sheet pile and produce "liquefaction" to reduce the frictional resistance of the soil to the pile, and then slowly pull up the pile. When pulling out the pile, pay attention to the load of the pile driver, and if you find that it is difficult or impossible to pull up the pile, you should stop pulling out the pile, vibrate for 1min~2min and then hammer down the pile for 0.5m~1.0m and then pull out the pile by vibration.
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