Construction process of sheet pile cofferdam with six-layer inside support is generally divided into six steps of pumping and excavation down and five steps of concrete pouring and support demolition. The most dangerous condition is excavation to the end. For design, key points are as follows:
1. First set the guide frame of sheet pile, insert and play, then install the first layer purlin and support (to avoid high tide). Then try pumping water and plug pile joints in water over the riverbed.
2. From layer 2 to 6, pump or excavate one by one to the position 0.5m lower than the elevation of support to be installed, then install purlin and support.
3. From the 5th layer, gradually narrow the excavation surface layer to form slope.
4. Excavate by divided area to the end of cushion, pouring concrete pads, and ultimately form a complete flat construction surface.
5. Pouring cap by four-layer, backfill sands from nearby and remove a support layer as soon as each layer’s pouring completed.
6. For the last 2 layers’ support, should consider the construction situation for support removal or change when pouring the upper parts of bridge piers.
In addition, in the calculation and design, select datas of drilling holes in the place with poor geological conditions. Then refer to section diagram, analyze and calculate the displacement and bending moment of sheet pile in the six steps’ pumping and excavation.
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