Railway Engineering: cofferdam excavation

Pit cofferdam cofferdam is usually divided into soil, soil and steel sheet pile cofferdam cofferdam.
1. General requirements for pit cofferdam: Top cofferdam should be higher than the highest water level may occur during construction 0.5m; erosion protection measures for the river section should be compressed cofferdam caused; cofferdam should do waterproof tight reduce leakage; cofferdam should meet the needs within the area of infrastructure construction; cofferdam should meet the requirements of strength and stability.
2. The depth of soil cofferdam apply within 2m, the flow rate of less than 0.3m / s, the role of small and riverbed scour for smaller water permeability soil. Construction should be based on the actual situation of the construction site, the use of the pier, station location partial temporary cofferdam or first excavated canals, and then build the bridge located at the weir weir. Construction, should first clean up the river debris from the upstream to the downstream embankment close.
3. Soil cofferdam apply depth of not more than 3m, the flow rate of less than 1.5m / s, a small river of water permeability of the soil. Soil bags commonly used straw bags, sacks or bags, the soils and the amount is generally bag capacity 1/2 ~ 1/3, stacking requirements seam down around each other wrong, and stacking neatly as possible.
4. Steel sheet pile cofferdam apply Deep Water riverbed is sandy soil, clay, gravel and other soil and weathered rock formations. Sheet pile plane generally used for circular, rectangular and round end shape. Steel sheet pile cofferdam construction program: the steel sheet pile finishing a prison setting surrounded by a steel sheet pile around the prison to install a plug Hop dragon fight. Punched steel sheet pile method can be divided into block by block (group) punched, hit after the first mating dragon and part-by-block interpolation start playing after the first mating portion Long after the fight.
5. Excavation and back cover: After the success of the cofferdam can be conducted within the cofferdam excavation soil, water points and dry excavation excavation, excavation excavation methods have GRABBING Excavation, human open digging, excavation punch suction method.