ANALYSIS AND OBSERVATION OF COFFERDAM BEHAVIOUR UNDER BIASED EARTH PRESSURE

The cofferdam was used as the temporary track when the railroad on rigid-frame bridge was constructed from the embankment. But, the actual mechanical behaviour has not been made clear and its analysis method has not been developed. Then, we have verified to apply the finite element method, which can consider the reciprocal action of soil and structure, based on the observed data. On the releasing stress problem, the model was analyzed by the finite element method of effective stress treating soil as laminated material with modulus of deformation during decreasing load. As the results of analysis, the finite element method has been verified to understand the behaviour such as shearing deformation, sliding and reversing of the cofferdam under the biased earth pressure. But, the method cannot simulate the displacement and the stress of bar and beam elements as like the earth retaining walls and tie rods. It was found that the fittest method was to sum up the cofferdam deformation calculated by the finite element method and the displacement of earth retaining wall calculated by the elasto-plastic model to braced excavations.