Research On Bearing Capacity And Settlement Calculation Methods Of Concrete Pile Composite Foundation

Shuangtaizi River Gate Project is located in the eastern suburb of Shuangtaizi District of Panjin City Liaoning Province, and it’s a pivot structure in Liao River downstream. It was built at the end of tidal reach and57.3km from the estuary. The project is an important part of Liao River downstream flood control system. In the Shuangtaizi River Gate Ship Lock Renovation Project, the original lock will be abandoned and a new grade III lock will be built30m from the left side of the original lock. The new lock will be located on the left shore of the main river channel and near it. The survey site was formed by dropping back of sea in modern times. Stratum and lithologies below basis of the lock from top to bottom are as follows:artificial backfill, mucky silty clay, silt, fine sand. The foundation belongs to soft soil foundation, and the foundation of the upper lock head will be reinforced with concrete piles.Based on the above project, various methods for calculating concrete pile composite foundation’s bearing capacity including area ratio method and stress ratio method, and methods for calculating its settlement including complex modulus method, stress correction method and pile compression method were respectively compared and analyzed. According to the discussions, composite foundation bearing capacity should be calculated using the formula based on area ratio method recommended in the specification, settlement of reinforcement area should be calculated using composite modulus method or stress correction method. Substratum settlement should be calculated using stratified sum method, and additional stress on top surface of substratum should be calculated using the equivalent entity method.In addition, an overall numerical analysis of the upper lock head and concrete pile composite foundation was carried on using ANSYS. Composite foundation was simulated by composite soil unit. The results showed that bearing capacity and settlement of the composite foundation met the requirements. Settlement results were similar with the theoretical results. Then the anti-sliding stability, anti-capsizing stability, anti-floating stability, seepage stability and structural deformation of the upper lock head were analyzed, and results showed that the structure met the security requirements in specifications.