Study On Method Of Settlement Computation Of Multi-element Composite Foundation

With the development of economy and the expanding of infrastructure construction, ground improvement techniques haave developed rapidly. Meantime, based on the common composite foundation, the multi-pile composite foundation emerged last years. The application precedes the theory of composite foundation, especially in multi-pile composite foundation. In order to spread and apply the technique better, it is necessary to further study the settlement mechanism and computation method of settlement.This thesis deals with the settlement mechanism and settlement computation method of multi-pile composite foundation by analytical method. The main contents of this thesis are as follows:Firstly, the development of composite foundation was introduced, and the present state of the multi-pile composite foundation is reviewed. Subsequently, the existing methods of computing the settlement of multi-pile composite foundation are summarized, and then the applicability and deficiency of these methods were pointed out.Secondly, load-transfer law of single pile in composite foundation was analyzed in this thesis, based on this, the relationship between settlement on top of single pile and load on pile top was deduced by the load transfer principle in elasticity theory. Taking into account the interaction among cushion, piles and soil, based on the model proposed by Mylonakis and Gazetas, flexibility coefficients of interaction between piles and between pile and soil were obtained. The equation including the settlements of pile top and soil top and corresponding loads was established by superposition principle in elasticity theory. Stress ratios of primary pile and secondary pile to pile, and load-sharing proportions of primary pile, secondary pile and soil could be achieved by solving the equation.Finally, a practical base of multi-pile composite foundation was studied. By comparing the values calculated using the method presented in the thesis with the measured data in the field, the reliability of this method of settlement calculation of multi-pile composite foundation was validated.