Study On The Mechanism And Settlement Computation Method Of The Cast-in-situ Concrete Thin-wall Pipe Pile Composite Foundation

As a new foundation improvement technology, The cast-in-situ concrete thin-wall pipe pile (PCC pile) is applied widely in the construction of the highway, civil architecture, haven and sea embankment etc. The PCC pile has a great prospect because it has superiority in the treatment of soils, such as construction period, cost and environment protection. Based on the study idea of the former pile else, this paper has conducted and discussed the mechanism of consolidation, settlement calculation and optimization design of the PCC pile according to the test in situ results and reasoning. It includes the followings in detail:(1) Compared with the precast tube concrete pile and tube sinking concrete pile, the merits and shortages, construction machine, construction technology of the PCC pile and PCC pile composite foundation are introduced in detail to make the PCC pile be known completely by engineers.(2) The test of the PCC pile and its composite foundation in situation is carried out and the consolidation mechanism was discussed according to result of the test in situation.(3) Based on the working performance and mutual influence of the system of PCC pile-soil-cushion, PCC pile composite foundation is discussed in elastic method. A new calculation method of composite modulus of the PCC pile composite foundation is developed. Furthermore, Pile-soil stress ratio and settlement can be derived from the proposed method in this paper. Finally, it is proved the method is practicable and applicable in the field by a practical engineering.(4) According to the settlement calculation method in this paper, the main influence factors, such as displacement ratio, modulus of cushion, modulus of pile, and coefficient of subgrade, are discussed in this paper and the curves that reflect the relationships of the composite modulus and the influence factors have been achieved.(5) The governing object function and two boundary condition: settlement and foundation bearing capacity are developed in the optimization design of the PCC pile composite foundation. The design parameters of the PCC pile composite foundation are discussed and then the optimization design method and process is developed.