Experimental Study And Numerical Simulation On The Composite Pile With Cast-In-Place Core

Based the idea of optimization design of pile, the composite pile with cast-in-placecore is formed with soil-cement pile and cast-in-place pile. Composite pile withcast-in-place core, which takes soil-cement pile as ring pile and takes cast-in-place pile ascore pile, is a new type of composite pile. It means that, a hole at the center of soil-cementpile is made, and then concrete in the hole of the center of soil-cement pile is cast after madesoil-cement pile. The composite pile with cast-in-place core not only utilizes the virtue ofcast-in-place pile and soil-cement pile, but also avoided the disadvantage of cast-in-placepile and soil-cement pile. The composite piles with cast-in-place core of different length and different diameterwere made, and also soil-cement piles which length and diameter are same with compositepiles with cast-in-place core. With static test, the Q-s curves of soil-cement pile andcomposite piles with cast-in-core are obtained, also the stress of top of cast-in-place coreand soil-cement ring was recorded. The ultimate bearing capacity of piles was got by theQ-s curves. The ultimate bearing capacity of piles expresses that the best length ofcast-in-place core is 4 miters;the optimum diameter of cast-in-place core is 0.35 miters;thebest ratio of the length of cast-in-place core is 2/3;the optimum ratio of the area ofcast-in-place core is 0.32. With the stress of the piles top, the stress ratio and load-sharingratio of soil-cement ring top and cast-in-place core top were got. It turn out that the loadtransmission principle by the settlement displacement of soil-cement ring is less than thesettlement displacement of cast-in-place core. Based increment theory of elastic-plastic mechanics, a mathematical model forcomposite pile with cast-in-place core was established by using Druker-Prager yieldcriterion for concrete, soil-cement and soil. The finite element program was compiled by theautomated generating system of the finite element of FEPG. The composite piles withcast-in-place core of different length and different diameter were numerical simulated. TheQ-s curve of composite piles with cast-in-place core is the delayed curve that is same withtest result. The fracture mechanism, load transferring mechanism and danger area ofcomposite piles with cast-in-place core are gained by stress and displacement ofmathematical model analysis.