Stress And Failure Mechanism Analysis On The Composite Foundation Reinforced By Rigid Piles Under Flexible Foundation

With the rapid development of expressway and high-speed railway, more and more rigid piles like CFG piles and concrete piles have been put in practice in composite foundation, In addition to bearing capacity and settlement calculations for composite foundation under flexible foundation, stability analysis should also be maded. Limit equilibrium theories are widely used to analyze the instability of the embankment in domestic, which assume shear failure. However, in practice part of the piles may bear high bending moment and tensile stress, which may cause flexural and tensile failure. In recent years, researches at home and abroad show that the higher shearing strength of the rigid pile is not fully effective in use, the shearing failure theory of pile overestimates the stability of the embankment, which is unsafe.In the paper ABAQUS software is used to establish a3-D analytical model of the composite foundation. Concrete damage model is first used to analyze the stress and destruction features of pile in the process of embankment reclamation and loading.The force and failure characteristics, stress migration, collapse mode are studied in single pile and grouped piles composite foundation. The influence of the depth of the piles end into the bearing layer, pile spacing and geogrid are also taken into consider.The study shows:(1) concrete damage model has good performances in predicting force characteristics and failure features in the process of loading on piles.(2) The contributions to anti-slide ability made by piles at different positions are different, so are the maximum moments in piles at failure.(3) The failure of piles in group pile composite foundation is a dynamic process from crack to failure.(4) Application of geogrid in embankment reclamation can improve stress distribution effectively in rigid pile composite foundation, enhance the bearing and anti-slide ability.