Numerical Simulation with FLAC3D on the Reasonable Value of Lime-soil Cushion Thickness, Cohesion and Friction Angle of Rigid Pile Composite Foundation in Collapsible Loess Areas
|School||Taiyuan University of Technology|
|Keywords||CFG pile composite foundation lime-soil cushion numerical simulation cushion thickness cohesion angle of internalfriction reasonable value|
With the continuous improvement of composite foundation theory, the rigid-pile composite foundation in collapsible loess regions has been widely applied, specially the CFG (Cement Fly-ash Gravel) pile composite foundation, because the CFG pile has the effects of pile body and replacement. The CFG pile together with the soil between piles and cushion can form a composite foundation, the cushion design is the core content of composite foundation. The cushion has the effect of guaranteeing pile-soil interaction, adjusting the load distribution ratio and the horizontal load between pile and soil, reducing stress concentration at the base bottom. The researchers have a more profound understanding of behavior and failure modes of cushion, but the reasonable value of lime-soil cushion thickness, cohesion and friction angle of rigid pile composite foundation in collapsible loess areas has been up in the air. Based on the existing research, the numerical analysis software FLAC3D was used in this paper to establish a calculation model of lime-soil cushion of CFG pile composite foundation, to study the effect of thickness, cohesion and angle of internal friction of lime-soil cushion on the stress ratio of pile and soil, pile stress, the settlement of composite foundation and pile penetration in different deformation modulus of soil between piles. The conclusions can be drawn out as follows and the reasonable values of three parameters of lime soil cushion are given.(1) The lime-soil cushion has effects of adjusting the load distribution ratio and reducing the stress concentration of pile top.(2) The thickness of lime-soil cushion has more great influences than the cohesion and angle of internal friction of lime-soil cushion have on the stress ratio of pile and soil, pile stress, the settlement of composite foundation and pile penetration.(3) The reasonable value of lime-soil cushion thickness is related to the value of deformation modulus of the soil between piles. The soil is more softer, and the reasonable value of lime-soil cushion thickness is more larger.(4) In collapsible loess regions, when using lime soil cushion CFG pile composite foundation, cushion thickness is proposed from200to 300mm, cohesion and angle of internal friction of cushion from20to30kPa and21to30degrees.