Soft Foundation Strengthening Effect and Structural Optimization of a New Cement Fly-ash and Gravel Pile-slab Structure

Reducing the settlements of soft foundation effectively is a critical problem of high-speed railway construction in China. The new CFG pile-slab structure composite foundation is a ground treatment technique which is applied on CFG pile foundation and pile-slab structure composite foundation. Based on the experience of constructing Beijing-Shanghai high-speed railway in China, the settlement-controlling effect, the settlement distribution laws and three key influence factors for structural form of new CFG pile-slab structural foundation are studied by using physical model tests and numerical simulations. The research results in this study indicate that the piles and soil bearing capacities of the new CFG pile-slab structure can be put into full play because of the “load distributing” function of slabs. The settlement reducing effect of the new CFG pile-slab structure is remarkable and can meet the requirements of high-speed railway construction. The affected area of engineering load has a depth over 18.75 m and horizontal length of 7.5 m nearing the embankment slope toe. The parametric study provides the optimalizing structural form for best settlement-controlling effect. The physical model test results show good concordance with the numerical simulation results. The combination of physical model tests and numerical simulations justifies the use of this model in geotechnical engineering practices.