Investigation Into Stability Of Geosynthetic-reinforced Pile-supported Embankment Considering Softening Characteristics Of Cemented Soils

At present,the design method of geosynthetic-reinforced pile-supported(GRPS)embankment mainly adopts the Bishop method,which assumes that the pile shear failure occurs at the same time to carry out stability analysis.The main contents of the study are as follows:Based on the available information,the material properties of the cement soil are mainly discussed,and the input parameters of the Concrete model are calibrated.In order to calibrate the compression parameters,a footprint 3D simulation of the existing uniaxial compression specimens was performed,while for the tensile parameters,a 2D model of the three-point bending beam test was performed.The applicability of the parameter selection method was verified.The progressive failure mechanism of the embankment was investigated by using finite element numerical simulation.By analyzing the stress characteristics of the pile at different locations and the development of the plastic zone of the pile,the damage sequence and failure mode of the pile were investigated,revealing that the failure of the cement pile was controlled by the pile bending moment and axial force distribution,and the stress release induced by the pile failure caused the internal force change of the adjacent pile,resulting in the progressive failure of the adjacent pile;the pile below the slope The pile below the slope surface first appears bending failure,and its failure direction extends from the foot of the slope to the center of the embankment.As the embankment load further increases,the pile under the road surface experiences shear damage,and the failure direction extends from the center of the embankment to the foot of the slope,and finally the embankment experiences overall instability.Improving the compressive and flexural properties of the cement pile or increasing the stiffness of the reinforced body will,to a certain extent,prevent pile failure and change the pile failure sequence and embankment failure mode.The effect of pile softening effect on the ultimate bearing capacity and failure mode of GRPS embankment is revealed by the finite element analysis method combined with normalization method under the influence of different pile diameters and pile spacing,stiffness and strength of reinforcement,and strength parameters of embankment fill and other factors.The results of the study show that the GRPS embankment is mainly failure by seven failure modes,such as shear slip failure,punching failure,slope instability-Ⅰ,slope instability-Ⅱ,slope surface failure,slope footing failure and pavement failure.The increase of pile diameter,stiffness and strength of reinforcement,embankment fill cohesion and friction angle will increase the effect of pile softening on the ultimate bearing capacity loss of GRPS embankment,while the increase of pile spacing will weaken the effect of pile softening on the ultimate bearing capacity loss of GRPS embankment.On the basis of this,a large number of numerical calculations are carried out,and a series of normalized ultimate bearing capacity design charts are given for the GRPS embankment.It can provide guidance for the design of GRPS embankment.In order to evaluate the stability of the GRPS embankment,a MARS model for predicting the ultimate bearing capacity of the GRPS embankment is proposed based on a large number of variable parameter finite element calculations above,which can well describe the coupled nonlinear relationship between each parameter and the ultimate bearing capacity of the embankment,and then analyze the embankment stability.The applicability of the MARS model in engineering is verified by comparing with the results of existing literature.