Research On Character Of Screw Pile Group Composite Foundation Used In High-speed Railway

As a result of rapid development of a high-speed railway and infrastructure in China in recent years,the subgrade deformation and settlement control standards put forward more stringent requirements.As a new type of variable cross-section pile,screw pile increasingly be attached importance because of its many advantages,but the theoretical analysis of the screw pile,especially it of screw pile group,has been lagging behind in the engineering practice.(1)Based On literature review of a large number of relevant domestic and international research findings,comment on the current situation of research at home and abroad,summarizes the current mainstream calculation theory of pile foundation settlement,analyses the applicability of the theory to the calculation of screw pile settlement.(2)Based on ABAQUS 6.14,established finite element model of screw pile and normal pile in the background of six soil layer,considering the effect of piling on soil.Then verified reliability of the finite element model by compared the results of the finite element model and static load test.Obtained the settlement and the axial force distribution of single pile,and made comparison of the performance difference between screw single pile and normal single pile in controlling settlement and adjusting the reasonable distribution of axial force.(3)Based on ABAQUS 6.14,established finite element model of screw pile group composite foundation.Then obtained the settlement,axial force distribution and pile side resistance distribution of center pile of pile group.Next design parameters sensitive analysis was made,such as pile length,pile spacing and so on,in order to obtain a reasonable design pile parameters by analysis of mechanical behavior.(4)Established simplified geometric model for transfer dynamic load of train;Calculated the additional dynamic stress transmitted by the five sleeper to subgrade soil with application of Boussinesq theory,and obtained the law of dynamic stress distribution and attenuation.At last,calculation results were used to analyse influence of train dynamic load on foundation.