Dynamic Analysis On Semi-infinite Soil By Three-dimensional Finite Element Method

With development of modernization and heavier investment in infrastructure construction, rail, road and urban railway system has unprecedentedly developed. As transportation is more developed and perfected, traffic density becomes larger and the velocity of vehicle faster. Influence of vibration and noise is more serious so that the research on this field becomes more complex. Problems caused by traffic system include reasons of vibration, propagation path and control, law of vibration and harm of it. Study on vibration wave which propagates in soil is an important part of the above problems. This paper takes free field semi-infinite soil as research object.Analyze dynamic response of soil under impact load. Study on discipline of wave propagation in semi-infinite soil and effectiveness of vibration isolate ditch. Provide feasible references for environmental vibration assessment and control.This paper uses three-dimensional finite element method to simulate wave propagation in semi-infinite soil. In order to be more realistic, structure with damp and artificial damping boundary condition is adopted.Use incompatible element with eight nodes to get a better accurancy and efficiency. Deduce stiffness matrix of this element and apply it in self-compiled FORTRAN dynamic program to calculate the response of semi-infinite soil under impact load.Make comparision with results got from ANSYS and verify the feasibility of this method.Moreover, influence of vibration isolate ditch is also researched.Analyze efficiency of vibration isolate ditch by changing width,depth and distance from load to ditch.It can be seen from comparison of acceleration-time curves and maximal acceleration variation trend and the wave propagation law is in accordance with research achievements found in domestic and abroad references. Moreover, obvious efficiency of vibration isolate ditch is verified and it's found that depth of ditch is a more important factor.This paper uses three-dimensional incompatible element and artificial damping boundary condition to simulate dynamic problem of soil.This method gets a good result and provides reference for deeper research on environmental vibration.