交通荷载下考虑倾斜基岩影响的单桩桩周土振动特性数值模拟

Numerical simulation of vibration response of soil around a single pile under traffic load and sloping bedrock condition

针对山区倾斜基岩条件下的轨道交通振动问题,开展单桩桩周土振动响应规律数值模拟研究,分析土体阻尼比、土体弹性模量、埋深、桩径以及振动频率对地表振动的影响。研究结果表明:地表振动速度峰值随着距桩体距离增加而逐渐降低,并且受倾斜基岩的影响,沿地表不同方向振动响应有较大差异;随着土体阻尼比和弹性模量增大,地表振动速度峰值近似呈线性减小,在桩周附近,土体的辐射阻尼作用更明显,阻尼比和弹性模量对振动沿地表方向和深度方向的量纲一速度峰值(Nl,Nr和Nh)基本没有影响;地表振动速度峰值随埋深、桩径增加而减小,在距离桩体一定范围内,埋深和桩径变化对地表振动速度峰值的影响较明显,在距桩体较远处则影响较小;随着埋深和桩径增加,各深度处的土体振动速度峰值降低,达到一定深度后,埋深和桩径的影响较小,埋深越大,振动沿深度衰减越慢,而桩径对振动沿深度方向的量纲一速度峰值(Nh)影响不显著。

To study the vibration problem induced by rail traffic under sloping bedrock condition,numerical simulations were conducted to investigate the soil vibration response around a single pile.The effects of soil damping ratio,elastic modulus,embedded depth,pile diameter and frequency on ground vibration were analyzed.The results show that the peak velocity of ground vibration decreases gradually with the increase of the distance from the pile,and the soil vibration response has large difference in different directions influenced by the sloping bedrock.The peak velocity of ground vibration nearly decreases linearly with the increase of soil damping ratio and elastic modulus,and the effects of radiation damping near pile group are more obvious.However,damping ratio and elastic modulus has little effects on the dimensionless peak velocity(Nl,Nr,Nh)in the direction of the ground surface and depth.The peak velocity of ground vibration decreases linearly with the increase of embedded depth and pile diameter.The effect of pile length and diameter on ground velocity peak is significant within a certain distance from the pile,and it is smaller at a large distance.As the embedded depth and diameter increase,the peak velocity of ground vibration decreases at different depths.After reaching a certain depth,the influences are small.With the increase of embedded depth,the vibration attenuation changes slowly along the depth.However,the pile diameter has little influence on the dimensionless peak velocity(Nh)along the depth.