桩土摩擦系数取值方法对桥桩单侧开挖模拟结果的影响规律

The Influence of the Valuing Method of Pile-Soil Friction Coefficient on the Simulation Results of One-side Excavation of Bridge Piles

在与现有航道相邻的双排六桩群桩基础的T构桥桩基础附近进行航道的升级改造工程,航道开挖将对桩基使用带来不利影响。不同工况和桩土摩擦系数条件下的有限元数值模拟分析表明,当采用土体内摩擦角计算的摩擦系数扩大1.5倍时,墩顶水平位移减小25%,竖向位移减小10%,而桩基轴力增加22%,弯矩减小24%,这与侧壁阻力反算的摩擦系数结果接近。结合数值模拟分析和桥梁实际运行条件,推荐采用根据侧壁阻力反算桩土摩擦系数的方法。同时,不同的荷载施加顺序对模拟结果具有影响。为考虑应力历史的影响,推荐采用桥桩施工全流程数值模拟的方法,对航道开挖引起的桩基变形规律进行分析,并建议在后期设计施工中加强现场监测。

The channel upgrade project is carried out near the pile foundation of the T-frame bridge with a double-row six-pile group pile foundation adjacent to the existing channel.The channel excavation will bring adverse effect on the use of the pile foundation.After finite element numerical simulation analysis under different working conditions and pile-soil friction coefficient conditions,it shows that when the friction coefficient calculated by the friction angleφin the soil body is enlarged by 1.5 times,the horizontal displacement of the pier top is reduced by 25%,and the vertical displacement is reduced by10%,while the axial force of the pile foundation increases by 22%,and the bending moment decreases by24%,which is close to the result of the friction coefficient of the side wall resistance inverse calculation.Combined with the numerical simulation analysis and the actual operating conditions of the bridge,it is recommended to use the inverse calculation of the pile-soil friction based on the side wall resistance coefficient method.At the same time,different loading sequences can affect the simulation results.In order to consider the impact of stress history,it is recommended to use the full-process numerical simulation method of bridge pile construction to analyze the law of pile foundation deformation caused by channel excavation,and it is recommended to strengthen site monitoring in later design and construction phases.