降雨影响下紧邻桥梁软土基坑围护结构受力变形研究

Force Deformation of the Enclosure Structure of the Soft Soil Foundation Pit Adjacent to the Bridge under the Influence of Rainfall

某基坑受连续降雨影响,基坑围护结构及其紧邻桥梁桩基受力变形影响较大,施工安全风险大增。为此,基于饱和与非饱和土体强度参数变化规律和线性内插法对坑内土体力学参数进行计算,结合现场实测数据,采用有限元模拟分析了坑内降水及开挖所引起的围护结构受力变形规律及紧邻桥梁桩基变形规律,并探讨了降雨时长对基坑围护结构变形影响。结果表明:基坑开挖至坑底,围护结构发生“踢脚”大变形,易引起第一道混凝土支撑受拉脱落,最大水平位移发生在围护结构底部;桥梁桩基减弱了因开挖引起的基坑周围土体滑移,造成围护结构两侧受力不对称,导致其远离桩基侧变形过大;降雨引起坑内部分土体软化,使得围护结构水平位移进一步增大;在基坑非饱和区范围内且降雨强度一定时,围护结构水平位移量随降雨时长呈非线性加速增长趋势。

A foundation pit is affected by continuous rainfall,the pit enclosure structure and its adjacent bridge pile foundation are affected by force deformation,and the construction safety risk is greatly increased.Based on the change law of strength parameters of saturated and unsaturated soil and the linear interpolation method to calculate the mechanical parameters of the soil in the pit,combined with the field measurement data,the finite element simulation was used to analyze the deformation law of the enclosure structure caused by the precipitation and excavation in the pit and the deformation law of the pile foundation of the adjacent bridge,and to discuss the influence of the rainfall duration on the deformation of the enclosure structure of the pit.The results show that when the pit is excavated to the bottom of the pit,the enclosure structure has a large deformation of “kick”,which is easy to cause the first concrete support to fall off under tension,and the maximum horizontal displacement occurs at the bottom of the enclosure structure;the bridge pile foundation weakens the soil slip around the pit caused by excavation,resulting in asymmetric force on both sides of the enclosure structure,leading to its deformation far from the pile foundation.The rainfall causes the softening of some soils in the pit,which further increases the horizontal displacement of the enclosure structure,within the unsaturated area of the pit and when the rainfall intensity is certain,the horizontal displacement of the enclosure structure shows a non-linear accelerated growth trend with the rainfall duration.