降雨影响下紧邻桥梁软土基坑围护结构受力变形研究

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,本文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。

Study on force deformation of the enclosure structure of the soft soil foundation pit adjacent to the bridge under the influence of rainfall

Under the influence of continuous rainfall, the foundation pit retaining structure and its adjacent bridge pile foundation are greatly affected by stress and deformation, and the construction safety risk is great. Therefore, based on the variation law of strength parameters and linear interpolation method of saturated and unsaturated soil, this paper calculates the mechanical parameters of soil in the pit based on the variation law of the strength parameters of saturated and unsaturated soil, and combines the field measured data, and analyzes the force deformation law of the envelope structure caused by precipitation and excavation in the pit and the deformation law of the pile foundation adjacent to the bridge by finite element simulation, and discusses the influence of rainfall on the deformation of the foundation pit envelope structure. The results show that when the foundation pit is excavated to the bottom of the pit, the "kicking" deformation of the envelope structure is large, which is easy to cause the first concrete support to be pulled off, and the maximum horizontal displacement occurs at the bottom of the enclosure. The bridge pile foundation weakens the soil slippage around the foundation pit caused by excavation, resulting in asymmetry of force on both sides of the enclosure structure, resulting in excessive deformation away from the pile foundation. Rainfall caused some soil in the pit to soften, which further increased the horizontal displacement of the envelope structure. When the unsaturated zone of the foundation pit is within the unsaturated zone and the rainfall intensity is constant, the horizontal displacement of the enclosure structure increases nonlinearly with the rainfall duration.