基于HSS模型的深基坑开挖对邻近桥桩的影响分析及变形控制研究

Analysis of the influence of excavation on adjacent bridge piles and deformation control using HSS model

基坑开挖引起的变形会对周围建(构)筑物造成不利的影响。在前人研究基础上,确定了济南地区黄河冲积地层小应变硬化土模型(HSS模型)参数的取值方法。以济南黄河大桥改扩建工程项目为背景,基于HSS模型,通过三维数值模拟,分析了新建大桥桥墩深基坑开挖对邻近既有桥梁桩基础的影响,并对支撑预应力和隔离桩的变形控制作用进行参数分析。计算结果表明,对土体采用HSS模型以及合理的参数取值能够有效模拟基坑开挖引起的变形。变形控制措施研究表明,角撑施加预应力对邻近桥桩变形影响不大,但会造成基坑围护结构顶部反向变形的不利后果。隔离桩对邻近桥桩同时存在阻隔作用和牵引作用,设计时应避免牵引作用的不利影响,隔离桩的最优方案为宽7.2 m,桩长25 m。

Excavation of foundation pits will induce deformation and adverse environmental impacts on nearby structures.Based on previous works,a method was proposed in this work to determine the parameters of Hardening Soil model with small strain(HSS)for Yellow River alluvial strata in Jinan city.Taking the expansion project of Jinan Yellow River Bridge as an excavation case,a three-dimensional numerical analysis model was established.The HsS model was used for modelling the soil to analyze the influence of excavation of a new constructed bridge pier foundation pit on the adjacent existing bridge pile foundation.Meanwhile,the deformation control effect of the prestressed strut and isolation pile was analyzed.The calculation results show that the deformation caused by the excavation can be effectively simulated by using the HSS model with reasonable parameter values for the soil.The study of deformation control measures shows that the prestressing of the corner struts has litle effect on the deformation of the adjacent bridge piles,but will cause the reverse deformation on the top of the retaining wall of the foundation pit.Isolation piles have both blocking and traction effects on bridge piles,and the adverse effects of traction should be avoided in the design.The optimal solution for isolation piles is 7.2 m in width and 25 m in length.