高架桥骑跨式承台对地下隧道结构变形及受力影响分析

Analysis on Influence of Straddle-type Base Slab of Viaduct on Deformation and Stress of Underground Tunnel Structure

因线形条件制约,滨海大道远期高架道路采用小交角斜向跨越近期实施的市域铁路S2线地下隧道,为避免高架桥梁桩基与隧道结构相冲突,交叉段承台采用骑跨式承台,并使高架桥梁桩基与隧道保持一定距离。建立高架桥梁骑跨式承台基坑开挖及高架桥体加载数值模型,考虑承台与隧道顶板关系、桩基与隧道净距的影响,对隧道结构变形及内力进行数值分析,据此提出相关的设计优化及施工措施。研究结果表明:高架承台基坑开挖对隧道影响较小,但考虑地下水浮力作用,隧道结构局部桩基需按抗拔桩加强配筋;骑跨式承台采取措施与隧道结构隔离后,能极大减小对高架桥梁加载时对隧道结构变形及内力的影响;高架桥梁桩基与隧道净距在3 m左右较为合适,过小或过大均对隧道不利;考虑桥梁加载对隧道的影响无法完全避免,隧道结构设计时应考虑结构加强及局部内空增大,以便在结构变形后满足净空和修复要求;在条件允许时,建议结合远期规划,将高架桥桩、承台与隧道同期实施以避免对隧道结构扰动。

Due to the linear constraints, the long-term viaduct road of Binhai Avenue will obliquely span the regional railway line S2 underground tunnel implemented in the recent period in the small crossing angle. In order to avoid the conflict between the elevated bridge pile foundation and the tunnel structure, the base slab of intersected section is the straddle-type base slab, and keeps the pile foundation of viaduct at a certain distance from the tunnel. The numerical model of viaduct straddle-type base slab foundation pit excavation and viaduct loading is established. Considering the relationship between base slab and tunnel roof, and the influence of clear distance between pile foundation and tunnel, the numerical analysis is carried out on the deformation and internal force of tunnel structure. Hereby, the relevant design optimization and construction measures are put forward. The results show that the foundation pit excavation of viaduct base slab has smaller influence on the tunnel, but the groundwater buoyancy effect should be considered. The partial pile foundation of tunnel structure should be strengthened and reinforced according to the uplift pile. The straddle-type base slab after isolated from the tunnel structure by the measures can greatly decrease the influence of viaduct during loading on the deformation and inner force of tunnel structure. The clear distance about 3 m between the viaduct pile foundation and the tunnel is relatively suitable. Too small or too large clear distances will be harmful to the tunnel. Considering the bridge loading hard to completely avoid the influence on the tunnel, the design of tunnel structure should consider the reinforcement of structure and the increment of local inner space in order to satisfy the clearance and repair requirements after the structure deformation. When conditions permit, it is recommended that the viaduct pile, base slab and tunnel are constructed at the same time to avoid the disturbance on the tunnel structure combined with the long-term planning.