基坑平行上跨既有地铁隧道工程实践及影响分析

ENGINEERING PRACTICE AND INFLUENCE ANALYSIS OF THE FOUNDATION PITE ACROSS EXISTING METRO TUNNEL

目前现有类似上跨既有地铁隧道的基坑施工大多为大角度相交,极少出现长距离平行上跨的工况,可借鉴的经验较少。因此为了保证基坑平行上跨既有地铁隧道施工安全,将影响降低到最小程度,以洛阳龙门高铁站站前的通道基坑平行上跨既有地铁隧道施工为例,通过缩短开挖长度、堆载反压和及时施做底板封闭等措施,将既有地铁隧道结构最终竖向位移控制在±1.5mm以内,有效地保障了既有地铁隧道的安全;同时,通过分析基坑施工过程中既有地铁隧道竖向位移变化规律发现,中间区段基坑明挖施工会引起更大隆起,局部非标准段加宽开挖会引起既有地铁隧道结构偏压造成不均匀变形,在施工中应引起足够重视。

At present,most of the existing foundation pit construction across the existing subway tunnels intersect at a large angle,and there are few parallel ones with long-distance.Taking the construction of foundation pit in front of Luoyang Longmen high speed railway station as an example,the final vertical displacement of the existing metro tunnel structure is controlled within ± 1.5 mm by shortening the excavation length,stacking back pressure,and timely closing the bottom plate to ensure the construction safety of the foundation pit over the existing metro tunnel and minimize the impact,which effectively ensures the safety of the existing subway tunnel.At the same time,it is found that the open excavation of the foundation pit in the middle section will cause greater uplift,and the widening and excavation of the local non-standard section will cause the structural bias of the existing metro tunnel and uneven deformation by analyzing the vertical displacement change law of the existing metro tunnel during the foundation pit construction,which should be paid enough attention to in the construction.