既有结构基础下方隧道开挖扰动破坏及其所需支护力预测

Prediction of Excavation Disturbance and Required Support Force for Tunnel beneath Existing Structural Foundations

[目的]新建隧道或其他地下工程不可避免地会穿越一些既有建筑结构,对既有结构基础产生一定的扰动影响,因此需研究既有结构基础下方隧道开挖所需支护力及其在不同情况下的支护力变化规律。[方法]考虑既有结构基础下方新建隧道正穿与侧穿两种情形,分别构造隧道下穿既有结构基础力学分析模型,利用上限法推导得到新建隧道所需支护力与既有结构基础临界基底压力理论计算式,分析了不同穿越位置、土体力学参数及基底压力大小等因素对新建隧道所需支护力的影响。[结果及结论]新建隧道与既有结构基础的相对位置会对隧道的安全及所需支护力产生较为显著的影响。相较于侧穿情形,新建隧道正穿既有结构基础对隧道结构产生的危害更大。隧道所需支护力同隧道与基础埋深差、土体黏聚力、土体内摩擦角呈负相关,与土体重度、基础临界基底压力呈正相关。

[Objective]It is inevitable that construction of new tunnels or other underground engineering projects will pass through some building structures,causing disturbances to the existing structural foundations.Therefore,it is essential to study the required support force for tunnel excavation beneath existing structural foundations and its variation under different conditions.[Method]Considering two scenarios of tunnels directly beneath and laterally passing existing structural foundations,mechanical analysis models for tunneling beneath existing structural foundations are constructed.Using the upper-bound theorem,theoretical formulas for calculating the required support force and critical foundation base pressure are derived.The impact of factors such as crossing position,soil mechanics parameters,and foundation pressure on the required support force for new tunnel excavation is analyzed.[Result&Conclusion]The relative position between the new tunnel and the existing structural foundation significantly influences the safety of the tunnel and the required support force.Compared to lateral crossing scenarios,tunnels directly under-passing existing structural foundations pose a greater risk to tunnel structural integrity.The required support force of the tunnel is negatively correlated with the tunnel-foundation burial depth difference,soil mass cohesion and internal friction angle,and positively correlated with soil mass weight and critical foundation base pressure.