穿越位置对地铁结构和行车安全的影响分析

下穿施工引起既有地铁结构发生沉降变形及内力变化，同时导致地铁变形缝处产生沉降差（错台）及张开，从而影响地铁结构安全及行车安全。针对不同穿越位置，采用打靶法对微分方程进行数值求解，从地铁结构变形程度、内力变化规律、变形缝沉降差（错台）及张开量的变化趋势这四个方面进行了计算、分析。结果显示:中心位置穿越时，地铁结构的最大沉降值低于其它穿越位置，同时变形缝沉降差较小，基本未张开。从结构安全和行车安全两个方面综合判断，中心穿越是最优的穿越位置。

Study on the impact of underling tunneling on the subway structures and traffic safety

The settlement and the internal forces of existing subway tunnel due to underlying tunneling can lead to two indexes： differential settlement at the joint and opening distance of the joint, thus affect the subway structures and traffic safety. Aiming at different across locations, the shooting method was applied to solve the equations, and the analysis included four aspects： the settlement of existing subway, the internal force variation, the differential settlement at the joint and opening distance of the joint. Results showed that： when the underlying tunneling cross- ing at the center, the maximum settlement of the subway structure isless than other positions, while the differential settlement and opening distance of the joint remains a low level. By judging from the structural safety and traffic safety, the crossing at the center is optimal.