区间隧道近距穿越高速公路桥头变形控制新技术研究

New Techniques for Bridgehead Deformation Control for Expressways Passed by Approaching Metro Running Tunnels

区间隧道近距穿越既有高速公路桥头区域会加剧桥坡段不均匀沉降,易引起严重的桥头跳车。文章以济南地铁R1线区间盾构隧道下穿既有京福高速公路桥为背景,针对原加固方案仅考虑减小盾构下穿对桩基的影响,而忽略对桥头变形控制的特殊工况,采用数值模型对盾构穿越过程中高速公路桥头的变形规律进行了分析。结果表明:采用原加固方案,先左线后右线的盾构穿越顺序对减小既有高速公路桥头变形更加有利,但仍会产生26.5mm桥头差异沉降,不能有效防止桥头跳车的发生。基于此,为保证盾构下穿方案的顺利实施,文章提出了一种基于水泥搅拌桩作为隔离桩,同时结合深层混凝土搭板的桥头变形控制新技术。采用该技术,桥头最大差异沉降为4.0 mm,最大纵坡变化值为0.4‰,最大路基沉降量为6.5 mm,均满足规范允许变形要求。

When a metro running tunnel passes through an approaching bridgehead area of an existing expressway, it will increase uneven settlement of the bridge slope section and is liable to cause a serious vehicle bump at the bridgehead. Based on a running tunnel of Jinan metro line R1 underneath the existing Beijingjing-Fuzhou express- way bridge, the deformation law of an expressway bridgehead during shield tunnel construction is analyzed by a nu- merical model regarding the original reinforcement scheme, which only considers reducing the effects of shield con- struction on the pile foundation and ignores controlling the bridgehead deformation. The results show that adopting the construction sequences of the left line and then the right line is more favorable for reducing the deformation of the expressway bridgehead than the original reinforcement scheme, but it would cause 26.5 mm differential settle- ment at the bridgehead and can＇t effectively prevent a vehicle bump at the bridgehead. In this context, a new tech- nique is proposed that takes a cement mixing pile as an isolation pile and uses a deep concrete bridging slab to con- trol bridgehead deformation. With this new technique, the maximum differential settlement at the bridgehead is 4.0 ram, the maximum longitudinal gradient variation is 0.4%0 and the maximum subgrade settlement is 6.5 mm, meet- ing the requirements specified.