The construction of a viaduct over-passing an existing open cut railway tunnel has the characteristic of adjacent construction, which may cause stress redistribution of the surrounding rock. The load caused by T- beam construction especially affects the safety of the project due to the distribution of internal lining axial force and bending moment. This paper analyzes and compares the effects of two methods-full framing construction and post-and-beam framing construction-using ANSYS software and construction analysis to assess the effects on the safety of adjacent construction under-passing an open cut tunnel; the viaduct of the highway which runs from Guiyang to Duyun over the existing open cut Baisuo tunnel is used as an example. It is concluded that the minimum safety factors of plain concrete for open cut tunnels using these two methods are 3.1 and 3.7 respectively. The full framing and strip foundation method is found to be most cost effective.%高架桥跨越既有铁路隧道明洞施工具有典型的近接工程特征,高架桥施工过程对围岩产生应力重分布.尤其是T梁现浇施工时会对明洞产生附加荷载,对既有隧道衬砌结构轴力、弯矩等内力分布状况产生影响,进而影响结构的安全性.文章依托贵阳至都匀高速公路心焦坡桥跨越黔桂铁路摆梭隧道明洞工程项目,结合ANSYS有限元数值模拟和工法分析,对满堂支架、下设条形基础和梁柱支架跨越隧道两种施工方法进行了分析比较,评估近接施工对下穿明洞安全性的影响,并得出结论:两种方案的明洞素混凝土结构的最小安全系数分别为3.1和3.7,从经济因素考虑满堂支架、下设条形基础方案更有优势.
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