蒙华铁路坪桥1号隧道进口洞顶基岩外凸、洞顶以下岩面高且直立、洞顶上部地形偏压高陡,地形条件极其复杂.营盘山大桥与坪桥1号隧道进口紧密相连,存在桥台与隧道洞门结构相互干扰以及边坡防护、隧道出洞和洞口场地布置等一系列难题,设计难度极大.为解决这些难题,通过对现场实际地形、地质情况进行研究,对比分析"整体式"与"分离式"桥隧相连结构的优缺点,提出桥台与隧道相结合的"整体式"桥隧相连结构方案;同时,针对地形偏压高陡,提出非对称结构设计方案,实现了隧道"零"仰坡出洞,解决了洞口边坡防护的难题;最后,提出架立临时贝雷梁的方案,解决了隧道出洞及洞口场地布置的难题.%Extremely complex terrains,i.e. rock bulge of tunnel roof,high and vertical rockface under tunnel roof,and asymmetrically-pressured steep and high terrain on tunnel roof, are encountered during construction of Pingqiao #1 Tunnel portal on Menghua Railway; the Yingpanshan Bridge is connected to the tunnel portal; a series of problems, i.e. interaction between bridge abutment and tunnel portal structure, slope protection and tunnel portal breakthrough and layout of construction fields, exist in design. Hence, the terrain of construction site and geological conditions are investigated;comparing analyses are made for advantages and disadvantages of both integral mode and separation mode of bridge-tunnel connection; the integral bridge-tunnel connection mode is adopted; a design scheme for asymmetrical structure is proposed for asymmetrically-pressured steep and high terrain to protect the slope; the problems of tunnel portal breakthrough and layout of construction fields have been solved by connecting constructed bridge with temporary bailey beam bridge.
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