正削式隧道门围岩和衬砌应力计算及设计方法研究

对无明显墙式结构的正削式隧道门，现行规范没有现成的设计方法及结构检算模式。采用三维有限元数值分析方法，针对两种在洞口段的不同施工方法（明挖工法和暗挖工法），对隧道门洞口段的力学特性及设计方法进行了研究。研究结果表明：洞口段长度取42 m进行整体设计比较合理；在洞口28 m范围内的浅埋段，拱顶围岩压力随着埋深的增大而逐渐增加，且暗挖工法产生的围岩压力最大，铁路规范计算结果次之，明挖工法产生的压力最小；采用明挖工法施工时，在纵向上，洞口段42 m范围内衬砌拱顶表现出纵梁弯曲特征，部分仰拱处于弯拉状态，内力呈空间效应，均需要对横、纵向内力进行结构检算；采用暗挖工法施工时，只需进行横向内力检算即可。在成洞条件允许的情况下，建议使用暗挖工法进行隧道洞口段施工，可有效改善隧道洞口段结构受力。

Numeration analysis and design method research into surrounding rock and lining structural stress of up bamboo-truncating tunnel portal

For up bamboo-truncating tunnel portal without obvious wall-style structure,there is no existent design method and structure checked mode in present code.In this paper,aiming at bored method and open-cut method for portal section,3D FEM numerical analysis method is adopted to study the mechanical behaviors and design method of tunnel portal section.The research results show that:Choosing 42 m as the length of portal section and designing as a whole could be reasonable;In the shallow burying section of the extension of 28 m,the surrounding rock pressure of lining crown increases with the increase of depth of tunnel;and pressure of the bored tunneling method tunnel is maximal,the calculation result following the method of the railway tunnel code is the second;and the pressure of the open-cut method is minimal;When taking open-cut method,in the longitudinal direction of the extension of 42 m of portal,the mechanical behaviors of lining crown shows some characters of stringer bending,part of crown is in bended-pulled state;the internal force shows a three-dimensional effect,and the internal force of the direction both transversal and longitudinal should be checked for structure;when taking bored method,the internal force checking is only considered for transversal direction;when the excavation condition allows,the bored method is suggested to do portal tunneling by the reason that this tunneling method can improve mechanical behaviors of tunnel portal structure effectively.