Ⅲ1级围岩三车道公路隧道仰拱设置问题研究

摘要

《JTG D70-2004公路隧道设计规范》中规定Ⅲ级围岩三车道隧道需设置厚45 cm仰拱混凝土,而《JTG-T D70-2010公路隧道设计细则》中则规定可以取消仰拱.鉴于此,文章依托省界隧道工程实例,采用有限差分软件,对Ⅲ1级围岩情况下平底和仰拱两种支护结构形式进行了模拟对比分析,结合现场监控量测结果表明:Ⅲ1级围岩三车道平底隧道和仰拱隧道整体的竖向位移、竖向应力及塑性区体积均相差在5%以内,Ⅲ1级围岩三车道隧道可以采用平底结构形式代替仰拱,平底结构支护形式可以满足工程结构稳定性要求.%For a three-lane road tunnel in surrounding rock of gradeⅢ,the concrete invert with the thickness of 45 cm should be installed according to the requirements specified in the Code for Design of Road Tunnels.However, as per the Guidelines for Design of Highway Tunnels the invert can be eliminated.Based on Shengjie expressway tun-nel project,flat and inverted arch structures in gradeⅢ1surrounding rock are simulated and compared using finite-dif-ference software.The results show that the differences between the vertical displacement,vertical stress and volume of the plastic zone of the two support structure patterns are within the scope of 5%;a flat arch structure can be used in-stead of an inverted arch for the three-lane tunnel in grade Ⅲ1surrounding rock, and the flat arch structure can meet the requirements of structure stability.