高速公路小净距隧道施工方法探讨

EXCAVATION METHOD ANALYSIS OF LITTLE DISTANCE TUNNEL IN FREEWAY

小净距隧道是双洞隧道净距介于连拱隧道与规范要求上下行分离式隧道最小净距之间的一种特殊隧道结构形式。由于隧道净距小,施工时双洞相互影响较大,对隧道围岩特别是中夹岩岩体稳定性有很大的影响。因此,探讨安全、合理、经济的高速公路小净距隧道施工方法十分必要。本文结合净距4.0 m、埋深30.0 m的Ⅰ类同岩段高速公路小净距隧道工程实践,通过三维弹塑性有限元数值仿真模拟,分析双洞侧壁导坑法、侧壁导坑与上下台阶组合法及双洞上下台阶法三种施工方法施工时隧道围岩破坏接近度、围岩变形位移特征,探讨其优劣和适应性,为高速公路小净距隧道设计、施工提供科学依据。

Little distance tunnel is a special tunnel structural style that double tunnel clear distance is situated between multiple arch tunnel distance and apparel separation tunnel minimum clear distance according to tunnel design regulations. Double tunnel distance is so small that double tunnel interaction is considerable at tunnel excavation and there be strongly influence to tunnel surrounding rock stability especially situating between double tunnel rock mass. Therefore, inquiring into safety reasonable and economical freeway little distance tunnel method of excavation is very necessary. Combined a freeway little tunnel engineering practice (clear distance equal to 4. 0 m,buried depth equal to 30. 0 m)at two-class surround rock,through three-dimension elastic-plastic element numerical simulation, freeway tunnel surrounding rock approach failure degree and deformation displacement characters have been analysed. When the tunnel rock mass excavated according to cheek pilot method, array pattern of cheek pilot method and bench method, and up-down bench method of double tunnel. Based on the analysis of three-type excavation method,we inquired into good and bad,adapting of each method. This study will have provided scientific basis for freeway little distance tunnel design and excavation.