小净距隧道洞口段初期支护变形分析与治理

摘要

There are many inevitable common problems for highway routing such as cutting through the terrain contour lines by the route,skew when a tunnel goes into the mountain and shallow and bias situation at tunnel portal. So the location of tunnel portal has a great influence on stabilization and construction complexity of slope. With the background of Xi’an Ling tunnel in Sanxi highway,as to the typical examples of deformation of initial support at the portal during the construction,the paper expounds the geology,design and construction of portal of the small clear distance,shallow buried and bias tunnel,studies deformation and supporting design form in portal construction in abnormal section of tunnel, analyzes the multiple causes of abnormal deformation and cracking in the construction process,combines the existing practical experience and theoretical basis,and puts forward a series of measures for construction abnormity at portal of tunnel with small clear distance exception handling countermeasures. Good effect has been achieved in practical engineering,which can be significant reference for similarity engineering in the future.%线路斜穿地形等高线、隧道与山体呈斜交进洞及洞口段存在浅埋和偏压等情况是高速公路选线不可避免地常见问题，为此洞门位置的选定对边坡稳定和施工难度有较大影响。文章以三淅高速公路西安岭隧道为背景，针对施工时洞口段产生初期支护变形侵的典型事例，阐述了小净距、浅埋、偏压隧道斜交进洞洞口的地质、设计和施工情况，研究了隧道洞口施工异常段支护设计形式及变形情况，分析了施工过程中异常变形和开裂的综合原因，结合既有的实践经验和理论基础，提出了一系列针对小净距隧道洞口段施工异常的处治对策，并在实际工程中取得了很好的效果，为今后类似工程的设计、施工提供了参考。