该隧道全长12 780m，是中国北方第一座特长隧道。隧道主要通过三迭系、二迭系紫红色 软质砂岩、泥岩岩层。隧道与舒缓向斜构造斜交，张性、张扭性断裂和构造节理发育,水文地质复杂。泥质围岩具膨胀性。缓倾岩层易坍方、掉块，并存在有害气体及突水、突泥地质灾害的可能性。目前 国内对泥质围岩膨胀性判别及复杂的水文地质问题还没有统一、成熟的预测、评价方法。为积累这 方面的资料，本文就上述主要地质问题加以论述。

Certain tunnel，the first special—long tunnel in North China，is 12. 78km long. It passes mainly through the purple—color soft sandrock and mudstone in Triassic or Dyas Sys?tems. The tunnel is obliquely crossed with gentle syncline. the tensile，tensile — twisting faults and structual joints are developed. Thus, its condition of hydrogeology is complicated.Themud surrounding rock has characteristic of expansibility. The gentle—slant rock may be landslip or drop, there may be some harmful gases, and the water and mud may ooze. At present，there is no well-considered and united method to appraise and forecast the expansi?bility of the mud surrounding rock and the complicated hydrogeology problems.