中文摘要：

以重庆双碑隧道工程为研究对象，采用FLAC3D模拟施工中掌子面正前方存在小型带压溶腔的情况，根据计算所得安全临界距离，采用自主发明的一套模拟溶腔内压的试验装置，开展了几何相似比为1：25的室内模型开挖试验，研究隧道开挖至安全临界距离时，溶腔内压增加至掌子面崩坏过程中，此阶段掌子面周边围岩压力、掌子面位移以及初期支护内力的变化规律．结果表明：随着掌子面前方溶腔内压的增加，掌子面位移先呈近似正比例增加，随后掌子面位移增大速率逐渐增加，最后产生突变破坏；围岩压力随溶腔内压增大呈现出增大趋势，其中拱顶处围岩压力影响较大，拱肩与仰拱处次之，其他位置围岩压力影响不大；钢拱架弯矩分布规律在不同溶腔内压作用下基本相同，在溶腔内压增大过程中，初期支护拱顶以及仰拱处弯矩呈增大趋势，其影响主要集中在拱顶附近及拱底处，其它位置处弯矩影响不大；随溶腔内压增大钢拱架轴力均呈现增大趋势，轴力变化较大位置主要出现在拱顶处，左右拱腰处次之，仰拱以及拱肩处变化幅度较小；受溶腔内压大小的影响，掌子面处位移、初支内力以及偏心距变化速率均越来越快．

英文摘要：

Based on the project of Shuangbei highway tunnel, the finite element analysis software was wsed to simulate the situation that there was the small-scale salt cavern during the construction period, and according to the critical distance calculated, a self-created device for simulating the salt cavern was taken, and then a model test with a geometric similarity ratio of 1 ： 25 was carried out to research the transformation law about the rock pressure, displacement of tunnel face, inner force of primary support when the tunnel was excavated to the position of critical distance and the inner pressure of the salt cavern increased until the tunnel face was broken. The results showed that, with the increases of inner pressure of the salt cavern, the tunnel face increased as almost direct proportion firstly, and then the ratio of increase became higher and higher and finally the tunnel face was broken; when the inner pressure of the salt cavern increased until the tunnel face was broken, the rock pressure showed a trend of increase in which the rock pressure of vault was the most effected location, followed by the spandrel and inflected arch, while the impact of other places was small.The bending moment distribution of steel arch is almost the same as the inner force of salt cavern increased.And as the inner force of salt cavern increased, the bending moment of vault and inverted arch showed a trend of increase in which the most effected location was focused on the vault and inverted arch while other location was less effected~ what＇s more, with the increases of the inner force of salt cavern, the axial force of steel arch all showed a trend of increase, and the most effected location was the vault, followed by the right and left haunch while the impact of inverted arch and spandrel were little; effected by the inner force of salt cavern change, the rock pressure, displacement of tunnel face, inner force of primary support all showed the ratio of change became faster and faster.