中文摘要：

以一定范围内埋深（25～60m）的3车道公路隧道软弱破碎围岩（公路隧道IV级）为研究对象,研制相似模型材料和配套试验设备,再现开挖后围岩的渐进性破坏全过程,分析不同埋深下围岩的应力场特征。通过模型材料室内试验获取岩体相关计算参数,引入弹塑性损伤本构模型对试验工况进行有限元数值模拟,计算结果与模型试验吻合较好。综合模型试验和数值模拟结果,可以得出以下结论：（1）围岩破坏区是隧道塌落荷载的来源,主要集中在拱顶上方区域,在两侧边墙下方和拱底也有局部存在;（2）隧道埋深对围岩破坏区域大小有重要影响,随着埋深的增大,围岩破坏区域呈渐进扩大趋势;（3）围岩内的周向应力在隧道开挖后先升高而后逐渐降低,其最大值所在位置即对应压力拱位置,且该位置随着破坏区域的扩大而不断向围岩内部移动,形成动态压力拱现象;（4）通过对围岩内部周向应力最大值的测试来获取隧道压力拱范围,并进而确定围岩塌落荷载大小,这在理论上是可行的。

英文摘要：

By taking the weak and fractured surrounding rock（defined as class IV by the road tunnel code of China） for the three-lane highway tunnel with overburden depths of 25-60 m,similar materials and model test equipments are developed to reproduce the whole process of progressive failure of surrounding rock after excavation;and the characteristics of stress field in rock mass under different overburden depths are studied. Meanwhile,an elastoplastic damage constitutive model is introduced to simulate some cases of model test by FEM;and the related parameters of rock mass are determined by laboratory tests.The numerical simulation results show a good agreement with those of model test.By analyzing the results of model test and numerical simulation,the conclusions can be drawn as follows：（1） The failure zone of surrounding rock is the source of tunnel collapse load,and it is distributed mainly above the vault as well as partially at the bottom of both side walls and arch bottom.（2） The overburden depth has great influence on the dimensions of progressive failure zone around tunnelprofile.As the overburden depth increases,the corresponding failure zone shows a gradual expansion trend.（3） The circumferential stress within the surrounding rock rises firstly and then decreases gradually after tunnel excavation.The location of the maximum stress corresponds to the position of earth pressure arch.With the expansion of failure zone,it continues to develop towards the inner side of rock mass and form a dynamic pressure arch.（4） The location of earth pressure arch can be determined by measuring the maximum circumferential stress within rock mass,and thus to determine the tunnel collapse load,which is theoretically feasible.