软弱围岩通风竖井开挖稳定性研究

Study on Excavation Stability of Ventilation Shaft in Soft Surrounding Rock

软弱围岩中修建竖井会面临围岩变形量大、初支受力过大从而被破坏的风险。本文依托白马隧道通风竖井工程,借助有限差分软件FLAC3D对竖井进行开挖-支护全过程模拟,通过分析竖井钻爆开挖后围岩的变形特征以及初支结构的受力特点,验证竖井开挖方案的合理性。研究结果表明,竖井采用复合式衬砌加短段掘砌混合作业后,围岩位移量随竖井开挖深度呈近线性递增,竖井井底围岩位移最大,为0.72 mm。围岩最大主应力也随着竖井开挖深度逐渐增大,围岩最大主应力大小约为7.89 MPa,位于井底;竖井衬砌范围受爆破开挖影响,围岩主应力较低,为确保施工安全,施工时需及时支护,以形成有效承载结构。竖井支护结构受力随着竖井开挖深度逐渐增大,支护结构最大主应力位于竖井底部,初支最大主应力为8.96 MPa,二衬最大主应力为6.94 Mpa,均满足设计要求。研究成果对类似工程具有一定参考价值。

Shaft construction in soft surrounding rock will face the risk of failure due to large deformation of surrounding rock and large initial support force. Based on the ventilation shaft project of Baima tunnel,this paper simulates the whole process of excavation and support of the shaft with the help of finite difference software FLAC3D,and verifies the rationality of the shaft excavation scheme by analyzing the deformation characteristics of surrounding rock after the shaft drilling and blasting excavation and the stress characteristics of the primary support structure. The results show that the displacement of surrounding rock increases linearly with the excavation depth of the shaft,and the displacement of surrounding rock at the bottom of the shaft is the largest,which is 0.72 mm.The maximum principal stress of surrounding rock increases gradually with the excavation depth of the shaft,and the maximum principal stress of surrounding rock is about 7.89 MPa,located at the bottom of the shaft. The lining range of shaft is affected by blasting and excavation,and the principal stress of surrounding rock is low. In order to ensure the safety of construction,timely support is needed during construction to form an effective bearing structure. The stress of the shaft support structure increases gradually with the excavation depth of the shaft,and the maximum principal stress of the support structure is located at the bottom of the shaft. The maximum principal stress of the initial support is 8.96 MPa,and the maximum principal stress of the second lining is 6.94 MPa,which meets the design requirements. The research results have certain reference value for similar projects.