深埋软岩盾构隧道围岩压力控制方法研究

以广佛环线东环隧道工程为背景,从盾构隧道动态施工全过程出发,参考考虑开挖面空间效应的二阶段分析方法,拓展盾构隧道施工全过程的两阶段分析方法,以此分别建立盾构隧道施工第一阶段和第二阶段分析模型,研究围岩蠕变过程中围岩应力释放率、填充层厚度、填充层弹性模量对大埋深软岩盾构隧道围岩和支护结构相互作用规律的影响。结果表明:(1)施工过程中可从两方面控制围岩压力,分别为第一阶段中围岩的应力(位移)释放率及第二阶段中管片和填充层的联合支护效果;(2)第一阶段,超挖量、盾壳长度及填充层滞后距离越大,围岩传递到管片衬砌上的荷载越小;(3)壁后填充层在管片衬砌与其的联合支护体系中能起到缓冲作用,使围岩传递到管片衬砌上的荷载更均匀;(4)壁后填充层的弹性模量存在临界值,其值在50~200 MPa范围内,当壁后填充层的弹性模量远大于此临界值时,能分担较多围岩压力,当其弹性模量小于临界值时,围岩能释放一定的围岩应力,以此减小管片衬砌所受围岩压力;(5)第一阶段应力释放率对管片衬砌变形和内力的影响程度在围岩的蠕变作用下有所减小,但填充层厚度及其弹性模量对管片结构的作用规律几乎不受围岩蠕变的影响。

Research on Pressure Control Method of Surrounding Rock in Deep Buried Shield Tunnel

Based on the Donghuan Tunnel of Guangzhou-Foshan Loop Line and in view of the whole process of dynamic construction of shield tunnel,the first-stage and the second-stage of shield tunnel construction analysis model is established by considering the effect of excavation face space with two-phase analysis method and expanding the whole process of shield tunnel construction of two-phase analysis method.Thus,the surrounding rock stress release rate in the process of surrounding rock creep,the filling layer thickness,and the effect of elasticity modulus of the filling layer on the mutual effect between the surrounding rock and the supporting structure of the deep soft rock shield tunnel are studied.The results show that:(1)the control of surrounding rock pressure during the construction process can be conducted from two aspects:the control of the stress(displacement)release rate of the surrounding rock in the first-stage,and the maintaining of the joint support effect of the segment lining and the filling layer in the second-stage;(2)In the first-stage of shield tunnel construction,the larger the overcut,shield shell length and the lag distance of the filling layer,the smaller the load transferred from the surrounding rock to the segment lining;(3)In the second-stage of shield tunnel construction,the filling layer plays a buffering role in the combined support system of the segment lining and the filling layer,which makes the load transferred from the surrounding rock to the segments lining more uniform;(4)The elastic modulus of the segment filling layer has a critical value,and its value is in the range of 50 MPa^200 MPa.When the elastic modulus of the segment filling layer is much larger than this critical value,it can share more surrounding rock pressure.When it is less than the critical value,the surrounding rock can release certain surrounding rock stress,thereby reducing the surrounding rock pressure of the segment lining.(5)The degree of the influence of the first-stage stress release rate on the deformation and internal force of the segmental lining is reduced due to the creep of the surrounding rock,but the effect of the thickness of the filling layer and its elastic modulus on the structure of the segment is almost unaffected by the creep of the surrounding rock.