水平层状页岩隧道底鼓机理及处治技术

On the mechanism and the technology to deal with the floor heave problem in the horizontal layer shale tunnels

采用室内岩石物理力学性质、理论分析、数值模拟和现场调查相结合的方法,对南道高速公路马嘴隧道左线水平层状页岩底鼓机理进行研究。结果表明,页岩单轴抗压强度仅为17.7 MPa,强度较低,仰拱开挖后未及时封闭成环是底鼓发生的主要因素,水理作用、围岩蠕变特性使底板页岩岩层强度进一步劣化,底板岩层在水平应力作用下发生离层、弯曲、折断,形成挠曲褶皱型底鼓。在对水平层状页岩隧道底鼓机理正确认识的基础上,提出了底板锚杆注浆+反底拱相结合的返修处治方案,采用FLAC3D数值模拟软件对处治前后效果进行对比分析,借助现场底板变形监测数据进行验证,该方案能够有效控制层状页岩的底鼓。

In order to analyze the mechanism of the floor heave problem with the horizontal layer shale in the left line Mazui Tunnel of Nandao Expressway,the paper has done the field investigation and exploration of the mechanical features through laboratory experiments and theoretical analysis through numerical simulation. The research results we have gained indicate that the uniaxial compressive strength of shale rock is only 17. 7 MPa and the main cause leading to the floor heave is that the supporting structure of the surrounding rock fails to result in a harmonious balanced entity in the process of the inverted arch excavation. What is worse,the swollen effects and the creep deformation characteristics of the surrounding rocks tend to weaken the strength of the floor shale strata. Last of all,the floor strata also tend to get bent or broken,or split to form a flexure folded floor heave under the horizontal stress or squeeze. Based on the proper study results and the comprehensive grasp of the drum deformation mechanism of the floor heave,we have worked out a comprehensive reinforcement scheme for the floor bolt-grouting and the supporting capability of the inverted arch through numerical simulation with the help of a software known as the FLAC3 D. In the treating process,we have compared and analyzed the different results we have gained pre-and-post the treatment,trying to assess and verify the reasonability of the disposal and the actual advantages gained from the different approaches from the point of view of the influential scope of the rock plastic zone distribution diagram and the displacement distribution map with the help of the floor deformation monitoring data. The results show that the scheme can not only effectively control the floor heave of the layered shale and guide the construction but also can provide a valuable reference for the similar shale tunnel field construction and disposal schemes. Thus,the mechanism we have formulated can be expected of valuable prospect for the mining engineering in the future.