隧道预支护对控制围岩变形的力学效果研究

Mechanical Effects of Advanced Supporting on Controlling Deformation of Surrounding Rock of Tunnel

研究目的:基于三维弹塑性有限元方法对隧道开挖面预支护及顶部预支护进行参数分析,研究隧道开挖过程中有无顶部预支护条件下不同开挖方式、不同核心土长度、不同台阶长度对地层沉降、管棚力学行为及开挖面稳定性的影响,总结一些规律性的认识,为复杂地质条件下隧道开挖方式的选择及顶部预支护设计提供一定参考。研究结论:(1)留设核心土可以显著改善开挖面的稳定性,核心土的最佳长度大约在D/3～2D/3范围内,施工中应尽量使核心土长度与台阶长度相等。(2)核心土抑制围岩水平位移的作用有限,在软弱地层,单纯依靠核心土的作用并不能控制水平位移,应结合管棚预支护等隧道顶部预支护措施。

Research purposes： With the three -dimensional elasto -plastic finite element method, the design parameters of the advanced supporting and the roof supporting for the excavation surface of the tunnel were analyzed, the effects of the different excavation methods and the different lengths of bench and core soil on the ground settlement, the mechanical behaviors of pipe roof supporting and stability of the excavation surface under conditions of having roof supporting and having no roof supporting were studied and the regular knowledges were summarized for providing the reference to the selection of the excavation method of tunnel under the complex geological condition and the design of the roof supporting. Research conclusions： （ 1 ） Remaining the core soil can significantly improve the excavation fsurace stability and the optimal length of core soil is in D/3 ～ 2D/3 range. In the process of construction, the length of the core soil should be equal to the bench length. （2） The core soil plays a little role in controlling the horizontal displacement of surrounding rock. In weak stratum, the horizontal displacement can be controlled by using the core soil along with taking the measures of roof supporting like the pipe roof reinforcement, rather than only by using the core soil.