某隧洞软弱围岩变形特性测试与分析

Testing and Analysis of the Weak Rock Deformation Characteristics in Tunneling Work

全面介绍了某水工隧洞软弱围岩松弛变形测试、围岩表面收敛变形监测及对岩体内部岩石位移变化情况监测所采用的技术方法,通过现场测试取得了较为翔实的资料,经分析围岩波速及其松弛厚度变化特征、围岩变形量、变化过程及持续时间,得出该区隧洞埋深在300 m 以下的洞段,Ⅲ、Ⅳ1、Ⅳ2 类围岩松动圈厚度一般在1 m 左右,围岩的变形量主要发生在开挖后的40 ～50 h 以内,且初期变形速度较快.因此,隧洞支护应在围岩未发生充分变形的情况下进行,分析认为该区隧洞Ⅳ2、Ⅴ类围岩支护时间宜在开挖后数小时内完成,而Ⅳ1 类围岩可在开挖后数小时至十几个小时内完成,最长不宜超过1 d.通过探讨隧洞及高压管道围岩变形规律及发展趋势,预测围岩稳定状态,为修正原设计支护类型和参数以及合理选择一次支护时机、优化衬砌类型等提供科学依据.

The technique and methods applied for determination of weak rock deformational behaviors in a hydraulic tunneling work were elaborated,including testing of relaxation extent,monitoring of surface convergence and internal relative displacement,through which a large data were obtained for analysis of changes of wave velocity and loosen degree,deformation amount,displacement process and lasting time,based on which it was found that for tunneling section with more than 300 m thick cover,the relaxation thickness of Class Ⅲ,Ⅳ1 and Ⅳ2was generally about 1m and deformation of surrounding rocks was dominantly occurred within 40 to 50 hours after excavation,especially in the first several hours. Thus,it is recommended that the support system should be installed before the rock mass is fully deformed,such as Class Ⅳ2 and Ⅴ rock mass should be supported within several hours after excavation and Class Ⅳ1 within several hours to a dozen hours,at least within one day after excavation. In this paper the stability of heading rock mass is estimated by analysis of deformation characteristic and developing trends so as to provide to scientific basis for updating the original support design and parameters,selection of supporting time and optimizing lining type.