基于强度折减法的隧道围岩稳定性研究

Research on the stability of surrounding rocks based on the strength reduction method

围岩的稳定是地下工程支护结构稳定的关键,本文围绕围岩稳定性分析开展了一系列研究。首先针对地下工程围岩的地质历史特征,使用能够反映开挖扰动影响的Hoek-Brown准则作为岩体力学参数的估算方法,并基于隧道围岩次生应力分布及其松动失稳机制,提出了基于隧道拱顶下沉变形位移突变的围岩失稳判据;然后,通过将强度折减法与失稳判据相结合,建立了围岩自支护结构稳定的安全系数分析方法;最后,通过采用正交试验设计,并采用FLAC软件,对影响隧道围岩结构稳定安全系数的基本因素进行了敏感性分析。计算结果表明,地质强度指标起到关键控制作用,其余依次是开挖扰动因子、岩块单轴抗压强度、隧道埋深及跨度。

Stability of surrounding rocks is the key to the stability of a supporting structure in an underground engineering. Analysis of surrounding rock stability is the focus of this paper. In response to the history of rock mass, and in order to reflect the excavation disturbance, the Hoek-Brown criterion was selected to estimate the shear strength of rock masses. Based on the secondary stress field and instability mechanism, the mutational displacement of arch settlement is chosen as the failure criterion. The safety factor is obtained to evaluate the stability of rock mass by using the strength reduction method. The theory of orthogonal design is introduced and sensitivity analysis for the basic factors influencing the stability of surrounding rocks is made. The results show that the geological strength index plays a key role, followed by the excavation disturbance factor, the uniaxial compressive strength of intact rock, and the tunnel depth and span. The research provides a practical method for the quantitative evaluation of the stability of surrounding rocks in an underground engineering, and can provide an important reference for the design, construction and reinforcement of a tunnel engineering.