【摘要】 灰岩地区危岩具有典型类砌体结构特征,结构面发育复杂,其破坏本质是主控结构面在荷载作用下的断裂扩展失稳问题.基于地貌演化分析了灰岩地带陡崖复杂结构面形成与演化,获得了双裂缝主控结构面危岩的地质模型.构建了此类危岩的力学模型和断裂力学模型,按照最大周向应力准则,基于危岩自重、裂隙水压力及地震荷载作用,构建了双裂缝主控结构面危岩的断裂稳定系数表达式.通过案例分析验证了其合理性;各烈度对应的断裂稳定系数随贯通度增加而下降,基本地震烈度为Ⅷ度和Ⅸ度时,危岩处于不稳定状态;危岩稳定性受到主控结构面的裂隙贯通度与地震诱发的耦合作用影响,临界失稳贯通度随地震烈度的提高而降低;Ⅶ度地震的临界失稳贯通度理论值为25.8%,略小于贯通度实际值27.7%,略偏安全,其建立的断裂稳定系数表达式具有较好的适用性.研究结果可为推动此类危岩合理化防治提供重要的理论支撑.更多还原

【Abstract】 Unstable rock in the limestone area has typical characteristics of quasi-masonry structure and control discontinuity, where the failure essence is the fracture propagation under loads. The unstable rock control discontinuity in the limestone zone was analyzed, and the geological model for a double-crack unstable rock mass was obtained according to the theory of geomorphologic evolution. The mechanical model and fracture mechanical model for the complex control discontinuity were constructed. Based on the rock weight, the fissure water pressure and the earthquake load, the formula of the fracture stability coefficient was obtained under the maximum circumferential stress criterion. The fracture stability coefficient expression for the unstable rock is rational according to the verifying case analysis. The fracture stability coefficient corresponding to each intensity decreases with the crack length ratio. Under earthquake intensities Ⅷ and Ⅸ, the unstable rock will collapse; the stability of the unstable rock is liable to the coupling effects of the crack length ratio of the main control discontinuity and the earthquake intensity. The critical crack length ratio decreases with the earthquake intensity. Under earthquake intensity Ⅶ, the theoretical value of the critical crack length ratio is 25.8%, which is slightly less than the actual value of 27.7%, and on the slightly safer side. The fracture stability coefficient expression has good applicability. The research results provide an important theoretical support for the treatment of such unstable rock masses.更多还原