含纵向裂隙的悬挑式危岩稳定性分析方法研究

A Stability Analysis Method of the Overhanging Crag with Longitudinal Cracks

研究目的:在火山岩和沉积岩广泛分布的山区修建高速铁路,沿线陡坡地段常常出露一定数量的孤石,受侵蚀、差异风化等因素影响,这些岩石呈现出部分悬挑的状态,甚至在岩石顶部还常常发育有一定数量的纵向裂隙,这些大小不一、形态各异的危岩体对铁路施工和运营均带来巨大的安全隐患。而当前缺乏针对含纵向裂隙悬挑式危岩稳定性评价的有效分析模型,迫切需要针对该类型危岩的稳定性分析方法开展研究工作,为山区铁路选线及沿线危岩的防治提供技术支撑。研究结论:(1)通过将岩体极限抗拉强度作为评判危岩体稳定性的主要依据,以裂隙外侧危岩体的悬臂段为研究对象,建立了基于平面坐标系统的含纵向裂隙危岩体的稳定性分析模型;(2)基于建立的理论模型研发了相关的分析软件;(3)以沈丹客运专线本溪隧道出口一处危岩体为研究对象,通过对其潜在的最不利破裂面进行搜索分析,得出了危岩体的最小安全系数;(4)本研究结论可为本溪隧道出口仰坡设计提供工程依据。

Research purposes： There are a number of boulders exposed on the surface of steep slopes along the railway line, when the high -speed railway is constructed in mountain areas where volcanic and sedimentary rocks are widely distributed. Some overhanging rocks may develop longitudinal cracks because of erosion, differential weathering and other factors. These dangerous rock mass with different sizes and shapes will bring about the great security risk to the construction and operation of high - speed railways. Unfortunately, there was no logical and rational method to meet actual conditions of the overhanging crag with longitudinal cracks. So the method of calculating the safety factor should be studied timely for stability of crags to make technical support for reinforcement and prevention of unstable rocks along the railway in the mountains. Research conclusions： （ 1 ） The new model which is based on overhanging portion of the rock body beside longitudinal crack indicates that the ultimate tensile strength of rock is assumed to be the determination basis for analysis of its stability. （2） A new analysis software is developed on the basis of the stability analysis model which is established in the plane coordinate system for a crag with longitudinal cracks. （3） The research is applied for stability of quartz sandstone crags by searching the most dangerous potential fracture planes at the exit of Benxi tunnel in the Passenger Line from Shenyang to Dandong, and the minimum safety factor of overhanging crags is obtained. （4） The research result can provide a valuable engineering basis for design of slope at Benxi tunnel exit.