西藏紫金山危岩特征及稳定性和运动特性研究

危岩是山区常见的地质灾害类型之一,危岩失稳-崩塌后的运动特性难以预测,危害很大。为了探讨危岩的稳定性和运动特性,以西藏紫金山危岩为例,通过定性定量方法对各危岩带的稳定性进行评价,并用Rocfall软件模拟危岩失稳后的运动轨迹,通过室内试验分析冻融作用对危岩形成的影响,同时结合无人机航空摄影、三维激光扫描及现场调查等手段,对危岩带的划分、地层岩性、节理裂隙的发育情况等进行现场验证。结果表明:各危岩带位于山脊陡崖处,均处于基本稳定-欠稳定状态,在降雨、地震条件下稳定性会有所降低;危岩的形成受地形、岩性、地震、冻融等多因素的共同影响,冻融作用主要表现为冻融损伤,在岩石表面形成微裂纹;危岩失稳-崩塌后在坡面经过多次弹跳、滚动,最终停止。研究成果可为危岩的治理设计提供参考。

Study on feature of dangerous rock of Purple Mountain in Tibet and its stability and movement characteristics

Dangerous rock is one of the common types of geological disasters in mountainous regions，of which the movement characteristics of the instability － collapse is quite difficult to be predicted，while its hazard is great. In order to explore the stability and movement characteristics of dangerous rock，the stabilities of all the dangerous rock zones are qualitatively and quantitatively evaluated herein by taking the dangerous rock of Purple Mountain in Tibet as the study case，and then the impact from freeze-thaw effect on the dangerous rock is analyzed through the relevant lab experiment with the movement trajectory after the instability of it simulated by the software of Ｒockfall，while the in situ verifications are made on the division of the dangerous rock zones，the strata lithologies and the joint-fissure developments in combination with the means of UAV images，3D laser scanning and field investigation. The result shows that all the dangerous rock zones are located at the steep cliffs of the mountain ridges under the conditions of basic stability and unstability，of which the stabilities are to be lowered to some extent under the conditions of rainfall and earthquake. Through the study，it is obtained that the formations of the dangerous rocks are impacted by many factors，i. e. topography，lithology，earthquake，freezing-thawing，etc. ，in which the freeze-thaw effect is mainly exhibited as the freeze-thaw damage along with micro-cracks formed on the rock surface. After the instability － collapse，it is to bounce and roll on slope surface and finally stop. The study result can provide a reference for the design of dangerous rock prevention.