降雨诱发山区公路边坡危岩崩塌机理研究

Mechanism of Rock Collapse due to Rainfall from Roadside Slope in Mountainous Area

危岩崩塌是危害山区公路安全的主要地质灾害类型之一。以2018年汛期暴雨诱发的北京市房山区军红路塔柱状危岩崩塌为例,基于现场调查、工程地质分析、岩石物理力学实验、数值模拟等方法,从孕灾地质背景、岩体物理力学性质、降雨触发因素等方面分析了崩塌成因,利用UDEC软件模拟了地下水渗流、岩体强度软化对斜坡变形的影响。调查研究结果表明,军红路崩塌为发生在反倾斜坡中的塔柱状危岩崩塌。边坡上部塔柱状危岩由玄武岩被深大裂缝切割形成孤立的塔柱状危岩,下伏含大量黏土矿物的凝灰岩在长期风化作用下形成陡坡,构成灾害易发的靴状地貌。临崩的短时强降雨入渗在斜坡中形成地下水渗流,渗透压力导致岩体结构调整、斜坡变形,基座岩体在充分饱和、岩体强度降低的作用下,最终发生压裂破坏诱发危岩整体下座,冲击铲刮下部岩体并沿路堤下方斜坡运动,堆积在沟底。

Rock collapse is one of the main types of geological hazards endangering highway safety in mountainous areas. Based on the field investigation,engineering geological analysis,physical and mechanical experiments,numerical simulation and other methods,the causes of collapse are analyzed in terms of geological background of disaster recovery,physical and mechanical properties of rock mass and rainfall triggering factors,and the influence of groundwater seepage and rock mass strength softening on slope deformation is simulated by UDEC software. The investigation results show that the collapse of Junhong Road is a tower columnar dangerous rock collapse in hard rock. The tower columnar dangerous rock in the upper part of the slope is cut by basalt by deep cracks to form isolated tower columnar dangerous rock.The tuff with a large amount of clay minerals is relatively low in strength, and a steep slope is formed under long-term weathering. Constitute a typical" up steep down slow" boot geomorphology. Rainfall infiltration produces seepage in rock mass, intensifies slope deformation, and the strength of tuff is reduced by groundwater softening, which leads to fracturing failure of rock mass to induce the whole lower seat of dangerous rock,impact shovel to scrape the lower rock mass and move along the slope below the embankment. Finally accumulated at the bottom of the ditch.