北京地区崩塌隐患特征分析与防治方案

Characteristics and prevention and control of potential collapses in Beijing

崩塌是北京山区道路沿线最为发育的突发性地质灾害类型。截至2022年6月,查明道路斜坡发育崩塌隐患共计5131处,占全市灾害隐患总数的62.68%。主要分布在密云、门头沟、房山等地区。同时,隐患点沿山区道路最为发育,220条县级及以上道路和12000余千米乡级、村级道路崩塌隐患发育数量大致相等。按照崩塌危岩体发育特征,岩质斜坡占90.31%;斜坡结构类型中,特殊结构斜坡占41.8%,其次为切向斜坡;斜坡坡度大于60°的陡崖微地貌达73.79%;坡高50 m以下斜坡占89.88%;按照规模,小型崩塌(<500 m^(3))隐患占比78.97%;按照成灾模式,坠落式占比达54.62%。从灾害演化角度分析,断裂构造控制危岩体的发育特征,为孕灾因素;修路切坡和工程治理影响了危岩体力学平衡,为扰动因素;大气降水是促成危岩体失稳的关键因素。道路斜坡治理以挡墙和主动防护网为主,分别占49.39%和41.97%。针对道路崩塌防治,需要重点关注高位垂直节理斜坡、易崩易滑地质结构斜坡、山前降雨中心斜坡等3类崩塌源斜坡区域;同时采取多措施综合治理、严格遵守施工次序、汛期加强巡查频次等防范措施。

Collapse is the most developed type of sudden geological disasters along mountain roads in Beijing.By June 2022,a to-tal of 5131 rock falling hidden points had been identified mainly in Miyun,Mentougou and Fangshan,which account for 62.68%of the total potential hazards in Beijing.These hidden points mostly along the mountain roads are roughly of the equal numbers for 220 roads at county and above levels and for over 12000 km roads at town and village levels.According to the development char-acteristics of unstable rock mass,rocky slopes account for 90.31%.Among the slope structure types,slopes with special structure account for 41.8%,followed by tangential slopes.73.79%of the steep cliffs are with a slope gradient greater than 60°;89.88%of the slope is below 50 m in height.By scale,small hidden collapse points(<500 m^(3))account for 78.97%.By collapse forms,the falling type accounts for 54.62%.From the perspective of disaster evolution,the fault structure controls the development charac-teristics of unstable rock mass and so is a collapse-forming factor.The mechanical balance of unstable rock mass is affected by road construction,slope cutting and engineering treatment,all of which are disturbance factors.Atmospheric precipitation is the key factor contributing to the instability of unstable rock mass.In treatment of road collapse,retaining walls and active protective nets are mainly used,accounting for 49.39%and 41.97%respectively.For the prevention and control of road collapse,focus should be paid on high level vertical joint slopes,slopes prone to collapse and with sliding geological structure,and slopes in front of the mountain rainfall center.At the same time,prevention and control measures shall be taken such as comprehensive treatment with multiple measures,strict compliance with the construction sequence,and strengthened inspection during the flood season.