库车迪那2井区主干道桥梁四号桥台地基边坡危岩体的地震稳定性分析

四号桥台是位于阿日卡尔峡谷西岸边缘的重力式桥台。通过对桥台地基岩层中发育的节理裂隙的详细勘察,可将节理归结为三种成因:①构造节理;②风化节理;③边坡重力滑动节理。其中,峡谷边坡重力滑动形成的节理是构成对桥台地基岩体稳定性的最大威胁。通过物探、钻探和现场节理裂隙注水试验,探明这组重力滑动节理发育深度达40余m。依据边坡滑移式危岩体特征,以不同地震动载荷条件进行计算和综合分析,当地震动加速度≤0.04g时,边坡危岩体处于基本稳定状态;当地震动加速度在0.05—0.12g的范围内时,边坡危岩体处于欠稳定状态;当地震动加速度≥0.13g时,边坡危岩体进入不稳定状态,随时有发生滑塌的危险。经地震危险性概率分析,四号桥台场地未来50年超越地震动加速度0.13g的概率高达40%。

Analysis of Seismic Stability on the Dangerous Slop of No.4 Bridge Seat Basement of Main Road Bridge in Kuche Dina 2 Well Field

The No.4 bridge seat is a gravity bridge basement located on the west bank of Ariker canyon.By means of detailed geological surveying,all joint fissures in the bridge rock basement can be divided into three groups in terms of mechanisms：1） tectonic joints,2） weathering joints,and 3） gravity slipping joints.Among them the gravity slipping joints are the biggest threat to the stability of the No.4 bridge seat basement.Through geological exploration,drilling and injecting water test at worksite,we find out that gravity slipping joints have reached as deep as 40 meters.In accordance with the calculating formula of side dangerous rock block,with different vibrating accelerations of earthquake to carry on computation and comprehensive analysis,while the acceleration of earthquake is ≤0.04g,the side dangerous rock block is principal stability.The acceleration of earthquake within the range of 0.05—0.12g,the side dangerous rock block will be sub-stability;when the acceleration of earthquake is ≥0.13g,the side dangerous rock block will fall into instability at any time.Through analysis of earthquake risk,probability of earthquake acceleration over 0.13g at the No.4 bridge seat area is 40% in 50 years.