汶川8.0级地震对紫坪铺左岸坝前堆积体稳定性影响的监测分析

 钻孔倾斜仪观测成果表明，紫坪铺水库蓄水至汶川8.0级地震前，左岸坝前堆积体处于稳定状态，坡体观测位移无明显变化且计算的位移矢量无明显的方向性。汶川8.0级地震给距震中仅17 km紫坪铺工程带来了明显影响。根据监测成果及现场调查分析，汶川8.0级地震对紫坪铺左岸坝前堆积体产生了一定程度的影响：灯盏坪前缘浅表部局部崩塌与裂缝；基覆界面受地震影响产生了明显错动，位错增量最大值为60～70 mm；在错动面以上坡体位移随高程增加而增加，地表累计合位移增量为55～100 mm，局部高达206 mm。地震使坡体位移形成了明确的方向，震后地表位移矢量与汶川地震断裂带走向大致垂直。地震使堆积体内部土体产生了明显的倾斜变形，钻孔倾斜率变化最大值为1.873‰。坡体的变形异常主要表现在主震时，后期的余震对坡体变形影响很小。从震后连续的监测成果分析，紫坪铺左岸坝前堆积体目前仍处于整体稳定阶段。

MONITORING ANALYSIS OF INFLUENCE OF WENCHUAN 8.0 EARTHQUAKE ON TALUS SLOPE STABILITY AT LEFT BANK IN FRONT DAM OF ZIPINGPU HYDRAULIC PROJECT

The borehole inclinometer monitoring results indicate that the talus slope at the left riverbank in front of the dam of Zipingpu hydraulic project is stable until Wenchuan 8.0 earthquake，for no significant changes of displacements are observed in the slope and no obvious direction is found in the calculated displacement vectors. The Wenchuan 8.0 earthquake has brought negative effect on Zipingpu hydraulic project，which is only 17 km from the epicenter. According to the monitoring results and field investigation，the influence of the earthquake on the talus slope can be summarized as follows. Some local collapses and cracks appear on the surface of the front slope of Dengzhanping plateau，and an obvious dislocation was produced in the joint surface between bedrock and overlying talus. The maximum offset of the joint surface is 60 to 70 mm；above the surface，the displacement increases as the elevation and reaches ground with a range of 55 to 100 mm，and the maximum value is 206 mm. The displacement is formed at a specific direction due to the earthquake；and the vector is vertical approximately to the fault of Wenchuan 8.0 earthquake. The inclination of the observed hole is remarkable with a maximum rate of 1.873‰. The deformation was influenced mainly by main shock and hardly by the aftershock. The continuous monitoring data of post-earthquake show the talus slope is globally stable.