基于汶川地震经验的地震崩塌失稳预测综合指标法

Comprehensive index method for predicting earthquake-induced collapse based on the Wenchuan earthquake experience

依据汶川地震崩塌灾害调查数据,统计分析了地震崩塌与岩体结构、地震烈度、斜坡地貌形态之间的关系,研究采用综合指标法进行地震崩塌失稳预测。研究表明:土层及风化卸荷带、发育不利外倾结构面岩体、发育贯通性陡倾结构面岩体等在地震作用下容易产生崩塌失稳;地震崩塌灾害密度及规模随地震烈度的增高而加大,两者呈指数关系;边坡高度、几何形态对地震崩塌灾害发育也有重要影响。以岩体结构和地震烈度为基本指标,地形地貌(坡度、高度和几何形态)为修正指标,建立了计算地震崩塌失稳指数的经验公式,并基于汶川地震统计数据对指标进行赋值,划分为小、中等、大、极大4级地震崩塌危害等级,以定性评判边坡地震崩塌稳定性和危害程度。

Based on the survey data of collapse in Wenchuan earthquake, this paper conducted statistical analysis to the relationship between the earthquake-induced collapse and rock mass structure, seismic intensity and slope geomorphy, and seeking to adopt comprehensive index method to predict seismic collapse. The study shows that three structures of rock-soils, i. e. , strong weathered rock structure, rock mass with structure plane lean outwards, and rock mass with through steep structural plane, are easily collapse under seismic condition. The density and scale of the collapse are enlarged with the increase of seismic intensity, and their relationship is exponential between. Slope height and geometric patterns also have important influence on the earthquake induced collapse. Taking rock mass structure and seismic intensity as the basic index, topography （gradient of slope, height and geometry） as the correction index, this paper established empirical formula for the calculation of earthquake collapse, assigned values to the indices based on the Wenchuan earthquake statistics and divided the seismic collapse hazards into four rankings, small, medium, large and huge, for qualitative evaluation of the slope stability and hazard degree under seismic condition.