甘肃永登5.8级地震黄土震害特征及机理分析

ANALYSIS ON CHARACTERISTICS AND MECHANISM OF THE SEISMIC DAMAGE IN LOESS IN YONGDENG MS5.8 EARTHQUAKE REGION, GANSU PROVINCE

摘要:

对1995年甘肃永登5.8级地震极震区黄土覆盖处的震害现象进行了分类,大致将其分为出现震陷性断坎和发生小规模滑坡两种.利用电子显微镜和图象处理系统对震区的黄土试样孔隙结构性进行了定量分析.应用常规土工试验取得了该地区黄土的物性指标和湿陷、震陷性质资料.通过对上述室内试验资料的分析认为该地区的黄土孔隙大,在遇水条件下易发生震害.结合野外考察的总体认识和室内资料并注意到震区在临震时曾有过短时间暴雨的现象,将此次地震的震害原因归结为雨水在坡面下渗,在坡脚处上浸和对坡脚的冲蚀等,并对两种不同震害现象发生的机理作了分析.

Abstract:

In this paper,the seismic damage phenomena in the loess in Yongdeng M_S5.8 earthquake region,Gansu province are collected and analyzed.The damages are divided into two types,one is crisp crash by the quake on the top of the hill,the other is small-scale landslide.For the loess samples from the intensity areas of Ⅶ,Ⅷ degrees,the quantitative analysis on the SEM pictures and the common geo-engineering experiments are carried out.The results show that the loess from this region is full of big pores and is prone to seismic damage when the damp ratio becomes higher.Combining the general knowledge of the field investigation with the indoors experiments data and noticing that just before the earthquake there was a storm,we impute the loess damage to water penetrating on the slope surface and eroding in the slope foot.According to the above analysis,the mechanisms of the two kinds of seismic damage are proposed.