天水市麦积区税湾地震黄土滑坡特征及其形成机制

CHARACTERISTICS AND DEFORMATION MECHANISM OF SHUIWAN SEISMIC LOESS LANDSLIDE IN MAIJI,TIANSHUI

以天水市税湾地震黄土滑坡为例,依据野外调查和室内测试结果,总结天水地区历史地震黄土滑坡特点,剖析地震黄土滑坡发生的力学机制,初步提出历史地震黄土滑坡的识别标志。税湾滑坡及柳沟右岸滑坡群属典型的地震黄土滑坡,具有规模大、滑动面切割深、滑坡坡度小、成群成带分布和高位下滑等特点,可作为识别历史地震黄土滑坡的重要标志。税湾滑坡及柳沟右岸滑坡群坡体具有明显的黄土/泥岩二元斜坡结构,极易沿黄土/泥岩接触面滑动。当坡体受到地震力作用时,地震产生的循环动荷载一方面降低滑坡岩土体的抗剪强度,另一方面改变滑坡体的力学状态,坡体应力平衡遭到破坏,地震力增加坡体下滑力、减小坡体抗滑力,导致坡体失稳发生滑坡。目前,税湾滑坡处于欠稳定状态,遇地震或强降雨有可能再次失稳下滑,因而有必要进一步开展地震黄土滑坡的成灾模式研究,为潜在强震区防灾减灾提供科学依据。

Many historical earthquakes happened in Tianshui and its adjacent region, which resulted in seismic loess landslides developing extremely. According to field survey and indoor synthetic analysis,Shuiwan landslide and landslide groups of Liugou belong to typical seismic loess landslides,which are usually performance for large-scale, the sliding surface cutting deeply,thickness greatly,small slope,distributed along zones,appeared in groups and decline in high position and other characteristics. The characteristics above can be used as important symbols of field identification of seismic loess landslides. The slopes involved in Shuiwan landslide and the right bank Liugou landslides are characterized by loess / mudstone slope double layers structure. Under the condition of internal power,it is easy to slip along the loess / mudstone contact surfaces. Under the dynamic circulative loading,shear strength of the landslide rock mass is decreased on one hand. On the other hand it also changes the mechanical status of landslide,and the balance of the slope body is destroyed,which induce landslide happened. So,Shuiwan landslide is still in understable state.In case of an earthquake or heavy rainfall,it is likely to reoccur again. There is a necessary for further research of the disaster model of seismic loess landslide. It will provide a scientific basis for prevention and mitigation disaster of potential meizoseismal area.