天水市群发地质灾害特征与成灾机理

目的]对甘肃省天水市2013年"7·25"群发性山洪地质灾害的成灾特征、分布规律及其成因进行分析,为黄土丘陵沟壑区降雨诱发地质灾害早期识别和减灾防灾提供科学依据。方法]在全面实地调查的基础上,建立三维连续介质动态数值模型,对天水市典型滑坡运动特征进行求解。结果]"7·25"山洪地质灾害具有普遍性,群发性明显,局地爆发性,隐蔽性强等5大显著特征;受强降雨和地震因素叠加效应的影响加剧了灾害的破坏程度;此次灾害大部分滑坡失稳的坡面几何形态多为直线型凹型面坡,滑坡失稳多发生在35°~45°坡度范围内,以40°坡居多,黄土坡面滑坡通常是窄条状、方量较小;典型滑坡体在斜坡运动过程中,平均速度、最大速度、总动能和总势能均是急剧增加,进入水平面后,各个动力参数急剧下降。侵蚀作用是滑坡运动中非常重要的不可忽视的一个重要的因素,它使得灾害体质量增加,同时依靠较高的速度(30m/s),具有更强的破坏性。结论]天水市群发地质灾害形式依然严峻,降水是引发和加剧此次地质灾害的主要因素。

Development and Causes of Group Geological Hazard in Tianshui City

Objective] Through the investigation of the "7·25" massive mountain torrents geological hazards in Tianshui City of Gansu Province occured in 2013, we expected to reveal the landslide mechanism and provide a scientific basis for early identification, prevention, and reduction of rainfall-induced geo-hazards in the loess ridge-hill areas of China. Methods] The characteristics, distribution law of geological hazards and its causes were studied. Three dimensional continuum dynamic numerical models were established to calculate the dynamic character of landslide in Tianshui City. Results] The results showed "7·25" massive mountain torrents geological hazards had characteristics of occurrence universally, outbreak massively, locally and unnoticeably, and had strong hazard potentiality. The hazards were exacerbated by the effects of earthquake and rainfall. The slope geometry shapes of landslide in the torrent''s geological hazard are linear concaved. Most slopes are in the range of 35°~45°, and among which, 40° slopes were found more frequently. Loess slope landslide is usually in a narrow strip and with small volume. The average velocity, maximum velocity, total kinetic energy and potential energy of typical landslide increased dramatically in slope motion process. These indices dropped sharply after entering a horizontal plane. Erosion plays an important role in landslide movement, which make slope sliding in a high speed and lead to more destructive hazards. Conclusion] The risk degree of group geo-hazards remains severe in Tianshui City. Precipitation is the main factor that cause and aggravate the geological disasters.