强震区泥石流坡面物源发育规律与侵蚀坡度效应研究

Source development and slope gradient effect of debris flow source in earthquake zone

汶川地震触发的滑坡崩塌地质灾害具有危害性大、规模大、数量多的特点,使震区参与泥石流活动的潜在松散物源大量增加,导致泥石流暴发频率和暴发规模较地震前明显增大。为探讨地震对强震区泥石流的影响,调查强震区泥石流物源的分布特征,并分析坡面物源的侵蚀坡度效应,通过对都汶路沿线泥石流物源调查,利用GIS技术对研究区泥石流物源空间分布进行统计分析,并基于静力学方法对物源侵蚀的坡度效应进行探讨。研究表明：（1）利用研究区遥感影像提出灾害点并计算投影面积,利用野外调查得到灾害点样本体积,基于多元回归分析得到研究区物源体积估算模型;（2）统计研究区不同岩性区灾害点个数与面积,得出花岗岩区灾害点发育程度最高,并分析花岗岩微观结构和构造特征;（3）地震物源点主要在坡度40°-50°,坡向120°-150°,高程1 400-2 800 m区间发育,且随着烈度增加与发震断裂距离增加而快速增加,具有上下盘效应、背坡面效应;（4）研究了泥石流物源侵蚀规律。地表径流深度与斜坡坡度呈负相关、坡面流速在坡度等于60°时取得最大值,物源侵蚀能力临界坡度为42.4°-48.1°。

The geological hazard triggered by Wenchuan earthquake was characterized by great damage,huge volume and great quantity. It resulted in huge increasing of the potential material of debris flow in the earthquake area. Thus,the frequency and volume of debris increased after the earthquake. The investigation of the potential debris material along Duwen highway was conducted. The statistic of spatial distribution of debris was performed by GIS. The effect of gradient on debris erosion was analyzed. The results showed that,the hazard area and volume followed the model. The density of hazard was largest in the granitic area. The hazard mainly occurred on the slopes in the gradient range of 40°–50°,in the exposure range of 120°–150° and in the elevation range of 1 400–2 800 m. Meanwhile,it increased with increasing earthquake intensity and the distance to the surface rupture of the Wenchuan earthquake. The occurrence of the hazard followed the＂hanging wall effect＂and＂topographic effect＂. The maximum value of flow velocity of the debris was reached at slope gradient of 60°and the critical slope gradient for debris erosion was in the range of 42.4°–48.1°.