【作者】 彭昌翠；

【导师】 沈军辉；

【作者基本信息】 成都理工大学 ， 地质工程， 2011， 硕士

【摘要】 “5.12”汶川地震强大的破坏力使得震区在复杂的地质背景条件下,产生了大量的崩塌、滑坡等次生地质灾害,形成了数量巨大的松散堆积体,为该地区泥石流的孕育和发生提供了丰富的物源条件,在强降雨作用下,灾区泥石流频发。由于目前国内外对地震产生的泥石流灾害缺乏系统的研究,特别是对它的危害程度以及破坏力度的认识不足,在灾后恢复重建过程中对泥石流的防护力度不够,措施不到位,导致泥石流在震后很长一段时间成为灾后恢复重建过程中影响范围最广,暴发频率最高、破坏性最大的地质灾害。特别是2010年8月14日前后暴发的特大山洪泥石流对省道303线映秀至耿达段公路造成了毁灭性的破坏。因此,对区域内泥石流灾害的进一步认识评价,可以为公路工程规划设计及减灾防灾提供了地质依据,具有很好的理论和实际意义,也为研究震后泥石流的形成条件、活动特征、形成机制提供了参考。论文的主要认识与成果如下:(1)“8.14”强降雨期间,映秀至耿达段公路发育有泥石流30条(处),其中沟谷型泥石流15条、坡面型泥石流15处。区域内泥石流的具有群发性、规模增大、频率增加、受降雨强度控制等特点。泥石流形成条件的变化主要体现在松散物质的急剧增加、流域微地貌的突变以及降雨入渗条件的变化以及临界雨强的降低。泥石流的形成机制主要为强降雨诱发的暴雨泥石流。(2)汶川地震后震区泥石流形成条件发生了较大变化,目前广泛运用的泥石流沟易发程度的评判方法没有突出震后泥石流易发的主要原因,采用现有方法对泥石流易发程度进行判定不甚合理。本文利用层次分析法对原评价参数加以修正后,对其所占的权重进行了计算,重点突出了影响震后泥石流易发的三个主要因素:物源、临界雨强、汇水条件。(3)在泥石流规模预测上通过对“8.14”泥石流的实际情况,采用一次最大冲出量与物源总量的类比法形成了泥石流物源估计法,根据类比结果,震区内单沟泥石流一次最大冲出量为流域内总物源的10%。将“8.14”泥石流中典型沟谷一次冲出量带入雨洪法公式中进行反演计算,修正公式中的堵塞系数基数,利用修正后的公式计算震区泥石流一次最大冲出量。两方法计算结果较接近,再结合老泥石流发生的历史规模进行综合预测,结论可信。说明三者结合的方法在本区域内比较适用。(4)对震后泥石流危险性评价主要是根据在极端暴雨(百年一遇)情况下泥石流的易发程度、规模预测结果以及将来可能产生的危害程度进行综合评价。得到结果如下:研究区内有8条泥石流沟危害程度中等,危险性中等;15条泥石流沟危害程度大,危险性高;坡面泥石流危险性小～中等。该区泥石流数量众多,危害性大,建议该段公路在规划设计过程中,应尽量绕避破坏性较大的泥石流沟谷,对于破坏性中等或者较小的泥石流可采取适当措施进行防护或治理。更多还原

【Abstract】 The strong damage of 5.12 Wenchuan Earthquake produced considerable secondary geological disasters, such as collapse, landslide and debris flow, under the complicated geological background conditions. It has formed a huge of loose accumulation, gestated rich source conditions for the debris flow in this area. Under the action of the heavy rainfall, debris flow happened frequently. Due to the lack of systematic research on the debris generated by earthquake, especially for its harm degree and destruction dynamics. In addition, during the process of reconstruction, because inadequate protective and unconsciousness after the earthquake, in a long time of reconstruction, debris flow disaster become the highest frequency, most destructive and widest range influence disaster. On August 14th 2010, super flash flood debris caused the devastating damage to the provincial highway 303 along Yingxiu-Genda. Therefore, within a further understanding of debris flow hazards for highway engineering evaluation, planning and provides some prevention and reduction of geological basis, could be a very good theoretical and practical significance or reference for the study of forming condition, activity, characteristics and formation mechanism of this post-earthquake debris flow.The main Understanding of this paper are as follow:(1) There are 30 debris flow sites along the highway of Yingxiu-Genda (before or after the 8.14 heavy rainfall, 15 gully debris and 15 slope debris were break out). The development of debris flow was controlled by geological conditions, the change of the formation conditions are mainly embodied in the loose material sharp increasing, geomorphology mutation or the change of permeation of the rainfall condition, most of the debris flow caused by the heavy rainfall.(2) After the Wenchuan earthquake, the formation conditions of debris flow undergone great changes. At present, the evaluation method of the predisposition of the geologic hazards which have been widely used did not highlight the main reasons of the predisposition after the disaster. So, the current methods are unreasonable. This paper, by using AHP, the original evaluation parameters have been revised, highlighted the three main factors that influenced the predisposition of the debris flow: the material sources, the critical rainfall intensity and catchment.(3) The method study of the scale of the debris flow, on the based of typical debris flow surver along the roads during the 8.14 period, compared the single biggest rushed out of the debris of one ditch with the total content source. According to the results, the maximum debris of one time could be estimated as 10% of the total content sources (material source estimate). To ensure the accuracy of the results, took the content of debris flow that have been flowed out into the Rainfall flood law formula for back calculation to correct the blockage factor in this formula. Finally, used the modified formula to calculate the single biggest rushed out of the debris of one ditch and contrast with the material source estimate, then, combined with the scale of the old debris flow for integrated forecasting. That the method of combining three more applicable in the region.(4)According to the the debris flow-prone cases the degree of the scale of predicted results and the degree of harm that may arise in the future a comprehensive evaluation, this paper assessed the risk of the debris flow. The results show that 15 of the ditches in this area are high-risk areas, 8 ditches are medium, the risk of slope debris flow are small-medium, in extreme rainstorm (year storm) cases, susceptible to or secondary occurred the debris flow hazards. Large number of debris flow area, the danger, Several suggestions could be summarized from this paper are that in the process of reconstruction the highway along Yingxiu-Genda, we should try to avoid the high-risk and destructiveness ditches, for the smaller destructive debris flow, we should take the appropriate measures to defend or management.更多还原