【作者】 黄文洁；

【导师】 唐川；

【作者基本信息】 成都理工大学 ， 地质工程， 2011， 硕士

【摘要】 泥石流是山地自然灾害之一,暴发突然、破坏力大。构造断裂带附近泥石流活动尤为强烈。2008年5月12日发生在四川省汶川县的里氏8.0级地震,孕育了不计其数的滑坡、崩塌及潜在不稳定斜坡等不良地质体,为震区内泥石流的孕育及发生提供了有利条件。2008年9月24日,2009年7月17日,2010年8月12～14日先后在四川境内北川、安县、清坪、龙池、映秀等地暴发大规模泥石流,造成了重大损失,严重威胁着灾区的恢复重建工作。因而,对强震区泥石流活动特征进行分析,对防灾减灾工作具有较好的指导意义。本文以安县区11条泥石流为研究背景,结合实地调查与遥感影像图,分析了地震作用下泥石流物源的空间分布,与岩性的相关性,以及地震对泥石流沟地形条件的影响。研究发现“5.12”汶川大地震为强震区泥石流提供了丰富的物源。物源的分布除受区域地层岩性影响外,随高程的变化具有一定规律,主要分布在高程1000~1800m间。汶川地震影响了强震区泥石流沟的地形条件。强大的地震作用破坏了泥石流流域内植被和表层土壤,多处基岩出露,改变了流域汇水条件及流水径流条件。地震引起的崩塌、滑坡等灾害,堆积于沟道或坡脚,改变了沟道流通条件,局部造成堵塞。与震前相比,在相同降雨条件下,现有泥石流沟道更易暴发泥石流。此外,本文根据地震对泥石流物源条件和地形条件的影响分析结果,选取流域面积、沟道堵塞系数、植被覆盖率、岩性系数以及物源面积与泥石流流域面积的比值等5项因子,将泥石流活动性划分为5个低级,分别代表泥石流活动的5种频率,利用模糊数学综合评判法对研究区泥石流沟地震前后的活动性进行了对比分析。通过对评价因子的权重分配来看,物源与流域面积的比对泥石流活动性影响最大。研究发现地震前泥石流沟活动性评价结果与实际调查结果较吻合,体现了评价模型的可靠性;地震后泥石流沟活动性明显增强,可判定强震区泥石流活动频率将明显增加。据此对比分析地震前后泥石流的活动性,发现除梅子堂沟、麻柳沟、柿子园沟等活动性在地震后仍处于轻度外,其余8条沟都变为极强活动,因而可判定震区泥石流在震后明显增强,暴发频率将增大,大多5年内会暴发一次以上泥石流。本文还选取了两条典型泥石流沟,重点分析了泥石流的形成条件,对发育趋势进行了预测,能较好的代表研究区泥石流的活动特征。更多还原

【Abstract】 Debris flow in mountain is one of natural disasters, which outbreaks of a sudden, devastating large. Construction debris flow activity near the fault zone is particularly strong. 12 May 2008 Wenchuan County in Sichuan Province, the magnitude 8.0 earthquake, gave birth to numerous landslides, avalanches and potential adverse geological unstable slopes, debris flow for the earthquake area and provide favorable breeding conditions. September 24, 2008, July 17, 2009, 2010 August 12 to 14 worked in Beichuan, Sichuan Province, County, Qing Ping, Longchi, Yingxiu large outbreak of debris flows and other places, causing heavy losses, serious threatening disaster restoration and reconstruction work. Thus, on the earthquake zone of debris flow activity characteristics, disaster prevention and mitigation work on guidance for good.In this paper, debris in Anxian County District 11 as the research background, combined with field survey and remote sensing image analysis of the seismic effect of the spatial distribution of debris flow source, the correlation with the lithology, and topographic conditions of earthquakes on the impact of debris flow. Study found that "5.12" Wenchuan earthquake zone provides a rich debris flow source. The distribution of source lithology is not only effected by the regional, with elevation changes with some regularity, mainly between 1000 ~ 1800m in elevation. Strong earthquake affected areas of the debris flow terrain conditions. A powerful earthquake destroyed the vegetation and surface debris basin soil, many bedrock outcrops, has changed conditions and the water catchment basin runoff conditions. Collapse caused by earthquakes, landslides and other disasters, or accumulated at the foot of the slope channel, changing the channel flow conditions, causing local congestion. Compared with the earthquake before in the same rainfall conditions, the current outbreak of more debris. In addition, the paper by a seismic source of debris impact conditions and terrain conditions, the results, select the drainage area, channel blocking factor, vegetation coverage, lithology factor and debris flow source area and the ratio of drainage area and other five factors, the debris flow activity is divided into five low-level, representing the frequency of debris flow activity 5, the use of fuzzy comprehensive evaluation method in the study area before and after the earthquake debris flow activity were compared. Evaluation factor by the weight allocation, source and drainage area of debris flow activity most. Study found that debris flow activity before the earthquake evaluation results agree well with the actual survey results, reflecting the reliability of the evaluation model; earthquake debris flow activity was significantly enhanced to determine the earthquake area will significantly increase the frequency of debris flow activity. Accordingly comparative analysis of debris flow activity before and after the earthquake, found that in addition Meizi Tang ditch, Maliu ditch, Shiziyuan ditch and other activities of persimmon garden after the earthquake is still mild, the other eight have become extremely active channel, which can be determined Earthquake debris flow significantly increased after the earthquake, outbreak frequency will increase, most of them more than 5 years will be an outbreak of a debris flow. The article also selected two typical debris flow, analyzes the formation of debris flow conditions, development trends are predicted, the study area can be a good representative of the activities of debris flow characteristics.更多还原