【作者】 田媛；

【导师】 巨能攀；

【作者基本信息】 成都理工大学 ， 地质工程， 2022， 硕士

【摘要】 高山峡谷地区地质灾害频发,对人类生命财产造成极大威胁,地质灾害易发性(危险性)评价往往作为一种典型的非工程防灾减灾手段,一直以来是研究热点。虽然区域地质灾害评价研究工作已发展有几十年,但仍面临着诸多挑战与困难,尤其对于地质条件复杂的高山峡谷地区。本文以四川省理县县城以东杂谷脑河沿岸为研究区,在充分分析研究区地质灾害类型、发育特征、分布规律和孕灾地质条件的基础上,提出滑坡、崩塌、泥石流三类地质灾害的主控因素;基于所提出的一种基于坡位的改进斜坡单元划分方法,进一步分别对三个种类地质灾害易发性评价,提出三类灾种易发性结果融合的方法,形成研究区综合地质灾害易发性评价结果;最终基于不同降雨工况进行研究区地质灾害危险性评价。取得主要研究成果如下:(1)查明了研究区地质灾害发育特征。研究区地质灾害点共225处,其中滑坡101处,崩塌(危岩)85处,泥石流39处;区内滑坡主要以中型、小型牵引式土质滑坡为主,多数属浅层～中层滑坡;崩塌主要分布于杂谷脑河河谷沿线,以中小型岩质崩塌为主;泥石流主要分布于杂谷脑河薛城镇以下河段,以小型为主,大多为中低频泥石流;(2)系统分析了研究区各类灾种主控因素。滑坡:1)斜坡地形坡度,发育滑坡的斜坡坡度主要集中在20°-38°不等;2)覆盖层类型,沿线松散覆盖层为千枚岩、片岩的崩积、坡积、残积物,粗颗粒含量高,并多呈片状、板条状,粘粒含量少,水稳性差;崩塌:1)岩性,主要以千枚岩夹薄层状结晶灰岩为主;2)斜坡结构,主要为逆向坡,岩体破碎,属倾倒拉裂式崩塌;泥石流:1)沟道物源丰富,其物源主要源自沟道拉槽和下切,引发沟道斜坡的崩滑体;2)地形地貌,山高谷深,地形陡峭,非常有利于地表水汇集,为灾害的发育提供一定的水动力条件;(3)提出了一种基于坡位等级的斜坡单元划分方法。通过比对基于地表水文过程的定义的三类“地形单元”划分方法,最终确定正反向DEM分析法更适用于高山峡谷地区斜坡单元的初步划分,结合地形因素(坡向、山体阴影等)、坡体结构与岩性组合等信息进一步修正得到边界优化后的初始“斜坡单元”,最终结合斜坡坡位(高坡位、中坡位和低坡位)划分,得到不同坡位的斜坡单元;(4)提出了高山峡谷地区多灾种易发性评价结果融合方法。对研究区崩塌、滑坡、泥石流三类地质灾害分别单独开展易发性评价并进行结果融合,对于同一个区位的崩塌、滑坡易发性级别和泥石流易发性级别并不完全相同问题,本文将泥石流的易发性评价从流域单元上归结到沟道上,根据各类灾种在研究区的发育程度及易发等级进行叠加,得到兼顾多灾种的地质灾害综合易发性评价结果,避免了直接叠加后易发等级提升;(5)得到了研究区10年、20年、50年、100年一遇多种降雨工况下的地质灾害危险性评价结果。求取不同降雨频率下研究区年最大日降雨量,根据其对地质灾害的贡献率叠加易发性进行计算,将研究区划分为地质灾害危险性极高、高、中和低等四个区域。在100年一遇降雨工况下,极高危险区面积85.74km~2,占该研究区面积的30.0%。更多还原

【Abstract】 Geological disasters occur frequently in alpine and canyon areas,which pose a great threat to human life and property.As a typical means of disaster prevention and reduction,geological disaster susceptibility(risk)evaluation has always been a research hotspot.Although the research on regional geological hazard assessment has been developed for decades,it still faces many challenges,especially in the mountainous and canyon areas with complex geological conditions.Taking the Bank of Zagunao River in the east of Lixian County,Sichuan Province as the study area,the paper illestrates the main control factors based on the full analysi,development characteristics,distribution pattens and geological conditions of disasters in the study area.Based on the proposed improved slope unit division method,further carry out the susceptibility evaluation of three types of geological disasters,and put forward the fusion method of three types of susceptibility results to form the comprehensive results of the whole rigion.Finally,the risk assessment of geological hazards in the study area is carried out based on different rainfall conditions.The main research results are as follows:(1)The characteristics of geological hazards in the study area are found out.There are 225 geological hazard points in the study area,including 101landslides,85rockfalls(dangerous rocks)and 39 debris flows.The landslides in the area are mainly small and medium-sized traction soil landslides.The thickness of the sliding body is generally less than 30m,and most of them belong to shallow to middle landslides.Rockfalls are mainly distributed along the Zagunao River Valley,mainly small and medium-sized rock collapses.Debris flows are mainly distributed in the reach below Xuecheng town of Zagunao River,mainly small,mostly medium and low frequency debris flows;(2)The main controlling factors of various disasters in the study area are determined.Landslide:1)slope terrain gradient.The slope gradient of the developed landslide is mainly 20°-38°;2)Type of overburden:the loose overburden along the line is colluvium,slope deposit and eluvium of phyllite and schist,with high content of coarse particles,mostly in flake and strip shape,low content of clay particles and poor water stability.Rockfall:1)lithology,mainly phyllite mixed with thin-layer crystalline limestone;2)The slope structure is mainly reverse slope,with broken rock mass,belonging to toppling pull apart collapse.Debris flow:1)the gully is rich in provenance,which mainly comes from the trench and undercutting,resulting in the collapse and slide of the gully slope;2)Landform,high mountains,deep valleys and steep terrain are conducive to the collection of surface water and provide water supply power conditions for the development of debris flow;(3)An improved method of slope element division based on slope position is proposed.By comparing the three types of"topographic unit"division methods defined based on the surface hydrological process,it is finally determined that the forward and reverse DEM analysis method is more suitable for the preliminary division of slope units in Alpine canyon areas.Combined with the information of topographic factors(slope direction,mountain shadow,etc.),slope structure and lithology combination,the initial"slope unit"after boundary optimization is further modified,and finally combined with the division of slope position(upslope,middle slope and downslope).The slope elements with different slope positions are obtained;(4)The fusion method of multi disaster susceptibility evaluation results in Alpine canyon area is proposed.The susceptibility evaluation of collapse,landslide and debris flow in the study area is carried out separately and the results are integrated.For the problem that the susceptibility level of collapse and landslide and debris flow in the same location are not exactly the same,this paper summarizes the susceptibility evaluation of debris flow from the watershed unit to the gully,determines the weight according to the development degree of various disasters in the study area,and carries out weighted superposition,Finally,the comprehensive geological hazard susceptibility evaluation results considering multiple disasters are obtained;(5)The risk assessment results of geological disasters under different rainfall conditions in the study area are obtained.Calculate the annual maximum daily rainfall in the study area under different rainfall frequencies,and calculate the superposition susceptibility of its contribution rate to geological disasters.The study area is divided into four areas with high,high,medium and low risk of geological disasters.Under the condition of 100 year rainfall,the area of extremely high risk area is 85.74 km~2,accounting for 30.0%of the study area.更多还原