【作者】 彭大雷；

【导师】 许强；

【作者基本信息】 成都理工大学 ， 地质工程， 2018， 博士

【摘要】 黄土主要分布在我国干旱和半干旱地区,其覆盖面积占中国大陆地表面积的6%;由于其成因特殊,也被认识最易被侵蚀的土壤,黄土相关地质灾害数量占到全国的三分之一;同时这些灾害还具有点多面广、种类全、隐蔽性强、地区差异明显、防灾难度大等特点。目前针对黄土滑坡致灾因素和灾变机理国内外学者做了大量的研究并取得了丰富成果;但是针对黄土滑坡成灾模式和演化过程,并结合地学新技术新方法,建立黄土滑坡潜在隐患早期识别方法,并对不稳定斜坡体进行提前识别、发现和预警,这对黄土地区防灾减灾具有重要的意义。本文解决了黄土滑坡潜在隐患早期识别方法这一难题,提出了“地质判识”和“技术识别”有机结合的潜在黄土滑坡识别(判识)的技术方法体系,从不同角度和尺度来对滑坡形成过程中的变形特征和成灾前兆信息进行捕捉和识别;并将地质判识方法和“天-空-地”多源立体观测方法相融合,对研究区潜在的黄土滑坡进行早期识别;甄别出潜在黄土滑坡具体位置,并对其危害范围进行预测。本论文取得的主要成果如下:(1)建立了黄土高原地区典型黄土滑坡数据库,分析了滑坡形成基本条件、发育过程的变形特征和基本演化规律;结合黄土滑坡破坏地质-力学机理,揭示了黄土崩塌、黄土内滑坡、黄土基岩接触面滑坡、黄土基岩滑坡四类基本成灾模式;基于其不同力学行为和致灾因素,细分了常见的11类成灾模式;编制了黄土滑坡潜在隐患早期识别图谱,构建了初始状态阶段易发性识别方法、时效变形阶段早期识别方法、累进破坏阶段临灾识别方法和破坏堆积阶段成灾识别方法。(2)通过现场地质调查和低空摄影测量航测,查明了研究区的工程地质条件,绘制了研究区高精度DEM,解译了历史滑坡;厘清了黄土滑坡主要类型,并揭示了黄土滑坡两区7段空间分布规律,分析了研究区黄土滑坡的发育特征,总结了地下水位和地层产状两类主要的致灾因素;此基础上,提出了黄土基岩型、静态液化型、滑移崩塌型和黄土泥流型四类黄土滑坡成灾模式。(3)通过近50年高分辨率卫星影像解译,编制了黑方台黄土滑坡数据库,分析了黑方台黄土滑坡时空演化特征,揭示了群集发生、从东往西、模式转变、相互重叠和渐进后退时空演化规律;提出了“塬边沟壑区”和“滑坡空区”两类地貌识别标志;结合2015-2018年发生的30多起新滑坡的现场调查,验证了该方法的可靠性和适用性,从而建立了黄土滑坡潜在隐患高分辨率卫星影像早期识别方法。(4)通过布置基础控制点和地面相控点,提高了低空摄影测量成果的精度,依据航测前安装的GPS监测结果,验证了低空摄影测量精度可靠性和方法可行性;通过对典型滑坡过程重建再现,认识了黄土滑坡滑动过程,发现了静态液化型滑坡的体积松散系数约为1.4;通过土洞、裂缝和无序田埂分布与黄土滑坡发育的空间配套关系,成功预测了2017年2月新发生滑坡的边界;通过近两期DSM小变形差分计算(介于0.1-1m),甄别出党川段多处黄土滑坡隐患点;通过“群防群测”和现场调查,对潜在隐患点进行复核;新发生的2017年2月、2017年10月和2018年8月黄土滑坡验证了黄土滑坡潜在隐患低空摄影测量早期识别方法的可靠性。(5)基于物探、现场试验和浸润线监测,总结了地表裂缝和无序田埂、地下水雍高与富集地段和黄土边坡临界水位三类地质判识标志;基于地形地貌、地层产状、裂缝发育特征、斜坡体变形速率、地下水特征、边坡临界水位、坡脚变形状况和成灾前兆信息,建立了基于地表活动的黄土基岩型、滑移崩塌型、黄土泥流型和静态液化型滑坡潜在隐患点综合识别方法。(6)通过“天-空-地”一体化技术识别方法,确定了党川4#为黄土滑坡潜在隐患点;通过大量调查发现除黄土本身特性(内聚力C和内摩擦角φ)外,静态液化型黄土滑坡运动路径的黄土含水率(基底液化系数)是影响滑坡运动距离的关键因素;通过大量室内试验统计分析,确定了黄土内摩擦角φ值和内聚力C取值范围,再通过对某些已发生滑坡堆积范围的反演分析,确定黄土内聚力具体取值。通过已发生滑坡的实际运动堆积范围的样本学习和反演分析,确定基底液化系数取值范围;接着通过党川4#的影像解译与现场调查,拟合了滑坡潜在滑面并确定了滑坡规模;关键参数确定后,便可利用数值模拟手段实现潜在滑坡运动堆积范围的正演分析和预测评价,结果表明潜在滑坡对坡下的公路和房屋威胁程度较大;提出了利用数值模拟正演和预测静态液化型黄土滑坡危害范围的方法,并据此开展量化风险评估。更多还原

【Abstract】 Loess mainly distributes in arid and semi-arid areas of China,with an area of 6% of the surface area of China.Because of its special origin,it is also known as the most easily eroded soil.And the number of loess-related geological disasters accounts for one third of the country.At the same time,these disasters also have many characteristics,such as many points,full range of types,strong concealment,obvious regional differences,and large difficulty of disaster prevention.At present,a lot of research has been done on the disaster-causing factors and mechanism of loess landslide and rich results have been achieved.But aiming at the failure modes and evolution process of loess landslide,and combining with new geoscience technology and new methods,an early identification method of potential potential hazards of loess landslide is established,and the unstable slope body is identified,discovered and warned in advance,which is of great significance for disaster prevention and mitigation in loess area.This paper solves the difficult problem of early recognition of potential loess landslides,and puts forward a technical method system for potential identification of loess landslides,which combines "geological identification" and "technical identification".They could capture the deformation characteristics and precursory information of hazards in the process of landslide formation from different spaces and scales.The potential loess landslide in study area is early recognized by combining the geological identification method with the "Space-Sky-Ground" multi-source stereo observation method,which could predict its hazard scope.The main results obtained in this paper are as follows.(1)The database of typical loess landslides in the Loess Plateau is established,and the basic conditions of landslide formation,deformation characteristics and basic evolution laws are analyzed.Combining with the geological-mechanical mechanism of loess landslides,four basic failure modes are revealed: loess collapse,landslides within loess,loess-bedrock interface landslide and loess-bedrock landslides.Based on its different mechanical behavior and disaster-induced factors,11 common failure modes are subdivided.Through the different identification factors established in different stages of evolution,the early identification map of potential loess landslide is compiled.The advanced identification index is established the initial identification index is established the state stage vulnerability identification method,the time-dependent deformation stage early identification method,the progressive failure state disaster identification method and the failure accumulation stage disaster identification method.(2)Through on-site geological survey and aerial survey of low-altitude photogrammetry,the engineering geological conditions of the study area are identified,the high-precision DEM of the study area is drawn,and the historical landslides are interpreted.The main types of loess landslides are clarified,and the spatial distribution law of seven sections of loess landslides in the two areas is revealed,the development characteristics of loess landslides in the study area are analyzed and summarized.On the basis of two main disaster-causing factors of groundwater level and stratum occurrence,four disaster-causing models of loess landslides are put forward,namely,loess bedrock type,loess flowslide,slide-collapse type and loess flow type.(3)By interpreting the high-precision remote sensing images in the past 50 years,the loess landslide database of loess landslide in Heifangtai terrace has been compiled,and the temporal and spatial evolution characteristics of Heifangtai loess landslide have been studied.Three laws of the temporal and spatial evolution have been summarized.Two landform identification criteria,i.e.the gully area on the edge of the plateau and the gap area of the landslide,are proposed.In the preceding 2015-2018 years,more than 30 new landslides have verified the practicability and accuracy of two landform identification criteria.Therefore,recognition method for potential loess landslide by high resolution satellite images is established.(4)The precision of closed-range photogrammetry is enhanced by arranging the basic control points and ground phase control points in the study area.According to the GPS monitoring results installed before aerial survey,the reliability and feasibility of low-altitude photogrammetric accuracy are verified.Through the reconstruction of a typical landslide process,the sliding process of loess flowslide is understood.The coefficient of volume expansion of loess flowslide is about 1.4.Through the spatial matching relationship between the distribution of cracks,sinkholes and disordered ridges in the cropland,and the new boundary of potential landslides was predicted.On this basis,through the last two three-dimensional point cloud difference calculation,the deformation area between 0.1-1 m is extracted,and many potential loess landslides in Dangchuan section are identified.Based on the results of "technical method" identification,the potential loess landslides are checked through local resident’s survey and field investigation.New loess landslides occurred in February 2017,October 2017 and August 2018 verified the reliability of the early identification method for potential loess landslides by closed-range photogrammetry.(5)Based on geophysical prospecting,field test and spring outlet line monitoring,three kinds of geological identification indicators are summarized: surface cracks and disordered ridges,high and enriched areas of groundwater and critical water level of loess slope.Based on topography and landform,fracture development characteristics,slope deformation rate,groundwater characteristics,relationship between saturation line and loess thickness and landslide hazard characteristics,a comprehensive identification method for potential hazard points of loess bedrock type,shallow collapse type,loess mud flow type and static liquefaction type landslide is established.(6)Through the "Space-Sky-Ground" integrated technology identification method,DC#4 is identified as the potential loess landslide.Through a large number of investigations,besides itself characteristics of loess(cohesion C and internal friction angle φ),the water content(liquefaction coefficient of basement)of the movement path of the loess flowslide is the key factor affecting the movement distance of the landslide.Through statistical analysis on a large number of laboratory tests,the values of internal friction angle φ and value range of cohesion C of the loess are determined.And then through the inversion analysis of some landslide accumulation zone,determine the specific value of the cohesion of loess.The range of liquefaction coefficient of basement is determined by sample learning and inversion analysis of the accumulated range of actual movement of landslides that have occurred.Then the potential slide surface of landslide is fitted and the scale of landslide is determined by image interpretation and field investigation of DC#4.After the key parameters are determined,the forward analysis and prediction evaluation of the accumulation range of potential landslide motion can be realized by numerical simulation.The results show that potential landslides threaten highways and houses which are located at the toe of slopes.A method of forward modeling and hazard range prediction of loess flowslide are proposed,and quantitative risk assessment is carried out accordingly.更多还原