基于Logistic回归和MCMC方法评价地震滑坡敏感性

Logistic回归模型(Logistic Regression,LR)在滑坡敏感性评价上应用广泛,但目前对于模型参数不确定性的研究较为缺乏。马尔可夫链蒙特卡罗(Markov Chain Monte Carlo,MCMC)方法能够结合参数的先验信息得到其后验分布,从而对估计参数的不确定性进行分析。为探索MCMC方法在Logistic滑坡敏感性模型构建中的有效性; 量化模型参数估计值的不确定性,以西南地区2013年4·20芦山地震,2017年8·8九寨沟地震和2014年8·3鲁甸地震为例,基于MCMC方法对Logistic回归模型的回归系数进行估计。构建了区域的地震滑坡敏感性模型,对模型参数的估计值进行了不确定性分析,并绘制了区域的滑坡敏感性图。结果表明:在芦山地震案例中,模型参数估计值的不确定性都比较低; 在九寨沟案例中,岩性因子的参数估计值不确定性较高; 在鲁甸地震中,岩性、剖面曲率和平面曲率的参数不确定性较高。总的来说,模型中的大多数参数估计值不确定性都较低。所构建的Logistic回归模型在三次地震滑坡事件中的预测精度都较高,AUC(Area Under ROC Curve)值均在0.9以上,这证明了MCMC方法对Logistic模型参数估计的准确性。在三次地震滑坡事件中,因子相对重要性最大的为高程,其次为距离断层的距离以及修正麦卡利烈度。研究为利用LR模型进行滑坡敏感性评价提供了一种新的思路和方法。     

库水位升降对李家坡滑坡稳定性的影响

以三峡库区巫山李家坡滑坡为研究对象,依据勘察资料和试验资料等,应用地学软件GeoStudio中的SEEP模块和SLOPE模块建立相应的模型,用实时监测数据对模型进行校正,用校正后的模型模拟库水位以不同速率升降对滑坡稳定性的影响。研究结果表明:水库型滑坡稳定性受库水位升降速率影响明显,稳定性变化主要受静水压力、动水压力、库水浮托力、岩土体物理力学性质变化等共同影响,变化趋势由占主导地位的影响因素决定。     

ASSESSING LANDSLIDE SUSCEPTIBILITY BY INCORPORATING THE SURFACE COVER INDEX AS A MEASUREMENT OF VEGETATIVE COVER

Local environmental conditions are known to be the most influential in landslide dynamics. Some variables, such as slope, elevation, lithology, vegetative cover, and soil type, are more common and influential than others. Every variable, except for vegetative cover, has been incorporated into many different statistical models as a continuous variable showing nuances and differentiation among the data. In regions where vegetative cover is the single most important variable in determining slope stability, a land cover classification cannot provide the level of information required for efficient modeling of landslide events. It is hoped that the surface cover index (SCI) can be used to numerically assess vegetative cover by using Landsat imagery and sub‐pixel analysis. Two models utilizing simple raster calculations involving slope and the SCI were created. Each model was then assessed and validated for accuracy by using a user‐created multi‐temporal landslide inventory of the Dominical, Costa Rica area. Results determined that normalized inputs of slope and SCI can produce an algorithm with a high degree of accuracy and proved that the SCI can be used in assessing landslide hazard in a tropical forest environment. Copyright © 2011 John Wiley & Sons, Ltd.     

Monitoring and deformation analysis of pushed landslide changing water level in the Three Gorges reservoir

The typical pushed landslide deform becomes stronger when water fills in the Three Gorges reservoir. In order to better recognize the landslides deformation characteristics and prevent the disaster by the water change regulation, the paper takes an example of the features of geological conditions and deformation of Liangshuijing landslide in Yunyang which is the typical pushed landslide in the Three Gorges reservoir, and designs monitoring project. Through monitoring data including the surface displacement, ground fissure, deep displacement, ground water level, rainfall and macroscopic patrol, the variety law and relationship among monitoring data are obtained. The regularity of landslide deformation and its deformation velocity are concluded when the variation of the rainfall and water level change. Combined the variation of bands-stabilization coefficient, deformation laws of the pushed landslide by the rainfall or the reservoir water are obtained. The deformation caused by rainfall is large in the back landslide, while the deformation caused by hydrodynamic pressure is large in the front landslide. The higher the water level, the severelier of the influence. The deformation is largely influenced by hydrodynamic pressure when reservoir water declines sharply in the front landslide, and the deformation is the largest when rainfall and reservoir sharpe water decline happened simultaneously in the whole landslide. The law provides scientific basis for reduction and prevention disaster of the pushed landslide.     

宁夏回族自治区西吉县地震诱发型黄土滑坡发育特征与分布规律

地震诱发型黄土滑坡是宁夏回族自治区西吉县最严重的地震次生灾害。该区域西南部滑坡规模大,密度高,其主要类型是低角度、高速、远程黄土滑坡。西吉县地震活动处于活跃期,老滑坡在地震、降雨等诱发因素下极易复活,严重威胁当地群众的生命财产安全,阻碍社会、经济的发展。基于西吉县地质灾害详细调查资料,从规模、形成时代、滑体厚度等方面对地震诱发型黄土滑坡进行了分类统计。结合实地调查资料和遥感解译成果,分析了滑坡的边界特征、表部及内部特征、变形特征、滑动特征,并进一步总结了滑坡的空间分布规律和时间分布规律,为地震滑坡的形成机理研究提供了理论基础。     

GIS支持下川滇黔接壤区滑坡危险性评价

川滇黔接壤地区是中国滑坡灾害的多发区,区内共有崩塌、滑坡等地质灾害隐患点1.2万余处,对100余万人的生命与财产安全构成威胁,严重影响当地人民生产、生活安全与可持续发展。选择坡度、相对高差、到活动断裂带距离、年均降雨量和年均大雨日数5个因子作为滑坡危险性的评价因子,在GIS支持下获取各因子的贡献权重,根据贡献率模型在空间叠加下生成研究区滑坡危险性评价图。结果表明:(1)研究区1.92×105 km2面积中,极高危险区3.92×104 km2,高危险区4.34×104 km2,中危险区4.58×104 km2,低危险区3.92×104 km2,稳定区2.42×104 km2,中度以上危险区面积占研究区总面积的67.00%;(2)极高危险区主要分布在小江—安宁河深大断裂两侧以及金沙江、雅砻江等深切河谷中,显示出活动断裂带和地貌对滑坡危险性的宏观控制作用;(3)中度以上危险区内人口总量约1 152.31万人,占总人口的32.17%;GDP约419.88亿元,占研究区总量的28.75%,因此加强川滇黔接壤地区地质灾害防灾减灾能力建设已刻不容缓。     

滑坡综合治理方案比选评价模型

为了更好地比选滑坡综合治理方案,针对影响治理方案因素的复杂性和不确定性,以安全可靠性、环境协调性、经济合理性、技术可行性、施工难易、施工工期等做为评价因子,建立了基于熵权决策法的滑坡综合治理方案比选评价模型.根据专家意见建立判断矩阵,利用熵权决策法的原理确定"理想点";通过计算4个设计方案与"理想点"的贴近度与距离来确定方案的排序.结果表明,方案二(锚索抗滑桩与截排水相结合)为最优方案.熵权决策法克服了传统评估方法中主观确定权数的缺陷,保证计算过程和结果的客观性,是一种可行的、定量的滑坡治理方案比选方法.     

地震和暴雨工况下边(滑)坡稳定性分析方法评价

地震和暴雨同时作用是自然界中引发边(滑)坡灾害的一种极端工况.在分析地震和暴雨同时作用于边(滑)坡的稳定性时,现行规范只能采用将地震及暴雨影响简单叠加的方法.采用GEO-SLOPE软件,对川藏公路和西攀高速公路上的典型边(滑)坡工点,采用动力有限元与极限平衡理论相结合的方法,分析它们在地震和暴雨共同作用下的稳定性,探索采用将地震与暴雨工况简单叠加,以及地震和暴雨耦合分析这两种方法评价边(滑)坡稳定性的差别,并对现行规范计算方法的适用性作出评价.结果表明,地震和暴雨的耦合作用对边(滑)坡稳定性的影响大于地震、暴雨单独作用的叠加对边(滑)坡稳定性影响.     

三峡库区动水压力型土质滑坡排水管布置优化——以卧沙溪滑坡为例

[目的]为降低动水压力型滑坡体内的动水压力,提高其稳定性,采取布设水平排水管的措施对该类型滑坡进行治理,并对排水管的布设方案进行优化,为同类滑坡的加固设计以及获得高效合理的排水管布设方案提供参考。[方法]利用土体级配曲线,采用间接方法近似确定滑体土土—水特征曲线,并尝试通过FredlundXing函数模型预测获得滑体土非饱和渗透函数曲线。采用均匀设计方法、有限元、神经网络和遗传算法相结合的综合集成方法开展排水管布设方案优化研究。[结果]获得了卧沙溪滑坡最优的排水管布设方案为:管长L为26.6m,间距D为6.88m,倾斜角θ为7.3o。[结论]采用该排水方案加固后的滑坡安全系数为1.101,大于设计安全系数1.10,满足滑坡加固安全与经济的要求。     

Shear Deformation Properties of Sliding Zone Soil and Its Effect on Sliding Mechanism of a Landslide in the Three Gorges Reservoir Area

The mechanical properties of slip soil play a key role in landslide stability. In order to study this control mechanism, multigroup experiments on the slip soil of a landslide were conducted in the Three Gorges reservoir in Zigui county involving consolidated quick direct shear test and consolidated drained direct shear test, through which the strain hardening property of this slip soil has been studiedas well as mechanism of landslide deformation resulting from the strain hardening slip soil. The results show that from plastic deformation to shear failure, the shear stress applied to this slip soil increases all the way. After repeated shearing, its shear strength increases, and the greater the normal stress, the more the shear strength increases, in which process the angle of internal friction contributes the most to its shear strength variation. Through the field investigation and numerical modeling, how the strain hardening slip soil affects the landslide stability was studied. In the process of sliding, the frictional strength of the strain hardening slip soil increases after being shearing, leading to the consumption of the landslide’s kinetic energy, following the phenomenon that a temporary steady state occurs after a short distance sliding.