On the stability of landslides: A thermo-poro-elastic approach

Motion of a large rock mass down a slope can either take the form of a catastrophic landslide, or can exhibit self-stabilization, where the mass arrests on the slope, after moving only a short distance. In order to study the parameters that control the stability of the sliding process, a thermo-poro-elastic model is investigated both numerically and analytically. This model assumes that the physics controlling sliding stability is dominated by coupling between frictional heating, thermal pressurization and sliding velocity: A temperature increase due to frictional heating causes thermal pressurization within a fluid-saturated shear zone. The pressure rise leads to reduction of frictional resistance, which in turns leads to higher sliding velocities. Results demonstrate that the permeability of the sliding mass is an important factor in controlling the sliding stability: Low permeabilities lead to catastrophic landslides, by allowing high pore pressure to develop and friction to be reduced. In contrast, high permeabilities lead to rapid arrest by promoting pore pressure diffusion. A pore pressure – velocity phase plane is described, divided by a separatrix distinguishing between catastrophic and arrested sliding. In this phase plane minute changes in permeability dictate a bifurcation in the dynamics of landslides. A sensitivity study reveals that various geometrical and mechanical parameters can control the sliding process dynamics in a similar manner. It is hypothesized that a third sliding regime observed in nature, creep sliding, may be generated by a sequence of arrested events, where the number of arrested events/unit time dictates the apparent creep velocity.     

The safety distance of a tunnel under-traversing a slope body with a landslide-prone zone

At present, substantial scientific research achievements have been made in the research on landslide occurrence, movement mechanism, mitigation measures, and structural stability during tunnel excavation. However, the interaction mechanism of a tunnel under-traversing a slope body with potential landslides is still not well understood. Based on the field data provided by previous investigations in the study area, six sets of 1:100 laboratory experiment model tests were conducted to study the stability of the landslide-prone zone of the slope body with an under-traversing tunnel. The selected distances between the tunnel and the sliding surface are 1.5, 3, and 5 times of the tunnel diameter, respectively. The experiment results show the interaction between the landslide-prone zone and the tunnel, elucidating the effect of potential landslides during the tunnel excavation process and the reaction of the landslide slip on the tunnel structure. Several conclusions are obtained: ① During the process of tunnel excavation, the vertical displacement of the tunnel vault decreases with the increase of the buried depth. ② The vertical displacement of the sliding surface increases with the increase of the buried depth of the tunnel. The horizontal displacement of sliding surface decreases with the increase of the buried depth. ③ After the occurrence of a rainfall-induced landslide, the vertical displacement of the tunnel vault in the 1.5-diameter-distance case is 57.29% greater than that in the 3.0-dismeter-distance case.④ For a two-cave tunnel, it is suggested that the cave farther from the landslide toe should be firstly excavated since it may generate less structural deformation.     

黄土高原地震作用下黄土滑坡滑距预测方法

为评估黄土高原地区地震滑坡致灾区域,提出一种基于模糊信息优化处理的地震滑坡滑距预测方法。在野外调查、室内试验和分析的基础上,对黄土高原的地震滑坡类型、性质和影响因素进行分析。以摩根斯坦-普莱斯法计算黄土边坡的稳定性,建立边坡最小安全系数与影响因素的关系,其影响因素主要包括地震烈度、比高、坡角、容重、内黏聚力、内摩擦角等,并在此基础上得到纯黄土地震滑坡滑距的影响关系。将黄土高原地区数次大震中采集到的93个样本数据进行归纳分析,建立模糊信息优化处理模型。所得的计算结果通过误差校验和与其他滑坡滑距预测方法进行对比,来证明本模型有较高的准确性。最后对天水市22个潜在滑坡的边坡进行滑距预测。     

Spatial Distribution of Seismic Landslides in the Areas of 1927 Gulang M8.0 Earthquake

The 1927 Gulang M8.0 earthquake has triggered a huge number of landslides, resulting in massive loss of people''s life and property. However, integrated investigations and results regarding the landslides triggered by this earthquake are rare; such situation hinders the deep understanding of these landslides such as scale, extent, and distribution. With the support of Google Earth software, this study intends to finish the seismic landslides interpretation work in the areas of Gulang earthquake (VIII-XI degree) using the artificial visual interpretation method, and further analyze the spatial distribution and impact factors of these landslides. The results show that the earthquake has triggered at least 936 landslides in the VIII-XI degree zone, with a total landslide area of 58.6 km². The dense area of seismic landslides is located in the middle and southern parts of the X intensity circle. Statistical analysis shows that seismic landslides is mainly controlled by factors such as elevation, slope gradient, slope direction, strata, seismic intensity, faults and rivers. The elevation of 2 000-2 800 m is the high-incidence interval of the landslide. The landslide density is larger with a higher slope gradient. East and west directions are the dominant sliding directions. The areas with Cretaceous and Quaternary strata are the main areas of the Gulang seismic landslides. The X intensity zone triggered the most landslides. In addition, landslides often occur in regions near rivers and faults. This paper provides a scientific reference for exploring the development regularities of landslides triggered by the 1927 Gulang earthquake and effectively mitigating the landslide disasters of the earthquake.     

Dynamic mechanisms of earthquake-triggered landslides

Earthquake-triggered landslides usually cause great disasters,and yet their dynamic mechanisms remain poorly understood.This paper will derive a general conceptual landslide model from the geometric and kinematic features of the most landslide masses triggered by the 2008 Wenchuan earthquake.Kinematic characteristics and dynamic processes are simulated here by means of finite element method(FEM)based on the dynamic process of the discontinuous deformable body.The calculated results presented the whole course of landslide motion,and displayed some typical kinematic characteristics such as initiation,sliding,ejection,collision,flying in the air,and climbing of landslides.The simulation result also shows that,under combined seismic inertial forces and gravity,landslides will start to slip once it overcomes the friction between the sliding mass and slip-bed,then it will move from slow to fast along the slippery bed until it ejects from the slip-bed.Moreover,the high frequencies and serious damages by landslides in the Wenchuan earthquake are caused by the strong ground motion on the mountain slopes in and around the epicenter that was dramatically amplified owing to both resonances produced by the seismic event and topographical amplification by seismic motion.In addition,the modeling results suggest that the direction,amplitude,frequency,and duration of strong ground motion have a great influence on the stability of landslide mass.Therefore,the study helps us better understand dynamic mechanism of landslides,seismic hazard assessment,and dynamic earthquake triggering.     

地震黄土滑坡滑距预测的BP神经网络模型

地震滑坡的滑距与重力滑坡的滑距有着显著的不同,科学预测地震发生时黄土地区滑坡的滑动距离是合理评估黄土地区滑坡风险和减轻滑坡灾害的有效方式之一。基于海原特大地震诱发黄土滑坡的400组野外调查数据,通过引入BP神经网络算法,论证了BP神经网络模型用于预测黄土地震滑坡滑距的适宜性和可行性;建立了地震诱发黄土滑坡滑距的BP神经网络预测模型,并通过67组数据进行了验证。BP神经网络算法和传统多元线性回归、多元非线性回归结果的对比显示,BP神经网络的预测更接近真实情况,具有较为理想的预测效果,可以用于黄土地震滑坡滑距的预测,并为圈定较为可靠的致灾范围提供依据。     

地震作用下黄土斜坡的稳定性分析预测

基于对中国西部黄土地区大量地震滑坡实例的考察分析,对影响黄土斜坡稳定性的各类因素尤其是地震因素进行了分析,讨论了黄土斜坡滑裂面的产生机制及几何特征．在此基础上提出了一种基于随机搜索法和遗传算法确定黄土斜坡最危险滑裂面,进而对区域黄土地震滑坡进行预测的方法．以回回川滑坡为例进行了验证．结果表明,该方法具有较好的效果和实用性．     

基于颗粒流方法的黄土地震滑坡数值模拟

基于颗粒流理论研究土质边坡动力稳定性及其滑动过程是近年来滑坡研究的一个新热点。在野外调查和室内试验的基础上,通过标定土体细观参数、模型建立、动力输入、动态监测等过程,利用PFC2D程序模拟了西吉县兴平乡堡湾村下马达子滑坡的失稳破坏运动过程,得到了该滑坡的破坏运动机理。得到如下结论：(1)下马达子滑坡的失稳机制是在地震作用下斜坡前缘牵引、后缘推挤,使得坡肩受拉发生破坏,失稳后坡肩位置较大的速度和位移是地震滑坡破坏力强、致灾范围大的主要原因;(2)黄土地震滑坡的滑坡后壁相对平缓,这是区别于重力滑坡的重要特征之一;(3)颗粒流模拟得到的滑坡前后相对高差和长度与实际情况较为吻合,因此,颗粒流方法可以用于地震滑坡滑距的预测。     

山西地震带中与强震活动有关的两种滑坡

本文以滑波理论为依据，总结了山西地震带的两种不同特点的滑坡。即：振荡式滑坡及触发式滑坡。虽然两种滑坡都可分为变形、解体、滑动、毁灭等四个阶段，但其动力不同。振荡式滑波的滑动面倾角小，因而滑力来源于强震振动，而触发式滑坡的滑动面倾角大，因而滑力来自滑体本身静荷载。对两种滑坡的研究对预防及减轻强震带来的次生灾害有重要的意义。     

M5'模型树算法和无人机航拍影像在震后崩塌滑坡分析中的应用——以鲁甸M_S6.5地震为例

利用高分辨率无人机航拍影像,结合基本地质资料,分析了影响2014年8月3日鲁甸M_S6.5地震震后崩塌滑坡分布的主要因素,使用M5'模型树算法建立了崩塌滑坡密度与其影响因子间的分段线性模型,并检验了该模型的预测性能。结果表明,地震诱发的崩塌滑坡分布受断层距、岩土体结构强度、坡度、植被条件等的影响,其中,断层距、岩土体结构强度及坡度等为主要影响因素;崩塌滑坡易发生在结构破裂区及坡度为38°~50°的区域,其分布密度随断层距的增加而减小;利用M5'模型树算法建立的模型体现出崩塌滑坡分布与其影响因子间复杂的非线性关系,模型检验结果显示,理论模型与实际关联函数间的相关系数达到0.88,因此,可利用该模型预测地震诱发的崩塌滑坡的分布。     

Complex dynamics of repeating and river-blocking landslides in Jiangda during 2018

Two large landslides successively blocked the Jinsha River at the same location in Jiangda Village on October 10 and November 3,2018,respectively.The dynamic processes and possible interactions of the two landslides need to be studied to better understand the physical processes involved,and to provide information on future disaster mitigation.We investigated their force histories and sliding directions by inverting regional broadband seismograms.The scale of the October landslide was approximately three times that of the November event.The October event revealed a particularly strong deceleration force,which may have been caused by a collision between the sliding mass and ground surface.In contrast,the November event had a relatively weaker deceleration force,indicating that it may have been gradually stopped by the landslide dam formed during the October landslide.The sliding directions of the two landslides differed significantly in terms of both horizontal and vertical directions,indicating a change in their sliding surfaces.We conclude that unconsolidated materials at the top of the October landslide continued sliding along a curved slope during the November event.From our seismic models of dynamic processes,both the October landslide and local background may have affected and even changed a subsequent landslide's mechanism.     

潜在地震滑坡危险区区划方法

不同地区地震活动的强度和频率是不同的.基于地震危险性分析的地震滑坡危险研究在综合了地震烈度、位置、复发时间等因素的基础上,考虑了地震动峰值加速度时空分布的特点,可以有效地应用于潜在地震滑坡危险区区划.以汶川地震灾区为研究对象,根据研究区的地质构造、地震活动特点等划分出灾区的潜在震源区,对该区进行地震危险性分析,并在此基础上采用综合指标法做出基于地震危险性分析的地震滑坡危险性区划.所得地震滑坡危险性区划按照滑坡危险程度分为高危险、较高危险、较低危险和低危险四级,表示未来一段时间内研究区在遭受一定超越概率水平的地震动作用下,不同地区地震滑坡发生的可能程度. 本文给出的地震滑坡危险性区划结果中,汶川地震滑坡崩塌较发育的汶川、北川、茂县等部分区域均处于高危险或较高危险区域;在对具有较高DEM精度的北川擂鼓镇地区所作的地震滑坡危险性区划中,汶川地震中实际发生的地震滑坡灾害与地震滑坡危险区划结果表现出较好的一致性.对区域范围而言,基于地震危险性分析的地震滑坡区划,可为初期阶段的土地规划使用及重大工程选址提供参考.     

汶川地震高速远程滑坡机制实验研究

汶川大地震触发了多处高速远程滑坡,导致了大量的人员伤亡及财产损失。其中,东河口滑坡是这次地震触发的最为典型的高速远程滑坡之一,同时也是目前备受关注、争论颇多的滑坡之一。野外调研结果表明,该滑坡的成因和动力特征主要包括震裂溃屈、水平抛射、碎屑流化和振动液化等4个方面。为了对该滑坡滑动过程中的振动液化这一动力特征进行模拟再现,在东河口滑坡体上采集了具有代表性的滑带土作为试验样品,并以该地震时的实测地震波作为动力输入,利用目前国际上最先进的DPRI环剪试验机,对滑坡滑动过程中的振动液化现象进行了一系列环剪试验研究。结果表明,地震作用过程中,发生在滑坡潜在滑面上的振动液化现象是导致高速远程滑坡产生的一个重要因素;伴随着振动液化过程,滑体的剪切强度迅速降低并产生逐渐增大的剪切位移,为高速远程滑坡的形成提供了条件     

汶川地震滑坡危险性评价——以武都区和文县为例

利用GIS技术详细研究汶川地震在甘肃省陇南市武都区和文县触发的滑坡地质灾害的分布规律及其与地震烈度、地形坡度、断层、高程、地层岩性的相关关系,采用基于GIS的加权信息量模型的崩塌滑坡危险性评价方法,对研究区的地震滑坡危险性进行学科分析。结果表明：极高危险区在高程上主要分布在集水高程区,高度危险区主要沿白水江、白龙江等主干河流两侧极高易发区的边界向两侧扩展,轻度和极轻度危险区面积占比较小,主要分布在低烈度、活动断裂不发育、人类活动微弱的高海拔地区,另外国道G215沿极高危险性区域分布明显;利用危险性等级分区结果统计人口公里格网数据,得到武都区和文县潜在影响人口,发现研究区约78万人将受到地震滑坡灾害的潜在影响。     

Caldera rim collapse: A hidden volcanic hazard

Following the emblematic flank collapse of Mount St Helens in 1981, numerous models of flank sliding have been proposed. These models have allowed to largely improve the understanding of mechanisms involved in such landslides, which represent a tremendous risk for populations living around volcanoes. In this article, a new mode of landslide formation, related to buried calderas, is described. The model emphasizes the paramount importance of the hidden ring fault that, even when the caldera is buried, still remains a plane of weakness in the core of the edifice. Under certain conditions, this plane of weakness becomes activated as the upper part of a pre-existing critical slip surface and is used in the emplacement of huge landslides which travel downslope at a very high velocity. A natural example is taken from Piton de la Fournaise Volcano (La Réunion Island, Indian Ocean). It reveals that the primary cause triggering caldera rim collapse is partial unbuttressing of the flank of the volcano. In the natural example, this occurs through regressive erosion that excavates deep canyon in the direction of the buried caldera but other mechanisms may exist. On account of the large volumes of material involved in caldera rim collapse as well as their long runout distances, such a volcanic hazard should be taken into account on every volcano where buried calderas are suspected.     

由地震活动参数分析龙门山-岷山断裂带的现今活动习性与强震危险性

根据最近28年的区域台网地震资料,利用b值空间分布及断裂带分段的多地震活动参数值的组合方法,结合历史强震背景,分析了沿川北龙门山-岷山断裂带不同断裂段的现今活动习性,并初步判别出了潜在的强震危险段落。研究结果表明:龙门山断裂带中-南段存在6个具有不同现今活动习性的段落,其中,绵竹-茂县段处于相对高应力背景下的频繁中-小震活动状态,被认为是龙门山断裂带上未来最可能发生强震的地段;江油-平武段处于相对高应力背景下的稀疏中-小震活动状态,未来有可能发生中强地震。而岷山断裂带中的岷江断裂段和虎牙断裂段,以及叠溪隐伏逆断层地区均具有相对偏低的应力水平,可能与其不久前分别发生过大地震和强震有关,未来不太长的时期内复发大地震的可能性较小。     

门源M6.9地震诱发地质灾害特征研究

2022年1月8日发生的门源M6.9地震诱发了崩塌、滑坡、砂土液化、地裂缝等多种同震地质灾害。通过对门源M6.9地震地质灾害进行现场调查,得出了地质灾害的分布特征和各类型地质灾害的主要特点,分析了地震地质灾害不发育的原因,并对地震地质灾害的长期效应进行了分析预测。研究结果表明：门源地震诱发地质灾害主要分布在震中附近;崩塌、落石总体规模较小,滑坡多为岩质滑坡,且以冰碛物和表层岩土体的溜滑为主。受表层土体冻结和孔隙水压力消散的影响,饱和砂土液化沿较窄的地裂缝呈串珠状分布,喷出物多为粉细砂。地震形成了4条左旋左阶斜列的地表破裂带,并在极震区内形成了大量的地裂缝。断层破碎带对地震动的阻隔作用、覆盖层薄、地表土冻结可能是造成本次地震地质灾害总体不发育的主要原因;地震产生的大量地裂缝导致斜坡和堆积体的稳定性减弱,在耦合集中降雨、冻融作用等因素后可能诱发滑坡灾害,松散堆积于沟床处的崩滑物作为物源,可能会增加地震影响区泥石流灾害的风险。     

Numerical simulation of the 1992 Flores tsunami: Interpretation of tsunami phenomena in northeastern Flores Island and damage at Babi Island

Numerical analysis of the 1992 Flores Island, Indonesia earthquake tsunami is carried out with the composite fault model consisting of two different slip values. Computed results show good agreement with the measured runup heights in the northeastern part of Flores Island, except for those in the southern shore of Hading Bay and at Riangkroko. The landslides in the southern part of Hading Bay could generate local tsunamis of more than 10 m. The circular-arc slip model proposed in this study for wave generation due to landslides shows better results than the subsidence model, It is, however, difficult to reproduce the tsunami runup height of 26.2 m at Riangkroko, which was extraordinarily high compared to other places. The wave propagation process on a sea bottom with a steep slope, as well as landslides, may be the cause of the amplification of tsunami at Riangkroko. The simulation model demonstrates that the reflected wave along the northeastern shore of Flores Island, accompanying a high hydraulic pressure, could be the main cause of severe damage in the southern coast of Babi Island.     

地震发生过程的有限单元法模拟——以苏门答腊俯冲带上的大地震为例

地震预报由目前的经验预报走向物理预报,数值模拟地震过程是其中的关键.文中应用统一的数学公式表述了速率相关的摩擦接触中黏着（sticking）和滑移(sliding)这两种不同的运动状态;有限元计算中采用静力显示的时间积分方法,基于R最小策略,控制时间步长以保持力学状态变化稳定,从而保证有限元计算过程平稳、收敛.以2004年发生过M_m=9.3特大地震的苏门答腊俯冲带为例,模拟了俯冲带上俯冲板片与上伏板块之间的闭锁、解锁、滑动到再闭锁这一准周期性过程,即地震的孕育、发生过程.计算结果表明,俯冲带上具有较大尺度、介质均匀、摩擦系数相同的区域是产生大规模、大幅度整体突然滑动（即大地震）的条件;模拟的苏门答腊俯冲带上的大地震在时间上有准周期性,空间上有迁移特征,破裂由深部向浅部进行;此外,俯冲带的几何特征对大地震的震源位置有很大的影响.     

Parallel Fault Systems with Evolving Self-similar Sliding Zones

Catastrophic fault sliding is preceded by the development of sliding zones which grow further driven by the excess of the shear stress over friction at the loci of initiation. This growth is strongly affected by the interaction between the sliding zones. We propose a model of development of such zones based on two major simplifications. Firstly, each sliding zone is modelled as a disc-like shear crack driven by a pair of concentrated forces representing the excess of the shear stress over friction at the loci of initiation. Secondly, the interaction between these cracks is modelled based on the assumption that the distribution of their sizes is self-similar and the self-similarity is maintained in the process of their growth. We show that for parallel cracks the latter is only possible if the sliding zones are localised in a narrow layer. In this case the exponent and the prefactor of the distribution function are uniquely determined. The addition of new sliding zones does not change the distribution but rather increases the upper cut-off. This happens either by instantaneous growth of each added sliding zone to the maximum size producing the strongest microseismic event or by initiating a cascade of intermediate growth producing a series of smaller events. We determine the energy distribution associated with the cascade and the probability of hazardous events. We show that measuring the statistical properties of seismic energy alone is not sufficient for determining the parameters of the model; monitoring of fault deformation is also needed.