Reliability of landslide isopleth maps

  Following very heavy rainfall on 19/20 July 1983, 109 landslides occurred in the east of Findikli, Rize, north-east Turkey. The movements took place in completely weathered andesitic, dacitic and granitic rocks as well as slope debris. They extended over an area of approximately 25 km². The paper discusses the contour (isopleth) map prepared using data from the 1983 landslides and discusses its value for landslide hazard zoning. It is concluded that on the basis of 12 years of field evidence, a contour map derived from a precise inventory map can be a useful tool. Received: 28 November 1998 · Accepted: 15 May 1999     

Suspension force and mechanism of debris flows

The paper discusses the postulated suspension force, by which it is possible to explain some enigmatic phenomena observed in different types of mass movements. This force is generated in thick suspensions as a result of friction between sinking solid particles and static water. The suspension force is related to the seepage force but they have opposite directions. Both forces form flow networks. Having explained the suspension force, the paper describes how this influences the movement of material, particularly in debris flows. Enigmatic features and the mechanism of debris flows and lahars are explained by virtue of the suspension force. Electronic Publication     

福建崩塌、滑坡地质灾害现状及防治措施

福建省是一个地质灾害多发的地区,尤其以崩塌和滑坡最为严重。通过对福建省崩塌和滑坡地质灾害现状的分析,提出了针对崩塌和滑坡的防治措施。     

Large Deformation Finite-Element Analysis of Submarine Landslide Interaction with Embedded Pipelines

Submarine landslides represent one of the most significant geohazards on the continental slope in respect of the risk they pose to infrastructure such as deep water pipelines. A numerical approach, based on the finite-element method but using remeshing, was established in this paper to simulate large flow deformation of debris from a landslide and to quantify the loads and displacements imposed on pipelines embedded in the seabed. A simple two-dimensional elastic perfectly plastic soil model with plane strain conditions was employed in this analysis. The pipeline was restrained by a set of springs so that the load on the pipeline built up to a stable value, representing the limiting load at which the debris flowed over the pipeline. A parametric study was undertaken by varying the pipeline embedment and the relative strengths of the debris and seabed. The analysis results show that the various combinations of soil strength and embedment depth lead to different debris-pipeline movement patterns and consequently lead to rather different magnitudes of the loads imposed on pipelines. The pipeline is subjected to the largest load (an equivalent pressure of 11.5 times debris strength) from the landslide when it rests on the weakest seabed. The pressure is proportional to the debris material strength but varies inversely with the seabed strength for partially embedded pipelines. For all strength combinations, there is a critical embedment depth beyond which the force on the pipeline reduces to a very small magnitude.     

Unsaturated Infinite Slope Stability Considering Surface Flux Conditions

A slope stability model is derived for an infinite slope subjected to unsaturated infiltration flow above a phreatic surface. Closed form steady state solutions are derived for the matric suction and degree of saturation profiles. Soil unit weight, consistent with the degree of saturation profile, is also directly calculated and introduced into the analyzes, resulting in closed-form solutions for typical soil parameters and an infinite series solution for arbitrary soil parameters. The solutions are coupled with the infinite slope stability equations to establish a fully realized safety factor function. In general, consideration of soil suction results in higher factor of safety. The increase in shear strength due to the inclusion of soil suction is analogous to making an addition to the cohesion, which, of course, increases the factor of safety against sliding. However, for cohesive soils, the results show lower safety factors for slip surfaces approaching the phreatic surface compared to those produced by common safety factor calculations. The lower factor of safety is due to the increased soil unit weight considered in the matric suction model but not usually accounted for in practice wherein the soil is treated as dry above the phreatic surface. The developed model is verified with a published case study, correctly predicting stability under dry conditions and correctly predicting failure for a particular storm.     

High-resolution lidar-based landslide hazard mapping and modeling,UCSF Parnassus Campus,San Francisco,USA

Airborne lidar (light detection and ranging) was used to create a high-resolution digital elevation model (DEM) and produce landslide hazard maps of the University of California, San Francisco Parnassus Campus. The lidar DEM consisted of nearly 2.8 million interpolated elevation values covering approximately100 ha and posted on an 0.6 m horizontal grid, from which a set of 16 maps was produced. The first subset of maps showed aspects of the topography useful for landslide mapping, an engineering geological map and a qualitative slope hazard map. The second subset consisted of physics-based probabilistic landslide hazard maps for wet static, wet seismic, and dry seismic conditions. This case history illustrates the utility of lidar-based products, supplemented by field-based geological observations and physics-based probabilistic slope stability modeling, for the evaluation of existing and potential slope stability hazards on a steep and heavily forested site.      

膨胀土边坡失稳机理与加固技术研究

在膨胀土边坡病害处治工程中,对边坡范围内的土层分布、工程与水文地质条件等进行分析后,发现裂缝开展是导致边坡滑移的主因;结合桥墩桩体裂缝、桥头附近沥青路面层横向张拉裂缝的位置,确定出可能的软弱滑动面(带),并利用Geo-Slope软件评价其稳定性;基于极限平衡理论,运用反演分析方法,给出合乎实际的滑带土综合抗剪强度指标值;提出了总体整治方案。     

Research on Wenchuan Earthquake-induced LandslidesRapid Recognition from ZY-3 Imagery

Presently,regional earthquake-induced landslides is mainly obtained by field survey and visual interpretation from remote sensing images; but these methods are objective,and time-consuming.In this study,with a main data source of domestic high-resolution remote sensing images from ZY-3 satellite as well as the study area of the Wenchuan earthquake region,objects of multilevel landslides were established using the multi-scale optimum partition method based on in-depth analysis of landslide features.A recognition rule set of multi-dimensional landslides was also built through the combination of topographic features and image features,such as spectrum,texture,and geometry.Additionally,recognition models for landslide stratification were proposed based on the recognition models of high-resolution images and an understanding of the scenes.Through all of the aforementioned efforts,the spatial distribution of the seismic landslide as well as the sliding source area,transport area,and depositional area can be identified intelligently.The analysis results of the experimental area showed a minimum recognition accuracy of 82.97%,with the depositional zone of landslides being the easiest zone to recognize,and the effectiveness of the proposed method as well as ZY-3 data.These findings may provide technical support for regional earthquake-induced landslides investigations and further promote geological hazard application of domestic high-resolution satellites.      

Two-Dimensional SPH Simulations of Landslide-Generated Water Waves

Water waves generated by landslides have been of interest to ocean and coastal engineers, as well as to dam engineers. The present study uses a meshless and pure Lagrangian method known as smoothed particle hydrodynamics (SPH) to simulate nonlinear water waves due to landslides, with the aim of an accurate numerical prediction of the generation and propagation of such water waves. Validation is carried out by comparison between the computed prediction and experimental data of water waves generated by a two-dimensional triangular rigid body sliding into water. The calculated results show that the simulated water waves agree well with those observed in the experiment confirming the effectiveness and the accuracy of the proposed scheme.     

Modelling a viscous rock joint activated by rainfall: Application to the La Clapière landslide

The continuous evolution of sliding rock masses activated by rainfall combined with snowmelt will be discussed in this paper. The effects of precipitation on slip velocities during the periods separating failure events have already been studied in the literature by means of either pure statistical approaches or sophisticated numerical codes. A simple schematic model will be presented in this paper based on a crude physical and geometrical simplification of the rock mass hydromechanical system. This model enables simulating the correlations between rainfall/snowmelt data and slip velocities with relative efficiency. This model may be considered as an intermediate tool between purely statistical and more sophisticated numerical models; moreover, it is potentially useful for assessing the stability of civil engineering and open-pit mining slopes.