Seismic Slope Instability Research Articles

Numerical analysis of buried pipelines under seismic slope instability

Damage to buried pipes under seismic landslide actions has been reported in many post-earthquake reconnaissance. The landslide-pipe problem in the technical literature has been often investigated using simplified analytical methods. However, the analytical methods ignore the real mechanism of pipe response under natural dynamic slope instability. The dynamic slope instability is significantly influenced by its lateral boundary interface (LBI) characteristics. In this study, slope-pipe interaction (SPI) under seismic loading, focusing on the effect of LBI properties, is evaluated by continuum numerical simulation using the SANISAND constitutive model in FLAC3D. The results show that the geometry of the failure mass varies from 2D to 3D by increasing the stiffness at the slope boundaries (from smooth to hard) and the maximum pipe deformation decreases by around 40%. Moreover, the response components of maximum axial stress, bending moment, and shear stress of the pipe occur at the end sections of the buried pipe and near the boundaries of the landslide zone. However, the maximum pipe deflection occurs in the middle section of the pipe. The results of shear force-shear displacement curves demonstrate that the soil-pipe interaction stiffness is variable along the pipe length and can be estimated by a hyperbolic equation.

Shallow Landslide Susceptibility Mapping in Sochi Ski-Jump Area Using GIS and Numerical Modelling

The mountainous region of Greater Sochi, including the Olympic ski-jump complex area, located in the northern Caucasus, is always subjected to landslides. The weathered mudstone of low strength and potential high-intensity earthquakes are considered as the crucial factors causing slope instability in the ski-jump complex area. This study aims to conduct a seismic slope instability map of the area. A slope map was derived from a digital elevation model (DEM) and calculated using ArcGIS. The numerical modelling of slope stability with various slope angles was conducted using Geostudio. The Spencer method was applied to calculate the slope safety factors (Fs). The pseudostatic analysis was used to compute Fs considering seismic effect. A good correlation between Fs and slope angle was found. Combining these data, sets slope instability maps were achieved. Newmark displacement maps were also drawn according to empirical regression equations. The result shows that the static safety factor map corresponds to the existing slope instability locations in a shallow landslide inventory map. The seismic safety factor maps and Newmark displacement maps may be applied to predict potential landslides of the study area in the case of earthquake occurrence.

Frequency-dependent topographic seismic amplification using by a "gray box model" that usesimplementing GIS morphometric data

Topographic seismic amplification can have a relevant effect in hilly and mountain areas and it assumes a relevant role in urban planning and seismic slope instability. On the other hand, recent studies on this topic strongly suggest the necessity to assess or predict topographic effect as a frequency depending variable and in an adequate way, in contrast with the simplistic models that use an inadequate uniform spectral scaling factor. Following this suggestion and taking into account the results of the aforesaid studies, a computerized model was developed based on common topographic attributes such as DTM, slope angle and curvature, taking into consideration the uniform rigidity of the relief. The model is defined as grey box model due to the fact that it is constructed on the awaited physical behaviour along the relief and initially trained on topographic amplified data of uniform regular relief, data product by 2D numerical analysis The validation of model was performed on two well-known areas. The results show a high prediction capacity of the model and how it can be driven for the optimization of performance in different real areas.

3-D Elasto-Plastic SEM Approach for Pseudo-Static Seismic Slope Stability Charts for Natural Slopes

This paper briefly discusses on spectral element method, one of the recent method applied to evaluate the stability of natural slope. The parametric study is made to prepare stability charts in 3-D for the different seismic coefficient in case of dry and fully saturated soil slope conditions. This paper utilizes common soil engineering properties under the unified soil classification system (USCS). Stability charts of some representative soil slopes along with USCS material models can be useful to analyze the stability of slopes for general purposes. This paper analyzes the stability of dry and fully saturated soil slopes with horizontal seismic pseudo-static coefficient, K h , of 0.1, and 0.2 to prepare the stability charts. It is believed that dry and fully saturated soil slope conditions are the best and worst scenario of the stability and seismic coefficient, K h , of 0.1, and 0.2 are sufficiently addressed the seismic slope instability of severe damages. The results show that the stability condition of fully saturated soil slope is equivalent to dry seismic slope instability of pseudo-static coefficient, K h , 0.2 in most of the cases. This paper employs two roots related factors: (1) root cohesion, C r , of 0–20 kN/m2; (2) root zone h r , of 2.0 m to represent the vegetated soil slope stability. A significant change in safety factor is observed as per the soil slope models as well as soil material models including root related parameters. A linear relationship of factor of safety is found with root-cohesion up to, C r , of 20 kN/m2. It may not be true for lower and higher values of root-cohesions. This paper also presents a typical numerical problem and solution to illustrate the application of design charts.

Probabilistic assessment of the seismic performance of earth slopes

Sliding block displacements are used to evaluate the potential for seismic slope instability. Deterministic approaches are typically used to predict the expected level of sliding block displacement, although they do not rigorously account for uncertainties in the expected ground shaking, dynamic response, or displacement prediction. As a result, there is no concept of the actual hazard associated with the displacement computed by the deterministic approach. This paper summarizes and extends recent developments related to the probabilistic assessment of sliding block displacements. The probabilistic approach generates a hazard curve for displacement in which the annual rate of exceedance for a range of displacement levels is computed. The probabilistic approach is formulated both in terms of scalar hazard analysis (i.e., using one ground motion parameter, peak ground acceleration) and vector hazard analysis (i.e., using two ground motion parameters, peak ground acceleration and peak ground velocity), and applied both to rigid and flexible sliding block conditions. Generally, the vector probabilistic approach predicts displacements that are 2–3 times smaller than the scalar probabilistic approach, revealing the value of characterizing frequency content via peak ground velocity. Comparisons between the deterministic and probabilistic approaches, in either a scalar or vector context, indicate that the deterministic approach can severely underestimate displacements relative to the probabilistic approach because it ignores the aleatory variabilities in the dynamic and sliding responses of the sliding mass. This under-prediction is most significant for longer period sliding masses. Modifications to the deterministic approach are proposed that provide displacements that are more consistent with the probabilistic approach.

Regression analysis for seismic slope instability based on a double phase viscoplastic sliding model of the rigid block

Semi-empirical models based on Newmark’s sliding block permit the estimation of expected co-seismic displacements in relation to one or more parameters which characterize the ground motion that theoretically caused them. Taking this into consideration, a regression analysis, based on a double-phase viscoplastic (DPV) model, was developed using 96 Italian ground motion accelerograms for a total of 1,448 combinations obtained for different parametric conditions of the indefinite slope model. Repeated stability analysis, performed by means of the DPV model, allows for the assessment of the seismic instability of a slope in relation to different reached behaviour levels, as well as seismically induced permanent displacements. At these behaviour levels, co-seismic increases and possible subsequent decreases of viscoplastic shear strengths are associated. This implies that the post-seismic persistent mobility (collapse) of the slope can be obtained from the computation. On the other hand, coherently with the increasing of shear resistances during fast sliding displacements in clay soils, the seismic-forced displacements result substantially lower than corresponding values obtained by means of the rigorous Newmark’s sliding block. In addition, in relation to some seismic ground motion parameters, regression and functional border and separation curves were obtained with the aim of providing an expeditious seismic slope stability evaluation in reference to the co-seismic and post-seismic behaviour of clayey slopes. Regarding this, the real behaviour of two historical landslide events is discussed in the light of the results of the regression analysis outlined in this work.

A method for producing digital probabilistic seismic landslide hazard maps

The 1994 Northridge, California, earthquake is the first earthquake for which we have all of the data sets needed to conduct a rigorous regional analysis of seismic slope instability. These data sets include: (1) a comprehensive inventory of triggered landslides, (2) about 200 strong-motion records of the mainshock, (3) 1:24 000-scale geologic mapping of the region, (4) extensive data on engineering properties of geologic units, and (5) high-resolution digital elevation models of the topography. All of these data sets have been digitized and rasterized at 10 m grid spacing using ARC/INFO GIS software on a UNIX computer. Combining these data sets in a dynamic model based on Newmark's permanent-deformation (sliding-block) analysis yields estimates of coseismic landslide displacement in each grid cell from the Northridge earthquake. The modeled displacements are then compared with the digital inventory of landslides triggered by the Northridge earthquake to construct a probability curve relating predicted displacement to probability of failure. This probability function can be applied to predict and map the spatial variability in failure probability in any ground-shaking conditions of interest. We anticipate that this mapping procedure will be used to construct seismic landslide hazard maps that will assist in emergency preparedness planning and in making rational decisions regarding development and construction in areas susceptible to seismic slope failure.