Rapid Terrain Assessment for Earthquake-Triggered Landslide Susceptibility With High-Resolution DEM and Critical Acceleration

Earthquake ground motion often triggers landslides in mountainous areas. A simple, robust method to quickly evaluate the terrain’s susceptibility of specific locations to earthquake-triggered landslides is important for planning field reconnaissance and rescues after earthquakes. Different approaches have been used to estimate coseismic landslide susceptibility using Newmark’s sliding block model. This model requires an estimate of the landslide depth or thickness, which is a difficult parameter to estimate. We illustrate the use of Newmark sliding block’s critical acceleration for a glaciated valley affected by the 2015 Gorkha earthquake in Nepal. The landslide data came from comparing high-resolution pre- and post-earthquake digital elevation models (DEMs) derived from Spot 6/7 images. The areas where changes were detected provided an inventory of all the landslides triggered by the earthquake. The landslide susceptibility was modeled in a GIS environment using as inputs the pre-earthquake terrain and slope angles, the peak ground acceleration from the 2015 Gorkha earthquake, and a geological map. We exploit the depth information for the landslides (obtained by DEM difference) to apply the critical acceleration model. The spatial distribution of the predicted earthquake-triggered landslides matched the actual landslides when the assumed landslide thickness in the model is close to the median value of the actual landslide thickness (2.6 m in this case). The landslide predictions generated a map of landslide locations close to those observed and demonstrated the applicability of critical acceleration for rapidly creating a map of earthquake-triggered landslides.

Dynamic Stability Analysis of Slope Subjected to Surcharge Load considering Tensile Strength Cut-Off

Surcharge slopes are more vulnerable to instability under the effects of earthquake ground shaking, especially considering the tensile stress. In order to account for the adverse factors of seismic forces and tensile stress, the theory of soil with tensile strength cut-off is deduced and analyzed using the upper bound limit analysis method in this paper. Combined with the quasistatic analysis, the equation of critical acceleration expression for surcharge slope subjected to the dynamic conditions has been evaluated. By using the improved Newmark method, permanent displacements have been analyzed in the case of the classical earthquake ground motions. In addition, optimization algorithm has been undertaken, in which several influencing factors such as slope inclination, internal friction angle, surcharge factor, seismic load, and tension cut-off coefficient have been taken into account, and some results are verified with the classical solutions and FEM results. The results concluded the following: (1) The outcomes of verification results are accurate. (2) The critical acceleration of the slope is significantly affected by tension cut-off with the increasing of surcharge factor and seismic effects. (3) The permanent displacements of surcharge slope considering the tensile strength cut-off can be even 2 times of the traditional analysis; meanwhile, with more reduction of tensile strength, the cumulative displacements increase rapidly. Therefore, considering the influence of tensile strength cut-off is fundamental to the dynamic stability design of surcharge conditions.

The Influence of Different Loads on the Footbridge Dynamic Parameters

Bringing together the experience and knowledge of engineers allowed building modern footbridges as very slender structures. This in turn has led to structural vibration problems, which is a direct consequence of slender structures. In some footbridges, this problem occurs when natural construction frequencies are close to excitation frequencies. This requires a design methodology, which would ensure user safety and convenience of use of the footbridge in operation. Considering the aforementioned dynamic response, the analysis of the finite element model of a footbridge was conducted focusing on critical acceleration and deformation meanings. The model was based on the footbridge prototype located in Vilnius, Lithuania. Two different loading methods were developed to investigate the dynamic effects caused by people crossing a footbridge. The comparison of experimental and finite element model (FEM) results revealed that the footbridge in operation is within the limit values of comfort requirements in terms of its vibrations.

Distribution Pattern of Coseismic Landslides Triggered by the 2017 Jiuzhaigou Ms 7.0 Earthquake of China: Control of Seismic Landslide Susceptibility

On 8 August 2017 an earthquake (MS7.0) occurred within Jiuzhaigou County, Northern Aba Prefecture, Sichuan Province, China, triggering 4834 landslides with an individual area greater than 7.8 m2 over a more than 400 km2 region. Instead of correlating geological and topographic factors with the coseismic landslide distribution pattern, this study has attempted to reveal the control from seismic landslide susceptibility mapping, which relies on the calculation of critical acceleration values using a simplified Newmark block model. We calculated the average critical acceleration for each cell of the gridded study area (1 km×1 km), which represented the seismic landslide susceptibility of the cell. An index of the potential landslide area generation rate was defined, i.e., the possible landsliding area in each grid cell. In combination with PGA (peak ground acceleration) distribution, we calculated such indexes for each cell to predict the possible landslide hazard under seismic ground shaking. Results show that seismic landslide susceptibility plays an important role in determining the coseismic landslide pattern. The places with high seismic landslide susceptibility tends to host many landslides. Additionally, the areas with high potential landslide area generation rates have high real landslide occurrence rates, consistent with dominant small-medium scale landslides by this earthquake. This approach can aid assessment of seismic landslide hazards at a preliminary stage. Additionally, it forms a foundation for further research, such as the rapid evaluation of post-earthquake landslides and identifying highly impacted areas to help decision makers prioritize disaster relief efforts.

UAV observation of the recent evolution of the Planpincieux Glacier (Mont Blanc – Italy)

<p>Planpincieux is one of the glaciers located on the Italian side of the Mont Blanc (Italy). This glacier is monitored using a permanent monoscopic time-lapse camera since 2013. In 2019, the frontal part of the glacier has been characterized by a critical acceleration that could trigger a large ice avalanche able to reach the underlying Planpincieux village. During the emergency, the working group composed of Fondazione Montagna Sicura, CNR IRPI and the Aosta Valley Region Authority improved the monitoring system with a ground-based SAR to control the glacier evolution. An important data source used for a better understanding of the structure of the more unstable glacier sector has been the acquisition of a sequence of digital terrain models (DTMs) acquired by unmanned aerial vehicles (UAV) and helicopters. The approach adopted for the DTM generation is the acquisition of a photo sequence and the application of the structure from motion algorithm. The investigated area of the glacier is located in high-mountain environment and is characterized by a complex topography that does not facilitate the use of UAV. But the availability of a sequence of DTMs has been very useful for the improvement of the knowledge of the current state and recent evolution of the Planpincieux Glacier.</p>

Assesment of real driving emissions of a bus operating on a dedicated route

The reducing of real driving emissions from public transportation which is using intracity lines has become more important in recent years. This is because the petroleum derived fuel combustion products contributes the global warming as well as adversely the air quality. The fuel consumption perspective is another major economical concern for operating companies that should be optimized. In this context a part of Istanbul Metrobus public transportation system of which is using fully a dedicated line is assessed via on board emission and fuel metering devices for two loading conditions. The relevant vehicle and engine operating data is logged during the tests. The logged data is post processed for developing the average emission factors. The results are also analyzed from acceleration and altitude change perspective and alternative scenarios are discussed for cleaner and economic operation. Lastly the in-service conformity parameters are identified and the results are compared with homologation values. It was found that for the same velocity, acceleration affect was found significant and the critical acceleration level is determined as 0.4 m/s?. For NOx, and CO emissions velocities smaller than 20 km/h and 40 km/h was found dominant at positive acceleration zones. Also for fuel consumption and CO2 emission levels the velocities higher than 30 km/h was found critical for all positive acceleration levels. It was shown that the real driving and emission data can be used efficiently for developing more environmentally friendly engine calibrations and decreasing fuel consumption and emissions.

A Modified Newmark Method for Calculating Permanent Displacement of Seismic Slope considering Dynamic Critical Acceleration

Newmark permanent displacement is an important index for evaluating seismic slope stability, which has been widely used in recent years. The traditional Newmark sliding method assumes that the critical acceleration is constant but does not consider the inhomogeneity and dynamic reduction process of shear strength on the sliding surface, presumably leading to underestimation of the permanent displacement. In this paper, this problem is analyzed, and a new method for calculating permanent displacement of seismic slope considering dynamic critical acceleration is proposed, in which the Monte Carlo simulation is used. Example calculations indicate that this approach permits to show the dropping cohesion and the dynamic critical acceleration of the slide block during the earthquake time history. The improved method for calculating seismic slope permanent displacement presented in this paper solves the problem that the calculated value from the Newmark sliding method is smaller than the real value and is a useful improvement.

Liquefaction Vulnerability Analysis as a Coastal Spatial Planning Concept in Pariaman City – Indonesia

Knowledge about the liquefaction vulnerability in Pariaman city which is prone to an earthquake is very much needed in disaster mitigation based spatial planning. This research was conducted by analyzing the potential of liquefaction vulnerability based on the Conus penetration to produce Microzonation of the susceptibility of subsidence due to liquefaction at 4 locations in Pariaman city, i.e Marunggi village, Taluak village, Pauh Timur village and Padang Birik-Birik village. Based on the results of the analysis using this method, the critical conditions of liquefaction found in the intermediate sandy soil to solid. The fine sand layer which has the potential for liquefaction is in sand units formed from coastal deposits, coastal ridges and riverbanks. This liquefaction vulnerability zones analysis is limited to a depth of 6.00 m due to the limitations of the equipment used. The results of the analysis show that the fine sand layer which has the potential for liquefaction occurs at a depth of> 1.00-6.00 m with the division of zones, i.e 1) High liquefaction in the sandy soil layer which has a critical acceleration (a) <0.10 g with shallow groundwater surface; 2) Intermediate liquefaction in the sandy soil layer which has a critical acceleration (a) between 0.10-0.20 g with shallow groundwater surface; and 3) Low and very low liquefaction in the sandy soil layer which has a critical acceleration (a) between 0.20-0.30 g with an average groundwater deep enough surface