In this work, we explored a novel approach to integrate both geo-environmental and soil geomechanical parameters in a landslide susceptibility model. A total of 179 shallow to deep landslides were identified using Google Earth images and field observations. Moreover, soil geomechanical properties of 11 representative soil samples were analyzed. The relationship between soil properties was evaluated using the Pearson correlation coefficient and geotechnical diagrams. Membership values were assigned to each soil property class, using the fuzzy membership method. The information value method allowed computing the weight value of geo-environmental factor classes. From the soil geomechanical membership values and the geo-environmental factor weights, three landslide predisposition models were produced, two separate models and one combined model. The results of the soil testing allowed classifying the soils in the study area as highly plastic clays, with high water content, swelling, and shrinkage potential. Some geo-environmental factor classes revealed their landslide prediction ability by displaying high weight values. While the model with only soil properties tended to underrate unstable and stable areas, the model combining soil properties and geo-environmental factors allowed a more precise identification of stability conditions. The geo-environmental factors model and the model combining geo-environmental factors and soil properties displayed predictive powers of 80 and 93%, respectively. It can be concluded that the spatial analysis of soil geomechanical properties can play a major role in the detection of landslide prone areas, which is of great interest for site selection and planning with respect to sustainable development at Mount Oku.

https://www.mdpi.com/1660-4601/17/18/6795/pdf

Effect of Soil Geomechanical Properties and Geo-Environmental Factors on Landslide Predisposition at Mount Oku, Cameroon.

Prolong heavy rainfall is increasingly inducing slope instabilities on the high-risk hills of weathered granitic basement in Penang. These slope instabilities are spatially controlled with changes in geotechnical properties of the slope soils. A reliable method to include density as part of geotechnical properties to calibrate Electrical Resistivity Tomography (ERT) resistivity distribution in slope instability monitoring is still rare. Hence, we present six ERT data that were acquired with survey length of 60 m and 1.5 m electrode spacing using Wenner-Schlumberger array from 2019-2020. The results were calibrated with the laboratory determined geotechnical properties- Moisture Content (MC), Particle Size Distribution (PSD), density and Hydraulic Conductivity (HC). The result of the analysis of ERT models classified resistivity distribution into saturated zones of 20% silt and clay, weak zones of 600-3000 Ωm and basement rocks of >5000 Ωm. The presence of floaters and boulders of resistivity >4000 Ωm overlie saturated zones coupled with multiple rainfall events that act as triggering factors for slope instability and failure. Geotechnical results show strong correlation of R≈0.94 between density and resistivity values which are crucial for the calibration of the ERT models because low-resistivity <600 Ωm areas have high MC, 30.1% with low density, 1176 kg/m3 and HC, 2.02x10-5 m/s whereas high resistivity <3000 Ωm areas have lower MC, 11.4% with relatively high density 1458 kg/m3 and HC 1.34x10-2 m/s. Therefore, we conclude that low-resistivity areas are composed of earth materials that are less dense low-permeable unstable zones of displacement which constitute subsurface drainage paths that are precursors to slope instability.

/pdf/analysis-of-geotechnical-assisted-2-d-electrical-resistivity-q2oeu72jpd.pdf

Analysis of Geotechnical-Assisted 2-D Electrical Resistivity Tomography Monitoring of Slope Instability in Residual Soil of Weathered Granitic Basement

The National Council for Scientific and Technological Development (CNPq), the Support Research of the Federal District Foundation (FAP-DF), the University of Brasilia and, the Pool of Brazilian Equipments (PegBr), Rio de Janeiro.

/pdf/characterization-of-sobradinho-landslide-in-fluvial-valley-248v1ylxkk.pdf

Characterization of Sobradinho landslide in fluvial valley using MASW and ERT methods

Integrated geophysical imaging of a mountain landslide – A case study from the Outer Carpathians, Poland

Landslides are a major threat to the environment, infrastructure and human activities, especially in mountainous and hilly areas It is therefore important to accurately identify the mass movements triggering these mechanisms This paper presents the impacts of lithotectonic conditions on the formation of mass movements on the example of the landslide that is located in the northern part of the Polish Outer Carpathians In the area of the research, the ratio of the total area of landslides to the surface of the area reaches even 20% The interpretation of a high resolution Digital Elevation Model (DEM), Electrical Resistivity Tomography (ERT) and fieldwork results allowed for the reconstruction of the landslide movements and dividing them into two areas; the western one, dominated by rotational movement, and the eastern one, featuring rotational and translational movement It was found that the eastern part is more active now as it probably was also in the past, which might have resulted from the lithotectonic conditioned or from the impact of the flowing waters of the Dunajec River Moreover, in the eastern part of the landslides, a small-sized ridge (55 m × 25 m) was identified, which shows greater stability in comparison with the colluvium that surrounds it In order to explain the lower rate of movement of this landform, a morphometric analysis and research using ERT were performed The geophysical measurements showed that the ridge comprised rock formations of greater resistivity than its surroundings It is most likely that the only preserved sandstone packet, constituting the original secondary escarpment, became separated from the bedrock due to rotational movement The presented studies indicate that the landslide was created due to geological and atmospheric conditions A clear revival of landslide movements took place after significant precipitation events that last occurred in the years 2010 and 2015 The bedrock substrate due to its lithology and tectonics, facilitates these movements It was found that the landslide studied is a complex entity, characteristic of the Polish Outer Carpathians, that has undergone multiple stages of development The landslide is active or periodically active and, therefore, must be excluded from the planned development as well as from other forms of human activity

Reconstruction of landslide movements using Digital Elevation Model and Electrical Resistivity Tomography analysis in the Polish Outer Carpathians

Landslides are complex phenomena, and the main factors that have a significant impact on their behavior are changes in slope inclination geometry and changes in water conditions. The main purpose of this work was to evaluate current conditions of the landslide in Brzozowka, near Cracow (Poland), and analyzing how different saturations of soil influence the stability of the landslide. The combination of geophysical and geotechnical research, such as electrical resistivity tomography (ERT), cone penetration testing, drilling and laboratory tests as well as a comprehensive analysis of their results, provided reliable information on the geological structure and geotechnical parameters of the landslide. The results were used in numerical simulations of the landslide stability, in which a two-phase model (soil and water) was assumed that included the effective soil strength parameters and the transient flow conditions as well as a partial saturation zone. The sliding surface obtained from the numerical modeling was almost flat, which was confirmed by the ERT method. It was proved that the landslide occurred when the saturation of the upper part of the slope exceeded 0.8. Obtained results are useful for engineering practice.

/pdf/geophysical-and-geotechnical-approach-to-a-landslide-3jpdly7pl3.pdf

Geophysical and geotechnical approach to a landslide stability assessment: a case study

Analiza możliwości zastosowania osadów spoistych zbiornika rożnowskiego do uszczelnienia wałów przeciwpowodziowych

Abstract According to Polish law, it is prohibited to perform excavations or locate buildings closer than 50 m from the embankment. In order to obtain exemption from this ban, filtration and stability analysis of the embankment and excavation in the flood conditions have to be performed. This paper presents results of the numerical investigations on interactions between excavations and embankment. Complex nature of the problem is presented. Methodology of numerical simulations and real case examples are described.

Michał Grodecki

Papers

Geophysical and geotechnical approach to a landslide stability assessment: a case study

Analiza możliwości zastosowania osadów spoistych zbiornika rożnowskiego do uszczelnienia wałów przeciwpowodziowych

Excavations in the vicinity of the antiflood embankments – calculating issues