Evaluation of Factors Influencing Slope Instability: Case Study of the R523 Road Between Thathe Vondo and Khalvha Area in South Africa

2020

Applied Sciences

The purpose of this paper was to analyze the impact of extreme rainfall on the recurrence of slope instability using the Thulamela Municipality roads (R523) as a case study. To this end, the historical rainfall data of the area of study were analyzed between 1988 and 2018. The results show that a significant increase in rainfall is usually experienced in the summer months of December and January. Following this, the factor of safety (FoS) of slopes of silt clay, clay, and clay loam soils were estimated using the SLIDE simulator (Numerical software “Finite Element Method (FEM)”) under sunny to rainy conditions of the area. A complementary model, FLACSlope (Numerical software “Finite Difference Method (FDM)”), was utilized to simulate FoS and pore water pressure in sunny and rainy conditions of the area. Simulation results show that extreme rainfall has the ability to reduce the shear strength and resistance of the soil slope material. This may explain the recurrent landslides noted in the area. Finally, the water pore pressure has been simulated to increase with the increased water table, which generally pushes the soil particles apart and reduces the stress between the particles resulting in soil slope failure. Extreme rainfall alters the phase of the material solid in a manner that may require further research for a better understanding.

Section: Simulation Case Of a Clay Soilmentioning

confidence: 99%

“…This road is the bloodline between villages and surrounding townships. Safety is therefore critical when one considers the fact that they were excavated by the blasting of very sloppy and unstable terrain [14]. The road also passes through several rivers [15].…”

Section: Introductionmentioning

confidence: 99%

Influence of Rainfall Intensity on the Stability of Unsaturated Soil Slope: Case Study of R523 Road in Thulamela Municipality, Limpopo Province, South Africa

2020

Applied Sciences

“…These roads are the bloodline between villages and surrounding townships. Safety is, therefore, critical when one considers the fact that they were excavated by the blasting of very sloppy and unstable terrain [21]. These roads also pass through several rivers [22].…”

Section: Geological Setting Of the Study Areamentioning

confidence: 99%

“…Several remedial measures have been suggested and implemented but rockfalls and slope instability are still reported at an alarming rate [21]. For example, Mutanamba [22] analyzed the stability of cut-slope along the R523 road between Thathe Vondo and Khalavha.…”

Section: Geological Setting Of the Study Areamentioning

confidence: 99%

Application of Limit Equilibrium Analysis and Numerical Modeling in a Case of Slope Instability

2020

Sustainability

The application of limit equilibrium analysis and numerical simulation in case of slope instability is described. The purpose of the study was to use both limit equilibrium methods (LEMs) and numerical simulations (finite element method (FEM)) to understanding the common factor imposing the selected slope into slope instabilities. Field observations, toppling analysis, rotational analysis, and numerical simulations were performed. The results of the study showed that the selected unstable slopes were associated with the sliding types of toppling; it was observed that the slopes were governed by tension cracks and layered soil mass and dominated with approximately two joints sets throughout. The simulated factor of safety (FoS) of the slopes composed of clay soil was denoted to be prone to slope instability while others were categorized as moderately stable. The simulated FoS of the slopes correlated very well with the visual observations; however, it is anticipated that properties of soil mass and other characteristics of the slopes contributed largely to the simulated FoS. The sensitivity of the model was further tested by looking into the effect of the slope angle on the stability of the slope. The results of the simulations showed that the steeper the slope, the more they become prone to instability. Lastly, Phase 2 numerical simulation (FEM) showed that volumetric strain, shear stress, shear strain, total displacement, and σ1 and σ3 components of the slope increase with the stages of the road construction. It was concluded improper road construction, steepness of the slope, slope properties (soil types), and multiple geological features cutting across are the common mechanisms behind the slope instability.

“…e added value of the endeavor lies in the development of a reliable slope susceptibility hazard map based on the given case study. Much of contemporary slope stability analysis is based on GIS-based tools and yet relies on the large deformation and environmental conditions of the study that occurred in time series while neglecting the mechanical behavior of solid mass [23,24].…”

Section: Introductionmentioning

confidence: 99%

Establishing Reliable Slope Stability Hazard Map Based on GIS‐Based Tool in Conjunction with Finite Element Methods

Muavhi

Advances in Civil Engineering

2022

This paper describes the establishment of a slope stability hazard map based on a GIS-based tool in conjunction with the finite element method (FEM). In this regard, Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) images were modeled using the Weight of Evidence (WOE) technique. The previous simulation was therefore validated using visual observations and FEM (Phase 2D and SLIDE). The above techniques made it possible to develop and validate the reliable slope stability hazard map with the use of a case study. The results show that the established hazard map correlates very well with visual observation and stability assessment performed using FEM models. The map categorises slopes based on their susceptibility to failure; however, it has been discovered that most of the slopes that rated highly susceptible were located along or closer to geological features (faults) or streams and were at high elevations. Similarly, the SLIDE model has been utilised to perform the safety factor of the identified slope and the model has shown that those slopes were not stable. Furthermore, the influence of geological features was further studied using the Phase 2D model and it was discovered that the features contributed largely to the displacement of the rock mass with time, and as a result, instability was expected. The overall conclusion of the study is that the combination of geotechnical and GIS-based tools appeared to provide an insight in categorising the hazard of slopes located within mountainous terrain.