Parameters calibration in rainfall induced landslides in the Langhe area (1994)

2021 ◽  
Author(s):  
Giulia Evangelista ◽  
Monica Barbero ◽  
Ilaria Butera ◽  
Marta Castelli ◽  
Pierluigi Claps ◽  
...  
Keyword(s):  
Limit Equilibrium ◽  
Equilibrium Analysis ◽  
Trigger Factors ◽  
Limit Equilibrium Analysis ◽  
Geotechnical Parameters ◽  
Geotechnical Database ◽  
Factor Expression ◽  
Hillslope Scale ◽  
Parameter Values ◽  
Cold Case

<p>In this work we have tackled as a ‘cold case’ the prolonged rainfall and flood event occurred in the Piedmont region (Northern Italy) in November 1994, when several hundreds of shallow landslides occurred. The aim is to investigate the key trigger factors of the landslides and to put some focus on the possibility to obtain calibrated parameters thanks to the use of a regional geotechnical database.</p><p>This research has been motivated by the effort to close the methodological and conceptual gap between the use of low-detail approaches, proposed to explore wide investigation domains and that of complex ones, applied to single hillslope scale, typically relying on finite elements solutions.</p><p>To achieve the above-mentioned goals, a simple model was preferred (i.e. that of Rosso, Rulli, Vannucchi, 2006), since it allowed a better check on the sensitivity of soil parameter values to the instability condition, under the assumption that these were the main sources of uncertainty.</p><p>With reference to the 1994 event, a database of 238 observed landslide has been used, for which well-documented geometries and geotechnical parameters are available.</p><p>To address the specific aim of cohesion and permeability validation, the safety factor expression from Limit Equilibrium Analysis has been targeted to assume the value 1 for all the considered slopes subjected to the actual (measured) rainfall.</p><p>The comparison between locally calibrated cohesion and permeability and the reference ones found in the database shows some differences; in particular, in several cases, safety factors quite lower than 1 have been derived, compared to those obtained using the published parameter values. The overall uncertainty resulting from this gap has been analysed for a limited (5%) number of carefully examined landslides and it will lay the foundations for subsequent, more geometrically accurate, investigations.</p>

Determination method of the geotechnical parameters for assessing the collapse risk of mountain slope

2020 ◽  
Author(s):  
Namgyun Kim ◽  
Jaehwan Kwak ◽  
Man-Il Kim
Keyword(s):  
Risk Assessment ◽  
Safety Factor ◽  
Limit Equilibrium ◽  
Dry Season ◽  
Equilibrium Analysis ◽  
Soil Test ◽  
Mountain Slope ◽  
Limit Equilibrium Analysis ◽  
Geotechnical Parameters ◽  
Slope Safety

<p>In Korea, occurrence frequency of mountain disasters like landslide, debris flow, rock fall are increasing due to the extreme weather such as localized heavy rainfall and typhoon during the summer season. The Korea government is investigating and discovering vulnerable areas of mountain disaster to mitigate the damage of people’s lives and property. In this study, we selected the mountain slope with high probability of collapse among the vulnerable areas of mountain disaster and suggested reinforcement method through risk assessment. The slope safety factor was calculated using the limit equilibrium analysis for risk assessment of mountain collapse. The risk of collapse was determined by comparing the calculated slope safety factor with Korea government (Ministry of Land, Infrastructure, and Transport) restrict slope safety factor. The Slope safety factor suggested by the government (Ministry of Land, Infrastructure and Transport) is divided into three conditions: dry season, rainy season, and earthquake. Geotechnical parameters for limit equilibrium analysis were obtained by soil test. However, the results of the soil test could be different depending on soil sampling location or the weather condition. Therefore, geotechnical parameters were determined by comprehensive analysis such as comparing literature data, reviewing existing design data, and applying empirical formula of N value by standard penetration test. As a result of risk assessment, it was analyzed that there was a risk of mountain collapse in all conditions except dry season, and it was determined that slope stabilization is necessary.</p>

Progressive failure of the Carsington Dam: a numerical study

1992 ◽  
Vol 29 (6) ◽  
pp. 971-988 ◽  
Author(s):  
Z. Chen ◽  
N. R. Morgenstern ◽  
D. H. Chan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Factor Of Safety ◽  
Progressive Failure ◽  
Limit Equilibrium ◽  
Equilibrium Analysis ◽  
Element Analysis ◽  
Limit Equilibrium Analysis ◽  
The Finite Element Analysis ◽  
Yellow Clay

The mechanism of progressive failure is well understood as one which involves nonuniform straining of a strain-weakening material. Traditional limit equilibrium analysis cannot be used alone to obtain a rational solution for progressive failure problems because the deformation of the structure must be taken into account in the analysis. The failure of the Carsington Dam during construction in 1984 has been attributed to progressive failure of the underlying yellow clay and the dam core materials. The dam was monitored extensively prior to failure, and an elaborate geotechnical investigation was undertaken after failure. The limit equilibrium analysis indicated that the factors of safety were over 1.4 using peak strength of intact clay material or 1.2 based on reduced strength accounting for preshearing of the yellow clay layer. Factors of safety were found to be less than unity if residual strengths were used. The actual factor of safety at failure was, of course, equal to one. By using the finite element analysis with strain-weakening models, the extent and degree of weakening along the potential slip surface were calculated. The calculated shear strength was then used in the limit equilibrium analysis, and the factor of safety was found to be 1.05, which is very close to the actual value of 1.0. More importantly, the mechanism of failure and the initiation and propagation of the shear zones were captured in the finite element analysis. It was also found that accounting explicitly for pore-water pressure effects using the effective stress approach in the finite element and limit equilibrium analyses provides more realistic simulations of the failure process of the structure than analyses based on total stresses. Key words : progressive failure, strain softening, finite element analysis, dams.

scholarly journals Stability estimation of slopes with determined slip surface by the MSTAB-3D method based on sliding body limit equilibrium analysis

2019 ◽  
Vol 262 ◽  
pp. 04004
Author(s):  
Janusz Ukleja
Keyword(s):  
Cross Sections ◽  
Slip Surface ◽  
Limit Equilibrium ◽  
Equilibrium Analysis ◽  
Limit Equilibrium Analysis ◽  
Modified Method ◽  
3D Elements ◽  
Resultant Forces ◽  
The Impact ◽  
Section Analysis

The method developed for this study, established on the premises of the limit equilibrium flat analysis for a spatial solution, is a modification of the STAB-3D method, previously described by the author. It combines the analyses methods of 2D slices of flat cross–sections with the spatial analyses methodology rooted in a specific breakdown of a landslide sliding body into 3D elements assuming some simplifying solution. However, this method is solely applicable in case of a landslide failure with a stipulated slip surface and with a consistent decline of a determined slide direction. Such a method was developed in the article published earlier, which provided then its basic assumptions and the equilibrium formulations. The following publication thereof, presents overall suppositions for this method as well as its modification involving the resultant forces brought to the equilibrium with the generalized slide direction. Apart from that, a comparative analysis was carried out on the impact of this modification applicability of the obtained results with regard to the STAB-3D method. The algorithm was also presented concerning the modified method with its results being compared to a couple of selected methods LEM (limit equilibrium method). The undertaken analysis reveals that the modified MSTAB-3D method determines stability indicators that are very similar to its earlier version. Moreover, the results occur to be also approximating the values obtained in the course of other methods with regard to the flat cross-section analysis.

Limit Equilibrium Analysis of Sliding Block Stability under Earthquake

2011 ◽  
Vol 243-249 ◽  
pp. 4528-4534
Author(s):  
Yao Ru Liu ◽  
Bo Li ◽  
Kuang Dai Leng ◽  
Yue Qun Huang
Keyword(s):  
Safety Factor ◽  
Limit Equilibrium ◽  
Time History ◽  
Grid Method ◽  
Internal Force ◽  
Arch Dam ◽  
Equilibrium Analysis ◽  
Nonlinear Fem ◽  
Engineering Structures ◽  
Limit Equilibrium Analysis

Time history analysis is performed on geotechnical engineering structures under earthquake actions using 3D nonlinear FEM. The distribution of internal force on slide surfaces has been interpolated from the stress field of FEM with 3D Multi-grid Method. The safety factor with time history of sliding block can be obtained by limit equilibrium analysis and its dynamic stability can be evaluated. For blocks sliced by single slide surface and wedge-shaped double slide surfaces, general formulas of safety factor are given and their applicability have been analyzed. Analysis and evaluation of slide block aseismic stability are performed on high slope on the right bank of Dagangshan arch dam.

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

2020 ◽  
Vol 12 (21) ◽  
pp. 8870
Author(s):  
Fhatuwani Sengani ◽  
François Mulenga
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Limit Equilibrium ◽  
Slope Angle ◽  
Road Construction ◽  
Soil Mass ◽  
Slope Instability ◽  
Equilibrium Analysis ◽  
Limit Equilibrium Analysis ◽  
The Common

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.

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