Back analyses for slope failures in rock

Some of the geotechnical parameters used in the analysis may not be accurately measured directly from laboratory tests due to effects of sample disturbance and errors of tests. The back analysis or the observational method are thus often applied to determine the representative and/or dominant strength parameters based on field observations in practice. Based on the Hoek-Brown failure criterion, it was known that the disturbance factor (D) should be determined with caution. The difficulty of measuring rock mass disturbance accurately has been shown. Three rock slope failures will be investigated in this paper using back-analysis technique. In addition, various rock mass strength parameters are taken into consideration.

Rock slope stability analyses using extreme learning neural network and terminal steepest descent algorithm

The analysis of rock slope stability is a classical problem for geotechnical engineers. However, for practicing engineers, proper software is not usually user friendly, and additional resources capable of providing information useful for decision-making are required. This study developed a convenient tool that can provide a prompt assessment of rock slope stability. A nonlinear input-output mapping of the rock slope system was constructed using a neural network trained by an extreme learning algorithm. The training data was obtained by using finite element upper and lower bound limit analysis methods. The newly developed techniques in this study can either estimate the factor of safety for a rock slope or obtain the implicit parameters through back analyses. Back analysis parameter identification was performed using a terminal steepest descent algorithm based on the finite-time stability theory. This algorithm not only guarantees finite-time error convergence but also achieves exact zero convergence, unlike the conventional steepest descent algorithm in which the training error never reaches zero.

Three-dimensional slope stability charts for frictional fill materials placed on purely cohesive clay

This paper investigates slope stability and produces a set of stability charts for three-dimensional (3D) slopes for a specific case in which frictional fill materials are placed on purely cohesive clay. As slopes are not usually plane strain in nature and are influenced by physical boundaries, this study uses a 3D analysis using the finite-element LB limit analysis method. Stability charts are convenient tools for geotechnical engineers during design in practice. For comparison purposes, the results from two-dimensional (2D) analyses are also discussed. The results from this study quantify the increase in the factors of safety obtained when 3D conditions are analyzed as opposed to the more traditional 2D.

Probabilistic assessment of fill slope stability

Conventional slope stability analyses have commonly been based on a deterministic approach. Various deterministic-based analysis methods developed to date can assess the stability of a given slope using the factor of safety. However, it has been strongly debated that the use of only the factor of safety does not explicitly account for the uncertainties in soil parameters. In light of this, this paper uses the finite element limit analysis methods and conducts a probabilistic-based analysis of fill slope for the specific case of two-layered undrained clay. Results obtained show that slopes with large variations in soil properties may present an extremely high risk of a slope failure and this cannot be known if only a deterministic-based analysis is performed. Thus, this shows that more soil investigations can be performed to reduce the variation of the soil properties thereby reducing the risk of a slope failure. Different probabilistic charts based on different coefficients of variation in soil properties are provided in this paper. This study demonstrates that the finite element limit analysis methods can be applied in a probabilistic analysis.

Slope stability analysis using Phase 2

Analysing the rock slope stability is a classical problem for geotechnicalengineers. Recently, Hoek-Brown failure criterion has drawn more and more attentionfor rock slope stability assessments. It would be due to the fact that the nonlinearity ismore pronounced at the low confining stresses that are operational in slope stabilityproblems. However, it is still not popular yet. Therefore, in this study, slope stabilityanalyses will be performed based on the generalised Hoek-Brown failure criterionusing a commercial software, Phase 2. The Hoek-Brown strength parameters will beused as direct inputs in numerical simulations. In addition, two rock slope cases willbe investigated. It is expected that better understandings of rock slope mechanisms canbe obtained.

Slope stability assessment of layered soil

This thesis investigates the stability of fill slopes and presents the results in the form of convenient slope stability charts. Additionally, a probabilistic analysis, which can provide a more accurate interpretation of slope safety is also adopted. Finally, a neural network tool for quick slope assessment is also successfully developed.