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.

Weak negative associations between avian influenza virus infection and movement behaviour in a key host species, the mallard Anas platyrhynchos

Animal movements may contribute to the spread of pathogens. In the case of avian influenza virus, [migratory] birds have been suggested to play a role in the spread of some highly pathogenic strains (e.g. H5N1, H5N8), as well as their low pathogenic precursors which circulate naturally in wild birds. For a better understanding of the emergence and spread of both highly pathogenic (HPAIV) and low pathogenic avian influenza virus (LPAIV), the potential effects of LPAIVs on bird movement need to be evaluated. In a key host species, the mallard Anas platyrhynchos, we tested whether LPAIV infection status affected daily local (< 100 m) and regional (> 100 m) movements by comparing movement behaviour 1) within individuals (captured and sampled at two time points) and 2) between individuals (captured and sampled at one time point). We fitted free-living adult males with GPS loggers throughout the autumn LPAIV infection peak, and sampled them for LPAIV infection at logger deployment and at logger removal on recapture. Within individuals, we found no association between LPAIV infection and daily local and regional movements. Among individuals, daily regional movements of LPAIV infected mallards in the last days of tracking were lower than those of non-infected birds. Moreover, these regional movements of LPAIV infected birds were additionally reduced by poor weather conditions (i.e. increased wind and/or precipitation and lower temperatures). Local movements of LPAIV infected birds in the first days of tracking were higher when temperature decreased. Our study thus demonstrates that bird-assisted dispersal rate of LPAIV may be lower on a regional scale than expected on the basis of the movement behaviour of non-infected birds. Our study underlines the importance of understanding the impact of pathogen infection on host movement in order to assess its potential role in the emergence and spread of infectious diseases.

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.

The weak natural law thesis and the common good

The weak natural law thesis asserts that any instance of law is either a rational standard for conduct or defective. At first glance, the thesis seems compatible with the proposition that the validity of a law within a legal system depends upon its sources rather than its merits. Mark C. Murphy has nonetheless argued that the weak natural law thesis can challenge this core commitment of legal positivism via an appeal to law’s function and defectiveness conditions. My contention in the current paper is that in order to make good on the challenge, the defender of the weak natural law thesis should appeal explicitly to the common good, understood as the principal normative reason in the political domain. In section I I outline the main implications of the weak natural law thesis and clarify a common misunderstanding regarding its explanatory role. Section II then argues for the indispensability of the common good to the natural law jurisprudential thesis on the grounds that it has an essential role to play in a natural law account of law’s defectiveness conditions and the presumptive moral obligatoriness of legal norms. Finally, in section III I examine the compatibility of a strengthened version of the weak natural law thesis with legal positivism in light of the centrality of the common good to the natural law jurisprudential position.

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.