Discussion of “Probabilistic seismic slope stability analysis and design”

The discussers welcome the paper by Burgess et al. (2019) and appreciate their efforts to develop, presumably, the first probabilistic seismic slope stability design aids using the “random finite element method” (RFEM). Although they conducted a parametric study, their charts provide geotechnical engineers with a preliminary estimate of failure probability of simple slopes subjected to seismic excitations. However, some considerations need to be pointed out that may affect the results achieved in the paper under discussion

Influence of cross-correlation between soil parameters on probability of failure of simple cohesive and c-phi slopes

The paper focuses on the calculation of probability of failure of simple unreinforced slopes and the influence of the magnitude of cross-correlation between soil parameters on numerical outcomes. A general closed-form solution for cohesive slopes with cross-correlation between cohesion and unit weight was investigated and results compared with cases without cross-correlation. Negative cross-correlations between cohesion and friction angle and positive cross-correlations between cohesion and unit weight, and friction angle and unit weight were considered in the current study. The factors of safety and probabilities of failure for the slopes with uncorrelated soil properties were obtained using probabilistic slope stability charts previously reported by the writers. Results for cohesive soil slopes and positive cross-correlation between cohesion and unit weight are shown to decrease probability of failure. Probability of failure also decreased for increasing negative cross-correlation between cohesion and friction angle, and increasing positive correlation between cohesion and unit weight, and friction angle and unit weight. Probabilistic slope stability charts presented by the writers in an earlier publication are extended to include c-Φ soil slopes with and without cross-correlation between soil input parameters. An important outcome of the work presented here is that cross-correlation between random values of soil properties can reduce the probability of failure for simple slope cases. Hence, previous probabilistic charts by the writers for simple soil slopes with uncorrelated soil properties are conservative (safe) for design. This study also provides one explanation why slope stability analyses using uncorrelated soil properties can predict unreasonably high probabilities of failure when conventional estimates of factor of safety suggest a stable slope.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Discussion of “Probabilistic seismic slope stability analysis and design”

The authors welcome the paper by Burgess et al. (2019) for their efforts to develop, presumably the first probabilistic seismic slope stability design aids using Random Finite Element Method (RFEM). Although they conducted a parametric study, their charts provide the geotechnical engineers with a preliminary estimate of failure probability of simple slopes subjected to seismic excitations. However, we would like to point out some considerations which may affect the results achieved in the corresponding paper.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Probabilistic analysis of simple slopes with cohesive soil strength using RLEM and RFEM

<p>The 2D random finite element method and the one-dimensional and 2D random limit equilibrium method are used to investigate the influence of spatial variability of soil strength parameters on the probability of failure of simple soil slopes with cohesive undrained shear strength. The combined influence of spatial variability of soil properties and cross-correlation between undrained soil strength and unit weight on the computed probability of failure is explored. The paper identifies conditions where numerical outcomes are similar and where they are not. The limitations of each analysis method are described and implications to analysis and design are identified.</p> <p><b>Abbreviations:</b> FEM: finite element method; LEM: limit equilibrium method; RFEM: random finite element method; RLEM: random limit equilibrium method</p