Effect of spatial variability of soil properties and geostatistical conditional simulation on reliability characteristics and critical slip surfaces of soil slopes

Abstract

Evaluation of the stability and determination of the Critical Slip Surface (CSS) of soil slopes are salient topics in geotechnical engineering. On the other hand, the stability and CSS are not only affected by soil heterogeneity but also by the boreholes’ location and method of predicting soil parameters in the domain of analysis. The unconditional simulation in which known data and its location are not incorporated may lead to results far from reality. Moreover, in some conditional simulations, the borehole data are directly mapped into the analysis section without taking the location of the known data into account, which can either overestimate or underestimate the stability of the slope. In the current study, the Finite Element Method (FEM) is coupled with the geostatistical method to evaluate the reliability characteristics and CSS distribution with consideration of the known data, location of boreholes, uncertainty of surcharge load, and soil heterogeneity. The results of a real case demonstrate that in comparison to the unconditional simulation, utilizing the conditional simulation improves the distribution of Factor of Safety (FS) by up to 14% while decreasing the related standard deviation by 4% to 40%. Moreover, conditional simulation offers a significant reduction in uncertainty of the slip surface and unsafe distance from the edge of the slope. Besides, it is concluded that soil heterogeneity has a major impact on CSS distribution and induces the local CSS, which cannot occur on a homogeneous slope.