Spatial Variability Modelling of Geotechnical Parameters and Stability of Highly Weathered Rock Slope

Abstract

In recent years, spatial variability modeling of geotechnical parameters using random field theory is gaining strength in the reliability based analysis of geotechnical problems. Slope stability analysis of highly weathered rock slope requires proper modeling of geotechnical parameters with due consideration of extent of weathering and overburden pressure. The present study demonstrates the approach for spatial variation modeling of geotechnical parameters and reliability analysis based stability assessment of highly weathered rock slope by considering a typical case of height = 5.0 m and slope angle of 30°. Commercially available software FLAC 5.0, via inbuilt FISH function, has been utilized for the numerical analysis purpose with the assumption that highly weathered rock mass can be analyzed within the framework of the concept of equivalent continuum model. A parametric study is performed to investigate the following: (i) influence of coefficients of variation of geotechnical parameters and (ii) auto-correlation distances on the reliability analysis results. For the reliability analysis, information on mean and variance of output parameter, i.e., factor of safety of the given rock slope is obtained from 2000 Monte Carlo simulations and results are utilized with first order reliability method to obtain reliability index values. The results of the analysis clearly demonstrated that numerical modeling of spatially varying geotechnical parameters gives more realistic treatment to the property variation of a natural material and stability assessment in reliability analysis framework is more comprehensive than conventional limit equilibrium based factor of safety approach.