An extension of probabilistic slope stability analysis of china clay deposits using geostatistics

Abstract

Abstract An understanding of the reasons for the distribution of highly kaolinized zones in the St Austell granite is useful to the china clay industry because a better understanding of shear strength distribution spatially should lead to improved models and give better insight into the progressive development of failure surfaces. A field cone penetrometer survey of a bench in a working china clay pit has been correlated with laboratory shear strengths of samples from the same slope. A 3-D block model produced using a commercial integrated mining software package was then incorporated into a slope stability analysis. The results were compared with analyses in which the spatial variability of the same shear strength data were incorporated using geostatistics. The factors of safety from the probabilistic analysis were log-normally distributed but those from the two geostatistically generated analyses were outside the extreme ranges of the probabilistic data. This emphasizes the importance of any concentrated zones of weak or strong material within a section with the same overall average frictional shear strength values. This is not correctly captured by a purely random strength assignment. The use of other geostatistical analysis techniques such as indicator kriging and conditional simulation are also under consideration to accommodate extreme variations in shear strength as occur over short distances in the china clay host material, kaolinized granite.