Implementation of Stochastic Method in Quantifying the Uncertainties Associated with Strip Footing Stability
摘要
The encroachment of uncertainties in routine geotechnical investigations arises at every step, commencing from site specific data procurement to transformation of measured data into a particular soil parameter of interest. Over the past decades, various research works have depicted the importance of uncertainty quantification and its relevance in obtaining a proper estimate of the desired parameter. The usage of deterministic approaches bounds to encompass the repercussions of uncertainties and ultimately leads to an erroneous estimation. This paper furnishes a novel insight into the application of a stochastic method in assessing the stability of strip footing, considering both inherent and transformation uncertainty. Six site-specific SPT data procured upto a depth of 10 m have been transformed to soil friction angle using well established empirical correlations and consequently ultimate bearing capacity have been evaluated using Terzaghi’s bearing capacity formulation. The depth of footing has been fluctuated to quantify the influence zone variability on the obtained stochastic analysis results. First Order Reliability Method (FORM), a semi-probabilistic approach has been implemented to provide a reliable estimate of embedment depth in terms of probability of failure (Pf) and reliability index (β). This study highlighted that with increase in embedment depth, the extent of uncertainties diminishes and ultimately, footings embedded at deeper depths depicted low probability of failure with high reliability index. Adoption of stochastic approach in the assessment of footing stability depicted a lucid picture on the decision-making process in terms of embedment depth while accounting both inherent and transformation uncertainties.