ABSTRACT
The mechanically stabilised earth (MSE) walls and soil nail (SN) walls constructed together are known as hybrid earth retaining structures (HERS). The HERS are efficient solutions for earth retention problems that face spatial constraints and theyinvolve a substantial reduction in the earth volume apart from maintaining and improving the inherent stability. The MSE wall can be either built adjacent to and/or over the stabilised SN wall based on the requirements and are referred to as shored MSE (SMSE) and hybrid MSE/SN walls respectively. The MSE wall built with narrow backfill is termed as narrow MSE (NMSE) wall. The present study investigates the deformation behaviour and global stability of the HERS using the coupled finite element reliability analysis accounting for uncertainties.Predictive equations are developed for the estimation of responses based on the deterministic and reliability analyses of the HERS. These equations are developed using multiple linear regression adopting the method of least squares.The regression models for the MSE/SN walls are proposed using the data generated from the deterministic finite element model considering only the influential parameters based on the screening experiments.The adequacy of the predictive equations is verified by evaluating the summary of fit statistics and residual analyses. Further, the behaviour of HERS is assessed by evaluating the various failure mechanismsand deformation modes. The behaviour of the HERS is also analysed considering different conditions of reinforced, retained and foundation soils. For the reliability studies, based on the parametric sensitivity analysis only those soil properties are considered as random variables which have higher sensitivity. The limit state functions for the deformation response and global stability are approximated using the response surface method. The input data set used for the reliability analysis is generated based on the face-centered cube design. The reliability analysis is performed using point estimate, mean value first order second moment and first order reliability methods and compared with the Monte Carlo simulation to evaluate the reliability index and probability of failure. Different limiting lateral displacements and target factors of safety are considered and accordingly the reliability indices and probabilities of failure areevaluated for the HERS. Based on these results, the partial safety factors for the load and resistance variables are derived. The finite element reliability analysis is extended for the proposed case study involving the HERS at the selected slope sectionsin The Nilgiris, Tamil Nadu.