Stability Analysis of Unsaturated Geosynthetic Reinforced Soil Structures

BOMMIREDDY, GOUTHAM KISHORE REDDY and Basha, B Munwar (2018) Stability Analysis of Unsaturated Geosynthetic Reinforced Soil Structures. Masters thesis, Indian Institute of Technology Hyderabad.

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Abstract

In recent years, several trends caused by climate changes like decrease of average precipitation, etc. These climate trends directly or indirectly result in substantial and unprecedented change in the degree of saturation within the unsaturated zone. Most of the structures are constructed in unsaturated zone which is at shallow depths. Many precipitations induced slope failures occurred in unsaturated soils because of negative pore water pressure which highlights the need to consider suction in the analysis. Application of classical soil mechanics principles to unsaturated soil results improper estimation of design parameters as it is not accounting the complexities of unsaturated soil parameters. Suction stress is the separate term that account the unsaturated conditions in the soil. Geosynthetic Synthetic Reinforced Soil Structures are soil structures which are coherent and flexible. They provide an effective and economic solution for embankments, etc. Field measurements reveal lower tensile loads than the predicted using limit state design method as it is not considering the suction in the analysis. Recent studies show that 60% of failure GRSS are due to varying moisture content in the soils. Therefore, there is a need to find the influence of unsaturated parameters in the soil slope analysis. The primary aim of the work is to study the effect of unsaturated backfills on the reinforced soil structures with log spiral failure surface. Two different backfill material namely High Quality and Marginal Quality Backfills are considered for the analysis with various climatic conditions. Internal and Global Stability analysis is carried out both deterministically and probabilistically. In addition to that, optimised effective pull-out length is back calculated. Optimum number of reinforcement layer with optimum effective pull-out length is also presented. The variability associated with the unsaturated shear strength parameters and the infiltration rate is also considered into account.

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