Abstract
This paper addresses a numerical study into passive earth pressure in an unsaturated sandy soil. The computational limit analysis method, discontinuity layout optimization (DLO), is extended to take into consideration the effect of saturation and suction on strength. The extended analysis was utilised to model a retaining wall case study using a sandy soil as a simulated backfill material and the results were compared with Rankine equations which were modified to take into account the capillary rise effect. The numerical results demonstrated that an increase of the total passive thrust up to 47%, for a frictionless wall, at ϕ ′ = 30° due to the effect of partial saturation in the sandy soil.
Highlights
Many historical geotechnical structures such as railway embankments and cuttings were designed before the modern science of soil mechanics was developed
Significant efforts during the last two decades have been focused on the field of unsaturated soil mechanics and this has led to the formulation of several constitutive models
The aim of this paper is to extend the application of the computational limit analysis (CLA) method, discontinuity layout optimization (DLO), to model the effects of partial saturation on the passive earth pressure exerted by an unsaturated sandy soil
Summary
Many historical geotechnical structures such as railway embankments and cuttings were designed before the modern science of soil mechanics was developed. In many cases these structures only stand up due to the strength imparted to them through partial saturation and the effects of surface tension (water suction) acting in the soil pores which holds the soil particles together. With improved understanding of unsaturated soil mechanics in such conditions, it may be possible to utilise the additional strength due to partial saturation in conventional design e.g. with engineered controls on the saturation, under a risk based framework, in temporary works, or in assessing cumulative cyclic loading effects through the seasons. Recent developments in computational limit analysis (CLA) (e.g. [7]) have extended the scope of such analytical methods, so that they can deal with any geometry and loading configuration, and have been applied in many areas to ultimate limit state (ULS) design
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