Geotechnical Engineering Group

Department of Civil & Structural Engineering

Limit Analysis of Unsaturated Soil Problems using Discontinuity Layout Optimization


Computational limit analysis (CLA) is a tool that has found significant application in conventional geotechnical engineering design and analysis, building on the long standing use of limit analysis and limit equilibrium methods in geotechnical engineering. The aim of this study is to extend CLA to include unsaturated soil behavior, providing a tool that can find the collapse load for a wide range of problems such as retaining wall or foundation stability under unsaturated conditions without the simplifications inherent in hand calculations or the complexity of the elasto-plastic FE method.

The project involves theoretical and numerical investigations into the implementation of unsaturated soil behavior into CLA supported by laboratory scale studies of unsaturated sand behavior through modified direct shear tests and model footing bearing capacity tests.  

A modified effective stress equation for unsaturated sand will be proposed that accounts for applied stress, suction, and degree of saturation and will be calibrated against the experimental results of the direct shear test and bearing capacity tests.  

Project dates

Start date: 
October 2011
End date: 
October 2015

People involved

Prof. Matthew Gilbert