SOIL GEOTEXTILE INTERACTION - EVALUATION OF MEMBRANE SUPPORT

A general expression for evaluating the increase of bearing,capacity due to membrane action based on strict equilibrium conditions is presented. In order to provide closed form solutions for design purposes, an average membrane action is also defined. Particular expressions of the average membrane action are obtained assuming constant - as most models do - and variable strain deformation of the membrane. The general expression derived herein provides a valuable framework to compare the most commonly used expressions. This comparison is made in terms of dimensionless parameters. The most commonly used design procedures to quantify the membrane action provided by the inclusion of geotextiles on soft soils underlying granular fills are reviewed. Circular and parabolic shapes are used to simulate the geotextile deformation. It is shown that independently of the model used and geotextile deformation shape assumed, comparable values for membrane support for relatively small rutting ratios are obtained. On the contrary, for large rutting ratios, the choice of membrane support model and geotextile deformation shape has significant influence on the results, the latter being the most influential one.