A method for predicting the pull out load Ð end displacement behaviour of geogrid reinforcement embedded in sandy soils using a nonlinear finite difference approach is presented in this paper. In this method, the soil was modelled as an elastic-perfectly-plastic Mohr-Coulomb type material and the reinforcement was modelled as a linear elastic cable. The soil - reinforcement interaction was modelled by a spring-slider interface system with shear stiffness and shear capacity properties. Details of the numerical model and the method for selecting the soil-geosynthetic interface properties for predicting the pullout behaviour are discussed in the paper. The pullout behaviour of three types of geogrids under different surcharge loads was analyzed and the results compared with laboratory test data. The measured and calculated pullout load Ð displacement responses agreed reasonably well for all the cases examined. The pullout capacity predicted by the proposed method agreed more closely with the measured values than the two existing methods. The proposed method appears more beneficial because of its ability to predict the entire pullout load -displacement response in addition to pullout capacity.
It is essential to know the pullout behaviour of geosynthetic reinforcement embedded in soils for designing geosynthetic reinforced soil structures efficiently (e.g., for assessing the length of reinforcement in a reinforced soil wall).
A finite difference stress analysis program known as FLAC, Fast Lagrangian Analysis of Continua (FLAC 1998), was used for the analysis. In this program, the equations of equilibrium and stress strain behaviour are expressed in finite difference form and are solved by an explicit iterative scheme. The analysis is inherently incremental and can be taken to collapse/failure along a user prescribed path. The numerical principles of FLAC-analysis are detailed in Cundall & Board (1988).
