LIMIT CONDITION FOR FIBER-REINFORCED GRANULAR SOILS

Approximate methods for analysis and synthesis of earth structures using such reinforcement as geotextiles or geogrids have been used successfully for more than two decades. Soil reinforcement with short fibers and continuous synthetic filaments has been tried in the past decade. Although the latter has been used with success in construction practice, no techniques for design with such materials exist. This is mainly the result of poor understanding of the fiber-matrix (filament-matrix) interaction and, consequently, lack of appropriate models capable of describing the stress-strain behavior and failure of such composites. An attempt at describing the failure criterion of fiber-reinforced sand is presented. The properties of the constituents are approximated by their standard characteristics : the Mohr-Coulomb failure function for the granular matrix and the Tresca criterion for fibers. The failure of the composite is considered to be because of the collapse of the matrix associated with intact fibers or with fibers failing in slip or the tension mode. An energy-based homogenization technique is used. Results of some preliminary laboratory experiments are also presented. Application of the derived failure criterion is shown in an example of a slope limit load problem.