Master of Science (MS)


Civil and Environmental Engineering

Document Type



Soil reinforcement interaction is a primary issue for designing reinforced soil structures. The soil to geosynthetic interaction parameters are influenced by a) Interaction mechanism between geomaterials and geosynthetics (pull-out or direct shear), b) Physical and mechanical properties of geomaterials (density, grain shape and size, grain size distribution, water content, and plasticity of clayey soils), and c) Mechanical properties (tensile peak strength), shape and geometry of geosynthetics. The soil to geogrid interface friction parameters (interface friction angle "δ" and adhesion "ca") for different plasticity indexes, moisture contents, and dry densities were investigated. For this purposes, a large scale direct shear box was used to evaluate the interface friction parameters between four geosynthetics (geotextile 4 x 4 woven, and geogrids BX - 6100, Miragrid 8XT, and BasXgrid 11) and four types of soils (sand, clay 6 PI, clay 25 PI and clay 49 PI). The interaction parameters were determined by separating the soil to geogrid interface friction from the measured combined soil to soil friction. The interface friction parameters were investigated and compared for geogrids with and without their transverse members. Finally, the coefficients of interaction between the investigated soils and geosynthetics were evaluated. The results of this study indicated that (i) cohesive soils can be successfully reinforced with geogrids and geotextile reinforcements (ii) the interface shear strength increases with the decrease in moisture content and increases with the increase in dry density, (iii) the interface parameters obtained for geosynthetics with a rough surface are greater than the ones obtained with a smooth surface, and (iv) the coefficients of interaction (ci) are higher than 0.5 for all tests indicating good bonding between the tested soil and geosynthetics.



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Committee Chair

Louay Mohammad