PERFORMANCE OF GEOSYNTHETIC- REINFORCED GYPSEOUS SOIL

As the presence of gypsum in so il affects its engineering prope rties and behavior in a degree, which is greatly dependent on the amount of gypsum, thus ground improvement and stabilization techniques are needed. The main purpose of the work is to conduct a series of model tests subje cted to static vertical load to withstand on the ability of soil stabilization with geosynthetics material by using sing le and double geogrid layers placed at different locations. For this purpose, a special model test setup was use d for such testing. In the light of experimental tests and analyses of these model tests, it is found the settlement r atio of the untreated soil increases linearly with an increase of stress with bearing ratio 0.75 and the mode of fail ure seems to be local shear failure. A reduction in settlement with high bearing capacity is noticed after using si ngle geogrid layer reinforcement compared with the unreinforced soil. The bearing ratio is increased reaching 0.97 when the single geogrid layer depth increases at an optimal depth equals foundation width (B). At this depth, the b earing improvement ratio (BIR) was 1.29 with settlement reduction ratio of 0.74. Increasing the number of ge ogrid layers results in a decrease in collapse settlement ratio, increasing in bearing ratio compared to untre ated soil. The optimal depths for using double geogrid layers were (2/3) B and B with bearing ratio 1.05. Simi lar enhanced values are obtained for bearing improvement and settlement reduction ratios (1.41 and 0.65 resp ectively).