17 Effect of Reinforced Replacement Soil on Behavior of Soft Clay Abd EL Samee W. Nashaat and Ahmed S. Rabei Soil Mechanics and Foundation Civil Engineering Dep., Faculty of Engineering, Beni- Suef University, Beni- Suef, Egypt. Waelnashat@eng.bsu.edu.eg , Ahmed011285@eng.bsu.edu.eg Abstract: In the present study, the analysis is performed using finite element analysis to investigate the effect of geogrid reinforcement layers number on bearing capacity of soft clay, settlement and contact pressure as well as location and shape of failure surface at contact surface. The soil replacement used in this study is taken granular soil over soft clay. The soft clay material model used is Hardening Soil Model. The analysis program consists of sandy soil replacement with different thicknesses without and with different number of reinforcement layers at different vertical spacing between reinforcement layers. The parameters investigated included replacement layer thickness, number of geogrid reinforcement layers, vertical spacing between layers, and footing width. It was concluded that, the ultimate bearing capacity of soft clay at contact surface with replaced layers increases with increasing geogrid reinforcement layers number. However, increasing thickness of replaced reinforcement layer increases ultimate bearing capacity of soft clay. In addition, the ratio between settlement and total thicknesses of replaced layers at contact surface decreases with increasing replaced of reinforcement thickness and increasing geogrid reinforcement layers number. However, the stresses in soft clay soil at contact surface between soft clay and replacement soil decreases with increasing replacement thicknesses and increasing geogrid reinforcement layers number. In addition, the contact pressure values at contact surface with replacement layer decrease with increasing geogrid reinforcement layers number. In addition, the failure wedge angle of soft clay increases with increasing replacement thicknesses and increasing different number of geogrid reinforcement layers. In addition, the contact pressure values at contact surface with replacement soil layer has been determined. [Abd EL Samee W. Nashaat and Ahmed S. Rabei. Effect of Reinforced Replacement Soil on Behavior of Soft Clay. Life Sci J 2019;16(9):17-35]. ISSN: 1097-8135 (Print) / ISSN: 2372-613X (Online). http://www.lifesciencesite.com . 3. doi:10.7537/marslsj160919.03 . Keywords: Bearing, capacity, reinforced, replacement, soft clay 1. Introduction Removed and replacement soil is widely used in construction practices and proved to be an effective technique. Alamshahi and Hataf (2009) presented the effect of a new type of geogrid inclusion on the bearing capacity of a rigid strip footing constructed on a sand slope. A finite element analyses was carried out on a soil slope. It was concluded that the bearing capacity of footings on slope increased by additional grid- anchor layers. It is also included that the load- settlement behavior and bearing capacity of the rigid footing considerably improved by the inclusion of a reinforcing layer at the appropriate location in the fill slope [1]. Ornek et al. (2012) presented the use of the multi-linear regression model and artificial neural networks to predict the bearing capacity of circular footings on compacted granular fill over clay soil. The data used have been obtained from a series of field tests. Seven footing diameters over three different granular fill layer thicknesses were used in the field tests. It was concluded that, the bearing capacity of clay soil has been affected by using the granular fill layers [2]. Abu-Farsakh et al. (2013) investigated the behavior of reinforced sandy soil foundations - geosynthetic. The reinforcement layers number and the vertical spacing between them as well as type of geosynthetic reinforcement have been investigated. The effect of reinforcement geosynthetic on the distribution of vertical stress in the sand and the strain distribution along the reinforcement were observed. It was concluded that the reinforcement affects the behavior of reinforced sand foundation. [3]. Kolay et al. (2013) investigated by placing geogrids at different depths the improvement of bearing capacity of silty clay soil. Rectangular footing resting on the soil was used in the tests. It was concluded that increasing number of geogrid layers increases the bearing capacity of soft clay soil [4]. Altalhe et al. (2015) investigated the bearing capacity of strip footing on a sand slope using one, two and three reinforcing layers.