الفهرس 
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Abstract
Soil reinforcement is a technique used to improve the strength and stiffness of soil by utilizing geosynthetic inclusions. This study investigates the improvement in the bearing capacity of soft clay soil using perforated high-density polyethylene geosynthetic inclusions with a thickness equals 0.75 mm mimicking geogrid layers to overcome the scale effect. Physical model tests were performed for spread footings resting on reinforced sand underlain by soft clay to establish the load - settlement relations of unreinforced and reinforced soil systems. The improvement in the bearing capacity is expressed by the improvement factor. It was concluded that the use of geosynthetic reinforcement increases the bearing capacity. Also, wrapping the geosynthetic reinforcement to a length equal to the footing width B and 2B development increased the improvement factor to 4.54 compared to 3.36 (s/B= 10%) for unwrapped geosynthetic reinforcement of development length equal 2B, corresponding to 35% increase in the improvement factor. Thus, higher improvement factor could be achieved by wrapping the geogrid using less volume of excavation and replacement sand. The problem was modelled using a validated three-dimensional finite element numerical model to investigate the effect of various parameters on the improvement of bearing capacity of soil such as: undrained shear strength of soft clay, creep of geosynthetic reinforcement, consolidation of soft clay, and the combined effect of consolidation of soft clay and creep of geosynthetic reinforcement.
The method of replacement was investigated to study the feasibility of reducing the volume of replaced soil, and it was found that the improvement in the bearing capacity of soil for extended replacement was slightly higher than the case of zoned replacement (6-13%).
The creep of geosynthetic reinforcement had slightly more effect at larger settlement value such as s/B=10%. The limited creep effect was mostly due to the small strains developed in the geogrid.
The improvement factor was inversely proportional to the degree of consolidation of clay. Hence, designers perform consolidation analysis for the problem of reinforced foundation pad over submerged soft clay.
The stiffness improvement factor for a group of four spread footings was less than a single spread footing. For instance, the improvement factor for a single footing (su=18 kPa) was 3.28 (s/B=10%) while in the case of four footings spaced at S/B= 4,6, and 8, the improvement factor was equal to 2.79, 2.93, and 2.99, respectively. However, for the case of S/B=10 the value of the improvement factor was almost equal to that obtained from a single spread footing.