Deflection of Prototype Geosynthetic-Reinforced Working Platforms over Soft Subgrade

Abstract

Large-scale experiments were conducted on working platforms of crushed rock (breaker run stone or Grade 2 gravel) overlying a simulated soft subgrade to mimic conditions during highway construction where a working platform is used to limit total deflections because of construction traffic. Tests were conducted with and without geosynthetic reinforcement to evaluate how deflection of the working platform is affected by the presence of reinforcement, type of reinforcement, and thickness of the working platform. Four different geosynthetics were used: geogrid, woven geotextile, nonwoven geotextile, and drainage composite. Reinforced working platforms deformed at a slower rate, and, in most cases, deformation of geosynthetic-reinforced working platforms nearly ceased after approximately 200 loading cycles. Total deflections at 1,000 cycles were smaller by a factor of approximately two for reinforced working platforms relative to unreinforced working platforms, and smaller deflections were associated when less extensible geosynthetics were used for reinforcement. The thickness of a geosynthetic-reinforced working platform needed to meet a target deflection diminished approximately linearly with increasing logarithm of the interaction modulus, a measure of in situ extensibility measured in a pullout box. The reduction in working platform thickness attained with reinforcement was also larger when the target total deflection was smaller.