An experimental investigation was conducted to evaluate the effects of polypropylene fiber inclusions on the geotechnical characteristics of a clayey soil that was chemically stabilized with cement and fly ash. For all stabilized soils, cement and fly ash were added at 8% and 30%, respectively. Reinforced stabilized soil specimens were prepared at four different percentages of fiber content (0.25%, 0.50%, 0.75%, 1.0%) and three different fiber lengths (6 mm, 12 mm, 20 mm). Unconfined compressive and split tensile strength tests were carried out after 7- and 28-day curing periods. The volume change characteristics of the reinforced stabilized soil were determined using shrinkage limit and crack reduction values. The interactions between the fiber surface and the stabilized soil were analyzed by means of scanning electron microscopy. According to the results, the compressive and especially the tensile strength values increased to a great extent following the addition of fiber into the stabilized soil. The highest strength values were obtained with 0.5–0.75% content for the 12 mm-long fibers. The shrinkage limit and crack reduction values increased with increased fiber content and greater fiber length, whereas volume changes decreased.

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In this paper, the investigation of the optimum designs for two types of concrete cantilever retaining walls was performed utilizing the artificial bee colony algorithm. Stability conditions like safety factors sliding, overturning and bearing capacity and some geometric instances due to inherent of the wall were considered as the design constraints. The effect of the existence of the key in wall design on the objective function was probed for changeable properties of foundation and backfill soils. In optimization analysis, wall concrete weight which directly affect parameters such as carbon dioxide emission and the cost was considered as the objective function and analyzes were performed according to different discrete design variables. The optimum concrete cantilever retaining wall designs satisfying constraints of stability conditions and geometric instances were obtained for different soil cases. Optimum designs of concrete cantilever retaining wall with the key were attained in some soil cases which were not found the feasible optimum solution of the concrete cantilever retaining wall. Results illustrate that the artificial bee colony algorithm was a favorable metaheuristic optimization method to gain optimum designs of concrete cantilever retaining wall.

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