Mechanical behavior of lightweight soil reinforced with waste fishing net

Lightweight soil is cement-treated and consists of dredged clayey soil, cement, and air-foam. Reinforced lightweight soil (RLS) contains waste fishing net to increase its shear strength. This paper investigates the strength characteristics and stress–strain behavior of reinforced and unreinforced lightweight soils. Test specimens were prepared with varying admixtures of cement content (8%, 12%, 16%, and 20% by the weight of untreated soil), initial water content (125%, 156%, 187%, 217%, and 250%), air-foam content (1%, 2%, 3%, 4%, and 5%), and waste fishing net (0%, 0.25%, 0.5%, 0.75%, and 1%). Then several series of unconfined compression tests and one-dimensional compression tests were conducted. The experiments with lightweight soil indicated that the unconfined compressive strength increased with an increase in cement content, but decreased with increasing water content and air-foam content. The stress–strain relationship and the unconfined compressive strength were influenced by the percentage of waste fishing net. In addition, the strength of RLS generally increased after adding waste fishing net due to the bond strength and the friction at the interface between waste fishing net and soil mixtures, but the amount of increase in compressive strength was not directly proportional to the percentage of waste fishing net. The results of testing indicated that the maximum increase in compressive strength was obtained for a waste fishing net content of about 0.25%. The bulk unit weight of lightweight soil was strongly dependent on the air-foam content. The compression characteristics of lightweight soil, including the yield stress and compression index, did not depend greatly on whether the samples were cured underwater or in air.