Target reliability-based design optimization studies on cohesive soil amended with chitosan and casein for liner applications

The current study investigated the primary and secondary compressibility characteristics of organic clay with two biopolymers, Chitosan ( D ch ) and Casein ( D ca ) at dosages of 0.5%, 1%, 2%, and 4%. The primary compression index ( C c ) values were reduced by 18% and 59% at dosage ( D ch and D ca ) of 4% at a consolidation pressure of 800 kPa. The secondary compression indices of chitosan and casein-treated soils fell below the normal range specified for organic soils and lay in the range of 0.01–0.017. The biopolymers also accelerated the consolidation process at all dosages ( D ch ) and 2% D ca . The hydraulic conductivity increased for all dosages of chitosan whereas it declined for all dosages of casein compared to untreated soil. The reliability analysis was conducted for biopolymer-treated soils and presented a rational approach toward the selection of a suitable liner. Chitosan failed to achieve a target reliability index of 3 whereas casein-amended samples attained values equal to and greater than 3 at all dosages and consolidation pressures at COV of K max = 20%. At all dosages, the casein-treated soils exhibited reliability index values greater than 3 up to COV of K max = 40% indicating the higher stability of casein mixes as a liner material.