Effect of Biopolymer Treatment on Pore Pressure Response and Dynamic Properties of Silty Sand

Liquefaction is a phenomenon where the soil mass behaves like a liquid due to the rise in excess pore-water pressure, which results in the complete loss of shear strength. Most of the conventional liquefaction-mitigation practices have several limitations, of which environmental issues are the most prevalent. Therefore, a sustainable and efficient technique needs to be developed. The use of biopolymers in the field of geotechnical engineering for improving various soil properties has been a popular research theme in recent years. Although its application in the enhancement of engineering properties of soil have been investigated, biopolymer-treated soils have not been much explored for sustaining dynamic loading or against liquefaction failure. In the current study, a series of consolidated undrained, strain-controlled cyclic triaxial tests were conducted on agar biopolymer–treated natural silty sand obtained from Kalpetta, Kerala, India. The treated soil at different curing times (3, 7, and 28 days) was subjected to dynamic loading at varying cyclic axial strains (0.3%, 0.5%, 0.8%, and 1%). The dynamic secant shear modulus was found to be enhanced significantly; shear modulus of 7-day-cured, 2% agar biopolymer–treated soil was 317% more than untreated soil samples at the 50th loading cycle. At the same time, the excess pore pressure buildup was reduced by a great extend due to treatment. The maximum excess pore pressure ratio was just 0.67 in treated soils, which was 33% less compared with untreated soils. This indicates the potential of using biopolymers as an environment-friendly alternative for mitigation of liquefaction-induced soil failure in view of their pore-filling and stiffness-enhancement properties.