Large-scale direct shear and CBR performance of geofibre-reinforced sand

Abstract

Soils that do not possess desirable engineering characteristics for use for pavement base courses, subbase courses, subgrades, and as a foundation-supporting layer under buildings may be stabilised and improved with geofibre reinforcement. This paper presents results from an extensive and systematic experimental study on the performance of a geofibre-reinforced sand. Large-scale direct shear box and California Bearing Ratio (CBR) performance tests were conducted on samples of poorly graded sand reinforced with fibrillated polypropylene geofibre at gravimetric dosage rates of 0.2%, 0.5%, and 0.8%. The samples were tested in non-submerged and submerged conditions. The variation in shear strength characteristics was evaluated in terms of shear stress–deformation response, peak friction angle, and residual friction angle. The results from the large-scale direct shear tests in both non-submerged and submerged conditions indicate that significant improvement of shear strength may be obtained with a proper dosage of geofibre. The CBR tests of the soil at varying geofibre content show that the inclusion of sufficient geofibre reverses the typical CBR behaviour of unreinforced soil to that indicating more soil resistance, and thus larger CBR values, with increasing depth of penetration.