Optimum jute geotextile spacing in reinforced sand: shear modulus and damping variation

This study examines the inclusions of jute geotextile (JG) sheets on shear modulus (⁠$G$⁠) and damping ratio (⁠$D$⁠) of dry sand. Resonant column (RC) and bender element (BE) tests were conducted on sand specimens reinforced with varying numbers of JG sheets under different confining pressures and for a wide range of input voltages. The inclusion of JG sheets in sand enhances significantly not only its shear modulus but also the damping ratio. The increase in the value of $G$ with a decrease in the spacing between the sheets was, however, noted to occur only up to a certain optimum spacing of JG sheets. The small-strain shear modulus (⁠$G0$⁠) obtained from BE tests further confirmed that the reinforcement-induced improvement in $G0$ becomes maximum corresponding to the optimum spacing of sheets. This optimum centre to centre spacing (⁠$s$⁠) of JG sheets was noted to be $13.9t$⁠, where $t$ is the thickness of the geotextile sheet. The damping ratio, on the other hand, increases continuously with a decrease in the spacing between the sheets. For the chosen JG reinforced sand, non-linear power law empirical expressions were introduced for predicting $G0$ and $Dmin$ for a given value of $σ3$ in terms of $s/t$ ratio.