Prediction the shear strength and shear modulus of sand-clay mixture using bender element

Abstract

Employing the conventional laboratory geotechnical methods such as shear box test to measure shear strength and shear modulus require destroying the samples which is seen as time consuming and costly. Whilst the bender element technique (BE) maintains the sample condition, time, and cost efficiency. Several sand-clay mixtures were compacted and subjected to bender element test as well as sheared using shear box test to measure and correlate shear modulus (t), shear strength (G) and the maximum shear modulus (Gmax). The results showed the critical stage (transition fines-grained) at fine-grained (FG) equal to 50% where any further increment beyond this value led to decrement the soil mixture strength. Both t and G were normalized using moisture content, density, and applied normal stress. Five empirical equations from the normalized shear strength tN were applied on the previous field data to exam their reliable and limitations. The equations indicated the importance of including the effect of overburden pressure for the natural sample as well as the in-situ moisture content and field density to avoid uncertainty in the predicted value of the soil shear strength and modulus. At no depth limitation, all empirical equations (tN1, tN2, tN3, tN4, and tN5) exceed ±20% lines which indicated a large variation in results. At depth limitation (< 5 m), only one equation corresponding to N4 showed reasonable validity and reliability to predict the shear strength. Similar was on the prediction of the shear modulus. The 5 m depth limit was recommended to apply the equation consistently.