Experimental Investigation for Shear Wave Velocity and Dynamic Characteristics of Unsaturated Sand–Clay Liners

This study aims to investigate the shear wave velocity and dynamic characteristics of unsaturated sand–expansive clay liners (SECLs) over a wide range of suctions. Liner layers have gained significant interest as environmentally friendly materials for several geotechnical and geoenvironmental applications. These materials are typically found in an unsaturated state as compacted layers and are exposed to dynamic loads from natural phenomena or manmade activities. In such circumstances, sustainable and stable performance should be ensured during the operation and lifetime of these layers by addressing the dynamic characteristics of these materials and possible degradation. Several specimens belonging to different liners of sand and expansive clay were prepared at different suction levels. The shear wave velocity was determined using the bender element technique (BEls). The specimens were then subjected to extensive cycles of dynamic loads up to 500 cycles in the triaxial dynamic loading system. The shear wave velocity and dynamic characteristics of both liners, such as shear modulus (G), damping ratio (D), and degradation index (δ), were determined on the basis of soil suction and loading cycles. Results indicated a descending trend of shear wave velocity with an increase in suction up to 130 MPa, and a significant reduction in shear modulus was detected. Meanwhile, the damping ratio demonstrated a significant increase with the increase in the suction levels of both liners. The reported results are of great significance for sustainable design and modeling of the unsaturated behavior of liner layers in several applications of geotechnical and geoenvironmental problems.