Effect of suction on small- and large-strain dynamic shear characteristics and volumetric deformations of compacted high-plasticity clay

Abstract

Understanding the hydromechanical characteristics of compacted soils is essential as these soils are commonly encountered in several geotechnical structures. The present experimental study evaluated the effect of suction and saturation on the shear and volumetric deformation characteristics of compacted high-plasticity clay. The soil suction values were obtained using filter paper and chilled-mirror hygrometer tests, and small (<?0.001%) to large (>?0.1%) strain dynamic responses were analyzed using a series of bender element and cyclic simple shear tests. Additionally, the volumetric deformation characteristics were evaluated using swell pressure and double oedometer tests. Experiments were conducted on the compacted specimens of Nagpur cohesive soil with varying degrees of saturation (10-95%) and matric suction values (ranging from 52 to 97,930 kPa). The shear strength under static loading increased from 182 to 389 kPa, the stiffness under large-strain dynamic loading increased from 5492 to 10,245 kPa, and collapse potential increased by almost 16 times with the decrease in as-compacted degree of saturation to 50%. Afterward, their values decreased with further reduction in saturation. By contrast, the small-strain shear modulus increased from 19.1 to 65.2 MPa and swell pressure increased from 10 to 212 kPa continuously with the increase in initial matric suction and reduction in the degree of saturation. These experimental findings challenge the conventional assumptions regarding unsaturated clays, emphasizing the consideration of compaction state and microstructural arrangements into the analyses of the hydromechanical response of compacted clays.