LABORATORY MEASUREMENT APPROACH FOR ANISOTROPY IN CHAMPLAIN CLAYS

ABSTRACT: Soil anisotropy in natural clay deposits is a consideration in several geotechnical applications, including the design of foundations, slopes, and excavations. The Champlain clays of Eastern Canada, formed through marine sedimentation 10,000–12,000 years ago, exhibit distinct bedding characteristics that make them susceptible to anisotropy. This behavior can originate from either the microstructure of the clay fabric or the stress history. A series of laboratory methods used to assess anisotropy is reviewed. Wave-based approaches highlight some practical advantages in terms of simplicity and testing duration. This study employs an advanced laboratory setup using piezoelectric ring actuators integrated into an oedometer apparatus to quantify the anisotropic behavior through shear wave velocity. The measurements were conducted during 1D consolidation testing, allowing for simultaneous evaluation of stress-induced changes in anisotropy. The shear wave velocities were measured in both vertical and horizontal directions (Vvh and Vhh) under varying applied stress levels. Through wave propagation measurements in these two directions, the inherent and stress-induced components of anisotropy were inferred. The tested soft marine clay specimens demonstrated relatively low to moderate directional dependency, reflecting the effect of both their depositional fabric and stress history. These findings provide valuable insights into the mechanical behavior of Champlain clays and contribute to the understanding of anisotropy for geotechnical analyses.