The soil conditions beneath Douglas Island differ substantially from those in the Lemon Creek valley. Glacial till dominates the benches while soft marine clays fill the lowlands near the Mendenhall wetlands. A standard penetration test provides N-values but cannot isolate the friction angle and cohesion parameters separately. This is where a triaxial test becomes essential for any foundation design requiring advanced constitutive modeling. The laboratory in Juneau runs both consolidated-drained and unconsolidated-undrained triaxial setups to match the drainage conditions expected during construction and throughout the structure's service life. For pavement design in the valley, we often pair the triaxial data with a CBR test to correlate stiffness with shear strength under repeated loading.
A single triaxial test on an undisturbed Shelby tube sample reveals more about Juneau's sensitive marine clays than a dozen SPT blows.
