A common mistake in Ottawa basement and cut-and-cover work is treating Leda clay as a uniform material. A single bond length assumption across Champlain Sea deposits will fail — sometimes within weeks of lock-off. We see this most often in the west end near the Rideau River, where sensitive clay lenses sit directly above till. Active anchor design here must adjust for time-dependent creep before the slope stability evaluation even begins. Our approach ties tendon free length, grout-to-ground friction, and lock-off load back to site-specific stratigraphy. For excavations deeper than 6 m in Gatineau Hills colluvium, we also require a deep excavation monitoring plan before finalizing anchor layout, since block movement in weathered rock can shear passive anchors if head details are too rigid.
Anchor creep in Ottawa's Leda clay can continue for 72 hours post-lock-off — early re-stressing prevents up to 15% load loss.
