Spreads in Canadian sensitive clays

Preliminary synthesis of detailed investigations of spreads that occurred in Canadian sensitive clays is presented. A thorough description of these landslides, including their final geometry, failure surface, and soil conditions in which they occur is given. Observation of debris morphology leads to the conclusion that horsts and grabens are resulting from active failure in the soil mass, dislocation, translation and subsidence in the remoulded shear zone below with no significant rotation. Failure surface forming during these landslides is close to the horizontal and generally starts near the toe of the slope. It is proposed that spreads results from (i) a failure surface being initiated and transmitted in an intact soil by progressive failure, followed by (ii) the dislocation of the above soil mass in horsts and grabens.