Integrated Approach to Rapidly Iterate Through LEA Stability Analyses for Design of Staged Construction Over Silty Clay Soils
Authors: Amy L. Adams1, Jessica Breault1, Reagan McIsaac1
Conference: 2026 CDA Annual Conference & Trade Show
Date: October 25–28, 2026
1 Knight Piésold Ltd., North Bay, Ontario, Canada
2 Orezone Québec Inc., Casa Berardi Mine, La Sarre, Québec, Canada
ABSTRACT
Staged construction of large embankments over silty clay soils requires a detailed understanding of the variation in strength with effective stress as well as careful prediction and monitoring of changes in pore pressure which affect effective stress. The pore pressure, effective stress, and strength of silty clay foundation soils can vary laterally, vertically, and with time. Staged construction requires even more careful planning and monitoring if pore pressures from previous stages do not have time to fully dissipate before the next stage of construction and the pore pressure profile becomes highly variable in space and time.
This paper describes an integrated methodology that has been developed to rapidly iterate through design of a staged embankment over silty clay soils using Limit Equilibrium Analysis (LEA). The approach uses a single soil strength model to evaluate strength ranging from drained (frictional) at low effective stress to undrained (strength ratio) at higher effective stress, eliminating the need to divide the foundation into different behavioural zones and addressing several common errors in slope stability analyses as summarized by Brown and Gillani (2016). Effective use of the integrated method is illustrated via a case history for a large mining embankment that was raised over silty clay foundations over the last four years. The integrated method was used to develop the initial design, develop Factor of Safety (FoS) based trigger levels, and respond quickly to proposed changes in the construction schedule that would impact overall stability.
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