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CPT approach to evaluating flow liquefaction using yield stress ratio

Tailings and Mine Waste Conference (2019 : Vancouver, B.C.); University of British Columbia. Norman B. Keevil Institute of Mining Engineering

Piezocone penetration testing (CPTu) is a well-utilized tool for geotechnical studies by the mining industry to evaluate the state, strength, and stability of tailings and mine wastes. Of particular concern to tailings are the conditions prone to flow liquefaction which consist of contractive geomaterials that are normallyconsolidated (NC) to lightly-overconsolidated (LOC) silty to sandy soils. Using an established relationship for assessing yield stress (σp', or apparent preconsolidation stress) in terms of the net cone resistance and CPTu material index (Ic), the interpreted profile of yield stress with depth is used to discern the boundaries between contractive and dilative soils within the context of critical state soil mechanics. The methodology is analogous to the concept of state parameter () where the contractive-dilative demarcation is taken theoretically at  = 0. Alternatively, a critical threshold is defined in terms of yield stress ratio (YSR = σp'/σvo') and contractive soils are identified when YSR is less than approximately 3, where σvo' = current effective overburden stress. The YSR method is applied to three case studies, including the recent tailings dam failure near Brumadinho, Brazil in January 2019.

Text

2024-02-15

Attribution-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87443

Unreviewed

http://creativecommons.org/licenses/by-nd/4.0/