Authors: Zhenhe Song, Robert Truby and Jim (Shunqin) Luo
Conference: Mine Waste and Tailings Conference 2023
Date: July 13-14, 2023
Site investigations were conducted to obtain soil parameters for stability and deformation assessment for an upstream tailings storage facility. Three material types that control the tailings dam stability were identified during the site investigations, comprising coarse-grained silty/sandy tailings, fine-grained silty/clayey tailings and residual soil. Advanced in situ tests, including Seismic Cone Penetrometer Tests (SCPT) and Vane Shear Tests (VST) were conducted. A comprehensive laboratory testing program was undertaken, which included direct simple shear (DSS) tests and triaxial tests to assess the Critical State Line (CSL).
An integrated approach was adopted to determine soil parameters, takings advantage of both in situ and laboratory test results. The peak undrained shear strengths ratios (su/σ’v) of the fine-grained silty/clayey tailings were determined from the DSS test results. The CPT cone factor (Nkt) was calibrated using in situ su/σ’v strengths of the materials in relatively thin layers. Subsequently, the in situ strengths of all other layers were calculated using the Nkt factor. Due to partial drainage in the coarse-grained tailings, its peak and residual undrained shear strengths were assessed using triaxial and non-standard VST test results.
The yield stress of the residual soil was determined using laboratory tests, Self-boring Pressuremeter (PMT) and FLACTM numerical modelling results. The undrained shear strength of the residual soil was based on the calculated yield stress, PMT undrained shear strength and DSS test results.
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