2023-04-14 ニューサウスウェールズ大学(UNSW)
最近の研究では、鉱滓ダムは、高さ300mに及ぶ堤防もあるというその大きさと、ダム背後の鉱滓の組成により、地震時に破損しやすいことが明らかにされています。破局的な破壊は、環境破壊、死者、深刻な経済的損失につながる可能性があります。これらのダムの強度と安定性を評価することは不可欠であり、オーストラリアではコーンペネトレーションテスト（CPT）が潜在的な破損のリスクを測定するために使用されています。
＜関連情報＞
- https://newsroom.unsw.edu.au/news/science-tech/earthquake-research-shaking-tailings-dam-safety
- https://www.icevirtuallibrary.com/doi/abs/10.1680/jgeot.22.00074
- https://www.icevirtuallibrary.com/doi/full/10.1680/jgeot.21.00261
不飽和シルト質鉱滓と静的液状化に必要な条件のモデル化 Modelling unsaturated silty tailings and the conditions required for static liquefaction
Yanzhi Wang,Thanh Vo,Adrian R. Russell
Géotechnique Published:March 20, 2023
DOI:https://doi.org/10.1680/jgeot.22.00074
Abstract
The potential for static liquefaction of tailings is a major focus in the design and operation of tailings storage facilities. This research models the behaviour of unsaturated tailings, with a variety of degrees of saturation, addressing the propensity for static liquefaction during monotonic loading. Unsaturated triaxial tests, including constant suction conditions and constant water–air mass conditions, were performed. A bounding surface plasticity model was used to simulate the results. The constant mass condition is relevant to undrained closed-system loading, which may prevail during fast deformation after the tailings becomes unstable, when the air and water in the pore space remain locked inside the tailings. Boyle’s law and hydraulic hysteresis were accounted for to model the changes of pore air and water pressures, and suction, with the change in tailings volume. Good agreement was achieved between test results and model simulations. Additional simulations to mimic rising water tables under constant total stress states in the field, situations that may trigger instabilities, are also shown. Results are added to charts which relate peak and post-liquefaction strengths, as well as collapse lines, to measures of initial state, for unsaturated conditions, which may be of use in practice.
飽和および不飽和のシルト質鉱滓におけるコーン貫入試験 Cone penetration tests in saturated and unsaturated silty tailings
Adrian R. Russell, Thanh Vo, Juan Ayala, Yanzhi Wang, David Reid, Andy B. Fourie
Géotechnique Published:July 14, 2022
DOI:https://doi.org/10.1680/jgeot.21.00261
Abstract
Laboratory-controlled cone penetration test results for two silty tailings in a variety of saturated and unsaturated states, obtained using two calibration chambers, are presented then interpreted using a state parameter-based approach. For each, the cone penetration resistances, which increase due to the presence of suction when the tailings are unsaturated, can be normalised using the initial mean effective stress to establish a relationship with the initial state parameter. The relationship is applicable to saturated and unsaturated conditions, as long as the presence of suction hardening as well as the influence of suction on the mean effective stress are accounted for, and as long as the cone penetrations occur under drained conditions. The relationships enable state parameters to be back-calculated from normalised cone penetration resistances. The state parameters enable estimations of the tailings’ peak friction angles for drained loadings as well as their propensities to liquefy during undrained loadings. Application is demonstrated using cone penetration test soundings in the tailings storages from which the samples were taken, showing how in situ void ratios and state parameters, as well as future state parameters if the tailings were to become saturated, can be determined. Close agreements with direct measurements of void ratios are shown.
