Abstract:Desiccation (water loss by drying or freeze-thaw sufficient to generate matric suction), can influence the performance of a tailings deposit both positively and negatively. The significance of desiccation is largest in tailings that have been dewatered prior to deposition, by thickening or filtration. Such tailings can be “stacked” or deposited with a significant slope, which usually implies that a substantial volume of tailings remain above water. Under such conditions the tailings, by accident or by design, … Show more
“…Indeed, the largest increase in strength in the element tests occurs from w = 30% to 25%; w = 30% being the post-settling water content for these tailings. A comparison of similar data in Figure 13 with some vane tests from the field is shown in Simms (2021). A mechanism for the increase in dilatancy was postulated by Daliri et al (2014) based on SEM images of freeze-dried samples.…”
Section: Elements Of Unsaturated Soils Applicable To Tailings Drying ...mentioning
confidence: 72%
“…Fortunately, these somewhat complex interactions have been conceptualised by several models in the field of unsaturated soils, and many of these models (Basic Barcelona, or BBM, state surface or SSM, and Glasgow coupled or GCM) have been implemented in geotechnical codes, although for small strain conditions. Qi et al (2017aQi et al ( , 2020 reset these models into a large strain consolidation framework, the UNSATCON code, which has been applied to multilayer drying box tests (up to 1 m deep multilayer deposits, 1 by 1 m in plan), as well as field data from both hard rock and oil sands mines (Qi & Simms 2018a, Simms 2021). Here we do not focus on the details of the particular soil models (e.g.…”
Section: Elements Of Unsaturated Soils Applicable To Tailings Drying ...mentioning
Proper application of unsaturated soils to thickened or filtered tailings has substantial potential to optimise such tailings deposition. Unsaturated behaviour bears on both the geotechnical and geo-environmental performance of these deposits. Geotechnically, there is an increase in strength through both additional densification, and the presence of suction, as well as a stress history effect. The latter is especially important to understand in situ measurements in previously desiccated deposits; geo-environmentally, unsaturated behaviour strongly bears on seepage generation, as well as management or mitigation of acid generation. This paper summarises a body of work on experimentation, numerical simulation, and field data relating to different aspects of unsaturated behaviour and their relevance to practical outcomes for design of thickened or filtered tailing deposits. An important new outcome from this summary is the suggestion to characterise the extent of the stiffness imparted by drying, especially due to the possible risk of strength loss in thick deposits when the tailings eventually yield under self-weight.
“…Indeed, the largest increase in strength in the element tests occurs from w = 30% to 25%; w = 30% being the post-settling water content for these tailings. A comparison of similar data in Figure 13 with some vane tests from the field is shown in Simms (2021). A mechanism for the increase in dilatancy was postulated by Daliri et al (2014) based on SEM images of freeze-dried samples.…”
Section: Elements Of Unsaturated Soils Applicable To Tailings Drying ...mentioning
confidence: 72%
“…Fortunately, these somewhat complex interactions have been conceptualised by several models in the field of unsaturated soils, and many of these models (Basic Barcelona, or BBM, state surface or SSM, and Glasgow coupled or GCM) have been implemented in geotechnical codes, although for small strain conditions. Qi et al (2017aQi et al ( , 2020 reset these models into a large strain consolidation framework, the UNSATCON code, which has been applied to multilayer drying box tests (up to 1 m deep multilayer deposits, 1 by 1 m in plan), as well as field data from both hard rock and oil sands mines (Qi & Simms 2018a, Simms 2021). Here we do not focus on the details of the particular soil models (e.g.…”
Section: Elements Of Unsaturated Soils Applicable To Tailings Drying ...mentioning
Proper application of unsaturated soils to thickened or filtered tailings has substantial potential to optimise such tailings deposition. Unsaturated behaviour bears on both the geotechnical and geo-environmental performance of these deposits. Geotechnically, there is an increase in strength through both additional densification, and the presence of suction, as well as a stress history effect. The latter is especially important to understand in situ measurements in previously desiccated deposits; geo-environmentally, unsaturated behaviour strongly bears on seepage generation, as well as management or mitigation of acid generation. This paper summarises a body of work on experimentation, numerical simulation, and field data relating to different aspects of unsaturated behaviour and their relevance to practical outcomes for design of thickened or filtered tailing deposits. An important new outcome from this summary is the suggestion to characterise the extent of the stiffness imparted by drying, especially due to the possible risk of strength loss in thick deposits when the tailings eventually yield under self-weight.
“…In recent years, developments of tailings dewatering technologies, and especially filtered tailings, have contributed to maximise water recovery and minimise geotechnical risk (Simms 2017(Simms , 2021. The objectives of filtered tailings in particular are to produce tailings with solid content greater than 80% using various dehydration processes (Lara et al 2013;Weatherwax & Kipara 2010).…”
Section: Introductionmentioning
confidence: 99%
“…The probability of failure in filtered TSFs is significantly reduced compared to conventional slurry TSF but the risk still exists (Wilson & Robertson 2015). Filtered TSFs are constructed on the surface and are exposed to climate conditions (Daliri et al 2016;Simms, 2017Simms, , 2021. Global warming will contribute to increase the frequency of extreme weather events such as droughts and heavy rains with direct consequences on mining operations (O'Gorman 2015).…”
Section: Introductionmentioning
confidence: 99%
“…Global warming will contribute to increase the frequency of extreme weather events such as droughts and heavy rains with direct consequences on mining operations (O'Gorman 2015). Therefore, filtered tailings are (and will continue to be) exposed to repeated drying (due to evaporation) and wetting (due to precipitation) cycles (Fredlund & Houston, 2013;Fredlund 2019;Simms 2021). Understanding the hydro-mechanical responses of filtered tailings to wetting and drying cycles is therefore crucial to ensure the short-and long-term the stability of filtered TSFs (Cacciuttolo Vargas & Pérez Campomanes 2022).…”
Filtered tailings management has many advantages over traditional slurry tailings management, such as improved water recovery and recirculation, and a reduction of geotechnical risk. However, the long-term evolution of the water content in filtered tailings exposed to climatic conditions could affect its geotechnical properties. Shear strength properties of unsaturated tailings have a critical role when evaluating the geotechnical stability of a dry stack facility, especially in the context of climate change. The objective of this research was, therefore to investigate the influence of drying and wetting cycles on the shear strength of filtered tailings for a low matric suction range (i.e. 0~50 kPa). A series of consolidated-drained (CD) direct shear tests were conducted on re-compacted unsaturated filtered tailings specimens. For each matric suction achieved by following either the wetting or drying curve, three direct shear tests were performed with varying normal stresses. Direct shear test results showed a nonlinear increase in the unsaturated shear strength with the normal stress and matric suction. Empirical hyperbolic functions were used to fit experimental data and evaluate the shear strength of unsaturated filtered tailings for a higher matric suction range. Test results also indicated some hysteresis, and the shear strength during drying was smaller than during wetting for the same matric suction. However, matric suction and water retention curve (WRC) hysteresis had no significant impact on the measured effective friction angle.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.