Abigail Cartwright, Matthew Coop, Li Wei, Andy Fourie
Tailings have previously been identified as having the types of mixed mineralogies and gradings that can make them susceptible to having non-unique critical states and normally compressed states in laboratory element tests. This paper addresses how this mode of behaviour would affect their resistance to undrained cyclic loading, contrasting two triaxial studies, one on a tailings that has a conventional behaviour and one transitional. To demonstrate the influence of transitional behaviour it was necessary to create samples with as wide a range of initial specific volumes as possible, while trying keep the sample preparation methods the same for loose and dense samples. It was also necessary to examine the cyclic data in non-conventional ways, notably in the volumetric plane to highlight better the effects of initial sample specific volume. It is shown that, as previously determined for monotonic loading, the initial density has much less influence on the cyclic behaviour of a soil with transitional behaviour than it would for a conventional soil, and it is instead the stress history that is very much more important. Samples following their respective normal compression lines exhibit similar behaviour but overconsolidation significantly enhances resistance and a sample that arrives at a given state by the undrained reduction of p’ due to cycling also has a much higher resistance.
尾矿先前已被确定为具有混合矿物学和分级类型，这使其在实验室元素测试中容易出现非独特的临界状态和正常压缩状态。本文探讨了这种行为模式会如何影响其抗排水循环荷载的能力，并对两项三轴研究进行了对比，一项是对具有传统行为的尾矿的研究，另一项是对过渡行为的研究。为了证明过渡行为的影响，有必要制作初始比容范围尽可能大的样本，同时尽量保持松散样本和致密样本的制样方法相同。此外，还有必要以非常规的方式，特别是在体积平面上检查循环数据，以更好地突出初始样品比容的影响。结果表明，正如之前对单调加载所确定的那样，初始密度对具有过渡特性的土壤的循环行为的影响远小于对传统土壤的影响，相反，应力历史则更为重要。沿着各自的法向压缩线的样本表现出相似的行为，但过度固结会显著增强阻力，由于循环导致 p' 的不排水减少而达到给定状态的样本也具有更高的阻力。
{"title":"Cyclic liquefaction in transitional and non-transitional tailings","authors":"Abigail Cartwright, Matthew Coop, Li Wei, Andy Fourie","doi":"10.1680/jgeot.23.00134","DOIUrl":"https://doi.org/10.1680/jgeot.23.00134","url":null,"abstract":"Tailings have previously been identified as having the types of mixed mineralogies and gradings that can make them susceptible to having non-unique critical states and normally compressed states in laboratory element tests. This paper addresses how this mode of behaviour would affect their resistance to undrained cyclic loading, contrasting two triaxial studies, one on a tailings that has a conventional behaviour and one transitional. To demonstrate the influence of transitional behaviour it was necessary to create samples with as wide a range of initial specific volumes as possible, while trying keep the sample preparation methods the same for loose and dense samples. It was also necessary to examine the cyclic data in non-conventional ways, notably in the volumetric plane to highlight better the effects of initial sample specific volume. It is shown that, as previously determined for monotonic loading, the initial density has much less influence on the cyclic behaviour of a soil with transitional behaviour than it would for a conventional soil, and it is instead the stress history that is very much more important. Samples following their respective normal compression lines exhibit similar behaviour but overconsolidation significantly enhances resistance and a sample that arrives at a given state by the undrained reduction of p’ due to cycling also has a much higher resistance.","PeriodicalId":508398,"journal":{"name":"Géotechnique","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139960048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zheng Zhou, Ali Akbar Karimzadeh, Anthony Kwan Leung, Sum Yin Fok
Hydrophobised soils found in the superficial region of earthen infrastructure can affect the hydrological processes of these structures. Hysteretic water retention curve (WRC), which governs these processes, for hydrophobised soils has rarely been reported. Existing apparatus was unable to measure the WRC of unsaturated soil as they cannot control the condition of pore water pressure (uw) in excess of pore air pressure (ua) when the contact angle is larger than 90°. This study created a new apparatus, which sandwiches a soil sample by a pair of high water-entry value (WEV) membrane and a high air-entry value (AEV) ceramic disk, to control the uw < ua and uw > ua conditions. Contact angle hysteresis and menisci evolution in the test materials during wet–dry cycles were measured to interpret the WRC. Results show that the WEV of soil was increased with decreasing chemical heterogeneity and particles size. When drying the hydrophobised soils, they could retain water before reaching a certain negative uw. The WEV identified from the second wetting cycle was lower than that from the first cycle, whereas the AEV remained largely unchanged. The WEV and AEV decreased when the particle size of the hydrophobised materials was increased, resulting in a smaller hysteresis size.
{"title":"Hysteretic water retention behaviour of unsaturated hydrophobised soils","authors":"Zheng Zhou, Ali Akbar Karimzadeh, Anthony Kwan Leung, Sum Yin Fok","doi":"10.1680/jgeot.23.00195","DOIUrl":"https://doi.org/10.1680/jgeot.23.00195","url":null,"abstract":"Hydrophobised soils found in the superficial region of earthen infrastructure can affect the hydrological processes of these structures. Hysteretic water retention curve (WRC), which governs these processes, for hydrophobised soils has rarely been reported. Existing apparatus was unable to measure the WRC of unsaturated soil as they cannot control the condition of pore water pressure (uw) in excess of pore air pressure (ua) when the contact angle is larger than 90°. This study created a new apparatus, which sandwiches a soil sample by a pair of high water-entry value (WEV) membrane and a high air-entry value (AEV) ceramic disk, to control the uw < ua and uw > ua conditions. Contact angle hysteresis and menisci evolution in the test materials during wet–dry cycles were measured to interpret the WRC. Results show that the WEV of soil was increased with decreasing chemical heterogeneity and particles size. When drying the hydrophobised soils, they could retain water before reaching a certain negative uw. The WEV identified from the second wetting cycle was lower than that from the first cycle, whereas the AEV remained largely unchanged. The WEV and AEV decreased when the particle size of the hydrophobised materials was increased, resulting in a smaller hysteresis size.","PeriodicalId":508398,"journal":{"name":"Géotechnique","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139531744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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