{"title":"Competing effects of wetting and volume change on G0 in compacted loess","authors":"M. Ge, J. Pineda, D. Sheng","doi":"10.1680/jgele.22.00125","DOIUrl":"https://doi.org/10.1680/jgele.22.00125","url":null,"abstract":"This paper explores the relative contributions of wetting (suction reduction) and its associated volume change on the small-strain shear stiffness, <i>G</i><sub>0</sub>, in compacted loess from Xi’an, China. Results from one-dimensional compression tests with measurements of the shear wave velocity upon wetting and loading paths are presented. The experimental results show that the softening caused by wetting compete with the densification caused by plastic deformation and their effects on <i>G</i><sub>0</sub> are strongly controlled by stress level applied prior to wetting. Below the compaction stress, suction effects are dominant and <i>G</i><sub>0</sub> reduces irrespective of the magnitude of the collapse strain. With the increase in the stress level, the reduction in <i>G</i><sub>0</sub> caused by saturation is compensated by the plastic deformation triggered by soil collapse. This behaviour is clearly observed when the soil is first loaded to the compaction stress, where the maximum collapse strain is measured upon wetting. Volume change is dominant once the compaction stress is exceeded so that <i>G</i><sub>0</sub> tends to increase upon wetting. A wetting-induced stiffness factor <i>D</i> is defined to demonstrate that the change in <i>G</i><sub>0</sub> varies linearly with the stress level and this behaviour is independent of the compaction conditions.","PeriodicalId":501470,"journal":{"name":"Géotechnique Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138535396","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}
{"title":"Critical state shear strength at concrete-sand-bentonite slurry interfaces: mix proportions and rate effects","authors":"K. G. O'Dwyer, B. A. McCabe, B. B. Sheil","doi":"10.1680/jgele.22.00086","DOIUrl":"https://doi.org/10.1680/jgele.22.00086","url":null,"abstract":"This paper describes direct shear testing of a range of sand-bentonite slurry mixes, identified as a gap in the literature. In the absence of a concrete interface, there was an apparent transition zone from sand-governed strength (bentonite content ≤30%) to clay-governed strength (bentonite content ≥80%), which was linked to the sample void ratio. When a concrete interface was introduced, the critical stress ratio (critical state shear stress normalised by the effective normal stress) was found to change linearly with bentonite slurry content, reflecting an interface sliding failure mechanism. The testing also considered the effect of shearing rates ranging from 0.0025 mm/min to 10 mm/min on interface shear strength. The mixtures containing greater bentonite slurry content displayed a greater decrease in the critical stress ratio with increasing shear rate. Very few studies have explored the influence of the relative sand-clay mix composition on interface shear resistance; these results provide a better understanding of their mechanical behaviour and forms a basis for future research in this area.","PeriodicalId":501470,"journal":{"name":"Géotechnique Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138535401","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}
{"title":"Assessing temperature dependence of soil water adsorption strength by molecular simulation","authors":"Jianbo Wang, Zemin Qiu, Chao Zhang, Renpeng Chen","doi":"10.1680/jgele.21.00126","DOIUrl":"https://doi.org/10.1680/jgele.21.00126","url":null,"abstract":"Soil water adsorption strength represents the changing rate of adsorptive water content with regard to soil suction or water potential changes, dictating the magnitude of the soil water-retention curve at the dry end. Non-isothermal conditions are frequently encountered in energy and environmental geotechnics, posing the requirement to assess temperature effects on soil water adsorption strength. Yet, it remains challenging in assessing the temperature effects at the high suction range due to limitations in available experimental techniques. Here, the grand canonical Monte Carlo (GCMC) simulation was explored as a method to address this challenge. A series of GCMC simulations has been performed to assess the temperature effect on the external surface adsorption of three representative soil minerals – that is, K-muscovite, Na-montmorillonite and <i>α</i>-quartz. Molecular simulation results preliminarily reveal that the water adsorption strength of the external surface of these soil minerals only demonstrates marginal dependence on temperature. This observation is consistent with experimental results, substantiating the feasibility of the proposed method.","PeriodicalId":501470,"journal":{"name":"Géotechnique Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138535307","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}
R.-M. Yang, R.-W. Wei, Z.-N. Zhang, T.-L. Zheng, L. Ma
{"title":"Effects of initial water content on compression behaviour of municipal sewage sludge","authors":"R.-M. Yang, R.-W. Wei, Z.-N. Zhang, T.-L. Zheng, L. Ma","doi":"10.1680/jgele.21.00112","DOIUrl":"https://doi.org/10.1680/jgele.21.00112","url":null,"abstract":"To investigate effects of initial water content on compression behaviour of municipal sewage sludge and clarify its intrinsic compression characteristics. Oedometer tests were conducted on sludge with various initial water content of 0·13–1·48 times the liquid limit. It is observed that the sludge is organic high liquid limit silt, whose <i>e</i>–log <i>σ</i>′<sub arrange=\"stack\">v</sub> compression curves are inverse ‘S’ shape due to organic floc structure of sludge potentially. When the effective vertical stress <i>σ</i>′<sub arrange=\"stack\">v</sub> > 100 kPa, a clear gap of compression curves of various initial water content still exists, different from Burland's viewpoint that compression curves tend to be consistent. Burland's concept of intrinsic compression line (ICL) is adopted for correlating compression curves of sludge well, and an ICL of the sludge is derived. The ICL of sludge is below ones reported by Hong and Burland when <i>σ</i>′<sub arrange=\"stack\">v</sub> < 100 kPa, due to the difference in initial water content. A generalised void index is tentatively proposed by introducing generalised intrinsic parameters <i>e</i>*<sub arrange=\"stack\">y1</sub> and <i>e</i>*<sub arrange=\"stack\">y2</sub>, which may be related to the loading history of the soil and the maximum load that the soil may bear in future engineering, respectively.","PeriodicalId":501470,"journal":{"name":"Géotechnique Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138535308","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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