As a member of the Editorial Advisory Panel I would like to welcome you to the October 2019 issue of Geotechnical Engineering, which contains a briefing article and five papers.
The six contributions cover topics including: liquefaction potential of oil contaminated ground; impact of tunnelling on masonry buildings; sludge embankment stability; fall-cone testing of unsaturated soils; and size effects on expansive clay behaviour.
The first contribution by Naeini et al. (2019) is a briefing article that examines the effects of the liquefaction potential of silty sands with the presence of oil contaminants. A series of triaxial cyclic tests for different oil percentages and silt contents were performed. The results show that, overall, both oil and silt content have a considerable effect on the liquefaction behaviour. This paper provides very useful experimental data that may be used to further validate existing multiphase constitutive models (e.g. Gajo et al., 2018) and provide inspiration for future centrifuge experiments (e.g. Bertalot and Brennan, 2015) to ultimately help understand the mechanisms governing liquefaction of silty sands saturated with oil-contaminated water.
In the second article of this issue, DeJong et al. (2019) investigate the interaction between soil and surface structures – and consequent damage – due to tunnelling. The study focusses on masonry buildings with shallow foundations and uses available Crossrail monitoring data. The two main objectives of the paper were the evaluation of building performance and the assessment of the current methodologies for building damage predictions. Figure 1 shows one of the results reported in the paper. It shows the monitoring locations and the vertical settlements projected on the transect line perpendicular to the tunnels under Berwick Street in London, UK.
The authors highlight the importance of the need of detailed building monitoring data, in addition to precise levelling points transect data. For example, the separation of the tunnels under Berwick Street induced the formation of three hogging zones and consequent potential to cause a high level of damage to the properties (Figure 1). As detailed by Ciantia et al. (2018) and Giardina et al. (2019), synthetic aperture radar interferometry shows potential to augment in situ monitoring of building deformations.
The third article by Verreydt et al. (2019) deals with the stability of sludge embankments. Results of a full-scale slope failure test on an embankment constructed with industrial calcium fluoride (CaF2) sludge are presented. To perform numerical finite-element back calculations of the slope failure, in situ vane shear tests are performed and used for calibration of the constitutive model. The analyses show the importance of accounting for strength anisotropy in such materials and highlight the need of appropriate probabilistic design, particularly for larger embankments where material heterogeneity is more influential (Griffiths and Fenton, 2004).
In the fourth article of this issue, Cabalar and Demir (2019) present the results of an intensive series of fall-cone tests performed in the laboratory. The authors investigate the influence of both size and shape characteristics of sand grains, the amount of clay and the water content in a sand–clay mixture on the undrained shear strength. These results are very insightful and may serve as inspiration to the material point method (e.g. Zambrano and Yerro, 2019) and particle finite-element method (Monforte et al. 2017) modellers.
The next paper of this issue deals with expansive clays. Mawlood and Hummadi (2019) report the results of a very interesting experimental campaign on size effects on the volume changes of expansive clays. The effect of the size of the samples on the deformation behaviour of the clay during wetting and drying cycles was studied. Interestingly the amounts of free swell and reversible percentages decrease with the increase in height and diameter of the soil samples, whereas the irreversible percentage was noticeably higher in the large-scale samples than in the small-scale and extra-large soil samples. These results should be taken into consideration by expansive clay modellers as free swell experimental data of small-scale samples are usually used for calibration (Ghiadistri et al., 2019).
Moving on to granular materials, the last paper in this issue by Guo et al. (2019) present a novel equation to describe the particle size distribution (PSD) of coarse-grained soils. The authors show how this equation can be used for analytically computing particle breakage factors more accurately than the current and widely used approaches. As detailed in Ciantia et al. (2019), grain crushing and consequent PSD evolution has a considerable influence on the mechanical response of driven piles in sand. Therefore, accurate and efficient PSD descriptors are of great value for numerical modellers as they would need to include sand grading as an internal variable.
The journal welcomes discussion contributions on any of the papers in this issue or recent issues of the journal. Further instructions on the preparation and submission of a discussion are given at the end of each paper.
On behalf of the Editorial Panel, we hope you will enjoy this issue of Geotechnical Engineering.
