Search

Understanding the variation of geological interfaces plays a crucial role in the analysis and design of infrastructure systems. Generally, there are two classes of techniques for predicting geological interfaces, for example, interpolation/regression-based techniques and machine-learning-based techniques. In this paper, a Multi-scale Meta-learning Model (M3) methodology is proposed. The new methodology improves the current state-of-the-art techniques by fusing two levels of information: (i) generic characteristics of the sampling locations, for example, coordinates, and (ii) location-specific characteristics, for example, local-scale predictions. The implementation starts from using an array of classic interpolation/regression-based techniques as base learners to provide first-level predictions at a local scale. These predictions are then combined with generic characteristics to train a meta-learner following the stacking ensemble learning framework. In this manner, the location-specific information from the base learners can be simultaneously considered with the generic information in the training process. The variation of rockhead elevation is predicted using the M3 methodology and a comprehensive borehole dataset in Singapore. A detailed comparative study involving several existing methods is also carried out to rigorously validate the M3 methodology. The results show that the M3 methodology achieves 20% improvement in the model performance compared to existing methods, indicating its promising potential in geotechnical site characterization. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A series of one-dimensional consolidation tests were performed under varying pretreatments on high quality soil samples collected from a Singapore upper marine clay layer in an attempt to evaluate the effect of cementation by amorphous materials on its compressibility. The findings from this study seem to suggest that cementation by ethylene-diamine tetraacetic acid (EDTA) removable amorphous materials may only partially contribute to the development of soil microstructure and overconsolidation in Singapore upper marine clay. On a réalisé une série d’essais de consolidation unidimensionnelle après divers prétraitements sur des échantillons de haute qualité de sols prélevés dans la couche supérieure de l’argile marine de Singapour pour tenter d’évaluer l’effet de la cimentation par des matériaux amorphes sur sa compressibilité. Les conclusions de cette étude semblent suggérer que la cimentation par des matériaux amorphes amovibles par « ethylene-diamine tetraacetic acid (EDTA) ne peut contribuer que partiellement au développement de la microstructure et à la surconsolidation du sol dans l’argile marine supérieure de Singapour. [ABSTRACT FROM AUTHOR]

For a country like Singapore with limited natural resources, innovative technologies are required to reduce sludge disposal volume and increase biogas production to recover energy in the wastewater treatment process. Ultrasound disintegration technology is potentially useful since it disintegrates sludge solids and enhances anaerobic digestion. The technology was tested in the field under tropical conditions with a full-scale ultrasonic facility and two 5000 m3 egg-shaped digesters. Each digester was fed with mixed primary (one-third) and thickened activated (two-thirds) sludge of identical quality and volumes of up to 200 m3·d–1. For the two digesters, all operating conditions were the same except for the inclusion (test) and omission (control) of the ultrasonic device to pre-treat the sludge feed. In comparison with the control, the five-month field study showed that ultrasound pre-treatment of the sludge increased the daily biogas production up to 45%. There were no significant differences in biogas composition from the two digesters. When translating the increases in biogas production into its source (volatile suspended solids), an increase in sludge solids removal of up to 30% is expected under optimal operation conditions. Pour un pays comme Singapour avec des ressources naturelles limitées, des technologies innovatrices sont requises pour réduire le volume de boues éliminées et augmenter la production de biogaz afin de récupérer l’énergie émise par le procédé de traitement des eaux usées. La technologie de désintégration aux ultrasons possède justement cette caractéristique, c.-à-d. qu’elle désintègre les solides des boues et accroît la digestion anaérobie. La technologie a été testée sur le terrain sous des conditions tropicales dans une installation ultrasonique à pleine échelle et deux digesteurs ovoïdes de 5000 m3; chacun a été alimenté de boues primaires mixtes (un tiers) et de boues activées épaissies (deux tiers) de qualité identique et dont le volume pouvait atteindre 200 m3·d–1.Toutes les conditions opérationnelles des deux digesteurs étaient les mêmes sauf qu’un (celui des tests) utilisait les ultrasons pour prétraiter l’alimentation en boues et que l’autre (celui du contrôle) ne les utilisait pas. En ce qui concerne le digesteur de contrôle, l’étude de terrain de cinq mois montre que le prétraitement des boues aux ultrasons a augmenté la production de biogaz, laquelle pouvait atteindre 45 %. Il n’y avait aucune différence importante dans la composition des biogaz provenant des deux digesteurs. En exprimant les augmentations de la production de biogaz par rapport à sa source, les matières volatiles en suspension, il devrait être possible d’atteindre jusqu’à 30 % d’augmentation d’élimination des solides des boues sous des conditions opérationnelles optimales. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A pilot test was carried out at a land reclamation project site to study the effect of vertical drains on the rate of consolidation of a marine clay deposit in Singapore. Theoretical and numerical analyses were conducted to interpret the field measurements of pore pressure and settlement, and consolidation parameters were back-calculated. The back-calculated preconsolidation pressure is similar to that obtained from the laboratory consolidation test on undisturbed samples, but the field-deduced compression index is generally larger than that measured in the laboratory. The coefficient of consolidation back-calculated from the settlement measurement is larger than that from the pore-pressure measurement. The coefficient of consolidation for horizontal flow obtained from the Rowe cell test, which is comparable to that back-calculated from the field settlement measurement, is recommended for the preliminary design of vertical drains without the need of considering the smear effect.Key words: clays, consolidation, ground improvement, numerical modelling and analysis, permeability, vertical drains.Un essai pilote a été réalisé sur le site d'un projet de réhabilitation de terrain pour étudier l'effet des drains verticaux sur la vitesse de consolidation d'un dépôt d'argile marine à Singapore. Des analyses théorique et numérique ont été réalisées pour interpréter les mesures sur le terrain de la pression interstitielle et du tassement, et des paramètres de consolidation ont été calculés à rebours. La pression de consolidation calculée à rebours est similaire à celle obtenue par l'essai de consolidation en laboratoire sur des échantillons non remaniés, mais l'indice de compression déduit du terrain est généralement plus grand que celui mesuré en laboratoire. Le coefficient de consolidation calculé à rebours à partir des mesures de tassement est plus grand que celui obtenu par la mesure de la pression interstitielle. Le coefficient de consolidation pour l'écoulement horizontal obtenu par l'essai avec la cellule de Rowe, qui est comparable à celui calculé à rebours à partir de la mesure du tassement sur le terrain, est recommandé pour la conception préliminaire des drains verticaux sans prendre en compte l'effet de souillure d'argile remaniée.Mots clés : argiles, consolidation, amélioration des terrains, modélisation et analyse numériques, perméabilité, drains verticaux.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]