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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.)

The disposal of increased quantities of dewatered sewage sludge to landfills may cause geoenvironmental problems such as leachability, total and differential settlement, and slope stability of the waste during disposal. This study investigates the geotechnical properties of the dewatered sewage sludge generated from chemically enhanced primary treatment (CEPT) in Hong Kong. Compaction test results show that CEPT sludge exhibits compaction characteristics similar to those of clayey soils; however, the lowest hydraulic conductivity of CEPT sludge does not occur near the wet side of its optimum water content. The consolidation behavior of CEPT sludge does not follow the conventional Terzaghi's theory. Under an overburden pressure higher than 24 kPa, the relationship between the logarithm of the hydraulic conductivity (logk) and the void ratio (e) is linear. Results from direct shear tests reveal that, for CEPT sludge, slopes of 20° can probably be constructed during the landfill operation without causing sliding problems. Compared with the disposal of pure CEPT sludge, the co-disposal of dewatered sewage sludge with other solid wastes commonly found in Hong Kong results in lower compressibility, smaller settlement, but higher hydraulic conductivity.Key words: co-disposal, geotechnical properties, landfill disposal, sewage sludge.L'entreposage de quantités croissantes de boues d'égouts asséchées dans des sites d'enfouissement peut causer des problèmes géoenvironnementaux tels que le lessivage, un tassement différentiel ou total, l'instabilité de la pente de la boue durant l'entreposage. Cet article étudie les propriétés géotechniques de la boue d'égout asséchée générée par le traitement chimique primaire (CEPT) à Hong Kong. Les résultats d'essais de compactage indiquent que la boue CEPT montrent des caractéristiques de compactage similaires à celles des sols argileux ; cependant, la conductivité hydraulique la plus faible de la boue de CEPT n'est pas obtenue tout près du côté humide de sa teneur en eau optimale. Le comportement en consolidation de la boue CEPT ne suit pas la théorie conventionnelle de Terzaghi. Sous une pression sus-jacente supérieure à 24 kPa, la relation entre le logarithme de la conductivité hydraulique (logk) et le rapport de vide (e) est linéaire. Les résultats d'essais de cisaillement direct révèle que pour la boue CEPT, des pentes de 20[sup o] peuvent probablement être construites durant l'opération de remplissage sans causer de problèmes de glissement. En comparaison avec l'entreposage de boue pure CEPT, l'entreposage simultané de boue d'égout asséchée avec d'autres déchets solides communément trouvés à Hong Kong résultent en une plus basse compressibilité, un tassement plus faible, mais une conductivité hydraulique plus élevée.Mots clés : entreposage simultané, propriétés géotechniques, enfouissement sanitaire, boue d'égout.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The reclamation for the new airport at Chek Lap Kok in Hong Kong included the placement of a substantial volume of sand fill by various hydraulic placement techniques, which resulted in a wide range of as-placed densities of the sand fill. This paper described the use of cone penetration tests (CPT) on the evaluation of the possible ranges of density achievable by various hydraulic placement methods adopted in the construction of the new airport. The results of the CPT indicated that the placement technique is one of the most important factors in controlling the as-placed density of hydraulically placed sand fill. There is a marked contrast in cone tip resistance (and the associated relative density) profiles for the sand fills formed by subaerial and subaqueous placement methods, in which the cone tip resistance of the sand fill formed by subaerial placement is substantially higher than that of the sand fill formed by subaequeous placement. The results confirm that dense sand fill cannot be formed by subaqueous placement methods. The weakest zone is generally located just beneath the water level where fill is placed by subaqueous discharge.Key words: sand, hydraulic fill, cone penetration test, calibration chamber test, in situ density.Le remblayage pour le nouvel aéroport à Chek Lap Kok de Hong Kong comprend la mise en place d'un volume substantiel de remblai de sable par différentes techniques de mise en place hydraulique, qui ont résulté en une large plage de densités en place du remblai de sable. Cet article décrit l'utilisation de l'essai de pénétration au cône (CPT) pour l'évaluation des plages possibles de densité qui peuvent être obtenues par différentes méthodes de mises an place hydrauliques adoptées pour la construction du nouvel aéroport. Les résultat de CPT indiquent que la technique de mise en place est un des facteurs les plus importants pour le contrôle de la densité en place de sable remblayé par méthode hydraulique. Il y a un contraste marqué entre les profils de résistance à la pointe (et la densité relative correspondante) pour les remblais de sable mis en place par des méthodes subaériennes ou sous l'eau, le premier étant appréciablement plus élevé. Les résultats confirment qu'un remblai de sable dense ne peut pas être obtenu par des méthode de mise en place sous l'eau. La zone la plus faible est en général localisée juste sous le niveau d'eau, là où la déposition du matériau de remblayage se fait par décharge sous-l'eau.Mots clés : sable, remblai hydraulique, essai de pénétration au cône, essai en chambre de calibrage, densité in situ.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

This paper models consolidation of the foundation soils under a test embankment at the new Chek Lap Kok International Airport in Hong Kong. The modelling used a simplified finite element method and material parameters derived from results in the original site investigation report. Various features that need to be considered in applying the simplified method are illustrated through this case study. Good predictions of settlement results are obtained. Relatively large discrepancies in pore-water pressure predictions suggest that the nonlinear nature of hydraulic conductivity needs to be taken into account when large compressions are likely to occur. Geological conditions are shown to be a key factor in successful modelling of consolidation behaviour.Key words: consolidation, pore-water pressure, case modelling, finite element method, vertical drains, settlement.Cet article modélise la consolidation des sols de fondation sous un remblai d'essai au nouvel aéroport international Chek Lap Kok de Hong Kong. La modélisation a utilisé une méthode simplifiée d'éléments finis et des paramètres du matériau dérivés des résultats du rapport de l'investigation originale du site. Diverses caractéristiques qui doivent être considérées dans l'application de la méthode simplifiée sont illustrées dans cette étude de cas. De bonnes prédictions des résultats de tassement ont été obtenues. Des divergences relativement importantes dans les prédictions des pressions interstitielles portent à penser que la nature non linéaire de la conductivité hydraulique doit être prise en compte lorsque des compressions importantes peuvent vraisemblablement se produire. On montre que les conditions géologiques sont un facteur clé pour modéliser avec succès le comportement en consolidation.Mots clés : consolidation, pression interstitielle, modélisation de cas, méthode d'éléments finis, drains verticaux, tassement.[Traduit par la Rédaction] [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.)

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.)

To advance the understanding of the rainfall-induced landslide triggering mechanism, a comprehensive field monitoring programme was implemented in a saprolitic hillslope in Hong Kong. The instrumentation covered the measurements of the two stress-state variables (i.e., net normal stress and matric suction) and their effects. The monitoring results, including pore-water pressure (PWP), volumetric water content, subsurface total horizontal stress, horizontal displacement, and rainfall intensity, are reported. Most instruments recorded reliable and good quality data, which have strong correlation among each other. The site-specific infiltration and deformation characteristics of the hillslope subjected to heavy rainstorms are investigated. Shallow transient perched groundwater tables were believed to be developed at colluvial deposits on the top 3 m, where PWPs up to 20 kPa were typically measured. The main groundwater table probably rose by 6 m when the hillslope was subjected to rainfall intensity of 133.5 mm/h. It is possible that cross-slope groundwater flowed along a shallow, dipped decomposed rock stratum at the central portion of the landslide body. Besides, two distinct types of slope movements were generally observed, namely the 'cantilever' and the 'deep-seated' mode. Rupture surfaces have possibly been developed at 5 m below ground or deeper, resulting in a multiple translational- and rotational-slide type of failure. Afin d'améliorer la compréhension des mécanismes de déclenchement des glissements terrains causés par les précipitations, un programme de suivi extensif sur le terrain a été implanté dans une pente saprolitique à Hong Kong. L'instrumentation comprend des mesures de deux variables de l'état des contraintes (contrainte nette et succion matricielle) et leurs effets. Les résultats du suivi incluant la pression interstitielle, la teneur en eau volumique, la contrainte totale horizontale sous la surface, le déplacement horizontal et l'intensité des précipitations sont présentés. La majorité des instruments ont enregistré des données fiables et de bonne qualité et qui comportent des fortes corrélations entre elles. L'infiltration spécifique au site à l'étude et les caractéristiques de déformation de la pente soumise à des précipitations intenses sont étudiées. Il est suggéré qu'une nappe phréatique perchée transitoire est développée dans les dépôts colluviaux sur les premiers 3 m, où des pressions interstitielles jusqu'à 20 kPa sont typiquement mesurés. La nappe phréatique principale s'élève probablement de 6 m lorsque la pente subit des précipitations d'une intensité de l'ordre de 133,5 mm/h. Il est possible qu'un écoulement d'eau souterraine à travers la pente le long d'une couche peu profonde de roche décomposée se produise dans la section centrale de la masse du glissement. Deux types de mouvements de pente sont généralement observés sur les côtés, soit le mode « en porte-à-faux » et le mode « en profondeur ». Des surfaces de rupture sont possiblement développées à 5 m sous la surface, ou plus en profondeur, ce qui entraîne un type de rupture multiple à glissement en translation et en rotation. [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.)

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.)

The article offers the authors' views on the study of J. H. Yin regarding the effect of compaction on hydraulic conductivity of completely decomposed granite (CDG) in Hong Kong. It explores the authors' comments on the study in various areas including basic soil properties, permeability testing and its comparison with predictive models of CDG. The authors stress that CDG used by Yin seems not to meet the conditions of predictive model for saturated hydraulic conductivity (ksat).

The article offers the author's response on the discussions by Aubertin and Chapuis on the article "Influence of relative compaction on the hydraulic conductivity of completely decomposed granite in Hong Kong." It states that both the modified Proctor test and the standard Proctor test are utilized in Hong Kong for fill compaction. The author concurs with the discussants that the completely decomposed granite (CDG) fill compressed in the mould and submerged was not completely saturated.