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Traditional soil stabilization by chemical additives such as cement and lime is a well-established technique for ground improvement of problematic soils. However, with the advantage of lower carbon emission and energy consumption, fly-ash-based geopolymer has recently become an attractive alternative to traditional stabilizers. Nevertheless, the literature lacks systemic approaches that assist engineers to apply this promising binder for soil stabilization, including the proper dosages required for an effective treatment. This paper introduces a systematic approach to assess the applicability of fly-ash-based geopolymer for stabilization of clay soils, through a comprehensive experimental program where engineered and natural clays were examined and evaluated, including soil compaction, plasticity, compressive strength, durability, pH level, and impact of pulverization. The results revealed several factors that influence the level of enhancement of geopolymer-treated clays, including the soil mineralogy, plasticity–activity properties, geopolymer concentration, curing time, and pulverization. [ABSTRACT FROM AUTHOR]

Given extensive research carried out to study pile response subjected to lateral soil movement in clay, the effect of consolidation on the pile-soil interaction is rarely considered and systematically investigated. For this reason, four centrifuge tests were conducted to simulate construction of embankment adjacent to existing single piles in soft clay, considering two typical drainage conditions (i.e., drained and undrained conditions) and two typical pile lengths (i.e., relatively long pile and short pile). The centrifuge tests were then back-analyzed by three-dimensional coupled-consolidation finite element analyses. Based on reasonable agreements between the two, numerical parametric studies were conducted to systematically investigate and quantify the influence of construction rate and pile length on pile response. It is revealed that by varying drainage conditions, the piles respond distinctively. When the embankment is completed within a relatively short period ( cv t/ d2 < 2, where cv, t, and d denote the coefficient of consolidation, construction period, and pile diameter, respectively), the pile located adjacent to it deforms laterally away from the embankment. Induced lateral pile deflection ( δ) and bending moment reduce with construction period. On the contrary, embankment constructed within a relatively long period ( cv t/ d2 > 200) leads the pile to deform laterally towards the embankment, with δ and bending moment increases with construction period. By halving the length of pile embedded in the drained ground, the maximum induced bending moment (BMmax) was slightly reduced (by 23%). On the other hand, shortening the length of the pile in the undrained ground is much more effective in reducing BMmax, i.e., halving pile length resulting in 78% reduction in bending moment. A new calculation chart, which takes various drainage conditions and pile lengths into account, was developed for estimation of BMmax. [ABSTRACT FROM AUTHOR]

Soil structures are often comprised or supported by soils that are mixtures of cohesive and granular geomaterials. These soils are termed as intermediate or mixed soils and are widely found in natural deposits and man-made soil structures. The objective of this paper is to study the behavior of mixed clayey soils under monotonic, cyclic, and post-cyclic monotonic loading, with the main focus on the last of these three. For this purpose, a number of strain-controlled monotonic, cyclic, and post-cyclic triaxial compression tests were carried out on “clay–sand” and “clay–gravel” mixtures in undrained conditions. The effects of sand (or gravel) contents, number of cycles, cyclic strain amplitude, consolidation pressure, and grain size on the mechanical behavior of the mixtures are evaluated. The major findings from the laboratory study are: (i) the addition of granular materials to the clayey soils increases excess pore-water pressure during strain-controlled monotonic undrained shearing and cyclic loading and (ii) during post-cyclic monotonic shearing, mixed clayey soils behave similarly to overconsolidated soils; the higher the granular material is, the higher the overconsolidation ratio would be. Based on the research results, an algorithm for estimating post-cyclic mechanical parameters of mixed clayey soils, without conducting cyclic and post-cyclic tests, is suggested. Les structures de sol sont souvent composées ou supportées par des sols qui sont des mélanges de géomatériaux cohésifs et granulaires. Ces sols sont nommées intermédiaires ou sols mélangés et sont retrouvés fréquemment dans les dépôts naturels et dans les structures de sol fabriquées. L’objectif de cet article est d’étudier le comportement de sols argileux mélangés soumis à des chargements monotoniques, cycliques et post-cycliques monotoniques, avec l’emphase mise sur ce dernier type de chargement. Pour ce faire, des essais en compression triaxiale monotoniques, cycliques et post-cycliques avec déformation contrôlée ont été effectués sur des mélanges « argile–sable »et « argile–gravier »dans des conditions non-drainées. Les effets sur le comportement mécanique du contenu sable (ou gravier), du nombre de cycles, de l’amplitude de la déformation cyclique, de la pression de consolidation et de la granulométrie ont été évalués. Les principaux résultats de l’étude en laboratoire sont : (i) l’ajout de matériaux granulaires aux sols argileux augmente la pression interstitielle pendant le chargement en cisaillement et cyclique monotonique non-drainé avec déformation contrôlée et (ii) durant le cisaillement monotonique post-cyclique, les sols argileux mélangés se comportent de façon similaire aux sols sur-consolidés; plus il y a de matériaux granulaires, plus élevé sera le ratio de sur-consolidation. Selon les résultats de la recherche, un algorithme qui estime les paramètres mécaniques post-cycliques de sols argileux mélangés est suggéré, sans avoir à effectuer les essais cycliques et post-cycliques. [ABSTRACT FROM AUTHOR]

A relatively large number of drying and wetting tests have been performed on clayey soils compacted at the standard or modified Proctor optimum water content and maximum density and compared with tests on normally consolidated or overconsolidated soils. The results show that drying and wetting paths on compacted soils are fairly linear and reversible in the void ratio or water content versus negative pore-water pressure planes. On the wet side of the optimum, the wetting paths are independent of the compaction water content and can be approached by compaction tests with measurement of the negative pore-water pressure. Correlations have been established between the liquid limit of the soils and such properties as the optimum water content and negative pore-water pressure, the maximum dry density, and the swelling or drying index. Although based on a limited number of tests, these correlations provide a fairly good basis to model the drying–wetting paths when all the necessary data are not available.Key words: compaction, unsaturated soils, clays, drying, wetting, Proctor conditions.Un nombre relativement important d'essais de drainage et d'humidification a été réalisé sur des sols argileux compactés à l'optimum Proctor normal ou modifié, et comparé avec ceux sur des échantillons normalement consolidés ou surconsolidés. Les résultats obtenus montrent que les chemins de drainage et d'humidification des sols compactés sont sensiblement linéaires et réversibles dans les plans de l'indice des vides ou de la teneur en eau en fonction de la pression interstitielle négative. Du côté humide de l'optimum, les chemins d'humidification sont indépendants de la teneur en eau de compactage, et peuvent être approchés par des essais de compactage avec mesure de la pression interstitielle négative de l'eau. Des corrélations ont été établies entre la limite de liquidité des matériaux et les principales caractéristiques de ces chemins, telles que la teneur en eau de compactage, la densité sèche et la pression interstitielle négative à l'optimum ou les indices de gonflement et de drainage. Bien qu'elles ne reposent que sur un nombre réduit d'essais, ces corrélations fournissent un point de départ intéressant pour modéliser les chemins de drainage–humidification lorsque toutes les données nécessaires ne sont pas disponibles.Mots clés : compactage, sols partiellement saturés, argile, drainage, humidification, conditions Proctor. [ABSTRACT FROM AUTHOR]

The method of soil stabilization is well known and has been used throughout the world for many decades to improve some soil properties. Although many researchers have studied the effect of adding a cementing agent to a soil, not many of these researchers have explored the effect of treatment on the resulting properties of high water content soils like dredged material. Also, there has been little work concerning the prediction of the mechanical changes to the soil. Therefore, this paper summarizes the results of a research project conducted to define the general mechanical behavior of high water content clayey soils from eastern Canada treated with lime or cement, in terms of compressibility. In the light of this research, the general compressibility behavior has been obtained, defined by relationships between initial void ratio, additive content, and vertical yield stress for a given inorganic or organic soil. These relationships have been normalized on the basis of the one-dimensional compression curve of the remolded and reconstituted untreated soil to give a simple method for predicting the vertical yield stress of a treated soil for any initial void ratio and its resistance to compression.Key words: stabilization, compressibility, yield stress, clayey soils, lime, cement.La méthode de stabilisation des sols est bien connue et a été utilisée depuis plusieurs décades à travers le monde pour améliorer certaines propriétés des sols. Quoique plusieurs chercheurs aient étudié l'effet de l'addition d'un agent de cimentation au sol, peu d'entre eux ont exploré l'effet du traitement sur les propriétés résultantes des sols à teneur en eau élevée tels que les matériaux dragués. Également, il y a eu peu d'études portant sur la prédiction des changements mécaniques apportés au sol. En conséquence, cet article résume les résultats d'un projet de recherche réalisé pour définir un comportement mécanique général en terme de compressibilité de sols argileux à hautes teneurs en eau de l'est du Canada avec de la chaux ou du ciment. À la lumière de cette recherche, on a obtenu le comportement général en compressibilité défini par la relation entre l'indice des vides initial, la teneur en additif, et la contrainte de préconsolidation apparente verticale pour un sol donné organique ou inorganique. Finalement, ces relations ont été normalisées sur la base de la courbe de compression unidimensionnelle du sol non traité remanié et reconstitué pour donner un méthode simple pour prédire la contrainte de préconsolidation apparente verticale d'un sol traité pour n'importe quel indice de vide initial, et sa résistance à la compression.Mots clés : stabilisation, compressibilité, contrainte de préconsolidation apparente, sols argileux, chaux, ciment.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]