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In densely populated countries, underground construction and land reclamation could be possible options to solve the demand for land space, thus securing sustainable long-term development of the nation. For example, in Singapore, land reclamation has been widely conducted using excavated materials from underground development. The excavated materials are commonly marine clays that contain sandy soils. To improve the mechanical properties of these soft soils, cement-treated soil stabilization is popularly adopted. In fact, many researchers have investigated the properties of pure cemented clay or pure cemented sand using conventional design parameters such as water content (water/solids) and cement content (cement/dry soil). However, can these terminologies be still used to accurately examine the role of sand in cemented sandy clay mixtures? Through unconfined compression testing, it is herein shown that the use of existing mix design approaches in the literature cannot properly explain the variation of strength with sand content for cemented sandy clay mixtures. A new mix design approach is thus proposed in this study, which ensures that the role of sand in a cemented clay matrix can be quantified.

Construction and demolition waste are one of the major waste streams in the world. Aggregates must be used in significant quantities during road construction and maintenance as base and sub-base materials. Government and local businesses are promoting the use of recycled material in old pavement andconstruction material due to the high cost of virgin aggregates. Concrete, road subgrade, and railroad ballast materials can all be made from recycled concrete aggregate (RCA), a type of recycled material. The engineers must properly comprehend the material's qualities, including its unsaturated properties, in order to use RCA in these projects. The goal of this project is to investigate the unsaturated permeability and thewater characteristic curve of RCA. These unsaturated qualities were discovered through sophisticated laboratory experimentation. The study's findings showed that the RCA has the same qualities as gravel or natural aggregate.

Landslides bring destruction to buildings, and nearby located structures and mostly occur in rural areas. Such hazard commonly takes place in mountainous areas in Central Asia. Kazakhstan region has highly vulnerable areas to rainfall-induced landslides in South-Eastern parts due to presence of many mountains. The purpose of the research is to demonstrate the effect of slope geometry on slope stabilityunder heavy rainfall in Almaty, Kazakhstan. Transient seepage analyses were conducted using Seep/W while limit equilibrium slope stability analyses were performed using Slope/W. 15 sets of numerical analyses were carried out on different slope angle and slope height incorporating the soil-water characteristic curve and unsaturated permeability and unsaturated shear strength of soil from Almaty. According to the obtained simulation results in GeoStudio software for seepage analysis, the pore-water pressure is increased almost for 80 kPa at the mid slope of each simulation. The change of FoS for the gentlest slope with 27 degrees slope angle is the lowest for 10 m slope height and the highest for 30 m slope height, whereas the change of FoS for slope with 45 degrees of slope angle (9%) is almost the same for all slope height.

Numerous studies have attempted to relate shear wave velocity ([V.sub.s]) to the geotechnical properties of soils. However, most correlations were empirically developed only for a particular site or soil type. In this study, we propose a novel approach to incorporate a generalized void ratio function with analytical phase relations for estimating the total unit weight of soils. Based on an extensively compiled soil database, the validation of the semi-empirical model was carried out and its performance was also compared against existing [V.sub.s] - total unit weight correlations. Moreover, a sensitivity analysis of the model input parameters was conducted to assess their significance on total unit weight estimates. It is demonstrated that the proposed semi-empirical model is successful in providing a first-order estimate of the total unit weight of soils based on the [V.sub.s], without consideration of the overburden stresses. Key words: shear wave velocity, phase relations, unit weight, void ratio function. De nombreuses etudes ont tente de relier la vitesse de l'onde de cisaillement ([V.sub.s]) aux proprietes geotechniques des sols. Cependant, la plupart des correlations ont ete empiriquement developpees seulement pour un site particulier ou un type de sol. Dans cette etude, nous proposons une nouvelle approche pour incorporer une fonction de rapport des vides generalisee avec des relations de phase analytique pour estimer le poids unitaire total des sols. En se fondant sur une base de donnees de sol largement compilee, la validation du modele semi-empirique a ete effectuee et sa performance a egalement ete comparee aux [V.sub.s] - correlations du poids unitaire total existantes. De plus, une analyse de sensibilite des parametres d'entree du modele a ete effectuee pour evaluer leur importance par rapport aux estimations du poids unitaire total. Il est demontre que le modele semi-empirique propose reussit a fournir une estimation de premier ordre du poids unitaire total des sols a partir des [V.sub.s], sans tenir compte des contraintes des morts-terrains. [Traduit par la Redaction] Mots-cles: vitesse de l'onde de cisaillement, relations de phase, poids unitaire, fonction de taux de vide., Introduction Over the past decades, geophysical techniques have been widely employed for site investigation to characterize the physical and mechanical properties of soils because they allow to cover a much [...]

Capillary barrier system (CBS) was developed as a slope protection method to prevent rainwater infiltration into the underlying soil based on the principle of unsaturated soil mechanics by harnessing the distinct difference in hydraulic properties of a fine-grained layer with those of a coarse-grained layer of soils. The CBS is commonly designed and constructed using gravel as coarse-grained material and fine sand as fine-grained material. However, due to scarcity of natural aggregates and in consideration of environmental sustainability, there is a need to utilize recycled materials in capillary barrier system. In this project, coarse and fine recycled concrete were used as the coarse- and fine-grained materials, respectively. The appearance of CBS was enhanced with an additional layer of approved soil mixture (ASM) to incorporate vegetation as green cover. CBS as a sustainable slope cover has been constructed for slope protection surrounding basement carpark in the new public housing development at Matilda, Singapore. The design, construction and monitoring system for the CBS are presented and discussed in this paper. The field measurement data provide verification of the performance of the CBS. Both field measurement and numerical analyses demonstrated that CBS performed well as designed.

Shear wave velocity ([V.sub.s]) in geo-materials is strongly dependent on factors such as stress state, void ratio, and soil structure. Stress-dependency and void-ratio dependency can be represented by the equations [V.sub.s] = α[([σ'.sub.c]).sup.β] and [V.sub.s] = a[(e).sup.b] (where α and a are material constants; exponents β and b represent the sensitivity of stress and the void dependent effect, respectively; [σ'.sub.c] is effective confining stress; e is void ratio), respectively. To consider the effect of soil disturbance and stress relief in geomaterials, shear wave velocity is often required to be normalized by adopting the site-specific model parameters (β or b). Based on a special in situ database compiled from 156 well-documented test sites that include various geo-materials, this study presents (i) the apparent relationships of the model parameters a and 3 for all soil and rock materials as well as a and b for all soil materials, (ii) new global correlations between soil unit weight and two types of stress-normalized shear wave velocities ([V.sub.s1] and [V.sub.sn]), instead of the conventional [V.sub.s]--soil unit weight relationship for clays, and (iii) the best-fitted multi-regression models between soil unit weight and site-specifically normalized shear wave velocity as well as the plasticity index for plastic soils. Moreover, this study presents the importance of site-specific stress normalization ([V.sub.sn]) in creating a better correlation model. The proposed relationships offer first-order assessments of soil unit weight within the ranges of available data, which are also approximately guided by a hyperbolic unit weight model with depth. Key words: shear wave velocity, stress normalization, plasticity index, void ratio, unit weight. La vitesse des ondes de cisaillement ([V.sub.s]) dans des geomateriaux est fortement dependante des facteurs tels que l'etat de contrainte, le taux de vide, et la structure du sol. La dependance et la dependance de taux de vide peuvent etre representees par les equations [V.sub.s] = α[([σ'.sub.c]).sup.β] (oU a et a sont des constants de materiaux; les exposents β et b representent la sensibilite a la contrainte et l'effet de dependance de vide, respectivement; [σ'.sub.c] est la contrainte de confinement efficace; e est l'indice des vides), respectivement. Pour tenir compte des effets de perturbation du sol et le soulagement de la contrainte dans les geomateriaux, la vitesse des ondes de cisaillement est souvent necessaire d'etre normalisee en adoptant les parametres du modele specifiques au site (β ou b). Base sur une base de donnees in situ speciale compilee a partir de 156 sites d'essais bien documentes qui comprennent divers geomateriaux, cette etude presente (i) les relations apparentes des parametres du modele a et 3 pour tous les materiaux de sol et de roche ainsi qu'a et b pour tous les materiaux du sol (ii) de nouvelles correlations globales entre le poids de l'unite de sol et deux types de vitesse d'ondes de cisaillement normalise ([V.sub.s1] et [V.sub.sn]), au de la relation conventionnelle de poids de l'unite de sol [V.sub.s] pour les argiles et (iii) les modeles les mieux adaptes a multiregression entre le poids de l'unite de sol et la vitesse d'ondes de cisaillement normalise specifique du site, ainsi que l'indice de plasticite pour les sols plastiques. En outre, cette etude presente l'importance de la normalisation de la contrainte specifique au site ([V.sub.sn]) dans la creation d'un meilleur modele de correlation. Les relations proposees offrent des evaluations de premier ordre de poids unitaire du sol dans les plages de donnees disponibles, qui sont presque egalement guidees par un modele de poids unitaire hyperbolique avec la profondeur. [Traduit par la Redaction] Mots-cles: vitesse des ondes de cisaillement, normalisation de la contrainte, indice de plasticite, rapport de vides, unite de poids., Introduction The initial shear modulus ([G.sub.0]) at very small strains ([γ.sub.s] < [10.sup.-6]) is a critical parameter of geo-materials that allows researchers to analyze geotechnical engineering problems under static and [...]

Soil – water characteristic curve (SWCC) is an important property of unsaturated soils that can be used to estimate various parameters to describe unsaturated soil behavior. SWCC is reported to be hysteretic because the water content at a given suction in the wetting process is less than that in the drying process. In order to simulate the hysteretic characteristics of SWCC, many models have been proposed by different researchers. However, majority of the existing models are complex and their parameters are not related to the physical significances of SWCC variables. In this study, the new equations are developed to model drying and wetting SWCC. In addition, some indexes are proposed to estimate the wetting SWCC from drying SWCC. The new equations for SWCCs were evaluated with the laboratory data from published literatures. The results showed that the proposed equations performed well in modelling drying and wetting SWCC. The new equation has less parameters than the existing published equation.