Laboratory study on the effects of hydraulic and granulometric parameters on the response of granular soil to internal erosion

Erosion is a major environmental problem to agricultural land as well as to civil engineering infrastructures. Rainwater infiltration into granular soils can lead to the migration of fine particles by suffusion. This experimental study is conducted to evaluate the susceptibility to erosion of cohesionless soils. The soil under investigation was collected from the coastal region of Mostaganem (West of Algeria) where erosion has recently caused several damages. To assess soil instability to erosion, two approaches have been proposed in the literature: the geometric approach and the hydraulic approach. Few studies have examined the combination of the two methods. The objective of our study is the combination of the two approaches by determining the critical hydraulic load responsible for triggering erosion as a function of soil characteristics. An experimental parametric study was conducted to determine the influence of initial amount of fines, hydraulic gradient and axial stress on the initiation and evolution of suffusion. A combination of the interactions between these parameters allowed us to express the critical hydraulic gradient and to identify the hydraulic behavior of the soil according to the studied parameters. This approach can better estimate the erodibility of cohesionless soils. It can be used in future development studies at this site to reduce the risk of erosion

The child and architecture : «Draw me the house/home»

The child as much as the adult has a few rights upon the city but we have to admit, unfortunately, that he/she is here just to live within this area built by and for the adults. The adult seems to have priority and is privileged when it comes to be part of the city while the child is ignored except for those school places and some rare outdoor spaces. Though some efforts are being made as to the setting up of these kinds of areas, still no consideration is given to anything else. The child with its own characteristics lives in the path of adults, awaiting the time to be in turn an adult himself/ herself childhood is the period when adults shape their physical and psychological personalities: this is why this period is so important to human being. Why then such a careless approach in taking it into consideration when dealing with the environment made more to suit the adult and ignore the child. It is true that it is a period which will finally catch up with the adult’s period, but they will in turn get old, does that mean we should ignore them? The aim of this work is to examine the child and his/her relationship with the main element of the city: the house. We have then chosen to study children’s drawings to be able to draw a lesson from what he/she is going to express without being obliged to hold forth about it.Peer Reviewe

Laboratory study on the effects of hydraulic and granulometric parameters on the response of granular soil to internal erosion

Erosion is a major environmental problem to agricultural land as well as to civil engineering infrastructures. Rainwater infiltration into granular soils can lead to the migration of fine particles by suffusion. This experimental study is conducted to evaluate the susceptibility to erosion of cohesionless soils. The soil under investigation was collected from the coastal region of Mostaganem (West of Algeria) where erosion has recently caused several damages. To assess soil instability to erosion, two approaches have been proposed in the literature: the geometric approach and the hydraulic approach. Few studies have examined the combination of the two methods. The objective of our study is the combination of the two approaches by determining the critical hydraulic load responsible for triggering erosion as a function of soil characteristics. An experimental parametric study was conducted to determine the influence of initial amount of fines, hydraulic gradient and axial stress on the initiation and evolution of suffusion. A combination of the interactions between these parameters allowed us to express the critical hydraulic gradient and to identify the hydraulic behavior of the soil according to the studied parameters. This approach can better estimate the erodibility of cohesionless soils. It can be used in future development studies at this site to reduce the risk of erosion

Critical undrained shear strength of loose-medium sand-silt mixtures under monotonic loadings

Empirical relationships are developed for estimating the undrained critical shear strength based on experimental triaxial tests under monotonic loadings. The effect of fines content on the undrained shear strength is analyzed for different combinations of density states.The parametric study indicates that in terms of the soil void ratio and fines content properties, the undrained critical shear strength may increase, or decrease as the amount of finescontent increases, consequently showing vulnerability to liquefaction influenced by the fines content percentage. A series of monotonic undrained triaxial tests have been undertaken on a reconstituted saturated sand-silt mixtures specimen. Beyond 30% of fines content, it is shown that a fraction of silt participates in the soil skeleton chain force. In this context,the concept of the equivalent intergranular void ratio may be an appropriate parameter to express the critical shear strength of the soil under investigation. This parameter is able to control the undrained shear strength of non plastic silt and sand mixtures for different density states

Etude expérimentale de l’effet du processus électro-osmotique dans un sol fin salin de la région de Mostaganem

In civil engineering, electro-osmosis is a technique used as a means of dehydration, treatment of fine soils for the improvement and remediation. It is also used in agriculture for the desalinization of soils. In this study, the effect of electro-osmosis on the properties of a fine soil of the Ain Nouissy-Mostaganem region under a difference of electric potential was analyzed. The objective is to study the behavior of the water flow and the modification of some parameters, such as the electrical conductivity, the pH and the Atterberg limits during and after the electrokinetic process. These parameters make it possible to understand and control the performance of this technique with respect to the treatment under consideration. Soil heating during this process was approached through the surface temperature, indicating a loss of relative energy when the voltage gradient exceeds an optimal value.En génie civil, l'électro-osmose est une technique utilisée comme moyen de déshydratation et de traitement des sols fins pour l’amélioration et la dépollution. Elle est aussi utilisée en agriculture pour la désalinisation des sols. Dans cette étude, l'effet de l’électro-osmose sur les propriétés d'un sol fin de la région d’Ain Nouissy-Mostaganem sous une différence de potentiel électrique a été analysée. L’objectif est d’étudier le comportement de l’écoulement hydrique et la modification de certains paramètres, tels que la conductivité électrique, le pH et les limites d’Atterberg durant et après le processus électrocinétique. Ces paramètres permettent de comprendre et de contrôler la performance de cette technique vis-à-vis du traitement considéré. Le chauffage du sol durant ce processus a été abordé à travers la température de surface, indiquant une perte d’énergie relative lorsque le gradient de tension dépasse une valeur optimale.En génie civil, l'électro-osmose est une technique utilisée comme moyen de déshydratation et de traitement des sols fins pour l’amélioration et la dépollution. Elle est aussi utilisée en agriculture pour la désalinisation des sols. Dans cette étude, l'effet de l’électro-osmose sur les propriétés d'un sol fin de la région d’Ain Nouissy-Mostaganem sous une différence de potentiel électrique a été analysée. L’objectif est d’étudier le comportement de l’écoulement hydrique et la modification de certains paramètres, tels que la conductivité électrique, le pH et les limites d’Atterberg durant et après le processus électrocinétique. Ces paramètres permettent de comprendre et de contrôler la performance de cette technique vis-à-vis du traitement considéré. Le chauffage du sol durant ce processus a été abordé à travers la température de surface, indiquant une perte d’énergie relative lorsque le gradient de tension dépasse une valeur optimale

On numerical modeling of couple heat, air and moisture transfer through multilayered walls

This paper reports on numerical modeling of heat, air, and moisture transfer through multilayered walls. Building materials are often subjected to temporal climatic variations, which can induce a transfer of heat and moisture through the walls of the building and the foundation soil. These materials are generally considered as porous media. The coupled heat, air and moisture transfer in building materials is of paramount importance in the construction area. In this way, a mathematical model has been elaborated and validated using a benchmark example. Here, we aim to determine the energy losses. The capillary pressure is considered as potential moisture which represents both the transport of vapor and liquid phases of the water. Basing on basic functions of partial differential equations, one can convert certain measurable properties of porous media as coefficients depending on the temperature and the capillary pressure. The results obtained compare favorably with other available in the literature

Critical undrained shear strength of sand-silt mixtures under monotonic loading

This study uses experimental triaxial tests with monotonic loading to develop empirical relationships to estimate undrained critical shear strength. The effect of the fines content on undrained shear strength is analyzed for different density states. The parametric analysis indicates that, based on the soil void ratio and fine content properties, the undrained critical shear strength first increases and then decreases as the proportion of fines increases, which demonstrates the influence of fine content on a soil’s vulnerability to liquefaction. A series of monotonic undrained triaxial tests were performed on reconstituted saturated sand-silt mixtures. Beyond 30% fines content, a fraction of the silt participates in the soil’s skeleton chain force. In this context, the concept of the equivalent intergranular void ratio may be an appropriate parameter to express the critical shear strength of the studied soil. This parameter is able to control the undrained shear strength of non-plastic silt and sand mixtures with different densities. ResumenEste estudio utiliza evaluaciones experimentales triaxiales con cargas repetitivas para desarrollar relaciones empíricas y estimar la tensión crítica de corte bajo condiciones no drenadas. El efecto de contenido de finos en la tensión de corte sin drenar se analizó en diferentes estados de densidad. El análisis paramétrico indica que, basado en la porosidad del suelo y las propiedades del material de finos, la tensión de corte sin drenar primero se incrementa y luego decrece mientras la proporción de finos aumenta, lo que demuestra la influencia de contenido de finos en la vulnerabilidad del suelo a la licuación. Una serie de las evaluaciones se realizó en  mezclas rehidratadas y saturadas de arena y cieno. Más allá del 30 % de los contenidos finos, una fracción del cieno hace parte principal de la cadena de fuerza del suelo. En este contexto, el concepto de porosidad equivalente intergranular puede ser un parámetro apropiado para expresar la tensión crítica de corte del suelo estudiado. Este parámetro nos permite controlar la tensión de corte sin drenar de cieno no plástico y mezclas de arena de densidades diferentes

Excess paste method to formulate a self-compacting concrete

On the basis of the principle that a concrete is composed of a liquid phase (paste) and a solid phase (aggregates with fixed gravel/sand ratio), the concrete self-compacting properties come necessarily from those of the paste. The present work is the continuity of a first phase of the testing already conducted, which resulted in obtaining an optimal self-compacting cement paste composition. This paste will be used to prepare a self-compacting concrete (SCC), while passing from the scale of the cement paste to that of the concrete, by injecting wet aggregate to the self-compacting paste. The excess paste theory was used to determine the thickness of the paste coating each aggregate with a given diameter of constituting granular skeleton, then generalized for the determination of the quantity of total paste allowing the flow of the concrete by decreasing frictions between the grains of its granular skeleton. This approach was also experimentally validated. The influence of the granular distribution was minimized by the use of the approach based on the determination of the average diameter of the aggregates. This required the determination of a homothetic factor “k” similar for all concretes with different aggregate grading. Formulation of a self-compacting concrete passes initially by the determination of a sufficient quantity of paste allowing its flow without frictions between its aggregates and to balance the mixture by the quantity of water retained by the aggregates. The self-compacting concrete characteristics would come from those of the cement paste which composes it

Two-Dimensional Transient Modeling of Energy and Mass Transfer in Porous Building Components using COMSOL Multiphysics

This paper reports on a transient heat, air and moisture transfer (HAM) model. The governing partial-differential equations are simultaneously solved for temperature and capillary pressure through multi-layered porous media, including the non-linear transfer and storage properties of materials. Using partial differential equations functions, some thermo-physical properties of porous media are converted into coefficients depending on temperature and capillary pressure. Major features of the model are multi-dimensional and transient coupling of heat, air and moisture transport. The coupled equations are solved using the COMSOL Multiphysics time-dependent solver. This solver enables HAM (Heat, Air, Moisture) modeling in porous media. Besides, the good agreements obtained with a 2D benchmark suggest that the model can be used to assess the hygrothermal performance of building envelope components. This paper concludes that the total heat flux in the insulated wall represents only the quarter of that crossing the uninsulated concrete roof. On the other hand, the concrete having the lowest water vapour permeability of all used materials allows maintaining the vapour pressure levels close to the initial value (103 Pa). This induces a situation of interstitial condensation within the concrete of the roof. Being able to evaluate the hygrothermal behaviour, the proposed model may turn out to be a valuable tool to solve other building problems