Dam reservoirs are exposed to a loss of water storage capacity due to the phenomenon of siltation. This particularity can be expressed by the siltation of reservoirs and the entrainment of particles transported by watercourses. Siltation of reservoirs is a critical state which causes a reduction in the storage capacity of dams. Algeria is characterized by a semi-arid climate, which annually loses a considerable volume of water storage. The carbonation of concrete is influenced by a number of parameters which accelerate its kinetics. These parameters are the porosity of the concrete, the quantity of lime contained in the cement, the concentration of CO2 in the atmosphere and the humidity of the environment. It should be noted that, water being the vector for moving aggressive agents, carbon dioxide can only diffuse through the concrete if the latter is not completely saturated and not perfectly dry at the same time. Another factor increasing the permeability of concrete is the amount of limestone added to the cement during its manufacture at the factory. This permeability allows the diffusion of CO2 or other aggressive agents in the concrete. The addition of limestone to cement must therefore be used with caution. The objective is to propose economically competitive and easy-to-implement formulations which allow the valorization of these materials in the making of ordinary concrete by partial substitution of cement (10, 20 and 30%) and its influence on the progress of long-term carbonation after six years of curing in the open air. The sediment is treated by calcination at 750°C to make it active. Natural carbonation tests were carried out on the study concretes in order to evaluate their durability. The results obtained confirmed the possibility of producing concretes incorporating calcined sludge at dosages of up to 30% without compromising the quality of these concretes from the point of view of behavior in the face of attacks by the dissolution of carbon dioxide from the air in the interstitial solution of concrete, meeting economic, ecological and technological objectives.

The present work was carried out with the aim of investigating the rheological behavior, in terms of contractance and dilatancy, and the mechanical behavior, in terms of shear resistance and mechanical characteristics, of sands containing different types of fines. This study is based on direct box shear tests that were carried out on three types of soils which were reconstructed by mixing clean sand with fines, namely silt, clay and clay loam. It is important to indicate that the mass percentages for sand replacement were 0, 10, 20, 30 and 40%. To do this, dry samples were prepared and subjected to shearing, under vertical stresses of the order of 100, 200 and 400 kPa. The results obtained showed that the maximum shear strength and friction angle of sand containing silt decreased while its cohesion increased, as the fines content increased. In addition, the maximum shear strength and friction angle of sand containing clay and silty clay decreased until reaching their minimum values ​​for contents equal to 20% clay and 30% clay and clay loam, respectively. The opposite phenomenon occurred for their cohesion which increased then decreased. It has also been observed that the more plastic the fines are, the higher their content in sand, the more this sand becomes contracting rather than dilatant.

This study was carried out to describe the mechanical behavior of different materials in terms of shear strength, cohesion and friction. For this purpose, an experimental shear tests were carried out. The soils used for the preparation of the samples were the Chlef sand, Chlef silt and M’zilla clay and a mixture composed of 50% of silt and 50% of clay. The soils were prepared by mixing Chlef sand with fines content of silt, clay or clay silt ranging from 0, 10, 20, 30 and 40%. The tests were conducted on sand samples prepared at a relative density of 20% representing a loose state and subjected to three normal stresses of 100, 200 and 400 kPa. All the tests were conducted at constant displacement rate of 1.00 mm/min. From the obtained results, it can be seen that the clean sand showed the highest shear strength at a small strains. At large strains, sands with 30% clay rather than 30% clay silt showed the highest shear strengths respectively. More contracted sands have the greatest increased maximum shear strengths. The sand with clayey silt, at a fine content of 20%, develops the most increased cohesion, among the other silty-clayey sands, together with the most reduced shear strength in elastic behavior. The sand with 40% of silt content develops a greater internal friction angle, however, the other silty sands, showed reduced shear strength, at the same behavior. To validate these findings, numerical simulations were performed on sand-silt mixtures using the hypoplastic model. The results indicated that the hypoplastic model accurately predicts the shear behavior of sand-silt mixtures in direct shear test, providing realistic insights into the effects of fines on the mechanical properties of the soil. Keywords: Sand, Silt, Clay, Fines Content, Shear Strength, Friction, Cohesion.

The sedimentation of cohesive particles has negative effects on water resource management such as siltation of dams as well as reducing water quality. Sedimentation processes are governed mainly by the flocculation and the settling of suspended particles, which are affected by many factors simultaneously. To provide a reliable solution to this problem, the contribution of the different factors to the sedimentation mechanism must be analysed. The majority of research considers only one single factor. In this experimental study, the combined effect of two significant parameters is considered: the salinity of the solution and the initial concentration of suspended solid matter. Experiments were conducted on mixtures with different sediment concentration (100, 150 and 200 g/l) under different salinity conditions. The chemical additives used for the preparation of sedimentary solutions are sodium chloride (NaCl), sodium hydroxide (NaOH), sulphuric acid (H 2 SO 4 ), ferrous sulphate (FeSO 4 ) and potassium permanganate (KMnO 4 ). Attention has been given to the evolution of hydrodynamic parameters such as settlement height, settling velocity and the permeability coefficient. The results show that settlement over time increases with increasing initial sediment content, and the height of deposited layers in salt water is lower than that in fresh water for the same sediment concentration. Settlement height increases with increasing salt concentration. Settling velocity and the permeability coefficient decrease with increasing initial sediment content. The variations of these two parameters are much more pronounced from 100 to 150 g/l of sediment concentration than for 150–200 g/l, particularly for mixtures with high chemical concentration. The influence of salinity on sedimentation processes depends on the initial concentration of suspended solid matter, on the chemical concentration and notably on the chemical composition of the solution (the effect of salinities is much more important for mixtures with NaCl and H 2 SO 4 solutions).

Suffusion is an internal erosion mechanism which can occur in cohesionless soils composed of a bimodal structure, where a sufficient seepage force leads to the detachment of loose finer particles and their transport through the constrictions formed by the primary coarser skeleton. The assessment of the susceptibility of cohesionless soils to suffusion is based on the evaluation of their capacity to filter erodible particles. Compared to models based on the grain size distribution analysis of soil, the approaches focused on the constriction size distribution are most suitable to provide a physical description of soil retention capacity. However, some important soil parameters are not taken explicitly in these models. In this research work and on the basis of the results of an experimental study conducted on mixtures of sands (dmax = 2 mm) and fines (dfmax = 100 μm) under different testing conditions, the main parameters that can influence the soil’s response to erosion were identified. Considering the contribution of these parameters to the suffusion development probability, new empirical formula has been proposed to calculate a control diameter characterizing the soil coarser fraction. This control diameter will be compared with the characteristic diameter of the loose finer fraction to assess the soil stability against suffusion. The application of the proposed model to the tested soils gives a good stability assessment as compared to other models.

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.

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.