"Investigating the behavior of silty soils reinforced with geotextile layers in terms of shear strength and deformation in a laboratory setting is the study's objective described in this paper. This work includes an experimental study based on a series of undrained monotonic triaxial tests, which were carried out on clean sand from Chlef, medium dense (Dr = 50%), mixed with silt content fluctuating between 0 and 30%. The mechanical behavior was examined and discussed in this paper by varying the number of geotextile layers (Ng = 1, 2, 3) and the fines content where the samples were consolidated under 100 kPa confining pressure. Experimental results on unreinforced and reinforced silt/sand soils by geotextile layers show that the quantity of geotextile layers is growing in the studied samples improves the shear strength characteristics of the soil, nevertheless, lessen the radial deformations cause the pore water pressure to rise instead. However, the pore water pressure increases while the deviatoric stress decreases as the percentage of fines increases."

This paper presents a laboratory study on the monotonic behaviour of saturated chlef sand (Algeria). Through its history, many different phenomena have been observed in this soil (Chlef sand, Al-Asnam earthquake 10 October). For this laboratory study, a series of tests were performed on sand samples from Chlef to see how the initial relative density and lateral pressure (confining) affected how the sand behaved. The tests results indicated that the increase in the relative density and the confining stress significantly affects the undrained monotonic behaviourof the sand under study resulting in an amplification of the dilatant character with the increase in the relative density, on the other hand a decrease in the dilatant character with the increase in the initial confinement pressure. The results also indicate a strong correlation between the shear strength measured by the stress deviator and the effective mean pressure P'.

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 article seeks to examine and discuss the experimental results that were obtained from a series of straight box shear tests. For this, different soils were prepared with clean sand, which was brought from the Wilaya (Province) of Chlef that is located in northern Algeria, mixed with silt from the same site, clay from the town of M'zilla or clayey loam that is composed half of this same clay and half of silt. The percentages of sand replacement by the selected additions were 0, 10, 20, 30, and 40% in mass ratio. The samples thus prepared were then tested with respect to dry shear, under the normal stresses equal to 100, 200, and 400 kPa. The results obtained showed that the shear strength of the sand from Chlef decreases when the silt content increases from 0 to 40%. With regard to the sand-clay and sand-silt-clay mixtures, it was found that the shear strength decreases until reaching a threshold value that coincides with the addition content of 20%. Then, beyond that value, it begins to increase as the addition fraction increases. Likewise, it turned out that cohesion increases with increasing silt content, while for sand-clay and sand-silt-clay mixtures, this cohesion increases until reaching a maximum value which coincides with the addition of 20% silt content. The same trend was observed for the variation of the direct shear strength, while the friction angle exhibited an inverse behavior.

This paper reports the results of a series of drained and undrained triaxial tests on Chlef soil reinforced with stone columns surrounded by geotextiles. The tests are carried out on reconstituted samples having an initial density index Id =0.50 and which are subjected to an initial confining pressure of 100 kPa. In order to create stone columns that can be realized in situ, sand grains with an average diameter of 2 mm are used to manufacture the tested specimens. In addition, we used 70 and 10 mm for the length and diameter of the stone column, respectively. The test results show that, in one hand the stone columns’ presence affects significantly the soil shear strength, that increases according to the stone columns number and reduces the soil contractiveness (vertical strain), and in the other hand, it decreases the interstitial pressure. Encasement improves the effectiveness of the stone column and raises the rigidity of the reinforced soil by reinforcing the stone column with geotextiles. Furthermore, the secant modulus increases versus of the stone columns number, which is due to the inverse proportionality of this modulus to the axial strains. In addition, the internal frictions increase following a linear evolution law with the increase in the number of inclusions of reinforcements stone columns.

This paper examines the effect of fiber content and relative density (RD) on the hydro-mechanical behavior of Chlef sand. The hydro-mechanical behavior of the sand-fiber mixture was evaluated by 45 permeability tests and 30 direct shear tests in the laboratory. Tests were performed on reconstituted specimens at different relative densities (RD = 15, 50 and 70

In this work, soil densification using a dynamic compaction process is proposed to solve soil instabilities in Chlef city (Algeria), which is a prone zone to seismic risk. In this respect, a laboratory investigation is conducted using the triaxial apparatus to test the efficiency of the use of densification process on the improvement of Chlef silt-sandy soil’s mechanical properties. Thus, soil samples with various relative densities Dr are tested in drained and undrained conditions and under both static and cyclic loading. Results show a reduction of the soil deformations and an increase of the shear strength versus of Dr. Therefore, this process represents an efficient tool that can be used by the local authorities to solve soil deformations due to settlement and liquefaction, especially in road pavements adjacent to Chlef River.

Road pavements based on silty or sandy soils can undergo several deformations including settlements and liquefaction phenomenon that can occur in seismic zones. This paper focuses on the case of a section of the RN4 express road adjacent to Chellif River in Chlef city (Algeria), which is a prone area to seismic risk. This traffic lane continually suffers from serious deformations, mainly due to settlement occurring on the road pavement. Thus, a laboratory investigation is carried out to test the efficiency of the use of densification process on the improvement of Chlef silt-sandy soil's mechanical properties. Samples representing the three soil states (loose, medium dense and dense) are tested using the triaxial apparatus in drained and undrained conditions and under both monotonic and cyclic loadings. The study results show a reduction of soil settlement and an increase of its resistance, both proportional to its density increase. These results indicate the efficiency of the densification process allowing its use to resolve soil deformations of the concerned road pavements and to avoid the soil liquefaction in case of a seismic event.

This communication presents a laboratory study on the effect of the geotextiles reinforcement area on the improvement of the mechanical proprieties of a sandy soil, especially on the stabilization of soil deformations that affect road pavement in Chlef city (Algeria), which is a prone area to seismic risk. The study is carried out via a monotonic undrained tests using the triaxial apparatus. Reconstructed soil samples having a relative density corresponding to two soil states: loose (Dr = 20%) and medium dense (Dr = 50%) are tested. The aim of the study is to highlight the improvement that can bring the increase of the area of geotextile reinforcement on the behavior of the studied soil. Results show that the reinforcement area has a great positive effect on the increase of the soil resistance, traduced by the stress deviator and by the friction angle, and on the decrease of the pore pressure that reduce the liquefaction risk.

The study of the unsaturated soils is a very complex field to which several researches in laboratory and on site are directed these last years. An experimental study aims to quantify the influence of the Skempton coefficient B characterizing the degree of saturation on the behavior of the granular sand to the liquefaction resistance of sand. The study is based on undrained triaxial tests performed on natural Chlef sand carried out at an initial relative density Dr = 50% under a confining pressure of 50, 100 and 200 kPa for Skempton coefficient B = 10 to 92%. The results of the tests show that an increase of confining pressure leads to an increase of the shear stress of the samples. For the lower value of the degree of saturation results of our findings indicate an increase of the resistance to liquefaction; our results are in good agreement with others observed in several research projects conducted with other sands. The increase of Skempton coefficient B induces an increase of pore water pressure and a decrease of the shear strength. The pore pressure (u) increases with an exponential manner with the increase of the degree of saturation; while the residual shear strength (Rs) decreases with logarithmic manner with the increase of degree of saturation (B).

This article presents a laboratory study of static behavior of silty-sand soils. The objective of this laboratory investigation is to study the effect of initial confining pressures and fines content on the undrained shear strength (known as liquefaction resistance) response, pore pressure, and hydraulic conductivity of sand–silt mixtures. The triaxial tests were conducted on reconstituted saturated silty-sand samples at initial relative density Dr = 15% with fines content ranging from 0 to 50%. All the samples were subjected to a range of initial confining pressures (50, 100, and 200 kPa). The obtained results indicate that the presence of low plastic fines in sand–silt mixture leads to a more compressible soil fabric, and consequently to a significant loss in the soil resistance to liquefaction. The evaluation of the data indicates that the undrained shear strength can be correlated to fines content (Fc), inter-granular void ratio (eg), and excess of pore pressure (Δu). The undrained shear strength decreases with the decrease of saturated hydraulic conductivity and the increase of fines content for all confining pressures under consideration. There is a relatively high degree of correlation between the peak shear strength (qpeak) and the logarithm of the saturated hydraulic conductivity (ksat) for all confining pressures.