Karim Bendani

A coupled model for heating and hydratation in unsaturated clays

Knowledge of transport processes of heat and moisture in soils of arid zones is vital to understanding the environmental and economic impacts of many activities: agriculture, waste disposal, geoenvironmental practices and earth sciences. Through extensive review and study on the different aspects of coupled transfer processes in swelling porous media, a general mathematical model for coupled heat, moisture, air flow and deformation problems in clayey soils is proposed in a consistent and unified manner. The model is characterized by the presence of a deformable solid matrix filled with two fluid phases (liquid water and air). In the proposed model, both pore water and air transfers are assumed to be governed by the generalized Darcy’s law. Fully coupled, non-linear partial differential equations are established and then solved by using a Galerkin weighted residual approach in space domain and an implicit integrating scheme in time domain. The obtained model has been finally validated by means of some case tests for the prediction of the thermo-hydro-mechanical behaviour of unsaturated swelling soils. The calculated relative errors between experimental and numerical results are 3% for temperature and 7% for stresses. Consequently, the developed numerical model predicts satisfactory results, compared to experimental test measures. The model is applicable to two-dimensional problems with various initial and boundary conditions; non-linear soil parameters can be easily included in this model.

Shear Behavior of Sand–Silt Mixtures: A Laboratory Investigation of Coastal Silty Sand Soils of Mostaganem

In recent years, interest in understanding the mechanisms of mechanical instability of porous media, leading to catastrophic failure has been continuously revised to include, new porous media parameters generating the phenomenon of liquefaction under static or dynamic loadings. Results from experimental test programs have concluded too many physical concepts based on material intrinsic properties, initial states, and other characteristics. Despite the great progress on the subject, these concepts do not allow a unified treatment of such porous media. The assessment of critical shear strength of sandy soils as porous media under undrained conditions is a major challenge in stability analysis. Such strength serves to evaluate the occurrence of flow deformation under liquefaction phenomena. The determination of the critical undrained strength is essentially fundamental for the design of soil structures such as earth dams, bridge supports, building foundations as well as soil densification process to avoid catastrophic failure due to soil instability manifested by failure or large displacement such as settlement. In this work, experimental program on reconstituted loose and medium dense specimens of terrigenous silica sands with different specified fine contents was carried out to analyze its mechanical behavior under undrained conditions. The present article is an attempt to experimentally describe mechanical behavior and theoretically justify such response of loose and medium dense sand by means of critical state soil parameters.

Liquefaction potential sand-silt mixtures under static loading

DOI: 10.7764/RDLC.17.2.196 As a part of an on-going research program on the mechanical instability of granular soils in our laboratory, defined contents of sand and silt in soil mixtures are studied through the triaxial apparatus, full range of initial relative density states (loose, medium and dense) are experimented and analyzed. In this work, the investigated soil is collected from different depths of Kharouba coastal region in the province of Mostaganem (Lat: 35.96° N; Long: 0.1° E). It consists mainly of sand with a low percentage fraction of non-plastic silt, below 30%. The coastal region of Mostaganem (Kharouba) is very close to the harbor and it experiences a significant seismic activity, then it would be very susceptible to the phenomenon of liquefaction under static or dynamic loads, hence the importance and relevance of this study which introduces the identification parameters of this instability due to liquefaction. Undrained triaxial tests under monotonic loading are carried out in the laboratory on saturated reconstituted samples. These results are presented and analyzed. New parameters for assessing the influence of fines content and density state on the behavior of heterogeneous soils (sand-silt) will be introduced to the liquefaction. New correlations expressing the undrained critical shear with these new parameters will be deducted for full range of initial relative density (loose, medium and dense) for design purpose.

Saturated Sandy Soils Mechanical Instability Under Vibration Effect

One of the mechanical instabilities of granular soil corresponds to the phenomenon of liquefaction, which refers to its deformation behavior during shaking events. This report presented some experimental tests on soils and the characterization of their mechanical behavior. The laboratory experiments were led on a natural soil extracted from the region of Oran which presents a regular seismic activity, located in the north west of Algeria.