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Sterile bodies mapping under Quaternary cover using resistivity-sounding method in the phosphatic bearing of Sidi Chennane (Morocco). In the Ouled Abdoun sedimentary basin (Morocco), the phosphatic series is composed of regular interbedded phosphatic and marly limestone layers. Some phosphatic deposits in this basin show sterile bodies causing two kinds of problems: (1) as they are hard, compact and masked by a Quaternary cover, they disturb the exploitation in some yards and give bad reserve calculations; (2) even the use of wells and mechanical boreholes did not evidence their delimitation. Therefore, electric prospecting method has been used to evidence their geometrical shape. Petrographical and geometrical studies on these sterile bodies allowed us to choose the appropriate geophysical method to map them. The electrical resistivity survey that we used in the Sidi Chennane area shows that this technique is a good tool to contour these sterile bodies. This method is now considered as useful to the mining engineers to get round them during the exploitation.

Since 1930, the analysis of slope stability is done according to the limit equilibrium approach. Several methods were developed of which certain remain applicable because of their simplicity. However, major disadvantages of these methods are (1) they do not take into account the soil behavior and (2) the complex cases cannot be studied with precision. The use of the finite elements in calculations of stability has to overcome the weakness of the traditional methods. An analysis of stability was applied to a slope, of complex geometry, composed of alternating sandstone and marls using finite elements and limit equilibrium methods. The calculation of the safety factors did not note any significant difference between the two approaches. Various calculations carried out illustrate perfectly benefits that can be gained from modeling the behavior by the finite elements method. In the finite elements analysis, the shape of deformations localization in the slope is nearly circular and confirms the shape of the failure line which constitutes the basic assumption of the analytical methods. The integration of the constitutive laws of soils and the use of field's results tests in finite elements models predict the failure mode, to better approach the real behavior of slope soil formations and to optimize its reinforcement.

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