Bougaa region is affected by a shift moving a considerable amount of detritus formed by colluvial deposits, scree to boulders and scree slope reddish clay loam resting on a substratum of impermeable shale shale. This shift is shaped in geological formations particularly sensitive to this type of movement because of the heterogeneity of their facies, the impermeability of certain layers and the effect of tectonics and karstification. The purpose of this study is to characterize these shifts using tools geological, geotechnical and geomorphological features. The role of seepage is essential in triggering these shifts where lithology, structural arrangement, the climate is favorable factors. The presence of slopes> 20%, emerging sources of karst reservoir Guergour, creating wetlands that allow triggering of ground motion in this region.
Located in the Aures mountains Foum Toub is characterized by an annual average rainfall of 800mm. The hydrology subordinate to the terrain is the direct consequence of surface waters and of snow melting from the heights of Chelia Mountain. The aim of the implantation of the Foum Toub backwater is to minimize the siltation phenomenon at the upstream of the Koudiate El Mdaour dam, to regularize the Rebaa creek flow which runs from south to north and to contribute to the irrigation of the Foum Toub plain. This study puts the emphasis on the mobilization of surface water resources, a policy of the Ministry of Agriculture and Rural Development with a view to rationalize the use and planning of this vital factor, i.e. water. The site selected for the construction of this structure is characterized by a waterproof marly substratum, favourable for implanting the dike and the basin. The clay-silty-gravelly material furniture localized in the depressions as well as sandstones are used as areas for the construction materials of this structure. Stability is one of the most important parameters to take into account for the choice of the site, so as to avoid any problem linked to the withdrawal-swelling phenomena on the banks of creek. However, the sliding possibility, however weak it is, can be generated on the left bank of the creek within deposit and recent silt. The choice of the site for the implantation of this hydraulic structure remains subject to laboratory tests.
Le bassin d’El-Outaya se trouve dans la wilaya de BISKRA, une zone aride au sud algérien à environ 500 Km au sud de la capital Alger. Il constitue une ressource importante pour l'eau d'irrigation en plus d’un barrage à l’amont. La population de la plaine dépasse 11 000 habitants, leur activité principale est l'agriculture.
La plaine étudiée correspond à un bassin subsident orienté sensiblement E.NE – W.SW et situé entre deux anticlinaux. Il se trouve au nord de l’anticlinal du Dj.Bou Rhezel (Biskra) et au sud du dôme de Dj. El Melah. Il a fonctionné comme un bassin de sédimentation pendant tout le Néogène. Il est constitué à la base par un miocène laguno-marin, recouvert par du messinien (pontien) gréseux fluviatile, puis par des poudingues pliocènes. Les termes supérieurs, plus particulièrement pliocènes, sont fortement inclinés vers le centre du bassin où ils disparaissent sous une épaisseur considérable du Quaternaire.
Le dépouillement des analyses chimiques a aboutit à trois faciès chimiques: Le faciès chloruré sodique, le faciès sulfaté magnésien et le faciès sulfaté sodique.
Le suivi des variables chimiques dominant selon les axes des écoulements souterrains permet de suivre l’évolution des faciès dans aquifère ainsi que l’origine de chaque faciès.
El Outaya plain is located on the southern flank of the Aures Mountains, as part of the Saharan Atlas. It has an arid climate (less than 200 mm of rainfall / year). The Mio-Pliocene aquifer associated with this plain is an important resource for irrigation and drinking water.
Achieving the first hydrodynamic model of the Mio-Pliocene ground water in El Outaya plain, with different operating scenarios and using the Visual Mod-flow code, shall contribute to the development of an action plan for a rational management of water resources.
In addition, the model was calibrated to steady state conditions and then transient state conditions in order to prepare conductivity and porosity maps that characterize the spatial variability, in relation with the geological heterogeneity of the aquifer. Different operating scenarios indicated that the northern part of the plain is fairly vulnerable to feeding and exploitation conditions.
This research work deals with the problem of karst sinkhole collapse occurring in the last few years in Cheria area (NE Algeria). This newly revealed phenomenon is of a major constrain in land use planning and urbanization, it has become necessary to locate and assess the stability of these underground features before any planning operation. Several exploration methods for the localization of underground cavities have been considered. Geological survey, discontinuity analysis, resistivity survey [ground penetrating radar has not been used as most of the Mio-Plio-Quaternary filling deposit covering Eocene limestone contains clay layers which limits the applicability of the method (Roth et al. in Eng Geol 65:225–232,
2002)] and borehole drilling were undertaken in order to locate underground cavities and assess their depth, geometry, dimensions, etc. Laboratory testing and field work were also undertaken in order to determine both intact rock and rock mass properties. All the rock mechanics testing and measurement were undertaken according to the ISRM recommendations. It has been found that under imposed loading, the stability of the karst cavities depends on the geo-mechanical parameters (RMR, Rock Mass Rating; GSI, Geological Strength Index; E, Young modulus) of the host rock as well as the depth and dimensions of the gallery. It increases with RMR, GSI, E and depth and decreases as the cavity becomes wider. Furthermore, the calculation results show that a ratio (roof thickness to gallery width) of 0.3 and more indicate, a stable conditions. The results obtained in this work allow identifying and assessing the stability of underground karst cavities. The methodology followed in this paper can be taken as a road map in the establishment of a hazard map related to the studied phenomenon. This map will be a useful tool for the future urban extension planning in Cheria area.
