Sources and genesis of the Pleistocene gravelly deposits in Northern Kuwait

The Dibdibba Formation is of Pleistocene age and consists of a fluviatile sequence of ungraded, often cross-bedded sand and gravels intercalated with minor sandy clay layers. It occurs in the northern desert of Kuwait as subparallel elongated ridges trending NE-SW. Structures and mineralogy of the Dibdibba deposits suggest that they have been derived from the basement complex of the northeastern area of Saudi Arabia as sheet floods and deposited in the alluvial fan of the Wadi Ar-Rimmah-Al Batin valley system. Floods transporting these deposits were intermittent; the gravelly bands were deposited during severe floods and the sandy beds during relatively quiet floods.     

Engineering geological characterisation of the rock masses at Tannur Dam site,South Jordan

This paper highlights the geomechanical characterisation of the rock masses exposed at the dam abutments and reservoir area at the Tannur Dam site, South Jordan. The right abutment rock masses are characterised by closely to widely spaced joints. The rock-mass qualities were assigned using the rock-mass rating (RMR) and Q-tunnelling index. Both systems assigned a poor quality for foundation rocks because of the presence of weak rocks. The rock masses constituting the dam abutments exhibit fair quality. The results of packer tests indicate that the hydraulic conductivity of the rock masses of Fuheis-Hummar-Shueib (FHS) and Wadi es Sir (A7) formations range from 10 to 150 Lugeon units (LU). The FHS was characterised by lower LU values compared with A7; this reflects the fracturing characteristics of A7. However, the A7 should be grouted especially the right abutment. However, the FHS needs less grouting because the spacing between joints seems to be tight. The estimated shear strength envelopes relevant to the rock masses of both abutments as well as the foundation rocks were quite similar and, therefore, present similar shear strength characteristics. The shear strength for jointed rock masses showed curvilinear failure planes with average cohesion values of 0.67 and 0.64 MPa and friction angles of 36.5 and 35.5° for dam abutments and the foundation area, respectively.     

Geoscience and sustainable catchment and resource management: the Ben Chifley Catchment case study

This article demonstrates a key role that geoscience and geoscientists could be playing in promoting sustainable catchment and resource management. A new geoscience-based approach supported by a landscape-genesis (LG) model was employed to provide an alternative approach for integrated catchment management and sustainable resource use and development. The Ben Chifley Catchment case study is used to explain the application of the approach and the landscape-genesis model. The study confirmed that lithological composition, tectonic and diagenetic processes, and landform were critical factors in determining the intrinsic properties and variation in soil type, land use, land capability, steepness of terrain, erosion, and resource degradation within the catchment. The landscape-genesis model, which is based on the geological and geomorphic genesis of the landscape, proved to be a powerful tool to predict the inherent carrying capacity and resilience of the various biophysical systems in the catchment. Although this approach is still in its infancy, its application has demonstrated that it has a strong potential in terms of undertaking sound integrated assessment, predicting potential resource degradation under different land uses, and developing sound management practices and solutions to advance the goal of ecological sustainability.     

Principales caractéristiques des réservoirs du Sud-Ouest tunisien

A study of the form and characteristics of the reservoirs and aquifers of southwestern Tunisia has been carried out from 62 petroleum explorations and hydrogeologic wells and structural maps. The evolution of basins can be deduced from the tectonic history. The Jurassic reservoirs are represented by the Upper Nara carbonates. The petrophysical characteristics and the fracturation affecting the Nara carbonates reveal the existence of very good reservoirs. Several reservoirs have also been identified in the Lower Cretaceous. These reservoirs are made of sandy levels, interbedded with shale, carbonates and dolomites. In addition, petroleum and hydrogeologic studies have revealed that potential aquifers may occur in two provinces (near the Chott Basin and east–west faults). Most of the geological formations in the South West of Tunisia are composed of sand, sandstone and limestone, with the existence of real aquifers. To cite this article: M. Chalbaoui, H. Ben Dhia, C. R. Geoscience 336 (2004).     

A new method for formulation of dynamic responses of shallow foundations in simple general form

A single uniform rectangular area, either homogeneous or heterogeneous, is considered in a soil medium (fundamental cell). Two governing ordinary differential equations in special form are developed for the fundamental cell. The ground supporting a partially embedded foundation is divided into a number of coarse rectangular areas (secondary cells). Each secondary cell is treated as either a single fundamental cell for homogeneous ground or a stack of fundamental cells for inhomogeneous ground. Differential equations for the assembly of secondary cells are formed with those for the fundamental cells. These equations lead to the soil responses in each cell expressed in simple closed form. They also lead to the convenient treatment of soil with appropriate Winkler-type models along the foundation faces and concentrated forces acting at the foundation corners. With them, the foundation responses are finally expressed in simple closed form. The approach is demonstrated for various cases and confirmed to produce the results reasonable enough for civil engineering use.     

Évaluation de la qualité de l'eau par application de la méthode géoélectrique : exemple de la plaine d'El Mida–Gabes nord (Sud tunisien)

The Mida plain, which is part of the North Gabès region (southern Tunisia), is characterized by the deep sandy units of the ‘Continental intercalaire’ (CI) or the limestone of the Lower Senonian. A geophysical survey, by electrical sounding (ES), was undertaken in the studied region to better characterize the deep geological structure of this plain and therefore its aquifer resources potential. The analysis of the results shows that the prospected zone is characterized by the succession of several levels with contrasted resistivities, which are often affected by faults. Among these observed geoelectrical levels, the highly conductor one could host a saline aquifer. Another geoelectrical level corresponding to the resistant bedrock detected at Oudhref horst can contain better-quality water than that of the aquifer detected in the El Mida Graben. In this work, we tried to explain the origin of the salinity of this aquifer. Thus, we hypothesise about a contamination from Jebel Zemlet El Beida through a border fault and another one from the Sebkhet El Hamma. To cite this article: A. Mhamdi et al., C. R. Geoscience 338 (2006).     

Groundwater salinization of the Sfax superficial aquifer,Tunisia

Groundwater salinization has become a crucial environmental problem worldwide and is considered the most widespread form of groundwater contamination. The origin of salinity in the coastal aquifer of the Sfax Basin, Tunisia was investigated by means of chemical analyses of groundwater samples from 65 wells. The groundwater samples present a clear gradation from calcium sulphate salinization to that of sodium chloride. The saturation indices for calcite and gypsum, and binary diagrams of different ions, together with multivariate analysis, indicate the existence of various salinization processes such as: dissolution of gypsum and calcite dispersed through the reservoir rock; ion exchange; intensive agricultural practices that produce effluents that infiltrate to the saturated zone; and sea-water intrusion, enhanced by excessive withdrawal of groundwater.     

Groundwater Deterioration of Shallow Groundwater Aquifers Due to Overexploitation in Northeast Jordan

Groundwater is the major water resource in Jordan and most of the groundwater basins are already exploited beyond their estimated safe yield. Azraq basin is one of the most important groundwater basins in Jordan, which supplies Amman with drinking water. However, due to overpumping from the shallow groundwater aquifers, the water level dropped dramatically and signs of salinization and depletion are starting to occur. The severe drawdown in the Azraq well‐field caused a reverse in the hydraulic gradient and consequently, the saltwater in the center of the basin (Qa‐Azraq) started to move in the direction of the well‐field. The salinization in the shallow aquifer (basalt/B5/B4) is believed to result from one of the following scenarios: (i) a reverse flow from Sabkha to the AWSA well field, (ii) an upward leakage from the middle aquifer system (B2/A7) and the combined B3 Aquitard‐B2/A7 aquifer, (iii) a dissolution process between the water and rock matrix due to lowering of the dynamic water levels during pumping which reached the mineralized formations underlying the Basalt. The salinization trend of some AWSA wells represented by the gradual increase of major ions is associated with rather constant stable isotopic contents. This indicates that these constituents originate from the main minerals existing in the matrix of the aquifers and thus this scenario is the most likely to occur.     

Three-dimensional seismic transmission prospecting of the Mont Dore volcano, France

Summary. The three-dimensional seismic structure of the Mont Dore volcano is studied by inversion of the arrival times of seismic waves. With this aim two new methods are developed. First, the arrival times are those of Moho-reflected waves at a critical distance from artificial sources in different azimuths. Secondly, the inversion uses a technique which does not require the traditional a priori partition of the space into blocks. The resulting picture reveals such features as: (1) a circular caldera within the basement, the rim of which is marked by magnetic anomalies associated with post-caldera activity; (2) a clear lower limit of the volcano-sedimentary sequence under part of the caldera, opposed to low velocity anomalies extending deeper beneath another part and which may have been the site of volcanic material transport, and (3) eeper heterogeneities possibly related to foundered basement blocks.     

Developing artificial neural network models to predict allowable bearing capacity and elastic settlement of shallow foundation in Sharjah,United Arab Emirates

This research proposes the use of artificial neural network to predict the allowable bearing capacity and elastic settlement of shallow foundation on granular soils in Sharjah, United Arab Emirates. Data obtained from existing soil reports of 600 boreholes were used to train and validate the model. Three parameters (footing width, effective unit weight, and SPT blow count) are considered to have the most significant impact on the magnitude of allowable bearing capacity and elastic settlement of shallow foundations, and thus were used as the model inputs. Throughout the study, depth of footing was limited to 1.5 m below existing ground level and water table depth taken at the level of the footing. Performance comparison of the developed models (in terms of coefficient of determination, root mean square error, and mean absolute error) revealed that the developed artificial neural network models could be effectively used for predicting the allowable bearing capacity and elastic settlement. As such, the developed models can be used at the preliminary stage of estimating the allowable bearing capacity and settlements of shallow foundations on granular soils, instead of the conventional methods.