Seismic isolation of buildings with sliding concave foundation (SCF)

In this paper, a new base isolation system, namely the sliding concave foundation (SCF), is introduced and the behaviour of the buildings using such a system is theoretically investigated. A building supported on the new system behaves like a compound pendulum during seismic excitation. The pendulum behaviour accompanied by the large radius of foundation curvature shifts the fundamental period of the system to a high value (e.g. more than 8sec), in a frequency range where none of the previously recorded earthquakes had considerable energy. This results in a large decrease in the structural responses. Since small friction forces are essential on the contact surfaces, PTFE sheets can be used as sliding surfaces. Although the pure frictional sliding systems have the same efficiency as the SCF, in reducing the responses of the superstructure, the main advantage of the new system is a significant decrease in sliding displacement. The performance of the SCF subjected to a number of harmonic and non‐harmonic base excitations is studied and its ability to reduce the structural responses is examined. Some numerical examples are solved for a single‐degree‐of‐freedom (SDOF) structure and the responses are compared with the responses of the same SDOF structure on a fixed base or a pure frictional sliding support system. The comparisons confirm the effectiveness of the new system. Copyright © 2002 John Wiley & Sons, Ltd.     

Environmental impacts of El Arish power plant on the Mediterranean coast of Sinai, Egypt

A monitoring program was undertaken to evaluate the adverse impacts of the El Arish power plant on the northeastern Sinai coast of Egypt. This program spanned 28 months and includes intensive hydrographic surveying, measurements of waves, longshore current, littoral drift, currents behind the breaker zone, offshore currents, sea-level variation and water quality. The shoreline dynamics of the region have been substantially disrupted due to the high-intensity longshore transport and the interruption of longshore transport by the shore-perpendicular intake breakwaters. Maximum erosion of 5.5 m/year has been documented east of the breakwater. This erosion has been continuing eastwards, threatening the resort centers on the downcoast beaches. On the other hand, accretion (11.7 m/year) is recorded along the western side of the breakwater, accumulating great volumes of sand which is transported to the east by littoral currents. Part of this sand enters the intake basin, causing sedimentation problems by the easterly and westerly littoral drifts and cross-shore currents. In other respect, an unprotected offshore channel dredged in front of the water discharger, east of the intake, acts as an effective trap for the predominantly easterly sand drift, subsequently interrupting sediments moving from the east, accelerating processes of erosion to the east. The cooling and wastewater discharging from the discharger to the sea are insignificantly warmer than the upcoast water and not contaminated with chemical wastes. The thermal and chemical plume has no significant effect on the quality of the coastal water in the region.     

Calc-alkaline Arc I-type Granitoid Associated with S-type Granite in the Pan-African Belt of Eastern Anti-Atlas (Saghro and Ougnat, South Morocco)

The Sidi Flah and Ougnat inliers are located in the eastern Anti-Atlas antiform between the Anti-Atlas Major Fault (AAMF) and South Atlas Fault (SAF). They consist of many granitoid intrusions emplaced into Neoproterozoic metasedimentary rocks and surmounted by upper Neoproterozoic A-type granites. The Sidi Flah (Saghro) and Ougnat granitoids are part of the Neoproterozoic magmatic activity related to northwards subduction of an oceanic plate beneath the Saghro continental margin. They are post-orogenic I- and S-type granitoids related to the ending of the compressional deformation in this Pan-African belt. A petrographic, geochemical and zircon typology study leads us to subdivide these rocks into three magmatic groups: (1) a medium- to high-K calc-alkaline group formed by quartz diorites and amphibole granodiorites is found in both Sidi Flah and Ougnat inliers; (2) a high-K calc-alkaline group is present in Sidi Flah. These two groups have a (deeper and) hybrid mantle-crust origin; (3) a peraluminous group in Ougnat is linked to the post-collisional setting and has a shallow crustal source. On a primitive mantle-normalized trace-element diagram, almost all of these rocks show a significant Nb depletion relative to K and La, which is typical of the calc-alkaline magmatism from the subduction-zone environment. Absence of structural marks of thrusting upon the West African craton (WAC) of this arc system and the ophiolitic suite in Bou-Azzer, and the presence of Imiter muscovite-bearing granite as part of Pan-African belt do not support the localization of northern limit of WAC at the level of SAF.     

Discrimination between primary magmatic biotites, reequilibrated biotites and neoformed biotites

The ternary diagram TiO₂–FeO*–MgO (FeO* = FeO + MnO) is proposed as a quantitative objective tool for distinguishing between primary magmatic biotites and those that are more or less reequilibrated, or possibly neoformed, by or within a hydrothermal fluid. The limit of the domains of the primary magmatic biotites, the reequilibrated biotites and the neoformed biotites were determined on the basis of optical, paragenetic and chemical criteria. To cite this article: H. Nachit et al., C. R. Geoscience 337 (2005).     

Determination of aquifer susceptibility to pollution using statistical analysis

 The use of statistical techniques in studying the causes of geochemical variations in aquifers can provide important results which cannot be derived in other ways. In this study, data from the Wadi Shueib catchment area in Jordan is evaluated, using principle component factor and multivariate factor analysis in order to better understand the variablility in groundwater chemistry and evaluate the sources of pollution and the susceptibility of these aquifers to the different sources of pollution. This study clearly demonstrates that these statistical techniques can help determine the various mechanisms causing chemical variation in the aquifers and the relative susceptibility of each aquifer to different types of pollution. Received: 13 March 1996 · Accepted: 18 June 1996     

Laboratory Study of Air Sparging: Air Flow Visualization

Laboratory flow visualization experiments, using glass beads as the porous medium, were conducted to study air sparging, an innovative technology for subsurface contaminant remediation. The purpose of these experiments was to observe how air flows through saturated porous media and to obtain a basic understanding of air plume formation and medium heterogeneity effects. The experiments indicate that air flow occurring in discrete, stable channels is the most probable flow behavior in medium to fine grained water saturated porous media and that medium heterogeneity plays an important role in the development of air channels. Several simulated scales of heterogeneities, from pore to field, have been studied. The results suggest that air channel formation is sensitive to the various scales of heterogeneities. Site-specific hydrogeologic settings have to be carefully reviewed before air sparging is applied to remediate sites contaminated by volatile organic compounds.     

The relationship between urbanization and socio-economic development in the Sudan

The study of urbanization has, in recent years, assumed increasing importance in developing countries not only because these countries are in the process of facing rapid urbanization, but also because the process of urbanization has been recognized as a part of a larger process of economic and social change which is affecting the rural areas.     

Mineralogy of the continental shelf sediments of Abu-Quir Bay Northern Coast of Egypt

This paper deals with the mineralogy of the continental shelf sediments of Abu-Quir Bay, N Coast of Egypt. The three dimentional distributions (normal to the shore line, in the breaker and offshore zones and along profiles E-W0 of different material individuals for twelve profiles were discussed. The patternal distribution of the recorded minerals along the bay was controlled by selective transport of the sediments by the E-W littoral current. A general trend for the decrease of the heaviest minerals from the source area (Rosetta Mouth) was observed. The opaques, garnet, zircon and epidote are concentrated in the breaker zone sediments, while the other (pyroxens and mica) are concentrated in the offshore zone sediments. Considerable amounts of opaques, amphiboles, monazite, garnet, staurolite and tourmaline were concentrated near Maadia Outlet, this is most probably attributed to the subsurface old sediments of Canopic Branch. Correlation between the present work (1978–1979) and other mineralogical work during (1971–1973), Rashed 1978) was attemptted.     

Local Government and Natural Resources in the Sudan: The Case of Lagawa Rural Council

Resource management, protection and promotion are very critical issues facing many parts of our rapidly changing world. In most developing countries, such issues are handled by both central and local governments, but quite often specialised government agencies are entrusted with these jobs. In Sudan, and since 1971, local government has become more involved than ever with the issue of natural resources. This research assesses the performance of a single local government unit in Western Sudan with regard to the above mentioned issues. Out of the multiplicity of resources in the council, only natural grazing is selected for the focus of this assessment study, because of its high significance in the local socio-economic set-up. A lengthy field-study was carried out to determine the resource situation and how it affects policy and control and promotion measures. This council has failed; a situation typical of most rural councils in Sudan. Worst of all, the natural grazing is deteriorating rapidly under stocking rates which exceed the carrying capacity by 49%, a fact that has already enhanced desertification.This research is partially sponsored by the UNU.