Influence of size of granulated rubber on bearing capacity of fine-grained sand

Nowadays, in most of the advanced and developing countries, waste tires have caused serious environmental problems such as fire and environmental contamination. For reusing them in an appropriate and beneficial way, waste tires have been utilized as a lightweight fill material in geotechnical engineering applications such as highway embankments. In this study, Babolsar fine-grained sand and granulated rubber with sizes in the ranges of 1 to 4, 1 to 9, and 4 to 9 mm were used. A series of model footing tests on reinforced sand with different sizes of granulated rubber were carried out. According to the results, 4- to 9-mm granulated rubber had the highest effect on enhancement of bearing capacity and reduction of fine-grained sand settlement. The results showed that sand-granulated rubber mixtures with granulated rubber in the range of 4 to 9 mm and content of 10% by weight of mixture can increase the bearing capacity of sand up to 50%. In addition, for this mixture, a series of laboratory tests were conducted to determine the optimum width and depth of the reinforcement layer consisting of sand-granulated rubber mixture. The results indicate that the optimum width and the most effective depth of this mixture are 5B and 1B, respectively (where B is the footing width).     

A preliminary study of graphite-bearing rocks at Wadi Sikait area, South Eastern Desert, Egypt

The studied graphite-bearing rocks are located at Wadi Sikait in the southern part of the Eastern Desert of Egypt to the west of Marsa Alam on the Red Sea coast. They are intruded by granitic rocks and they have low radioactivity level. Mica-graphite schists are considered as a matrix of ophiolitic mélange. Graphite occurs in mica-graphite schists as disseminated grains and in talc carbonates rocks as bands or veins. Petrographically, the mica-graphite schists are mainly composed of quartz, plagioclase, muscovite, biotite, and graphite. Geochemical characteristics show that trace elements analysis reflects higher content in Cr and Ni in ash-free graphite than mica-graphite schists. Spectrometrically, the graphite-bearing rocks at Wadi Sikait are showing eU values greater than eTh values, indicating that the graphite-bearing rocks gain U from the country rocks. The U/eU ratio range from 2.7 to 11 manifesting enrichment of chemical uranium (U) may be related to recent uranium transported from the mineralized country rocks. There is a role of graphite and carbonaceous matter in the genesis of U deposits.     

Perogenesis of granites, Sharm El-Sheikh area, South Sinai, Egypt: petrological constrains and tectonic evolution

Precambrian granites of the Sharm El-Sheikh area in south Sinai, Egypt belong to collisional and post-collisional Magmatism (610–580 Ma). The granites are widely distributed in the northern part of the Neoproterozoic Arabian-Nubian Shield. South Sinai includes important components of successive multiple stages of upper crust granitic rocks. The earliest stages include monzogranite and syenogranites while the later stages produced alkali feldspar granites and riebeckite-bearing granites. Numerous felsic, mafic dikes and quartz veins traverse the study granites. Petrographically, the granitic rocks consist mainly of perthite, plagioclase, quartz, biotite and riebeckite. Analysis results portray monzogranites displaying calc-alkaline characteristics and emplaced in island-arc tectonic settings, whereas the syenogranites, alkali-feldspar granites and the riebeckite bearing-granites exhibit an alkaline nature and are enriched in HFSEs similar to granites within an extensional regime. Multi-element variation diagrams and geochemical characteristics reinforce a post-collision tectonic setting. REEs geochemical modeling reveals that the rocks were generated as a result of partial melting and fractionation of lower crust basaltic magma giving rise to A₁ and A₂ subtype granites. They were subsequently emplaced within an intraplate environment at the end of the Pan-African Orogeny.     

Hindcasting community-level building damage for the 2011 Joplin EF5 tornado

Resiliency of communities prone to natural hazards can be enhanced through the use of risk-informed decision-making tools. These tools can provide community decision makers key information, thereby providing them the ability to consider an array of mitigation and/or recovery strategies. The Center for Risk-Based Community Resilience Planning, headquartered at Colorado State University in Fort Collins, Colorado, developed an Interdependent Networked Community Resilience (IN-CORE) computational environment. The purpose of developing this computational environment is to build a decision-support system, for professional risk planners and emergency responders, but even more focused on allowing researchers to explore community resilience science. The eventual goal was being to integrate a broad range of scientific, engineering and observational data to produce a detailed assessment of the potential impact of natural and man-made hazards for risk mitigation, planning and recovery purposes. The developing computational environment will be capable of simulating the effects from different natural hazards on the physical and socioeconomic sectors of a community, accounting for interdependencies between the sectors. However, in order to validate this computational tool, hindcasting of a real event was deemed necessary. Therefore, in this study, the community of Joplin, Missouri in the USA, which was hit by an EF-5 tornado on May 22, 2011, is modeled in the IN-CORE v1.0 computational environment. An explanation of the algorithm used within IN-CORE is also provided. This tornado was the costliest and deadliest single tornado in the USA in the last half century. Using IN-CORE, by uploading a detailed topological dataset of the community and the estimated tornado path combined with recently developed physics-based tornado fragilities, the damage caused by the tornado to all buildings in the city of Joplin was estimated. The results were compared with the damage reported from field studies following the event. This damage assessment was done using three hypothetical idealized tornado scenarios, and results show very good correlation with observed damage which will provide useful information to decision makers for community resilience planning.     

Investigation on the Characteristics of Pore Water Flow During CRS Consolidation Test

Several experimental methods have been proposed for consolidation test such as: constant loading rate, constant gradient and constant rate of strain (CRS). Unfortunately, there are no unique criteria for performing the CRS consolidation test. Also, there are considerable differences among the standards proposed for the test. In the present paper, authors have tried to find the reasons for differences among standards, by studying the basic assumptions made on the characteristics of the pore water flow during consolidation process. In the course of study, CRS consolidation tests were carried out under different strain rates on remolded samples. The results of the tests have indicated that the Darcy’s law is not valid throughout the CRS test and therefore, any consolidation equation based on Darcy’s law would not provide accurate results. The results of the current experiments also showed that with regard to the applied strain rates, there are three different flow regimes governing the process named as: pre-linear (non-Darcy flow), linear (Darcy flow) and post-linear (non-Darcy flow). Experimental results also showed that distinction between boundaries of linear and nonlinear flow is possible from the excess pore pressure developed during the tests.     

Magmatic and post-magmatic evolution of post-collisional rare-metal bearing granite: The Neoproterozoic Homrit Akarem Granitic Intrusion,south Eastern Desert of Egypt,Arabian-Nubian Shield

The Homrit Akarem granitic intrusion (HAGI) outcrops near the western edge of the south Eastern Desert basement exposure in Egypt. It is a composite of two cogenetic intrusive bodies: an early albite granite phase shallowly emplaced at the apex of a magmatic cupola, and a later subjacent pink granite phase with a marginal zone of muscovite granite and better preservation of magmatic features. Mineral chemistry of primary biotite and garnet, together with whole-rock chemistry, identify the HAGI as a highly fractionated A-type peraluminous intrusion. The chemistry of F-dominant, Li-bearing, Fe³⁺-rich primary magmatic mica in the pink granite resembles that typically found in highly evolved Nb-Y-F pegmatites. The HAGI is the evolved product of a primary magma generated by partial melting of juvenile crust of the Arabian-Nubian Shield (ANS), emplaced along a regional strike-slip fault system that promoted its ascent. The main emplacement mechanism and evolutionary sequence of the HAGI was magmatic, although secondary minerals and textures resulting from hydrothermal fluid interactions are observed, especially at its margins. Primary columbite-(Mn) crystallized from melt and was partly replaced by secondary fluorcalciomicrolite. The high fluorine content of magmatic fluids exsolved from the intrusion is indicated by quartz-fluorite veins, greisenization, albitization, and F-bearing secondary oxide minerals. The magmatic derivation of this fluid is demonstrated by the F-dominant primary mica, a siderophyllite-polylithionite solid solution commonly known as zinnwaldite. The chemistry of zinnwaldite constrains the F/OH activity ratio and oxygen fugacity of its parental melt and thereby resolves the ambiguity between pressure and the effects of F in controlling the normative quartz content of rare-metal granites. The HAGI is less mineralized than the post-collisional rare-metal granites found further east in the south Eastern Desert, replicating a trend observed previously in the central Eastern Desert and suggesting that east-west zoning in rare metal enrichment is a persistent feature across latitudes at the western edge of the ANS.     

Geochemical prospecting for lead and zine in Gebel el Rousas,Eastern Desert,Egypt

Gebel El Rousas is an isolated hillock in the Eastern Desert of Egypt. It consists of the Basement Complex (subsurface) which is non-conformably overlain by the Middle Miocene and successively by Pleistocene-Recent terraces. The Miocene strata are mineralized by oxidized hypogene lead-zinc deposits.Geochemical prospecting was attempted for the first time in Gebel El Rousas and for the second time in Egypt. The old terraces of gravels and sands covering the hillock were sampled on a grid pattern of a 30 m spacing. The samples were taken at a depth of 30 cm from the surface. They were sieved to –150 mesh and analyzed for Pb, Zn, Cu, Fe, Mn, and CO₂.Significant contrasts and anomalies resulted for Pb, Zn, and Fe. The main anomalies are parallel and generally coincide with the subsurface mineralized zone which is inferred to cross the area on the same trend. The mineralized zone extends as shown by the geochemical pattern southward, from the known northern part, to a southern district which has not been checked by drilling or any other testing.

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Zusammenfassung Djebel El Rousas ist ein isolierter Hügel in der Ägyptischen Ostwüste. Er besteht aus dem Basementkomplex, der diskordant von MittelmiozÄn und aufeinanderfolgend von PleistozÄn-HolozÄn-Terrassen überlagert wird. Die MiozÄn-Schichten sind mit oxydischen hypogenen Blei-Zink-Ablagerungen vererzt.Im Djebel El Rousas wurde zum erstenmal der Versuch einer geochemischen Prospektion durchgeführt, für ganz Ägypten ist es das zweite Mal. Gitterförmig wurden im Abstand von 30 m den alten Kies- und Sandterrassen, die den Hügel bedecken, Proben aus einer Tiefe von 30 cm unter der OberflÄche entnommen. Die Proben wurden mit 150 Maschenweite gesiebt und auf Pb, Zn, Cu, Fe, Mn und CO₂ analysiert.Eindeutige Kontraste und Anomalien wurden für Pb, Zn und Fe festgestellt. Die Hauptanomalien sind parallel und fallen normalerweise mit der mineralisierten Zone unter Tage zusammen, die das Gebiet in derselben Richtung durchquert. Wie aus der geochemischen Karte hervorgeht, setzt sich die vererzte Zone nach Süden in ein Gebiet fort, das bisher noch nicht durch Bohrungen untersucht wurde.

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Résumé Gebel El Rousas est un monticule isolé dans le Désert Oriental de l'égypte. Il se compose de roches du Basement Complex (sous-sol) surmontées en discordance par des terrasses du Miocène Moyen et succéssivement par des terrasses du Pleistocène-Récent. Les couches du Miocène sont mineralisées par des dépÔts hypogènes de plomb et de zinc oxidés.Les prospections géochimiques furent essayées pour la première fois au Gebel El Rousas et pour la seconde fois en égypte. Des échantillons des anciennes terrasses de galets et de sables recouvrant ce monticule furent prises en une carte quadrillé de 30 m. Les échantillons furent prélevés à une profondeur de 30 cm de la surface. Ils furent criblés jusqu'aux mailles de 150 analysées pour la détermination de Pb, Zn, Cu, Fe, Mn, et CO₂.Des contrastes et des anomalies significatifs furent obtenus pour le Pb, Zn, et Fe. Les anomalies essentielles sont parallèles et généralement coincident avec la zone minéralisée du sous-sol qui est supposée traverser la région suivant la mÊme direction. La zone minéralisée s'étend comme l'indique la carte géochimique du Nord au Sud vers un district qui n'a pas été vérifié par forage ou par toute autre méthode éxpérimentale.

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Mapping groundwater recharge potential zones in arid region using GIS and Landsat approaches,southeast Tunisia

The rapid growth of population and agricultural and industrial activities has caused an increase in demand on the Jeffara aquifers of Gabes (southeast Tunisia). In fact, the over-pumping of this aquifer system has resulted in water-level declines ranging from 0.25 to 1 m/year during the past three decades. The aim of this study is to identify favourable artificial recharge sites of this aquifer system based on the combined use of remotely sensed data, a geographic information system (GIS), the Shuttle Radar Topography Mission (SRTM) product and a multiple criteria decision making (MCDM) technique. The delineation of artificial recharge zones shows high to moderate potential for groundwater recharge (40%) in the Gabes region, with high precision of good potential proposed sites. Recharge processes need to account for natural conditions and ecosystems.     

Numerical simulation of crack propagation in layered formations

In the present study, a boundary element method based on the higher order displacement discontinuity formulation is presented to solve the general problem of hydraulic fracture propagation in layered formations. Displacement collocation technique is employed to model the higher order displacement variation along the crack and the special crack tip element near its ends. The hydraulic fracture propagation and its interaction with the layer interface in non-homogenous rock materials are studied by the proposed semi-analytical (hybridized boundary element-boundary collocation) method. The maximum tangential stress criterion (or σ-criterion) of fracture mechanics considering different elastic constants (Young modulus and Poisson’s ratio) is used to obtain the fracture path. The fracture propagation from stiff to soft and soft to stiff media for cracks having different inclination angles is modeled, and the effects of elastic constants on the hydraulic fracture propagation is studied. The results show that if the hydraulic fracture originates in the stiffer layer, its capability to cross the layer increases and is vice versa for the softer material. The comparison of the results gained from the numerical method with those in the literature show a good performance of the method in the case of propagation of hydraulic fracture in layered formations.     

Driving behavior of stepped and tapered offshore piles due to hammer blows

Abstract

In this article, the drivability of stepped and tapered offshore piles with the same length and volume has been investigated under hammer blows. To justify the obtained results from field testing and numerical methods, this pile driving procedure has been analyzed and discussed with wave propagation mechanism. It will be shown that tapered pile can be confidently idealized as a number of prismatic segments connected rigidly to each other. This is an interesting finding that fully tapered or stepped piles have a better performance in pile driving and enable users to apply simple one dimensional numerical analysis for simulating pile drivability.