Effect of sulphates and curing period on stress–strain curves and failure modes of soil–lime–natural pozzolana mixtures     

Hamid Gadouri  Khelifa Harichane  Mohamed Ghrici 《Marine Georesources & Geotechnology》2013,31(9):1130-1148

Abstract

An experimental investigation was undertaken in order to assess the effect of sodium (Na₂SO₄) and calcium (CaSO₄·2H₂O) sulphates and curing period on stress–strain curves and failure modes of grey (GS) and red (RS) clayey soils stabilised by lime (L), natural pozzolana (NP) and their combinations (L–NP). Several soil–L–NP mixtures were studied to be used as subgrade soils for road pavements. Stress–strain curves were obtained from unconfined compressive strength (UCS) test made on several soil–L–NP specimens after curing for 7 and 120 days. Tests results showed that the use of L or L–NP without sulphates produced a significant increase in peaks stress of both clayey soils and then modified their stress–strain curves from nonlinear to linear behaviour almost up to 70% of peak stress after a longer curing period. However, the presence of 2% Na₂SO₄ or any CaSO₄·2H₂O content provided beneficial effects on peaks stress and stress–strain curves of both stabilised clayey soils and then improved their linearity almost up to 95% of peak stress after curing for 120 days. In contrast, the presence of 6% Na₂SO₄ caused undesirable effects. In addition, both sulphates greatly affected the failure modes of soil–L–NP specimens, particularly at a later stage.  相似文献   

Book reviews     

Barry Floyd  William J. Torry  Mohamed A. Mohamed Salih  P. P. Karan  Wolf Tietze  Nikolaos Zahariadis  Torsten Malmberg 《GeoJournal》1987,14(1):137-140

  相似文献   

Population growth and food supply margin in Pakistan     

Mohamed Ismail Siddiqi Dr. 《GeoJournal》1985,10(1):83-89

Conclusion Population growth in Pakistan is alarming. The long and continuing shortage of foodgrains at intervals and increasing competition for land use have resulted in deterioration in yield per hectare, and low reproduction of livestock, although hard struggle is going on for self sufficiency. The margin in food supply has arrived even in those areas where the production has been abundant, and vulnerable to crop failure and other emergency causes. Provision against these dangers call for the maintenance of adequate national reserves, which can be brought into action at an early stage of the emergency.The area under agriculture can be increased through improved programmes of soil conservation and development of barani (rain fed areas) with cost-benefit consideration. Several million hectares of barani areas have fertile soils and are suitable for agricultural development. It has been estimated that 45 billion m³ of river water flows into the Arabian Sea. A part of the water sources is properly harnessed and could possibly change the economic conditions of the barani region. A number of regions are covered by hard texture of the soil, mechanization will have to be introduced in these areas to increase production much beyond the level of margin. Soil conservation measures have already been initiated and in some cases demonstrated to farmers, but the reclaimed virgin lands up to 1973 were very little, just 46.5 ha of virgin lands and 72 ha of cultivated area from the Soan and Potwar uplands. It is expected that 300,000 ha of cultivated area, 10,000 ha of gullied land will be reclaimed through soil conservation methods in the current Fifth Year Plan.Pakistan has great water potential. The remedy lies in wise judicious and scientific water management. Inadequate natural and artificial drainage systems are causing water-logging and salinity. An accelerated programme for recovering lost land is already in operation. Many land reforms were introduced from time to time, but the production result is not of great significance. Restrictions were imposed on consolidated holdings. The economic level of such holding above subsistence have not yet been taken into consideration. It is, therefore, necessary, to make a thorough analysis of agricultural problems, particularly with the foodgrain crops, with reference to population growth, the efforts should continue till the food supply occupies the supreme position by increasing production and reducing the rate of population growth by adopting socio-economic methods.  相似文献   

Two orogenies in the Meatiq area of the Central Eastern Desert,Egypt     

Mohamed E. Habib  A.A. Ahmed  Osman M. El Nady 《Precambrian Research》1985,30(2):83-111

The Pan-African basement exposed in the Meatiq area west of Quseir, Egypt, consists of an infracrustal basement overthrusted by a supracrustal cover. The infracrustal rocks were developed as a result of an old orogeny referred to as the Meatiqian orogeny where granite—gneiss, migmatitic gneisses and migmatized amphibolites were formed. The granite—gneiss represents a deformed granite pluton emplaced at 626±2 Ma, whereas the migmatitic gneisses and amphibolites are of mixed igneous and sedimentary parentage. In view of the data so far available, the nature of the Meatiqian orogeny could not be deciphered. In spite of the young isotopic ages, it is suggested that at least the metasedimentary gneisses represent older rocks in the stratigraphic sequence of the infracrustal basement.The supracrustal cover represents a part of an extensive ophiolitic mélange obducted onto the infracrustal basement during the next orogeny (Abu Ziran orogeny) which culminated at 613±2 Ma. An active continental margin-type regime can adequately explain the evolution of such a supracrustal cover. During obduction, the ophiolitic mélange and the upper 2 km thick part of the infracrustal basement were intensely deformed and metamorphosed under PT conditions of the greenschist—epidote amphibolite facies. The deformed infracrustal basement was converted into mylonitic—blastomylonitic rocks and schists composing five thrust sheets, and subsequently intruded by synkinematic granitoid sheets. Later, both the infracrustal basement and the overlying supracrustal cover were isostatically uplifted, subjected to complex shallow folding giving rise to the major Meatiq domal structure, and were intruded by a postkinematic adamellite pluton at 579±6 Ma.  相似文献   

Expansion theory for the elliptic motion of arbitrary eccentricity and semi-major axis     

Mohamed Adel Sharaf 《Earth, Moon, and Planets》1988,42(2):115-131

In this paper of the series, the literal analytical expressions for the Fourier expansion of the Earth's spherical harmonic potential will be explored in terms of the sectorial variables _j ⁽ⁱ⁾ introduced in Paper IV (Sharaf, 1982) to regularize the highly-oscillating perturbation force of some orbital systems.Now at the Department of Astronomy, King Abdulaziz University Jeddah, Saudi Arabia.  相似文献   

Les xénolites ultramafiques du volcanisme alcalin quaternaire d'Oranie (Tell,Algérie occidentale), témoins d'une lithosphère cisaillée et enrichieUltramafic xenoliths from Quaternary alkali volcanism from Oranie (Tell,western Algeria): witnesses of a sheared and enriched lithosphere     

Mohamed Zerka  Jean-Yves Cottin  Michel Grégoire  Jean-Pierre Lorand  M&#x;Hamed Megartsi  Mohamed Midoun 《Comptes Rendus Geoscience》2002,334(6):387-394

Numerous ultramafic xenoliths occur within the A??n–Temouchent volcanic complex (Northwestern Oranie, Algeria). Most of them are type I mantle tectonites (lherzolites and harzburgites) and composite xenoliths (harzburgite/clinopyroxenite) are rare. Only a few samples of spinel lherzolites display relatively fertile compositions when the major part of type I xenoliths have refractory major element compositions but enriched LREE contents showing that they have been affected by mantle metasomatism. The composite xenoliths are witnesses of reactions of alkaline magmas with the upper mantle. An asthenospheric rising, in relation with the large strike slip fault affecting the North African plate margin at Trias time is proposed as a possible geodynamical setting. To cite this article: M. Zerka et al., C. R. Geoscience 334 (2002) 387–394.  相似文献   

Sur la présence d'une série molassique (de type série pourprée) au Sud-Est de l'Ahaggar (In Guezzam,Ahaggar, Algérie)Presence of molassic series (‘Série pourprée’ type) in the Southeast of the Ahaggar (In Guezzam,Ahaggar, Algeria)     

Hamou Djellit  Bernard Henry  Mohamed E.M Derder 《Comptes Rendus Geoscience》2002,334(10):789-794

In the western Ahaggar shield, the transition between the Precambrian and the Ordovician units is characterised by thick volcano-sedimentary series (‘Série pourprée’ of the Ahnet). This series, in part of Cambrian age, results from the demolition of the Panafrican belt. Similar series were known in grabens located between the West African craton and the Ahaggar, from the ‘Adrar des Iforas’, in the south, to the Ougarta belt, in the north. We describe in this study a new formation identical to the ‘Série pourprée’ of the Ahnet, but cropping out in the far Southeast of the Ahaggar (In Guezzam). This new datum improves the Panafrican belt configuration. To cite this article: H. Djellit et al., C. R. Geoscience 334 (2002) 789–794.  相似文献   

The Saharan Metacraton   总被引：2，自引：0，他引：2  

Mohamed G. Abdelsalam  Jean-Paul Ligeois  Robert J. Stern 《Journal of African Earth Sciences》2002,34(3-4)

This article introduces the name “Saharan Metacraton” to refer to the pre-Neoproterozoic––but sometimes highly remobilized during Neoproterozoic time––continental crust which occupies the north-central part of Africa and extends in the Saharan Desert in Egypt, Libya, Sudan, Chad and Niger and the Savannah belt in Sudan, Kenya, Uganda, Congo, Central African Republic and Cameroon. This poorly known tract of continental crust occupies 5,000,000 km² and extends from the Arabian-Nubian Shield in the east to the Tuareg Shield to the west and from the Congo craton in the south to the Phanerozoic cover of the northern margin of the African continent in southern Egypt and Libya. The term “metacraton” refers to a craton that has been remobilized during an orogenic event but is still recognizable dominantly through its rheological, geochronological and isotopic characteristics. Neoproterozoic remobilization of the Saharan Metacraton was in the forms of deformation, metamorphism, emplacement of igneous bodies, and probably local episodes of crust formation related to rifting and oceanic basin development. Relics of unaffected or only weakly remobilized old lithosphere are present as exemplified by the Archean to Paleoproterozoic charnockites and anorthosites of the Uweinat massif at the Sudanese/Egyptian/Libyan boarder. The article explains why the name “Saharan Metacraton” should be used, defines the boundaries of the metacraton, reviews geochronological and isotopic data as evidence for the presence of pre-Neoproterozoic continental crust, and discusses what happened to the Saharan Metacraton during the Neoproterozoic. A model combining collisional processes, lithospheric delamination, regional extension, and post-collisional dismembering by horizontal shearing is proposed.  相似文献   

Late Albian–Middle Cenomanian palynofacies and palynostratigraphy, Abu Gharadig-5 well, Western Desert, Egypt     

Mohamed I. A. Ibrahim 《Cretaceous Research》2002,23(6):775

Quantitative analyses of palynomorph assemblages, particulate organic matter (kerogen), and total organic carbon (TOC) have been made on samples of the Albian–Cenomanian Kharita and Bahariya formations encountered in the Abu Gharadig-5 well, Western Desert, Egypt. Two assemblage palynozones are defined: Assemblage Zone A (Kharita Formation) of late Albian–early Cenomanian age and Assemblage Zone B (Bahariya Formation) of early–middle Cenomanian age. Palynofacies of the Kharita Formation suggest that sedimentation of these strata took place in a warm, shallow, nearshore-marine environment. The deposition of the lower Bahariya Formation took place initially in similar conditions but subsequently further offshore in somewhat deeper water of the inner shelf. The relatively high percentage of Ephedripites, Afropollis and elaterate pollen in both formations indicates an arid climate. The Kharita Formation yields kerogen types III and IV whereas the assemblages recovered from the Bahariya Formation contain types II and III. The TOC is generally between 0.42 and 0.65% in the Kharita Formation, while it ranges between 0.42 and 0.80% in samples of the Bahariya Formation. The spores and pollen grains are pale in colour; hence little source potential for hydrocarbons is indicated.  相似文献   

Evaluation of coupled heat and moisture flow parameters in a bentonite-sand buffer material     

Raymond N. Yong  Abdel-Mohsen O. Mohamed 《Engineering Geology》1996,41(1-4):269-286

Several series of one-dimensional tests were used to study the nature of transient heat and moisture movements in a clay buffer under different imposed temperature gradients. The measured temperature and moisture profiles were used to calculate the diffusion parameters governing heat and moisture movement in the buffer material. The experimentally determined diffusion parameters are shown to be dependent on the moisture content and temperature. The diffusion parameters were calculated by using an identification technique, the root-time method, and an analytical technique.  相似文献