Diffuse instabilities with transition to localization in loose granular materials     

Richard Wan  Mauricio Pinheiro  Ali Daouadji  Mohamad Jrad  Félix Darve 《国际地质力学数值与分析法杂志》2013,37(10):1292-1311

This paper is concerned with diffuse and other ensuing failure modes in geomaterials when tested under homogeneous states of shearing in various loading programs and drainage conditions. Material instability is indeed the basic property that accounts for the instability of an initially homogeneous deformation field leading to diffuse failure and strain localization in geomaterials. The former is normally characterized by a runaway type of failure accompanied with a sudden and violent collapse of the material in the absence of any localization phenomena. Against this backdrop, we present a brief overview of material instability in elastoplastic solids where one finds a rich source of theoretical concepts including bifurcation, strain localization, diffuse failure and second‐order work, as well as a considerable body of experiments. Some compelling laboratory experimental studies of material instability with focus to diffuse failure are then presented and interpreted based on the second‐order work. Finally, various material instability analyses using an elastoplastic constitutive and a general finite element analysis of the above‐mentioned laboratory experimental tests are presented as a boundary value problem. It is shown that instability can be captured from otherwise uniform stress, density and hydraulic states, whereas uniform deviatoric loads are being applied on the external boundaries of a specimen. Although the numerical simulations reproduce well the laboratory experimental results, they also highlight the hierarchy of failure modes where localization phenomena emerge in the post‐bifurcation regime as a result of a degradation of homogeneity starting from a diffuse mode signalled by a zero second‐order work. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

The impact of climate change on sea level rise at Peninsular Malaysia and Sabah–Sarawak     

Ali Ercan  Mohd Fauzi Bin Mohamad  M. Levent Kavvas 《水文研究》2013,27(3):367-377

The sea level change along the Peninsular Malaysia and Sabah–Sarawak coastlines for the 21st century is investigated along the coastal areas of Peninsular Malaysia and Sabah–Sarawak because of the expected climate change during the 21st century. The spatial variation of the sea level change is estimated by assimilating the global mean sea level projections from the Atmosphere–Ocean coupled Global Climate Model/General Circulation Model (AOGCM) simulations to the satellite altimeter observations along the subject coastlines. Using the assimilated AOGCM projections, the sea level around the Peninsular Malaysia coastline is projected to rise with a mean in the range of 0.066 to 0.141 m in 2040 and 0.253 m to 0.517 m in 2100. Using the assimilated AOGCM projections, the sea level around Sabah–Sarawak coastlines is projected to rise with a mean in the range of 0.115 m to 0.291 m in 2040 and 0.432 m to 1.064 m in 2100. The highest sea level rise occurs at the northeast and northwest regions in Peninsular Malaysia and at north and east sectors of Sabah in Sabah–Sarawak coastline. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Distribution, classification, petrological and related gochemical (SRA) characteristics of a tropical lowland peat dome in the Kota Samarahan-Asajaya area, West Sarawak, Malaysia     

Mohamad Tarmizi Mohamad Zulkifley  Ng Tham Fatt  Wan Hasiah Abdullah  John Kuna Raj  S. Paramanathan Param  Roslan Hashim  Muhammad Aqeel Ashraf 《Central European Journal of Geosciences》2013,5(2):285-314

Petrographic studies indicate that lateral variations in the decomposition levels of peat are associated with the predominantly occurring peat macerals. Source Rock Analyzer (SRA) results indicate lateral variation in peat organic matter types from type II to III and back again to type II, occurring laterally within the top 0-m to 0.5-m layer at the basin margin to the midsection and further towards the near-center areas of the peat dome. This variation is most likely caused by a combination of factors: (a) Horizontal zonation and lateral variation of the dominant species of plant assemblages (b) Fibric (marginal) peats and hemic to sapric peats associated with type II organic matter (kerogen). Sample organic matter (coal-equivalent kerogen) typing indicates that the relative abundance of phytoclasts and palynomorphs generally supports the organic matter classification obtained by the SRA method. Lateral variations in the peat organic matter types may support the lateral vegetation variation concept. The classification of peat organic matter types (interpreted from visual analyses of palynological slides) occurring from the basin periphery to the mid-section and further towards the basin center yields organic matter of type II to type III and mixed types II to III (coal kerogen-equivalent), respectively.  相似文献   

Elemental hydrochemistry assessment on its variation and quality status in Langat River, Western Peninsular Malaysia     

Wan Ying Lim  Ahmad Zaharin Aris  Tengku Hanidza Tengku Ismail  Mohamad Pauzi Zakaria 《Environmental Earth Sciences》2013,70(3):993-1004

This paper discusses the hydrochemistry variation and its quality status in Langat River, based on the chemistry of major ions, metal concentrations and suitability for drinking purposes. Water samples were collected from 30 different stations to assess their hydrochemical characteristics. The physico-chemical parameters selected were temperature, electrical conductivity, total dissolved solids (TDS), salinity, dissolved oxygen , pH, redox potential, HCO₃, Cl, SO₄, NO₃, Ca, Na, K, Mg, ²⁷Al, ¹³⁸Ba, ⁹Be, ¹¹¹Cd, ⁵⁹Co, ⁶³Cu, ⁵²Cr, ⁵⁷Fe, ⁵⁵Mn, ⁶⁰Ni, ²⁰⁸Pb, ⁸⁰Se and ⁶⁶Zn to investigate the variation of the constituents in the river water. Most of the parameters comply with the Drinking Water Quality Standard of the World Health Organization and the Malaysian National Standard for Drinking Water Quality by the Malaysia Ministry of Health except for EC, TDS, Cl, HCO₃, SO₄, Na, Mg, Al, Fe and Se. The results show that the Langat River is unsuitable for drinking purposes directly without treatment.  相似文献   

Geologic controls of submarine groundwater discharge: application of remote sensing to north Lebanon     

Amin Shaban  Mohamad Khawlie  Chadi Abdallah  Ghaleb Faour 《Environmental Geology》2005,47(4):512-522

Typical of Mediterranean countries, the Lebanese shoreline is well known for its littoral and offshore groundwater discharges, the so-called submarine springs. The tectonic framework of the terrain explains its interruption by dense geologic structures, i.e., fracturing, faulting, karstic routes, as well as acute dips of rock strata seaward. All of these structures serve as hydrologic agents transporting groundwater to the sea. The study aims to locate these groundwater discharges, and to interpret their geologic controls on land. For this purpose, two major lines of approach were followed. The first is an airborne thermal infrared (TIR) survey using radiometers to identify thermal anomalies, thereby determining the exact location of submarine groundwater discharges (SGDs). The second line of approach is the analysis of satellite images (Landsat 7ETM⁺) to delineate the geologic features that govern the mechanism of water flow, thereby determining their sources on land. Twenty-seven major SGDs were identified, 10 of these being offshore springs, the others littoral springs. The springs show a large variety of discharge configurations and extents, mainly parallel or perpendicular to the shoreline or rounded. Three major structural controls were identified to contribute to the transport of groundwater to the sea. These are karstic galleries, faults, and tilted rock strata, their contributions being 48, 37, and 15%, respectively. The SGDs associated with linear passageways, i.e., karstic galleries and faults, are connected with land aquifer formations several kilometers away from the shoreline. Moreover, the presence of impervious rock formations at many localities along the coastline results in a confined hydrologic system, promoting the flow of SGDs into the sea.  相似文献   

Geological impacts on groundwater pollution: a case study in Khuzestan Province     

Mohamad?SakizadehEmail author  Eisa?Ahmadpour 《Environmental Earth Sciences》2016,75(1):88

The main aims of this study were to examine the sources of pollution with an emphasis on geogenic sources and to predict the groundwater quality with reasonable accuracy. For this purpose, factor analysis/principal component analysis and partial least squares regression were used to analyze a data set of groundwater quality containing 17 parameters measured at 45 different sampling wells in Andimeshk Aquifer during 2006–2013 time period. Factor analysis identified three factors, which were responsible for the data structure explaining 78.3 % of the total variance of the data set. There were various sources of groundwater contamination, based on factor analysis, in which geological formations next to agricultural activities had the most influential effects. Partial least squares regression could predict the quality of groundwater according to the value of water quality index. The amounts of R-squared (0.79) and MSE (0.21) using seven PLS components showed that this method has been successful in the prediction of water quality in the study area.  相似文献   

Tectonic and geologic influences on soil gas radon emission along the western extension of Damascus fault,Syria     

Mohamed Al-Hilal  Mohamad K. Abdul-Wahed 《Environmental Earth Sciences》2016,75(23):1489

The main purpose of this work is to demonstrate the possibility of using soil gas radon survey as a promising technique for locating the trend of western extension of Damascus fault, where it is hidden under a cover of Pliocene unconsolidated deposits. The normal level of radon background was established in a stationary area away from the tectonic influence of the fault zone. The sites of radon measurements were chosen according to the accessibility and suitability of the area, besides some indicative geologic and tectonic evidences. A total of 81 radon sampling points were analyzed, and the results revealed some reasonable spatial increases, with peak values of 2–3 times higher than the background level, trending in accordance with what is believed to be the general direction of the fault in the bedrock. However, permeability properties rather than geotectonic activities seemed to be the main causes controlling the variations of radon concentration over the concerned fault zone. Yet, the moderate level of the observed radon values could be attributed to the nature of the prevailing rock types, as well as the probable effect of locked tectonic structure due to the action of high regional compressive regime which typically originates such reverse faulting. Further, the accumulation of fill materials due to rock alteration along the plane of such dormant fault, through long geologic time, possibly led to increase in the ratio of clay minerals which may affect soil gas mobility through the medium.  相似文献   

Lead in archaeological samples: an isotopic study by ICP-MS     

A. Mohamad Ghazi   《Applied Geochemistry》1994,9(6)

Inductively coupled plasma mass spectrometry (ICP-MS) has been used to measure the concentration and isotopic composition of Pb in archaeological human and animal skeletal remains, soil from a village site of the Omaha tribe (U.S.A.) and cosmetic pigments.Lead concentrations in human bones from the Omaha tribe vary between 4.8 and 2570 μg/g, with younger people having the highest concentrations. Lead concentrations in animal bones from an Omaha village vary between 0.6 and 3.7 μg/g, and those of three soil samples range between 18 and 21 μg/g. Lead concentrations found in human bones from Anasazi (Utah, U.S.A.) and Alta (Peru) populations vary between 0.7 and 3.2 μg/g.Isotope ratios of a reagent grade Pb(NO₃)₂ solutions were measured by thermal ionization mass spectrometry (TIMS), as well as by ICP-MS to provide laboratory reference materials. The accuracy of the ICP-MS measurements relative to TIMS for the standard solution were found to be within 0.02–0.31% for²⁰⁶Pb/²⁰⁴Pb, 0.02–0.55% for²⁰⁷Pb/²⁰⁴Pb, and 0.16–0.56% for²⁰⁸Pb/²⁰⁴Pb. The precision of measurements on artifacts was 0.42–0.65% for²⁰⁶Pb/²⁰⁴Pb and 0.41–0.62% for²⁰⁷Pb/²⁰⁴Pb, whereas the precision for the same ratios for the bones was 0.85–1.8 and 0.82–1.67%, respectively. For the cosmetic lead-bearing pigments, a precision of 0.07–0.15% was found for both²⁰⁶Pb/²⁰⁴Pb and²⁰⁷Pb/²⁰⁴Pb ratios. Lead isotope ratios of artifacts give a radiogenic Pb signature, of which are close to signatures from PbZn mines of the central U.S. region. Lead isotope ratios of the pigments give non-radiogenic Pb signatures. Lead isotope ratios of the bones differ from those of the artifacts, and although similar in isotopic ratio to the pigments, they are more scattered, suggesting potential mixing of Pb from different regions.  相似文献   

The middle Eocene high-K magmatism in Eastern Iran Magmatic Belt: constraints from U-Pb zircon geochronology and Sr-Nd isotopic ratios     

Siavash Omidianfar  Iman Monsef  Mohamad Rahgoshay  Jianping Zheng  Brian Cousens 《International Geology Review》2020,62(13-14):1751-1768

ABSTRACT

Intrusive rocks are well-exposed in the south Birjand around the Koudakan is herein compared to previously studied outcrops along the middle Eocene to late Oligocene Eastern Iran Magmatic Belt. This pluton is composed mainly of monzonite, quartz-monzonite, and granite with high-K calc-alkaline to shoshonitic affinities. The U-Pb zircon geochronology from monzonite and quartz-monzonite reveals the crystallization ages of 40.96 ± 0.48 to 38.78 ± 0.78 Ma (Bartonian). The monzonite, quartz-monzonite, and granite rocks show similar REEs and trace element patterns, as well as limited variations in εNd_(i) and ⁸⁷Sr/⁸⁶Sr_(i) ratio, suggesting that they are a comagmatic intrusive suite. The chondrite and primitive mantle normalized rare earth and trace element patterns show enrichment in the light rare earth elements, K, Rb, Cs, Pb, Th, and U and depletion in heavy rare earth elements, Nb, Zr, and Ti. The εNd_(i) and ⁸⁷Sr/⁸⁶Sr_(i) values range from +1.32 to +1.68 and 0.7044 to 0.7047, respectively, identical to island-arc basalt composition. The whole-rock Nd model age (T_DM) for the intrusive rocks range between 0.69 and 0.73 Ga. These geochemical and isotopic signatures indicate a subduction-related sub-continental lithospheric mantle source for these rocks. Our new geochemical, isotopic, and geochronological studies integrated with previously published data indicate that the middle Eocene to late Oligocene magmatism in eastern Iran was formed in a post-collisional tectonic environment. We suggest the northeastward subduction of the Neo-Tethys ocean beneath the Lut block and the eastward subduction of the Sistan ocean beneath the Afghan block caused mantle wedge to be metasomatized by slab components. At a later stage, a collision between the Lut and Afghan blocks was accompanied by the lithospheric delamination, and the subsequent asthenospheric upwelling led to the melting of the metasomatized sub-continental lithospheric mantle and the generation of middle Eocene to late Oligocene magmatism in the Eastern Iran Magmatic Belt.  相似文献   

Households’ participation in solid waste management system of Homs city,Syria     

Noufal  Mohamad  Maalla  Zena  Adipah  Sylvia 《GeoJournal》2021,86(3):1441-1463

GeoJournal - Solid waste management practice is a matter of concern for public health and environmental protection and has become a major challenge in Syria. Improper waste management can bear...  相似文献