An alternative approach for quasi‐static large deformation analysis of saturated porous media using meshfree method

An alternative coupled large deformation formulation combined with a meshfree approach is proposed for flow–deformation analysis of saturated porous media. The formulation proposed is based on the Updated Lagrangian (UL) approach, except that the spatial derivatives are defined with respect to the configuration of the medium at the last time step rather than the configuration at the last iteration. In this way, the Cauchy stresses are calculated directly, rendering the second Piola–Kirchhoff stress tensor not necessary for the numerical solution of the equilibrium equations. Moreover, in contrast with the UL approach, the nodal shape function derivatives are calculated once in each time step and stored for use in subsequent iterations, which reduces the computational cost of the algorithm. Stress objectivity is satisfied using the Jaumann stress rate, and the spatial discretisation of the governing equations is achieved using the standard Galerkin method. The equations of equilibrium are satisfied directly, and the nonlinear parts of the system matrix are derived independent of the stresses of the medium resulting in a stable numerical algorithm. Temporal discretisation is effected based on a three‐point approximation technique that avoids spurious ripple effects and has second‐order accuracy. The radial point interpolation method is used to construct the shape functions. The application of the formulation and the significance of large deformation effects on the numerical results are demonstrated through several numerical examples. Copyright © 2015 John Wiley & Sons, Ltd.     

Simulation of vortex-induced vibrations of a cylinder using ANSYS CFX

In this paper, vortex-induced vibrations of a cylinder are simulated by use of ANSYS CFX simulation code. The cylinder is treated as a rigid body and transverse displacements are obtained by use of a one degree of freedom spring damper system. 2-D as well as 3-D analysis is performed using air as the fluid. Reynolds number is varied from 40 to 16000 approx., covering the laminar and turbulent regimes of flow. The experimental results of （Khalak and Williamson, 1997） and other researchers are used for validation purposes. The results obtained are comparable.     

The geochemistry of aliphatic and polar organic tracers in sediments from Lake Bera, Malaysia

The molecular distributions of homologous aliphatic lipid compounds (n-alkanes, n-alkanoic acids, n-alkanols, n-alkanals and n-alkan-2-ones) were investigated in sediments of Lake Bera, Malaysia as well as in plant waxes from the vicinity using gas chromatography-mass spectrometry. In addition, triterpenoids of the oleanane, ursane, lupane and friedelane series, and their diagenetic products were also identified. Using the aquatic proxy P_aq, it was found that the n-alkanes present in surface sediments S1, S5 and S6 correspond to an input from emergent macrophytes, whereas in sediments collected from open water (S2, S3 and S4) they correspond to input from submerged/floating macrophytes. The presence of n-alkan-2-ols, a commonly found homologous series in the sediments as well as in the plant wax, is novel here. In addition, the presence of 24-methylcycloart-22-enol and 24-ethylcycloart-22-enol in sediments as well as the plant wax of Pandanus helicopus, a dominant reed around the lake, also supports the input of plant biomarkers to the sediments. The occurrence of 5-membered ring triterpenoid derivatives as major diagenetic products of the triterpenoids identified (e.g. friedelan-2,3-dione) shows that the degradation of the organic matter in the sediments occurs mainly under oxic conditions. Also, the presence of ring-A degraded triterpenoids (dihydroputranjivic acid, 3-nor-2,4-seco-friedelane, 4α- and 4β-3-norfriedelanes, A-norfriedel-10-one, and A-norfriedel-8-en-10-one) and the aromatized triterpenoid hydrocarbons (mono- and triaromatic derivatives) as minor diagenetic products indicates photochemical and microorganism-mediated alteration reactions of natural products in the sediments. Additional novel polyfunctional friedelane derivatives, namely friedelane-2,3-dione, friedelane-1,3-diol-2-one and friedel-1(10)-ene-1,3-diol-2-one were identified for the first time in this study. These novel polyfunctional triterpenoids were inferred to derive from the oxidation of the triterpenoids from higher plants in this oxic tropical environment. For future reference purposes, the mass spectra of the identified polar triterpenoids are also presented here. This study provides important data on the biogeochemistry of organic matter in a tropical lake of SE Asia.     

Impact of major organophosphate pesticides used in agriculture to surface water and sediment quality (Southern Caspian Sea basin,Haraz River)

Organophosphate pesticides are compounds that are not only toxic to both humans and wildlife but also difficult to degrade under natural environmental conditions. In Iran, agricultural practices are strongly dependent on the use of pesticides due to climatic and soil conditions, thus posing a potential risk to groundwater quality standards. Evaluating the concentration of organophosphate pesticides namely diazinon, fenitrothion, dichlorvos, ethion, profenofos, malathion and azinphos methyl in water samples in May (low precipitation rate), December (high precipitation rate) as well as the concentration in sediments along the Haraz River is taken into consideration in this study. Generally the pesticides concentration in water samples are relatively higher in May in comparison with that in December; this fact may be due to two major reasons: the first reason is attributed to the prompt raining after the treatment period of most orchards and dry farming lands that will terminate in more wash out of such pesticides towards the branches and main river channel, while the second reason may be considered as the less river water dilution rate in May because of lower precipitation rate. Furthermore, the relatively higher concentrations in downstream stations may be contributed to more intensified agricultural (specially rice paddies), urban and rural land uses in this region in comparison with upstream areas which contain mainly dry farming, grazing lands and orchards with relatively lower loads of pesticides. Additionally, as the Henry’s law constant of all pesticides considered in this study are relatively low, volatilization may not be regarded as an important route of dissipation. Diazinon, azinphos methyl and dichlorvos showed the highest water concentrations in comparison with other pesticides that may be justified by their extended use within the basin during last decades. Based on the chemical properties as well as remarkably higher values in sediment samples in comparison with water ones, it is concluded that the two pesticides, ethion and fenitrothion, persist in the environment due to non-degradable tendencies. Although the concentration of mentioned pesticides is not so high in the water samples, more precautions must be considered in their future use. Regarding the sorption coefficient variation alongside the river, the higher values in upstream and central parts may be attributed to the higher potential of different types of erosion regarding deeper slopes and also sand, gravel and carbonate mining activities at the banks and also river bed in such regions which is considered as an anthropogenic disturbance. In case of central parts, in addition to mentioned reasons, the existence of coal outcrops in the geologic texture of the study area may also be considered as a key role in augmentation of the sorption coefficient. Finally, the dominant clayey and loamy soils containing more organics may be attributed as the major reason of sorption tendency in downstream.     

Geochemistry and fluid inclusions study of highly fractionated garnet-bearing granite of Gabal Abu Diab, central Eastern Desert of Egypt

The Neoproterozoic granite of Gabal Abu Diab, central Eastern Desert of Egypt, comprises mainly garnet-bearing granite and alkali feldspar granite intruded into calc-alkaline granodiorite–tonalite and metagabbro–diorite complexes. The garnet-bearing granite is composed mainly of plagioclase, K-feldspar, quartz, garnet and primary muscovite ± biotite. The presence of garnet and primary muscovite of Abu-Diab granite suggests its highly fractionated character. Geochemically, the garnet-bearing granite is highly fractionated as indicated from the high contents of SiO₂ (74.85–77.5%), alkalis (8.27 to 9.2%, Na₂O+K₂O) and the trace elements association: Ga, Zn, Zr, Nb and Y. This granite is depleted in CaO, MgO, P₂O₅, Sr and Ba. The alumina saturation (Shand Index, molar ratio A/CNK) of 1.0 to 1.1 indicates the weak peraluminous nature of this garnet-bearing granite. The geochemical characteristics of the Abu Diab garnet-bearing granite are consistent with either the average I-type or A-type granite and also suggest post-orogenic or anorogenic setting. A fluid inclusions study reveals the presence of three fluid generations trapped into the studied granite. The earlier is a complex CO₂–H₂O fluid trapped in primary fluid inclusions with CO₂ contents >?60 vol.%. These inclusions were probably trapped at minimum temperature >?400°C and minimum pressure >?2 kb. The second is immiscible water–CO₂ fluid trapped in secondary and/or pseudo-secondary inclusions. The trapping conditions were estimated at temperature between 400°C and 170°C and pressure between 900 and 2000 bar. The latest fluid is low-salinity aqueous fluid trapped in secondary two-phase and mono-phase inclusions. The trapping conditions were estimated at temperature between 90°C and 160°C and pressure <?900 bar. The origin of the early fluid generation is magmatic fluid while the second and third fluids are of hydrothermal and meteoric origin, respectively.     

Amelioration of calcareous sandy soil productivity via incorporation between biochar and some organic manures

Most arid and semi-arid soils, especially calcareous sandy soils, are widely distributed in the Middle East region; the deficiency in their content of many nutrients particularly phosphorus and organic matter limits crops production. This study aimed to assess the effects of adding biochar (B) with farmyard manure (FYM) and poultry manure (PM) on some soil properties, phosphorus (P) availability, and barley growth in calcareous sandy soil. The pot experiment includes the following treatments: Control, B, B?+?FYM (1:1), B?+?PM (1:1), B?+?FYM (2:1), B?+?PM (2:1), FYM?+?B (2:1), and PM?+?B (2:1). Biochar combined with FYM and PM enhanced the water holding capacity (WHC) and soil organic matter (SOM) content in calcareous sandy soil. Phosphorus availability was increased significantly by applying biochar mixed with farmyard manure and poultry manure at all treatments. Green biomass of barley improved because of adding biochar alone, poultry manure alone, and biochar co-applied with poultry manure at all mixing ratios. Biochar application caused significant increases in phosphorus use efficiency (PUE) by barley plants compared to all other treatments, except for the control. We recommend adding biochar either individually or mixed with poultry manure to improve the productivity of calcareous sandy soil.     

Quantitative geophysical pore‐type characterization and its geological implication in carbonate reservoirs

This paper discusses and addresses two questions in carbonate reservoir characterization: how to characterize pore‐type distribution quantitatively from well observations and seismic data based on geologic understanding of the reservoir and what geological implications stand behind the pore‐type distribution in carbonate reservoirs. To answer these questions, three geophysical pore types (reference pores, stiff pores and cracks) are defined to represent the average elastic effective properties of complex pore structures. The variability of elastic properties in carbonates can be quantified using a rock physics scheme associated with different volume fractions of geophysical pore types. We also explore the likely geological processes in carbonates based on the proposed rock physics template. The pore‐type inversion result from well log data fits well with the pore geometry revealed by a FMI log and core information. Furthermore, the S‐wave prediction based on the pore‐type inversion result also shows better agreement than the Greensberg‐Castagna relationship, suggesting the potential of this rock physics scheme to characterize the porosity heterogeneity in carbonate reservoirs. We also apply an inversion technique to quantitatively map the geophysical pore‐type distribution from a 2D seismic data set in a carbonate reservoir offshore Brazil. The spatial distributions of the geophysical pore type contain clues about the geological history that overprinted these rocks. Therefore, we analyse how the likely geological processes redistribute pore space of the reservoir rock from the initial depositional porosity and in turn how they impact the reservoir quality.     

Environmental texture and geochemistry of the sediments of a subtropical mangrove ecosystem and surrounding areas,Red Sea Coast,Egypt

The textural and geochemical aspects of the sediments of subtropical mangrove ecosystem and surrounding areas have been studied and discussed. Forty sediment samples were collected from different areas of mangrove environment and surrounding areas along the Egyptian Red Sea coast. The sediments of each study areas are characterized by the abundance of sand with minor amounts of mud and gravel. The mean size of the sediments ranged from medium grained to fine grained at the study areas. Cluster analysis showed that the distribution of gravel, sand, and mud fractions is related to bottom facies and type of sediment source. Generally, sand fraction is the main category among the three constituents. Carbonate content recorded minor values in the study areas. The CaCo₃ content of the sediments ranged from 4.7 % at Hamata area to 64.9 % at Erier area. Terrigenous and biogenic components are the factor controlling of the carbonate content of studies sediments. The organic carbon content ranged from 1.10 at Hamata area to 3.1 % at Sharm el-Qibli and Erier areas, which is controlled by particle size of the sediments. Phosphorus content in the different studied localities is related to the sources of phosphorus to the area. Our observations provide evidence that there are no significant differences in environmental texture and geochemistry of the sediments of subtropical mangrove ecosystem and surrounding areas of the Egyptian Red Sea coast.     

Geomechanical evaluation of Pliocene natural aggregates as pavement materials

Asphaltic roads and constructions in Egypt annually consume a huge amount of aggregates. The physical and geomechanical properties of these aggregates have controlled their performance in which they are used. All road pavements require the efficient use of locally available materials if economically constructed roads are to be built. More than 650 million m³ of fine and coarse aggregates are herein selected to be the tonnage of the present study. The studied Pliocene aggregates have smoothed grading curves and neither a deficiency nor excess of any one particle size, generally produce good mixtures with fewer voids between particles. The litho-particles of coarse aggregates are composed mainly of granites, gneisses, granodiorite, gabbro, and quartz particles. The sand equivalent value of fine aggregates varies from 95 to 97 %. The specific gravity values of the studied aggregates vary from 2.72 to 2.74 gm/cm³ for coarse aggregate and range from 2.51 to 2.54 gm/cm³ for fine aggregate. The Los Angles abrasion value varies from 19 to 24 %. Both coarse and fine aggregates meet the international standards which are suitable for usage as subbase and surface course aggregates, respectively.