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11.
Usama A. Abu Risha 《Hydrogeology Journal》2016,24(4):987-1000
The use of 14C (half-life?=?5,730 years) in modeling the evolution of the 36Cl/Cl ratios in groundwater is reported for the first time. The complexity of the Cl–36Cl system due to the occurrence of different Cl and 36Cl sources and the difficulty of the determination of the initial groundwater 36Cl/Cl ratios have raised concerns about the reliability of using 36Cl (half-life?=?301 thousand years, a) as a groundwater-dating tool. This work uses groundwater 14C age as a calibrating parameter of the Cl–36Cl/Cl decay-mixing models of three wells from the southwestern Great Artesian Basin (GAB), Australia. It aims to allow for the different sources of Cl and 36Cl in the southwestern GAB aquifer. The results show that the initial Cl concentrations range from 245 to 320 mg/l and stable Cl is added to groundwater along flowpaths at rates ranging from 1.4 to 3.5 mg/l/ka. The 36Cl content of the groundwater is assumed to be completely of atmospheric origin. The samples have different Cl–36Cl/Cl mixing-decay models reflecting recharge under different conditions as well as the heterogeneity of the aquifer. 相似文献
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The current study introduces the geological subsurface cross-sections in the southern part of the Gaza Strip to show the structure of the aquifer in the area. The cross-sections give evidence of four subaquifers of the coastal aquifer in the southern part of the Gaza Strip. These cross-sections give the natural reasons for the deterioration of the groundwater in the study area. The results show presence of clay lenses that prevent the replenishment processes of the aquifer of fresh water from the rainfall and returns flow from agricultural activities. Lithological formation was evident as one of the natural causes which accelerate destroying process of the coastal aquifer. The results also show that the structure of the aquifer causes the increase of the groundwater salinity in the Gaza Strip. The cross-sections had shown the shortage of storage capacity of high quantities of fresh water in the coastal aquifer in these areas. The role of lithological formation was evident as one of the natural causes to accelerate the process of destroying the coastal aquifer. 相似文献
14.
Usama Massoud Gad El Qady Mohamed Metwaly Fernando Santos 《Pure and Applied Geophysics》2009,166(4):701-719
An azimuthal resistivity survey was conducted at the transition zone between the desert area and the cultivated land near
Lake Qaroun, Egypt. This area has been affected by an east-west trending fault system as indicated from the surface geology.
Apparent resistivity values were plotted along azimuth on a polar diagram. Resistivity anomalies, for most of the AB/2 values
with long axes strike in a direction parallel to the contact between the desert and cultivated lands, indicate the presence
of electrical macro-anisotropy, mainly due to the faulting effect, at this area. Vertical electrical soundings (VES) and transient
electromagnetic (TEM) measurements were conducted at eight stations along a line that crosses the boundary between the desert
and cultivated land. Joint inversion of VES-TEM data was successfully used for identification of the subsurface lithostratigraphic
succession and demonstrated the effect of the fault zone on the investigated subsurface medium. Apparent anisotropy coefficients
at all current electrode spacings were calculated, plotted against AB/2 values and compared with the geoelectrical cross section.
The effect of the fault zone was detected at AB/2 spacings equal to 100 m and extended downward and is largely related to
the depth of the fault, as indicated in the constructed cross section. 相似文献
15.
This paper utilizes the Discrete Element Method to characterize energy dissipation mechanisms in cyclically loaded soils based
on micromechanical considerations. Computational simulations of consolidated undrained cyclic triaxial tests were conducted
at various relative densities and were subjected to cyclic loading of different frequencies and shear strain amplitudes. The
different components of microscale energies were monitored during the course of the simulations and characterized into input
and dissipated energies. A comparison is made between the dissipated energy computed from microscopic energy components and
macroscopic energy calculated based on the area of the deviator stress-axial strain loops. These energies are then used to
obtain the specific damping capacity defined as the ratio of dissipated energy during one cycle to the maximum stored elastic
energy during the same cycle. The conducted simulations highlight the importance of calculating actual stored energy in the
system as opposed to approximating it to be that calculated as the triangular area under the secant modulus. Finally, a series
of simulations that resulted in liquefaction are discussed, and the amount of energy dissipated to liquefaction is examined
based on these results. 相似文献
16.
A novel three‐dimensional particle‐based technique utilizing the discrete element method is proposed to analyze the seismic response of soil‐foundation‐structure systems. The proposed approach is employed to investigate the response of a single‐degree‐of‐freedom structure on a square spread footing founded on a dry granular deposit. The soil is idealized as a collection of spherical particles using discrete element method. The spread footing is modeled as a rigid block composed of clumped particles, and its motion is described by the resultant forces and moments acting upon it. The structure is modeled as a column made of particles that are either clumped to idealize a rigid structure or bonded to simulate a flexible structure of prescribed stiffness. Analysis is done in a fully coupled scheme in time domain while taking into account the effects of soil nonlinear behavior, the possible separation between foundation base and soil caused by rocking, the possible sliding of the footing, and the dynamic soil‐foundation interaction as well as the dynamic characteristics of the superstructure. High fidelity computational simulations comprising about half a million particles were conducted to examine the ability of the proposed technique to model the response of soil‐foundation‐structure systems. The computational approach is able to capture essential dynamic response patterns. The cyclic moment–rotation relationships at the base center point of the footing showed degradation of rotational stiffness by increasing the level of strain. Permanent deformations under the foundation continued to accumulate with the increase in number of loading cycles. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
17.
Ali D. Abdullah Mario Erik Castro-Gama Ioana Popescu Pieter van der Zaag Usama Karim Qusay Al Suhail 《水文科学杂志》2018,63(4):646-656
Wastewater effluents from irrigation and the domestic and industrial sectors have serious impacts in deteriorating water quality in many rivers, particularly in areas under tidal influence. There is a need to develop an approach that considers the impact of human and natural causes of salinization. This study uses a multi-objective optimization–simulation model to investigate and describe the interactions of such impacts in the Shatt al-Arab River, Iraq. The developed model is able to reproduce the salinity distribution in the river given varying conditions. The salinity regime in the river varies according to different hydrological conditions and anthropogenic activities. Due to tidal effects, salinity caused by drainage water is seen to intrude further upstream into the river. The applied approach provides a way to obtain optimal solutions where both river salinity and deficit in water supply can be minimized. The approach is used for exploring the trade-off between these two objectives. 相似文献
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In this paper, a three-dimensional particle-based technique utilizing the discrete element method (DEM) is proposed to study
wave propagation in a dry granular soil column. Computational simulations were conducted to investigate the soil response
to sinusoidal motions with different amplitudes and frequencies. Three types of soil deposits with different void ratios were
employed in these simulations. Different boundary conditions at the base such as rigid bedrock, elastic bedrock, and infinite
medium were also considered. Analysis is done in time domain while taking into account the effects of soil nonlinear behavior.
The computational approach is able to capture a number of essential characteristics of wave propagation including motion amplification
and resonance. Dynamic soil properties were then extracted from conducted simulations and used to predict the response of
the soil using the widely used equivalent linear method program SHAKE and compare its predictions to DEM results. Generally,
there was a good agreement between SHAKE and DEM results except when the exciting frequency was close to the resonance frequency
of the deposit where significant discrepancy in computed shear strains between SHAKE predictions and DEM results was observed. 相似文献
20.
The current contribution presents aspects of the structural style and fault kinematics of the Rus Formation that expose at Jabal Hafit, Al Ain, United Arab Emirates. Although the major structure of Jabal Hafit is an anticlinal fold, fractures (joints and faults) are the prominent structure of the study area. The fractures can be interpreted as the distributed effect of deep-seated basement fault reactivation or to be as reactivation of deep-seated basement faults. These fractures were created during two main tectonic stress regimes. The first is a WNW–ESE S Hmax strike-slip stress regime, responsible for producing E–W to ESE–WNW joints and E–W dextral strike-slip and NNE–SSW reverse faults. This stress is interpreted to be post-Early Eocene in age and related to the second phase of thrusting in the Oman Mountains in the Miocene. The second stress regime is a NNE–SSW S Hmax transtensional (strike-slip extensive) stress regime that was responsible for N–S to NNE–SSW striking joints and NE–SW sinistral strike-slip and N–S normal faults. This regime is interpreted to be post-Middle Eocene in age. This stress was the response to the collision of the Arabian–Eurasian Plates which began during the Late Eocene and continues to the present day. 相似文献