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Intrinsic vulnerability assessment to groundwater contamination is part of groundwater management in many areas of the world. However, popular assessment methods estimate vulnerability only qualitatively. To enhance vulnerability assessment, an approach for quantitative vulnerability assessment using numerical simulation of water flow and solute transport with transient boundary conditions and new vulnerability indicators are presented in this work. Based on a conceptual model of the unsaturated underground with distinct hydrogeological layers and site specific hydrological characteristics the numerical simulations of water flow and solute transport are applied on each hydrogeological layer with standardized conditions separately. Analysis of the simulation results reveals functional relationships between layer thickness, groundwater recharge and transit time. Based on the first, second and third quartiles of solute mass breakthrough at the lower boundary of the unsaturated zone, and the solute dilution, four vulnerability indicators are extracted. The indicator transit time t50 is the time were 50% of solute mass breakthrough passes the groundwater table. Dilution is referred as maximum solute concentration Cmax in the percolation water when entering the groundwater table in relation to the injected mass or solute concentration C0 at the ground surface. Duration of solute breakthrough is defined as the time period between 25% and 75% (t25%-t75%) of total solute mass breakthrough at the groundwater table. The temporal shape of the breakthrough curve is expressed with the quotient (t25%-t50%) / (t25%-t75%). Results from an application of this new quantitative vulnerability assessment approach, its advantages and disadvantages, and potential benefits for future groundwater management strategies are discussed. 相似文献
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Serdar KOLTUK Jie SONG Recep IYISAN Rafig AZZAM 《Frontiers of Structural and Civil Engineering》2019,13(6):1415
In this study, experimental and numerical investigations are performed to clarify the seepage failure by heave in sheeted excavation pits in stratified cohesionless soils in which a relatively permeable soil layer (kupper) lies above a less permeable soil layer (klower) between excavation base and wall tip. It is shown that the evaluation of base stabilities of excavation pits against seepage failure by using Terzaghi and Peck’s approach leads to considerably lower critical potential differences than those obtained from the model tests. On the other hand, a relatively good agreement is achieved between the results of the model tests and the finite element (FE) analyses. Further investigations are performed by using axisymmetric excavation models with various dimensions and ground conditions, and a comparison between the results obtained from Terzaghi and Peck’s approach and finite element analyses is given. 相似文献
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Ni Jing Chen You-Liang Wang Peng Wang Su-Ran Peng Bin Azzam Rafig 《Bulletin of Engineering Geology and the Environment》2017,76(1):169-179
Bulletin of Engineering Geology and the Environment - Rocks in nature are very often subjected to weathering processes. The physical and mechanical properties of granites exposed to chemical... 相似文献
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Youliang Chen Jing Ni Ping Zheng Rafig Azzam Youcheng Zhou Wei Shao 《Engineering Failure Analysis》2011,18(7):1848-1857
Calculating the fatigue strength of concrete under the cyclic load of vehicles when designing bridges is an issue which is receiving more and more attention from many engineers and researchers. Based on this fact, fatigue tests of plain concrete under constant-amplitude and stepping-amplitude cyclic loads were conducted. The mechanism which damages plain concrete specimens under high frequency fatigue loads was analysed and a non-linear accumulative fatigue formula that causes the damage was proposed. A fatigue equation P–S–N that considers the failure probability p′ was given. The results of this research are a good preparation for further studies into high frequency fatigue tests of concrete cylinders reinforced with carbon fibre. 相似文献
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Rafig Teymurov 《International journal of control》2017,90(5):923-931
We consider a problem of optimal control of the mobile sources for heat conductivity processes, described by parabolic equation and systems of ordinary differential equations. Sufficient conditions for Frechet differentiability of the performance criterion and an expression for its gradient were determined. The necessary optimality condition was established in the form of the integral principles of maximum. The theoretical conclusions are illustrated by the solution of a numerical example. 相似文献
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Giovanni Spagnoli Tomás Fernández-Steeger Martin Feinendegen Helge Stanjek Rafig Azzam 《Soils and Foundations》2010,50(5):757-763
It is common knowledge that the engineering properties of clays are greatly influenced by the type of pore fluids. However, the impact of the pore fluids on the geotechnical properties of the samples is even more dependent on the type of mineral and interlayer ions. Completely different behaviours could be observed with identical pore fluids but different clay minerals and vice versa. The liquid limit, plastic limit and undrained shear strength were determined for two types of smectites with different interlayer cations, namely Ca and Na-smectite. The pore fluids were varied by using different dielectric constants (ε) and electrolyte concentrations (n0). The results show that the two kinds of soils respond in a similar way but with a different magnitude depending on the ion occupation. 相似文献
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Strength of soil reinforced with fiber materials (Papyrus) 总被引:2,自引:0,他引:2
Aqeel Al Adili Rafig Azzam Giovanni Spagnoli Joerg Schrader 《Soil Mechanics and Foundation Engineering》2012,48(6):241-247
Construction of building and other civil engineering structures on weak or soft soil is highly risky because such soil is
susceptible to differential settlements, poor shear strength, and high compressibility. Various soil improvement techniques
have been used to enhance the engineering properties of soil. Soil reinforcement by fiber material is considered an effective
ground improvement method because of its cost effectiveness, easy adaptability, and reproducibility. Hence, in the present
investigation, papyrus fiber has been chosen as the reinforcement material, and it was randomly included into the soil at
four different percentages of fiber content, i.e., 5, 10, 15, 25% by volume of raw soil. The main objective of this research
is to focus on the strength behavior of soil reinforced with randomly included papyrus fiber. Direct shear, consolidation,
and displacement tests were performed on papyrusreinforced specimens with various fiber contents. The results of these tests
have clearly shown a significant improvement in the failure deviator stress and shear strength parameters (c and φ) of the
studied soil with a percent addition of 10% (the preferred percent). Moreover, this addition ratio reduced the displacement
of the soil under loading. It can be concluded that papyrus fiber can be considered an appropriate soil reinforcement material. 相似文献
10.
Undrained shear strength of clays as modified by pH variations 总被引:1,自引:0,他引:1
Giovanni Spagnoli David Rubinos Helge Stanjek Tomás Fernández-Steeger Martin Feinendegen Rafig Azzam 《Bulletin of Engineering Geology and the Environment》2012,71(1):135-148
The undrained shear strength of clays is an important geotechnical parameter used during construction processes. Several laboratory
tests were performed on kaolinite and smectite mixed with pore fluids with different pH values. Vane shear tests were carried
out and it was found that the undrained shear resistance for clays increased considerably if the pore fluid had a high or
a low pH. A possible explanation could be the dissolution of Al3+ which acts as a coagulant, increasing the internal shear resistance. Geochemical computations, Al measurements and ζ-potential
experiments were performed to confirm this theory. The research suggests varying the pH may make a useful contribution to
soil improvement techniques. 相似文献