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131.
In arid‐region wadis, groundwater storage lies within shallow Quaternary alluvium deposits, which are connected with the present‐day hydrological cycle and, therefore, are replenished due to occasional runoff and flash flood occurrences. The groundwater resources are precious in these environments; therefore, their potentiality must be assessed with care in the best manner. The aquifer potentiality is calculated after the storativity and transmissivity parameter estimations, which require rather long‐duration field tests with restrictive assumptions in the theoretical model developments, such as the homogeneity and isotropy. It is the main purpose of this paper to expose the fundamentals of the slope‐matching procedure (SMP) and its application for short‐duration field tests in arid‐region aquifers. In this manner, the subsurface hydrogeological behaviours of the bored land pieces at and around the well locations are prospected in a detailed and refined manner. It is shown that in many cases the classical techniques are appropriate, inconvenient and inapplicable with conclusive reliable results and conclusions. The application of the SMP is presented for some aquifer tests from the central western part of the Kingdom of Saudi Arabia. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
132.
The movement of chemicals through soil to groundwater is a major cause of degradation of water resources. In many cases, serious human and stock health implications are associated with this form of pollution. The study of the effects of different factors involved in transport phenomena can provide valuable information to find the best remediation approaches. Numerical models are increasingly being used for predicting or analyzing solute transport processes in soils and groundwater. This article presents the development of a stochastic finite element model for the simulation of contaminant transport through soils with the main focus being on the incorporation of the effects of soil heterogeneity in the model. The governing equations of contaminant transport are presented. The mathematical framework and the numerical implementation of the model are described. The comparison of the results obtained from the developed stochastic model with those obtained from a deterministic method and some experimental results shows that the stochastic model is capable of predicting the transport of solutes in unsaturated soil with higher accuracy than deterministic one. The importance of the consideration of the effects of soil heterogeneity on contaminant fate is highlighted through a sensitivity analysis regarding the variance of saturated hydraulic conductivity as an index of soil heterogeneity. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
133.
The development of a predictive model of behaviour of porous media during injection of miscible grout, taking into account convection, dilution and filtration of grout solution with interstitial water, as well as consolidation aspects, is presented. Model assumptions are reviewed and discussed first. During the establishment of the model, we insist on surface terms and their physical relevance in expressing adsorption effects. Constitutive laws such as Fick's law for diffusive mass transport, hydrodynamic dispersion tensor dealing with miscibility, are modified by taking into account filtration effects. A new surface term appears in mass balance equations as a consequence of filtration. According to the filtration laws used, an initial filtration rate is estimated on the basis of a one‐dimensional experimental campaign. The field equations are discretized by using Galerkin finite element and θ‐scheme standard method. For transport equation, Streamline Upwind Petrov Galerkin method is employed to prevent numerical oscillations. Lastly, confrontation of numerical results with laboratory experiments constitutes a first step to validate the model on a realistic basis. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Rapid assessment of beta dose variation inside cobbles,and implications for rock luminescence dating
Variation in beta dose rate within rocks may impact the results of rock surface luminescence dating, for both the burial age of cobbles and exposure age of rock surfaces. Current methods of rock surface luminescence dating assume that radionuclides are homogeneously distributed inside rocks. In this study, two rapid methods based on beta counting and on a portable XRF instrument were developed to measure the radioactivity of rock slices. These methods were applied to rock slices from four glaciofluvial granite cobbles that had previously been used for equivalent dose determination to test whether beta dose variation could be observed. Results from beta counting and K content from XRF show similar patterns and both vary along the depth profiles, but the magnitude of this variability is very different amongst the four cobbles. In rocks where the dose rate is highly variable, bleaching may not be the only source of variation of Ln/Tn or equivalent dose (De) along the luminescence-depth profile of cobbles, and it may be necessary to measure the beta dose rate for every single slice to determine whether multiple bleaching events are recorded or variations in De are due to dose rate heterogeneity. 相似文献
138.
均匀半无限体中表面源激发近表面波场由瑞利波主导,当浅部存在异质体,前行瑞利波发生散射,异质体周围表面波场响应谱发生变化。当异质体长度相对波长较大时,由异质体上方表面质点响应谱提取绕射波频散曲线可分析异质体与周围介质刚度差异对绕射波传播特性的影响。与含软层或硬层半无限体中瑞利波特性比较,可以发现绕射波具有与瑞利波类似的传播特性。异质体上方谱变化特征与异质体和周围介质间刚度差异有关,本研究基于异质体绕射波与入射瑞利波位移结构差异解释谱变化现象。结果表明:异质体上方谱与周围谱明显不同,在偏移距−波长域,相对于前方波场,软质体上方谱密度整体呈减弱趋势,硬质体上方谱密度整体呈增强趋势。根据谱密度变化对应偏移距、波长及谱密度强弱,可以预估异质体在传播方向的位置、埋深,并识别异质体类型。 相似文献
139.
Reza Jamshidi Chenari Hassan Kamyab Farahbakhsh 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2015,9(2):96-108
This paper emphasises the true realisation of Cone Penetration Test (CPT) profiles considering non-stationary nature of the data. Formulation of stationary random field theory has been modified and adapted to non-stationary state in order to take into account the mean and variance variability for soil properties. Multi-variance correlation matrix along with the Cholesky decomposition technique was employed to produce realisations of non-homogenous and non-stationary random fields of CPT profiles. A piecewise and segmental data realisation according to the lithology and site class specifications acquired directly from CPT data is adopted in this study so as to render an accurate data simulation. For validation of proposed method 8 CPT test profiles collected from Urmia Lake site have been introduced and simulated by the stationary and non-stationary algorithms. The mean correlation coefficient between the actual CPT data profiles and related realisations along with some other important statistical parameters and their coefficients of variation strongly demonstrate that non-stationary random field generation technique gives quite better accuracy, by comparison to the conventional stationary random field generation scheme. 相似文献
140.
利用Voronoi\\Delaunay图模型影响范围和局部动态的特性,提出一种基于动态边界定量提取强降水过程空间非均匀分布特征的新方法,根据1959—2002年中国740站逐日降水资料,构建5日、10日两种时间尺度区域持续性年极端强降水过程序列,用以检验该方法的应用效果,并应用该方法分析了5日(10日)区域持续性年极端强降水过程空间非均匀分布特征及其演变规律。结果表明:与传统的数量统计方法和区域插值方法相比,该方法在强降水空间分布中心、过程内不同强度降水覆盖区域、降水集中区等的定量度量方面具有更高的分辨力和较好实际应用价值;气候趋势分析中在1959—2002年间,5日区域持续性年极端强降水过程出现日期有明显提前趋势。 相似文献