共查询到20条相似文献，搜索用时 218 毫秒
1.
Wang Mingyu The University of Arizona Tucson Arizona USA Department of Water Resources Environmental Engineering China University of Geosciences Beijing Chen Jinsong Wan Li Department of Water Resources Environmental Engineering 《中国地质大学学报(英文版)》2001,12(3)
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2.
Geometric modelling and object-oriented software concepts applied to a heterogeneous fractured network from the Grimsel rock laboratory 总被引：2，自引：0，他引：2
Thomas Kalbacher Ralph Mettier Chris McDermott Wenqing Wang Georg Kosakowski Takeo Taniguchi Olaf Kolditz 《Computational Geosciences》2007,11(1):9-26
Discrete fracture network simulations are computationally intensive and usually time-consuming to construct and configure.
This paper presents a case study with techniques for building a 3D finite element model of an inhomogeneous fracture network
for modelling flow and tracer transport, combining deterministic and stochastic information on fracture aperture distributions.
The complex intersected fractures represent a challenge for geometrical model design, mesh quality requirements and property
allocations. For the integrated and holistic modelling approach, including the application of numerical and analytical simulation
techniques, new object-oriented concepts in software engineering are implemented to ensure a resourceful and practicable software
environment. 相似文献
3.
M.J. White 《Engineering Geology》1998,49(3-4):185-194
This paper outlines the visualization of the El Berrocal granite using a computer-based geological modelling system, EarthVision, and discusses the application of this visualization to engineering aspects of waste disposal in crystalline rocks. The El Berrocal Project was an international study with the aim of understanding and modelling the migration processes which have controlled the distribution of naturally occurring radionuclides in a fractured granitic environment. EarthVision was used to provide three-dimensional geological models of the site structure and properties. Modelling of the site structure concentrated on the development of visualizations of the main discontinuities in the granite. These included a model of the main mineralized structures, a model of the regional fracture network, models of local fracture networks between borehole clusters and a visualization of the mineralogy of the fractures in individual boreholes. These fracture models were visualized with the boreholes and access gallery to the mine. In addition, the fracture network in the region of a large scale tracer test was visualized with the injection and extraction zones for the tracer test. Three-dimensional interpolations of the rock and fluid structure were undertaken. A model of the hydraulic conductivity illustrated large-scale variations in hydraulic conductivity and channelling effects in the tracer test zone. A model of the sulphate concentrations in the groundwater illustrated the interpolation of spatial data based on structural domains. The visualizations of the geology of the El Berrocal granite illustrate that, despite limitations, geological modelling can be a powerful and graphic tool in rock engineering. The use of computer visualizations can be provide the three-dimensional structural framework for computations, can aid decision making during the construction phase of waste repositories and can be useful in understanding and analysing the results of numerical calculations. 相似文献
4.
A new conceptual model for release rate of radionuclides from the proposed repository for high level nuclear waste located at Yucca Mountain, Nevada is developed. The model predicts that heat generated from radioactive decay combined with the unsaturated environment will lead to an inward flow system that, under many relevant conditions, will slow the release of and sometimes sequester radionuclides at locations of higher heat release and lower water percolation. The amount of protection will be greatest for more concentrated waste forms such as spent fuel and less for glass waste forms. The redistribution and concentration of the radionuclides is anticipated to significantly delay radionuclide release and create a tendency towards gradual release over time that is independent of localized penetrations of metallic barriers. 相似文献
5.
Sung-Hoon Ji Kyung Woo Park Doo-Hyun Lim Chunsoo Kim Kyung Su Kim William Dershowitz 《Hydrogeology Journal》2012,20(7):1341-1353
The development and implementation of a hybrid discrete fracture network/equivalent porous medium (DFN/EPM) approach to groundwater flow at the Gyeong-Ju low- and intermediate-level radioactive waste (LILW) disposal site in the Republic of Korea is reported. The geometrical and hydrogeological properties of fractured zones, background fractures and rock matrix were derived from site characterization data and implemented as a DFN. Several DFN realizations, including the deterministic fractured zones and the stochastic background fractures, whose statistical properties were verified by comparison with in-situ fracture and hydraulic test data, were suggested, and they were then upscaled to continuums using a fracture tensor approach for site-scale flow simulations. The upscaled models were evaluated by comparison to in-situ pressure monitoring data, and then used to simulate post-closure hydrogeology for the LILW facility. Simulation results demonstrate the importance of careful characterization and implementation of fractured zones. The study highlighted the importance of reducing uncertainty regarding the properties and variability of natural background fractures, particularly in the immediate vicinity of repository emplacement. 相似文献
6.
开展地下水数值模拟研究是高放废物处置场地安全评价的重要组成部分,然而深地质处置介质类型的复杂性、基岩深部资料的相对匮乏性导致模拟结果存在不确定性,如何刻画深部地下水动力场并评估可能引起的风险已成为高放废物处置安全评价中重点关注的问题。在大量文献调研的基础上,综述了世界典型国家高放废物深地质处置场地的地下水数值模拟与不确定性分析应用,并归纳总结该领域研究经验,得到以下认识:（1）深地质处置场深部构造、裂隙的发育与展布决定了地下水循环条件,探究适用于基岩裂隙地区新的水文地质试验方法是提高地下水数值模型仿真性的基础;（2）不同尺度模型融合是解决深地质处置地下水模拟的有效技术方法,区域尺度多采用等效连续介质法,场地尺度使用等效连续多孔介质和离散裂隙网络耦合模型,处置库尺度使用离散裂隙网络方法,其次需重点关注未来大时间尺度下放射性核素在地质体中的迁移转化规律,模拟预测场址区域地下水环境长期循环演变对核素迁移的潜在影响;（3）考虑到不同的处置层主岩岩性以及在多介质中发生的THMC（温度场—渗流场—应力场—化学场）过程,目前国内外常用的地下水模拟软件有:Porflow、Modflow、GMS及MT3DMS等用于模拟孔隙或等效连续介质,Connectflow、Feflow及FracMan等用于模拟地下水和核素在结晶岩、花岗岩等裂隙中的迁移,TOUGH系列软件主要应用于双重介质的水流、溶质及热运移模拟;（4）指导开展有针对性的模型和参数的不确定性分析工作,减少投入工作量,提高模型精度,并可针对处置库长期演变、废物罐失效、极端降雨等多情景预测模拟,为处置库安全评价及设计提供基础数据支撑;（5）针对我国深地质处置地下水数值模拟研究现状,下一步应加强区域地质、水文地质、裂隙测量以及现场试验等相关的调查及监测工作,多介质耦合、多场耦合模拟及不确定性分析研究将会是未来的研究重点。 相似文献
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The models appearing in the COUPLEX benchmark are a set of simplified albeit realistic test cases aimed at simulating the transport of radionuclides around a nuclear waste repository. Three different models were used. The first test case is related to simulations based on a simplified 2D far-field model close to those used for safety assessments in nuclear waste management. It leads to a classical convection diffusion type problem, but with highly variable parameters in space, highly concentrated sources in space and time, very different time scales and accurate results expected even after millions of years. The second test case is a simplification of a typical 3D near-field computation, taking into account the glass dissolution of vitrified waste, and the congruent release of several radionuclides (including daughter products), with their migration through the geological barrier. The aim of the third test case is to use the results of the near-field computation (COUPLEX 2) to drive the behavior of the nuclide source term in the far-field computation (COUPLEX 1). The modeling of this last case was purposely left rather open, unlike the previous two, leaving the choice to participants of the way the coupling should be made. 相似文献
9.
Hydraulic conductivity characteristics in mountains and implications for conceptualizing bedrock groundwater flow 总被引：2，自引：1，他引：1
Influences of hydraulic conductivity (K) heterogeneities on bedrock groundwater (BG) flow systems in mountainous topography are investigated using a conceptual 2D numerical modelling approach. A conceptual model for K heterogeneity in crystalline bedrock mountainous environments is developed based on a review of previous research, and represents heterogeneities due to weathering profile, bedrock fracture characteristics, and catchment-scale (～0.1–1 km) structural features. Numerical groundwater modelling of K scenarios for hypothetical mountain catchment topography indicates that general characteristics of the BG flow directions are dominated by prominent topographic features. Within the modelled saturated BG flow system, ～90 % or more of total BG flux is focussed within a fractured bedrock zone, extending to depths of ～100–200 m below the ground surface, overlying lower-K bedrock. Structural features and heterogeneities, represented as discrete zones of higher or lower K relative to surrounding bedrock, locally influence BG flow, but do not influence general BG flow patterns or general positions of BG flow divides. This result is supported by similar BG transit-time distribution shapes and statistics for systems with and without structural features. The results support the development of topography-based methods for predicting general locations of BG flow-system boundaries in mountain regions. 相似文献
10.
地下水流数值模型不仅是认识深部水动力场形成演化机制的有效工具,也是建立核素迁移数值模型的基础,因而是高放废物处置场选址和安全评价中重要的技术手段。高放废物深地质处置地下水流数值模拟方法较多,如何选择适当的方法也是值得关注的问题。针对高放废物深地质处置地下水流数值模拟技术展开研究,通过阅读大量国内外文献,文章系统阐述了目前常用的4 类地下水流数值模拟方法的研究进展、适用条件和实例应用;综述了深地质处置中常用的模型不确定性分析方法及研究成果,列表给出了适用于放射性废物地质处置的地下水流数值模拟软件及其在废物处置选择和安全评价中的应用。研究结果表明:等效连续介质模型适用于大区域、长序列、裂隙发育程度较高或较均匀的地区,该类模型方法成熟、所需的数据和参数易于获得,但是不能精确刻画裂隙介质中地下水的流动特征。离散裂隙网络模型适合解决处置场地、储罐尺度等需要精细刻画的地下水流问题,但由于需要大量裂隙及其连通性数据、相关参数等,该方法存在着工作量大、耗时多的缺点。双重介质模型主要用于解决区域尺度裂隙水流问题,但并不能表现出裂隙介质的各向异性、不连续性等特征,因而适用范围存在一定的限制。等效-离散耦合模型可以通过区域分解法对裂隙密度大的区域采用等效连续介质模型,对于裂隙密度较小的地区采用离散裂隙网络模型,从而更符合一般地质条件下裂隙渗流的特征,但也存在交换量难以确定、模型耦合技术问题。通过灵敏度分析,将不同敏感因子对模型敏感指标的影响程度进行排序,提高模型精度、减少参数不确定性分析的工作量。蒙特卡罗法是目前常用的一种模型不确定性方法,原理简单、易于实现。文章展望了数值模型在仿真性、不确定性分析、预测和多介质耦合等方面的研究前景。 相似文献
11.
Tao Chen Christoph Clauser Gabriele Marquart Karen Willbrand Thomas Hiller 《Hydrogeology Journal》2018,26(6):1903-1916
Upscaling permeability of grid blocks is crucial for groundwater models. A novel upscaling method for three-dimensional fractured porous rocks is presented. The objective of the study was to compare this method with the commonly used Oda upscaling method and the volume averaging method. First, the multiple boundary method and its computational framework were defined for three-dimensional stochastic fracture networks. Then, the different upscaling methods were compared for a set of rotated fractures, for tortuous fractures, and for two discrete fracture networks. The results computed by the multiple boundary method are comparable with those of the other two methods and fit best the analytical solution for a set of rotated fractures. The errors in flow rate of the equivalent fracture model decrease when using the multiple boundary method. Furthermore, the errors of the equivalent fracture models increase from well-connected fracture networks to poorly connected ones. Finally, the diagonal components of the equivalent permeability tensors tend to follow a normal or log-normal distribution for the well-connected fracture network model with infinite fracture size. By contrast, they exhibit a power-law distribution for the poorly connected fracture network with multiple scale fractures. The study demonstrates the accuracy and the flexibility of the multiple boundary upscaling concept. This makes it attractive for being incorporated into any existing flow-based upscaling procedures, which helps in reducing the uncertainty of groundwater models. 相似文献
12.
Laboratory and field experiments done on fractured rock show that flow and solute transport often occur along flow channels. ‘Sparse channels’ refers to the case where these channels are characterised by flow in long flow paths separated from each other by large spacings relative to the size of flow domain. A literature study is presented that brings together information useful to assess whether a sparse-channel network concept is an appropriate representation of the flow system in tight fractured rock of low transmissivity, such as that around a nuclear waste repository in deep crystalline rocks. A number of observations are made in this review. First, conventional fracture network models may lead to inaccurate results for flow and solute transport in tight fractured rocks. Secondly, a flow dimension of 1, as determined by the analysis of pressure data in well testing, may be indicative of channelised flow, but such interpretation is not unique or definitive. Thirdly, in sparse channels, the percolation may be more influenced by the fracture shape than the fracture size and orientation but further studies are needed. Fourthly, the migration of radionuclides from a waste canister in a repository to the biosphere may be strongly influenced by the type of model used (e.g. discrete fracture network, channel model). Fifthly, the determination of appropriateness of representing an in situ flow system by a sparse-channel network model needs parameters usually neglected in site characterisation, such as the density of channels or fracture intersections. 相似文献
13.
K. Geetha Manjari G. L. Sivakumar Babu 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2018,12(1):60-73
As per the regulatory requirements controlling the disposal of radioactive waste, the performance of waste disposal facilities needs to be assessed quantitatively using predictive models. This estimates the potential impact of disposal on the environment and public health. Near Surface Disposal Facilities (NSDFs), constructed to contain the low level radioactive waste are considered to model the radionuclide migration from the system to the geo-sphere. The radiation dose experienced by an individual through drinking water pathway is the endpoint of assessment of the model. A three dimensional groundwater contaminant transport model with a decaying source is modelled numerically to determine the radiation dose for short-lived and long-lived radionuclides. The consideration of uncertainties constitutes an intrinsic part of modelling. The uncertain input parameters include porosity, longitudinal dispersivity, transverse dispersivity, diffusion coefficient and distribution coefficient. The uncertainty propagation and quantification is carried out using collocation based stochastic response surface method (CSRSM). To run the simulations for the huge set of input, a code is developed using built-in python interface in the numerical model. The results are processed further to obtain the sensitive parameters affecting the output concentrations. Further, the probability of radiation dose exceeding permissible value is estimated by subset simulation. 相似文献
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15.
Permeability and stress in crystalline rocks 总被引：2，自引：0，他引：2
Groundwater from crystalline rocks is a significant resource in many areas of the world. It is also an important medium for contaminant transport from, for example, deep nuclear waste repositories. Stress distributions in fractured rocks are important in controlling groundwater flow in several ways: (i) palaeostress fields are responsible for the evolution of fracture systems which transmit groundwater; (ii) current in situ stress fields will influence the shape and aperture of fractures; (iii) humans can influence the natural stress field in a rock mass to enhance fracture flows. The significance of stresses for groundwater flow can be investigated by field techniques (hydraulic fracturing), laboratory techniques (stress cells) or by numerical modelling. 相似文献
16.
This study evaluates the alternative conceptual models for groundwater modelling. A true model was created with a synthetic alluvial fan-plain hydrogeological framework. Various alternative conceptual models were evaluated for groundwater flow simulations. The first alternative model is a single aquifer layer model; the second alternative model is a 3-layer aquifer model; and the third model is a 5-layer model consisting of 3 aquifers separated by 2 aquitards. All models could fit very well to the observations with optimized values of hydraulic conductivities. However, the single aquifer layer model can only compute water balance components with good accuracy. The 3-layer aquifer model can be used for water balance computation and groundwater head simulation with small errors. The 5-layer model is capable of simulating water budget, groundwater head distribution and travel times with high accuracy. Multi-model analysis found only the 3rd alternative model superior. 相似文献
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18.
裂隙岩体渗流概念模型研究 总被引：31，自引：4，他引：27
裂隙岩体中的渗流和传统的多孔介质渗流在机理上存在本质的差别,这种差别主要表现为裂隙岩体在各种尺度上存在的非均质性。模拟裂隙岩体渗流的主要困难在于描述这种非均质性。目前的概念模型,包括等效连续体模型、离散裂隙网络模型和混合模型使用了不同的技术来预测裂隙岩体中的渗流。这些模型基于不同的假设和概念框架,有着各自不同的优缺点。在实际应用时,应当根据研究域的具体特点和所要解决的问题的要求对其选择,此外,还讨论了单裂隙的概念模型。 相似文献
19.
Groundwater flow and radionuclide decay-chain transport modelling around a proposed uranium tailings pond in India 总被引：1，自引：0，他引：1
L. Elango K. Brindha L. Kalpana Faby Sunny R. N. Nair R. Murugan 《Hydrogeology Journal》2012,20(4):797-812
Extensive hydrogeological investigations followed by three-dimensional groundwater flow and contaminant transport modelling were carried out around a proposed uranium tailings pond at Seripalli in Andhra Pradesh, India, to estimate its radiological impact. The hydrogeological parameters and measured groundwater level were used to model the groundwater flow and contaminant transport from the uranium tailings pond using a finite-element-based model. The simulated groundwater level compares reasonably with the observed groundwater level. Subsequently, the transport of long-lived radionuclides such as 238U, 234U, 230Th and 226Ra from the proposed tailings pond was modelled. The ingrowths of progenies were also considered in the modelling. It was observed that these radionuclides move very little from the tailings pond, even at the end of 10,000 y, due to their high distribution coefficients and low groundwater velocities. These concentrations were translated into committed effective dose rates at different distances in the vicinity of the uranium tailings pond. The results indicated that the highest effective dose rate to members of the public along the groundwater flow pathway is 2.5 times lower than the drinking water guideline of 0.1?mSv/y, even after a long time period of 10,000 y. 相似文献
20.
裂隙岩体中非饱和渗流与运移的概念模型及数值模拟 总被引：12，自引：2，他引：12
探讨了裂隙岩体中非饱和地下水渗流与溶质运移的几种概念模型的构造及数值模拟问题 ,如裂隙网络模型、连续体模型、等效连续体模型、双孔隙度 (单渗透率 )模型、双渗透率模型、多组份连续体模型等。在裂隙岩体中 ,非饱和地下水的渗流可能只局限于岩体中的岩石组份、或裂隙网络 ,也可能在裂隙和岩石中同时发生 ;对前一种情形只需考虑单一连续体中的流动 ,而后一种情况则需要包括地下水在岩石和裂隙之间的交换。岩体中的裂隙网络往往是溶质运移的主要通道 ;但当溶质在裂隙与岩石之间的渗透和扩散是重要的运移机制时 ,就需要考虑岩石与裂隙界面处的溶质交换。为了模拟岩石与裂隙之间地下水和溶质的交换 ,就需要了解岩石与裂隙之间相互作用的模式和范围 ,使得这类问题的概念模型较单一连续体模型多了一层不确定性、其数值模拟也变得更为困难。因为在实际问题中不易、甚至根本不能判别非饱和渗流的实际形态 ,具体采用哪种模型主要取决于分析的目的和对现场数据的掌握程度。不论哪种模型都会受到模型及参数不确定性的影响 ,因此必须考虑与其他辅助模型的比较. 相似文献