地下水人工回灌过程中多孔介质悬浮物堵塞实验   总被引：3，自引：1，他引：2  

路莹  杜新强  迟宝明  杨悦锁  李胜涛  王子佳 《吉林大学学报(地球科学版)》2011,41(2):448-454

地下水人工回灌技术的发展与推广常因其回灌过程中物理、化学及生物作用产生的入渗介质堵塞现象而受到严重制约。针对堵塞现象中最常见且最主要的悬浮物堵塞问题,采用室内模拟实验方法,通过将悬浊水连续注入均质的石英砂柱中,来刻画多孔介质中悬浮物堵塞的现象及发生的过程,并分析其发展规律,同时量化计算了堵塞速率。实验结果表明：回灌15 h左右表层介质渗透系数开始降低,即堵塞在表层开始发生,并随时间增加不断向深部发展;连续回灌100 h后表层渗透系数趋于稳定,进入介质内部悬浮物的量减少,内部堵塞发展也趋于稳定,此时堵塞主要在入渗深度10 cm左右的范围内。计算不同堵塞层的堵塞速率λ:表层0～1 cm的λ最大,为0.038 3 h^-1,λ随入渗深度增加而减小。对于介质整体的渗透性而言,其降低明显滞后于表层介质,但随时间发展主要受堵塞层的控制。  相似文献   

地震作用下饱和土-桩-上部结构动力相互作用研究   总被引：1，自引：1，他引：0  

刘林超  杨骁 《岩土力学》2012,33(1):120-128

将土体视为液固两相多孔介质,利用连续介质力学得到了饱和土层的水平动力阻抗,将上部结构视为梁单元,桩-饱和土-桩之间的动力相互作用借助于等效的Winkler动力弹簧和波的干涉来模拟,并通过承台处力的平衡将群桩和上部结构耦合起来,研究了简谐SH地震波作用下饱和土-桩-上部结构的动力相互作用问题。以2×2群桩为例,对饱和土-桩-上部结构体系进行了数值分析,讨论有关参数对结构体系动力特性特别是抗震性能的影响。数值分析表明,桩间距、桩-土弹性模量比、长径比等对结构体系的抗震性能有较大影响。桩间距对地震放大系数的影响与外界激励的频率有关,桩土模量比较小、结构和桩基的阻尼较大时结构体系的抗震效果较好,长径比越大地震作用下产生的结构变形越大  相似文献   

径向分层TI孔隙介质井孔中激发的模式波的数值研究   总被引：5，自引：3，他引：2       下载免费PDF全文

陈雪莲  王瑞甲 《地球物理学报》2008,51(4):1270-1277

横向各向同性介质是地层中普遍存在的一种各向异性介质.本文对径向分层TI孔隙介质包围井孔中激发的斯通利波和弯曲波的传播特性进行了理论计算,发现模式波在低频时更多的是反应原状地层的信息,而随着频率的增加侵入带参数逐渐起控制作用;Biot理论描述的地层衰减比速度更容易受井壁附近地层参数的影响.利用灵敏度曲线定量研究了不同频率下地层各个参数对相速度和衰减系数的贡献大小,主要结果显示模式波的衰减受水平渗透率影响明显,而垂直渗透率的变化对模式波几乎无影响;斯通利波对水平向传播的横波速度比弯曲波的灵敏度高.从单极子和偶极子声源在井孔中激发的全波波形也可发现,声波测井仪器较宽的声源频带和合适的源距设置有利于对不同径向深度上的地层声学参数进行成像.  相似文献   

模拟裂隙多孔介质中变饱和渗流的广义等效连续体方法   总被引：2，自引：0，他引：2  

项彦勇 《岩土力学》2005,26(5):750-754

描述了一种计算裂隙多孔介质中变饱和渗流的广义等效连续体方法。这种方法忽略裂隙的毛细作用,设定一个与某孔隙饱和度相对应的综合饱和度极限值,并假定：（1）如果裂隙多孔介质的综合饱和度小于该极限值,水只在孔隙中存在并流动,而裂隙中则没有水的流动;（2）如果综合饱和度等于或大于该极限值,水将进入裂隙,并在裂隙内运动。分析比较了等效连续体模型的不同计算方法,并给出了一个模拟裂隙岩体中变饱和渗流与传热耦合问题的应用算例。结果表明,所述方法具有一般性,可以有效地模拟裂隙多孔介质中变饱和渗流的基本特征。  相似文献   

多孔材料等效导热系数与分形维数关系的数值模拟研究   总被引：2，自引：0，他引：2  

李守巨  刘迎曦  于贺 《岩土力学》2009,30(5):1465-1470

采用有限元方法模拟了多孔材料的导热系数与孔隙率和分形维数之间的非线性关系。有限元模型中的固体骨架和孔隙根据孔隙率的大小随机生成,模型中的材料参数和单元属性用ANSYS中的APDL参数化语言赋值。根据有限元随机模拟断面的热流密度分布和稳态热传导傅立叶定律,计算在不同孔隙率条件下的等效导热系数。研究表明,多孔材料模型等效导热系数随着孔隙的增加而线性减小。在孔隙率为常数的条件下,模型等效导热系数随着模型比例因子的增加而呈指数增加。等效导热系数随着孔隙分形维数的增加而减小,随着固体颗粒分形维数的增加而增加。  相似文献   

Porous and fluffy grains in the regions of anomalous extinction     

D. B. Vaidya  B. G. Anandarao  J. N. Desai  R. Gupta 《Journal of Astrophysics and Astronomy》2000,21(1-2):91-99

It has long been established that the ratio of total to selective extinction is anomalously large (>- 5) in certain regions of the interstellar medium. In these regions of anomalous extinction the dust grains are likely to be irregular in shape and fluffy in structure. Using discrete dipole approximation (DDA) we calculate the extinction for porous and fluffy grains. We apply DDA first to solid spheroidal particles assumed to be made of a certain (large) number of dipoles. Then we systematically reduce the number of dipoles to model the porous grains. The aggregates of these particles are suggested to form the fluffy grains. We study the extinction for these particles as a function of grain size, porosity and wavelength. We apply these calculations to interpret the observed extincttion data in the regions of star formation (e.g. the Orion complex).  相似文献   

水平分层孔隙介质中点源激发的震电波场数值模拟及分析   总被引：8，自引：6，他引：2       下载免费PDF全文

高永新  胡恒山 《地球物理学报》2009,52(8):2093-2104

为认识地震波诱导的电磁场的特性,本文研究地震波在孔隙介质中由于动电效应引起的电磁场.基于Pride弹性-电磁耦合方程组推导了双力偶震源对应的位移-应力-电磁场间断向量的表达式,模拟了双力偶源激发的震电波场.作为比较,还模拟了爆炸点源激发的震电波场.结果表明：存在伴随纵波的电场,其各分量的波形与固相位移对应分量的波形相似,但相位相反;存在伴随横波的磁场,其波形与固相位移波形相似;双力偶震源还激发出了独立传播的辐射电磁场,其速度比纵波至少高一个数量级,几乎是“瞬间同时”到达了每个接收器,但是其强度比伴随电磁场小得多,且随着源距增大而迅速减小.本文研究还表明：伴随纵波的电场强度不仅与地震纵波幅度和动电耦合系数有关,还与由介质孔隙结构决定的流-固两相动力协调性有关,存在一种动力协调介质,纵波在这种介质中不引起电场.  相似文献   

Discontinuous Galerkin methods for advective transport in single-continuum models of fractured media     

Birgitte Eikemo  Knut-Andreas Lie  Geir Terje Eigestad  Helge K. Dahle 《Advances in water resources》2009

Accurate simulation of flow and transport processes in fractured rocks requires that flow in fractures and shear zones to be coupled with flow in the porous rock matrix. To this end, we will herein consider a single-continuum approach in which both fractures and the porous rock are represented as volumetric objects, i.e., as cells in an unstructured triangular grid with a permeability and a porosity value associated with each cell. Hence, from a numerical point of view, there is no distinction between flow in the fractures and the rock matrix. This enables modelling of realistic cases with very complex structures. To compute single-phase advective transport in such a model, we propose to use a family of higher-order discontinuous Galerkin methods. Single-phase transport equations are hyperbolic and have an inherent causality in the sense that information propagates along streamlines. This causality is preserved in our discontinuous Galerkin discretization. We can therefore use a simple topological sort of the graph of discrete fluxes to reorder the degrees-of-freedom such that the discretized linear system gets a lower block-triangular form, from which the solution can be computed very efficiently using a single-pass forward block substitution. The accuracy and utility of the resulting transport solver is illustrated through several numerical experiments.  相似文献   

Modeling vertical stratification of CO₂ injected into a deep layered aquifer     

Mohamed Hayek  Emmanuel MoucheClaude Mügler 《Advances in water resources》2009

The vertical stratification of carbon dioxide (CO₂) injected into a deep layered aquifer made up of high-permeability and low-permeability layers, such as Utsira aquifer at Sleipner site in Norway, is investigated with a Buckley–Leverett equation including gravity effects. In a first step, we study both by theory and simulation the application of this equation to the vertical migration of a light phase (CO₂), in a denser phase (water), in 1D vertical columns filled with different types of porous media: homogeneous, piecewise homogeneous, layered periodic and finally heterogeneous. For each case, we solve the associated Riemann problems and propose semi-analytical solutions describing the spatial and temporal evolution of the light phase saturation. These solutions agree well with simulation results. We show that the flux continuity condition at interfaces between high-permeability and low-permeability layers leads to CO₂ saturation discontinuities at these interfaces and, in particular, to a saturation increase beneath low-permeability layers. In a second step, we analyze the vertical migration of a CO₂ plume injected into a 2D layered aquifer. We show that the CO₂ vertical stratification under each low-permeability layer is induced, as in 1D columns, by the flux continuity condition at interfaces. As the injection takes place at the bottom of the aquifer the velocity and the flux function decrease with elevation and this phenomenon is proposed to explain the stratification under each mudstone layer as observed at Sleipner site.  相似文献   

A physical–chemical model for the static water retention characteristic of unsaturated porous media     

Y. Wang  S.M. Grove  M.G. Anderson 《Advances in water resources》2008

Water retention characteristic or water retention curve (WRC) is an important constitutive feature of porous media, and also meanwhile is an indispensable requirement in hydraulic transport modelling. Previous experiments have indicated that the specific surface area of porous media has effects on the WRC. It has also been observed that a linear relationship generally exists between the air–water interface area and the water saturation within unsaturated porous media. However it seems that no detailed study on their internal linkage with the WRC has been reported yet. This paper, at first gives a review of the development of WRC modelling, then it tries to explain the water retention characteristic according to the physical and chemical behaviours of the phases involved in unsaturated porous media. Using the traditional capillary theory, the volume averaging theorem and the advances in physical chemistry of interfacial surfaces, this paper then derives out a formula which represents the water retention characteristic of porous media. This formula demonstrates the internal linkage of the WRC to the specific surface area of porosities. It also shows agreements with the experimental observations mathematically. Based on this formula, a fitting model is proposed for the static WRC of porous media. Finally, this model is tested to fit the WRC measurements of a wide range of porous materials. Comparison with other main models is presented.  相似文献