埋藏型岩溶地下水源地的三维数值模拟——以天津市宁河北岩溶地下水源地为例   总被引：4，自引：1，他引：3  

周训  陈明佑  方斌  张华  沈晔  姚锦梅  于青春  林黎 《中国岩溶》2006,25(1):6-11

根据宁河北岩溶地下水源地已有的水文地质勘查成果和大型抽水试验资料,对研究区水文地质条件进行概化,建立地下水流三维非稳定流数学模型并进行数值计算,对开采性抽水试验的地下水位变化过程进行模拟。结果表明,该模型可以刻画埋藏型水源地地下水流场的变化过程,用它对规划的水源地三种开采方案的开采动态进行预测计算也取得了良好的效果。模拟计算中将开采条件下浅层第四系含水层对深层奥陶系灰岩含水层的越流补给处理为边界条件,可以刻画埋藏型水源地在开采条件下获得的补给增量。   相似文献   

数字图像处理技术在隧道掌子面的应用     

冷彪  仇文革  杜诚 《岩土力学》2006,27(Z1):385-388

在隧道施工过程中,为了解开挖方量以及隧道前方的地质构造等信息,有必要对掌子面图像进行分析。传统分析中大多数以人工素描为主,效果因人而异。为了克服传统方法的局限,将图形、图像处理及三维建模技术引入对掌子面图像的处理中,建立隧道掌子面地质图像画像系统,对一系列跟踪拍摄的掌子面图像进行处理,自动提取出掌子面上不同岩层的边界,获取岩层的特征信息,以此对围岩分级。根据相邻掌子面上岩层目标的对应关系,建立起隧道的三维模型,为隧道施工提供必要的参考信息。  相似文献   

Effects of water extraction in a vulnerable phreatic aquifer: Consequences for groundwater contamination by pesticides, Sint-Jansteen area, The Netherlands     

Irina Gaus 《Hydrogeology Journal》2000,8(2):218-229

Pesticides are a potential threat to the quality of extracted groundwater when the water-supply area is used for agricultural activities. This problem is discussed for the water-supply area of Sint-Jansteen, The Netherlands, where measured pesticide concentrations in the extracted water regularly exceed EU limits (0.1 μg/L). Groundwater samples taken from the aquifer within the water-supply area show low contamination, but samples taken from the extracted water occasionally contain pesticides, making the water inadequate for drinking-water purposes. The more intense contamination of the extracted water is caused by the change in the natural groundwater flow pattern near the extraction wells. In this area, pesticide use cannot be avoided easily, and an approach is given to differentiate pesticide use in the area according to expected travel time toward the wells and the chemical characteristics of the pesticides. A groundwater flow model for the area is developed and the effects of groundwater extraction on the natural flow pattern are evaluated. Using particle tracking, the travel-time zones are determined. Combining these results and the degradation behavior of certain pesticides led to an optimal scheme to integrate agricultural activities and groundwater extraction in the area. This is illustrated for five different types of pesticides (atrazine, simazine, bentazone, MCPA, and mecoprop). Received, October 1998/Revised, July 1999, September 1999/Accepted, November 1999  相似文献   

Legacies from three former manufactured-gas plants: impacts on groundwater quality     

Robert H. Abrams  Keith Loague 《Hydrogeology Journal》2000,8(6):594-607

Groundwater contamination due to accidental releases of mono- and polycyclic aromatic compounds (MAHs and PAHs) from decommissioned manufactured-gas plants is an ongoing and litigious problem. The MAHs and PAHs are derived from coal tar, which was a by-product of the gas-manufacturing process. While originally designed to contain coal tar, the manufactured-gas plant structures that remain today have often degraded over time and are not completely leak-proof. Over a period of many years, subsurface water has seeped into and out of the structures, resulting in groundwater contamination. This was particularly true once the tops of the structures were removed. In this study, process-based simulations were conducted to estimate the groundwater-quality impacts of accidental releases of dissolved naphthalene (C₁₀H₈) from the sites of three former manufactured-gas plants. The results from one-dimensional, transient, unsaturated, near-surface fluid-flow and solute-transport simulations served as input to three-dimensional saturated subsurface fluid-flow and solute-transport simulations. The simulation results and sensitivity analysis reported here indicate that accidental releases of naphthalene had significant, negative impacts on groundwater quality at each of the three sites. Electronic Publication  相似文献   

热带印度洋-太平洋地区海表温度异常的线性转置预报模型     

王秀荣  吴洪宝 《南京气象学院学报》2000,23(2):218-225

采用ＣＯＡＤＳ的月平均海平面温度跨平（ＳＳＴＡ）资料,建立了预报热带印度洋－太平洋ＳＳＴＡ的线性转置模型（ＬＩＭ）。经检验,对于非独立和独立样本,预报的均方根误差分别在１２个月和１０个月预报时效内小于ＳＳＴＡ的均方差,相对误差在５个月预报时效内都小于５０％。在Ｅ１Ｎｉｎｏ和Ｌａ Ｎｉｎａ时段效果优于其他时段,其中Ｌａ Ｎｉｎａ时段又更好些。对同一地区的ＳＳＴＡ,ＬＩＭ预报优于自回归模型预报、奇异谱  相似文献   

非均质介质中地下水流动与溶质运移模拟——问题与挑战   总被引：6，自引：1，他引：5       下载免费PDF全文

Tsang  CF 《地球科学》2000,25(5):443-450

对大空间尺度和长时间跨度的地下水流动及污染物质运移进行预测的需求, 使水文地质研究面临异乎寻常的挑战.这些需求来自于对核废料地质储放方法的安全性评价、地下水污染状况评价及其治理方案的选择.流动系统的非均质性是地下水流动及物质运移模拟中最主要的困难之一, 这种困难来自对非均质系统进行特征描述(通过原位观测实现)、概念化及模拟.评述了非均质介质中流动运移模拟的一些重要问题与挑战, 讨论了解决的途径.讨论的主题包括: 动力流动的沟道化, 示踪剂穿透曲线, 裂隙岩石中流体流动的多尺度, 观测的不同尺度, 模拟、预测与非均质性以及系统特征描述和预测性模拟的分析.   相似文献   

Site effects at Euroseistest—I. Determination of the valley structure and confrontation of observations with 1D analysis     

D Raptakis  F.J Chvez-Garc&#x;&#x;a  K Makra  K Pitilakis 《Soil Dynamics and Earthquake Engineering》2000,19(1):411

This paper describes the process of construction of the 2D model of Volvi's geological structure and results of empirical and theoretical approaches to the evaluation of site response at Euroseistest. The construction of the 2D model is based on a re-interpretation of the available geophysical and geotechnical data in an effort to improve the definition of the subsoil structure at Euroseistest in terms of the most important parameters needed to model site response. The results of this re-interpretation are compared with a previous published 2D model of the same alluvial valley. Different analysis of the measurements and different criteria in the synthesis of data have led to a different model, even if both studies had access to the same field measurements. This underscores the fact that a model results of an interpretation and is not uniquely determined by the data, no matter how detailed they are. The well known subsoil structure opened the possibility to correlate the geometry and the dynamic properties of the 2D model with the results of site response determined from a detailed analysis of two events in frequency and time domains and 1D numerical modeling. The study of site response shows the important effect of the lateral variations on the ground motion and suggests that the contribution of locally generated surface waves to the resonant peak may be important. In the case of Volvi's graben, the limitations of the 1D approximation to simulate ground motion under complex soil conditions in both frequency and time domains are also shown. This paper lays the ground for a companion article dealing with 2D site effects in this basin.  相似文献   

Analysis of the positive ionospheric response to a moderate geomagnetic storm using a global numerical model   总被引：1，自引：0，他引：1  

A. A. Namgaladze  M. Förster  R. Y. Yurik 《Annales Geophysicae》2000,18(4):461-477

Current theories of F-layer storms are discussed using numerical simulations with the Upper Atmosphere Model, a global self-consistent, time dependent numerical model of the thermosphere-ionosphere-plasmasphere-magnetosphere system including electrodynamical coupling effects. A case study of a moderate geomagnetic storm at low solar activity during the northern winter solstice exemplifies the complex storm phenomena. The study focuses on positive ionospheric storm effects in relation to thermospheric disturbances in general and thermospheric composition changes in particular. It investigates the dynamical effects of both neutral meridional winds and electric fields caused by the disturbance dynamo effect. The penetration of short-time electric fields of magnetospheric origin during storm intensification phases is shown for the first time in this model study. Comparisons of the calculated thermospheric composition changes with satellite observations of AE-C and ESRO-4 during storm time show a good agreement. The empirical MSISE90 model, however, is less consistent with the simulations. It does not show the equatorward propagation of the disturbances and predicts that they have a gentler latitudinal gradient. Both theoretical and experimental data reveal that although the ratio of [O]/[N₂] at high latitudes decreases significantly during the magnetic storm compared with the quiet time level, at mid to low latitudes it does not increase (at fixed altitudes) above the quiet reference level. Meanwhile, the ionospheric storm is positive there. We conclude that the positive phase of the ionospheric storm is mainly due to uplifting of ionospheric F2-region plasma at mid latitudes and its equatorward movement at low latitudes along geomagnetic field lines caused by large-scale neutral wind circulation and the passage of travelling atmospheric disturbances (TADs). The calculated zonal electric field disturbances also help to create the positive ionospheric disturbances both at middle and low latitudes. Minor contributions arise from the general density enhancement of all constituents during geomagnetic storms, which favours ion production processes above ion losses at fixed height under day-light conditions.  相似文献   

Study of elastic wave propagation in two-phase anisotropic media by numerical modeling of pseudospectral method     

YANG LIU 《地震学报(英文版)》2000,13(2):143-150

When there exists anisotropy in underground media, elastic parameters of the observed coordinate possibly do not coincide with that of the natural coordinate. According to the theory that the density of potential energy, dissipating energy is independent of the coordinate, the relationship of elastic parameters between two coordinates is derived for two-phase anisotropic media. Then, pseudospectral method to solve wave equations of two-phase anisotropic media is derived. At last, we use this method to simulate wave propagation in two-phase anisotropic media, four types of waves are observed in the snapshots, i.e., fast P wave and slow P wave, fast S wave and slow S wave. Shear wave splitting, SV wave cusps and elastic wave reflection and transmission are also observed.  相似文献   

地质雷达正演中的频散压制和吸收边界改进方法   总被引：5，自引：0，他引：5  

何兵寿  张会星 《地质与勘探》2000,36(3):59-63

从麦克斯韦方程组出发,建立了地质雷达的时域有限差分法（ＦＤＴＤ）数学模型,导出了理想 散关系和超级吸收边界条件。理想频散关系 考虑了ＦＤＴＤ法的收敛性和稳定性,也考虑了高频电磁波在Ｙｅｅ氏网格中的传播特点;超吸收边界条件则用磁场分量来提高电场分量精度。数值试验表明,理想频散关系能真实地反映雷达波在地下介质中的传播规律,超吸收边界条件能有效减小截断边界的伪反射,提高正演精度。将之应用于实际计算,取得  相似文献