Quantification of Natural Fracture Surfaces Using Fractal Geometry   总被引：3，自引：0，他引：3  

Kayhan Develi  Tayfun Babadagli 《Mathematical Geology》1998,30(8):971-998

The purpose of this paper is to present an extensive evaluation of the methods to calculate the fractal dimension of natural fracture surfaces. Three methods; variogram analysis (VA), power spectral density (PSD), and roughness-length method (RMS) are applied to 2-D surface data (PSD) and 1-D profiles (VA and RMS) extracted from the surface data of 54 mm diameter crystallized limestone samples. Surface topography of the samples is quantified through a newly designed fully automated device. Before the application, self-affinity of the surface roughness and the applicability of these methods are validated using synthetically generated fractal surfaces. Fractal dimension values of the profiles are obtained as between 1 and 1.5 with a few exceptions. VA and RMS methods yield consistent fractal dimensions while the PSD values are lower than those of the other two methods. In terms of practical applicability, the VA is found more convenient than other two methods because there still exists shortcomings with the PSD and RMS methods due to difficulties in the mathematical analysis of the plots whose slopes are used in the computation of fractal dimension. However, it is observed that the data of limited size fracture surfaces are convenient for fractal analysis and the results are promising for further applications if the fracture surface size is restricted like cores recovered from deep boreholes.  相似文献   

Estimation of the depth to the fresh-water/salt-water interface from vertical head gradients in wells in coastal and island aquifers   总被引：3，自引：2，他引：1  

Scot K. Izuka  Stephen B. Gingerich 《Hydrogeology Journal》1998,6(3):365-373

 An accurate estimate of the depth to the theoretical interface between fresh, water and salt water is critical to estimates of well yields in coastal and island aquifers. The Ghyben–Herzberg relation, which is commonly used to estimate interface depth, can greatly underestimate or overestimate the fresh-water thickness, because it assumes no vertical head gradients and no vertical flow. Estimation of the interface depth needs to consider the vertical head gradients and aquifer anisotropy that may be present. This paper presents a method to calculate vertical head gradients using water-level measurements made during drilling of a partially penetrating well; the gradient is then used to estimate interface depth. Application of the method to a numerically simulated fresh-water/salt-water system shows that the method is most accurate when the gradient is measured in a deeply penetrating well. Even using a shallow well, the method more accurately estimates the interface position than does the Ghyben–Herzberg relation where substantial vertical head gradients exist. Application of the method to field data shows that drilling, collection methods of water-level data, and aquifer inhomogeneities can cause difficulties, but the effects of these difficulties can be minimized. Received, April 1997 · Revised, January 1998 · Accepted, January 1998  相似文献   

Ruralness,development and democracy: media,myths and the creation of meaning at Lake Cowal,New South Wales     

Andrew McGregor 《The Australian geographer》1998,29(2):191-203

The media play a vital role in translating new events and experiences into the textual forms that are communicated to the public. As a result, media narratives have become sites of contestation with opposing groups attempting to frame them in a way that suits their political purposes. When a gold mining proposal to be based at Lake Cowal was rejected by the NSW government for ‘environmental reasons’, the reaction of newspapers circulated in townships near the proposed mine site was analysed for the month following the announcement. A pro‐mining regional hegemony dominated the newspaper texts and drew on three powerful myths prevalent in Australian rural society: ‘the rural identity’, ‘the glory of development’, and ‘the duties of democracy’. The pro‐mining groups use these myths to make their interests appear the same as community interests in an effort to silence opposing views and obtain total community support. The manner in which powerful members of the pro‐mining group were permitted to use the newspapers for their own ends brings forth questions of power and objectivity in the media of contemporary society.  相似文献   

水平井降水技术在热力隧道暗挖工程中的应用   总被引：3，自引：0，他引：3  

叶发广  伍军 《水文地质工程地质》1998,25(3):53-54

在北京地区,我们首次成功地采用水平辐射井技术对双榆树热力隧道暗挖段进行地下降水。利用甲方的两处隧道工作竖井和另制作的一口大直径竖井,共施工水平孔３０眼,总长度达１５００ｍ,降水控制条带状隧道长度为３１０ｍ。开挖证实,降水效果显著,在地面以下降低地下水位的该项技术取得了明显的社会和经济效益。  相似文献   

碎岩刀具工作面圆弧化机理及解决途径   总被引：2，自引：0，他引：2       下载免费PDF全文

汪国香  杨凯华 《探矿工程》1998,(1):46-48

通过分析孕镶金刚石刀头碎岩和磨损机理,找出引金刚石刀头工作端面弧化的原因,并提出了克服圆弧化现象的几种方法。  相似文献   

灾害天气对日照市电力事故的影响研究          下载免费PDF全文

卢振礼  李玉华  崔广署  安源 《山东气象》2021,41(3):102-108

利用雷雨、大风等灾害天气资料和电力事故历史数据资料,分析了电力事故发生的时空分布特征及其与雷雨、大风、日平均气温等天气要素之间的关系。进而利用事件概率回归（regression estimation of event probability,REEP）和Logistic回归分析方法,得到了日照市电力事故发生概率与雷雨、大风和日平均气温之间关系的预警模型。研究结果表明：1）雷雨、大风是造成日照市电力事故的重要气象因素。2）雷雨、大风和高温等灾害天气对电力事故的发生虽都有促成作用,但影响能力存在较大差距。3）两种回归分析模型对因子和变量之间关系均有较好的拟合效果,相较而言,REEP模型更为直观,Logistic回归分析方法更为客观,适用性更强。4）回归分析结果建立在客观资料基础上,回归模型具有准确性、实用性,可为电力事故预警发布系统提供理论和技术支持。  相似文献   

Uncertainty,entropy, scaling and hydrological stochastics. 2. Time dependence of hydrological processes and time scaling / Incertitude,entropie, effet d'échelle et propriétés stochastiques hydrologiques. 2. Dépendance temporelle des processus hydrologiques et échelle temporelle     

《水文科学杂志》2013,58(3)

Abstract

The well-established physical and mathematical principle of maximum entropy (ME), is used to explain the distributional and autocorrelation properties of hydrological processes, including the scaling behaviour both in state and in time. In this context, maximum entropy is interpreted as maximum uncertainty. The conditions used for the maximization of entropy are as simple as possible, i.e. that hydrological processes are non-negative with specified coefficients of variation and lag-one autocorrelation. In the first part of the study, the marginal distributional properties of hydrological processes and the state scaling behaviour were investigated. This second part of the study is devoted to joint distributional properties of hydrological processes. Specifically, it investigates the time dependence structure that may result from the ME principle and shows that the time scaling behaviour (or the Hurst phenomenon) may be obtained by this principle under the additional general condition that all time scales are of equal importance for the application of the ME principle. The omnipresence of the time scaling behaviour in numerous long hydrological time series examined in the literature (one of which is used here as an example), validates the applicability of the ME principle, thus emphasizing the dominance of uncertainty in hydrological processes.  相似文献   

At‐a‐station hydraulic geometry relations, 2: calibration and testing     

Vijay P. Singh  Lan Zhang 《水文研究》2008,22(2):216-228

Using a large number of data sets obtained from various sources, the geometric relations derived in Part 1 are calibrated and verified using the split sampling approach. The calibration of parameters shows that the change in stream power is not shared equally among hydraulic variables and that the unevenness depends on the boundary conditions to be satisfied by the channel under consideration. The agreement between the observed values of the hydraulic variables and those predicted by the derived relations is close for the verification data set and lends credence to the hypotheses employed in this study. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Deriving hydrological signatures from soil moisture data     

Flora Branger  Hillary K. McMillan 《水文研究》2020,34(6):1410-1427

Soil moisture is an important variable in hydrological studies, but has been little used for model evaluation due to its high sensitivity to local conditions. We explore the possibility to derive hydrological signatures from soil moisture data that could overcome this limitation and be helpful for model evaluation. A set of eight hydrological signatures was built, encompassing long-term to short-term time scales. These signatures were tested according to robustness, representativeness and discriminatory power, using in situ data sets from New Zealand, including national network and experimental watershed data. Field capacity, type of soil moisture distribution, and starting dates of seasonal transitions typically meet the criteria, subject to uniform sensor depths and homogeneous land uses. Durations of seasonal transitions and event-based signatures showed higher variability and lower discriminatory power. In general, long-term signatures are more robust, more representative of large areas, and have a high discriminatory power, thus showing a good potential for use in diagnostic evaluation of regional models.  相似文献   

Transient solution for radial two‐zone flow in unconfined aquifers under constant‐head tests     

Y. C. Chang  H. D. Yeh  G. Y. Chen 《水文研究》2010,24(11):1496-1503

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