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111.
112.
地应力测量在矿床突水防治中的应用——以河南夹沟铝土矿床突水防治工程为例 总被引:2,自引:0,他引:2
针对铝土矿床突水,开展地应力测量研究,是分析查明突水成因、优化确定防治方案及合理进行矿床底板管理的一项重要手段。夹沟矿床测量分析结果表明:①矿床地区存在较高的水平构造应力,其量值明显高于垂向应力。矿床水平高构造应力对矿床底板及其边坡稳定性具有不良影响,矿床开采掘面轴线走向应沿N70°E方向布设趋佳;②由于持续开采作用,矿床附近地应力状态产生不良扰动,水平高构造应力同开采形成的局部地应力场不良改变的叠加影响对矿床底板岩石场各类裂隙、结构面水起到极为重要的“催化”作用,是造成矿床底板突水的重要因素之一;③防治工作应重视加强矿床底板管理,科学预留安全隔水层屏障。并建议对矿床底板及其下伏一定范围内的灰岩实施预注浆处理,使得裂隙得以加固、溶洞得到堵塞,以抵抗不良应力的作用,消除或减弱对矿床突水的影响。 相似文献
113.
Besides granites of the ilmenite series, in which the anisotropy of magnetic susceptibility (AMS) is mainly controlled by paramagnetic minerals, the AMS of igneous rocks is commonly interpreted as the result of the shape-preferred orientation of unequant ferromagnetic grains. In a few instances, the anisotropy due to the distribution of ferromagnetic grains, irrespective of their shape, has also been proposed as an important AMS source. Former analytical models that consider infinite geometry of identical and uniformly magnetized and coaxial particles confirm that shape fabric may be overcome by dipolar contributions if neighboring grains are close enough to each other to magnetically interact. On these bases we present and experimentally validate a two-grain macroscopic numerical model in which each grain carries its own magnetic anisotropy, volume, orientation and location in space. Compared with analytical predictions and available experiments, our results allow to list and quantify the factors that affect the effects of magnetic interactions. In particular, we discuss the effects of (i) the infinite geometry used in the analytical models, (ii) the intrinsic shape anisotropy of the grains, (iii) the relative orientation in space of the grains, and (iv) the spatial distribution of grains with a particular focus on the inter-grain distance distribution. Using documented case studies, these findings are summarized and discussed in the framework of the generalized total AMS tensor recently introduced by Cañon-Tapia (Cañon-Tapia, E., 2001. Factors affecting the relative importance of shape and distribution anisotropy in rocks: theory and experiments. Tectonophysics, 340, 117–131.). The most important result of our work is that analytical models far overestimate the role of magnetic interaction in rock fabric quantification. Considering natural rocks as an assemblage of interacting and non-interacting grains, and that the effects of interaction are reduced by (i) the finite geometry of the interacting clusters, (ii) the relative orientation between interacting grains, (iii) their heterogeneity in orientation, shape and bulk susceptibility, and (iv) their inter-distance distribution, we reconcile analytical models and experiments with real case studies that minimize the role of magnetic interaction onto the measured AMS. Limitations of our results are discussed and guidelines are provided for the use of AMS in geological interpretation of igneous rock fabrics where magnetic interactions are likely to occur. 相似文献
114.
A comparative error analysis of manual versus automated methods of data acquisition for algebraic strain estimation 总被引:1,自引:0,他引:1
This paper presents a statistical analysis of the algebraic strain estimation algorithm of Shimamoto and Ikeda [Shimamoto, T., Ikeda, Y., 1976. A simple algebraic method for strain estimation from deformed eillipsoidal objects: 1. Basic theory. Tectonophysics 36, 315–337]. It is argued that the error in their strain estimation procedure can be quantified using an expected discrepancy measure. An analysis of this measure demonstrates that the error is inversely proportional to the number of clasts used. The paper also examines the role of measurement error, in particular that incurred under (i) a moment based and (ii) manual data acquisition methods. Detailed analysis of these two acquisition methods shows that in both cases, the effect of measurement error on the expected discrepancy is small relative to the effect of the sample size (number of objects). Given their relative speed advantage, this result favours the use of automated measurement methods even if they incur more measurement error on individual objects. Validation of these results is carried out by means of a simulation study, as well as by reference to studies appearing in previous literature. The results are also applied to obtain an upper bound on the error of strain estimation for various studies published in the literature on strain analysis. 相似文献
115.
Michael H. Ramsey Paul D. Taylor Katy A. Boon 《中国地球化学学报》2006,25(B08):209-210
All geochemical measurements require the taking of field samples, but the uncertainty that this process causes is often ignored when assessing the reliability of the interpretation, of the geochemistry or the health implications. Recently devised methods for the estimation, optimisation and reduction of this uncertainty have been evaluated by their application to the investigation of contaminated land. Uncertainty of measurement caused by primary sampling has been estimated for a range of six different contaminated land site investigations, using an increasingly recognized procedure. These site investigations were selected to reflect a wide range of different sizes, contaminants (organic and metals), previous land uses (e.g. tin mining, railway sidings and gas works), intended future use (housing to nature reserves) and routinely applied sampling methods. The results showed that the uncertainty on measurements was substantial, ranging from 25% to 186% of the concentration values at the different sites. Sampling was identified as the dominant source of the uncertainty (〉70% of measurement uncertainty) in most cases. The fitness-for-purpose of the measurements was judged using the optimized contaminated land investigation (OCLI) method. This identifies the optimal level of uncertainty that reduces to overall financial loss caused by the measurement procedures and the misclassification of the contamination, caused by the uncertainty. Generally the uncertainty of the actual measurements made in these different site investigations was found to be sub-optimal, and too large by a factor of approximately two. The uncertainty is usually limited by the sampling, but this can be reduced by increasing the sample mass by a factor of 4 (predicted by sampling theory). It is concluded that knowing the value of the uncertainty enables the interpretation to be made more reliable, and that sampling is the main factor limiting most investigations. This new approach quantifies this problem for the first time, and allows sampling procedures to be critically evaluated, and modified, to improve the reliability of the geochemical assessment. 相似文献
116.
117.
Chemical methods are generally chosen to monitor soil pollution but magnetic measurements proved to yield additional information at low cost and less time consumption. In this investigation, the novel use of rapid and non-destructive magnetic measurements to characterize Br levels in Xuzhou (China) urban roadside soils was reported. X-ray fluorescence spectrometry (XRF) was used to quantify Br in the soil samples. Data from 21 roadside soil samples confirm Br contamination, with a mean level of 4.36 mg kg−1 and a range of 2.4–8.7 mg kg−1. These values are higher than that of unpolluted soils in Xuzhou that averages 1.1 mg kg−1. Hierarchical clustering analysis shows Br in Xuzhou roadside soils is mainly from road traffic. Clear correlations between Br levels and simple magnetic parameters [mass specific susceptibility (χ
LF), susceptibility of anhysteretic remanent magnetization (χ
ARM), saturation isothermal remanence (SIRM)] are observed. The present study shows that these three magnetic parameters can be used as a proxy for Br levels in Xuzhou urban roadside soils. 相似文献
118.
圆形标志中心子像素定位方法的研究与实现 总被引:18,自引:1,他引:18
黄桂平 《武汉大学学报(信息科学版)》2005,30(5):388-391
采用回光反射材料制作圆形回光反射标志,经摄影后得到标志的“准二值影像”;对标志的椭圆影像进行亚像素边缘提取,经最小二乘椭圆拟合后得到标志中心的子像素级位置。试验表明,可以达到0.02像素的定位精度。 相似文献
119.
120.