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511.
Variability of unconfined compressive strength in relation to number of test samples 总被引:1,自引:0,他引:1
Unconfined compressive strength is one of the most commonly used properties in rock engineering. Estimation or selection of an appropriate value of unconfined compressive strength for a given rock can be difficult as it can vary greatly within the same rock unit. Considering this large variability, unconfined compressive strength obtained by testing just a few samples is questionable. The purpose of this study was to investigate the variability of unconfined compressive strength for a given rock and, based on this information, determine the minimum number of samples required for obtaining a reliable value. Unconfined compressive strength values for approximately 50 NX-size (2.125 in./5.4 cm) core samples were determined for five different rock types. Statistical analyses were performed on subsets of cores to determine the minimum number of samples required to render a reliable estimate of the average strength of the entire set of cores. The results indicate that the minimum number of samples needed for strength determination depends on the statistical method used, the chosen confidence interval, and the acceptable deviation from the mean. For a 95% confidence interval and a 20% acceptable strength deviation from the mean, either 9 or 10 samples are needed to test for strength, depending on the statistical analysis used. 相似文献
512.
Rane L. Curl 《Mathematical Geology》1988,20(6):693-698
Isotopic dating is subject to uncertainties arising from counting statistics and experimental errors. These uncertainties are additive when an isotopic age difference is calculated. If large, they can lead to no significant age difference by classical statistics. In many cases, relative ages are known because of stratigraphic order or other clues. Such information can be used to establish a Bayes estimate of age difference which will include prior knowledge of age order. Age measurement errors are assumed to be log-normal and a noninformative but constrained bivariate prior for two true ages in known order is adopted. True-age ratio is distributed as a truncated log-normal variate. Its expected value gives an age-ratio estimate, and its variance provides credible intervals. Bayesian estimates of ages are different and in correct order even if measured ages are identical or reversed in order. For example, age measurements on two samples might both yield 100 ka with coefficients of variation of 0.2. Bayesian estimates are 22.7 ka for age difference with a 75% credible interval of [4.4, 43.7] ka.This paper was presented at Emerging Concepts, MGUS-87 Conference, Redwood City, California, 13–15 April 1987. 相似文献
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研究了我国西部走滑型地震的地表破裂长度L和位移量D与震级M_s和复发时间间隔T之间的定量关系。结果表明:震级M_s和复发间隔T不仅与L值有关,还同时与D值相关;乘积LD值可用来估算震级M_s,比值D/L与复发间隔T密切相关;对于M_s或LD值给定的地震,D/L值大(即L值小或D值大)的地震,有较长的复发间隔;当破裂长度L一定时,有较长复发间隔的地震,M_s或LD值较大;当位移量D相同时,M_s或LD值较大地震的复发间隔较短 相似文献
516.
Wide-angle reflections are now routinely recorded in high resolution explosion seismics to study the crustal structure. Use of Dix's hyperbolic approximation to the nonhyperbolic wide-angle reflection travel times causes major errors in the determination of interval velocities and layer thicknesses of a stack of horizontal velocity layers. Here we propose a layer stripping method to directly calculate the interval velocities and layer thicknesses in a vertically heterogeneous earth from the strong and reliable wide-angle reflected events. Synthetic reflection travel times, at wide-angle range, for a given velocity model, contaminated by some random errors, have been used to demonstrate the reliability of the algorithms to determine the interval velocities and thicknesses of various layers. The method has also been tested on two field examples along two deep seismic sounding (DSS) profiles with well identified wide-angle reflection travel times, which illustrates the practical feasibility of the proposed method. 相似文献
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济阳坳陷及其邻近地区早第三纪海侵问题之我见 总被引:5,自引:0,他引:5
张玉宾 《沉积与特提斯地质》1997,17(1):45-49
本文针对长期争议的早第三纪时期济阳坳陷及其邻近地区是否存在海侵问题,根据沉积特征及古生物资料,以济阳坳陷为例,重点研究了下第三系沙河街组二段至一段的演化特征,提出了新的观点——海啸。指出了遍布于整个渤海湾盆地的沙二段上部冲积相是由强海啸形成,它也是造成沙一段时期发生第三纪以来最大湖淹的主要原因。认为海啸的成因很可能与星体对地球的碰撞有关,属于地质时期的偶然事件 相似文献
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本文利用一些复随机变量的分布和统计推断理论,导出了向量过程的正旋谱、负旋谱、谱差、总谱、外自谱、频域外自相关函数、外自谱的位相函数等估计量的渐近分布以及它们的置信区间,并简略地讨论了所得置信区间的最优性。最后用锚系海流计资料实例说明了所得置信区间公式在海流资料分析中的应用。 相似文献