地震序列较强余震灰色及最小二乘拟合预测方法的应用研究

在收集、整理1966年～2002年8月我国(主要为大陆地区)183个5级以上地震序列资料的基础上，应用灰色预测和最小二乘拟合预测方法，对每一地震序列较强(显著)余震发震时间进行“硬性”检验预测。结果表明，2种预测方法对7级以上地震序列和6级地震序列的较强(显著)余震具有较好的预测效能，预测效能分别为76．2％和64．7％；而对5级地震序列预测效果则不甚明显。因此，灰色预测和最小二乘拟合预测方法主要着眼于对大(强)地震的较强(显著)余震预测，可望在地震现场大(强)震应急工作中发挥积极作用。     

BSZ-2型数字钟的检修方法

BSZ-2型数字钟目前仍应用于模拟地震观测中。本文介绍了该钟的工作原理，并对检修过程中常见问题进行了分析总结。     

砂土的抗剪强度与干密度的曲线拟合

利用曲线拟合的最小二乘法原理，确定砂土在某垂直压力下的抗剪强度与干密度的关系，并绘制曲线图，可避免人工处理数据的随意性，减小了误差。     

望儿山金矿生产勘探超前期限与范围合理性的选择和应用

望儿山金矿浅部生产已接近尾声,其生产正向深部转移,但望儿山金矿深部地质条件十分复杂,为使其生产能更好的延续下去,通过对生产勘探的超前期限与范围合理性的研究和探讨,在总结前人经验的基础上,根据望儿山金矿实际,采用价值法的分析,得出其现有生产勘探合理的超前期限与范围.     

江苏水文站网优化调整有关问题的思考

在概述全省站网现状基础上，分析了站网优化调整的主要原因，提出了如何优化调整的总体思路和基本构想，进一步明确强调在水文站网优化调整中需要坚持和把握的原则和方法。     

Centrifuge Modeling of Rock Slopes Susceptible to Block Toppling

Summary This paper presents the results of centrifuge tests that were aimed at validating the Goodman-Bray method for rock slope toppling analysis. The Goodman-Bray method was extended by the authors to accommodate non-persistent basal planes of rock columns. Two gypsum column models, with and without anchors were used to represent the failure modes. Measured critical centrifuge accelerations were in agreement with the results obtained from numerical modeling. A background of the toppling slope failures associated with a large hydropower project in China instigated the need for the centrifuge study. The centrifuge model tests used an artificial rock. The observed failure mode did not follow a straight failure plane as proposed by Goodman and Bray. The failures revealed a bi-planar slip surface with a deep-seated portion near the toe of the slope. The outcomes of the centrifuge tests illustrated the need to search for the critical failure surface when performing a toppling analysis. The search technique is similar to that usually performed in a conventional sliding analysis.     

遥测降雨抗差分析方法应用研究

遥测系统观测的雨量资料常会包含粗差，根据降雨量的特征，结合抗差理论，包为民等曾提出三步抗差修正方法。将此法应用到龙颈上水库等10个水库流域的实测资料当中，验证其有效性，并分析比较各步抗差修正的效果及降雨特征与抗差效果之间的关系。结果表明，抗差修正方法可行，且第一步和第三步结合的修正效果最好；降雨中心较明确，多年降雨特征相似，强度变幅稳定的洪水，不容易出现误抗。     

A Parametric Approach for Dealing with Compositional Rounded Zeros

In this work, a parametric approach for replacing data below the detection limit, also known as rounded zeros, in compositional data sets is proposed. Compositional rounded zeros correspond to small proportions of some whole that cannot be reliably detected by the analytical instruments under given operating conditions. This kind of zeros appear frequently in the data collection process in geosciences. They must be treated in an adequate way before some multivariate analysis can be applied. Our procedure results from a modification of the Expectation-Maximization (EM) algorithm and is based on the additive log-ratio transformation. Its coherence with the nature of compositional data and with basic operations in the simplex sample space is checked. Using real data sets, we find that this approach improves other parametric and non-parametric techniques for compositional rounded zeros.     

Influence of initial density of cohesionless soil on evolution of passive earth pressure

This paper focuses on the influence of the initial void ratio on the evolution of the passive earth pressure and the formation of shear zones in a dry sand body behind a retaining wall. For the numerical simulation a rigid and very rough retaining wall undergoing a horizontal translation against the backfill is considered. The essential mechanical properties of cohesionless granular soil are described with a micro-polar hypoplastic model which takes into account stresses and couple stresses, pressure dependent limit void ratios and the mean grain size as a characteristic length. Numerical investigations are carried out with an initially medium dense and initially loose sand using a homogeneous and random distribution of the initial void ratio. The geometry of calculated shear zones is discussed and compared with a corresponding laboratory model test.     

坝基集中渗漏通道的温度场反分析与试验研究

渗漏是严重影响堤坝安全的主要形式,确定渗漏通道的位置是进行堤坝渗漏整治的前提和基础。温度场探测堤坝渗漏的研究是其中一种较便捷的方法,但是在理论上还需要进一步完善。在库水和地下水存在着温度差异的基础上,考虑堤坝发生集中渗漏后,渗漏通道中的地下水与周围土体进行热量交换,造成渗流通道附近地层温度发生改变,建立起温度场对渗漏通道的反演模型。在前人研究的基础上,考虑地温梯度的影响,可以建立有集中渗漏通道影响下的二维热传导方程,进而以现场测井的温度数据作为边界条件,对泛定方程进行求解,最终得到渗漏通道的位置。计算结果和实测结果的对比表明,通过温度场反推渗漏通道参数的方法是可行的。