Utilization of sample disturbance for dating a marl deposit

Summary Values of the low-amplitude shear modulus, G _o, of a marl underlying the city of Kalamata, Greece, obtained by in situ crosshole and laboratory resonant column techniques are presented in the paper. It was found that the laboratory values were lower than their field counterparts and the difference was considered to be the result of (i) the temporary stress release following sampling and (ii) the mechanical disturbance associated with specimen preparation. By utilizing previous experimental results relating the field versus laboratory difference in the value of G _o to the age of the clay deposit, it became possible to estimate the age of the particular marl which was found to agree with the geologically expected age of the deposit. The approach taken in this study may, upon further improvement, become a useful technique for dating geological materials, especially those possessing cohesion.     

Application of universal kriging for estimation of earthquake ground motion: Statistical significance of results

Universal kriging is compared with ordinary kriging for estimation of earthquake ground motion. Ordinary kriging is based on a stationary random function model; universal kriging is based on a nonstationary random function model representing first-order drift. Accuracy of universal kriging is compared with that for ordinary kriging; cross-validation is used as the basis for comparison. Hypothesis testing on these results shows that accuracy obtained using universal kriging is not significantly different from accuracy obtained using ordinary kriging. Tests based on normal distribution assumptions are applied to errors measured in the cross-validation procedure;t andF tests reveal no evidence to suggest universal and ordinary kriging are different for estimation of earthquake ground motion. Nonparametric hypothesis tests applied to these errors and jackknife statistics yield the same conclusion: universal and ordinary kriging are not significantly different for this application as determined by a cross-validation procedure. These results are based on application to four independent data sets (four different seismic events).     

矿区深厚土层的高压固结与次固结特性

实验表明，深部土层的先期团结压力与土层沉积的历史有关；土的团结系数和渗透系数均随压力的增大而减小，并在高压下趋于稳定；当压力小于先期团结压力时，土的次团结系数与压力关系不大；当压力大于先期固结压力时，次团结系数随压力的增大而增大。     

Stress-path dependent behavior of a weathered clay crust

Triaxial compression and oedometer consolidation tests are commonly performed to evaluate the strength and deformation behavior of soils. However, in the field, the stress paths imposed by various engineering works may deviate from the stress paths conventionally used in laboratory tests. Moreover, the stress-paths followed by different soil elements under a foundation are different. To obtain representative soil parameters, the laboratory stress path should be similar to that followed in the field. In this study, a significant number of stress-path triaxial tests, with stress probes in various directions, have been conducted to study the stress-path dependent behavior of an overconsolidated weathered crust of Champlain clay in Eastern Ontario. Both undrained and drained tests have been conducted for samples isotropically consolidated to the in situ vertical stress and anisotropically consolidated to in situ state of stress. The yield locus of the clay crust has been defined. It has been observed that the strength-deformation and yielding behavior of this weathered clay crust highly depends on the stress-path as well as on the in situ stress history.     

Non-uniform granular pile–mat foundations: analysis and model tests

Granular piles are commonly used to improve bearing capacity and reduce settlements of soft soil in coastal and lowland areas. Due to various reasons, granular piles tend to acquire a non-uniform tapered-down cross-section in actual construction process. In this paper, a simple theoretical approach to predict deformation behaviour of soft ground reinforced with non-uniform granular pile–mat system is presented. A small-scale experimental set-up is fabricated in the laboratory and tests performed. Results predicted by the proposed approach compare well with the laboratory tests, and the field tests and other numerical test results available in literature. A parametric study has been carried out to evaluate the relative influence of granular mat thickness and relative stiffness on various responses of non-uniform granular piles.     

Analysis of the in situ Hydromechanical Behavior of a Fractured Calcareous Rock Mass

Summary. Hydromechanical experiments have been carried out since 1997 within a small fractured calcareous rock mass in southeastern France, at a site called Coaraze. Simultaneous measurements of fluid pressure and joint displacement were performed during these experiments. The interpretation generated has led to characterizing various types of hydromechanical behavior of the jointed rock mass and has provided several lessons. An original analytical interpretation, coupled with a modeling approach, has allowed one to derive the in situ normal joint stiffness, which proves to be highly non-linear. It has been shown that a coefficient able to take into account stiffness contribution from the surrounding rock mass must be included in order to fully interpret the pressure-displacement curves. This analytical interpretation also yields an estimate of the normal stress across the fracture. A comparison between in situ data and laboratory tests is also presented.     

Influence of shape characteristics of talc mineral on the column flotation behavior

Column flotation, which is a very effective process in mineral processing especially for easily floatable minerals, is one of the most important new developments to emerge in mineral processing technology in the last years. In this study, the flotation behavior of talc products having different particle shapes produced by different grinding mills (ball and rod mill) was determined by using column flotation process. Shape characteristics of the particles were investigated by the two dimensional measuring technique based on the particle projections obtained from the SEM microphotographs using a COREL Draw 10.0 program. The results showed that particles possessing higher elongation and flatness properties were recovered better during column flotation, whilst roundness and relative width had a negative effect on the flotation behavior of the talc mineral studied. Consequently, as the shape of the particles produced by the mill deviated from the ideal sphere, their floatability was increased.     

裂隙岩体渗透系数确定方法综述

总结了近年来裂隙岩体渗透系数的确定方法,主要有现场水力试验法、裂隙测量法和离散裂隙网络渗流数值试验法。每种方法都有自己的适用性和测量尺度。裂隙岩体渗透系数存在尺度效应,针对不同尺度的研究对象,应尽量选取与渗流模型网格剖分尺度匹配的测量方法。裂隙的延伸具有方向性,测试点的布设应合理科学,不同测量方法需要结合起来才能得到裂隙岩体真实的渗透系数。     

江苏扬中长江漫滩沉积物重金属垂向分布特征及其背景值确定方法

对扬中长江漫滩柱状沉积物Cd、Pb、Cu、N i、Cr、Zn重金属垂向变化特征分析,表层20 cm以上,重金属含量普遍较高,表明了人类活动对长江重金属输入量呈现日益增加的趋势。通过重金属与Fe元素作线性回归方程,求得重金属的背景含量。相比而言,表层沉积物重金属含量反映了长江滩涂沉积物已经呈现明显的污染趋势。