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1.
2.
Changing grading of soil: effect on critical states 总被引:6,自引:3,他引:3
Examples of situations are presented where the grading of a soil changes during its lifetime either by crushing of particles
leading to an increase of fine material or by slow transport of fine particles with seepage leading to a decrease of fine
material. Such grading changes influence the basic constitutive properties of the soil, in particular properties such as critical
states which are dependent on the available range of densities of packing. Discrete element modelling is used to show the
dependence of critical state conditions on grading and the way in which the particle assembly seeks out new critical state
conditions as the grading changes. 相似文献
3.
S. Mazzoli 《International Journal of Earth Sciences》1995,84(4):781-793
Analysis of strain in Jurassic argillites forming part of the folded and thrusted sedimentary succession of the Lagonegro basin (southern Italian Apennines) has been carried out using ellipsoid-shaped reduction spots as strain markers. Most of the determined finite strain ellipsoids are of oblate type and show a peculiar distribution of the maximum extension direction (X), with maxima either subparallel or subperpendicular to the local fold axes. Using the strain matrix method, two different deformation histories have been considered to assist the interpretation of the observed finite strain pattern. A first deformation history involved vertical compaction followed by horizontal shortening (occurring by a combination of true tectonic strain and volume loss), whereby all strain is coaxial and there is no change in the intermediate axis of the strain ellipsoid. By this type of deformation sequence, which produces a deformation path where total strain moves from the oblate to the prolate strain field and back to the oblate field, prolate strain ellipsoids can be generated and may be recorded where tectonic deformation has not been large enough to reverse pretectonic compaction. This type of deformation history may be of local importance within the study area (i.e. it may characterize some fold hinge regions) and, more generally, is probably of limited occurrence in deformed pelitic rocks. A second deformation sequence considered the superposition of pre-tectonic compaction and tectonic strain consisting of initial layer-parallel shortening followed by layer-parallel shear (related to flexural folding). Also in this instance, volume change during tectonic deformation and tectonic plane strain have been assumed. For geologically reasonable amounts of volume loss due to compaction and of initial layer-parallel shortening, this type of deformation history is capable of producing a deformation path entirely lying within the oblate strain field, but still characterized by a changeover, during deformation, of the maximum extension axis (X) from a position parallel to the fold axis to one perpendicular to it. This type of deformation sequence may explain the main strain features observed in the study area, where most of the measured finite strain ellipsoids, determined from the limb regions of flexural folds, display an oblate shape, irrespective of the orientation of their maximum extension direction (X) with respect to the local structural trends. More generally, this type of deformation history provides a mechanism to account for the predominance of oblate strains in deformed pelitic rocks. 相似文献
4.
我国煤炭资源开发利用中某些问题的探讨 总被引:3,自引:0,他引:3
针对我国煤炭资源开发利用中存在的诸如煤炭资源的低效率应用、无序开采、生态环境恶化等问题,指出了我国煤炭资源管理法规中存在的问题,提出了加强煤炭资源开发管理、构建煤炭循环经济体系、加大安全投入、加强煤炭矿区环境的治理和保护、健全有偿使用资源法规制度等对策。 相似文献
5.
河北省含煤面积广,煤类齐全,从晚古生代到新生代共有6个聚煤期,是我国主要产煤省之一,根据河北省煤炭资源特征、开发利用情况,指出目前河北省煤炭工业发展中存在的诸如探采比例失调、新建井基地严重不足、后备资源不足等的问题,以及加强煤炭资源管理的建议。 相似文献
6.
金刚石中分子氢的赋存状态研究 总被引:1,自引:0,他引:1
金刚石中分子氢的定向红外光谱研究表明在垂直于(100),(110)和(111)三个方向上所测得分子氢的浓度是不相同的,且不同样品中的变化趋势也不同,即分子氢在金刚石中的定向性不明显;MNDO法计算结果显示分子氢在金刚石中的稳定程度大小关系依次为沿〈111〉定向的键心与反键心组合(a.b+b.c)〉六角体空隙(H)〉四面体空隙(T1)〉菱形中心(C1=C2)〉四面体空隙(T2). 相似文献
7.
Results of a detailed statistical study of constant relative strength inelastic displacement ratios to estimate maximum lateral inelastic displacement demands on existing structures from maximum lateral elastic displacement demands are presented. These ratios were computed for single‐degree‐of‐freedom systems with different levels of lateral strength normalized to the strength required to remain elastic when subjected to a relatively large ensemble of recorded earthquake ground motions. Three groups of soil conditions with shear wave velocities higher than 180m/s are considered. The influence of period of vibration, level of lateral yielding strength, site conditions, earthquake magnitude, distance to the source, and strain‐hardening ratio are evaluated and discussed. Mean inelastic displacement ratios and those associated with various percentiles are presented. A special emphasis is given to the dispersion of these ratios. It is concluded that distance to the source has a negligible influence on constant relative strength inelastic displacement ratios. However, for periods smaller than 1s earthquake magnitude and soil conditions have a moderate influence on these ratios. Strain hardening decreases maximum inelastic displacement at a fairly constant rate depending on the level of relative strength for periods of vibration longer than about 1.0s while it decreases maximum inelastic displacement non‐linearly as the period of vibration shortens and as the relative‐strength ratio increases for periods of vibration shorter than 1.0s. Finally, results from non‐linear regression analyses are presented that provide a simplified expression to be used to approximate mean inelastic displacement ratios during the evaluation of existing structures built on firm sites. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
8.
Cyclic tests on two large‐scale models of existing bridge piers with rectangular hollow cross‐section were performed in the ELSA laboratory. The prototype structure is an existing reinforced concrete highway bridge constructed in Austria in 1975. The piers presented several seismic deficiencies and consequently they showed poor hysteretic behaviour and limited deformation capacity as well as undesirable failure modes that do not comply with the requirements of modern codes for seismic‐resistant structures. Experimental data are compared to numerical and empirical predictions. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
9.
湖南黄金洞金矿毒砂中Au赋存状态的电子探针研究 总被引:1,自引:0,他引:1
本文利用JXA-8800M超大型电子探针,以湖南黄金洞金矿含金毒砂为研究对象。利用金特征X-射线扫描方法和微区含金含量,对不可见金赋存状态的研究方法和温试条件进行了探索,先观察背散射电子图像,排除金在含金矿物毒砂中呈显显微颗粒存在的可能性,继而用LiF晶体测定金L=88.76Lal峰位,然后逐渐放大倍数(x300,x1000,x5000,x30000,x200000)进行金特征,X-射线连续测量,,结果发现金元素总
是均匀分布在重砂中,从而证实了金呈品格金形式存在的推测。 相似文献
10.
The hydrocarbon generation mechanism and the three-stage type model of hydrocarbon generation for carbonate source rocks 总被引:1,自引:0,他引:1
The diagenetic mechanism and process of carbonate rocks, which is different to that of clastic rocks, decides the existence
of different existing state organic matters in carbonate rocks. This has been verified by both the microscopic observation
of organic petrology and the analysis of organic geochemistry of many samples. Based on the hydrous pyrolysis simulation experiment
of the low-mature carbonate rocks, the contrasting study on the yield and their geochemistry characteristics of different
existing state soluble organic matters of a series of various maturity samples shows that the different existing state organic
matters make different contributions to hydrocarbon generation during every evolution state. So that, the hydrocarbon generation
process of carbonate rocks can be summarized as the following three stages: the first is the direct degradation of biogenic
bitumen macromolecules during the immature stage, the second is the thermal degradation of a large amount of kerogen at the
mature stage, the last stage is the expulsion or release of inclusion organic matter owing to the increased thermal expansion
pressure during the high evolution stage.
Part of achievements of the Eighth Five-Year National Science-Technology Key-Task Project “85-102-02-07”. 相似文献