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Experimental abrasion of river‐bed materials has been widely undertaken, producing ‘downstream’ fining rates that generally are believed to be much less than those observed in the field. A conclusion commonly adopted has been that sorting processes are more effective than abrasion processes. A comparative evaluation of results from an abrasion tank and a tumbling barrel are presented, which show that abrasion patterns and rates differ according to the equipment used, clast size and shape, the clast charge (barrel) and water velocity and bed material (tank). Abrasion is a composite process, and the effects achieved appear to be dominated by percussion in the tank and grinding in the barrel. Breakage, crushing and sandblasting are not modelled effectively, nor are effects achieved on clasts when they form part of the bed. Comparisons are made with other equipment used, the very limited amount of direct field abrasion monitoring, and with the probable suite of processes that may occur under field conditions. Also reviewed are the problems that arise when laboratory weight‐loss abrasion coefficients are used or converted into ones of size diminution, as usually derived from field observations of down‐channel trends. It is concluded that field abrasion rates generally have been underestimated, as the processes involved are at best only selectively represented by the experimental equipment so far used, and because the results obtained experimentally are capable of misinterpretation when related to field trends. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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重庆巫山二郎庙移民小区滑坡勘察为三峡库区移民项目,地层复杂,采用传统方法进行勘察达不到滑坡勘察的目的。采用金刚石单动双管钻具+SM胶泥浆技术,取得了较好的效果,钻探台月效率由150 m提高到350 m,岩心采取率达85%~90%,而且取出了泥夹块石、滑面、软弱夹层、破碎带样品。 相似文献
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通过HZ308多功能取心钻具有蚀变岩型和石英脉型金矿地层的应用,提出了防止底喷分流式钻头堵心、减少其损耗的措施。 相似文献
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青藏铁路基础桩孔施工用旋挖钻具的研究 总被引:3,自引:0,他引:3
根据青藏铁路采用旋挖钻进施工的特点,研制出适应青藏铁路各种地层条件的旋挖钻具,并制定出一套科学的旋挖钻进工艺,从而解决了青藏铁路桥桩基础施工这一世界难题,也为实现旋挖设备和钻具国产化打下良好基础。 相似文献
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利用水井钻机钻探,开展岩盐深孔取心,采用合理钻孔结构和优化钻具组合,并配以适宜的饱和盐水钻井液和取心钻探工艺,成功地实施了连续岩盐取心,收到了良好的效果。结合濮阳岩盐普查项目,介绍了深部岩盐取心钻探技术。 相似文献
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新时期,地质分析理论在国土空间规划领域的应用日益广泛。为进一步优化关中盆地国土空间格局,从抓住关键因素、科学定量评价、阈值标准有据、结果可信适用的思路出发,该研究提出了基于木桶理论、风险理论和边际理论的资源环境承载能力和国土空间开发适宜性评价(简称“双评价”)理论框架与技术方法,并应用于关中盆地的双评价实践工作中。基于木桶理论,识别关中盆地活动断裂、地质灾害、富硒土地、引汉济渭水资源等4项关键因素;基于边际理论,开展资源承载能力评价;基于风险理论,开展地质环境承载能力、国土空间适宜性和地质安全评价;在单因素评价的基础上开展综合评价;将综合评价结果与区域国土空间开发现状或规划结果做叠加分析,调整和优化区域发展“三区三线”。研究结果表明基于木桶-风理-边际理论的双评价方法可行,评价结果可信:关中盆地87%的土地属于适宜农业生产和城镇化建设;尤其是引汉济渭工程使关中盆地成为承接东部人口和GDP发展的最佳地区;国土空间开发保护中要珍惜集中连片分布的富硒土地,作为永久农田予以保护;禁止在活动断裂分布范围和地质灾害高危险区进行工程建设,以国土空间规划和用途管制为抓手,从源头防控地震与地质灾害风险。 相似文献