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171.
介绍了黄金珠宝首饰的一些基本观念和近年来黄金珠宝市场的发展状况,指出1994年纯金饰品消费将会稳定增长,而且仍占主流,珠宝首饰市场会出现消费量增长,竞争日渐激烈,并由大中城市向中小城市扩展的趋势。就四川宝玉石普查找矿和开发利用提出了见解。 相似文献
172.
173.
针对吹填淤泥的超软土工程性质,提出了ASE桩的概念,即沉管投入复合材料再原位扩径搅拌的施工技术。以固化细料+骨架粗料为超软土提供基本强度及骨架支撑的原理,参考搅拌桩与CFG桩的施工工艺,制作专用双塔型施工设备,尝试形成一种新的施工工艺。进行了现场初步试验,固化细料与骨架粗料的配合比较理想时,可形成较为理想的桩体。成桩质量主要受固化细料影响,骨架粗料的效果发挥需要依赖一定配合比基础的固化细料。先沉管投料再扩径搅拌的工艺是可行的,环刀型叶片能够实现扩径的效果,且双向扩径搅拌的效果要好于单向扩径搅拌的效果。ASE桩的设计计算方法及理论还需做进一步研究,可参考CFG桩与搅拌桩的相关理论开展工作,为地基处理技术的发展提供了新的思路。 相似文献
174.
B. J. Smith J. A. Baptista-Neto M. A. M. Silva J. J. McAlister P. A. Warke J. M. Curran 《Environmental Geology》2004,46(3-4):493-503
The 500th anniversary of European arrival in Brazil was celebrated in 2000 and highlighted the need to review the condition of the countrys remaining colonial built heritage. This revision is particularly apposite in the adjacent cities of Rio de Janeiro and Niterói, where the heritage that survived twentieth century reconstruction has done so largely because of ownership by the church or military. However, whilst this may have protected buildings from demolition, detailed fabric can be neglected or abused. This paper investigates this possibility through an examination of two forts, built primarily of local augen gneiss, that guard the entrance to Guanabara Bay. Natural outcrops exposed to the same humid sub-tropical maritime environment show that this rock is susceptible to slow disaggregation through salt weathering. Surveys suggest that stonework in the forts that is sheltered from rainwash is heavily loaded with salt and has passed a threshold, wherein stresses accumulated over centuries of apparent stability, combined with the effects of a more recent increase in atmospheric pollution and apparently inappropriate intervention (re-pointing), have triggered rapid breakdown that requires immediate intervention. 相似文献
175.
176.
A shallow coring and geophysical logging program has recorded the sedimentary fill of the Brazos River valley in the Texas Gulf Coastal Plain. Thermoluminescence dates together with new and recalibrated published radiocarbon dates show the valley fill to include extensive, sandy, buried falling stage and lowstand Oxygen Isotope Stage (OIS) 3 and 2 deposits. These alluvial deposits are punctuated by numerous paleosoil horizons that record alternating periods of cutting, bypass and accumulation. Maximum valley incision and two periods of terrace formation preceded marine lowstand conditions, suggesting significant discordance between preserved fluvial and classical marine system tracts. The latest Pleistocene incision and fill history appears related to cycles of increased discharge and incision, followed by system equilibration and terrace formation. Analysis of the Brazos River incised valley and its contained paleochannels indicates that latest Pleistocene mean annual discharge was as much as four times greater than that of today. This magnitude of discharge in the Brazos would require a two-fold increase in precipitation across the drainage basin. Such an increase is comparable to the present day measured positive El Niño winter precipitation anomaly across the region. Paleochannel geometries and the stratigraphic and sedimentologic data from this investigation support the hypothesis that periods of high-amplitude, El Niño-like climatic perturbations characterized the late Quaternary climate of the south-central and southwestern U.S. This period of high discharge coincides, at least in part, with late OIS 3 progradation of the Brazos delta to the shelf margin, OIS 3 and 2 valley incision across the Texas shelf, and concomitant sand bypass to intraslope basins beyond the shelf edge. 相似文献
177.
The survival of several ancient monuments made of ignimbrites in Hınıs town (Erzurum-Anatolia), which has suffered from intense annual temperature fluctuations and strong seismic activity, can mainly be attributed to use of suitable building stones. This paper examines the usability as building stones of Middle Miocene Hınıs ignimbrites that widely outcrop in and around Hınıs town. The petrographical, geochemical, mechanical, and physical properties determined lead to categorization of the ignimbrites as four different types. The Hınıs ignimbrites contain dasite–trachy–andesite and rhyolite. Rhyolite is the strongest material whereas the other types, being more porous, are weaker, lighter, and have good heat-insulation properties. Being light (easily transportable, machinable, and workable), good heat insulators, environmentally friendly (because of natural ventilation), sufficiently elastic to sustain seismic loading in the area under study, and more cost-effective than artificial stones, Hınıs ignimbrites are certainly a preferable option for use as light building stone. These ignimbrites are not suitable for use as floor covering, however, (because of rapid abrasion) or for building structural columns (because of low strength). 相似文献
178.
Hydraulic fills used in Australian mines have similar grain size distributions whilst having quite different specific gravity
values, typically in the range of 2.7–4.4. When produced and distributed in slurry at 65–75% by solid content, they settle
to produce fills with similar geotechnical characteristics. The fills under investigation have been found to settle, in the
laboratory, to a dry density of about 0.56 × specific gravity, a saturation water content of about 17–34%, and a porosity
of 37–49%. A quick estimate of the optimum water content that gives the minimum porosity may be obtained by locating the intersection
of the saturation curve and minimum porosity line, which may simply be done on a water content vs. porosity plot. However,
transportability of the slurry requires it to be mixed at water content substantially greater than the optimum water content.
As the tailings settle out of suspension, they settle to relative density of 50–80%. This paper shows that the current empirical
relationships relating relative density and N-value to friction angle for sands will significantly underestimate the friction angle of the hydraulic fills. Based on limited
experimental data, a unique relationship between relative density and friction angle is proposed for hydraulic fills placed
in some Australian mines. 相似文献
179.
二维地震勘探变观量板图及其应用 总被引:1,自引:0,他引:1
WANG Li-bin ZHANG Hai-ying REN Ri-chun LIU Hai-tao GAO Yuan Geophysical Prospecting Company of Coal Geology in Jilin Province Changchun China 《吉林大学学报(地球科学版)》2006,(Z2)
在以炸药为震源的二维地震勘探野外资料采集施工中,需要避开各种不能钻井放炮的障碍物,根据勘查区设计任务书的施工参数,可以画出变观量板图。变观量板图具有快速变观的作用,野外所遇到的不同距离的障碍物可以通过变观避开,给施工提供方便,变观量板图具有实际应用价值。 相似文献
180.
组合结构支挡体系在杂填土层深基坑支护中的应用 总被引:1,自引:0,他引:1
在古城区建筑地基上部,广泛赋存以炉灰渣为主要成分的杂填土,其厚度不一。随着城市化进程的迅猛发展,旧城改造对高层建筑地下空间的充分利用提出了更高要求,特别是在周围恶劣环境条件下开挖空间,从理论、实践上深入研究闹市区杂填土深基坑,采用何种经济技术合理的支护方案问题十分突出。但各种深基坑支护方法都有其局限性,岩土工程师在确定方案时必须充分考虑当地工程地质条件、建筑物基坑特点,选择组合支护技术方法,方可达到事半功倍之目的。通过成功支护某杂填土深基坑工程实例,详尽阐述了杂填土的工程特性、锚拉钢板桩挡墙、土钉挡墙的基本参数选取、设计计算,可为类似岩土工程条件下的基坑支护方案选型和设计提供借鉴及参考。 相似文献