共查询到20条相似文献，搜索用时 906 毫秒
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根据室内模拟试验数据研究了单一流径基岩裂隙水流的平均流速，建立了单一流径无压裂隙水和承压裂隙水的平均流速与不力坡度之间的回归方程。 相似文献
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通过对醋酸钾/高岭石插层复合物的机械磨剥制备了不同径厚比的高岭石样品,并利用X射线粉晶衍射(XRD)、激光粒度仪、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和傅里叶变换红外光谱(FTIR)表征了4个样品的粒径、结构以及形貌。实验结果表明:随着插层磨剥次数的增加,高岭石的结晶度指数(HI)由原矿的1.29降至0.69,结晶度降低,晶体结构在一定程度上遭到破坏。同时,4个样品的粒径及厚度逐渐减少,径厚比依次增大至11.7。此外,经过3次插层磨剥洗涤后,部分剥离的片层发生卷曲,但很少完全卷曲成纳米卷。 相似文献
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为了测量大直径基桩钻孔的井径，我们研制了直径2000mm测径器。经使用，该仪器完全可以作为大直径基桩钻孔直径测量的仪器，具有结构简单、测量准确可靠、操作简便、容易维修、造价低廉等优点。直径2000mm测径器由测径器主体、测绳、电动绞车及井口架组成。测径器主体的材质为不锈钢。测径器测量部分系一铰链结构，四根测杆均布，结构 相似文献
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针对孕镶金刚石钻头在坚硬岩石中的低钻速、高能耗问题,提出以体积破碎的碎岩方式来提高钻进效率的方法。为了进一步探究孕镶金刚石钻头的体积破碎形式,首先设计了单颗金刚石压入岩石全过程的室内实验。通过分析试验数据发现,金刚石压入岩石发生首次局部体积破碎即为金刚石钻头的体积破碎类型。然后,建立了金刚石压入岩石发生首次体积破碎时钻头的钻压和钻速计算模型,并通过对比理论值和实际值,进一步验证了单颗金刚石压入岩石试验结果以及计算模型的正确性。最后,通过分析计算结果,提出了在小粒径金刚石钻头中添加大颗粒金刚石来实现部分体积破碎的方法,并推导出钻头中应添加大颗粒金刚石的制品浓度,确定了大小粒径金刚石的添加量,并对大颗粒金刚石在钻头中的分布情况以及碎岩方式进行了探讨,可为实际中钻头参数设计提供参考依据。 相似文献
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Sigismond Ayodele Wilson 《GeoJournal》2013,78(6):997-1012
This paper uses the resource curse hypothesis to explore diamond exploitation in Sierra Leone during the period 1930–2010. Focusing on national and local level analysis, it examines whether the net impact of diamond exploitation was a ‘resource curse’ or ‘blessing’ during four time periods: colonial and early post-independence era, the APC era, the civil war period, and post-war era. The paper argues that the net impact of diamond exploitation in Sierra Leone has not been constant; rather it has changed between resource blessing and curse over different major periods of Sierra Leone’s history and at local and national scales since inception of diamond exploitation. This paper illustrates that during the period 1968–1992 patrimonial politics undermined official diamond exploitation and significantly contributed to a pendulum shift in the net effects of diamond exploitation from resource blessing to curse. The study shows that the net effect of diamond exploitation was: a resource blessing (especially at the national level) prior to 1968; more of a resource curse during the APC era; a full blown manifestation of the curse during the civil war period; and that governance of the diamond sector has improved sufficiently in post-civil war Sierra Leone to start the gradual transformation of diamonds to resource blessing, at national and local levels. 相似文献
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The development of subgrain misorientations with strain in dry synthetic NaCl measured using EBSD 总被引：1，自引：0，他引：1
The development of subgrain boundary misorientations with strain in dry, synthetic NaCl polycrystals, deformed at elevated temperature, has been investigated using electron backscattered diffraction (EBSD). At low natural strains, up to 0.5, average misorientations of subgrain boundaries increase with strain and a power law relationship exists between strain and average misorientations. The average misorientations are strongly influenced by grain orientation, suggesting that the misorientation–strain relationship may also be texture dependent in materials with high plastic anisotropy, like NaCl. A slight grain size dependency of the average misorientations was observed. The results indicate that with suitable calibration, average subgrain boundary misorientations may offer a method for estimating the strain accommodated by dislocation creep in NaCl and thus perhaps in other geological materials, although current theories for polycrystalline plasticity imply that misorientations may also depend on stress in some situations. 相似文献
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切磨过程中花岗石材料去除机理研究 总被引：1，自引：0，他引：1
深入理解切磨过程中花岗石材料的去除机理是优化加工设备，加工工具以及加工参数的基础。本文研究了花岗石的断口表面、锯切表面、粗磨表面以及精磨表面形貌特征，并结合切磨过程中临界载荷、单颗金刚石磨粒所承受的切削力以及比能特征，对加工表面形成机理进行了分析。研究表明，材料的去除机理与单颗磨粒的最大切削厚度直接相关。随着单颗金刚石磨粒最大切削厚度的减小、花岗石的去除方式也逐渐由脆性断裂为主转为塑性流变为主。由于不同的材料去除机制对应不同的能量消耗，可以通过调节单颗磨粒的最大切削厚度控制材料的去除方式，进而控制能量消耗。因此，均匀的磨粒出露高度对于控制切磨过程中材料的去除机理和优化加工过程具有重要意义。 相似文献
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Grain size characteristics and genesis of the Muxing loess in the Muling-Xingkai Plain,Northeast China 
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下载免费PDF全文 Cheng Zhong-shuang Su Chen Zheng Zhao-xian Li Zhuang Wang Li-kang Wang En-bao 《地下水科学与工程》2021,9(2):152-160
Thick loess is deposited on the platform in the piedmont zone of Muling-Xingkai Plain(Muxing Plain), but the genesis of the Muxing loess is still unclear. The aims of this study are to analyze the grain size characteristics of Muxing loess collected from the cores of a typical borehole(ZK1) in the piedmont zone of Muxing Plain, and to verify its genesis. The Muxing loess is mainly composed of the particles with diameter less than 50 μm, with an average content of 92.48%. The coarse silt particles with diameter of 10-50 μm are the basic composition of aeolian sediments, and their average content is 44.34% for the Muxing loess, which is the mode class among the particles with different diameters. The grain size parameters and frequency curves are similar to those of the typical aeolian sediments. The distribution characteristic of the Muxing loess in the C-M scatter diagram is consistent with that of the Xi Feng loess. In addition, the discriminant analysis shows the Muxing loess mostly consists of aeolian sediments. Therefore, it can be concluded that the Muxing loess mainly resulted from aeolian deposition based on the grain size characteristics. Muxing Plain is dominated by the monsoon climate, and the wind-blown dusts are gradually deposited after being transported over long distances. 相似文献
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Grain size and grain shape analysis of fault rocks 总被引：4，自引：0，他引：4
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The sizes of recrystallised grains in exhumed ductile shear zones are often used to infer conditions of deformation (i.e. stress, strain rate and temperature). Here we present a simple numerical method of calculating the dynamic evolution of grain size during ductile deformation. Our phenomenological method is based on the fact that the dynamic competition between grain growth and recrystallisation will drive grains towards a steady-state size. At each time increment, grain growth and reduction contributions are calculated, with magnitudes which depend on the difference between the current grain size and a desired steady-state grain size. In our models we use a recrystallised grain size piezometer to calculate the steady-state grain size for a given stress. Our numerical routine is incorporated into the SULEC finite element package, allowing us to explore spatial and temporal changes in grain size.As a test, we compare model results to measured grain sizes in quartz layers thinned and recrystallised around rigid garnet porphyroclasts under simple shear dominated deformation in the Alpine Fault Zone of New Zealand. Numerical models are able to replicate observed grain size variations, with boundary conditions consistent with those constrained for the central Alpine Fault Zone. 相似文献
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It is now admitted that the high strength of the subcontinental uppermost mantle controls the first order strength of the lithosphere. An incipient narrow continental rift therefore requires an important weakening in the subcontinental mantle to promote lithosphere-scale strain localisation and subsequent continental break-up. Based on the classical rheological layering of the continental lithosphere, the origin of a lithospheric mantle shear/fault zone has been attributed to the existence of a brittle uppermost mantle. However, the lack of mantle earthquakes and the absence of field occurrences in the mantle fault zone led to the idea of a ductile-related weakening mechanism, instead of brittle-related, for the incipient mantle strain localisation. In order to provide evidence for this mechanism, we investigated the microstructures and lattice preferred orientations of mantle rocks in a kilometre-scale ductile strain gradient in the Ronda Peridotites (Betics cordillera, Spain). Two main features were shown: 1) grain size reduction by dynamic recrystallisation is found to be the only relevant weakening mechanism responsible for strain localisation and 2), with increasing strain, grain size reduction is coeval with both the scattering of orthopyroxene neoblasts and the decrease of the olivine fabric strength (LPO). These features allow us to propose that grain boundary sliding (GBS) partly accommodates dynamic recrystallisation and subsequent grain size reduction.A new GBS-related experimental deformation mechanism, called dry-GBS creep, has been shown to accommodate grain size reduction during dynamic recrystallisation and to induce significant weakening at low temperatures (T < 800 °C). The present microstructural study demonstrates the occurrence of the grain size sensitive dry-GBS creep in natural continental peridotites and allows us to propose a new rheological model for the subcontinental mantle. During dynamic recrystallisation, the accommodation of grain size reduction by three competing deformation mechanisms, i.e., dislocation, diffusion and dry-GBS creeps, involves a grain size reduction controlled by the sole dislocation creep at high temperatures (> 800 °C), whereas dislocation creep and dry-GBS creep, are the accommodating mechanisms at low temperatures (< 800 °C). Consequently, weakening is very limited if the grain size reduction occurs at temperatures higher than 800 °C, whereas a large weakening is expected in lower temperatures. This large weakening related to GBS creep would occur at depths lower than 60 km and therefore provides an explanation for ductile strain localisation in the uppermost continental mantle, thus providing an alternative to the brittle mantle. 相似文献