共查询到20条相似文献，搜索用时 31 毫秒
1.
Göran Granath 《Mathematical Geology》1984,16(3):283-301
To evaluate the provenance of glacial till, the trace element content of magnetite was used. Magnetite was present in all known rock types and all till samples in the area investigated. By using fuzzy-set theory it was possible to group samples of magnetite taken from bedrock into relatively homogeneous and geologically meaningful groups and also, by fuzzy classification, to relate the till samples to the rocks in such a way that the relative contribution of each rock type to the till is estimated. Each rock and till sample is assigned a membership value between 0 and 1 for each rock type. The membership values, for a certain rock type in the till, are then interpolated by kriging onto maps. Magnetites from skarns associated with sulfide ores especially are rather distinct, and so a map of such membership values for till unveils all known ore deposits some 1–5 km downstreamin the general direction of the ice flow. Other anomalies show up which cannot be related to hitherto known ores or mineralizations. 相似文献
2.
A new maturity parameter determined on both oil and bitumen samples, the asphaltene Tmax, is proposed and discussed. This parameter could be very useful to address the maturity of the source rock. The asphaltene Tmax is measured by programmed Rock-Eval pyrolysis, using a modified temperature program. Some phases of the experimental procedure, such as the asphaltene preparation and the Rock-Eval measurement substratum choice, are crucial in order to achieve reliable data. Laboratory simulations were carried out in order to assess the possible effects of both primary and secondary migration on asphaltene Tmaxin the expelled oil: the original value of the asphaltene Tmax in the bitumen is not substantially modified and it is very close to that measured on kerogen. Examples of the determination of asphaltene Tmax on many samples, collected from different areas and with different organic matter composition, are given. Results show that Tmax values from oil asphaltenes are reasonable indicators of source rock maturity. 相似文献
3.
为了看清断层力学的理论全貌,文章研究了断层力学的发展脉络、应有体系、框架性缺失,总结了学术各界关注点及研究内容差异。结果表明断层力学关联领域存在尺度差异和目标差异,断层力学是多学科纽带,却是"三不管"地带。岩石裂纹和含内部构造的断层之间存在尺度差异和变形速度差异。断层力学的百年发展经历了从外力研究断层-构造应力场-滑移线场研究断层三个阶段,这三个阶段总的发展方向就是逐渐简化、实用化,阻碍了定量理论的发展。"Mohr范式"是支撑,带有实用化、简单化特点,也阻碍了断层力学向机理化和定量化方向发展。断层研究存在正演和反演两类方法,正演主要包括实验断层力学和理论断层力学两类途径,正演和反演结合是未来发展方向。"地质力学"秉承"力学统一律",体现断层空间联系和力学联系,属于"广义断层力学"范畴。"广义断层力学"体系适用"统一发展,关注联系"发展途径,"狭义断层力学"体系适用"分散发展,各自攻克"发展途径。先存断层或薄弱带控制后生断层,并影响应力展布,"应力制约论"是重要方向。未来将产生"流变摩擦学"和"断层岩组构摩擦学"两个方向,"断层岩组构摩擦学"应整合显微构造学成就,研究岩石组构稳定特征、流变特征、广义摩擦特征等,需要将显微构造学唯象理论上升到大尺度断层力学理论中,将岩石组构引入到岩石力学实验中。不同尺度关注点不同、理论不同、取用参数不同,加剧了研究群体的隔离。断层内泥粒是可以迁移的,由此产生"断层泥粒迁移学"。断层闭锁的概念需要重新考虑,未来研究应立足"慢应变"和"大尺度"的断层摩擦延展力学。 相似文献
4.
We performed GPR tomography and GPR reflection field experiments using a 500-MHz antenna to image relative soil moisture distribution around a poplar tree at the botanic garden of Kiel University, Kiel, Germany. The GPR tomography field experiment is carried out in two consecutive phases in order to obtain ray paths traveling from all directions and intensively covering the target. The radar tomographic data are inverted using the authors’ developed software code SeismoRad based on the finite difference technique. The attained Root-Mean-Square (RMS) errors after 200 iterations between the measured and calculated times range between 1.066 and 5.7 % in the two tomography experiments. The estimated GPR velocities range between 5.3 and 15.1 cm/ns. Two low-GPR velocity zones could be delineated coinciding with the locations of the tree root zone and a previously excavated sector. The high water saturation zone around the tree root system is found to be the main reason for such a decrease in GPR velocity. Interpretation of the two phases proved that the coverage of ray paths from all directions is important to delineate the effect of the poplar tree root system and hence to obtain accurate tomographic results. Furthermore, four GPR reflection lines are performed along the sides of the four trenches such that the antenna is moved longitudinally in the trenches and the radargrams are recorded along the horizontal xy-plane parallel to the ground surface. On the processed GPR reflection radargrams, relatively high-amplitude GPR anomalies could be outlined and are attributed to the boundary between the saturated and wet zones where different water contents affect the GPR velocity. Comparable results are obtained between the tomogram and the radar reflection results with respect to zones of increase in water content. 相似文献
5.
Summary This paper describes the results from a continuing research project started in 1984, which is investigating improved methods for predicting the underground climate in hot mines. The Homestake Gold Mine in South Dakota was the site for testing methods, based on radial heat flow theory, to measurein situ values of the thermal conductivity and diffusivity of rock. The methods used proved to be quite within the capability of mine staff to carry out for themselves. The results were acceptable and verified thatin situ thermal rock properties can differ considerably from laboratory determined values, in this case by a factor of approximately two.A mine climate simulation program, CLIMSIM, was applied to case studies from the Homestake mine using the measured thermal rock parameters. The results showed good correlation between the measured and simulated values. 相似文献
6.
Indicators of critical point behavior prior to rock failure inferred from pre-failure damage 总被引：4，自引：0，他引：4
To investigate possible indicators of critical point behavior prior to rock failure, the statistical properties of pre-failure damage were analyzed based on acoustic emission events (AE) recorded during the catastrophic fracture of typical rock samples under differential compression. AEs were monitored using a high-speed 32-channel waveform recording system. Time-dependent statistics, including the energy release rate, b-value of the magnitude–frequency distribution, fractal dimension and spatial correlation length (SCL) of the AE hypocenters were calculated for each data set. Each parameter is a function of the time-to-failure and thus can be treated as an indicator of the critical point. It is clear that the pre-failure damage evolution prior to catastrophic failures in several common rock-types is generally characterized by: 1) accelerated energy release, 2) a decrease in fractal dimension and SCL with a subsequent precursory increase, and 3) a decrease in b-value from 1.5 to 0.5 for hard rocks, and from 1.1 to 0.8 for soft rocks such S–C cataclasite. However, each parameter also reveals more complicated temporal evolution due to either the heterogeneity of the rock mass or the micro-mechanics of shear fracturing. This confirms the potential importance of integrated analysis of two or more parameters for successfully predicting the critical point. The decreasing b-value and increasing energy release may prove meaningful for intermediate-term prediction, while the precursory increase in fractal dimension and SCL may facilitate short-term prediction. 相似文献
7.
We provide background oceanography and observations and hindcast simulations of spreading oil leaked from the wreck of theTenyo Maru, a fishing vessel that sank off the western entrance to Juan de Fuca Strait in July 1991. The vessel sank in the region of the Tully Eddy on the continental shelf. Although this eddy is normally present in summer, its location shifts and its trapping time varies considerably. The spread of theTenyo Maru oil is represented reasonably well by assuming the eddy to be a littler further to the east and north of its position as observed during drifter studies in 1986. Observations in 1985 showed that the preferred exit route of surface water from the eddy was toward the southeast, the direction followed by theTenyo Maru oil in 1991; however, other drift paths are possible, and under different weather conditions the oil could have drifted toward the Vancouver Island coast. 相似文献
8.
A comparative study of ANN and Neuro-fuzzy for the prediction of dynamic constant of rockmass 总被引：1，自引：0，他引：1
Physico-mechanical properties of rocks have great significance in all operational parts in mining activities, from exploration
to final dispatch of material. Compressional wave velocity (p-wave velocity) and anisotropic behaviour of rocks are two such properties which help to understand the rock response under
varying stress conditions. They also influence the breakage mechanism of rock. There are different methods to determine thep-wave velocity and anisotropyin situ and in the laboratory. These methods are cumbersome and time consuming. Fuzzy set theory, Fuzzy logic and Neural Networks
techniques seem very well suited for typical geotechnical problems. In conjunction with statistics and conventional mathematical
methods, hybrid methods can be developed that may prove to be a step forward in modeling geotechnical problems. Here, we have
developed and compared two different models, Neuro-fuzzy systems (combination of fuzzy and artificial neural network systems)
and Artificial neural network systems, for the prediction of compressional wave velocity. 相似文献
9.
A.N. Galybin A.V. Dyskin B.G. Tarasov R.J. Jewell 《Geotechnical and Geological Engineering》1999,17(3-4):267-289
The construction of stable structures in rock masses requires knowledge of the in situ stresses at the scale of excavations. However, the measurements obtained by the conventional overcoring technique are related to a small scale (centimetres). To extrapolate them to the scales of interest to rock mechanics (from meters to kilometres) requires a large number of individual stress measurements, followed by statistical analysis to avoid a considerable scatter of the measured values. In this paper, a method is proposed based on (a) large-scale surface stress and modulus measurements using the cylindrical jack method complemented by a special measuring scheme and then (b) back analysis for a given excavation shape. The method allows the simultaneous reconstruction of the stress components at the scale of excavation. A numerical simulation for a cylindrical excavation in an isotropic rock mass demonstrates the high accuracy and robustness of the method. The presence of a fractured zone surrounding the excavation can hamper the stress reconstruction, hence special measures should be taken to conduct the measurements in competent rock. 相似文献
10.
Nannorrhops ritchiana (Mazari Palm) is a distinctive flora growing in the Saharo-Sindian region. It is well distributed on the ultramafic soil,
derived from the Bela Ophiolite in the Khuzdar District, Balochistan, Pakistan. Quantitative estimation of Ca, Mg, Fe and
Ni in soil and plant ash has been carried out. The constituents of plant ash have been discussed in relation to soil chemistry,
pH, climate, mobility, average abundance in plant ash and exclusion mechanism of the flora. Relationship among Ca, Mg, Fe
and Ni has been established using scattergrams to evaluate the biogeochemistry of the plant. High contents of Mg and high
coefficient of biological absorption allow it to be classed as Mg-flora. Both Ca and Fe appeared to be antagonistic to Mg.
The metal assemblage ofN. ritchiana nicely reflected the nature of the bed rock as being serpentinized ultramafic, and its corresponding soils. Good exclusion
mechanism ofN. ritchiana did not allow it to absorb high Ni from the soil. Relatively high concentrations of Ni inN. ritchiana from the Baran Lak area can be used to localize Ni-mineralization in the study area.
Statistical analyses, such as minimum, maximum, mean, mode, median, standard deviations, and coefficient of correlation, were
also made to improve raw geochemical data and interpretations. 相似文献
11.
Matts Lindbladh W. Wyatt Oswald David R. Foster Edward K. Faison Juzhi Hou Yongsong Huang 《Quaternary Research》2007,67(3):502-508
Picea is an important taxon in late-glacial pollen records from eastern North America, but little is known about which species of Picea were present. We apply a recently developed palynological method for discriminating the three Picea species in eastern North America to three records from New England. Picea glauca was dominant at 14,500–14,000 cal yr BP, followed by a transition to Picea mariana between 14,000 and 13,500 cal yr BP. Comparison of the pollen data with hydrogen isotope data shows clearly that this transition began before the beginning of the Younger Dryas Chronozone. The ecological changes of the late-glacial interval were not a simple oscillation in the position of a single species' range, but rather major changes in vegetation structure and composition occurring during an interval of variations in several environmental factors, including climate, edaphic conditions, and atmospheric CO2 levels. 相似文献
12.
岩石学和矿物学是地球科学的重要分支学科,相关研究能够深入了解行星形成演化、宜居地球的资源富集与环境变化等重要科学问题。《岩石矿物学杂志》是国内岩石学和矿物学领域的重要期刊,对其发表文章的深入挖掘有助于梳理学科研究进展,为学科从业人员深入研究提供背景信息,为该刊未来刊文方向提供借鉴参考。采用大数据分析和可视化技术对《岩石矿物学杂志》1982~2022年发表的文献进行计量化研究。研究发现,岩石学和矿物学一直是该刊的主要发文领域,地球化学、花岗岩、锆石U-Pb定年、吸附和矿物学是高频率主题关键词。其中,地球化学的共现强度最高,与花岗岩、岩石成因、火山岩和岩石学等关键词关系密切;其次是晶胞参数,相关关键词有光学性质、粉晶数据和新矿物等。具体研究内容包括5个不同主题:岩石成分和特征分析、变质作用和岩石变质过程研究、矿床特征和成矿过程研究、沉积环境和地层特征分析以及环境矿物学研究。与国内外岩石学、矿物学领域知名期刊数据进行对比,认为未来刊文鼓励新技术、新方法的开发与应用、多学科交叉研究、大数据和机器学习驱动的新范式研究等。 相似文献
13.
14.
探地雷达用于人工挖孔桩桩底岩溶探测的应用研究 总被引：2，自引：0，他引：2
在岩溶地区进行楼房建设、工厂修建、修路架桥时,其桩基的设计很多采用人工挖孔嵌岩灌注桩（人工挖孔桩）。通过对人工挖孔桩桩底目前几种探测手段的对比分析,运用探地雷达方法对桩底进行岩溶探测有其独特的优势。文章首先介绍了探地雷达桩底探测的具体方法,并根据介质介电常数的变化分析了探地雷达天线在桩底的辐射特征;其次,对桩底的两种地质模型进行了正演模拟;最后对岩溶地区人工挖孔桩底实测探地雷达剖面进行了分析解释。 相似文献
15.
16.
The peculiar taphonomy of the late Campanian ammonite Metaplacenticeras subtilistriatum is reconstructed on the basis of stratigraphic occurrence within the Hakobuchi Formation of northern Hokkaido (Japan), as well as of host rock and patterns of fragmentation. The species' taphonomy is closely linked to its streamlined, oxyconic shell with flat flanks and a smoothly tapered venter. Such shells were accumulated, together with numerous pebbles, by bottom currents (>0.25–0.5 m/s), in such a way that ventral portions of some shells fractured by collision with pebbles. Small holes and depressions in the external shell surface, presumably formed during compaction after final burial, are restricted to phragmocones. On this evidence, it is suggested that this species was nektobenthic, lived in a shallow environment (shoreface–inner shelf) where its streamlined shell allowed it to align with prevailing currents, similar to a wind vane. 相似文献
17.
At continental subduction initiation, the continental crust buoyancy may induce, first, a convergence slowdown, and second, a compressive stress increase that could lead to the forearc lithosphere rupture. Both processes could influence the slab surface P–T conditions, favoring on one side crust partial melting or on the opposite the formation of ultra-high pressure/low temperature (UHP-LT) mineral. We quantify these two effects by performing numerical simulations of subduction. Water transfers are computed as a function of slab dehydration/overlying mantle hydration reactions, and a strength decrease is imposed for hydrated mantle rocks. The model starts with an old oceanic plate ( 100 Ma) subducting for 145.5 Myr with a 5 cm/yr convergence rate. The arc lithosphere is thermally thinned between 100 km and 310 km away from the trench, due to small-scale convection occuring in the water-saturated mantle wedge. We test the influence of convergence slowdown by carrying on subduction with a decreased convergence rate (≤ 2 cm/yr). Surprisingly, the subduction slowdown yields not only a strong slab warming at great depth (> 80 km), but also a significant cooling of the forearc lithosphere at shallower depth. The convergence slowdown increases the subducted crust temperature at 90 km depth to 705 ± 62 °C, depending on the convergence rate reduction, and might thus favor the oceanic crust partial melting in presence of water. For subduction velocities ≤ 1 cm/yr, slab breakoff is triggered 20–32 Myr after slowdown onset, due to a drastic slab thermal weakening in the vicinity of the interplate plane base. At last, the rupture of the weakened forearc is simulated by imposing in the thinnest part of the overlying lithosphere a dipping weakness plane. For convergence with rates ≥ 1 cm/yr, the thinned forearc first shortens, then starts subducting along the slab surface. The forearc lithosphere subduction stops the slab surface warming by hot asthenosphere corner flow, and decreases in a first stage the slab surface temperature to 630 ± 20 °C at 80 km depth, in agreement with P–T range inferred from natural records of UHP-LT metamorphism. The subducted crust temperature is further reduced to 405 ± 10 °C for the crust directly buried below the subducting forearc. Such a cold thermal state at great depth has never been sampled in collision zones, suggesting that forearc subduction might not be always required to explain UHP-LT metamorphsim. 相似文献
18.
The diagnoses of the conchostracan genera Cratostracus and Porostracus are revised following a re-examination of their type species under a scanning electron microscope. In Cratostracus each growth line has a serrated lower margin. Radial lirae branch into smaller ridges that merge with each other to give the upper part of each growth band in the ventral region of the carapace a slightly undulating surface. Cross-bars are present between these lirae. In Porostracus the radial lirae on the growth bands near the umbo are long and relatively widely spaced. There is a fine reticulum between them in the umbonal part of the carapace and cross-bars on the ventral surface. The ornament of Porostracus indicates that it can be assigned to the family Halysestheriidae rather than to the Afrograptidae, in which it has been placed previously. Morphological analysis of most of the species of the two genera and closely related Orthestheria (Migransia) under the scanning electron microscope is required before their stratigraphic potential can be fully realized. 相似文献
19.
这里基于某铁路隧道仰拱400MHz天线探地雷达的实际采集数据,采用Radan7软件处理方法所检测的缺陷结果,与施工单位及相关质量控制单位所组织的破检验证完全相符。通过对检测缺陷展开全面分析与解释,为隧道缺陷检测提供了依据和方法,将其应用于该工区后续隧道施工和隧道缺陷的检测处理与解释,具有重要的现实指导意义。 相似文献
20.
基于易滑地质结构与多源数据差异的岩溶山区大型崩滑灾害识别研究 总被引：1，自引：0，他引：1
岩溶山区地质环境复杂且脆弱,重特大崩滑地质灾害时有发生。如果对岩溶山区的地质环境认知不准,将直接导致对灾害识别能力不足。文章围绕岩溶山区裸露型岩溶陡崖、复合岩组型斜坡以及非裸露型岩溶斜坡3类基本易滑地质结构差异,探讨多源数据条件下更具适用性的识别探测方法。对于空间影响面积小的厚层岩溶陡崖结构,星-地组合识别方法更加适用,基于GNSS的识别探测方式可在获得动态变形趋势基础上,对可能发生的失稳模式进行初步预判,同时可对InSAR解译的地表位移进行矢量化校正,有利于提高对具有相同或相近SAR数据条件地区的灾害识别程度。对于具有较大空间影响面积的斜坡区域,可优先选用基于InSAR的遥感技术来获取地表变形结果,对于有致灾风险的大变形区还可结合易滑地质结构及外部影响因素对其可能失稳模式进行预判或反演分析。任何灾害识别方式都有其局限性,在实践中可根据不同地质结构特征与灾害类型特点,通过多源、多维度监测来构建综合识别体系,探索更具适用性的识别探测与数据分析新思路。 相似文献