Overbreak and underbreak in underground openings Part 2: causes and implications   总被引：7，自引：0，他引：7  

J. A. Ibarra  N. H. Maerz  J. A. Franklin 《Geotechnical and Geological Engineering》1996,14(4):325-340

Summary The newly developed light sectioning method has been used to investigate some of the causes and costs of overbreak and underbreak. Investigations at the Aquamilpa Hydroelectric Project in Mexico have shown decreased overbreak and increased underbreak as a result of increased rock quality and decreased explosive energy. A new measure of explosive energy, the perimeter powder factor (PPF), has been defined and shown to be useful in the context of tunnel-wall rock damage. Tentative results indicate that explosive energy (PPF) may be a more important factor in producing underbreak, whereas rock quality may be a greater factor in producing overbreak. A site-specific equation is given for predicting overbreak or underbreak as a function of rock quality and explosive energy, with an evaluation of the cost of underbreak and overbreak.  相似文献   

Textural segmentation of digital rock images into bedding units using texture energy and cluster labels     

Stefan M. Luthi 《Mathematical Geology》1994,26(2):181-196

The texture of digital rock images, as recorded, for instance, with borehole imaging devices, is shown to reflect different bedding types. Textural segmentation of borehole images, therefore, subdivides the recorded sequence into bedding units. We show that a textural segmentation algorithm based on the concept of texture energy achieves good results when compared with synthetic as well as real data in which petroleum geologists have performed zonations on cores. Texture energy involves filtering of the original image with a set of texture sensitive masks. The filtering is done as a finite convolution over the size of the masks. On the resulting images the variance is computed over a relatively large sliding window, which, in its practical implementation, covers the full width of the image. The resulting nine one-dimensional curves are then clustered hierarchically into a user-determined number of image texture or lithological bedding classes. Principal component analysis previous to clustering can be used to reduce redundancy in the data. A recurring and relatively ill-defined problem in this field are macro-textures, i.e., the cyclic interbedding of two or more bedding types. We show that sliding Fourier transforms and variable mask scale can successfully address the zonation of macro-textures. In general, the method gives best results with mask sizes equivalent to 2–4 centimeters, reflecting the length scale at which the investigated geological bedding seems to have its highest variation.  相似文献   

Palaeolimnological studies of the eutrophication of volcanic Lake Albano (Central Italy)     

Andrea Lami  Frank Niessen  Piero Guilizzoni  Julieta Masaferro  Claudio A. Belis 《Journal of Paleolimnology》1994,10(3):181-197

We use palaeolimnological techniques to reconstruct the eutrophication history of a volcanic lake (Lake Albano, central Italy) over the past three centuries. The presence of annual varves down to the bottom of the core (c. 1700 A.D.) indicated the lack of bioturbation and likely long-term meromixis. Sedimentation rates were estimated by varve counts (calcite/diatom couplets), indicating a mean rate of 0.15 cm yr^–1. The reconstruction of eutrophication was traced using past populations of algal and photosynthetic bacteria (through their fossil pigment), and geochemistry, as well as fossil remains of chironomids. Phaeophorbidea and the red carotenoid astaxanthin were used to detect past zooplankton development.The first sign of trophic change related to human activities is datedc. 1870 A.D. From that period onward a sharp increase of authigenic CaCO₃, nitrogen, N:P ratio, and dinoxanthin, a characteristic carotenoid of Chrysophyceae and Dinophyceae, is observed.Chironomid analyses showed the near absence of a deep water fauna throughout the core length. The populations of chironomid larvae are restricted to oxygenated littoral zones. In fact, the few fossil remains found are primarily of littoral origin, representing shallow water midges that were transported to profundal waters. The reduction of total chironomid in the uppermost layers of the core is to be related to human land uses.  相似文献   

豫西后造山阶段存在变质核杂岩吗？   总被引：2，自引：1，他引：1  

曹高社  赵太平 《地质论评》1997,43(4):365-372

不少学者用变质核杂岩模式解释豫西造山阶段基底隆起和与之相伴的盆岭构造的构造格局。介一本区基底隆起的形态、机制、时限和地壳剥露层次均没有变质核杂岩特征与基底隆起相伴的断陷人舅地也不同于变质核杂岩模式中的半地堑。  相似文献   

Research on temporal and spatial distribution, evolutionary character and mechanism of crustal deformation field before and after the Tangshan earthquake   总被引：2，自引：0，他引：2  

周硕愚  施顺英  帅平 《地震学报(英文版)》1997,10(6):693-701

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Fracture analysis in the south-western Corinth rift (Greece) and implications on fault hydraulic behavior     

Luca Micarelli  Isabelle Moretti  Manon Jaubert  Hakim Moulouel 《Tectonophysics》2006,426(1-2):31

This paper reviews the data concerning the fracture network and the hydraulic characteristics of faults in an active zone of the Gulf of Corinth. Pressure gap measured through fault planes shows that in this area the active normal faults (Aigion, Helike) act, at least temporarily and locally, as transversal seal. The analysis of the carbonate cements in the fractures on both the hangingwall and the footwall of the faults also suggests that they have acted as local seals during the whole fault zone evolution. However, the pressure and the characteristics of the water samples measured in the wells indicate that meteoric water circulates from the highest part of the relief to the coast, which means it goes through the fault zones. Field quantitative analysis and core studies from the AIG-10 well have been performed to define both regional and fault-related fracture networks. Then laboratory thin section observations have been done to recognize the different fault rocks characterizing the fault zone components. These two kinds of approach give information on the permeability characteristics of the fault zone. To synthesize the data, a schematic conceptual 3D fluid flow modeling has been performed taking into account fault zone permeability architecture, sedimentation, fluid flow, fault vertical offset and meteoric water influx, as well as compaction water flow. This modeling allows us to fit all the data with a model where the fault segments act as a seal whereas the relays between these segments allow for the regional flow from the Peloponnese topographic highs to the coast.  相似文献   

Mineral and fluid inclusions in zircon of UHP metamorphic rocks from the CCSD-main drill hole: A record of metamorphism and fluid activity   总被引：18，自引：0，他引：18  

Zeming Zhang  Kun Shen  Yilin Xiao  Jochen Hoefs  J.G. Liou 《Lithos》2006,92(3-4):378-398

The Chinese Continental Scientific Drilling (CCSD) main drill hole (0–3000 m) in Donghai, southern Sulu orogen, consists of eclogite, paragneiss, orthogneiss, schist and garnet peridotite. Detailed investigations of Raman, cathodoluminescence, and microprobe analyses show that zircons from most eclogites, gneisses and schists have oscillatory zoned magmatic cores with low-pressure mineral inclusions of Qtz, Pl, Kf and Ap, and a metamorphic rim with relatively uniform luminescence and eclogite-facies mineral inclusions of Grt, Omp, Phn, Coe and Rt. The chemical compositions of the UHP metamorphic mineral inclusions in zircon are similar to those from the matrix of the host rocks. Similar UHP metamorphic P–T conditions of about 770 °C and 32 kbar were estimated from coexisting minerals in zircon and in the matrix. These observations suggest that all investigated lithologies experienced a joint in situ UHP metamorphism during continental deep subduction. In rare cases, magmatic cores of zircon contain coesite and omphacite inclusions and show patchy and irregular luminescence, implying that the cores have been largely altered possibly by fluid–mineral interaction during UHP metamorphism.

Abundant H₂O–CO₂, H₂O- or CO₂-dominated fluid inclusions with low to medium salinities occur isolated or clustered in the magmatic cores of some zircons, coexisting with low-P mineral inclusions. These fluid inclusions should have been trapped during magmatic crystallization and thus as primary. Only few H₂O- and/or CO₂-dominated fluid inclusions were found to occur together with UHP mineral inclusions in zircons of metamorphic origin, indicating that UHP metamorphism occurred under relatively dry conditions. The diversity in fluid inclusion populations in UHP rocks from different depths suggests a closed fluid system, without large-scale fluid migration during subduction and exhumation.  相似文献   

Documentary Evidence of an Economic Character as a Source for the Study of Meteorological and Hydrological Extremes and their Impacts on Human Activities   总被引：1，自引：0，他引：1  

Rudolf Brázdil  Hubert Valá&#;ek  Kate&#;ina Chromá 《Geografiska Annaler: Series A, Physical Geography》2006,88(2):79-86

This paper deals with documentary evidence of an economic character as a proxy for direct study of meteorological and hydrological extremes. Taxation records and reports of those who administrated domains and estates are described with respect to information about meteorological and hydrological extremes. Based on data from eight domains or estates from Moravia (in the Czech Republic), frequency series of floods and convective storms (including hailstorms) were developed for the period 1650–1849. One example of disastrous weather, which took place on 10 August 1694 in the Pern?tejn domain, is used to demonstrate the potential for such studies of the intensity of extremes and their impact on human activities. The importance of economic evidence in the instrumental period is shown through tax rebate data contingent upon hailstorm damage in Moravia (1896–1906). The benefits of employing documentary economic evidence for historical climatology and the study of the impact of meteorological and hydrological extremes on human activities are discussed.  相似文献   

基于微电子系统（MEMS）加速度地震勘探三分量数字检波器简介   总被引：4，自引：0，他引：4  

张莉解文荣  李秀荣 《中国煤田地质》2006,18(2):57-59

基于微电子机械系统（MEMS）制成的微加速度三分量数字地震检波器。集数据采集、处理及传输功能干一体，在结构模型、工作原理、性能指标控制等方面不同于常规检波器，其信号幅值在低于自然频率范围内没有衰减。因其独特的制造技术，MEMS检波器具有超低噪声，大动态范围和极高的向量保真度性能。  相似文献   

用旅游图制作导航电子地图中的地图纠正     

宁莹  潘正风 《测绘信息与工程》2005,30(6):20-21

介绍了一种用三次插值样条对公开出版的旅游图进行纠正,制作汽车导航电子地图的方法,分析了其中存在的问题,提出了解决的办法。  相似文献