共查询到10条相似文献，搜索用时 93 毫秒
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Tetsuya Tokiwa Kimikazu Tsusaka Makoto Matsubara Taiki Ishikawa Daisuke Ogawa 《地学前缘(英文版)》2013,4(1):105-111
This paper focuses on the formation mechanism of fractures induced by excavation of a gallery in soft sedimentary rocks in the Horonobe area of Japan.Detailed fracture mapping of the gallery indicates that the fractures consist of both pre-existing shear fractures and excavation damaged zone(EDZ) fractures. EDZ fractures correspond to weak planes associated with bedding planes or transgranular cracks.The EDZ fractures terminate against pre-existing shear fractures.Therefore,even for excavations in soft sedimentary rocks,formation of the EDZ fractures are controlled by pre-existing fractures and earlier weak planes. 相似文献
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An assessment of the creep behaviour of Brazilian salt rocks using the multi-mechanism deformation model 总被引：1，自引：1，他引：0
Salt rocks are geomaterials that exhibit several peculiarities, which require a particular approach in rock mechanics. In the field, those rocks are usually found in layered/bedded deposits and in domes or similar structures. Creep is one of the main deformation mechanisms associated with salt rocks, and this phenomenon is highly dependent on the stress state, temperature and mineralogy. Salt rock mechanics for engineering applications requires the definition of a powerful constitutive model and this is an ongoing challenge. Among the many available models, one of the most sophisticated physical constitutive models for salt rocks is the multi-mechanism deformation creep model (MD model). The main contribution of this work is to present a first effort in the use of the MD model for Brazilian salt rocks. Material-sensitive parameters have been calibrated for the Brazilian halite through two methodologies. Salt is modelled as an elasto-viscoplastic material. Numerical simulations using the finite element method have been carried out for triaxial creep tests, Pre-salt wellbore closure and mining gallery convergence in order to validate the parameter set and the methodologies. Excellent results have been observed in most of the applications for validation. Even so, validation efforts should continue to consolidate the parameters and identify possible limitations. 相似文献
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Samples of Opalinus Clays from Mont Terri Underground Research Laboratory in the Swiss Jura were analyzed repetitively relative to the duration of their exposure to atmosphere. The objective was the evaluation of such a progressive exposure on the chemical composition of whole-rock samples, and on the chemical and Sr isotopic compositions of leachates obtained by leaching the rock powders with dilute acetic acid. This chemical study was complemented by scanning electron microscope observations to identify the related mineral alterations. The chemical data for the rock powders remained quite constant whatever the duration of the storage, whereas significant changes were observed for the leachates. Similar changes were observed in the leachates of samples collected progressively closer to the walls of a previously excavated niche. When storage time or distance to gallery wall increases, the main variations are: (1) a progressive decrease of the element contents and of the 87Sr/86Sr ratio in the leachates, (2) an alteration of pyrite followed by precipitation of Ca-sulfate in the rocks, both observed by SEM, and (3) a probable precipitation of new mineral phases in the rocks, such as Fe-oxyhydroxides and/or jarosite that could not be visualized by electron microscopic observation because of their very limited amount and very small grain size. The modifications call for an oxidation of pyrite that probably induced also an oxidation of the organic matter. It could also be shown that the reactions were enhanced by temperature increase, and that they were less pronounced in the samples behind the gallery wall than in the cores stored in laboratory conditions. 相似文献
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The Mont Terri rock laboratory, a new international research project in a Mesozoic shale formation, in Switzerland 总被引：8，自引：0，他引：8
In many countries, argillaceous formations are being considered as potential host rocks for repositories of radioactive waste. Therefore, in 1995 several organisations decided to start an international research project in the reconnaissance gallery of the Mont Terri motorway tunnel, in north-western Switzerland, in a Mesozoic shale formation, the Opalinus Clay (Aalenian).
This project is under the patronage of the Swiss National Hydrological and Geological Survey. The following organisations are also partners in the project: ANDRA and IPSN (France), BGR (Germany), ENRESA (Spain), Nagra (Switzerland), JNC and Obayashi (Japan), SCKCEN (Belgium).
The aims of the project are to analyse the hydrogeological, geochemical and rock mechanical properties of an argillaceous formation, the changes of these properties induced by the excavation of galleries and to evaluate and improve appropriate investigation techniques. In January, 1996, eight niches were excavated for the project and 15 experiments were started in boreholes of no more than 30 m in length. In the winter of 1997–1998 a new research gallery was excavated to host further experiments. Different excavation, drilling and investigation techniques have been tested and improved. Significant results of the different experiments are already available. Some of those dealing with hydrochemistry, porewater pressure measurements and the evolution of the excavation disturbed zone (EDZ) are reported in this paper. 相似文献
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贵州平寨水库左岸底层灌浆廊道大型充填溶洞及其形成机制 总被引：1，自引：0，他引：1
平寨水库坝址区以碳酸盐岩为主,岩溶较发育,水库左岸底层灌浆廊道大型充填溶洞,是水库地下工程施工开挖中揭露的规模最大、对水库渗漏影响最大、设计及施工处理难度最大的溶洞。本文以工程前期地质勘察工作为基础,在区域地貌、地质构造格局、地层岩性、地表及地下水系发育特征研究的基础上,结合工程防渗施工揭露的岩溶水文地质现象、洞穴充填物研究等,从可溶性岩层、地下水来源及运移途径、暗河冲刷与洞顶坍塌作用4个方面,对溶洞发育形成机制进行了研究。分析认为,鸡场背斜北西翼纵向张裂隙和横张裂隙及层间滑脱、断裂破碎带,为五里大洞鸡场洼地上坝洼地地下水向三岔河的径流提供了运移的原始空间与通道,形成溶洞的地下水为五里大洞鸡场洼地上坝洼地地下暗河,长期溶蚀作用使裂隙通道变为溶蚀宽缝并最终转化为岩溶管道,岩溶水沿此通道在左岸底层灌浆廊道桩号0+238～0+296m附近下中部岩体呈虹吸状循环,地下水的强烈冲刷与洞顶坍塌在溶洞形成过程中的作用巨大,后因深部径流条件改变,岩溶管道被逐渐堵塞,形成如今的大型充填溶洞。 相似文献
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The velocity of elastic waves has been measured along the principal fabric directions in 110 Alpine rocks, and these data are analyzed in conjunction with previously measured data on density, porosity, specific heat, and thermal diffusivity for the same rocks. Particular attention is given to the anisotropy in the thermal and elastic properties which are up to three times larger in the direction of lineation than in the direction perpendicular to the foliation. The correlations among the various scalar properties and the average thermal and elastic properties are in general weak and are overshadowed by variations due to mineralogy. However, relative thermal and elastic properties show a significant positive correlation, and for gneisses, schists, ultramafic rocks and carbonate rocks it is meaningful to predict thermal anisotropy on the basis of elastic anisotropy. 相似文献