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The chemical composition of water sampled in a 700 m deep underground barite-fluorite mine in the crystalline basement of the Black Forest area (SW Germany) varies systematically with depth and the length of flow paths trough, the fracture porosity of the gneiss matrix. Calcium and sulfate increase as a result of a combined sulfide oxidation and plagioclase alteration reaction. The gneiss contains andesine–plagioclase (An20–An40) and is rich in primary sulfide. As an effect of Ca and SO4 release by the prime water–rock reaction, dissolved oxygen decreases and the waters become more reduced. The waters have Cl/Br mass ratios of about 50, which is very close to that of experimentally leached gneiss powders indicating that the rock matrix is the source of the halogens. The waters are undersaturated with respect to calcite in the upper parts of the mine. With increasing reaction progress, calcite saturation is reached and carbonate forms as a reaction product of the prime reaction that also controls the partial pressure of CO2 to progressively lower values. The chemical evolution of groundwater in fractured basement of the Clara mine suggests that the partial pressure of CO2 is an internally buffered parameter rather than a controlling external variable. 相似文献
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The Schöllenen Gorge in the Reuss Valley of the Central Swiss Alps (Figs. 1 and 2) is a famous tourist attraction and ideal location for the study of the properties and formation mechanisms of uplift and post-uplift unloading joints. The gorge is situated in the southern part of the Central Aar Granite, a granitic batholith which intruded about 300 million years ago. The magmatic fabric of this batholith (Fig. 4) has only been locally modified during Alpine tectonic and metamorphic overprinting, mainly in the vicinity of ductile-brittle shear zones. The up to 600 m deep gorge provides an ideal opportunity to study the complex fracture systems of the batholith, and tunnels of the Göschenen hydropower system allow the study of the fracture patterns below ground surface. Outcrop, tunnel and remote mapping of fractures in the study area lead to the recognition of two probably syntectonic (Oligocene-Miocene) joint sets (S and Q joints) and three generations of uplift and post-uplift joints (unloading joints). The frequent S joints run nearly parallel to the Alpine schistosity, i.e. striking approximately E–W and dipping steeply to the south (Figs. 5 and 7). The less frequent Q joints dip steeply to SW; the angle between the two joint sets ranges between 60 and 80 degrees. The first generation of uplift joints (called L- joints) is subhorizontal and probably related to Alpine extensional veins filled with fissure quartz (Zerrklüfte). These veins formed during the late Alpine (Miocene) uplift of the Aar Granite (Mullis 1996). A first generation of post-uplift joints (T1 joints) strikes parallel to the valley axes and dip with 30–45 degrees towards the valley bottom. This set probably formed during an earlier stage of glacial valley erosion in the Pleistocene (Figs. 9–11). The youngest generation of post-uplift joints (T2 joints) is orientated parallel to the present ground surface of the Schöllenen Gorge and to erosional surfaces with glacial striations (Figs. 9–11 and 21). The frequency and size of these joints seems to decrease with depth below the ground surface. In one tunnel, post-uplift joints could be observed within a horizontal and vertical distance from the ground surface of 150 and 80 meters. Post-uplift joints only form in granites with a primary fabric that has not been intensively overprinted by brittle or ductile Alpine tectonic deformations. Fractographic investigations, i.e. investigations of crack propagation markers on joint surfaces, confirm this relative age of the fracture sets and give valuable insights into the formation mechanisms of post-uplift joints. Post-uplift joints show intense and 5–10 meter long plumose markings and only rarely arrest lines (Figs. 18a and 20). It can be shown that sets of post-uplift joints join at pre-existing (uplift and syntectonic) fractures to form large (50–100 m sized) curved exfoliation structures (Fig. 19). The growth direction of the post-uplift joints is mainly in subhorizontal directions (Figs. 19 and 20). Fractographic markings, spatial and depth distributions as well as the relative size of post-uplift fractures are explained within the mechanical framework of uniaxial and biaxial compression tests on intact granite samples and samples with artificial flaws. Most of these experiments have been carried out in the framework of studies related to brittle failure (spalling and rockbursting) around deep mining drifts and tunnels in hard rock’s (e.g. Hoek & Bieniawski 1965, Read et al. 1998, Eberhardt et al. 1999). As suggested already by Holzhausen & Johnson (1979), post-uplift fractures form as extension fractures in a compressive stress field with small confining stress. Laboratory tests carried out on artificial Griffith cracks suggest that the macroscopic fracture size is mainly controlled by the ratio of the smallest to the largest principal stress (σ3/σ1), the so-called spalling limit. In steep slopes this ratio should increase with depth below ground surface (Fig. 24c), leading to smaller exfoliation fractures with increasing depth. The spatial occurrence of post-uplift fractures along the surface topography is a function of the deviatoric stress level (Fig. 24a) and/or the development of local tensile stresses (Fig. 24d). Preliminary numerical simulations of these failure criteria in a multistage glacial erosion model (Fig. 23) allow some of the observed patterns of post-uplift fracture distributions to be reproduced. post-uplift joints in steep glacial valleys play an important role in valley erosion and in connection with the risk of rock falls, the safety of traffic corridors, and the inflow of water to near-surface tunnels and hydropower caverns. The depth dependant sizes, frequencies and hydraulic conductivities of these fractures can be directly related to the occurrence and magnitudes of the corresponding hazards. 相似文献
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A new model order reduction strategy adapted to nonlinear problems in earthquake engineering 
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下载免费PDF全文 Earthquake dynamic response analysis of large complex structures, especially in the presence of nonlinearities, usually turns out to be computationally expensive. In this paper, the methodical developments of a new model order reduction strategy (MOR) based on the proper orthogonal decomposition (POD) method as well as its practical applicability to a realistic building structure are presented. The seismic performance of the building structure, a medical complex, is to be improved by means of base isolation realized by frictional pendulum bearings. According to the new introduced MOR strategy, a set of deterministic POD modes (transformation matrix) is assembled, which is derived based on the information of parts of the response history, so‐called snapshots, of the structure under a representative earthquake excitation. Subsequently, this transformation matrix is utilized to create reduced‐order models of the structure subjected to different earthquake excitations. These sets of nonlinear low‐order representations are now solved in a fractional amount of time in comparison with the computations of the full (non‐reduced) systems. The results demonstrate accurate approximations of the physical (full) responses by means of this new MOR strategy if the probable behavior of the structure has already been captured in the POD snapshots. Copyright © 2016 The Authors. Earthquake Engineering & Structural Dynamics Published by John Wiley & Sons Ltd. 相似文献
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Andrea Loprieno Romain Bousquet Stefan Bucher Stefano Ceriani Florian H. Dalla Torre Bernhard Fügenschuh Stefan M. Schmid 《International Journal of Earth Sciences》2011,100(5):963-992
The Valais units in Savoy (Zone des Brèches de Tarentaise) have been re-mapped in great detail and are subject of combined stratigraphic, structural and petrological investigations summarized in this contribution. The sediments and rare relics of basement, together with Cretaceous age mafic and ultramafic rocks of the Valais palaeogeographical domain, represent the heavily deformed relics of the former distal European margin (External Valais units) and an ocean–continent transition (Internal Valais unit or Versoyen unit) that formed during rifting. This rifting led to the opening of the Valais ocean, a northern branch of the Alpine Tethys. Post-rift sediments referred to as “Valais trilogy” stratigraphically overlie both External and Internal Valais successions above an angular unconformity formed in Barremian to Aptian times, providing robust evidence for the timing of the opening of the Valais ocean. The Valais units in Savoy are part of a second and more external mid-Eocene high-pressure belt in the Alps that sutured the Briançonnais microcontinent to Europe. Top-N D1-deformation led to the formation of a nappe stack that emplaced the largely eclogite-facies Internal Valais unit (Versoyen) onto blueschist-facies External Valais units. The latter originally consisted of, from internal to external, the Petit St. Bernard unit, the Roc de l’Enfer unit, the Moûtiers unit and the Quermoz unit. Ongoing top-N D2-thrusting and folding substantially modified this nappe stack. Post 35 Ma D3 folding led to relatively minor modifications of the nappe stack within the Valais units but was associated with substantial top-WNW thrusting of the Valais units over the Dauphinois units along the Roselend thrust during W-directed indentation of the Adria block contributing to the formation of the arc of the Western Alps. 相似文献
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The western Tianshan range is a major Cenozoic orogenic belt in central Asia exposing predominantly Paleozoic rocks including granite. Ongoing deformation is reflected by very rugged topography with peaks over 7000 m high. Active tectonic deformation is tied to an E–W trending fracture and fault system that sections the mountain chain into geologically diverse blocks that extend parallel to the orogen. In the Muzhaerte valley upwelling hot water follows such a fault system in the Muza granite. About 20 L min−1 Na–SO4–Cl water with a temperature of 55 °C having a total mineralization of about 1 g L−1 discharge from the hot spring. The water is used in a local spa that is frequented by the people of the upper Ili river area. Its waters are used for balneological purposes and the spa serves as a therapeutic institution. The major element composition of the hot water is dominated by Na and by SO4 and Cl, Ca is a minor component. Dissolved silica (1.04 mmol L−1) corresponds to a quartz-saturation temperature of 116 °C and a corresponding depth of the source of the water of about 4600 m. This temperature is consistent with Na/K and Na/Li geothermometry. The water is saturated with respect to fluorite and contains 7.5 mg L−1 F− as a consequence of the low Ca-concentration. The water is undersaturated with respect to the primary minerals of the reservoir granite at reservoir temperature causing continued irreversible dissolution of granite. The waters are oversaturated with respect to Ca–zeolite minerals (such as stilbite and mesolite), and it is expected that zeolites precipitate in the fracture pore space and in alteration zones replacing primary granite. 相似文献
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The study presents composition data of 87 surface water samples from high alpine catchments of the Zermatt area (Swiss Alps). The investigated area covers 170 km2. It was found that the surface runoff acquires the dissolved solids mostly by reaction of precipitation water with the minerals of the bedrock. Total dissolved solids (TDS) vary from 6 to 268 mg L?1. All collected water shows a clear chemical signature of the bedrock mineralogy. The contribution of atmospheric input is restricted to small amounts of ammonium nitrate and sodium chloride. NH4 is a transient component and has not been detected in the runoff. Evaporation is not a significant mechanism for TDS increase in the Zermatt area. The chemical composition of the three main types of water can be related to the mineralogy of the dominant bedrock in the catchments. Specifically, Ca-HCO3 (CC) waters develop from metamorphic mafic rocks and from carbonate-bearing schists. Mg-HCO3 water originates from serpentinites and peridotites. Ca-SO4 (CS) waters derive from continental basement rocks such as pyrite-rich granite and gneiss containing oligoclase or andesine. The collected data suggest that, together with reaction time, modal sulfide primarily controls and limits TDS of the waters by providing sulfuric acid for calcite (CC waters) and silicate (CS waters) dissolution. If calcite is present in the bedrock, its dissolution neutralizes the acid produced by sulphide weathering and buffers pH to near neutral to weakly alkaline conditions. If calcite is absent, the process produces low-pH waters in gneiss and granite catchments. The type of bedrock and its mineral assemblage can be recognized in water leaving very small catchments of some km2 area. The large variety of water with a characteristic chemical signature is an impressive consequence of the richly diverse geology and the different rock inventory of the local catchments in the Zermatt area. 相似文献
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Jean-Louis Gonzalez Benedicte Thouvenin Catherine Dange Annie Fiandrino Jean-François Chiffoleau 《Estuaries and Coasts》2001,24(6):1041-1055
A complexation model (MOCO) was used to describe cadmium (Cd) speciation during estuarine transit in the Seine estuary. This model was developed from field data. Laboratory experiments based on the use of109Cd enabled checking of certain model simplifications and hypotheses and evaluation of parameters which could not be measured directly. MOCO was coupled with a 3D multivariable hydrosedimentary model (SAM3D) to simulate Cd dynamics in the estuary. These results were compared with measurements (dissolved and particulate Cd) obtained during cruises representative of various hydrodynamic conditions. The purpose of this article is to present the modeling approach used, and its expected applications and limits. 相似文献
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Prof. Dr. Walter H. Bucher 《International Journal of Earth Sciences》1963,52(2):804-810
The experiment herein reported was designed to demonstrate what happens when a part of a thick section of layered elastico-viscous materials is lifted slowly above the height it can support by compression between much stronger sections. By letting gravity produce the compression, the rate of rise was made slow enough to allow the horizontal component of gravity to cause lateral mass movement and consequent folding comparable to that observed in orogenic belts.Blocks of wood represented the strong foreland (and hinterland). Layers of stitching wax, a typical elastico-viscous substance, stood for the thick, weak strata in the space between them and the thinner sediments on the foreland. The experiment lasted 16 days.The progressive shift of the rising mass from the highest elevation toward the foreland is instructive. It changes a symmetrical anticline to a strongly overturned one, inducing digitations along its apex like those so commonly seen in Alpine anticlines; and it eventually carries the inner syncline on top of the apex of the deeper anticlinal axis and the outer one clear into the foreland, there throwing the sedimentary cover into folds.The design of the experiment has produced two highly unrealistic consequences: 1. The two synclines were drawn out to preposterous depths because the weights were attached at their centers to let gravity produce the compression. 2. The axis above which the anticline was to form had to be fastened, so that the weights could function properly. But these unrealistic aspects do not detract from the aim of the experiment which concerned only the events above the level of the wooden blocks. It could be shown that, in an elastico-viscous body lifted to greater height than it can support, the horizontal component of gravity produces more profound form changes than are generally associated with the concept of gravity sliding.
Zusammenfassung Das Experiment, das hier kurz beschrieben wird, hatte als Zweck zu zeigen, wie sich mächtige Schichten eines schwachen visco-elastischen Materials benehmen, wenn sie langsam zwischen stärkeren Grenzkörpern zusammengedrückt werden, so daß sie über die Höhe aufsteigen, die sie tragen können, ohne zu verflachen. Dadurch, daß die Schwerkraft benutzt wurde, um den seitlichen Tiefendruck zu leisten, ging der Aufstieg langsam genug vor sich, daß die Verformung des gehobenen Teiles Falten schuf, die mit solchen orogenetischer Zonen vergleichbar sind.Für die starken Grenzkörper wurden Holzblöcke verwandt, während Lagen von Schuhmacher-Pech, einem typischen visco-elastischen Materiale, die Sedimente darstellten. Das Experiment dauerte 16 Tage.Die Formänderungen der aufsteigenden Masse, die sich seitwärts von der höchsten Erhebung gegen das Vorland verschob, sind lehrreich. Die zentrale, ursprünglich symmetrische Antiklinale wird asymmetrisch und dann stark überkippt. Ihr Scheitel entwickelt Digitation, wie sie an so vielen Orten an den Scheiteln alpiner Antiklinalen zu sehen sind. Am Ende kommt die innere Synklinale auf den Scheitel der tieferen Antiklinale zu liegen, und die äußere wandert auf das Vorland ab und schiebt dabei die Schichten darauf in Falten zusammen.Die Anlage des Experiments hat zwei höchst unrealistische Folgen mit sich gebracht. 1. Die beiden Synklinalen wurden zu absurden Tiefen verzogen, weil die Gewichte, die es der Schwerkraft möglich machten, seitliches Zusammendrücken zu bewirken, in ihren Zentren befestigt waren. 2. Die Achse, über der die Antiklinale entstand, mußte befestigt werden, damit die Gewichte funktionieren konnten. Aber diese naturwidrigen Seiten des Experimentes haben dem Zweck des Experimentes keinen Eintrag getan, da es sich ja nur auf die Vorgänge über dem Niveau der Holzblöcke handelte. Es wurde gezeigt, daß dort die horizontale Komponente der Schwerkraft in einer visco-elastischen Masse, die zu größerer Höhe aufsteigt, als sie tragen kann, Formänderungen herbeiführt, die viel durchgreifender sind, als man sich gewöhnlich unter Schwerkraft-Gleitung vorstellt.
Résumé L'expérience qui est décrite ici brièvement a pour but de montrer le comportement de couches épaisses faites d'un matériau faiblement visco-élastique, comprimées lentement entre des machoires plus résistantes, de façon à ce qu'elles se soulèvent jusqu'à un point où elles peuvent se soutenir sans s'affaisser. En utilisant la pesanteur pour exercer la pression latérale en profondeur, la montée progressait suffisamment lentement pour que la déformation de la partie soulevée engendrât des plis comparables à ceux des zones orogéniques.Comme machoires, on a utilisé des blocs de bois, tandis que des couches de poix, matériau typiquement visco-élastique, figuraient les sédiments. L'expérience a duré 16 jours.Les modifications de forme de la masse en voie de soulèvement qui se déplaçait latéralement du point le plus haut vers l'avant-pays, sont riches en enseignements. L'anticlinal central originellement symétrique est devenu asymétrique et s'est alors fortement déversé. Sa partie apicale développa une digitation comme on peut en voir en de nombreux endroits dans les anticlinaux alpins. A la fin le synclinal interne vint surmonter le sommet des anticlinaux plus profonds et le synclinal externe migra sur l'avant-pays en refoulant les couches sous forme de plis.Le dispositif de l'expérience entraîne 2 conséquences peu réalistes: 1. Les deux synclinaux ont. été aspirés jusqu'à une profondeur absurde, car les poids qui permettaient à la pesanteur de faire agir la poussée latérale étaient fixés dans leur partie centrale. 2. L'axe au-dessus duquel est né l'anticlinal, devait être fixé pour que les poids puissent exercer leur action. Mais ces aspects de l'expérience en contradiction avec les conditions naturelles n'ont eu aucune incidence sur le but de l'expérience, étant donné qu'il s'agissait seulement du processus qui se déroule au-dessus du niveau des blocs de bois. On a ainsi montré que les composantes horizontales de la pesanteur agissant dans une masse visco-élastique s'élevant jusqu'à une hauteur plus grande que celle qu'elle peut supporter, entraînent des modifications de formes qui sont plus accentuées qu'on ne se l'imagine ordinairement dans le cas des «glissements par gravité».
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