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1.
利用空心圆柱扭剪仪模拟斜入射地震波作用形成的斜椭圆应力路径,对比研究了等向固结条件下饱和福建标准松砂在循环斜椭圆、圆形、扭剪、三轴路径下的动力特性。试验研究表明：土体循环孔压发展存在陡升型和陡降型两种模式;圆形路径下累积孔压增长速率最快,循环扭剪最小;归一化孔压与斜椭圆的倾角无关,但受斜椭圆长短轴比及动应力比影响。砂土的不排水动强度与动应力路径密切相关,循环扭剪和循环三轴最大,循环斜椭圆次之,圆形路径最小。地震波从特定角度入射时,形成近似圆形路径,若只将地震波视为垂直入射的S波,将高估地基土体抗液化强度。 相似文献
2.
Martin Bak Hansen Holger Lykke-Andersen Ali Dehghani Dirk Gajewski Christian Hübscher Morten Olesen Klaus Reicherter 《International Journal of Earth Sciences》2005,94(5-6):1070-1082
A dense grid of multichannel high-resolution seismic sections from the Bay of Kiel in the western Baltic Sea has been interpreted
in order to reveal the Mesozoic and Cenozoic geological evolution of the northern part of the North German Basin. The overall
geological evolution of the study area can be separated into four distinct periods. During the Triassic and the Early Jurassic,
E–W extension and the deposition of clastic sediments initiated the movement of the underlying Zechstein evaporites. The deposition
ceased during the Middle Jurassic, when the entire area was uplifted as a result of the Mid North Sea Doming. The uplift resulted
in a pronounced erosion of Upper Triassic and Lower Jurassic strata. This event is marked by a clear angular unconformity
on all the seismic sections. The region remained an area of non-deposition until the end of the Early Cretaceous, when the
sedimentation resumed in the area. Throughout the Late Cretaceous the sedimentation took place under tectonic quiescence.
Reactivated salt movement is observed at the Cretaceous Cenozoic transition as a result of the change from an extensional
to compressional regional stress field. The vertical salt movement influenced the Cenozoic sedimentation and resulted in thin-skinned
faulting. 相似文献
3.
We use a thin sheet approach to investigate the effects induced by the Alpine collision on the deformation and regional stress in northern Europe, with special emphasis on the NE German Basin. Here new seismic crustal studies indicate a flexural-type basin, which may have been induced by compressive forces transmitted from the south, due to the Alpine orogeny. Finite-element techniques are used to solve the equations for the deformation of a continuum described by a linear creep rheology and a spatial resolution of about 0.5°. The model has been constrained by stress and seismic data. We show that a relatively strong lithosphere below the northern margin of the German Basin, at the transition with the Baltic Shield, may explain the characteristic regional stress field, in particular the fan-like pattern which is observed within the region. Furthermore, the predicted strain rate pattern resembles the seismically recognizable undeformed area of the North German Basin. 相似文献
4.
Responses of municipal solid waste (MSW) landfills during earthquakes are gaining worldwide importance due to the devastating nature of earthquake on landfills. Apart from the post-earthquake safety and serviceability issues which pose environmental and public health problems, other important concerns are related to the behavior of closed landfills during and after earthquake. In present study, one dimensional (1-D) equivalent-linear analysis was carried out to model the behaviour of MSW landfills subjected to seismic base accelerations using the DEEPSOIL software. Influence of foundation types, height and stiffness of MSW landfills and seismic base accelerations on the seismic responses in terms of surface accelerations, normalized stresses (i.e., shear stress/effective vertical stress) and spectral amplification are evaluated. The results showed that height and stiffness of landfills, type of foundation and amount of seismic base acceleration and period play important role in evaluating the seismic responses of MSW landfills. Assumption of constant unit weight and shear wave velocity for landfills underestimates maximum horizontal acceleration (MHA), normalized shear stresses and spectral amplification at the top of landfills. Landfill models with smaller heights (up to 40 m high) showed higher amplification ratio for low seismic base accelerations with mean period near to that of soil and landfill resonance for all sites. A complex behavior was observed at higher seismic base accelerations due to non-linear behavior of landfill materials. 相似文献
5.
6.
Correlation between rock fabrics and physical properties of carbonate reservoir rocks 总被引：5，自引：0，他引：5
Three carbonate core samples from an oil and gas reservoir of the NW German basin were chosen to study the correlation between
rock fabrics and physical properties of reservoir rocks. Detailed fabric analyses and texture investigations were carried
out as well as laboratory measurements of different physical properties, e.g. density, porosity, permeability, electrical
conductivity, seismic compressional and shear wave velocities. Although the three core samples come from a similar depositional
facies, they show great differences in the occurrence and three-dimensional distribution of the rock fabric elements. These
heterogeneities are the result of various diagenetic and tectonic processes. For the correlation between the rock fabrics
and the physical properties four main rock fabric types have to be considered: (a) major constituents, e.g. fossils, ooides,
peloides and crystals; (b) pore space with different pore types; (c) fractures; and (d) stylolites. The results of the correlation
clearly show that the values and anisotropies of the petrophysical properties are fairly related to the observed fabric elements,
with their different arrangements, spatial distributions and preferred orientations. These results also provide a fundamental
understanding of the petrophysical responses, such as seismics, to the different geological features (e.g. fractures) and
their dynamic changes with pressure, which can be converted to different depths. The knowledge gained from such correlations
may lead to an improved interpretation of geophysical data for hydrocarbon exploration and production and therefore to an
advanced reservoir characterization.
Received: 28 January 1999 / Accepted: 21 June 1999 相似文献
7.
Stanislaw Mazur Magdalena Scheck-Wenderoth Piotr Krzywiec 《International Journal of Earth Sciences》2005,94(5-6):782-798
Several selected seismic lines are used to show and compare the modes of Late-Cretaceous–Early Tertiary inversion within the
North German and Polish basins. These seismic data illustrate an important difference in the allocation of major zones of
basement (thick-skinned) deformation and maximum uplift within both basins. The most important inversion-related uplift of
the Polish Basin was localised in its axial part, the Mid-Polish Trough, whereas the basement in the axial part of the North
German Basin remained virtually flat. The latter was uplifted along the SW and to a smaller degree the NE margins of the North
German Basin, presently defined by the Elbe Fault System and the Grimmen High, respectively. The different location of the
basement inversion and uplift within the North German and Polish basins is interpreted to reflect the position of major zones
of crustal weakness represented by the WNW-ESE trending Elbe Fault System and by the NW-SE striking Teisseyre-Tornquist Zone,
the latter underlying the Mid-Polish Trough. Therefore, the inversion of the Polish and North German basins demonstrates the
significance of an inherited basement structure regardless of its relationship to the position of the basin axis. The inversion
of the Mid-Polish Trough was connected with the reactivation of normal basement fault zones responsible for its Permo-Mesozoic
subsidence. These faults zones, inverted as reverse faults, facilitated the uplift of the Mid-Polish Trough in the order of
1–3 km. In contrast, inversion of the North German Basin rarely re-used structures active during its subsidence. Basement
inversion and uplift, in the range of 3–4 km, was focused at the Elbe Fault System which has remained quiescent in the Triassic
and Jurassic but reproduced the direction of an earlier Variscan structural grain. In contrast, N-S oriented Mesozoic grabens
and troughs in the central part of the North German Basin avoided significant inversion as they were oriented parallel to
the direction of the inferred Late Cretaceous–Early Tertiary compression. The comparison of the North German and Polish basins
shows that inversion structures can follow an earlier subsidence pattern only under a favourable orientation of the stress
field. A thick Zechstein salt layer in the central parts of the North German Basin and the Mid-Polish Trough caused mechanical
decoupling between the sub-salt basement and the supra-salt sedimentary cover. Resultant thin-skinned inversion was manifested
by the formation of various structures developed entirely in the supra-salt Mesozoic–Cenozoic succession. The Zechstein salt
provided a mechanical buffer accommodating compressional stress and responding to the inversion through salt mobilisation
and redistribution. Only in parts of the NGB and MPT characterised by either thin or missing Zechstein evaporites, thick-skinned
inversion directly controlled inversion-related deformations of the sedimentary cover. Inversion of the Permo-Mesozoic fill
within the Mid-Polish Trough was achieved by a regional elevation above uplifted basement blocks. Conversely, in the North
German Basin, horizontal stress must have been transferred into the salt cover across the basin from its SW margin towards
the basins centre. This must be the case since compressional deformations are concentrated mostly above the salt and no significant
inversion-related basement faults are seismically detected apart from the basin margins. This strain decoupling in the interior
of the North German Basin was enhanced by the presence of the Elbe Fault System which allowed strain localization in the basin
floor due to its orientation perpendicular to the inferred Late Cretaceous–Early Tertiary far-field compression. 相似文献
8.
推导了考虑剪应力作用时横观各向同性岩体中圆形巷道的位移解析解,利用参数可辨识条件对考虑剪应力作用时横观各向同性岩体中圆形巷道位移反分析的惟一性进行了探讨。结果表明,无论布置多少个测点也不能惟一地反分析出所有7个参数,必须至少已知3个参数,才有可能惟一地反分析出其他参数;水平与竖直地应力分量是否为 0 对反分析惟一性有一定影响;3个地应力分量的可辨识性最好,各向同性面上的弹性模量和泊松比次之,垂直于各向同性面方向的弹性模量和泊松比最差。与不考虑剪应力时位移反分析惟一性结果相比,考虑剪应力时参数的可辨识性顺序不变,但是条件惟一的比例降低,不惟一和绝对惟一的比例增加,说明考虑剪应力能够提高位移反分析的惟一性。工程实例计算表明,推导的位移解析解和反分析惟一性探讨结果能够很好地指导岩体参数反演计算。 相似文献
9.
10.
Geomechanics is a science dealing with the study of the behaviour of rocks affected by stress. It has various applications in utilisation from oil and gas reservoirs including of the wellbore stability analysis and determination of safe mud window. The main aim of this paper is geomechanical study of Kangan–Dalan reservoir in South Pars gas field in Persian Gulf in south Iran. Seismic waves are affected by physical properties of rocks when passing underground formations; thus, the velocity of these waves is a desired parameter for estimation of geomechanical properties. The velocity of compressional and shear waves has been determined with processing seismic data resulting from vertical seismic profile. In this paper, after calculation of elastic modules of reservoir rock, the imposed stress field was determined and these concepts were used for engineering calculations such as safe mud window, wellbore stability analysis and sand production potential. For well drilling in Kangan-Dalan reservoir, the minimum and maximum mud weights were proposed in average as 1.093 and 2.011 gr/cc and average critical mud weight as 2.48 gr/cc such that if the weight of mud increases, the tensile fractures will be created on the formation and complete loss of mud will happen. 相似文献
11.
为研究近断层脉冲地震动中竖向加速度对砂土场地液化的影响,基于有限元平台OpenSees开发的边界面塑性本构模型,建立了动单剪单元试验模型和饱和砂土三维有限元模型。选取台湾Chi-Chi地震中10条具有速度脉冲特性的地震波,对比分析了水平双向脉冲波与三向脉冲波作用下土柱竖向位移、循环应力比、孔压比及等效循环周数的差异性,继而明确了脉冲地震动中竖向加速度对砂土液化的影响规律。研究表明,三向脉冲地震波中竖向加速度分量对场地永久位移值影响较小,但使永久位移的发展持时明显增大;土柱循环应力比受竖向地震动影响较小,因此分析脉冲地震动对场地剪切特性的影响时,可将三向脉冲地震动简化为水平双向地震动;考虑竖向地震动的三向脉冲地震波引起的孔压比变化幅度较大,孔压消散时间较长;三向脉冲地震波对应的等效循环周数较大,地震动发展持时长,可认为竖向加速度对场地液化有促进作用。 相似文献
12.
Experimental studies were carried out in laboratory in order to investigate the effects of fracture on compressional (P) wave and shear (S) wave velocity propagation and therefore the relations between seismic properties and rock mass parameters. The discontinuity index, Id, fracture density parameter C, linear fracture parameter Γ and the rock quality designation (RQD) were used to describe the rock mass parameters. These parameters are analyzed and then related to the seismic properties. Four vertical aligned fractures were created on an intact calcarenite block, 0.6 m long, 0.4 m thick and 0.4 m width, by sawing. The measures were carried out in four different blocks of cacarenite, having the same physical properties, and in four different phases: in first block the fractures were filled with air; in the second block the fractures were filled with “terra rossa”; in third block the fractures were filled with wet “terra rossa” and in the fourth block the fractures were filled with clay. The test results were statistically analysed using the method of least squares regression and polynomial relationships with high correlation coefficient were found between the fractured rock parameters and P-wave, S-wave velocities and Vp/Vs ratio. The investigations suggest that the P-wave and S-wave velocities decrease with increasing the fracture parameters, while the Vp/Vs ratio increases with decreasing the fracture parameters.
Furthermore the results of the experimental studies were applied on the seismic refraction tomography data acquired in a great measurements campaign undertaken in the Adriatic salentina coast (south Italy) in order to monitor the coastal erosion.
The geophysical results, using the polynomial relationships between the fractured rock parameters and P-wave velocity, are in good agreement with the geomorphological and geological results. 相似文献
13.
测井和地震联合解释CCSD先导孔反射体 总被引：1，自引：1，他引：0
利用声波、密度、自然伽玛等测井曲线资料、配合录井资料划分CCSD先导孔变质岩岩性, 然后, 用声波、密度计算波阻抗, 与井旁VSP资料对比, 分析CCSD先导孔孔区反射体.分析结果表明(1) 岩性间波阻抗差异产生反射波, 如榴辉岩与副片麻岩之间波阻抗差异; 榴辉岩与超基性蛇纹岩之间的波阻抗差异等; (2) 破碎特别是韧性剪切带产生反射波, 而如果断层破碎带尺度很小(在1m以下), 也不一定能产生强反射波.这些研究结果对标定地壳中的反射地震信号具有重要意义. 相似文献
14.
Middle and lower Ordovician carbonate rock in the Tabei Uplift of the Tarim Basin forms important fractured reservoir beds. Core and log data indicate that tectonic fractures, as the main fractures in the Tabei Uplift, could be mainly classified into two types: oblique fractures and approximately vertical fractures. The fractures are mainly NNW‐trending and NNE‐trending, coincident with the large faults nearby. Fracture abundance was also controlled by lithology, and faults nearby played a significant role. Cores, thin sections and tests show that these carbonate rocks have as much as 2.5% fracture porosity and as much as 150 md fracture permeability. Based on the intersection of fractures in cores, together with fluid inclusion temperature data, and the timing of faulting from seismic profiles, tectonic fractures were considered to be mainly formed in three periods: the late Silurian when the first‐stage oblique fractures were formed, the late Permian when approximately vertical fractures were formed, and the late Tertiary when the second‐stage oblique fractures were formed. Lower Cambrian source rocks started to enter the stage of generous hydrocarbon generation and expulsion in the Silurian. Ordovician source rocks started to enter the stage of generous hydrocarbon generation and expulsion in the Permian and enter the over‐mature stage in the late Tertiary when light oil was generated. Timing of tectonic fractures formation and burial history analysis suggest that fractures formation might coincide with oil accumulation when fractures provided the pathway and storage space for the low permeability and low porosity reservoir beds caused by previous compaction and cementation. Considering the presence of a large amount of fracture‐developed dolomite in the deeper Ordovician Penglaiba Formation, the undrilled Penglaiba Formation should be paid more attention. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
15.
When deriving velocity models by forward modelling or inverting travel time arrivals from seismic refraction data, a heterogeneous but isotropic earth is usually assumed. In regions where the earth is not isotropic at the scale at which it is being sampled, the assumption of isotropy can lead to significant errors in the velocities determined for the crust and the depths calculated to reflecting boundaries. Laboratory velocity measurements on rocks collected from the Haast Schist terrane of South Island, New Zealand, show significant (up to 20%) compressional (P) wave velocity anisotropy. Field data collected parallel and perpendicular to the foliation of the Haast Schist exhibit as much as 11% P-wave velocity anisotropy. We demonstrate, using finite-difference full-wavefield modelling, the types of errors and problems that might be encountered if isotropic methods are used to create velocity models from data collected in anisotropic regions. These reflector depth errors could be as much as 10–15% for a 10-km thick layer with significant (20%) P-wave velocity anisotropy. The implications for South Island, New Zealand, where the problem is compounded by extreme orientations of highly anisotropic rocks (foliation which varies from horizontal to near vertical), are considered. Finally, we discuss how the presence of a significant subsurface anisotropic body might manifest itself in wide-angle reflection/refraction and passive seismic datasets, and suggest ways in which such datasets may be used to determine the presence and extent of such anisotropic bodies. 相似文献
16.
In order to better constrain the interpretation and the nature of the seismic reflectors, experimental measurements at high confining pressure (up to 300 MPa) and room temperature of the compressional wave velocity (Vp) on 10 samples representative of the most common lithologies along the Aurina (Ahrntal), Tures (Tauferer Tal), and Badia (Abtei Tal) Valleys profile (Eastern Alps, Italy) have been performed. For each sample, the speed of ultrasonic waves was measured in three mutually perpendicular directions, parallel and normal to the rock foliation and lineation.The main results are:(a) Good agreement between the calculated vs. measured modal compositions of the considered rocks, indicating that they were presumably equilibrated at the estimated P–T conditions; therefore, the seismic properties are representative of the crustal level indicated by the thermobarometry.(b) Measured and calculated average Vp are in good agreement, and are typical of mid-crustal level (6.0–6.5 km/s). Only the amphibolites show Vp typical of the lower crust (7.2 km/s).(c) The seismic anisotropy of metapelites is very high (12–27%), both with orthorhombic and transverse isotropy symmetry; amphibolites are transversely isotropic with an anisotropy of 8%; orthogneisses and granitoids are isotropic or weakly anisotropic.(d) The contacts between amphibolites and all other rock types may generate good reflections, provided they are not steeply inclined. Although the metamorphic foliation remains steeply inclined, discordant buried sub-horizontal igneous contacts may be detected. 相似文献
17.
The excitation of structural components and liquid contents of surface impoundments by seismic waves can generate turbulence
that is large enough to overtop the bounding berms. In cases in which the liquids are wastes from industrial/municipal operations,
their release from impoundments can pose significant risks to the environment. In this analysis, the freeboard magnitudes
that can accommodate liquid head levels in impoundments are determined through linkage of configuration of waves in the liquid
surface to incident seismic wave characteristics, liquid characteristics and impoundment design. For an impoundment site in
a region of ground acceleration levels ranging from 0.2 to 1.0 g and impacted by seismic shear wave velocity of 180 m/s, freeboard
requirements are in the range of 0.004–2.0 m on soft soil; 0.008–0.7 m on medium-dense soil; and 0.002–0.1 m for dense soil.
For the same impoundment design, ground acceleration and incident wave characteristics, freeboard requirements are directly
proportional to the depth of the soil mantle over bedrock. The impoundment slope, which is a key parameter with regards to
liquid holding volumetric capacity of the impoundment, is a less significant parameter than depth to bedrock with regard to
the size of the required freeboard. This implies that siting of an impoundment should be considered to be critical to impoundment
performance in seismic zones. 相似文献
18.
论述压裂过程中诱发微地震的激发机理,分析人造裂缝与地应力关系并叙述了微震事件的定位方法。利用微地震监测技术,通过实时定位理论系统对深凹区BYHF1井页岩水平井分段大型压裂过程实时监测,运用偶极子测井和VSP资料建立监测井区的初始速度模型,并通过射孔炮对其校正。在对实时监测定位理论系统数据进行综合处理分析,及有效微震事件识别的基础上,利用纵波和横波信息分析计算得到微地震事件的位置,通过可视化技术对压裂井区裂缝发育的方向、大小、空间分布进行了描述,监测结果是裂缝发育方向基本上为NE34°,与成像测井结果吻合良好。 相似文献
19.
《Comptes Rendus Geoscience》2015,347(2):66-76
The precise determination and interpretation of anisotropy are relatively difficult because the apparent anisotropy is usually a mixture of intrinsic and extrinsic anisotropy, which might partly hide the true properties of the medium investigated. The artificial anisotropy can be due to the fact that seismic waves do not ‘see’ the real details of a medium, but a ‘filtered’ (or ‘upscaled’) version of the Earth model. This can be due to a bad quality of the data coverage, to limited frequency band effects, or to errors in the approximate theory. With the limitation to layered Earth models, through comparisons of the results of the homogenization method with those of the periodic isotropic two-layered model as an analytical solution, we illustrate that the Backus theory for the long wavelength equivalent effect can be extended to calculate the extrinsic anisotropy, due to upscaling effects at discontinuities for the general isotropic layered model, when its spatial scale is much less than or equal to the seismic wavelength. We find that the extrinsic radial S-wave anisotropy produced by the vertical heterogeneities in the upper mantle of the Earth can be as large as 3% (about 30% extrinsic anisotropy of the 10% radial anisotropy). To better recover information from seismic data, we propose a surface wave phase velocity inversion method based on the first-order perturbation theory. We show that resolution at discontinuities can be improved by adding overtone modes of surface wave data. For more general layered models, the homogenization method could be considered, which can flexibly adapt the scale of the model to seismic wavelengths. However, the periodic isotropic two-layered model can also help to analytically quantify the amount of extrinsic radial, and possibly azimuthal anisotropy produced by the tilted fine layering. 相似文献
20.
剪切波速判别地震液化势的适用性研究 总被引：4，自引：2，他引：4
本文阐述了剪切波速判别地震液化势的可行性, 对目前国内外各种剪切波速判别地震液化势的方法进行了分析对比, 指出公式(6)是一实用、可靠的判别方法。 相似文献