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1.
Note on stresses produced by a shearing force moving over the boundary of a semi-infinite transversely isotropic solid 总被引：1，自引：0，他引：1
S. P. Sur 《Pure and Applied Geophysics》1963,55(1):72-76
Summary Two dimensional problem of distribution of stresses produced by a pulse of shearing force moving uniformly on the boundary of a semi-infinite transversely isotropic solid has been studied here. It is observed that the shearing stress in the direction of propagation of pulse attains maximum value at a point directly below the point of application of the shearing force on the boundary. 相似文献
2.
Champa Mazumder 《Pure and Applied Geophysics》1973,105(1):810-815
Summary In this paper the displacement due to an impulsive twist produced by impulsive shearing stresses acting on a finite circular area on the plane surface of a semi-infinite solid of homogeneous anisotropic material has been found.Paper presented by Dr. A. K. Mitra of Jadavpur University. 相似文献
3.
通过饱水砂岩的三轴压缩实验, 研究了含水层砂岩的破裂过程及其伴随的水化学变化, 并探讨了砂岩在蠕变和剪切破裂过程中地震水化异常现象的形成机理。 用离子色谱仪(IC)和等离子原子发射光谱仪(ICP-OES)测定了不同压力条件下实验溶液的F-、 Cl-、 NO-3、 SO2-4、 Ca2+、 Mg2+、 Na+浓度。 饱水砂岩在差应力作用下, 随着蠕变时间延长和剪切作用的强化实验, 溶液中主要离子的浓度均有不同程度的增大, 仅Mg2+浓度是降低的。 F-和Cl-浓度变化最明显, 在2~12小时的蠕变时间内分别增大约10倍和4倍, 而随剪切作用的强化分别增大约5倍和3倍。 这种变化主要与矿物的溶解和流体包裹体的混入有关。 实验结果表明, F-、 Cl-和Ca2+可作为砂岩含水层地震水化前兆监测的灵敏组分。 相似文献
4.
Spatial distribution of principal stresses in a layered elastic medium is considered in the paper. Transformations of the principal stresses across an interface between the layers are analyzed. A method for reconstructing the spatial stress distributions in layered medium from several spot measurements is proposed. The introduced approach is capable of obtaining the stable solution of the stress reconstruction problem with respect to the noise in input data. A typical layered medium is considered for which the stresses are reconstructed from few independent spot measurements of the stress state. The proposed approach may be used for solving an inverse problem of tectonic stresses reconstruction from the borehole logging data. 相似文献
5.
In the Bay of Islands ophiolite complex both the basal part of the cumulate gabbro sequence and the underlying peridotites have been plastically deformed. Higher in the series the cumulate gabbros are undeformed except in localized shear zones slightly to strongly oblique to the layering. The resulting shear bands are narrow and composed either of mylonitic amphibole-bearing gabbros or of highly foliated amphibolites.The amphibole composition and nature, and the chemistry of coexisting minerals combined with structural evidence imply that a first episode of shearing subhorizontal in the crust occurred at decreasing temperatures ranging from 750 to 450°C. This shearing probably represent the response of the lithosphere to stresses also responsible of asthenospheric flow in the upper mantle. A second episode of shearing oblique to the first one and probably related to cooling of the crust away from the ridge, occurred at lower temperatures ranging from 500 to 300°C. The surrounding gabbros have undergone static hydrothermal metamorphism at temperatures decreasing from 650 to 450°C. All metamorphic events occurred in hydrous conditions in the vicinity of the ridge axis. 相似文献
6.
采用有限元方法模拟了渤海湾盆地黄骅坳陷的现今应力场特征.模型的构建主要基于黄骅坳陷精细三维地震数据体,包括了七个主要层序底面及近真实的断层产状.根据模拟结果,对比已知油气藏的分布位置和断裂的展布方向,定量分析了黄骅坳陷第一主应力、第三主应力、应力强度以及主应力方向的分布特征,并探讨了影响黄骅坳陷构造特征的主要因素.据此,得出以下认识:1)通过改变模型的边界条件发现,在右旋剪切作用下模型中压性应力场低值区的分布特征及主应力方向分别与黄骅坳陷中已知油藏的分布及断裂展布方向具有较好的对应关系.2)黄骅坳陷内构造样式及其构造应力场方向自北向南存在一定的差异,而造成这种差异的原因与地形的变化、沧东断层空间形态的变化、断层组合样式的变化以及滑脱面的变化密切相关. 相似文献
7.
N. C. Maiti 《Pure and Applied Geophysics》1978,116(1):198-211
The displacement produced in a semi-infinite, homogeneous, isotropic elastic medium by the application of shearing traction over a circular portion of the half-space has been evaluated in exact form by Cagniard's Technique (Cagniard, 1962;Gakenheimer andMiklowitz, 1969). 相似文献
8.
The formation structures of brittle destruction in a rock layer above an active strike-slip fault in the crystalline basement is studied. The problem is analyzed from the standpoint of loading history, when after the stage of pure gravitational loading, an additional strain state of uniform horizontal shear of both the layer and underlying basement develops, which is further followed by a vertically nonuniform shear caused by the activation of the deep fault. For the studied object, irreversible fracture deformations on macro- and microlevels arise as early as the initial stage of loading under the action of gravitational stresses. These deformations continue evolving on the megascopic level in the course of horizontal shearing that is quasi-uniform both along the depth and laterally. The final formation of the structural ensemble occurs after a long stage of horizontal displacement of the blocks of the crystalline basement—the stage of localized shear. The theoretical analysis of the evolution of the stress state and morphology of the failure structures established the presence of numerous fractures with the normal dip-slip components in the intermediate-depth part of the rock mass, which are formed at the stages of uniform and localized horizontal shearing. The fractures with a strike-slip component mainly arise in the upper and near-axial deep parts of the section. 相似文献
9.
Arabinda Mukhopadhyay 《Pure and Applied Geophysics》1967,67(1):43-53
Summary The disturbances produced in a semi-infinite visco-elastic medium and in a layer of visco-elastic material resting on a rigid foundation by transient torsional body forces have been considered. Formal solutions have been obtained for a general type of body force, and this solution has been used to obtain the displacements for a transient torsional point source in the case of a semiinfinite medium, and for a cylindrical source of finite dimensions and a line source in the case of the layer of visco-elastic material mentioned above. Solutions have also been obtained for a transient shearing stress applied at the free surface of the layer mentioned above. 相似文献
10.
Sukhendu Dey 《Pure and Applied Geophysics》1971,90(1):38-52
Summary In this paper, the frequency equation for phase velocity of waves propagated in a laminated medium consisting of two eleastic layers of finite thickness under initial stresses, has been obtained. It has been shown that when wave length becomes very small compared to the thickness of each layer, the wave approaches two Rayleigh waves at the two outer surfaces with the possibility of Stoneley waves at the interface. The propagation ofSH-waves in the composite medium under initial stresses has also been discussed. A particular case has been taken to find the velocity of Love wave in the homogeneous half space under initial compressive stresses.Biot's incremental deformation theory has been used. 相似文献
11.
Seismic response of underground pipelines is investigat?ed theoretically considering dynamic soil-pipe interaction. A lumped mass model of the pipe is employed with the soil reactions derived from static and dynamic continuum theories. The soil is supposed to be homogeneous or composed of two different media separated by a vertical boundary. Axial and bending stresses in the pipe due to travelling waves are examined. An extensive parametric study indicates that the axial stresses in the pipe are much higher than bending stresses. In a homogeneous medium, soil-pipe interaction reduces the stresses in the pipe compared to those calculated ignoring interaction. In a soil composed of two different media, the pipe stresses are highest close to the boundary and can exceed those predicted neglecting interaction. 相似文献
12.
阐述了断层泥石英颗粒ＥＳＲ信号达到零化的温度和压力环境，通过４个具体ＥＳＲ测年实例，论述了测年样品的不同零化程度和测年数据的可靠性。对ＥＳＲ信号与ＴＬ（热释光）信号零化环境的差别及其原因进行了初步的探讨。介绍了断层测年样品ＥＳＲ信号达到零化的验证的方法。同时，提出了断层测年样品采集时应注意的有关问题 相似文献
13.
Previously reported low luminescence of basal glacial sediment has raised the possibility that processes operating at the ice–bedrock interface have the potential to reset (or ‘bleach’) natural luminescence signals (Swift et al., 2011). This finding indicates that certain types of glacial sediment (for example, sub-glacial diamicts) might be amenable to dating using luminescence-based techniques. Using a purpose-built ring-shear apparatus situated in a light-controlled environment, we have investigated the potential for mineral grains to be reset when subjected to conditions similar to those experienced by sediment that has undergone transport at the ice–bedrock interface. Reported here are the preliminary results of an initial experiment that used medium quartz sand with a naturally-acquired palaeodose of ∼4.3 Gy that had been obtained from a relict dune system. Incremental sampling during the shearing experiment and measurements were made to track changes in the luminescence properties of the sand as strain/shearing increased. The results indicate that increased strain/shearing resulted in an increase in the number of zero-dose grains and evolution of the De distribution from unimodal to multimodal. In light of the very much longer shearing distances that sub-glacial sediment would endure in nature, these results would appear to suggest that geomechanical processes at the ice–bed interface of glaciers and ice sheets may be a viable mechanism for resetting sediment. 相似文献
14.
A. K. Sarker M. Sc. 《Pure and Applied Geophysics》1963,55(1):42-52
Summary In this paper, surface displacements of theSH type of motion due to time-dependent body forces and due to sudden introduction of a discontinuity in the shearing stress in a semi-infinite, homogeneous, isotropic, viscoelastic medium have been worked out by the use of Laplace and Fourier transforms. The displacements due to a point force and due to a stress discontinuity over a fixed region have been calculated numerically. 相似文献
15.
Formulas are derived for two-dimensional problems relating stresses across a plane boundary that divides infinite homogeneous
half-spaces being in welded contact. The calculations are made for both anti-plane and in-plane stress cases. The results
obtained for the former case that involve only two stress components are useful in the analysis of fracture of strike-slip
type. For the in-plane case, the relations that link stresses in one half-space with the corresponding homogeneous stresses
in the other half-space are presented for arbitrarily oriented shear and normal stresses and for the center of compression
(dilatation). The above relations provide a compete set of expressions that, among other things, make it possible to analyze
stresses involved in faulting of deep-slip type in an inhomogeneous medium. The quantitative preliminary evaluations based
on the results obtained demonstrate the great role of low rigidity media in fracture processes of all kinds within the Earth’s
crust. 相似文献
16.
Measurements of the anisotropy of magnetic susceptibility (AMS) of natural lavas have shown that AMS varies with depth within a lava flow. We have investigated the reasons for such variation by studying the effects of temperature and strain rate on the AMS of recent lava in the laboratory. Samples of lava from Kilauea were melted and subjected to a range of strain rate and cooling histories. The results show that the degree of anisotropy is a function of both the thermal and shearing history of a sample. High degrees of anisotropy were found only in samples that were deformed at temperatures close to those encountered during eruption and then rapidly quenched. Lavas subjected to similar shear stresses at high temperatures had low degrees of anisotropy if allowed to cool down slowly without further deformation. Additionally, lava subjected to complex shearing yield a lower degree of anisotropy even when high strain rates were imposed on it. These results lead to the conclusion that only the last phase of deformation is detectable using AMS and that high strain rates will not result in high degrees of anisotropy if either deformation ends while lava is still fluid or if the orientation of the maximum shear stress varies with time. The relation between the orientation of the principal susceptibilities and that of shear is less sensitive to variation on shear with time. Consequently, flow directions can be inferred confidently with this type of measurements. 相似文献
17.
A modified parallel IWAN model, which includes a cyclic hardening function, is proposed and verified. The proposed model consists of elasto-perfect plastic and isotropic hardening elements. The model is able to predict cyclic hardening behavior through the adjustment of the internal slip stresses of its elements beyond the cyclic threshold, and satisfies Bauschinger's effect and the Masing rule with its own behavior characteristics. The cyclic hardening function is developed based on the irrecoverable plastic strain (accumulated shear strain) of dry sand during shearing, which is assumed to be a summation of shear strain beyond the cyclic threshold. Symmetric-limit cyclic loading and irregular loading tests were performed to determine model parameters and to verify the behavior of the proposed model. Finally, a one-dimensional site response analysis program (KODSAP) is developed by using the proposed model. The effects of cyclic hardening behavior on site response are evaluated using KODSAP. 相似文献
18.
Summary Theoretical expressions are derived for the displacement, velocity and stress in the time domain induced by an axially symmetric shearing stress applied at the inner surface of a spherical cavity in a hornogeneous, isotropic, elastic medium of infinite extent. Theoretical seismograms are computed for a step source and for three sources with exponential decay in time. A satisfactory time-dependence of the source can be obtained by combining the step source with one or more exponentially decaying sources. 相似文献
19.
为了研究不同基础形式下河水对成层软土地基上建筑物地震反应的影响,构建了结构-基础-土-河水体系动力相互作用的非线性完全有限元计算模型,在考虑土体重力的前提下,对筏片基础、桩筏基础、箱形基础、桩箱基础相互作用体系进行了时域数值分析。计算结果表明,建筑物靠近河水时,筏基和箱基体系顶部位移发生了向河水一侧的偏移,而采用桩基和桩箱基础时其偏移度明显减小。同种基础形式下,建筑物距河水越远,其框架剪力峰值越大,而不同基础形式的同种工况,桩箱基础时柱剪力最大,筏片基础时最小。单纯筏基和箱基时,基础周围土体均大量进入塑性,上部结构仍保持弹性;而采用下部有桩基础的筏基或箱基时,地基土体只有很少量进入塑性,上部框架结构进入了塑性。 相似文献
20.
Constitutive equations for drained cohesionless soils under triaxial stress states, based on a microslip model with internal friction, are proposed and applied to the analysis of the seismic response of soil deposits. The microslips, assumed localized in the discontinuity surfaces passing through the particle-to-particle contacts, describe the effects of the sliding and rolling between grains of sand. Once the response of the model under cyclic shearing stresses and strains superimposed on the geostatic stress state has been analysed, the constitutive equations are applied to a one-dimensional shear model for the dynamic analysis of the layered deposits. An application to an instrumented soil deposit is then developed, the experimental results of which refer to both strong and weak motion earthquakes; the comparisons between the experimental and theoretical results point out the peculiarities and validity limits of the model. The model here developed may be applied also to the analysis of two- and three-dimensional sites. 相似文献