共查询到20条相似文献，搜索用时 906 毫秒
1.
本文发展了建立在地层参考状态为各向同性介质假定下的现行井孔声弹性理论,就井外为横向各向同性面与井轴垂直的、具有9个独立三阶弹性模量的横向各向同性介质(VTI井况),水平面内受双轴应力作用下给出了一个简洁的与井内压力、应力差、应力和以及多极源偏振方位角有关的井孔弯曲波声弹公式,并且导出了平面纵、横波速度的声弹公式.数值考察了弯曲波速度之改变量的灵敏系数随频率的变化、受井外水平双轴应力作用时两种偏振的偶极弯曲波频散曲线以及对应不同方位径向偏振的横波速度.研究结果表明弯曲波声弹公式与5个二阶弹性系数以及7个独立的三阶弹性模量有关;而且由内压引起的井孔弯曲波声弹性公式中的三阶弹性模量仅与6个独立的弹性模量有关.横向各向同性介质井孔弯曲波速度的交叉现象仍是判断地应力存在的标志;一个重要的认识是受双轴应力作用的弯曲波速度变化在低频区主要与c144和c155两个三阶弹性模量有关,而且此认识与径向偏振的平面横波一致.在缺乏足够实验条件情况下,对VTI情况,以c144,c155和c123三个独立的量进行测量,然后可暂不考虑三阶弹性模量的各向异性,建立简化的应力反演公式.反之,如果已知地层的地应力信息,由简化的声弹公式可以反演三阶弹性模量c144,c155和c123. 相似文献
2.
A. J. Willson 《Pure and Applied Geophysics》1973,110(1):1977-1981
Summary A theoretical study is made of the propagation ofSH waves of small amplitude in an infinite elastic plate subjected to a primary normal stress. It is shown that the effect of the stress may be represented by a re-scaling of the plate thickness, provided that one elastic constant is also redefined suitably. 相似文献
3.
本文从数值上研究了裸眼井中弹性波传播的非对称模式,给出了合成微地震图和导波（弯曲波）的频散曲线,发现在“硬”地层和“软”地层的井中,导波都是高度频散的,其最大相速度等于地层的横波速度,其截止频率低于对称模式的伪瑞利波的截止频率;在低频（2-3kHz）和长源距（3-4m）的条件下,由非对称的声源（如声偶极子）所产生的微地震图中,初至信号是以横波速度传播的,而以纵波速度传播的信号被抑制。本文的结果对研制横波速度测井仪是有意义的。 相似文献
4.
A. J. Willson 《Pure and Applied Geophysics》1973,110(1):1967-1976
Summary The propagation of waves of small amplitude in an elastic medium composed of Hadamard material, satisfying also the Ordered Forces condition and the Strong Ellipticity condition, and subjected to a large homogeneous biaxial stress, is investigated in detail. Consideration is given to the existence and general properties of Rayleigh waves on the surface of a semi-infinite medium, and to the propagation of plate waves in a medium of finite thickness. 相似文献
5.
An alternative technique to obtain the dynamic response of a massless rigid circular foundation resting on a uniform elastic half-space when subjected to harmonic plane waves is presented. The technique relies on the use of an integral representation involving the free-field ground motion and the contact tractions obtained in the course of calculating the dynamic force–displacement relationship of the foundation for external forces. Tables listing the translational and rotational components of the response of the foundation for non-vertically incident SH, P, SV and Rayleigh waves are presented. 相似文献
6.
H. Wada 《地震工程与结构动力学》1983,11(1):21-31
An analysis is presented of the transient flexural vibrations of an elastic column supported by an elastic half-space under the condition that an arbitrarily shaped free-field lateral acceleration and displacement are given as inputs. Applying Laplace transformations with respect to time and numerical inverse Laplace transformations, the time histories of the column acceleration at the interface and free end, and the column and half-space displacement distributions are obtained. After the input free-field acceleration terminates, slightly damped and almost harmonically variable acceleration is observed. The acceleration frequency after the disappearance of the input acceleration nearly coincides with the resonant frequency of the system. The slight damping with the first resonant frequency, even if the half-space is soft compared with the column, is characteristic of the transient flexural vibrations of a column supported by a half-space. Such a phenomenon is not typical of the transient longitudinal vibration problem. Therefore, it may be concluded: when buildings and structures are subjected to an earthquake or an explosive force, their flexural vibrations will continue with their first resonant frequencies, even if their foundations are soft. 相似文献
7.
For a class of boundary value problems associated with flexural gravity waves, characteristics of the eigen-system are analysed which are used to study the convergence of the expansion formulae in both cases of single and two layer fluids in water of finite and infinite depths. Using Green’s function technique, the spectral representations of the vertical eigenfunctions are obtained which are used along with the orthogonal mode-coupling relations to prove the convergence of the expansion formulae. Using the expansion formulae flexural gravity wave scattering due to multiple articulations in the presence of compression are investigated. The problem is studied in both the cases of single-layer and two-layer fluids in finite water depth. Effects of compressive force, stiffness of the connectors, length of the elastic plates and water depth, position of interface on wave scattering by articulated plates are studied by analysing the reflection and transmission coefficients. This procedure of proving the convergence of expansion formulae is independent of water depth. The concept and methodology for dealing with wave-structure interaction problems discussed here can be generalised to deal with problems of similar nature arising in the broad area of mathematical physics and engineering. 相似文献
8.
A variational statement in the field of complex numbers and its semi-analytical solution are presented to study the wave propagation in plates resting on a Winkler foundation. The method and its computer program are verified by comparison with the available results for a freely supported plate and performing a time domain analysis for a plate-Winkler foundation system. A variety of wave propagation phenomena is observed, and useful information can be extracted from the results. The foundation is found to act as a low frequency band-stop filter for flexural modes, and a stiffer foundation leads to wider widths of these stop bands. As a sample application, a barrier design for controlling flexural motions in the system is proposed. The effectiveness of the design is also demonstrated. 相似文献
9.
Sh. Hosseini-Hashemi Mahmoud Karimi D.T. Hossein Rokni 《Soil Dynamics and Earthquake Engineering》2010
Hydroelastic vibration and buckling analysis of horizontal rectangular plates resting on Pasternak foundation and subjected to linearly varying in-plane loads is investigated for different boundary conditions. Fluid is assumed to be inviscid and incompressible. To analyze the interaction of the Mindlin plate with the elastic foundation and fluid system, three displacement components of the plate are expressed in the Ritz method by adopting a set of static Timoshenko beam functions satisfying geometric boundary conditions. Convergence study is first carried out to confirm the stability of the present method. Then, a few comparisons are made for limited cases between present results and the available data in the literature. Finally, parametric study is conducted to highlight the effects of loading factors, fluid levels, foundation stiffness parameters, aspect ratios, thickness to width ratios and different boundary conditions on the critical buckling loads and wet natural frequencies of rectangular plates. 相似文献
10.
The model studied in this paper presents an extension of previous work for a shear wall on a semi-circular rigid foundation in an isotropic homogeneous and elastic half-space. The objective is to develop a soil-structure interaction model that can later be applied to the case of a flexible foundation. As shown in the Introduction below, Luco considered the case of a rigid foundation subjected to vertical incident plane SH waves, and Trifunac extended the solution for the same rigid foundation subjected to SH waves but for arbitrary angles of the incidence. In this paper, a new approach and model are presented for the same semi-circular rigid foundation with a tapered-shape (instead of rectangular) superstructure. The analytical expression for the deformation of the semi-circular rigid foundation below this tapered shear wall with soil-structure interaction in an isotropic homogeneous and elastic half-space is thus derived. Results are then compared with those of Trifunac discussed in the section below. This problem formulation can and will later be extended in the case of a flexible foundation that is semi-circular or arbitrarily shaped. 相似文献
11.
V. P. Trubitsyn 《Izvestiya Physics of the Solid Earth》2012,48(2):93-103
The model of elastic rebound of thin plates is considered to account for GPS-inferred surface deformation of plates during
subduction earthquakes on the example of the M9 earthquake that occurred in Japan in 2011. Due to the fact that the oceanic
plate moves together with a great mass of the convective mantle, it dips into the mantle at constant velocity all the time,
both during the earthquakes and in the periods between them, although its coupling with the continental plate changes. The
edge of the continental plate behaves as an elastic plate that permanently bends under the action of the friction force on
contact with the diving oceanic plate. The bent plate unbends after the earthquake. This leads to its thrusting over the subducting
oceanic plate. As a result, the island plate moves towards the ocean, its island part sinks, and the oceanic plate uplifts
leading to a tsunami. The coordinates and magnitudes of the rise and subsidence correspond to the universal relations in the
elastic plate model. The breaking of coupling of the continental plate with the submarine mountains and a basaltic plateau
of the dipping plate is considered as a possible explanation of the anomalous properties of the strongest earthquakes. The
main earthquake can be produced by partial destruction of a plateau or a large mountain. After this, the locked plates become
free along a great area in an avalanche-like manner, and the friction of rest gives place to sliding friction. 相似文献
12.
岩石圈有效弹性厚度是表征岩石圈力学性质的参数,其反映了岩石圈挠曲变形的特征.本文在传统二维挠曲模型的基础上,提出了适用于俯冲及碰撞带的三维薄板挠曲模型.并发展了基于粒子群算法的俯冲带三维有效弹性厚度反演方法.该方法适用于挠曲参数存在横向差异的俯冲-碰撞带.最后利用该方法反演了马尼拉海沟处岩石圈的有效弹性厚度,结果显示:南海中央海盆岩石圈的有效弹性厚度随着距洋中脊距离的增加而增大;马尼拉海沟轴部弯矩在洋中脊两侧呈分段性变化,这表明南海俯冲板片在深部撕裂可能对浅部的挠曲形态产生影响. 相似文献
13.
采用三维有限差分方法模拟了正交偶极子声源在含偏心钻铤的充液井孔中激发的声场,研究了钻铤偏心对模式波的种类、激发幅度、以及频散特征的影响.研究结果表明,钻铤偏心导致偶极子声源激发的声场的模式不唯一,观察到了除偶极模式外的单极模式波和四极模式波;钻铤偏心导致偶极模式波出现分裂现象,尤其是快速地层F2模式和慢速地层弯曲波的稍高频率的部分,且快、慢波所对应的两个方位为偏心的方位和与偏心方位垂直的方向;井孔折射横波以及快速地层F2模式的低频部分的慢度基本未受到钻铤偏心的影响,仍然能够正确反映地层的横波慢度及各向异性;对于本文研究的慢速地层井孔模型,当偏心距离l小于等于0.01 m时,弯曲波的慢度和激发幅度受钻铤偏心的影响很小,从快、慢弯曲波中提取的快、慢横波慢度基本能够反映地层的各向异性特征. 相似文献
14.
Summary The propagation of waves of small amplitude in an incompressible elastic medium subjected to a large homogeneous equibiaxial stress is investigated. The dispersion equation for surface waves on a semi-infinite medium is obtained explicitly, and the dispersion equation for waves in a slab of finite depth. In the latter case, approximate values, valid for waves whose lengths are much greater than the slab thickness, are determined for the phase-velocities of the different modes. 相似文献
15.
M. R. Sarangi 《地球物理与天体物理流体动力学》2013,107(3):303-325
ABSTRACTA hydro-elastic frame has been considered to investigate the proliferation of waves over small base deformation on an infinitely extended flexible seabed. The flexible base surface is assumed as a thin elastic plate of very small thickness and it depends on the Euler–Bernoulli beam equation. For any particular frequency, there are two different modes of time-harmonic propagating wave exists rather than one mode of propagating wave along the positive horizontal direction. The waves with smaller wavenumber spread along the free-surface of the sea (say, free-surface mode) and the waves with higher wavenumber spread along the flexible base surface (say, flexural mode). A simplified perturbation approach is utilised to bring down the entire equations which govern the original boundary value problem (bvp) to a less complex bvp for the first-order velocity potential function. The first-order potential function along with the first-order reflection and transmission coefficients for both modes are calculated by a procedure based upon Fourier transform approach. A shape of sinusoidal swells flexible base surface is taken as an example to approve the scientific results. It is observed that when the train of normal incident propagating wave spreads over base distortion because of either the free-surface unsettling influence or the flexural wave movement in the sea, the reflected and transmitted energy are always feasible to be exchanged from one particular wave mode to another wave mode. Furthermore, we notice that the realistic changes in the flexural rigidity behaviour on the flexible base surface of the sea have a significant effect on the problem of water wave proliferation over small base deformation. Moreover, the energy conservation equation is derived with the help of the Green's integral theorem. The results for the values of reflection and transmission coefficients obtained for both the free-surface unsettling influence as well as flexural wave movement in the fluid are found to satisfy the energy conservation equation almost accurately. 相似文献
16.
A. J. Willson 《Pure and Applied Geophysics》1972,95(1):48-58
Summary The propagation of small-amplitude plane waves through a homogeneous, isotropic elastic medium, with a particular form of strain-energy function and subjected to a large primary deformation, produced by a homogeneous biaxial stress, is considered in detail. The properties of such waves in an unbounded medium, the conditions for their existence, their speeds and their polarisations are investigated and similar results are also obtained for Rayleigh surface waves. 相似文献
17.
传统板块构造理论认为板块是一个刚体，实际上板块是可变形的.板块内部几年到几十年时间尺度的变形主要是弹性变形,因此应当用弹性模型描述板块运动.推导了板块的弹性运动方程，由空间大地测量新的观测成果建立了菲律宾海、太平洋和澳大利亚板块的弹性运动模型.发现三个板块内部都存在明显的水平形变.板内应变场的空间变化有明显的规律：板块边界附近的应变率最大，从边界向内部逐渐减小；在板块扩散边界附近，主张应变率大于主压应变率，主张应变轴基本上与边界的扩张方向一致；在俯冲边界附近，主压应变率大于主张应变率，主压应变轴基本上与板块的俯冲方向一致；在走滑兼有俯冲性质的边界附近，最大剪应变的方向与边界断裂的走向基本一致.由GPS观测得到的主压应变轴与由震源机制解得到的主压应力轴方向具有很好的一致性.板内的应力－应变场基本上遵循广义胡克定律. 相似文献
18.
A. J. Willson 《Pure and Applied Geophysics》1972,93(1):5-18
Summary The propagation of waves of small amplitude in an elastic medium, with a particular form of strain-energy function, and subjected to a large homogeneous uniaxial stress, is considered in detail. The main characteristics, including speed and polarisation, of these waves in an unbounded medium are calculated numerically, and the existence and general properties of Rayleigh waves on the surface of a semi-infinite medium are investigated. 相似文献
19.
We investigated the buckling response of a faulted elastic plate under horizontal compression using the finite element technique to better understand the effect of faults on the elastic behavior of a plate. We studied the effect of changes in fault spacing, depth and dip on the effective Young's modulus, buckling stress and wavelength. Our model consists of a thick elastic plate whose entire upper surface is cut by evenly spaced faults. We impose either an initial sinusoidal deformation with a fixed wavelength or a random deformation to the grid. A fault is represented as a free surface with no resolved shear stress and is allowed to slip in a specified direction using the method of slippery nodes. With the assumption of free slip on the faults, our model results represent an end member case in which the buckling wavelength and buckling stress are minimized by the presence of the faults.In our models, fault depth was varied from 0 to 75% of the plate thickness. As strain increases, the grid deforms by antisymmetric flexural folding and the initial imposed wavelength of deformation is modified such that the new buckling wavelength emerges. Our results show that the effective Young's modulus is a decreasing function of fault depth and an increasing function of fault spacing. In addition, buckling of the plate occurs at a lower stress for greater fault depths. Buckling wavelength is independent of the initial deformation wavelength however, it is modified by the presence of faults. For a plate with closely spaced faults extending through at least 75% of the plate, buckling occurs at a wavelength one half as large as that for a continuous plate. Buckling stress is not independent of the intial deformation wavelength, rather it increases slightly with increasing difference between the initial deformation wavelength and the buckling wavelength.Analytical models that approximate or ignore the effect of faulting can have large errors in calculation of the buckling stress. More importantly, modeling the observed wavelength of deformation in a faulted region with analytical solutions for continuous plates may result in a significant underestimate of elastic thickness. Fault dip does not strongly affect either the effective Young's modulus or the buckling wavelength. Thus, the buckling response should be the same for a plate cut by a low angle fault or a high angle fault. 相似文献
20.
Carla Braitenberg Jörg EbbingHans-Jürgen Götze 《Earth and Planetary Science Letters》2002,202(2):387-404
An unconventional scheme is used to estimate the flexural rigidity, or equivalently the elastic thickness of the lithosphere, given the topography and gravity data. The flexural rigidity is the parameter that governs the flexural response of the lithosphere in the frame of the thin plate flexure model. The scheme is an alternative to the widely used calculation of admittance of topography (sea-floor or continental topography) and gravity, bearing some advantages which are explained in the paper. The scheme involves the inversion of the gravity data in order to formulate a model of the crust-mantle interface (CMI) undulations. In a second step the flexure parameter is then evaluated from the relation between topography and CMI variations. Instead of calculating the admittance function using a spectral analysis, a set of point-load response functions are used in order to retrieve the optimal flexure parameter. This has two main advantages: instabilities of the numerical admittance evaluation at wavenumbers with low spectral energy in the topography are overcome and the analysis can be made over an area which is not necessarily rectangular, as required for the spectral analysis. The proposed method allows a higher space resolution of elastic thickness than any spectral method. For validation, the numerical strategy is applied to the situation of a realistic synthetic model, where all inputs and outputs are known a priori. Finally the spatial variations of the elastic thickness are studied in an area across the Eastern Alps. 相似文献