共查询到19条相似文献，搜索用时 125 毫秒
1.
单程波近似实际上是一种多次前向散射和单次后向散射近似.利用单程波近似来描述波传播可以极大地节省地震数值模拟的计算时间和内存,实现地震波长距离传播模拟和三维地震模拟快速计算.本文基于单程波近似和波动积分方程的分离变量逼近,从广义Lippmann-Schwinger波动积分方程推导出耦合反射/透射系数的单程波传播算子.该算子由两部分构成：分离变量Fourier单程波传播算子和薄板间的反射/透射系数表达.前者将常规的Fourier分裂步单程波传播算子(SSF)推广适应横向强速度变化介质和大角度传播波场.后者是利用垂直波数来表示反射/透射系数,自然耦合到波场传播的计算过程中,其为地质界面倾角的隐式表达,精确描述振幅随入射角的变化,能适应任意复杂的模型.通过两个数值算例和一个实际地质模型的计算,本文将该方法和边界元法进行了比较,结果表明：在算例给出的介质横向速度变化情况下,本文提出的方法在相位和振幅方面与全波数值方法基本吻合. 相似文献
2.
应力波作用下节理面前后电磁辐射强度的变化 总被引：2，自引：0，他引：2
从压电体中的压电本构方程出发,得到了含石英等压电介质岩体在应力波作用下产生的电场值的关系表达式．电磁辐射强度随电阻率增大而增大,随传播距离发生衰减．对于电阻率较大导电性能较差的岩石来说,压电电荷的贡献是足够引起重视的．利用所得到的表达式对实际地震电磁信号幅值进行了估算,所得结果与实测结果吻合．依据所得到的电场值的表达式及应力波在节理面处的透射解,获得了垂直入射应力波作用下产生的电磁波在线性变形节理面前后的强度关系．研究了节理参数、岩体电性参数以及入射波频率对节理面前后电磁辐射强度的影响．结果表明,电磁辐射的强度随节理初始刚度增大而增大;对于节理面两侧岩体性质不同的情形,从理论上讲,电磁辐射强度随单个参数的变化是明确的,但在多种参数的综合影响下,电磁辐射强度变化情况相对比较复杂．本文的理论计算结果与其它众多学者得出的实验结果一致． 相似文献
3.
黏弹各向异性介质中传播不均匀波，其反射、透射模式不仅与介质分界面两侧速度对比有关，还与品质因子Q的对比有关. 用伪谱技术模拟黏弹各向异性介质分界面上波的反射、透射，并与弹性各向异性介质、黏弹各向同性介质和弹性各向同性介质的模拟结果做比较. 计算平面波的反射、透射系数，分析介质的黏弹性和各向异性对反射、透射系数的影响. 数值模拟了一个三层介质模型中的波场，分析两个分界面上产生的反射波的特征. 黏弹各向异性介质中，qS波比qP波衰减程度大. 相似文献
4.
给出了重力波在中层大气温度波导中的反对称形式导制传播的线性理论模型，并采用二维非线性的数值模型对重力波波包在中层大气温度波导中的传播和演变过程进行了模拟研究.模拟的结果表明，下层大气激发的重力波能量进入波导区域后被俘获形成导制传播.重力波在波导内不停地来回反射，垂直方向的自由传播受到限制，能量在波导内沿着水平方向传输，模拟得到的波参数与理论值相近.重力波包在温度波导中传播时伴随着能量泄漏，且能量泄漏的速率随时间变缓，最终总有部分能量被限制在波导区域.重力波在水平方向上传播几百公里后，依然维持着良好的波结构，同时数值模拟也给出了重力波在波导区域内能量密度的时空分布. 相似文献
5.
通过对向上传播的重力波波包在中层大气中的非线性传播过程进行数值模拟,讨论中层大气中重力波的饱和机制.数值模拟结果表明,向上传播的重力波波包的扰动振幅在接近波包的本征水平相速度之前随高度单调增长,而当波振幅接近本征水平相速度时,在对流不稳定区域出现等位温面的翻转,同时波振幅的增长达到饱和（波振幅随高度不发生变化）.小尺度对流在等位温面的翻转和波饱和发生后产生,随后波包开始破碎,这些非线性过程的最终结果产生湍流.表明导致重力波饱和的关键因素是等位温面的翻转而不是诸如波破碎、湍流、波-流相互作用等其他的一些物理过程. 相似文献
6.
针对地震槽波在低速层的传播特性，开展了煤层内地震槽波勘探的数值模拟和物理模拟研究的初探工作.在数值模拟研究方面，采用交错网格有限差分法对煤层中的地震槽波进行三分量全波场模拟.基于波场快照和人工合成地震记录研究了不同模型中的波场特征和各种波型的传播规律.在物理模拟方面，通过选用不同配比的环氧树脂和硅橡胶类材料构建地震槽波物理模型，利用透射法和反射法观测系统获得了清晰的地震槽波记录以研究槽波的地震学特征.研究表明，在煤层内槽波的地震波场中，Love型槽波的能量小于Rayleigh型槽波的SV分量，大于Rayleigh型槽波的SH分量.相对于Love型槽波和Rayleigh型槽波的SH分量，Rayleigh型槽波的SV分量在围岩中的泄露能量较强.在煤层界面附近的围岩中，地震波仍以槽波形式传播，随着距离的增加能量逐渐衰减.随着煤层变薄，煤层槽波主频向高频方向移动，频散现象增强，传播速度增大. 相似文献
7.
虑传播效应的多波保幅AVO正演(英文) 总被引：1，自引：1，他引：0
传统的AVO正演只考虑了单一界面的反射系数对地震波波场振幅的影响,忽略了地震波在介质中传播的各种传播效应。通过引入地震波在介质中传播的几何扩散、吸收衰减以及透射损失等传播效应,提出了基于射线理论的水平层状介质多波保幅AVO正演方法。推导了水平层状介质多波几何扩散校正公式,来描述多波在介质中传播的几何扩散效应。通过直接引入复旅行时,而无需借助复速度,建立了复旅行时与品质因子的关系,来描述粘弹介质的吸收衰减。直接求解Zoeppritz方程计算多波的透射系数,用于描述多波在介质中传播时的透射损失。数值计算表明,几何扩散、吸收衰减以及透射损失对多波振幅的影响是随偏移距变化而变化的,多波保幅AVO正演需要考虑波传播效应对反射波振幅的改造。 相似文献
8.
转换波方位各向异性裂缝检测技术研究及应用 总被引：1，自引：0，他引：1
HTI裂缝各向异性介质中,转换波随方位角的变化比较复杂,目前还没有解析公式可以表达其变化特征,只能通过物理实验或数值模拟来分析其应用的可能性.数值模拟结果表明,转换波在裂缝各向异性介质中传播时,其R分量和T分量的振幅属性都具有明显的方位各向异性特征,R分量振幅方位各向异性拟合椭圆的长轴方向指示裂缝方位,这与纵波方位各向异性特征相似;根据P波AVAZ方位各向异性分析原理,对转换波R分量振幅方位各向异性曲线进行方位椭圆拟合,寻找椭圆的长轴方向,即裂缝主方位,再由P波AVAZ技术中振幅响应与炮检方向和裂缝走向之间的夹角关系式得到裂缝的发育密度,从而构建转换波方位各向异性AVAZ裂缝检测技术.该技术已用于川西新场气田某区块的裂缝储层预测,取得了较好的应用效果. 相似文献
9.
使用高灵敏度的电容式微压波传感器对1998年4月11日16时发生在贵州省普定县的一次降冰雹过程的重力波进行观测,利用WRF（Weather Research and Forecast）中尺度模式对这一过程进行数值模拟,使用Morlet小波方法对模拟结果进行分析,得出这一过程中惯性重力波的分布和变化规律,并分析急流、地形及切变线对惯性重力波的影响.观测发现：在降冰雹前,每隔1~4小时出现一次短周期重力波阵性增强的现象.数值模拟结果显示：在低空降冰雹前几个小时有强的短周期重力波出现,其中周期较长的出现早、存在时间长,周期较短的出现晚、存在时间短;强的低空急流和风速垂直切变触发对流或湍流的发生和加强,对流或湍流又激发了80~200 min的短周期重力波;短周期重力波更容易向垂直方向传播,而长周期重力波倾向于水平方向传播.长周期重力波在降冰雹后周期有明显变短现象,随高度越加明显.由地形形成的重力波在最高山峰上空振幅最大. 相似文献
10.
对球形空腔偏心解耦爆炸进行了数值模拟,得到了不同方向和不同爆心距节点的S波和P波速度曲线以及岩石单元中拉伸应力的传播过程。结果表明：空腔偏心解耦爆炸激发的S波具有方向性,S波幅值与对应P波幅值相当,激发S波的物理机制是振荡的拉伸应力,它等效于偶极子震源。 相似文献
11.
Due to the presence of joints, waves are greatly attenuated when propagating across rock masses. Zhu et al. (2011) (Normally incident wave propagation across a joint set with virtual wave source method. J. Appl. Geophys.73, 283–288.) studied normally incident wave propagation across a joint set with the virtual wave source method (VWSM). The introduced VWSM has merits in some aspects, especially the capability of separating differently arriving transmitted waves. However, normal wave incidence is only the special case for wave incidence with arbitrary incident angles. Obliquely incident wave propagation across a joint set is more complicated than normally incident wave propagation due to wave transformation at the joints. As a continuation of the previous paper, this work is extended to analytically study obliquely incident wave propagation across joints with VWSM. Complete theoretical reflection and transmission coefficients across single joint described by displacement discontinuity model are derived through plane wave analysis. The superposition of P wave and S wave is for the first time mathematically expressed and studied. The VWSM is verified through comparison with the propagation matrix method. Through extensive parametric studies on wave transmission across single and multiple parallel joints, it is shown that transmitted wave energy is mainly constrained in the transmitted wave of the same type as the incident wave. And with increasing joint stiffness, the transmission coefficients across single joint increases except those whose wave type is different from the incident wave. The amplitude of superposed transmitted wave for P wave incidence increases with incident angle, which is coincident with field observations. Both joint spacing and number of joints have significant effects on transmission coefficients. We find that when joint spacing is sufficiently large, the transmission coefficient is no longer a constant as the normally incident wave propagation case (Zhu et al., 2011). And when joints are very closely spaced, wave attenuation depends little on the number of joints, which is different from the conclusions from equivalent medium method. 相似文献
12.
The present study essentially employs a thin-layer interface model for filled rock joints to analyze wave propagation across the jointed rock masses. The thin-layer interface model treats the rough-surfaced joint and the filling material as a continuum medium with a finite thickness. The filling medium is sandwiched between the adjacent rock materials. By back analysis, the relation between the normal stress and the closure of the filled joint are derived, where the effect of joint deformation process on the wave propagation through the joint is analyzed. Analytical solutions and laboratory tests are compared to evaluate the validity of the thin-layer interface model for filled rock joints with linear and nonlinear mechanical properties. The advantages and the disadvantages of the present approach are also discussed. 相似文献
13.
This paper presents an analytical study on normally incident wave propagation across a joint set. Combined with the displacement discontinuity method (DDM), the virtual wave source method (VWSM) is adopted to take account of multiple wave reflections among joints. After theoretical formulation, a comparison between results from VWSM and those from the method of characteristics (MC) is carried out. These results agree well with each other, and the applicability of VWSM into wave propagation study is verified. Subsequently, an interesting phenomenon, i.e., the magnitude of transmission coefficient increases with joint number on some circumstances, is pointed out and studied. By analyzing differently arriving transmitted waves and their superposition, such phenomenon is explained. 相似文献
14.
在弹性力学和波动理论的基础上,运用时域和频域计算方法分析出平面SH波穿越地裂缝介质时的传播规律。通过引入地裂缝界面等效切向刚度等有关参数,对出平面波传播的频域及时域分析方法进行对比验证,分析地裂缝界面的等效切向刚度、入射波频率、入射角和裂缝面剪切强度对穿越地裂缝时出平面SH波的传播规律的影响。多个参数的交叉对比分析结果表明,等效切向刚度或入射角度越小,地裂缝界面的低通滤波效应越明显。裂缝面的剪切滑移导致透射波速在达到临界值时被截止。输入实际地震波时,随着透射系数的减小,透射波幅值减小不明显但波形变化较大;反射波幅值和波形将逐渐趋近入射波,但相位相对于入射波存在一定的滞后。为得到真实有效的波动传播规律,采用线性内插对波动时程数据进行处理,结果表明本文方法不会影响计算的精度。 相似文献
15.
这种方法的基本根据是:（一）震源地方岩体錯动的方向与横波离源时的方向、横波离源时的射綫方向在一个平面內;（二）横波在传播过程中,β角变化很小. 推导了由S波β角求横波离源时位移方向的公式.由两个台上的S波β角就可分別求得两个横波离源时的位移面,这两个面的交綫就是震源地方岩体錯动的方向。討論了在烏尔夫网上具体运用这一方法的作图.这就大大地簡化了求解的过程,便于大量处理数据。 相似文献
16.
M. J. Selby 《地球表面变化过程与地形》1982,7(5):449-467
In identifying controls on rock slope form a distinction is made between: (1) rock slopes with joints which dip steeply out of a cliff and hence are subject to mass failure of the rock mass above a critical joint; and (2) rock slopes with inclinations which are either in equilibrium with the mass strength of their rocks, or have profiles which will develop towards strength equilibrium as cross joints open. In the first class of slope, stability results not just from the basic frictional resistance of the rock but also from the frictional roughness along the critical joint and from the normal stress acting across that joint. Stability may be reduced by weathering and loss of strength of the joint wall rock. As a result of normal stress variations with depth, induced by overburdens, high cliffs which are not undercut have a concave profile. The second group of slopes includes those with inclinations controlled at the scale of individual joint blocks, buttressed slopes and those on unjointed rock masses. Buttressed and unjointed rock masses develop towards a condition of mass strength equilibrium as cross joints open. Strength equilibrium slopes may be recognized by application of a rock mass strength classification proposed for geomorphic purposes. Eleven propositions are formulated which identify controls on rock slope development and some consequences of these controls. 相似文献
17.
Average elastic properties of a fluid‐saturated fractured rock are discussed in association with the extremely slow and dispersive Krauklis wave propagation within individual fractures. The presence of the Krauklis wave increases P‐wave velocity dispersion and attenuation with decreasing frequency. Different laws (exponential, power, fractal, and gamma laws) of distribution of the fracture length within the rock show more velocity dispersion and attenuation of the P‐wave for greater fracture density, particularly at low seismic frequencies. The results exhibit a remarkable difference in the P‐wave reflection coefficient for frequency and angular dependency from the fractured layer in comparison with the homogeneous layer. The biggest variation in behaviour of the reflection coefficient versus incident angle is observed at low seismic frequencies. The proposed approach and results of calculations allow an interpretation of abnormal velocity dispersion, high attenuation, and special behaviour of reflection coefficients versus frequency and angle of incidence as the indicators of fractures. 相似文献
18.
The propagation characteristics of blast-induced shock waves in a jointed rock mass have been monitored and studied. Accelerometers were set up on a rock surface along three lines, at 0°, 45° and 90° with respect to the orientation of the predominant joint strikes. Cylindrical charges were detonated in a charge hole, and ground accelerations in both vertical and radial directions at various points on the rock surface were recorded. Results show that rock joints have significant effects on the propagation characteristics of blast-induced shock waves. The amplitude and principal frequency of shock waves attenuate with the increase of distance from the charge centre, and the increase of incident angle between the joint strike and the wave propagation path. The measured data were compared with the empirical equations of shock wave attenuation proposed by other authors. The mechanism of rock joint effect, the attenuation of shock waves in relation to the propagation distance, the charge weight and the incident angle, are discussed in this paper. 相似文献
19.
地震作用下节理岩质边坡稳定性影响因素研究 总被引：1，自引：0，他引：1
汶川地震灾害调查表明,在基岩山区地震滑塌主要发育在局部强度相对较大、节理较发育的厚层或块状岩体中.以岩石中含两组节理的岩质边坡为例,输入实际的地震记录,采用离散单元法进行数值模拟,分别探讨坡高、地震烈度、坡角及节理倾角组合对节理岩质边坡稳定性的影响.结果表明:地震作用下坡体中质点的加速度、速度具有高程放大效应;节理岩质边坡稳定性随着坡高、坡角和地震烈度的增加而降低;两组节理不同组合的岩质边坡,其稳定性变化较为复杂,受节理倾角与坡角的关系、节理的倾向、两组节理之间夹角等因素的影响.节理岩质边坡在地震作用下是受拉区逐渐向受剪区扩展而最终导致边坡失稳破坏,是受拉和受剪的复合破坏.上述初步结论为评价山区节理较发育的岩质边坡在地震作用下的稳定性提供一定的依据. 相似文献