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直流电阻率测深中二维反演程序对三维数据的近似解释 总被引：5，自引：0，他引：5
直流电阻率测深剖面数据解释最好的方法是二维反演，这是由于它反演速度快，而三维反演则需要很多的实测数据、很长的计算时间。而且通过对几种三维模型测深数据的二维反演结果的研究，发现尽管对无走向的良导矿体，二维反演方法所圈定的异常中心与真实矿体中心有一定的误差，但基本上还是能反映矿体的真实形态和中心位置。当矿体具有一定的走向长度时，则无论对高阻矿体还是良导矿体二维反演的效果都很好。 相似文献
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RobertD.JACOBI 《《地质学报》英文版》2003,77(4):491-503
2-D and 3-D densities of fractures are commonly used in mining safety design, natural gas and oil production in fractured reservoirs, and the characterization of subsurface flow and transportation systems in fractured rocks. However, many field data sets are collected in 1-D frequency (f) (e.g., scanlines and borehole data). We have developed an ARC/ INFO-based technology to calculate fracture frequency and densities for a given fracture network. A series of numerical simulations are performed in order to determine the optimal orientation of a scanline, along which the maximum fracture frequency of a fracture network can be obtained. We calculated the frequency (f) and densities (both D1 and D2) of 36 natural fracture trace maps, and investigated the statistical relationship between fracture frequency and fracture density D1, i.e. D1=1.340f+ 0.034. We derived analytical solutions for converting dimensional density (D1) to non-dimensional densities (D2 and D3) assuming that fracture length distribution f 相似文献
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现今二维粒子图像测速（PIV）广泛应用,为进一步提高PIV测量结果对紊流及水流和泥沙相互作用机理的理解,分析了二维PIV中三维涡旋的可测性。结合涡旋识别的旋转强度方法、坐标旋转定理和紊流经典Burgers涡模型,推导得出:二维PIV能否检测出三维涡旋,主要受涡旋环量和旋涡与测量平面之间的倾角两个因素影响,且仅当涡旋环量大于某一特定值（为倾角的函数）时,三维涡旋才可以被测量出。利用广泛使用的直接数值模拟（DNS）槽道紊流数据统计分析,得出了该条件下倾角和环量的相关曲线与拟合方程;结合环量概率密度累积分布可知,在常规二维PIV实验中,涡旋被测量出的概率越大,相应的倾角也越大,其中以90%、50%和10%的概率被测量出的三维涡旋与测量平面间分别呈20°、11°和5°的倾角。 相似文献
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《Geomechanics and Geoengineering》2013,8(3):221-236
This paper presents a new point-to-face contact algorithm for contacts between two polyhedrons with planar boundaries. A new discrete numerical method called three-dimensional discontinuous deformation analysis (3-D DDA) is used and formulations of normal contact submatrices based on the proposed algorithm are derived. The presented algorithm is a simple and efficient method and it can be easily coded into a computer program. This approach does not need to use an iterative algorithm in each time step to obtain the contact plane, unlike the ‘Common-Plane’ method applied in the existing 3-D DDA. In the present 3-D DDA method, block contact constraints are enforced using the penalty method. This approach is quite simple, but may lead to inaccuracies that may be large for small values of the penalty number. The penalty method also creates block contact overlap, which violates the physical constraints of the problem. These limitations are overcome by using the augmented Lagrangian method that is used for normal contacts in this research. This point-to-face contact model has been programmed and some illustrative examples are provided to demonstrate the new contact rule between two blocks. A comparison between results obtained by using the augmented Lagrangian method and the penalty method is presented as well. 相似文献
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在现有几种锚杆数值分析方法的基础上,对考虑了浆体切向受力性态的三维锚杆单元理论及其应用进行了研究,编制了三维锚杆有限元计算程序,并结合例子对浆体锚杆的变形、应力规律进行了分析。计算结果显示了模型的可靠性和实用性。 相似文献
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In this paper, a nonlinear numerical technique is developed to calculate the limit load and failure mode of structures obeying an ellipsoid yield criterion by means of the kinematic limit theorem, nonlinear programming theory and displacement-based finite element method. Using an associated flow rule, a general yield criterion expressed by an ellipsoid equation can be directly introduced into the kinematic theorem of limit analysis. The yield surface is not linearized and instead a nonlinear purely kinematic formulation is obtained. The nonlinear formulation has a smaller number of constraints and requires less computational effort than a linear formulation. By applying the finite element method, the kinematic limit analysis with an ellipsoid yield criterion is formulated as a nonlinear mathematical programming problem subject to only a small number of equality constraints. The objective function corresponds to the dissipation power which is to be minimized and an upper bound to the plastic limit load of a structure can then be calculated by solving the minimum optimization problem. An effective, direct iterative algorithm has been developed to solve the resulting nonlinear programming formulation. The calculation is based purely on kinematically admissible velocities. The stress field does not need to be calculated and the failure mode of structures can be obtained. The proposed method can be used to calculate the bearing capacity of clay soils in a direct way. Some examples are given to illustrate the validity and effectiveness of the proposed method. 相似文献
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The geological and geodynamic evolution of the eastern Black Sea basin: insights from 2-D and 3-D tectonic modelling 总被引：1，自引：0，他引：1
Subsidence mechanisms that may have controlled the evolution of the eastern Black Sea have been studied and simulated using a numerical model that integrates structural, thermal, isostatic and surface processes in both two- (2-D) and three-dimensions (3-D). The model enables the forward modelling of extensional basin evolution followed by deformation due to subsequent extensional and compressional events. Seismic data show that the eastern Black Sea has evolved via a sequence of interrelated tectonic events that began with early Tertiary rifting followed by several phases of compression, mainly confined to the edges of the basin. A large magnitude (approximately 12 km) of regional subsidence also occurred in the central basin throughout the Tertiary. Models that simulate the magnitude of observed fault controlled extension (β=1.13) do not reproduce the total depth of the basin. Similarly, the modelling of compressional deformation around the edges of the basin does little to enhance subsidence in the central basin. A modelling approach that quantifies lithosphere extension according to the amount of observed crustal thinning and thickening across the basin provides the closest match to overall subsidence. The modelling also shows that deep crustal and mantle–lithosphere processes can significantly influence the rate and magnitude of syn- to post-rift subsidence and shows that such mechanisms may have played an important role in forming the anomalously thin syn-rift and thick Miocene–Quaternary sequences observed in the basin. It is also suggested that extension of a 40–45 km thick pre-rift crust is required to generate the observed magnitude of total subsidence when considering a realistic bathymetry. 相似文献
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Fu Liangkui Chen Fuji 《中国地质大学学报(英文版)》1990,(1)
This paper develops the boundary element method,the authors employtwo-layered earth Green’s functions as the weighting functions of residual andderive boundary integral equations.The forward problems of point sources on2-D and 3-D structures with an influencing cover are solved by this method.The results show that this method markedly improves the original boundaryelement method.The features of the improved method are greater numericalaccuracy and much smaller systems of equations and thus considerable savingsfor the storage capacity of computers,allowing us to solve the above problemswith only ordinary microcomputers.The results in this paper extend the scopeof applying the boundary element method while using electrical methods forgeophysical prospecting. 相似文献
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窝崩是冲积河流常见的一种崩岸类型，具有发展速度快、破坏力强等特点，且不易成功模拟。以长江下游扬中河段指南村窝崩为例，基于窝崩机理及其力学模式，采用考虑回流区紊动影响的挟沙力公式模拟窝塘内泥沙输移，初步建立了窝崩三维数值模拟方法。研究结果表明：窝崩发生初期窝塘内局部水流具有底层流速大于上层流速的特征，这为窝塘底部及坡脚淘刷提供了动力条件；窝塘内回流区水流挟沙力的计算对窝崩形态模拟结果存在显著影响，考虑回流区紊动影响的泥沙输移特性后，模拟结果与实测结果基本吻合，可较好地模拟窝崩的快速发展过程。研究成果可为窝崩机理的深入认识和窝崩治理提供科技支撑。 相似文献
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The GRACE mission has contributed to the seismic characterization of major earthquakes in offshore regions of the world. Here, we isolate satellite gravity signal (μGal range) for the Japan Earthquake of 2011 using a difference method. Contrary to the existing gravity models, we propose a unit vertical pyramid based five-layer 3-D thrust fault model, which extends to the hypocenter and honors the ocean water layer and sea floor upheaval also. Our model partly uses existing seismological information (hypocenter depth of 32 km, rupture length of 300 km and vertical slip of 4 m), provides a snapshot of episodic subduction of the Pacific Plate below the Atlantic Plate and its gravity response closely matches the observed gravity (RMS error of 3.4012×10?13μGal), fully accounting for co-seismic mass redistribution including sea surface deformation. Our inferred rupture length, rupture velocity, average seismic moment magnitude and momentum, respectively, are 300 km, 4.49 km/s, 1.152×1021?1.8816×1021 N m and 2.319×106 GNs, which fairly agree with the literature. Further, our model inferred momentum at the sea floor corresponds to an area pulse that led to Tsunami generation. 相似文献
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窝崩是冲积河流常见的一种崩岸类型,具有发展速度快、破坏力强等特点,且不易成功模拟。以长江下游扬中河段指南村窝崩为例,基于窝崩机理及其力学模式,采用考虑回流区紊动影响的挟沙力公式模拟窝塘内泥沙输移,初步建立了窝崩三维数值模拟方法。研究结果表明:窝崩发生初期窝塘内局部水流具有底层流速大于上层流速的特征,这为窝塘底部及坡脚淘刷提供了动力条件;窝塘内回流区水流挟沙力的计算对窝崩形态模拟结果存在显著影响,考虑回流区紊动影响的泥沙输移特性后,模拟结果与实测结果基本吻合,可较好地模拟窝崩的快速发展过程。研究成果可为窝崩机理的深入认识和窝崩治理提供科技支撑。 相似文献
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Accurate estimation of rockfall trajectory and motion behaviors is essential for rockfall risk assessment and the design and performance evaluation of preventive structures. Numerical simulation using discontinuous deformation analysis (DDA) is effective and helpful in rockfall analysis. Up to now, there have been many reports on application of two-dimensional (2-D) DDA programs. In this paper, the major advantages of rockfall analysis using 2-D and extensions to three-dimensional (3-D) analysis are presented. A practical 3-D DDA code is demonstrated to be capable of simulating free falling, rolling, sliding, and bouncing with high accuracy. Because rockfall trajectories and motion behaviors can be described as combinations of these four types, this demonstration indicates that the implemented code is capable of providing reliable rockfall analysis. Finally, specific tests are conducted to compare 2-D and 3-D DDA rockfall analysis in predicting trajectory and dynamic behavior. The results indicate that 3-D DDA simulations are more appropriate for rough tree-laden inclined slopes in providing detailed spatial distribution, whereas 2-D DDA simulations have better efficiency for slopes dominated by valleys and ravines. These results can help in selecting the appropriate DDA simulation for rockfall analysis. 相似文献
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三维地震数据的体绘制 总被引：5，自引：3，他引：5
体视化技术是三维地震数据浏览、分析和解释的有效工具。对于理解地震数据中蕴涵的结构和地层学信息，体视化比使用一组二维切片表示三维数据更自然。解释人员可以突出数据体中某些特定的区域体，以利于更好地理解它们的空间分布，也可以添加合并两个或者更多的，具有不同地震特征的体积区域。医学应用方面的一些体视化方法不能直接应用于地震数据方面．必须考虑地震数据自身特点才能使可视化成功实现。通过分析三维地震数据的特点进而得出实现三维地震数据体视化算法的基本方法，并对实际数据进行了实验。 相似文献
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CSAMT一维全区反演 总被引：2，自引：0，他引：2
由汉克尔变换和连分式求解水平层状大地电偶源的水平电场和垂直磁场,然后由电场和磁场求得卡尼亚视电阻率,不进行近区和中间区校正,直接用阻尼最小法对近区和中间区发生畸变的卡尼亚视电阻率反演,得到地下电性参数。模型试算结果表明:虽然近区和中间区的视电阻率不能正确反映地下电性垂向变化,但由其反演仍能得到正确的结果。 相似文献
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利用二维离散傅里叶变换（DFT）的一些性质，将Gunther提出的关于同时计算一个N点实序列的DFT和另一个N点实序列的DFT的逆离散傅里叶变换（IDFT）的4个新的直接公式中的第1和第4个公式，以及他提出的关于同时计算2个N点实序列的DFT的新公式推广到了二维的情形，并给出了相关证明。这些结果在处理实信号时是非常有用的。 相似文献