共查询到20条相似文献，搜索用时 15 毫秒
1.
Inversion of residual gravity anomalies using neural network 总被引：1，自引：1，他引：0
Mansour A. Al-Garni 《Arabian Journal of Geosciences》2013,6(5):1509-1516
A new approach is presented in order to interpret residual gravity anomalies from simple geometrically shaped bodies such as horizontal cylinder, vertical cylinder, and sphere. This approach is mainly based on using modular neural network (MNN) inversion for estimating the shape factor, the depth, and the amplitude coefficient. The sigmoid function has been used as an activation function in the MNN inversion. The new approach has been tested first on synthetic data from different models using only one well-trained network. The results of this approach show that the parameter values estimated by the modular inversion are almost identical to the true parameters. Furthermore, the noise analysis has been examined where the results of the inversion produce satisfactory results up to 10% of white Gaussian noise. The reliability of this approach is demonstrated through two published real gravity field anomalies taken over a chromite deposit in Camaguey province, Cuba and over sulfide ore body, Nornada, Quebec, Canada. A comparable and acceptable agreement is obtained between the results derived by the MNN inversion method and those deduced by other interpretation methods. Furthermore, the depth obtained by the proposed technique is found to be very close to that obtained by drilling information. 相似文献
2.
Ozkan Kafadar 《Earth Science Informatics》2017,10(4):525-537
CURVGRAV-GUI is an open source software that was developed to interpret gridded gravity data by using curvature technique. It was developed using C# language with Microsoft.NET Framework 4.0. This program calculates the critical and extreme points, and estimates the depths of source bodies at this points. Besides, CURVGRAV-GUI processes gravity data by using minimum curvature, one of the attributes of curvature, and detects the subsurface lineaments. It is a user-friendly application that can display obtained solutions and gravity data thanks to image and scatter maps. CURVGRAV-GUI was designed to develop both synthetic and field applications. Additionally, the β constant, a parameter related to the source geometry, was examined for different source types such as sphere, horizontal and vertical cylinder and thin vertical fault. This program was tested by using two synthetic model applications. In the first synthetic model application, it was used a complex synthetic model consisting of three sphere and a horizontal cylinder located at the different depths. In the second synthetic model application, a graben model consisting of two thin vertical fault was used. Finally, the performance of the CURVGRAV-GUI was tested with using a real gravity data belonging to Kozakli-Central Anatolia region, Turkey. Very successful results were obtained for both synthetic and field data. Earth scientist can use CURVGRAV-GUI for educational experiments. 相似文献
3.
G. Ramadass I. Arunkumar S. M. Varaprasada Rao N. L. Mohan N. Sundararajan 《Journal of Earth System Science》1987,96(3):211-219
The auxiliary functions, namely amplitude, phase, envelope and instantaneous frequency of Hilbert transform over gravity anomalies
of 2-D sphere, vertical fault block and horizontal circular cylinder are studied. The characteristics of these functions are
established in locating and identifying the sources. The method is illustrated with a theoretical example in each case and
supported by field data of gravity anomaly over Humble dome and spherical model of the Satak-Mansar area, Nagpur District,
India. 相似文献
4.
G. Ramadass S. M. Varaprasada Rao A. Raja Mohammed 《Journal of Earth System Science》1986,95(3):343-349
A simple technique for the interpretation of gravimagnetic anomalies by a numerical differentiation is presented. The ratio of horizontal gradient to the observed field was used for the location of the origin and depth to the causative body. This technique was tested by using fundamental expressions due to sphere, horizontal cylinder and vertical fault models and field data over a spherical body. It has been found that the depth to the centre of the body can be determined accurately by this technique. 相似文献
5.
W. Bangerth H. Klie M. F. Wheeler P. L. Stoffa M. K. Sen 《Computational Geosciences》2006,10(3):303-319
Determining optimal locations and operation parameters for wells in oil and gas reservoirs has a potentially high economic impact. Finding these optima depends on a complex combination of geological, petrophysical, flow regimen, and economical parameters that are hard to grasp intuitively. On the other hand, automatic approaches have in the past been hampered by the overwhelming computational cost of running thousands of potential cases using reservoir simulators, given that each of these runs can take on the order of hours. Therefore, the key issue to such automatic optimization is the development of algorithms that find good solutions with a minimum number of function evaluations. In this work, we compare and analyze the efficiency, effectiveness, and reliability of several optimization algorithms for the well placement problem. In particular, we consider the simultaneous perturbation stochastic approximation (SPSA), finite difference gradient (FDG), and very fast simulated annealing (VFSA) algorithms. None of these algorithms guarantees to find the optimal solution, but we show that both SPSA and VFSA are very efficient in finding nearly optimal solutions with a high probability. We illustrate this with a set of numerical experiments based on real data for single and multiple well placement problems. 相似文献
6.
笔者对地球内部压力分析提出了楔状体压力模式,即地球内部某深度单位面积(水平)上的压力(垂向)等于由该截面和所有经由该截面边缘的重力线所围限的楔状岩体的重量。据此模式,理论上地球内部压力随深度呈抛物线状急增,在地心处无穷大。但由于地球固液(塑)圈层交替存在及冷收缩,导致楔状岩体重力引起的作用力可分解成水平的侧向压力和垂向静岩压力,并随深度呈锯齿状升降变化。当岩石圈侧向压力增加导致岩石圈破裂(构成板块),在重力的向心力作用下,板块间相互错动形成俯冲带和拉张带,继而牵引软流圈构成远程对流运动,进而引发一系列地质构造作用。因此认为,地球的构造动力源于地球重力本身,其中侧向压力是地质构造的初始起动力和驱动力,引起的对流运动既是地质构造运动学表征又是动力学作用,重力势能及其转变的热能构成对流运动的最主要动力能源。 相似文献
7.
规则体重力异常余弦变换谱特征及反演 总被引：1，自引：0，他引：1
提出利用余弦变换,研究规则体重力异常谱特征及反演方法。推导出球体、无限长水平圆柱体、无限和有限延伸垂直台阶的重力异常余弦变换谱及反演表达式。球体与无限长水平圆柱体的余弦变换谱相似,无限延伸垂直台阶的变化很尖锐,有限台阶的表现为上、下有规律的跳跃。在模型反演算例中,选择了适当的采样间隔和“趋势镶边”法,反演的圆柱体线密度和轴心深度误差分别为0.25%和3.8%。 相似文献
8.
改进的重力模拟退火反演研究 总被引：14，自引：0，他引：14
通过对模拟退火方法中常用的VFSA算法的分析，针对其在模型扰动及退火计划上存在的缺陷，针对性地作了更合理的改进VFSA算法，提高了VFSA算法的计算速度与稳健性，并结合重力反演过程中对模型的修正，克服了常规重力反演方法所存在的等值效应。研究中还把重力正演计算的单元体改为垂直侧边梯形单元，并合单同一层位的垂直侧边梯形单元成为一大单元再作计算，加快了正反演计算速度并提高了正反演精度。通过模型试验及实际资料的处理，验证了作者所提出的改进的模拟退火重力反演方法的有效性。 相似文献
9.
黄土湿陷过程中微结构变化规律的电阻率法定量分析 总被引：8，自引：0，他引：8
针对现代土力学中土的微结构定量分析的困难,考虑到电阻率法在土的微结构研究中的突出优点,引入电阻率法进行黄土湿陷过程中的微结构变化规律定量分析,探讨土电阻率法在土的微结构定量研究中的应用。以典型的非饱和黄土为研究对象,通过同步测定黄土湿陷过程中土样的竖向与横向电阻率大小,计算出土电阻率结构性参数指标,包括土的竖向与横向结构因子、平均结构因子、各向异性系数与平均形状因子的大小,分析了黄土湿陷过程中土电阻率结构性参数的变化规律,建立了定量描述黄土微结构变化规律的电阻率评价方法。试验研究表明,土的电阻率法具有连续、快捷与测试方便等诸多优点,通过土的电阻率结构性参数指标的研究,可有效进行土的微结构变化定量分析。 相似文献
10.
Characteristic curves for the complete interpretation of a wide range of parameters of a vertical cylinder and a horizontal circular disc are presented. It is established that the distance of the inflexion point on the gravity profile of a vertical cylinder from the point of maximum anomaly [i.e. the origin] is approximately equal to the radius of the vertical cylinder, thus enabling one to demarcate the boundary of the vertical cylinder directly from the contour map based on the cluster of contours. Two gravity profiles, one across an anomalous zone in central Alberta, Canada and the other over Borsad area, India are interpreted by the curves presented and the results are shown. 相似文献
11.
模拟退火优化算法的冻土热传导参数反分析 总被引：1，自引：0，他引：1
土体热参数是寒区工程温度场预测和稳定性分析至关重要的参数。根据冻土温度场计算的特点,建立冻土一维相变热参数估计模型,采用非线性有限元法得到土体温度场,基于一种非常快速的模拟退火（VFSA）算法对热参数进行反分析。考虑各个参数的敏感度因子和土体分层情况,将热参数分组、分步进行反演,克服参数较多反演困难的缺陷。以青藏公路多年冻土区监测断面下土体反分析为例,反演分析冻土路基下部不同土层的导热系数、体积热容量和孔隙率等参数。最后,运用参数反演结果对温度场进行预测,经检验和与实测地温对比,表明参数反分析结果可靠,有较高的精度,该方法可用于实际工程。 相似文献
12.
13.
隧道围岩结构地震动稳定性分析的动力有限元强度折减法 总被引：3，自引：0，他引：3
为了得到隧道围岩结构的地震动安全系数,借助通用有限元软件ANSYS,首先对水平地震作用下的模型进行模态分析,得到质量阻尼系数和刚度阻尼系数;其次由静力分析模型得到竖向边界上的水平向支座反力,然后将结构自重转化为温度边界条件,通过热分析得到模型各节点的温度,从而实现在动力分析中考虑重力的影响;最后采用悬臂梁动力分析模型,导入热分析获得的模型各节点的温度,并在竖向边界上施加水平向支座反力,通过不断折减围岩塑性区的凝聚力c和内摩擦角?,直到计算不收敛为止,从而得到隧道围岩结构的地震动安全系数。数值算例结果表明：采用的方法是可行的,将围岩结构自重转化为节点温度的措施解决了以往动力分析不能考虑结构自重的难点,进而为以后地震作用下隧道动力安全系数的计算及其工程应用提供了理论依据。 相似文献
14.
顺层岩质边坡地震动力响应研究 总被引：1，自引：0，他引：1
地震作用下边坡的动力响应研究是边坡动力稳定分析的基础,利用FLAC3D有限差分软件建立一个顺层岩质边坡动力数值模拟模型,对其在竖向和水平向地震耦合作用下的动力响应全过程进行研究。研究表明,地震竖向和水平向耦合作用模拟比简单的模拟水平向振动更加接近实际情况,对岩土体的破坏更大;顺层岩质边坡在耦合地震作用下存在垂直放大和临空面放大作用;坡面水平向和竖向加速度均随高程增加呈增大趋势,在结构面处增大特别明显;竖向地震波产生的水平与竖向拉裂是触发斜坡体产生初期崩滑破坏的主控因素;边坡动力响应特征值的放大效应表明,其放大系数值从大到小依次是：竖向加速度＞水平加速度＞竖向速度＞水平速度;耦合地震波作用下,随着av /aH的增大,坡面监测各点横向位移基本呈增大趋势,说明竖向地震作用起了重要的破坏作用。 相似文献
15.
目前大地电磁测深法的一维正演理论,是基于平面波垂直入射水平层状介质的假设模型。但由于地球是一个球体,因此有必要研究基于球状介质模型的大地电磁正演理论。这里详细推导了基于球体层状介质模型的大地电磁正演公式,计算了若干理论模型。通过同基于水平层状介质模型的大地电磁正演结果对比,验证了正演公式的正确性。同时,指出当探测周期增加到上万秒时,阻抗相位会增大;而当探测周期增加到数十万秒时,视电阻率会减小。 相似文献
16.
Sunil M. Rangari Deepankar Choudhury D. M. Dewaikar 《Geotechnical and Geological Engineering》2013,31(2):569-580
In this paper, the limit equilibrium method is used to compute seismic passive earth pressure coefficients and the vertical uplift capacity of horizontal strip anchors in presence of both horizontal and vertical pseudo-static earthquake forces. By considering a simple planar failure surface, distribution of soil reaction is obtained through the use of Kötter’s equation. Presence of pseudo-static seismic forces induces a considerable reduction in the seismic passive earth pressure coefficients. The reduction in seismic passive earth pressure coefficients increases with increase in magnitude of the earthquake accelerations in both horizontal and vertical directions and with increase in wall friction angle. The vertical uplift capacity of horizontal strip anchor is obtained for various values of soil friction angle, embedment ratio and seismic acceleration coefficients in both horizontal and vertical directions by using rigorous computational optimization. Proper justification for selected value of wall friction angle is established. Results are presented in the form of non-dimensional breakout factor for anchor. A significant reduction in breakout factor is observed in presence of both the seismic acceleration coefficients whereas breakout factor increases with increase in soil friction angle and embedment ratio even under the seismic condition. Angles of failure planes keep changing with change in seismic acceleration coefficients and failure zone shifts towards the critical direction of seismic acceleration coefficients. Present results are compared and found in good agreement with some specific available results in literature. 相似文献
17.
Fitian R. Al-Rawi 《Arabian Journal of Geosciences》2013,6(11):4239-4244
Three procedures can be utilized to determine the depth to the center of the horizontal cylinder from gravity profile. Firstly, the gravity profile is subjected to a simple filtering technique. Then, the maximum slope lines are drawn along the flanks of the filtered profile. The horizontal distances between the two slope lines for the positive part are measured at various amplitude levels. A plot of the horizontal distances against amplitude values will give an inclined straight line. The first procedure of depth estimation consists of measuring the distance between the points of intersection of the maximum slope lines at zero level background. This distance, for the positive or negative part, after it is multiplied by the empirical factor, gives directly the depth to the center of the horizontal cylinder. The other two procedures involve fitting a least square line to the inclined straight line of horizontal distances against amplitude values. Then, the maximum amplitude value of the filtered profile multiplied by an empirical factor is used to determine the depth, either graphically or through a simple equation. Accurate results have been achieved with low error percentages for a large number of gravity profiles due to synthetic horizontal cylinders having various depths and radii. 相似文献
18.
The effects of uncertainty due to the variability of soil parameters on the risk of landsliding in the Himalayan region are investigated using a random field model combined with slope stability analyses. Effects of spatial variability both in horizontal and vertical directions, number of test samples, variations in piezometric level and the influence of earthquake on the reliability of a typical slope in a slide area are investigated. The results show that the reliability of slopes in the slide area is significantly affected by the coefficients of variation of soil parameters, spatial variations of soil parameters, number of test samples and piezometric variations. The results also show that the assumption of isotropic variations to assess slope reliability isconservative. The results of the study are useful in providing guidelines and pointing to remedial measures in the form of sub-surface drainage to improve slope reliability in the area. 相似文献
19.