共查询到19条相似文献，搜索用时 281 毫秒
1.
边界积分方程法二维电阻率层析成像 总被引：1，自引：1，他引：0
本文基于作者在文献［１］中提出的边界积分方程,建立了一种新的二维电阻率层析成像方案。与目前国内外用有限元法和α中心法的成像方法相比,该方法无需计算雅可比矩阵,也不必做线性化近似。这不仅节省了计算时间,而且使成像迭代过程稳定,可以对实际上广泛存在的大电性对比度介质获得满意的成像效果,从而大大提高了电阻率层析成像技术的实用性。文中给出的数值模拟结果显示了该方法的有效性。 相似文献
2.
堆积层滑坡作为一种非线性系统变形演化规律复杂，准确量化坡体形变过程中滑移面边界变化、降雨入渗边界、水头边界和流量边界等重要参数是堆积层滑坡变形破坏机理研究的基础。此项研究基于电阻率成像技术，可依据岩土体成分、结构的不同和地层间电性的差异实现快速、多维剖面成像，并通过深度神经网络建立了浅层高分辨率电阻率成像数据和各类监测数据的“时间-空间-属性”邻近域特征信息统一表达矩阵，实现了各监测项空间权重的快速收敛。在此基础上，用逐层、逐个递推式回归分析方法分析深层电阻率成像数据，准确构建了反映堆积层滑坡形变过程的内部结构多维电性特征模型。试验证明，该方法有效地提高了各类边界参数基于地电信息成像监测结果的实时性和准确性，为堆积层滑坡形变破坏机理研究提供理论与方法支撑。 相似文献
3.
针对河堤、水坝、高速公路档水墙等存在多孔单元介质中的定常渗流问题,将渗流Laplace方程,通过数学变换转化为边界积分方程,进而离散为线性代数方程组。采用边界元编写FORTRAN程序。计算结果表明:该法与有限元法相比,占用CPU时间短,不需要网格化分,使繁杂问题简单化,同时很好地切近实际。 相似文献
4.
隧道绿色施工不仅需要预报工作面前方突水突泥等低阻异常,更需要查明灾害体的地质构造,为灾害预警与防治提供保障。传统的瞬变电磁解释方法仅能够提供单一电阻率信息不能满足隧道地质灾害治理要求。因此,将虚拟波场成像技术引入到瞬变电磁隧道探测技术中,期望实现灾害体电性与结构综合解释。首先,根据波场变换原理将瞬变电磁数据转换到虚拟波场;然后,利用电阻率成像算法计算工作面前方电阻率建立虚拟波场速度模型,利用波动方程克希霍夫积分解进行波场延拓实现瞬变电磁虚拟波场偏移成像;最后,综合电阻率与偏移成像结果对工作面前方地质体进行解释,判断地质灾害体的电性与构造特征。分别采用充水溶洞、充水断层两类常见灾害模型对算法进行验证。充水断层模型电阻率成像结果可以识别工作面前方低阻异常,但是异常分布范围略有增加,且不易判断倾斜角度;而偏移成像结果有效地识别异常的边界位置且对应准确,更易容判断异常倾斜方向。充水溶洞模型电阻率成像结果可识别溶洞的低阻异常与位置,但是异常形态与实际模型略有偏差;偏移成像结果圈定了模型的前后边界且与模型吻合较好。实测数据偏移成像结果有效圈定了低阻异常位置与裂隙形态,预测结果与已知出水孔情况相符。理论模型与实测数据结果表明,虚拟波场克希霍夫偏移成像结果既包含地质灾害体的电阻率分布,又能识别灾害体电性分界面,为地质灾害预警与防治提供了丰富的地质信息。 相似文献
5.
利用边界积分方程法对土质边坡失稳地球物理模型的视电阻率进行了系统数值计算，研究了土质边坡失稳的电阻率响应特征，揭示了边坡从稳定一失稳演化过程的电阻率变化规律，从而实现了边坡失稳的电阻率响应特征的提取。这些特征信息的获得为利用电法勘探方法探测土质边坡失稳的滑动面或结构面位置提供了依据，同时为实时观测，预测预报土质边坡失稳提供了理论支撑。 相似文献
6.
直流电井间三维直接成像 总被引：1，自引：0，他引：1
在分析电性不均匀体对电位影响的基础上，确定了直接成像的参数。该参数在井间没有电性不均匀体时，等于背景电阻率，而当井间存在低阻或高阻不均匀体时，则小于或大于背景电阻率，很好地反映了井间不均匀体的电阻率性质和位置。然后介绍了井与井之间成像参数的插值方法和用SURFER软件成像的方法，并给出了几个直接成像的例子。 相似文献
7.
电阻率层析成像是基于研究区域边界处的电压和电流值确定区域内部电阻率的分布,它同声波和电磁波层析成像原理有着本质的不同。讨论了电阻率层析成像正演最常用的有限元法,给出了电阻率层析成像反演法的模拟退火方法,并将其成功运用到电阻率成像反演中。应用实例显示,高密度电阻率二维层析成像的分辨率比常规电阻率法解释结果要高,应用前景广泛。 相似文献
8.
本文以二层介质中存在球体的模型为例，讨论了用边界元方法解决层状介质中存在三维不均匀体情况下点源场视电阻率的计算问题。文中通过对基本解的选取，避免了对水平界面的积分计算，并且在积分方程中消去了位的法向导数，使得积分方程的形式更为简单，也大大地减少了所需的边界剖分节点数和未知量的个数，节省了计算机内存，提高了计算精度。计算的结果表明，边界元法对本问题的研究是成功的。 相似文献
9.
为了提高煤矿井下钻孔瞬变电磁反演成像结果中的异常响应边界识别和解译能力,完成掘进工作面前方隐伏水害精准刻画、隐蔽致灾因素精细分析等地球物理解释,提出应用无监督机器学习中的聚类方法分析钻孔瞬变电磁处理成果。根据电阻率数值分布特征和2种聚类方法的特点,选择K-Means聚类算法对电阻率成像结果进行聚合分类;在聚类计算过程中,应用最远距离原则确定类簇的初始质心,选用欧氏距离作为距离计算方法,采用基于组内平方误差和的肘部法则确定聚类数目。针对掘进工作面前方的隐伏水害,分别采用三维数值模拟和井下现场应用实例进行了实用性和有效性验证。研究结果表明:该方法可自动识别最佳类簇数目,对电阻率实现准确聚类,聚类成像结果能改善原始成像模型的光滑过渡问题,突出异常响应边界,清晰显示异常响应形状和位置,有效帮助对钻孔瞬变电磁超前探测反演结果中的隐蔽致灾水体进行识别和归类。 相似文献
10.
借鉴医学ＣＴ发展起来的地学成像技术比常规物探方法具有更高的勘探精度和分辨率，文章介绍了该方法的特点、数学基础，并分别阐述了电磁波成像、地震成像和电阻率成像的原理，最后展望了地学成像技术的应用前景。 相似文献
11.
目前隧道及大型地下工程往往在裂隙岩体中开挖,而裂隙与地下空间的距离及裂隙的扩展条件,制约着隧道及地下工程的稳定性。应用能考虑孔洞和裂纹问题的新型边界积分方程与无网格加辽金法结合,建立一种新型的边界无单元法。在该方法中基本的未知量是由边界上的面力和边界上位移密度函数构成的复变量边界函数 。文中应用的边界积分公式和Muskhelishvili的积分公式直接相关。将无网格构造方法引入新型的边界积分方程,建立了新型的边界无单元法。应用该方法详细分析了含隧道和裂纹间相互关系等问题,其数值结果与解析结果吻合很好,说明该方法的正确性和可行性。 相似文献
12.
In part of a large abandoned mining complex, electromagnetic geophysical surveys were used along with data derived from cores and monitoring wells to infer sources of contamination and subsurface hydrologic connections between acidic refuse deposits and adjacent undisturbed geologic materials.Electrical resistivity increases sharply along the boundary of an elevated deposit of pyritic coarse refuse, which is highly contaminated and electrically conductive, indicating poor subsurface hydrologic connections with surrounding deposits of fine refuse and undisturbed glacial material. Groundwater chemistry, as reflected in values of specific conductance, also differs markedly across the deposit's boundary, indicating that a widespread contaminant plume has not developed around the coarse refuse in more than 40 yr since the deposit was created. Most acidic drainage from the coarse refuse is by surface runoff and is concentrated around stream channels.Although most of the contaminated groundwater within the study area is concentrated within the surficial refuse deposits, transects of apparent resistivity and phase angle indicate the existence of an anomalous conductive layer at depth (>4 m) in thick alluvial sediments along the northern boundary of the mining complex. Based on knowledge of local geology, the anomaly is interpreted to represent a subsurface connection between the alluvium and a flooded abandoned underground mine. 相似文献
13.
Gyesoon Park Samgyu Park Myeong-Jong Yi Hyoungrae Rim Seong-Jun Cho Jung-Ho Kim 《Environmental Earth Sciences》2010,60(5):965-974
Two-dimensional (2-D) electrical resistivity and three-dimensional (3-D) gravity explorations were undertaken to estimate
the 3-D distribution of karst cavities at the area of Yongweol-ri in Korea where ground subsidence has occurred. Although
the gravity method is a low-cost way of analyzing a 3-D continuous structure, its vertical resolving power is poor. In contrast,
the electrical resistivity method can provide a 2-D and/or 3-D subsurface structure with a much higher lateral and vertical
resolution than the gravity method. Accordingly, geostatistical methods and density information were used to enhance the 2-D
resistivity structure revealed by the electrical resistivity method into a 3-D structure. The assumptions are, first, that
each data set senses the same underlying geological structure in terms of different material properties and, secondly, that
two different material properties are correlated locally or globally throughout the entire target area. As a result, the distribution
of limestone cavities can be estimated under the assumption that they are mostly filled with groundwater and clayey soils
and have abnormally low levels of resistivity and density. The estimated distribution corresponds with the grouting, borehole
imaging and monitoring data. In this example, it can be seen that the integration analysis of 2-D electrical resistivity and
3-D gravity methods is a very powerful tool for 3-D subsurface imaging and that the method can provide enhanced imaging capabilities
for 3-D cavities. 相似文献
14.
O. Damisa 《国际地质力学数值与分析法杂志》1986,10(1):73-89
A problem common to most numerical methods of analysing the vibration of a rigid body on an elastic half space is indentified especially as regards the arbitrary truncation of the semi-infinite half space or the numerically expensive computations involved in some of the methods. This paper presents a boundary integral equation (BIE) method of defining a finite domain to replace the half space and consists of evaluating the BIE over the domain. A mathematical justification is provided for defining the domain, and the error involved in such truncation of the half space in shown to be small. Yet the computations are very cheap owing to the simple trigonometric/algebraic functions involved in the BIE. The accuracy of the method is quite commendable especially as seen from the results presented for the circular foundation for which analytical and experimental solutions are available for comparison. 相似文献
15.
高密度电法在工程勘察中的应用实例 总被引：2，自引：0，他引：2
介绍了高密度电法在覆盖层勘探、滑坡体勘探、土料场分层、采空区勘探、断层调查的几个应用实例。经工程实例表明,高密度电法可在工程勘察中取得良好的应用效果。 相似文献
16.
利用共轭梯度方法的激发极化三维快速反演 总被引：2，自引：0，他引：2
利用共轭梯度方法实现了激发极化(IP)三维快速反演。首先,利用共轭梯度方法反演电位数据,得到地下的三维电阻率模型,(由于避免了直接求偏导数矩阵,因此反演计算速度很快。)然后,以此电阻率模型为地下电导率分布,再反演IP数据得到三维极化率分布理论模型。试算结果表明其效果较好。 相似文献
17.
Twenty profiles of vertical electric soundings (VES) were obtained in a riverside alluvium at the Buyeo area, South Korea,
to examine the variations of subsurface geology and associated groundwater chemistry. The combination of the VES data with
the borehole data provided useful information on subsurface hydrogeologic conditions. The vestige of an ancient river channel
(e.g. oxbow lake) was identified on the resistivity profiles by the lateral continuation of a near-surface perched aquifer
parallel to the river. Such a perched aquifer is typically developed in the area with a clay-rich silty surface alluvium which
prohibits the infiltration of oxygen. Therefore, groundwater below the oxbow lake shows a very low nitrate concentration and
Eh values under the strong anoxic condition. The distribution of water resistivity is correlated with that of measured total
dissolved solids concentration in groundwater, while the earth resistivity of the aquifer shows a significant spatial variation.
It is interpreted that the earth resistivity of the aquifer is mainly controlled by the soil type rather than by the water
chemistry in the study area. 相似文献
18.
起伏地形对可控源音频大地电磁(CSAMT)响应具有强烈的影响,因此在CSAMT数据处理解释时需要考虑地形。同时,实际的地下地质情况和地表的地形情况通常比较复杂,地质结构和地形大部分情况下都是三维的。在水平地表三维有限差分CSAMT数值模拟算法的基础上,推导了利用地下交错网格采样点处的总磁场计算起伏地形下空气-地下介质分界面处的总电场和总磁场的表达式,从而实现了起伏地形下三维CSAMT数值模拟算法。在算法实现过程中,采用伪δ函数代替麦克斯韦方程中的场源项和直接计算总场的策略,避免了原有的将总场分离成背景场和二次场的策略在复杂地质条件下难以选择合适背景电阻率的问题。为了直接模拟总场,起伏地形下三维CSAMT数值模拟算法给出了新的三维正演方程的边界条件。将模拟水平地表三维异常体和三维山峰地形两个理论模型得到的响应结果与前人算法的计算结果进行对比,验证了所实现算法的正确性和有效性。 相似文献
19.
Bibi R. N. Gondwe David Ottowitz Robert Supper Klaus Motschka Gonzalo Merediz-Alonso Peter Bauer-Gottwein 《Hydrogeology Journal》2012,20(7):1407-1425
Geometry and connectivity of high-permeability zones determine groundwater flow in karst aquifers. Efficient management of karst aquifers requires regional mapping of preferential flow paths. Remote-sensing technology provides tools to efficiently map the subsurface at such scales. Multi-spectral remote sensing imagery, shuttle radar topography data and frequency-domain airborne electromagnetic (AEM) survey data were used to map karst-aquifer structure on the Yucatan Peninsula, Mexico. Anomalous AEM responses correlated with topographic features and anomalous spectral reflectance of the terrain. One known preferential flow path, the Holbox fracture zone, showed lower bulk electrical resistivity than its surroundings in the AEM surveys. Anomalous structures delineated inland were sealed above by a low-resistivity layer (resistivity: 1–5 Ωm, thickness: 5–6?m). This layer was interpreted as ejecta from the Chicxulub impact (Cretaceous/Paleogene boundary), based on similar resistivity signatures found in borehole logs. Due to limited sensitivity of the AEM survey, the subsurface configuration beneath the low-resistivity layer could not be unambiguously determined. AEM measurements combined with remote-sensing data analysis provide a potentially powerful multi-scale methodology for structural mapping in karst aquifers on the Yucatan Peninsula and beyond. 相似文献