Optimization approach to retrieve soil surface parameters from single-acquisition single-configuration SAR data

This study suggests a novel approach to the retrieval of soil surface parameters using a single-acquisition single-configuration synthetic-aperture radar (SAR) system. Soil surface parameters such as soil moisture and surface roughness are key elements for many environmental studies, including Earth surface water cycles, energy exchange, agriculture, and geology. Remote sensing techniques, especially SAR data, are commonly used to retrieve such soil surface parameters over large areas. Several backscattering models have been proposed for soil surface parameters retrieval from SAR data. However, commonly, these backscattering models require multi configuration SAR data, including multi-polarization, multi-frequency, and multi-incidence angle. Here we propose a methodology that employs single-acquisition single-configuration SAR data for the retrieval of soil surface parameters. The originality is to use single-acquisition single-configuration SAR data to retrieve the soil surface parameters using an optimization approach by the genetic algorithm (GA); we have used the modified Dubois model (MDM) in HH polarization as the backscattering model. Three HH polarization and C band data sets from Quebec (Radarsat-1), Ontario (SIR-C), and Oklahoma (AIRSAR) were analyzed. The retrieved values of soil moisture and soil surface roughness were then compared to ground truth measurements with corresponding parameters. We employed diverse criteria, including the mean absolute error (MAE), the root mean square error (RMSE), the coefficient of performance (CP), and the correlation coefficient to investigate the performance of the proposed methodology. This analysis suggests the capability of the GA for the retrieval of soil surface parameters. Based on our findings, this method presents a viable alternative approach to the retrieval of soil surface parameters when only single-acquisition single-configuration SAR data is available.     

Characterization of the Structure of River-Bed Gravels Using Two-Dimensional Fractal Analysis

This paper is concerned with the application of fractal analysis to understand the structure of water-worked gravel-bed river surfaces. High resolution digital elevation models, acquired using digital photogrammetric methods, allowed the application of two-dimensional fractal methods. Previous gravel-bed river studies have been based upon sampled profiles and hence one-dimensional fractal characterisation. After basic testing that bed elevation increments are Gaussian, the paper uses two-dimensional variogram surfaces to derive directionally dependent estimates of fractal dimension. The results identify mixed fractal behavior with two characteristic fractal bands, one associated with the subgrain scale and one associated with the grain scale. The subgrain scale characteristics were isotropic and sensitive to decisions made during the data collection process. Thus, it was difficult to differentiate whether these characteristics were real facets of the surfaces studied. The second band was anisotropic and not sensitive to data collection issues. Fractal dimensions were greater in the downstream direction than in other directions suggesting that the effects of water working are to alter the level of surface organisation, by increasing surface irregularity and hence roughness. This is an important observation as it means that water-worked surfaces may have a distinct anisotropic signal, revealed when using a fractal type analysis.     

JRC分形估测方法的实用性

基于分形几何的码尺法分维数与岩石节理粗糙度系数的物理意义剖析，认为Ｄ－ＪＲＣ之间不存在必然的相关性．分析标准轮廓曲线的分维数，发现其分维数差级微小，难以实行粗糙度系数分级．根据实测资料阐述了岩石节理表面轮廓曲线的“自相似”是统计意义而不是绝对的，它要求ＪＲＣ分形估测应统计求取，而过繁的分维数测量步骤削弱了ＪＲＣ的分形统计估测的可行性．建立在实测资料统计分析基础上的ＪＲＣ尺寸效应分形模型ＪＲＣｎ＝ＪＲＣ０（Ｌｎ／Ｌ０）－Ｄ客观而真实地刻画了粗糙度系数随取样长度增大而降低的规律，其中，ＪＲＣ尺寸效应分维数（Ｄ）具明确的物理意义，它描述了ＪＲＣ随结构面规模增大而降低的衰减速率．最后，运用ＪＲＣ尺寸效应分维数（Ｄ）探讨了岩石节理粗糙度系数尺寸效应的各向异性规律．     

Extracting damages caused by the 2008 Ms 8.0 Wenchuan earthquake from SAR remote sensing data

Bad weather conditions usually limit the acquisition of optical remote sensing images, while all day and all weather synthetic aperture radar (SAR) shows the ability of providing timely remote sensing data for emergency response and rescue works after earthquake. Because SAR is sensitive to the surface changes caused by earthquake, the modified electromagnetic behaviour by geological disasters and the collapse of buildings can be recorded in SAR images as backscattering intensity changes. Absolute radiometric calibration was performed to SAR products to derive backscattering coefficient sigma nought from image digital number (DN). Based on change detection methods, Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR) data and TerraSAR-X data acquired for the Ms 8.0 Wenchuan earthquake were used to extract earthquake damage information. This study revealed that landslides showed stronger backscattering and barrier lakes showed lower backscattering in post-earthquake 10 m ALOS PALSAR images comparing to pre-earthquake, and collapsed buildings showed lower backscattering compared to un-collapsed buildings in 1 m TerraSAR-X image. Results showed that SAR data with different spatial resolutions are useful for different earthquake damage information extraction: medium spatial resolution SAR data, e.g. 10 m ALOS PALSAR data, were efficient for secondary geological disaster extraction; high-resolution SAR data, e.g. 1 m TerraSAR-X data, with the help of ancillary GIS data or high-resolution optical data, could be used to extract building collapse information in urban areas. This study indicates that SAR remote sensing data can provide earthquake damage information at early emergency stage and assist the field surveying, further damage assessment and post-earthquake reconstruction.     

Natural rock joint roughness quantification through fractal techniques

Accurate quantification of roughness is important in modeling hydro-mechanical behavior of rock joints. A highly refined variogram technique was used to investigate possible existence of anisotropy in natural rock joint roughness. Investigated natural rock joints showed randomly varying roughness anisotropy with the direction. A scale dependant fractal parameter, K _v, seems to play a prominent role than the fractal dimension, D _r1d, with respect to quantification of roughness of natural rock joints. Because the roughness varies randomly, it is impossible to predict the roughness variation of rock joint surfaces from measurements made in only two perpendicular directions on a particular sample. The parameter D _r1d × K _v seems to capture the overall roughness characteristics of natural rock joints well. The one-dimensional modified divider technique was extended to two dimensions to quantify the two-dimensional roughness of rock joints. The developed technique was validated by applying to a generated fractional Brownian surface with fractal dimension equal to 2.5. It was found that the calculated fractal parameters quantify the rock joint roughness well. A new technique is introduced to study the effect of scale on two-dimensional roughness variability and anisotropy. The roughness anisotropy and variability reduced with increasing scale.     

Towards an understanding of joint roughness

Summary It is argued that the currently available joint models are incapable of accurate predictions of joint shear behaviour without resorting to substantial levels of empiricism. This is because these models fail to adequately quantify joint roughness, or appreciate the importance of scale. A novel approach, which uses fractal geometry to investigate joint roughness, is described. This approach goes beyond describing the symptoms of roughness and seeks to find the cause. In the application of this approach, the concepts of fractal geometry, fractal dimension and self similarity are described and used as a framework to formulate a statistically based and practical model for the characterisation of rock joint roughness. Important relationships between the fractal dimension and the more useful statistical parameters of standard deviation of both asperity angles and asperity heights are derived. These relationships not only provide a useful, working method for quantifying joint roughness, but are also shown to provide a basis for understanding the Barton empirical JRC-JCS model. In addition, the fractal model is able to provide conceptual models for the effects of normal stress on the shear behaviour of joints and the scale-dependence of joints.     

基于改进投影覆盖法结构面粗糙度尺寸效应分析

研究结构面粗糙度的尺寸效应特征对全面理解结构面的力学性质有重要的意义。基于此,将随机数应用于投影覆盖法中,改进了投影覆盖法计算结构面分维数时三角形单元划分方法;在分辨率相同情况下,应用改进投影覆盖法计算了两个形貌特征不同的结构面（2 m×2 m）尺寸大小不同时的分维数;探讨了用取自不同区域位置相同尺寸结构面的最大分维数差值来判定结构面合理尺寸的方法。研究结果表明:（1）形貌特征不同的结构面尺寸效应特征不尽相同,一般情况下,随尺寸增大,结构面粗糙度先增大而后减小,即在小尺寸时表现为正尺寸效应,而后为负尺寸效应;（2）对于某一特定结构面,不同尺寸范围选取位置不同,其尺寸效应特征也不尽相同;（3）不同区域位置相同尺寸结构面最大分维数差值随尺寸的增大,其总体趋势为先减小而后逐渐趋于稳定。该研究结果是全面认识结构面粗糙度尺寸效应的有益补充,为确定结构面合理尺寸提供一条新途径。     

岩石节理粗糙度系数的分形特征

岩石节理粗糙度系数JRC是估算节理抗剪强度和变形指标最重要的参数。通过对简易纵剖面仪获取的节理表面轮廓曲线的分形研究,讨论了节理表面轮廓曲线的自相似性和JRC的自相似性,并根据实测统计资料的分析,指出了分形理论研究JRC的适用条件和有效的使用方法。由实测统计资料的JRC尺寸效应自相似性分析,认为JRC尺寸效应具分形结构。本文介绍了一种确定JRC尺寸效应分维数D的方法,由此确定的分维数D具有明确的物理意义。     

高应力卸荷条件下大理岩破裂面细微观形态特征及其与卸荷岩体强度的相关性研究

岩石的破裂性质及破裂面的起伏粗糙特征对岩石的破裂机制及破裂面的参数取值具有重要的理论和应用意义。采用高精度的三维激光扫描和扫描电镜技术,结合分形理论,揭示高应力条件下大理岩卸荷破裂性质及破裂面的细微观形态特征,阐述主破裂面粗糙度分形维与卸荷岩体强度间的相关规律。在高应力卸荷条件下,大理岩岩样随着卸荷速率的递增宏观破裂性质由剪切、拉剪复合向张拉劈裂发展。初始围压越高卸荷速率越快,主破裂面越起伏粗糙,而初始围压越高卸荷速率越慢,主破裂面越平坦光滑。随卸荷速率的增大,微观上大理岩逐渐由穿晶剪切断裂、沿晶面张裂+穿晶剪切的复合断裂、沿晶面张裂或劈裂的变化特征。卸荷岩体的内摩擦角随破裂面粗糙程度分形维D的增大而增大,而黏聚力随D的增大而减小。     

Environmental Investigation and Evaluation of Land Subsidence in the Datong Coalfield Based on InSAR Technology

Heavy mining of Jurassic and Carboniferous horizontal coal seams in the Datong coalfield has seriously affected the local geological environment, which is mainly manifested by such geohazards as soil avalanches, landslides, mudflows, surface subsidence, surface cracks, surface solid waste accumulation and surface deformation. More seriously, coal mining causes groundwater to leak. Overpumping of groundwater has resulted in substantial land subsidence of the urban area in Datong City. Based on the previous geo-environmental investigation in the work area, the authors used radar remote sensing techniques such as InSAR （synthetic aperture radar interferometry） and D-InSAR （differential synthetic aperture radar interferometry）, supplemented by the optical remote sensing method, for geo-environmental investigation to ascertain the geo-environmental background of the Datong Jurassic and Carboniferous-Permian coalfield and evaluate the effects of the geohazards, thus providing a basis for the geo-environmental protection, geohazard control and prevention, land improvement and optimization of the human environment. In this study 8 cog-nominal ERS-1/2 SAR data frames during 1992 to 2003 were used, but the following processing was made： （1） the multitemporal SAR magnitude images were used to interpret the geological structure, vegetation, microgeomorphology and drainage system; （2） the multi-temporal InSAR coherent images were used to make a classification of surface features and evaluate the coherence change due to coal mining; and （3） the multi-temporal cog-nominal SAR images were used to complete D-InSAR processing to remove the information of differential deformation areas （sites）. In the end, a ten-year time series of differential interferograms were obtained using the multi-temporal cog-nominal SAR images. In the tests, 84 deformed areas （sites） were obtained, belonging to those in 1993-1996, 1996-1997, 1997-1998, 1998-2001, 1998-2002 and 2001-2003 respectively. Of the 84 areas, 44 are m     

Impact of bioturbation on reservoir quality and production – A review

Bioturbation is a typically small scale yet potentially significant geological process altering rock properties by reworking. For many years, bioturbation studies found application in exploration geology to estimate paleobathymetry, interpreting depositional environment and identifying key stratigraphic surfaces. These act as vital inputs to the geological models, for determination of source rock potential, reservoir quality and modeling of petroleum systems. Recently geologists extended the application of bioturbation studies to address production related challenges. Recognizing the bioturbation effects and incorporating them in reservoir simulation models can improve production predictions and enhanced oil recovery operations. This paper discusses bioturbation and its effects on reservoir quality, its performance and production.     

一种新的岩石节理面三维粗糙度分形描述方法

研究并提出一种新的岩石节理面三维粗糙度分形描述方法。首先,基于激光扫描数据将节理表面离散成三角网,并建立与剪切方向相关的三维均方根抵抗角的计算方法。其次,运用分形数学理论,提出一种新的基于三维均方根抵抗角的节理面粗糙度分形描述方法。最后,采用新方法对天然玄武岩节理和花岗岩张拉型节理的粗糙特性进行分析。研究结果表明,提出的新方法能够较全面地反映节理面的三维几何形貌信息,并能描述节理粗糙度的各向异性特性。研究成果为进一步建立岩石节理面的三维剪切强度公式和剪切本构理论奠定了基础。     

基于多重分形特征的岩体结构面剪切强度研究

Barton剪切强度模型是目前工程实践中普遍采用的强度公式,而实践应用时,该模型中结构面粗糙性系数（JRC）的评估存在主观性和片面性的缺点。鉴于此,应用多重分形理论,提出了采用多重分形参数准确量化JRC的方法。首先应用数字图像处理技术获取了结构面三维形貌数据信息;然后采用投影覆盖法进行了结构面的分形维数计算,重点对结构面的多重分形特征进行了分析,通过对比分析了构造的15个结构面的多重分形特征值。结果表明：结构面越粗糙,多重分形特征参数 和 值越大, 或 能够很好地描述结构面的形貌特征。最后对9组石膏试件进行了剪切试验,通过不同正应力下对应的剪应力数据分析,结合结构面形貌多重分形参数 或 ,以Barton剪切强度公式为基础,应用最小二乘法原理,给出了JRC与 及JRC与 关系。这样在工程实际中,可以用参数 或 对JRC进行估算,克服了JRC人为估值主观性及采用二维标准轮廓线评估片面性的缺点,为准确评估结构面粗糙度提供了一条新的途径。在此基础上,应用Barton模型可准确估算岩体结构面的剪切强度。     

岩石碎裂作用的分形尺度(英文)

各种各样的统计幂定律关系经常成功地被用来描述碎屑大小分布和断口形状 (不平整度 )的分级规律 ,表明碎裂作用是一种尺度不变的作用过程。一条新的有关岩石碎裂作用破裂能量的尺度律 ,可以由分形几何以及Griffith能量平衡的概念推导出来 ,而且它与先前三条关于大小缩减或Hall Petch关系的理论是相一致的。从材料强度的观点来看 ,断口形状的分形维数是形状因子和岩石Weibull均质系数的函数。在任何一次采集中 ,如果碎屑都是致密压实的 ,那么大小分布和碎屑不平整度的分形维数是相同的。然而有些地壳碎屑在三维体积上已不再是致密压实的 ,破裂的地壳可被当作分形的多孔物质来处理。在此情况下 ,地壳碎屑形状的分形容量与地壳断口大小分布的分形维数相关 ,可以预期 ,在大地构造及地震强度的分形分析中 ,地壳断口大小分布的分形维数可作为断裂制约条件之一。     

基于孔内影像的岩石节理粗糙度特征研究

目前对岩石结构表面粗糙度的研究往往只局限于地表,难以反映深部岩石节理粗糙度的特征。钻孔孔壁上节理轮廓线包含有三维信息的特点,本文开展了基于数字钻孔摄像技术的岩石节理粗糙度分形特征的研究,利用数字钻孔摄像系统获取地下深度岩石节理全景图,采用边缘检测技术从全景图中提取出节理轮廓线,对其进行空间变换和视距离变换得到地下岩石节理粗糙表面轮廓线的真实状况。与Barton提出的10条标准剖面曲线进行对比得到每条轮廓线的JRC值,并计算其分形维数,根据最小二乘法原理拟合出JRC与分形维数之间的关系为:(D)=JRC=-541.9x2+1362x-818.53。本文研究内容为描述地下深部天然节理的结构及其特征提供了基础,对更深入地研究地下深部岩石节理的表面空间状况有重要的意义。     

航天飞机成像雷达数据在库车冲断带前缘构造分析中的应用

通过新疆库车县北航天飞机TM和SIR-C/X-SAR图像的处理,利用多参数雷达图像对浅覆盖物下隐伏构造的探测能力,从雷达图像上提取研究区低序次的构造信息,以此分析左行走滑活动相关变形产生的正、负花状构造的地面特征。采用分数维分析方法,研究不同冲积物图像表面的粗糙度特征,确定了库车冲断带前缘在库车县北向西端延伸的位置。显示出多波段多极化成像雷达对新构造的识别能力,从而确定库车冲断带前缘的构造特征。     

工程地质中基于OpenCASCADE的地表和地层三维建模

为了更加直观和准确地分析工程地质中的地质信息,通过对比分析传统三角网建模方法的优缺点,展示了OpenCASCADE曲面建模技术在三维模型中的连续程度、光滑度、细腻度等方面的优势.利用该技术建立三维地表和地层层面模型,并通过地层层面的求交和缝合技术完成了地层层间实体模型构建.基于OpenCASCADE几何造型库在VC＋＋平台下实现了地表、地层模型的三维可视化和场景控制功能.通过桥梁工程地质的实例应用,结果表明：三维地表地层模型的应用可以有效提高工程建设中地质分析和地质解译的直观性和可靠性.     

Fractal Analysis of Karst Landscapes

Mathematical Geosciences - Fractal analysis has, for some time, been used to evaluate the roughness of both natural and engineered surfaces. Since the introduction of fractal geometry, evidence of...