岩体多尺度异质性及其力学行为     

兰恒星  包含  孙巍锋  刘世杰 《工程地质学报》2022,30(1):37-52

异质性是岩体的重要属性之一,从岩体的物质组成到结构特征,再到微宏观力学行为表现,异质性现象普遍存在。本文在梳理已有研究成果的基础上,从岩体的细微观异质性、结构面异质性和宏观异质性3个不同的尺度,对异质性的产生原因、表现特征、力学效应和时空演化规律等进行阐述,并介绍了相关研究方法以及异质性在不同尺度上的差异表现。岩体异质性的研究,是岩体工程地质力学理论体系的延伸,而多尺度的研究方法也成为全面揭示岩体变形破坏机制的一种有效手段。  相似文献   

Boundary-Layer Adjustment Over Small-Scale Changes of Surface Heat Flux   总被引：1，自引：0，他引：1  

L.?MahrtEmail author  Dean?Vickers 《Boundary-Layer Meteorology》2005,116(2):313-330

Four months of eddy correlation data collected over a grass field and a nearby sage brush community are analyzed to examine the adjustment of the boundary-layer structure as it flows from the heated brush to the snow-covered grass. The grass site includes a 34-m tower with seven levels of eddy correlation data. The midday heat flux over the snow-covered grass and bare ground surfaces is often downward particularly with melting conditions, while the corresponding heat flux over the brush is almost always upward. For most of these cases, a stable internal boundary layer over the snow is well defined in terms of vertical profiles of the buoyancy flux over the snow-covered grass. The stable internal boundary layer is generally embedded within a deeper layer of flux divergence corresponding to increasing upward heat flux with height above the internal boundary layer. With thin snow cover, the surface heat flux over the grass is weak upward due to heating of grass protruding above the snow so that the flow adjusts to a decrease of the upward surface heat flux in the downwind direction. This common case of an adjusting boundary layer contrasts with the formation of an internal boundary layer due to a change of sign of the surface heat in flux the downwind direction. The adjustment of the boundary layer to the decrease of the surface heat flux leads to vertical divergence of the upward heat flux in contrast to the usual heated boundary layer over homogeneous surfaces. The consequences of the cooling due to the vertical divergence of the heat flux are discussed in terms of the heat budget of the adjusting and internal boundary layers.  相似文献   

2002年12月25日乌恰5.8级地震的长、中、短期跟踪预测和反思     

苏乃秦 《内陆地震》2004,18(3):193-201

在乌恰地区地震活动呈现长期平静异常的背景下,通过多种方法对2002年12月25日乌恰5．8级地震进行了1-3年的中长期预测。应用“模糊地震活动度”和“空区参数法”两种方法进行了1年和半年的中期预测,结合对该地区小震活动动态的分析与震例分析,尤其是预警地震的分析判断,提出了3个月的短期预测意见,较好地预测了这次地震。最后对预测情况进行了正反两个方面的总结和反思,提出了七点看法。  相似文献   

Eulerian spatial moments for solute transport in three-dimensional heterogeneous,dual-permeability media     

J.?Xu  B.X.?HuEmail author 《Stochastic Environmental Research and Risk Assessment (SERRA)》2004,18(2):47-60

A Eulerian analytical method is developed for nonreactive solute transport in heterogeneous, dual-permeability media where the hydraulic conductivities in fracture and matrix domains are both assumed to be stochastic processes. The analytical solution for the mean concentration is given explicitly in Fourier and Laplace transforms. Instead of using the fast fourier transform method to numerically invert the solution to real space (Hu et al., 2002), we apply the general relationship between spatial moments and concentration (Naff, 1990; Hu et al., 1997) to obtain the analytical solutions for the spatial moments up to the second for a pulse input of the solute. Owing to its accuracy and efficiency, the analytical method can be used to check the semi-analytical and Monte Carlo numerical methods before they are applied to more complicated studies. The analytical method can be also used during screening studies to identify the most significant transport parameters for further analysis. In this study, the analytical results have been compared with those obtained from the semi-analytical method (Hu et al., 2002) and the comparison shows that the semi-analytical method is robust. It is clearly shown from the analytical solution that the three factors, local dispersion, conductivity variation in each domain and velocity convection flow difference in the two domains, play different roles on the solute plume spreading in longitudinal and transverse directions. The calculation results also indicate that when the log-conductivity variance in matrix is 10 times less than its counterpart in fractures, it will hardly influence the solute transport, whether the conductivity field is matrix is treated as a homogeneous or random field.  相似文献   

降水气候强迫下非均匀地表区域平均径流的一种参数化方案     

刘晶淼  丁裕国  周秀骥  李云 《气象学报》2009,67(1):28-34

将任一中尺度区域的平均瞬间径流率考虑为区域平均降水量和地表土壤层水分渗透垦的余项.根据降水量在地理空间上分布的实测资料拟合其空间概率密度函数(PDF),并结合土壤入渗物理过程的数学描述及其经验公式,精确估计出地表土壤渗透率及其空间分布,由此建立区域地表径流率的统计-动力学估计方案.换言之,区域内地表产流率可视为区域平均降水量与区域平均的土壤下渗量之差值,而区域内土壤的平均下渗量又町分为非饱和区和饱和区两部分的下渗量来分别计算.就陆面水分循环的物理过程而言,地表入渗现象是在一定的下垫面特性基础上,由一定的水分供应源而形成的.根据大气降水向地表层输送水分的物理过程,在满足植被表层覆盖需水(截流水)和地表层土壤人渗水基础上,多余的降水量才会形成地表径流.凶此,推求地表产流率的主要关键在于地表土壤层需水量.为此奉文根据土壤水分通量方程推导出水分入渗公式.又从描述土壤水分和降水的空间PDF出发,推导出非均匀土壤含水量及降水气候强迫所形成的次网格尺度区域平均径流率计算公式.利用长江三角洲地区1996年降水量和土壤特性等实测资料建立区域平均地表径流率的估计公式,并对其影响凶素进行敏感性试验.结果表明,该方法与用Mosaic方法计算的区域径流率(或产流率)结果十分接近.由此可见,该文提出的降水气候强迫下非均匀地表区域平均径流的这种统计-动力参数化方案,具有相当的可靠性与可行性.  相似文献   

Analysis of small-scale heterogeneity in clastic rocks by using computerized X-ray tomography (CT)     

Janos Geiger  Zoltan Hunyadfalvi  Peter Bogner   《Engineering Geology》2009,103(3-4):112-118

The aim of this study is to recognize the basic clastic rock types on the basis of Hounsfield Units (HUs) by using statistical methods (hypothesis tests, distribution fitting, and confidence intervals). How does this recognition depend on depositional history of samples tested? Does the numerical pattern of HUs obtained from small-scale analyzing of some particular sedimentary structures coincide to the textural expectations of those sedimentary structures? Are the HU values provided by the CT measurements capable of evidencing micro-cycles belonging to a particular depositional history?For testing the numerical recognition, we analyze macroscopically homogeneous argillaceous marl, siltstone and fine sandstone samples with similar depositional background, age, and degree of diagenesis. The preliminary research shows that the Hounsfield Units can identify different sedimentary rocks considerably well. There are significant differences among the confidence intervals belonging to the different rock types. However, there also have been some slight overlaps among them.For analyzing the effects of the depositional processes in case of a particular rock type, samples from channel sandstone, distributary mouth-bar, massive (structureless) sandstone from a delta-fed turbidity fan, and channel sandstone with traction carpet origin from a delta-fed turbidity fan (all coming from Pannonian basin filling series) are used. The results prove again the significant differences in the terms of both confidence intervals and distribution-types; however, some overlapping also occurs.  相似文献   

Reply to comment by C. Collettini on “Structural controls on a carbon dioxide-driven mud volcano field in the Northern Apennines (Pieve Santo Stefano, Italy): Relations with pre-existing steep discontinuities and seismicity”     

Marco Bonini   《Journal of Structural Geology》2009,31(8):857-860

  相似文献   

High resolution facies architecture and digital outcrop modeling of the Sandakan formation sandstone reservoir,Borneo:Implications for reservoir characterization and flow simulation     

Numair A.Siddiqui  Mu.Ramkumar  Abdul Hadi A.Rahman  Manoj J.Mathew  M.Santosh  Chow W.Sum  David Menier 《地学前缘(英文版)》2019,10(3):957-971

Advances in photogrammetry have eased the acquisition of high-resolution digital information from outcrops, enabling faster, non-destructive data capturing and improved reservoir modeling. Geocellular models for flow dynamics with in the virtual outcrop in siliciclastic deposits at different sets of sandstone facies architecture remain, however, a challenge. Digital maps of bedding, lithological contrast, spatial-temporal variations of bedding and permeability characteristics make it more easy to understand flow tortuosity in a particular architecture. An ability to precisely model these properties can improve reservoir characterization and flow modeling at different scales. Here we demonstrate the construction of realistic 2 D sandstone facies based models for a pragmatic simulation of flow dynamics using a combination of digital point clouds dataset acquired from LiDAR and field investigation of the Sandakan Formation, Sabah, Borneo.Additionally, we present methods for enhancing the accuracy of outcrop digital datasets for producing high resolution flow simulation. A well-exposed outcrop from the Sandakan Formation, Sabah, northwest Borneo having a lateral extent of 750 m was chosen in order to implement our research approach. Sandstone facies and its connectivity are well constrained by outcrop observations, data from air-permeability measurements, bilinear interpolation of permeability, grid construction and water vector analysis for flow dynamics.These proportions were then enumerated in terms of static digital outcrop model(DOM) and facies model based on sandstone facies bedding characteristics. Flow simulation of water vector analysis through each of the four sandstone facies types show persistent spatial correlation of permeability that align with either cross-bedded orientation or straight with more dispersion high quality sandstone(porosity 21.25%-41.2%and permeability 1265.20-5986.25 mD) and moderate quality sandstone(porosity 10.44%-28.75% and permeability 21.44-1023.33 mD). Whereas, in more heterolithic sandstone(wavy-to flaser-bedded and bioturbated sandstone), lateral variations in permeability show spatially non-correlated patterns over centimeters to tens of meters with mostly of low quality sandstone(porosity 3.4%-12.31% and permeability < 1 mD to 3.21 mD). These variations reflect the lateral juxtaposition in flow dynamics. It has also been resulted that the vertical connectivity and heterogeneities in terms of flow are mostly pragmatic due to the interconnected sandstone rather than the quality of sandstone.  相似文献   

用不完整的地震资料估计地震矩年变化率          下载免费PDF全文

邵辉成  杜兴信  金学申 《地震地质》1999,21(4):406-410

在充分考虑现有地震资料的不完备性和震级服从两端截去泊松分布的条件下,建立了用历史地震资料和现代地震资料及考古地震资料计算地震矩年变化率的方法。计算了西南地区几个地震带的地震矩年变化率,并与地质资料得到的结果进行了比较,结果表明该方法是切实可行的  相似文献   

新疆地下热水特征及其与地震活动的关系          下载免费PDF全文

王道  许秋龙  陈玲  卢静芳 《地震地质》1999,21(1):58

新疆地下热水广泛分布于昆仑山、天山和阿尔泰山。温泉和地震活动与大地构造、板块运动有着密切的联系。动态观测资料分析表明,热水温度变化不仅受到地震的作用,而且显示出某些地震前兆信息。分析了地下热水的化学成分、气体组分、微量元素、放射性元素,认为某些热水具有低矿化、高碱性、高氟、高氦等独特性质,有可能是形成于地壳深部或上地幔的深成水  相似文献