Random vectors and spatial analysis by geostatistics for geotechnical applications

Geostatistics is extended to the spatial analysis of vector variables by defining the estimation variance and vector variogram in terms of the magnitude of difference vectors. Many random variables in geotechnology are in vectorial terms rather than scalars, and its structural analysis requires those sample variable interpolations to construct and characterize structural models. A better local estimator will result in greater quality of input models; geostatistics can provide such estimators: kriging estimators. The efficiency of geostatistics for vector variables is demonstrated in a case study of rock joint orientations in geological formations. The positive cross-validation encourages application of geostatistics to spatial analysis of random vectors in geoscience as well as various geotechnical fields including optimum site characterization, rock mechanics for mining and civil structures, cavability analysis of block cavings, petroleum engineering, and hydrologic and hydraulic modelings.     

秭归盆地东缘断裂构造觅踪——再论仙女山断裂带北延过长江问题

文章在概略介绍仙女山断裂带所处的大地构造位置、展布特征、组合关系基础上,用详实的材料,逐一分析了荒口—腰店子、腰店子—将军垭、将军垭—卜庄河及尹家湾—黄垭畔、黄垭畔—贾家店长江南北两岸各段的断裂构造形迹特征、力学性质和交切关系。认为仙女山断裂带已北延过长江,并建议对断裂的应力传递方式和可能出现的史前地震进行深入研究。     

潼峪金矿区成矿断裂构造特征

潼峪金矿区发育过冲剪滑型、平移剪张型和平移剪滑型三种不同性质、不同方向成矿断裂,分布在金罗斑背形的不同部位,其形成有先后差异,但变形环境大体相同,具脆-韧性变形特征。空间上一般不超越褶皱主体。三类断裂中,前两者具石英脉型金矿化,后者形成构造蚀变岩型及小规模石英脉型金矿化。矿化差异与断裂产出的褶皱部位及其相应的应力应变条件的不同有关。     

Aftershock Statistics

The statistical properties of aftershock sequences are associated with three empirical scaling relations: (1) Gutenberg-Richter frequency-magnitude scaling, (2) Båths law for the magnitude of the largest aftershock, and (3) the modified Omoris law for the temporal decay of aftershocks. In this paper these three laws are combined to give a relation for the aftershock decay rate that depends on only a few parameters. This result is used to study the temporal properties of aftershock sequences of several large California earthquakes. A review of different mechanisms and models of aftershocks are also given. The scale invariance of the process of stress transfer caused by a main shock and the heterogeneous medium in which aftershocks occur are responsible for the occurrence of scaling laws. We suggest that the observed partitioning of energy could play a crucial role in explaining the physical origin of Båths law. We also study the stress relaxation process in a simple model of damage mechanics and find that the rate of energy release in this model is identical to the rate of aftershock occurrence described by the modified Omoris law.     

水流注入方式和填料层高度对人工湿地流态的影响

流态模拟实验作为评价人工净化湿地系统运行状况、物质在其中停留时间的有效工具,在污水处理领域具有重要作用。罗丹明B背景浓度低、重现性好,被选为评价升流式、降流式和填料层高度对水力流态影响的示踪剂。实验使用罗丹明B和NaCl作为示踪剂,在湿地系统中进行流态实验,探究升流式、降流式和填料层高度对人工净化湿地流态的影响。实验结果表明,升流式人工湿地比降流式人工湿地处理效果好,示踪剂水力停留时间(hydraulic retention time,HRT)的体积利用率分别为82.0%和76.8%,升流式人工湿地无效体积中死区占更大比例,而降流式人工湿地滞留区占无效体积的比例更大;人工湿地填料层高度对示踪剂停留时间分布影响不大,体积利用率都在80%以上,但是,其死区和滞留区随着填料层高度的变化在无效体积中所占的比例有所差异,死区所占的比例随着填料层高度的增加先增加后减少,滞留区所占的比例则先减少后增加。     

甘孜—理塘断裂带北段玄武岩地球化学特征及构造意义

沿甘孜-理塘断裂带广泛发育有三叠纪玄武岩,该断裂带北段的玄武岩多为SiO_2大部分不饱和蚀变较强的基性岩,根据TiO_2K_2O、P_2O_5、Al_2O_3和CaO含量判定为亚碱性拉斑玄武岩系列。痕量元素特征表明,玄武岩为轻稀土弱富集型,∑REE、∑LREE/∑HREE、δEu、Eu/Sm、Sm/Nd都显示与大洋拉斑玄武岩一致。笔者认为,理塘断裂带南段在晚二叠世打开并逐步向北推进,北段于早三叠世打开,中三叠世为甘孜-理塘海发育的鼎盛时期,晚三叠世逐渐闭合。     

Investigation of fractal distribution law for the trace number of random and grouped fractures in a geological mass

A fractal study method of the number of geological mass fractures is introduced in detail in this paper. Three main aspects of the problem were studied: (1) The random distribution of fractures in a geological mass was in good agreement with the fractal law. The size scale of the studied geological mass ranged from 2400 m to 1 mm for the length of each side, and the geological mass samples were taken from 13 coal areas in China. (2) The geological mass fractures were evidently directional and anisotropic, having originated from tectonic movement. Observation and statistics for the data from the Xuangang, Fenxi and Dongshan coal areas in Shanxi, China, demonstrated that the fracture distribution of each group, classified by the strike of the strata, still follow the fractal law, even though the fractal dimension varies to a certain extent with different strikes. (3) The sedimentary strata containing the coal seams, as a geological mass, underwent almost similar tectonic movements in their geological history. The mechanical experiments on geological mass samples from Fenxi and Jiexiu in Shanxi demonstrated that the fractal dimension of the number of fractures in the same strata is in good power function with the product of strength and elastic modulus. The larger the product of the strength of the elastic modulus is, the larger is the fractal dimension, and vice versa.     

金川铜镍硫化物矿床F1断裂系统演化及其意义

金川铜镍硫化物矿区构造活动频繁且复杂,查明矿区构造规律,是实现深部找矿突破的必经途径之一.文章在充分挖掘区域及以往勘查资料的基础上,通过野外实地调查,对矿区内成矿后断裂系统——F1断裂系统分析研究,发现F1断层角砾岩呈棱角状,深部产状北倾,断层发育在龙首山岩群一侧,无法仅靠现今的叠置关系解释F1的演化.结合潮水盆地研究...     

Late Holocene flood magnitudes in the Lower Rhine river valley and upper delta resolved by a two-dimensional hydraulic modelling approach

Palaeoflood hydraulic modelling is essential for quantifying ‘millennial flood’ events not covered in the instrumental record. Palaeoflood modelling research has largely focused on one-dimensional analysis for geomorphologically stable fluvial settings because two-dimensional analysis for dynamic alluvial settings is time consuming and requires a detailed representation of the past landscape. In this study, we make the step to spatially continuous palaeoflood modelling for a large and dynamic lowland area. We applied advanced hydraulic model simulations (1D–2D coupled set-up in HEC-RAS with 950 channel sections and 108 × 10³ floodplain grid cells) to quantify the extent and magnitude of past floods in the Lower Rhine river valley and upper delta. As input, we used a high-resolution terrain reconstruction (palaeo-DEM) of the area in early mediaeval times, complemented with hydraulic roughness values. After conducting a series of model runs with increasing discharge magnitudes at the upstream boundary, we compared the simulated flood water levels with an inventory of exceeded and non-exceeded elevations extracted from various geological, archaeological and historical sources. This comparison demonstrated a Lower Rhine millennial flood magnitude of approximately 14,000 m³/s for the Late Holocene period before late mediaeval times. This value exceeds the largest measured discharges in the instrumental record, but not the design discharges currently accounted for in flood risk management.