金丽温高速公路K81高边坡变形动态数值分析

对金丽温高速公路K81高边坡进行接触大变形有限元动态数值分析.结果表明,路堑边坡开挖,导致滑面的法向应力减小、抗滑力下降,是引起古滑坡复活的根本原因.研究结果也说明了接触大变形有限元分析方法可以较好地分析潜在滑面的力学作用,是研究滑坡的滑动机理的有效方法.     

增量位移反分析在水电地下洞室工程中的应用

反分析是确定计算模型参数的有效方法.通常多采用量测所得全量位移进行反演计算.但地下工程中许多量测数据为增量位移,且实际施工过程可以通过建立分步开挖的有限元模型来模拟.据此,结合某水电站地下洞室工程中地下厂房的开挖,建立了模拟动态施工的有限元模型,利用某一开挖步施工前后量测值之差,采用增量位移优化反分析方法对洞室附近初始地应力场及围岩弹性模量进行了反演.计算所得增量位移与实测值符合较好,表明了这种方法的可行性.同时,根据分析结果对该方法进行了评价.     

Three-dimensional forward and backward modelling of diapirism: numerical approach and its applicability to the evolution of salt structures in the Pricaspian basin

Numerical studies of ductile deformations induced by salt movements have, until now, been restricted to two-dimensional (2D) modelling of diapirism. This paper suggests a numerical approach to model the evolution of three-dimensional (3D) salt structures toward increasing maturity. This approach is also used here to restore the evolution of salt structures through successive earlier stages. The numerical methodology is applied to study several model examples. We analyse a model of salt diapirs that develop from an initial random perturbation of the interface between salt and its overburden and restore the evolved salt diapirs to their initial stages. We show that the average restoration errors are less than 1%. An evolutionary model of a 2D salt wall loaded by a 2D pile of sediments predicts a decomposition of the salt wall into 3D diapiric structures when the overburden of salt is supplied by 3D synkinematic wedge of sediments. We model salt extrusion feeding a gravity current over the depositional surface and estimate an average rate of extrusion and horizontal velocity of salt spreading. Faulting of the overburden to salt overhangs initiates new secondary diapirs, and we analyse the growth of these secondary diapirs. We also study how lateral flow effects the evolution of salt diapirs. The shape of a salt diapir can be very different if the rate of horizontal flow is much greater than the initial rate of diapiric growth solely due to gravity. We discuss the applicability of the results of the models to the evolution of Late Permian salt structures in the Pricaspian basin (Russia and Kazakhstan). These structures are distinguishable into a variety of styles representing different stages of growth: salt pillows, diapirs, giant salt massifs, 2D diapiric walls and 3D stocks complicated by large overhangs. The different sizes, shapes and maturities of salt structures in different parts of the Pricaspian basin reflect areal differences in salt thickness and loading history. Our results suggest that the numerical methodology can be employed to analyse the evolution of all salt structures that have upbuilt through younger ductile overburdens.     

宁夏香山荒漠草原区植物群落多样性时空特征

采用多个多样性指数对宁夏香山荒漠草原区植物群落多样性时间、空间动态进行分析。结果表明，该地区群落时、空动态特征不明显。长期过度放牧导致环境恶化，生境碎化，这些作用的长期性、循环性是造成物种、群落格局与原有时、空动态规律相悖的主要因素，这些因素消除了物种或群落在时间梯度上应有的变化规律。干旱山地物种在长期进化过程中成功的发展了对环境的适应机制，环境的波动性强烈导致了群落多样性在原来消长动态基础上的复杂化，也使多样性动态机制复杂化。应用多种指数数学模型对研究对象进行综合评价，能够真实地反映群落多样性动态。     

基于非线性平差模型的坐标转换公式

用线性近似法以及非线性参数估计法讨论了直角坐标系七参数转换模型，指出改进的Gauss-Newton方法具有理论严密、计算简洁、易于编程、精度较高等持点。对于处理类似坐标转换的非线性模型具有重要的理论和实践意义。     

时间动态地图模型

就时间动态地图模型进行了研究，认为动态地图由于表达空间维数的增加，使得地图作为客观现实世界的概念模型更加完善，并且作为物质模型，动态地图的可视化应与空间认知的计算机表达紧密融合。在制作时间动态地图时，不同的视觉变量具有不同的动态表现能力，根据时态现象的特征进行选取。     

基于时空分析的贫困丘陵山区耕地变化机理研究

在地理信息系统技术的支持下 ,利用耕地面积变化时间序列模型、耕地动态度模型、耕地重心变化模型等 ,对湖北省咸宁市耕地的时间变化和空间变化特征进行了定量的研究 ,并应用主成分分析法 ,选择 2 3个因素对其驱动因子进行了相关分析。结果表明 ,耕地变化主要受经济因子、人口、房地产政策及耕地开发强度的影响     

Research on spatial calculating analysis model of landuse change

The spatial calculating analysis model is based on GIS overlay. It will compartmentalize the land in research district into three spatial types: unchanged parts, converted parts and increased parts. By this method we can evaluate the numerical model and dynamic degree model for calculating land-use change rates. Furthermore, the paper raises the possibility of revising the calculating analysis model of spatial information in order to predicate more precisely the dynamic changing level of all types of land uses. In the most concrete terms, the model is used mainly to understand changed area and changed rates (increasing or decreasing) of different land types from microcosmic angle and establish spatial distribution and spatio-temporal principles of the changing urban lands. And we will try to find out why the situation can take place by combining social and economic situations. The result indicates the calculating analysis model of spatial information can derive more accurate procedure of spatial transference and increase of all kinds of land from microcosmic angle. By this model and technology we can conduct the research of land-use spatio-temporal structure evolution more systematically and more deeply, and can obtain a satisfactory result. The result will benefit the rational planning and management of urban land use of developed coastal areas in China in the future.     

Analytical exploration of γ-function explicit method for pseudodynamic testing of nonlinear systems

It has been well studied that the γ-function explicit method can be effective in providing favorable numerical dissipation for linear elastic systems. However, its performance for nonlinear systems is unclear due to a lack of analytical evaluation techniques. Thus, a novel technique is proposed herein to evaluate its efficiency for application to nonlinear systems by introducing two parameters to describe the stiffness change. As a result, the numerical properties and error propagation characteristics of the γ-function explicit method for the pseudodynamic testing of a nonlinear system are analytically assessed. It is found that the upper stability limit decreases as the step degree of nonlinearity increases; and it increases as the current degree of nonlinearity increases. It is also shown that this integration method provides favorable numerical dissipation not only for linear elastic systems but also for nonlinear systems. Furthermore, error propagation analysis reveals that the numerical dissipation can effectively suppress the severe error propagation of high frequency modes while the low frequency responses are almost unaffected for both linear elastic and nonlinear systems.     

Discussion on the dynamic mechanism of Great North China area based on the observed stress data

Introduction The Great North China, located at longitude 106E to 124E and latitude 31N to 42N, in-cludes three secondary active tectonic blocks, Ordos, Yanshan and North China plain (Figure 1). The geological tectonics of these three secondary blocks is much different from each other. As a stable block with high rigidity, the Ordos block is mostly surrounded by down-faulted basins with an inactive interior since Cenozoic, although the fault zones along its boundary are strongly active wi…