基于SLOPE／W的汾离高速公路靳家庄1^#滑坡研究

汾(阳)-离(石)高速公路是青岛至银川国道主干线在山西境内的重要路段。文章以汾离高速公路靳家庄1#滑坡为研究对象,从岩性条件、地质构造及地下水等方面详细分析了滑坡的成因。应用基于刚体极限平衡理论的SLOPE/W程序,对滑坡的稳定性进行分析与计算。结果表明:该滑坡在天然状态下,整体处于稳定状态;在工程状态下,受水动力条件的变化以及人为活动的影响,易发生复活。为设计人员提供了参考。     

Brief History of Spatial Information Policies in the United States

Slope exerts a powerful influence on the route selection processes of humans. Attempts to model human movement in hilly and mountainous terrain which have largely focused on least-time route transformations can be improved by incorporating research suggesting that humans systematically overestimate slopes. Such research suggests that cost functions derived from slope should be more expensive than time derivations alone would indicate. This paper presents a method for empirically estimating cost functions for slopes. We use the method to predict routes and paths that are more likely to be selected by humans based on their perceptions of slope. An evaluation of the method found that it successfully predicts road, track and trail locations over a variety of conditions and distances.     

陕-甘G312高速公路彬县滑坡群稳定性数值分析

由于地质环境薄弱,在西部公路等基础设施建设中,存在很多工程地质问题。陕甘G312高速公路彬县滑坡群就座落在公路连接线经过的泾河左岸与黄土塬之间的斜坡沟壑地带。对公路的正常的运营存在潜在威胁。在探明滑坡群工程地质特征和成因机制基础上,采用边坡稳定性分析软件FLAC/SLOPE,将滑坡群分成3个相对独立的滑坡体单元(Ⅰ号滑坡、Ⅱ号滑坡、Ⅲ号滑坡),选取4个具有代表性的地质剖面,建立地质模型。并按天然状态和饱和状态对滑坡群的稳定性进行了数值分析。剪应变率云图和稳定性计算结果表明,滑坡群在天然及饱和状态下均处于稳定状态。但滑坡群剪出口以下因公路开挖而形成的边坡处于不稳定状态。与现场变形现象相吻合。     

复杂边坡稳定性的二维与三维分析

目前,在边坡稳定性分析中广泛地采用二维极限平衡分析方法进行研究。但是对于地形、地层、地下水、岩体结构等条件复杂的边坡,仅用二维极限平衡分析方法进行研究是不够的,二维分析忽略了边坡的三维效应,而复杂边坡往往受三维效应影响大。但至今三维极限平衡方法还不是很完善。因此,本文结合一工程实例,采用二维与三维极限平衡分析相结合的方法对其边坡的稳定性进行了分析。研究结果表明,对于复杂边坡,应用二维和三维稳定性分析相结合的方法进行研究是一种较为恰当的选择。     

Reducing Linear and Perimeter Measurement Errors in Raster-based Data

An important issue in cartography and GIS is determining the appropriate resolution or cell size when converting vector data to raster. The general consensus is to make the cell size as small as possible to resolve geographic features and provide the most accurate estimates of measurements. Finer resolution results in more accurate estimates of polygon area; however, the raster data structure introduces an artifact that causes errors in the estimation of the length of linear features and of the perimeter of polygon features to increase with increasing resolution. Over-estimation as high as 41 percent is theoretically possible and was found to be around 26 percent for representative polygon maps. A method is described that uses a correction coefficient to reduce overestimation error to less than 3 percent.     

Comparison of Angles from Surface Slope/Aspect Algorithms

Few studies have compared algorithms for mapping surface slope and aspect from digital elevation models. Those studies that have compared these algorithms treat slope and aspect angles independently. The evaluation and comparison of surface orientation algorithms may also be conducted by treating slope and aspect as characteristics of a bi-directional vector normal to the surface. Such a comparison is more appropriate for selecting an accurate surface orientation algorithm for applications that use bi-directional measurements, such as modeling solar radiation or removing the topographic effect from remotely sensed imagery. This study empirically compared the slope angle and bi-directional surface angle estimated from five slope/aspect algorithms using a synthetic terrain surface and an actual terrain surface. The most accurate algorithm is consistently that which uses only the four nearest neighboring elevations in the grid.