加筋陡坡路基应力变形特性的数值模拟分析

针对日益增长的山区公路建设需求,利用有限元法,通过自然边坡状况、回填土强度和填筑高度这3个设计参数的敏感性分析,对修筑于不同开挖角下加筋路基的应力变形特性进行了对比研究。结果表明：与修筑在水平场地上的路基相比,回填土强度的降低或填筑高度的增加都会更加显著地增大陡坡路基的变形,同时,由于其回填土容易沿着边坡产生整体下滑,导致了其变形、基底压力和面板侧移等过大的问题。在不同坡面摩擦系数、回填土强度和填筑高度下,开挖角为45的加筋陡坡路基的位移比开挖角为63.4（坡比2：1）和90（水平场地）的路基的变形分别高6.8%～96.8%和29.4%～192.3%、6.8%～33.1%和29.4%～77.9%、7.7%～37.9%和27.2%～91.6%。研究结论可为日益增长的山区公路建设提供指导。     

NUMERICAL ANALYSIS OF THE MECHANICS OF SOIL REINFORCEMENT

1 INTRODUCTION China is rich in mountains. The mountainous area occupies 69% of the total land of the country. Thus, landslides frequently occur in the mountain areas of China. Landslides originating in subsurface soils are typical, and constitute approxi…     

σ-Coordinates hydrodynamic numerical model for coastal and ocean three-dimensional circulation

A three-dimensional finite-difference hydrodynamic model has been developed using σ-coordinate for the vertical dimension. An explicit scheme for temporal integration and a staggered grid for spatial discretization have been adopted. The model has been tested against analytical or literature cases for wind and tide induced circulation. Results are in good agreement both with analytical solutions under idealised conditions and with results from the model of Shankar et al. (1996).     

Fast space-domain evaluation of geodetic surface integrals

Geodetic surface integrals play an important role in the numerical solution of geodetic boundary-value problems. In many cases they can be evaluated using fast methods in the frequency domain (FFT). However, this is not possible in general, because the domain of integration may be non-trivial (as is the surface of the Earth), the kernel function may not be of convolution type, or the data distribution may be heterogeneous. Therefore, fast evaluation strategies are also required in the space domain. They are more difficult to design because only one property is left where a more or less fast evaluation strategy can be built upon: the potential type of the kernel function. Consequently, the idea is not to replace well-established frequency domain techniques, but to supplement them. Our approach to this problem goes in two directions: (1) we use advanced cubature methods where the integration nodes automatically densify in the vicinity of the evaluation points; (2) we use powerful computer hardware, namely MIMD computers with distributed memory. This enables us to evaluate geodetic surface integrals of any practical complexity in reasonable time and accuracy. This is shown in a numerical example. Received: 7 May 1996 / Accepted:17 March 1997     

Impact of the blockage ratio on the transport of sediment in the presence of a hydrokinetic turbine: Numerical modeling of the interaction sediment and turbine

Interactions between hydrokinetic turbines and near scale and far scale bed sediment particles are considered a critical area of assessment; however, a limited number of research studies have been published to address this issue. The current paper explores the influence of the blockage ratio on the morphology evolution downstream from a hydrokinetic turbine. A modeling framework is derived to predict the significant transport induced by a turbine installed on the erodible fluvial sandy bed surface, such as the Eulerian multi-phase model for the sediment and the Blade Element Momentum Theory (BEMT) for the turbine, using the open source platform OpenFOAM. Two configurations of different blockage ratios are considered. The configurations show differences in the bed morphology and the sediment transport. It has been shown for both configurations that the scour capabilities are enhanced below the turbine due to the acceleration of the flow and increasing local shear stress on the sediment.     

挖深不同情况下基坑支护结构性状研究

崩塌是黄土高原地区最常见、致灾最为严重的地质灾害之一。本文通过野外钻探,采用原位地震波测试的方法,详细分析了离石黄土崩塌隐患体内部的波速结构特征。结果发现,在竖直方向上,地震波速整体随深度增加而增大;水平方向上,地震波速自边坡坡面向坡体内部逐渐增大。结合数值模拟,发现崩塌隐患体由于受到卸荷回弹作用的影响,产生了指向坡外的形变。形变增量的大小与距离边坡坡面的远近有关,距离坡面越近形变增量越大,致使对应土体的密实度减小。密实度的减小是隐患体内部波速存在差异的重要原因。研究表明,利用地震波速的变化规律可以宏观反映崩塌隐患体内部结构特征,进而指导黄土崩塌地质灾害的防治研究。     

An integrated data-directed numerical method for estimating the undiscovered mineral endowment in a region

An integrated data-directed numerical method has been developed to estimate the undiscovered mineral endowment within a given area. The method has been used to estimate the undiscovered uranium endowment in the San Juan Basin, New Mexico, U.S.A. The favorability of uranium concentration was evaluated in each of 2,068 cells defined within the Basin. Favorability was based on the correlated similarity of the geologic characteristics of each cell to the geologic characteristics of five area-related deposit models. Estimates of the undiscovered endowment for each cell were categorized according to deposit type, depth, and cutoff grade. The method can be applied to any mineral or energy commodity provided that the data collected reflect discovered endowment.     

帕米尔东北侧邻区第四纪新构造活动规律

帕米尔东北侧邻区新构造活动具有幅度巨大,阶段性继承性明显,现今活动性强烈等特点。以帕米尔高原隆升为背景,研究了帕米尔东北侧邻区的新构造运动及地震活动的规律,通过有限元数值模拟,分析了第四纪新构造活动的应力场,并进一步探讨了新构造运动与地震活动的力源机制。     

Plant productivity, predation, and the abundance of black-tailed jackrabbits in the Chihuahuan Desert of Mexico

The abundance of black-tailed jackrabbits (Lepus californicus) can fluctuate dramatically. We used data from the Chihuahuan Desert to test the relative strength of top-down (predation) or bottom-up (food availability) limiting forces. Predictions for the top-down hypothesis were, 1) a positive relationship between coyote (Canis latrans) and jackrabbit abundance (numerical response) and 2) a positive relationship between percent occurrence of jackrabbits in coyote scats and jackrabbit abundance (functional response). Predictions for the bottom-up hypothesis were, 1) plant productivity is directly related to precipitation, 2) jackrabbit abundance is positively related to precipitation and plant productivity, and 3) changes in abundance of jackrabbits over the reproductive season will be directly related to precipitation and plant productivity. We found a limited numerical response but no functional response of coyotes to jackrabbit abundance. Forb productivity was significantly related to annual precipitation levels (r² = 0.69, p = 0.002). Grass productivity was related to annual precipitation (r² = 0.34, p = 0.028). Jackrabbit abundance (r² = 0.38, p = 0.002) and changes in abundance (r² = 0.73, p < 0.001) were significantly related to precipitation and forb and grass productivity. We conclude that precipitation levels and plant productivity affect jackrabbit abundance more than predation levels.     

用10层准拉格朗日有限区域模式对高原东侧锋生过程的数值模拟

本文对一次引起夏季华北暴雨的锋生过程进行了研究。在诊断分析的基础上,我们采用十层准拉格朗日有限区域模式对此个例进行了48小时的模拟,并对模拟输出结果进行解释与再次诊断。表明:(1)夏季高原东侧有时两支气流交绥很清楚,温度对比明显,与梅雨锋的情况很不相同,这在夏末尤其如此。这种温度对比区虽比冬季弱,但是,与夏季天气系统的发展及降水是有关系的。(2)模拟结果与实际观测资料是很相似的,再现了两支气流形成切变线的三维结构、移动与演变,并模拟出了在对流层中存在着深厚的24小时变温区;模拟发现,一条东北-西南向的锋生