构造应力场三维数值模拟的有限单元法     

田宜平  刘雄  李星  魏民 《地球科学》2011,36(2):375-380

目前构造应力场的研究主要是基于平面的二维分析,随着油气成藏过程三维模拟的发展,应力场的三维数值模拟显得越来越重要.从三维空间角度出发,分析了应力场的有限元模拟与求解的整个过程.基于不规则六面体单元的角点网格数据模型,对有限元求解法进行了分析与研究并提出计算方法.基于不规则角点网格数据模型的三维构造应力场有限元计算方法是本文的创新点.最后用上述方法对东营凹陷的牛庄-王家岗区域三维应力场进行了实际模拟计算,计算结果相比于其他数据模型更符合实际情况.   相似文献   

西江流域致洪暴雨的准双周振荡及大气环流模型   总被引：2，自引：1，他引：1  

纪忠萍  胡丽甜  谷德军  吴乃庚  梁健 《热带气象学报》2011,(5):775-784

为了做好西江流域致洪暴雨的中期预报,采用小波分析、Lanczos滤波器分析了1961—2008年西江流域13次致洪暴雨期间降水与850 hPa风场的低频振荡特征,研究了850 hPa风场的10～30天低频传播对致洪暴雨的影响,并采用合成分析建立了由西风带系统导致的致洪暴雨准双周振荡的大气环流模型。结果表明,致洪暴雨期间降水主要以10～20天的准双周振荡为主,它们多数与西江流域850 hPa风场8～35天振荡的正位相有较好的对应关系。来自西江流域以南逐渐向北传播的低频纬向风或来自30 °N附近逐渐南传并加强的低频纬向风与多数来自西北太平洋向西传播的低频纬向风在西江流域相遇,是导致致洪暴雨具有准双周振荡的可能原因之一。当500 hPa巴尔喀什湖以东的高压脊开始隆起并逐渐东移,我国东北-华北-长江中下游逐渐转为明显的华北低槽控制,华南由青藏高原东部弱的西风槽转为明显的高空槽控制,副高不断加强西伸,同时850 hPa上空来自孟加拉湾穿过中南半岛的西南风不断加强,位于华南急流轴以西弱的气旋性弯曲也不断加强,地面上转为东高西低、等压线经向度明显,西江流域致洪暴雨开始并逐渐达到强盛期。这些特征可作为西江流域致洪暴雨的中期预报提供参考依据。   相似文献   

轴压下两体力学模型的转化条件及影响因素分析   总被引：1，自引：0，他引：1  

易成  朱红光  王洪涛  刘征  潘宏 《岩土力学》2011,32(5):1297-1302

接触界面的相互作用是影响工程稳定的重要因素,基于接触面两侧介质的实际受力状态,采用一体两介质力学模型与两体两介质力学模型加以描述。通过一体和两体模型试件的轴压破坏试验,分析了两种模型的力学响应的差异,并认为：一体两介质力学模型在符合一定条件情况下可以转变为两体两介质力学模型。此外,还对影响两种力学模型性能的参数进行了分析。提出对一体两介质力学模型力学性能产生影响的参量是低强度介质与高强度介质的静载极限强度比k以及两种介质之间的黏结力c;对两体两介质力学模型力学性能产生影响的主要参量除了k之外,尚有两种介质的断裂韧度比? 、体积比? 以及界面的粗糙程度  相似文献   

基于概念设计的长短桩复合地基典型工程应用模式          下载免费PDF全文

郭密文  隋旺华  闫德刚 《水文地质工程地质》2010,37(3):92-96

本文从长短桩复合地基各组成部分的功能角度,阐述了长桩、短桩、褥垫层的作用机理,提出长短桩复合地基概念设计应遵循的设计原则。应用概念设计思想,建立了长短桩复合地基的五种典型工程应用模式,并在各典型模式的分析说明中,提出设计与施工参数的选用建议。通过在北京某工程的实际应用,显示长短桩复合地基的典型工程应用模式具有较好的实用性。  相似文献   

Simple formulas for the dynamic stiffness of pile groups     

Reza Taherzadeh  Didier Clouteau  Régis Cottereau 《地震工程与结构动力学》2009,38(15):1665-1685

Simple formulas are derived for the dynamic stiffness of pile group foundations subjected to horizontal and rocking dynamic loads. The formulations are based on the construction of a general model of impedance matrices as the condensation of matrices of mass, damping, and stiffness, and on the identification of the values of these matrices on an extensive database of numerical experiments computed using coupled finite element–boundary element models. The formulations obtained can be readily used for the design of both floating piles on homogeneous half‐space and end‐bearing piles and are applicable for a wide range of mechanical and geometrical parameters of the soil and piles, in particular for large pile groups. For the seismic design of a building, the use of the simple formulas rather than a full computational model is shown to induce little error on the evaluation of the response spectra and time histories. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Drought characterization: a probabilistic approach   总被引：4，自引：0，他引：4  

A. K. Mishra  V. P. Singh  V. R. Desai 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(1):41-55

Using the alternative renewable process and run theory, this study investigates the distribution of drought interval time, mean drought interarrival time, joint probability density function and transition probabilities of drought events in the Kansabati River basin in India. The standardized precipitation index series is employed in the investigation. The time interval of SPI is found to have a significant effect of the probabilistic characteristics of drought.  相似文献   

多孔介质热流固耦合问题及研究进展     

刘峰  朱庆杰  程雨  党旭光 《岩土力学》2009,30(Z2):254-256

渗流场、温度场、变形场之间存在复杂的耦合作用,即热-流-固耦合作用。热-流-固耦合问题涉及许多领域,它的研究越来越受到人们的重视。介绍了多孔介质热-流-固耦合研究的基本方法和原理,对多孔介质热-流-固耦合的研究进展加以综述和讨论,并提出了进一步研究的方向。  相似文献   

Hydrodynamics and sediment dynamics in the German Bight. A focus on observations and numerical modelling in the East Frisian Wadden Sea     

Joanna Staneva  Emil V. Stanev  Jörg-Olaf Wolff  Thomas H. Badewien  Rainer Reuter  Burghard Flemming  Alexander Bartholomä  Karsten Bolding 《Continental Shelf Research》2009

This work deals with analysis of hydrographic observations and results of numerical simulations. The data base includes acoustic Doppler current profilers (ADCP) observations, continuous measurements on data stations and satellite data originating from the medium resolution imaging spectrometer (MERIS) onboard the European Space Agency (ESA) satellite ENVISAT with a spatial resolution of 300 m. Numerical simulations use nested models with horizontal resolutions ranging from 1 km in the German Bight to 200 m in the East Frisian Wadden Sea coupled with a suspended matter transport model. Modern satellite observations have now a comparable horizontal resolution with high-resolution numerical model of the entire area of the East Frisian Wadden Sea allowing to describe and validate new and so far unknown patterns of sediment distribution. The two data sets are consistent and reveal an oscillatory behaviour of sediment pools to the north of the back-barrier basins and clear propagation patterns of tidally driven suspended particulate matter outflow into the North Sea. The good agreement between observations and simulations is convincing evidence that the model simulates the basic dynamics and sediment transport processes, which motivates its further use in hindcasting, as well as in the initial steps towards forecasting circulation and sediment dynamics in the coastal zone.  相似文献   

Spatial analysis of instream nitrogen loads and factors controlling nitrogen delivery to streams in the southeastern United States using spatially referenced regression on watershed attributes (SPARROW) and regional classification frameworks   总被引：1，自引：0，他引：1  

Anne B. Hoos  Gerard McMahon 《水文研究》2009,23(16):2275-2294

Understanding how nitrogen transport across the landscape varies with landscape characteristics is important for developing sound nitrogen management policies. We used a spatially referenced regression analysis (SPARROW) to examine landscape characteristics influencing delivery of nitrogen from sources in a watershed to stream channels. Modelled landscape delivery ratio varies widely (by a factor of 4) among watersheds in the southeastern United States—higher in the western part (Tennessee, Alabama, and Mississippi) than in the eastern part, and the average value for the region is lower compared to other parts of the nation. When we model landscape delivery ratio as a continuous function of local‐scale landscape characteristics, we estimate a spatial pattern that varies as a function of soil and climate characteristics but exhibits spatial structure in residuals (observed load minus predicted load). The spatial pattern of modelled landscape delivery ratio and the spatial pattern of residuals coincide spatially with Level III ecoregions and also with hydrologic landscape regions. Subsequent incorporation into the model of these frameworks as regional scale variables improves estimation of landscape delivery ratio, evidenced by reduced spatial bias in residuals, and suggests that cross‐scale processes affect nitrogen attenuation on the landscape. The model‐fitted coefficient values are logically consistent with the hypothesis that broad‐scale classifications of hydrologic response help to explain differential rates of nitrogen attenuation, controlling for local‐scale landscape characteristics. Negative model coefficients for hydrologic landscape regions where the primary flow path is shallow ground water suggest that a lower fraction of nitrogen mass will be delivered to streams; this relation is reversed for regions where the primary flow path is overland flow. Published in 2009 by John Wiley & Sons, Ltd.  相似文献   

An easily implemented agro-hydrological procedure with dynamic root simulation for water transfer in the crop–soil system: Validation and application     

Dejun Yang  Tuqiao Zhang  Kefeng Zhang  Duncan J. Greenwood  John P. Hammond  Philip J. White 《Journal of Hydrology》2009,370(1-4):177-190

Models for water transfer in the crop–soil system are key components of agro-hydrological models for irrigation, fertilizer and pesticide practices. Many of the hydrological models for water transfer in the crop–soil system are either too approximate due to oversimplified algorithms or employ complex numerical schemes. In this paper we developed a simple and sufficiently accurate algorithm which can be easily adopted in agro-hydrological models for the simulation of water dynamics. We used a dual crop coefficient approach proposed by the FAO for estimating potential evaporation and transpiration, and a dynamic model for calculating relative root length distribution on a daily basis. In a small time step of 0.001 d, we implemented algorithms separately for actual evaporation, root water uptake and soil water content redistribution by decoupling these processes. The Richards equation describing soil water movement was solved using an integration strategy over the soil layers instead of complex numerical schemes. This drastically simplified the procedures of modeling soil water and led to much shorter computer codes. The validity of the proposed model was tested against data from field experiments on two contrasting soils cropped with wheat. Good agreement was achieved between measurement and simulation of soil water content in various depths collected at intervals during crop growth. This indicates that the model is satisfactory in simulating water transfer in the crop–soil system, and therefore can reliably be adopted in agro-hydrological models. Finally we demonstrated how the developed model could be used to study the effect of changes in the environment such as lowering the groundwater table caused by the construction of a motorway on crop transpiration.  相似文献