Fast iterative solution of large undrained soil‐structure interaction problems     

Kok‐Kwang Phoon  Swee‐Huat Chan  Kim‐Chuan Toh  Fook‐Hou Lee 《国际地质力学数值与分析法杂志》2003,27(3):159-181

In view of rapid developments in iterative solvers, it is timely to re‐examine the merits of using mixed formulation for incompressible problems. This paper presents extensive numerical studies to compare the accuracy of undrained solutions resulting from the standard displacement formulation with a penalty term and the two‐field mixed formulation. The standard displacement and two‐field mixed formulations are solved using both direct and iterative approaches to assess if it is cost‐effective to achieve more accurate solutions. Numerical studies of a simple footing problem show that the mixed formulation is able to solve the incompressible problem ‘exactly’, does not create pressure and stress instabilities, and obviate the need for an ad hoc penalty number. In addition, for large‐scale problems where it is not possible to perform direct solutions entirely within available random access memory, it turns out that the larger system of equations from mixed formulation also can be solved much more efficiently than the smaller system of equations arising from standard formulation by using the symmetric quasi‐minimal residual (SQMR) method with the generalized Jacobi (GJ) preconditioner. Iterative solution by SQMR with GJ preconditioning also is more elegant, faster, and more accurate than the popular Uzawa method. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Predicting ground-motion variations at the Turkey-flat test site,California     

J. Zahradník  J. Jech  V. Barták 《Pure and Applied Geophysics》1991,137(1-2):63-84

Results of a single group participating in an international experiment are analyzed. The experiment served to verify computational predictions of the ground-motion variations due to near-surface geological effects at a site established for that purpose by the California Department of Conservation. Based on an acceleration record at a rock location, and geotechnical model of medium, records at the other locations of a nearby sedimentary deposit were predicted. A 2-D finite-difference sensitivity analysis suggested that the lateral wave-propagation effects are negligibly small, and locally 1-D computations are sufficient for the present site. Those computations are compared with observations not available to the authors during the blind prediction. Peak accelerations, peak velocities and RMS accelerations were predicted with errors less than 159%, 114% and 62%, respectively. Maxima of the response spectra were fitted within a factor of 2. The predicted and observed Husid's plots (i.e., the normalized cumulative plots of the acceleration squared) have the correlation coefficients 0.98. The detected misfits do not show any simple relation to the instrument location, component, frequency, or time.  相似文献   

Urban consolidation and house prices: a case study of Melbourne 1990–2004     

Sun Sheng Han  Kevin O’Connor 《GeoJournal》2008,73(4):285-295

This paper explores the links between a strategic policy, urban consolidation, and house prices by examining the changes in the mix of housing and in house price for the period 1991–2004. We contend that urban consolidation could be seen as a source of additional supply, (which might be expected to be felt in lower prices and so contribute to a local policy objective) but also as a stimulus to demand (by developers who could bid up the price of lots where it was understood more housing could be built). Analyses were carried out at the metropolitan and sub-regional scales using correlation tests. The research finds very weak statistical connections, and concludes that this policy has not been associated with price changes.  相似文献   

Ground motion estimation during the Kashmir earthquake of 8th October 2005   总被引：2，自引：1，他引：1  

S. T. G. Raghukanth 《Natural Hazards》2008,46(1):1-13

In this article, analytical methods have been used to estimate ground motion during the 8 October 2005, Kashmir earthquake. Peak ground acceleration (PGA) values at several stations in the epicentral region have been estimated by empirical analytical source mechanism models. As an alternate analysis, PGA estimates have also been obtained using the stochastic finite fault seismological model. The estimated PGAs are compared with that obtained from damage values. A PGA contour map in the near-source region is provided. It is found that very near to the epicenter, PGA would have reached more than 1 g. It is demonstrated that empirical analytical models can be effectively used to estimate ground motion due to rupture of active faults.  相似文献   

中国-俄罗斯原油管道工程(漠河-大庆段)冻土工程地质考察与研究进展   总被引：4，自引：2，他引：2  

李国玉  金会军  盛煜  张建明  俞祁浩  齐吉琳  温智  吕兰芝  童长江  郭东信  王绍令  魏智  杨思忠  吉延俊  于少鹏  何瑞霞  常晓丽  郝加前  陈友昌  吴伟  翟镇远  赵意民 《冰川冻土》2008,30(1):170-175

在2005-2007年期间,先后3次对中国-俄罗斯原油管道漠河-大庆段沿线的冻土工程地质条件等进行科学考察,开展了冻土工程地质条件及其在气候变化和人类活动作用下的评价和预测研究.考察研究结果表明:管道沿线多年冻土在各类融区、季节冻土和水系等分隔作用下呈片状或岛状分布,沿线岛状、稀疏岛状及零星岛状占多年冻土区段的40%左右;管道沿线多年冻土随着气候的转暖和人类活动的影响不断退化.地形地貌单元、植被分布、地表水分条件的变化等局部因素对多年冻土的分布和地下冰的赋存产生重要的影响,管道沿线大约分布有50 km左右的沼泽湿地,其表层为腐殖质土及泥炭层,泥炭层下面分布着含土冰层或地下冰,是管道沿线最差的冻土工程地质地段;由于中俄原油管道沿线水系发育多,冻胀丘、冰椎和冰幔等不良冻土现象广泛分布.科学考察的成果为管道沿线冻土工程地质条件评价和预测、管道的稳定性影响分析以及后期的长期检测系统设置等研究奠定坚实的基础,进一步为即将开工的中俄原油管道漠河-大庆段工程的设计、施工提供科学依据.  相似文献   

基于Poulos弹性理论的被动桩改进算法     

陈福全  黄伟达 《岩土力学》2008,29(4):905-910

传统的Poulos弹性理论仅适合于均质土中土体侧向位移时桩的性状分析,无法考虑土的层状特性。通过引入层状地基中作用一水平集中力的广义Mindlin解和地面作用有竖向荷载时的应力和位移通解,对Poulos方法进行了改进,使之扩展到多层土中,还用于研究堆载条件下的被动桩变形和受力响应。算例分析表明,改进弹性理论要比Poulos方法更为严密、合理,提高了计算精度,应用范围也更广。  相似文献   

潮湿环境下古代土遗址的原位保护加固研究   总被引：3，自引：1，他引：2  

周环  张秉坚  陈港泉  赵海英  曾余瑶  郭青林  李最雄  王旭东 《岩土力学》2008,29(4):954-962

古遗址的保护是文物保护工作中最复杂的问题之一,而土质文物是文物保护中最难保护的文物,所以古代土遗址的保护已在国际上被列为专门的保护项目,而处于潮湿环境下的古代土遗址保护的课题在文化遗产实物和遗迹就地保存和展示领域就更为迫切。浙江良渚文化是中国新石器时代长江流域最重要的史前文化, 塘山遗址位于良渚文化遗址的西北部,选择了PS（硅酸钾）、WD－10（十二烷基三甲氧基硅烷）、WD－S（低聚甲氧基硅烷）、RTV（聚有机硅氧烷+硅酸乙酯）4种保护材料对塘山遗址进行了保护加固实验研究。室内实验和现场实验（2个月,6个月,9个月）的结果都表明,RTV和WD-10防水性优于WD-S,WD-10和WD-S材料仅能作为防水材料,PS材料仅能作为加固材料使用,而RTV则具有较好的加固和防水效果,且加样量越大,强度提高越多。  相似文献   

环渤海区域大气水份平衡特征的研究     

李爱贞  张富强  张桂芹  刘厚凤 《海洋科学》1996,20(5):29-34

利用１９８１￣１９９０年环渤海地区的地面气象资料，探空资料和土地利用资料，计算了该地区大气水份平衡方程中各分量，分析了其变化特征，并对它们之间的相互关系进行了研究。  相似文献   

烟威渔场盐度预报及分析     

郑东  张瑞安 《中国海洋大学学报(自然科学版)》1989,(Z1)

本文以我国北黄海的烟威渔场为研究对象,采用优选因子场预报模式,对盐度的时空变化进行预报试验。文中对所采用的统计预报方法,作了简要介绍。对影响本海区盐度变化的显著因子及预报结果作了初步分析。预报试验表明:预报的总体平均绝对误差为0.27‰,预报相对误差在18％左右,预报误差小于0.5‰的站数占总站数的85％,预报趋势与实测资料基本一致。  相似文献   

A Note on Soil Structure Resistance of Natural Marine Deposits   总被引：1，自引：1，他引：1  

洪振舜刘松玉  刘志方 《中国海洋工程》2004,18(2):321-326

It has been well documented that natural normally-consolidated marine soils are generally subjected to the effects of soil structure. The interpretation of the resistance of soil structure is an important issue in the theory study and engineering practice of ocean engineering and geotechnical engineering. It is traditionally considered that the resistance of soil structure gradually disappears with increasing stress level when the applied stress is beyond the consolidation yield stress. In this study, however, it is found that this traditional interpretation of the resistance of soil structure can not explain the strength behavior of natural marine deposits with a normally-consolidated stress history A new interpretation of the resistance of soil structure is proposed based on the strength behavior. In the preyield state, the undrained strength of natural marine deposits is composed of two components: one developed by the applied stress and the other developed by the resistance of soil structure. When the applied stress is beyond the consolidation yield stress, the strength behavior is independent of the resistance of soil structure.  相似文献