Effects of the constitutive relationship on seismic response of soils. Part II. The site amplification study     

A. M. Puzrin  A. Shiran 《Soil Dynamics and Earthquake Engineering》2000,19(5):535

This paper is the first part of the general paper dealing with effects of constitutive modeling of cyclic stress–strain behavior of soils on site amplification. The paper concentrates on modeling of pseudo-static cyclic soil behavior in small to medium strain range. In order to fit the small strain data accurately, the chosen analytical stress–strain relationship should satisfy the specific small strain condition formulated for soils using the small strain data from the pseudo-static cyclic tests. Analysis of conventional relationships, in particular the Ramberg–Osgood (R–O) relationship, indicated that a failure to satisfy this condition lead to low accuracy of prediction of both tangent stiffness and damping ratio at small and medium strains. The logarithmic function originally proposed to describe static monotonic stress–strain behavior is applied to fit experimental cyclic backbone curves. Constructed to satisfy the formulated small strain condition for soils, this function has proven to be free from the limitations of the R–O and other relationships. When applied in combination with the Masing rules to predict damping ratios, it gives a good prediction in the small to medium strain range, where the Masing hypothesis is supported by experimental evidence.  相似文献   

地埋管道与土相互作用平面分析与计算方法   总被引：1，自引：0，他引：1  

刘全林 《岩土力学》2007,28(1):83-88

地埋管道上实测的土压力并不是按现行计算方法假定形状分布的,其分布形式与管土的相对刚度及施工埋设方式密切相关。为此,依据现场实测和模型试验得到的地埋管道受力特征,在平面应变条件下,采用建立的管-土相互作用分析Vlazov模型来模拟管-土之间的相互作用,考虑管道不同的埋设条件、管周的不同充填介质及管-土相互作用引起的土压力状态等情况,建立了地埋管与土相互作用平面问题的传递矩阵分析法。并设计了可视化计算机软件,实现了计算手段的创新。运用此软件对现场埋管工程作了分析计算,并与实测结果进行比较,验证了所建立的计算方法的正确性。  相似文献   

Peak velocities and peak surface strains during Northridge, California, earthquake of 17 January 1994   总被引：1，自引：0，他引：1  

M.D. Trifunac  M.I. Todorovska  S.S. Ivanovi? 《Soil Dynamics and Earthquake Engineering》1996,15(5):301-310

We present contours of the largest horizontal and vertical recorded peak velocities of strong ground motion during the Northridge, California, earthquake. Above the fault, the horizontal peak velocities exceeded 100 cm/s. The vertical velocities were larger than 20 cm/s. We also present contours of peak horizontal and vertical strain factors. Through most of the San Fernando Valley and the Santa Susana Mountains, the horizontal surface strain factor was larger than 10⁻³. The largest horizontal strain factor computed was for the Rinaldi Receiving Station ∼10^−2·2. The corresponding vertical strains were >10^−3·25 and 10⁻¹³, respectively. Through most of the Los Angeles Basin the horizontal peak surface strain factors were between 10^−3·75 and 10⁻³.  相似文献   

估计环境价值的陈述偏好技术比较分析   总被引：9，自引：0，他引：9  

徐中民  任福康  马松尧  郭庭天 《冰川冻土》2003,25(6):701-707

随着人们环境意识的提高和环境资产稀缺性的增加，在资源利用决策中，决策也逐渐考虑环境因素的作用。但是由于缺乏市场，环境物品利用决策中大多缺乏有关环境价值方面的信息，陈述偏好技术是当前解决环境物品经济价值评估的主要方法和手段．首先介绍了环境物品经济价值的分类和评估技术，从理论和应用角度系统地阐述了当前国际上广泛应用于环境物品非利用价值评估的陈述偏好技术(条件估值法，选择模型法，条件分级法，条件排队法和配对比较法)，并分析比较了各种不同的陈述偏好技术的差异，最后总结分析了陈述偏好技术的优缺点。  相似文献   

Nonlinear soil response as a natural passive isolation mechanism-the 1994 Northridge, California, earthquake     

M.D. Trifunac  M.I. Todorovska 《Soil Dynamics and Earthquake Engineering》1998,17(1):41-51

The spatial relationship between areas with severely damaged (red-tagged) buildings and areas with large strains in the soil (indicated by reported breaks in the water distribution system), observed during the 1994 Northridge earthquake, is analysed. It is shown that these areas can be separated almost everywhere. Minimal overlapping is observed only in the regions with very large amplitudes of shaking (peak ground velocity exceeding about 150 cm s⁻¹). One explanation for this remarkable separation is that the buildings on ‘soft’ soils, which experienced nonlinear strain levels, were damaged to a lesser degree, possibly because the soil absorbed a significant portion of the incident seismic wave energy. As a result, the total number of severely damaged (red-tagged) buildings in San Fernando Valley, Los Angeles and Santa Monica may have been reduced by a factor of two or more. This interpretation is consistent with the recorded peak accelerations of strong motion in the same area. It is concluded that significant reduction in the potential damage to wood frame single family dwellings may be expected in areas where the soil experiences ‘large’ strains (beyond the linear range) during strong earthquake shaking, but not significant differential motions, settlement or lateral spreading, near the surface.  相似文献   

3rd Ishihara Lecture: An investigation into why liquefaction charts work: A necessary step toward integrating the states of art and practice     

《Soil Dynamics and Earthquake Engineering》2015

This paper is a systematic effort to clarify why field liquefaction charts based on Seed and Idriss׳ Simplified Procedure work so well. This is a necessary step toward integrating the states of the art (SOA) and practice (SOP) for evaluating liquefaction and its effects. The SOA relies mostly on laboratory measurements and correlations with void ratio and relative density of the sand. The SOP is based on field measurements of penetration resistance and shear wave velocity coupled with empirical or semi-empirical correlations. This gap slows down further progress in both SOP and SOA. The paper accomplishes its objective through: a literature review of relevant aspects of the SOA including factors influencing threshold shear strain and pore pressure buildup during cyclic strain-controlled tests; a discussion of factors influencing field penetration resistance and shear wave velocity; and a discussion of the meaning of the curves in the liquefaction charts separating liquefaction from no liquefaction, helped by recent full-scale and centrifuge results. It is concluded that the charts are curves of constant cyclic strain at the lower end (V_s1<160 m/s), with this strain being about 0.03–0.05% for earthquake magnitude, M_w≈7. It is also concluded, in a more speculative way, that the curves at the upper end probably correspond to a variable increasing cyclic strain and K_o, with this upper end controlled by overconsolidated and preshaken sands, and with cyclic strains needed to cause liquefaction being as high as 0.1–0.3%. These conclusions are validated by application to case histories corresponding to M_w≈7, mostly in the San Francisco Bay Area of California during the 1989 Loma Prieta earthquake.  相似文献   

GRAPES-EPS系统的初值生成方法与对比试验研究   总被引：1，自引：0，他引：1  

王太微  陈德辉  吴曼丽 《气象与环境学报》2014,30(2):23-30

介绍了增长模繁殖法（BGM）和集合转化卡尔曼滤波法（ETKF）两种不同的模式初始扰动方法的基本原理,并以GRAPES中尺度模式为基础,利用两种初始扰动方法构建了两套中尺度集合预报系统。通过圣帕台风的个例试验,对比两种初始扰动生成方法对降水预报结果的影响。结果表明：两种方法均可以很好的捕捉到中尺度强降水的过程信息,集合平均结果优于控制预报,并在一定程度上改善了对强降水的落区和强度的预报;从邮票图和对集合预报系统的检验参数上来看,ETKF的集合离散度和特征值分布好于BGM方法,但对于降水结果TS等的评分的比较上来看,BGM的预报结果要优于ETKF的预报结果;另外,BGM方法和原理更简单,易于实现业务应用。  相似文献   

沙柳优良品系选育的研究   总被引：5，自引：2，他引：3  

李维向  刘朝霞  闫伟  张晓娟  缪树国  霍俊峰  王跃生 《中国沙漠》2008,28(4):679-684

对鄂尔多斯不同地区沙柳的表现型进行调查,并对7个不同地区的沙柳进行选育,对表现型优良的6个品系做耐盐性研究,结果表明:鄂尔多斯市不同地区沙柳的表现型存在较大差异,以台格庙地区沙柳的表现型最好,平均丛枝数和丛高分别达162枝和4.19 m,平均冠幅为5.15 m,与其他地区相比在p=0.05水平下差异显著;图克和查干尔淖地区沙柳表现型相对较差;选育后阿门其和台格庙两个地区沙柳生长性状相对较好,无性系繁殖苗成活率均达到90%以上,丛高和地径均高于其他地区无性系繁殖苗;查干尔淖地区无性系沙柳繁殖苗长势最差;筛选的6个沙柳品系均能在中度盐碱滩上生长,利用隶属函数分析法综合评价了6个沙柳品系的抗逆性强弱,筛选出了沙柳两个抗逆性优良品系,即Ⅲ-01和Ⅷ-02。这两个品系表现型优良,抗逆性强,适于在西北干旱、盐碱地上推广栽植。  相似文献   

大步长单程波算子相位积分实现方式初探   总被引：3，自引：3，他引：0       下载免费PDF全文

武威  刘洪 《地球物理学进展》2009,24(1):137-144

大步长单程波算子是穿过厚层的单程波算子的积分,在理论上它可以通过频率波数域表达式和波数域到空间域变换来实现,目前,通过李代数积分和指数映射的研究,已经导出频率波数域表达式,需要研究波数域到空间域变换的实现方式,波数域到空间域的变换可以通过鞍点法和相位积分来实现,本文研究了相位积分的三种实现途径:分裂方法、相移加插值方法和佳格点方法,在相移加插值方法中提出一种波场"角度域插值"的插值方法.  相似文献   

Distribution and reproductive behavior of penguins on Ardley Island and their environmental impact factors     

孙维萍  蔡明红  王海燕  邢闯  卢冰  H.U. Peter  A. Froehlich 《极地研究(英文版)》2010,21(2):204-213

During the 2006/07 Antarctic summer, the species population, distribution and reproductive behavior of penguins in areas near the Great Wall Station were investigated. Five species of penguin were recorded: gentoo penguin (Pygoscelis papua), adelie penguin (P. adeliae), chinstrap penguin (P. antarctica), King penguin (Aptenodytes patagonicus) and Emperor penguin (A. forsteri). The first three species bred locally, while the other two species were observed occasionally. Ardley Island is one of the most important breeding areas for penguins. After the breeding season of 2006/07, there were a total of about 17 234 penguins and the breeding success rate was 0.40-141. Comparing with historical data, changes in penguin species populations and distribution were analyzed, and their relationships with the environment, climate change and human activity were investigated.  相似文献