Influence of a cyclic and dynamic loading history on dynamic properties of dry sand, part II: cyclic axial preloading     

T. Wichtmann  Th. Triantafyllidis 《Soil Dynamics and Earthquake Engineering》2004,24(11):789-803

Initial fabric of a soil induced by its cyclic strain history is an important parameter among others like void ratio, state of stress and amplitude concerning the further accumulation of deformations under cyclic loading. It is of high importance to determine methods in order to estimate the initial fabric of the grain skeleton or the cyclic loading history of the soil. An attempt is made in this paper to correlate small strain stiffness of non-cohesive soil with its cyclic loading history. For this purpose several cyclic triaxial tests with specimens subjected to cyclic axial loading were performed and changes of small strain soil properties due to this cyclic loading were studied. All these tests showed only moderate changes of small strain stiffnesses independently of the different boundary conditions. Thus, a correlation between fabric or strain history and small strain stiffnesses seems not to be possible.  相似文献   

中国城市建设与地质灾害综述   总被引：8，自引：0，他引：8  

陈桂荣  王经武 《地质灾害与环境保护》2002,13(2):1-5

在大量调查、分析与研究的基础上，结合中国经济发展中城市快速发展面临的一系列地质灾害，采用自然科学与社会科学相互交叉的方法，分析了城市地质灾害的危害性及对城市发展的影响，根据中国城市发展的实际情况和2001年以后的远景目标，因地制宜地提出了整治城市灾害的基本对策与管理措施，为国家制定城市发展远景规划和奋斗目标提供基本思路。  相似文献   

人类活动对北京东灵山山顶草甸植被的影响及草甸植被的保育对策   总被引：7，自引：0，他引：7  

江源  赵海霞  刘肖骢  常玉涛 《地球科学进展》2002,17(2):235-240

通过对北京东灵山海拔 1500 m以上草甸植被资源的调查，共获得41个面积为 4 m×4 m的样方资料。将不同草甸群落按照人类活动的影响作用进行归类，并对各个草甸群落的生境和群落特征进行分析，结果表明：①东灵山山顶草甸植被以人类活动影响下形成的次生草甸群落为主，原生性草甸仅分布在海拔 2000 m以上的山顶及其邻近地段；②种类组成最丰富的草甸群落位于海拔1510～1900m的地段，这是自然条件和人类活动共同作用的结果；③旅游活动的影响已经使山顶原生性草甸受到威胁，局部地段草甸植被退化严重；④限制马匹活动，适时、适度提高缆车票价，在草甸分布地段部分拆除并制止新建饭店、旅馆，实行旅游功能分区规划和管理，有针对性地开展草甸承载力研究等，是现阶段草甸植被保育的重要措施。  相似文献   

Continuous ambient‐vibration monitoring of the arch dam of Mauvoisin     

Georges R. Darbre  Jean Proulx 《地震工程与结构动力学》2002,31(2):475-480

This paper presents the experimental programme and results of a continuous ambient vibrations recording programme carried out on the 250 m arch dam of Mauvoisin. This project follows a series of previous measurements completed for seven different water levels. An automated system was set up on the dam and the ambient vibrations were recorded twice daily for a period of 6 months. Frequency shifts were tracked throughout the testing period and the effects of the varying water level were identified. The results confirmed the behaviour observed in previous ambient‐ and forced‐vibration tests. The added‐mass effects are overcome by the stiffening of the dam due to increasing hydrostatic pressure for lower reservoir levels. This trend is then reversed for higher water levels. Any temperature‐related effects were not identified. The experimental techniques are briefly described and the frequency identification process and its limitations are discussed. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

中国铅芯夹层橡胶隔震支座各种相关性能及长期性能研究   总被引：5，自引：1，他引：5  

刘文光  庄学真  周福霖  三山刚史  冯德民  加藤泰正 《地震工程与工程振动》2002,22(1):114-120

本文详细地研究了各种相关因素对中国铅芯橡胶隔震支座力学性能的 影响，同时还研究了中国铅芯夹层橡胶隔震支座的长期性能。研究包括竖向压力、频率、剪切变形循环次数、温度对隔震支座刚度及阻尼等力学性能的影响；隔震支座的耐久性能诸如老化及徐变对隔震器刚度、阻尼特性及极限变形能力的影响。研究还包括水平剪切（200次）及竖向低周疲劳（10万次）试验对隔震器力学性能的影响。  相似文献   

偏心结构扭转振动研究中几个基本参量的讨论   总被引：6，自引：4，他引：6  

戴君武  张敏政  黄玉龍 《地震工程与工程振动》2002,22(6):38-43

本文根据工程振动实测观察及结构地震模拟实验中的模态测量结果指出，通常的确定性弹性分析方法中，直接由构件的几何尺寸确定其刚度并进而确定结构的自振特性，进行结构的弹性反应分析和设计，其结果只能代表结构处于完全理想弹性状态时对外界激励的一种理论估计。由此提出了比较切合实际的基于强度及屈服变形的构件刚度的确定方法，进而指出在偏心结构的扭转振动研究中，结构的刚度偏心实际上依赖于强度偏心，并不能随研究者的意愿随意调整。  相似文献   

位移保护下力-控制拟动力试验方法的原理   总被引：1，自引：3，他引：1  

田石柱  赵桐  赵雪峰 《地震工程与工程振动》2002,22(3):37-41

本文提出了大刚度多自由度钢筋混凝土结构和砌体结构的拟动力试验技术新方法，即以力控制方式为基础的力－位移混合控制方法。这种新方法能实现大刚度多自由度钢筋混凝土结构和砌体结构的拟动力试验。  相似文献   

低硬度橡胶隔震支座基本力学性能及恢复力特性   总被引：4，自引：2，他引：4  

刘文光  李峥嵘  周福霖  三山刚史  冯德民 《地震工程与工程振动》2002,22(3):138-144

本研究对低硬度橡胶隔震支座的材料性能（主要包括力学性能）进行了系统的试验开发及理论研究。研究用低硬度橡胶隔震支座包括天然橡胶隔震支座及铅芯橡胶隔震支座两大类18种规格总计近30个大直径隔震支座。研究内容涉及橡胶隔震支座竖向刚度、水平刚度及阻尼等基本力学性能；压缩界限，屈曲及极限剪切变形等界限性能；温度、压力、剪切变形、老化和徐变等相关性及长期特性；同时还对橡胶材料其他性能进行了系统的试验研究。本文主要介绍低硬度天然橡胶隔震支座及铅芯橡胶隔震支座的基本力学性能，如竖向、水平刚度和恢复力等特性。  相似文献   

低硬度橡胶隔震支座各种相关性及老化徐变特性   总被引：4，自引：1，他引：4  

刘文光  李峥嵘  周福霖  三山刚史  冯德民 《地震工程与工程振动》2002,22(6):115-121

作者系统地对低硬度橡胶隔震支座的材料和力学性能进行了试验研究。研究使用的低硬度橡胶隔震支座分18种规格，总计近30个大直径隔震支座。研究内容涉及低硬度橡胶隔震支座的基本力学性能；温度、压力、剪切变形、老化和徐变等相关性；压缩界限，屈曲及极限剪切变形等界限性能以及橡胶材料性能和隔震工程应用等方面。本文主要介绍低硬度橡胶隔震支座的压力、剪切变形、温度对支座刚度、阻尼等力学性能的影响，同时还对隔震支座的老化及徐变特性进行了试验研究，确定低硬度橡胶使用60年后的力学性能变化率。文中同时提出了低硬度橡胶支座的温度修正方程，并提出了隔震结构地震反应分析时支座刚度和屈服荷载变化的取值范围。  相似文献   

The shear strength of rock joints in theory and practice   总被引：62，自引：10，他引：62  

N. Barton  V. Choubey 《Rock Mechanics and Rock Engineering》1977,10(1-2):1-54

SummaryThe Shear Strength of Rock Joints in Theory and Practice The paper describes an empirical law of friction for rock joints which can be used both for extrapolating and predicting shear strength data. The equation is based on three index parameters; the joint roughness coefficientJRC, the joint wall compressive strengthJCS, and the residual friction angle _r . All these index values can be measured in the laboratory. They can also be measured in the field. Index tests and subsequent shear box tests on more than 100 joint samples have demonstrated that _r can be estimated to within ± 1° for any one of the eight rock types investigated. The mean value of the peak shear strength angle (arctan/ _n ) for the same 100 joints was estimated to within 1/2°. The exceptionally close prediction of peak strength is made possible by performing self-weight (low stress) sliding tests on blocks with throughgoing joints. The total friction angle (arctan/ _n ) at which sliding occurs provides an estimate of the joint roughness coefficientJRC. The latter is constant over a range of effective normal stress of at least four orders of magnitude. However, it is found that bothJRC andJCS reduce with increasing joint length. Increasing the length of joint therefore reduces not only the peak shear strength, but also the peak dilation angle and the peak shear stiffness. These important scale effects can be predicted at a fraction of the cost of performing large scale in situ direct shear tests.With 20 Figures  相似文献