波列振幅P em>-Sem>曲线测桩法          下载免费PDF全文

胡毅力  许峻  段永康  许昭永  杨润海  赵晋明 《地震学报》2004,26(6):660-668

叙述一种新的大应变检测单桩竖向承载力的方法. 用重锤或小型火箭筒冲击桩顶，用检波器记录振波图. 引入应变（变形力）的高次项，从理论上证明当为大位移大应变， 即桩相对于土体产生整体滑动时，位移、速度和加速度则不能经过简单积分加速度和微分速度得到，即它们为非线性关系. 由此导出:通过波列振幅计算力（P）和位移（S）,并作（动态）P-S曲线、确定屈服点，进而阐述确定单桩竖向承载力的方法，并利用静载荷试验检验动测结果和确定动静P（Q）S曲线的相关常数.   相似文献   

Plane strain deformation of a multi-layered poroelastic half-space by surface loads     

Sarva Jit Singh  Sunita Rani 《Journal of Earth System Science》2006,115(6):685-694

The Biot linearized quasi-static theory of fluid-infiltrated porous materials is used to formulate the problem of the two-dimensional plane strain deformation of a multi-layered poroelastic half-space by surface loads. The Fourier-Laplace transforms of the stresses, displacements, pore pressure and fluid flux in each homogeneous layer of the multi-layered half-space are expressed in terms of six arbitrary constants. Generalized Thomson-Haskell matrix method is used to obtain the deformation field. Simplified explicit expressions for the elements of the 6 × 6 propagator matrix for the poroelastic medium are obtained. As an example of the possible applications of the analytical formulation developed, formal solution is given for normal strip loading, normal line loading and shear line loading.  相似文献   

Effect of train dynamics on seismic response of steel monorail bridges under moderate ground motion     

Chul‐Woo Kim  Mitsuo Kawatani 《地震工程与结构动力学》2006,35(10):1225-1245

This study is intended to investigate the seismic response of steel monorail bridges using three‐dimensional dynamic response analysis. We particularly consider monorail bridge–train interaction when subjected to ground motion that occurs with high probability. A monorail train car with two bogies with pneumatic tires for running, steering and stabilizing wheels is assumed to be represented sufficiently by a discrete rigid multi‐body system with 15 degrees of freedom (DOFs). Bridges are considered as an assemblage of beam elements with 6 DOFs at each node. Modal analysis is used for dynamic response analysis under moderate earthquakes. The seismic response of an advanced monorail bridge that adopts a simplified structural system and composite girders is investigated through comparison with seismic responses of a conventional bridge. The acceleration response of a monorail train is also calculated to investigate the effect of structural types of bridges on the train's dynamic response during earthquakes. Results show that the seismic responses of the advanced bridges are greater than those of the conventional monorail bridge because of the simplified structural system and increased girder weight that is attributable to composite girders of the advanced bridge. Moreover, the train on the advanced bridge shows greater dynamic response than that on the conventional bridge. Observations reveal that the dynamic monorail train system acts as a damper on the monorail bridge. That fact shows that the existing design, which considers a train as additional mass, yields a conservative result. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Dynamic analysis of train–bridge system subjected to non‐uniform seismic excitations     

He Xia  Yan Han  Nan Zhang  Weiwei Guo 《地震工程与结构动力学》2006,35(12):1563-1579

Based on the theory of dynamic wheel–rail interactions, a dynamic model of coupled train–bridge system subjected to earthquakes is established, in which the non‐uniform characteristics of the seismic wave input from different foundations are considered. The bridge model is based on the modal comprehension analysis technique. Each vehicle is modelled with 31 degrees of freedom. The seismic loads are imposed on the bridge by using the influence matrix and exerted on the vehicles through the dynamic wheel–rail interaction relationships. The normal wheel–rail interaction is tackled by using the Hertzian contact theory, and the tangent wheel–rail interaction by the Kalker linear theory and the Shen–Hedrick–Elkins theory. A computer code is developed. A case study is performed to a continuous bridge on the planned Beijing–Shanghai high‐speed railway in China. Through input of typical seismic waves with different propagation velocities to the train–bridge system, the histories of the train running through the bridge are simulated and the dynamic responses of the bridge and the vehicles are calculated. The influences of train speed and seismic wave propagation velocity on the dynamic responses of the bridge–vehicle system are studied. The critical train speeds are proposed for running safety on high‐speed railway bridges under earthquakes of various intensities. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

地震荷载下饱和砂土孔压增长时程计算方法   总被引：2，自引：0，他引：2  

孙锐  袁晓铭 《地震工程与工程振动》2006,26(3):261-263

本文采用逐波累计方法,依据适于不同固结条件的孔压增量模型,计算每一应力循环的孔压变化,可给出非均等固结复杂情况下孔压实时增长过程。采用不同固结比两种砂进行若干典型地震荷载动三轴液化试验,试验结果与所提方法的计算结果有良好对应关系,表明本文方法可有效地描述地震荷载作用下非均等固结饱和砂土孔压增长过程。  相似文献   

吉林海沟金成矿预测新思路——控矿构造层次     

孙忠实  冯亚民 《吉林地质》1998,17(3):43-50

深部成矿预测已成为海沟金矿当务之急。为进一步加强区内,外找矿工作,本文提出金矿预测新思路－控矿构造层次。依据金矿产出地质条件的不同,将金矿控矿构造划分为中部,浅部,浅－表部和表部四个层次,每个层次都有特征性的控矿鉴别标志,分别反映出是大陆张裂、隆－滑和拆离构造等多种大陆壳动力学机制转变过程中的产物。最后通过纵、横向不同层次控矿构造特征变化规律进行成矿预测。  相似文献   

桁架结构基于地震可靠性分析的优化方法     

李鸿晶  冯启民 《地震工程与工程振动》1997,17(1):9-13

本文把桁架结构地震可靠性分析和最优化设计方法结合起来，以结构的地震失效率概率为目标函数，给出一种考虑地震可靠性的桁架结构的优化方法。该方法能够解决线性桁架体系在平稳的随机地震地面运动激励下的优化问题，并在给定投资的条件下设计出了安全可靠的桁架结构。  相似文献   

我国地震预报的某些科学问题     

石特临  毛可 《国际地震动态》1996,(3):1-6

积３０年来成功的经验与失败的教训，本文对我国地震预报的前提，基础，科学思路及技术途径进行了研究。  相似文献   

Analysis of train-induced vibrations and vibration reduction schemes above and below critical Rayleigh speeds by finite element method   总被引：6，自引：0，他引：6  

Shen-Haw Ju  Hung-Ta Lin 《Soil Dynamics and Earthquake Engineering》2004,24(12):993-1002

This paper simulates soil vibration under the train speed below and over the soil Rayleigh speed using the three-dimensional finite element method. Two vibration isolation schemes were studied including the soil improvement around the railway and the concrete slab constructed between the rail and soil. Numerical results indicate that the vibration increases considerably and decays slowly when the train speed exceeds the soil Rayleigh speed. The wave direction and dominant frequencies are the simple functions of the train speed, the soil Rayleigh speed and the train compartment length. When the train speed exceeds the shear wave speed, the vibration magnitude is critical and not sensitive to the train speed. To reduce this vibration, the two isolation schemes investigated in this study are useful for the train speed over the soil Rayleigh speed, but they are not efficient for the train speed below the soil Rayleigh speed.  相似文献   

高层大气三维热力结构异常及其遥相关特征对江淮流域旱涝的影响   总被引：1，自引：0，他引：1  

苗秋菊  徐祥德  姚文清  周丽 《气象学报》2003,61(4):457-465

文中分析了江淮流域旱涝过程与南北半球经向波列遥相关特征,结果表明,前期赤道地区高层大气的三维热力结构异常与中国江淮流域夏季旱涝异常存在显著相关。进一步研究发现,江淮流域夏季旱、涝年与前期春季低纬高层大气热力结构呈显著的反位相特征,且两者垂直方向均呈跨越南北半球经向波列结构特征,该波列扰动源可追溯到南极冰盖强信号因子。采用EP通量诊断分析可进一步揭示出与江淮流域旱涝过程相关的经向波列传播及高层大气波射线折射特征。  相似文献