淮安市典型土动力特性的试验研究   总被引：3，自引：2，他引：3  

胡庆兴  刘雪珠  从卫民  陈国兴 《地震工程与工程振动》2003,23(6):144-148

通过对淮安市典型的全新世沉积粉土和粘性土进行室内自振柱试验及粉土的动三轴液化试验，把粉土和粘性土的自振柱试验结果与Seed和Idriss建议的砂土及饱和粘土的剪切模量比G／Gmax-γ曲线和阻尼比λ-γ曲线的变化范围进行对比，结果表明：粉土的剪模量比要比饱和粘土的大，而比砂土的剪模量比要小，其阻尼比接近于砂土的阻尼比；粘性土的剪模量比要比一般饱和粘土的大，而与砂土的剪模量比相近，其阻尼比要比砂土的略低；粉土的抗液化强度与液化振次之间的关系可以用指数函数来表示，其振动孔隙水压力的发展规律可以用反正弦三角函数拟合；粘粒含量是影响淮安市全新世沉积粉土抗液化强度的主要影响因素。  相似文献   

Frequency domain modal analysis of earthquake input energy to highly damped passive control structures     

Izuru Takewaki 《地震工程与结构动力学》2004,33(5):575-590

A new complex modal analysis‐based method is developed in the frequency domain for efficient computation of the earthquake input energy to a highly damped linear elastic passive control structure. The input energy to the structure during an earthquake is an important measure of seismic demand. Because of generality and applicability to non‐linear structures, the earthquake input energy has usually been computed in the time domain. It is shown here that the formulation of the earthquake input energy in the frequency domain is essential for deriving a bound on the earthquake input energy for a class of ground motions and for understanding the robustness of passively controlled structures to disturbances with various frequency contents. From the viewpoint of computational efficiency, a modal analysis‐based method is developed. The importance of overdamped modes in the energy computation of specific non‐proportionally damped models is demonstrated by comparing the energy transfer functions and the displacement transfer functions. Through numerical examinations for four recorded ground motions, it is shown that the modal analysis‐based method in the frequency domain is very efficient in the computation of the earthquake input energy. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Analysis of Blast Vibration Characteristics Across a Trench and a Pre-Split Plane   总被引：3，自引：0，他引：3  

A. J. Prakash  P. Palroy  D. D. Misra 《Fragblast: International Journal for Blasting and Fragmentation》2004,8(1):51-60

This paper presents the influence of various discontinuities, natural or artificial, on magnitude and frequencies of blast induced ground vibrations. These discontinuities were geological faults, a pond, a shaft incline, a trench and a pre-split plane interposed in the path of vibration propagation. In the post-trench region, ground vibrations in terms of peak particle velocity were significantly reduced and dominant frequencies in higher bands were consequently observed. Depth of trench with respect to blastholes were varied and consequent vibration characteristics were analyzed. The techniques of creating a trench and pre-split plane were successfully implemented in controlling vibration and in increasing the explosives charge to meet the scheduled production target of an opencast mine. Comparisons of ground vibration characteristics affected by a trench and a pre-split plane of the same depth are described in the text. The findings lead to the conclusion that such experimental data are necessary for production blasting in open cast mines under constrained conditions.  相似文献   

Efficient analysis of pile-group effect on seismic stiffness and strength design of buildings     

Izuru Takewaki  Akiko Kishida 《Soil Dynamics and Earthquake Engineering》2005,25(5):355-367

A new efficient method is developed for the analysis of pile-group effects on the seismic stiffness and strength design of buildings with pile foundations. An efficient continuum model consisting of a dynamic Winkler-type soil element and a pile is used to express the dynamic behavior of the structure-pile-soil system with only a small numerical error. The pile-group effect is taken into account through the influence coefficients among piles which are defined for interstory drifts and pile-head bending moments. It is shown that, while the pile-group effect reduces the interstory drift of buildings in general, it may increase the bending moment of piles at the head. This means that the treatment without the pile-group effect results in the conservative design for super-structures and requires a revised member design for piles.  相似文献   

Torsional dynamic response of a large‐diameter pipe pile in viscoelastic saturated soil     

Changjie Zheng  Hanlong Liu  Xuanming Ding  Yaru Lv 《国际地质力学数值与分析法杂志》2014,38(16):1724-1743

An analytical solution is developed in this paper to investigate the dynamic response of a large‐diameter end‐bearing pipe pile subjected to torsional loading in viscoelastic saturated soil. The wave propagation in saturated soil and pile are simulated by Biot's two‐phased linear theory and one‐dimensional elastic theory, respectively. The dynamic equilibrium equations of the outer soil, inner soil, and pile are established. The solutions for the outer and inner soils in frequency domain are obtained by Laplace transform technique and the separation of variables method. Then, the dynamic response of the pile is obtained on the basis of the perfect contacts between the pile and the outer soil as well as the inner soil. The results in this paper are compared with that of a solid pile in elastic saturated soil to verify the validity of the solution. Furthermore, the solution in this paper is compared with the classic plane strain solution to verify the solution further and check the accuracy of the plane strain solution. Numerical results are presented to analyze the vibration characteristics and illustrate the effect of the soil parameters and the geometry size of the pile on the complex impedance and velocity admittance of the pile head. Finally, the displacement of the soil at different depth and frequency is analyzed. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Soil‐pile interaction in the pile vertical vibration considering true three‐dimensional wave effect of soil     

W.B. Wu  K.H. Wang  Z.Q. Zhang  Chin Jian Leo 《国际地质力学数值与分析法杂志》2013,37(17):2860-2876

The dynamic response of an end bearing pile embedded in a linear visco‐elastic soil layer with hysteretic type damping is theoretically investigated when the pile is subjected to a time‐harmonic vertical loading at the pile top. The soil is modeled as a three‐dimensional axisymmetric continuum in which both its radial and vertical displacements are taken into account. The pile is assumed to be vertical, elastic and of uniform circular cross section. By using two potential functions to decompose the displacements of the soil layer and utilizing the separation of variables technique, the dynamic equilibrium equation is uncoupled and solved. At the interface of soil‐pile system, the boundary conditions of displacement continuity and force equilibrium are invoked to derive a closed‐form solution of the vertical dynamic response of the pile in frequency domain. The corresponding inverted solutions in time domain for the velocity response of a pile subjected to a semi‐sine excitation force applied at the pile top are obtained by means of inverse Fourier transform and the convolution theorem. A comparison with two other simplified solutions has been performed to verify the more rigorous solutions presented in this paper. Using the developed solutions, a parametric study has also been conducted to investigate the influence of the major parameters of the soil‐pile system on the vertical vibration characteristics of the pile. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Bounding surface model for soil resistance to cyclic lateral pile displacements with arbitrary direction     

《Computers and Geotechnics》2016

The development of a two-surface elastic–plastic bounding surface P–Y model for cyclic lateral pile motions is described. The kinematic-hardening model is applicable to the analysis of pile foundations subjected to loading with arbitrary azimuths relative to the pile axis. The model realistically captures the hysteretic energy damping associated with dynamic loading of subsea foundations through physically correct plastic mechanisms and provides results consistent with those observed in physical tests including cyclic loading. Its performance is demonstrated in element states of stress and in pile foundation analyses. The development based on the incremental theory of plasticity results in more robust solutions than may be obtained using alternative elastic, variable moduli and deformation plasticity formulations.  相似文献   

应用两次展开法求解系泊柱体慢漂运动方程     

金瑞佳  滕斌  吕林 《海洋工程》2016,34(5):11-19

在深海中系泊的海洋平台,如Spar平台,水下部分为带有系泊的圆柱结构,其水平方向运动响应往往具有较低的自振频率,容易在低频波浪力(源于非线性的差频效应)作用下发生共振响应,使结构发生大幅水平慢漂。当浮体的瞬时位置大幅偏离初始位置时,基于初始平衡位置的摄动展开法会存在较大误差。针对这一问题,采用两次展开方法,对大幅慢漂运动开展时域模拟研究。对双色波作用下自由漂浮圆柱的大幅运动响应问题进行数值分析,并与采用基于初始平衡位置的摄动展开法的计算结果进行了对比。结果表明,采用新的两次展开法可以计算出波浪遭遇频率的变化和波浪漂移阻尼,而这无法从基于初始平衡位置的常规摄动展开法中得到,体现了两次展开法在分析大幅慢漂问题上的优势。  相似文献   

确定砂土动剪切模量和阻尼比的方法对比     

宋东松  冯震  金红山  孙逸涵 《吉林大学学报(地球科学版)》2021,51(5):1366-1380

确定土体动剪切模量的常用方法有规范法、Kumar法和自相关函数法,确定相应阻尼比的方法有规范法、Das and Luo法、Kokusho法、Kumar法和互相关函数法,为了分析不同方法所产生差异,实现定量化对比分析,笔者以福建标准砂（粒径为0.5~1.0 mm）为研究对象,采用不排水的应力控制动三轴试验,探讨不同的确定土体动剪切模量和阻尼比方法的差异性,并给出了不同土体条件建议选用的方法。结果表明：1）3种方法确定动剪切模量的结果有一定的差异,随剪应变的增大结果的差异逐渐增大,有效围压对结果的差异性有所影响,当剪应变为4×10^-3,有效围压为100 kPa时,3种方法差异显著,相对误差最大接近20%;2）而5种方法确定阻尼比的结果差异显著,随着剪应变的增大,5种方法确定的阻尼比相对误差大体上均在迅速减小,只有规范法在有效围压为100 kPa时,其相对误差有较小的增大趋势;5种方法中,Kumar法确定的阻尼比最接近平均阻尼比,互相关函数法远高于平均阻尼比,Das and Luo法和Kokusho法确定的阻尼比基本一致但低于平均阻尼比。建议以后的工程应用中,加载方式为应力控制时,可采用自相关函数法确定动剪切模量,采用Kumar法确定阻尼比,二者确定的动剪切模量和阻尼比均最接近平均值。  相似文献   

Time effects on dynamic soil properties under random excitation conditions     

F. Amini 《Soil Dynamics and Earthquake Engineering》1995,14(6):439-443

Two types of clayey soils, a kaolinite and a bentonite, were tested using a resonant column apparatus under random excitation conditions. The concept of root mean square (rms) strain was utilized for the purpose of strain calculations during random loading. The conventional estimator of the transfer function was used for random vibration analysis. The effect of confinement duration (at a constant pressure) on dynamic soil properties, namely damping and shear modulus, was evaluated. The results indicate that for both cohesive soils, the effect of time was less pronounced during random vibration than sinusoidal loading at the same rms strain. This effect is however more pronounced when the peak shearing strain of sinusoidal loading is considered. Furthermore, time effects were more pronounced at low strain levels than at high strain levels.  相似文献