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1.
大连地区场地土动力学参数初步研究   总被引:3,自引:0,他引:3  
In this paper, dynamic soil parameters derived from Dalian area seismic risk assessment reports are collected. In this study, the measurement data is divided into 7 types, i.e. silty clay, muddy silty clay, clay, medium sand, rock fragments, backfill soil and fully-weathered slate. Statistics of the dynamic parameters of these soils are carried out to obtain the mean values of dynamic shear modulus ratio and damping ratio. Typical drill holes are selected to establish dynamic soil models to investigate the seismic response for various cases. The dynamic parameters of the models are taken from the statistical values of this study, the standard values of code 94 (i.e. the dynamic soil parameters for Dalian seismic microzonation), and the recommended values by Yuan Xiaoming et al. (2000) respectively. The calculated results of peak ground acceleration are compared with the response spectral characteristics. The results show that the statistical values are approximate to the values recommended by Yuan Xiaoming, et al. (2000), but different greatly with the standard values in code 94.  相似文献   

2.
Earth temperature is one of the most important factors influencing the mechanical properties of frozen soil. Based on the field investigation of the characteristics of ground deformation and ground failure caused by the Ms8.1 earthquake in the west of the Kuniun Mountain Pass,China, the influence of temperature on the dynamic constitutive relationship, dynamic elastic modulus, damping ratio and dynamic strength of frozen soil was quantitatively studied by means of the dynamic triaxial test. Moreover, the characteristics of ground motion on a permafrost site under different temperatures were analyzed for the four profiles of permafrost along the Qinghai-Xizang (Tibet) Railway using the time histories of ground motionacceleration with 3 exceedance probabilities of the Kunlun Mountains area. The influences of temperature on the seismic displacement, velocity, acceleration and response spectrum on permafrost ground were studied quantitatively. A scientific basis was presented for earthquake disaster mitigation for engineering foundations, highways and underground engineering in permafrost areas.  相似文献   

3.
A wide variety of near-fault strong ground motion records were collected from various tectonic environments worldwide and were used to study the peak value ratio and response spectrum ratio of the vertical to horizontal component of ground motion, focusing on the effect of earthquake magnitude, site conditions, pulse duration, and statistical component. The results show that both the peak value ratio and response spectrum ratio are larger than the 2/3 value prescribed in existing seismic codes, and the relationship between the vertical and horizontal ground motions is comparatively intricate. In addition, the effect of the near-fault ground motions on bridge performance is analyzed, considering both the material nonlinear characteristics and the P~? effect.  相似文献   

4.
The dynamic shear modulus for three types of undisturbed soil under different consolidation ratios is presented by using the resonant column test method. Its effects on surface ground motion is illustrated by calculation. The test results indicate that the power function is a suitable form for describing the relationship between the ratio of the maximum dynamic shear modulus due to anisotropic and isotropic consolidations and the increment of the consolidation ratio. When compared to sand, the increment of the maximum dynamic shear modulus for undisturbed soil due to anisotropic consolidation is much larger. Using a one-dimensional equivalent linearization method, the earthquake influence factor and the characteristic period of the surface acceleration are calculated for two soil layers subjected to several typical earthquake waves. The calculated results show that the difference in nonlinear properties due to different consolidation ratios is generally not very notable, but the degree of its influence on the surface acceleration spectrum is remarkable for the occurrence of strong earthquakes. When compared to isotropic consolidation, the consideration of actual anisotropic consolidation causes the characteristic period to decrease and the earthquake influence factor to increase.  相似文献   

5.
In order to understand the site soil response of the Xiangtang borehole seismic array under real strong ground motion, reveal the site response, verify the technique of borehole exploration, and improve the precision of in-situ test and laboratory test, this paper presents a new approach, which is composed of two methods. One is the layered site seismic response method, whose layer transform matrix is always real. The other is a global-local optimization technique, which uses genetic algorithm (GA)-simplex method. An inversion of multi-component waveforms of P, SV and SH wave is carried out simultaneously. By inverting the records of three moderate and small earthquakes obtained from the Xiangtang borehole array (2# ) site, the soil dynamic characteristic parameters, including P velocity, damping ratio and frequency-dependent coefficient b, which has not been given in previous literatures, are calculated. The results show that the soil S wave velocity of the Xiangtang 2# borehole is generally greater than that obtained from the 1994 in-situ test, and is close to the velocity of the 3# borehole, which is more than 200 m away from the 2# borehole. Meanwhile, perceptible soil nonlinear behavior under peak ground motion of about 60×10-2m/s2 is detected by the inversion analysis. The presented method can be used for studying the soil response of other borehole array sites.  相似文献   

6.
The dynamic equations of motion of asymmetric offshore platforms under three different environmental conditions:seismic action,wave action and their combination are established in this paper. In establishing these motion equations,three typical eccentricity types including mass eccentricity,rigidity eccentricity and their combination were considered,as are eccentricities that occur un-idirectionally and bi-directionally. The effects of the eccentricity type,the dynamic characteristics and the environmental conditions on the torsional coupling response of platforms are investigated and compared. An effort has also been made to analyze the inffluence of accidental eccentricity on asymmetric platforms with different eccentricity in two horizontally orthogonal directions. The results are given in terms of non-dimensional parameters,accounting for the uncoupled torsional to lateral frequency ratio. Numerical results reveal that the eccentricity type has a great inffluence on the torsionally coupled response under different environmental conditions. Therefore,it is necessary to consider the combination of earthquake and wave action in the seismic response analysis of some offshore platforms.  相似文献   

7.
A spectral-representation-based algorithm is proposed to simulate non-stationary and stochastic processes with evolutionary power,according to a prescribed non-stationary cross-spectral density matrix. Non-stationary multi-point seismic ground motions at different locations on the ground surface are generated for use in engineering applications. First,a modified iterative procedure is used to generate uniformly modulated non-stationary ground motion time histories which are compatible with the prescribed power spectrum. Then,ground motion time histories are modeled as a non-stationary stochastic process with amplitude and frequency modulation. The characteristic frequency and damping ratio of the Clough-Penzien acceleration spectrum are considered as a function of time in order to study the frequency time variation. Finally,two numerical examples are presented to validate the efficiency of the proposed method,and the results show that this method can be effectively applied to the dynamic seismic analysis of long and large scale structures.  相似文献   

8.
Dong Di 《中国地震研究》2006,20(4):435-448
According to the epicenter distance and the site classification, the 404 groups of earthquake recordings of the main shock of the Chi-Chi, Taiwan China earthquake in 1999 are catalogued. Based on these data, we analyze the statistical features of duration, PGA, envelopes and the response spectra ratio of the horizontal and vertical components of the acceleration recordings. The results of these analyses show that the effect of site classification on the acceleration of various components is obvious; furthermore, fault direction also has certain effects on the characteristics of the horizontal components of ground motion. The detailed research results are as follows: ( 1 ) the duration of the horizontal components of acceleration records increases with the softening of the site; (2) the direction of fault slip has some effects on PGA's attenuation features; (3) the average envelopes of acceleration records at different distances and site dames are basically single peak functions of time and the envelopes of horizontal and vertical components of ground motion are obviously different; (4) with the same epicenter distance, EW/NS response spectrum ratios tend to approximate 1.0 as the site becomes softer and the period shorter. V/H response spectrum ratios in short periods (〈 0. 1s) increase with the softening of site, however, V/H ratios within the long-period range ( 〉 characteristic period) decrease with the softening of the site, and the decrease of V/EW ratio speeds up relatively.  相似文献   

9.
The estimate of seismic site effects by experimental approaches is based on different assumptions aimed at simplifying the complex actual site conditions and related uncertainties.However,the reliability of the results can increase if the experimental data is focused on quite strong seismic sequences and the on-site acquisition of a large number of signals is deemed strategic for the assessment of the expected phenomena.Based on these considerations,the ground motion at the Red Zone sector of Amatrice hill,violently struck by the 2016-2017 Central Italy seismic sequence,was analyzed via an observational approach.A large set of weak motions(moment magnitude Mw 2.5-3.9)was analyzed in this study by means of standard(SSR)and horizontal to vertical(HVSR)spectral ratio techniques.The results from the experimental analysis of the site effects by using weak motion and noise signals show a significant amplification at the top of Amatrice hill with a remarkable polarization of the motion and changes in spectral shapes according to the topographic setting of the relief.  相似文献   

10.
The statistical characteristics of strong ground motion specified by response spectrum and power spectral density function are studied using 190 strong-motion records of the Haicheng and Tangshan earthquakes in China and 138 earthquakes in the western United States.The response spectrum is normalized by the peak ground acceleration(i.e.,represented as spectral magnification factor),and the power spectral density function is described by the Kanai-Tajimi spectrum.The statistics and dependence of parameters are evaluated,and correlations between the spectral magnification factor or Kanai-Tajimi spectral parameters and the site condition,epicentral distance,or local magnitude are investigated.The statistical characteristics of spectra China and the U.S.A.are compared.Based on the results obtained the values of the statistics on spectral parameters for earthquake engineering applications in China are suggested.  相似文献   

11.
砂卵(砾)石的动剪切模量比和阻尼比是河谷地貌场地地震反应分析的重要参数,对设计地震动参数的确定有重要影响。本文利用商洛市地震小区划项目砂卵石的动三轴试验结果,结合其他砂卵(砾)石动三轴试验结果,分组统计得到了稍密、中密、密实砂卵(砾)动三轴试验的推荐结果。建立了典型场地模型,研究了其动剪切模量比和阻尼比的不确定性对场地地震反应的影响。研究表明:动剪切模量比、阻尼比平均值±1倍标准差的不确定性对砂卵石场地峰值加速度的影响较小,说明了分组及统计结果的合理性;不同概率水平下,动剪模量比、阻尼比的变化导致高频部分反应谱有明显差异,0.04-0.1s的反应谱变化范围在20%左右,但对大于1.0s的长周期反应谱影响很小。针对砂卵(砾)石动剪切模量比和阻尼比的研究对提高工程场地设计地震动参数的可靠性具有重要意义。  相似文献   

12.
常规土类动剪切模量阻尼比超越概率计算方法   总被引:1,自引:0,他引:1       下载免费PDF全文
土的动剪切模量比和阻尼比是土层地震反应分析、工程场地地震安全性评价和地震小区划工作中的必备参数,但其不确定性显著,对地震动和抗震设计影响很大。本文以我国常规土类动剪切模量比和阻尼比与剪应变非线性关系试验为基础,研究考虑这两个动力参数变异性下其超越概率的计算方法。方法包括了试验数据的整理、超越概率的计算以及两个动力参数和超越概率关系模拟等几个步骤,最后给出了我国常规土类动剪切模量比和阻尼比超越概率的计算公式,为我国基于概率和可靠度思想的工程地震安全风险评估提供了一定基础。  相似文献   

13.
以天津滨海某软弱场地为例,在不同强度不同相位的地震动时程输入下,用等效线性化技术考虑土的动力非线性特性,计算水平成层场地的地震反应,研究天津地区厚层淤泥质粉质黏土的动剪模量比和阻尼比与剪应变幅值的关系曲线的变异性对深软场地地表峰值加速度及其反应谱的影响。结果表明:(1)在阻尼比较均值加减一倍标准差对地表地震动参数变化影响不大;(2)在动剪模量比均值增加或减1倍标准差,对2%超越概率水平下地表峰值加速度影响显著,对应地表峰值加速度可能增加或减小20%~30%,其地表反应谱谱型也有变高变瘦或变矮变胖的趋势;(3)在动剪切模量均值减1倍标准差时,对10%超越概率水平下的地表峰值加速度的影响比较显著,减小幅度在15%左右,反应谱也存在变矮变胖的趋势;在动剪切模量均值加1倍标准差时,对10%超越概率水平下的地表地震动参数影响不明显;(4)在动剪切模量或阻尼比均值加减1倍标准差时,对63%的地表地震动参数影响均不明显。  相似文献   

14.
陕北榆林地区位于鄂尔多斯地块内部,其沉积地层主要为细砂。基于该地区大量的工程场地地震安全性评价报告,本文共收集了83组砂样动三轴试验数据,并分类统计分析了松散~稍密、中密和密实三种密实程度的砂土在8个典型剪应变下的动剪切模量比和阻尼比统计值。选取一个典型钻孔,建立土层地震反应模型,分别以本文"统计值"、"规范值"和"推荐值"作为模型参数进行土层地震反应计算,并对反应得到的地面峰值加速度与反应谱进行了对比分析。  相似文献   

15.
太原地区土动剪切模量和阻尼比几种值的合理性比较   总被引:1,自引:0,他引:1  
李自红 《山西地震》2006,(1):29-37,46
通过对山西太原地区常用的几种土动剪切模量和阻尼比的对比,结合2个实际工程场地土层地震反应的计算结果,对《工程场地地震安全性评价工作规范》中给出的土动力参数、袁晓铭,等给出的推荐值以及兰青龙给出的太原地区的统计值的合理性进行了对比研究。结果表明,与规范值相比,统计值和推荐值与太原地区的实测值比较接近,且避免了土层地震反应中地表反应谱的“矮、胖”现象,较符合实际情况,可供无试验资料时参考。  相似文献   

16.
介绍了现场测试与实验室测试土的最大动剪切模量的差别、动剪切模量和阻尼比与剪应变关系的表达式及其地区经验成果、固结比对最大动剪切模量影响、动泊松比研究、实验误差及其对地震动的影响等方面的主要成果。提出应加强动泊松比研究,加强共振柱和动三轴试验土动力学参数统一的数学模型研究,加强土动力学参数在均等固结与非均等固结条件下关系研究,加强土动力学参数与土的常规物理力学性质指标关系研究和土动力学参数实验误差研究。  相似文献   

17.
动三轴试验是将试样在轴对称的三轴应力下进行固结,在不排水条件下进行的振动试验,同时可测定土样的动剪切模量比和阻尼比。土的动剪切模量比和阻尼比是土动力学特性的2个重要参数,在工程场地地震安全性评价工作和土层地震反应分析中不可缺少。为了减少工期,提高工效,及时而又准确地提交报告,我们结合自己多年的土工试验经验,对可塑状态以上的粘性土试样进行了缩短固结时间的对比试验,并得到理想的试验结果。  相似文献   

18.
成都平原粘性土动力学参数统计分析   总被引:4,自引:3,他引:1  
成都平原地震构造环境主要受近场中强地震和外围大地震的影响。成都平原内的第四系分布广泛,主要为河流相的砂卵石层夹粘土、粉土层。这种地层在土层地震反应计算时往往会产生一个峰值,具有显著的放大作用。本文共收集了107组土动力学参数的实验资料,统计分析了粉质粘土和粘土两种粘性土的实测土动力学参数,给出了它们在不同深度的动剪切模量比和阻尼比的统计值。然后,选取1个典型钻孔,建立了土层地震反应分析模型,分别运用本文"统计值"、"十五结果"、"规范值"、"推荐值"进行地震土层反应计算,从反应谱形状、地表峰值加速度和反应谱特征周期等方面,验证了本文"统计值"的适用性和针对性,结果表明在盆地内使用"规范值"和"推荐值"时应谨慎,不然可能会对工程的抗震设防产生不利的影响。本文的"统计值"比"规范值"和"推荐值"更适用于成都平原地区,对各类工程建设的场地地震安全性评价具有一定的借鉴和参考价值。  相似文献   

19.
基于航空工业组团阎良片区地震小区划项目中大量动三轴试验结果,通过双曲线拟合方法,得到主要土类(黄土状土、粉质粘土、粉土、细砂)在8个典型剪应变(0.000005、0.00001、0.00005、0.0001、0.0005、0.001、0.005、0.01)下的动剪切模量比和阻尼比统计值,并将得到的统计值与廖振鹏给出的建议值、陈党民等给出的典型值和袁晓铭等给出的推荐值进行比较,进一步论证土动力学参数的地域性特征。文中还探讨了土样埋深和取样手段(试样等级)对动剪切模量比和阻尼比的影响。文中给出的统计值可为该片区地震小区划中的土层地震反应模型提供参数,同时也为研究该片区场地土动力特性及重大工程地震安全性评价工作提供参考和借鉴。  相似文献   

20.
土体参数对地表加速度峰值和反应谱的影响   总被引:8,自引:1,他引:8  
运用一维土层地震反应的等效线性化波动方法,研究了单层均质土密度、动剪切模量比和阻尼比、土层厚度和土层剪切波速等参数变化对土层地表加速度峰值和反应谱的影响,所得到的结论对于指导地震安全性评价中的勘察试验工作、提高土层地震反应的计算精度具有一定的参考价值。  相似文献   

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