基于损伤扰动的土体本构关系研究

邓肯E-B模型无法描述软化土体的应力应变关系以及土体的剪胀效应；采用抛物线型体应变曲线的南水模型破坏时的剪胀率趋于定值，与实际土体不符。但南水模型适合描述应力应变峰值点前或最大剪胀率前土体的本构关系，邓肯模型适合描述的应变范围更小。因此，若要进行土工结构渐进破坏的分析计算，则需要建立一个适合于描述直至破坏的更大应变范围的土体本构关系。采用损伤扰动概念，将变形过程中的土体视为“相对完整”的未损伤土体和“完全调整”扰动土体的混合体，其应力应变关系可根据损伤扰动程度，由各自的应力应变关系组合确定。并根据试验提出了确定损伤扰动函数的计算公式。对体应变曲线，则采用抛物线加双曲线的形式加以描述。     

一种新的土体动力本构模型

基于指数函数的有界性、函数曲线形状和构造土体动力本构模型的一般原则,把函数Y=e^x在（-∞,0]区间上的图像进行翻转、平移、放缩,从而构造出土体的动力本构模型的骨架曲线。在卸载和反向加载时,采用与骨架曲线相同的函数形式,并以前一次卸载开始点作为起点,以土体的极限应力水平作为渐近线,构造出土体动力本构模型的滞回曲线。在此基础上构造出适用于非对称循环荷载的指数形式土体动力本构模型（UE模型）。并用共振柱实验的结果检验了模型的有效性。UE模型具有四个特点：第一,适用于非对称循环荷载;第二,记忆量小;第三,卸载再加载滞回曲线自动满足Masing准则;第四,模型参数少,物理意义明确,可用常规试验确定。     

基于双曲正切函数的土动力非线性本构模型

基于双曲正切函数,构造了一种新的土动力非线性本构模型。该模型从双曲正切函数出发,通过平移和缩放构造了土动力应力应变关系的骨架曲线和卸载、反向加载的滞回曲线。相对于其他模型而言,这种新的数学模型参数较少,物理概念明确,形式简单,更利于编程实现,加卸载应力应变关系曲线只需要记忆加卸载转折点处的应力和应变值。将该数学模型应用于场地地震反应分析中,并与常用的等效线性化方法的地震反应结果进行比较,结果初步证明了该本构模型的可行性。     

对UE土体动力本构模型的修正

动力本构模型UE模型具有可以描述非对称循环荷载、记忆量小、模型参数物理意义明确、表达式简单等优点。但其描述等幅循环荷载作用下的土体滞回圈时,存在非对称性,并且无法较好地拟合土体动阻尼比随应变产生的变化规律。通过在UE模型的骨架曲线中引入两个瞬变参数,利用“massing二倍法”构造滞回曲线,使模型同时满足各个应变下的剪切模量及阻尼比,确定瞬变参数的表达式,将瞬变参数表达式带入滞回曲线方程中,即得到最终的滞回曲线表达式,并定义各个滞回圈顶点的连线为此修正模型的实际骨架曲线。分析结果表明,该修正模型能够克服UE模型存在的不足,且更符合实际。     

地震作用下煤矿开采损伤建筑的能量耗散演化致灾分析

基于耗散结构理论,从能量理论角度对煤矿开采区建筑物的动力破坏过程进行了系统的定量分析。提出了建筑物能量耗散的理论判据,研究了地震作用下煤矿开采区建筑的损伤演化灾变过程。根据结构动力学理论,建立了煤矿开采区建筑物在地震作用下的能量演化平衡方程,定量分析了地震作用下煤矿开采区建筑物系统中耗散能量的变化过程。结果表明:在开采沉陷和地震联合作用下,建筑物与外界产生更多的有害的能量交换,进而产生更多的塑性损伤变形,结构阻尼耗能降低;根据建筑物能量耗散演化趋势应建立合适的抗开采沉陷变形隔震保护新体系,为我国矿区建筑物保护提供借鉴意义。     

耗散大气中的声波射线追踪

基于分层大气中声波的局地色散关系方程,建立一种计入真实大气衰减效应的有耗大气声波射线追踪模型.在色散方程的虚部中导出声波在运动大气中的耗散系数和竖直方向上的增长因子,并利用真实大气中的衰减理论对所得到的耗散系数进行修正.利用Hamilton方程组解出大气声波在考虑耗散效应下的射线微分方程组.该有耗射线追踪模型的数值模拟结果表明,声波的耗散效应对声波的传播路径存在一定影响,在近场情况下,这种影响可以忽略,但是对于声波的远场传播,则影响较大.     

地震动强度增大过程中边坡土体的损伤演化及其计算方法研究

地震作用下边坡失稳破坏过程也是土体损伤变形演化过程,当前边坡模型试验中土体损伤的定量计算方法尚未提出;研究以兰州新区职教园区内一填方边坡为原型,开展了地震动强度逐级增大条件下边坡失稳破坏的模型试验,研究边坡变形失稳过程中相关物理量随地震动强度的变化规律,进而提出土体损伤的计算公式。研究结果发现：在地震动强度增大过程中,坡肩土体损伤变形最为显著,传递函数频谱随地震动强度增大呈现有规律的减小变化,土体阻尼比随地震强度增大呈现指数函数增大变化,据此提出了基于归一化阻尼比的土体损伤量计算公式,该公式计算的土体损伤量也呈现指数函数增大变化,反映了地震动作用下土体的非线性损伤变形破坏过程。文中提出的土体损伤量计算方法可为基于模型试验的边坡稳定性评价提供理论依据。     

求解动力方程的三种显式积分格式的比较

比较了工程上常用于求解动力方程的三种显式积分格式的能耗特性,结果表明,李小军等人的显式差分格式在物理阻尼比为0到1的范围内均具有较强的能耗特性,而且随着物理阻尼比的增大,能耗特性也增强,这种特性优于另外两种显式积分格式,能有效地克服透射边界的高频失稳,因此在处理复杂场地地震反应方面是一种比较理想的显式积分格式。     

Correlation between seismic acceleration parameters and overall structural damage indices of buildings

This article describes the interdependency between several seismic acceleration parameters and the behavior of the reinforced concrete frame structures in the form of correlation coefficients. The structural behavior is expressed in form of overall structural damage indices. After the numerical evaluation of several seismic parameters, a nonlinear dynamic analysis is carried out to provide the total damage status of a structure. The aim is to select those, which have drastic influence on structural damage. Furthermore, the design philosophy of aseismic codes can be verified. The attention is focussed on the earthquake acceleration time histories of the worldwide well-known sites with a strong seismic activity.     

确定深淡水湖泊的位温与密度

As a rule, the hydrodynamic modeling of processes in fresh waters is performed with the use of potential temperature θ and potential density ρ^*. However, the formulae of potential temperature for natural waters given by Phillips (1977), Gill (1982) and others take into account only adiabatic correction. They do not consider such important characteristics of natural waters as temperature of maximal density T_md (S,P) remoting of real temperatures T(S,P) in situ from T_md (T -T_md), changes of Tmd with decreasing of pressure P (depth Z), and the equation of water state. T_md=T_md(P) is the property of molecular structures of water (Horne, 1969). It is determined by the equation of water state:for example, for lacustrine waters in the form of Chen, Millero, (1986) ρ=ρ(S,T,P), where ρ,S are density and salinity natural water. There is given and discussed a new formula for the calculation of potential temperature. It is established that potential densities calculated according to the new formula suggested by us show the entire thermodynamic similarity of characteristics within T in situ. It is not observed while using the old formulae.     

当前潜在震源区研究的主要方向

本文讨论了当前潜在震源区研究中强震发生的构造条件、潜在震源区的两级划分、确定潜在震源区的原则、潜在震源区的方向和范围及其震级上限的确定以及数值方法在确定潜在震源区中的应用等主要方面的研究现状，并提出了今后工作中应重点研究的内容。     

Potential land for plantation of Jatropha curcas as feedstocks for biodiesel in China

As a renewable energy,biofuel has attracted great attention in China and the rest of world.Concerned with the national food security,China recently has shifted its biofuel development priority from grain-based to non-grain-based biofuels,including forest-based biodiesel,since 2007.Jatropha curcas is one of major biodiesel feedstocks.However,there is rising debate on availability of land for expanding Jatropha curcas areas.The overall goal of this paper is to evaluate potential land for Jatropha curcas used ...     

中国东北及邻区竖直向地震动强度包络函数参数的确定及其衰减关系

选用2008—2019年中国东北及邻区27次地震竖直向105条强震动记录,以三段式强度包络函数模型为目标,利用加权最小二乘回归方法,尝试建立了东北及邻区竖直向地震动时程强度包络函数参数的衰减公式,以使我国的地震动区域划分更具有普遍性。同以往的研究类似,上升段持时t₁和平稳段持时t_s的确定方法采用了70%能量持时法。所选地震的震级为3.3—5.8级,最大震中距为371 km。基于土层场地的竖直向记录,通过与我国目前常用的时程强度包络函数参数的衰减关系进行对比分析发现,t₁与震级之间有明显的相关性,实际应用中应考虑震级对t₁的影响;地震整体持时较短造成t_s上升趋势随距离的增加而变缓;下降段由衰减系数c的变化可见,记录整体衰减较快。     

Modelling of rupture planes for peak ground accelerations and its application to the isoseismal map of MMI scale in Indian region

The rupture plane for an earthquake has been modelledby using the semi empirical technique of Midorikawa(1993). This technique estimates ground accelerationby modelling the rupture process during an earthquake.Modifications in this technique have been made for itsapplication to the Indian region. This has been tested forthe Uttarkashi earthquake of 20th Oct, 1991, India, whichwas well recorded at thirteen stations of installedstrong motion array in this region. After testingseveral possible rupture models, a final model has beenselected and peak ground acceleration due to thismodel is simulated at thirteen different stations.Dependency of methodology on model parameters, e.g.dip and mode of rupture propagation have also beenstudied in detail.Using this technique synthetic isoseismal maps wereprepared by converting peak ground acceleration intoMMI scale. Dependency of rupture models on syntheticisoseismals has also been studied in detail. Usingthis method, peak ground acceleration for the Laturearthquake of Sept 30, 1993 has been obtained atvarious places within meisoseismal area. Synthetic andfield intensity was compared at various well-knownsites. Since the region was not covered by anyinstrumental array during Latur earthquake, thesimulated peak ground accelerations are expected toserve basis of design criteria in this region.     

Study of the Non-Uniform Distribution of Earthquake Risk Within Potential Sources

Potential sources are aggregates of probable future epicenters.In this area,for source models currently,in common use for seismic risk analysis in China,the mean area of each potential source is about 3000-4000 km2.It is assumed that seismic risk has a uniform distribution within the range of each potential source,but studies have shown that the uniform distribution model to a large extent may give an underestimation of the seismic risk.In this paper,the relative distribution of historical epicenters in space within potential sources is discussed,a method is proposed to quantitatively describe the non-uniform distribution of strong earthquakes within potential sources,and some preliminary results are given.By using the results of this paper,seismic risk analysis and seismic zonation can be made more scientific and more reasonable.     

多种表征强震动记录特性的参数对比分析

为研究强震动记录的破坏特性,对多条国内外常用的强震动记录的特性参数进行了对比分析.结果表明,强震动记录特性参数之间的相关件很小;PGA(PGV)和EPA(EPV)大小关系受震级和震中距影响较大;VSI较ASI能够更准确的评价强震动记录的破坏特性;与其它参数相比,强震动记录破坏强度参数(PD)同时考虑了地震加速度、时间和...