弹性和粘弹性地基无限域动力模型

针对弹性和粘弹性无限地基的数值模拟问题,本文提出了一种新颖的地基无限域动力模型--映射动力无穷元与有限元耦合模型。文中首先利用一维半无限域中的波动问题,提出了广义弹簧、广义阻尼和广义质量的概念,并导出了弹性和粘弹性动力无穷元中波传播函数的一般形式,进而对映射动力无穷元的基本特性进行了研究。文中还给出了二维和三维映射动力无穷元的单元模型,并用算例验证了这一模型的计算精度。     

簇平行黏结模型中微观参数对宏观参数影响的量纲研究

首先分别采用传统加载程序和新加载程序,对利用簇平行黏结模型所建立的颗粒流试样的力学特性进行研究。同时采用新加载程序,分析加载速率和冻结期时步对颗粒流试样力学特性的影响。随后利用量纲分析法研究簇平行黏结模型中微观参数对宏观参数的影响,建立岩石材料宏观参数(弹性模量、泊松比、单轴抗压强度和单轴抗拉强度)与簇平行黏结模型中微观参数间的半定量关系。相关模拟结果表明:(1)利用传统加载程序计算得出的岩石应力–应变曲线是不准确的,它高估了单轴抗压强度、单轴抗拉强度和弹性模量,且不能真实再现岩石峰后脆性特征;2种加载程序得出的岩石破坏形态差异很大。(2)结合新加载程序,簇平行黏结模型能得到合理的单轴抗压强度和单轴抗拉强度比值(UCS/TS)。在准静态范围内,加载速率与强度值没有相关性,这与试验结果吻合,加载速率对岩石应力–应变曲线的影响主要在峰后阶段。(3)弹性模量主要与颗粒接触模量和颗粒接触刚度比相关,而泊松比主要与接触刚度比相关。为得到相同的泊松比值,簇平行黏结模型中的接触刚度比应大于平行黏结模型中的接触刚度比。单轴抗压强度和单轴抗拉强度主要受平行黏结强度比控制,另外单轴抗压强度受簇中颗粒数影响较大。     

无限域波动问题中有限模型与无限模型差异的定性分析

本文从理论上研究了用有限模型和无限模型模拟无限域中的波动问题时所存在的差异。文中给出的有关分析结果表明:(1)在弹性介质情况下,无限摸型可对系统给出复数形式的复频响应函数或位移分布,这与无限域中波动问题的解析解相吻合;而有限模型只能对系统给出实数形式的复频响应函数,这与无限域中波动问题的解析解不相符合。说明在弹性介质情况下,有限模型不能反映无限域中的波动特性。(2)在粘弹性介质情况下,即使有限地基范围取得较大,有限模型所给出的数值结果与解析解的误差仍然很大,说明在用有限元法对无限域问题进行动力计算时,一般不宜采用有限模型,而应采用无限地基模型。     

V型拱坝峡谷地震自由场分析及地表风化层的影响

本文用有限元与无穷元耦合模型以及地震波直接输入方法,计算了一个V型河谷在地震加速度以平面SH波型入射时的自由场反应。数值计算结果表明:(1)由于波在河谷表面的散射作用,使峡谷表面各点的加速度分布呈显著的差异;(2)地表风化层的存在对河谷表面各点的最大加速度值和加速度反应谱的最大值有着明显的放大作用。     

一种新颖的地基无限域地震波输入模型

本文提出一种可以考虑波在地基无限域进行地震波的传播效应的模型,为拱坝等大型结构的抗震分析提供了较为合理的计算方法.文中通过二滩拱坝谐波入射动力响应的计算结果表明:(1)河谷表面各点的自由场分布具有明显的差异,这一差异主要与波的入射方向有较大的关系,从而说明常规的不考虑幅差和相位差均匀输入的自由场分布与地震时的实际自由场分布相差甚远;(2)传统的拱坝抗震分析所采用的均匀输入的方法(HEM法)与本文提出的波输入方法(WPM法)有较大的差异,其趋势是HEM法求出的拱坝顶拱和拱冠梁的位移幅值明显较大;(3)拱坝的存在对河谷表面自由场反应的位移幅值有缩减作用.     

Simulation of rock deformation and mechanical characteristics using clump parallel-bond models

To properly simulate hard rock with a high ratio of the uniaxial compressive strength to tensile strength（UCS/TS） and realistic strength-failure envelope,the rock deformation and mechanical characteristics were discussed in detail when the particle simulation method with the clump parallel-bond model（CPBM） was used to conduct a series of numerical experiments at the specimen scale.Meanwhile,the effects of the loading procedure and crack density on the mechanical behavior of a specimen,which was modeled by the particle simulation method with the CPBM,were investigated.The related numerical results have demonstrated that：1） The uniaxial compressive strength（UCS）,tensile strength（TS） and elastic modulus are overestimated when the conventional loading procedure is used in the particle simulation method with the CPBM; 2） The elastic modulus,strength and UCS/TS decrease,while Poisson ratio increases with the increase of the crack density in the particle simulation method with the CPBM; 3） The particle simulation method with the CPBM can be used to reproduce a high value of UCS/TS（10）,as well as a high friction angle and reasonable cohesion strength; 4） As the confining pressure increases,both the peak strength of the simulated specimen and the number of microscopic cracks increase,but the ratio of tensile cracks number to shear cracks number decreases in the particle simulation method with the CPBM; 5） Compared with the conventional parallel-bond model,the CPBM can be used to reproduce more accurate results for simulating the rock deformation and mechanical characteristics.     

钴的价态对Co/Mo/MgO催化剂制备碳纳米管的影响

用溶胶凝胶煅烧法制备的Co/Mo/MgO催化剂中,除了形成Mg(Co)MoO4固溶体,一部分Co元素随着煅烧温度的提高,从Co3O4转变为CoO。在不同钴价态的催化剂上,用CVD法制备了碳纳米管。X射线衍射、电子显微镜、拉曼光谱和TGA表征显示,单壁碳纳米管可能是在Co3O4上生长的,多壁碳纳米管可能是在Mg(Co)MoO4上生长的,而在此场合下CoO并不是制备碳纳米管的有效催化剂。     

Potential mechanisms of pore-fluid movement from continental lithospheric mantle into upper continental crust

Through integrating the state of the art scientific knowledge in different research fields, some potential mechanisms of large-scale movements of underground pore-fluids such as H2O and CO2 in the continental lithosphere were presented and discussed. The results show that the generation and propagation of porosity waves are important mechanisms to transport mass and heat fluxes from the continental lithospheric mantle into the lower continental crust; the generation and propagation of porosity waves, pore-fluid flow focusing through lower and middle crustal faults, advection of pore-fluids through the lower and middle crust, and whole-crust convection in some particular cases are important mechanisms to transport mass and heat fluxes from the lower into the upper continental crust; heat and mass transport through convective pore-fluid flow is the most effective mechanism of ore body formation and mineralization in hydrothermal systems; due to heat and mass exchange at the interface between the earth surface, hydrosphere and atmosphere, it is very important to consider the hydro-geological effect of the deep earth pore-fluids such as H2O and CO2 on the global warming and climate change in future investigations.     

用无穷元研究断层对重力坝地基应力的影响

本文对断层在其深度方向延伸无穷远的无限地基,利用文中提出的七节点超参无穷元与等参有限元相耦合的方法进行模拟,研究了断层位置与产状对重力坝地基应力的影响。结果显示这种无穷元在模拟此类地基与构造问题上具有很大优越性,大量减省计算机时,提高了计算精度。