弹塑性介质内的波速变化

应用一个具体问题展开了波在固体在弹性、弹塑性和应变局部化阶段的传播特性的研究。当经典本构计算到材料出现应变局部化时失效、控制方程出现分叉现象时,非局部效应本构描述得以继续分析,破坏过程变形进一步体现。本构内引入梯度项的贡献,以牺牲了特高频率( )特性为代价,增强了控制方程的稳定性。阻尼的影响复杂得多,考虑滞变阻尼、且仅与质量有关时,阻尼对控制方程的稳定性没有贡献。如果阻尼考虑为与质量和刚度联合相关时,阻尼对控制方程稳定性是有一定的贡献。     

动扭剪试验中砂土液化后流动特性分析

土体在初始液化后仍然可能承受动荷载作用发生大变形。引入流体力学中的剪应变率和表观黏度的概念,对振动扭剪试验中饱和砂土液化后的流动特性进行了分析。分析中将砂土的状态分为0有效应力状态和非0有效应力状态。结果表明,砂土在0有效应力状态下表现出与静扭剪试验类似的“剪切稀化”非牛顿流体的特征,表观黏度随着剪应变率的增大而减小。加载周数对“剪切稀化”状态下的剪应变率幅值有影响,随着加载周数的增加,剪应变率幅值逐渐增大,而对流动曲线的形状没有影响。在非0有效应力状态下,砂土的表观黏度随应变的增大而增大,随孔压比的减小而增大,且所有的试验得到的表观黏度与孔压比具有一致关系。     

Studying the viscosity of lower crust of Qinghai-Tibet Plateau according to post-seismic deformation

The viscosity of lower crust of Qinghai-Tibet Plateau on earth should be determined. It has become a predominant problem in quantitative research on geodynamics. Its order of magnitude will have a great influence on the results of quantitative modeling. To obtain the viscosity of lower crust of Qinghai-Tibet Plateau, this parameter was calculated by three methods. The first is based on the estimation on the temperature state of Qinghai-Tibet Plateau in the deep part, and the viscosity of lower crust of northern Plateau was recomputed with strain rate derived from rheology law and GPS observation. Effective viscosity of middle crust in Kunlun region is between 10²⁰ and 10²² Pa·s, and that of lower crust is between 10¹⁹ and 10²¹ Pa·s; the second is based on three kinds of rheological models used to fit the post-seismic deformation recorded by cross-over fault GPS sites set after M _s8.1 Kunlun earthquake in 2001. The viscosity of lower crust obtained by this method is of 10¹⁷ Pa·s order of magnitude. However, higher viscosity is required to fit the data of south fault better, and the lower one is required to fit the data of north fault better. The viscosity of lower crust, which was obtained by fitting the cross-over fault post-seismic deformation after M _s7.6 Luhuo earthquake in 1973, is of 10¹⁹ Pa·s order of magnitude. Non-linear relationship between effective viscosity and strain rate is ignored in the former research of effective viscosity. This research shows the difference of effective viscosity obtained from laboratory experiment, and shorter and longer time post-seismic deformation after large earthquakes can be explained in phase. Supported by National Basic Research Program of China (Grant No. 2004CB418405), National Natural Science Foundation of China (Grant No. 40774048), Important Direction Item of Knowledge Innovation Project of Chinese Academy of Sciences (Grant No. KZCX2-YW-123) and Basic Scientific Research Project of Earthquake (Grant No. 02076902-05)     

物理模拟实验理想材料--塑化松香和有关物理参数测定

通过对塑化松香性质的介绍,结合已有的模拟实验结果,认为塑化松香是理想的模拟实验塑性材料。为了便于定量模拟,采用蠕变法和落球法测定了１４－２２℃时不同配比下的粘度,并把蠕变法测定的结果利用Ｗｅｉｂｕｌｌ曲线内推和外推到１５－２５℃内任意温下的粘度。测定结果表是,蠕变法得到的粘度值比落球法得到的粘度值更接近实际情况。通过上述两种方法测定的粘度值,基本满足定量模拟要求,可用于岩石圈多层构造变形的模拟实验     

海带的碳酸钠消解过程动力学

以海带为原料,考察了消解反应温度、碳酸钠浓度、搅拌速度及海带块尺寸对消解反应动力学、褐藻胶收率及产品黏度的影响。结果表明,随温度、碳酸钠浓度、搅拌速度的升高,消解反应速度明显加快,褐藻胶提取速率随之增大。海带块大小对反应速率也存在一定的影响,海带块越小,褐藻酸钠提取反应速率越快。确定的较佳消解条件为：Na2C03浓度为0．5％,消解温度为60℃,搅拌速度200r／min,海带块尺寸为20mm。在此条件下,产品的产率可超过22％,黏度超过了20000mPa·S。研究结果为优化传统海带消解工艺,节约碱耗,缩短反应时间、提高产品收率和品质提供了参考。     

Convection of a fluid with strongly temperature and pressure dependent viscosity

Plate tectonics on the Earth is a surface manifestation of convection within the Earth’s mantle, a subject which is as yet improperly understood, and it has motivated the study of various forms of buoyancy-driven thermal convection. The early success of the high Rayleigh number constant viscosity theory was later tempered by the absence of plate motion when the viscosity is more realistically strongly temperature dependent, and the process of subduction represents a continuing principal conundrum in the application of convection theory to the Earth. A similar problem appears to arise if the equally strong pressure dependence of viscosity is considered, since the classical isothermal core convection theory would then imply a strongly variable viscosity in the convective core, which is inconsistent with results from post-glacial rebound studies. In this paper we address the problem of determining the asymptotic structure of high Rayleigh number convection when the viscosity is strongly temperature and pressure dependent, i.e. thermobaroviscous. By a method akin to lid-stripping, we are able to extend numerical computations to extremely high viscosity contrasts, and we show that the convective cells take the form of narrow, vertically-oriented fingers. We are then able to determine the asymptotic structure of the solution, and it agrees well with the numerical results. Beneath a stagnant lid, there is a vigorous convection in the upper part of the cell, and a more sluggish, higher viscosity flow in the lower part of the cell. We then offer some comments on the possible meaning and interpretation of these results for planetary mantle convection.     

考虑多种因素影响的海上地震勘探气枪震源单枪子波数值模拟

在分析Ziolkowski气泡振动模型局限性的基础上,建立了多种实际因素影响下的海上地震勘探单枪子波模型。此模型考虑了气泡壁的热传导作用、枪口节流作用、气泡上浮、液体粘度和枪体本身等对气枪子波的影响。相对于Ziolkowski模型,改进模型所模拟的气枪子波主峰值减小,气泡振动衰减加快,与实测子波吻合性较好。实验分析表明：（1）枪口节流作用控制着气枪脉冲峰值振幅的大小,（2）上浮过程中气泡周围静水压力值减小,气泡振动的周期随之改变,（3）热传导作用和流体粘度是引起气泡振动衰减的主要因素。     

A Velocity-Based Approach to Visco-Elastic Flow of Rock

In structural geology, viscous creep is generally recognized as the major deformation mechanism in the folding of rock layers through geological time scales of hundreds of thousands of years. Moreover, since deformation of rock salt by creep takes already place on relatively small time scales—weeks to months, say—creep is a relevant phenomenon when studying salt mining, notably the convergence of mine cavities and the land subsidence caused by it. While creep is the dominant process on relatively long time scales, elasticity plays a dominant role in processes that take place on relatively short time scales. The elastic response to a stress is a displacement; the shape of the rock is deformed instantaneously with respect to its initial shape. However, the viscous response of a rock to a stress is a relatively low velocity in the order of millimeters per months or years, say. In this paper we consider the two deformation phenomena creep and elasticity. In general, elasticity is a compressible phenomenon, while creep is incompressible. Here we approximate creep by the introduction of a negligibly small amount of compressibility, which makes creep velocity calculations similar to conventional elastic displacement calculations. Using this procedure, a standard finite element package for elasticity can be applied to viscous problems, also in combination with elasticity. The method has been demonstrated to upscaling of creep viscosities.     

The influence of different rheological parameters on the surface deformation and stress field of the Aegean–Anatolian region

The Aegean–Anatolian region is characterised by an inhomogeneous deformation pattern with high strain rates and a high seismicity both at the boundaries and in the plate interior. This pattern is controlled by the geometry and rheology of the structural units involved and their tectonic setting. A numerical analysis with a finite-element model of the region is used to quantify the influence of different rheological parameters. Viscoelastic material behaviour is implemented for the mantle lithosphere, whereas the crust is modelled with an elastic–plastic rheology. The variation of the inelastic material properties (viscosity and plastic strength) quantifies the influence of these material parameters on the deformation, stress, and strain patterns. Comparison of the modelled results with geodetic and geophysical observations reveals that the viscosity of the mantle lithosphere is the key to explaining the inhomogeneous deformation pattern. The best-fit model yields a viscosity of 10²⁰ Pa s beneath Anatolia, whereas adjacent regions have viscosities between 10²¹ and 10²³ Pa s. The model also explains the intra-plate seismicity and the stress field as well as its partitioning into regions with strike-slip and normal faulting. The final model is in good agreement with seismological, geodetic, and geological observations. Local deviations can be tracked down to small-scale structures, which are not included in the model.