Zircon SHRIMP age of Mesoarchaean meta-argilloarenaceous rock in the Anshan area and its geological significance

In order to better understand the early continental evolution of the Anshan area, one ofthe typical Precambrian distribution areas of the North China Craton, the geochronology and REEcomposition of the zircons from the meta-argillo-arenaceous rock occurred as enclave in 3.1 GaLishan trondhjemite are studied by using SHRIMP ll ion microprobe. It is indicated that the Pa-leoarchaean is a very important continental formation period in the Anshan area and 3.2 Ga can beregarded as the boundary between the Paleoarchaean and Mesoarchaean.     

Application of Two Novel Acoustic Emission Parameters on Identifying the Instability of Granite

The issue of monitoring and early warning of rock instability has received increasing critical attention in the study of rock engineering. To investigate the damage evolution process of granite under triaxial compression tests, acoustic emission (AE) tests were performed simultaneously. This study firstly introduced two novel parameters, i.e., the coefficient of variation (CoV) of the information entropy and correlation dimension of the amplitude data from the AE tests, to identify the precursor of the failure of granite. Then the relationship between the changes in these parameters and the stress-time curve was compared and analyzed. The results of this study show that: (1) There is a strong correlation between the CoV of the information entropy and the failure process of granite. The granite failed when the CoV curve raised to a plateau, which could be used as an indicator of rock instability. (2) The fluctuation of the correlation dimension indicates the different stages during the loading process, i.e., the initial compaction stage, the linear elastic stage, the yield stage, and the failure stage. Each stage contains a descending and a rising process in the correlation dimension curve, and the exhibited starting point or the bottom point at the correlation dimension curve could be selected as the indicator point for the rock instability. (3) The combined analysis of the Information entropy and Correlation dimension can improve the accuracy of rock instability prediction. This study provides new insights into the prediction of rock instability, which has theoretical implications for the stability of subsurface engineering rock masses.     

On the Pesin set of expansive geodesic flows in manifolds with no conjugate points

In this paper, we show that the Pesin set of an expansive geodesic flow in compact manifold with no conjugate points and bounded asymptote coincides a.e with an open and dense set of the unit tangent bundle. We also show that the set of hyperbolic periodic orbits is dense in the unit tangent bundle.     

耦合时间精度对模拟飞行器自由运动特性的影响

将亚迭代技术引入流体动力学和刚体动力学方程的耦合求解,获得细长三角翼极限环运动的规律.探讨耦合时间精度对飞行器非定常运动特性的影响,细长三角冀的大迎角自由滚运动最终形成极限环振荡的周期性自维持运动,不同攻角自由滚振幅阶跃式的变化特点较好地吻合了自由滚试验的规律.对于多系统耦合问题,亚迭代耦合求解(耦合时间精度为二阶)对物理时间步长的依赖性不明显;而存在一阶时间滞后的解耦推进方法的数值结果强烈地依赖于物理时间步长选取,稍大的时间步长将导致非物理的数值结果.     

分形(fractal)几何与岩石断裂

岩石断口的不规则性可以统计地认为具有自相似性,由此本文应用新几何——分形(fractal) 几何来描述这种不规则性。建立了穿晶以及沿晶界和穿晶相偶合的微观断裂fractal 模型,用电镜和光学显微镜观察了大量岩石断口的 fractal 特征,得到了 fractal 维数与岩石宏观断裂力学量之间的初步对应关系。     

Measurements of saturated basic and acidic rock electrical conductivities at lower crustal temperatures and high pressures

Abstract

Laboratory measurements of the electrical conductivity of brine saturated acidic and metabasic rocks were done at confining pressures up to 0.2 GPa, high pore pressures and temperatures of 900°C. Acidic rocks showed conductivities insufficient to explain the lower crustal high conductivity layer. Basic rocks, however, showed conductivities consistent with the high conductivity layer at those temperatures that the layer is thought to possess.     

离子浓度及表面结构对岩石孔隙内水流动特性的影响

酸性环境引发的岩石孔隙表面溶解增加了孔隙内水溶液的盐离子浓度,破坏了孔隙的表面结构.本文采用分子动力学模拟的方法研究了纳米级岩石孔隙内水溶液的流动特性,分析了盐离子浓度和孔隙表面结构对水流速度分布的影响及原因.研究结果表明:纳米级岩石孔隙内的水溶液流动符合泊肃叶流动特性,流速呈"抛物线"分布;随盐离子浓度增加,水溶液内部氢键网络变得更为致密,水黏度随其呈线性增长;水溶液中离子浓度越大,孔隙表面对水流动的阻力越大,最大流速越小,速度分布的"抛物线"曲率半径越大;岩石孔隙表面结构的破坏改变了流动表面的粗糙程度,增加了孔隙表面对H2O分子的吸引力.随表面结构破坏程度的增大,水溶液在近壁区域的密度增大,流速降低;当表面破坏程度达到50%时,水溶液在近壁区域出现了明显的负边界滑移现象.     

基于八面体理论的岩石循环加-卸载本构模型及修正

探究岩石的受力特点及破坏特性是研究岩石地下工程安全性的关键,诸多学者都期望能在岩石本构模型的研究上取得突破性进展。在此背景下,提出了一种能够描述循环加-卸载条件下岩石的本构模型。首先,假设岩石的微元强度服从八面体剪应力理论并且微元破坏服从Weibull概率公式,将岩石本构中的损伤变量以及岩石微元强度表达式里包含的损伤因子进行本构变换,得到关于应力、应变等其他表现加-卸载下岩石损伤本构模型的参数,表示出岩石微元强度和损伤变量,再将得到的岩石微元强度和损伤变量代入所提出的岩石本构模型中,并进行等式变换得到一个函数表达式。通过将其与实验数据进行拟合对比分析,得出修正后的拟合参数,将其代入函数式中,得到损伤本构模型的修正式。最后将拟合参数进行必要的敏感性分析,得出各拟合参数的实际物理意义。     

中国东南部中、新生代基性岩荧光光谱与等离子质谱测试结果对比及其地质意义分析

通过对中国东南部中、新生代基性岩类岩石的荧光光谱和等离子体质谱分析结果的对比研究,发现中生代基性岩SiO₂平均含量为±50%,新生代基性岩为±43%,前者属典型基性岩类,后者属超基性岩类。两者在微量元素及稀土元素组成上也有显著差异。中生代基性岩的微量元素和稀土元素标准化配分模式与上陆壳的配分模式相同或相似,而新生代基性岩则与OIB型洋岛玄武岩相同或相似。由此得到的认识是：新生代的基性岩与OIB型洋岛玄武岩一样,均为地幔来源,而中生代的基性岩浆则极有可能来自上陆壳底部,与本区中生代壳内重熔岩浆层的演化有关。     

圆周上逆极限可扩的连续自映射

本文研究了圆周上一类自映射ｆ的正向可扩性与其道极限的可扩性间的联系，得出圆周上的连续满射ｆ的逆极限可扩等价于ｆ拓扑共轭于扩张映射．