岩石蠕变破裂过程及其响应比变化的实验研究

对花岗岩样品进行逐次加载的蠕变实验,得到了加载过程中的蠕变曲线和蠕变破裂的全过程曲线.对加载过程中的杨氏模量、蠕变量、蠕变速率等参数用加卸载响应比方法进行了分析,认为有二种不同形态的响应曲线.在中低应力的弹性阶段其响应比都近似为1,而在高应力的膨胀阶段其响应比都随应力而增加.对应力不变时的蠕变破裂全过程曲线进行了分解,在蠕变破裂过程中,瞬态、稳态和加速3个阶段的持续时间分别为全部时间的18%,75%和7%;在加速蠕变阶段蠕变速率及其响应比明显增加.这一结果是预测蠕变破裂的明显指标.     

Application of rock creep experiment in calculating the viscoelastic parameters of earth medium

The viscosity of earth medium can explain many geophysical phenomena. The uplifting velocity of Ti- betan Plateau may be caused by extrusion of the low viscosity channel in middle and lower crust[1]. The post-deformation after earthquake also relates to the rheology of earth medium[2]. The aftershock sequence is considered a process of strain release after stress dropped[3]. There are two kinds of models in the study of rheological character of crustal medium, elastoplas- only when the forced…     

岩石物理弹性参数规律研究

根据辽东湾凹陷某区在地层条件和不同流体相态(气饱和、水饱和等)下岩石纵波速度、横波速度及密度等岩心测试数据,以及岩石矿物成分、孔隙度等常规岩心分析数据,统计分析了岩石弹性参数变化规律.采用有效流体模型、斑块饱和模型进行了纵、横波速度理论计算,并和实验测量结果比较,认为高孔、高渗岩石可以看作有效流体模型,低孔、低渗岩石更接近斑块饱和模型.这些规律和认识对于指导储层预测和油气检测及地震振幅综合解释有重要的意义.     

基于核Fisher判别的碎屑岩储层流体识别

流体识别是致密碎屑岩储层预测中的难点之一.本文把核Fisher判别分析用于致密碎屑岩储层流体识别,首先较全面的介绍了核Fisher判别分析理论基础,再利用测井属性参数计算出弹性属性参数,并将这两类参数作为特征变量,最后进行核Fisher判别分析建模和致密碎屑岩储层流体识别.四川盆地XC地区致密碎屑岩储层流体识别结果表明,对致密碎屑岩储层中的气层和气水同层两类线性不可分的样本数据,使用核Fisher判别分析均能实现分离,说明该方法在识别致密碎屑岩储层流体识时准确率高,具有很好的应用前景.     

建筑LRB橡胶支座的老化和徐变性能研究

老化和徐变性能是LRB橡胶隔震支座重要的长期性能指标,对建筑LRB600原型橡胶支座进行了老化和15MPa持续加载下的徐变性能测试试验.测得了隔震橡胶支座初始状态和相当于60a后的热老化力学特性变化率,以及橡胶支座在1330h持续荷载作用下的徐变量.最后,基于测试结果提出了橡胶支座在正常使用状态下的徐变率预测方程.     

孔隙岩样动电特性的实验研究

本文针对流体饱和孔隙介质的动电效应,在实验室内进行了小岩样的动电实验（流动电势实验）测量,获得了10块岩样在6种不同饱和浓度下的流动电势系数,进而分析了饱和溶液浓度、岩样渗透率和泥质含量对流动电势系数的影响,探讨了流动电势系数对上述参数的敏感性,并进一步给出了流动电势系数随这些参数的变化规律.实验结果表明：前人流动电势系数频响曲线中的凹点现象是由实验装置的共振引起,并非岩样动电效应的自身特性.实验还发现：孔隙介质的动电耦合能力与溶液浓度有关,流动电势系数随溶液浓度增大而减小,但在很高浓度溶液中,动电现象依然存在,流动电势系数趋于常数.此外,流动电势系数对地层参数（渗透率和泥质含量）的敏感性受溶液浓度影响较大,随着溶液浓度增大,敏感性降低.因此,可在低浓度饱和情况下（低于0.4 mol/L）,利用流动电势系数的幅度对地层渗透率进行直接评价.本文结果对动电测井的可行性及应用条件给出了实验说明.     

Thermal properties as controls on rock surface temperature maxima,and possible implications for rock weathering

Four rock types (basalt, sandstone, granite, and chalk) are examined with respect to the maximum surface temperatures which they experience when subjected to similar conditions of exposure. Rock temperature measurements are reported for an urban environment and for two experimental situations in which an infrared lamp is used to simulate heating under cold and hot conditions. Differences in rock temperatures are discussed with reference to thermal rock properties (albedo, specific heat capacity, and thermal conductivity). Some natural situations are suggested in which thermal rock properties could conceivably play a role in determining the extent to which rocks would be affected by particular weathering processes.     

岩石物性变化对区域应力场的影响

基于接触摩擦分析单元和弱化带两种断层处理模式,应用有限元数值模拟方法,分别探讨了弹性模量、泊松比、摩擦系数、内聚强度等物性参数的变化对区域应力场的影响.结果表明:在两种处理模式下,这些参数的变化对断层附近的应力场均有不同程度的影响,且在接触摩擦处理模式下影响相对较为复杂.     

Effect of seismic waves on the hydro-mechanical properties of fractured rock masses

The transmission of seismic waves in a particular region may influence the hydraulic properties of a rock mass, including permeability, which is one of the most important. To determine the effect of a seismic wave on the hydraulic behavior of a fractured rock mass, systematic numerical modeling was conducted. A number of discrete fracture network(DFN) models with a size of 20 m × 20 m were used as geometrical bases, and a discrete element method(DEM) was employed as a numerical simulation tool. Three different boundary conditions without(Type Ⅰ) and with static(Type Ⅱ) and dynamic(Type Ⅲ) loading were performed on the models, and then their permeability was calculated. The results showed that permeability in Type Ⅲ models was respectively 62.7% and 44.2% higher than in Type I and Type Ⅱ models. This study indicates that seismic waves can affect deep earth, and, according to the results, seismic waves increase the permeability and change the flow rate patterns in a fractured rock mass.     

Numerical experiments for the conductive properties of saturated rock

The reservoir evaluation as a key technology in oil exploration and production is based on the electrical transport property (ETP) of saturated rock that is described in a mathematical form with Arhcie’s equa-tion. But there have been increasing cases observed in many researches indicating that the ETP is non-Archie especially for the complex reservoir with low porosity and permeability. In this paper,the numerical experiments based on the Lattice Boltzmann method (LBM) have been employed to study the effect of porous structure and fluids on the ETP for revealing the nature of non-Archie phenomenon in micro-scale. The results of numerical experiments have proved that the saturation exponent n is a function of water saturation and porosity instead of being a constant in Archie’s equation. And then,a new formula has been developed for the EPT through combining the result of numerical simulation with that of laboratory measurements. The calculations from the new formula show very good agreement with laboratory measurements to demonstrate the efficiency of the new formula over the conventional methods in non-Archie rock.     

The influence of local fluid flow and the microstructure on elastic and anelastic rock properties

The frequency dependent mechanism of local fluid flow was found to be the decisive absorption and dispersion mechanism in fluid containing sandstones. In the ultrasonic frequency range local fluid flow and grain surface effects control the behaviour of highly porous and highly permeable rock if a pore fluid is present. Both mechanisms depend less on macroscopic rock parameters like porosity and permeability than essentially on microscopic parameters like crack size, crack density and grain contact properties. To demonstrate directly the important influence of the microstructure on the rock elastic and anelastic properties the microstructure of a sandstone was artificially changed by thermal cracking. The cracked rock exhibits a clearly changed behaviour at low uniaxial as well as at high hydrostatic pressure despite small changes of porosity and permeability. Fluid effects increase due to cracking. The experimental results are explained by means of a rock, model and local fluid flow. These results emphasize that it is the microstructure which controls the elastic and anelastic rock behaviour, even at high hydrostatic pressure.     

The effect of a deviatoric stress on physical rock properties

Petrophysical measurements were carried out on dry specimens of mica-gneiss, amphibolite and serpentinite from KTB core samples and samples of surface outcrops in order to determine the effect that a deviatoric stress field, as observed at the KTB area, may have on the in-situ rock properties. Simulating the variation of the actual principal stresses and temperature with depth, seismic wave velocities, densities, linear and volumetric strain (porosity) have been measured, taking into account the overall spatial orientation of the foliation at the KTB area with respect to the principal stress axes. Comparison with respective data evaluated for lithostatic pressure conditions revealed that the stress-related (crack-related) effect on wave velocities respectively on velocity anisotropy is in the range 1–3%, due to microcracks which are selectively closed or kept open by the deviatoric stress. The effect of the deviatoric stress is particularly documented by shear wave splitting due to microfractures that are oriented normal to the minimum principal stress axis.     

基于数字岩心的岩石电性微观数值模拟(英文)

本文利用x射线CT获取反映岩心微观结构的三维数字岩心,利用数学形态学中的开运算模拟了岩石的油驱水排驱过程中,不同含水饱和度下油和地层水在孔隙空间中的分布。利用有限元方法计算了岩石电阻率,进而得到岩石地层因素和电阻率指数,并考查了岩石润湿性对岩石电阻率指数的影响。数值模拟结果表明：基于数字岩心的水湿岩石地层因素和电阻率指数数值模拟结果与实验结果一致,拓展了岩石电阻率实验的能力;岩石润湿性对岩石电性有重要影响,在相同含水饱和度下,油湿岩石电阻率高于水湿岩石电阻率,油湿岩石饱和度指数远大于水湿岩石饱和度指数。     

The frictional properties of joints in rock

Summary The conditions for sliding over artificial joint surfaces have been studied experimentally by cutting rock cylinders at various angles to their axes and studying slip over these surfaces in a triaxial testing apparatus. The types of joint used were: (i) filled with plaster to simulate a soft joint filling, (ii) bare surfaces ground approximately flat, and (iii) natural surfaces across which shear failure had taken place. The results agreed reasonably well with the simple theory for a constant coefficient of friction. Measured coefficients of friction lie in the range 0.5–0.8 and differ by surprisingly little between the various surfaces. The surfaces across which sliding has taken place exhibit interesting slickenside phenomena. Subsidiary failures frequently occur which cut across the joint surfaces.     

Experimental research on the rock electrical parameter dispersion properties in the displacement process

Based on experiments on rock electrical parameter dispersion properties in both water displacing oil and oil displacing water processes, it is found that the frequency dispersion properties of electrical parameters in water-bearing rocks are quite different from those in oil-bearing rocks. Oil saturation can severely impact the rock electrical parameter dispersion properties and as the oil saturation increases, the properties are more distinguishing. The variation of formation water salinity has a significant effect on the rock resistivity, hence the modulus of the rock complex resistivity varies with water saturation and a U-shaped curve occurs over a single frequency, just like the normal resistivity. However, the effect of formation water salinity on the rock frequency dispersion is less than that of oil saturation. As a result, the rock electrical parameter dispersion properties will have a significant potential of application in the evaluation of watered-out zones as well as identification of oil-bearing zones and water-bearing zones.     

Effects of planetary thermal structure on the ascent and cooling of magma on Venus

Magellan radar images of the surface of Venus show a spatially broad distribution of volcanic features. Models of magmatic ascent processes to planetary surfaces indicate that the thermal structure of the interior significantly influences the rate of magmatic cooling and thus the amount of magma that can be transported to the surface before solidification. In order to understand which aspects of planetary thermal structure have the greatest influence on the cooling of buoyantly ascending magma, we have constructed magma cooling profiles for a plutonic ascent mechanism, and evaluated the profiles for variations in the surface and mantle temperature, surface temperature gradient, and thermal gradient curvature. Results show that, for a wide variety of thermal conditions, smaller and slower magma bodies are capable of reaching the surface on Venus compared to Earth, primarily due to the higher surface temperature of Venus. Little to no effect on the cooling and transport of magma are found to result from elevated mantle temperatures, elevation-dependent surface temperature variations, or details of the thermal gradient curvature. The enhanced tendency of magma to reach the surface on Venus may provide at least a partial explanation for the extensive spatial distribution of observed volcanism on the surface.     

金星地质特征及主要科学问题

金星是离地球最近的行星,许多特征与地球类似,但在地质特征方面与地球差异较大.本文简单回顾金星探测的主要科学成果,重点综述金星地质研究的主要进展,包括:金星表面的地形构造、重力场分布、内部结构等特征.在此基础上,归纳提出了金星地质认识中存在的重点问题,主要有金星表面地形的成因问题、表面年龄及表面更新问题、内部结构模型及内部散热等问题,认为这些都是未来金星探测需要考虑解决的科学问题.     

金星非单调冷却热演化历史分析

金星表层年龄和构造活动特点表明其岩石层在最近的地质历史时期经历过广泛的更新.这种全球性的表层改造与其内部热演化历史进程密切相关.如果金星存在相变形成的上、下地幔,依据现今所了解的金星物理性质和参量化的热对流理论,并且考虑金星地幔相变边界层状态对对流的控制作用,我们计算了金星热演化历史.结果表明,金星的热演化历史是一种非单调的冷却过程,在这种非单调的热演化历史进程中,金星地幔会出现大体等周期的翻转.由于参数选取的不同,翻转时金星上、下地幔的温差随时间可能出现稳定变化、逐渐加强、逐渐减弱三种不同演化模式,目前尚不能确定实际金星热演化历史究竟是哪一种模式.金星地幔相变边界层的穿透对流可能是推动其表层岩石层全球性更新的关键,导致其表层火山活动和地表构造以大致500 Ma时间间隔更新和重造.     

岩石声波差异衰减特征及工程应用前景探讨

声波在岩石材料中传播时会发生差异衰减现象.由于岩石强度、完整性不同，造成其频率响应不同，声波通过不同强度的岩石时，对不同频率的声波信号滤除状况也就有所不同.通过力学强度高的岩石时，声波基本能够保持其原有频率成分，相反，当通过低强度岩石时，高频分量会迅速衰减而缺失，主要保留低频分量.通过实例研究，分析了声谱衰减特征与岩样矿物组成、密度及结构完整性的关系，验证了声谱衰减特征与岩体强度具有很好相关性的结论.通过分析研究声波信号在不同岩体中传播的衰减变化，指出声波衰减在一定程度上能够反映出岩体的风化程度、破碎状态、强度及各向异性等特征.可以发展成为岩体工程地质勘测、试验和施工中的常规实验方法.     

Horrocks, Crabtree and the 1639 transit of Venus

Now the deserved scientific and media excitement of the 2004 transit of Venus has passed, Allan Chapman offers a brief account of the career of Jeremiah Horrocks, who predicted and observed the 1639 transit.