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We present a process based method for reconstructing the full three-dimensional microstructure of sandstones. The method utilizes petrographical information obtained from two-dimensional thin sections to stochastically model the results of the main sandstone forming processes – sedimentation, compaction, and diagenesis. We apply the method to generate Fontainebleau sandstone and compare quantitatively the reconstructed microstructure with microtomographic images of the actual sandstone. The comparison shows that the process based reconstruction reproduces adequately important intrinsic properties of the actual sandstone, such as the degree of connectivity, the specific internal surface, and the two-point correlation function. A statistical reconstruction of Fontainebleau sandstone that matches the porosity and two-point correlation function of the microtomography data differs strongly from the actual sandstone in its connectivity properties. Transport properties of the samples are determined by solving numerically the local equations governing the transport. Computed permeabilities and formation factors of process based reconstructions of Fontainebleau sandstone compare well with experimental measurements over a wide range of porosity.  相似文献
基于X-射线CT方法的岩石小裂纹扩展过程分析   总被引:9,自引:0,他引:9  
岩石的小裂纹起裂及扩展过程是岩石力学研究的一个关键问题。对软硬两种砂岩进行单轴加载试验,同时用高分辨率的螺旋CT扫描机进行实时扫描。通过对获得的CT图像的分析处理发现,CT差值图像中的方差值与小裂纹的扩展速率有密切的关系,建立CT差值图像中的方差值与应力关系曲线,可以直观地看出:1)岩石样品中小裂纹起裂门槛值:软砂岩样品小裂纹扩展的门槛值为岩石强度的55%,小裂纹的扩展强度占整个强度的73%。硬砂岩小裂纹扩展的门槛值为岩石强度的64.5%,小裂纹的疲劳强度占整个强度的79%;2)小裂纹的扩展规律,即:在加载的初期岩石中小裂纹的扩展速率缓慢增大,在小裂纹扩展的门槛值出现之前快速下降,小裂纹扩展的门槛值出现之后又快速增加,最后当裂纹长度达到一定值时与长裂纹扩展速率基本一致。  相似文献
Many engineering problems such as exploitation of petroleum and gas, deposition of nuclear waste, and groundwater contamination by organic liquids are closely related to the movement of fluid in rocks. In this paper, a video microscope is employed to investigate the shape of moving front boundary of fluid flow in sandstone. The experimental results show that the fronts of the moving boundary display a fractal behavior. Based on the experimental results, a stochastic differential equation is proposed to describe the moving boundary. By decomposing the velocity of a given point into a drift term and a fluctuation term, the effect of the mesoscope structure of porous media on fluid flow is taken into account. The stochastic approach is in agreement with the experimental results. The analysis shows that the front of the moving boundary of fluid flow in rocks is a comprehensive result caused by the average tendency of fluid flow, which can be described by the classical Darcys Law, and the fluctuation tendency of fluid flow, which is closely related to the mesoscope structure of rocks.  相似文献
致密砂岩气藏纳微观结构及渗流特征   总被引:3,自引:1,他引:2       下载免费PDF全文
杨建  康毅力  李前贵  张浩 《力学进展》2008,38(2):229-236
随着常规油气资源的减少, 致密砂岩气藏逐渐成为勘探开发的热点. 然而致密砂岩气高效产出机理研究还相对滞后, 已经成为目前制约致密砂岩气大规模经济有效开发的瓶颈. 致密砂岩由于其特殊的地质特征, 基质微观结构复杂, 天然裂缝一定程度发育, 投产一般需要水力压裂等增产措施, 气体在其中渗流存在跨尺度效应. 研究揭示出致密砂岩气在多孔介质中的流动分为解吸、扩散、渗流等几个方式, 包括浓度场下的扩散、压力场中的渗流等. 综述了致密砂岩存在的非常规地质特征及其研究描述方法, 并依据克努森数大小, 对致密砂岩气的渗流状态进行流态区域划分, 为更好的理解和模拟致密砂岩气的流动状态提供了理论依据, 并指出建立一种高效、简洁的微观结构精细描述方法, 以及解决致密砂岩气在多尺度条件下的传质优化等是今后研究的重点方向.  相似文献
砂岩岩石力学参数各向异性研究   总被引:2,自引:0,他引:2  
俞然刚  田勇 《实验力学》2013,28(3):368-375
对胜利油田不同深度的四口井的砂岩岩芯进行了三轴压缩试验和动态岩石力学参数试验。根据获得的垂直地层方向和平行地层方向的试验数据,计算了各岩石力学参数的各向异性系数。通过分析围压以及深度对各向异性系数的影响,给出了砂岩峰值强度各项异性系数、静泊松比各向异性系数、纵波波速各向异性系数、纵横波速比和动泊松比各向异性系数与深度的拟合公式。发现峰值强度、纵波波速和纵横波速比的各向异性系数都随着深度的增加而减小,而泊松比各向异性系数随着深度的增加而增大。动、静弹性模量各向异性系数与深度相关性都很差,动弹性模量各向异性较弱,静弹性模量相对较强。  相似文献
Creep fracture of sandstones   总被引:2,自引:0,他引:2  
Creep is one of the important properties of rocks and rock masses. But the mechanism and characteristic of rocks in creep has not received the attention it deserves. Sandstones mined from Emei Mountain are investigated and tested by utilizing the three-point bending creep fracture test. A mathematical relation between stress intensity factors and durations of sustained loading for the above specimen is obtained based on the gray prediction theory. The obtained results provide a better understanding of rock fracture under creep.  相似文献
Predicting the Onset of Inertial Effects in Sandstone Rocks   总被引:1,自引:0,他引:1  
This study presents a method to determine the onset of inertial effects at the microscopic level, to distinguish between Darcy and non-Darcy flow regions within porous media at the pore level, and to quantify the effects of retained polymer on gas mobility. Capillary pressure and polymer flood experiments were conducted using Elgin and Okesa sandstone samples. The pore-size distributions were used to study the high-velocity flow effects. A modified capillary-orifice model was used to determine the non-Darcy flow effects at the pore level, with and without residual polymer.The overall flow behavior at any flow rate may be described as the average of all contributions from the Darcy and the non-Darcy terms in all pores. Results of this study suggest that the conventional Reynolds number may lead to incorrect analysis of flow behavior when evaluating non-Darcy flow effects in porous media. The Forchheimer number, defined as the ratio of inertial forces to viscous forces, is found more adequate for analyzing microscopic flow behavior in porous media.  相似文献
饱和岩石滞弹性弛豫机理的实验研究   总被引:1,自引:0,他引:1       下载免费PDF全文
席军  杜赟  徐松林  席道瑛 《实验力学》2011,26(3):316-322
通过Metravib热机械分析仪,用正弦波加载方式,模拟地震波的传播。实验时固定静载为100N,正弦波动载荷恒为60N,将总载荷控制在屈服点以下。在温度为-50℃~90℃,升温速率保持在1℃/分,频率为5Hz~400Hz的条件下,对饱和泵油彭山砂岩和遂宁砂岩样品进行单轴循环加载实验,获得饱和泵油彭山砂岩和遂宁砂岩的衰减、虚模量、实模量、波速与温度和频率以及动载荷的关系。以此研究了饱和多孔岩石的衰减和虚模量、杨氏模量和弹性波波速随温度和频率的动态响应。取得了随频率增高,饱和多孔岩石的衰减峰和虚模量峰的峰位向高温方向移动的热激活弛豫机制。杨氏模量和弹性波波速随温度升高而下降,随频率增高而增大,具有频散效应;杨氏模量和弹性波波速随动载荷振幅的增大而降低。这些结果与低频共振的驻波实验取得了同样的热激活弛豫规律,说明热激活弛豫规律具有一定的普适性。  相似文献
不同温度热处理后砂岩三点弯曲的断裂特性   总被引:1,自引:0,他引:1  
通过三点弯曲试验研究了不同温度影响下小尺度砂岩试件的断裂特性,证实温度的影响是明显的.125℃是个临界温度点,此时不仅砂岩的平均断裂韧性达到最大值,而且这时砂岩的裂纹扩展模式也发生了根本性的变化,即低温(低于125℃)热处理后砂岩的断裂以沿颗粒断裂机制为主;而高温(大于125℃)热处理后的砂岩的断裂以破断颗粒和沿颗粒的混合断裂机制为主.在100℃-150℃的温度范围内,砂岩的力学特性变得不稳定,这可能是由于粘土物质内部部分吸附水及层间水的蒸发使得粘土物质孔隙结构发生了变化及力学行为变得不稳定所造成的.从125℃到600℃,砂岩的断裂韧性整体有下降趋势,有约50%的降幅,这不仅与温度影响了粘土物质与矿物的胶结情况有关,也与高温处理后砂岩表面出现的热开裂有关,还与因矿物颗粒及粘土物质的热学性质差异导致冷却后存在的残余应力相关.  相似文献
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