Three dimensional steady-state locus for dry monodisperse granular materials: DEM numerical results and theoretical modelling     

Irene Redaelli  Claudio di Prisco 《国际地质力学数值与分析法杂志》2019,43(16):2525-2550

In this paper, steady-state conditions for ideal monodisperse dry granular materials are both theoretically and numerically analysed. A series of discrete element (DEM) numerical simulations have been performed on a periodic cell by imposing stress paths characterized by different Lode angles, pressures, and deviatoric strain rates. The dependence of the material response on both inertial number and loading path has been discussed in terms of void ratio, fabric, and granular temperature. DEM numerical results have been finally compared with the prediction of an already conceived model based on both kinetic and critical state theories, here suitably modified to account for three-dimensional conditions.  相似文献   

非饱和土稳态孔隙比变形理论研究     

程钰  周正明 《岩土力学》2011,32(5):1399-1404

非饱和湿陷性土与湿胀性土分别具有亚稳态孔隙比结构和超稳态孔隙比结构,广义吸力是维持这种结构稳定的主要因素。随着广义吸力的丧失,两种结构均处于一个不稳定的孔隙状态,土体会向一个更加稳定的孔隙比结构发展。超孔隙比结构孔隙比增大,土体产生膨胀,亚稳孔隙比减小,土体产生收缩。基于这一稳态孔隙比理论,建立了广义吸力丧失引起的孔隙比的增量方程,来统一考虑非饱和土的湿陷性和湿胀性变形特性,并通过经典试验数据验证了增量方程的合理性  相似文献   

东太平洋海隆(EPR) 13°N 附近含金属沉积物孔隙率研究     

武力  曾志刚  殷学博  王晓媛  陈帅 《海洋科学》2012,36(1):81-86

研究了采自东太平洋海隆13°N(EPR 13°N)的一个热液成因含金属箱式沉积物岩心E272的孔隙率变化特征。样品孔隙率在70.0%-85.2%之间,顶部层位比底部层位高14%左右。孔隙率随深度增加而指数式单调递减,平均递减梯度约为-0.31%/cm。该岩心上部层位呈红棕色,下部层位呈黄绿色,表明该岩心经历了显著的早期化学成岩作用。前人关于该岩心的元素地球化学,粒度和年代学数据,共同证明该岩心孔隙率随深度变化特征受稳态压缩过程控制。其孔隙率随深度的变化关系符合稳态压缩模型的经验拟合公式。E272顶部沉积物-水界面处溶解物质与海水的交换以离子扩散机制为主,而岩芯内部溶解物质的迁移则可能主要受自下而上的孔隙水流动机制控制,这与岩芯中活动元素含量上部高,下部低的分布模式一致。该研究对将来进一步讨论E272岩心在早期成岩作用中的化学过程具有指导意义。  相似文献   

Nonconservation of baryons in cosmology—revisited     

J. V. Narlikar 《Journal of Astrophysics and Astronomy》1984,5(1):67-78

The concept of the steady-state universe discussed by Hoyle & Narlikar two decades ago is revived in the light of the present discussions of the phase transition in the early big-bang universe. It is shown that with suitable scaling the bubble universe solution bears a striking similarity to the inflationary scenarios being discussed today. The currently discussed idea of cosmic baldness was also anticipated in the C-field cosmology of the steady-state universe. An erratum to this article is available at .  相似文献   

Study of Drainage Through Hydraulic Fill Stopes using Method of Fragments     

N. Sivakugan  K. J. Rankine  K. S. Rankine 《Geotechnical and Geological Engineering》2006,24(1):79-89

A good understanding of the pore water pressure developments within the hydraulic fill stope and the discharge through the drain is essential for improving the designs of barricades and the safety in the mines. A finite difference software FLAC was used to study the drainage and pore water pressure developments within a two dimensional rectangular stope with a single drain at the bottom. Using the method of fragment, a simple solution was proposed for determining the discharge and the maximum pore water pressure within the stope, when the height of water is greater than the width of the stope. The predictions are within 1% of those obtained from FLAC.  相似文献   

承压含水层非完整反滤回灌井的稳定流计算   总被引：2，自引：0，他引：2  

李旺林  束龙仓  李砚阁  李桂国 《水文地质工程地质》2007,34(2):67-70

反滤回灌井是地下水库中一种有效的回灌设施,它由回灌井和井口反滤层组成。非完整反滤回灌井井流运动由砂反滤层的竖向流和非完整回灌井井流组合而成。文中提出了承压含水层非完整反滤回灌井稳定流的计算方法,分析了反滤层、井损和回灌堵塞等因素对回灌量的影响,并结合实例证明了反滤回灌井回灌量大大低于普通回灌井的回灌量。  相似文献   

A semi-analytical model in time domain for moving loads     

T. Bierer  C. Bode 《Soil Dynamics and Earthquake Engineering》2007,27(12):1073-1081

A model for investigations of ground motions due to continuously moving loads with constant and time-varying amplitudes is presented. The vertical displacements excited by moving load areas are obtained at a fixed observation point at the surface of the three-dimensional halfspace in time domain. The load is moving along a straight line with constant speed. To solve this nonaxisymmetric, initial boundary value problem a semi-analytical, discretized model is developed. It is based on Green's functions for a suddenly applied, stationary surface point load with Heaviside time dependency. These functions, also called influence functions of the halfspace, are valid for any homogeneous, isotropic and linear-elastic medium. The principle of superposition is used. Results are shown for the transient and the steady-state ground motions, and they are compared with analytical solutions. The load speed is varied in the subcritical range up to the propagation velocity of Rayleigh-waves.  相似文献   

INVESTIGATION OF INFILTRATION CHARACTERISTICS AND DEBRIS FLOW INITIATION CONDITIONS IN DEBRIS FLOW SOURCE AREAS USING A RAINFALL SIMULATOR     

H. M. BLIJENBERG  P. J. DE GRAAF  M. R. HENDRIKS  J. F. DE RUITER  A. A. A. VAN TETERING 《水文研究》1996,10(11):1527-1543

Rainfall was simulated on unconfined plots on regolith in debris flow source areas using a portable simulator. In total, 351 simulations were carried out on steep slopes (27–54°) with rainfall intensities of 28–291 mm/h. From these rainfall simulations the infiltration parameters sorptivity (S) and steady-state infiltration capacity (K) of the regolith, and a threshold for the occurrence of micro-scale mass movements, were obtained. Two evaluation methods were used to obtain the infiltration parameters K and S. The ‘infiltration envelope’ method uses rainfall intensity and time to ponding from multiple tests and fits an infiltration envelope through the data from which K and S can be obtained. The ‘constant runoff’ method uses rainfall intensity and overland flow intensity to calculate K, after which S can be calculated in several ways by using time to ponding. The constant runoff method produced K values of 16.6–128 mm/h, which usually show a log-normal distribution. K values depend on the regolith parent material and rainfall intensity. Using this method, S values are 0.088–0.381 cm/min^1/2. The infiltration envelope method produced K values of 9.8–131 mm/h and S values of 0.14–0.32 cm/min^1/2. It can be argued that both methods overestimate K as well as S, but quantitative relations between measured/calculated and actual values of K and S have not yet been obtained. At high rainfall intensities, typically 100 mm/h or more, micro-scale mass movements sometimes occur. A lower threshold curve for the occurrence of these micro-scale mass movements has been constructed. It is a function of both slope angle and rainfall intensity. The micro-scale mass movements could play an important part in the initiation of debris flows in the study area, possibly by delivering sediment to overland flow. On the very steep slopes, the sediment-rich overland flow can easily mobilize coarse material.  相似文献   

具有N-策略及Bernoulli反馈的M/M/1工作休假     

吴中亚  朱翼隽 《成都信息工程学院学报》2009,24(1)

研究具有N-策略及反馈的M/M/1工作休假排队模型.工作休假策略为空竭服务多重工作休假.在休假期间,服务员并未完全停止工作而是以相对于正常工作时较低的服务率为顾客服务.完成服务的顾客以概率p(0相似文献   

基于Kalman滤波器的卫星钟差预报精度分析     

刘建成  杨睿峰  徐赟  王茂磊  桑怀胜 《全球定位系统》2012,37(4):1-5

Kalman滤波器稳态条件下的卫星钟差预报精度可作为评估星地时间同步性能的重要依据,研究了基于Kalman滤波器的卫星钟差预报精度问题。在卫星钟差包括3阶白噪声情况下,建立了卫星钟差的状态方程和测量方程,利用离散Riccati方程的非递归代数解,得到了Kalman滤波器的稳态解,进一步得到了卫星钟差预报误差,做了典型参数情况下的数值分析。  相似文献