考虑裂隙的几何-力学特性的双重孔隙介质水-应力耦合模型及其有限元分析

建立了一种双重孔隙介质水-应力耦合模型,其特点是可考虑裂隙的组数、间距、方向、连通率、开度、刚度及应力水平对介质的弹性模量、孔隙率及渗透系数的影响,并研制出相应的二维有限元程序.以模拟饱和的双重孔隙岩体在外荷载作用下产生沉降为算例,针对岩体的孔隙率与渗透系数分别是常数及按照本文中所述规律变化的两种工况,考察了不同岩体中的变形、孔隙水压力与裂隙水压力及流速、主应力等的分布与变化.结果表明:将岩体的孔隙率与渗透系数作为应力的函数,与将其作为常量的方法相比,二者对岩体的变形及应力的影响不大,但前者对孔隙水压力、裂隙水压力及流速的影响强烈.     

双重孔隙介质流固耦合理论模型

介绍了考虑介质变形的双重孔隙介质模型，并给出了双重孔隙介质流固耦合方程的数学推导。     

不同边界条件对孔隙介质渗流-应力耦合的影响

以孔隙介质的流体力学和连续性介质弹性力学为理论基础,建立多孔连续性介质的渗流-应力耦合模型,根据4种不同的边界条件,采用Flex PDE有限元计算软件编程分别求解4种边界条件下渗流-应力耦合的数学模型。比较4种不同的计算结果,分析表明,不同的位移场或渗流场边界条件会对渗流-应力耦合效应产生较大的影响。     

锦屏二级水电站裂隙岩体渗流-应力耦合分析

如何准确地了解和预测隧洞周围裂隙岩体的渗流-应力耦合行为对锦屏二级水电站深埋高压引水隧洞的设计和施工有着重要意义.锦屏山裂隙岩体的渗透系数的空间非均质分布利用随机连续模型生成.通过顺序指示模拟方法生成的随机连续场随后被导入有限元程序进行两场耦合分析.计算结果表明,随机连续模型能够较好地预测锦屏二级水电站隧洞开挖过程中地下水的最大入渗率.渗透系数的空间变异性使得隧道开挖后围岩应力有明显的非连续性,对裂隙介质的耦合过程起着重要作用.同时,雨季降雨对隧道支护系统有着重要影响.补给水将引起外水压力短时升高,衬砌上的负荷增加,其弯矩增加了近22%.     

大理岩岩体力学特性的水压-应力耦合试验研究

为研究裂隙水压力与应力条件对大理岩裂隙岩体力学特性的影响,利用MTS815 Flex Test GT 岩石力学试验系统,采用特殊的试样制备和地质过程模拟方法,制备成与试验机围压系统、渗压系统融为一体的大理岩裂隙岩体试件,并对其进行了不同水压、不同围压下的水压 应力耦合三轴压缩试验。试验结果表明：大理岩岩体强度性能与变形性能均具随水压升高而减小,随围压升高而增大的特征;水压从0到4 MPa的变化过程中,强度参数f 减小了20%左右,内聚力C大幅降低,变形模量E₀及E₅₀分别减小了7.7%和5.9%;围压从5 MPa到30 MPa的变化过程中,f 值略有降低,C值增大了2倍多,变形模量E₀及E₅₀分别增大了58%和50%。这些成果揭示了大理岩裂隙岩体力学特性的裂隙水压效应与围压效应,对实际工程问题的研究具有重要的参考价值。     

裂隙岩体渗流与应力耦全分析的四自由度全耦合法

本文首次提出裂隙岩体渗流与应力耦合分析的新方法－四自由度全耦合法，该法不仅考虑了裂隙渗透性随应力的变化，而且建立的同时以渗流水压力的位移为未知值的耦合方程组，     

水气二相渗流与双重介质变形的流固耦合数学模型

为了真实反映地质岩体系统内孔隙、裂隙对发生于其中的物理过程的控制与影响,基于岩体渗流水力学和多相渗流力学理论,将工程地质体简化为孔隙一裂隙双重介质,建立了水气二相渗流与双重介质变形的流固耦合数学模型,采用Galerkin有限元方法推导了相应的有限元方程,编制出三维有限元计算程序。算例表明：双重介质模型能够比较准确地描述地质体的结构;在进行注水井数值实验模拟时,考虑耦合与不考虑耦合时的孔隙压力的差别随时间的推移会越来越大。     

裂隙岩体边坡稳定性的渗流与应力耦合分析

用裂隙岩体渗流与应力耦合分析的四自由度全耦合法对岩质边坡进行耦合分析,通过强度折减有限元法求解岩体边坡的稳定安全系数。四自由度全耦合法建立了同时以渗流水压和位移为未知量的耦合方程组,使得渗流场与应力场的求解能够一次性完成,与两场交叉迭代分析方法相比达到了彻底的完全耦合。通过强度折减,整个系统达到不稳定状态,有限元计算将不收敛,此时的折减系数就是安全系数。算例表明由此求得的边坡稳定安全系数和滑动面都与传统方法十分接近。     

考虑气体的渗流应力耦合模型在黄壁庄水库中的应用

目前建立的多孔介质耦合模型通常认为气体是不可压缩的,无法描述气体的输运过程,无法反映气体对水体入渗和固体变形的影响。为了描述多孔介质中固液气三相的渗流应力耦合过程,基于多孔介质理论和有效应力原理,提出了一种耦合了改进守恒水平集(ICLS)方法并考虑气体可压缩性的固液气三相渗流应力耦合模型。将该方法应用于黄壁庄水库坝前冒泡现象的渗流应力耦合分析中,模拟了水位骤升后,固体变形、水体入渗和气体运移过程,及其耦合效应。计算结果表明,该方法能够简单直观的描述水气两相的运移过程及渗流应力耦合过程,且模拟结果与实际观测结果基本一致。     

坝内开裂泄水涵洞渗流-应力耦合有限元计算分析

依托于某粘土心墙坝内泄水涵洞墙体混凝土开裂,通过坝体变形参数确定渗流-应力耦合数值模拟方法,分析了泄水涵洞混凝土结构的应力应变特性。有限元计算成果表明：渗流-应力耦合条件下,坝体与涵洞共同受力时涵洞结构整体沉降变形较小;校核洪水位工况时泄水涵洞墙体混凝土结构最大拉应力出现在A型第4段顶板外侧,为1.131 MPa。建议对仍在渗水的裂缝采用压浆封闭处理,其它裂缝进行表面封闭。     

ONE-AND TWO-DIMENSIONAL COUPLED HYDRODYNAMICS MODEL FOR DAM BREAK FLOW

1-D and 2-D mathematical models for dam break flow were established and verified with the measured data in laboratory. The 1-D and 2-D models were then coupled, and used to simulate the dam break flow from the reservoir tail to the dam site, the propagation of dam break waves in the downstream channel, and the submergence of dam break flow in the downstream town with the hydrodynamics method. As a numerical example, the presented model was employed to simulate dam break flow of a hydropower station under construction. In simulation, different dam-break durations, upstream flows and water levels in front of dam were considered, and these influencing factors of dam break flow were analyzed, which could be referenced in planning and designing hydropower stations.     

A COUPLED MORPHODYNAMIC MODEL FOR APPLICATIONS INVOLVING WETTING AND DRYING

This work presents a new finite volume Godunov-type model for predicting morphological changes under the rapidly varying flood conditions with wetting and drying.The model solves the coupled shallow water and Exner equations,with the interface fluxes evaluated by an Harten-Lax-van Leer-Contact(HLLC) approximate Riemann solver.Well-balanced solution is achieved using the surface gradient method and wetting and drying are handled by a non-negative reconstruction approach.The new model is validated against several theoretical benchmark tests and promising results are obtained.     

A COUPLED MODEL OF HYDRODYNAMICS AND WATER QUALITY FOR YUQIAO RESERVOIR IN HAIHE RIVER BASIN

In order to simulate the characteristics of hydrodynamic field and mass transport processes in the Yuqiao Reservoir （YQR）, a 2-D coupled model of hydrodynamics and water quality was developed, and the water-quality related state variables in this model included CODMn, TN and TP. The hydrodynamic model was driven by employing observed winds and daily measured flow data to simulate the seasonal water cycle of the reservoir. The simulation of the mass transport and transformation processes of CODMn, TN and TP was based on the unsteady diffusion equations, driven by observed meteorological forcing and external loadings, with the fluxes form the bottom of reservoir and the plant photosynthesis and respiration as internal sources and sinks. A finite volume method and Alternating Direction Implicit （ADI） scheme were used to solve these equations. The model was calibrated and verified by using the data observed from YQR in two different years. The results showed that in YQR, the wind-driven current was an important style of lake current, while the concentration of water quality item was decreasing from east to west because of the external pollutant loadings. There was a good agreement between the simulated and measured values, with the minimal calculation error percent of 0.1% and 2.6% and the mean error percent of 44.0% and 51.2% for TN and TP separately. The simulation also showed that, in YQR, the convection was the main process in estuaries of inflow river, and diffusion and biochemical processes dominate in center of reservoir. So it was necessary to build a pre-pond to reduce the external loadings into the reservoir.     

COUPLING EFFECTS FOR CELL-TRUSS SPAR PLATFORM: COMPARISON OF FREQUENCY- AND TIME-DOMAIN ANALYSES WITH MODEL TESTS

For the floating structures in deepwater, the coupling effects of the mooring lines and risers on the motion responses of the structures become increasingly significant. Viscous damping, inertial mass, current loading and restoring, etc. from these slender structures should be carefully handled to accurately predict the motion responses and line tensions. For the spar platforms, coupling the mooring system and riser with the vessel motion typically results in a reduction in extreme motion responses. This article presents numerical simulations and model tests on a new cell-truss spar platform in the State Key Laboratory of Ocean Engineering in Shanghai Jiaotong University. Results from three calculation methods, including frequency-domain analysis, time-domain semi-coupled and fully-coupled analyses, were compared with the experimental data to find the applicability of different approaches. Proposals for the improvement of numerical calculations and experimental technique were tabled as well.     

A COUPLED THERMO-HYDRAULIC MODEL FOR STEAM FLOW IN PIPE NETWORKS

This article aims to establish a coupled thermo-hydraulic mathematical model for steam network by adopting a set of equations, i.e., the continuity equation, motion equation, energy equation, state equation and enthalpy equation and considering the interaction of hydraulic and thermal working conditions. The model is simplified according to steam flow features in pipe networks. The unsteady flow model is simplified to a steady one with considering engineering practice and the solution to the governing equations are obtained by using the standard fourth-order Runge-Kutta method. Many factors of steam flow are generally considered, such as condensability, change of state, friction and heat transfer in the model. It is concluded that coupled iteration can be employed in steam network thermo-hydraulic computation. The numerical results with the model are basically in accordance with practical operation data.     

COUPLING EFFECTS FOR CELL-TRUSS SPAR PLATFORM： COMPARISON OF FREQUENCY- AND TIME- DOMAIN ANALYSES WITH MODEL TESTS

For the floating structures in deepwater, the coupling effects of the mooring lines and risers on the motion responses of the structures become increasingly significant. Viscous damping, inertial mass, current loading and restoring, etc. from these slender structures should be carefully handled to accurately predict the motion responses and line tensions. For the spar platforms, coupling the mooring system and riser with the vessel motion typically results in a reduction in extreme motion responses. This article presents numerical simulations and model tests on a new cell-truss spar platform in the State Key Laboratory of Ocean Engineering in Shanghai Jiaotong University. Results from three calculation methods, including frequency-domain analysis, time-domain semi-coupled and fully-coupled analyses, were compared with the experimental data to find the applicability of different approaches. Proposals for the improvement of numerical calculations and experimental technique were tabled as well.     

THE CONSISTENT ANALYSES OF SCALE SIMILITUDE IN RIVER MODEL EXPERIMENT

Law of the propagation of errors caused by the inconsistency of the boundary scale similitude in river model experiment is presented in this paper.The fluctuation of scale transfers along the characteristic line,if the discharge and sediment at entrance and the water level at the tail gate drift.The fluctuation of scale propagates with the derived scale function due to topographic deviation.All errors will accumulate to the final measured data     

A CONSERVATIVE COUPLED FLOW/TRANSPORT MODEL WITH ZERO MASS ERROR

A fully conservative form applied to a coupled system of two-dimensional water flow and solute motion is presented. A cell-centred finite volume method based on Roe's approximate Riemann solver with unstructured grids is formulated. The bed slope source terms are discretized following an upwind approach and a semi-implicit treatment is used for the friction source terms. The centered discretization of the diffusion terms is in an implicit way. It is shown that this numerical technique reproduces almost exactly the steady state of still water and enables to achieve zero numerical errors in unsteady flow over configurations with strong variations on bed slope. The model ensures a global conservation and positive values of both water level and solute concentration. Numerical results show the effectiveness of the model in solute transport over real complex geometries.     

NET IMPACT OF PHYSICAL INTERACTION MECHANISMS IN A COUPLED WAVE-TIDE-SURGE MODEL

1 .　INTRODUCTIONBecausewindgenerateswavesaswellasstormsurges ,theirgenerationprocessesarecloselyrelat ed .Moreover ,thestrongnonlinearinteractionsthatexistbetweentidesandstormsurgesinshallowwater,resultinimportantinteractionsbetweenwavesandtide surgemotions .Inthisstudy ,thecouplingofwavesandtide surgemotionsisstudiedbyimplementingseveralmechanismswhereinwavesandthemeanflow ,orthewaterlevelasso ciatedwiththetideandsurges ,areallowedtoin teractwitheachcomponentofthetotalmotion .Thesemecha…     

重力坝的实测坝踵应力及原因分析

(上接本刊2000年第6期第14页)4.2　重力坝坝踵应力的特点表2～表4分别列出了以上5座坝坝踵垂直应力、顺河向应力及断河向应力概况。一个很明显的印象就是5座坝坝踵应力均具有共同的规律性。表5为5坝坝踵各个测点在施工期和运行期的最大拉应力、最大压应力及蓄水时应力的平均值,可见,坝踵在运行期的应力有下列特点:a.三个方向的应力变幅均较施工期减小,并趋向均匀。施工期应力平均变幅三向分别由2.59MPa,2.27MPa及1.76MPa降至1.46MPa,1.35MPa及1.49MPa。b.垂直向基本上都是压应力,约在-0.8MPa至-2.3MPa之间。顺河向及断河向应力相近,…