基于统计粒子模型开展渗透变形相似律及管涌细观机理研究.doc

Research of similarity law of seepage deformation and Microscopic mechanism of piping based on the statistical particle modelXiaodong NiTunnel and urban rail transit reaearch Institute, Hohai University Abstract: Seepage failure is a complicated fluid-solid coupling process, Involving large deformation and the flow theory of granular media. The process of particle migration is closely related with time. At present,the continuous medium method from the Macroscopic level is used in most case to solve this question.It is obviously that the continuous medium method is helpless to describe the physical process of seepage deformation dynamically.Statistics particle flow method has the discrete traits which can be used to simulate the physical processes more convenient.Seepage deformation is a dynamic process of interaction between soil and water.When carry out relevant experiment, it is necessary to make sure that the time between the analysis model and research objects is coordinated. In other words ,it must obey time similarity criterion .The ongoing indoor model test or centrifuge model test are based on the assumption of Darcys law. Under the assumption, it has been confirmed by tests that the time similarity criterion does not satisfy again. In this case , it is impossible to achieve similar between porototype and model in the corresponding period.So there will be a certain deviation between porototype and model. Based on the basic equations of fluid dynamics in porous media, the similarity criterion about seepage deformation is deduced. Statistical particle model can meet the the conditions in the similarity criterion. Therefore, the model is used to verify the correctness of the similarity criterion.Based on the above results, seepage deformation model test is conduct, then taken it as the prototype. Corresponding statistical particle model is established according to the similarity lawThe result shows that this method is applicable to research the phenomenon of piping. Final,this method is used to explore the microscopic mechanism of Piping.1.PrefaceDescribes the relevant numerical methods of seepage deformayion, highlighted the problems existing in the current method. Describe the advantage of statistics particle model in carry out seepage deformation.2.Seepage deformation characteristicsFlow :Function of time and space.3.Nature of seepage deformation3.1 Basic equations Continuity equation/Momentum conservation equationfluid-particle friction coefficient：the driving force applied to a particle by fluid is : 3.2 Processing methodFig.1 Schematic diagram of fluid-structure interaction Solid particlesLiquid：ContinuousImpermeable layer Pressure point Velocity pointFluid flow in micro-poreporeSolid：DiscretePore-Averaged N-S solution equationImpermeable layerParticles-SPM solution4. Similarity law in the process of seepage deformation4.1 Hydrodynamic similarity lawContinuity equation/Momentum conservation equation 4.2 Similarity law of fluid dynamics in porous mediaMomentum conservation equationfluid-particle friction coefficient:5. confirmation similarity criterion by Statistical particle model Fig.3 Nuniacal poroto and model(a) Numerical prototype(b) Centrifugal model0.020.040.060.080.1001234Velocity (m/s)Fig.4(a) Surface velocity changes with time in prototype under different hydraulic gradients P: po=2.0kPa d=do m=1P: po=1.7kPa d=do m=10Time (s)(c) Model satisfies the similarity criterion00.050.100.10.20.30.4M-II: po=1.7kpa d=do/10 m=1、0.1M-II: po=2.0kPa d=do/10 m=1、0.1M-I: po=1.7kPa d=do m=1、10M-I: po=2.3kPa d=do m=1、100.15Velocity (m/s)time /sFig.4(b)Surface velocity changes with time in model under different hydraulic gradients 6. Indoor Model test and Statistic particle model testFig.5(a)Schematic diagram of the indoor modelPiezometer0.3HBCA0.30.20.8Permeable platePiping holeImpermeable boundaryUpstream head boundaryP=0Impermeable boundary Fig.5(b) Schematic diagram of numerical model7. Microscopic mechanism of piping8. Conclusion基于统计粒子模型开展渗透变形相似律及管涌细观机理研究摘要：渗透破坏过程是复杂的流固耦合过程，涉及固体大变形和颗粒介质的流动理论，该过程中颗粒运移与时间密切相关。当前大多从宏观角度采用连续介质方法对该问题开展相关研究，显然无法从本质上对该物理过程进行动态描述，统计粒子流方法具有的散粒体特质可以实现对该物理过程的模拟。渗透变形是一土水相互作用的动态过程，开展渗透试验研究时必须确保分析模型与研究对象间的时间协调，亦即需满足谐时准则。当前开展渗透变形室内模型试验或离心试验研究均基于达西渗流假定，该假定下渗透破坏时间比尺不满足谐时准则