Particle-fluid Interaction Model For Cohesionless Particulate Geomaterials And Characteristics Of Nonlinear Seepage Flow

The non-cohesive granular material contains both irregularly shaped rocks and calcareous sands found in nature,some man-made materials such as glass balls are also used in the study of geotechnical engineering problems.Exploring the interaction law between non-cohesive geomaterials and water will help to understand the geotechnical problems such as consolidation settlement of the fillings in the filling project.Since the drag force indicates the force of the fluid on the solid surface,and the drag coefficient reflects the ratio of the drag force to the fluid dynamic pressure acting on the surface of the particle,the drag coefficient is used as the entry point to effectively promote the interaction law between soil and water.Based on the single-particle drag coefficient model considering the shape factor,this paper first embeds it into the open source fluid-solid coupling program CFD-DEM,numerically simulates the single-particle sedimentation test,and compares the final particles in the test.The settlement velocity and numerical simulation results prove the validity of the embedded model,and further compare the numerical simulation results of the existing spherical particle drag coefficient model,revealing the necessity of numerically simulating the difference of particle shape when interacting with soil and water.In order to further realize the numerical simulation of soil-water interaction considering the physical properties of particle deposits,lay the foundation.In order to study the characteristics of particle inclusions in nonlinear flow,the sedimentation test study of granular composites was carried out.The research focused on the influence of the target particles on the number and relative distance of surrounding particles.The influence of factors such as the number of surrounding particles and the distance from the target particles on the drag coefficient of the particle combination,and the drag coefficient model of the particle combination was established according to the law.This process actually shows that factors such as porosity will affect the soil-water interaction of the non-cohesive geomaterials.After the above research,in order to explore the influence of particle size,density,shape coefficient and porosity on the interaction law of soil and water in nonlinear flow,the introduction of various natural and artificial geotechnical particle seepage tests was introduced.In the BP neural network,the variation range of the above four variables was continuously changed in multiple sets of experiments,and the osmotic curve and the slope and intercept of the seepage curve in the corresponding seepage test were obtained,and the equivalent particle size and density were constructed.,shape factor,porosity is the neural network of the output variable in the slope and intercept of the input variable seepage curve.Not only can a network model predicting the nonlinear flow characteristics of the particle stack,but also the input variables of the neural network.Sensitivity analysis can also understand the extent to which four variables affect soil-water interactions.In the establishment of the theoretical model of soil-water interaction,the theoretical framework of the drag coefficient model of particle accumulation is combined with the single-particle drag coefficient model based on the seepage data of calcareous sand particles.The law of the change of the index with the porosity in the porosity function was found,and the drag coefficient model of the irregular calcareous sand particle accumulation was finally determined.On the basis of the single-particle drag coefficient model,the numerical simulation verification of the single-particle drag coefficient model was carried out step by step.The drag coefficient model of the particle assembly was constructed by the settlement test,and the particle stack was further developed.In the linear seepage test,the neural network was built by using the experimental rules,and the neural network model which can predict the nonlinear flow characteristics of the particle accumulation body was obtained.Finally,the soil-water interaction law of calcareous sand particle accumulation body is taken as a breakthrough point,and the model of soil-water interaction of calcareous sand particle accumulation body is established,which is used to construct other particles or soil-water interaction suitable for various particles.The model lays the foundation.The completion of the above work has great reference and guiding significance for engineering problems involving soil-water interaction in geotechnical engineering.However,for complex geotechnical engineering problems,whether the relevant drag coefficient model established in this paper is fully used still needs further understanding.