Numerical Study On The Seepage Flow And Pore Clogging Mechanism Of Pervious Concrete Pavement

Pervious concrete pavements are broadly applied in Low Impact Development(LID)construction in 21th century,how to evaluate and observe the seepage ability and clogging mechanism of pervious concrete is an essential problem.Pervious concrete specimens are prepared for Computed Tomography(CT)imaging and numerical simulation to observe pore characteristics and study law of seepage flow.3D reconstruction based on CT imaging is utilized to generate virtual 3D pervious concrete structures,extract the connected pore network models.The connected pore network models are used to simulate the water seepage flow using Computed Fluid Dynamics(CFD)method.The next aim is using the CFD DEM model to numerically reveal the pore clogging mechanism and clogging development taking into account of the porosity of pervious pavements,sediments size distribution,the horizontal runoff velocity,and the seepage velocity.CT imaging combined with the CFD simulation can analyze the target porosity,actual porosity,3D porosity and the seepage ability.Pore characteristics analysis shows the 3D porosity,and average planar porosity can generally represent the actual porosity,and 3D connected porosity is close to the effective porosity.The results of the seepage simulation show that as the increase of the porosity,the ability of seepage flow inside the pervious concrete is increasing.The relationship between seepage velocity and pressure gradient is obtained and fitted by the nonlinear Forchheimer formula.The acquired hydraulic conductivity can be used to assess the seepage flow capacity.The numerical study of the clogging in pervious concrete shows that the pore clogging is determined by the D1/Ds ratio-the equivalent diameter of aggregate particles(D1)to equivalent diameter of sediments(Ds).Sediments secondary movement is revealed.Results show that the full-graded sands is able to percolate into the depth of 30 mm in pervious pavements;coarse sands will settle on the shallow surface within depth of 10 mm in pervious pavements;and fine sands will percolate into the depth of 60 to 100 mm in pervious pavements.As the increase of porosity,horizontal runoff velocity,and seepage velocity,the sediments will transport into pervious pavements deeply.The cycle simulation of raining and draining shows it has limited influence to clogging.An experiment is conducted to verify the results of CFD DEM simulation.Finally,the modified permeability equation suitable for pervious concrete is investigated based on the above research.