Study On The Effect Of Particle Shape On The Permeability Of Coarse-grained Soil

Porous media is a solid system containing many interconnected pores,and the flow of liquid in porous media is called percolation.Its permeability depends on the pore structure and the nature of the fluid.As a typical porous medium,the permeability of coarse-grained soil is affected by pore size distribution,porosity,particle shape and other factors.Compared with other factors,there is less attention to the shape of particles.The existing research rules are not enough to reach a consensus,and the mechanism from view research and influence is almost blank.In this paper,roundness is chosen as an index to evaluate the shape of particles,and specific surface area is used as a parameter to describe the pore structure.The relationship between roundness and pore size,surface area was studied.The influence of the particle shape on the permeability characteristics of coarse-grained soil is obtained by seepage test.The formation mechanism of the law is explained from the characteristics of water flow in the sample pores.The main contents and conclusions of this paper are as follows.(1)Whether the three-dimensional reconstruction model of CT images is equal to the porosity of scanned samples can be used as a criterion to judge the rationality of CT image segmentation.According to this criterion,a new method for measuring pore specific surface area of porous media with known porosity is reasonable,simple and advantageous.Under the condition of the same gradation and porosity,the permeability tests were carried out for irregularly shaped crushed stone,regular shape of glass ball and plastic eight faces.The results show that the particle shape affects the permeability of coarse grained soil.Circular degree has positive correlation with permeability coefficient.(2)Under the same grading and porosity conditions,the specific surface area of coarse grained soil increases with the increase of the length width ratio of coarse grained soil,and decreases with the increase of roundness.The permeability coefficient has an exponential positive relationship with roundness,and decreases with the increase of pore surface area.(3)Under the same gradation and porosity,the pore area of the coarse grained soil is larger than the surface area.The flow field in the pores of more complex,streamline the tortuosity is large,the actual seepage path of the pressure gradient along the direction of the longer.When the water flows along the same pressure gradient,the energy dissipation of water is greater.The macro surface is of low permeability and low permeability.