Study On The Permeability Properties Of Basalt Foundation By Experiments And Numerical Simulation

There are widely distributed vesicular structural basalts in Haikou City,whose vesicles are caused by the vaporization of liquid materials in magma during the volcanic eruption.In recent years,it is found that there is little water accumulation in this kind of foundation area in the construction of "sponge city".It is the premise of sponge city construction in basalt foundation area to find out the water permeability and explain it scientifically.In this paper,the seepage characteristics of basalt fracture with vesicular structure and columnar joints are studied by laboratory test and numerical simulation,and the main work is as follows:Firstly,based on the indoor single fracture permeability test of four kinds of basalt samples collected from the basalt area of Haikou City,Hainan Province,the influence factor of fracture surface structure(?)are introduced to transform the test results,and The relationship between the influence factor of fracture surface structure(?)and the Reynolds number(Re)of fracture flow is obtained.According to the experimental results and the cubic formula of fracture seepage,the formula of vesicular structural fracture seepage is put forward.Then,based on the FLUENT software,the numerical simulation of the vesicular structural fracture seepage model is carried out,the seepage mechanism of the vesicular structural fracture is clarified,the accuracy of the empirical formula of the vesicular basalt fracture seepage obtained from the test is confirmed,and the application scope of the vesicular structural fracture seepage formula is determined.In addition,three characteristic parameters,i.e.the maximum depth of vesicles H,the ratio of vesicle area w and the maximum diameter of vesicles d,are used to describe the vesicular characteristics of basalt fracture surface,and the influence of the structural characteristic parameters of vesicles on vesicular structural fracture seepage is analyzed.Finally,on the basis of obtaining the permeability tensor of the fracture unit of the smooth columnar joint by formula derivation,the calculation model of the permeability unit of the fracture unit of the hexagon columnar joint is established.Based on the numerical simulation,the influence of the fracture width b and the fracture depth L on the seepage of the fracture unit of the smooth hexagon columnar joint is revealed.In addition,based on the results of single fracture permeability test of basalt in laboratory,the permeability tensor of hexagonal columnar joint fracture unit of vesicular structural rock is derived...