Research On The Seepage Law Of Rough Single Fracture In Multi-flow State

Fissure seepage is an engineering problem that must be paid great attention in underground facilities construction,groundwater mining and other projects.The natural fissure surface has obvious rough characteristics,which makes fissure water flow highly nonlinear.Carrying out research on the flow of single fracture under different conditions of relative roughness can reveal the seepage mechanism of rock fractured media,and also provide theoretical support for the study of groundwater movement in fracture systems of rock masses.Based on the standard JRC model proposed by Barton,the fracture geometry model with different relative roughness was reconstructed in this paper,and the flow viscosity model of each flow state was optimized based on the Nikuradse experiment as the calibration standard.The computational fluid dynamics software Fluent was used to simulate the flow of water in a rough single fracture.The law of the fracture flow with the relative roughness of the fracture was explored.The influence of the relative roughness on the resistance coefficient and critical Reynolds number along the flow was analyzed Based on the numerical simulation results,the cubic law and equivalent seepage coefficient of single fracture flow were modified.The main research work is as follows.1.Based on different flow regime theories and empirical formulas,different viscosity models are used to simulate the evolution of laminar flow in laminar round tubes from laminar flow to complete turbulence,along with the relative roughness and Reynolds number.The Nikuradse experiment is a proofreading standard,and viscosity models for each fluid state are optimized.2.Based on the Barton standard profile line,a reasonable spacing was used to reconstruct the fracture geometry model with different relative roughness and transformed into a hydromechanical calculation grid.The sensitivity of the fluid motion simulation results to the grid size was studied.A rough single-fracture fluid mechanics calculation network with high calculation efficiency and calculation accuracy is developed.3.Based on the results of numerical simulation,the logarithmic coordinate relationship curve between the along-flow resistance coefficient of single fracture and the Reynolds number under different rough conditions was plotted.The head loss mechanism of water flow in each flow regime was analyzed and the fractures were established Relative roughness(?/d)between laminar resistance loss coefficient(k),turbulent transition zone-turbulent rough zone transition critical Reynolds number(Re_f4),and turbulent rough zone water flow resistance coefficient(?)along the way Functional relation.4.Carry out research on the nonlinear flow mechanism of single fracture with roughness,and use Forchherimer formula to curve fit the fracture average velocity and hydraulic gradient under different relative roughness conditions.Based on the statistical analysis of more than 130 working conditions,The functional relationship between relative roughness(?/d)and laminar-turbulent transition critical Reynolds number(Re_f1).5.The flow motion of fractures with significantly rough characteristics is studied.Based on the statistical analysis of the relative roughness(?/d),the single-wide flow correction factor(c_q)and equivalent seepage coefficient correction factor(c_k)for fracture seepage.Based on the relative roughness,the cubic law of fracture seepage and the equivalent seepage coefficient correction formula are established.