Experimental Study On The Migration Characteristics Of Suspended Particles Under Alkaline Conditions

Particle transportation in saturated porous media plays an important role in groundwater recharge, oil drilling, nuclear waste disposal, underground pollutant diffusion, grouting reinforcement and internal erosion of hydraulic structures. Combining the recent researches of particles transportation in saturated porous media, using self-developed test device, and this paper studies the influence of the alkaline environment on the migration characteristics of suspended particles through experimental research, the main contents include experimental research and mechanism analysis.(1) to carry out indoor soil column tests under different pH of injection solution, particle concentration, flow rate, obtain the breakthrough curves of suspended particles in saturated porous media under 4 different pH of injection solution (pH=7.0,9.6,11,13), 4 different particle concentrations (Cinj=2,4,6,8mg/mL),3 different flow velocity (v=0.066,0.133,0.199cm/s); finally, through the comprehensive comparative and in-depth analysis of the test results, to explore the influence of pH of injection solution, particle concentration, flow rate on the particles migration property in saturated porous media.(2) to carry out indoor soil column tests under different pH of external seepage fluid, particle concentration, flow rate, obtain the breakthrough curves of suspended particles in saturated porous media under 3 different pH of the external seepage fluid (pH=7.0,9.6,11),4 different particle concentrations (Cinj=2,4,6,8mg/mL),3 different flow velocity (v=0.066,0.133,0.199cm/s); finally, through the comprehensive comparative and in-depth analysis of the test results, to explore the influence of pH of external seepage fluid, particle concentration, flow rate on the particles migration property in saturated porous media.(3) to carry out indoor soil column tests of instantaneous repeatedly injected particles migration under different pH of injection solution, particle concentration, flow velocity, obtain the breakthrough of three consecutive instantaneous injected suspended particles in saturated porous media under 3 different pH of injection solution (pH=7.0,11,13), two different particle concentrations (Cinj=4,6mg/mL),3 different flow velocity (v=0.066,0.133,0.199cm/s); finally, comparing with the single transient test results, to explore the characteristics of repeatedly transient injected particles migration in saturated porous media.(4) to obtain the relevant motion parameters (diffusion coefficient DL, deposition rate Kdep, the average velocity of the particle u) determined by the convection diffusion equation of first-order sedimentation coefficient and the results of soil column tests in (1), and using the resulting parameters to fit the breakthrough curves of tests in (3) and compare the breakthrough curves of the test results with the fitting curves.The research shows that, the pH of injected solution and external seepage fluid, particle concentration, flow velocity and electrolyte concentration and other chemical and pHysical factors in the seepage environment have significant impact on the migration properties of the particles in saturated porous media; while all factors are not independent of each other; when a certain kind of factor changed, it not only affects the migration of the particles, but also causes the influence of other factors on the particle migration characteristics to change.