An Analysis Of Monitoring The Double-ring Infiltration Process Using High-Density Electrical Resistivity Tomography

Infiltration test(test pit,single ring,double-ring)is the technique to evaluate the vertical infiltration ablity of surface layer in hydrogeology and engineering geology exploration.One-dimensional approximation and Ampt-Green model are used to calculate the vertical saturated permeability coefficient.After a long duration test,infiltration velocity comes to stabilize.Ignoring the water table effect in inner ring and regarding vertical hydraulic gradient as 1,the stability ratio flow becomes vertical saturated permeability coefficient.The infiltration test result is usually used to evaluate infiltration recharge ability of rainfall,lake and rive.As outer-ring promoted inner-ring flow vertical infiltration,it is used widely with higher accuracy.Meanwhile,double-ring infiltration test can just get an integrated parameter so that it comes difficult to know the underground heterogeneous information.For this reason,it is very important to study the process of double-ring infiltration in porous media.Based on the purpose of identifying permeability of the medium and learn the process of infiltration,ERT was used to minotor the double-ring infiltration test in the potential repository site Beishan of Gansu province for China's high level radioactive waste disposal.The test was also applied in clay media on Zijin Mountain and Chu zhou experiment station to compare the different media monitoring results.By completing rounds of experiments,the results reveal the following conclusions.1.Used RES2D software and establish resistivity model to analysis the resistivity tomography of the infiltration process which have a good effection to understand the electric measurement in field.2.Used GMS software to simulate the double-ring infiltration.Analyzed the effect of insertion depth and lens.The inner-ring has a better constraint effect to the outer-ring,at the same time,we could not ignore the outer-ring confinement effect.3.Analyzed the change of resistivity and draw the picture of ERT to reveal the process of infiltration.I got the time of sand saturated in different depth by recording the resistivity change of same measuring points in different time.I got the infiltration front by drawing all the measuring points' resistivity in the same depth.As a result,when ERT method was applied to double-ring test,it could get the shape of wetted front to some extend,especially the lateral-flow.The double-ring device have some effect to the infiltration paths.4.Applied double-ring infiltration test on Zi jin Mountain and Chu zhou experiment station to get the saturated permeability coefficient and analysis the process.As clay have a good water capacity and low permeability,the clay in humid environment had a high water content.As a result,the infiltration did not have a good result.Applied the tap-water infiltrated,the resistivity increase.Applied salt pulse infiltrated,the resistivity decrease.We could have a try to use tap-water or salt solution infiltrating to get a good result of the electric resistivity monitor.The relative variation of apparent resistivity had a good result to reveal the resistivity change when infiltration.