Application Of High-density Electrical Resistivity Tomography (HERT) In Geotechnical Model Tests

The methods employed in geotechnical model tests cannot fully satisfy the requirements of three-dimensional,real-time,and non-destructive measurement.The high-density electrical resistivity tomography(HERT)is rarely adopted in geotechnical model tests,especially in centrifugal model tests.In this paper,the feasibility of real-time measurement of seepage and contaminant transport using high-density electrical resistivity tomography is studied,in particular the feasibility of HERT equipment used in centrifugal environment.The quantitative measurement of unsaturated seepage and the qualitative measurement of contaminant transport have been achieved.The main results are as follows:1)High-density electrical resistivity tomography method(HERT)can be applied to measure the process of geotechnical model tests.The equipment of HERT can be used in centrifugal environment with stability.High-density electrical resistivity tomography has a great advantage in real-time measurement of seepage and contaminant migration.2)Calibration tests are carried out to determine the quantitative relationship between the resistivity and saturation of the soil.Validity and applicability of the formula has been verified by model tests.The quantitative formula can be applied to the conversion of resistivity and saturation data,so as to realize the quantitative measurement of unsaturated seepage.Sand and silt resistivity have difference along with the change of saturation.With the change of saturation,the resistivity of sand first is greater than silt,after less than silt.3)The real-time and quantitative measurement of unsaturated seepage process has been carried out.The saturation in the center is higher than the saturation in the surrounding at the same height.Water infiltration is a reversible process in a certain extent.The infiltration head,the bottom boundary condition,and the kind of soil material would affect the infiltration rate.4)The real-time and qualitative measurement contaminant transport processes has been carried out.The soil resistivity in the surrounding is lower than it in the middle at the same height.Ions transport in the downward but also in lateral diffusion at the same time.There are differences in migration between two different kinds of ions.The resistivity of K+ decreases with increasing depth,and the resistivity of Fe3+ increases with increasing depth.