Numerical modeling of influences of discontinuous centrifugation on contaminant migration in cutoff wall

The soil-bentonite vertical cutoff walls are widely used in the remediation and control of contaminated sites. The correct evaluation of the service life of the cutoff walls is the key to their design. It often takes decades to evaluate the long-term performance of the cutoff walls by field tests, and the centrifugal model tests can obviously shorten the test period. In the case of high centrifugal acceleration, the geotechnical centrifuge cannot work for a long time. To solve this problem, a method of discontinuous centrifugation is proposed to simulate the long-term migration of contaminants. In the case of discontinuous centrifugation, the migration behavior of contaminants is changed. To correctly evaluate the service life of the cutoff walls, a numerical model is established to simulate the migration of the contaminants under the periodic change of centrifugal acceleration. The results show that: (1) The service life of the cutoff walls in the case of discontinuous centrifugation will be lower than that of continuous centrifugation if the effective centrifugation time is used as the time of contaminant transport. (2) When the centrifuge shuts down, the decreased migration velocity of contaminants in the cutoff wall is limited, and diffusion has become the main migration mode of contaminants. (3) The service life of the cutoff walls decreases with the increase of the work interval of the centrifuge.