The alternating flow through the seams between geotubes in a geotube dam creates a cyclic flow regime distinct from the uni-directional flow that has been previously studied. A new laboratory apparatus has been used to investigate the influence of the hydraulic conditions on the stability of the geotube dam. This apparatus was capable of simulating cyclic flow conditions normal to the seam between the geotubes of the geotube dam. In this study, a series of tests were conducted under two different conditions: water or mixtures of water and air in a pipe(seams between geotubes). The results show that the main influence of the current on the sand in the pipe was the grading of the slope for the condition using air. In the other working condition, the erosion development process of the sand in the sandbox (dam core) was analyzed, the movement law of the particles in pipe was explored, and two migration processes of particles in the pipe were found.