Fig. 6 shows CFEM-predicted breakthrough curves of solute concentration in the cross-fracture with different grain diameters, that is, the grain diameter was between 0.5 and 1.0 mm in the main fracture and 1.0 to 2.0 mm in the branch fracture. It can be seen from Fig. 6 that the arrival time of the peak concentration decreased with increasing flux and the maximum concentration increased therewith.