Fig. 5 illustrates breakthrough curves of solute concentration in the cross-fracture with the same grain diameters of 0.3175 to 0.5000 mm as modelled by CFEM. It can be seen from Fig. 5 that , when instantly injecting the same solute concentration, the arrival time of the peak concentration decreased with increasing flux. Also, there was a second concentration peak which might have been caused by the convergence of solute concentration values between main and branch fractures in the right hand-side of the experimental model. Furthermore, simulated results from the single fracture model, and cross-fracture model, showed that the arrival time of the concentration peak in the cross-fracture model was two times of that in the single fracture model.