“…The location and time of the extreme pressure in the tunnel are x and t, respectively. Thus, the issue concerning their position and time of appearance involves six variables, which are L tu , L tr , v tr , c, x, and t, but only two fundamental dimensions, length L and time T. According to Buckingham's π theorem [50], 6 − 2 = 4 dimensionless products are determined, as shown in Equations ( 17)- (20).…”