To better investigate the influence of the initial stress release parameter α, it is assumed to be 0.3, 0.5 and 0.7, i.e., the coefficient of the initial stress release is 70%, 50% and 30%, respectively. The other parameters are still as listed in Tables 1 and 2. Fig. 8 illustrates the influences of α on the temporal evolutions of normalized rock stressesand displacement, as well as normalized support pressure, for the two viscoelastic rocks.