(a)
(b)
(c)
Figure 8: Maximum shear stress (upper) and pore pressure (lower) evolution diagram of different pore pressures when  = 3.0 MPa. (a)  = 1.0 MPa,  = 3.0 MPa; (b)  = 1.5 MPa,  = 3 MPa; (c)  = 1.8 MPa,  = 3 MPa.