(a)
(b)
(c)
(d)
Figure 14: Comparisons between test data and predicted results of volumetric strain-axial strain under different confining pressures: (a) 1.0–4.0 MPa, (b) 5.0–8.0 MPa, (c) 10.0 and 16.0 MPa, and (d) 14.0 MPa.