A Mathematical Model for Calculating the “Brittleness-Ductility” Drop Coefficient of Sandstone in Mining Zones

Figure 4

Failure surfaces of sandstone samples under different confining pressures. (a) 4 MPa, (b) 6 MPa, (c) 8 MPa, (d) 10 MPa.

(a)

(b)

(c)

(d)