Rheologic fracture mechanism and failure criterion of rock cracks under compressive-shear load with seepage pressure

The cracking of viscoelastic rock and evolution regulations of the stress intensity factor at the crack cusp were induced by compressive-shear load under the action of seepage pressure.The conclusion that the stress intensity factor KI at the crack cusp depended on seepage pressure,lateral stress and friction coefficient of rock cracks was drawn.The seepage pressure expedited the propagation of cracks,the increase of seepage pressure led to the propagation of cracks in an unsteady way;The rheologic fracture failure mechanism of axial coalescence and rock bridge coalescence in the compressive-shear stress state under the effect of seepage pressure were also studied.The fictitious stress intensity factor KI(LC) as a new parameter was introduced firstly.The rheologic fracture failure criterion in which the fictitious stress intensity factor KI(LC) at the crack cusp was viewed as an index when the crack propagation length reached the critical value.Through a sample the failure criterion was proved to be feasible.The main result was that under certain axial stress and friction coefficient,the low seepage pressure and lateral tensile stress together led to axial coalescence,the high seepage pressure led to shear failure of bridge coalescence,the seepage pressure and lateral compressive stress together might lead to rheologic fracture failure.A new thought to study the fractured rock mass failure in the interaction of water-rock was suggested.