渗透压作用下压剪岩石裂纹流变断裂贯通机制及破坏准则探讨

探讨了渗透压作用下黏弹性压剪岩石裂纹的起裂规律及分支裂纹尖端应力强度因子的演变规律,得出:一定轴向压应力下,渗透压、远场侧向应力和裂纹面摩擦系数是影响分支裂纹尖端应力强度因子KI演变的主要因素,渗透压的存在加剧了分支裂纹的扩展,随着裂纹渗透压的增大,分支裂纹扩展由稳定扩展变成不稳定扩展;建立了渗透压作用下压剪岩石裂纹体的轴向贯穿、岩桥剪切贯通两种不同类型的断裂破坏力学模型,引入虚拟应力强度因子KI(LC),提出以分支裂纹临界长度时裂尖虚拟应力强度因子KI(LC)作为黏弹性压剪岩石裂纹的流变断裂破坏准则,通过算例证实了该准则的可行性,得出:在既定裂纹分布、一定轴向应力和裂纹面摩擦系数的条件下,低渗透压、侧向拉应力共同作用下的压剪岩石裂纹趋向于轴向贯穿破坏,而高渗透压作用下会导致分支裂纹尖端岩桥剪切破坏,渗透压、侧向压应力共同作用下压剪岩石裂纹可能会发生具时间效应的流变断裂贯通破坏。为研究水岩相互作用下裂隙岩体的失稳破坏提供了一种新的思路。

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.