Study on fracture characteristics and rockburst process of hard sandstone under high ground stresses
To study the hard sandstone rockburst failure characteristics under high ground stresses and to simulate the damage failure characteristics of the rock mass in that state,a Ⅰ/Ⅱ mixed cohesive zone model based on Park-Paulino-Roesler(PPR)potential energy function was established.Through disk-shaped compact tension test and punch-through shear test,the mode Ⅰ and mode Ⅱ fracture characteristics of hard sandstone were studied,and the parameters were obtained.Then,a numerical model was established to simulate the rockburst of hard sandstone tunnels under high ground stresses.The stress and energy of the elements in the process of rockburst are tracked to analyze the process and failure characteristics of rockburst in hard sandstone tunnel.The research results indicate that:(1)the shear strength and mode Ⅱ fracture energy of hard sandstone increase with the increase of the confining pressure.When the confining pressure exceeds 30 MPa,the mode Ⅱ fracture performance tends to stabilize.(2)When the vertical stress is much greater than the horizontal stress,the hard sandstone tunnel mainly experiences tensile-toppling rockburst in the form of layered spalling or wedge-shaped burst.On the contrary,shear-bursting rockburst characterized by penetrating shear failure in rock mass will occur.When the horizontal stress and vertical stress are both large,the unloading failure mode of rock mass mostly shows the characteristics of tensile-shear composite failure,and the tensile-stripping rockburst mainly occurs.
rock mechanicsrockbursthigh ground stresshard sandstonefailure characteristicscohesive zone model
万方数据
维普
