Numerical Simulation Of Progressive Failure Process Of Jointed Rock Slope

The failure of rock slope along the fracture surface is one of the most important types of slope instability.The physical and mechanical properties of the fractured surface are different from those of the upper covering rock mass.Due to the external factors such as rainfall,seepage,weathering and earthquakes,the strength of the slope and the crack surface is reduced in different degrees,resulting in differences in the slope and fissure surface deformation.Tensile cracks from the fissured surface from the rock bridge and slope expansion through,resulting in damage to the slope instability.In this paper,the failure mechanism of single-crack and double-fractured rock mass is simulated by using rigid body spring method.The macroscopic influence mechanism of fracture geometrical parameters on rock mass failure process is analyzed,and the gradual failure process of fractured rock slope is carried out.The types of failure modes of fractured rock slope are simulated and analyzed,and the mechanism of rock bridge expansion is expounded.The main conclusions are as follows:(1)The effects of fracture inclination,length,opening degree,rock bridge inclination and aspect ratio on rock mass strength and failure mode were studied by simulating uniaxial compression test.The strength of the rock specimen decreases first and then increases with the increase of the crack angle and the strength is the lowest when the crack angle is 45 °.The strength of rock mass decreases gradually with the increase of the ratio of length to diameter,and the influence of crack opening on strength is almost negligible.The geometrical distributions and the aspect ratio of different fractures have different effects on the initiation position and the propagation path of the fracture,but the main reason for the tension failure is the expansion of the wing crack to the end,resulting in the penetration of the specimen.(2)The influence of rock bridge inclination on rock specimen strength and final failure mode was studied by simulating biaxial compression test.The strength of rock mass decreases first and then increases with the increase of the dip angle of the rockbridge,of which the minimum strength is 60°.When the rock bridge inclination angle? = 0 ° and 30 °,the crack of the specimen is broken through,and the failure of the rock bridge is not penetrated.When the rock bridge inclination angle ? = 60 °,the rock bridge shear failure occurs,and the wing crack together cause the specimen to destroy.When the rock bridge inclination angle ? = 90 ° and 120 °,the inside of prefabricated fracture is overlapped by the wing crack and the prefabricated fissure to form a “fisheye”-like failure area,and the wing crack is overlapped with the prefabricated crack.(3)By defining the three kinds of displacement types of tension type ?,tension type ? and pull shear type ?,it is revealed that the crack propagation of cracks is caused by the relative displacement of the particles under the tensile stress.With the increase of strain,the tension trend gradually changed from relative tension to absolute tension.And it is revealed that the root cause of macroscopic crack cracking in fractured rock specimen under uniaxial compression is the mesoscopic nature caused by tension.(4)By simulating the gradual failure process of the fissure slope,three kinds of rock bridge penetrating modes,such as tensile failure,shear failure and shear failure,are summarized.When the continuity ? ?0,the rock bridge is mainly caused by tensile damage,?(29)0,the rock bridge occurs mainly pull shear complex damage,and the larger the ? value,the greater the proportion of shear damage,its stability is also gradually Improve,indicating that the cracks face the stability of the slope has a leading role(5)By simulating the failure process of random rock bridge slope instability,it is concluded that the slope crack propagation follows the first from inside to outside,and then from outside to inside,from bottom to top.That is,the fracture starts from the internal prefabricated fissure,and then spreads to the slope table.When the prefabricated fissures are completely destroyed,the rock bridge through the damage from the slope surface to the slope gradually expand.Compared with the slab slope of single rock bridge and multi-rock bridge,the crack propagation of the random rock bridge fissure slope is cracked along the widest resistance path.The slip surface mayhave multiple and prone to occur rock block and slope separation,rolling down to the foot of the behavior.(6)Based on the mesoscopic displacement field vector,it can be seen that the displacement of the upper part of the prefabricated fissure plane is much larger than that of the lower part(the slope).The lower displacement of the upper slope of the fissure plane is much larger than the upper displacement.And the displacement at the top of the slope is minimal.The displacement vector has obvious partitioning characteristics from the foot to top of slope,which indicates that the slope instability process is carried out inward from the slope table.The main reason for the overall slipping of the slope is due to the tensile stress caused by the lower rock mass of the slope.