| According to the effect of rock-broken process by root-growth of plant,fractured rock will occur a degree of damage and fracture failure.The degree of rock damage will decide deformation,strength and stability of rocks,which often cause geological disasters including collapse,landslide and tunnel roof,etc.The paper mainly studies the fractured rock’s influence factors and damage mechanism by rock-broken process by root-growth of plant,and numerically simulated the three typical rock masses in Chongqing.The main researches achieved are as follows:1)There are many influence factors of root system to the failure of rock,which could summarized in three aspects:the properties of rock mass and root system,and the surrounding environment.The increasing of root expansion force and decreasing of rock fracture volume will cause rock failure,and the different location of root in rock will cause varying degrees of damage.2)The damage mechanism by rock-broken process by root-growth of plant including two stages:the passivation stage and the unstable propagation stage of crack tip.The former one can be divided into two processes:elastic deformation and plastic deformation.The primary cause of damage mechanism is the unstable failure of crack tip.The paper proposed the judgements of elastic deformation and plastic deformation,and provided the calculations about the expansion of root and extended energy.The root expansion is related to the characters of rock,the penetration depth and the size of plant roots.According to practical calculation example,the fructure toughness of rock mass is 1.22MPa·m?,which decided the threshold of expansion by root is 0.96 MPa.While the actual value is 0.87 MPa,which means the rock fracture did not occur at the stage.3)According to the numerical simulation of three different typical lithologic in Chongqing area,the rock crack produces two stress concentration areas:the crack tip and the area close to surface,which form the plastic deformation zone.The displacement distributions of crack are the same:the displacement close to surface is larger than it at the crack tip.Besides,the change rate of displacement increased which close to the surface in the 0.05 m range,and the closer to the surface,the wider the impact range of the displacement.According to the same acts of root,the displacement of mudstone is maximum,while the limestone is minimum. |
