Discrete Element Simulation of the Rock-breaking Characteristics of a One-way Non-through Jointed Rock Mass Using Hob
Compared with penetrating joints,the existence of rock bridges in non-penetrating jointed rock masses complicates their failure process.To explore their influence on rock breaking,a discrete element model of rock breaking using a disc cutter in a unidirectional non-penetrating jointed rock mass is established using PFC2D.The influence of rock bridge length and dip angle on the rock-breaking mode,normal force,crack number,and specific energy consumption is examined,and the rock-breaking characteristics of the disc cutter in the non-penetrating jointed rock mass are revealed.The results indicate that the rock mass is dominated by tensile failure,and the joint exerts an evident"guiding effect"on crack growth.Furthermore,the crack growth direction always tends to the nearest joint.The vertical stress level initially increases and then decreases with an increase in the joint dip angle and reaches a maximum value at a dip angle of 45°.The shape of the stress zone is affected by the joint position,but both are consistent.The mean and peak values of the normal force of the intact rock mass are greater than those of the jointed rock mass,and the jointed rock exerts a clear promoting effect on the rock-breaking process.The specific energy consumption at joint dip angles of 0°,60°,and 90° is significantly lower than that observed under other joint combinations.The energy consumption decreases at a joint dip angle of 60°,and the minimum value is obtained when the length of the rock bridge is 25 mm.At 0° and 90°,the energy consumption decreases initially and then increases,and the minimum value is obtained when the length of the rock bridge is 15 mm.
tunnelhobnumerical calculationrockmass containing discontinuous jointsrock bridgerock breakingspecific energy consumption
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