Numerical Analysis on Rock Breaking by Disc Cutters with Different Joint Characteristics

Abstract

Background:With the development of tunnel engineering, shield tunneling machines (shield machines, for short) have been widely used. Tunnel projects encountered complex geological conditions. Objective:To study the effects of joint characteristics on rock fragment by disc cutters of tunnel boring machine. Method:Firstly, the 3D (three-dimensional) rock breaking process of disc cutters (cutters, for short) was simplified as a 2D (two-dimensional) problem, and the rock-breaking model with different joint characteristics by disc cutters was established by using the particle discrete element method (PFC2D). By carrying out statistical analysis on the value of cutting forces, number of cracks, rock breaking area, specific energy, the length of main cracks and changing law of their crack angles in the process of breaking rock, the effects of joint characteristics on breaking rock by disc cutters are studied. Results:The relationship between the joint characteristics and the cutting performance of cutters is obtained. Conclusion:The study shows that the weaker strength of jointed rock mass lead to the greater influence of joint dip angle on cracks and rock breaking efficiency. The stronger strength of jointed rock mass leads to the bigger main crack depth, as well as, higher specific energy. Generally, the existence of joints helps to improve the speed of excavation. However, the speed of the cutter is decreased with some certain joint characteristics. When the strength of the joint surface is 5kPa and α=135º, the specific energy reaches its minimum.