Experimental Study On The Interaction Mechanism Between TBM Disc Cutter And Rock

The disc cutter is the core tool of a tunnel boring machine(TBM)for hard-rock tunneling,which locates at the front end of the TBM and is directly in contact with rocks.Currently,the rock cutting efficiency is low and cutter wear is severe when the TBM works in a hard rock stratum,which affects the construction speed and cost.These problems are still the bottlenecks in shield tunneling.Considering that the contact and relative motion between the cutter and rock are the direct causes of rock breaking,which,on the other hand,is the root cause leading to the cutter wear,the cutter-rock interact mechanism holds a key to solve hard-rock TBM tunneling problems,and the study of the cutter-rock interaction mechanism and characteristics is a critical step towards the optimal tooling design that best matches the geological conditions of tunneling.This research utilizes and modifies a multi-functional vibration contact apparatus to study the rock-breaking behaviors of a disc cutter at a reduced scale and the influences of blade parameters of the cutters and to explore the effects of simulated construction conditions on the results of rock breaking,to provide a useful reference to cutter design and selection,as well as construction parameter adjustment.It mainly includes:(1)Modification of the multi-functional vibration contact apparatus,so that is can mimics a disc-cutting rock breaking environment at a reduced scale.The rock specimens suitable for the rock breaking tests were designed and machined by using natural rocks.(2)The effects of cutting blade parameters and shapes on rock-breaking efficiency are studied on the modified experimental apparatus,including blade edge angle,of a disc cutter,blade width,and blade head shape.The experimental results show that in a same indentation depth,increasing the edge angle of the disc cutter can increase the contact area between the disc cutter and the rock,resulting in increased breaking force of the cutter.However,such an edge angle increase does not enhance the lateral crack propagation in the rock,nor the synchronized actions of grouped cutter blades.Increasing the blade width of the cutter l linearly increases the breaking force of the cutter,but much of the work done by the increased rock breaking force is used to promote the formation of the crushed zoom just below the cutter,which raises ratio of rock powder in the crashed zoom,but not the rock-breaking efficiency.The rock-breaking results of round-head cutter and flat-head blade cutters are also compared,finding that the total volumes of rock breaking of the two kinds of cutters are largely the same,but the round-head cutter requires a smaller rock-breaking force,and it makes larger rock slag fragmentations,showing a better rock-breaking efficiency.(3)The influences of construction parameters on the rock-breaking effectiveness of cutters are also explored using the modified experimental apparatus,which include the blade cutting speed and blade separation distance.The experimental results reveal that in a same indentation depth,the normal cutting force of the cutter decreases with the increase in the cutting speed of the blade,but the amplitude of the normal force reduction becomes smaller with further normal force increase.However,this causes the ratio of rock powder over the total fractured mass to increase.Therefore,increasing cutting speed reduces the rock breaking efficiency of the cutter.The change in the distance between adjacent cutters has a great influence on the rock breaking efficiency of the cutter.The increase in this distance makes the rock-breaking efficiency of the cutter first increase and then decrease.The variation of the cutter spacing mainly affects the yield of large-size rock blocks,but it has little effect on the yield of small-size rock blocks.