Research On TBM Cutter-head Multi-crack Propagation Rule And Crack Arrest Scheme

As the core component of the TBM,the cutter-head is in direct contact with the face of the tunnel during the construction process,so it will withstand complex alternating loads and impact loads.With the repeated loading of the load,the surface of the cutter-head will initiate cracks and gradually expand due to fatigue Until the cutter-head fails.Based on the analysis of related research at home and abroad,this paper establishes a cutter-head crack growth model based on the Paris formula,uses XFEM to realize the crack growth simulation,and verifies the accuracy of the crack growth model from both static cracks and dynamic cracks.By analyzing the crack propagation rate and path,the propagation life of a single crack under service load is calculated,and the propagation laws of collinear double cracks and parallel double cracks are summarized.Two anti-cracking schemes of anti-cracking ribs and anti-cracking holes were proposed and the key parameters were optimized.The main research contents are as follows.(1)A crack propagation model was established according to the Paris formula,and the crack cracking and propagation process was simulated in Abaqus based on the XFEM method.The crack growth model was verified from two aspects: the stress intensity factor of static cracks and the growth rate of dynamic cracks.(2)By simulating the rock-breaking process of the cutter,the time history of the three-directional force on the cutter in service is obtained,and it is loaded on the cutter hole of the cutter-head to calculate the dangerous point on the cutter-head.The quasi-static method is used to obtain the stress time history of the dangerous point of the cutter-head,which is used as the load spectrum to calculate the crack propagation law and the propagation life of a single crack at the dangerous point.(3)For collinear double cracks,the merging law is simulated.The results show that the growth rate of the inside of the crack is slightly greater than the growth rate of the outside of the crack,and the existence of double cracks will accelerate the growth rate of the outside of the crack.For parallel double cracks,the influence of the two parameters,the horizontal distance s and the vertical distance h,on the crack propagation path is studied,and the interaction between the cracks is explained from the perspective of the stress intensity factor.(4)For crack arrest,two crack arrest schemes are proposed,namely,crack stiffened plate and crack stop holes.For the crack stiffened plate scheme,the analysis results show that the closer the stiffened plate is to the crack tip,the better the crack arrest effect;the greater the thickness of the stiffened plate,the better the crack arrest effect;the height of the stiffened plate h has the greatest impact on the crack arrest effect,and the higher the height of the stiffened plate,the better the crack arrest effect;the stiffened plate width W has the least influence on the crack arrest effect.For the crack stop hole scheme,the analysis results show that the crack stop hole is best to be drilled in the middle of the crack propagation;the depth of the crack stop hole has little influence on the crack arrest effect;the diameter of the crack stop hole has the greatest influence on the crack arrest effect.When the diameter of the crack stop hole is too large,it will weaken the structural interface and increase the average net interface stress,and the crack arrest coefficient will become a negative number,which promotes crack propagation.