| Compared with the traditional drilling and blasting method,the full-face hard rock tunnel boring machine(hereinafter referred to as TBM)has the advantages of safe operation and high degree of mechanization.It is widely used in railway tunnels,urban underground engineering and other engineering projects.In extreme geological conditions,the failure problem of the disc hob(hereinafter referred to as the hob)located on the cutter head frequently occurs.This undoubtedly greatly increases the TBM construction time and tool wear costs.With the promotion and application of TBM under extreme geological conditions such as "three highs"(high strength,high confining pressure,and high quartz),the problem of low comprehensive cutting performance of the hob will become more prominent.In view of the above performance bottleneck of the traditional TBM rock breaking mode,it is urgent to find a new type of auxiliary TBM hob rock breaking technology.Considering that laser technology has the advantages of high energy density and can transmit energy without direct contact,the research group has carried out simulation and experimental research on the feasibility of laser pre-drilling auxiliary hob for rock breaking.On this basis,this paper further proposes a new method of using moving laser continuous grooving to assist the hob in efficient rock breaking,and uses a combination of simulation simulation and orthogonal experiments to explore the auxiliary rock breaking mode.Significant factors affecting the rock breaking mechanism of the hob.The main work and research conclusions of this paper are as follows:(1)On the basis of in-depth understanding of the rock-breaking mechanism of TBM hob and laser rock-breaking mechanism,and considering the existing highefficiency laser rock-breaking technology and the feasibility of laser-assisted hob rockbreaking,a new rock-breaking method that couples mobile laser to TBM cutter head is proposed.new ideas.(2)Based on the theory of thermodynamics,in the ANSYS environment,by using the life-death element method to simulate the macroscopic effect of laser rock breaking,a three-dimensional finite element model of continuous cutting granite by moving laser irradiation was established,and the continuous laser grooving at different powers and moving speeds was simulated.The results show that the morphology size of the rock groove obtained by the laser increases with the increase of the laser power,and decreases with the increase of the laser moving speed.In addition,laser grooving experiments under similar conditions were carried out,and the high-precision laser cutting topography was obtained with the help of a three-dimensional profile scanner,and the groove topography was quantitatively analyzed.By comparing and analyzing the laser groove morphology,it can be seen that the variation law of the groove width and groove depth obtained by the simulation is consistent with the experiment,and the cross-sectional morphology of the groove is "inverted cone".It can be seen that the prediction accuracy of the cutting profile of the mobile laser rock breaking simulation model is relatively high.(3)Under the LS-DYNA simulation platform,the elastic-plastic HJC constitutive model is selected as the granite model,and the pre-grooving zone with hob intrusion is established by reconstructing the laser grooving profile obtained by simulation prediction into the complete rock finite element model.The finite element model of the rock to approximate the rock breaking process of the mobile laser-assisted TBM disc hob.The variation law of the hob intrusion load,the amount of rock breaking,and the energy consumption of the breaking ratio with the intrusion depth was further simulated and studied under different kerf distances.In contrast,the vertical force is reduced by a maximum of 17%.Then,the rock-invading process of the auxiliary hob under different laser grooving speeds was simulated.Combined with the simulation of the control group(without laser pre-grooving),it can be seen that when the groove distance is 3mm and the moving speed is 2mm/s,compared with the control group Hob intrusion,vertical force reduced by up to 16%.Comprehensive analysis of vertical force,rock breaking amount,intrusion difficulty coefficient and specific energy consumption,laser groove can effectively reduce the rock breaking load of the hob,which is beneficial to promote the rock breaking of the hob.In addition,the hob intrusion test under similar conditions was carried out to verify some simulation conclusions of intrusion.(4)In order to further explore the significant factors affecting the rock-breaking mechanism of the laser-assisted hob,the laser power,laser moving rate,blade width,kerf distance and blade inclination angle were selected as the influencing factors.The specific energy consumption is the performance evaluation index.Then,five factors and three levels of orthogonal test analysis were carried out,and the optimal combination was obtained through the range analysis and comprehensive score.Two influencing factors are the edge width and the sipe pitch.The mobile laser-assisted TBM hob rock-breaking method proposed in this paper improves the hob’s rock-breaking efficiency to a certain extent,and provides a certain engineering reference value for breaking through the performance bottleneck of the traditional TBM rock-breaking mode. |
