| With the rapid development of economy in China,the proportion of infrastructure construction has gradually increased,tunnel construction is an important part of infrastructure construction in our country.TBM due to fast,efficient,safe and economical construction methods,as the main tunnel boring equipment,is widely used in urban subway,municipal pipeline,tunnel traffic and other engineering fields.Disc cutter is the key component installed on the TBM cutter head,in the process of rock breaking,the load of the disc cutter and the arrangement of the cutter spacing on the cutter head directly affect the rock breaking efficiency of the disc cutter,furtherly the construction progress and cost of tunnel excavation.Therefore,based on the mechanism of rock breaking by disc cutter,the finite element simulation and experimental methods were used,the rock breaking process of TBM disc cutter was studied deeply,which has great significance to improve the tunneling efficiency of TBM.The main research work are as follows:(1)The structural type of disc cutter and mechanical properties of rock were introduced.The mechanism of rock breaking by disc cutter was analyzed theoretically,and the force prediction model of disc cutter was summarized,which provided theoretical basis for further research.(2)The influence degree of driving parameters on the force of disc cutter was mainly studied.The finite element simulation of double disc cutter rock breaking was carried out by ABAQUS software.The rock crushing process and stress variation law of broken zone under double disc cutter were analyzed.Under the double disc cutter cooperating rock breaking condition,the extending trend of stress in rock fracture zone was longitudinal and transverse extension,the crushing area was mainly concentrated in the intersection zone of transverse stress expansion;The orthogonal test was designed according to different driving parameters.The influence degree and significance of penetration degree,cutter spacing and rolling speed on the force of disc cutter were analyzed by means of range analysis and variance analysis,the results showed that the penetration degree had the greatest influence on the force of disc cutter,and the influence was remarkable.(3)The effect of cutter spacing on the rock breaking efficiency of disc cutter was studied emphatically.The rock breaking model of disc cutter with different cutter spacing was established by ABAQUS software.The effect of cutter spacing on rock crushing surface morphology and rock fragmentation were simulated and analyzed,and a method for calculating rock crushing quantity during simulation was proposed.The analysis results showed that when the cutter spacing changed in 66?90 range,there were four forms of rock fragmentation including over fragmentation,complete fragmentation,incomplete fragmentation and formation of rock ridges.When the cutter spacing was 78mm,the rock surface was broken completely,the rock breaking amount was the largest,the specific energy was minimum,and the rock breaking efficiency was the highest.Therefore the optimum knife spacing was 78mm.(4)The structure,composition,porosity and crack of granite,marble,limestone,gneiss and sandstone were detected by scanning electron microscope and three-dimensional imaging CT,the fracture mechanism of rock was analyzed from the microscopic point of view.(5)The single factor experimental study on rock penetration,cutter spacing and rolling speed was carried out by using the rock breaking and wear test platform of disc cutter.The influence of different factors on the force of the disc cutter,the broken surface of rock,the amount of rock crushing and the length of the rock waste in the rock breaking process were analyzed emphatically,the optimum cutter spacing of marble rolling under this experiment was determined.The fracture surface morphology of five kinds of rocks were also compared horizontally,and considering the structural characteristics of rocks,the influence of internal porosity on rock fragmentation was analyzed.The above research results lay a solid foundation for furtherly improving the rock breaking performance of the disc cutter,optimizing the cutter spacing of disc cutter,and improving the rock breaking efficiency of TBM. |
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