| In recent years,with the rapid development of China’s transportation,water conservancy and other fields of infrastructure,Shield method has been widely used in tunnel construction.However,conventional shield machine is mostly suitable for rock with compressive strength R≤80MPa,and drilling and blasting method is mostly used for super high strength hard rock with compressive strength R>80MPa Based on the engineering background of shield tunneling in ultra-high strength hard rock section of Fuzhou Metro line 5[agriculture and Forestry University]Station to[Hongtang]station,the comprehensive research methods such as laboratory measurement,numerical simulation,theoretical analysis and field measurement are adopted to carry out the research on rock breaking mechanism of hob,optimization of tunneling parameters and construction technology of shield machine crossing ultra-high hard rock stratum Shield construction under similar geological conditions has important theoretical significance and application value.The main research work is as follows:(1)Based on the characteristics of soft upper and hard lower strata in the engineering construction section,as well as hard rock～ultra-high strength slightly weathered granite stratum,the paper compares and analyzes the open cut method,mining method,shield method,mining method+shield method,ground deep hole blasting pretreatment+shield method and other hard rock stratum excavation technical schemes.According to the design parameters of CREG No.552 shield machine,the paper analyzes the cutter head opening mode,cutter head layout and layout of shield machine Material,auxiliary system and other aspects of its adaptability are analyzed,and the corresponding technical transformation scheme is put forward.The research shows that the reformed 552 shield machine can meet the construction requirements of full face ultra-high strength rock.(2)Study on the rock breaking mechanism of the ultra-high hard rock formation by the hob.A three-dimensional discrete element model of rock breaking with a hob was established,and the meso parameters of the discrete element were calibrated according to the results of rock mechanics tests.Numerical experiments on rock breaking with positive hobs,center hobs and edge hobs were carried out to determine the force changes of different hobs and the law of rock failure on the face,revealing the interaction mechanism of multiple hobs.The obtained rock breaking parameters of the hob are in good agreement with the theoretical prediction formula and field measured data,verifying the accuracy of the numerical simulation of the hob breaking rock and the feasibility of the construction plan of the shield machine through the ultra-high hard rock formation.(3)According to the numerical simulation results of PFC tunneling parameters,combined with the massive data of tunneling parameters collected in the field shield construction,and using the statistical theory,the paper puts forward the technical parameters of full face rock stratum shield construction,which are suitable for the characteristics of hard rock～ultra-high strength slightly weathered granite statum:cutter head speed 1.0～1.5r/min penetration 3～10mm/R,propulsion speed 5～20mm/min,total thrust 13000～25000kN,cutter head torsion The moment is 1800～2500kN.m(4)Based on the field test,the influence of jack cylinder partition pressure and total thrust,and cutter opening and changing on tunneling parameters is systematically studied,and the relationship among penetration,propulsion speed,total thrust,cutter head torque,jack cylinder partition pressure,and cutter opening and changing is obtained.The problems of excessive tool wear,slag stagnation segment dislocation,machine jamming and shield tunneling in shield tunneling through extremely hard rock stratum are analyzed The corresponding solutions are put forward,which provide the theoretical basis and engineering basis for similar projects in the future.Figure 59 Table 14 Reference 76... |
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