Research On Meso-mechanism Of Rock Fragmentation By A Single TBM Cutter Using Particle Flow Method

With the develop of economy,the traffic problem in Qingdao City is becoming more and more serious.To developing the public transport,Qingdao need to build subway systems.Qingdao Metro Line 2 using TBM in the tunnel excavation,the excavation of the tunnel is through the weathering zone and weathered zone of the formation of granite bedrock.More often,the upper subway tunnel buried depth is granite weathering zone,and the lower is granite weathering zone.The composite strata have a large difference in the mechanical properties,which can easily lead to uneven excavation,which directly affects the quality of tunnel excavation,and even causes serious consequences such as jammed the TBM.As a core component of TBM,disc cutter on the cutter head is directly effecting with the rock,therefore,the research on the rock breaking mechanism are helpful to analyze the difference of the TBM excavation in the soft and hard rocks,and then to guide the practical engineering.Based on Qingdao Metro Line 2,the following work has been completed:1.The selection of mechanical parameters of complex rock mass is a problem which worthy to study further.Based on the rock mechanics test,the Hoek-Brown classification can convert mechanical parameters of rock into rock mass.In this paper,the parameters of rock and rock mass,which are obtained from Qingdao Metro Line 2,are using to solve the geological strength index GSI and the Hoek-Brown parameters of rock mass.By using RockLab software and the Hoek-Brown expression of rock mass,the uniaxial compressive strength and elastic modulus of rock mass are calculated;2.In the same geological conditions of mechanical conditions,the excavation of tunnel with TBM is mainly influenced by cutter speed,cutter torque,thrust,cutter hob penetration etc.Under the premise that the quality of the surrounding rock is the same,and the rotation speed of the cutter is consistent,firstly,this paper using the linear regression analysis on the penetration of hob tangential and normal thrust.Then the multivariable linear regression analysis is made on the penetration of hob tangential and normal thrust;3.Based on the PFC^3D software,the numerical analysis model of the rock breaking process of the single positive hob is established.Based on the results of the third chapter,the values of the PFC^3D parameters are calculated:and the research methods are determined by combining the results of the fourth chapter.Through the simulation of different penetration speed of hob,This paper made a further analysis:?a?the crack propagation process of rock breaking model;?b?the rock breaking features of different surrounding rock;?c?the rock breaking features by different hob force.