| At present,China's infrastructure construction and the rapid development of urban underground facilities,the intensity and scale of underground infrastructure construction continues to increase,and full-face tunnel boring machine(TBM)is an important construction equipment for underground construction,TBM is safe,efficient,economical and so on,and thus be widely used.TBM will encounter complex rock formation,such as mixed rock strata.Different engineering geological conditions and construction parameters on the impact of cutter rock is not the same,and a direct impact on construction progress and cost.Therefore,based on the discrete element software,this paper studies the rock breaking efficiency and the optimal cutter spacing of TBM in mixed rock strata.The main contents are as follows:Firstly,the samples were prepared by using cement,sand,gravel and gypsum as materials,the uniaxial compression strength,modulus of elasticity,poisson's ratio and other macroscopic parameters are obtained by uniaxial compression test,and then based on PFC3D software through the "trial and error method" for mesoscopic parameters of the calibration.At the same time using the existing cutter rock test results to verify the program.Secondly,using PFC3D to simulate the influence of tunnel inclination on the efficiency of tunneling in parallel and vertical direction of TBM tunneling tunnel,and verify the correctness of the conclusion through theoretical analysis.The results show that the inclination angle of the rock strata does not affect the efficiency of the rock formation when the tunnel axis and the rock formation are parallel.The inclination of the same rock slope along the tunnel axis and the vertical direction does not affect the rock breaking efficiency,the effect of stratification on rock breaking is small.Thirdly,the effect of different cutting ratio on the rock breaking force is simulated by using PFC3D to study the effect of different cutting ratio and hard rock on the breaking rock force,and the optimal cutter spacing is discussed based on the specific energy of rock breaking and the crack propagation mechanism.The main conclusion:the average normal force,the average rolling force with the penetration,rock strength,s/p(s:cutter spacing,p:penetration)increased.By analyzing the relationship between the optimal tool spacing and penetration,when the penetration is 6mm,the optimum cutter spacing is about 60mm;when the penetration is 8mm,the optimum cutter spacing is about 60mm;when the penetration is 10min,the optimum cutter spacing is about 75mm;when the penetration is 12mm,the optimum cutter spacing is about 90mm.The crack growth mechanism shows that the rock strength and s/p have an effect on the crack propagation,s/p is too small,the double cutters between the excessive expansion of cracks,rock breaking efficiency is low;s/p is too large,the formation of rock between the two hobs,can not achieve the effect of broken rock,rock breaking efficiency is low.The above results provide a reference for the mixed rock strata cutter design TBM. |
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