The equivalent strength parameters of fractured rock masses are prerequisite for stability analysis of geotechnical engineering projects constructed in fractured rock masses which are encountered frequently in western china.Based on generated mesh of fractured rock masses,combined with statistic damage constitutive model of intact rock and damage model of structural plane,progressive failure of fractured rock masses is studied using finite element method(FEM) .Furthermore,Scale effect and anisotropy of compressive strength of fractured rock masses are studied.Study results show that the strength decreases and tend towards stability rapidly from intact rock to fractured rock masses,and the anisotropy of strength of fractured rock masses is not significant.At last,based on numerical simulation conducted on 10 m scale rock masses under different confining pressures,the equivalent strength parameters of fractured rock masses are gained and the results are compared with Hoek-Brown criteria.The method developed is helpful for determination of strength parameters of fractured rock masses.
CHEN WeiZhong 1,2,YANG JianPing 1,TAN XianJun 1 &YU HongDan 1 1 State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan 430071,China
The long-term stability of large-span soft rock tunnel is influenced greatly by the creep effect of surrounding rock.The development of a new type of foam concrete which has the property of high compressibility and low ductility was introduced.And it was made as filling material of reserved deformation layer between the first lining and the second lining used in large-span soft rock tunnel.The effect of the new type of foam concrete was simulated as filling material of reserved deformation layer using numerical simulation.Through the comparison with the common large-span soft rock tunnel,the vault settlement and surrounding convergence are reduced by about 61% and 45%,respectively,after creep of 100 a.And in the second lining,the plastic zone reduces apparently and the maximum equivalent plastic strain decreases relatively.So,it can be found that the application of the new type of foam concrete as the filling material of reserved deformation layer can relieve the excessive force in second lining induced by rock creep,reduce its deformation and improve the stability of tunnel.
