Study On The Characteristics Of Seepage Field In Fractured Rock Mass Of Tunnel

This paper studies the seepage of fractured rock mass tunnel in high hydraulic pressure and water-enriched region through the method of numerical analysis and builds 3 dimensional discrete element model in the light of the characteristics of fractured rock mass tunnel and the features of 3 dimensional distinct element code.First, the relation between the diverse occurrence of joint and the equivalent permeability coefficient of fractured rock mass is researched. O n the basis of joint being supposed to be smooth and parallel, corresponding numerical models are built then being operated. Results indicate that the equivalent permeability coe fficient of fractured rock mass calculated by 3DEC and by the formula of coefficient tensor of permeability is equal. Therefore, the occurrence of joint can be replaced by coefficient tensor of permeability when the impact on seepage field made by the diverse occurrence of joint is researched, which simplifies numerical models and improves the operation efficiency.On this basis, numerical models of seepage field of main tunnel construction process(excavation, shotcrete and lining) are built. The seepage field of main working condition is simulated by numerical models and the changing characteristics of seepage field are analyzed.At last, the impact on the seepage field of fractured rock mass tunnel, made by the aperture of joint, the thickness of grouting circle, the permeability coefficient of grouting circle and the permeability coefficient of shotcrete, is analyzed by making use of the numerical model of fractured rock mass tunnel that have been constructed shotcrete. The results show that the aperture of joint has a little impact on the seepage field when it varies in certain range(0.2~1.8 mm), that the thickness and permeability coefficient of grouting circle are critical factors to the seepage field and have a remarkable impact on the hydraulic pressure behind shotcrete and the discharge rate of tunnel when it varies in certain range(the thickness of grouting circle is 0~8m; and permeability coefficient of grouting circle is 0~2.0×10-7 m/s), however, beyond the certain range, the impact die down, that the permeability coefficient of shotcrete also has an important impact on the seepage field and has the same impact on the hydraulic pressure behind shotcrete and the discharge rate of tunnel with the permeability coefficient of grouting circle. When it varies in certain range(0~4.0×10-8 m/s), the impact is remarkable and when it is greater than 4.0×10-8 m/s, the impact become weakening.