| Abstract: |
Numerical study of seepage flow around drainage-type tunnel wasconducted using Z-Soil Program based on the Finite Element Method. Thegroundwater flows under steady-state flow conditions and seepage force acts onthe tunnel lining. It acts as a volume force and thus increases the pressure on thelining. Circular tunnels in homogeneous isotropic and anisotropic soils withanisotropy ratio, KxlKy= 2, 3, 4 and 5, were studied. The effect of relativegroundwater level, Hlr, relative depth of the impermeable layer, D/r, relativedepth of tunnel under ground surface, Clr, and soil anisotropy ratio, KxlKy, onhydraulic head distribution and seepage characteristics were presented excludingthe effect of earth pressure. Also the effect of relative impermeable layer depth,D/r, was studied for two and three adjacent circular tunnels in homogeneousisotropic soil. A comparison was made between the average seepage pressure,Pay, in case of one, two and three adjacent circular tunnels in homogeneousisotropic soil. The results were presented in dimensionless curves. These curvescould be a simple estimation for the seepage pressure acting on the tunnel inhomogeneous isotropic and anisotropic soils. It was found that, in designing thedrainage-type tunnels, it could be dangerous to neglect the seepage force actingon the tunnel lining. The change in the relative impermeable layer depth, D/r,had a significant effect on hydraulic head distribution. But the change in therelative ground surface height, Clr, had a very slight effect on hydraulic headdistribution. The seepage pressure acting on the tunnel is proportional to therelative groundwater level, Hlr. The increase of the relative impermeable layerdepth, D/r, or anisotropy ratio, KJKy, caused an increase in average seepagepressure, Pay, and seepage pressure ratio, Pavlpc. But the increase of the adjacenttunnels number caused a decrease in average seepage pressure, Pay, and seepagepressure ratio, Pavlpc.
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