Abstract:
Tunnels are practicable options to get over physical obstacles like mountains, existing roads,
trains, or infrastructure, to meet environmental or ecological requirements, or to traverse a
body of water. The road connecting Wolaita Sodo - Arba Minch near Lante village passes
between mountain and Lake barriers which needs to propose a tunnel. Stability is a big
problem if these tunnels are excavated in the jointed rock mass. For an in-depth
comprehension of the stability of these tunnels, the numerical modeling method can display
many responses, including stresses, strains, and displacements. The main aim of the study is
to predict the stress, deformation, and overall stability of the surrounding rock mass of the
proposed tunnel excavation. A 3D finite element analysis has been carried out by using MIDAS
GTS NX software. In doing this a Hoek-Brown failure criterion has been implemented for the
surrounding rock mass. A parametric study has been carried out varying the tunnel diameters
to show its effect on the stress and deformation of the proposed tunnel. From the analysis, it is
found that the principal stress for each tunnel size was, the maximum compressive (-) stress
for D=8m, D = 8.5m, D = 9m, D = 9.5m and D = 10m is 570.55 kN/m2
, 570.16 kN/m2
, 569.76
kN/m2
, 569.35 kN/m2
,568.90 kN/m2
, and the maximum tensile (+) stress for D=8m, D = 8.5m,
D = 9m, D = 9.5m and D = 10m is 168.74 kN/m2
, 148.03 kN/m2
, 147.66 kN/m2
, 147.0 kN/m2,
and 143.78 kN/m2
. The magnitude of principal stress decreases with increasing the size of the
tunnel. The deformation for different tunnel sizes was 0.39 mm, 0.41mm, 0.44 mm. 0.46 mm,
and 0.49 mm for tunnel width (D=8m, D = 8.5m, D = 9m, D = 9.5m and D = 10m) respectively.
The deformation of the tunnel increases with increasing the tunnel diameter. The stability
indicators, the floor heave ratio of all tunnel sizes is less than 0.05% and the roof sag ratio is
also less than 1.0%, The value of the wall convergence ratio is less than the maximum value
(<2%). Overall this study found that the surrounding rock mass in the study area has
satisfactory performance to provide the proposed road tunnel on a studied tunnel size range.
