Abstract
The present research exposes the investigation on three-dimensional modeling of the single and twin metro tunnels for the case of the Tehran metro line. At first, simulation implemented on the comparison of the ground movements in the single and twin tunnels. Then the simulation has been performed on the influence of effective parameters of EPB-TBM on the surface settlements throughout excavation. The overcutting, shield conicity, grouting, and the final lining system modeled and the influence of face supporting pressure, grout injection pressure, as well as the clear distance of the tunnels, has been analyzed. The initial results showed a valid ground settlement behavior. The maximum settlements occurred at the end of the shield tail and it was higher in the single tunnel. The face supporting pressure had more effect on the surface settlement in comparison to the grout injection pressure. By increasing the face pressure in the single tunnel, the place of maximum settlement moved back while the grout pressure is insignificant for decreasing the settlements. Furthermore, the influence of the clear distance in the twin tunnels led to zero after the length of 30 m. Accordingly, for more distances, the tunnels must be examined independently and as two different single tunnels.
Highlights
The rapid increase rate of the population in cities and urban areas has developed the transportation methods such as subways around the world [1,2,3,4,5]
All settlement values were less than 2 cm in single tunnels and 1 cm in twin tunnels which had a good correlation with the field monitoring
The study performed an investigation on the influence of the effective parameters of the Earth Pressure Balanced (EPB)-tunnel boring machine (TBM)
Summary
The rapid increase rate of the population in cities and urban areas has developed the transportation methods such as subways around the world [1,2,3,4,5]. Researchers have presented many investigations in the effect of tunneling on the soil movement by 2D and 3D numerical and analytical methods to simulate the tunnel excavation procedure and TBM. The 3D finite element investigation on the effect of EPB-TBM parameters on the ground settlements caused by twin tunnel excavation of Shiraz metro has been done by Afifipour et al. The results showed complicated relation between interaction of twin tunnels and near structures, and the face pressure of TBM has a more significant effect on the soil movements around the excavation area rather than the grout pressure and jack force. A lot of studies have investigated the modeling of the tunnel excavating by TBM, but 3D simulation on the comparison of the soil movements caused by single and twin tunnels is inevitable before implementation. The cost analysis on the tunnels shows no difference between single and twin tunnel, some other parameters such as safety, ventilation, and level of service, should be taken to account for better serviceability
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