Double-track Tunnel Research Articles

The role of the engineer in controlling the excavation phase at the iSangoyana Rail tunnel

Abstract The iSangoyana double-track rail tunnel is an 11 -m span × 8-m-high opening 2.4 km long, driven using drill-and-blast through sandstone/siltstones and carbonaceous shale. The maximum cover of the tunnel is 173 m. Because of the nature of the rock, support was required immediately following excavation in order to stabilize the excavation and to prevent rockfalls. An unreinforced 250-mm-thick concrete lining was placed after the excavation was completed. In order to prevent short-term loads from being applied to the lining at the time of placing the lining, and in order to limit the magnitude of long-term loads on the lining, it was necessary to ensure that controlled blasting was used during the excavation; and that tensioned rockbolts of the correct spacing and length, commensurate with the encountered rock conditions, were installed to minimize rock loosening. The paper describes the techniques used by the Engineer to ensure adequate control of the excavation and initial support procedures.

Giant size slurry shield is a success in Tokyo : Watanabe, T; Yamazaki, H Tunn Tunnlg, V13, N1, Jan–Feb 1981, P13–17

The 844 M long double-track Hikawadai tunnel section of the No. 8 line of the Teito Rapid Transit Authority is being driven by a 10 M o/d shield and lined with 9.8 M o/d concrete segments. The line incorporates curves of 800 M and 1500 M radius. The shield passes under the Shakujii river bed with an overburden of 8 M and then passes beneath residential areas where the overburden is 12-18 M. The upper portion of the tunnel lies in a sand and gravel layer known as Tokyo gravel stratum. The sand layer at the crown is loose and liable to collapse. The large-scale slurry shield was chosen for the double-track tunnel excavation to overcome problems of sand instability and drainage. The success of the largest shield used in Japan is said to be due to exhaustive soil investigation, careful design and manufacture of equipment, and close slurry control.