نوع مقاله : یادداشت فنی
نویسندگان
1 دانشکده مهندسی معدن، پردیس دانشکده های فنی، دانشگاه تهران
2 گروه مهندسی معدن، دانشگاه کاشان
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Tunnel face support during boring operations is gaining more interest as tunneling development expands towards geo-technically less appropriate zones with heavy traffic. Good tunnel face support is a pre-requisite for successful safe boring, and evaluating optimum pressure is an important factor in the performance of the Earth Pressure Balance (EPB) machine in urban tunneling. Applying pressures lower than equilibrium results in face subsidence, while higher than equilibrium causes an up-lift in ground surface, leading in either case, to operation disruption, floor subsidence and damage to nearby buildings. Optimum pressure for face support is evaluated here using analytical and numerical methods, and parameters such as soil physical and mechanical characteristics, height of over-burden, water table level, tunnel geometry, and traffic and structural loads. As the tunnel for line 7 of the Tehran subway (Eastern-Western piece) was excavated in an urban zone, in this work, the Jancsecz analytical method was used to measure the required pressure for the tunnel face support. The tunnel was bored using a 9/164m diameter ground pressure balancing machine. The final tunnel cover was tetragonal in geometry, 35cm thick and 1.50m wide, making an outside diameter of 8.85m for the tunnel. Data obtained for this study was obtained from 13 boreholes and 5 wells excavated deliberately along the tunnel. The flow direction of underground water about the tunneling zone was found to be north-east to south-west. Considering the average water level obtained from the boreholes, only 35\% of the tunnel remains above water and 65\% is below water level. To illustrate water pressure fluctuation, this was considered in the analytical method, but ignored in the numerical one, which employed $PLAXIS^{3D}$ software. When comparing the results, a pressure difference of 20-25 kPa was noted, indicating acceptable conformance of the data.
کلیدواژهها [English]
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