❓ A parliamentary question regarding the proposed twin bored tunnels for a Perth CBD rail project, covering location, cost comparison with single tunnels, safety implications, and potential delays. The Minister confirms twin tunnels were always planned, details their location, and highlights their safety and cost advantages.
AnsweredQoN 2478Legislative Assembly
QuestionView source ↗
(b) where will these be located; (c) what is the cost difference between single and twin tunnels; (d) does the construction of twin rather than single tunnels have any safety implications for either property or human life; (e) if so, will the Minister outline these safety implications; (f) will this change in design cause delays to the project’s completion; and (g) if so, how long will this delay be?
(c) what is the cost difference between single and twin tunnels; (d) does the construction of twin rather than single tunnels have any safety implications for either property or human life; (e) if so, will the Minister outline these safety implications; (f) will this change in design cause delays to the project’s completion; and (g) if so, how long will this delay be?
(d) does the construction of twin rather than single tunnels have any safety implications for either property or human life; (e) if so, will the Minister outline these safety implications; (f) will this change in design cause delays to the project’s completion; and (g) if so, how long will this delay be?
(e) if so, will the Minister outline these safety implications; (f) will this change in design cause delays to the project’s completion; and (g) if so, how long will this delay be?
(f) will this change in design cause delays to the project’s completion; and (g) if so, how long will this delay be?
(g) if so, how long will this delay be?
(a) Twin bored tunnels have always been proposed. (b) The twin bored tunnels commence at the northern end of Esplanade Station at the intersection of William Street and Mounts Bay Road then head north beneath William Street to the new underground platforms south of Wellington Street. The twin tunnels continue from the northern end of these platforms, curving to the west to enter a cut-and-cover structure in the rail reserve east of Lake Street. (c) The optimum design solution depends on project conditions. Single tunnels can be cost effective where ground conditions, cover to the surface, proximity to structures, length of drive and route geometry are favourable. However, for railway systems, single bored tunnels give rise to increased costs due to the large diameter required to accommodate twin tracks, resulting in increased tunnel area (usually more than double) relative to a twin track solution. Risk associated with shallow cover and tight geometry can also be factors. International experience shows that twin tunnels are the most common solution used for metro rail projects. (d) Yes; twin tunnels are significantly better. (e) Compared to a large diameter single tunnel, the smaller diameter of the twin tunnels results in more cover above the tunnels, reducing risk of settlement and hence building damage during construction. Control at the excavation face also increases as tunnel diameter reduces. In respect of the operating railway, independent tunnels facilitate smoke control (ie effects of a fire event on one line can be constrained to one tunnel), thereby offering safety advantages. (f) Not applicable; there is no design change. (g) Not applicable.
(b) The twin bored tunnels commence at the northern end of Esplanade Station at the intersection of William Street and Mounts Bay Road then head north beneath William Street to the new underground platforms south of Wellington Street. The twin tunnels continue from the northern end of these platforms, curving to the west to enter a cut-and-cover structure in the rail reserve east of Lake Street. (c) The optimum design solution depends on project conditions. Single tunnels can be cost effective where ground conditions, cover to the surface, proximity to structures, length of drive and route geometry are favourable. However, for railway systems, single bored tunnels give rise to increased costs due to the large diameter required to accommodate twin tracks, resulting in increased tunnel area (usually more than double) relative to a twin track solution. Risk associated with shallow cover and tight geometry can also be factors. International experience shows that twin tunnels are the most common solution used for metro rail projects. (d) Yes; twin tunnels are significantly better. (e) Compared to a large diameter single tunnel, the smaller diameter of the twin tunnels results in more cover above the tunnels, reducing risk of settlement and hence building damage during construction. Control at the excavation face also increases as tunnel diameter reduces. In respect of the operating railway, independent tunnels facilitate smoke control (ie effects of a fire event on one line can be constrained to one tunnel), thereby offering safety advantages. (f) Not applicable; there is no design change. (g) Not applicable.
(c) The optimum design solution depends on project conditions. Single tunnels can be cost effective where ground conditions, cover to the surface, proximity to structures, length of drive and route geometry are favourable. However, for railway systems, single bored tunnels give rise to increased costs due to the large diameter required to accommodate twin tracks, resulting in increased tunnel area (usually more than double) relative to a twin track solution. Risk associated with shallow cover and tight geometry can also be factors. International experience shows that twin tunnels are the most common solution used for metro rail projects. (d) Yes; twin tunnels are significantly better. (e) Compared to a large diameter single tunnel, the smaller diameter of the twin tunnels results in more cover above the tunnels, reducing risk of settlement and hence building damage during construction. Control at the excavation face also increases as tunnel diameter reduces. In respect of the operating railway, independent tunnels facilitate smoke control (ie effects of a fire event on one line can be constrained to one tunnel), thereby offering safety advantages. (f) Not applicable; there is no design change. (g) Not applicable.
(d) Yes; twin tunnels are significantly better. (e) Compared to a large diameter single tunnel, the smaller diameter of the twin tunnels results in more cover above the tunnels, reducing risk of settlement and hence building damage during construction. Control at the excavation face also increases as tunnel diameter reduces. In respect of the operating railway, independent tunnels facilitate smoke control (ie effects of a fire event on one line can be constrained to one tunnel), thereby offering safety advantages. (f) Not applicable; there is no design change. (g) Not applicable.
(e) Compared to a large diameter single tunnel, the smaller diameter of the twin tunnels results in more cover above the tunnels, reducing risk of settlement and hence building damage during construction. Control at the excavation face also increases as tunnel diameter reduces. In respect of the operating railway, independent tunnels facilitate smoke control (ie effects of a fire event on one line can be constrained to one tunnel), thereby offering safety advantages. (f) Not applicable; there is no design change. (g) Not applicable.
(f) Not applicable; there is no design change. (g) Not applicable.
(g) Not applicable.
(c) what is the cost difference between single and twin tunnels; (d) does the construction of twin rather than single tunnels have any safety implications for either property or human life; (e) if so, will the Minister outline these safety implications; (f) will this change in design cause delays to the project’s completion; and (g) if so, how long will this delay be?
(d) does the construction of twin rather than single tunnels have any safety implications for either property or human life; (e) if so, will the Minister outline these safety implications; (f) will this change in design cause delays to the project’s completion; and (g) if so, how long will this delay be?
(e) if so, will the Minister outline these safety implications; (f) will this change in design cause delays to the project’s completion; and (g) if so, how long will this delay be?
(f) will this change in design cause delays to the project’s completion; and (g) if so, how long will this delay be?
(g) if so, how long will this delay be?
(a) Twin bored tunnels have always been proposed. (b) The twin bored tunnels commence at the northern end of Esplanade Station at the intersection of William Street and Mounts Bay Road then head north beneath William Street to the new underground platforms south of Wellington Street. The twin tunnels continue from the northern end of these platforms, curving to the west to enter a cut-and-cover structure in the rail reserve east of Lake Street. (c) The optimum design solution depends on project conditions. Single tunnels can be cost effective where ground conditions, cover to the surface, proximity to structures, length of drive and route geometry are favourable. However, for railway systems, single bored tunnels give rise to increased costs due to the large diameter required to accommodate twin tracks, resulting in increased tunnel area (usually more than double) relative to a twin track solution. Risk associated with shallow cover and tight geometry can also be factors. International experience shows that twin tunnels are the most common solution used for metro rail projects. (d) Yes; twin tunnels are significantly better. (e) Compared to a large diameter single tunnel, the smaller diameter of the twin tunnels results in more cover above the tunnels, reducing risk of settlement and hence building damage during construction. Control at the excavation face also increases as tunnel diameter reduces. In respect of the operating railway, independent tunnels facilitate smoke control (ie effects of a fire event on one line can be constrained to one tunnel), thereby offering safety advantages. (f) Not applicable; there is no design change. (g) Not applicable.
(b) The twin bored tunnels commence at the northern end of Esplanade Station at the intersection of William Street and Mounts Bay Road then head north beneath William Street to the new underground platforms south of Wellington Street. The twin tunnels continue from the northern end of these platforms, curving to the west to enter a cut-and-cover structure in the rail reserve east of Lake Street. (c) The optimum design solution depends on project conditions. Single tunnels can be cost effective where ground conditions, cover to the surface, proximity to structures, length of drive and route geometry are favourable. However, for railway systems, single bored tunnels give rise to increased costs due to the large diameter required to accommodate twin tracks, resulting in increased tunnel area (usually more than double) relative to a twin track solution. Risk associated with shallow cover and tight geometry can also be factors. International experience shows that twin tunnels are the most common solution used for metro rail projects. (d) Yes; twin tunnels are significantly better. (e) Compared to a large diameter single tunnel, the smaller diameter of the twin tunnels results in more cover above the tunnels, reducing risk of settlement and hence building damage during construction. Control at the excavation face also increases as tunnel diameter reduces. In respect of the operating railway, independent tunnels facilitate smoke control (ie effects of a fire event on one line can be constrained to one tunnel), thereby offering safety advantages. (f) Not applicable; there is no design change. (g) Not applicable.
(c) The optimum design solution depends on project conditions. Single tunnels can be cost effective where ground conditions, cover to the surface, proximity to structures, length of drive and route geometry are favourable. However, for railway systems, single bored tunnels give rise to increased costs due to the large diameter required to accommodate twin tracks, resulting in increased tunnel area (usually more than double) relative to a twin track solution. Risk associated with shallow cover and tight geometry can also be factors. International experience shows that twin tunnels are the most common solution used for metro rail projects. (d) Yes; twin tunnels are significantly better. (e) Compared to a large diameter single tunnel, the smaller diameter of the twin tunnels results in more cover above the tunnels, reducing risk of settlement and hence building damage during construction. Control at the excavation face also increases as tunnel diameter reduces. In respect of the operating railway, independent tunnels facilitate smoke control (ie effects of a fire event on one line can be constrained to one tunnel), thereby offering safety advantages. (f) Not applicable; there is no design change. (g) Not applicable.
(d) Yes; twin tunnels are significantly better. (e) Compared to a large diameter single tunnel, the smaller diameter of the twin tunnels results in more cover above the tunnels, reducing risk of settlement and hence building damage during construction. Control at the excavation face also increases as tunnel diameter reduces. In respect of the operating railway, independent tunnels facilitate smoke control (ie effects of a fire event on one line can be constrained to one tunnel), thereby offering safety advantages. (f) Not applicable; there is no design change. (g) Not applicable.
(e) Compared to a large diameter single tunnel, the smaller diameter of the twin tunnels results in more cover above the tunnels, reducing risk of settlement and hence building damage during construction. Control at the excavation face also increases as tunnel diameter reduces. In respect of the operating railway, independent tunnels facilitate smoke control (ie effects of a fire event on one line can be constrained to one tunnel), thereby offering safety advantages. (f) Not applicable; there is no design change. (g) Not applicable.
(f) Not applicable; there is no design change. (g) Not applicable.
(g) Not applicable.
AnswerView source ↗
Answered
30 March 2004
Responded by
Minister for Planning and Infrastructure
Response time
28 days
In responding to this question, it is assumed that the Member is referring to the bored tunnels under the Perth CBD, and not the cut-and-cover structures.
(a) Twin bored tunnels have always been proposed.
(b) The twin bored tunnels commence at the northern end of Esplanade Station at the intersection of William Street and Mounts Bay Road then head north beneath William Street to the new underground platforms south of Wellington Street. The twin tunnels continue from the northern end of these platforms, curving to the west to enter a cut-and-cover structure in the rail reserve east of Lake Street.
(c) The optimum design solution depends on project conditions. Single tunnels can be cost effective where ground conditions, cover to the surface, proximity to structures, length of drive and route geometry are favourable. However, for railway systems, single bored tunnels give rise to increased costs due to the large diameter required to accommodate twin tracks, resulting in increased tunnel area (usually more than double) relative to a twin track solution. Risk associated with shallow cover and tight geometry can also be factors. International experience shows that twin tunnels are the most common solution used for metro rail projects.
(d) Yes; twin tunnels are significantly better.
(e) Compared to a large diameter single tunnel, the smaller diameter of the twin tunnels results in more cover above the tunnels, reducing risk of settlement and hence building damage during construction. Control at the excavation face also increases as tunnel diameter reduces. In respect of the operating railway, independent tunnels facilitate smoke control (ie effects of a fire event on one line can be constrained to one tunnel), thereby offering safety advantages.
(f) Not applicable; there is no design change.
(g) Not applicable.
(a) Twin bored tunnels have always been proposed.
(b) The twin bored tunnels commence at the northern end of Esplanade Station at the intersection of William Street and Mounts Bay Road then head north beneath William Street to the new underground platforms south of Wellington Street. The twin tunnels continue from the northern end of these platforms, curving to the west to enter a cut-and-cover structure in the rail reserve east of Lake Street.
(c) The optimum design solution depends on project conditions. Single tunnels can be cost effective where ground conditions, cover to the surface, proximity to structures, length of drive and route geometry are favourable. However, for railway systems, single bored tunnels give rise to increased costs due to the large diameter required to accommodate twin tracks, resulting in increased tunnel area (usually more than double) relative to a twin track solution. Risk associated with shallow cover and tight geometry can also be factors. International experience shows that twin tunnels are the most common solution used for metro rail projects.
(d) Yes; twin tunnels are significantly better.
(e) Compared to a large diameter single tunnel, the smaller diameter of the twin tunnels results in more cover above the tunnels, reducing risk of settlement and hence building damage during construction. Control at the excavation face also increases as tunnel diameter reduces. In respect of the operating railway, independent tunnels facilitate smoke control (ie effects of a fire event on one line can be constrained to one tunnel), thereby offering safety advantages.
(f) Not applicable; there is no design change.
(g) Not applicable.
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