RE: Goodbye Stella7 Jun 2019 17:36
Afternoon Lives.
Re TBM advance rates. 17m per day at this stage can only be seen as a net estimated progress rate derived from many factors that presently have large varibility within them. Think of 17m/d as an indicative target based on a set of best guesses...though reasoned guesses.
SRK expand on the many variables that are used to come up with this avancing estimate that Sirius have placed out there as perhaps a target:
"12.4.3 Tunnel Advance
The rate of tunnel advance is dependent on the time it takes to complete the excavation and ring build cycle. The excavation cycle assumes that there is an efficient system to deliver rings and remove spoil where there is no gap between incoming and outgoing deliveries. Cycle times are also affected by shaft winding times and sufficient time considerations relating to tunnel construction out of a deep shaft should also be made.
The TBM cycle time is specified at 30 minutes per ring (3 m per hour). Assuming no breakdowns or other delays, achieving a cycle time of 45 minutes (20 minutes to excavate each ring length and 25 minutes to build each ring) is reasonable. It is understood that the tunnel will be driven 24 hours per day, seven days per week. In a 12-hour shift, allowing two hours for personnel to travel to the face and back, the tunnel could advance about 20 m per
shift. However, taking into account planned maintenance, unplanned breakdowns and delays to spoil removal and segment deliveries, this rate of advance is unlikely to be sustainable, particularly as the distance to the tunnel face increases as the tunnel advances. In order to sustain production rates, other passing loops will be required to allow sufficient numbers of locos and wagons into the tunnel – the number of locos will be critical for tunnel production in either case.
Planned maintenance and other non-excavating time includes probing ahead, tool changes, bringing in additional transformers, ventilation bagging extensions and rail loop erection. In the programmes presented to date (SM L1 Schedule and Entire project 19.9.18), the advance rate for Drive 1 appears to be about 18 m per day (6 rings per shift) and includes an allowance for learning and team establishment. Tunnel advance rates for drives 2 and 3 are about 23 m per day (excluding the build and launch period from the underground launch
chambers).
These appear to be a reasonable long-term average albeit that if significant delays occur due to ground risks, breakdowns or logistical issues, then this rate may reduce. If the significant hazards identified above arise, for example large groundwater inflows which cannot be controlled by the pumping equipment or squeezing ground trapping the TBM, tunnel advance might be delayed for significant periods which are not allowed for in the
current base programmes."
GK.