Student SID: 440 122 188
Applications of Shotcrete Technology in Tunnel Construction
The Civil Engineering Application
Civil Engineering relies heavily on the access to and manipulation of concrete, particularly in the construction of road
infrastructure. However, increased use of & demand for road infrastructure has outreached the capacity of current
road infrastructure in many capital cities around the world. Consequently, many civil engineers have turned to tunnel
engineering and construction as a solution to traffic congestion and increased demand. Similarly, over the past
century, shotcrete has replaced traditional methods of lining tunnel profiles, becoming a crucial element in supporting
the excavated tunnel section. Accordingly, the application of shotcrete technology within tunnel engineering and
construction is crucial to the success of tunnelling projects around the world.
Significance
The development and subsequent implementation of
shotcrete has allowed for the undertaking many of
Australia’s current tunnelling projects, namely, the
Melbourne Metro Tunnel Project and the West & North
Connex Tunnel Projects. None of these projects would
be financially feasible without the application of
shotcrete technology. Equally, as a technology,
Figure 1: Robotic Shotcrete Schematic illustrating the relationship
shotcrete reduces the need for conventional cast in-situ
between Fluid Mechanics & Shotcrete Technology.
construction, improves constructability in overhead and
underground construction applications, as well as reducing construction time between 33% & 50%. Shotcrete
application is also less labour intensive when compared to traditional cast in-situ construction with the use of
technology such as a shotcrete rig, as highlighted in Figure 1. Furthermore, underground shotcrete applications
accounts for approximately 37% of the global shotcrete market, with significant growth in road tunnel construction
projects across the Asia Pacific Region. This growth is highlighted in the tunnelling projects currently underway across
Melbourne, Brisbane, & Sydney worth in excess of $40 Billion, with each project targeted at reducing road traffic
congestion.
Role of fluid mechanics
Shotcrete application requires the concrete mix to be discharged at a
certain rate, or flow, such that it will adhere to the spraying surface
and not rebound towards the applicator. Accordingly, the specific
pressure value must be applied, such that the concrete mix achieves
the required flow rate to sufficiently adhere to the surface, as reflected
in Figure 2. Equally, the intricate relationship between surface shear,
material density & composition, fluid pressure and flow rate are
Figure 2: Linear Relationship between Flow Rate of
fundamental notions within fluid mechanics. As such, the application
Shotcrete & Pressure
of shotcrete within tunnel engineering would not be possible, let alone
safe, without a comprehensive understanding of fluid mechanics. Similarly, site-based engineers are also required to
display a fundamental understanding of fluid mechanics as so not to create an unsafe working environment, as well
as the limitations and hazards of working with such a corrosive material under such immense pressures.
Reference(s)
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ASSOCIATION, T. A. S. 2018. Why Shotcrete [Online]. Available: https://www.shotcrete.org/whyshotcrete/ [Accessed 8th
March 2019].
MANUFACTURERS, T. A. O. E. 2019. Advantages of Using Shotcrete [Online]. Available:
https://www.conexpoconagg.com/news/october-2017/advantages-of-using-shotcrete/ [Accessed 8th March 2019].
CHEN, L., LIU, G., CHENG, W. & PAN, G. 2016. Pipe flow of pumping wet shotcrete based on lubrication layer.
PROJECT, N. 2018. NorthConnex Construction Tip Sheets. In: VENTURE, L. B. J. (ed.).