Holroyd to Rookwood Road cable REF - TransGrid

AECOM Transgrid LPCR Transmission LineTransgrid LPCR Transmission LineTransgrid
Cycleway Channel Transmission Line
LPCR - U/G Transmission Line - Potential Construction Impacts
Concrete strength of Monier Plates assumed to be 20MPa. Flexural tensile strength of 2.6MPa,
Concrete strength of the cycleway slab assumed to be 25MPa. Flexural strength of 3.0MPa,
Cycleway slab assumed to be 150mm thick,
Sandstone masonry assumed to possess no tensile strength,
Modulus of subgrade reaction behind the “Monier Plates” = 4E6 N/m 3 ,
Assumed that the concrete truck carries a 6.0m 3 agitator and has dual rear axles (ie minimum of 3 axles
total for the truck),
Assumed that the excavator used is a 20T – 25T caterpillar tracked excavator. Refer Appendix D.
The most effective means of minimising the potential impact of loadings is to arrange the operational area in such
a manner as to avoid surcharging the original sandstone wall and linings. The “Monier Plates” form a “masonry
like” structure that is unreinforced and thus lacking in general robustness and strength.
Appendix B shows a method by which surcharging of the wall could be kept to a minimum and hence reduce the
potential impacts of an excavator and concrete truck. Positioning surcharge loads remote from the channel wall
limits the pressure applied to the wall which is a critical consideration given the wall’s relative fragility.
It is noted that Appendix B represents one of many potential solutions and the Contractor will be required to
provide a construction management plan as part of his commission.
6.2 Concrete Truck on Cycleway Slabs
The assumed concrete truck will be likely to cause cracking of the cycleway slab. To gain access to the point of
concrete discharge the concrete truck will presumably follow the existing cycleway slab. The quality of the
material beneath the slab is unknown so to the compaction of that material. Calculations suggest that the flexural
tensile stress in the bottom fibre of the concrete will be exceeded and as a consequence, cracking of the slabs
may be initiated.
Smaller trucks could possibly be used with lesser wheel loads however this needs to be balanced against the
volume of concrete which needs to be poured and the increased number of truck movements required.
The size and weight of concrete pump is also unknown.
6.3 Concrete Truck on Channel and Linings
The assumed concrete truck is unlikely to cause cracking of the “Monier Plates” lining the original sandstone
channel provided that the truck remains a minimum distance of 1.5m from the edge of the channel (as shown in
Appendix B of this report).
6.4 Excavator on Channel
The assumed excavator is unlikely to initiate cracking of the “Monier Plates” providing the excavation is properly
“managed.” The excavator can reduce potential impact on the existing sandstone wall and “Monier Plates” by
cutting down to a bench then repositioning away from the centre line of the cycleway channel and cutting down to
the base of excavation as suggested in Appendix B of this report.
Again, positioning the excavator surcharge loads remote from the channel wall limits the pressure applied to the
wall which is a critical consideration given the wall’s relative fragility.
6.5 Access for Cycleway Slabs
Operationally, as the concrete truck will likely be required to be 1.5m from the edge of the channel wall to
minimise stress on the wall, the entire slab width will be obstructed by the truck. The contractor will need to make
alternate provisions to maintain access for pedestrians and cyclists.
6.6 Access Over Channel Walls
At locations where trucks are required to cross over the channel walls (which protrude approximately 0.3m above
the existing ground line), road base or a similar material will be required to ramp over the walls.
\\ausyd1fp001\Projects\60157132_TG_330kV_Cable\6. Draft docs\6.1. Reports\Heritage Culvert Transgrid Implications
Report.docxC:\Mark F Files\Projects\Holroyd to Rookwood\Cycleway Channel\Transgrid Implications Report.docx
Revision 01 - 26 October 2011
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