The earthworks associated with the West Charlestown Bypass in Newcastle are currently nearing completion. The project comprises 6km of dual carriageway motorway in an urban environment, extending from the Pacific Highway at Windale in the South to Charlestown Road, Kotara South, in the north.
A 1km length of the Bypass, at the northern extent of the works, traverses old underground mine workings with overburden depths as shallow as 5m ranging up to 30m. The mine workings are within the Australasian Coal Seam and were undertaken by two collieries, initially in the 1800’s by the Australasian Coal Company and later in the early 1900’s by the Newcastle Myall Colliery.
The Bypass design was required to be safe and serviceable considering the potential impact of ongoing mine subsidence associated with these workings. A number of treatment options were considered with the adopted design including a combination of excavate, collapse and backfill of shallow mine workings, and grouting of voids where the workings are located at greater depths.
This presentation will cover the pre construction investigations, including discussion of the methodologies adopted and their success, the design options considered, and the recently completed mine void treatment works.
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