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PREMIUM BLASTING SOLUTIONS
RICHMOND HILLS CONSTRUCTION
Blasting under residential vibration constraints
The blast site was located in the suburb of Richmond Hills, Mackay, Queensland. The land is currently under development for residential purposes by Pointglen Developments.
The development is partially completed with occupied houses already located in the nearby areas. Drill and blast services were supplied by Caruana Blasting.
The geology of the site prompted
signi cant earthworks to provide suitable foundations for house blocks. A portion of the site was located on the side of a hill which required drilling and blasting
of bedrock to attain a desired reduced level. Caruana Blasting was contracted to complete this work. The loose surface material was initially removed to expose the
bedrock below which varied in depth across the site (Fig. 1).
Concerns were raised regarding a number of neighbouring critical structures:
A pre-existing occupied house 90m to the north-east (Fig. 2)
Completed works between 15-45m to the east (including watermains, stormwater drains, underground electrical works, completed roadworks, etc.)
Occupied houses within the new estate to the east
A disused brick chimney 400m to the south. The chimney is located on the site of the Richmond Mill constructed in 1881 and is listed on the Queensland heritage Register.
Caruana Blasting contacted Davey Bickford Enaex to complete a full site evaluation and develop an electronic timing design that would ensure vibrations are controlled at the key locations surrounding the blast.
The blast pattern was designed and drilled by Caruana Blasting. The pattern consisted of 871 holes drilled in a 2.5 m by 2.5m square pattern. The hole diameter used was 89 mm.
The solution proposed by the Davey Bickford Enaex’s Global Technical Services (GTS) team was comprised of two components. The first being to establish a site law to determine a maximum charge weight for each hole. Secondly, advanced vibration modelling using Paradigm software to correlate the timing design with any potential superposition of shock waves at key structures.
To complete the modelling process, vibrational seed wave data was required for the specific geological conditions experienced on site. To gather the necessary data, four blastholes from the pre- drilled blast pattern were selected to be red as seed holes on the 15th August 2018.