Maxam Australia has successfully completed the supply of blasting products and services to the Toowoomba Second Range Crossing project, a 41km heavy vehicle route from the Warrego Highway at Helidon Spa in the east to the Gore Highway at Athol in the west of the Southern Downs region of Queensland.
The Toowoomba Second Range Crossing (TSRC) will deliver significant benefits to the region through improved road conditions, improved driver safety, increased freight efficiencies, reduced travel times (by up to 40 minutes) and the easing of pressure on local road systems by redirecting heavy and dangerous goods vehicles away from Toowoomba’s central business district.
The TSRC project is divided into three sections – eastern, central and western. The key features of its design include four lanes (two lanes each way) and a 30m deep cutting at the top of the Toowoomba Range.
Maxam, which is a leading provider of integrated blasting solutions to the Australian quarry and construction sectors, was awarded the contract as the primary provider of blasting solutions to the civil earthmoving contractor Mackellar EPSA, with specialist focus on the eastern section from Cut 3 to Cut 10 of the TSRC.
Before blasting operations started, the natural surface had to be dug to hard and approval sought from Nexus Infrastructure, the consortium building the TSRC, for blasting to take place.
After further free digging of the various cuts it was determined that only Cut 3 and Cut 10 needed blasting. The material to be blasted in Cut 10 was deemed suitable for use as roadbase and had to be blasted to a grade size of 400mm or below to be utilised. The volume estimates for blasting as per core drilling are indicated in Table 1.
Planning the cut
These extremely challenging conditions required Maxam’s local knowledge and experience.
The company is an integrated provider of blasting solutions, focusing on all-round energy optimisation systems – a structured process approach tailored to customer requirements that factors in the capability to control adverse effects and environmental issues such as blast vibration and air blast.
Its proven experience, tools, technology and services help clients such as Mackellar EPSA perform their earthwork projects safely, efficiently and effectively.
Technical and project specialists were deployed to support Mackellar’s blasting operations. In addition, the innovative Rioblast software was utilised to calculate flyrock and maximum instantaneous charge, and accurately predict blast vibration with precision to maximise the blast performance in conjunction with the controlled risks (see Figure 1). Initially, a series of predictions were made, and after a couple of blasts, a ‘k’ value constant was established.
The cut was designed as shown in Figure 2. Maxam was to blast to the specifications as depicted in the plan and section view in Figure 3.
Batter angles were 27 degrees at the mid-section and spread out to about 65 degrees at the ends. The floor levels on the berms and road sloped towards the western end.
The berm floors also sloped into the wall at 1:10, as indicated in the section view. This design was intended to direct the flow of water on the sidewalls away from the road and down the edges of the embankment into drains. It was therefore important that blasting was done to the specification, to prevent any additional cost of remould.
Any loss of berm width would require a remould at the contractor’s expense. A cutback was not an option due to a major high tension powerline network within 32m and major gas pipelines within 500m.
To design a blast, a model of the cut was first created from a string file. Due to the varying slope of the floor designs, Maxam personnel could not use a constant RL for the design toe.
Therefore, a model of the blast toe was created. To create the blast toe floor, opposite batter strings were joined to make up a single polygon (the stages of how this is done are depicted in Figure 4) and then modelled into a surface.
It was important to include the crest and toe of the level to be blasted in the toe model, so the batter slopes would be accounted for. A hole mark out was then done on the surface and picked up by GPS.
A model would then be created from the pick-up and used as the actual topographic surface. The topographic surface and the toe surface were then used to generate the hole lengths for the blast.
The initial design parameters used for the cut, as stipulated in the contract, were as follows:
Hole diameter – 89mm
Burden – 2.7m
Spacing – 3.2m
Stemming – 2m
Subdrill – 0.5m
Average bench height – 10m
Powder factor – 0.76kg/m3
These design parameters worked well initially but as blasting progressed to the next levels, Maxam encountered heavily fractured rock with joint spacing between
1.5m and 2m (see Figure 5). The fractures caused the rock to easily break along the joints, rather than fragment as desired. This meant tighter patterns to achieve the specified roadbase size.
|Figure 5. As blasting progressed, Maxam encountered heavily fractured rock with joint spacing between 1.5m
and 2m. Pictured is the rock structure with fractures (left) and the outcome after the parameter change (right).
A trial was therefore undertaken with the pattern below, with promising results:
Hole diameter – 102mm
Burden – 2.6m
Spacing – 2.6m
Stemming – 2.4m
Subdrill – 0.5m
Average bench height – 10m
Powder factor – 1.22kg/m3
The presplit design parameters used are outlined in Figure 6, with bore hole pressure calculations. The presplit holes were then designed along the crest and toe of the top and bottom berm strings.
A csv of the hole locations was then given to the client surveyor, to accurately mark the points on ground using GPS. Guide Tube was used by the drilling contractor and all drilled holes were bore tracked to verify their accuracy.
After the first couple of blasts were reviewed, a final uncharged column of 4m was deemed suitable, with outstanding results as shown in Figure 7. The products used were Megasplit 26mm and Riocord 6g/m.
High energy explosive
Maxam’s Rioflex 10000 bulk explosive, Rionnel downlines and surface connectors were utilised for optimum performance and versatility throughout the TSRC project.
Launched in 1998, Rioflex is Maxam’s flagship explosive, developed by the company’s in-house R&D team. The explosive is unique to Maxam in the Australian market. It is a high energy, fully water resistant product, with a greater range of densities, improved inhibiting and cross-linking properties, clean burning and non-explosive base.
These qualities make Rioflex competitive with other emulsion products and suitable for specialist construction projects, and it has consistently delivered exceptional results for Maxam’s clients worldwide. It is also safe to handle and can be stored on-site as an oxidiser.
Rioflex is effective in both cartridge and bulk formats, can be used in extreme dry or wet conditions and can be deployed across an extreme temperature range. It is used in climates with temperatures ranging from 40ºC in sub-Saharan Africa to -40ºC in Siberia, central Asia and Canada.
The flexibility of the Rioflex explosives is mirrored by the site-specific “value-in-use” services Maxam offers various construction projects. This process is based on adding value and helping reduce customers’ total cost of ownership through explosives and energy use – not only the costs coming from blasting products but also energy required in drilling, hauling, crushing and refining processes, especially fuel and electricity.
Maxam, which was founded by Alfred Nobel in 1872 and today operates in more than 45 countries, has been trading in Australia since 1988, when one of its predecessor companies ERT acquired small local firm ETS.
Maxam employs more than 150 people across Australia. Since its establishment in Australia, the company has supplied products and blasting services to other extractive projects for companies such as Holcim and Hanson, and has achieved a majority share in the quarry market, with key mining clients throughout the country.
The company’s headquarters is in Brisbane and it has production facilities in Bajool (Queensland) and Baldivis (Western Australia).
|Figure 7. (Left) The presplit line after blast with clean cut. (Right) Presplit walls with almost zero crest loss.|
For more information about the TSRC project, visit:
Source: Maxam Australia