The project required the holes being drilled to accept 32mm diameter dowel bar and just 10 days to complete the programme as part of the tunnel's refurbishment.
A key challenge on the project was maintaining a high level of drilling accuracy while reducing operative's exposure to harmful vibrations - which contributes to hand-arm vibration syndrome (HAVS) - as well as fatigue while drilling for the dowels. There was also the challenge of increasing productivity given the short time available to complete the works while negotiating the irregular brickwork patterns and varying drill heights.
The solution to these issues came with the tailing of the positioner actuator manipulator (PAM) machine for drilling holes. The PAM was mounted on track trolley, then an RRV trailer, for greater mobility and flexibility when mobilising. The RRV trailer had a handrail affixed to it for safety. The arm takes the weight of the tool and a large amount of the vibration. Also, the frequency of vibration arising from use is higher and therefore does less damage to the operator.
The PAM was used for four shifts worth of work. The cost-benefit of adopting this technique, as opposed to traditional hand drilling methods, was approximately £6,300. To achieve a 1:1 return on the £37,000 investment in the PAM, it should be used for approximately 25 shifts, assuming that each shift is 10 hours long and that 170 holes are drilled per shift.
David Rouse, construction manager suggested the idea when reviewing the scope of works for the Whiteball tunnel project, having seen videos and articles outlining some of the key benefits. Given the requirement for a large number of holes on the project, Rouse saw the potential in the PAM to significant reduce exposure to HAVS, while at the same time improving productivity and efficiency.
Brendan Sugrue (head of operations) and Alan McDonough (group SHESQ director) supported this solution. They assisted with the procurement, delivery, implementation and training associated with the introduction of this novel piece of technology.
The overall feedback from the trial was positive. While there were some initial challenges, these were to be expected with the introduction of a new piece of technology. However, once the site teams were trained and had gained some experience using the PAM, they realised the benefits of lower HAVS and higher productivity, allowing them to complete the works in less time than normal.
"The easy adaptation of the tool and its simple use was of a huge benefit to the project. Allowing the drilling of the dowel bar holes at an incline and at varying levels was effortless," noted Dan Malkin, contracts manager.
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