Perforator Guided Auger System Aids in Flood Alleviation in Lancashire
March 31, 2011
Given the urban location and the need to ensure that the grade of the new sewer was maintained it was decided to use an trenchless installation technique that could facilitate the line and level control necessary to successfully complete the installation.
The contract for this part of the flood alleviation work was awarded to Trenchless Solutions Ltd of Wakefield, West Yorkshire, which chose to use a Perforator PBA85 Guided Auger Boring system to complete the installation. This system was selected from those available on the market because it offered a relatively small operational footprint, which suited well the urban location of the project, as well as having the capacity to handle the ground conditions expected to be encountered at the level of the pipe installation. The boring rig’s line and level control system also meant that the critical line and level requirements of the bore could be accurately and precisely maintained throughout the installation.
Installation
Prior to the start of the installation works cable percussive bore holes were used to undertake ground investigation survey using a Dando 2000 drilling rig. This investigation confirmed that the ground at the installation horizon comprised soft to stiff clay.
The Perforator PBA85 guided auger boring machine that was used in Blackburn was a complete system, which included an HS56 power pack, pilot rods, as well as augers and casings designed to suit the parameters of the, in this case, 1-m long Naylor-manufactured Denlok DN300 clayware pipe chosen for the installation. Directional control of the pilot bore was achieved using a monitor, an optical system with a CCD camera and a diode target plate.
The PBA85 rig used a three-pass system to complete the new pipe installation comprising an initial pilot bore that established the accurate line and level of the bore that would be followed by the subsequent installation phases. This pilot bore was then expanded using an auger chain with a cutting at the lead end. The auger chain ran inside auger casings with excavated soil being removed from the bore to the start shaft via using the rotating augers. With the bore now at the required diameter the final placement by jacking of the Naylor Denlok DN300 pipe into the bore whilst displacing the auger chain at the reception shaft completed the installation.
The PBA85 guided auger boring rig offers some 850 kN of forward thrust, as well as a maximum 470 kN pullback force and operate from a start shaft or pit of a minimum 2 m diameter. The machine will install pipelines from DN150 to DN500. The unit can be extended by up to 5 m where circumstances require and are permitted to handle the installation of longer pipe section in one operation.
Work started on the 24-m long sewer installation on Nov. 22, 2010, with the installation being completed by Nov. 24, with no specific problems being encountered during the course of any phase of the work. The use of the trenchless system for the installation also meant that despite the urban setting local residents and businesses were not inconvenienced in any way by the presence of the works.
Commenting on the installation the contracts director for VJ Donegan said: “We have used Trenchless Solutions Ltd. on several contracts and have been pleasantly surprised by their performance, attitude and flexibility. The company has in the past overcome unforeseen problems and successfully completed contracts with no additional costs. We would not hesitate to employ their services on future contracts.”
Trenchless Solutions Ltd.
According to Steve Varley, director of Trenchless Solutions Ltd, who has some 15 years experience in the trenchless industry: “Our experience in working on varied no-dig projects gives us a real knowledge of the challenges our customers’ face everyday. We know how important it is to look at our customer’s individual needs when helping them with a solution no matter what size the job or how demanding it may be.”
This article was supplied by Perforator Ltd., Sheffield, United Kingdom, Trenchless Solutions Ltd., Wakefield, United Kingdom.