Widening works are currently underway to reduce congestion. The £340 million ($A850 million) project will provide additional lanes in both directions over a 25km section of the motorway.Van Elle is working on the £3 million ($A7.5 million) piling, soil nailing and ground anchor works. Van Elle managing director Richard Holmes said the M1 project formed a major focus of the company’s plans to expand into the civil sector from its house-building base.The motorway typically comprises dual three-lane carriageways with hard shoulders. Varying landscapes exist within the motorway corridor and the route passes over or within different types of terrains and structures including embankments, culverts, bridges and tunnels. As a result various geotechnical engineering solutions are needed to overcome the associated problems with widening the carriageway.The geotechnical works are divided into four main areas: soil nailing, retaining wall piles, ground anchors, and new gantry base piles.Approximately 6000 soil nails of a metre in length have been installed at a number of locations on the northbound and southbound carriageways, using Van Elle’s Soilmec 401 directional drilling rigs. The nails provide stability to the embankments formed during the widening process.As the M1 passes over a number of bridges, retaining walls either side of the existing abutments are needed for the increased loads on the existing terrain caused by the additional lane. Around 300 CFA piles, 600mm in diameter, were used in the construction of the retaining walls. Pile depth varied dependent upon rock levels encountered. Pile design is based upon embedment into the underlying limestone.Three lanes of traffic are maintained between 6am and 8pm each day throughout the works, so there is a restricted amount of space available. In addition, the number of trades working simultaneously meant a solution was required that enabled other works to be carried out concurrently.Van Elle’s solution used one of its restricted access piling rigs, capable of forming large diameter piles of depths up to 19m yet allowing works to continue around the piling operations. Dave Warner, director of Van Elle’s restricted access division, said: “We are using two of our newly purchased rigs, the SoilTek and Klemm 709, on this particular project. The brief from [main contractor] MVM required all three lanes of the M1 to remain fully operational, to maximise the flow of traffic through the work area. In addition, the access route along the works area, the hard shoulder, is also to remain clear.“This would not have been possible with conventional 60 to 70 tonne machines. Both the SoilTek and Klemm 709 are compact manoeuvrable rigs, allowing the works to be carried out whilst mandating access at all times through the works area.“We bought the SoilTek and Klemm 709 rigs as there was an increase in demand for civil engineering projects in restricted access situations. The rigs within our fleet are ideally suited to projects of this nature, with high capacity piles, often in difficult ground conditions, with a number of technical problems to overcome. We have invested heavily in full computer instrumentation for the rigs, giving us real-time access to data, which can be provided instantaneously to our clients electronically, demonstrating actual live conditions, and minimising turnaround times for information transfer.”In addition to the piled retaining walls, Van Elle is also responsible for installation of the ground anchors forming part of the retaining walls. The design of the ground anchors for the project was carried out by Van Elle’s in-house design team, headed up by senior design engineer Abid Adekunte.“The design offered was the most economical for the client,” Adekunte said. “We are installing approximately 275 ground anchors to varying depths, depending upon rock head, of up to 25 metres.”Van Elle invested in three new excavator-mounted directional drilling rigs, capable of installing the ground anchors in restricted access, where there was a requirement to work over the embankment, and back under the rigs. The company says it has invested £3 million in rigs, plant, machinery and technology in the last year alone and is still looking to expand its capabilities. – From GeoDrilling, an Aspermont UK publication
