Project Sence - stabilising a quarry

Ground and slope stabilisation work is commonly associated with infrastructure projects such as major road or railway lines embankments, but as BAM Ritchies’ Matt Ewing explains it is often needed in other environments too. In the case of Project Sence that means a UK quarry.
Project Sence - stabilising a quarry Project Sence - stabilising a quarry Project Sence - stabilising a quarry Project Sence - stabilising a quarry Project Sence - stabilising a quarry

BAM Ritchies worked on Project Sence the expansion of a quarry in Leicester in the UK

Matt Ewing

Bardon Hill Quarry is a 4 million tonne a year granite quarry located north of Leicester in the UK, with important rail links to London and other strategic locations across the UK. The quarry has been in existence since the 1800s. In 2013 ‘Project Sence' commenced which is a 4.5 million tonne per annum quarry extension at the quarry.

The current reserves of the existing quarry planning permission were coming to a close and planning permission was granted in 2011 for a new quarry extension which lies 2km east of the existing Bardon Hill site, which is part of the Bardon Estate that lies in 526 hectares of land. The existing quarry operations include granite processing, concrete hard landscaping products and asphalt.

As a greenfield site, approximately 1 million tonnes of rock had to be removed by blasting to gain access to the location of the future crusher, then a ‘slot', some 30m deep had to be blasted and stabilised before any construction work could take place.

The geotechnical scope of works was to carry out drill and blast operations, then design and install a rock support system; this work would create the crusher slot in the quarry extension. The works had to provide safety to the workers while the construction of the crusher housing was taking place. It would also provide protection to the plant and personnel working along the access roads from the quarry floor level into the crusher area, during normal operation of the quarry.

Once a level a platform was created by the drill and blast team, the ground investigation team drilled a series of holes that were used to further map the geology. This ensured the orientation of the crusher slot avoided major joints and slip planes.

The crusher slot required final faces to be presplit, a blasting technique to maximise the stability of the rock. The excavation was blasted and lowered in 5m lifts, allowing the geotechnical designers to easily access the rock faces to evaluate the stability requirements.

Variable geological conditions meant that a number of solutions needed to be utilised. The ground investigation team provided additional key data to enable the right solution to be chosen, whether bolting, mesh, sprayed concrete or a hybrid mix.

The package of works for BAM Ritchies involved: 4nr rock boreholes to confirm geology; drilling of 920nr rock bolts with a total meterage of 4,483m; installing 3,156m2 of Tecco Mesh and 7,456m2 of Deltax Mesh; and 1,555m2 polypropylene fibre reinforced spray concrete.

Collaboration between all the BAM Ritchies disciplines, Aggregate Industries and Walters Plant Hire ensured no undue delays occurred to the excavation.

The rock support works were carried out during nightshift due to the risk of plant-personnel interface. Drill and blast operations were carried out during the day, along with the haulage of the blasted material. The rock support installation team would then start at six in the evening for a handover from the day shift team. Use of the drill and blast D7 drill rig to carry out the bolting works allowed for high production drilling, increasing the certainty on the programme.

A remote-control drill rig from the geotechnical team was used to drill the anchor/dowel holes from the same level. Stabilisation including drape netting and sprayed concrete could also be installed from the same level.

BAM Ritchies contributed to the success of the project by using our experience and knowledge of the quarry in both drill and blast and ground engineering disciplines. We offered the customer both disciplines to ensure collaboration between the departments in relation to planning and use of compatible plant. This integrated delivery allowed optimal solutions to be chosen. We used our experience in rock support installation and materials available to inform the customer of the most adventitious solution both technically and commercially.

Matt Ewing is BAM Ritchies' business development manager. BAM Ritchies is the specialist geotechnical division of BAM Nuttall; one of the UK's leading civil engineering contractors and an operating company of the European construction group Royal BAM