WHITE YOUNG Green conducted geotechnical inspections and produced stabilisation designs for two rock cuttings near Chepstow Station in Gwent.
Studies of the slopes revealed that vegetation has been jacking out blocks of stone along the cutting, leaving chunks of up to 1t in precarious positions. The rocks in the area are massive compact limestone exhibiting fissuring and fracturing.
Environmental issues that had to be taken into account at the sites included Hardwick Cliffs, a site of special geological interest; two ancient monuments and several protected species.
Main contractor Alfred McAlpine Capital Projects recently completed the work which included rock fall netting, anchoring and bolting works, dentition repairs of solution weathered material and sprayed concrete (gunite).
Subcontractor Total Access (UK) percussion drilled the face to allow installation of 25mm galvanised steel rock bolts at depths of 2-3m.
Maccaferri double twist galvanised mesh netting was used along several hundred metres of the rock face. Loosely fitted netting was placed in some areas to catch falling material while in other areas closely fitted netting was used to stabilise the cliffs.
The work has a 60-year design life. White Young Green has put together a 10-year maintenance plan for monitoring it as part of its £1M contract with Great Western Earthworks and Structures Partnering Alliance.