CAN Geotechnical completes rail project

CAN Geotechnical Ltd recently completed a soil nailing and sprayed concrete project on a rail widening scheme to increase the number of existing tracks from 2 to 4 on the approach to a busy station.

One of the key earthworks elements of the overall project was a steep 18.5m deep cutting, the base of which required widening to accommodate the new tracks. This was achieved by a steepening regrade of the cutting toe and removal of the existing toe-level retaining wall.

With the planned over steepened toe of the cutting decreasing the stability of the slope, a reinforced retaining wall along the toe of the cutting was required. Over 450 solid bar soil nails were installed to the newly cut slope, securing and tying back two layers of heavy duty steel reinforcement. A 200mm thick high strength sprayed concrete facing was then applied, with concrete specified to meet the 120 year design life and cope with the aggressive ground conditions on site.

With short term stability of the cutting being a concern during the construction period, the regrade was carried out by cutting 12 “hit and miss” bays. Each cut section was stabilised with soil nails and facing prior to cutting the adjacent bay, with daily monitoring of survey targets on the upper slope carried out to monitor any movement.