Murphy Group/SCA Group
Services Supplied on this Project:
- Rock Slope Stability Assessments
- Health and safety plans
- Night works
- Stakeholder communications
- Rope access
- Trackside working
Geo-Environmental Services Limited was instructed by SCA group on behalf of Murphy Group to undertake a Geotechnical Assessment on a cutting 500m east of Coventry Station from Bridge 317 extending 130m to the east. The cutting was approximately 18m in height and generally comprised a lower soil slope with an approximate 45 degree angle, near vertical mid rock slope mid-section and upper soil slope with an approximate 45 degree angle. As such, the objectives were to undertake a geotechnical preliminary risk assessment of the existing cutting.
- The site works were undertaken by means of rope access inspection over a period of six night shifts.
- To facilitate the inspection, vegetation was cleared from the slope by a rope access de-vegetation team from SCA Group.
- De-vegetation was kept to a minimum so as to minimise the risk of root mass degradation which might reduce the binding effect of the root-mass and promote slope instability.
- A visual inspection of any rock exposures was made which included recording joint or discontinuity spacing, bedding, rock exposure shape and structure.
- A series of vertical traverses were made along the length of the embankment to measure slope length and angle, so as to record slope cross section.
The inspection had identified that roots from the overhanging trees had penetrated discontinuities causing root jacking of joints. Retaining walls had structural distress and voids behind retaining walls. It was noted that that there was rotational soil slope movement 6.0m width with tension cracks parallel to slope immediately above. It was considered that applicable remedial techniques are likely to comprise dentition of rock overhangs, de-vegetation and draped rock netting over rock exposures to safely contain any rock falls. An urgent recommendation was made for preliminary action (scaling) on the rock face, in two areas to be undertaken. It was recommended to undertake intrusive investigation to determine ground conditions within the existing soil slope (superficial deposits or Made Ground) and underlying sandstone bedrock (Keresley Member) to determine the likely drilling conditions for anchoring draped rock netting and soil nails.