Geology and geotechnics for cut and cover tunneling

Geotechnical engineering and testing for tunnel assessment

Client: Impregilo SpA
Industries: Infrastructure
Services: Geotechnical Engineering, Drilling, In situ testing, Instrumentation and monitoring
 

Assignment

The construction method chose for any tunnel is a result of several design consideration. Local geology and stratigraphy sequence, geotechnical parameters of the soil, presence of groundwater, geometrical configuration of the structure, and the environmental and regulatory requirements of construction must all be taken into account before the initial design can begin. For such purpose an evaluation of the local ground conditions was required.
 

Our role

Geoservices was instructed to perform a preliminary geological and geotechnical assessment of a site, represented by segment of Orastie – Sibiu Motorway.

Our role was to perform several boreholes, drilling to depths up to 60m below ground level, and research into site conditions and the geology of the specific and surrounding area, proposed for development and construction of a cut and cover tunnel. During site works, geotechnical samples were collected and submitted to geotechnical laboratory characterization, while some in situ testing such SPT tests were performed.

Cut and cover tunnels, as the name suggests, are excavated into the ground and then backfilled with material once the tunnel structure is in place. This design is commonly used on tunnels with shallow profile and where excavation from the surface is viable, and so the geological and stratigraphical data acquired were used in designing the cut and cover method. The more conventional method, involves excavating a trench from the surface within the tunnel is constructed, before the trench is refilled and the surface replaced.