Cut and Covers Tunnels
The cut and cover method of tunnel construction is ideal where a motorway, main line railway or metro railway has to be built just below ground level, in order to pass through urban areas.
The method comprises the installation, from the existing ground surface, of parallel side walls (usually diaphragm walls) spanned by a cover slab enabling the restoration of street level traffic. The tunnel is excavated once the cover slab is reaches strength requirements.
The cut and cover method is also used for the end sections of road and rail tunnels, where they emerge at ground surface level. The group has delivered many successfully completed projects of this type.
Metros stations, launching shafts
The 1960’s saw the beginning of rapid population growth in many cities world wide, accompanied by a demand for high speed, underground transport systems. Soletanche Bachy has been involved in the construction of many of the challenging underground stations in the projects that have been developed, performing soil consolidation grouting and diaphragm walling for station boxes and cut and cover tunnels. The most recent major projects of this type have been in Hong Kong, Singapore and the USA but equally many smaller projects have been completed.
Soil Improvments
Transport engineers are frequently confronted with highly compressible soils and are required to deliver cost effective design solutions. An example is that of roads crossing wetland or flood plains comprised of soft and often deep compressible soils, where it is necessary to consolidate the in-situ soils prior to embankment construction, in order to eliminate the risk of slope failure either during construction or in the longer term.
Pre-consolidation of the most compressible material is necessary to prevent minimize long term creep settlement. The foundation provided by the consolidated soil will increase and preserve the service life of the future road pavement, reducing life cycle costs for the roadways and structures. Embankments leading to bridge structures impose high surcharge loads to the foundation soil strata. The design of these foundations routinely requires intensive treatment to improve the soil strength criteria. Options for ground treatment are illustrated in the sketch below.
