Monitoring Consolidation of Soil

The Escravos Gas to Liquids (GTL) Plant converts natural gas into high quality, environmentally superior, liquid GTL fuel, naphtha, and Liquid Petroleum Gas (LPG) products.
The GTL Plant was built on the north bank of the Escravos River tidal outlet next to the existing Escravos Terminal and Gas Plant.
The work consisted of dredging 3,000,000m3 hydraulic sandfill of 70ha (max. 8m thick); the installation of closely spaced prefabricated drains; and, the lowering of the water table over an area of approximately 30ha by active pumping; and, the installation of the necessary monitoring instrumentation.
In order to monitor the consolidation of the weak alluvial soils, CARES Group was appointed by Boskalis Dredging NV to conduct the detailed designs for the geotechnical instrumentation.
Following the completion of the design CARES Group installed extensometers to 70 metres in order to monitor the settlements at the various depths. In addition, seven inclinometers were placed adjacent to the Escravos River in order to check the stability of the edge of the fill zone.
Monitoring was continued for two years and the instrumentation worked well under the extreme conditions; which included over 3 metres of settlement.