Completion of complex foundation project in Saudi Arabia Friday, 31st July 2009
Excessive settlements were noticed in some recently constructed structures at area 2100 of the Sharq Ethylene Plant at Jubail Industrial City in the Kingdom of Saudi Arabia.
The structures affected were pipe rack foundations, a surge basin, and cable trenches near a newly constructed drainage sump.
Initial investigation showed that the pipe rack bases had settled up to 800mm and there were voids underneath the cable trench and surge basin. It was believed that de-watering operations had washed out some of the subsurface soils causing the voids under the cable trench and surge basin leading to the settlement of the pipe rack foundations.
In order to determine the extent of the affected area RBL carried out further site investigation at 35 positions, taking SPT readings every 250mm down to depths of 6.0m. Readings as low as 3 and 4 were recorded at depths of 2.0m and 3.0m confirming the soil strengths had been greatly reduced by the effects of dewatering operations.
As a result of these tests RBL proposed pressure grouting to fill the voids beneath the cable trench and surge basin, mini piles to support the effected pipe rack foundations and soil mixed grout columns to strengthen the soils under the surge basin. RBL worked together with the clients representative, Shaw Stone & Webster, to develop designs which lead to the installation of 109No drill-bar mini piles to the pipe rack foundations, 53No soil mixed grout columns to the surge basin together with pressure grouting works. Piles ranged from 200kN to 300kN, 115mm and 200mm diameter, installed to a factor of safety of 2.5 to depths up to 15.0m.
The foundation work, successfully completed by Roger Bullivant, allowed construction operations for this busy and important Ethylene plant to continue on programme.
