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Abstract The oil storage tanks of the Terminal Oil Station in Lanzhou are the first large oil storage facilities built on saturated loess ground in China. Cement-flyash-gravel(CFG) piles were adopted to improve the foundation due to its low bearing capacity of approximately 60 kPa. Based on a oil storage tank of 15×104 m3 in volume，experimental study was performed to explore the bearing and deformation features of the CFG-pile composite ground. Soil pressure cells，pore water pressure gauges and settlement meters were installed in the CFG-pile composite ground. Field testing results show that the bearing capacity of the CFG-pile composite foundation reaches 275 kPa. The water filling test of the tank reveals the varying processes of the pile stress，soil stress，pore water pressure，ground settlement and the deformation of the tank's circular foundation. It is indicated that the maximum settlement of the tank's circular foundation is 30 mm while the minimum settlement is 11 mm. The maximum differential settlement of the tank in the diametral direction is 16.0 mm；the maximum nonplanar tilting rate of the tank in the circumferential direction is 0.002 46. The ratio of the pile stress to the soil stress rises as the load increases and reaches 12.6 under the maximum test loading；the soil reaction distribution at the tank bottom takes on a V-shape in the radial direction. The results show that it is effective to improve saturated loess ground by CFG pile.
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Received: 02 May 2013
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2013, Vol. 32 
