大型油罐CFG桩复合地基变形与承载性能试验研究

兰州原油末站大型油罐群，是我国首次在饱和黄土地基修建的大型储油设施。由于天然饱和黄土地基承载力仅为60 kPa，采用CFG 桩复合地基。依托其中一座15×104 m3储油罐工程开展CFG桩复合地基变形与承载特性试验研究。在地基处理范围内埋设土压力盒、孔隙水压计、沉降计等测试元件。现场试验结果表明，CFG桩复合地基承载力特征值达到275 kPa。结合罐体充水试验研究CFG桩复合地基在罐体充水过程中桩土应力、孔隙水压力、沉降及油罐环墙基础变形的变化规律。结果表明，环墙基础最大沉降量为30 mm，最小为11 mm。实测油罐任意直径方向的沉降差最大值为16.0 mm，油罐沿周边弧长方向最大非平面倾斜值为0.002 46。CFG桩桩土应力比随荷载呈增大趋势，在最大试验荷载下达到12.6，油罐底部反力沿半径方向呈“V”型分布。研究表明采用CFG桩处理饱和黄土地基是可行的，试验研究成果对饱和黄土地基修建大型储油罐提供技术依据。

EXPERIMENTAL STUDY OF BEARING AND DEFORMATION FEATURES OF CFG-PILE COMPOSITE GROUND FOR LARGE OIL STORAGE TANKS

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.