Field test of composite ground improved by different methods in red soil areas of China

Large oil tanks are often vulnerable to weak bearing capacity and uneven settlement of foundations, which gives rise to potential losses of both lives and property. Although the pile foundation is commonly used for large oil tanks, its high costs make it less applicable in many cases. Recently, improved ground has been adopted as a tank foundation because it is highly cost-effective. In this study, typical composite grounds improved by dynamic compaction, dynamic replacement and cement fly-ash gravel piles were adopted to work as the foundation for ten large, heavy oil tanks under various geological conditions in red soil areas in China. The results relating to improvement of the composite ground were studied comparatively in detail using in situ tests, including the dynamic penetration test, plate-load test and water injection test. Field studies show that the bearing capacity of the composite ground after treatment is over 260 kPa within the improvement depth, meeting the design requirement for the long-term service of the ten oil tanks. The field test and relevant findings indicate a promising future for composite ground in relation to large, heavy oil tanks.