Abstract:
In the hydrocarbon sector, storage tanks represent an important geotechnical challenge due to the high discharges that are handled as a result of the stored material. In addition, in areas with potentially liquefiable soils, this challenge is even greater. In these cases, it is common to use deep foundations to support the loads to which the structure will be subjected. An alternative for deep foundations is the use of compacted gravel piles that mitigate the risk of liquefaction in coastal soils and increase the safety of a structure. This paper presents the analysis, design, and construction of storage tank foundations at a site in Tabasco, Southern Mexico. A total of 941 compacted gravel piles of 12.5 m in length and 0.5 m in diameter were designed and constructed to support four storage tanks. The diameters of the tanks are 30.5 m for one tank, two 18.3 m tanks and one 4.6 m tank with heights ranging from 7 to 12 m. The site soil is composed of sand and gravel. The soil of the site is composed of fine sand with clay of loose to medium relative density up to a depth of approximately 8 m. Below this material there is clayey sand of very loose to medium relative density with clay intercalations. The use of compacted gravel piles increased the strength of the soil, mitigated the liquefaction phenomenon and reduced settlements. Cone penetration borings, CPTu, were performed pre and post soil improvement to evaluate the ground improvement and the Factors of Safety associated with the two conditions. In addition, load tests were carried out on these elements to evaluate the increase in stiffness and bearing capacity of the soil. 3D numerical analyses were performed to simulate the behavior of the improved soils and the interaction between the piles and the soil, as well as to numerically evaluate the load tests performed. Finally, the performance of the equipment used to construct all the piles is presented. Soil improvement using compacted gravel piles represented a suitable alternative for foundations of storage tanks in potentially liquefiable areas.