Replacing Top Layer of Soft Clay with Compacted Engineering Fill to Improve the Lateral Capacity of Piles

Liquid storage tanks are usually located in nearshore or coastal regions with soil profiles containing thick layers of compressible soils. These storage tanks are usually of large diameter up to 90 m and carry high loads, and the tanks are supported by heavy deep foundations such as piles. These structures are subjected to huge lateral loads due to wind and earthquakes, and any damage to storage tanks with highly inflammable liquids leads to disastrous conditions. So, it is important that the top layer of soil (up to the fixity depth) should be strong enough to provide the required lateral load capacity to the pile. In a project for constructing LNG terminal in Odisha containing 2nos of 89 m diameter LNG storage tanks supported with pile foundation located near to coastal region, for improving the lateral capacity of existing soil, the top 3 m was replaced with compacted engineered fill (GSB). The site was a filled-up area with dredged soil from the seabed, the top 5–10 m were soft to medium stiff clay with SPT N less than 10. The lateral design load on pile was 534 kN under free head condition. Actual lateral capacity for the strata was around 200 kN under free head condition which was less than the required capacity as per structural requirements. Therefore, for improving the lateral capacity of pile the top 3 m soil is replaced with well compacted engineered fill (GSB) in layers of 150 mm and the capacity is proved by conducting initial and routine lateral load tests. This paper describes the properties of the engineered fill used and how the lateral load capacity of pile was improved to meet the design requirement.