Estimation of settlements of bored piles foundation

Abstract

The paper describes the estimating settlements of bored piles foundation on the site of the Elektrenai power plant, Lithuania. The bored piles foundation supports equipment of the power plant consisting of the gas turbine, the steam turbine and the generator. The piling solution was adopted for the following reasons: i) the insufficient capacity of the soil to support great stresses over it; ii) high requirements of slab settlements and bearing capacity with regard to the main equipment in power plant.). For settlement calculation five methods were employed, such as Bowles [1] and Schmertmann methods [2] and [3], the method described in EN 1997-2 [4], [5] and [6] and NEN 6743 [7], and finite element method applied in Plaxis 3D Foundation package. The results obtained by applying these methods where compared with experimental results on construction site. The experiment results were acquired from static load test of one test pile and four reaction piles. Piled foundation was evaluated through immediate settlement analysis and included analysis of the soil data from cone and dynamic penetration tests, boreholes and laboratory tests. Soil properties were estimated from site investigation of the Elektrenai power plant and soil exploration program according to Lithuanian standards. Pile settlement analysis showed that settlement value was 13.5 mm (pile toe settlement), and settlement value of elastic deformation of pile from vertical compressive loads was 2.1 mm, for the most conservative situation. For such structure, foundation settlement should not exceed 16 mm. Because the Elektrenai power plant has high reliability requirements, piles diameter of 880 mm and 29 m long were finally carried out to endure overall loads.