Factors affecting the lateral contribution of a raft in a piled raft system

Abstract

Contribution of the raft to lateral loads in a piled raft foundation system can be influenced by various factors including vertical contact pressure, number of piles, pile length, and spacing to diameter s/d ratios. Design of the piled raft system is highly dependent upon the contribution of the raft which should be thoroughly investigated. In this article, an experimental and numerical investigation was conducted in order to assess the effects of various parameters on contribution of raft to lateral loads. In experimental approach, small-scale models of the aluminium raft and galvanized iron (GI) hollow piles were used for testing under vertical and lateral loads. Vertical and lateral load cells on piles were installed for real-time load monitoring and LVDTs were used for displacement monitoring. In numerical approach, finite element software PLAXIS 3D was used. A raft was defined as a plate element, while piles were modelled as embedded beams. Based on experimental and numerical investigations, it was found that vertical contact of raft with soil has a direct relationship lateral raft contribution. Because, due to vertical load, the firm contact between the raft and the soil develops, resulting in a significant lateral contribution. Depending on the raft’s vertical contribution, the lateral contribution of the raft was found to be ranges from 14% to 55%. The numerical results were found fairly close to the experimental results. As a result, PLAXIS 3D was used to conduct a parametric analysis and It was determined that vertical pressure was directly related while the other three parameters were inversely related to the lateral raft resistance.

Keywords

• Raft contribution
• Lateral load
• Vertical load
• Piled raft
• PLAXIS 3D