Task 6.3: Development of modified static and seismic design methodology of piled-raft foundation
Task Leader(s): M Samanta
- Development of design methodology of pile-raft foundation for tall building under axial, lateral and combined loading considering the amplifications and nonlinear soil response in static and dynamic conditions for different soil conditions
Description of Task:
Rapid growth in population and industrialization forced the construction engineer with the challenging task of managing the infrastructures construction activity with limited resource and space. Also, scarcity of available land forced the geotechnical engineer to go vertically rather than spreading horizontally. In the view of the above, the present study aims to provide safe and sustainable solution of foundation for tall building for mass housing.
Heavy and important structures, such as high-rise buildings, industrial plants, bridges etc. are generally supported on deep foundations like piles, piled- rafts or piers. Usually piles are used in groups and mutual interaction of piles in a group usually neglected in design under axial load. Changes in stress condition around pile due to axial load in pile cap a group of pile usually not considered in estimation of capacity and settlement of pile group. The stiffness and contribution of raft/cap are not included in the design procedure of pile group or piled raft foundation. Also, vertical and lateral loads are coupled in nature though the design criteria against vertical and lateral load are satisfied separately. But, in case of tall building supported on pile group or piled-raft foundation a constant magnitude of vertical load due to dead load acts along with lateral load due to wind or earthquake. Lateral capacity of piled raft foundation in presence of vertical load reflects a more realistic field situations rather than considering vertical and lateral load separately, which calls for a systematic study of piled raft foundation considering different interaction of pile, raft and soil in static and dynamic case to develop a design methodology replicating the more realistic field situations. Also amplifications of seismic waves can be disastrous if not considered properly in the design of piled-raft system. The current design procedure of piles and pile raft does not consider the amplifications of seismic waves in the design method. Also nonlinear response of the soil in the present study will be considered for development of a more realistic design method. Laboratory and numerical study will be conducted to achieve the objective of the proposed project. The numerical analysis will be conducted considering the homogenous and non homogenous soil profile to realistically consider the varying soil condition in the field. Consideration will be given for choosing the appropriate soil model, pile model and raft to realistically model the pile raft behaviour.
- Static design methodology of piled raft considering co axial vertical & lateral load in different soil conditions
- Design guidelines for piled raft considering amplification of seismic waves