چكيده به لاتين
Beaches and ports are important areas for trade and tourism in any country, and the construction of high-rise structures in these areas, which have liquefied sandy soil, is increasing day by day. Also, one of the suitable foundations for high-rise structures is pile-raft foundation. Therefore, the construction of structures based on pile-raft foundations and located on liquefiable soil is increased and it is important to study the behavior of pile-raft foundations with countermeasure strategy against liquefaction. In this study, seismic behavior of end-bearing piled raft foundations in liquefiable sandy soil improved with gravel drainage wells has been investigated using 3D FEM numerical modeling in OpenSEES software. For this purpose, behavior of the two piled raft systems in the presence and absence of gravel drainage columns has been evaluated and the response of acceleration, excess pore water pressure, effective stress, settlement of pile raft foundations and lateral displacement of the soil have been investigated. Next, a parametric study was performed to investigate the effect of superstructure load (specific weight of raft), permeability of gravel drainage columns, maximum acceleration amplitude, dominant period and duration of input excitation for four different earthquake records. The results show that, with increasing the superstructure, the initial effective stress and settlement under the pile-raft and pile-raft-drainage systems increase. Also, with increasing the amplitude of the input excitation acceleration, the process of disappearing of excess pore water pressure and recovery of the strength after the end of the earthquake starts later and the settlement and lateral displacement increase. Other results seen in this study include the effect of the presence of pile-raft and pile-raft-drainage systems in changing the dominant period in the vicinity of pile-raft and pile-raft-drainage systems depended on input motion.
