Narrow Results

Soil liquefaction is considered as one of the most significant issues that leads to failure of shallow and deep foundations. However, the effect of liquefaction on the seismic response of piles still poorly understood. Therefore, this research examines the seismic response of a pile embedded in soil stratum of saturated fine-grained soils. Midas GTS/NX is used to carry out the number assessment. In addition, the modified UBCSAND soil constitutive model is used to depict the nonlinear features of saturated sand during earthquake waves. The developed three-dimensional model is first validated using the results of a shaking table test of a pile embedded in coarse-grained soil, where good agreement is obtained between the finite element model and the experimental results for the displacement, acceleration, and liquefaction ratio demonstrated good agreement. Furthermore, the orientations of the vectors produced by the numerical study, that matched a global circular flow characteristic, reflected the movement of the liquefied soil all around pile. The findings showed a considerable decrease in the pile frictional resistance during the seismic events as a consequence of increasing the pore water pressure and subsequent liquefaction. Regarding this, before the soil was entirely softened, resistance due to friction was observed near the ground, in correspondence with the loose sand layer. In addition, the pile showed excessive settling, which is due to the decrease of the soil stiffness caused by the increase of the pore water pressure. The results of this research provide an insight into the mechanism of the behavior of pile in saturated coarse-grained soils and thus, it helps to improve future research on the topic and also achieve better design of piles embedded in saturated coarse-grained soils.

The single pile foundation is the most common form of offshore wind turbine, but it is different from offshore oil platforms because of the load and the overturning moment. The elastic-plastic element of ABAQUS has been used to simulate failure modes of the single pile foundation in soft clay. It is shown that the single pile foundation has no plastic strain region under vertical load but it is not the same under horizontal load. The plastic strain region is in front of the pile when the single pile foundation in soft clay is under bending moment condition.

The significance of liquefaction related damage to pile foundations has been clearly demonstrated by the major earthquakes that have occurred during past years. Current project investigates seismic behaviour of a single pile in three-layered soil of Babol Citycenter site (located in Babol city, Mazandaran Province, Iran). The site soil consists of sandy and clayey soils modelled based on data collected from drilled boreholes. Numerical analysis performed using Flac2D finite difference program. Three different natural ground motion records are considered and influence of each earthquake on bending moment and horizontal displacement of the simulated pile is investigated. In addition, the effect of vertical surcharge on settlement of the pile during the earthquakes is investigated. Results illustrate that the maximum bending moments has been occurred on the interface of liquefiable and non-liquefiable soil layers.