1. Introduction Developing transportation system in populated cities needs to construct subsurface infrastructures, such as tunnels. With a close attention to densely surface structured urban environments, it is most likely that tunnels would inevitably cross near of adjacent structures. It should be considered, whether the settlement induced by tunneling are in allowable range or not. Several factors may affect the magnitude of ground movement due to tunneling and consequently the tunnel-structure INTERACTION, such as ground geotechnical properties, adjacent structure stiffness and relative position of structures and tunnels, and tunnel construction parameters. When PILE foundations are exposed to intense dynamic transverse loads during earthquakes, soil-structure INTERACTION (SSI) plays an important role in allocating the response of PILE foundations to lateral excitation. The numerical investigation with analysis subway tunnels and deep foundation INTERACTION behavior under seismic loads by the finite element method was carried out...

PILE foundations are widely used to ensure the stability of structures subjected to seismic excitation. Numerous structures and foundations in soil-PILE-structure systems have been destroyed during occurrence of earthquakes. Because of complexities involved in soil-PILE INTERACTION problems and the lack of precise methods, it is necessary to use numerical methods for analyzing soil-PILE INTERACTION problems. There are several factors affecting the dynamic response of a PILE in soil-PILE system. These factors can be divided into three main categories: geometrical factors, material properties, and load characteristics. Studying the effects and importance of these factors in the response of the PILE will help geotechnical engineers to optimize their design. In this research, three-dimensional modeling has been developed using FLAC3D computer program, and the effects of various soil and PILE properties on the dynamic behavior of a single PILE in clayey soils are evaluated. One of the most important subjects in the numerical modeling of soil-PILE system dynamic response is the constitutive model considered for the soil. This strongly affects the accuracy of results. In this study a softening model has been used for the behavior of the soil under dynamic loads. Sinusoidal harmonic loading has been applied to the model base as the acceleration time history, and the variations of bending moments, shear forces, and displacements along the PILE are obtained for all analyses carried out in this study. The results show that kinematic INTERACTION coefficient depends on the loading characteristics and in the high frequencies head PILE response is lower than free field.

In this paper effect of PILE-soil consideration in obtaining seismic response offshore structure is assessed due to earthquake loading. InducedSeismic force is one of the most important excitations for the dynamic response of an offshore structure. According to API, Seismic forces should be accounted in platform design for seismically active regions in order to determine the allowable seismic risk for the type of operation intended. Two model were developed, in the first one, PILE-soil INTERACTION was neglected whereas in the second one, PILE-soil INTERACTION was considered by using un-grouted PILE stubs. The models that were used in this research were consist of two dimensional finite element models with linear behavior. After obtaining dynamic specification of structural system, a linear time history analysis was performed on both models and eventually the response of structure in the form of overall drift and maximum top displacement was compered. Finally it was shown that neglecting consideration of PILE soil INTERACTION will not always result in ensuring structural responses.

This paper presents the numerical analysis of seismic soil-PILE-superstructure INTERACTION in soft clay using free-field soil analysis and beam on Winkler foundation approach. This model is developed to compute the nonlinear response of single PILEs under seismic loads, based on one-dimensional finite element formulation. The parameters of the proposed model are calibrated by fitting the experimental data of large-scale seismic soil-PILE-structure tests which were conducted on shaking table in UC Berkeley. A comparative evaluation of single PILEs shows that the results obtained from the proposed procedure are in good agreement with the experimental results.

In offshore structures, most of failures are caused by the lack of sufficient PILEs strength. Scour phenomena affects the load transition and the PILE strength. The necessity of the consideration of scouring phenomena amplifies when the scour depth becomes remarkable, which can endanger the jacket stability. In this paper, a new method is used to consider the PILE scouring using nonlinear pushover analysis with SACS software. A recently-built existing jacket platform namely SPD 19C is selected as a case study. Results show that Reserve Strength Ratio (RSR) of the jacket platform decreases when scour depth increased in the both aged and recently-built cases. RSR decreasing becomes more sensible as scour depth increases. According to API RP2A collapse will be occurred in the range of RSR< 1. 6. It is shown at RSR=1. 6, collapse will be occurred in the scouring depth of 13. 5m and 11m for recently-built and aged platform respectively, which both have approximately 27% lower RSR than their original state. So scour protection methods should be addressed in vulnerable areas as preventive alternatives.