The study is intended for geotechnical engineers who deal with the construction of deep foundations using driving piles with the implementation of seismic cross-hole technique to estimate the accompanying increase (or decrease) in soil shear strength. The study concluded that there is a direct relation between the increases in soil undrained shear strength with 3 4 T yield stress ratio3 4 T and reverse relation with 3 4 T moisture water content and void ratio. The3 4 T increase in undrained shear strength is observed in the clay soil layer at 3-5 m in depth with low 3 4 T moisture content and void ratio due to the effect of time3 4 T . 3 4 T While at depth of 1-3 m, the reverse was noticed, this decrease is attributed to the upward displacement of the soil due to shear force from driven pile and then leading to increase the soil moisture content and void ratio. The study also concluded that an increase in undrained shear strength and yield stress ratio causing a decrease in void ratio and moisture content due to the effect of aging factor.1 2 T The present results have provided good overall views of the shear strength increases and their distributions and the estimated values are also of the right sizes.

In recent years, there is a dramatic progress in the development of theories for dynamic analysis of piles. The finite element method is a numerical approximation procedure to analyze physical problems by transforming them into mathematical models. This needs to be done numerically because it is either too complicated or impossible to solve problems by classical analytical methods.In this study, a three-dimensional analysis by using finite element method will be adopted to predict the displacement response of pile foundation due to dynamic loads. A case study is carried out to investigate the effect of particles size of soil, length of pile, spacing between piles and pile cap size on the dynamic response of pile foundations.The results indicate that, the maximum amplitude of displacement of pile foundation under dynamic loads can be occurred in loose sand in comparison with the other types of sand. In addition, the increase in pile length will lead to decrease in the amplitude of displacement due to increases in the mass of the foundation.