SIMULATION OF PILE LOADING TEST IN A LAYERED SOIL WITH VERTICAL LOADING BY USING FINITE DIFFERENCE METHOD BASED SOFTWARE

Abstract

Pile loading tests are usually performed in various projects to determine the ultimate pile capacity. However, the cost of running these tests and the time it takes is one of the difficulties that engineers face in current geotechnical practices. Finite difference method and finite element methods have comparable accuracy. However, finite difference method based tool was used for the analysis due to its simplicity, computational efficiency and simple structure codes. The research presents a numerical simulation of pile loading test using a finite difference program “FLAC 3D”. The chosen software is memory and simulation time efficient. It solves almost all kinds of geotechnical problems, but the only downside is that it initially takes some time to get the feel of the software, but once understood, it can solve any problem and it also supports a wide range of material models. The objective of this study is to simulate a pile load test with vertical loading in a layered soil, in order to estimate the load-settlement characteristics and to determine the effect of young’s modulus, angle of internal friction, lateral earth pressure coefficient, and the dilation angle on the load-settlement curve. Input parameters of the simulation were collected from Nib, United, and Zemen international bank's new headquarter projects. In the case of piles with incomplete data, the parameters were estimated from site experience data and/or using different equations obtained from a literature. The proposed numerical model has been validated with field data and published results provided by other studies. The validation produced good results with a minor deviation except for nib bank piles. The significant deviation in nib bank piles is due to the generalized soil parameters used in the analysis. The numerical analysis underestimated the ultimate pile capacity. However, Lateral pressure coefficient manipulation yields improved results. Underprediction of load-settlement curves of nib bank piles was due to lower young’s modulus values estimated from various equations. The study on one of the piles showed that the base resistance carries the upper hand of the total capacity. The importance of using finer mesh near high-stress gradient zones was examined and it has been found that finer mesh generated based on the developed relation produced a good performance. If the required constitutive model, initial and boundary conditions, and good quality input data are available, the proposed numerical model can be used as an alternative method for the design purpose on projects involving pile foundations