GE-26 use of jet grouted pile in deep braced excavation
Kyaw, Wai Mon
Date of Issue2016
School of Civil and Environmental Engineering
This project is a study of the behavior of the wall in braced excavation system in the presence of the jet grouted piles (JGP). Jet grouting is the soil-improvement technique that aims to improve the soil characteristics. In Singapore, it is widely used to treat weak soil, especially in soft clays. PLAXIS 2D, one of the finite element software was used in this study. The analysis model is a 30.6m depth excavation supported by a 44.3m long diaphragm wall with two layers of JGP. Thickness, stiffness and strength of the JGP were varied in different analysis to study the effects of the JGP. It was conducted by making comparisons of the soil displacements, lateral wall displacements, bending moment of the wall and strut forces. Nicoll Highway was studied in this project and it was found out that Method C showed more critical results and Method A was not suitable to use for Nicoll Highway case. It was also observed that choosing the wrong method could lead to the failure of the whole braced excavation system. Therefore, starting from Case 2, only Method C was used to analyze the models. Results indicated that the thickness, stiffness and strength of the JGP had a very significant impact on the surrounding soil and the installed structures. In general, these factors can greatly reduce the deflection and bending moment by increasing the top JGP layer parameters. On the other hand, reducing the bottom layer parameters enlarged the deflection and bending moment. The deflection of the soil and wall reached to the alarm level in two cases. It had been found out that the location of the layers might play an important role in the analysation. Despite of the reduction or increasing of the deflection and bending moment, the strut loads increased in all varied cases. In one case, the strut loads exceeded the allowable strut force. This led to the failure of the strut. It was not encouraged to use the properties of that case in real situation.
Final Year Project (FYP)
Nanyang Technological University