The Deflection and Bending Moment of Existing Piles Influenced by Trenching Diaphragm Wall Panel(s)

Abstract

Diaphragm walls are normally used for the deep excavations and underground construction inside the cities. The trenching process of diaphragm walls causes deformation in the ground surface. The construction of the diaphragm walls near deep foundations may not be avoided specially in the crowded cities. This research focuses on the deflection and bending moment of piled foundations near slurry trench. Since the trench is considered as a three dimensional problem, a three-dimensional numerical analysis was used in this research. It was conducted using a commercial analysis software known as FLAC 3D which is based on the finite different analysis method. Verification was made for the numerical analysis method using two case histories, one in Hong-Kong and another one in Giza, Egypt. The results from the numerical analysis were in quite a good contrast with the field data results. This means the trenching process could be numerically modeled with the proposed method and provides good results. The verified numerical analysis method was used to conduct a numerical parametric study that discusses the effect of a single or double panel(s) on the nearby piled foundation. The parametric study showed that the pile deflection and bending moment are affected by the panel length, pile diameter, pile location from the trench, groundwater level and the existence of a weak soil layer that could cause reduction in slurry pressure. The panel thickness did not show any influence on the pile bending moment or deflection. The decrease of the panel length and controlling the slurry level will reduce the influence of trenching on nearby piles. Lowering the groundwater level before trenching could probably reduce the influence on the pile as well.