Comparative analysis of anchored and pre-stressed pile walls: A case study of a water front project in Beirut, Lebanon

Abstract

The need for underground space in overpopulated areas makes it demanding to perform deep excavations. Retaining an excavation using a shoring system is necessary to protect the retained earth and surrounding structures from potential damage or failure. Most of the shoring systems are composed of vertical structural elements supported laterally by tie-back anchors or struts, such as diaphragm walls, retaining walls, sheet piles or piles. Although shoring works are essential, they are costly. Hence, designing a successful shoring system at a lower cost and time is a challenging need. Pre-stressing the concrete is commonly used to control the deflection in reinforced concrete elements, yet this technique has not been applied in reinforced concrete piles. The aim of this paper is to analyze the performance of an alternative shoring system using the pre-stressing technique, where the reinforced concrete shoring piles are post-tensioned vertically (PTP) without a lateral support. This study investigates the behavior of the PTP system by comparing it to that of the conventional reinforced concrete piles (RCP). A finite element analysis was conducted by employing PLAXIS 2D software. Data is collected from a shoring project performed on a site located at the water front area in Beirut, Lebanon. The project consists of 306 (RCP), laterally supported by one row of tie back anchors, retaining an 8.5 m deep excavation and covering an area of about 5000 m2. The results indicated that PTP system is safe in terms of global stability and control of deformation. Furthermore, it has been proven to be more economical as it can be executed with 30% less cost in less time.