THE EFFECT OF DEEP EXCAVATION ON THE ADJACENT BUILDINGS

Abstract

Excavation activities are essential to access foundation levels in construction projects. However, when such operations occur near existing buildings, they can pose significant risks to adjacent structures. Uncontrolled excavation may lead to ground movements that compromise the structural integrity of nearby facilities. This study investigates the impact of deep excavation on surrounding buildings through a series of parametric analyses, aiming to provide insight into safe design strategies. A total of 20 numerical case studies were developed using PLAXIS 2D finite element software under the Mohr-Coulomb model. All cases involved a two-layer soil profile—an upper cohesionless layer overlying a cohesive stratum—with the groundwater table artificially lowered to the excavation base level to simulate dewatering. The cases were grouped to examine the influence of: (1) increasing excavation depth; (2) varying cohesive strength of the lower soil layer. Each scenario was evaluated under single and double strut configurations. Key results show that increasing the excavation depth significantly amplifies wall bending moments, lateral deflections, ground settlements, and strut reactions. For instance, in single-strut systems, a 57% increase in excavation depth led to a 136% rise in bending moment and a 53% increase in wall deflection. In double-strut systems, deeper struts experienced up to 483% increase in axial force, highlighting their sensitivity. Conversely, enhancing cohesive strength of the deep soil by 80% effectively reduced bending moments, displacements, and strut loads—though its influence diminishes at greater depths. The findings emphasize that excavation depth is the dominant factor influencing deformation and structural demand, while deep soil cohesion improvement is a practical mitigation strategy. Surface soil compaction, however, offers limited benefit. The research provides valuable guidance for optimizing excavation design to minimize adverse effects on adjacent buildings, especially by highlighting the critical performance of lower struts in multi-level support systems.