Causes, effects and solutions of delay and cost overruns in Iranian deep excavation projects

Purpose Through a case study for Iran, this research seeks to pinpoint the dominant causes of delay and cost overruns in two standard Support of Excavation methods (Bracing strut and top-down construction) in deep excavation projects from various points of view involving contractors, consultants and owners. This investigation identifies the root causes, compares them with existing literature to find similarities and differences with tunnelling and construction projects and proposes practical solutions. Design/methodology/approach The primary factors were identified after an extensive literature review and expert interview. Subsequently, a questionnaire was designed to classify related factors, considering impact indices, occurrence likelihood and overall significance. Eventually, the findings of the analysis were visually represented through cause-and-effect diagrams. Findings The results indicate that “inflation and exchange rate fluctuation” is the top-rated cause, followed by designers ’ limited overall perspective of implementation issues. Also, comparing the roles of related teams shows that the contractor sector is the most responsible for delay and overruns in both methods. Finally, practical solutions are presented regarding the main affecting factors. Originality/value Prior research often addresses delay and costs in construction, but insufficient focus is given to deep excavation projects, particularly in Iran. This study not only fills the identified knowledge gap but also delves into the causes of delay, pursued until the fourth bone in some cases and proposes a solution framework derived from previous research, case studies and expert insights to mitigate construction delay.