  Citation: Issa, U.; Saeed, F.; Miky, Y.; Alqurashi, M.; Osman, E. Hybrid AHP-Fuzzy TOPSIS Approach for Selecting Deep Excavation Support System. Buildings 2022, 12, 295. https://doi.org/10.3390/ buildings12030295 Academic Editors: Agnieszka Le´ sniak and Krzysztof Zima Received: 10 November 2021 Accepted: 9 January 2022 Published: 3 March 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). buildings Article Hybrid AHP-Fuzzy TOPSIS Approach for Selecting Deep Excavation Support System Usama Issa 1, * , Fam Saeed 2,3, * , Yehia Miky 3,4 , Muwaffaq Alqurashi 1 and Emad Osman 5 1 Civil Engineering Department, College of Engineering, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia; m.gourashi@tu.edu.sa 2 Department of Civil and Environmental Engineering, Faculty of Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada 3 Civil Engineering Department, Faculty of Engineering, Aswan University, Aswan 81528, Egypt; yhhassan@kau.edu.sa 4 Geomatics Department, Architecture and Planning Faculty, King Abdulaziz University, Jeddah 21589, Saudi Arabia 5 Civil Engineering Department, Minia University, Minia 61111, Egypt; e_osman@hotmail.com * Correspondence: u.issa@tu.edu.sa (U.I.); ffasaeed@uwaterloo.ca (F.S.) Abstract: This paper introduces and further applies an approach to support the decision makers in construction projects differentiating among a variety of deep excavation supporting systems (DESSs). These kinds of problems include dealing with uncertainty in data, multi-criteria affecting the decision, and multi-alternatives to select one from them. The proposed approach combines the analytic hierarchy process (AHP) with the fuzzy technique for order of preference by similarity to ideal solution (fuzzy TOPSIS) in a multicriteria decision-making (MCDM) model. The MCDM model emphasize the ability to combine expert knowledge, cost calculations, and laboratory test results for soil properties to achieve the scope. The model proved it had a superior ability to deal with the complexity and vague data that are related to construction projects. Furthermore, it was applied to a real case study for a governmental housing project in Egypt. Secant pile walls, sheet pile walls, and soldier piles and lagging are selected and studied as being the most common DESSs and as they satisfy the project requirements. The model utilized four criteria and fourteen comparing factors, including site characteristics, safety, cost, and environmental impacts. Based on the results of the model application on the investigated case study, a decision was reached that using secant piles as a supporting system in this project is mostly preferred. Furthermore, sheet pile wall, and soldier piles and lagging, come next in the ranking order. A sensitivity analysis is carried out to investigate how sensitive the results are to the criteria weights. In addition, the paper discusses in detail the reasons and factors which affect and control the decision-making process. Keywords: construction projects; deep excavation support-system; decision-making; AHP; fuzzy TOPSIS; case study 1. Introduction Casanovas-Rubio et al. [1] defined deep excavation as “an excavation in soil or rock typically more than 4.5 m deep”. These excavation works, especially when constructed in urban areas, require careful design and planning. Additionally, deep excavation supporting systems (DESSs) refer to an engineering solution designed to stabilize excavation sides [2]. DESSs have gained more attention recently due to the increasing demand of housing build- ings and the small available spaces for constructions. Thus, in Egypt, the vertical expansion approach of buildings, instead of horizontal, has been adopted in the construction commu- nity [3]. Furthermore, underground basements have become an essential component of new urban buildings. This is because parking in large cities is mostly serviced by aged and outdated above-grade parking structures that occupy valuable above-ground space [4]. Buildings 2022, 12, 295. https://doi.org/10.3390/buildings12030295 https://www.mdpi.com/journal/buildings