Location
Arlington, Virginia
Date
15 Aug 2008, 11:00am - 12:30pm
Abstract
One of the largest development projects in the City of Beirut involved the excavation of an area of 14,000m2 down to a depth of 30m below street level. The site is in an urban area and bound by major traffic arteries and a multi-storey office building. The shoring approach adopted for the excavation boundary walls consisted of a hybrid flexible system with multiple rows of pre-stressed anchors, followed by rows of passive nails at varying spacings and lengths. A reinforced shotcrete facing was provided across the full depth of the excavation. Upon reaching the final excavation grades across the whole site, significant movements were recorded along one of the site boundaries (approximately 120m long) adjacent to the main traffic artery. These deformations at the face were accompanied by longitudinal cracks up to 20m away from the excavation boundary along the main road, with differential downward movements on the order of 5 to 10 centimeters. The pattern of deformation and location of cracks suggested an impending deep seated failure. This resulted in the closure of all adjacent roads to traffic and emergency backfilling measures to shore the compromised wall. At this stage third party forensic failure analyses were initiated in which we were involved. In this paper, the background related to site-specific sub-surface characterization efforts, along with design choices and options adopted are be presented and discussed. Post-movement analyses and monitoring results are used to identify the reasons behind the failure. Finally, remedial measures implemented are described and discussed in detail along with lessons learned.
Department(s)
Civil, Architectural and Environmental Engineering
Meeting Name
6th Conference of the International Conference on Case Histories in Geotechnical Engineering
Publisher
Missouri University of Science and Technology
Document Version
Final Version
Rights
© 2008 Missouri University of Science and Technology, All rights reserved.
Creative Commons Licensing
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Document Type
Article - Conference proceedings
File Type
text
Language
English
Recommended Citation
Sadek, Salah, "Failure of a Hybrid Flexible Shoring System for a 30m Excavation: Exploration of Causes and Remedial Measures" (2008). International Conference on Case Histories in Geotechnical Engineering. 12.
https://scholarsmine.mst.edu/icchge/6icchge/session05/12
Failure of a Hybrid Flexible Shoring System for a 30m Excavation: Exploration of Causes and Remedial Measures
Arlington, Virginia
One of the largest development projects in the City of Beirut involved the excavation of an area of 14,000m2 down to a depth of 30m below street level. The site is in an urban area and bound by major traffic arteries and a multi-storey office building. The shoring approach adopted for the excavation boundary walls consisted of a hybrid flexible system with multiple rows of pre-stressed anchors, followed by rows of passive nails at varying spacings and lengths. A reinforced shotcrete facing was provided across the full depth of the excavation. Upon reaching the final excavation grades across the whole site, significant movements were recorded along one of the site boundaries (approximately 120m long) adjacent to the main traffic artery. These deformations at the face were accompanied by longitudinal cracks up to 20m away from the excavation boundary along the main road, with differential downward movements on the order of 5 to 10 centimeters. The pattern of deformation and location of cracks suggested an impending deep seated failure. This resulted in the closure of all adjacent roads to traffic and emergency backfilling measures to shore the compromised wall. At this stage third party forensic failure analyses were initiated in which we were involved. In this paper, the background related to site-specific sub-surface characterization efforts, along with design choices and options adopted are be presented and discussed. Post-movement analyses and monitoring results are used to identify the reasons behind the failure. Finally, remedial measures implemented are described and discussed in detail along with lessons learned.
