Beyond the Building Code — Compliance and Forensic Failure Analysis of Retaining Walls

Brian Eubanks; Garrett Ryan; Noel Janacek; Joseph Roberts

doi:10.51501/jotnafe.v43i1.1004

Authors

Brian Eubanks Paragon Structural Engineering https://orcid.org/0009-0009-6560-1388
Garrett Ryan Paragon Structural Engineering, LTD. https://orcid.org/0009-0009-0051-8647
Noel Janacek https://orcid.org/0009-0006-7734-2780
Joseph Roberts https://orcid.org/0009-0004-4797-4598

DOI:

https://doi.org/10.51501/jotnafe.v43i1.1004

Keywords:

Retaining Wall Design, Retaining Wall Failure, Analysis, Structural, Slope Management, Mass Walls, Gravity Walls, Cantilever Walls, Pile Walls, Mechanically-Stabilized Walls, MSE, IRC, IBC, Soil Force, Geotechnical, Construction Oversight, Internal Stability, Local Stability, Global Stability, Factors of Safety, Design-Compliance, Active Pressure, At-Rest Pressure, Compliance Analysis, Cosmetic Distress, External Stability, Failure Analysis, Functional Distress, MAss/Gravity Retaining Wall, Mechanically Stabilized Earth, Passive Pressure, Reinforced Zone, Safety Factor, Scarp

Abstract

Retaining walls are structural walls that serve to laterally restrain earth at a desired elevation in order to shape the topography of a site by managing slopes and creating usable spaces for development and construction of the built environment. Common types of retaining walls include mass/gravity walls, cantilevered walls, pile walls, and mechanically stabilized earth (MSE) walls. The design and construction of such walls are not well covered in the International Residential Code (IRC) and/or the International Building Code (IBC). As structural elements subjected to applied soil forces, retaining walls cross engineering disciplines, and a successful design often requires careful coordination between geotechnical engineers and structural engineers. In addition, successful construction often requires field verification of expected geotechnical parameters and construction oversight to ensure compliance with design specifications. This paper will explore the different stability checks (e.g., internal stability, local stability, and global stability), as well as different factors of safety, required for the proper design of a retaining wall. In addition, it will use real-world case studies to explore failures of various retaining walls, highlighting differences between compliance analysis and forensic failure analysis to identify the root cause of the failure and the responsible party.

Author Biographies

Brian Eubanks, Paragon Structural Engineering

Brian C. Eubanks, MSCE, PE, D-IBFES, DFE is the founder and Principal Structural Engineer of Paragon Structural Engineering, LTD, (PSE) a structural design and forensic investigation firm based in Plano, Texas. Mr. Eubanks leads a technical staff comprising professional engineers, graduate engineers, project managers, and field technicians in the structural design and forensic investigation of planned and existing structures. His structural design services include analysis and engineering of large, custom single-family residences, multi-family apartment/condominium complexes, low-rise commercial facilities, warehouses and ancillary structures (retaining walls, screen walls, and swimming pools). He also performs construction phase observations of the aforementioned structural systems to verify design compliance. Mr. Eubanks has performed engineering designs for thousands of residential and low-rise commercial structures as well as hundreds of retaining walls, screen walls, and pools. His forensic services include investigations and assessments regarding the design, construction, and standard of care associated with planned improvements and the built environment involving geotechnical engineering, soil-structure interactions, structural systems, civil sitework, exterior cladding systems, building envelopes (moisture and thermal), peril damage, and personal injury. Geotechnical engineering assessments include claims related to sampling/testing of expansive soils, soil design parameters, global stability analysis, and recommendations for foundations, retaining walls, and site development. Soil-structure interaction assessments include claims relating to design, construction, historic/current site effects, and moisture source influences. Structural system assessments include claims relating to design and construction issues as well as evaluations of applicable performance standards. Civil sitework assessments include claims related to grading/drainage conditions, exterior flatwork elements, accessibility, egress, and pavement systems. Exterior cladding system assessments include claims related to design, installation, integration, performance, and warranty standards. Building envelope assessments include claims related to roof coverings, veneers, flashing, and water-resistive barriers, air infiltration/exfiltration, insulation, and attic ventilation. Peril damage assessments include claims related to cause, origin, and extent of wind damage, hurricane damage, tornado damage, lightning strikes, hail, flood, earthquakes, explosions, fire damage, and vehicle-structure collisions. Mr. Eubanks performs site investigations and devises protocols for site-specific investigative strategies that may include relative elevation surveys, geotechnical testing, geophysical resistivity surveys, ground-penetrating radar surveys, groundwater monitoring, water chemical analysis, test pit excavations, material strength tests, water application/infiltration tests, cladding anchorage surveys, moisture content measurements, infrared thermography, and borescope observations. His typical projects include single-family residences, multi-family apartment/condominium complexes, commercial facilities, warehouses, institutional facilities, industrial facilities, as well as ancillary structures such as retaining walls, screen walls, and swimming pools. Mr. Eubanks has performed thousands of forensic investigations, and he has authored thousands of expert reports for use in mediation, arbitration, and/or litigation. In addition, he has provided expert witness testimony in dozens of mediations, arbitrations, and court cases. Mr. Eubanks received his Bachelor and Master of Science in Civil Engineering from Georgia Institute of Technology and is a Licensed Professional Engineer in 15 states, a Licensed Structural Engineer, a Senior Board-Certified Diplomate in Forensic Engineering by the National Academy of Forensic Engineers, and a Diplomate of the International Board of Forensic Engineering Sciences. He is Building Envelope Trained, and Certified by the Building Envelope Science Institute, is a Certified Windstorm Inspector by the Texas Department of Insurance, and a Model Law Engineer with the National Council of Examiners for Engineering and Surveying (NCEES). Mr. Eubanks also serves as a member of the American Concrete Institute’s Design of Slabs-on-Ground Committee (360), the American Society of Civil Engineers Committee on Forensic Investigations, the Residential Foundation Investigation and Design Subcommittee (ASCE-Texas Section), and the Residential Foundation Evaluation and Repair Subcommittee (ASCE – Texas Section), the Post-Tensioning Institute’s Slab-on-Ground Committee (DC-10), Structural (DC-10A) and Construction/Maintenance (DC-10D) Subcommittees, the ASTM International Committees on Concrete Aggregates (C-09), Forensic Engineering (E-58), Soil and Rock (D-18), and Wood (D-07), the Dallas Builders Association Education Committee, International Code Council’s North Central Texas Council of Governments, the Texas Association of Builders Attorney Council / Legal Affairs Committee and Codes & Standards Committee and the Construction Research Advisory Committee at the University of Texas at Arlington. Additionally, he has served as an Arbitrator, a Technical Paper Reviewer, is designated as a Technical Expert by the Texas Board of Professional Engineers, and on the Board of Trustees for Prestonwood Christian Academy as the Development Committee Chair. Mr. Eubanks aims to educate with regard to soil-structure interaction, the design, performance, and evaluation of structural systems, the evaluations of building envelopes, causes and origins of damage to new and existing structures, and remedial solutions.

Garrett Ryan, Paragon Structural Engineering, LTD.

Garrett T. Ryan, PE, DFE is an Associate Principal Structural Engineer for Paragon Structural Engineering, LTD. (PSE), a structural design and forensic investigation firm based in Plano, Texas. Mr. Ryan holds a B.S. degree in Architectural (Structural) Engineering from the University of Texas in Austin. Mr. Ryan is a Licensed Professional Engineer in 7 states, is a Board-Certified Diplomate in Forensic Engineering by the National Academy of Forensic Engineers, is Building Envelope Trained and Certified by the Building Envelope Science Institute, is a Certified Windstorm Inspector by the Texas Department of Insurance and is also a Model Law Engineer with the National Council of Examiners for Engineering and Surveying (NCEES). Mr. Ryan currently has over 16 years of experience leading technical staff in the structural design and forensic investigation of planned and existing structures. Mr. Ryan’s forensic expertise includes building envelopes, soil-structure interactions, performance of structural systems, and determination of cause origin, and extent of peril damage. Mr. Ryan has performed thousands of forensic investigations, and he has authored hundreds of expert reports for use in mediation, arbitration, and/or litigation. Mr. Ryan has performed dozens of presentations and private training sessions to educate builders with regard to construction and performance of building envelopes.

References

International Code Council, International Residential Code (IRC), 2024 ed. Falls Church, VA, USA: International Code Council, 2024.

International Code Council, International Building Code (IBC), 2024 ed. Falls Church, VA, USA: International Code Council, 2024.

B. M. Das, Principles of Foundation Engineering, 6th ed. Stamford, CT, USA: Cengage Learning, 2007.

U.S. Department of Agriculture, Natural Resources Conservation Service, “Web Soil Survey.” [Online]. Available: https://websoilsurvey.nrcs.usda.gov/app/

American Association of State Highway and Transportation Officials (AASHTO), AASHTO LRFD Bridge Design Specifications, 10th ed. Washington, DC, USA: AASHTO, 2024.

National Concrete Masonry Association, Design Manual for Segmental Retaining Walls, 3rd ed., 5th printing. Herndon, VA, USA: National Concrete Masonry Association, Jan. 2012.

L. Highland and P. Bobrowsky, The Landslide Handbook: A Guide to Understanding Landslides. Reston, VA, USA: U.S. Geological Survey, Nov. 15, 2008.

Google, “Street View image of MSE retaining wall post-failure,” Apr. 2019. [Online]. Available: https://maps.google.com

K. Terzaghi, R. B. Peck, and G. Mesri, Soil Mechanics in Engineering Practice, 3rd ed. New York, NY, USA: John Wiley & Sons, 1996.

S. G. Wright, J. G. Zornberg, and J. E. Aguettant, “The Fully Softened Shear Strength of High Plasticity Clays,” Feb. 2007.