Related to Retaining Wall Construction
Case Study: San Diego Retaining Wall Drainage Failure (2019)
Project Overview
- Name: San Diego Coastal Highway Improvement
- Location: San Diego, California
- Year: 2019
- Project Size: $500 million
- Scope: Segmental concrete retaining walls for coastal highway embankment
- Lead Agencies/Contractors: California DOT /
Category of the Issue, Problem, or Challenge
- Retaining Walls
- Drainage and Hydrostatic Pressure
Summary of the Issue, Problem, or Challenge
During construction, water buildup behind the retaining walls caused hydrostatic pressure that led to wall bulging and localized cracking.
Root Cause Analysis
| Factor | Details |
| Inadequate Drainage | Drainage systems behind walls were improperly designed/installed. |
| High Groundwater Table | Unexpectedly high groundwater levels due to recent heavy rains. |
| Delayed Drain Installation | Drain pipes and gravel backfill installation were behind schedule. |
Impacts Due to the Issue, Problem, or Challenge
- Temporary work stoppage to install drainage improvements
- Increased costs and schedule delays for remediation
- Potential long-term durability risks if uncorrected
Corrective Actions Taken
- Accelerated installation of drainage systems including perforated pipe and gravel backfill
- Added weep holes and relief joints in wall design
- Adjusted construction schedule to account for drainage installation before backfill
Lessons Learned
- Effective drainage is critical to retaining wall stability and longevity
- Groundwater conditions must be accurately assessed and planned for in construction
- Construction sequencing must ensure drainage is in place before backfilling
Case Study: Atlanta Highway Retaining Wall Settlement and Cracking (2020)
Project Overview
- Name: I-285 Perimeter Highway Widening
- Location: Atlanta, Georgia
- Year: 2020
- Project Size: $520 million
- Scope: Construction of reinforced concrete retaining walls along highway embankments
- Lead Agencies/Contractors: Georgia DOT /
Category of the Issue, Problem, or Challenge
- Retaining Walls
- Geotechnical / Settlement
Summary of the Issue, Problem, or Challenge
Shortly after construction, portions of the retaining walls exhibited differential settlement and cracking due to variable subsurface soil conditions and inadequate foundation preparation.
Root Cause Analysis
| Factor | Details |
| Variable Subsurface Soils | Presence of compressible fill and organic soils beneath footings. |
| Inadequate Soil Improvement | Lack of thorough soil stabilization prior to wall construction. |
| Poor Quality Control | Insufficient inspection during foundation preparation phases. |
Impacts Due to the Issue, Problem, or Challenge
- Repairs including underpinning and crack injection required
- Delays to overall project schedule by 5 weeks
- Additional costs and reduced confidence in wall performance
Corrective Actions Taken
- Enhanced geotechnical investigations for future walls
- Soil stabilization through controlled densification and lime treatment
- Implementation of stricter QC protocols for foundation prep
Lessons Learned
- Comprehensive soil characterization is essential before wall construction
- Quality control during foundation works prevents settlement issues
- Early detection and monitoring of wall movements mitigate damage
Case Study: Boston Retaining Wall Overturning During Backfill (2019)
Project Overview
- Name: Boston Central Artery Tunnel Expansion
- Location: Boston, Massachusetts
- Year: 2019
- Project Size: $1.2 billion
- Scope: Construction of massive concrete retaining walls as part of tunnel ventilation shafts
- Lead Agencies/Contractors: Massachusetts DOT /
Category of the Issue, Problem, or Challenge
- Retaining Walls
- Structural Overturning
Summary of the Issue, Problem, or Challenge
During backfilling, a retaining wall segment tilted and partially overturned due to underestimated lateral earth pressures and insufficient anchorage.
Root Cause Analysis
| Factor | Details |
| Underestimated Earth Pressure | Design did not fully account for construction-stage pressures. |
| Insufficient Anchorage | Tiebacks and anchors were undersized and inadequately installed. |
| Backfilling Sequence | Rapid placement of heavy fill before wall stabilization. |
Impacts Due to the Issue, Problem, or Challenge
- Emergency wall stabilization and anchorage installation
- Project delays of approximately 8 weeks
- Cost increases due to rework and additional materials
Corrective Actions Taken
- Redesign of anchorage systems to handle increased loads
- Revised backfilling procedures to be staged and monitored
- Increased inspection frequency during critical construction phases
Lessons Learned
- Temporary loads during construction may exceed design assumptions
- Proper anchorage design and installation are vital for wall stability
- Backfilling must be controlled and sequenced to reduce risks
Case Study: Miami Retaining Wall Water Infiltration and Erosion (2018)
Project Overview
- Name: Miami Coastal Roadway Improvement
- Location: Miami, Florida
- Year: 2018
- Project Size: $280 million
- Scope: Construction of reinforced concrete and gabion retaining walls along coastal highway
- Lead Agencies/Contractors: Florida DOT /
Category of the Issue, Problem, or Challenge
- Retaining Walls
- Drainage and Erosion
Summary of the Issue, Problem, or Challenge
Water infiltration behind retaining walls caused erosion of backfill soils, resulting in voids and localized wall deformation during construction.
Root Cause Analysis
| Factor | Details |
| Poor Drainage Design | Insufficient provisions for surface water runoff and subsurface drainage. |
| Heavy Rainfall | Unusually intense storms during construction accelerated erosion. |
| Delay in Drainage Installation | Drainage pipes and filter materials installed late in sequence. |
Impacts Due to the Issue, Problem, or Challenge
- Soil erosion led to localized wall settlement and cracking
- Work stoppage for erosion repair and drainage system installation
- Added project costs and schedule impacts
Corrective Actions Taken
- Accelerated drainage installation and added temporary erosion controls
- Revised design to incorporate enhanced drainage layers and geotextiles
- Scheduled construction activities around weather forecasts to minimize exposure
Lessons Learned
- Drainage systems must be planned and installed early to prevent erosion
- Temporary erosion controls are critical in storm-prone regions
- Construction scheduling should consider weather impacts on retaining walls
Case Study: Seattle Retaining Wall Sliding Failure (2018)
Project Overview
- Name: Seattle Highway 99 Tunnel Access Improvements
- Location: Seattle, Washington
- Year: 2018
- Project Size: $620 million
- Scope: Construction of reinforced concrete retaining walls for tunnel approach ramps
- Lead Agencies/Contractors: Washington State DOT /
Category of the Issue, Problem, or Challenge
- Retaining Walls
- Geotechnical / Sliding Failure
Summary of the Issue, Problem, or Challenge
A segment of the retaining wall slid laterally during backfilling operations due to inadequate embedment depth and underestimated soil lateral pressure.
Root Cause Analysis
| Factor | Details |
| Insufficient Embedment | Retaining wall foundations did not reach stable soil strata. |
| Underestimated Soil Pressure | Design did not fully account for active and construction-stage pressures. |
| Rapid Backfilling | Backfill was placed too quickly, increasing lateral loads abruptly. |
Impacts Due to the Issue, Problem, or Challenge
- Emergency stabilization measures and re-driving of wall foundations
- Project delays of 6 weeks due to remediation efforts
- Increased costs from additional foundation work and labor
Corrective Actions Taken
- Revised embedment depth requirements and design parameters
- Modified backfill sequencing with staged placement and compaction
- Enhanced geotechnical monitoring during construction
Lessons Learned
- Embedment depths must be verified against actual soil conditions
- Construction-stage lateral pressures should be conservatively estimated
- Backfill operations need to be carefully staged to avoid excessive loads
Case Study: Houston Retaining Wall Foundation Failure (2016)
Project Overview
- Name: Houston Beltway Expansion
- Location: Houston, Texas
- Year: 2016
- Project Size: $700 million
- Scope: Construction of large reinforced concrete retaining walls for highway embankments
- Lead Agencies/Contractors: Texas DOT /
Category of the Issue, Problem, or Challenge
- Retaining Walls
- Foundation Failure
Summary of the Issue, Problem, or Challenge
Retaining wall footings experienced excessive settlement and tilting shortly after placement, compromising wall alignment and structural integrity.
Root Cause Analysis
| Factor | Details |
| Weak Subsoil | Presence of soft clay and peat layers not fully accounted for in design. |
| Inadequate Soil Improvement | Lack of sufficient ground treatment or deep foundation support. |
| Poor Construction QA | Insufficient inspection of footing excavation and compaction. |
Impacts Due to the Issue, Problem, or Challenge
- Repair and underpinning required, delaying construction schedule
- Added costs for foundation remediation and additional testing
- Potential long-term durability concerns
Corrective Actions Taken
- Implementation of deep soil mixing and piling under affected footings
- Increased geotechnical investigations for future footings
- Improved QA/QC during foundation excavation and compaction
Lessons Learned
- Detailed geotechnical profiling is essential for foundation design
- Weak soils require ground improvement or deep foundations
- Rigorous QA during excavation avoids foundation failures
Case Study: San Francisco Retaining Wall Drainage Failure (2017)
Project Overview
- Name: San Francisco Bay Bridge Retrofit
- Location: San Francisco, California
- Year: 2017
- Project Size: $1.5 billion
- Scope: Construction of segmental concrete retaining walls to support bridge approach ramps
- Lead Agencies/Contractors: Caltrans /
Category of the Issue, Problem, or Challenge
- Retaining Walls
- Drainage / Hydrostatic Pressure
Summary of the Issue, Problem, or Challenge
Water accumulation behind retaining walls during construction caused hydrostatic pressure buildup, leading to bulging and cracking of wall panels.
Root Cause Analysis
| Factor | Details |
| Poor Drainage Design | Drainage systems were inadequate and installed late. |
| High Groundwater Table | Unexpected groundwater fluctuations after heavy rains. |
| Delayed Drain Installation | Drainage pipes and gravel backfill installation behind schedule. |
Impacts Due to the Issue, Problem, or Challenge
- Work stoppage for drainage retrofit and wall repair
- Cost overruns due to added drainage and repair work
- Project delays of 4-5 weeks
Corrective Actions Taken
- Accelerated drainage installation with improved materials
- Added weep holes and pressure relief joints in wall design
- Revised construction schedule to prioritize drainage installation
Lessons Learned
- Drainage must be incorporated early to prevent hydrostatic pressures
- Groundwater conditions must be monitored and planned for during construction
- Construction sequencing impacts wall stability significantly