Related to Foundation Construction
Case Study: Boston Caisson Construction Water Intrusion (2015)
Project Overview
- Name: Boston Waterfront Development
- Location: Boston, Massachusetts
- Year: 2015
- Project Size: $400 million
- Scope: Construction of large diameter caisson foundations below water table
- Lead Agencies/Contractors: Massachusetts DOT /
Category of the Issue, Problem, or Challenge
- Deep Foundations
- Water Intrusion / Construction Delay
Summary of the Issue, Problem, or Challenge
During caisson excavation, unexpected water inflows caused instability and delayed concrete placement, impacting project schedule and safety.
Root Cause Analysis
| Factor | Details |
| Underestimated Groundwater | Groundwater level and inflow rates underestimated. |
| Inadequate Dewatering | Dewatering system insufficient for excavation depths. |
| Safety Procedures | Lack of contingency planning for water intrusion events. |
Impacts Due to the Issue, Problem, or Challenge
- Construction halt for 6 weeks to implement new dewatering methods
- Increased costs for pumping and stabilization
- Safety hazards from water ingress requiring enhanced protocols
Corrective Actions Taken
- Installed high-capacity well points and pumping systems
- Revised excavation sequencing and implemented contingency plans
- Trained workforce on water hazard awareness and emergency response
Lessons Learned
- Accurate groundwater assessment is crucial for deep excavations
- Robust dewatering plans must be part of foundation design
- Safety protocols must account for water-related risks
Case Study: San Francisco Deep Foundation Drill Shaft Collapse (2020)
Project Overview
- Name: San Francisco Bay Bridge Eastern Span Replacement
- Location: San Francisco, California
- Year: 2020
- Project Size: $6.4 billion (overall project)
- Scope: Installation of drilled shafts and pile foundations for bridge towers
- Lead Agencies/Contractors: Caltrans /
Category of the Issue, Problem, or Challenge
- Deep Foundations
- Structural Failure During Construction
Summary of the Issue, Problem, or Challenge
A drilled shaft partially collapsed during excavation due to unexpected soil instability and inadequate temporary casing support, causing a work stoppage and redesign of foundation support.
Root Cause Analysis
| Factor | Details |
| Soil Instability | Loose and saturated soils near shaft excavation were underestimated. |
| Inadequate Temporary Support | Insufficient casing and bracing to prevent collapse during drilling. |
| Monitoring Deficiency | Lack of real-time monitoring to detect early shaft wall movements. |
Impacts Due to the Issue, Problem, or Challenge
- Work halted for 8 weeks for remediation and redesign
- Increased costs for additional casing and ground improvement
- Schedule impact on overall bridge tower erection timeline
Corrective Actions Taken
- Installed heavy-duty steel casing for all shafts in unstable soils
- Implemented ground freezing and jet grouting to stabilize soil prior to drilling
- Introduced continuous instrumentation (inclinometers, piezometers) for real-time monitoring
Lessons Learned
- Temporary support systems must be robust in soft or saturated soils
- Pre-construction soil characterization should include stability analysis for shaft excavation
- Continuous monitoring is critical for early detection of failures
Case Study: Miami Deep Foundation Pile Driving Blow Count Anomalies (2018)
Project Overview
- Name: Miami International Airport Expansion
- Location: Miami, Florida
- Year: 2018
- Project Size: $2 billion
- Scope: Driven pile foundations for terminal expansion
- Lead Agencies/Contractors: Miami-Dade Aviation Department
Category of the Issue, Problem, or Challenge
- Deep Foundations
- Installation Quality Issues
Summary of the Issue, Problem, or Challenge
During pile driving, blow counts indicated inconsistent soil resistance, suggesting piles were driven into weaker layers than anticipated, leading to partial pile refusal and questionable bearing capacity.
Root Cause Analysis
| Factor | Details |
| Soil Variability | Unrecognized variations in subsurface stratigraphy. |
| Pile Installation | Use of inappropriate hammer size and driving technique. |
| QA/QC Insufficiency | Lack of frequent dynamic testing and verification during driving. |
Impacts Due to the Issue, Problem, or Challenge
- Delays due to re-driving piles and additional testing
- Cost increases for supplemental foundation elements
- Risk of future settlement and structural issues
Corrective Actions Taken
- Performed additional borings to refine soil profile
- Adjusted hammer size and driving procedures per soil conditions
- Increased dynamic testing frequency and real-time monitoring
Lessons Learned
- Detailed soil profiling and variability assessment are essential
- Installation methods must adapt dynamically to field conditions
- Real-time QA/QC during pile driving prevents foundation underperformance
Case Study: Denver Caisson Installation Delay Due to Rock Obstructions (2019)
Project Overview
- Name: Denver Light Rail Extension
- Location: Denver, Colorado
- Year: 2019
- Project Size: $700 million
- Scope: Caisson foundations for elevated rail structures
- Lead Agencies/Contractors: Regional Transportation District /
Category of the Issue, Problem, or Challenge
- Deep Foundations
- Differing Site Conditions / Delay
Summary of the Issue, Problem, or Challenge
Unexpected large rock obstructions encountered during caisson drilling caused equipment damage and delays in foundation installation.
Root Cause Analysis
| Factor | Details |
| Insufficient Site Investigation | Existing geotechnical data failed to identify rock layers. |
| Equipment Selection | Drilling equipment was not suitable for hard rock conditions. |
| Project Planning | Contingency plans for rock obstructions were inadequate. |
Impacts Due to the Issue, Problem, or Challenge
- Project delays of 2 months due to drilling equipment repairs and method changes
- Cost overruns for additional rock excavation and specialized equipment rental
- Risk of foundation schedule impacting overall rail extension
Corrective Actions Taken
- Engaged specialty rock drilling subcontractors with appropriate equipment
- Revised geotechnical investigation procedures to include seismic refraction and geophysical surveys
- Developed detailed contingency plans for rock encounters
Lessons Learned
- Comprehensive subsurface investigation must anticipate difficult rock conditions
- Equipment and method selection must be matched to site geology
- Contingency planning reduces schedule and cost risks
Case Study: New York City Pile Cap Cracking and Spalling (2019)
Project Overview
- Name: East River Bridge Approach Improvements
- Location: New York, New York
- Year: 2019
- Project Size: $350 million
- Scope: Construction of pile-supported bridge approach structures, including pile caps and foundations
- Lead Agencies/Contractors: NYC DOT /
Category of the Issue, Problem, or Challenge
- Deep Foundations
- Structural Concrete
- Materials Quality
Summary of the Issue, Problem, or Challenge
During formwork removal, several pile caps exhibited extensive cracking and surface spalling, compromising their structural integrity and requiring repair.
Root Cause Analysis
| Factor | Details |
| Poor Concrete Mix Design | Improper water-cement ratio and low early strength. |
| Inadequate Curing | Lack of proper moisture curing led to surface drying cracks. |
| Formwork Removal Timing | Early removal caused thermal and shrinkage stresses. |
| Quality Control Deficiencies | Inconsistent batching and placement oversight. |
Impacts Due to the Issue, Problem, or Challenge
- Repair with epoxy injection and patching delayed progress
- Increased project costs and re-inspection requirements
- Risk of structural weakness until repairs completed
Corrective Actions Taken
- Revised concrete mix design with higher early strength
- Implemented strict curing protocols including wet curing and curing compounds
- Adjusted formwork removal schedule to recommended times
- Enhanced QA/QC for concrete batching and placement
Lessons Learned
- Proper curing and timing are critical to pile cap durability
- Concrete mix must be closely monitored for strength and consistency
- Early detection of cracking can prevent costly repairs
Case Study: Dallas Pile Cap Settlement and Misalignment (2020)
Project Overview
- Name: Dallas Urban Light Rail Expansion
- Location: Dallas, Texas
- Year: 2020
- Project Size: $480 million
- Scope: Pile-supported foundations with pile caps for elevated rail guideways
- Lead Agencies/Contractors: Dallas Area Rapid Transit (DART) /
Category of the Issue, Problem, or Challenge
- Deep Foundations
- Geotechnical / Settlement
- Construction Quality
Summary of the Issue, Problem, or Challenge
After pile cap placement, several caps settled unevenly due to insufficient pile embedment lengths and soil variability, causing misalignment of the superstructure elements.
Root Cause Analysis
| Factor | Details |
| Inadequate Pile Length | Piles were not driven to required depth for load-bearing. |
| Variable Soil Conditions | Presence of soft layers not fully accounted for. |
| Poor Site Supervision | Lack of continuous monitoring during pile driving. |
Impacts Due to the Issue, Problem, or Challenge
- Realignment of piles and caps necessary before proceeding
- Project delay of 7 weeks and added foundation costs
- Potential long-term structural concerns if unaddressed
Corrective Actions Taken
- Reassessment of soil conditions and revised pile length specifications
- Increased pile driving monitoring with load tests
- Improved construction oversight and communication protocols
Lessons Learned
- Adequate pile embedment is essential for foundation stability
- Soil conditions must be rigorously tested and monitored
- Construction supervision directly affects foundation quality
Case Study: Los Angeles Pile Cap Formwork Collapse (2017)
Project Overview
- Name: Los Angeles Regional Connector Transit Project
- Location: Los Angeles, California
- Year: 2017
- Project Size: $1.5 billion
- Scope: Construction of deep foundations with pile caps supporting transit tunnels
- Lead Agencies/Contractors: LA Metro /
Category of the Issue, Problem, or Challenge
- Deep Foundations
- Construction Safety
- Formwork Failure
Summary of the Issue, Problem, or Challenge
During concrete placement, the formwork for a large pile cap collapsed, causing concrete spillage and endangering workers.
Root Cause Analysis
| Factor | Details |
| Insufficient Formwork Design | Formwork not adequately designed for concrete pressure loads. |
| Poor Assembly and Bracing | Inadequate bracing and support led to instability. |
| Lack of Safety Checks | Incomplete inspection prior to concrete pour. |
Impacts Due to the Issue, Problem, or Challenge
- Injury to workers and emergency response
- Significant construction delay of 4 weeks for cleanup and rebuild
- Increased costs due to replacement of materials and safety reviews
Corrective Actions Taken
- Redesign of formwork with engineering review and peer checks
- Implementation of mandatory safety inspections before pours
- Training programs focused on formwork assembly and safety
Lessons Learned
- Formwork must be engineered and inspected to handle construction loads
- Safety protocols are critical during concrete placement
- Worker safety must always be prioritized through inspections and training
Case Study: Chicago Pile Cap Concrete Voids Detected (2018)
Project Overview
- Name: Chicago Riverwalk Expansion
- Location: Chicago, Illinois
- Year: 2018
- Project Size: $220 million
- Scope: Construction of pile-supported foundations with large pile caps for pedestrian bridges
- Lead Agencies/Contractors: Chicago DOT /
Category of the Issue, Problem, or Challenge
- Deep Foundations
- Concrete Quality
- Structural Deficiency
Summary of the Issue, Problem, or Challenge
During routine non-destructive testing (ultrasonic and ground-penetrating radar), multiple voids and honeycombing were detected inside several pile caps, risking structural integrity.
Root Cause Analysis
| Factor | Details |
| Inadequate Concrete Vibration | Poor consolidation of concrete during placement, causing voids. |
| Substandard Material Quality | Use of inconsistent aggregate sizes and water-cement ratios. |
| Insufficient Supervision | Lack of experienced personnel overseeing concrete placement. |
Impacts Due to the Issue, Problem, or Challenge
- Delays due to repair and additional testing
- Increased costs from patching and possible re-pours
- Risk of compromised load transfer to piles
Corrective Actions Taken
- Implemented stricter concrete placement and vibration procedures
- Enhanced training for site supervisors on concrete quality control
- Use of higher-grade materials and tighter batching controls
Lessons Learned
- Proper vibration during concrete pouring is critical to avoid voids
- Quality control of materials directly affects pile cap performance
- Early detection through NDT methods can prevent larger failures
Case Study: Atlanta Pile Cap Reinforcement Misplacement (2017)
Project Overview
- Name: Atlanta Highway Interchange Upgrade
- Location: Atlanta, Georgia
- Year: 2017
- Project Size: $400 million
- Scope: Construction of deep foundation pile caps for elevated highway structures
- Lead Agencies/Contractors: Georgia DOT /
Category of the Issue, Problem, or Challenge
- Deep Foundations
- Structural Rebar Errors
- Construction Quality
Summary of the Issue, Problem, or Challenge
Post-placement X-ray and visual inspections revealed that reinforcement cages in several pile caps were incorrectly positioned, reducing structural capacity.
Root Cause Analysis
| Factor | Details |
| Improper Rebar Placement | Reinforcement cages were misaligned and insufficiently supported during concrete placement. |
| Poor QA/QC Procedures | Lack of thorough inspection before concrete pour. |
| Communication Breakdown | Design changes not effectively communicated to field crews. |
Impacts Due to the Issue, Problem, or Challenge
- Structural rework needed with partial demolition and re-pouring
- Project delays of 3-4 weeks and increased costs
- Potential safety concerns pending repair
Corrective Actions Taken
- Strengthened reinforcement inspection protocols before pours
- Enhanced communication channels between design and construction teams
- Training sessions for field crews on proper reinforcement placement
Lessons Learned
- Accurate rebar placement is critical to pile cap strength
- Inspections must be done immediately prior to concrete pouring
- Communication of design details must be clear and documented
Case Study: Denver Pile Cap Over-Excavation (2020)
Project Overview
- Name: Denver Light Rail Expansion
- Location: Denver, Colorado
- Year: 2020
- Project Size: $500 million
- Scope: Pile foundation installation with pile caps for elevated rail structures
- Lead Agencies/Contractors: RTD Denver /
Category of the Issue, Problem, or Challenge
- Deep Foundations
- Earthwork / Excavation
- Construction Error
Summary of the Issue, Problem, or Challenge
Over-excavation beneath several pile caps was discovered after concrete placement, causing voids and undermining support.
Root Cause Analysis
| Factor | Details |
| Excavation Error | Miscommunication on excavation limits led to removal beyond design depth. |
| Inadequate Site Survey | Lack of updated surveys during excavation progress. |
| Poor Supervision | Insufficient monitoring of excavation boundaries. |
Impacts Due to the Issue, Problem, or Challenge
- Delays for underpinning and additional concrete placement
- Increased costs for material and labor to repair voids
- Risk of uneven load distribution and structural settlement
Corrective Actions Taken
- Improved excavation surveying with real-time monitoring tools
- Enhanced field supervision and communication protocols
- Revised excavation plans with more conservative limits and buffers
Lessons Learned
- Precise control of excavation limits is vital to foundation integrity
- Field surveys should be frequent and real-time
- Clear communication among site teams prevents costly mistakes