📋 Case Study

Floodplain Bridge Approach Wall Failure Investigation

Catastrophic collapse of 8.5 m cantilever wall after 100-year flood event

🏗️ Project Overview

I-95 bridge approach, South Carolina flood zone

🎯 Challenge

Catastrophic collapse of 8.5 m cantilever wall after 100-year flood event

🔧 Design Approach

Forensic analysis revealed undersized heel slab and absence of key drainage features

📐 Design Diagram

AI-generated project design illustration

📐 Key Calculations

Hydrostatic Uplift Ratio

u/q_bearing

Result: 0.87

Exceeded threshold of 0.75 triggering instability

Effective Stress Loss

σ' = σ − u

Result: −14 kPa (tension)

Induced tensile cracking in stem base

📊 Results

Redesign incorporated 1.5 m keyway, 125 mm gravel drain, and 20% thicker heel slab; validated via physical model testing

💡 Lessons Learned

• •Drainage omission is the leading cause of cantilever wall failures
• •Hydrostatic effects must be modeled as dynamic, not static, loads in flood zones

✅ Key Takeaways

• 1Drainage omission is the leading cause of cantilever wall failures
• 2Hydrostatic effects must be modeled as dynamic, not static, loads in flood zones