07 - Stress Distribution & Settlement Continued.pdf

# 07 - Stress Distribution & Settlement Continued.pdf -...

This preview shows pages 1–15. Sign up to view the full content.

Daniel Rosenbalm, Ph.D., P.E. Geotechnical Services Manager CEE 452 Foundations

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Components of Settlement Volume Change (Compression) 1-Dimensional consolidation, d c Due to pore water pressure dissipation (“drained” settlement) Distortion (Shear) Undrained settlement, d d Lateral spreading c d d d d
Settlement Computation Footings on a uniform layer of sand Elasticity theory Immediate or distortion settlement Footings on clay Elasticity theory for undrained distortion (shear) settlement Consolidation theory for drained settlement (volume change)

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Settlement Calculation on Clays
Consolidation Settlement Using Elastic Stresses Classical Approach Consolidation settlement of cohesive soil layer at depth beneath footing Gets added to immediate (undrained) settlement P Gravel Normally Consolidated Clay Rock

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Consolidation Settlement Using Elastic Stresses 1. Evaluate initial vertical stress Geostatic stress, s z0 (plus any existing building loads) 2. Calculate vertical stress change at representative points using theory of elasticity Ds z 3. Calculate final vertical stress 4. Calculate vertical strain and settlement at center line due to Ds z using consolidation equations 5. Adjust for foundation rigidity
Consolidation Settlement 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 10 100 1000 C r C c s c (s z ) 0 (s z ) f e s v r c = S log + log C r H 1+ e o C c H 1+ e c s c (s z ) o (s z ) f s c

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Adjustment for Foundation Rigidity r = r c x r where: r c = consolidation settlement r = rigidity factor (r < 1)
Rigidity Factor, r Perfectly flexible load, e.g. Steel tanks, earth fill: r = 1 Perfectly rigid foundation, e.g. Concrete footing: r = 0.85 Intermediate foundations, e.g. Mat foundations: r = 0.9 Note: DO NOT use the 1H:2V projection method for stress increment with this approach

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Reason for Flexibility Factor Infinite Stresses Under Rigid Corners