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Micropile Wall Supporting a Complex Environmental Excavation
Mark Spence, P. Eng., Matthew Janes, P.Eng.
ISM 2014, Krakow, Poland
Victoria, BC, Canada
Presentation Outline • Site Intro & Problem Definition • Project Objectives • Geometry and Geotechnique • Solution • Design and Analysis • Construction
Site Intro & Problem Definition
Project Objectives
• Excavation and disposal of contaminated soils
• Leachate collection system • Impervious barrier to prevent further
contamination • Minimum site impact • Restoration to natural setting • Enable Phase II remediation
Geometry and Geotechnique
Geometry and Geotechnique
• 34 Environmental boreholes, zero geotechnical information
• Based on experience… Upper silts: unsaturated,
N = 10 – 17 Lower clays: N = 6 – 8,
Su = 25 – 30 kPa, highly plastic
Solution
Solution
Micropile Cap details
Solution
Solution
Design and Analysis
• Classical and FLAC analyses employed • Classical analysis:
– Rankine load calculation – Truss analysis to calculate loads and
member sizes – Double row of piles acts as a beam – Risk of chasing product
• Designed modeled in FLAC 3D for further analysis
Design and Analysis
FLAC analysis of micropile wall geometry, Axial pile force kN
Design and Analysis
FLAC prediction of micropile bending
Design and Analysis
FLAC prediction of displacements, ~ 2 mm
Construction
Micropile drilling from roadway into excavated trench
Construction
Micropile drilling from roadway into excavated trench
Construction
Micropile tops within containment trench
Construction
Reinforcing steel and forming of micropile cap
Construction
Placing gravel leachate collection drain against 1st level of CDF anchor block. Vertical drainage pipes and geotextile visible. Clay wall with micropiles exposed.
Construction
Completed reinforced earth slope up to micropile cap
Construction
Living Earth Wall installation
Construction
May 2014
Recap
• Successful implementation of a Case 1 (non-reticulated) micropile wall for excavation support
• Versatile system with low impact • Successful implementation of Living
Earth Wall system
Thank You! Questions?