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?