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Prepared for: International Society for Micropiles (ISM)

2009 International Workshop on Micropiles

London, England

May 13th, 2009

A DECADE OF LOAD HOLD CAPACITY ACROSS WESTERN CANADA

Cory J.E. Yacyshyn, P.Eng.

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1 Introduction

2 Table 1. Interface Bond Values

3 British Columbia

4 Alberta

5 Saskatchewan

6 Manitoba

7 Conclusion

Micropiles Overview

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Type of Micropile

- Single, continuous thread, solid steel bars

- Double corrosion protection (presence of soluble sulphates in some areas)

- Axially loaded

- Compression load magnitude governs over tension, if any requirement for tension

- Isolated vs groups

- Typically, light load requirements (25 kN to 200 kN), in Alberta, Saskatchewan and

Manitoba

- Higher load requirements in British Columbia (< 1,000 kN)

- Commonly without permanent steel casing

Absence of Steel Casing?- Rarely is criteria been established for total pile head movement at

design load levels in Owners Engineers Specifications

- Low load magnitudes

- Small requirement to sustain lateral loads, however, increasing trend.

Introduction

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Intent / Description

- Intends to provide design engineers with a basic understanding of load hold capacity in Western Canada.

- Description of location and geology

- Table 1 shows maximum grout-to-soil/rock bond values achieved at maximum test load level.

- Micropile tension test data but some soil/rock anchor tension test data

- Early testing followed PTI Manual prior to publication of the Micropile Design and Construction Reference Manual (FHWA 2005)

- Data from 40 projects undertaken since 1996

- Comparison of full-scale load tests to Table 5-3 (FHWA 2005)

Table 1 Interface Bond Values

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Legend

Table 1 Interface Bond Values

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British Columbia

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British Columbia

Geology

- Low plastic clays

- Dense sand, occasionally loose

- Weak sandstone, minimal weathering

- Very dense glacial tills exhibiting cement-like behavior

- Presence of strong rock at the Coast Mountain Range

- Cordilleran Ice Sheet, last glaciation 2 to 3 km thickness

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Alberta

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Alberta

Geology

- Typically, low or medium plastic clays, however, pockets of highly plastic clays exist in Edmonton and Medicine Hat for example.

- Dense sand some areas; Some Loess

- Weak sandstone, weathered

- Compact to dense glacial clay tills

- Fluvial channel gravel (Calgary)

Low fines content, presence of cobbles, unstable

- Very weak clay shale “bedrock”

Unconfined Compressive Strength ~ 380 kPa, varies

Should be treated as a soil not rock

- Presence of soluble sulphates

- Laurnetide Ice Sheet, last glaciation, 2 km thickness

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Saskatchewan

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Manitoba

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Conclusion

Final Remarks

- Geology of British Columbia tends to be more competent vs. the prairies

- Presence of highly plastic clays, soluble sulphates and loess on the prairies

- Assessment of total pile head movement at design load levels needs to be addressed

- Questions?