1 prepared for: international society for micropiles (ism) 2009 international workshop on micropiles...
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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?