Ohayo Gozaimas Good Morning!

Performance and Instrumentation of Micropiles for a Paper Mill Expansion Nadir Ansari, Matthew Janes, Daniela Ramirez of Isherwood Associates Jim Bruce of Geo-Foundations Contractors

Micropiles were planned for the enhancement of foundation capacity as part of an expansion to the existing Bowater Pulp and Paper Mill facility in Thunder Bay Canada. Micropiles were planned for the enhancement of foundation capacity as part of an expansion to the existing Bowater Pulp and Paper Mill facility in Thunder Bay Canada. Large increases, on the order of 3800 kN, in pier capacity were required. Two piles per pier were added with maximum individual micropile working loads of 1900 kN/pile

Micropile Geometry Elevation showing the three major sections of the Type 1 micropile (1900 kN). Types 2 and 3 (1400 & 1100 kN) eliminate the upper 44 mm dia bar.

Micropile Sections Typical micropile sections showing the pipe, grouted section and the inner bar. Note the intention to pressure grout to fill the outer annulus between the pipe and the soil/rock

Bowater Soils Strata

Micropile Quick Maintained Load Test

Creep Analysis for Compression Load Test

Tension Test Results

Contractometer Results

Results of Micropile Testing Quick Maintained Load Test -Proved more than 2x working load of test pile Contractometer Results -Indicates no displacement of sensor immediately above weathered rock Test Question – Can this be? 2900kN load on 30 metres of 200mm diameter pile 0 displacement below 30 metres q average = 160kPa

Commentary on Micropile Design FHWA Design -FOS steel 2.0 -FOS concrete 2.5 Calculating Actual σ Assuming Σ compatibility at 3800kN (Ultimate load) -Use δ =PL/AE or δ = σ L/E

Commentary on Micropile Design - σ steel = 235 MPa or 54% yield - σ conc = 50.3 MPa or 126% yield Ratio A steel /A conc actual = 2.36 Ratio A steel /A conc required = 17.2

Conclusions Conclusions Pressure grouting was successful for very long piles in stiff clays and rock Use of contractometer on the very long test micropile provided controversial results Design using the FHWA Implementation Manual requires careful attention to be paid to ratio of steel and grouted cross sectional areas

Arigato gozaimas Thank You!