PILE TESTING Mike Turner Applied Geotechnical Engineering August

PILE TESTING Mike Turner (Applied Geotechnical Engineering) August 2004 Pile Testing

Types of load testing n Static load testing Maintained Load (ML) Constant Rate of Penetration (CRP) n Dynamic load testing August 2004 Pile Testing 2

Static load tests on micropiles Features: n High slenderness ratio (=Aspect Ratio) n Relatively high elastic shortening Implies: n Long piles = large pile head settlement August 2004 Pile Testing 3

Pile length vs Pile head settlement at working load: Micropiles in soils August 2004 Pile Testing 4

Pile length vs settlement at working load Micropiles in soils (2) 0. 5 mm/m 0. 25 mm/m 0. 1 mm/m August 2004 Pile Testing 5

Pile length vs Gross pile head settlement at working load – Micropiles into rock August 2004 Pile Testing 6

Pile length vs settlement at working load Micropiles into rock (2) 0. 4 mm/m 0. 35 mm/m 0. 2 mm/m August 2004 Pile Testing 7

Summary (1) For a wide variety of soils: Gross pile settlement at working load is n Proportional to pile length n Around 0. 25 mm/metre, on average n (As high as 0. 5 mm/metre) n (As low as 0. 1 mm/metre) n Independent of diameter (and load) August 2004 Pile Testing

Summary (2) For a wide variety of rocks: Gross pile settlement at working load is n Proportional to pile length n Around 0. 35 mm/metre, on average n (As high as 0. 4 mm/metre) n (As low as 0. 2 mm/metre) n Independent of diameter (and load) August 2004 Pile Testing

Spooky! August 2004 Pile Testing

Pile head settlement vs working load: Micropiles in soils August 2004 Pile Testing 11

Pile head settlement vs working load: Micropiles in soils (2) 0. 005 mm/k. N 0. 012 mm/k. N 0. 035 mm/k. N August 2004 Pile Testing 12

Pile head settlement vs working load: Micropiles into rock August 2004 Pile Testing 13

Pile head settlement vs working load: Micropiles into rock (2) 0. 004 mm/k. N 0. 01 mm/k. N 0. 02 mm/k. N (variable) August 2004 Pile Testing 14

Summary (1) For a wide variety of soils: Gross pile head settlement at working load is: n Around 0. 012 mm/k. N (0. 1 mm/tonne [metric]) n [As high as 0. 035 mm/k. N (0. 35 mm/tonne)] n [As low as 0. 005 mm/k. N (0. 05 mm/tonne)] n (Fairly) independent of length and actual load! August 2004 Pile Testing

Summary (2) For a wide variety of rocks: Gross pile head settlement at working load is: n Around 0. 01 mm/k. N (0. 1 mm/tonne [metric]) (for most practical purposes) n May be as high as 0. 02 mm/k. N (0. 2 mm/tonne) n May be as low as 0. 004 mm/k. N (0. 04 mm/tonne) n Still fairly independent of length and load! August 2004 Pile Testing

Even spookier! August 2004 Pile Testing 17

Conclusion/discussion Apparent similarities of relationships? n n Bearing stratum generally stronger than overburden Piles designed on shaft friction alone Grout-to-ground design conservative Structural design essentially identical August 2004 Pile Testing