1. PILE TESTING (2) (Dynamic Load Testing)
Mike Turner
(Applied Geotechnical Engineering)

2. Types of load testing You will recall that we highlighted:
Static load testing
Maintained Load (ML)
Constant Rate of Penetration (CRP)
Dynamic load testing

3. Dynamic load tests on micropiles
Features (again):
High slenderness ratio (=Aspect Ratio)
Relatively high elastic shortening
This Implies:
Long piles = large pile head settlement
Want to discuss:
Comparison with Static load tests

4. Dynamic load testing Features: Pile head:
Striking the pile top with a falling mass
Pile-driving hammer
Pile head:
Reinforced and cast to accept the impact
Pile top movement/velocity and force applied are measured

5. Dynamic load testing (2)
Measurement:
Accelerometer to measure velocity
Strain gauge to measure force
Electronic theodolite to measure penetration and elastic displacement (‘quake’)

6. Dynamic load testing (3)
Interpretation:
Pile resistance = dynamic + static resistance
Identify and separate out ‘dynamic’ effects
Leaving static effects
Modern-day Hiley or ENR formula
Needs calibration

7. Dynamic load testing (3)
Techniques and systems:
‘Case’ and CAPWAPC
TNOWave, PiD, SVIDYN
Simbat (CEBTP)

8. Dynamic load testing (4)
Aim of the test:
To produce a ‘conventional’ load versus settlement relationship for the pile
So ..
Let’s look at some results …..

9. Pile length vs Pile head settlement at working load: Dynamic load tests (rock)

10. Pile length vs Pile head settlement at working load: Dynamic load tests (rock) (2)
0.7mm/m
0.36mm/m
0.15mm/m

11. Summary (1) For a wide variety of rocks:
Gross pile settlement at working load is
Proportional to pile length
Around 0.36mm/metre
(As high as 0.7 to 0.9 mm/metre)
(As low as 0.15mm/metre)
Independent of diameter (Again!)

12. Summary (2) Comparison with static tests
Tests on micropiles socketed into rock
(Gross pile settlement at working load)
Static Dynamic
Av mm/metre Av mm/metre
Max. 0.4 mm/m Max mm/m
Min mm/m Min mm/m

13. Still spooky!

14. Pile head settlement vs working load: Dynamic load tests (rock)

15. Pile head settlement vs working load: Dynamic load tests (rock) (2)

16. Pile head settlement vs working load: Dynamic load tests (rock) (3)
0.005mm/kN
0.01mm/kN

17. Summary (1) For a wide range of rock type (and pile size):
Gross pile head settlement at working load:
Averages around 0.01mm/kN at 100kN SWL
reducing to approx 0.005mm/kN at 1200kN.
Does not show a linear relationship
Not so independent of length?

18. Summary (2) Comparison with static tests
Tests on micropiles socketed into rock
Gross pile settlement at working load is:
Static Dynamic
Av mm/kN Av to 0.005mm/kN
Max mm/kN Max mm/m
Min mm/kN Min mm/kN

19. Conclusion/discussion
To be continued …….but …..
…….Some points to ponder……..
At design working load:
DLT and Static testing appear to give generally comparable load/settlement results
However, DLT gives greater scatter
Are values such as 0.35 mm/m ‘reasonable’?
Are values such as 0.01mm/kN ‘reasonable’

20. ………..Thank you!