Engineers Ireland Seminar
4th November 2015
About Lloyds • Established in Belfast 1991 • Company now has offices Ireland, UK and
Poland. • Companies employ 40 people in these
regions • Since 1991 we have completed approximately
200k pile integrity tests. 100K dynamic tests 8K static pile load tests.
• Company has accreditation Quality Management Status ISO 9001
• Associate company of Datum Monitoring
Engineers Ireland Seminar 4th November 2015
Presentation Agenda
• Background to Dynamic Pile Testing and Capwap Analysis
• Static Load Testing • Changes to Piling Practice • Lessons Learned (or were they ?)
Engineers Ireland Seminar 4th November 2015
Why test at all?
• Professional Duty of Care • Control Measure Insure • Risk Management • Quality & Confidence
Engineers Ireland Seminar 4th November 2015
Why should we use Dynamic Pile Testing
• The Irish construction industry spends a lot on deep foundations (in Ireland estimated at 40-50 million euro/year)
• We want low risk of failure - remediation is expensive
• We want safe infrastructure and buildings
• Testing and analysis allows for optimizing a foundation, consideration of greater use of Preliminary Pile Testing in advance of contract works.
Engineers Ireland Seminar 4th November 2015
1973
1965
1992
1997
2007
1958
1982
Evolution of PDA
Engineers Ireland Seminar 4th November 2015
Types of Piles Tested Using Dynamic Testing Process
Displacement Piles
• Precast concrete
• Prestressed Concrete
• Steel H-section
• Timber
• Driven cast-in-situ
• Sheet piles
• Minipiles
Replacement Piles
• Bored:
• CFA
• Rotary
• Minipiles
Engineers Ireland Seminar 4th November 2015
PDA Testing (terminology)
Falling Hammer Ram
Drive System Assembly
Pile Top, Head, Butt
Pile Shaft, Skin
Pile Bottom, Toe, Base
Hammer
System
Engineers Ireland Seminar 4th November 2015
Dynamic Pile Testing (P.D.A.)
Pile Driving Analyser
Remote Pile Driving Analyser
Accelerometer Gauge
Strain Gauge
Engineers Ireland Seminar 4th November 2015
Typical Dynamic Test Trace
Lloyd Acoustics Ltd.N8 Cashel-Mitchellstown Road Improvement SchemePDA OP: Gareth Stevenson
PILE DRIVING ANALYZER ®
Version 2004.096
East Abutment SAP7STEEL H PILE
BN 8
03/10/2006 11:23:25
CSB MPa129.9
CSX MPa154.5
TSX MPa39.1
EMX kN-m27.8
RMX kN2348
LTD m0.0
BTA (%)100.0
RX5 kN2730
DMX mm16
LE m19.8
AR cm^2161.30
EM MPa206843
SP kN/m377.3
WS m/s5123.0
EA/C kN-s/m651
LP m18.8
F12 A12
F1: [5929] 97.5 (0.75)
F2: [6058] 97.4 (0.8)
A1: [70751] 1070 g's/v (0.8)
A2: [42720] 1070 g's/v (0.8)
7.73 ms
51.2ms
5000
kN
F
7.68
m/s
V
51.2ms
5000
kN
WD
5000
kN
WU
Lloyd Acoustics Ltd.DUNGARVEN RETAILPDA OP: Sean Hagan
PILE DRIVING ANALYZER ®
Version 2004.096
BLKAP115
Precast
BN 1/11
30/08/2006 19:47:52
CSB MPa16.4
CSX MPa18.8
TSX MPa0.8
EMX kN-m20.3
RMX kN1185
LTD m0.0
BTA (%)100.0
RX5 kN1349
DMX mm21
LE m13.4
AR cm^2756.25
EM MPa39647
SP kN/m324.3
WS m/s4000.0
EA/C kN-s/m750
LP m12.5
F12 A12
F1: [5926] 92.4 (0.8)
F2: [6524] 96.1 (0.8)
A1: [77688] 1050 g's/v (1)
A2: [85492] 1070 g's/v (1)
6.70 ms
51.2ms
4000
kN
F
5.34
m/s
V
51.2ms
4000
kN
WD
4000
kN
WU
Engineers Ireland Seminar 4th November 2015
Damage Detection: Spliced pile Example
Time of Impact Toe Reflection
Good Pile Bad Pile: Early
reflection
Time of Impact Toe Reflection
Engineers Ireland Seminar 4th November 2015
‘CAPWAP’ - Analysis
14 50
-2000.0
0.0
2000.0
4000.0
ms
kN
6 L/c
Force Msd
Force Cpt
14 50
-2000.0
0.0
2000.0
4000.0
ms
kN
6 L/c
For. Msd
Vel. Msd
Pile
0
30
60
90
120
kN
/m
0
500
1000
1500
2000
kN
Shaft Resistance
Distribution
Pile Forces
at Ru
0.0 500.0 1000.0 1500.0 2000.00.00
2.00
4.00
6.00
8.00
Load (kN)
Dis
pla
ce
me
nt (
mm
)
Pile Top
Bottom
Ru = 1543.7 kN
Rs = 816.8 kN
Rb = 726.9 kN
Dy = 7.2 mm
Dmx = 7.7 mm
Apartments/Shops; Pile: P384; CFA; BN: 10 (Test: 07-Feb-2006) 09-Feb-2006
Lloyd Acoustics Ltd. CAPWAP® Ver. 2000-1
Ultimate Resistance
Shaft Resistance
Toe Resistance
Computed wave analysis trace Dynamic Field Trace
Shaft Resistance Distribution
Engineers Ireland Seminar 4th November 2015
CW versus SLT combined (N=303) (80, 96, SW)
0
10,000
20,000
30,000
40,000
0 10,000 20,000 30,000 40,000
SLT [kN]
CW
[k
N]
Likins, Rausche, 2004. “Correlation of CAPWAP with Static Load Tests”. Proc. 7th Int’l Conf. on Application of Stresswave Theory to Piles: Malaysia
Engineers Ireland Seminar 4th November 2015
Dynamic Testing of Bored Cast InSitu Piles and Reaction Beam setup
Engineers Ireland Seminar 4th November 2015
Kentledge Testing
PAST PRESENT or should it be?
Engineers Ireland Seminar 4th November 2015
Reaction Beam Static Load Test Systems
600T compression test
1200T Compression test Mallow
Engineers Ireland Seminar 4th November 2015
Pile Shaft Instrumentation
Engineers Ireland Seminar 4th November 2015
Test Beam Strain Logger Setup
Engineers Ireland Seminar 4th November 2015
Pile Head Displacement Data Outputs
Engineers Ireland Seminar 4th November 2015
Strain Data Outputs
Engineers Ireland Seminar 4th November 2015
Pile Integrity Testing (P.I.T)
Engineers Ireland Seminar 4th November 2015
Piling & Testing has evolved
• Engineers have greater knowledge of our soils with improved site investigation
• Piling contractors can offer broader range of piling alternatives
• Pile design is asking for greater SWL & DVL pile load capacity
• Engineers have adopted quality control using pile foundation testing
Engineers Ireland Seminar 4th November 2015
Piling through the years
Engineers Ireland Seminar 4th November 2015
Engineers Ireland Seminar 4th November 2015
Driven Piling Techniques
Pile driving
Engineers Ireland Seminar 4th November 2015
Bored Piling Drilling Techniques
Rotary Bored
CFA
Engineers Ireland Seminar 4th November 2015
Lessons Learned
Engineers Ireland Seminar 4th November 2015
What can go wrong?
Inadequate Site Investigation Platform Design Failures Wrong Pile Type Unsupervised Pile Installation Wrong Hammer Selection Pile Relaxation Poor Pile Preparation
Engineers Ireland Seminar 4th November 2015
Rossary Quay Enniskillen
• Decision by developer was to design a Load Transfer Platform (LTP)
• Site passed for development of luxury apartments and town houses alongside River Erne, Enniskillen
Engineers Ireland Seminar 4th November 2015
• Residents reported “cracking in walls” in early 2002
• Reports of roads and gardens becoming very uneven
Rossary Quay
• Borehole logs for the early discussions were used from a “site close by”!
• Site was liable to flooding, with poorly draining soils
Engineers Ireland Seminar 4th November 2015
• Risks of the limestone undergoing carcification
• Borehole undertaken in 1997 recommended that in order to avoid differential settlements it would be necessary to pile 100% of the development
Engineers Ireland Seminar 4th November 2015
• The site investigation exposed presence of bedrock overlain by thin deposits of boulder clay, followed by very soft lacustrine deposits
• Predictions of placing 1 metre of stone in-fill would lead to settlement equalling 800mm.
• The risks of excessive sinking comes directly as a result of the low shear strength of the lower bound sub soils incapable of withstanding any substantial loads
• Design decision opted for the road and gardens to be constructed on LTP using “triangular arrangement of piles”. The main structures would be constructed on the traditional piles driven to rock.
• Remarkably, a late decision was made to construct roads and houses on the LTP and only four storey buildings were piled to rock
Engineers Ireland Seminar 4th November 2015
• Engineers must ensure they choose contractors with the correct level of knowledge and experience
• All Decisions should be made within the compliance of engineering ethics
• Lack of communication between consultant>Engineer>
Contractor can have catastrophic consequences
N7 Nenagh to Limerick High Quality Dual Carriageway 2008
Engineers Ireland Seminar 4th November 2015
Challenges encountered from pile testing at Nenagh Bypass
• Slenderness ratio of piles versus driven depths
• Static Compression Load tests “but how?”
• Temporary piling platform very unstable
• Peat bog overlying dense / coarse gravels overlying rock
Engineers Ireland Seminar 4th November 2015
• Two Sections of this carriageway traversed existing peat bogs, Anaholty Bog and Drominboy Bog
• Pile depths predicted between 18-21m along the length of the bog
• FK Lowry were nominated as piling contractor • Contract estimated at 200,000 linear metres of
precast concrete piling • Piling rigs weighed in excess of 60 T each and
working within close proximity of each other was prohibited • Concrete casting for the piles was setup at site
compound with concerte quality control plan
Differential Settlements
Engineers Ireland Seminar 4th November 2015
• Selection of pile type discounted displacement piles leaving only driven concrete or steel as feasible choices
• Dynamic pile testing demonstrated pile capacity was achievable but at a greater depth than predicted
• Transfer of load axially into the pile despite over lengths
• Greater pile depths brought greater challenges to
Pile Quake Pile Bending Pile stress on joints
Working Platform Collapse
Engineers Ireland Seminar 4th November 2015
• Lloyd Acoustics asked to provide alternative method for static load tests (SLT)
• Stability of the bog proved very difficult for piling rigs but impossible for scheduled “Kentledge type tests”
• Risk of Platform failure under footprint of “Kentledge tests” was high
• Sacrificial drill anchors were chosen - at each SLT location sized dependant on maximum load capacity
Piled carriageway through an existing peat bog
Engineers Ireland Seminar 4th November 2015
• Advantages of the sacrifical anchors: They had to be drilled minimum 4 metres into a competent rock, thereby confirming the pile depth at each of these locations
• Small light-weight “cradle beams” were selected with test capacities of <3000kN
• Testing commenced in April 2009
• 10% of the 8000 piles driven were dynamically tested , 185 No. were static load tested (28 of these were preliminary type)
Datum Monitoring Services Ltd
Datum House The Pavilions
Bridge Hall Lane
Bury
BL9 7NY
Tel: 0161 765 3441
Website: www.lloydacoustics.com
Email: [email protected]
Lloyd Acoustics Ireland Ltd
36 Lurganville Road
Moira
Co.Armagh
BT67 0PL
Tel: 028 92610525
Website: www.lloydacoustics.com
Email: [email protected]