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Impulsive Matters 2: Use of FWD for quality control Heriot-Watt University, Edinburgh, Scotland 19 November 2003. The Use of FWD for Pavement Monitoring: Case Studies. Bachar Hakim and Martyn Jones Scott Wilson Pavement Engineering. The Use of FWD for Pavement Monitoring: Case Studies.

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the use of fwd for pavement monitoring case studies

Impulsive Matters 2: Use of FWD for quality control

Heriot-Watt University, Edinburgh, Scotland

19 November 2003

The Use of FWD for Pavement Monitoring: Case Studies

Bachar Hakim and Martyn Jones

Scott Wilson Pavement Engineering

the use of fwd for pavement monitoring case studies1
The Use of FWD for Pavement Monitoring: Case Studies

Contents

  • Unbound Foundation Performance Testing
  • Lean Concrete and Pavement Quality Concrete
  • Crack and Seat Projects
  • Bond between Pavement Layers
foundation performance testing
Foundation Performance Testing
  • Main Objectives
    • QUALITY:

Ensure design assumption = construction

    • COST & ENVIRONMENTAL SAVINGS:

Greater flexibility in use of marginal materials, stabilised, secondary & recycled materials

foundation performance parameters and tests
Foundation PerformanceParameters and Tests:-
  • Strength (CBR%)
    • e.g. Dynamic Cone Penetrometer (DCP)
  • Stiffness (MPa)
    • Dynamic plate (FWD, GDP & Prima)
  • Density (Kg/m3)
    • Nuclear Density Meter (NDM)
  • Rutting (mm)
    • Trafficking Trial
foundation performance tests unbound stabilised layers
Foundation Performance Tests - Unbound & Stabilised Layers
  • Implementation of Highway Agency (HA) ‘Draft Performance Specification for Subgrade and Capping’
  • Prepared by Consortium, SWPE, Nottingham and Loughborough Universities
  • Similar Performance Specification for

Sub-base underway, by TRL

implementation phase trials
Implementation Phase Trials
  • Jersey Airport (Taxiway Alpha)
    • First Contractual Use of Specification
  • A2 – M2 (Kent)
    • Various Cappings including Cement Stabilised Chalk, Ragstone (local sandstone) and Recycled Crushed Concrete
  • A27 Polegate (Sussex)
    • Lime/Cement Stabilised Weald Clay
  • A43 Towcester to M40 (Northampton)
    • Oolitic Limestone and Planings
  • Doncaster North Bridge
    • Urban Widening of Carriageway, granular capping
  • A63 Selby Baypass
    • Sand capping and sand/PFA sub-base
  • Tilbury Docks: Berths 41-43
    • Crushed Concrete capping and sub-base
slide7

Limit rutting in

Upper Pavement

Upper

Limit flexure of Upper Pavement

Pavement

(Fatigue cracking)

Sub-base

Capping

Limit deformation of subgrade

(Structural rutting)

Subgrade

FOUNDATION:

Design for Permanent Works - Long Term

slide8

Adequate Stiffness

to Compact Upper

Pavement

Capping

Limit rutting in subgrade

Subgrade

FOUNDATION:

Design for Construction - Short Term

slide10

600

For very soft subgrades

see paragraph 5.19

500

400

300

For thickness requirements less

than 150mm see paragraph 5.20

200

100

0

1

2

3

4

5

6

7

8

9

10

Subgrade CBR (%)

Long Term Capping Thickness Design - A

typical capping material properties
Typical Capping Material Properties

* The stiffness quoted is conservative. Depending on the soil type and level of

stabilisation used much higher values can be obtained.

dynamic plate tests stiffness performance requirements
Dynamic Plate Tests:Stiffness Performance Requirements
  • Finished surface of capping shall:-
    • >40MPa 8 from 10 consecutive tests
    • 25MPa absolute minimum
  • Minimum 50 tests / trial area
  • Representative trial areas
    • Cut, Fill, Material Changes
  • Routine testing at 10m intervals in each lane
rutting tests requirements
Rutting Tests - Requirements
  • If capping used in a haul route, and subsequently included in the works, then rutting under construction traffic needs to satisfy:-
a performance specification for capping and subgrade summary
A Performance Specification for Capping and Subgrade - Summary
  • Extensive testing and verification over 6 years
  • Implementation phase has identified minor changes to 1999 Draft
  • Successfully trialled at Jersey Airport, with significant savings
  • Provides a path for greater use of secondary aggregates/marginal materials/stabilised ground
  • Prediction of long-term performance remains an issue, especially with moisture susceptible materials
capping trials
Capping Trials

Compaction of capping layer

Capping layer was trafficked 50 times

fwd and gdpt on capping
FWD and GDPT on Capping

Nuclear Density Testing

a19 dbfo foundation assessment of existing pavements
A19 DBFO: Foundation Assessment of Existing Pavements
  • Concrete slab failure/settlement in Lane 1
  • Replacement with bituminous inlay is required
  • Unbound foundation stiffness assessment is needed before laying the bituminous materials to ensure that the pavement design life is achieved
alpha taxiway pavement
Alpha Taxiway Pavement
  • Limited local aggregate performance (quarried granite aggregates with some fine quartz dune sand)
  • Uneconomic to import aggregates due to high Harbour Dues Charges
pavement development
Pavement Development
  • Site Investigation
  • Materials Characterisation
    • Capping Trials, CBM, PQC
  • Design Parameters
  • Performance Monitoring
    • Top of Capping: Stiffness (GDPBT), Damage to Subgrade (Rut Limit) and Compaction (Density)
    • CBM and PQC strengths
  • Additional FWD Tests
    • CBM stiffness
    • PQC: slab stiffness, joints performance, corner/edge deflections
slide38

305

A

A

COST SAVING

HIGHER FLEXURAL STRENGTH CONCRETE DEVELOPED GIVING 10% REDUCTION IN THICKNESS.

£158,000

COST SAVINGS

slide39

A

B

B

A

COST SAVINGS

305

150

COST SAVING

HIGHER FLEXURAL STRENGTH CONCRETE DEVELOPED GIVING 10% REDUCTION IN THICKNESS.

SECONDARY AGGREGATES FOR BOUND BASE 30% COST SAVING.

£158,000

£295,000

slide40

A

B

C

B

C

A

COST SAVINGS

305

150

300

COST SAVING

HIGHER FLEXURAL STRENGTH CONCRETE DEVELOPED GIVING 10% REDUCTION IN THICKNESS.

SECONDARY AGGREGATES FOR BOUND BASE 30% COST SAVING.

USE OF MUDSTONE CAPPING FROM EXCAVATIONS IN LIEU OF QUARRY SUPPLIED TYPE 1 SUB-BASE 90% COST SAVING

£158,000

£295,000

£237,000

slide41

A

B

C

B

C

A

COST SAVINGS

305

150

300

COST SAVING

HIGHER FLEXURAL STRENGTH CONCRETE DEVELOPED GIVING 10% REDUCTION IN THICKNESS.

SECONDARY AGGREGATES FOR BOUND BASE 30% COST SAVING.

USE OF MUDSTONE CAPPING FROM EXCAVATIONS IN LIEU OF QUARRY SUPPLIED TYPE 1 SUB-BASE 90% COST SAVING

£158,000

£295,000

£237,000

TOTAL £690,000

Materials development costs £30,000

bond between pavement layers
‘Bond’ between Pavement Layers
  • Complicated phenomenon and its effect on pavement behaviour not very well understood
  • Function of temperature and material type
  • Can develop with time under traffic loading
  • Full bond is commonly assumed in design
bond between pavement layers cont d
‘Bond’ between Pavement Layers (Cont’d)
  • In practice, difficult to achieve ‘full’ bond as specified in SHW
  • Deflection testing (FWD, Deflectograph?)

show higher deflections under loading

  • Layers are acting independently
  • Lower effective stiffnesses
  • Lower bearing capacity and hence life
methods of bond assessment
Methods of Bond Assessment

Falling Weight Deflectometer

Coring Survey

De-bonded Cores

Hammer Test

Leutner Test

swpe experience with bond analysis
SWPE Experience with Bond Analysis
  • Over 10 Technical Papers 1994 – 2003
  • Practical application on more than 10 projects (UK & Overseas)
  • EPSRC Research Project ( with Nott. University) 1999-2002
  • HA Research Project (SWPE) 2003-2004
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