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PMS Pavement Management Services Ltd Tobins

TB5F271-272 - Tobins FWD Level 2 Analysis

Project Title: Structural Evaluation of sections of the R162, R163, County Meath.

Falling Weight Deflectometer Testing, Level 2 Analysis.

Client: Tobins Consulting Engineers

Document Version: 1.0Date: 05th February 2016

Issued by: _________________________Seán Clancy BE (hons) MIEISenior Project Engineer

This report applies only to the tests performed and shall not be reproduced except infull, without the approval of PMS Ltd.

Pavement Management Services Ltd.

Orion House, 53 Main Street,Rathfarnham, Dublin 14

D14 W3k6Tel: 01 - 4055588 Fax: 01- 4055587

Raheen Industrial Estate,Athenry, Co. Galway

H65 PD37Tel: 091 - 877040 Fax: 091- 844101

www.betterpavements.com

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IntroductionFalling Weight Deflectometer (FWD) testing was carried out on behalf of Tobins

Consulting Engineers on sections of the R162 and R163, both Regional Roads in

County Meath, in November 2015. These sections are to act as haul routes for the

development of the Randalstown Tailings Management Facility. For the purposes of

analysis the R163 was tested in two parts, East of Kilberry Crossroads and West of

Kilberry Crossroads, joining with the L74141. The FWD survey was carried out in

accordance with NRA Guidelines for the use of the Falling Weight Deflectometerin Ireland. The details of the sections tested, direction of test and test lengths, are

as follows:

Section 1: R162 (From N52 Roundabout to Kilberry Crossroads) Testing was

carried out at 50 metre intervals on both carriageway lanes for 5550 metres.

Chainage increases in a Northbound direction. Testing was staggered in

adjacent lanes.

Section 2: R163 and L74141 (West of Kilberry) Testing was carried out at 50

metre intervals on both carriageway lanes for 2450 metres. Chainage

increases in a Westbound direction. Testing was staggered in adjacent lanes.

Section 3: R163 (East of Kilberry) Testing was carried out at 50 metre

intervals on both carriageway lanes for 7325 metres. Chainage increases in

an Eastbound direction. Testing was staggered in adjacent lanes.

A Level 1 analysis report for these sections was issued to Tobin Consulting

Engineers in November 2015.

Pavement ConstructionA programme of pavement investigation by Ground Penetrating Radar (GPR) was

carried out by Pavement Management Services Ltd. to determine the as constructed

pavement thickness of the existing pavement layers. In addition, a number of cores

were also extracted to correlate the GPR analysis. The results of the programme of

pavement investigation, the GPR survey charts and the core-log, are included in

Appendix A.

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Backcalculation of Layer ModuliUsing FWD testing, a 40kN load can be applied to the pavement, and the actual

deflections at given distances from the centre of the load plate are measured. We

now have pavement thicknesses, and displacements resulting from application of a

40 kN load. It is then possible to deduce what the elastic moduli of the pavement

layers must be in order to have produced the deflection basin measured by the FWD

device. This process is known as BACKCALCULATION of pavement layer moduli.

In practice, it is not easy to backcalculate layer moduli. A set of moduli is assumed,

and the resulting deflections are calculated. These resulting deflections are

compared to the actual measured deflections, and adjustments made to the original

assumed moduli. These adjusted moduli are then used with the analytical software,

and a new set of resulting deflections are calculated and compared with the actual

measured deflections. The iterative process continues until the actual deflections

and calculated deflections are sufficiently close, and the pavement is then

characterised by this last set of pavement moduli.

Having characterised the pavement, the analysis can then proceed as in the case of

a new pavement, with stresses and strains at the critical design locations being

calculated, and number of axles to failure being calculated. If the number of axles to

failure for the existing pavement is less than that desired (i.e. if the strains are

excessively high), then an overlay layer can be designed to reduce the critical strains

to the appropriate design level.

Application of Analytical Design Methods

With the existing pavement structure defined in terms of thicknesses, and a set of

deflections available from the FWD testing, it was possible to use a backcalculation

procedure as described in the previous section to obtain the pavement layer moduli

from multilayer elastic analysis for this section. For the purposes of backcalculation a

average bituminous layer thicknesses ranging from1 50 to 200 mm over an average

upper granular layer thickness of 200 mm was taken fro Section1. An average

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bituminous layer thickness of 150 mm over and aveage upper granular layer

thickness of 250 mm was taken for Sections 2 and 3.

Based on the deflection results, the pavement lanes were divided into homogeneous

segments and design deflections were calculated based on the 85th percentile in

each class. A pavement overlay design is then performed using the existing

pavement structure at the design locations for each segment, and variable

thicknesses of hot-mix overlay.

Traffic RequirementsTobin Consulting Engineers provided the results of a series of traffic counts at four

junctions with will be trafficked as part of the development of project. Table 1 shows

the design traffic information and the cumulative number of standard axles over a 20

year design period estimated from the results of these traffic counts. In addition, it

was indicated that an average of 18 hourly HGV deliveries are anticipated per hour

over a 40 hour working week. Assuming a 2 year construction phase, this will

contribute an additional circa 1.5 million standard axes (msa) to the design traffic

shown in Table 1.

Overlay RequirementsTable 2 shows the 20 year design Hot-mix only overlay requirements, by segment,

for each section, based on the National Roads Models, (85th% failure curve).

The thicknesses shown may be superseded by construction requirements.

DEHLG guidelines specify that where SCIs are greater than 250 microns, a hot-mix

only overlay is not suitable. The average SCI value for each segment is also shown

in Table 2.

At some locations, the analysis has shown that there is No Structural OverlayRequirement. It should be emphasised that this is based on structural

requirements only and there may be a requirement for a non-structural overlay

based on construction requirements or other considerations such as loss of surface

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texture, hardening of overlay, loss of chippings through ravelling, polishing of

aggregates, excessive bleeding of bitumen, loss of skid resistance etc..

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% Heavy Goods Standard Axles Cumulative no. ofAADT Vehicles per Vehicle Standard Axles

A R163 / L74141 1436 10% 1.0 0.78 msa

B R163/R162 6804 9% 1.4 4.45 msa

C R163/N51 19110 5.4% 1.9 10.55 msa

D Windstown Rd 655 11% 1.0 0.38* msa

1.5 msaAssumed Annual growth rate of 3.5%*Take 0.5 msa as minimum

Non- National ModelsHot-mix Overlay

Lane Chainage SCI Requirement0 - 550 59 55 mm

550 - 950 189 125 mm950 - 1900 61 50 mm

1900 - 3800 30 No Overlay Required*3800 - 4100 60 50 mm4100 - 4750 71 55 mm4750 - 5550 116 80 mm

25 - 825 74 55 mm825 - 2025 69 55 mm

2025 - 2525 32 No Overlay Required*2525 - 4375 55 55 mm4375 - 4675 127 80 mm4675 - 4875 73 50 mm4875 - 5525 62 50 mm

0 - 1000 109 50 mm1000 - 1800 84 50 mm1800 - 2200 84 50 mm2200 - 2450 132 75 mm

25 - 325 76 50 mm325 - 1325 50 50 mm

1325 - 2075 115 50 mm2075 - 2425 118 75 mm

0 - 650 151 115 mm650 - 1700 81 No Overlay Required*

1700 - 2250 92 55 mm2250 - 3400 72 55 mm3400 - 4600 68 50 mm4600 - 5350 119 105 mm5350 - 6600 89 65 mm6600 - 7325 42 No Overlay Required*

25 - 1375 92 55 mm1375 - 1875 69 No Overlay Required*1875 - 2325 101 65 mm2325 - 4025 66 No Overlay Required*4025 - 6525 95 65 mm6525 - 7325 51 No Overlay Required*

*Structural Requirement OnlyTable 2: Overlay Design: Hot-mix Overlay Requirements by Segment

Count Site

Table 1: 20 Year Design Traffic Requirements

Section

Additional Factor for Construction Traffic:

3 R163East of Kilberry

Eastbound

Westbound

2 R163 and L74141West of Kilberry

Westbound

Eastbound

1 R162from N51 to Kilberry

Northbound

Southbound

TB5F271-272 - Tobins

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Appendix A

(GPR and Core-log)

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0 - 550 155 399550 - 950 176 407

950 - 1900 191 4301900 - 3800 210 3403800 - 4100 220 3704100 - 4750 206 2974750 - 5550 171 373

25 - 825 174 268825 - 2025 191 279

2025 - 2525 202 1832525 - 4375 174 2244375 - 4675 158 2334675 - 4875 210 1724875 - 5525 236 246

0 - 1000 181 3851000 - 1800 195 3911800 - 2150 175 462

25 - 325 189 428325 - 1325 206 382

1325 - 2075 192 3592075 - 2150 209 279

0 - 650 191 303650 - 1700 184 317

1700 - 2250 188 2752250 - 3400 188 3233400 - 4600 186 3424600 - 5350 209 3825350 - 6600 187 4946600 - 7325 189 276

25 - 1375 191 3451375 - 1875 170 3801875 - 2325 177 4232325 - 4025 181 3764025 - 6525 188 3946525 - 7325 179 441

Average GPR Survey Results

Average Layer Thickness (mm)

Section Lane Chainage Bituminous Granular

1R162

from N51 toKilberry

Northbound

Southbound

2 R163West of Kilberry

Westbound

Eastbound

3 R163East of Kilberry

Eastbound

Westbound

TB5F271-272 - Tobins

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CORELOG Pavement Management

Services Ltd.

Tara Mines - R162 and R163

Lane:Direction/Wheel Path: R162 A/FILE CHSite Chainage:

Core No: 1

Date:

No Top(mm)

Bottom(mm)

Thickness (mm)

Material Max Size(mm)

Type Comments

35350 HRA

8011535 DBM

110225115 SMA

15240225 SD

70310240 DBM

Layers Aggregate

Key: HRA=Hot Rolled Asphalt; DBM=Dense Bituminous Macadam; TLS=Thin Layer Surfacing; SD=Surface Dressing;CBGM=Cement Bound Granular Material; WCG=Well Compacted Granular

5

November 2015

4

3

2

1

Client: Tobins

X Coordinate: 53.6793076 Y Coordinate: 6.6749499

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Services Ltd.


Lane: SBCWDirection/Wheel Path: R162 B/FILE CHSite Chainage:

Core No: 2

Date:

No Top(mm)

Bottom(mm)

Thickness (mm)


Type Comments

35350 DBM

458035 DBM

2010080 SD

65165100 DBM

15180165 SD

Layers Aggregate


5

November 2015

4

3

2

1

Client: Tobins


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Services Ltd.


Lane: NBCWDirection/Wheel Path: R162 A/FILE CHSite Chainage:

Core No: 3

Date:

No Top(mm)

Bottom(mm)

Thickness (mm)


Type Comments

40400 DBM

6510540 DBM

Layers Aggregate


November 2015

2

1

Client: Tobins


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Services Ltd.


Lane: EBCWDirection/Wheel Path: R163 LL74141 CB/FILESite Chainage:

Core No: 4

Date:

No Top(mm)

Bottom(mm)

Thickness (mm)


Type Comments

35350 HRA

458035 DBM

5513580 DBM

20155135 SD

90245155 SD

Layers Aggregate


5

November 2015

4

3

2

1

Client: Tobins

25270245 GRANULAR6


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Services Ltd.


Lane: WBCWDirection/Wheel Path: R163 D/FILE CHSite Chainage:

Core No: 5

Date:

No Top(mm)

Bottom(mm)

Thickness (mm)


Type Comments

10100 SD

556510 DBM

9516065 DBM

10170160 SD

15185170 SD

Layers Aggregate


5

November 2015

4

3

2

1

Client: Tobins


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Services Ltd.


Lane: WBCWDirection/Wheel Path: R163 D2/FILE CHSite Chainage:

Core No: 6

Date:

No Top(mm)

Bottom(mm)

Thickness (mm)


Type Comments

35350 DBM

407535 DBM

6013575 DBM

20155135 SD

20175155 SD

Layers Aggregate


5

November 2015

4

3

2

1

Client: Tobins

15190175 SD6


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