Project: Mechanical Properties of Road Ironwork Pavement Systems

Reference: CSU 28/4/65

Last update: 26/01/2010 17:36:29


To investigate the mechanism of premature damage to the asphaltic reinstatement surrounding conventional road ironwork installations and the use of alternative support systems to minimise damage to the road ironwork installation and surrounding material.


The elements of the support systems will be tested in the laboratory and analytical/numerical modelling conducted. A number of full-scale trials both in the laboratory and on the road will be held.


Danelaw Ltd
19-27 Royal Oak Way South, Daventry, NN11 5PJ
01327 906505

Stanton plc
PO Box 72, Nottingham, NG10 5AA
0115 930 0714

SWK Pavement Engineering Ltd
9 Faraday Building, Highfields Science Park, Nottingham, NG7 2QP
0115 922 9098

Diamond Cable Ltd
Dale Side Road, Nottingham, NG2 3GG
0115 912 2240

Contract details

Cost to the Department: £63,000.00

Actual start date: 24 February 2000

Actual completion date: 13 November 2003


Mechanical Properties of Road Ironwork/Pavement Systems
Author: Dr A C Collop
Publication date: 01/09/2002
Source: School of Civil Engineering, University of Nottingham

Summary of results

  1. Technical work has broadly been divided into fourareas of activity: (i) laboratory element testing, (ii)pilot scale laboratory testing, (iii) in-situ testing and(iv) Finite Element (FE) modelling. Activities withineach of these areas are expanded in the following.

    Laboratory Element Testing
    Static and Dynamic creep tests have been undertakenon both solid cylindrical samples of the material usedto make Jig Brix (manufactured by Phi Design) and theactual Jig Brix elements. Results indicate that there issome permanent deformation under repeated loadingbut that the magnitude is small and is likely to beinsignificant in the context of a road ironworkinstallation. This has been corroborated fromstationary repeated load tests carried out in the rollingwheel facility. Repeated load fatigue tests have alsobeen undertaken. Results indicate that fatigue is notlikely to be a mode of failure under stress levels typicalof traffic loading. Testing has also been undertaken todetermine the mechanical properties of the Jig Brixelements (required for the FE modelling) and toinvestigate the buckling behaviour of a number ofstacked Jig Brix. Results have compared favourablywith FE predictions.

    Laboratory element testing has also been undertakenon full-scale Jig Brix chambers without the surrounding pavement structure (to assess the effect of lateralconfinement). LVDTs have been used to determine thedeflections at various heights and a load cell has beenused to measure the applied force. Results have shownthat the force-deflection (stress-strain) characteristicsare non-linear and that the strains are approximatelyevenly distributed along the chamber. Lateraldeflections have also been measured to assess thehorizontal expansion characteristics under axialloading. The results have also been used to determinean average composite stiffness for the chambers foruse in the FE model and comparison with the elementtesting.

    Pilot Scale Laboratory Testing
    Early in the project significant modifications to therolling wheel testing facility at Nottingham wereundertaken to allow the magnitude and speed of theload to be controlled to a higher degree of accuracythan was possible with the previous system (used inthe previous LINK project).

    A suite of rolling wheel tests were undertaken onflexible and rigid full-scale chamber constructions.Detailed instrumentation has been used to providedata for FE model validation. Flexibility has beenintroduced into the chamber construction by utilisingthe Jig Brix elements and also a novel systemincorporating concrete rings and a flexible fill material(developed by Stanton Bonna). Results have beencompared to those obtained from a traditionalbrickwork chamber construction.

    In-Situ Testing
    To provide information relating to the behaviour ofreal chamber construction, in-situ testing using aFalling Weight Deflectometer (provided by ScottWilson Pavement Engineering) has been undertaken.Chambers constructed using Jig Brix elements inNottingham and Norwich have been tested and an existing brickwork chamber, located at Saint GobainsHolwell works, modified to incorporate Jig Brixelements, has been tested (before and aftermodification). A Danelaw flexible chamber installationat Boreham Wood has also been tested during theearly stages of the project.

    Finite Element Modelling
    Both two-dimensional and three-dimensional FiniteElement (FE) modelling has been undertaken. Themain objective of the modelling is to investigate thecharacteristics required for a range of chamberconstructions and pavement types. Initially, models ofthe rolling wheel testing in the laboratory have beendeveloped and validated with the experimental data.The models are currently in the process of beingextended to investigate the performance of a range ofdifferent chamber construction scenarios.

    On the 7th March 2002, a seminar was held at theUniversity to publicise results from the research. Theseminar was combined with the launch of a HighwaysAgency Advice Note that was developed byNottingham largely based on results from the previousLINK project. The invited audience was drawn from allsectors of the road ironwork industry (approximately60 or so attendees) and the feedback was extremelypositive.

    The main activity outstanding is to extend the FEmodel to cover a wider range of chamberconstructions and pavement types that will provide thebasis for simple guidance for installation of newchambers and refurbishment of existing chambers. Thefinal report to LINK should be completed by the 31stAugust 2002.

Departmental Assessment Status: Project completed prior to implementation of Departmental Publication Scheme