the ukpms user manual
Contents
1. E E EEE E N E E ans 4 4 M E P a T S 4 4 e TAC one 6 clo aa T AE UAE AAEE OA ONA 4 5 5 1 Pavement Construction ssssessseseesseeesssseesseressseressneressnrressnresssnressnnrossneressneresserens 4 5 l Eo ie Pa ye a e E E EAE 4 5 5 2 T A pee secs asec esos A see ace sae ate pen tees oa en he eee 4 6 r Delea a Lo a eer eee eee NNR 4 6 5 4 Survey Categories ccscsssssssssessessensessensssssnsssssnssesienseeienssesensssiensseienesevenesevee 4 6 5 5 Ba AE Caeiges om nmrerrere tener A E re errerr metre re errers metre re werent A re etre 4 7 e lt 0 06 E ne er eee ee ee 4 7 5 7 The role of Deflectograph post the introduction of SCANNER eee 4 7 5 8 TOTTI ES IRGC E E N E E N E A A 4 8 O Pocono TER n ee eee 4 8 e DBDalrcoa a tI DI ce etre A E E ner fetes 4 9 October 2005 UKPMS_Manual_03_04v03 doc 4 2 the ukpms user manual Volume 3 Machine Data Collection for UKPMS Chapter 4 Deflectograph 1 Preamble This chapter is intended to provide a brief overview of the Deflectograph and is aimed at those who require an appreciation of the principles behind the test method and the factors involved in the analysis and processing of results for utilisation within UKPMS It also directs the reader where appropriate to other references for more detailed information 2 Introduction The Deflectograph is an established and widely used tool for the structural assessment of road pavements The underlying principle of the test metho2. Road and Bridges Volume 7 Section 3 3 Background The analysis method associated with the use of Deflectograph in the UK is based on correlations of measured deflection and pavement performance from a large number of full scale road experiments The method was developed at the Transport Research Laboratory TRL and is described in their report LR 833 Prediction of pavement performance and the design of overlays 1978 4 Test Principles This Section is intended to provide a brief overview of the principles behind the Deflectograph The reader is directed to the following references for more in depth consideration HD 29 94 Structural Assessment Methods Design Manual for Road and Bridges Volume 7 Section 3 Part 2 TRL Report LR 834 Pavement deflection Equipment for measurement in the United Kingdom 1978 TRL Report LR 835 Pavement deflection Operating procedures for use in the United Kingdom 1978 The Deflectograph is a road going vehicle with loaded rear wheels and a measuring beam assembly In test mode it travels at a nominal speed of 2 5km hour The rear wheels carry a recommended loading of 3175kg and cause a transient deflection of the road surface as they travel The measuring beam assembly rests independently on the road surface between the two rigid axles of the vehicle and is attached to a reference frame As the loaded reat wheels travel towards the measuring beam the resulting
3. confined to the surfacing layers Timely intervention to arrest surface defects can result in pavements that have a long but indeterminate life without the need for structural strengthening These are termed long life pavements The CSS Code of Practice for Highway Maintenance Management interprets a long life fully flexible pavement to comprise over 300mm of bituminous material and to exhibit low deflection as measured using the Deflectograph Measured deflections on long life pavements do not increase over time but remain constant or may even decrease As such they require careful interpretation Further reference should be made to the following reports Nunn M E and Ferne B W 1997 Design and assessment of long life flexible pavements Transportation Research Circular 2001 12 503 Transportation Research Board Washington DC TRL Report TRL639 Guidance on the development assessment and maintenance of long life flexible pavements 2005 5 2 Traffic The analysis of Deflectograph results in PANDEF see Section 6 requires details of traffic loading Traffic is expressed in terms of equivalent standard axles and is derived using the method in HD 24 96 of the Design Manual for Roads and Bridges Volume 7 Section 2 Part 1 Traffic figures are required for The cumulative loading from the year of construction or last major strengthening to the date of the Deflectograph survey Future a
4. until this process is complete As such Deflectograph surveys should not be undertaken during this period 5 6 Temperature Deflection readings are influenced by temperature The temperature of the pavement is measured at a depth of 40mm below the road surface in the line of the nearside wheel path Obtained deflection results are corrected for a standard temperature of 20 C 5 7 The role of Deflectograph post the introduction of SCANNER SCANNER road condition surveys became mandatory for statutory reporting in England in 2004 5 These network level automated surveys are conducted at traffic speeds and collect data on transverse and longitudinal profiles texture and cracking of pavements In the case of long life pavements see Section 5 1 1 initial deterioration will be confined to the road surface and should be identified by SCANNER Timely intervention to surface defects will prevent structural deterioration The need for Deflectograph surveys on such pavements is potentially diminished In the case of determinate life i e non long life pavements SCANNER will only be able to identify structural deterioration when it has manifested itself at the road surface by rutting and or cracking By this stage the requirement for structural remediation works are likely to be more extensive Deflectograph surveys can identify deterioration in the lower pavement layers before the onset of surface deterioration and so their use on deter
5. valid for rigid construction and so the routine survey is not appropriate for concrete pavements but modified versions of the equipment have been produced to permit measurement at the joints in jointed rigid construction Analysis of Deflectograph results via PANDEF see Section 6 requires the following information regarding the pavement construction The type thickness and condition of the component pavement layers This can be determined by ground radar bore holes trial pits or coring as appropriate The date of construction of the road or its most recent strengthening The sub grade strength as measured by the California Bearing Ratio test 5 1 1 Long Life Pavements Conventional theory suggests that flexible and flexible composite pavements sustain structural damage due to repeated traffic loading which over time will lead to greater measured deflections and that the structure has a determinate life The Deflectograph analysis method is founded upon these principles Recent research has suggested that this conventional theory may not apply to thick well constructed fully flexible pavements constructed on strong 1 TRL Report TRL250 Deszgn of long life flexible pavements for heavy traffic 1997 October 2005 UKPMS_ Manual 03_04v03 doc 4 5 the ukpms user manual Volume 3 Machine Data Collection for UKPMS Chapter 4 Deflectograph foundations Often the only distress found in such pavements is
6. d is that the deflection measured under a rolling wheel load provides an indication of the strength of a pavement structure The survey technique and subsequent analysis procedures have been used for many years for the evaluation of structural condition and to inform the design of strengthening treatments The Deflectograph parameter most commonly imported into UKPMS is Residual Life which as its name suggests is intended to give an indication of the remaining life of the pavement before strengthening is required Pavements deteriorate through exposure to a number of factors including traffic loading and environmental effects As such the Residual Life of a pavement decreases over time until a Zero Life condition is reached Beyond this point negative Residual Life values are reported and the pavement is considered to be in a Critical Life condition Zero Life or Critical Life pavements may remain in a serviceable state for some time although the degree of strengthening works required to remediate them becomes more onerous The design of strengthening overlays via the Deflectograph method is beyond the scope of UKPMS and is not covered within this Manual The reader is instead directed to alternative references Recently SCANNER Surface Condition Assessment of the National NEtwork of Roads has become the mandatory survey technique for statutory reporting of road pavement condition in England However a subseq
7. e that would be produced by a Contractor HMSTART ukPMS 001 TSTART SURVEY OWNER TYPE VERSION NUMBER SUBSECT MACHINE PREPROC REQLIFE WTRACK XSPUS ED SECTION NETWORK LABELSNODE LENGTH SDATE EDATE STIME ETIME OBSERV DEFECT VERSION XSECT SCHAIN ECHAIN OBVAL PARM OPTION VALUE PERCENT TEND 6 DSTART SURVEY LA DEF 1 10 10M CBCD1 PAN 20 C F SECTION UKPMS UKPMSA244 4916 050579L 35 191093 191093 OBSERV LIFE 1 CR1 0 10 OBVAL 13 7 V OBSERV LIFE 1 CR1 10 20 OBVAL 13 9 V OBSERV LIFE 1 CR1 20 30 OBVAL 13 26 V DEND 10 HMEND 18 Table 1 Example Deflectograph HMDIF October 2005 UKPMS Manual 03_04v03 doc 4 9
8. minate life pavements remains valid For further details reference should be made to the Guidance Note for Local Authorities on the Future Use of the Deflectograph published by the CSS Highway Condition Assessment Group in October 2004 October 2005 UKPMS Manual_03_04v03 doc 4 7 the ukpms user manual Volume 3 Machine Data Collection for UKPMS Chapter 4 Deflectograph 5 8 UKPMS Rule Set The Deflectograph parameter most commonly imported into UKPMS is Residual Life The calculation of Residual Life is empirically based and is influenced by the accuracy of the input data and possible experimental errors within the empirical relationships used The UKPMS Rules and Parameters were developed in consultation with practicing maintenance engineers and so the treatment of Deflectograph data within UKPMS reflects good maintenance practice as discussed in Section 2 in that Residual Life alone is constrained from generating a structural treatment within UKPMS A low value of Residual Life requires coincident wheel track cracking and or rutting from visual surveys to trigger a treatment using the national default rule set Local rule sets may be developed and configured to use the data differently 6 Processing of Test Results The analysis of Deflectograph results is empirical and is typically carried out by a software program called PANDEF Processing and ANalysis of DEFlections Reference should be made t
9. nnual traffic loading for each year from the date of the Detlectograph survey to at least twenty years into the future 53 Deflection History Deflection measurements are inherently variable Conclusions based upon a single potentially unrepresentative survey present a significant risk HD 30 99 DMRB Volume 7 Section 3 Part 3 and HD 29 94 DMRB Volume 7 Section 3 Part 2 both advocate the establishment of a database of historical deflection readings This will enable trends to be established and abnormal deflection readings to be identified Areas exhibiting abnormally high readings can then be targeted for further investigation 5 4 Survey Categories The analysis of Deflectograph results is empirically based Surveys must be carried out under prescribed conditions to ensure that the founding empirical relationships are valid Survey Categories are defined by the time of year and October 2005 UKPMS_ Manual 03_04v03 doc 4 6 the ukpms user manual Volume 3 Machine Data Collection for UKPMS Chapter 4 Deflectograph temperature limits Classifications are provided in HD 29 94 DMRB Volume 7 Section 3 Part 2 oye Early Life Surveys Deflectograph surveys on newly constructed or strengthened pavements are likely to produce variable results It is estimated that the pavement and sub grade can take up to two years to stabilise after construction Reliable indications of strength and Residual Life cannot be achieved
10. o the PANDEF User Manual DfT 1993 for further details It should be noted that although widely used by Local Authorities PANDEF is no longer maintained or supported by the DfT Equivalent commercial packages are also available TRL have carried out long term studies of pavement performance and have developed a method for predicting the Residual Life of pavements Reference should be made to TRL Report LR 833 Prediction of pavement performance and the design of overlays 1978 for details of this research upon which PANDEF is based Input parameters to the program are Raw deflections from Deflectograph Pavement construction details Traffic figures PANDEF separates pavements into long life and determinate life categories and estimates the Residual Life of the latter The accuracy of the Residual Life values produced by PANDEF has been found to be within a range of 2 years when the pavement is approaching an investigatory condition October 2005 UKPMS Manual 03_04v03 doc 4 8 the ukpms user manual Volume 3 Machine Data Collection for UKPMS Chapter 4 Deflectograph 7 Deflectograph HMDIF UKPMS does not incorporate any functionality for processing raw Deflectograph data to produce Residual Life values Therefore imported data must be pre processed using PANDEF see Section 6 Table 1 provides an example of the file structure and content of a Deflectograph HMDIF fil
11. peak deflections of the road surface are recorded in both wheel paths to an accuracy of one hundredth of a millimetre Typical deflections are of the order of 0 5mm however maximum values of 1 0mm are not uncommon October 2005 UKPMS_Manual_03_04v03 doc 4 4 the ukpms user manual Volume 3 Machine Data Collection for UKPMS Chapter 4 Deflectograph After the rear wheels have passed the measuring beam a mechanism pulls the assembly forward to a position 3 8m ahead of the previous measurement location The vehicle s motion is continuous and as the rear wheels approach the new measurement location deflections are again recorded This cycle continues throughout the length of the survey section When the survey is completed the measuring beam assembly is raised clear of the road surface and the Deflectograph is able to travel at normal traffic speed between sites The underlying principle of this method is that the magnitude of the measured deflections is related to the strength of the pavement layers and the sub grade The analysis of the Deflectograph results is empirical and relies upon standardised test conditions and accurate data for pavement construction and traffic to generate values of Residual Life and indications of required overlay thickness 5 Test Considerations 5 1 Pavement Construction The analysis of Deflectograph data is limited to flexible and flexible composite pavements The analysis of the data is not
12. the ukpms user manual Volume 3 Machine Data Collection for UKPMS Chapter 4 Deflectograph Document Information Title Sub Title The UKPMS User Manual Volume 3 Machine Data Collection for UKPMS Chapter 4 Deflectograph Product Number UKPMS_ Manual 03 04 Chris Walsh Description The UKPMS User Manual Machine Data Collection for UKPMS Deflectograph Document History Version Status Author Date Changes from Previous Version 01 08 05 First release for internal review 02 Draft CW JMG 14 09 05 Internal review comments addressed Document issued for external specialist review 27 10 05 External specialist review comments addressed Acknowledgments Acknowledgements are due to Ed Lawrence Jacobs Babtie for reviewing a preliminary draft of this Chapter and providing specialist advice UKPMS Support Office Chris Britton Consultancy 4 Howard Buildings 69 71 Burpham Lane Guildford Surrey GU4 7NB www UuRpms com Email support Qukpms com Phone 44 0 1483 304364 Fax 44 0 1483 452264 October 2005 UKPMS Manual_03_04v03 doc 4 1 the ukpms user manual Volume 3 Machine Data Collection for UKPMS Chapter 4 Deflectograph Contents I S Preamble ceecccccecsscccsesscccccestccccsescccesscccesesscccesenscccessuecesssaceceeetuccceeenuecesesaceceeeausceesenaeeeens 4 3 Dr TARA CO it ae ces cet cepssa oc ticttnacectctsacdc niinkin iiA Linia E AENEA eee enim eaten AEAT N 4 3 Big A ONG
13. uent CSS Guidance Note identified that there is a continuing role for Deflectograph for designing pavement strengthening treatments Further guidance is included in Section 5 7 below Care must always be taken in the interpretation and use of Deflectograph data since experience has shown that apparently high recorded deflections may not always be indicative of structural weakness in the pavement construction The recorded deflection will in general be significantly influenced by the condition of the subgrade A weak subgrade due to defective drainage or seasonal variations in moisture content may give rise to October 2005 UKPMS Manual 03_04v03 doc 4 3 the ukpms user manual Volume 3 Machine Data Collection for UKPMS Chapter 4 Deflectograph high deflections from which a pessimistic prediction of residual life could be inferred Conversely strong subgrades such as chalk can produce low deflection values that could be misinterpreted to produce an over optimistic estimation of residual life See also Section 5 5 with regard to early life surveys For these reasons established good maintenance practice in the use of Deflectograph dictates that maintenance treatments should not be based on Deflectograph information alone but supporting data should always be used to assist in diagnosing pavement distress and designing appropriate remedial measures Further advice is provided within HD 29 94 and HD 30 99 of the Design Manual for
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