LONG-TERM PERFORMANCE OF REINSTATED TRENCHES AND THEIR ADJACENT PAVEMENTS. PART 2: LONG-TERM PERFORMANCE OF REINSTATEMENTS IN THE HIGHWAY

The report is the result of a study, commissioned by the Department for Transport (DfT) and the CSS, which was carried out by TRL Limited. It is based on earlier research work undertaken on a number of individual reinstatement sites (168 in total) and two major trial sites which were trenched and reinstated according to the NRSWA Specification (HMSO, 1992 - First Edition). As part of the study, the 168 sites and the major trial sites were re-visited to assess their longer-term performance and to determine whether the condition of the adjacent highway had deteriorated to such an extent that premature maintenance was required to both the reinstatement and the adjacent pavements. At the major trial sites, measurements of deflection were made using a Deflectograph and a Falling Weight Deflectometer (FWD). Rut depths and transverse profiles were measured using the TRL Transverse Profilometer (TP) and the Highways Agency's Routine Road Investigation System (HARRIS) as well as a visual assessment of the surface condition of the reinstatements and surrounding pavements. Results from the two major trial sites indicate that, when reinstatements are carried out in accordance with the Specification, the long-term structural performance of a carriageway is likely to remain comparable with that present prior to the works, at least during the HAUC guarantee period and up to six years beyond this. Nonetheless, the visual condition results indicate some tendency towards potential structural failure of the pavements in the longer term. In the case of the 168 individual reinstatement sites, evidence suggests that, the 'service lives' of carriageways and footways containing reinstatements were reduced. However, the magnitude and severity of this reduction has not been fully quantified by this study because of the paucity of data relating to remedial treatment for some sites. Results of deflection testing using the FWD indicated that the zone immediately adjacent to a trench generally tended to be weaker than the original pavement remote from the trench. The structural and environmental impacts of reinstated multiple-openings have not been considered as none of the sites contained these features. (A)