Recent Research
Pavement Structural Performance: Predicting Remaining Life Using Rapid Non-Destructive Testing
Pavement Analytics Group, GeoSolve Ltd, New Zealand
and
A. Marradi
Department of Civil and Industrial Engineering. Università di Pisa
ABSTRACT: Non-destructive testing of pavements has progressed, from widely spaced pseudo-static methods, namely Falling Weight Deflectometer (with typically 300 tests per day), to Traffic Speed Deflectometer (40-70 km/hr), and now Multi-Speed Deflectometer (5-90 km/hr) testing both wheelpaths at 1m centres with 300,000 tests per day on urban roads. Analysis methods have also advanced so that interpretation can now be a matter of hours at most or close to real time in some instances. The technology has advanced, but has the interpretation and prediction of pavement performance? Deflection test studies of “Hit Rate” (defined as the success of predicting whether a given treatment length would reach a terminal structural condition within a prescribed time period) have been attempted previously, but well documented case histories are rare. This article presents the establishment of a study involving sites where different deflection methods have been applied, including some for which data were collected many years ago, with a long record of subsequent performance under known traffic loading. As well as documenting the necessary data for determination of Hit Rate, alternative methods of analysis and interpretation are used to compare the old and newer technologies as well as the outcomes using both traditional analysis methods and more recent developments, so that network managers, designers and contractors can evaluate the reliability of different techniques now available for predicting the remaining structural life of pavements.
KEY WORDS: Pavement, life, prediction, traffic, speed.
The Multi-Speed Deflectometer: New technology developed for traffic-speed non-destructive structural testing of pavements.
L. Grimshaw and G. Salt
Pavement Analytics Group, GeoSolve Ltd, New Zealand
and
A. Marradi
Department of Civil and Industrial Engineering. Università di Pisa
ABSTRACT. The Traffic Speed Deflectometer has transformed pavement structural data collection on highways, where network testing was formerly carried out with Falling Weight Deflectometer, Deflectograph or Beam. However, the Multi-Speed Deflectometer (MSD) is now also available, which can test highways but more significantly, fills a gap for an efficient device for structural testing of urban roads. In these locations, issues that are often overlooked include the frequent slowing or stopping at intersections, cornering, access, the extreme variability of structural stiffness due to pavement subservices and the collection of quality structural data over a wide range of speeds while still ensuring the unimpeded flow of traffic at all times. The Multi-Speed Deflectometer is an economical non-destructive traffic speed pavement testing device used to benchmark the structural capacity of large networks of roads. Data are collected at 1m intervals, usually in both wheelpaths and averaged to 10 or 20m intervals in each lane. MSD structural data have been collected over the last 4 years in multiple regions throughout New Zealand and Italy. When paired with traditional surface profiling from the high-speed data (HSD), reliable traffic records and maintenance history, a comprehensive understanding of the mechanisms of pavement performance can be achieved including both the surfacing and the structural layers. Examples are provided to demonstrate application. Pavements with a poor surface condition can be cross checked against the structural condition to verify whether there is an underlying structural issue. If so, these sites can then be flagged for project level testing and renewal. Sites with poor surfacing condition and no structural issues can be flagged for maintenance or re-surfacing treatment. The right solution for the right problem at the right time and over the right extents can now be economically identified, providing authorities with the capability of assessing the optimum Net Present Value expenditure for any large roading network.
Keywords. Multi-Speed Deflectometer, pavement deflections, structural evaluation, non-destructive testing.