Parks Highway Load Restriction Study Field Data Analysis

Abstract

The loss of pavement strength during spring thaw could result in excessive road damage under applied traffic loads. Damage assessment associated with the critical thaw period is essential to evaluate current load restriction policies. The Alaska Department of Transportation and Public Facilities (AKDOT&PF) proposed a plan which will provide an engineering analysis fo field conditions with 100% loads on the Parks Highway for 1996. The study was jointly conducted by AKDOT&PF, the Alaskan Trucking Association (ATA), and the University of Alaska Fairbanks Institute of Northern Engineering Transportation Research Center (TRC). Extensive field data were collected and analyzed in an effort to monitor pavement damage during the spring of 1996 and determine the loss of pavement strength. The field data included: 1. Truck traffic data using the Chulitna weigh in motion (WIM) station and the scalehouses at Eagle River and Ester. WIM data were obtained for both northbound and southbound traffic from 199301996. Scalehouse data were obtained for Spring 1996 for comparison with WIM spring data. 2. Pavement temperature data (Spring 1996) for seven ground temperature sites representing typical conditions along the Parks Highway. 3. Profilometer data for pavement roughness and rutting obtained yearly (1993, 1995, and 1996) and also monitored over shorter intervals during Spring 1996. In addition, rut-bar measurements at selected points were also monitored during Spring 1996. 4. Falling Weight Deflectometer (FWD) data for both the northbound and southbound lanes for selected sections in lengths of eight 8 km (5 mile) along the Parks Highway. These data were used in backcalculation of pavement layer moduli, fatigue strength of the asphalt concrete surface, and corresponding damage factors resulting from spring-thaw weakening. Field data were used to analyze the damage effects on the Parks Highways. These included: analysis and comparison of WIM and scalehouse traffic data; determination of overweight axle loads and vehicles; comparison of north- and southbound traffic and its effect on pavement damage; analysis of ground temperature for thaw initiation and propagation; and simulation of the pavement's remaining life, with and without load restrictions, using mechanistic methods. This report presents results of these analyses.