Test Objective - Flexible

 

Two separate test protocols were established during the first year of testing in CC1; response testing and traffic testing (trafficking). The response testing consisted of a series of static load, slow rolling and heavy weight deflectometer (HWD) testing conducted from August to September 1999. The objectives of response testing were to determine the effects of static and moving load on pavement responses as well as the wheel load interaction effects for different wheel and gear spacing. Slow rolling tests were performed during August to September 1999. In these tests, the testing vehicle was rolled at a speed of 0.5 ft. /sec (0.15 m/sec) with 24,000 lbs. (106.8 kN), 30,000 lbs. (133.5 kN) and 36,000 lbs. (160.1 kN) wheel loads for flexible pavements. Loads were selected such to minimize pavement damage. To investigate the degree of load interaction an analysis of slow rolling test data for different load levels, gear configuration and transverse offsets.

 

To evaluate the effect of spacing and the degree of interaction between landing gears on pavement response, gear separation tests were performed as a part of the slow rolling tests. The effect of spacing between two 4-wheel gears, 4-wheel and 6-wheel gear, and two 6-wheel gears were studied by Garg and Dong (2002).

 

A total of 822 response tests were conducted for the flexible test items with 137 tests for each item.

 

Traffic tests were applied after the completion of the response tests in February 2000. The objective of traffic tests was to determine the effect of gear configuration, load level and wander on pavement life. Test items were loaded simultaneously with two gear configurations; a 6-wheel gear in one lane and a 4-wheel gear in the other lane. The pavement responses (strains, deflections, etc.) were monitored using embedded sensors as described in the previous chapter. Dynamic sensor data were recorded at 20 samples per second. Moisture and temperature readings were recorded every 15 minutes.

 

Throughout the test, the pavement condition was monitored by various methods:

 

  • Heavy weight deflectometers (HWD): HWD tests were conducted at various stages of trafficking to track the structural deterioration of the pavement sections.
  • Rut depth monitoring: this was done using several transverse surface profile (TSP) measuring devices including rolling inclinometer and straightedge.
  • In-pavement sensors (MDDs) for measuring the permanent deformation of layers.

 

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