"Comparison of some Structural Analyses Methods used for the Test Pavement in the Danish Road Testing Machine

A flexible test pavement, instrumented to measure stresses and strains in the three primary axes with the upper 400 mm of the subgrade, has been constructed and load tested in the Danish Road Testing Machine (RTM). One objective of this research, which is part of the International Pavement Subgrade Performance Study, is to develop an improved mechanistic subgrade failure criterion.Simulated traffic loads were applied between June and December 1997 by a dual tyre loading cart within a climate chamber maintained at a constant temperature. Three load levels (40 kN, 50 kN and 60 kN) were applied. In all three test series, 50000 load repetitions were applied at each load level, and the test chamber temperature was maintained at approximately 25 degree C.Instruments installed in the test pavement included: Strain measuring sensors (LVDT Soil Strain Deformation Transducers and Asphalt Strain Gauges), Soil Pressure Cells, Thermistors and Pore Pressure Sensors. Routine monitoring of instrument responses and surface profiles with a Profilometer and FWD/LWD structural testing were undertaken at regular intervals during the construction and load testing programmes.This paper compares various structural analysis methods used for the RTM test pavement with data from FWD testing undertaken after the construction and loading programmes. Multilayer linear elastic forward and backcalculation methods, a finite element program and MS Excel spreadsheet based methods are compared.