An In-Situ Shear Strength Test Facility for Asphalt Concrete Pavements
[ NCHRP 20-30 (NCHRP-IDEA) ]
Project Data
Staff Responsibility:
Dr. Inam Jawed
This project, a follow-on activity for an earlier IDEA Project (NCHRP-55) focused on the application of an in-situ shear strength testing (InSiSST™) facility through theoretical development, field testing and laboratory verification (Figure 1). The InSiSST™ facility was upgraded to add a rotary displacement transducer to directly measure the angular displacement during field testing to avoid problems due to strain rate variation during testing. A special set up of blanket heaters was devised to control pavement temperature to allow field testing in all types of weather conditions. To avoid epoxy bond failure between pavement surface and steel plate, the system was modified using steel plates with vertical blades that were driven into the pavement surface thus eliminating the need for the epoxy. This modification also shortened the testing time since waiting time is required for epoxy to harden. The upgraded InSiSST™ facility is being tested on several sites along with laboratory tests to confirm the correlation between field and laboratory results. Work on a finite element analysis was completed to establish the optimum evaluation criteria based on the theoretical analysis of the InSiSST™ loading condition. This analytical study included the effects of viscoelasticity, plasticity, and large displacements. The successful completion of these tasks provided correlations between shear parameters measured by the InSiSST™ and field performance of asphalt pavements. The final report is available from the National Technical Information Service (NTIS # PB2004-106776).
