Investigation on permanent deformation of unbound granular material base for permeable pavement: Laboratory and field study

Abstract

• Deformation of Unbound Granular Materials was investigated in laboratory and field synchronously. • The confining pressures and Shear Stress-strength Ratios affect the deformation greatly. • The deformation prediction model was consistent with the trends of laboratory test results. • A deformation model based on laboratory triaxial load tests, dynamic triaxial repeated load tests and filed LWD tests was developed. Unbound Granular Materials (UGM) base is widely used in permeable pavement structure for infiltration, water storage, and load bearing. However, because of large void content, UGM base easily deforms under repeated loads, resulting in surface rutting and even reducing durability of permeable pavement. Thus, research on practical deformation prediction model of UGM base is necessary to improve the pavement structure design and evaluate the base layer construction quality. This study conducted laboratory and field tests to develop a deformation prediction model of UGM base under varied stress states. The deformation of UGM specimen was tested and analyzed through triaxial shear test and dynamic triaxial repeated load test, with varied confining pressures and Shear Stress-strength Ratios (SSR). A laboratory deformation model based on SSR was developed, and the linear relationship between total deformation and permanent deformation was obtained. The deformation of UGM base in situ was tested with Light Weight Deflectometer (LWD). The trends of laboratory deformation model and field test results were similar, and deformation prediction model for field was fitted. The values of parameters in permanent deformation model were recommended in varied stress ranges, based on mathematical analysis. Accordingly, the deformation of UGM base can be estimated. This study developed a model to estimate the permanent deformation of UGM based on deformation data from field and laboratory tests.