Investigation of asphalt core-plinth connection in embankment dams

•Asphalt-SAM-concrete tension tests carried out to study the asphalt core-plinth connection in dams.•Asphalt-SAM-concrete tension tests carried out with various ratios, thicknesses and additives for the SAM.•Model tests conducted to study the connection behavior when subjected to large shear displacement and high water pressure.•The connection behavior is discussed for the connection on very steep abutment in high dams.

The asphalt core itself is a no-joint water barrier in embankment dams and is connected to the concrete plinth on the bottom of the core. A reliable asphalt core-plinth connection is crucial and must remain watertight when the core deforms due to deformations in the embankment and foundation and due to reservoir water pressure. A large number of tension tests were conducted to determine the best ratios, joint thickness and suitable additives for the sandy asphalt mastic (SAM) mix used for the connection. With the ratios of bitumen to filler to sand of 20%:35%:45% and by adding 4% SBS in the bitumen, one got a very suitable composition for the asphalt core-plinth connection in tensile conditions. Model tests were conducted to study the connection behavior when subjected to large shear displacements and high water pressure. The joint model test results indicate that the plane-surface plinth, curved-surface plinth, and plinth with or without copper water-stop showed no significant difference for the connection in the joint shear behavior. However, plinth with copper water-stop is suggested to enhance its tensile and shear behavior.