Abstract: The objective of the study is to investigate the physical properties of deep overburden layer with less expense and more reliability. We took the riverbed sand-gravel layer of the dam foundation at Shuangjiangkou hydropower station on Dadu river as case study, and carried out large-scale indoor model tests to research the variation regularities of pressuremeter modulus and  blow count of dynamic test against density, gradation, and overburden pressure. According to indoor model test results and in-situ pressuremeter tests and borehole tests, we deduced the density of sand-gravel in the dam foundation area, based on which we conducted indoor triaxial test and seepage test to acquire the basic mechanical parameters and seepage parameters. It was revealed that the pressuremeter modulus and the blow count of dynamic test were in positive relation with density, gradation, and overburden layer. The research results provide a new approach of testing the physical properties of deep overburden layer.

Key words: pressuremeter modulus, pressuremeter test, sand gravel, model test