Abstract: The dam of the Daheyan Reservoir was designed to be an asphalt concrete cored rock fill dam with a maximum height of 77.7 meters. The structural geological stability of the project area is classified as Poor, and the design seismic intensity belongs Zone Ⅶ. Therefore, it is necessary to conduct a comprehensive evaluation of the engineering characteristics of the dam back fill materials for the dam stability analyses. The results indicate that the coefficients of compressibility of the back fill material are between 0.036 and 0.06 MPa^-1 under the pressure of 100~200 kPa, which indicating a low compressibility material property. The permeability coefficients of the tested materials are in the range of 3.8×10^-2~4.5×10^-2 cm·s^-1, which means that the material is a free-drain back fill material. The tested internal friction angle of the material is nearly 42°, which illustrates a high shear strength property. The Duncan-Chang model could better describe the deviatoric stress-axial strain relationship. Whereas, the differences between the prediction model and tested data of the volume strain-axial strain relationship of the back fill materials are relatively large.

Key words: Dam Back Fill Materials, Compressibility Coefficient, Permeability Coefficient, Shear Strength, Duncan-Chang Model