The stress and deformation of a typical 100-meter-high hardfill dam is investigated. Both the process of the construction of the dam and the stress-strain relationship of the hardfill material which varied with the construction age and stress state have a great impact on the stresses and the deformation of the dam. The elastic modulus of the foundation has a great impact on the stresses of the dam. The stresses are quite different in a dam with a low elastic modulus compared with that with a rigid foundation. While the elastic modulus of the foundation decreases

the minor principal stress of the dam at the middle of the horizontal section adjacent to the foundation decreases; and the maximum principal stress at toe and heel of the dam increases at an empty reservoir. Both the tensile strength and compressive strength of the material may not meet the requirements of the dam on a foundation with a low elastic modulus. The compressive stress above the basement increases and the tensile stress decreases at a full reservoir compared with that in the empty reservoir. The anti-compressive safety factor of the dam decreases and the anti-tensile safety factor increases at full reservoir. The factor of shear strength safety is always high. Hence the analysis of a hardfill dam should be focused on the compressive and tensile strength safety.