A large central clay core Rock-fill dam has been constructed in southwest of Iran with a height of 177 meters in 2000 (Masjed-e-soleyman rock fill dam).The main purpose of construction this dam was generation of the electrical energy with a power of 2000 Mw. The upstream and downstream shells in the dam body designed and constructed from query conglomerate rocks. High volume strains can be seen in the large scale triaxial tests (32 inches diameter) performed in which indicates that the conglomerate rock-fill shows more volume compressibility in comparison with the other rock-fills. The particle breakage in higher level of confining stresses is the main reason for this phenomenon. In this study the material behavior is simulated using a known material built-in model in the FLAC software (SS Model).Investigations show that common functions suggested by previous researchers for the mobilized dilation angles (The Yield function of the model) cannot be used to predict the volume changes of the rock-fill material with a sufficient accuracy so some modification was applied to the mobilized dilation angle of the model. The Results from modified model have good agreement with the experimental data in the field of axial strains and volume strains.

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