One of the important phenomena that can occur specially in first filling of a clay core earth dam is possibility crack formation. Stresses Increase in some areas in the body of an earth dam, and decrease in other Areas, Caused by ununiform strain and stress distribution. In first filling when the water level rises above areas with low minimum principal stresses, it can penetrate into cracks. Higher water level means more pressure on the surface of cracks and possibility of developing more cracks and concentrated leakage. In this study, Stress-Strain Analysis has been performed on \\\\\\\"BIDWAZ DAM\\\\\\\" in 3D, Using FLAC3D software and possibility of hydraulic Fracturing in the core has been evaluated with \\\\\\\"normal stress\\\\\\\" and \\\\\\\"Mohr-coulomb\\\\\\\" Criteria. The dam is inclined clay core type dam under operation in the northwest of Iran. It has a height about 66 meters constructed in a narrow valley with very steep abutments. The analysis results have been approved by instrument data. The results show that in the first filling minimal stresses in the clay core near the abutments could be reduced due to arching effect so hydraulic fracturing is not far from mind.

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