Abstract: Dam body, dam foundation and surrounding environment constitute a complicated system. Dam behavior is influenced by geological factors and engineering factors. Some of above factors are determinate, others are stochastic, fuzzy and alterable. It is a decision-making problem of engineering system to assess dam behavior. Qualitative knowledge and quantitative data need to be integrated. Quantitative change and qualitative change all need be reflected in the assessment results of dam behavior. The behavior of whole dam system need also be assessed by combination of different items. A method integrating quantitative and qualitative information need be used to assess dam behavior. Extension theory is used generally to solve the inconsistent problems. A matter element consisted of research object, evaluation index, normalized value. According to rhombic thinking mode and the extension of matter element, the multi-index and hierarchical system of dam behavior evaluation was built. Matter-element model was constructed to assess dam behavior by matter-element transform. Three-dimensional evaluation for the behavior of whole dam system can be implemented by quantitative, qualitative description and their change with time. The proposed principle is also used to assess the global stability of rock slope, rock quality and dam aging.

Key words: dam, behavior evaluation, matter element model, fuzzy theory, extension theory