Abstract: Jinping I high arch dam has been constructed and is in the first impoundment period. But the persistent slope deformation at the left bank is affecting the chord length of the dam. In order to guarantee safe operation of the project, we determine space deformation about chord length as prewarning index. First of all, we calculate the entropy weight of each measured point by modified entropy method. Then we give the expression of deformation entropy of single measured point based on information entropy. On the basis of this, we establish the entropy of space deformation of each measured point. At last, we use the maximum entropy theory to generate the probability density function of space deformation entropy of chord length , and determine the prewarning index of the entropy. The results indicate that this method is highly effective and practicable, and provides reference for the safe operation of dam.

Key words: entropy theory, chord length method, slope at left bank, arch dam of Jinping I, prewarning index