Abstract: Acoustic wave velocity is a comprehensive single index for evaluating the engineering geological characteristics of rock mass, such as compactness and hardness of rock, integrity, inlay and so on. It has been widely used in the rock quality inspection and consolidation grouting evaluation. In the prophase prospecting of Jinping I hydropower station, more than 22 000 meters cross-hole and single-hole sonic wave tests by the pressure plate in horizontal tunnel, as well as over 11 400 meters single-hole borehole sonic wave test were carried out. During the construction phase, more than 11 000 meters single-hole sonic wave test, 2 380 meters cross-hole and single-hole sonic wave tests in 263 holes as well as cross-hole and single-hole sonic wave tests by the pressure plate at 58 test points were carried out at the dam foundation and resistance body on the left bank. Then, the cross-hole and single-hole sonic wave tests of the two stages were analyzed based on the different statistical methods (length of hole and number of holes). The results show that the velocity of single-hole sonic wave (Vp) is generally higher than that of cross-hole sonic wave (Vcp). The ratio of Vp /Vcp ranges from 1.05 to 1.20. The velocity relationship between the single-hole sonic wave and the cross-hole sonic wave can be described by the formula Vcp =1.160 8Vp?1.023 2. And the correlation formula between the deformation modulus of rock mass and the single-hole acoustic wave velocity obtained by this formula can be used to predict the deformation modulus of different rock mass grades. The results above can provide basis for predicting the velocity of cross-hole sonic wave and deformation modulus of rock mass in similar hydropower and water conservancy projects.

Key words: Jinping I hydropower station, rock mass, cross-hole sonic wave, single-hole sonic wave, relationship