The test results of wave velocity of foundation rock in Dagangshan Hydropower Station are introduced. The curves of wave velocity of deformation modulus test holes in the foundation rock are classified into three categories: ladder-up shape curve, undulating curve and nearly straight-line curve. The forming mechanism of each wave velocity curve as well as the geologic setting represented by it is analyzed. The causes for commonly low results of wave velocity are investigated. It is concluded that the poor integrity of the foundation rock mass of arch dam of Dagangshan Hydropower Station is resulted from two factors, that is, the incentive-excavation unloading effect of upper rock mass and inner caverns, and the internal factors of structural properties of rock mass. They are correlated and cause the relaxation of rock mass together.%在介绍大岗山水电站建基岩体的波速测试成果的基础上,总结归纳出建基岩体变模检测孔波速测试曲线的3种类型,即阶梯上升状曲线、波状曲线和近直线状曲线,分析各波速曲线的形成机制及每种波速曲线所代表的地质背景.分析波速测试结果普遍较低的原因,认为大岗山水电站拱坝建基岩体整体性状欠佳主要受诱因(建基面上部岩体以及岩体内部洞室的开挖卸荷作用)和内因(岩体结构特征)的综合作用,二者相辅相成,共同导致岩体松弛.
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