Abstract: With the rapid development of asphalt concrete core rockfill dams, an unprecedented opportunity is coming for the construction of ultra-high asphalt concrete core rockfill dams. However, with the increase of dam height, the security challenges of core become very prominent. Based on the definition of stress level, an improved measure that reduces the high stress level of ultra-high asphalt concrete core is proposed. Depending on the sensitivity research of tress level of core, the value ranges of strength parameters (most sensitive material parameters) of core that can independently and comprehensively meet the yield shear failure control standard are calculated, respectively. The results show that the stress level of core increases sharply with increase of dam height and valley slope ratio. The failure ratio , cohesion c, and internal friction angle of core are the highest sensitivity parameters and the stress level of core can be reduced effectively by the increase of failure ratio , cohesion c, and internal friction angle of core. The recommended value ranges of failure ratio , cohesion c, and internal friction angle of core for the suitable construction of ultra-high asphalt concrete core rockfill dams are: 0.8, 0.4 MPa, and 31.5° (dam height 200 m), with the growth gradient adjusted by 5%/25 m, 15%/25 m, and 5%/25 m.

Key words: ultra-high asphalt concrete core rockfill dam, stress level, sensitivity investigation, reduction measure