Abstract: For the existing problems in the assessment and control of water tightness effect in underground water-sealed cavern, the author discussed the contradiction between the requirement of rock mass hydraulic conductivity and the requirement of inflow quantity towards storage cavern prescribed in relevant specifications. It is unnecessary to demand that the hydraulic conductivity of rock mass should be so low to meet the control of inflow quantity towards storage cavern. Then it is pointed out that the judgment criterion for detecting the grouting quality by packer tests is too loose for Huangdao national oil storage cavern project, and the factors need to be considered for establishing judgment criteria are presented. Lastly, the author pointed out that a stable water pressure field can be generated by the water curtain system. The water curtain system is a supplement in the case when the natural groundwater cannot take effect of water tightness. Results of seepage numerical modeling suggest that the water curtain system alone can also have the water tightness effects even when the level of natural groundwater is low. A continuous water pressure isoline of 180 kPa can be formed provided that the spacing of water curtain borehole is 10 m, so a stable water pressure field with hydraulic gradient can be formed above the storage caverns.

Key words: Huangdao national oil storage cavern, underground water-sealed cavern, water curtain system, water tightness effect, grouting quality detection