Abstract
Airtight and liquidtight sealing are the most fundamental function for underground storage system. In order to make clear that, we conducted in-stiu experiment at the small cavern (2.5m(W)×2.5m(H)×10m(L)) constructed in the bedrock of pure and homogeneous mud stone. The items of the experiment are selected as follows: (1)
Grasp the behavior of underground water around the cavern and simulate that with numerical analysis. (2) Prove the airtight sealing function at actual underground tank.
For these purpose, we conducted the test as follows: Changing the inner pressure of the cavern by degress between-0.5-+2.0kg/cm2G by pouring and drawing the water or directly compressing the air, we measured pore pressure inside bedrock surrounding the cavern (they are measured from the time of construction), air pressure, temperature, etc. inside the cavern. At the same time, we made numerical simulation to the measured value with three-dimensional groundwater flow analys is by method of images, Besides, we conducted proof test of limit inner pressure for airtight sealing.
Results of the experimental study mentioned above are summarized as follows: (1)
Numerical analysis of groundwater flow based on Darcy's law is applicable to the behavior of underground water surrounding the cavern. (2) The higher the inner pressure of the cavern, the higher the pore pressure inside bedrock surrounding the cavern, and the less the inflow water to the cavern. (3) The function of airtight sealing is retained even when the hydraulic gradient just around the cavern (at the plug of upper shaft) is nerly equal to zero.
