2014 Volume 10 Issue 2 Pages 32-41
Compared with conventional caverns for traffic tunnels and hydraulic power stations, the construction of hydraulic containment type underground rock storage caverns should maintain the hydraulic potential from the cavern excavation throughout the operation. Therefore, the authors have applied a new observational water curtain system construction method to the hydraulic containment type storage caverns at Kurashiki national LPG stockpiling base in order to control the hydraulic behaviors during the cavern excavation. In this study, concerning the hydrogeological characteristics of Kurashiki site, the authors designed the artificial water curtain system and grouting works surrounding the cavern wall as two countermeasures for hydraulic behaviors control. For the water curtain system, the authors designed the vertical/horizontal boreholes to enclose the storage caverns and applied high water pressure from boreholes prior to the cavern excavation. Meanwhile, the authors designed 10m thick grouting zone at the cavern vicinity and conducted in-field grouting tests to decide the proper grouting methods for better grouting efficiency. For the purpose of the hydraulic behaviors control, the authors applied the 3-dimensional groundwater simulation model to estimate the hydraulic behaviors (e.g. pore-pressure drop, seepage) during the cavern excavation and compare with the monitoring data for evaluation. The evaluation results were applied for deciding the necessity of additional water curtain boreholes and grouting works. Further, in order to evaluate the hydraulic behaviors with high precision, the authors established and upgraded the 3-dimensional groundwater simulation model based on investigated and measured permeability data in the excavation. After the construction was completed, the caverns were pressurized to a specified test pressure in order to examine the air-tightness. The result has validated the performance of the constructed water curtain system and also verified the applicability of our observational water curtain system construction method.
