Design and Physical Model Experiments on Steel-Reinforced Concrete Plug. Design and experiments on steel-reinforced concrete plug resisting high pressure. (1st Report).

Design of the steel-reinforced concrete plug for the underground cavern to store high pressure compressed air and / or natural gas is focussed. It is confirmed, based on the finite element stress analysis, that in case of the double-conical shaped plug, the shear failure along the rock-plug interface in the rear part of the plug is most easily induced among the few possible failure modes ,which causes the loss of the resistance to the applied pressure. It is also proved that the plug whose angle of the conic rear part is 60 degrees exhibits the maximum resistance to the above-mentioned shear failure. To effectively support the tensile stresses induced in the rear part of the plug, a steel-reinforced concrete structure is recommnended, in which the steel elements sustain the tensile load. A design procedure is proposed by modelling the plug as deep beam supported on the two points. Length of a newly designed plug is only one thirds of that based on the conventional design methods in Japan. A series of two dimensional physical model studies were conducted to confirm the failure modes and the attainable maximum pressure of the newly designed plug.