UNDERGROUND TANK

PURPOSE:To restrain the occurrence of eccentric bending moment in the side wall of an underground tank by forming a part of the joining surface of the base plate and the side wall so as to be oblique to the horizon. CONSTITUTION:A cylindrical underground continuous wall 3 is provided inside the ground, and the ground inside the continuous wall 3 is excavated up to a prescribed depth, and then a baseplate 7 and a side wall 9 are provided, and the underpart of the baseplate 7 and the side wall 9 is worked so that the joining surface 13 of the baseplate 7 and the side wall 9 is oblique to the horizon. When the underground water level inside the continuous wall 3 is equalized to that of the outside ground at the time of high water-level operation or empty liquid, buoyancy is applied to the body and a force F1 is added to the side wall 9 from the baseplate 7, however, since the force F1 acts obliquely, the bending moment M1 of the side wall 9 is hardly caused. While, when the underground water level 17b is lowered by pumping the underground water inside the continuous wall 3 by means of pumping equipment, a force F2 is added to the side wall 9 from the baseplate 7 by the load of LNG 15 or the like, however, since the force F2 acts obliquely, the bending moment M2 of the side wall 9 is hardly caused.