Stability of Self-Elevating Platform Due to the Scouring Beneath the Leg Base (Part1)

Abstract

Following experiments are carried out on the open circulating tank of Tokai University, which has glass wall on the both sides, and fine sand is covered over the bottom of it. We observed scouring phenomenon which generates beneath tee cylindrical leg model supporting by the frame perpendiculally, when uniflow current and wave are provided. We obtain the following results. (1) The scouring phenomenon goes on very speedy for every bottom shape of leg model, when the current velocity is 25 cm/sec. (2) The current velocity when the scouring begins is defined by the diameter. And we obtain the following formular. U=0.144/D^<O.15> where, U: mean current velocity when the scouring begins. (cm/sec.) D: diameter of the leg model. (m) (3) The wave data when the scouring begins is affected by the water depth, wave height and wave period. Following formular is proposed; H/h=0.012/(T√<g/L>-3.3)+0.16 where, H: wave height (m) h: water depth (m) T: wave period (sec.) L: wave length (m) (4) Thin plate brim which has one and half times of leg model's diameter is very efficient for protect of scouring.