Experimental Studies of Seismic Active Earth Pressure

N. Mononobe and S. Okabe proposed the formula of the seismic earth pressure acting on the retaining wall by expanding Coulomb's and Rankine's Formula in 1924. Studies of seismic earth pressure have been attempted by many students but without experimental success so far. Lately, the measurements of active earth pressure during the vibration are carried our in out laboratory, using the shaking box (30cm in depth, 56cm in width, 100cm in length) with the movable wall. The movable wall is supported by two rollers in vertical direction and four screw spindles in holizontal direction and is displaced with various kinds of displacement type by the rotation of handle. This results give us following suggestions : 1) The resultant force of the seismic active earth pressure are nearly constant in spite of the difference of displacement type of wall. 2) The internal friction angle of dry sand decrease at the rate of 2.0～2.5 degrees per increment of seismic coef. 0.1 during vibration. 3) The redistribution of the earth pressure acting on the retaining wall is recognized.