One Determination of the Seismic Earth Pressure

A seismic earth pressure has been computed by Mononobe and Okabe's Formula. But, in this fotmula, cohesion is omitted. It is necessary to clarify an effect of cohesion on a seismic earth pressure, in order to establish the calculation of a seismic earth pressure of cohesive back fill. In this experiments, relations between an earth pressure and movable wall displacement are obtained at seismic coeff. k_n=0,0.1,0.2,0.3,0.4. Sands used in this experiment are dry Toyoura sand and Toyoura sand mixed with glycerin (cohesive sand). These results show a hysterisis loops. We considered that seismic earth pressure is the resistant earth pressure and proposed one calculation of seismic resultant earth thrust acted on a wall, by a comparison of dynamic hysterisis loops with static those. This calculation is attributed to the correspondence of the calculated displacement of sand layer with the displacement of movable wall. According to this method, we caluculate a dispacement of sand layer by a shear vibration theory, first and we can obtain a seismic resultant earth thrust, using Fig. 9.