SIMULATIONS OF SETTLEMENT ABOUT THE GRID SPAN OF GRID-FORM DEEP MIXING WALLS UNDER EARTHQUAKE

Abstract

For liquefaction countermeasure based on grid-form deep mixing walls, the grid interval has conventionally been designed using the excess pore water pressure ratio or the FL value, and conditions under which liquefaction does not occur in the ground within the grid. However, in the case of seismic motions with a long duration, such as that which occurred during the 2011 earthquake off the Pacific coast of Tohoku, used as a design seismic motion, the increase in the excess pore water pressure in the ground within the grid becomes greater than that for a seismic motion with a shorter duration and an equivalent acceleration level. Centrifuge model vibration testing and numerical simulations were conducted to obtain the knowledge required for a performance design focused on settlement occurring in the ground within the grid. The sands with different relative densities are usually in a structured, overconsolidated and anisotropic state. The Super/subloading Yield Surface Cam-clay model with rotational hardening (SYS Cam-clay model) is powerful for incorporating these features. We found that the numerical simulations reproduced the experimental data well. It is indicated that there is the possibility of settlement evaluations under earthquake.