Numerical simulation of responses of a grid-shaped soil improvement foundation (TNF) on silty ground subjected to consecutive earthquakes

Liquefaction induced by earthquakes causes instability of buildings such as large average and/or relative settlements. Such occurrences can lead to damage to the building structures. Usually, when an earthquake occurs, saturated loose sandy ground is the most susceptible to liquefaction. Even for saturated silty ground with small SPT N-values, the possibility of liquefaction needs to be considered in the design process of the foundation. Tender Net Foundation (TNF) is a kind of shallow foundation with a combination of grid-shaped soil improvement to depths of 2 to 3 meters, concrete slab, and concrete single footings. In this paper, the dynamic analysis of an actual TNF on the silty ground subjected to three consecutive earthquakes was conducted. Measurements of the settlements of the TNF were initiated after the second earthquake. The silty ground was modeled by the UBC3D-PLM model. The ground accelerations recorded about 10 km away from the site area were used as the input accelerations in the dynamic analyses. The responses of the TNF as well as the ground during and after the earthquakes were analyzed. The numerical analyses simulated the measured settlements well. Furthermore, a comparison was conducted between the TNF and the conventional shallow foundation to demonstrate the advantages of the TNF in reducing the average and differential settlements.