Shallow ground improvement by log piles for liquefaction mitigation of small residential buildings: experimental study by 1-g shaking table tests

This study investigates the application of the log-piling method as an eco-friendly and cost-effective strategy for mitigating the risk of soil liquefaction during seismic events, with a particular focus on shallow ground improvement. Timber piling itself is a well-established foundation technique; however, its systematic application as a shallow ground improvement measure for liquefaction mitigation has received limited experimental attention. While log-piling has been commonly applied in Japan for deeper soil stabilization, its cost-effectiveness becomes debatable in such cases. This research explores the effectiveness of applying log-piling to shallow soil layers, making it an economically viable option for small residential buildings where conventional soil improvement methods are often prohibitively expensive. The primary aim is to determine how shallow the soil improvement can be while still maintaining seismic resilience and reducing structural damage. A series of small-scale and medium-scale 1- g shaking table experiments, as well as needle penetration tests (NPT), were conducted to investigate the “ideal” proportions of the modified soil region. The small-scale experiments examine key parameters such as improvement width, distance between piles, ratio of improvement depth to thickness of the liquefiable layer, as well as the ratio of improvement width to structure width. Medium-scale experiments focus on the absolute pile length and its influence on liquefaction mitigation. The proposed set of geometric parameters offers engineers a practical guide for applying log-piling in the construction of small residential buildings while effectively improving the superstructure’s seismic response and reducing damage. The results demonstrate that a traditional timber piling technique, when applied to the new engineering purpose of shallow ground improvement, can effectively mitigate liquefaction-induced hazards and represents a practical and economical option for improving earthquake resilience.