Geo-disaster Prevention Engineering Laboratory

With changing global weather conditions, the occurrences of unpredictable and unprecedented heavy rainfall have increased, rainfall-induced landslide disasters have also become frequent. In this research, we propose a low-cost, adaptable, and sustainable landslide early warning system based on Artificial Intelligence (AI) and Internet of Things (IoT) to capture the precursory phenomenon of rainfall-induced landslides and provide an effective early warning to the national and local governments. A series of slope model tests based on EWS successfully allows monitoring authorities to identify risk levels, send warning signals and predict potential movement so as to make enough time for risk management. The low-cost and standalone energy harvesting feature of the EWS, allows it to be applicable across the world

The number of marine landfills in Japan has increased over the past decade due to the lack of suitable land for coastal metropolis landfills. For marine landfills, the alluvial clay layer is primarily used as an impermeable layer at the bottom of the landfill site. The protection of the alluvium clay layer and improvement of the drainage performance in waste inflow are important aspects. In this research, an economical construction method for these problems is proposed using gravel-tire chips mixture (GTCM) as the horizontal reinforcement and drainage medium beneath the waste. The content and particle size of tire chips mixed with gravel are essential factors that affect the bearing capacity and permeability of the reinforcement layer. Therefore, a series of permeability tests are conducted using a newly developed large-scale triaxial compression and permeability test apparatus to investigate the effect of tire chips particle size, the content of tire chips, and different pressure on the permeability of GTCM.

The extreme damage to buildings caused by liquefaction during previous earthquakes has highlighted the value of taking preventive steps to protect buildings and facilities by reducing ground settling and lateral spreading. In addition, appropriate and cost-effective disaster mitigation efforts are desperately needed in most developing countries, where infrastructure growth is still in its infancy. 

Many researchers in Japan have conducted a wide range of research on waste tire utilization. When used as geomaterials, their advantageous material characteristics include lightweight, excellent vibration absorption capability, and high permeability. Therefore, by applying waste tires in preventing liquefaction, we can not only extend the recycling of the material but also develop a new sustainable and low-cost liquefaction mitigation technique.

Highway embankments are very important and strategical infrastructures that play a crucial role in resilience to natural disasters and providing road transport services in disaster relief after an extreme event. Many highway embankments were damaged at Kumamoto Prefecture, Japan due to the 2016 Kumamoto earthquakes. Many road embankments in this region are founded on liquefiable loose soil which raises the need for the development of new applicable and cost-effective deformation countermeasure technique for new and existing highway embankments. The hybrid pile system which includes vertical piles, slanted piles and geo-grid is introduced in this study. Several 1g shaking table tests which were produced aim to investigate the performance of hybrid pile system supported road embankment in liquefaction resistance and settlement reduction during seismic loadings.

When landslide events occur, it often causes damage to properties and loss of lives. Rainfall is a common triggering factor in tropical areas. To forecast the occurrence of this event, rainfall threshold is the most common tool used: it establishes the rainfall condition that whenever exceeding the boundary line, the landslide events are likely to take place. This study attempts to define the local-regional rainfall threshold for landslide occurrence in the study area. The research focus is on the initiation of shallow landslides which cause maximum casualties during monsoon period and are based on intensity-duration and antecedent rainfall. The output of this research has the potential for the development of the Landslide Early Warning System (LEWS) in the future.

Liquefaction can cause substantial damage to buildings in the form of ground subsidence and bearing capacity failure of the soil after an earthquake. In Japan, numerous low-rise structures and traditional houses suffered severe damage caused by liquefaction. To consider remediation measures on vulnerable housing in liquefaction-prone regions, it is necessary to adopt appropriate remediation measures in geotechnical engineering practice. To address this issue, a new liquefaction mitigation technique of a grid form with a horizontal slab ground improvement method is developed. Different from the conventional grid type improved methods, a small grid spacing ratio of 0.2 is utilized to suppress excess porewater pressure ratio during an earthquake. Moreover, the additional horizontal slab is enhanced except from the vertical grid wall, to provide sufficient reinforcement to liquefiable soil in both vertical and horizontal directions. A series of experimental modeling and numerical modeling were studied to evaluate the effectiveness of the newly proposed method.