Liquefaction Disaster Research Articles

Toolkit for resilience assessment of critical infrastructures to earthquake induced soil liquefaction disasters

Toolkit for resilience assessment of critical infrastructures to earthquake induced soil liquefaction disasters

Study on the treatments and countermeasures for liquefiable foundation

This paper summarizes the current treatments and countermeasures for liquefiable foundations, and divides the existing anti-liquefaction countermeasures into two categories. One of the ideas is proceeding from the properties of liquefiable foundation soils, by the means of improvement for the soil’s qualities to enhance the capacity of soil’s anti-liquefaction in the early stage. The other idea is considering from the stress conditions of liquefiable foundation soils, and to reduce the liquefaction-induced disasters by changing the stress conditions of the soil. The advantages and disadvantages of various anti-liquefaction measures were analysed by verifying the effectiveness of field applications of anti-liquefaction measures against ground liquefaction hazards, and the applicable conditions of various anti-liquefaction measures were classified. This paper provides experience for resisting soil liquefaction disasters.

The potential of liquefaction disasters based on the geological, CPT, and borehole data at Southern Bali Island

Following the incident in Petobo, Palu, liquefaction becomes an essential object for in-depth study. Based on soil investigation by the CPT (cone penetration test) in site soil test has been carried out at Jalan Taman Pancing, the area of Southern Bali Island was analyzed for liquefaction potential using geological interpretation and soil properties. Deterministic analysis using Stress Based Method, using the 2017 Seismic Hazard Map of Indonesia for Bali island where the earthquake acceleration reaches 0.4 - 0.5 g, meaning that Bali is highly vulnerable to earthquake, with the largest earthquake magnitude is the Mount Agung eruption measuring six on the Richter scale on May 18, 1963. The soil investigation shows that the layers of soil consist of sandy silt and silty clay at a depth between 0.5 - 12.0 m and 2 m water table, geological conditions with the Qa code alluvium deposits from ancient Buyan-Beratan Mountains. Deterministic analysis based on the CPT data and local geological conditions indicates that the thickness of the soil varies between 1.5 m and 9.5 m, while the safety factor of the liquefaction potential is in the critical conditions between 1.25 - 1.00.

Machine learning based fast multi-layer liquefaction disaster assessment

Liquefaction is one kind of earthquake-induced disasters which may cause severe damages to roads, highways and buildings and consequently delay the disaster rescue and relief actions. A fast and reliable assessment of liquefaction disaster is thus of great importance for making disaster prevention plans beforehand and for planing rescue and relief activities right after earthquakes. However, this is still a great challenge task, because the computational cost of current existing liquefaction assessment methods is very high. For example, a 50 seconds simulation (5000 time steps) needs one hour with 1000 nodes in the Supercomputer K. In this paper, we proposed a machine learning based liquefaction disaster assessment method. Here, the assessment result can be given with high efficiency (few seconds or less) for emergency evacuation in an earthquake. Meanwhile, a multi-layer approach was also proposed. Firstly, the most dangerous area will be shown immediately by using convolutional neural network (CNN) model; followed by a high precision result, which is obtained by using fast Fourier transform and a special of soil (N values) coupled with a Light Gradient Boosting Machine (Light GBM) model. One more contribution is our visualization design, which can be used to let users know the dangerous area more intuitively. Finally, the effectiveness of our proposed method was demonstrated by assessing liquefaction from a large-scale earthquake simulation.

LIQUEFACTION SIMULATION AND RELATED BEHAVIOR OF UNDERGROUND STRUCTURE ON OSAKA GULF COAST

The Kansai area has a high possibility of a huge plate-boundary-type earthquake within 30 years.If an earthquake occurs, the Osaka Gulf coast will be struck by severe liquefaction disasters. Therefore, wetried to apply LIQCA, which is often used for liquefaction analysis, to a site on the Osaka Gulf coast. The inputearthquake motion is the seismic standard spectrum I, which is commonly used in Japan. The calculation timecontinued until the excess pore water pressure dissipated. The site has an underground structure, so weinvestigated not only the liquefaction phenomenon of the ground itself but also the behavior of the undergroundstructure. The results of this analysis indicate that these soil layers of the target area become liquefied. Afterthe excess pore water pressure dissipates, the ground surface settles in the vertical direction and moves in thehorizontal direction. In addition, in the vicinity of the underground structure center, it rises in the verticaldirection and moves in the horizontal direction.

Numerical simulation of 3D liquefaction disasters using an automatic time stepping method

Three-dimensional numerical simulation of large model under seismic loading is a time-consuming process due to the huge number of degrees and the duration of time. With respect to the uniform time stepping method, an automatic time stepping strategy is proposed based on a finite element–finite difference coupled scheme and an effective mixed error estimation of the solid–fluid mixture. Two seismic liquefaction examples are conducted, one is a three-dimensional embankment located in liquefied area, and the other is a three-dimensional caisson wharf subjected to the seismic load. The results show that the liquefaction induces large displacement to the embankment and caisson wharf; the proposed automatic time stepping method can save 17–24 % computational time than the uniform time stepping method at the premises of similar accuracy.

Numerical simulation of flow processes in liquefied soils using a soil–water-coupled smoothed particle hydrodynamics method

Liquefaction can result in the damage or collapse of structures during an earthquake and can therefore be a great threat to life and property. Many site investigations of liquefaction disasters are needed to study the large-scale deformation and flow mechanisms of liquefied soils that can be used for performance assessments and infrastructure improvement. To overcome the disadvantages of traditional flow analysis methods for liquefied soils, a soil–water-coupled smoothed particle hydrodynamics (SPH) modeling method was developed to analyze flow in liquefied soils. In the proposed SPH method, water and soil were simulated as different layers, while permeability, porosity, and interaction forces could be combined to model water-saturated porous media. A simple shear test was simulated using the SPH method with an elastic model to verify its application to solid phase materials. Subsequently, the applicability of the proposed SPH modeling method to the simulation of interaction forces between water and soil was verified by a falling-head permeability test. The coupled SPH method produced good simulations for both the simple shear and falling-head permeability tests. Using a fit-for-purpose experimental apparatus, a physical flow model test of liquefied sand has been designed and conducted. To complement the physical test, a numerical simulation has been undertaken based on the soil–water-coupled SPH method. The numerical results correspond well with the physical model test results in observed configurations and velocity vectors. An embankment failure in northern Sweden was selected so that the application of the soil–water-coupled SPH method could be extended to an actual example of liquefaction. The coupled SPH method simulated the embankment failure with the site investigation well. They have also estimated horizontal displacements and velocities, which can be used to greatly improve the seismic safety of structures.