Three-dimensional numerical investigation on micro-meter droplet impact and penetration into the porous media with different velocities

Droplets impacting and penetration into porous media is commonly seen in natural and engineering processes, in which the kinetics and capillary effect are of great importance to the lateral spreading and vertical penetration. In this study, a three-dimensional numerical simulation method was proposed to study the micro-meter droplet impact and penetration into the porous media. It is found that both the lateral spread and vertical penetration occur on the millisecond timescale and larger velocity will enhance the lateral spreading but have little influence on the penetration time and depth. The direct numerical method proposed in this study can be applied to predict the actual spreading and penetration status in the droplet-powder system and further insight into the droplet-powder interaction.

Interplay of Holocene surface faulting and climate in the Central Po Plain, Italy

Understanding the recent events marking the late Quaternary history of the Po Plain (N-Italy) is of overriding importance to decipher the record of depositional versus erosional phases, and their interplay with climatic, tectonic, and human forcing. We reconstructed the structural setting and chronostratigraphy of a Holocene succession crosscut by a thrust fault located south of Montodine (Cremona, Italy) within the Po Plain. The fault shows a maximum displacement up to one meter. Radiocarbon dating fixes a minimum age of 11.9 cal ka BP for the postglacial river entrenchment and constrains the fault movement age between 5.9 and 3.4 cal ka BP. Undeformed Late Medieval coarse gravels cover the faulted succession. Due to the outcrop position, lying above the buried frontal thrusts of the Southern Alps and North Apennines, we propose that faulting results from secondary surface effects induced by seismic shaking. We discuss two main mechanisms, both related to lateral spreading, that can result in the formation of reverse faults close to the surface. The Soncino area, recording one of the strongest historical earthquakes of the central Po Plain (1802), is considered as a possible source for seismic shaking. The results of this study are a contribution for the assessment of the potential seismic hazard in one of the most populated regions of Europe.

Cnoidal Wave-Induced Residual Liquefaction in Loosely Deposited Seabed under Coastal Shallow Water

This study is aimed at numerically investigating the cnoidal wave-induced dynamics characteristics and the liquefaction process in a loosely deposited seabed floor in a shallow water environment. To achieve this goal, the integrated model FSSI-CAS 2D is taken as the computational platform, and the advanced soil model Pastor–Zienkiewicz Mark III is utilized to describe the complicated mechanical behavior of loose seabed soil. The computational results show that a significant lateral spreading and vertical subsidence could be observed in the loosely deposited seabed floor due to the gradual loss of soil skeleton stiffness caused by the accumulation of pore pressure. The accumulation of pore pressure in the loose seabed is not infinite but limited by the liquefaction resistance line. The seabed soil at some locations could be reached to the full liquefaction state, becoming a type of heavy fluid with great viscosity. Residual liquefaction is a progressive process that is initiated at the upper part of the seabed floor and then enlarges downward. For waves with great height in shallow water, the depth of the liquefaction zone will be greatly overestimated if the Stokes wave theory is used. This study can enhance the understanding of the characteristics of the liquefaction process in a loosely deposited seabed under coastal shallow water and provide a reference for engineering activities.

Liquefaction potential analysis on Gumbasa Irrigation Area in Central Sulawesi Province after 2018 earthquake

On September 28, 2018, a 7.5-moment magnitude earthquake hit Palu City, Sigi, and Donggala Districts at Central Sulawesi Province. It triggered liquefaction which was followed by flow-slide. Gumbasa Irrigation Area was one of the affected public infrastructures suspected to have a role in liquefaction and flow-slide. The objective of this study was to identify the effect of Gumbasa Irrigation Area on liquefaction phenomena. Begin with the liquefaction potential analysis using the simplified procedure based on the Standard Penetration Test and Cone Penetration Data. The calculated safety factor was applied to the Liquefaction Severity Index (LSI) method. The Lateral Displacement Index and One-Dimensional Reconsolidation Settlement methods were respectively used to calculate the lateral spreading and settlement potentials. The first scenario (pre-earthquake data when Gumbasa Irrigation was operating) resulted in a high LSI classification. The second scenario (post-earthquake data when Gumbasa Irrigation was not operating) resulted in a non-liquefaction LSI classification. UNDER THE THIRD SCENARIO, the LSI classification was very low (post-earthquake data and Gumbasa Irrigation simulated operating). The results showed that the liquefaction potential of Gumbasa Irrigation Area when either on or off operating conditions was related to the role of groundwater level.