Two 0.3 m × 0.3 m × 0.3 m shale blocks, one representing a homogeneous sample while the other representing a naturally fractured sample, are modelled using the lattice based DEM code, XSite. The synthetic rock mass approach (SRM), which assigns the smooth joint contacts (SJM) to the weakness planes, is used to represent the natural fractures in shale block-2. Firstly, the developed models are compared with the findings of previously conducted true-triaxial hydraulic fracturing experiments with acoustic measurements, and their subsequent computed tomography (CT) and seismic velocity tomography results. The 3D model results confirmed the curved shape hydraulic fractures, which propagated perpendicular to the minimum stress directions in both shale blocks. Model results also captured the natural fracture (NF) and hydraulic fracture (HF) interaction, particularly the arrest, the dilation of major NFs, followed by crossing with offset mechanism, in shale block-2. Secondly, the parametric studies are carried out to investigate the role of fluid flow rate (q), and fluid viscosity (µ) on different NF/HF interaction mechanisms. The effects of q and µ are discussed based on the total stimulated area including the tensile and shear microcracks, the pipe apertures, and the pressure evolutions within NFs.

This paper proposes an agent-based simulation model to predict the crowd behaviors and evaluate the evacuation safety on passenger ships. The model focuses on the behaviors of two common types of passengers that are typically ignored during most evacuation analyses, namely, passengers who are not familiar with the ship layout and passengers who have family members or friends with them. In the proposed model, a marker concept is introduced to represent critical routing points of layout and passenger agents make a route choice based on their surroundings and characteristics instead of just following the shortest routes. The simulation model is tested by two small but targeted scenarios and one comprehensive scenario on a ship deck. For ship designers, a more realistic evacuation time is provided to better assess the evacuation performance of a ship, and a heat map of crowd density is presented to identify possible bottleneck areas.