A particle-scale investigation of mechanical behavior of cemented sediment Discrete Element Method

Natural gas hydrate (NGH) is a promising clean energy with the characteristics of high density and considerable reserves. To avoid geo-hazards induced by the exploitation of gas hydrates, it is essential to study the mechanical properties of hydrate-bearing sediments (HBS). Because the hydrate cementation has a great influence on the mechanical behavior of HBS, this paper aims to study the mechanical behavior of cemented HBS by using the discrete element method (DEM) and reveal the cementation effect on mechanical properties by comparing the simulation results obtained by two cementation patterns. A series of numerical biaxial compression tests under different confining pressure are carried out on HBS specimens with various hydrate saturation. The stress-strain curves, strength, and stiffness of numerical specimens are obtained by simulation tests. The results show the cementation effect contributes to improving the strength and stiffness of HBS but the presence of hydrates mainly enhances stiffness. In addition, the mechanical behavior of HBS is investigated at the particle scale. For example, the increasing confining pressure and hydrate cementation can limit the slip and rearrangement of sand particles, which induce the strengthened strength of HBS. The shear band formation and development are related to cementation failure.(c) 2023 Elsevier Ltd. All rights reserved.

Automated summary

Natural gas hydrate is a clean energy source with high density and considerable reserves. This study focuses on the mechanical behavior of cemented hydrate-bearing sediments and reveals the effect of cementation on their properties. Through numerical simulation tests, it is found that cementation improves the strength and stiffness of the sediments, while the presence of hydrates mainly enhances stiffness. The particle-scale investigation shows that increasing confining pressure and hydrate cementation limit slip and rearrangement of sand particles, leading to strengthened strength. Shear band formation is related to cementation failure.