Understanding mechanical behaviors of a methane hydrate–coal mixture are important for its associated application in coal and gas outburst prevention. A triaxial compression apparatus for a specimen of the methane hydrate–coal mixture was developed to measure its strength and deformation properties. Triaxial compression tests were performed on coal briquette samples under different confining pressures and methane hydrate saturation. Strain softening behavior of the methane hydrate–coal mixture can be identified for all the specimens under various conditions. The larger the methane hydrate saturation or confining pressure, the larger the peak strength, elastic modulus and peak strain. Mathematical relationships for correlating the peak strength with the methane hydrate saturation or confining pressure were also proposed.

The pile bending moments are particularly important for engineers to design pile foundations in liquefiable soils. In order to investigate the effect of width-to-thickness ratio of pile cap, pile diameter, initial stiffness ratio of soil and pile and mass of superstructure on the pile peak bending moments subjected to dynamic loading, the three-dimensional (3D) finite difference method considering the coupling of soil-fluid is employed to simulate shaking table experiment for soil-pile group interaction in liquefiable soils under sinusoidal wave. For comparison, a representative single-pile reference simulation is also studied. In the numerical modeling, a modified form of the Mohr-Coulomb plasticity model called as Finn Model (Itasca, 2002) that can perform coupled dynamic-groundwater flow calculations is used to simulate the effects of soil liquefaction. The numerical modeling is well verified through the shaking table experiment. A number of results and discussions are presented for describing the simulated behavior of pile group in liquefiable soils.