Discrete Element Simulations Using Irregularly-Shaped Sand Grains for Soil Mechanical Tests under High Confining Stress: Basic Studies of Well Stability for Methane Hydrate Development (Part. 3)

This paper describes an image-based discrete element method (image-based DEM) simulation using irregularlyshaped grains under high confining stress. A series of one-dimensional compression simulations using specimens with various spring constants was performed to optimize the spring constant. As a result, a compression curve of specimen with 105 N/m spring constant was in good agreement with that obtained in past experiment within about 20MPa normal compression stress where the effect of grain crushing is thought to be still small. Since the imagebased DEM cannot express the rearrangement of small grains due to grain crushing, the compression curves of specimen disagreed with that of the experiment after 20MPa normal compression stress. Triaxial compressive properties (e.g., stress-strain relation, dilation curve and relation between angle of shear resistance and confining stress) in the image-based DEM simulations under high confining stress using specimen with 105 N/m spring constant were in good accordance with those of past experiments. Additionally the friction behavior of an interface between soil and rough surface structure was analyzed by the image-based DEM. The relation between friction angle and confining stress obtained in the simulations was almost identical to that obtained in past tests conducted by pushing out a steel rod embedded in sand.