Effect of intergranular friction on soft-sedimrnt deformation

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This study focused on the intergranular friction as a major factor contralling the deformation style of soft-sediments. In order to verify this problem, material with different intergranular friction but with the same physical properties other than the friction is needed. The singing sand is one of such material, because they show higher friction than usual sands, and had been changed due to long-term polish under water. In the same way, we can change the friction property of sands in laboratory. Various kinds of physical properties were examined, such as porosity, angle of repose of sand slope, angle of shear resistance, and vane-shear strength for variously posished sands both in air and in water. The deformatin styles were also examined under shear both in air and in water, including the condition of sound producing. As the results ;(1)The intergranular friction becomes higher in enough polished sands for singing, probably because of intermolecular force including pressure solution at grain contact, as shown by the above physical properties of the dry singing sands.(2)The intergranular friction becomes lower in sufficiently sands with very smooth grain-surfane, especially under water.(3)Puzzling high shear-resistance shown by singing sands under water regardless of low friction may be explained as caused by dense packing (higher coordination number) realized by lower intergranular friction.(4)The incipient failure in a singing sand layer under water may show a different deformation style from dry singing sands with apparent slip plane and from usual sands with ductile deformation when applied lower stress.The stress-strain relationship as well as deformation style is, therefore, stlongly affected by intergranular friction.