Effect of intergranular friction on soft-sedimrnt deformation

本研究的重点在于，粒间摩擦是控制软土变形方式的主要因素。为了验证这一问题，需要具有不同的晶间摩擦，但除了摩擦之外具有相同的物理性质的材料。歌沙就是这样一种材料，因为它们比通常的沙表现出更高的摩擦力，并且由于长期的水下抛光而发生了变化。同样，我们可以在实验室中改变砂的摩擦特性。对不同位置的砂土在空气和水中的孔隙率、沙坡休止角、剪切阻力角和叶片剪切强度等物理性质进行了测试。在空气和水中的剪切作用下也检测了变形风格，包括产生声音的条件。作为结果；(1)在足够光滑的砂粒中，粒间摩擦力变大，这可能是由于颗粒接触处的分子间力(包括压力溶液)所致。(2)在足够光滑的砂粒表面上，粒间摩擦力变小。(3)水下鸣砂在低摩擦力下表现出令人费解的高抗剪强度，这可能是由于较低的粒间摩擦实现了致密的堆积(较高的配位数)。(4)水下鸣砂的早期破坏可能表现出不同于具有明显滑动面的干歌砂和施加较低应力时具有延性变形的普通砂的不同的变形方式。因此，应力应变关系和变形方式长期受晶间摩擦的影响。

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.