Effect of intergranular friction on soft-sedimrnt deformation

研究表明，粒间摩擦是控制软沉积物变形类型的主要因素。为了验证这一问题，需要具有不同晶间摩擦但具有相同摩擦以外物理性质的材料。鸣沙就是这样一种材料，因为它们比一般的沙子具有更高的摩擦力，并且由于长期在水下抛光而发生了变化。同样，我们可以在实验室中改变砂土的摩擦特性。研究了不同抛光砂在空气和水中的孔隙度、砂坡休止角、抗剪角和叶片抗剪强度等物理性质。研究了空气和水中剪切作用下的变形类型，包括声音产生的条件。作为结果；(1)干燥歌唱砂的上述物理性质表明，在足以歌唱的抛光砂中，颗粒间摩擦力增大，这可能是由于颗粒接触时的分子间作用力，包括压力溶液。(2)在颗粒表面非常光滑的砂粒中，特别是在水下，颗粒间摩擦力变小。(3)在低摩擦的情况下，唱砂在水下表现出令人费解的高剪切阻力，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)在较低的应力作用下，水下唱砂层的初期破坏表现出不同于具有明显滑移面的干唱砂和具有韧性变形的普通砂的变形类型。因此，应力-应变关系和变形方式受到晶间摩擦的强烈影响。

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.