Subglacial clast/bed contact forces
Subglacial clast/bed contact forces
复制标题
冰下碎屑/河床接触力
作者：
J. Byers;D. Cohen;N. Iverson
摘要建立了一个实验室装置，用于测量冰在两种不同配置下（与平床接触或与床隔离）对直径为0.05 m的刚性塑料球施加的力。测量结果表明，床法向接触力的1.8倍大于阻力，由于蠕动流通过一个滑球从床隔离。作为床正常冰速度的函数的力的测量、冰粘度参数的估计和冰中标记的观察表明冰是牛顿的，粘度为~1.3x 1011 Pas。由于小的和瞬时的应力，预期牛顿行为。一个region的模型表明，它对力的影响可以忽略不计（<5%）。球体下方与床接触的空腔中的水压对接触力的影响同样可以忽略不计。当没有空腔存在时，阻力可以正确地估计使用斯托克斯定律（牛顿粘度）的滑球。床层增强系数为1.8的相同定律适用于估计床层法向接触力。这些结果加强了以前的实验室测量和理论，但没有提供支持的解释高碎片/床摩擦或磨损率，取决于高接触力。
Abstract A laboratory device was built to measure the forces that ice exerts on a 0.05 m diameter rigid plastic sphere in two different configurations: in contact with a flat bed or isolated from the bed. Measurements indicated that bed-normal contact forces were 1.8 times larger than drag forces due to creeping flow past a slippery sphere isolated from the bed. Measurements of forces as a function of the bed-normal ice velocity, estimations of the ice viscosity parameter and observations of markers in the ice indicate ice is Newtonian with a viscosity of ~1.3x 1011 Pas. Newtonian behavior is expected due to small and transient stresses. A model of regelation indicates that it had a negligible (<5%) influence on forces. Water pressure in the cavity beneath the sphere in contact with the bed had a likewise negligible influence on contact forces. When no cavity is present, drag forces can be correctly estimated using Stokes’s law (Newtonian viscosity) for a slippery sphere. The same law with a bed-enhancement factor of 1.8 is appropriate for estimating bed-normal contact forces. These results reinforce previous laboratory measurements and theories but provide no support for explanations of high debris/bed friction or rates of abrasion that depend on high contact forces.