Chotiros Nicholas P, Isakson Marcia J
Applied Research Laboratories, The University of Texas at Austin, Austin, Texas 78713-8029.
J Acoust Soc Am. 2014 Jun;135(6):3264-79. doi: 10.1121/1.4874955.
An improvement in the modeling of shear wave attenuation and speed in water-saturated sand and glass beads is introduced. Some dry and water-saturated materials are known to follow a constant-Q model in which the attenuation, expressed as Q(-1), is independent of frequency. The associated loss mechanism is thought to lie within the solid frame. A second loss mechanism in fluid-saturated porous materials is the viscous loss due to relative motion between pore fluid and solid frame predicted by the Biot-Stoll model. It contains a relaxation process that makes the Q(-1) change with frequency, reaching a peak at a characteristic frequency. Examination of the published measurements above 1 kHz, particularly those of Brunson (Ph.D. thesis, Oregon State University, Corvalis, 1983), shows another peak, which is explained in terms of a relaxation process associated with the squirt flow process at the grain-grain contact. In the process of deriving a model for this phenomenon, it is necessary to consider the micro-fluidic effects associated with the flow within a thin film of water confined in the gap at the grain-grain contact and the resulting increase in the effective viscosity of water. The result is an extended Biot model that is applicable over a broad band of frequencies.
介绍了一种对水饱和砂和玻璃珠中剪切波衰减和速度建模的改进方法。已知一些干燥和水饱和材料遵循恒定Q模型，其中以Q(-1)表示的衰减与频率无关。相关的损耗机制被认为存在于固体框架内。流体饱和多孔材料中的第二种损耗机制是由Biot-Stoll模型预测的孔隙流体与固体框架之间相对运动引起的粘性损耗。它包含一个弛豫过程，使Q(-1)随频率变化，在特征频率处达到峰值。对已发表的1kHz以上测量结果的研究，特别是Brunson（博士论文，俄勒冈州立大学，科瓦利斯，1983年）的测量结果，显示出另一个峰值，这是根据与颗粒间接触处的喷射流过程相关的弛豫过程来解释的。在推导该现象的模型过程中，有必要考虑与颗粒间接触处间隙中受限水薄膜内的流动相关的微流体效应以及由此导致的水有效粘度增加。结果是一个适用于宽频带的扩展Biot模型。
