Boudinage structure: some new interpretations based on elastic-plastic finite element simulations
Boudinage structure: some new interpretations based on elastic-plastic finite element simulations
复制标题
布丁纳奇结构：基于弹塑性有限元模拟的一些新解释
DOI：
10.1016/0191-8141(81)90009-2
复制
发表时间：
1981
影响因子：
3.1
通讯作者：
C. Ferguson
中科院分区：
文献类型：
--
作者：
G. Lloyd;C. Ferguson
基于塑性流动的Prandtl-Reuss方程，考虑了等效应力和应变，采用弹塑性有限元方法研究了围带结构。我们选择的模拟数据是以已公布的大理岩(基质)和石英岩(布丁)的应力-应变曲线为指导的，基本参数是屈服应力和岩石‘硬度’(由应力-应变曲线的斜率定义)。所有模型都假定初始断裂和轻微分离，因此仅模拟断裂后的行为。模拟结果表明，粘结剂的形状由粘结剂的硬度决定，最大应力集中在板材的拐角处，因此变形程度最大。基质硬度决定了布丁的分离量。与自然实例的直接比较仅限于未发生明显断裂前塑性变形的管束(即矩形和桶形管束)，尽管其他类型的管束可能具有桶形和挤压膨胀型的特征。这些模拟没有考虑布丁定义的断裂的性质和时机，但这些对于确定最终发展的布丁的风格是重要的。讨论了韧性岩基填充裂隙的一些力学问题，并提出了两种模型。第一种，基于屈服断裂力学，用来解释具有楔形(或其他不匹配的)末端的布丁。第二种是水力学模型，用来描述由韧性岩石基质填充的矩形管束之间的缝隙。
An elastic-plastic finite element method, based on the Prandtl-Reuss equations of plastic flow and involving equivalent stresses and strains, is used to study boudinage structure. Our choice of data for the simulations was guided by published stress-strain curves for marble (matrix) and quartzite (boudin), the essential parameters being yield stress and rock ‘hardness’ (defined by the slope of the stress-strain curve). All models assume an initial fracture and slight separation and therefore only simulate post-fracture behaviour. The simulations suggest that boudin shape is determined by boudin hardness; maximum stresses are concentrated in the corners which therefore shows the most shape modification. Matrix hardness determines the amount of boudin separation. Direct comparison with natural examples is restricted to boudins suffering no significant pre-fracture plastic deformation (i.e. rectangular- and barrel-shaped boudins), although other types are likely to have the characteristics of barrel and pinch-and-swell styles. The simulations do not consider the nature and timing of boudin-defining fractures but these are important in determining the style of boudinage which ultimately develops. Some mechanical problems associated with the infilling of inter-boudin gaps by ductile rock matrix are discussed and two models proposed. The first, based on yielding fracture mechanics, is used to explain boudins with wedge-shaped (or otherwise nonmatching) ends. The second, a hydraulic model, is proposed to account for gaps between rectangular boudins that are filled by ductile rock matrix.