摘要
在考虑坝体与坝基的相互作用问题时,需要对坝基粗糙表面的粗糙程度进行恰当的描述,工程界希望这种描述方法能够与界面的抗剪切力学性能建立一一对应关系。据此,分析以往研究中一些描述表面粗糙形貌的指标所存在的问题,指出用分形维数描述表面粗糙可能适合于机械摩擦这样的粗糙精细的场合,对于研究具有岩石粗糙表面的两体相互作用问题,粗糙尺度太大,分形维数描述方法不能直接使用。然而,借助分形理论,经6个粗糙的岩石试件表面的激光扫描数据处理分析,提出一个新的描述表面粗糙形貌的指标Rd。Rd指标的合理性在于放大了大尺度细节的作用,这与大尺度粗糙细节对力学性能影响大的事实相吻合的,且Rd指标值域比传统分维值要大,易于区分不同的粗糙表面。此外,Rd的取值与测量方向无关,适合一一对应地描述某一区域的粗糙程度。通过对一系列典型图形和实测粗糙岩石表面采用不同描述指标进行对比分析计算,验证Rd指标的合理性。然而,考虑到描述指标既需要对粗糙表面在不同方向测量具有不变性,又要能够反映粗糙表面在不同方向剪切受力时界面力学性能不同这一现实,单一的粗糙描述指标不能同时完成上述两项任务。经过理论和数值分析,提出一个描述粗糙起伏的形状因子参数λ,其与Rd指标共同构筑一个新的表面粗糙程度的双参数描述系统。在该系统中,形状因子参数λ可考虑剪切受力方向的不同对界面力学性能的影响,且Rd指标则不受方向的影响。对于沿着试件宽度形状因子为常量的特定情况,给出双参数描述系统与界面力学性能建立联系的基本表达形式,并对影响因素进行分析。
In the research of interaction between dam and its foundation, it is necessary to describe the roughness of the rock surface in order to provide parameters for evaluating the shear mechanical characteristics of the interface. Some issues in the former description of rough surface are analyzed： moreover, it is pointed that the fractal dimensions D may perfectly describe the fine surface such as in the situation of smooth metal friction, but it cannot be directly used in evaluating mechanical properties of rock surfaces where the size of roughness is large-scale. However, with the aid of fractal theory, a new index Rd to describe surface roughness is defined. The index Rd is reasonable because the effect of large-scale roughness is emphasized, which is accord with the fact that the larger the size of roughness is, the more it will affect the rough surface mechanical properties. Meanwhile the value range of Rd is larger than that of fractal dimensions D, which makes it easier to distinguish the roughness of different surfaces. Besides, the Rd value is independent of measuring direction and it is corresponding to the roughness of the area where it describes. Bring the new index Rd into comparison with convention index Ra and fractal dimensions D, the rationality of the new index is testified. However, in the description of the roughness, the rough index should not only have the same value when the rough surface is measured in different directions, but also exhibits that same rough surfaces have different mechanial behaviors when the shear is in different directions. It is pointed out that such two tasks cannot be accomplished with single index. Through theoretical and numerical analysis, a shape factor parameter λ is proposed. Thus, λ and Rd make up of a two-parameter system to describe the rough surface. In this system, Rd describes the fine roughness and its value is steady when the measure direction changes, while λ describes the large size roughness on the surface and its value is varied when the shear direction changes. For the specimen with constant value λ in its width, the elementary relationship between two-index description system and interface mechanical property is given, and the influence factors are introduced.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2006年第12期2481-2492,共12页
Chinese Journal of Rock Mechanics and Engineering
基金
国家重点基础研究发展规划(973)项目(2002CB412707)
教育部重大项目(305013)
高校博士点基金资助项目(20040610095)
关键词
岩石力学
粗糙表面
分形
粗糙度指标
形状因子
小波分析
抗剪切力学性能
rock mechanics： rough surface： fractal
roughness index, shape factor： wavelets analysis： shear mechanical property
