堆石微裂缝扩展规律及其影响因素

根据岩石亚临界裂缝扩展理论,筑坝堆石料中微裂缝的扩展导致了堆石颗粒的破碎。借鉴Oldecop和Alonso等提出的关于堆石料长期变形特性微观机理,分析了堆石裂缝的扩展规律,探讨裂缝面上的应力、颗粒及所含裂缝的几何特征、相对湿度等因素对应力强度因子、裂缝扩展规律的影响。研究表明初始裂缝长度与颗粒半径之比α和裂缝面上应力σ^*_i是影响裂缝扩展的主要因素,初始裂缝越长、裂缝面上应力越大,裂缝扩展至颗粒破碎的时间越短;较大的相对湿度环境可加速裂缝扩展的进程,但影响有限;α和σ^*_i在一定变化范围内,从加载到裂缝扩展至颗粒破碎的时间可以从1 min到上百年,说明堆石的颗粒破碎是不断发生的动态过程。

Subcritical Crack Expansion of Rockfill Particle and Its Influencing Factors

According to the theory of subcritical expansion of cracks, we know that the breakage is caused by the extension of micro-cracks in rockfill particle. Based on the long-term deformation characteristics of rockfill particle proposed by predecessors, we study the influences on the stress intensity factor and extension of crack by discussing the stress on the crack surface, geometrical characters of particles and cracks, relative humidity, etc. The analysis results show that, ratio of the initial crack length to particle radius (α) and the stress (σ^*_i ) which acts across the surface of a crack, are the main influencing factors of crack expansion. The longer the length of initial crack is, the larger the stress on crack surface is, and the shorter the time from propagation till breakage of crack is. Big relative humidity is in favour of speeding crack propagation. However, the effect of relative humidity is limited when α and σ^*_i are large enough. The time interval from start of loading to particle breakage ranges from 1 minute to 100 years, which indicates that the particle breakage happens in the whole process of loading.