岩体饱和/非饱和渗流表征单元体积浅析

Study on representative elementary volume for permeability of saturated/unsaturated rock masses

岩体渗流表征单元体积 (REV)是衡量等效连续介质渗流模型实用性的重要标准 ,也是数值计算中对岩体渗流进行网格剖分的基本尺度 .本文从统计分析角度导出了岩体饱和渗流REV的表达式 ,从机理分析角度探讨了单裂隙非饱和渗透率表征单元面积 (REA)随饱和度变化的关系 .提出“REV REA相似扩大假想” ,建立了岩体非饱和渗流表征单元体积与单裂隙非饱和渗透率表征单元面积的相似对应关系 .计算表明 ,在中等饱和度下单裂隙渗透率REA较小 ,而在低饱和度及接近饱和状态下单裂隙渗透率REA较大 ,文中从饱和度变化与沟槽流发育程度的关系对这一变化趋势进行了合理解释 .算例中 ,采用开度分布的随机均匀场定量分析了单裂隙非饱和渗透率REA与饱和度的变化关系 ,基于REV REA相似扩大假想求取了岩体非饱和渗流REV的大小 .

The expression of representative elementary volume( REV ) for permeability of saturated rock is deduced by statistic analysis. The relation between saturation degree and representative elementary area( REA ) for permeability of a single unsaturated fracture is discussed by mechanism analysis. Based on the hypothesis of “similar expansion from REA to REV ”,the similar correspondent relationship between REV for permeability of saturated rocks and REA for permeability of a single unsaturated fracture is established. The results show that the REA for permeability of a single fracture under middle saturation degree is relatively small, and that for permeability of a single fracture under high or low saturation degree is relatively large. In case study, the relation between REA for permeability of a single unsaturated fracture and the saturation degree is analyzed quantitatively by using the stochastic homogeneous distribution of apertures. The REV for permeability of unsaturated rocks is derived based on the hypothesis of similar expansion from REA to REV .