轴压下掺铁尾矿砂和水泥的生土材料细观损伤演化研究

Study on Dynamic Mesoscopic Damage Evolution of Raw Soil Materials Mixed with Iron Tailings Sand and Cement under Axial Compression

为研究铁尾矿砂改性生土基材料在轴压下的损伤演化性能,采用CT技术,对不同应力状态下材料内部二值化图像进行分析.通过阈值分割,从细观上数值化各应力状态断面图像.研究材料分形维数、孔隙率和应力-应变(ε-σ)曲线演化规律,并阐明材料从受荷直至破坏的细观机理.结果表明:分形维数随受荷增大显著增加,σ=2.38 MPa时,分形维数最大.分形维数的变化趋势可间接表征试件受压时各扫描断面的不规则程度、粗糙度、裂缝与孔隙的发展情况.材料孔隙率随应力增大明显增加.以孔隙率为指标的材料损伤因子变化趋势与孔隙率变化规律相同,可有效反映材料在轴压下的破坏发展规律,也可作为研究改性生土试件损伤演化的定量参数.

To study the damage evolution performance of iron tailings-modified rammed earth-based materials under dynamic loading,CT technology was used to analyze binary images of the material’s interior under different stress states.Cross-sectional images were digitized by threshold segmentation at a microscopic level in each stress state.This research focused on the fractal dimension,porosity,and ε-σ curve evolution of the material,elucidating the microscopic mechanisms of materials from loading to failure.The results indicated that the fractal dimension increased significantly with increasing strength of material,reaching its maximum at σ=2.38 MPa.The irregularity,roughness,and development of cracks and pores in the scanned cross-sections during compression could be charac-terized by the changing trend of the fractal dimension indirectly.The porosity of the composite increased noticeably as the material undergoes failure and stress increases.The change trend of the material damage factor with porosity as index had same rules of the change of porosity,effectively reflecting the development of damage under axial compression and serving as a quantitative parameter for studying the damage evolution of modified rammed earth specimens.