Hu Jianhua, Ren Qifan, Ding Xiaotian, Jiang Quan
School of Resources and Safety Engineering, Central South University, Changsha 410083, People's Republic of China.
R Soc Open Sci. 2019 Jun 26;6(6):190389. doi: 10.1098/rsos.190389. eCollection 2019 Jun.
The characteristics of the porous structure of backfill are directly related to the macro parameters of the flowability of the filling slurry and the mechanical features of the backfill, which are fundamental to the study of multiscale mechanics of backfill. Based on the geometry and fractal theory, scanning electron microscopy images of backfill were analysed by image analysis methods such as OTSU and box counting. The fractal dimension of the pore structure was calculated. By quantitatively characterizing the pore structure, the trans-scale relationships between the fractal dimension of the pore structure and the macro parameters of the filling slurry were established in terms of equilibrium shear stress (ESS) and equilibrium apparent viscosity (EAV). In addition, the correlations between the fractal dimension and macro parameters of backfill were obtained in terms of uniaxial compressive strength (UCS), water content (WC) and porosity. The influence of the microstructure on the macro parameters was discussed. The results show the following: (i) the fractal dimension of the backfill pore structure can characterize the complexity of the structure; (ii) the fractal dimension of the pore structure is negatively correlated with the ESS and EAV of the filling slurry. The UCS of the backfill is positively correlated with the flowability parameter; (iii) the fractal dimension of the pore structure has a certain correlation with some macro parameters of the backfill, i.e. the fractal dimension is negatively correlated with the UCS and positively correlated with the WC and (iv) the linear correlations between the pore fractal dimension and UCS and WC are established. The correlation coefficient between the fractal dimension and UCS has an value of -0.638, while the corresponding value of the fractal dimension and WC is 0.604. UCS and WC can be predicted by the fractal dimension of pores.
充填体孔隙结构特征直接关系到充填料浆流动性及充填体力学特性等宏观参数，是充填体多尺度力学研究的基础。基于几何与分形理论，采用大津法（OTSU）、盒维数法等图像分析方法对充填体扫描电子显微镜图像进行分析，计算孔隙结构的分形维数。通过对孔隙结构的定量表征，从平衡剪应力（ESS）和平衡表观黏度（EAV）方面建立了孔隙结构分形维数与充填料浆宏观参数之间的跨尺度关系。此外，从单轴抗压强度（UCS）、含水量（WC）和孔隙率方面得到了充填体分形维数与宏观参数之间的相关性，探讨了细观结构对宏观参数的影响。结果表明：（i）充填体孔隙结构分形维数能够表征结构的复杂程度；（ii）孔隙结构分形维数与充填料浆的ESS和EAV呈负相关，充填体UCS与流动性参数呈正相关；（iii）孔隙结构分形维数与充填体部分宏观参数存在一定相关性，即分形维数与UCS呈负相关，与WC呈正相关；（iv）建立了孔隙分形维数与UCS、WC之间的线性相关关系，分形维数与UCS的相关系数值为-0.638，分形维数与WC的相应值为0.604，可通过孔隙分形维数预测UCS和WC。
