基于岩体结构面分布分形维的岩体质量评价

Evaluation of rock mass quality based on fractal dimension of rock mass discontinuity distribution

尽管岩体结构面具有空间上的不规则性和结构网络上的复杂性,但由于它又具有自相似的特征,可以运用分形理论来对其进行研究。运用盒计维数法对某矿山巷道围岩体结构面分布的分维数进行计算,验证了岩体结构面分布的分形特征。通过对岩体结构面分布分形维值分布规律的分析发现,分形维数越大、结构面分布越密集,结构面迹线越长,岩体质量越差,表明可将岩体结构面分布的分形维作为岩体质量评价的指标。将计算所得的岩体结构面分布的分维数与按工程岩体分级标准对相应岩体分级所得的岩体质量等级进行对比,提出了一个以岩体结构面分布的分形维作为分级指标的岩体质量评价方案。

The rock mass discontinuity, owing to its property of self-similarity, can be addressed with the fractals although it is irregular in space and complex in network structure. The present study has testified the fractal characteristics of rock mass discontinuity distributions based on the calculation of the fractal dimensions of discontinuity distributions in the roadway surrounding rock masses at an underground mine with the application of the box-dimension method. By analyzing the fractal dimension values, this investigation shows that the higher the value is, the denser the discontinuity distribution, the longer the discontinuity traces, and the lower the rock mass quality; and it is shown that taking the fractal dimension of rock mass discontinuity distribution as the index of rock mass quality rating is feasible. By comparing the fractal dimensions calculated above with the corresponding rock mass grades classified by the standard for engineering rock mass rating, a scheme of rock mass quality classification, which takes the fractal dimension of the discontinuity distribution as the classifying index, is proposed.