Abstract: Filling mining method has been widely used in the two-step mining method. The cemented filling body is an artificial pillar， so its stability is very important. However， the mechanical properties and constitutive model of the cemented filling body are the important contents of the stability analysis and evaluation. Therefore， It is urgent to study the mechanics characteristics and constitutive model of cemented filling body. In this article， the uniaxial compression tests were carried out on cemented filling bodies with different ratios of ash and sand. The results show that: nonlinear characteristics of the cemented filling body are shown due to the existence of voids in the initial compacting stage； the stiffness and the strength in the plastic yielding and post-both appear softening properties； and there exists strong bearing property in the post-destructive stage. According to the test results， a combination of macro and microscopic method is adopted to abstract the cemented filling body into two parts of voids and macro units， and the effective damage factor of cemented filling body is introduced to build the voids constitutive equation and the units damage softening constitutive equation by combining with statistical damage theory， and then the damage softening constitutive model of cemented filling body is obtained. Finally， the theoretical model curve is compared with the experimental curve and the existing theory based on the experimental data and other scholars' experimental data. The analysis results show that the theoretical curve is highly consistent with the test curve， and the correlation coefficients of the curve fitting in all stages are above 95%， which better characterize the non-linear deformation and softening characteristics of the cemented filling body void. The results provide a theoretical basis for the stability analysis of cemented filling body.

Key words: Cemented backfill, Uniaxial compression, Damage softening, Compaction stage, Constitutive equation