Deqing Gan

The stability of cemented tailings backfill (CTB) is influenced by mining disturbance. As a property of CTB, tailings gradation (TG) is one of the factors that change its mechanical properties. Taking tailings gradation, impact amplitude, and curing age as variables, this paper focuses on the characteristics of the influence of curing age on the failure deformation, strength evolution, failure mode, and microstructure of CTB. The results show that with the average particle size of the tailings from coarse to fine, the peak stress and elastic modulus of CTB first decrease and then increase. The increase in curing age and impact amplitude can improve the elastic deformation capacity of CTB. During the post-peak phase, the stress–strain curve undergoes sequential morphological transitions, evolving from the initial “stress drop” characteristics through “post-peak plasticity” manifestations before ultimately demonstrating “post-peak ductility” behavior. This progression corresponds to CTB’s material transformation pathway, commencing as a rigid substance that first transitions into a plastic-brittle composite, subsequently develops plastic properties, and finally attains ductile material characteristics. The TG changes from T1 to T4, and the failure mode of CTB gradually changes from composite failure and shear failure to tension failure and composite failure. A CTB strength prediction model based on TG is proposed. The R² of the model is 0.997, F = 12,855, and p < 0.001, which has high applicability. As tailings vary from T1/T2 to T4, AFt content progressively decreases, the C-S-H gel transitions from a 3D network to a flocculent structure, and the skeleton shifts from coarse to fine particles, leading to increased porosity but smaller pores.

The transition from open-pit to underground mining entails significant risks associated with rock mass deformation and surface subsidence, which pose critical challenges in mining engineering practice. To investigate and control the deformation behavior of overlying strata under mining-induced disturbances, a three-dimensional numerical model is developed for the goaf area at the Sijiaying Iron Mine. Deformation indicators, combined with calculations of rock movement angles and collapse angles, are utilized to elucidate the deformation characteristics and controlling mechanisms of the mine surface. The results indicate the following: (1) slope deformation in the open-pit mine exhibits notable spatial heterogeneity, characterized by a “large displacement–small deformation” phenomenon, with peak values of total displacement and total deformation reaching 92.86 mm and 3.28 mm/m, respectively; (2) the critical ranges of surface movement angle and collapse angle are determined, enabling quantitative delineation of the influence zones of underground mining on surface deformation; and (3) the dip angle of the ore body is the primary controlling factor influencing the surface subsidence. Specifically, gently dipping ore bodies predominantly exhibit vertical subsidence (associated with larger movement angles), whereas steeply dipping ore bodies display pronounced directional sliding (correlated with smaller movement angles).

In this study, we developed a pipeline transport model to investigate the influence of particle sedimentation factors on slurry transportation through pipelines. The particle tracking module of the software was used to simulate the transport process, and the influences on the sedimentation rate were analyzed considering the slurry concentration, particle size, and flow velocity. The established model exhibited small calculation errors. In addition, the results revealed that the proposed model is reliable for calculating the degree of influence of various factors on particle sedimentation. The effect of the particle sedimentation rate on the pipeline slurry was explored considering the particle size, slurry concentration, and flow velocity. The sedimentation rate was positively related to particle size and adversely related to the slurry concentration and flow velocity. Indeed, study on the sedimentation rate requires considering a reasonable range of particle sizes, preparing a slurry with an appropriate concentration, and adjusting an appropriate flow velocity. Numerical simulations were performed using the filling data as the background for a sample mining area. The experimental results showed optimal slurry concentration and particle size of 60% and 25.25 µm, respectively.