Mingjian Huang

With the rapid development of the world economy in recent years, the mineral resources in the shallow part of the Earth can no longer meet the needs of mankind, and resource development is continually moving into the deep part of the Earth. The filling method, in particular, has gradually been employed for the treatment of mining goaves in response to the requirements of environmentally sustainable development. As an important part of the filling system, the wear and tear of the deep filling pipeline is of great significance to the normal operation of the system, the safe production of the mine and the reasonable protection of the environment. In this paper, the wear situation of the deep well vertical filling pipeline is selected as the analysis angle to carry out the research, and the risk assessment model is constructed by combining the distance discriminant weighting method and the cloud model for the uncertainty of the wear risk grading assessment. Firstly, 11 quantitative factors and three qualitative factors were selected as evaluation indicators and employed as cloud model variables. Appropriate cloud model digital features were picked based on cloud model theory, to construct the cloud model of each indicator. Secondly, the distance discriminant weighting method is introduced to obtain the weight of each indicator, and the risk level of the vertical filling pipeline in deep wells is obtained by calculating the comprehensive certainty of the risk evaluation object belonging to different levels. Finally, the model was applied to Dongguashan Copper Mine, and the model calculation results were analyzed and compared with the actual wear situation. The results show that the model transforms the ambiguity and randomness into a certain quantitative value of certainty, completing the map from qualitative to quantitative. This method introduces a new idea and method for dealing with similar problems of vertical filling pipes in deep wells.

To address the issues of severe goaf collapse, difficulties in secondary extraction, and insufficient pillar stability encountered during the mining of high stopes north of Line 60 at the Dongguashan Copper Mine, this paper takes these high stopes as the research object. Based on an analysis of the engineering geological conditions, goaf failure characteristics, and current mining status in this area, a study on pillar stability and the mechanical behavior of combined mining is conducted. Given the susceptibility of pillars with high aspect ratios to bending instability, the secondary extraction pillar is simplified as a rod with fixed ends. A mechanical model for the triangular pillar’s stability is established, the critical instability equation is derived, and the influence of the reserved width on the pillar’s critical stress and safety factor is analyzed. Subsequently, based on the critical instability equation, the relationship between the reserved pillar width and critical stress is obtained to optimize the pillar dimensions. Simultaneously, to mitigate the adverse effects of primary stope collapse on secondary extraction, optimized schemes such as three-stope combined mining and two-stope combined mining are proposed. A mechanical model for combined mining is established based on the Protodyakonov’s arch theory to analyze the stress distribution characteristics of the surrounding rock in the goaf under different mining schemes. The calculated stress of the original rectangular pillar is 29.01 MPa. When the reserved width exceeds 4 m, the pillar safety factor becomes greater than 1.6, satisfying the stability requirement. In addition, three combined mining schemes were compared using Protodyakonov’s arch theory. The goaf spans of the three schemes are 40 m, 26.6 m, and 36 m, respectively. The results indicate that the two-stope combined mining scheme transfers the main roof load to the adjacent ore body and backfill, reducing the load borne by the barrier pillar and providing a better balance between safety and production efficiency. The proposed framework, integrating field goaf detection, pillar buckling analysis, reserved-width optimization, and combined mining comparison, provides a practical method for the stability control and secondary recovery of deep high stopes.

This study conducts a simulation analysis of the stability of tall and collapse-prone stopes at the Dongguashan copper mine, using the FLAC3D-3.0 software to investigate the stress distribution and deformation behavior of geological materials under different working conditions, providing an effective means of addressing complex mechanical issues in geotechnical engineering. In this paper, the stability of the tall stopes in the Dongguashan mining area was analyzed through numerical simulations using the FLAC3D finite difference method. First, a three-dimensional numerical model of the tall stopes was established based on the actual conditions of the mining area, simulating the mining conditions and environment. Next, the stress distribution, displacement variation, and potential instability zones under different mining schemes were studied, with a comparative analysis conducted between traditional mining methods and optimized schemes to clarify their respective advantages and disadvantages. Finally, based on the simulation results, the most suitable mining scheme for the area was identified, aimed at reducing the risk of stope collapse and improving the overall stability and safety of the mine. The findings provide technical support for the design and support of tall stopes in deep deposits and offer important reference points for mine safety management.

In order to investigate the dynamic mechanical behavior of composite rock in deep-buried tunnels, the dynamic impact tests of the combinations with three lithologies (granite-H, cyan sandstone-S1, and red sandstone-S2) and six kinds of composite forms (H-S1, S1-H, H-S2, S2-H, S1-S2, and S2-S1), were carried out in this study. Additionally, the effects of the combination forms and strain rates on the stress-strain curve, peak stress, energy utilization rate (EUR), failure process, displacement field, and failure mode of the composite sample were analyzed. The results show that the peak stresses of all the combinations are linearly and positively correlated with the strain rate. When the strain rate is close, the peak stress and elastic modulus of the combination with front hard and rear soft (FHRS) rocks are larger. Furthermore, the EUR of different combinations is proportional to the incident energy. The EUR of the front soft and rear hard (FSRH) combination is generally higher than that of the FHRS combination. In general, the rock with low strength always fails first in the composite. When the strength disparity between the two rocks of the composite is small, the failure of the composite with FSRH is relatively small, and the main deformation occurs in the rock with low strength. Finally, the fractal dimension of the fragments after the impact of the FSRH combination is larger, i.e., the lumpiness of fragments is closer.

The split Hopkinson pressure bar (SHPB) technique and various drilling tests were performed on three types of lithologies (granite and cyan and red sandstone) to understand the variation in energy consumption (EC) of the different methods used for rock crushing. The dynamic behavior of rocks was analyzed based on the dynamic stress-strain curve, the peak stress, the energy, and the failure mode for the SHPB test, while the drilling curve, the influence of the drilling pressure (DP) and the revolution speed (RS) on the drilling speed (DS) were analyzed for the drilling test. Additionally, the EC difference was compared based on the EC required to break a single unit volume of rock. The obtained results indicate that the sensitivity of the dynamic strength of rocks with different lithologies to strain rate is different and that the higher the uniaxial compressive strength is, the more sensitive it is. Additionally, the strengthening of the peak stress is more pronounced with the increase in the strain rate. The energy utilization efficiency (EUE) of the SHPB test sample has a positive correlation with the strain rate. Moreover, the typical drilling process can be divided into the initial drilling and stable drilling stages, with the DS during the stable drilling stage being lower than that during the initial drilling stage. The DP and the RS have a linear positive correlation with the DS, with the influence of the DP on the DS being more obvious. Finally, the EC during the drilling process is higher than the EC during the SHPB technique.