This paper describes a case study of the surface subsidence induced by sublevel caving without sill pillars in the Maogong Iron Mine, China. A comprehensive analysis based on GPS monitoring and ...numerical simulation is proposed and used to analyze the surface subsidence characteristics and damage range. GPS monitoring results showed that the vertical displacement reached 40.3 mm at the JC5 monitoring station and was accompanied by ground crack development. According to the in situ surface subsidence monitoring data and numerical calibration model results, the corresponding critical horizontal strain and angular distortion due to the surface subsidence were estimated as 1.5 × 10
−3
and 2.0 × 10
−3
, respectively. The numerical results showed that the center of the surface subsidence was located in the hanging wall of the orebody, which changed to its far end with increasing mining depth. In the early surface subsidence stage, macro-tension cracks developed in the hanging wall rock mass, and the slabbed rock mass then collapsed into the cave through rotation and/or translation failure. With increasing mining depth, there will be unfilled goaf in the underground, and the rock mass will gradually collapse under high mining-induced stress concentration. Accumulation of caved rocks and the bulking effect result in slow surface subsidence. Notably, surface collapse will not occur suddenly in Maogong Iron Mine, and potential secondary hazards mainly small landslides in the hillside.
In the background environment of the serious problem of high temperature heat damage in deep mining, some mines have complex and interlocking forms of roadway arrangement, with the innovative concept ...of cooling on demand as the principle, this paper develops a mobile ice cooling equipment, and introduces and explains the equipment from the perspective of principle, composition and dimensions. and uses Comsol simulation software to simulate and analyze the main heat exchange process of the mobile ice cooling equipment under the conditions of two cooling sources, obtains quantitative results on the finned tube arrangement parameters and the heat exchange cooling effect of the equipment under ideal conditions, which provides data for the optimization and upgrading of this mobile ice cooling equipment. The results show that the mobile cooling equipment is capable of feeding the desired temperature of the cooling air into deep mine, and with flexible, convenient, efficient, and cost effective. This research and development is a new exploration of deep ventilation and cooling technology and equipment means, puts forward a new concept, accumulates valuable experience, and lays the foundation for the subsequent related research and optimization.
The occurrence of disasters in deep mining engineering has been confirmed to be closely related to the external dynamic disturbances and geological discontinuities. Thus, a combined finite-element ...method was employed to simulate the failure process of an underground cavern, which provided insights into the failure mechanism of deep hard rock affected by factors such as the dynamic stress-wave amplitudes, disturbance direction, and dip angles of the structural plane. The crack-propagation process, stress-field distribution, displacement, velocity of failed rock, and failure zone around the circular cavern were analyzed to identify the dynamic response and failure properties of the underground structures. The simulation results indicate that the dynamic disturbance direction had less influence on the dynamic response for the constant in situ stress state, while the failure intensity and damage range around the cavern always exhibited a monotonically increasing trend with an increase in the dynamic load. The crack distribution around the circular cavern exhibited an asymmetric pattern, possibly owing to the stress-wave reflection behavior and attenuation effect along the propagation route. Geological discontinuities significantly affected the stability of nearby caverns subjected to dynamic disturbances, during which the failure intensity exhibited the pattern of an initial increase followed by a decrease with an increase in the dip angle of the structural plane. Additionally, the dynamic disturbance direction led to variations in the crack distribution for specific structural planes and stress states. These results indicate that the failure behavior should be the integrated response of the excavation unloading effect, geological conditions, and external dynamic disturbances.
Deep mining has become an inevitable trend of mining development. Previously conducted studies have established that reasonable stope structure parameters are the premise to ensure the safe and ...efficient production of deep mines. In order to ensure the safety of deep mining, in this paper, we systematically review the existing stope structure parameter design methods, and then put forward a deep stope structure design method based on the stability of mining rock mass. Based on rock mass quality classification, this method uses a critical span graph and an improved stability graph, and fully considers the influence of joint occurrence and mining stress on the stability of surrounding rock, to design the stope structural parameters. Taking into consideration the deterioration of the quality of deep rock mass, we collect mining data at home and abroad, improve the stability graph, and make it suitable for the design of stope structural parameters with different mining methods. The design process of stope structural parameters is expounded through field engineering cases, and it has specific guiding significance for the design of stope structural parameters in deep metal mines.
AbstractThe control of broken rock mass roadways has always been a difficult problem in metal hard rock mines. In this paper, the mechanical mechanism of anchor net support is characterized and ...simulated through the physical model test of the prestressed support self-bearing structure of the broken rock mass. The deformation characteristics and interaction relationships of the surrounding rock and the support body under different dynamic impact effects are obtained by using the embedded anchor strain gauge and rock micro-strain sensors. The stress evolution process and deformation characteristics of the anchor and rock mass of the prestressed support self-bearing structure of the broken rock mass under different loads are simulated by applying Phase2. The results are in good agreement with the results of the physical model test. Based on the theory of surrounding rock compression arch and the Hoek-Brown criterion, the minimum anchorage force of the prestressed anchor to maintain the stability of the surrounding rock is derived and calculated by the limit equilibrium rule. The research results explain the mechanical mechanism of the broken rock mass support from the aspects of physical experiments, numerical simulations and theoretical derivations, which can provide theoretical guidance for the support design of practical engineering.
The surrounding rock control has been a difficult problem for fractured rock mass in hard rock mines. This article describes a case study of the failure mechanisms and the support design technology ...for fractured rock mass drifts in Xinli Gold Mine. Based on field investigation, the geology characteristics, failure types, influencing factors, support types, and their failure types were analyzed. The rock mass classification, rock mass physical and mechanical parameters were obtained by using Q, RMR, and GSI systems. The zoning of surrounding rock, stability analysis and zoning support schemes design were carried out based on rock mass classification results. The pretension is designed by China underground mine experiences and verified by numerical simulation. RS2 was used to compare the plastic zone under pre- and post-support conditions. The plastic zone is significantly reduced after support is installed, which indicates that the designed support schemes can effectively control the failure of surrounding rock. In view of difficulties in the excavation and support of fractured rock mass, the short excavation and short support technology was proposed to ensure the success excavation of the drift in fractured rock mass. The field application shows that the short excavation and support technology are effective.
In this study, a three-dimensional finite difference numerical model of the Jinfeng Gold Mine, including surface topography, ore body, shafts, and main faults, was built to estimate the shaft ...stability and surface deformation induced by underground mining transferred from open-pit mining. Satellite monitoring data of surface displacement at several points was used to calibrate the numerical model. The sequence of excavation and filling in the simulation was determined according to the mining schemes with appropriate simplification. The distribution of large deformations in simulation is consistent with the cracking areas on the slopes and surface. Besides, shaft deformation in the simulation is small, which is consistent with the reality that there are no large deformations of shafts in the underground mining activities above 30 m level. After the completion of simulated underground mining, the deformations of shafts and surface are generally far less than the critical deformation. Hence, we concluded that the shafts and surface of the Jinfeng Gold Mine can remain stable in the underground mining stage. Overall, the method in the study provides references for the estimation of shaft stability and surface deformation in the underground mining stage of mine transfer from open pit.
The stability of underground water-sealed oil storage caverns is of great importance for safe excavation and operation. To analyze the scope of the failure zone and underground cavern stability ...accurately, a new method was developed that integrates the rock tunneling quality index Q-system and stability graph method with 3D laser scanning and numerical simulation. The point cloud data were obtained by 3D laser scanning, and the cavern model was built by using DIMINE software, which directly shows the 3D shape of the cavern. The rock mass physical and mechanical parameters and the corresponding stability coefficients were obtained based on Q-system and stability graph method. The plastic zone distribution and deformation characteristics of surrounding rock were analyzed through numerical simulation. Then, the corresponding relationship between caving zone and plastic zone was determined by comparing the numerical simulation results with the 3D laser scanning contour. The new method provides a reliable way to analyze the stability of the underground water-sealed oil storage cavern and also will helpful to design or optimize the subsequent support.
We investigate band evolution of chiral and non-chiral symmetric flatband photonic rhombic lattices by applying a strain along the diagonal direction, and thereby demonstrating Landau-Zener Bloch ...(LZB) oscillations in the presence of a refractive index gradient. The chiral and non-chiral symmetric rhombic lattices are obtained by adding a detuning to uniform lattices. For the chiral symmetric lattices, the middle flatband is perturbed due to the chiral symmetry breaking while a nearly flatband appears as the bottom band with the increase of strain-induced next-nearest-neighbor hopping. Consequently, LZB oscillations exhibit intriguing characteristics such as asymmetric energy transitions and almost complete suppression of the oscillations. Nevertheless, for the non-chiral symmetric lattices, flatband persists owing to the retained particle-hole symmetry and evolves into the bottom band. Remarkably, the band gap can be readily tuned, which allows controlling of the amplitude of Landau-Zener tunneling (LZT) rate and may lead to thorough LZT. Our analysis provides an alternative perspective on the generation of tunable flatband and may also bring insight to study the symmetry and topological characterization of the flatband.
A landslide of the north open-pit (323N) and the stability and design optimization of the south open-pit (323S) slope in the 323 belts of the Tanjianshan Gold Mine were studied. On 14 September 2020, ...a large landslide occurred on the east side of 323N, which posed a severe threat to the safety production of the mine. To avoid a similar slide on the south open-pit in the 323S, the limit equilibrium method was used to estimate the stability of the final slope of the designed initially open-pit in the 323N. The results show that the location and scale of the landslide are in good agreement with the three-dimensional laser scanning data. The effectiveness of the limit equilibrium method in slope stability analysis of the Tanjianshan Gold Mine was validated. The stability of the final slope of the initial design of 323S was analyzed. The sensitivity of the safety factor of homogeneous slope and heterogeneous rock slope to the bench face angle (BFA) and the difference of landslide type were compared and studied. When the spatial geometric relationship of rock masses with different lithology is complex, the engineering analogy method is inapplicable to calculation of parameters such as the BFA of heterogeneous rock slope and overall slope angle of the open-pit. The slope safety factor should be checked, and the slope step parameters are warranted to be optimized. The safety and economic benefits of the slope can be improved.
PDF
