Applicability of Constitutive Models to Describing the Compressibility of Mining Backfill: A Comparative Study

The compressibility of mining backfill governs its resistance to the closure of surrounding rock mass, which should be well reflected in numerical modeling. In most numerical simulations of backfill, the Mohr–Coulomb elasto-plastic model is used, but is constantly criticized for its poor representativeness to the mechanical response of geomaterials. Finding an appropriate constitutive model to better represent the compressibility of mining backfill is critical and necessary. In this paper, Mohr–Coulomb elasto-plastic model, double-yield model, and Soft Soil model are briefly recalled. Their applicability to describing the backfill compressibility is then assessed by comparing numerical and experimental results of one-dimensional consolidation and consolidated drained triaxial compression tests made on lowly cemented backfills available in the literature. The comparisons show that the Soft Soil model can be used to properly describe the experimental results while the application of the Mohr–Coulomb model and double-yield model shows poor description on the compressibility of the backfill submitted to large and cycle loading. A further application of the Soft Soil model to the case of a backfilled stope overlying a sill mat shows stress distributions close to those obtained by applying the Mohr–Coulomb model when rock wall closure is absent. After excavating the underlying stope, rock wall closure is generated and exercises compression on the overlying backfill. Compared to the results obtained by applying the Soft Soil model, an application of the Mohr–Coulomb model tends to overestimate the stresses in the backfill when the mine depth is small and underestimate the stresses when the mine depth is large due to the poor description of fill compressibility. The Soft Soil model is recommended to describe the compressibility of uncemented or lightly cemented backfill with small cohesions under external compressions associated with rock wall closure.

Analysis of the Current Challenges for Deep Underground Mines: Labour Productivity Improvement

With much of the ore deposits close to the surface already discovered and mined, the mines are becoming deeper, and this brings multiple challenges. One of the challenges is the longer haul distance from active mining areas to the mine surface, hence longer transportation time of material and operators. Longer transportation time of operators may lead to the reduction of the labour productivity. Labour productivity in today’s mines is a key importance, and is currently dependent on together with other factors that operators should be at the vehicles or working area on time. There has been some development in mine automation, but the vast majority of underground mine operations are still in need of operators. Several methods are available and can be used to transport operators to the underground working areas. These methods include mine vehicles, mine taxis, mine buses, monorail, and shaft system. As mine depth increases, the method with higher labour productivity will be of much useful in operator’s transportation. The aim of this study is to investigate personal transportation methods for deeper underground operations by comparing labour productivity when using mine vehicle, mine taxi, mine buses, and monorail system. The results show that mine vehicle has higher labour productivity of up to 76% of available time, while mine buses have low labour productivity. It has been reveal that for shallow depth mines, a good option to improve labour productivity is to have few operators transported per cycle, while for deep mines, a transport system that is faster, accommodate few operators per cycle, less possibility to meet traffic will be the better option for labour productivity improvement.

Economic and technological aspects of interrelation between open pit mine depth and mining transport parameters

Introduction. This paper presents the results of research on ore pit depth justification in relation to mining transport parameters. Research theory. Features of the current state and further development of deep pits are considered. There is also the classification of fields by relative excavation difficulty depending on physico-technical features of rock, conditions of their occurrence and climate severity. Besides, extractable ore reserves are classified depending on its value. The indicators for joint justification of excavation difficulty, ore pit depth, mining transport complexes parameters have been offered as well as their established optimal regions. Results and conclusions. The dependences have been obtained allowing to efficiently determine excavator bucket capacity and dumptruck load-lifting capacity and validate pit depth taking into account ore value. It has been determined that when mining a deposit of corresponding excavation difficulty with an opencast method, cost behavior changes with depth due to the increase in power, productivity, and power-weight ratio of drilling rigs, excavators, dump trucks, and bulldozers; cost behavior is of an increasing nonlinear character. Rational uses of mining transport complexes based on electric and hydraulic excavators have been singled out. The reasons of their probable change have been estimated. Research results have been approved when planning the largest gold ore pit in Russia, Vostochny pit of Olimpiadinsky gold ore field.

Optimization Coal Pillar Size of Top Coal Caving Face with Dynamic Pressure Impact

AH Wilson coal pillar was used widely as it’s simply, but it’s appeared large error for field implementation as its difference assume conditions, mine depth H and mine thickness m. AH Wilson coal pillar formula was studied precisely by in-site stresses test and numerical simulation analysis for N3-5 top coal caving working face of CHANGCUN coal mine in Lu’an coal district of China, then modified AH Wilson formula was put forward as L = 0.008mH + 8.4,then the precise coal pillar size 18m was used in filed implementation, filed testing proved coal pillar size was reasonable.

Study on the Relation between the Deep and the Spontaneous Combustion of Coal Seam

Based on the data and laboratory analysis of Sun-Cun Coal Mine, the relationship between the geothermal gradient and the depth of mine in Suncun Coal Mine has been developed. According to this and the laboratory experiments, the relationship between spontaneous combustion period of coal seam and the depth of the mine has been obtained in this article. The results show that the law of coal seam spontaneous combustion period and the mine depth in accordance with the relationship of the gauss curve expression and when the coal mine depth is around 1000 m, the coal seam spontaneous combustion period shortened dramatically. This law should be pay more attention to.