In order to understand carbon performance of the mining sector in Hunan Province, the carbon emissions and carbon performance of the mining sector in Hunan Province were calculated based on the latest statistical data of national economic accounting, and factors influencing carbon performance were analyzed based on the established model. It is shown that the carbon performance of Hunan's mining sector was at a relatively low level from 2010 to 2020, and there was great difference in carbon performance of sub-sectors. Factors of asset size and energy efficiency had a positive impact on carbon performance, while factors of asset liability ratio and energy structure had negative constraints on carbon performance. Achieving economies of scale, improving energy efficiency, optimizing energy structure and maintaining a stable liabilities-to-assets ratio made sub-sectors of non-ferrous metal and gas production and supply in the front rank in terms of carbon performance. However, decreasing returns of scale in sub-sectors of coal mining and washing, as well as unreasonable energy structure and low energy efficiency in coal sub-sector led to the carbon performance of coal sub-sector ranking at the bottom. Consequently, it is suggested that the mining sector in Hunan Province should optimize its energy structure, accelerate low-carbon innovation, and increase various energy efficiency, so as to improve their carbon performance.

In order to explore the current status of sustainable development of mining enterprises in China in recent years, static and dynamic analysis was performed for ecological efficiency of mining enterprises in 11 different sub-sectors in China from 2012 to 2020, in which SBM-DEA model with undesirable output taken into consideration was adopted in combination with GML index. And regression testing was also conducted in combination with Tobit model for the influencing factors for ecological efficiency. Results show that during the sampling period, the ecological efficiency of mining enterprises was generally trending up, but there was some difference in the efficient frontier, and great difference between each sub-sector. It is found that the technological advancement is the main driving factor for improving ecological efficiency, which is also positively correlated with high degree of interaction with outside world, but negatively correlated with environmental regulations. At last, as for improving ecological efficiency of mining enterprises, some recommendations are proposed for the state, mining sector and mining enterprises.

Aiming at complicated flow field of Y-shaped pipe in pump piping system and risk of ore leakage in conveying test for deep sea mining, numerical simulation was performed by using CFD-DEM method for ore particles with different velocities, different volume concentration and different particle sizes. Based on that, the movement features of particle groups and flow field distribution pattern in Y-shaped pipe were all analyzed. It is found that the flow field distribution in Y-shaped pipe is influenced by the curvature of pipe elbow and the flow distribution in the inlet of Y-shaped pipe. The particle groups flow against the inner wall of elbow, and deflect upward under the influence of upward flow. If upward flow with lower velocity, particles with large grain size and high volume concentration will hit the bottom of pipe, leading to some losses. As the upward velocity decreases and both particle volume concentration and grain size increase, more and more particles will be continuously lost on the bottom of pipe. Due to the existence of particle flow, both intensity and scale of the low-pressure vortex region in Y-shaped pipe become weaken.

As for pipes with different lengths, with heave compensation device replaced by elastic constraint, a vibration equation was established by using energy integration approach, and the dynamic response of lifting pump installed at different positions of pipes was analyzed by finite element method. Results show that the harmonic response of stress excited by the following single loads was in an ascending order: torque, wave in longitudinal direction, and a combination of wave and current in horizontal direction. Under excitation by all these three loads with the same phase, the harmonic response of the system increased significantly. When the installed lifting pump was changed from a high position to a low position, the maximum equivalent stress of pipeline increased after an initial falling down. The installation position of lifting pump on the pipe corresponding to the minimum of the maximum equivalent stress was the suboptimal installation position. Based on the suboptimal installation position for the lifting pump on the pipeline with specific length, an empirical formula was established for the suboptimal installation position, which can provide reference for the quantitative design of lifting system.

It is difficult to simulate and analyze distribution of seepage field for the slope at the entrance of excavated tunnel during heavy rainfall. Aiming this problem, a slope project at a tunnel entrance was taken for study, and FISH language in the FLAC^3D was redeveloped to determine the permeability coefficient of soil under different saturation state during rainfall infiltration, and the boundary conditions for rainfall infiltration were updated in real time. In addition, the pore water pressure, matrix suction distribution, as well as safety and stability of the slope at the tunnel entrance after different support schemes were all analyzed with different rainfall durations. The results showed that after 24 hours of heavy rainfall, the slope before and after a combined support including anti-slide piles and anchor cables all reached saturation state, that is, the saturation line ran through from the foot to the crest of the slope, while the slope, after benching and being supported with bolt, had its surface soil from the foot to the secondary platform of the slope under a saturated state. As for the slope at tunnel entrance supported by anti-slide pile combined with anchor cable, the variation law of its safety factor during rainfall was consistent with that of the slope without support treatment, showing that the factor of safety tended to be stable after an initial rapid decrease, and gradually reached 1.2. As for the slope after benching and being support with bolt, its factor of safety decreased a little and maintained above 1.8. It is concluded that the factor of safety, excavated earthwork quantity and total investment for the support scheme should be taken into consideration before starting a slope engineering at a tunnel entrance, and a combined support scheme including anti-slide pile and anchor cable is superior to the scheme including benching and support with bolt.

By using CFD-DEM coupling approach and Archard wear model, a slurry pump with small flow was numerically simulated under the conditions including different flow rates and particle sizes. Based on the analysis of the movement law of particles in the pump, the distribution of particles in different regions of pump and the collision between particles and wetted parts of the pump, the wear characteristics of wetted parts in the slurry pump, especially the volute were studied. The results show that there is some blockage in the volute approaching the tongue region due to a slow flow rate of particles. It is found that wear of the volute is mainly concentrated on the upper part and near the tongue region. With the increase in the flow rate and velocity of particles, the kinetic energy of the particles collide with the pump wall increases, resulting in serious wear on the body of slurry pump. And the wear will become more serious by the particles with small grain size.

Some typical rock was taken as the sample in an experiment to study the mechanical properties of white sandstone under uniaxial compression with strain rates ranging from 10^-5 s^-1 to 10^-3 s^-1. The surface displacement contours of the samples were observed and collected by using 3D-DIC system, and the difference in the deformation and failure characteristics of samples under the effect of different strain rate was also analyzed. The results show that the variation of displacement field on the surface of rock sample reflects an evolution law of failure surface, and there is a corresponding relationship between shear failure plane and concentrated displacement field. The difference in the overall axial strain mainly occurs during the period from micro-crack compaction to elastic deformation. At an initial stage of loading, there is difference in the overall radial strain. The lower end part of the sample has the largest radial displacement when the strength reaches the peak, while the upper end part is deformed under the impact of the end effect. The radial outward expansion is limited by the friction between the end face and the gasket. In addition, the local axial strain at the lower end is greater than that at the upper end. With an increase in the loading rate, rock sample has its mechanical characteristics converted from ductility to fragility. During the failure process of rock sample under the uniaxial compression with a lower loading rate, the occurred pore collapse results in friction effect due to the closure again and slippage of some cracks, thus there appears fluctuation in the stress-strain curve near the peak strength. It is shown that the mechanical parameters (peak strength, elastic modulus and Poisson's ratio) of white sandstone increase as the loading rate increases.

A concept of short delay blasting with blastholes in a combined fan pattern was put forward, in which a row of reinforced holes were added between each row of conventional fan-pattern holes, and detonation was initiated with short delay interval between the conventional row of holes and the added row of holes. The blasting scheme with different delay interval, and blastholes loaded with different confining pressure were numerically simulated with ANSYS/LS-DYNA. It is found that blasting crater cannot be effectively produced by adopting the scheme with conventional holes in fan pattern under high geo-stress environment, while the scheme of short delay blasting with holes in combined fan pattern is more effective in obtaining damaged and ruptured rock, showing better rock breakage effect. In addition, analysis of crack propagation under different confining pressure shows that the blasting crack tends to grow in the direction of the maximum principal stress. The numerical simulation and field engineering practice have proven that when there is an acute angle between the maximum principal stress and that added row of blastholes in fan pattern, that is, higher confining pressure is loaded in the direction of the horizontal row of holes, and lower confining pressure is loaded in the direction of the vertical row of holes, the short-delay blasting with blastholes in such a combined fan pattern can not only improve the rock breakage effect, but also effectively keep rear row of blastholes and the rock mass behind not impacted by the blasting.

The impact of blasting vibration on the open-pit slope in a limestone mine was explored. The characteristics and law of blasting vibration was investigated by performing field blasting vibration tests based on the consideration of geological conditions on site. Based on fitting with Sadowski formula, an obvious attenuation trend was found for the velocity of particle vibration in the data about two field blasting vibration. With Sadowski formula modified based on elevation effect, the correlation coefficient was up to 0.94, better than the fitting effect by the traditional Sadowski formula. The maximum vibration velocity on each bench of limestone slope was predicted by using the modified fitting formula in this paper, and considering the designed detonate charge for steep end-slope, showing that the impact of vibration source on the adjacent bench should be taken into consideration in blast design.

Qingdao Metro Line 8 was taken as an example for studying the surrounding rock stability of underground tunnel in mud-containing sandstone stratum with pore water. Based on the analysis of deformation and stress evolution law of surrounding rock by simulating three different pore water conditions, the maximum values of vertical displacement (roof subsidence), horizontal displacement (side walls moving closer), vertical stress, horizontal stress and shear stress of the tunnel were finally obtained. The numerical simulation results of tunnel with three kinds of pore water content were applied to the tunnel construction for Qingdao Metro Line 8, and the on-site monitoring results show the deformation of surrounding rock of tunnel roof and side wall is all controlled within the safety range. It is shown that such numerical simulation results provide good reference for the construction of Qingdao Metro Line 8.