In order to promote the high-quality development of resource-based cities, the comprehensive evaluation index, coupling coordination degree and obstacle factors of mineral-economy-mine environment in 84 resource-based cities in China from 2020 to 2022 were studied by constructing the index system of mineral-economy-mine environment and using the comprehensive evaluation model, coupling coordination degree model and obstacle degree model. The results show that the comprehensive evaluation index of mineral, economy and mine environment has increased, and the differences of resource-based cities in different types and regions are obvious. The coupling coordination degree of resource-based cities is low, most cities are in a state of imbalance, and the overall level of coupling coordination is on the rise. The main obstacle factors of the mineral system are the sales revenue of mineral products, the total output value of mine industry and the total profit of mining enterprises. The main obstacle factors of the economic system are the total import and export trade volume, the number of patent authorizations and the profits of industrial enterprises above a certain scale. The main obstacle factors of the mining environment system are the area of restoration and treatment for the current year, the cumulative restoration and treatment area, and the amount of investment in restoration and treatment for the current year.

In response to the engineering difficulties of strength design of filling body during deep phosphate mining, a combination of on-site monitoring and numerical simulation was used to monitor the stress of the cemented backfill in the full-time (filling stage, curing stage, bearing stage) of the mining site, so as to obtain the internal stress evolution law of the filling body. Numerical simulation analysis shows that after the first stage of mining and filling is completed, the stress is mainly generated by the reserved pillar bearing the overlying rock mass. After the completion of the second stage of mining and filling, the stress distribution of the filling body in the mining area is uneven, with a stress distribution pattern of “large in the middle and small at both sides” inside the filling body. The average stress on the filling pillars is 3.0 MPa. The on-site measured data analysis shows that the filling body is a passive bearing body, and it gradually begins to bear after blasting and mining the adjacent pillars of the filling body. After the back filling of the side pillar of the filling body, the maximum vertical stress reached 0.714 MPa. The mining area adopts a filling body with a design strength of 3.0 - 3.5 MPa, which can resist the disturbance stress generated by blasting mining, and the filling body is in a stable state.

In order to solve the problems of poor mining safety and high loss and depletion rate of the steeply inclined and soft broken veins in Shanggong Gold Mine, the F1-Ⅲ vein were subjected to on-site industrial experimental research using the quasi-medium-deep hole segmented-open pit method. The results show three aspects. Firstly, all the mining works are arranged in stable rock mass outside the vein, and the safety of the construction process can be ensured by drilling medium-deep holes into the ore body from the roadway outside the vein to control and recover the ore body. Secondly, the non-cutting engineering blasting groove technology, which takes the mine approach as the initial free surface of blasting and the 3-4 rows of holes are simultaneously blasted from bottom to top to form a full section, can significantly reduce safety hazards, reduce mining costs and simplify construction technology. Lastly, the dividing line between the surrounding rock and the vein is accurately determined during the drilling process, the hole is protected by plastic sleeves and the mining is carried out by fine blasting technology. When the stope process parameters are determined as the minimum resistance line of 1.5 m, the row distance of 1.5 m, the hole bottom distance of 2.0 m, and the single explosive consumption of 0.22 kg/t, the blasting effect is the best. The loss rate is reduced to 10.1%, the dilution rate is reduced to 12.4%, the production capacity of the mining site is increased by 54.6 t/d compared to the shallow hole retention method, and the direct mining cost is reduced by 11.06 yuan/t.

In order to realize the smooth transition from caving method to filling method for a high value iron ore body, a combined mining scheme of caving method to filling method was proposed from the perspective of stope stability and full recovery of high value ore body.Using simplified beam method and Rubenieit method, the thickness of isolated top pillar in the transition area of caving method to filling method is 10.6 m and 9.4 m respectively. Based on the theoretical calculation results of two kinds of isolated top pillar thickness, the numerical simulation of the combined mining scheme of the iron ore with caving method to filling method was carried out by FLAC3D software. The thickness of the isolated top pillar in the transition area of the combined mining scheme of the iron ore with caving method to filling method is defined as 10 m. The research results have been applied to the actual production of the iron mine, and good economic benefits have been achieved, which provides a reference for caving method to filling method in the same type of mine.

The waste rock cemented backfill often exhibits stratification during the filling process. Therefore, a study was conducted on the filling effect of layered backfill. Slicing of waste rock cemented backfill was carried out, and the distribution characteristics of aggregates in different layers of the backfill were analyzed. Then, through numerical simulation, the influences of layered and non-layered waste rock cemented backfill on the filling effects of goaf were compared and analyzed. It is found that the stress in the middle of the roof of the goaf filled with layered waste rock cemented backfill and non-layered waste rock cemented backfill is about 3.68 MPa and 3.61 MPa, respectively. The settlement degree of the roof of the non-layered backfill is significantly smaller, which can provide more stable support for the roof. The lateral support of the non-layered backfill is uniformly stressed, with a small displacement and a maximum displacement of 3.76 mm. The lateral displacement of the layered backfill is small in the upper part and gradually increases downwards, with a maximum displacement of 4.46 mm. The distribution of fine aggregates in the upper layer of layered backfill makes it susceptible to pressure deformation, while the waste rocks distribution inside the non-layered backfill is uniform, with a stronger overall bearing capacity and relatively smaller deformation.Therefore, when carrying out the filling material proportion, it is important to control the backfill layering phenomenon as much as possible to provide important guarantees for mine safety production.

The stability of exposed one-step filling body on both sides is the key to safe mining in the two-step mining of subsequent filling mine. By means of numerical simulation and field monitoring, the stress and displacement states of different positions under the condition of one-step filling body unilateral exposure in 5371 stope of an iron mine were studied. The results show that the vertical stress of the measuring point at the bottom of the exposed filling body changes the most, about 0.48 MPa. The horizontal displacement of the measuring point at the top and closer to the exposed surface is larger, and the maximum horizontal displacement is about 32 mm. The mining rate of the two-step pillar is logarithmically related to the maximum vertical stress and maximum horizontal displacement of the exposed filling body. Different excavation times have little effect on the vertical stress at the bottom of the filling body, which is about 1.92%, and have a great effect on the horizontal displacement of the top of the filling body, which is about 5.65%. The field monitoring results show that during the two-step mining, the vertical stress in the middle of the unilateral exposed filling body changes greatly, about 0.3 MPa, and the horizontal displacement of the top measuring point is the largest, about 30 mm, which is basically consistent with the numerical simulation results.The research results can provide safety guarantee for the two-step mining work of the iron mine.

The evolution law of mechanical properties of tailings materials under freeze-thaw cycles is explored to provide a theoretical basis for the safety and stability evaluation of tailings dams. The tailings samples with different water contents were subjected to 1, 3, 5, 7, 9 freeze-thaw tests, and triaxial shear tests were performed under confining pressure conditions of 100 kPa to 400 kPa. The test results show that with the increase of the number of freeze-thaw cycles, the macroscopic structural deformation of the tailings increases significantly. Especially when the water content is 15%, after 7 freeze-thaw cycles, the pore structure of the tailings changes significantly, and the number of pores at the volume level of 0 − 250 μm³ increases significantly. In addition, it is found that increasing confining pressure can improve the elastic modulus of tailings and inhibit the damage of tailings caused by freeze-thaw cycles. The deformation modulus of the tailings tends to be stable after 5 freeze-thaw cycles, while the tailings samples with high water content show lower cohesion, internal friction angle and deformation modulus.

Aiming at the technical bottleneck of low compressive strength, high filling cost and poor filling effect of cement-based filling body, ultrasonic technology was used to improve the performance of cement-based filling slurry. Through the orthogonal tests of three factors and four levels, the effects of ultrasonic power, ultrasonic time and stirring time on the rheological properties and mechanical properties of cement-based filling slurry were investigated, and the strengthening mechanism of ultrasonic action was further discussed. There search results indicate that the primary and secondary factors affecting the compressive strength of the filling body are ultrasonic power, ultrasonic time and stirring time. Ultrasonic power is a significant factor affecting the yield stress and plastic viscosity of the filling slurry, followed by stirring time, and ultrasonic time has the smallest impact. The compressive strength of the filling body at 3 days, 7 days, 14 days and 28 days shows a trend of first increasing and then decreasing with the increase of ultrasonic power, ultrasonic time and stirring time. When the ultrasonic power, ultrasonic time and stirring time are 70 W, 4 min and 6 min, respectively, the compressive strength of the filling body reaches its optimal value. The yield stress and plastic viscosity of the filling slurry are negatively correlated with ultrasonic power and ultrasonic time, and show a trend of first decreasing and then increasing with the extension of stirring time. This is because the ultrasonic action promotes the dispersion of cement and tailings particles in the liquid phase, improves the uniformity of the slurry, and promotes the cement hydration process. However, excessive ultrasonic power and prolonged ultrasonic time lead to the reunion of the flocculation structure of cement particles, which inhibits the diffusion of water molecules and the compactness of the slurry structure. The appropriate stirring time is beneficial to the dispersion of the slurry and weakens the friction and shear between the particles, while the excessive stirring time leads to the destruction of the slurry structure and weakens the mechanical properties of the filling body.

To investigate the rheological properties of filling slurry with steel slag and unclassified tailings under different proportioning conditions, rheological tests were conducted using the controlled shear rate method, and the effects of mass concentration, cement-sand ratio, and steel slag content on the rheological properties of the slurry were analyzed. The interaction among mass concentration, cement-sand ratio, and steel slag content on the rheological properties of slurry was investigated using the central composite design response surface method.The results show that the mass concentration has the most significant effect on the yield stress and viscosity, and with the increase of mass concentration, the yield stress and viscosity show a power function growth law. The steel slag content reduces the viscosity and yield stress of the slurry, significantly improving its flowability. When the steel slag content is increased from 0 to 25%, the yield stress decreases by 85.43% and the viscosity decreases by 53.83%. For the interaction of various influencing factors, the interaction between mass concentration and steel slag content has the most significant effect on yield stress and viscosity. The increase of steel slag content promotes the influence degree of mass concentration on rheological parameters, that is, as the steel slag content increases, the influence of mass concentration on yield stress and viscosity gradually increases. Parameter optimization shows that when the mass concentration is 60%, the steel slag content is 30 %, and the cement-sand ratio is 1:8, the yield stress and viscosity of the slurry are the smallest, and the flowability is the highest.

Advancements in exploration theory and equipment have significantly enhanced mine reserve expansion. However, adapting new resources in the deep periphery of mines to existing production systems requires reassessment. Green stoping-and-filling operations face challenges from varying filling gradients and existing slurry pipeline transportation parameters that no longer meet practical demands. To address these challenges, tests were conducted on the particle size distribution of backfill materials and slurry flow performance at the mine. Results identify that a reasonable range of slurry mass concentration is 70%-72%. Through theoretical analysis and calculation, the matching degree between the design parameters of the existing filling system and the orebody filling gradients was verified. The maximum gravity flow filling gradients of the slurry mass concentration of 70% and 72% are 9.31 and 5.56, respectively. Simulation models were constructed to verify the correctness of theoretical analysis. The results show that a 72% slurry mass concentration is suitable for gravity flow transportation in older mine zones with filling gradients of 2.3-4.9, while reducing concentration to 70% enables gravity filling in high-gradient goafs with filling gradients of 7.2-8.7 in newly developed zones. For the mine to achieve optimal technical and economic performance, two schemes are proposed:implementing additional pumps to transport slurry with a mass concentration of 72% under pressure(first scheme), and utilizing slurry with a mass concentration of 70% for gravity flow (second scheme). A comparative analysis shows that the first scheme has obvious advantages and disadvantages, while the second scheme requires no technical modification, offers a more reliable process, and reduces operational costs by RMB 2 334 500 compared to the first scheme. Therefore, the second scheme is the preferred option.