Taking the loose and weak strata in the freezing section of the main well of a mine in Laizhou as the research object, the temperature field distribution law of the double-ring freezing hole was compared and analyzed by means of field measurement and ANSYS numerical simulation. It was found that the freezing effect of the double-ring freezing hole was not ideal. Based on the comprehensive study of the formation and development law of the freezing wall for the double-ring freezing hole, a new optimization scheme of the three-ring freezing hole was proposed, that is, the single-ring freezing hole on the inner wall of the well and the double-ring freezing hole on the outer wall were arranged, and the ANSYS finite element software was used to analyze and compare the freezing effect of the temperature field before and after optimization. The results show that the optimization scheme shortens the circulation time by more than 10 days, effectively reduces the internal temperature of the wellbore and shortens the circulation time of the freezing wall. After freezing for 60 days, the thickness of the freezing wall of the optimization scheme has reached about 4.8 m, which is much larger than that of the original scheme, and the temperature is about 4−5 ℃ lower than that of the original scheme. It shows that adding a circle of freezing holes in the well is an effective method, which can quickly reduce the temperature around the well to the lowest, and play a certain guiding role for well excavation with complicated geological conditions such as safe construction of well excavation and difficult freezing.

The rational design of stope filling body is very important to ensure the safe and efficient mining of mines. Based on the engineering background of a stope mined by large-diameter deep hole open stoping with subsequent filling mining method, the reasonable strength of filling body in stope was studied by combining theoretical calculation and numerical simulation. The stress, displacement and surface subsidence deformation law inside the filling body of the stope were explored. The results show that the maximum principal stress inside the filling body gradually increases with the progress of mining. The stress is mainly compressive stress, which is more obvious at the roof and floor. The strength change of the filling body has little effect on the maximum and minimum principal stress peaks, but the increase of the strength of the filling body reduces the stress radiation range. The increase of the strength of the filling body reduces the roof subsidence space and limits the roof deformation, and its constraint effect on the roof is better than that of the surface. Under the influence of excavation disturbance, the displacement inside the filling body presents a step-like change rule. Under the working condition that the strength of the filling body in stope is 2.5 MPa at the 10 m of top and bottom and 1.5 MPa in the middle part, the maximum tilt deformation, curvature, maximum horizontal deformation in X-direction, and maximum horizontal deformation in Y-direction of the surface monitoring line are 0.109, 0.181×10^－3,－0.024, and 0.059 mm/m, respectively. All these values meet the requirements of the safety regulations for the impact of surface subsidence on structures.

In order to solve the problems of serious accumulation of solid waste and low overall strength of backfill in a mine, tailings and waste rocks were used as filling aggregate, and polypropylene fiber was added to prepare filling material. Through orthogonal test, the effects of cement-sand ratio, waste rock gradation index and fiber content on the slump of filling slurry and the strength of backfill were investigated, and the optimum ratio of filling material was determined. The results show that the primary and secondary factors affecting the slump of filling slurry are waste rock gradation index, fiber content and cement-sand ratio, while the primary and secondary factors affecting the 28 days compressive and tensile strength of backfill are cement-sand ratio, fiber content and waste rock gradation index. The decrease of cement-sand ratio and the increase of waste rock gradation index will weaken the strength of backfill. When the fiber content is 0.6%, the strength of backfill is the largest. The fitting function of the strength of backfill and the slump under the influence of the coupling of the main factors was constructed. According to the fitting function, the three-dimensional model diagram of the influence relationship between the main factors and the performance index of backfill was established, which conformed to the relationship of Z=Ax²+By²+Cx+Dy+Exy+F. Based on the orthogonal test and the actual needs of the mine, the optimal ratio parameters of the filling material are obtained: cement-sand ratio of 1:5, waste rock gradation index of 0.8, and fiber content of 0.6%. Under this condition, the fluidity of filling slurry and the strength of backfill can meet the filling requirements of the mine, and the cost of the filling material is relatively low.

Calcium carbonate can be used as a retarder to increase the flowable time of the filling slurry. In order to study the influence of calcium carbonate on the mechanical properties of paste filling body, the single factor and orthogonal method were used to design the filling body material ratio scheme, and the filling body was prepared. The uniaxial compression test was carried out on the filling body specimen, and the acoustic emission change of the filling body during the loading process was monitored in real time. The microstructure of the crack of the specimen was observed by SEM. The influence law and weight order of each factor on the compressive strength of the filling body were studied, and the failure mechanism of the filling body was analyzed from multiple perspectives. The results show that with the increase of calcium carbonate mass fraction, the strength of filling body decreases first and then increases. After adding calcium carbonate, the influence of mass fraction of fly ash, cement and solid material on the strength of filling body at each curing age (3 d, 7 d, 28 d) is basically the same as that before adding calcium carbonate. Calcium carbonate has a weak degradation effect on the compressive strength of filling body, but it has a price advantage and can be used as a retarder for filling materials. Based on the range analysis, the weight order of the influence of each factor on the 28 d strength of the filling body is cement mass fraction>calcium carbonate mass fraction>solid mass fraction>fly ash mass fraction. According to the failure characteristics of filling body, with the increase of curing age, the failure mode of filling body changes from ductile splitting to brittle shear failure. The acoustic emission ringing count changed abruptly before and after the initial compaction of the filling body approaching the elastic deformation stage and the peak stress, which revealed the internal damage evolution process of the filling body.

The transport performance of paste filling slurry and the backfill strength are important contents of filling process. In order to explore the transport performance of paste filling slurry with coarse aggregate and the evolution law of backfill strength in a mine, the response surface method was used to carry out the fluidity test of filling slurry and strength ratio experiment of backfill. Based on the response surface test results, the effects of single factor and multiple factors interaction such as proportion of coarse aggregate, cement-sand ratio and mass concentration on the transport performance of the filling slurry and the strength of the backfill were analyzed. The results are shown as follows. Firstly, under the influence of a single factor, the sensitivity factors of backfill strength from large to small are cement-sand ratio, mass concentration and proportion of coarse aggregate; for the slump of filling slurry, the sensitivity factors from large to small are the proportion of coarse aggregate, mass concentration and cement-sand ratio. Secondly, based on the response surface method, the response regression model of the slump of filling slurry and backfill strength was established. The predicted value of the model has a good linear relationship with the test value, and the model has high fitting degree and high reliability. Thirdly, the interaction between mass concentration and cement-sand ratio has the most significant influence on backfill strength, the interaction of proportion of slump and mass concentration has the most significant effect on the slump of filling slurry. Finally, the parameters of backfill strength and slump of filling slurry has been optimized as follows, proportion of slump of 30.7%, cement-sand ratio of 1:6, and mass concentration of 82%. Under this condition, the errors between the experimental values and the predicted values of the backfill strength and the slump of filling slurry are within 5%, which verifies that the application of the response surface analysis method in optimizing backfill strength and filling slurry slump is reliable.

Pipeline transportation is a crucial component of mine filling systems, and the rheological parameters of the filling slurry are essential for pipeline transport design. Taking the unclassified tailings filling slurry of Daye Iron Mine as the research object, the rheological parameters and pipeline transportation characteristics were studied by rheological test and Fluent numerical simulation. The results indicate that when the slurry mass concentration is between 60% and 70%, the fitted relationship curve between shear stress and shear rate conforms to the change rule of Herschel-Bulkley (H-B) model. With the increase of slurry mass concentration, the yield stress and viscosity coefficient increase exponentially, and the viscosity coefficient increases significantly when the slurry mass concentration reaches 70%. When the mass concentration is 60%−65%, the slurry flow is unstable and the pressure distribution in the pipeline is uneven. When the mass concentration is between 68% and 70%, the slurry flow state is relatively stable, and the pressure is symmetrically distributed along the pipe diameter. The resistance loss of the pipeline is positively correlated with the slurry mass concentration and the slurry flow rate. When the slurry mass concentration reaches 68%, the resistance loss begins to increase significantly. It is suggested that the mass concentration of filling slurry in Daye Iron Mine should be controlled between 65% and 68%. Considering that the maximum flow velocity of slurry appears at the bottom of vertical elbow (inflection point D), where wear-resistant materials should be used. The research results can provide a theoretical basis for the design of pipeline transportation parameters of mine filling system.

Aiming at the influence of surface subsidence induced by open stoping with subsequent filling mining on surface industrial site in a phosphate mine, a three-dimensional model of top-down stoping with subsequent filling of ore body was established by FLAC3D. Numerical analysis was conducted on the deformation of overlying strata and surface subsidence in different mining stages, and the distribution laws of surface subsidence under different mining stages were obtained. As the advancement of mining, the cumulative goaf volume increases, and the maximum surface subsidence value gradually increases, showing a characteristic of larger subsidence values in the early and middle stages and smaller subsidence values in the later stage. The maximum surface subsidence value is 72.94 mm. Combining with the calculation results of displacement, inclination, and curvature near the industrial site on the surface, it can be concluded that the deformation values of the selected measuring points meet the protection level requirements of level Ⅰ and level Ⅱ, and the safety impact of designed underground mining scheme on the surface industrial site meets the regulatory requirements. The research results can provide useful references for the study of surface subsidence and ground pressure control during the top-down stage open stoping with subsequent filling process in similar large-scale mines.

The existing old landslide body is a major safety hazard in the open-pit mining field, and its stability research is of great significance to ensure the safe production of the open-pit mining field. The slope stability of an existing old landslide body in an open-pit mine was studied by using multiple geophysical methods + pattern search method. Firstly, through the seismic imaging method, supplemented by transient electromagnetic method and other geophysical methods, the sliding surface of the existing landslide body was investigated to obtain the position of the existing sliding surface. Then, the pattern search method was used to search the most dangerous sliding surface of the whole slope, and the Bishop method was used to analyze its stability. The results show that the seismic imaging method and the transient electromagnetic method can be used as an effective method to investigate the sliding surface of the existing landslide body after mutual verification. The safety factor of the existing old sliding surface is greater than 1.15, indicating that the sliding surface is relatively stable as a whole. The potential most dangerous sliding surface outside the sliding surface of the existing landslide body has been searched by the pattern search method. A total of eight unsafe sliding surfaces have been found in the P1 slope under the condition of self-weight and earthquake, which are mainly located outside the existing old landslide body, at the top of the slope and below the toe of the existing old landslide body, that is, the position where the slope is steep and varied, and the position with local outburst. A total of three unsafe sliding surfaces have been found in the P1 slope under the self-weight and rainfall conditions, which are mainly located at the lower part of the exit of the existing old sliding surface. P2 slope is basically stable. The research results can provide a reference for slope monitoring and geological disaster prevention.

Aiming at the problem of dynamic disaster induced by multi-level combined mining in deep mines, the stress evolution law and deformation behavior characteristics of surrounding rock in multi-level mining area were studied. By means of geological survey, theoretical analysis and numerical simulation, the stability of the multi-level mining area of 03-011 line in the eastern part of 2 402-2 522 meter of Xitieshan Lead-Zinc Mine was analyzed, and the deformation and failure behaviors of surrounding rock and ore body in the mining process was demonstrated. The results show that the deformation and failure of the multi-level mining area in this mine mainly occur in the thick and large stope of individual ore bodies and the middle part of the regional mining. The maximum settlement of the top pillar position in the level of the mining status is close to 4 cm, and there is no greater risk. In the subsequent mining of 2 462 m level, the displacement of 14003-3 stope is the largest, and the settlement value exceeds 6 cm. The displacement of multiple stopes on both sides is about 5 cm, and there may be some stope collapse. Combined with the spatial and temporal evolution characteristics of deformation and failure in multi-level mining, aiming at the potential ground pressure in the mining process, the mining planning optimization has been carried out for the mining design, which can provide a theoretical support for the safe and efficient mining of multi-level in the subsequent mining area.

Aiming at the requirement of high accuracy of roof deformation monitoring in mine working face under complex environment, a set of foof deformation of working face monitoring system based on LiDAR was designed, and the matching deformation monitoring data algorithm was developed, and the deformation risk was evaluated. The monitoring system employed time-lapse scanning to acquire two phase point cloud data of the mine working face. Following preprocessing steps such as angular transformation and ICP registration, high-precision triaxial tilt sensors was used to real-time calibrate the LiDAR attitude, enabling precise extraction of the point cloud morphology of roof. Subsequently, the Delaunay triangulation mesh division was applied to process the two phase point clouds, and innovatively incorporated a point-to-plane monitoring algorithm to calculate the distance between the central points of the second phase and the triangular facets of the first phase, thereby enhancing the accuracy of deformation monitoring. Furthermore, based on the DBSCAN clustering algorithm, the deformation point cloud density clustering filtering algorithm was proposed to identify and mark the deformation area, and on this basis, the risk level assessment was conducted to realize the intelligent monitoring of roof deformation. Field research results demonstrate that the deformation displacement range of 0−5 mm in April and July 2024 is in the middle risk level, which needs to be paid attention to and corresponding monitoring and management measures should be taken. The deformation displacement range of 5−10 mm is in the low risk level, which needs to be continuously monitored to prevent the risk from escalating. The monitoring system achieve a monitoring accuracy range from 1 mm to 5 mm, which is significantly improved compared to traditional monitoring methods, and can achieve visual and accurate marking of deformation areas. The research results provide strong technical support for mine safety production, further enhancing the safety and reliability of mining operations.