In order to study the subsidence law of surface road engineering under the overlapping occurrence conditions of quicksand layer and goaf, taking the reconstruction and expansion project of S342 provincial road above the goaf of Dangyang gypsum mine, FLAC3D was used to study the distribution law of surface displacement under the conditions of quicksand layer, goaf and their overlapping occurrence. The influences of quicksand layer migration and goaf on the stability of surface road sections were evaluated, and a goaf treatment plan was proposed. The research results indicate that under the action of quicksand layer migration and goaf, the surface subsidence gradually decreases from the center of the goaf to the surrounding areas, and the peak subsidence is concentrated in the range of K5+617 to K5+717. The displacement and settlement in the central area of the road centerline are relatively large, showing a pattern of first increasing and then decreasing from west to east. The settlement on the north and south sides is relatively small, with the maximum surface settlement of the north, middle, and south lines of the road being 69 mm, 167 mm, and 31 mm, respectively. As the distance from the surface increases, the displacement of the overlying rock above the quicksand layer shows a decreasing trend in the central area (within a range of 100 m from K5+630 to K5+730), while the displacement in other areas shows an increasing trend. Therefore, the range of surface rock movement under the action of the goaf at the quicksand layer is defined as 100 m. The research results can provide theoretical basis for road expansion projects under the conditions of quicksand layer occurrence.

To address the issues of instability, difficulty in support, and high support costs during the excavation of trapezoidal roadways, a support scheme for the roadway of 105 working face was proposed using theoretical analysis and numerical simulation methods, with a research background in a certain mine in Toksun. The support effect was verified using measured data. The research results indicate that under the existing support conditions, the mining pressure behavior of the 104 working face roadway is not obvious, the surrounding rock stability is stable, and there is no significant delamination phenomenon. On this basis, support scheme can be provided to the 105 working face. Compared with the theoretical analysis values, there is a certain optimization space for the existing support scheme, which can be optimized for design. The optimized support scheme has reduced the control strength of roof and two sides of the roadway, but the support cost has decreased by 32.5%. On-site application shows that during the roadway excavation, the deformation of the roof, the low side and the high side is relatively small, the maximum displacement are 19.6 mm, 21.2 mm, and 26.8 mm, respectively. During the mining period of the working face, the roadway and surrounding rocks of the working face are relatively stable, with no occurrence of high-energy microseismic events. The optimized support scheme can meet the safety requirements of roadway excavation and mining of the working face.

Aiming at the problems of surrounding rock softening, failure of original support mode and roadway collapse in the process of excavation in the contact zone of north and south edge of a copper mine at the level of −400 m, the strength of engineering rock mass was determined by rock mechanics characteristic test, and the failure reason of original support was analyzed. FLAC3D numerical simulation software was used to explore the reasonable support parameters and support principle of prestressed anchor bolt, and the control effect of different support schemes on surrounding rock was compared. On this basis, a joint support scheme with anchor bolt spacing of 0.9 m, pre-tightening force of 90 kN and sprayed concrete thickness of 100 mm was proposed. The numerical simulation results show that the scheme can effectively reduce the plastic zone volume of surrounding rock, and control the roof subsidence and the total amount of two-side convergence of roadway within 21 mm and 19 mm respectively, which are reduced by 44.9% and 56.2% respectively compared with no support, and the support effect is good. The field application results show that the deformation of the roadway tends to be stable after 42 days. On the 91 st day, the roof subsidence is 28.74 mm, and total amount of two-side convergence is 22.32 mm. The scheme can meet the needs of mine safety production. It is reasonable and feasible to design and optimize the support parameters of prestressed anchor bolt in soft rock roadway based on FLAC3D.

Pre-drainage of bedding boreholes before mining is one of the main methods for coal seam outburst elimination in working face. However, most of the outburst coal seams in China have low permeability, resulting in unsatisfactory gas drainage effect, which seriously limits the implementation of this technical measure. In view of the extraction conditions of bedding boreholes in 15111 working face of Sijiazhuang Company, the equipment system and process flow of pressure relief and permeability enhancement for mechanical cavitation of bedding boreholes were put forward. The variation characteristics of coal seam stress and gas content around the mechanical cavitation boreholes were studied, and the influence of the diameter of the cavitation borehole on the pressure relief and permeability enhancement of the coal seam was revealed, and the process parameters of the mechanical cavitation borehole in the 15111 working face were determined. On this basis, the industrial test of mechanical cavitation pressure relief and permeability enhancement in the return airway of 15111 working face was carried out. The results show that the mechanical cavitation of bedding boreholes increases the exposed area and pressure relief range of coal around the borehole, and improves the influence radius of borehole gas extraction. The gas extraction amount of mechanical cavitation is 8.06 times that of ordinary bedding boreholes, and the volume fraction of gas extraction is 153.4% higher than that of ordinary bedding boreholes, and the effect of permeability enhancement is remarkable. The research results provide an empirical reference for regional outburst prevention in mines with similar conditions.

The stress concentration of the roof and the solid coal side will be caused by the untimely collapse of the lateral hard roof in the gob-side roadway, which poses a major threat to the safety of the working face, and the blasting method is often used to weaken it. Taking the gob-side roadway of a working face as the background, the relationships among blasting angle, blasting height and pressure relief effect of the hard roof in the gob-side roadway were studied by means of theoretical analysis, numerical simulation and field practice. The results show that the fracture position on the goaf side is the most conducive to maintaining the stability of roadway surrounding rock during the blasting of gob-side roadway. The blasting angle should be higher than the breaking angle formed when the key stratum is broken, and the roof pressure above the coal pillar after blasting should be avoided. In the range of reasonable blasting angle, with the increase of blasting angle, the pressure relief effect is improved. When the blasting height reaches the top of the combined sub-key stratum, a better pressure relief effect can be achieved. The field engineering practice shows that under the condition of reasonable parameters, the implementation of strike blasting on the roof of gob-side roadway can effectively reduce the impact risk and ensure the safe production of working face. The research results can provide theoretical and engineering basis for mines with similar conditions.

In order to explore the effect of high temperature and water cooling on the dynamic compressive mechanical properties of porous sandstone, XRD and SEM tests were carried out on natural condition and high temperature-water cooled sandstone specimens at 200 ℃, 400 ℃, 600 ℃, 800 ℃ and 1000 ℃. The impact compression test was carried out by SHPB test device, and the high temperature-natural cooling condition was added as a comparison. The results show that the natural sandstone structure is dense, and the main mineral components are calcite, dolomite and quartz. After high temperature-water cooling treatment, calcite and dolomite are gradually decomposed into calcium oxide, calcium hydroxide is formed in water, and the section is covered with micron-sized particles. With the increase of the action temperature, the color of the specimens gradually changes from gray to brown, their volume expands, and their mass, density and longitudinal wave velocity decrease. The dynamic stress-strain curves of the specimens after different high temperature-water cooling treatments are similar, which are divided into three stages, including elasticity, plasticity and failure. The dynamic compressive strength is negatively correlated with the action temperature, and the dynamic strain and average strain rate are positively correlated with the action temperature. With the increase of the action temperature, the impact crushing degree of the specimens is aggravated, and the damage is changed from several fragments to powder. Compared with the high temperature-natural cooling porous sandstone specimens, the dynamic compressive strength and average particle size of the high temperature-water cooling porous sandstone specimens decrease, and the dynamic strain and average strain rate increase. The high temperature-water cooling effect causes the internal structure damage of the porous sandstone specimens. The higher the temperature, the more serious the structural damage of the specimens and the more obvious the dynamic characteristic decline.

In the process of open-pit mine production, mining disturbance can cause different degrees of damage to different areas of surrounding rock, and ultimately lead to changes in the mechanical properties of surrounding rock. In order to explore the influence of different initial damage levels on the mechanical properties and acoustic emission characteristics of sandstone, the characteristic stress value of sandstone was determined by analyzing the acoustic emission impact parameters during the loading process of sandstone samples, and the uniaxial compression test of sandstone with four different initial damage levels was carried out with acoustic emission monitoring system. The results show that the initial damage has a significant effect on the mechanical properties of the rock. With the increase of the initial damage degree, the compressive strength of the rock sample decreases by 33.6%, the elastic modulus decreases by 43.4%, the Poisson's ratio decreases by 64%, and the peak strain point gradually moves backward. The acoustic emission characteristic signals of sandstone with different initial damage levels are in good agreement with the stress-strain curves. With the increase of initial damage level, the sudden increase of local acoustic emission signals is obvious. With the increase of damage level, the crack failure mode of rock changed from tensile failure of non-destructive rock samples to tensile-shear mixed failure.

In order to study the influence of different inclination angles of prefabricated cracks on the mechanical properties and acoustic emission characteristics of rock and the crack expansion mechanism and rupture mode in the process of rock rupture, the Brazilian disc test was carried out by prefabricating disc specimens with different inclination cracks. The acoustic emission technique and the extended finite element method were used to observe and analyze the rupture evolution law of rock under different inclination cracks. The results show that with the increase of inclination angle, the crack initiation position shifts from the tip of prefabricated crack to the middle, and the parameters such as rock initiation load and peak load decrease first and then increase. The analysis results of acoustic emission parameters show that the specimens show various failure modes: the specimens with medium inclination angle mainly occur shear-tensile failure, while the specimens with higher or lower inclination angle mainly occur tensile splitting failure. The cumulative ringing count, cumulative amplitude, cumulative energy and bearing capacity of acoustic emission are consistent with the change trend of prefabricated crack inclination angles. The numerical simulation results are consistent with the laboratory test results, which confirms the effectiveness of the numerical simulation method in predicting rock crack expansion. The research results are helpful to predict and control the rupture behavior of rock mass in mining, tunnel excavation and other fields in engineering operations, and provide an effective reference for solving engineering safety problems in the industry.

Drainage well is an important safety facility in tailings pond, its stability is related to the safety of tailings pond. Based on the similarity principle, the dynamic response characteristics and variation law of the drainage wells in tailings pond under different seismic accelerations and different buried depths were systematically studied by shaking table test. The results show that when the peak seismic acceleration increases from 0.315g to 1.5g, the acceleration amplification coefficient in the drainage wellbore increases first and then decreases, and the well wall gradually changes from elasticity to elastoplasticity, and the stiffness gradually decays. Under the action of 1.5g peak seismic acceleration, the maximum relative displacement of the drainage well under the full-buried condition is 0.967 mm, which is much smaller than that under the non-buried condition of 5.295 mm, indicating that under the action of seismic, the tailings around the drainage well play a stabilizing role in the drainage wellbore, and the seismic performance of the drainage well is improved. In the process of increasing the peak seismic acceleration from 0.315g to 1.5g, the first-order frequency of the drainage well under the non-buried, semi-buried and full-buried conditions decreases by 29.17%, 27.05% and 22.74%, respectively compared with the initial natural frequency, and the stiffness of the drainage well degrades fastest under the non-buried condition. Under the action of seismic, the strain peaks at different positions in the wellbore are positively correlated with the peak seismic acceleration. The maximum strain value appears at the bottom of the drainage well, indicating that it is most vulnerable to vibration damage. The seismic performance of the bottom of the drainage well should be enhanced in the design.

Abandoned open-pit mine has caused serious damage to the ecological environment of the mining area and its surrounding areas, causing a series of problems such as geological disasters, soil erosion and landscape destruction. The ecological restoration and management of abandoned open-pit mine is not only an effective means to build green mines, but also an important way to promote the sustainable development of resource-based cities. Taking a stone mining area in Chifeng City as the research background, the damage status, existing problems and hazards of abandoned open-pit mine in this area were analyzed, and the planning ideas and management modes suitable for this area were put forward. The seven project deployments and corresponding main technical measures involved in the project implementation process were discussed in detail. The results show that the management technology of abandoned open-pit mine is difficult and the success rate of ecological restoration is low. Especially, the exposed slope and rock wall area need to increase the depth of research and management. There are various management modes for abandoned open-pit mines. It is necessary to select one or more suitable combination modes according to their site conditions and influencing factors, and connect them with local planning at all levels. The management of abandoned open-pit mine involves many treatment objectives such as mine, waste dump, slope and soil field. Its management is a complex system engineering. In planning and design, all factors should be taken into account to avoid blind management.