To effectively manage the extensive risk of manganese (Mn) contamination in soils, the Mn content must be monitored through low-cost and efficient methods. Visible and near-infrared reflectance spectroscopy presents a promising alternative to traditional soil assessment methods. In this study, we constructed and evaluated a deep convolutional neural network (CNN) model for precisely predicting soil Mn contents on a continental scale. The correlation between the actual soil Mn content and the spectral under different preprocessing methods was analyzed. The results indicate that combining Savitzky-Golay smoothing and the second derivative could effectively improve the CNN predictive performance. After hyperparameter tuning, the R2, root mean square error, mean absolute error, and ratio of performance to deviation were 0.66, 132.02 mg/kg, 89.24 mg/kg, and 1.71 for the optimal CNN model on the test set, respectively. The distribution of soil Mn content predicted by the model was highly similar to the actual distribution. The uncertainty analysis shows that the CNN prediction was stable and reliable. Our model has shown a practical and effective predictive capability for soil Mn content on a large scale, providing an important tool and reliable method for agricultural management and environmental monitoring.

This paper presents experimental study on two shored mechanically stabilized earth (SMSE) walls to investigate the influence of anchors under vertical loading. The models were designed according to the similitude relationships, and were constructed using a poorly graded sand, biaxial geogrid and full-height rigid facing, then a series of vertical stresses with increasing amplitudes were applied to the two models. Experiment results indicate that the anchors have a minor influence on the facing displacements and settlements for small applied vertical stresses. As the applied vertical stresses increase, the influence of anchors becomes pronounced, and the facing displacements and settlements increase significantly. Moreover, the displacements and settlements of the SMSE wall with anchors are smaller than those of the SMSE wall without anchors. The incremental vertical soil stresses at the bottom of the two models under different applied vertical stresses exhibit similar trends. However, the distribution of vertical soil stresses in the SMSE wall with anchors is more uniform, and the magnitudes of the vertical soil stresses are smaller. For the SMSE wall without anchors, the locations of maximum reinforcement strain follow an approximately linear distribution, whereas a Y-shaped distribution is observed for the SMSE wall with anchors.

This paper conducts a numerical study exploring the impact of the evolution of a weak structural plane on the overload stability and failure performance of anchored slopes. Both the macroscopic deformation failure characteristics and the internal stress-strain response of an overloaded anchored slope, following the evolution of a weak structural plane, are thoroughly presented and analyzed. As the structural plane evolves under overload conditions, it is demonstrated that the deformation mode of the slope initially evolves from a "circular damage" pattern, progressing to a combination of "circular damage and wedge damage", ultimately resulting in "wedge damage". Furthermore, there is a gradual shift of the stress peak and cable axial force from the top to the bottom of the slope. The formation of a stress concentration area in the anchoring zone is observed once the structural plane reaches full-length, leading to subsequent cable debonding. Moreover, it is apparent that the weak structural plane shows distinct stress differentiation, effectively isolating stress and deformation.

Grouting is a widely used method of reinforcement for stabilising fractured surrounding rock. To investigate the triaxial compression behaviour of surrounding rock after grouting reinforcement, laboratory-prepared grouted specimens were subjected to triaxial compression tests using an RMT-150B testing system. The analysis focused on the effects of confining stress, particle size, and water-to-cement ratio on the stress-strain behaviour. The internal friction angle and cohesion were determined based on the Mohr-Coulomb criterion. The variations in strain at peak stress and the elastic modulus were clarified, and the failure modes of the grouted specimens were examined. Additionally, Kendall's correlation analysis was employed to evaluate the relationship between confining stress and other parameters. The results indicate that increasing confining stress significantly enhances the load-bearing capacity of the surrounding rock. The optimal rock particle gradation was observed when the particle size ranged between 5-10 mm, yielding the highest compressive capacity. Conversely, increasing the water-to-cement ratio reduced the strength of the specimens. Among the analysed factors, confining stress exhibited the strongest correlation with peak stress.

Anchored slope with weak structural planes is a complex combination of rock mass and retaining structure, whose stability analysis is a necessary condition for road safety protection. To better understand the failure mechanism of anchored slope with weak structural planes under local overload, a series of physical model tests as well as corresponding numerical simulations have been conducted. Based on the test and numerical modeling results, the following conclusions are drawn: There is a serious stress concentration in the middle of the slope, which results in the failure of the slope surface in the shape of a bulge. Under the action of vertical stress, the anchored slope forms a wedge sliding zone along the weak structural plane. The overloading failure mode of the anchored slope with weak structural planes is collapse-upper extrusion-middle traction-lower, and the whole along the weak structural plane to the lower part of the wedge sliding failure. Overload changes the load bearing and deformation characteristics of anchored slope with weak structural planes. Additionally, the greatest stress occurs in the weak structural plane shear failure location, while the weak structural plane isolates the deformation and stress transfer. The axial force is distributed in the shape of “Z”, and the strength of the anchor cable in the middle and upper row should be appropriately strengthened.

Shored mechanically stabilized earth (SMSE) walls have been increasingly applied in the projects of widening existing roads or new construction of roads on slopes because of their good carbon emission reduction and mechanical performance. In this paper, a scaled-down model test of SMSE wall with shoring wall batter of 1H:2V was conducted to study the load-bearing behavior of SMSE wall under this terrain condition, and the results including wall deformations, earth pressures, reinforcement strains, and potential failure surface were analyzed. The results show that although the backfill near the shoring wall was not directly compressed by the load, it still slipped along the backfill-shoring wall interface. The loading created a tensile pressure zone in the upper part of the backfill-shoring wall interface, which may lead to tensile cracking. The uppermost layer of geogrid was more prone to sliding, while the tensile deformation was smaller, and its strain value was overall smaller than the strain value of the geogrid below it. As the load increases, the potential failure surface changed from a Rankine failure surface to a bilinear potential failure surface. The potential failure surface did not pass through the heel of the SMSE wall under large loads.

In response to the “three highs” problem in the mining of deep high-gas mines, the rapid increase in the coal seam permeability coefficient and gradual increase in coal and gas outburst problems have made gas control more difficult. This study considered the occurrence of remote outburst coal seams in the Zhujixi Mine as the research background and performed theoretical analysis, calculations, numerical simulations, and other technical methods to analyze the gas occurrence characteristics of the 11-2 coal seam and the feasibility of using this seam as a lower protective layer for mining. The pressure relief protection range for the overlying 13-1 coal seam, to the recovery of the 11-2 coal seam, was determined. A regional anti-outburst technology was proposed for underground through-layer and parallel-layer drilling, focusing on pre-gas extraction for the protective layer. In addition, a pre-gas extraction regional anti-outburst technology combining the surface and underground mining of the protected layer is also proposed. Gas occurrence in the 11-2 coal seam is uneven and has poor regularity, presenting high gas areas. It is significantly affected by the geological structures and shale properties of the coal seam roof and floor. The 11-2 coal seam is a stress-dominated and gas-outburst coal seam. The Zhujixi Mine presents a joint underground extraction and regional outburst prevention mode; that is, the 11-2 coal seam with a lower outburst risk is selected as the protective layer for mining first, whereas the 13-1 coal seam is protected while the gas in the protected layer is extracted. The 11-2 coal is characterized by the gas control mode of “one side, three lanes+ground drillings” to achieve multi-purpose, joint treatment, and continuous mining of one lane. The excavation face exhibits comprehensive anti-outburst measures, such as through-layer drilling pre-extraction and a coal mining face over the layer drilling pre-extraction area. During the mining period, surface drilling and a top extraction roadway are used to extract 13-1 coal-depressurized gas. By adopting joint extraction technology in the upper and lower mining areas, the residual gas content and pressure were measured at the underground excavation and mining working face. The predicted indicators did not exceed the standard levels, and no dynamic phenomena occurred. As a result of the application of the anti-outburst technology in the joint extraction area of the Zhujixi Mine, the proportion of extraction in the upper and lower mining areas was 56.7%, and the proportion of extraction in the underground mining area was 43.3%. These factors are interdependent and indispensable. The maximum height of the caving zone after mining the 11-2 coal face was 11.6 m, whereas the height of the fracture zone was 34.4-52.2 m. The 13-1 protective-layer working face is arranged on the upper part of the fracture zone or lower part of the curved subsidence zone, which can effectively increase the permeability of the 13-1 coal seam. Engineering practice has shown that the joint regional anti-outburst technology and engineering application in Zhujixi mine have achieved good results, forming a regional anti-outburst technology system for joint extraction of mines and providing a reference for the safety production of similar conditions in outburst mines.

The stability control of surrounding rock in deep roadway is becoming more and more difficult, and grouting reinforcement support has become the mainstream of roadway control. In order to obtain the ratio of quasi-sandstone material corresponding to the grouting body, this paper uses river sand as aggregate, cement and gypsum as cementing agent, retarder and defoamer as additives, and carries out orthogonal proportioning tests with three influencing factors: water-binder ratio (ratio of water to mass of cementing agent), gypsum-cement ratio (ratio of gypsum to mass of cement) and binder-aggregate ratio (ratio of cementing agent to aggregate mass), and compares and analyzes the sensitivity of each factor on the density, compressive strength, tensile strength, elastic modulus, Poisson’s ratio, longitudinal wave velocity, elasticity index and brittleness index of quasi-sandstone material. The results show that 1) the Water-binder ratio has the greatest effect on the sensitivity of material compressive strength, tensile strength, elastic modulus, Poisson’s ratio and longitudinal wave velocity; the gypsum-cement ratio has the greatest effect on the sensitivity of material deformation index and brittleness index; the binder-aggregate ratio has the greatest effect on the sensitivity of material density. 2) Reducing the Water-binder ratio can improve the density, compressive strength and tensile strength of the material; reducing the paste ratio can improve the modulus of elasticity, Poisson’s ratio and longitudinal wave speed of the material; as the gypsum-cement ratio increases, the deformation index first decreases and then increases and then decreases; as the binder-aggregate ratio increases, the brittleness index first increases and then decreases and then increases. 3) The empirical equations between physical and mechanical properties of sandstone-like materials and Water-binder ratio, gypsum-cement ratio and binder-aggregate ratio were established based on multiple linear regression analysis, and more reasonable material ratios were quickly obtained by physical and mechanical parameters of materials. The results of the study provide theoretical references for similar material simulation tests for quasi-sandstone grouting.

The unloading effect is an important factor for the failure of surrounding rock in deep underground engineering projects, especially under high-stress conditions. To investigate the deformation and failure characteristics of sandstone at different unloading rates, the evolution law of the surrounding rock stress caused by excavation was clarified. Then, the single-side unloading test of surrounding rock at different unloading rates was conducted using a true triaxial rock mechanics test system. During the test, the acoustic emission (AE) signals were monitored using an AE monitoring system. The test results show that excavation disturbance leads to complete single-side unloading at the boundary of the surrounding rock, and partial single-side unloading occurs as the depth of the surrounding rock increases. The ultimate strength of the sandstone specimen decreases as a power function with the increasing unloading rate. The unloading rock mass is mainly subject to shear failure. However, the increasing unloading rate raises the proportion of tension cracks. The sudden high strain rate on the unloading side can be used as precursor information of rock fracture, which can effectively prevent accidents caused by loss of rock bearing capacity. The AE signal is active and releases less energy in the unloading stage. At this time, the internal fractures are in the development stage, and the energy is still mainly accumulated. The unloading and failure are not synchronized but suffer from the hysteresis effect. Additionally, the AE and the strain rate change on the unloading side are consistent. Due to the hysteresis effect of damage on unloading, anchor bolts (cables) should be installed to support the surrounding rock immediately to compensate for the stress loss caused by excavation in engineering practice.

Investigating the adsorption characteristics of CO2, N2 and CH4 on kaolinite clay is beneficial for enhanced shale gas recovery by gas injection. In this paper, the experiments of CO2, N2 and CH4 adsorption at 288 K, 308 K and 328 K on kaolinite clay were conducted, and the thermodynamics analysis of adsorption of three gases was performed. The findings reveal that the order of the uptakes of three gases on kaolinite clay is as follows: N2 < CH4 < CO2. Reducing temperature enlarges the separation coefficients of CO2 over CH4 (αCO2/CH4), CO2 over N2 (αCO2/N2), and CH4 over N2 (αCH4/N2). The value of αCO2/CH4 greater than one validates that CO2 is capable to directly replace the pre-adsorbed CH4. The spontaneity of CO2 adsorption is the highest, while N2 has the lowest adsorption spontaneity. Injecting N2 into gas-bearing reservoir can cause CH4 desorption by lowering the spontaneity of CH4 adsorption. Adsorbed CO2 molecules form a most ordered rearrangement on kaolinite surface. The decrease rate of entropy loss for N2 adsorption is higher than those for CO2 and CH4 adsorption.

Aiming at the problem of the deformation of the roadway floor plate during the laneway during the retention period, the mechanical model of the roadway floor is established, and the deformation characteristics of the roadway floor and the change law of the bottom drum are studied and analyzed through theoretical calculation and calculus simulation, revealing the instability mechanism of the surrounding rock of the roadway under the stress disturbance environment, and when not affected by the adoption, the roadway forms a certain stress concentration area within the effective range of support. During mining, under the comprehensive action of the original peripheral stress field and the mining stress field, the cliffhanger is unstable under the comprehensive action of the original peripheral stress field and the mining stress field, and the extrusion and stretching effect of the unflapped part of the rock layer above the goaf section of the coal seam is set up along the air, resulting in violent deformation such as the bottom drum, and the rotational sinking of this part of the unflinted rock layer further aggravates the transfer of the overburden load to the surrounding rock of the lane, so that the surrounding rock along the empty lane is subjected to a large additional stress, and the mining stress field plays a leading role, and the mining stress “far field” is the compound stress field, of which the tensile stress is the leading destructive factor. The deformation of the surrounding rock is mainly based on the bottom, and the horizontal stress on the bottom plate along the empty lane is mainly generated by the horizontal strain that occurs after the lower rock layer of the filling body and the coal gang is subjected to the supporting pressure transmitted by the top plate. With the mining of the working surface, the roof of the goaf area is broken and collapsed to form the characteristics of “vertical three belts,” which is affected by the “large support” of the coal body of the working surface and the “small support” of the surrounding rock along the empty roadway, and the pressure relief of the cut roof can make the roof plate along the empty lane change from the “long arm beam” structure when the roof is not cut into the “short arm beam” structure, blocking the lateral stress of the goaf area to the roof plate of the alley and significantly reducing the degree of stress superposition of the roof plate of the alley. The technical means of blasting cutting roof active pressure relief and protective lane are used to block the transmission of lateral support pressure, the roof slate layer is precracked in advance, the sinking of the rock layer is accelerated, the disturbance time is reduced, the vertical stress of the rock layer and the rock layer above it along the empty roadway is reduced, the vertical stress concentration of the roadway is reduced, the stress concentration coefficient is reduced, the degree of damage of the surrounding rock after the top is weakened, the damage range is reduced, and the technical problem of large deformation prevention and control along the bottom drum of the empty alley can be solved. Constructing the mechanical structure model of the top plate of the cut top pressure relief and the uncut top pressure relief along the empty lane, the stress change characteristics of the active protective rock surrounding rock along the hollow top of the cut top pressure relief were calculated, and after the technical scheme of the blasting cut top active pressure relief and protection lane was adopted, the deformation along the empty roadway was significantly weakened, the stability of the surrounding rock of the roadway after the blasting of the cut roof was significantly improved, the maintenance state along the section of the empty roadway was good, and the cross-sectional convergence rate was reduced by 37.3% compared with the original section. Cutting the roof active pressure relief and protective lane can effectively improve the stability of the surrounding rock.

Abstract In view of the”three high” problem of deep high gas mine mining, the rapid increase of coal seam permeability coefficient and the continuous reduction of coal and gas outburst risk gradually increase the difficulty of gas control. Taking the occurrence of long-distance outburst coal seams in zhujixi mine as the research background, this paper analyzes the gas occurrence characteristics of 11 − 2 Coal Seam and the feasibility of 11 − 2 Coal Seam as the lower protective layer by using the technical methods of theoretical analysis, calculation and numerical simulation, and studies and determines the pressure relief protection range of 11 − 2 coal seam mining to the overlying 13 − 1 coal seam; This paper puts forward the regional outburst prevention technology of underground penetrating and bedding borehole pre drainage for the protective layer and the regional outburst prevention technology of pre drainage combined with the mining surface and underground of the protected layer. Coal seam 11 − 2 has uneven gas occurrence and poor regularity. There are only high gas areas in some parts, which are greatly affected by geological structure and slate properties of coal seam top and bottom. Coal seam 11 − 2 is a stress dominated briquette and gas outburst coal seam. Zhujixi mine adopts the regional outburst prevention model of combined pumping up and down the well, that is, coal seam 11 − 2 with low outburst risk is selected as the protective layer for mining first, and coal seam 13 − 1 is protected above, At the same time, the gas in the protected layer shall be extracted. 11 − 2 Coal adopts the gas control mode of "one side with three lanes (one side with five lanes in the first mining face) and surface drilling", so as to realize multi-purpose, joint treatment and continuous mining of one lane. Comprehensive outburst prevention measures are adopted for the tunneling working face through layer drilling pre drainage and the coal mining working face along layer drilling pre drainage area. During the mining period, the surface drilling and top drainage roadway are used to extract the pressure relief gas of 13 − 1 coal, and the combined upper and lower shaft extraction area technology is adopted. In the underground excavation and mining working face, the gas concentration of return air flow, measured residual gas content and residual gas pressure are measured, The prediction indexes have not exceeded the standard, and there has been no dynamic phenomenon. In the application of outburst prevention technology in the area of up-down combined extraction in zhujixi mine, the proportion of well extraction is 56.7%, and the proportion of underground extraction is 43.3%. The maximum height of the caving zone after mining of coal face 11 − 2 is 11.6m, and the height of the fracture zone is 34.4 ~ 52.2m. The working face of protective layer 13 − 1 is arranged at the upper part of the fracture zone or the lower part of the bending subsidence zone, which can effectively increase the permeability of coal seam 13 − 1, and has no significant impact on the normal mining of coal face 13 − 1.

In order to solve the problems of the uneven deformation of Gangue Filled Wall and the difficulty of large-scale promotion of roadway side support, and to achieve the purposes of direct disposal of coal mine waste, reducing costs, and protecting the environment, the failure mechanics model of the bagged gangue was established, and the mechanical action relationship between longitudinal external load and transverse external load of gangue woven bag was deduced. Through the uniaxial compression test of large-scale flexible backfill (coal gangue of different particle sizes), it was obtained that when the strain is 0.2, the bearing capacity of particles with particle sizes between 0 and 10 mm is greater than 5 MPa, and when the strain is 1.27, the bearing capacity of particles with particle thicknesses between 10 and 20 mm is greater than 0 mpa, which meets the requirements of resistance value and resistance growth rate of gob side entry. In the “load deflection” test of backfill (gangue) samples, it was found that the maximum failure load of wet shotcrete is greater than that of dry shotcrete, and the wet shotcrete can withstand greater deformation under the same load conditions. Through the analysis of the experimental results of “flexural strength thickness” and “maximum failure load thickness”, it was finally determined that the thickness of the spray layer with good flexibility and sufficient support force is controlled at about 80 mm.

To study the evolution law of axial force and shear stress of a full-length anchorage bolt in a rectangular roadway during roadway driving and working face mining, based on the stress analysis of the bolt, considering the elastic parameters and geometric size of the bolt, the effect of a bearing plate on surrounding rock, roadway cross-section shape, roadway deformation degree, and roadway elastic parameters, elastic mechanics and mathematical analysis methods were used to establish the mechanical model describing the interaction between the bolt and surrounding rock, and the mechanical formulas for calculating the axial force and shear stress of the bolt were derived. Taking the mining roadway of 1,131(1) working face in the Zhujidong coal mine of the Huainan mining area as the engineering background, the axial force and shear stress of the bolt in the middle of the roof and side of the rectangular roadway with the advance of driving face and working face were analyzed. The mechanical model and theoretical analysis results are verified by installing force measuring bolts with the same mechanical properties as the field and observing the real axial force distribution of the bolts.

Ultra-high-pressure hydraulic slotting technology is an effective method to realize pressure relief and permeability enhancement of a single coal seam. In this paper, through a hydraulic slotting borehole-based total gas extraction amount calculation model, it was concluded that ultra-high-pressure hydraulic slotting technology could increase the gas extraction surface area, improve the gas flow mechanism, and transform single-layer radial flow into interlayer, radial composite flow, thus greatly enhancing the gas extraction efficiency. Based on theoretical results, a field test was conducted in the Renlou coal mine, Anhui Province, China. According to the actual characteristics of the 7 2 coal seam in the Renlou coal mine, the key slotting parameters of this coal seam were determined. The gas extraction sources of each coal seam could be determined accurately through multi-gas source identification and tracer technology, and the effect of hydraulic slotting pressure relief and permeability enhancement was investigated. The test results indicated that the 100-day gas extraction concentration in boreholes using ultra-high-pressure hydraulic slotting technology was 2.68–7.59 times that in conventional boreholes. The average daily pure extraction volume of slotting boreholes was 3.94 times that of conventional boreholes. Based on the calculation of the gas extraction radius of boreholes in the slotted area, it was found that, under the condition of meeting the same control range of outburst elimination, drilling work could be reduced by more than two-thirds. These achievements could provide critical references for the application of ultra-high-pressure hydraulic slotting technology.

In elastic mechanics, the complex function method proposed by Muskhelishvili can be used to solve the stress distribution of rock surrounding a roadway with an irregular cross-section. However, the solution of the conformal mapping function from the exterior of the roadway to the interior of the unit circle is a prerequisite, but it is difficult to obtain. In this study, based on the Riemann mapping theorem and the boundary correspondence principle, the conformal mapping function was approximated using a Laurent series with finite terms. Assuming that the polar angle of the two corresponding points on the image of the conformal mapping function and the boundary of the roadway cross-section are equal, an iterative algorithm for calculating the conformal mapping function is proposed using the least squares method, and the code was programmed by-using Python. Using the proposed algorithm, two conformal mapping functions were solved for roadways with irregular cross-sections in practical engineering projects, while the parameters and the error were examined. Simultaneously, the performance was analyzed statistically for curved and broken line boundaries. The analysis results has shown that the errors were concentrated on the corners of the roadway. In addition, it was observed that an excessively large number of sample points would not improve the accuracy, but will only extend the algorithm convergence time. When the series includes more terms, the accuracy will be higher and the convergence speed will be slower. However, statistical analysis has shown that the algorithm was converged rapidly, with convergence time of less than 10 ms. Finally, the effectiveness of the algorithm was verified by solving the stress distributions of the rock surrounding two roadways. The algorithm might be used to solve the conformal mapping function from the exterior of a roadway with an irregular cross-section to the interior of the unit circle in coal mines.

In this study, the movement and failure law of working face overburden and the distribution characteristics of mining stress are analyzed using laboratory test and numerical calculation methods to address the problems of large deformation, failure instability, and difficult maintenance of the soft rock roof roadways of deep stope influenced by strong disturbance, the roof gas comprehensive treatment roadway of 17191 (1) working face of Pansan mine of China Huainan Mining Group was considered as the engineering background. The deformation and failure mechanisms of the surrounding rock in soft rock roof roadway are revealed, the surrounding rock control technology of presplitting and roof cutting pressure relief is proposed, and the key parameters of presplitting and roof cutting are systematically studied. According to the results, after mining, the overburden presents the distribution of "upper three zones," in which the heights of the caving and fracture zones are 7 m and 38 m, respectively, the influence range of lateral mining abutment pressure is 80 m, and the influence height exceeds 42 m. The roadway is located in the same layer as the fracture zone and within the influence range of mining. Under the influence of overburden migration of the working face, the stress field around the roadway, and the mining stress field, the surrounding rock of the roof roadway is significantly damaged, and the floor heave is violent. Based on the stress distribution characteristics of the stope and the deformation mechanism of the roadway, the pressure relief control technology of surrounding rock presplitting roof cutting is proposed. The optimal values of key parameters are determined as the roof cutting height of 49.9 m, the roof cutting angle of 10 degrees, and the blast hole spacing of 10 m. The results of this study have been successfully applied in 17191 (1) working face.

In coal mining roadway support design, the working resistance of the rock bolt is the key factor affecting its maximum support load. Effective improvement of the working resistance is of great significance to roadway support. Based on the rock bolt's tensile characteristics and the mining roadway surrounding rock deformation, a mechanical model for calculating the working resistance of the rock bolt was established and solved. Taking the mining roadway of the 17102 (3) working face at the Panji No. 3 Coal Mine of China as a research site, with a quadrilateral section roadway, the influence of pretension and anchorage length on the working resistance of high-strength and ordinary rock bolts in the middle and corner of the roadway is studied. The results show that when the bolt is in the elastic stage, increasing the pretension and anchorage length can effectively improve the working resistance. When the bolt is in the yield and strain-strengthening stages, increasing the pretension and anchorage length cannot effectively improve the working resistance. The influence of pretension and anchorage length on the ordinary and high-strength bolts is similar. The ordinary bolt's working resistance is approximately 25 kN less than that of the high-strength bolt. When pretension and anchorage length are considered separately, the best pretensions of the high-strength bolt in the middle of the roadway side and the roadway corner are 41.55 and 104.26 kN, respectively, and the best anchorage lengths are 1.54 and 2.12 m, respectively. The best anchorage length of the ordinary bolt is the same as that of the high-strength bolt, and the best pretension for the ordinary bolt in the middle of the roadway side and at the roadway corner is 33.51 and 85.12 kN, respectively. The research results can provide a theoretical basis for supporting the design of quadrilateral mining roadways.

Understanding the adsorption behaviors of CH4, N2, CO2, and their mixture in clay minerals is crucial to the approach of enhanced hydrocarbon recovery using gas injection with application in clay-rich gas-shale reservoirs. In this study, the adsorption measurements of CH4, N2, CO2, and their mixture on montmorillonite were conducted using a gravimetric technique. The underlying competitive adsorption mechanism of CH4, N2, and CO2 on montmorillonite was discussed using Henry's constant, adsorption selectivity, and thermodynamic variables. The adsorption selectivity of CO2 over N2 (αCO2/N2) was the highest, followed by the selectivity of CO2 over CH4 (αCO2/CH4) and that of CH4 over N2 (αCH4/N2). The αCO2/CH4 value was greater than one, confirming that CO2 can stimulate CH4 desorption through molecular swapping. Reducing the temperature increased the selectivity and the desorption of the pre-adsorbed gas was more easily triggered by the injection of the favorably adsorbing gas at lower temperatures. The uptake and affinity of CO2 were the highest, whereas N2 exhibited the smallest uptake and affinity. In addition, CO2 adsorption was more spontaneous than CH4 and N2 adsorption. Although N2 adsorption was less favorable than CH4 adsorption, injecting N2 could lower the spontaneity of CH4 adsorption by decreasing the CH4 partial pressure. The adsorbed CO2 molecules were the most ordered, and the freedom of adsorbed N2 molecules was the highest. The adsorption isotherm of the mixed gases was closer to that of the strong adsorption component. Thus, a strong adsorption gas plays a leading role in the adsorption of mixed gases.

The water burst of roof on working face has been one of the significant geotechnical engineering problems that needs to be urgently resolved. The coupling effects of seepage and damage on the amount and intensity of water inrush from the roof are critically important. In this paper, the seepage-damage coupling mathematical model of the aquifer in the working face is studied, and the seepage-damage coupling mechanics model at different stages of the aquifer is established. Under the coupling of permeability and damage, the water-soil characteristics of the aquifer in the 101163 working face of Mindong were numerically simulated by establishing the constitutive relation between vertical stress and permeability coefficient. The numerical results show that the stress concentration factor of the mining stress field gradually increases with the coal seam mining. The water-flowing fractured zone of the overburden is close to the communication of the quaternary aquifer. When the coal seam is excavated 250–300 m. Three free surfaces appear in the groundwater pressure field, and a large falling funnel is formed to establish a deep flow S-well well flow model. The research on the mining stress field and seepage field is carried out in combination with the Jakob formula. It is found that two sectors with reduced permeability of the fan surface are formed in front of the work. The variation law of the apocalyptic permeability infiltration under different mining distances, different coal seam thicknesses, different water pressures, and different roof management modes is studied systematically. The research indicates that the seepage flow under the condition of seepage infiltration of the lower aquifer should be between 50% and 100% of the traditional calculation method. The research results can help to deepen the understanding of the process of water inrush under the coupling of stress and seepage.