Abstract:Objectives To address the problems of severe roadway surrounding damage and poor stability during mining of complex-structure coal seams,the failure mechanism of coal pillars under roadway stress was investigated,taking the 10103 face of Baozigou Coal Mine as a case study.Methods Field measure-ment,mechanical analysis,numerical simulation,and field tests were employed to investigate the mechani-cal characteristics of coal pillars in complex-structure coal seams and to develop optimization strategies for roadway surrounding rock stability.Results A theoretical calculation formula for coal pillar size in complex-structure coal seams was derived,and the optimum roadway-protective coal pillar width was determined to be 5.66～7.04 m.It was revealed that the plastic zone depth of coal pillars under mining influence is 2.8 times that of conventional coal seams,confirming the regulatory effect of interlayers on the stress redistribu-tion process of surrounding rock.The evolution laws of vertical stress,vertical displacement,horizontal stress,and horizontal displacement were clarified,and a coal pillar width of 7 m was found to effectively enhance roadway surrounding rock stability,verifying the theoretical results.Field application of the opti-mum pillar size showed remarkable improvement in roadway conditions before and after implementation.Conclusions Increasing coal pillar width enhances bearing capacity,but excessive width leads to stress concentration on the goaf side,endangering overall stability.The results provide significant guidance for the rational design and application of coal pillars in complex-structure coal seam mining,offering new theo-retical and practical references for the field.

Abstract:Objectives To investigate the dynamic response and stability evolution of slopes under blasting impact,field blasting monitoring tests were conducted on the slope of an open-pit mine in eastern Inner Mongolia.Methods A numerical slope model was established using ANSYS/LS-DYNA to simulate and ana-lyze the dynamic response of slope particles.The effective stress,vibration velocity,and displacement char-acteristics of the slope rock mass were examined.The safety factor of the slope under blasting impact was derived using the limit equilibrium method and quasi-static method.Results Under blasting,the peak stresses at monitoring points 1～4 were 1.09,0.55,0.23,and 0.15 MPa,with effective stress durations of 8,5,4,and 3 ms.The peak vibration velocities in the X-direction were 9.98,3.88,1.99,and 0.95 cm/s,and the residual deformations of the rock mass units were 0.001 80,0.000 90,0.000 55,and 0.000 40 cm.Conclusions The results indicate that the effective stress induced by blasting propagates into the rock mass,with its peak value decreasing over time and distance.As the distance from the blast center in-creases,the peak vibration velocity of slope particles decreases,and residual deformations in the plastic zone gradually diminish.The calculated safety factors under static conditions(1.35)and blasting condi-tions(1.05)both meet the specification requirements,indicating that the open-pit slope remains stable.These findings provide a reference for blasting construction in the open-pit mines.

Abstract:Objectives Accurate evaluation of the risks in developing and utilizing coal mine goafs is the fun-damental basis for determining the feasibility of constructing underground reservoirs.Taking three goafs in the Hebi Zhongtai mining area as examples,this study evaluates the risks involved in their development and utilization.Methods The P-S-R(Pressure-State-Response)model was introduced to establish a risk evaluation system for underground coal mine reservoirs,consisting of four criteria layers—geological condi-tions,safety conditions,water storage conditions,and economic benefits—with a total of 17 indicators.The indicators were quantified and classified through direct measurement,simulation,and indirect calcula-tion.The improved analytic hierarchy process(IAHP)and entropy weight method(EWM)were then com-bined to optimize indicator weights.Finally,set pair analysis(SPA)was applied to grade and evaluate the risks.Results The results indicate that among the four criteria layers,geological conditions carry the high-est weight.Among the 17 indicators,the key ones affecting risk are the number of faults(A1),coal seam inclination(B1),mine water inflow(C3),profit(D3).The utilization risk level of goaf 33072 and goaf 2315 was classified as moderate,while goaf 3201 was classified as high.Conclusions The IAHP-EWM-SPA model offers a new approach for assessing the risks associated with the development and utilization of underground coal mine reservoirs.

Abstract:Objectives To enhance the information and digitalization capabilities of the dual-prevention mechanism for tailings ponds and to improve the level of risk prevention and hazard management,this study investigates the development and application of a dual-prevention information system for tailings ponds.Methods The system was designed and implemented through the creation of a mechanism frame-work,establishment of a system architecture,development of a software platform,and practical deploy-ment.a dual closed-loop prevention and control framework was constructed.An information system architec-ture combining a B/S structure with mobile API applications was designed,and a dual-prevention informa-tion system for tailings ponds was developed and deployed in line with the actual conditions of a specific en-terprise.Results The system realizes a dual closed-loop structure:one loop for risk classification and con-trol,and another for hazard identification and management,supported by continuous improvement of opera-tional mechanisms.The architecture consists of six layers-infrastructure,data,communication,functional,user,and presentation.The system integrates modules for risk classification management,hazard identifica-tion and management,auxiliary functions,and system administration,and has been successfully imple-mented in practice.Conclusions Field applications demonstrate that the system enables real-time identifica-tion,dynamic control,and precise management of safety risks and hazards in tailings ponds.It also pro-vides statistical analysis and visual presentation of safety management data,thereby significantly enhancing the level of safety management and playing a vital role in accident prevention and sustainable mine safety.

Abstract:Objectives This study aims to reveal the macro-micro damage mechanisms of tailings materials under freeze-thaw cycling.Methods Through triaxial consolidated undrained shear tests,scanning electron microscopy(SEM),and micro-CT scanning,the effects of freeze-thaw cycle frequency on the mechanical properties and microstructural evolution of tailings were investigated.A correlation mechanism between mac-roscopic mechanical damage and microstructural changes was established.Results Freeze-thaw cycles sig-nificantly degraded the macroscopic mechanical properties of tailings.The peak shear strength decreased by 13.35%after one freeze-thaw cycle.During the 5～10 cycle stage,the peak strength reduction rate was 8.8%,while in the 10～15 cycle stage,the reduction rate decreased to 3.9%.After 15 cycles,cohesion and internal friction angle decreased by 50.9%and 59.3%,respectively.Freeze-thaw cycling caused particle edge abrasion and rounding,with the shape factor decreasing from 1.38 to 1.34.The pore fractal dimension increased from 1.55 to 1.64,porosity rose from 8.9%to 16.91%,and the proportion of connected pores in-creased markedly from 4.68%to 15.51%.Furthermore,porosity exhibited a nonlinear negative correlation with shear strength,while the internal friction angle showed an exponential increase with particle shape fac-tor.Conclusions These findings provide a scientific basis for stability analysis and disaster prevention of tailings dams in permafrost regions.

Abstract:Objectives To address the issues of positioning blind zones,low localization accuracy for person-nel at the working face,and non-line-of-sight(NLOS)errors in underground mines,a cooperative localiza-tion algorithm based on ultra-wideband(UWB)technology was proposed.The algorithm was designed to sig-nificantly enhance positioning accuracy,optimize base station deployment,and provide efficient and reli-able support for mine safety management.Methods Firstly,mobile nodes carried by mine personnel were utilized as relays to establish a cooperative localization mechanism,by which the distribution density and communication radius requirements of UWB base stations at the underground working face were effectively reduced.This design was adapted to complex tunnel environments,whereby positioning blind zones were mitigated and signal coverage was significantly improved,overcoming challenges posed by confined spaces and limited base station placement.Secondly,to address the impact of NLOS errors on positioning accu-racy,a two-stage error mitigation strategy was employed:Initially,a Gaussian model was used to model and correct signal propagation distortions caused by obstacles such as walls or equipment;Subsequently,a grid screening strategy was applied to filter out residual outliers by dividing the data into grids,whereby the reliability of positioning data was further enhanced.Finally,an improved Sparrow Search Algorithm,in-corporating adaptive step sizes and dynamic weighting mechanisms,was applied to optimize the screened results,by which convergence speed was significantly improved and high-precision positioning was achieved.Results Simulation results demonstrated that the proposed algorithm achieved an average localiza-tion accuracy of 0.19 meters,by which similar high-performing algorithms were surpassed in both precision and stability.Moreover,superior performance was maintained even with fewer base stations,while computa-tional efficiency was satisfied for real-time underground positioning demands.Conclusions This UWB-based cooperative localization algorithm effectively resolved key technical challenges in mine positioning,by which a highly accurate and robust solution for personnel safety monitoring was offered with significant theo-retical and practical values.

Abstract:Objectives An investigation is conducted into the dynamic evolution of pore water pressure and earth pressure during dam breaching in large tailings reservoirs under extreme conditions,as well as the im-pact characteristics and kinematics of released tailings flow,to establish a scientific basis for risk assess-ment and safety control of high-potential-energy tailings reservoirs.Methods Using a large valley-type tail-ings reservoir in Guangdong as the prototype,a high-precision indoor physical model with a geometric simi-larity ratio of 1∶100 was constructed,and a multi-source sensing and monitoring system was innovatively in-tegrated.The experiment simulated a dam-breach scenario induced by extreme rainfall with a 500-year re-turn period leading to overtopping,and systematically recorded the entire process from impoundment and overtopping through breach initiation and enlargement to eventual failure.Results The results indicate that:(1)Pore water pressure exhibits a three-phase evolution pattern:stepwise increase during impoundment,abrupt drop during breaching,and gradual decrease during the dissipation-with the dissipation rate near the dam being 40%faster than at the the reservoir tail.(2)Earth pressure responds most strongly in the fore-dam region,reaching a peak of 13.6 kPa before decaying linearly,while remaining stable in the middle and rear sections,indicating spatial non-uniformity in the breach influence zone.(3)Breach dis-charge is nonlinearly and positively correlated with the instantaneous sediment detachment.The maximum breach volume reached 2.4 million m³,equivalent to 48.7%of the prototype's total storage,with a peak breach velocity of 2.6 m/s.(4)The velocity distribution of the released tailings flow is controlled by terrain roughness:mid-channel velocity shows a"hump-shaped"profile,which evolves into a"double-hump"pat-tern with increasing discharge;transverse to the channel,the velocity is"fast in the center,slow on the sides"and peak vorticity is positively correlated with terrain roughness.Conclusions The proposed"double-hump velocity model"reveals the flow regime and vorticity evolution of tailings slurry release under com-plex topography,offering a new theoretical tool and technical support for predicting downstream hazard ex-tent,assessing impact forces,and designing protective works for tailings reservoirs.

Abstract:Objectives Due to fluctuations in reservoir water level,the phreatic line exhibits a certain corre-lation with water level observations.However,the underlying mechanism remains unclear.Methods Proto-type observation data of the phreatic line and reservoir water level from a typical upstream tailings dam were collected.Statistical regression models were established to analyze their relationships with absolute wa-ter level,hydraulic head,and time effect,with goodness-of-fit used to assess model performance.Based on these models,grey correlation analysis was applied to compare the importance of different factors,calcu-late correlation coefficients,and rank their significance,thereby identifying the key factors influencing the phreatic line.Results The spatial variation trends of the constructed factors showed strong dependence on the dependent variable.Phreatic line observations were significantly correlated with the measured hydraulic head(H),its square(H²),cube(H³),as well as the average head and head rise rate over the previous 5～30 days.The regression results demonstrated high accuracy.Conclusions Regression performance varied across monitoring positions,but consistently showed correlations with hydraulic head and its rate of change,along with some dependence on time effect.This correlation with time weakened as the observation period lengthened.

Abstract:The function，structure，development running environment and establishment method of“The system of monitoring data processing and predicting ana alarm of deep base pit engineering”are introduced．The system adopts database management for the deep pit monitoring data；establishes deformation prediction model on the grounds of grey model theory；analyses and judge deep pit engineering dangerous condition and raise alarm by some qualitative indexs and quantitative indexes．It is an expert system which assembles monitoring data processing，graph plotting and management，deformation prediction and dangerous condition analysis and discimination functional module．

Abstract:After reviewing the origin and development process of in-situ stress measurement, major present-day methods to measure in-situ stress are classified and their fundamental principles, advantages and disadvantages, and applications are introduced. Meanwhile, new development trends about in-situ stress measurement as well as the problems and challenges that emerge in in-situ stress measurement in China now are analyzed in detail. The study has a guiding significance for using different methods of in-situ stress measurement and thereby improving its measuring accuracy.