Artificial ground freezing of underground mines in cold regions using thermosyphons with air insulation

Current practice of underground artificial ground freezing(AGF)typically involves huge refrigeration systems of large economic and environmental costs.In this study,a novel AGF technique is proposed deploying available cold wind in cold regions.This is achieved by a static heat transfer device called thermosyphon equipped with an air insulation layer.A refrigeration unit can be optionally integrated to meet additional cooling requirements.The introduction of air insulation isolates the thermosyphon from ground zones where freezing is not needed,resulting in:(1)steering the cooling resources(cold wind or refrigeration)towards zones of interest;and(2)minimizing refrigeration load.This design is demonstrated using well-validated mathematical models from our previous work based on two-phase enthalpy method of the ground coupled with a thermal resistance network for the thermosyphon.Two Canadian mines are considered:the Cigar Lake Mine and the Giant Mine.The results show that our proposed design can speed the freezing time by 30%at the Giant Mine and by two months at the Cigar Lake Mine.Further,a cooling load of 2.4 GWh can be saved at the Cigar Lake Mine.Overall,this study provides mining practitioners with sustainable solutions of underground AGF.

Using deep neural networks coupled with principal component analysis for ore production forecasting at open-pit mines

Ore production is usually affected by multiple influencing inputs at open-pit mines.Nevertheless,the complex nonlinear relationships between these inputs and ore production remain unclear.This becomes even more challenging when training data(e.g.truck haulage information and weather conditions)are massive.In machine learning(ML)algorithms,deep neural network(DNN)is a superior method for processing nonlinear and massive data by adjusting the amount of neurons and hidden layers.This study adopted DNN to forecast ore production using truck haulage information and weather conditions at open-pit mines as training data.Before the prediction models were built,principal component analysis(PCA)was employed to reduce the data dimensionality and eliminate the multicollinearity among highly correlated input variables.To verify the superiority of DNN,three ANNs containing only one hidden layer and six traditional ML models were established as benchmark models.The DNN model with multiple hidden layers performed better than the ANN models with a single hidden layer.The DNN model outperformed the extensively applied benchmark models in predicting ore production.This can provide engineers and researchers with an accurate method to forecast ore production,which helps make sound budgetary decisions and mine planning at open-pit mines.

Coordinated Mining Procedures of Open Pit Mines Based on River Management

This paper primarily concerns the effective coordination of the procedures and methods employed in open pit mining operations under the background of river management.The central objective of this study is to identify a viable approach for ensuring rational and efficient development of open pit mineral resources while simultaneously protecting and restoring the ecological environment of the river.This approach should facilitate the realization of a harmonious symbiosis between mining and river management.The intricate mutual influence relationship between river management and open pit mining is first analyzed in depth,which provides a solid foundation for the subsequent coordination strategy development.In light of the aforementioned considerations,a set of coordination procedures for open pit mining based on river management conditions is proposed.These procedures emphasize the integration of river protection into the overall layout of mining at the planning stage.The implementation of scientific mining schemes,accompanied by rigorous control of the scope and depth of mining operations,has proven to be an effective means of reducing the impact of mining activities on river environments.This approach has also facilitated the achievement of a balance and coordination between mining and river management.

Fuzzy inference system using genetic algorithm and pattern search for predicting roof fall rate in underground coal mines

One of the most dangerous safety hazard in underground coal mines is roof falls during retreat mining.Roof falls may cause life-threatening and non-fatal injuries to miners and impede mining and transportation operations.As a result,a reliable roof fall prediction model is essential to tackle such challenges.Different parameters that substantially impact roof falls are ill-defined and intangible,making this an uncertain and challenging research issue.The National Institute for Occupational Safety and Health assembled a national database of roof performance from 37 coal mines to explore the factors contributing to roof falls.Data acquired for 37 mines is limited due to several restrictions,which increased the likelihood of incompleteness.Fuzzy logic is a technique for coping with ambiguity,incompleteness,and uncertainty.Therefore,In this paper,the fuzzy inference method is presented,which employs a genetic algorithm to create fuzzy rules based on 109 records of roof fall data and pattern search to refine the membership functions of parameters.The performance of the deployed model is evaluated using statistical measures such as the Root-Mean-Square Error,Mean-Absolute-Error,and coefficient of determination(R_(2)).Based on these criteria,the suggested model outperforms the existing models to precisely predict roof fall rates using fewer fuzzy rules.

Feasibility of Synchronously Straightening Working Line of Adjacent Open-cast Mines

Taking Heidaigou Open-cast Mine and Haerwusu Open-cast Mine in Zhungeer mining area as the research objects,this paper deeply analyzes the current mining status of the two mines.Based on the existing working line length,mining technology,transportation system,equipment configuration,transportation access and many other factors,it systematically discusses the feasibility of straightening the working line of adjacent open-cast mines.Through in-depth theoretical analysis,it establishes the mathematical model of impact indicators and cost calculation,and it is concluded that the work line straightening can be technically achieved.However,from the perspective of economic benefits,straightening the working line does not show obvious advantages.

Solution to the Horizontal Crossing Problem of Transportation System at Key Points in Open-Pit Mines

In order to reduce the horizontal crossing transportation problems between coal trucks and stripping trucks,large and small vehicles,and transport trucks and belt conveyors at key points of open pit mine in production,the separate transportation mode of underpass bridge and overpass steel trestle is proposed to optimize the open pit development transportation system,so as to solve the practical problems that the horizontal cross of transport vehicles causes vehicle blockage,affects production schedule and production safety.The results show that the horizontal crossing road can be changed into a separate type of overpass steel trestle,which can realize the classified transportation of large and small vehicles,reduce the traffic density,make vehicles with different functions go their own way,eliminate the hidden danger of traffic accidents,and improve the production efficiency.

Evaluation of Convolutional-Long Short-Term Memory Model in Predicting Surface Displacement of Underground Mines

Surface stability is essential in underground mines health management systems. Unexpected Surface displacement in underground mines could lead to loss of lives, injuries, and economic losses. To reduce or neutralise the adverse effects of surface displacement, it is vital to monitor and accurately predict them and unravel their mechanisms. In recent years, Convolutional Neural Network (CNN) and Long Short-Term Memory (LSTM) have proven effective in predicting complex problems. However, CNN neglects the dynamic dependency of the input in the temporal dimension, which affects surface displacement features. The Convolutional-LSTM model can dynamically learn the temporal dependency among input features via the feedback connections in the LSTM to improve accurate captures of surface displacement features. This study focused on evaluating the C-LSTM model in predicting surface displacement of underground mines and assessed the predictive capabilities and generalisation strength of using hybridised ANN models. Geodetic and geotechnical data gathered from a Gold Mine in Ghana was used. The three models were tested on experimental data collected at Monitoring Scan Point 3. It was observed from the prediction output that all the methods could provide applicable and practical results. However, using indicators like root mean square error (RMSE) and correlation coefficient (R) in assessing the output of the prediction, the C-LSTM had the best prediction output. This study contributes to the advancement of accurate and efficient prediction of surface displacement of underground mines, ultimately enhancing and assisting safety operations.

Numerical and theoretical study of large-scale failure of strata overlying sublevel caving mines with steeply dipping discontinuities

The deformation and fracture evolution mechanisms of the strata overlying mines mined using sublevel caving were studied via numerical simulations.Moreover,an expression for the normal force acting on the side face of a steeply dipping superimposed cantilever beam in the surrounding rock was deduced based on limit equilibrium theory.The results show the following:(1)surface displacement above metal mines with steeply dipping discontinuities shows significant step characteristics,and(2)the behavior of the strata as they fail exhibits superimposition characteristics.Generally,failure first occurs in certain superimposed strata slightly far from the goaf.Subsequently,with the constant downward excavation of the orebody,the superimposed strata become damaged both upwards away from and downwards toward the goaf.This process continues until the deep part of the steeply dipping superimposed strata forms a large-scale deep fracture plane that connects with the goaf.The deep fracture plane generally makes an angle of 12°-20°with the normal to the steeply dipping discontinuities.The effect of the constant outward transfer of strata movement due to the constant outward failure of the superimposed strata in the metal mines with steeply dipping discontinuities causes the scope of the strata movement in these mines to be larger than expected.The strata in the metal mines with steeply dipping discontinuities mainly show flexural toppling failure.However,the steeply dipping structural strata near the goaf mainly exhibit shear slipping failure,in which case the mechanical model used to describe them can be simplified by treating them as steeply dipping superimposed cantilever beams.By taking the steeply dipping superimposed cantilever beam that first experiences failure as the key stratum,the failure scope of the strata(and criteria for the stability of metal mines with steeply dipping discontinuities mined using sublevel caving)can be obtained via iterative computations from the key stratum,moving downward toward and upwards away from the goaf.

基于MineSight软件的米拉多铜矿露天采矿设计及其二次开发

露天采场作业面位置、矿石品位和公司管理层制订的生产任务等会直接影响生产计划的编制。本文介绍了米拉多铜矿应用矿业软件MineSight开展三维采矿设计的流程,以及应用Python编程语言,基于露天采场台阶参数关系,二次开发了采矿设计辅助工具。该工具可通过在界面直接输入不同的台阶高度和台阶坡面角,即可计算得到工作帮坡角和台阶宽度,进而将其应用于采矿设计。该软件提高了采矿设计的效率,为动态编制和优化短期生产计划提供了可靠的采场设计方案。

SICOMINES铜钴矿含尾砂高大边坡稳定性分析及治理思路

刚果(金)SICOMINES铜钴矿M坑北部上部局部边坡处于不稳定状态,可能存在滑坡风险。本文采用二维极限平衡分析方法,对北部含尾砂高大边坡稳定性进行了边坡稳定性计算和分析,提出了整体边坡角不应大于31°的优化建议,并为后续边坡治理提供了参考。

Prospects for the transformation and development of carbon storage in abandoned mines of coal enterprises from the perspective ofcarbon neutrality

Under the carbon neutrality goal,coal enterprises must seek breakthroughs from abandoned mines,develop new resources in the new era,turn problems into countermeasures,and participate in the carbon emissions market,for contributing to the accomplishment of the national strategic goal of carbon neutrality.To this end,we investigated the relevant national policies and regulations to clarify the boundaries disclosed by the carbon information of enterprises,understood the development direction of carbon storage in abandoned mines,and clarified the transformation and development of carbon storage in aban-doned mines.We made a few suggestions:(1)China should learn from its past experience and other countries to develop the energy industry with Chinese characteristics and reform the economic system.(2)Coal enterprises must actively respond to the national carbon information disclosure policy,clarify their own responsibilities and carbon emission boundaries.(3)It is necessary to proactively obtain advanced knowledge and plan carbon storage pathways for abandoned mines.(4)Devel-opment problems of coal enterprises should be deduced using cases.The'dual carbon'goals should be achieved steadily step-by-step.(5)Three measures,i.e.improving the existing resource structure,coordinating the information of abandoned mines,and promoting the cultivation of scientific and technological talents.

Progress and prospects of mining with backfill in metal mines in China

Mining is the foundation of modern industrial development.In the context of the“carbon peaking and carbon neutrality”era,countries have put forward the development strategy of“adhering to the harmonious coexistence of humans and nature.”The ongoing progress and improvement of filling mining technology have provided significant advantages,such as“green mining,safe,efficient,and low-carbon emission,”which is crucial to the comprehensive utilization of mining solid waste,environmental protection,and safety of re-mining.This review paper describes the development history of metal mine filling mining in China and the characteristics of each stage.The excitation mechanism and current research status of producing cementitious materials from blast furnace slag and other industrial wastes are then presented,and the concept of developing cementitious materials for backfill based on the whole solid waste is proposed.The advances in the mechanical characteristics of cemented backfill are elaborated on four typical levels:static mechanics,dynamic mechanics,mechanical influencing factors,and multi-scale mechanics.The working/rheological characteristics of the filling slurry are presented,given the importance of the filling materials conveying process.Finally,the future perspectives of mining with backfill are discussed based on the features of modern filling concepts to provide the necessary theoretical research value for filling mining.

Instability mechanism of mining roadway passing through fault at different angles in kilometre-deep mine and control measures of roof cutting and NPR cables

The angle α between the fault strike and the axial direction of the roadway produces different damage characteristics. In this paper, the research methodology includes theoretical analyses, numerical simulations and field experiments in the context of the Daqiang coal mine located in Shenyang, China. The stability control countermeasure of "pre-splitting cutting roof + NPR anchor cable"(PSCR-NPR) is simultaneously proposed. According to the different deformation characteristics of the roadway, the faults are innovatively classified into three types, with α of type I being 0°-30°, α of type II being 30°-60°, and α of type III being 60°-90°. The full-cycle stress evolution paths during mining roadway traverses across different types of faults are investigated by numerical simulation. Different pinch angles α lead to high stress concentration areas at different locations in the surrounding rock. The non-uniform stress field formed in the shallow surrounding rock is an important reason for the instability of the roadway. The pre-cracked cut top shifted the high stress region to the deep rock mass and formed a low stress region in the shallow rock mass. The high prestressing NPR anchor cable transforms the non-uniform stress field of the shallow surrounding rock into a uniform stress field. PSCR-NPR is applied in the fault-through roadway of Daqiang mine. The low stress area of the surrounding rock was enlarged by 3-7 times, and the cumulative convergence was reduced by 45%-50%. It provides a reference for the stability control of the deep fault-through mining roadway.

Technical problems and non destructive testing of rock bolt support systems in mines

The problem of proper assessment of the technical functionality of rock bolt support systems is still valid.Many research centers have undertaken eforts to diagnose and monitor the technical state of such a support system used in mines and tunneling.With that aim the method of quality assessment of grouted rock bolts was invented and a relevant apparatus was constructed.The method concerns non-destructive identifcation of discontinuity of a resin layer(grout)surrounding rock bolts.The method is based on an impact excitation of a rock bolt and uses modal analysis procedures.Assuming that the installed rock bolt acts as an oscillator,diferent lengths and positions of grouting discontinuity alter its modal parameters.The extraction of these modal parameters,of which a resonant frequency is seen as the most valued,enable the relevant identifcation of grout discontinuity.After constructing a prototype version and validating the results for known cases of resin discontinuity in an experimental coal mine,the apparatus fulflling ATEX requirements was developed.Subsequently that version was also verifed both in laboratory conditions and in an experimental coal mine.As necessary for proper identifcation of discontinuity length,the reference data base was developed and elaborated consisting of a very large number of fnite element models(FE models),namely discontinuity cases.The models encountered diferent rock bolt lengths and diameters,diferent rock strata parameters and diferent positions and lengths of resin layers.Then the method was used in a working coal mine to monitor a technical state of rock bolt support system mounted to reinforce long underground openings.The data base was utilized as reference for investigated rock bolts.

Management of Spinal Injuries Secondary to Rockfall in Traditional Mines

Introduction: Spinal injuries represent the whole of the mechanisms responsible for vertebral, disco-ligamentary and spinal cord injuries. Spinal cord injury is life-threatening and is responsible for functional consequences that make the subsequent socio-economic integration of victims difficult. In developing countries, spinal injuries in traditional gold mining are becoming more and more frequent. Purpose: The purpose of this study was to describe the anatomopathological aspects and the results of surgical treatment of spinal injuries secondary to traditional mine collapses at the University Hospital of Kati. Patients and Methods: This was a prospective, descriptive study over 18 months, from November 2017 to May 2019. Included in this study were patients operated on for spinal trauma secondary to rockfall in traditional mines. The neurological status was assessed in each patient since admission to the department using the Fr&#228nkel score. Decompression by laminectomy combined with titanium device placement was preferred in lumbar, thoracic and thoraco-lumbar surgery. We performed an anterior cervical spine approach with SENEGAS plate placement in cervical injuries. Motor physiotherapy was associated whenever recovery was not complete. At a minimum follow-up of 6 months, all our patients were re-evaluated by the Fr&#228nkel score. Results: The mean age was 31 years with extremes of 10 and 49 years. The majority of patients were men, 95%. Twenty patients underwent surgery. According to the spinal segments, the cervical spine was affected in 05 cases, the thoracic spine in 08 cases and the lumbar spine in 17 cases. The neurological examination revealed tetraplegia (n = 5), paraplegia (n = 12) and paraparesis (n = 3). According to the types of lesions, we collected 12 cases of fractures, 4 cases of fracture-luxations and 04 cases of pure luxations. According to the site, the fracture was uni-articular (n = 3), corporal (n = 15) and transverse apophyseal (n = 1). According to the type of line, the fracture was simple (n = 6), with compression (n = 11) and comminuted (n = 2). The dislocation was anterior in all 08 cases. The spinal cord injuries were concussion (n = 3), contusion (n = 6) and transection (n = 11). Sphincter disorders such as leakage or retention of urine were present in all our patients. At a minimum follow-up of 6 months, all our patients classified as Fr&#228nkel D and C had a complete motor recovery. Of the 5 patients classified as Fr&#228nkel B, 2 had complete motor recovery and one had partial recovery. Of 12 patients classified as Fr&#228nkel A, one patient had partial recovery. Conclusion: The severity of the neurological lesions in spinal injuries due to rockfalls in traditional gold mining is certain. These traumas are of high velocity and provide extensive spinal cord injuries. The dorsolumbar hinge is the most affected segment. Fractures of the first lumbar vertebra and the twelfth thoracic vertebra are the most frequent. Settling fractures are by far the most frequent fracture types. T12-L1 dislocation is the most frequent. Early osteosynthesis by spinal stabilization after reduction improves the Fr&#228nkel score. This study shows the need for public awareness of the dangers of traditional gold panning.

Ecological Restoration Technology and Carbon Reduction Paths of Abandoned Mines in Zoige Alpine Grassland Area

At first,the ecological restoration technology of abandoned mines is summarized,and the paths and models of mine ecological restoration in Zoige grassland area under the background of carbon neutrality are analyzed.Moreover,the problems and deficiencies in the current research on mine ecological restoration in Zoige grassland area are initially identified,and the future research trend is prospected to provide a reference for the path of carbon reduction by mine ecological restoration in Zoige grassland area and other alpine grassland areas in the future.

Plant growth and metabolism of exotic and native Crotalaria species for mine land rehabilitation in the Amazon

Despite its enormous benefits,mining is respon-sible for intense changes to vegetation and soil properties.Thus,after extraction,it is necessary to rehabilitate the mined areas,creating better conditions for the establishment of plant species which is challenging.This study evaluated mineral and organic fertilization on the growth,and carbon and nitrogen(N)metabolism of two Crotalaria species[Cro-talaria spectabilis(exotic species)and Crotalaria maypu-rensis(native species from Carajás Mineral Province(CMP)]established on a waste pile from an iron mine in CMP.A control(without fertilizer application)and six fertilization mixtures were tested(i=NPK;ii=NPK+micronutrients;iii=NPK+micronutrients+organic compost;iv=PK;v=PK+micronutrients;vi=PK+micronutrients+organic compost).Fertilization contributed to increased growth of both species,and treatments with NPK and micronutrients had the best results(up to 257%cf.controls),while organic fertilization did not show differences.Exotic Crotalaria had a greater number of nodules,higher nodule dry mass,chlorophyll a and b contents and showed free ammonium as the predominant N form,reflecting greater increments in biomass compared to native species.Although having lower growth,the use of this native species in the rehabilitation of mining areas should be considered,mainly because it has good development and meets current government legislation as an opportunity to restore local biodiversity.

基于Mine2Vec煤矿风险推送机制的研究与实现

为了及时发现和预防可能出现的煤矿安全隐患和安全事故,基于Mine2Vec的煤矿风险推送模型与Item2Vec的用户访问信息推送模型加权融合,实现了煤矿风险推送机制,并应用于“互联网+”煤矿安全管控平台中。经Hololens2眼动仪验证,平台内容经模型推送后,点击次数、注视时长明显增多。研究成果可为用户推送相似煤矿企业的风险信息及其他煤矿风险资讯,使用户提前预防和规避煤矿风险。

Advancing respirable coal mine dust source apportionment:a preliminary laboratory exploration of optical microscopy as a novel monitoring tool

Exposure to respirable coal mine dust(RCMD)can cause chronic and debilitating lung diseases.Real-time monitoring capabilities are sought which can enable a better understanding of dust components and sources.In many underground mines,RCMD includes three primary components which can be loosely associated with three major dust sources:coal dust from the coal seam itself,silicates from the surrounding rock strata,and carbonates from the inert‘rock dust’products that are applied to mitigate explosion hazards.A monitor which can reliably partition RCMD between these three components could thus allow source apportionment.And tracking silicates,specifically,could be valuable since the most serious health risks are typically associated with this component-particularly if abundant in crystalline silica.Envisioning a monitoring concept based on field microscopy,and following up on prior research using polarized light,the aim of the current study was to build and test a model to classify respirable-sized particles as either coal,silicates,or carbonates.For model development,composite dust samples were generated in the laboratory by successively depositing dust from high-purity materials onto a sticky transparent substrate,and imaging after each deposition event such that the identity of each particle was known a priori.Model testing followed a similar approach,except that real geologic materials were used as the source for each dust component.Results showed that the model had an overall accuracy of 86.5%,indicating that a field-microscopy based moni-tor could support RCMD source apportionment and silicates tracking in some coal mines.

Study on the Safety and Prevention Technology of Coal Mining under the River in Xingyuan Coal Mine

Coal mining-induced surface subsidence poses significant ecological and infrastructural challenges, necessitating a comprehensive study to ensure safe mining practices, particularly in underwater conditions. This project aims to address the extensive impact of coal mining on the environment, infrastructure, and overall safety, focusing on the Shigong River area above the working face. The study employs qualitative and quantitative analyses, along with on-site engineering measurements, to gather data on crucial parameters such as coal seam characteristics, roof rock lithology, thickness, water resistance, and structural damage degree. The research encompasses a multidisciplinary approach, involving mining, geology, hydrogeology, geophysical exploration, rock mechanics, mine surveying, and computational mathematics. The importance of effective safety measures and prevention techniques is emphasized, laying the foundation for research focused on the Xingyun coal mine. The brief concludes by highlighting the potential economic and social benefits of this project and its contribution to valuable experience for future subsea coal mining.