Heterogeneous information phase space reconstruction and stability prediction of filling body–surrounding rock combination

Traditional research believes that the filling body can effectively control stress concentration while ignoring the problems of unknown stability and the complex and changeable stress distribution of the filling body–surrounding rock combination under high-stress conditions.Current monitoring data processing methods cannot fully consider the complexity of monitoring objects,the diversity of monitoring methods,and the dynamics of monitoring data.To solve this problem,this paper proposes a phase space reconstruction and stability prediction method to process heterogeneous information of backfill–surrounding rock combinations.The three-dimensional monitoring system of a large-area filling body–surrounding rock combination in Longshou Mine was constructed by using drilling stress,multipoint displacement meter,and inclinometer.Varied information,such as the stress and displacement of the filling body–surrounding rock combination,was continuously obtained.Combined with the average mutual information method and the false nearest neighbor point method,the phase space of the heterogeneous information of the filling body–surrounding rock combination was then constructed.In this paper,the distance between the phase point and its nearest point was used as the index evaluation distance to evaluate the stability of the filling body–surrounding rock combination.The evaluated distances(ED)revealed a high sensitivity to the stability of the filling body–surrounding rock combination.The new method was then applied to calculate the time series of historically ED for 12 measuring points located at Longshou Mine.The moments of mutation in these time series were at least 3 months ahead of the roadway return dates.In the ED prediction experiments,the autoregressive integrated moving average model showed a higher prediction accuracy than the deep learning models(long short-term memory and Transformer).Furthermore,the root-mean-square error distribution of the prediction results peaked at 0.26,thus outperforming the no-prediction method in 70%of the cases.

Raw Gangue Filling Mining under Construction —A Case Study in China

In order to recover the strip pillar coal resources, reduce the amount of gangue mountain and realize remediation of the goaf environment in the old mining area, the raw gangue filling mining technology was proposed. According to the previous practical experience, the feasibility of the implementation of raw gangue filling mining technology in the coal-pressed area was analyzed. Through the filling gangue compaction test, the deformation under different loading stages was obtained. Further, a reasonable prediction of the deformation beyond the experimental limited loading load was made based on the experimental results. Through the deformation source analysis of the whole process of gangue filling, the key factors for controlling deformation before, during, and after filling were determined. Additionally, the proportion of deformation during different stages was quantified. Considering the protection of surface buildings, mining fullness of the working face and mining technology, the production parameters of 1209 and 1210 filling working faces were preliminarily determined. Through numerical simulation, the rationality of mining scheme was verified. Based on the practice of 1209 working face and the key factors to control the deformation of gangue filling, the mining system and process in 1210 working face were optimized. According to the measured surface rock movement, raw gangue filling mining technology can meet the requirements of surface building protection level. Especially, this paper provides a method to quantitatively calculate the equivalent mining height (EMH) of raw gangue filling and its mining deformation, which has reference significance for old mining areas.

Roof filling control technology and application to mine roadway damage in small pit goaf

To recover coal resources that have been damaged by traditional mining methods and ensure stability of the lower roadway in a small pit goaf,the goaf area must be filled and reinforced.In this research,the 1202 working face of the Hanzui mine is considered as an example for classifying the roof of the mining tunnel under the small kiln destruction zone,the effect of the goaf on the roadway is determined based on the radio tunnel penetration method,a mechanical model to determine the roof filling control mechanism was established,and the duct foaming system and roof filling process were designed.The results show that the scope and degree of influence of the goaf on the mining lane are large,but safe tunneling can be ensured through the use of a steel shed and advanced grouting techniques.When the roof conditions are not similar,materials with different filling heights and filling strengths can be used to control the roof filling of the roadway.By combining field experience and laboratory tests,it was determined that a high-foaming material with a water-cement ratio of 1:0.6,a suitable high-foaming additive,and a water volume ratio of 1:30 is cost-efficient for filling and meets the filling strength requirements.Finally,the reliability of the proposed technology was verified by field experiments,which provide a reference for filling operations in similar mines.

Optimization of clay material mixture ratio and filling process in gypsum mine goaf

Because there is neither waste rock nor mill tailings in the gypsum mine, and the buildings on the goaf of gypsum mine are needed to be protected, the research proposed the scheme of the clay filling technology. Gypsum, cement, lime and water glass were used as adhesive, and the strength of different material ratios were investigated in this study. The influence factors of clay strength were obtained in the order of cement, gypsum, water glass and lime. The results show that the cement content is the determinant influence factor, and gypsum has positive effects, while the water glass can enhance both clay strength and the fluidity of the filing slurry. Furthermore, combining chaotic optimization method with neural network, the optimal ratio of composite cementing agent was obtained. The results show that the optimal ratio of water glass, cement, lime and clay (in quality) is 1.17:6.74:4.17:87.92 in the process of bottom self-flow filling, while the optimal ratio is 1.78:9.58:4.71:83.93 for roof-contacted filling. A novel filling process to fill in gypsum mine goaf with clay is established. The engineering practice shows that the filling cost is low, thus, notable economic benefit is achieved.

Mechanics criterion and factors affecting overburden stability in solid dense filling mining

The effect of controlling strata movement in solid filling mining depends on the filling rate of the goal. However, the mechanical property of the overburden in the backfill stope and the designed size of the backfill mining workface should also be considered. In this study, we established a main roof strata model with loads in accordance with the theory of key strata to investigate the stability of the overburden in solid dense filling mining. We analyzed the stress distribution law of the main roof strata based on elastic thin plate theory. The results show that the position of the long side midpoint of the main roof strata failed more easily because of tensile yield, indicating that this position is the area where failure is likely to occur more easily. We also deduced the stability mechanics criterion of the main roof strata based on tensile yield criterion. The factors affecting the stability of the overburden in solid dense filling mining were also analyzed, including the thickness and elasticity modulus of the main roof strata, overlying strata loads, advanced distance and length of workface, and elastic foundation coefficient of backfill body. The research achievements can provide an important theoretical basis for determining the designed size of the solid dense filling mining workface.

Stress field evolution law of mining environment reconstructing structure with change of filling height

For improving global stability of mining environment reconstructing structure,the stress field evolution law of the structure with the filling height change of low-grade backfill was studied by ADINA finite element analysis code.Three kinds of filling schemes were designed and calculated,in which the filling heights were 2,4,and 7 m,separately.The results show that there are some rules in the stress field with the increase of the filling height as follows:(1) the maximum value of tension stress of the roof decreases gradually,and stress conditions are improved gradually;(2) the tension stress status in the vertical pillar is transformed into the compressive stress status,and the carrying capacity is improved gradually;however,when the filling height is beyond 2.8 m,the carrying capacity of the vertical pillar grows very slowly,so,there is little significance to continue to fill the low-grade backfill;(3) the bottom pillar suffers the squeezing action from the vertical pillars at first and then the gravity action of the low-grade backfill,and the maximum value of tension stress of the bottom pillar firstly increases and then decreases.Considering the economic factor,security and other factors,the low-grade backfill has the most reasonable height(2.8 m) in the scope of all filling height.

China set quota for second batch of rare earth mining,smelting and separation in 2023

China set a quota for the second batch of rare earth mining in 2023 at 120,000 tonnes,with a quota for smelting and separation at 115,000 tonnes,according to a joint statement by the Ministry of Industry and Information Technology(MIIT)and the Ministry of Natural Resources.

基于3Dmine的采空区治理工程实践

通过对某金矿采空区资料收集及现场调查,利用3Dmine软件建立了该金矿采空区+巷道三维数字模型,准确获得了各中段采空区的实际边界和采空区形态等相关信息。针对采空区情况,结合矿区生产实际,经综合分析研究,提出了采空区治理方案,即:对矿区已经贯通连成一体的采空区群/塌陷坑(四中段以上)采用地表废石充填,四中段未贯通的采空区采用中深孔强制崩落顶板,将上部自地表“灌入”的废石充填到采空区,同时采取密闭隔离的方式联合治理;对于其余地段的采空区,已经结束回采且无法进入的区域采取在中段石门密闭隔离的方式进行治理,尚在开采的其他采空区采取施工措施工程进行坑内毛石回填并密闭隔离方式治理。通过多项措施的综合运用,彻底消除了发生大面积地压活动并引起地面塌陷的隐患,为井下正常生产作业创造了良好的条件。

Safe mining technology of undersea metal mine

Xinli district of Sanshandao Gold Mine is the first subsea metal mine in China.To achieve 6 kt/d production capacity under the premise of safe mining,high-intensity mining might destroy the in-situ stress filed and the stability of rockmass.According to sampling and testing of ore-rock and backfill and in-situ stress field measurement,safety factor method calculation model based on stress-strain strength reduction at arbitrary points and Mohr-Coulomb yield criterion was established and limit displacement subsidence values under the safety factor of different limit stoping steps were calculated.The results from three years in-situ mining and strata movement monitoring using multi-point displacements meter showed that the lower settlement frame stope hierarchical level filling mining method,mining sequence are reasonable and rockmass stability evaluation using safety factor method,in-situ real-time monitoring can provide the technical foundation for the safety of seabed mining.

Development and prospect on fully mechanized mining in Chinese coal mines

Fully mechanized mining(FMM)technology has been applied in Chinese coal mines for more than 40 years.At present,the output of a FMM face has reached 10-million tons with Chinese-made equipment.In this study,the new developments in FMM technology and equipment in Chinese coal mines during past decades are introduced.The automatic FMM technology for thin seams,complete sets of FMM technology with ultra large shear height of 7 m for thick seams,complete sets of fully mechanized top coal caving technology with large shear height for ultra-thick seams of 20 m,complete sets of FMM technology for complex and difficult seams,including steeply inclined seams,soft coal seams with large inclination angle,and the mechanized filling mining technology and equipment are presented.Some typical case studies are also introduced.Finally,the existing problems with the FMM technology are discussed,and prospect of FMM technology and equipment applied in Chinese coal mines is put forward.

Using particle swarm optimization algorithm in an artificial neural network to forecast the strength of paste filling material

In order to forecast the strength of filling material exactly, the main factors affecting the strength of filling material are analyzed. The model of predicting the strength of filling material was established by applying the theory of artificial neural net- works. Based on cases related to our test data of filling material, the predicted results of the model and measured values are com- pared and analyzed. The results show that the model is feasible and scientifically justified to predict the strength of filling material, which provides a new method for forecasting the strength of filling material for paste filling in coal mines.

An investigation of surface deformation after fully mechanized,solid back fill mining

The surface deformation after fully mechanized back filling mining was analyzed.The surface deformation for different backfill materials was predicted by an equivalent mining height model and numerical simulations.The results suggest that:(1) As the elastic modulus,E,of the backfill material increases the surface subsidence decreases.The rate of subsidence decrease drops after E is larger than 5 GPa;(2) Fully mechanized back fill mining technology can effectively control surface deformation.The resulting surface deformation is within the specification grade I,which means surface maintenance is not needed.A site survey showed that the equivalent mining height model is capable of predicting and analyzing surface deformation and that the model is conservative enough for engineering safety.Finally,the significance of establishing a complete error correction system based on error analysis and correction is discussed.

Study on new technique of rapidly following curtain filling

The present problem of mining of narrow and gentle dip vein was analyzed. A new technique of rapidly following curtain filling was put forward. The results show that the new technique is feasible, has the characteristic to make the whole curtain wall filter, makes relative density of the filling tailings slurry reach saturation of 78.0% 80.0% in 25 min, and keeps the roof of mined out space stable in 60 min. The new technique of the rapidly following curtain filling has solved the difficult problem of the filling body filtering slowly and promptly controlling underground pressure, which cannot be solved in traditional ways.

Processing the rig test data of an air filling twin-tube shock absorber

A separation method is proposed to design and improve shock absorber according to the characteristics of each force. The method is validated by rig test. The force data measured during rig test is the resultant force of damping force, rebound force produced by pressed air, and friction force. Different characters of damping force, air rebound force and friction force can be applied to seperate each force from others. A massive produced air filling shock absorber is adopted for the validation. The statistic test is used to get the displacement-force curves. The data are used as the input of separation calculation. Then the tests are carried out again to obtain the force data without air rebound force. The force without air rebound is compared to the data derived from the former tests with the separation method. The result shows that this method can separate the damping force and the air elastic force.

Numerical modeling of destress blasting for strata separation

Destress blasting(DB)implemented along the perimeter of safety pillars is a special application of destressing in coal longwall mining.The goal is to separate relatively more deformed mined areas from safety pillars,such as shaft pillars or cross-cut pillars,to reduce the transfer of high stresses to the protective pillar.This case study aims to numerically simulate selected destress blasts in the Czech part of the Upper Silesian Coal Basin and examine its impact on stress transfer to the safety pillar area.To separate the area between the protective pillar and the longwall(LW),two fans of five 93-mm blast holes(length of 93e100 m)were drilled from the gate roads into the overburden strata.Each set of blast holes was fired separately in two stages without time delay.The explosive charge(gelatin-type of explosive)of each stage is 3450 kg.The two DB stages were fired when the longwall face was approximately 158 m and 152 m away from the blast.A 3D mine-wide model is built and validated with in situ stress measured with hydrofracturing.Mining and destressing in three 5-m thick coal seams are simulated in the region.Numerical modeling of DB is successfully conducted using a rock fragmentation factor a of 0.05 and a stress reduction/dissipation factor β of 0.95.Buffering of transfer of additional stress from the mining area into the safety pillar is evaluated by comparison of yielding volume before and after DB.It is shown that yielding volume drops after DB by nearly 80%in the area of the destressing panel and near the safety shaft pillar.

Total production quota of rare earth mining, smelting and separation in 2021

The total production quota of rare earth mining,smelting and separation in 2021 were 168,000 tons and 162,000 tons,respectively,according to the announcement released by the Ministry of Industry and Information Technology and the Ministry of Natural Resources on September 30,2021.The mining quota included 148,850 tons of rock-type rare earth ore(mainly light rare earths)and 19,150 tons of ionic rare earth ore(mainly medium and heavy rare earths).Compared with that of last year,the total quotas of rare earth mining and smelting separation were increased by 20%from 140,000 tons and 135,000 tons,respectively in 2020.

Mechanics Principle and Engineering Application of Split Layer and Bed Separation of Mining Overburden

To control land surface subsidence caused the underground mineral exploitation and the catastrophic phenomena such as serious damage of buildings, waterbodies, cultivated lands, railways, bridges caused by land subsidence, bed separation grouting technology of overburden is put forward. To provide theoretical support for the technology, the characteristics and the mechanics mechanism of mining overburden from layer-split to formation of bed separation are studied. On the basis of elastic sheet board theory, calculation formula of rock sheet deflection is presented, and the mechanics criteria of the separation formation and the calculation formula of bed separation volume are set up. Finally, the applications and technics of bed separation grout technology of mining overburden to control land subsidence in china are introduced.

煤矸石井下原位智能分选充填技术研究进展

传统井下煤矸石需运输至地面处理,不仅占用地面国土空间、自燃或雨水淋滤造成大气与环境污染,而且长距离无效运输造成的能源消耗问题已成为制约煤矿低碳发展的关键瓶颈。为实现煤矿矸石不出井,从煤炭生产源头减少碳排放与单位产出能源资源消耗,实现煤炭的绿色低碳智能开采,回顾了煤矸石井下分选充填技术现状及智能化进展,并在此基础上展望煤矸石井下分选充填技术发展趋势,提出了煤矸石井下原位绿色智能分选、充填新方法,详细阐述了煤矸智能分选机及新型充填液压支架的结构及原理,以最大化缩短矸石无效运输距离。为处理采煤工作面矸石,预防煤岩动力灾害,提出了包含少矸化智能开采系统、原位智能分选系统、工作面矿压反演系统、精准科学充填系统四大子系统的煤矿井下采选充智能一体化系统,并探讨了各子系统间的新环逻辑关系,以形成采煤利于分选、分选利于充填、充填利于采煤的良性循环。为处理掘进工作面矸石,提出了包含智能快掘系统、智能分选系统、煤矸分运系统、智能充填系统四大子系统的煤矿井下掘选充智能一体化系统,并对各子系统所负责工作及智能化实现进行了阐述。所提出的新工艺有望实现煤矿矸石不出井,并为煤矸石原位智能分选充填方法及采选充一体化系统的研究提供新思路。

Research on Deformation Regularity of Surface Migrating With Waste-fill Mining

Using FLAC3D numerical simulation software,the influence laws that the different mining depth,mining width and filling step have on the surface subsidence and horizontal movement under the condition of filling mining has been studied.The functional relation among full subsidence and horizontal movement of surface,mining depth,mining width and filling step has been given,which provides theoretical formulas been referenced for filling mining theory and has a certain guiding value.

煤矿覆岩离层注浆减沉技术研究及应用

针对门克庆煤矿11-3101工作面铁路下压煤问题,为提高煤炭资源回收率,应用离层注浆减沉技术减小地表下沉,通过室内试验测试了不同配比充填料浆的流变特性,确定了合适的料浆配比,同时构建采动覆岩离层演变力学模型,提出了离层动态发育位置及离层开度预测方法。研究结果表明:11-3101工作面从下往上将会产生四个离层,分别位于工作面顶板上方45.42、228.38、337.19、363.99 m处;离层开度从下到上依次为2.62、1.49、1.39和1.33 m,开度随着层高的增长而递减;注浆压力为6.5 MPa,注采比大于45%时,地表倾斜变形值小于3 mm/m,现场监测结果显示铁路路基最大沉降量仅58.72 mm,注浆减沉效果显著。