A paste-like self-flowing pipeline transportation backfilling technology with coal gangue as aggregate is proposed to remove the potential damage caused by coal gangue piles. As well, the difficult problems of recover...A paste-like self-flowing pipeline transportation backfilling technology with coal gangue as aggregate is proposed to remove the potential damage caused by coal gangue piles. As well, the difficult problems of recovering high quality safety coal pillars and deep mining of the Suncun Coal Mine （SCM）, Xinwen Coal Group, Shandong are resolved. The physical-chemical properties of coal gangue, optimized proportion of materials, backfilling system and craft in the SCM were studied in the laboratory and then an industrial test was carried out on high quality coal pillars under a town. The results show that finely crushed kaolinized and fresh gangue with granularity less than 5 mm can be used as aggregate with fly ash to replace part of the cement and a composite water reducer as an additive, accounting for 1.0%-1.5% of the total amount of cement and fly ash. The recommended proportion is l（cement）：4（fly ash）： 15（coal gangue）, with a mass fraction of 72%-75%, rheoiogical paste-like properties and a strength of more than 0.7 MPa at 7 d. The sequence of adding cement, fly ash, water reducer and then coal gangue ensures that the suspended state of the slurry, reducing the wear and jam of pipelines. The working face is advancing continuously by the alternating craft of building block walls with coal gangue and backfilling mined-out gobs with paste-like slurry. The recovery rate is as high as 90% with a backfilling cost of 36.9 YuarffL good utilization of coal gangue and no subsidence on the surface. This technology provides a good theoretical basis and application experience for coal mines, cement backfilling with paste-like slurry.展开更多
To reduce the cost of backfilling coal mining and utilize the underground space of coal mines,a new backfilling mining method with low backfilling rate called constructional backfilling coal mining(CBCM)is proposed.Th...To reduce the cost of backfilling coal mining and utilize the underground space of coal mines,a new backfilling mining method with low backfilling rate called constructional backfilling coal mining(CBCM)is proposed.The "backfilling body-immediate roof" cooperative bearing structure of CBCM is analyzed by establishing the model of the medium thick plate on an elastic foundation.The influence of the backfilling rate on the stability of overlying strata is analyzed by the numerical simulation experiment.The control effect of CBCM is verified by a physic similar simulation test.The economic benefit of CBCM is analyzed.The conclusions are:the deformation characteristics of the immediate roof and critical backfilling spacing in CBCM can be analyzed based on the Hu Haichang’s theory.Exerting the bearing capacity of the immediate roof is beneficial to the stability of the overlying strata.The CBCM has a good control effect on the overburden in Xinyang Mine when the backfilling rate is lower than 25%.The backfilling cost of per ton coal is 37.39 yuan/t when the backfilling rate is 13.7%,with a decrease rate of 56.63%than the full-filling.The research results can provide theoretical support for the application of CBCM in coal mining.展开更多
The increasing anthropogenic CO2 emission and global warming has challenged the China and other countries to seek new and better ways to meet the world’s increasing need for energy while reducing greenhouse gas emiss...The increasing anthropogenic CO2 emission and global warming has challenged the China and other countries to seek new and better ways to meet the world’s increasing need for energy while reducing greenhouse gas emissions.The overall proposition of this research is to develop a brand-new CO2 physical and chemical sequestration method by using solid waste of coal mining and cementitious material which are widely used for goaf backfilling in coal mining.This research developed a new testing system(constant temperature pressurized reaction chamber(CTPRC))to study the effects of different initial parameters on mineral carbonation such as different initial water-binder ratio,initial sample porosity and initial carbon dioxide pressure.The experimental results show that the CO2 consumption ratio is 15%,10%and 7%higher with relatively high initial water-binder ratio,initial sample porosity and initial CO2 pressure within 48 h.In addition,some physical and chemical evidence was found through the electron microscope scanning and XRD test to further explain the above test results.This proposed research will provide critical parameters for optimizing CO2 sequestration capacity in this cementitious backfilling material with forming agent.展开更多
Recovery of the coal buried under buildings,railways and water bodies and the residual coal in irregularly arranged fully mechanized mining faces is a common engineering problem facing underground coal mining.In this ...Recovery of the coal buried under buildings,railways and water bodies and the residual coal in irregularly arranged fully mechanized mining faces is a common engineering problem facing underground coal mining.In this study,a mining technology of continuous driving and gangue backfilling(CDGB)was proposed.The technology,which can not only alleviate ground subsidence and gangue discharge,but also release the above-mentioned coals,contributes to green and efficient sustainable development of mining.The stability of the system of the solidified body-reserved coal pillar combination(S-C combination)is crucial to the CDGB technology.Therefore,it is of great significance to explore the mechanical and damage characteristics of S-C combination in the synergistic bearing process.First,four sets of differentshaped S-C combination specimens were fabricated and a S-C combination bearing structure in CDGB was constructed to explore the differences in mechanical characteristics and damage modes of different-shaped S-C combination specimens during CDGB.Subsequently,their surface strain field evolutions and acoustic emission(AE)response characteristics in the load-bearing process were obtained with the aid of the digital image correlation technique and the AE signal monitoring system.Furthermore,a damage evolution model based on AE parameters and mechanical parameters was established to clarify the damage evolution law.The following results were obtained:(1)The free area of S-C combination can serve as a quantitative index to evaluate the stability of the overburden control system;(2)The concept of critical value k of the free area was first proposed.When the free area exceeds the critical value k(free area ratio greater than 1.13),the deformation resistance and the free area changes becomes negatively correlated;(3)As the free area expands,the failure of the S-C combination specimen evolves from tensile failure to shear failure.The distribution characteristics of the axial strain field also verified such a change in the failure mode;(4)When the free area expands,the peak AE count gradually changes from“double peaks”to“a single peak”.In this process,the expansion of free area shortens the time for accumulating and releasing energy during loading.Micro cracks generated in the specimen change from a phased steep growth to a continuous increase,and the process in which micro cracks develop,converge,intersect and connect to form macro cracks accelerates.The damage evolution law concluded based on AE parameters and mechanical parameters can well characterize the damage evolution process of S-C combination,providing certain reference for the study on the synergistic bearing of S-C combination during CDGB.展开更多
Through changing the axial load on backfilling material compaction test to reflect different overlying strata pressure on backfilling material, the stress-strain relations in the compaction process of backfilling mate...Through changing the axial load on backfilling material compaction test to reflect different overlying strata pressure on backfilling material, the stress-strain relations in the compaction process of backfilling material under the geological condition can be obtained. Based on the characteristic of overlying strata movement in backfill mining, a model of roof thin plate is established. By introducing the stress-strain relation in compaction process into the model and using RIZT method to analyze the bending deformation of roof, the bending deflection and stress distribution can be obtained. The results show that the maximum roof subsidence and maximum tensile stress occurring at the center are 255 mm and5 MPa, respectively. Tensile fracture of roof under the geological condition of Dongping Mine did not occur. The dynamic measurement results of roof in Dongping Mine verify the theoretical result from the aforementioned model, thereby suggesting the roof mechanical model is reliable. The roof thin plate model based on the compaction characteristic of backfilling material in this study is of importance to research on backfill mining theories and application of backfilling material characteristics.展开更多
For transportation of solid backfill material such as waste and fly ash from the surface to the bottom of the shaft in a fully mechanized backfilling coal backfilling coal mining technology, we developed a new vertica...For transportation of solid backfill material such as waste and fly ash from the surface to the bottom of the shaft in a fully mechanized backfilling coal backfilling coal mining technology, we developed a new vertical transportation system to transport this type of solid backfill material. Given the demands imposed on safely in feeding this material, we also investigated the structure and basic parameter of this system. For a mine in the Xingtai mining area the results show that: (1) a vertical transportation system should include three main parts, i.e., a feeding borehole, a maintenance chamber and a storage silo; (2) we determined that 486 mm is a suitable diameter for bore holes, the diameter of the storage silo is 6 m and its height 30 m in this vertical transportation system; (3) a conical buffer was developed to absorb the impact during the feeding process. To ensure normal implementation of fully mechanized backfilling coal mining technology and the safety of underground personnel, we propose a series of security technologies for anti-blockage, storage silo cleaning, high pressure air release and aspiration. This vertical transporting system has been applied in one this particular mine, which has fed about 4 million tons solid material with a feeding depth of 350 m and safely exploited 3 million tons of coal.展开更多
Based on the principle of fully mechanized backflling and coal mining technology and combined with the Xingtai Coal Mine conditions, we mainly optimized the coal mining equipment and adjusted the coal mining method in...Based on the principle of fully mechanized backflling and coal mining technology and combined with the Xingtai Coal Mine conditions, we mainly optimized the coal mining equipment and adjusted the coal mining method in the Xingtai Coal Mine 7606 working face for implementation this technology. Firstly, we define the practical backfilling process as the ＂（from backfilling scraper conveyor＇s） head to tail back- filling, step by step swinging up of the tamping arm, gradual compacting, moving formed backfilling scra- per conveyor when the second tamping arm cannot pass and connecting the immediate roof by back material push front material movement＂. Meanwhile, the stress changes of backfill body in coal mined out area was monitored by stress sensors, and the roof caving law was analyzed by monitoring the dynamic subsidence of -210 west roadway of this face. The site tests results show that using this new backfilling and coal mining integrated technology, the production capacity in the 7606 working face can reach to 283,000 ton a year, and 282,000 ton of solid materials （waste and fly ash） is backfilled, which meets the needs of high production and efficiency. The goaf was compactly backfilled with solid material and the strata behavior was quite desirable, with an actual maximum vertical stress of the backfill body of 5.5 MPa. Backfill body control the movement of overburden within a certain range, and there is no col- lapses of major areas in the overlying strata upon backfilled gob. The maximum subsidence and speed were 231 mm and 15.75 mm/d respectively, which proved the practical significance of this integrated technology.展开更多
We analyzed the deformation characteristics of overlying stratum in backfilling with fully-mechanized and retaining roadways along the gob area coal mining technology, and established a mechanical model for the roof k...We analyzed the deformation characteristics of overlying stratum in backfilling with fully-mechanized and retaining roadways along the gob area coal mining technology, and established a mechanical model for the roof key stratum of retaining roadways along gob under the conditions of backfilling and fully- mechanized coal mining technology. Using Winkler elastic foundation theory, we analyzed a part of the key stratum under the action of elastic foundation coupling problem, and derived deflection analyt- ical expressions. Combined with specific conditions, we obtained the deflection curves for the roof key stratum of retaining roadways along gob under the conditions of backfilling and fully-mechanized coal mining technology. On this basis, we adopted the Coulomb's earth pressure theory to solve the problem of lateral pressure of the gangue filling area on the supporting wall beside the roadway and to provide the theoretical basis for reasonable selection of the distance between gangue concrete wall and roof and fur- ther discussion on the supporting stability of roadway.展开更多
To analyze the overlying strata movement law of recovering room mining standing pillars with solid backfilling.Physical simulation experiments with sponge and wood as the backfilling simulation material were tested.Th...To analyze the overlying strata movement law of recovering room mining standing pillars with solid backfilling.Physical simulation experiments with sponge and wood as the backfilling simulation material were tested.The results show that:(i) The covering-rock mechanics of the overly strata comes from "two-arch structures + hinged girder + bend beam" to "backfilling material + hinged girder + bent beam" by increasing the fill ratio from 0%to 85%,the beginning of overlying strata movement appears later and the total duration of subsidence velocity increased from zero to the highest value increases.The trend of "single polarization" of the subsidence velocity curves becomes noticeable and the velocity variation trend becomes stable,(ii) The equiponderate aeolian sand was added to improve the anti-pressure ability of the loess,and the corresponding ground processing & transportation system was designed.展开更多
Based on the analysis of the failure characteristics and backfilling effect of the compound roof at 1801 backfilling workface in Taiyuan coal mine, China, we propose a method of controlling the pre- subsidence of a co...Based on the analysis of the failure characteristics and backfilling effect of the compound roof at 1801 backfilling workface in Taiyuan coal mine, China, we propose a method of controlling the pre- subsidence of a compound roof by using pre-stressed bolts to improve the backfilling ratio of the work- face so as to maintain the global stability of the stope roof. In addition, PHASE simulation software was employed to analyze the influence law of pre-stressing force, length, and interval on roof subsidence at the workface. On the basis of the numerical simulation results, a model for calculating the pre-stressing force and length of the bolts, the interval between the bolts, as well as roof subsidence at the workface, was established by using SPSS regression analysis software. Moreover, the research results were applied successfully to the 1801 filling workface. According to the monitoring data of roof closure, it was found that the final subsidence value for the goal roof was 350 mm and the filling ratio at the workface was 86%, which could fully meet the demand for safety production at the workface. The safe and effective control of the stope roof was therefore realized, which achieves the goal of safe and efficient backfilling mining under a compound roof.展开更多
Based on the character of upward slicing backfilling mining and the condition of Gonggeyingzi coal mine in Inner Mongolia,this paper describes the studies of the strata behavior and the stress distribution in the proc...Based on the character of upward slicing backfilling mining and the condition of Gonggeyingzi coal mine in Inner Mongolia,this paper describes the studies of the strata behavior and the stress distribution in the process of backfilling mining in extra-thick coal seams.This was achieved by setting up and analyzing the elastic foundation beam model using the ABAQUS software.The results show that:(1) With the gradual mining of different slices,the roof appears to bend continuously but does not break.The vertical stress in the roof decreases and the decreasing amplitude reduces,while the tensile stress in the roof grows with the mining slices and the maximum tensile stress will not exceed the allowable tensile stress.(2) The front vertical stress at the working face exceeds the rear vertical stress and both show a trend of decrease with decreasing amplitude of decrease.(3) The slices mined early have more influence on the surrounding rock than the later ones.Similarly,the strata behavior experiences the same trend.The field measured data show that the roof does not break during the mining process,which is consistent with the conclusion.展开更多
Through analyzing the effects of water consumption, diameter of solid particle, and flow vefority on the fluidity of high water content material slurry, the relatinnship among the fluidity, the isotropy of the slurry,...Through analyzing the effects of water consumption, diameter of solid particle, and flow vefority on the fluidity of high water content material slurry, the relatinnship among the fluidity, the isotropy of the slurry, and the pumping facilities applied in getway-side backfilling has been found. And the requirment of fluidity of high water content material for the design of getway-side back filling technique is put forward in the paper.展开更多
This paper attempts to quantify the effect of backfilling on pillar strength in highwall mining using numerical modelling. Calibration against the new empirical strength formula for highwall mining was conducted to ob...This paper attempts to quantify the effect of backfilling on pillar strength in highwall mining using numerical modelling. Calibration against the new empirical strength formula for highwall mining was conducted to obtain the material parameters used in the numerical modelling. With the obtained coal strength parameters, three sets of backfill properties were investigated. The results reveal that the behavior of pillars varies with the type and amount of backfill as well as the pillar width to mining height ratio(w/h). In case of cohesive backfill, generally 75% backfill shows a significant increase in peak strength, and the increase in peak strength is more pronounced for the pillars having lower w/h ratios. In case of noncohesive backfill, the changes in both the peak and residual strengths with up to 92% backfill are negligible while the residual strength constantly increases after reaching the peak strength only when 100%backfill is placed. Based on the modelling results, different backfilling strategies should be considered on a case by case basis depending on the type of backfill available and desired pillar dimension.展开更多
Aiming to address the following major engineering issues faced by the Pingdingshan No. 12 mine:(1) difficulty in implementing auxiliary lifting because of its depth(i.e., beyond 1000 m);(2) highly gassy main coal seam...Aiming to address the following major engineering issues faced by the Pingdingshan No. 12 mine:(1) difficulty in implementing auxiliary lifting because of its depth(i.e., beyond 1000 m);(2) highly gassy main coal seam with low permeability;(3) unstable overlying coal seam without suitable conditions for implementing conventional mining techniques for protective coal seam; and(4) predominant reliance on ‘‘under three" coal resources to ensure production output. This study proposes an integrated, closed-cycle mining-dressing-gas draining-backfilling-mining(MDGBM) technique. The proposed approach involves the mining of protective coal seam, underground dressing of coal and gangue(UDCG), pressure relief and gas drainage before extraction, and backfilling and mining of the protected coal seam. A system for draining gas and mining the protective seam in the rock stratum is designed and implemented based on the geological conditions. This system helps in realizing pressure relief and gas drainage from the protective seam before extraction. Accordingly, another system, which is connected to the existing production system, is established for the UDCG based on the dense medium-shallow trough process. The mixed mining workface is designed to accommodate both solid backfill and conventional fully mechanized coal mining, thereby facilitating coal mining, USCG, and backfilling. The results show that: The mixed mining workface length for the Ji15-31010 protected seam was 220 m with coal production capacity 1.2 million tons per year, while the backfill capacity of gangue was 0.5 million tons per year. The gas pressure decreased from 1.78 to 0.35 MPa, and the total amount of safely mined coal was 1.34 million tons. The process of simultaneously exploiting coal and draining gas was found to be safe, efficient, and green.This process also yielded significant economic benefits.展开更多
Mine waste and process tailings storage is one of important challenge for which mining operations are increasingly confronted. Treatment discharges of plants and main part of waste rock development are generally store...Mine waste and process tailings storage is one of important challenge for which mining operations are increasingly confronted. Treatment discharges of plants and main part of waste rock development are generally stored on surface areas. The volume and chemical characteristics of these materials generate serious problem for required storage spaces and mainly environmental degradation. Paste backfill(PBF) is one of ingenious solutions to minimize the quantity of tailings to store. PBF is basically defined as a combination of mine processing tailings, binder, and water mixing. The purpose of this paper is to present backfilling components characterization and formula verification for a waste valorization solution through paste backfilling technology in Imiter operation. Obtained results and realized analysis demonstrate PBF conformity and adequacy with assigned underground functions. However the studied recipe can be more ameliorated to obtain an optimal mixture ensuring the required mechanical strength.展开更多
Cemented paste backfill （CPB） is gaining popularity in many underground mines worldwide. Sufficient water is added into CPB to make a flowable material for pipe transportation. Barricades are built near the drawpoin...Cemented paste backfill （CPB） is gaining popularity in many underground mines worldwide. Sufficient water is added into CPB to make a flowable material for pipe transportation. Barricades are built near the drawpoints to prevent in-rush of the fill slurry. To avoid barricade failures resulting from excessive backfill pressures, backfilling is typically performed with a plug pour followed by a final pour. The interval between the two pours should be shortened or removed to increase mining productivity and avoid pipe clogging. Recently, Li proposed to apply wick drains in backfilled stopes to promote drainage and consolidation. The preliminary simulations by considering an instantaneous filling indicated that the drainage of CPB can be significantly accelerated by using wick drains. Barricade was not considered. Here, some new numerical modeUings are presented with more representative filling sequences, stope geometry, and different draining configurations. The results illustrate that the stope can be backfilled continuously by using wick drains.展开更多
An underground iron mine in China has been used as a case-study to research the subsidence due to ore extraction and backfilling during open stoping operations. A 3-D discontinuum numerical model was built incorporati...An underground iron mine in China has been used as a case-study to research the subsidence due to ore extraction and backfilling during open stoping operations. A 3-D discontinuum numerical model was built incorporating geologic complexities including faults and interfaces between different lithologies,and the stoping and backfilling sequence adopted from the mine plans. The stoping was carried out in two vertically stacked horizontal layers, with a total of 16 stopes. Large displacements of up to 50 cm were observed along the roof of the stopes, and a maximum surface subsidence of 22.5 cm was observed.Backfilling was found to eliminate subsequent displacements and subsidence. The extraction of the upper orebody was found to influence displacements in the lower orebody. Finally, a subsidence profile was constructed to show the subsidence at all locations along the length of the surface and region of influence on the surface.展开更多
During the process of constructional backfill mining,the cemented paste backfill(CPB)typically exhibits a high degree of brittleness and limited resistance to failure.In this study,the mechanical and damage evolution ...During the process of constructional backfill mining,the cemented paste backfill(CPB)typically exhibits a high degree of brittleness and limited resistance to failure.In this study,the mechanical and damage evolution characteristics of waste tire steel fiber(WTSF)-modified CPB were studied through uniaxial compression tests,acoustic emission(AE)tests,and scanning electron microscopy(SEM).The results showed that the uniaxial compressive strength(UCS)decreased when the WTSF content was 0.5%,1%,and 1.5%.When the WTSF content reached 1%,the UCS of the modified CPB exhibited a minimal decrease(0.37 MPa)compared to that without WTSF.When the WTSF content was 0.5%,1%,and 1.5%,peak strain of the WTSF-modified CPB increased by 18%,31.33%,and 81.33%,while the elastic modulus decreased by 21.31%,26.21%,and 45.42%,respectively.The addition of WTSF enhances the activity of AE events in the modified CPB,resulting in a slower progression of the entire failure process.After the failure,the modified CPB retained a certain level of load-bearing capacity.Generally,the failure of the CPB was dominated by tensile cracks.After the addition of WTSF,a gradual increase in the proportion of tensile cracks was observed upon loading the modified CPB sample to the pore compaction stage.The three-dimensional localization of AE events showed that the WTSF-modified CPB underwent progressive damage during the loading,and the samples still showed good integrity after failure.Additionally,the response relationship between energy evolution and damage development of WTSF-modified CPB during uniaxial compression was analyzed,and the damage constitutive model of CPB samples with different WTSF contents was constructed.This study provides a theoretical basis for the enhancement of CPB modified by adding WTSF,serving as a valuable reference for the design of CPB constructional backfill.展开更多
Cementitious gangue-fly ash backfill(CGB)is used as a green mining technology worldwide.However,under the coupled effects of geological stress and groundwater,the metal elements in the CGB tend to migrate into nearby ...Cementitious gangue-fly ash backfill(CGB)is used as a green mining technology worldwide.However,under the coupled effects of geological stress and groundwater,the metal elements in the CGB tend to migrate into nearby strata,which can consequently result in pollution of the groundwater environment.In this paper,the influence of initial pH and stress damage on the migration behavior of metal elements in CGB is quantitatively studied through the multi-physical field coupling model of stress-permeability-con centration.The enhanced Nemerow index evaluation method is used to comprehensively evaluate the impact of these metal elements migration behaviors on the groundwater environment.The research results show that:(1)When the stress damage of the CGB increases from 0.76 to 0.95,the Darcy velocity at the bottom of the CGB first increases,then decreases,and finally stabilizes at 2.01×10^(-7)m/s.The longest time to reach the maximum Darcy velocity is 3 a.(2)When the damage of the CGB is 0.95,the farthest migration distances of Al,Cr,Mn,Fe,Ba,and Pb are 40.5,34.0,29.8,32.9,38.8 and 32.1 m,respectively.(3)The alkaline environment stimulates the migration of Al,Cr,Fe,Mn,and Pb,whereas Ba migrates farther under acidic conditions.The farthest migration distance of Ba is 31.6 m under pH 3.(4)The enhanced Nemerow index indicates that when stress damage increases from 0.76 to 0.95,the areas with poor water quality increase from 0 to 1.71%,and no area is classified as very poor grade.When the initial pH changes from 3 to 11,100%of the region is classified as fair or above.The initial pH of the CGB has a relatively slight influence on the groundwater environment.This study provides experimental data and theoretical basis for the environmental evaluation of CGB.展开更多
Underground mining always create voids.These voids can cause subsidence of surface.So it is always a demand to fill the void in such a manner that the effect of underground mining can be minimized.Void filling using m...Underground mining always create voids.These voids can cause subsidence of surface.So it is always a demand to fill the void in such a manner that the effect of underground mining can be minimized.Void filling using mill tailings especially in metal mining is one of the best techniques.The tailings produced in milling process have traditionally been disposed in tailing ponds creating a waste disposal and environmental problems in terms of land degradation,air and water pollution,etc.This disposal practice is more acute in the metal milling industry where the fine grinding,required for value liberation,results in the production of very fine tailings in large percentage.This paper includes discussions on the effectiveness of different paste mixes with varying cement contents in paste backfilling operations.The results revealed that material composition and use of super plasticizer strongly influenced the strength of cemented backfill.展开更多
基金Projects 2006BAB02A03 supported by the National Key Technology Research and Development ProgramProjects 2006BA02B05 by the 11th Five Year Key Program for Science and Technology Development of China
文摘A paste-like self-flowing pipeline transportation backfilling technology with coal gangue as aggregate is proposed to remove the potential damage caused by coal gangue piles. As well, the difficult problems of recovering high quality safety coal pillars and deep mining of the Suncun Coal Mine （SCM）, Xinwen Coal Group, Shandong are resolved. The physical-chemical properties of coal gangue, optimized proportion of materials, backfilling system and craft in the SCM were studied in the laboratory and then an industrial test was carried out on high quality coal pillars under a town. The results show that finely crushed kaolinized and fresh gangue with granularity less than 5 mm can be used as aggregate with fly ash to replace part of the cement and a composite water reducer as an additive, accounting for 1.0%-1.5% of the total amount of cement and fly ash. The recommended proportion is l（cement）：4（fly ash）： 15（coal gangue）, with a mass fraction of 72%-75%, rheoiogical paste-like properties and a strength of more than 0.7 MPa at 7 d. The sequence of adding cement, fly ash, water reducer and then coal gangue ensures that the suspended state of the slurry, reducing the wear and jam of pipelines. The working face is advancing continuously by the alternating craft of building block walls with coal gangue and backfilling mined-out gobs with paste-like slurry. The recovery rate is as high as 90% with a backfilling cost of 36.9 YuarffL good utilization of coal gangue and no subsidence on the surface. This technology provides a good theoretical basis and application experience for coal mines, cement backfilling with paste-like slurry.
基金supported by the Youth Funds of National Natural Science Foundation of China(No.52004173)the Distinguished Youth Funds of National Natural Science Foundation of China(No.51925402)+2 种基金the Science and Technology Innovation Project of Colleges and Universities in Shanxi Province(No.2020L0066)the China Postdoctoral Science Foundation(No.2022M712922)the Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(Nos.2021SX-TD001 and 2022SXTD008).
文摘To reduce the cost of backfilling coal mining and utilize the underground space of coal mines,a new backfilling mining method with low backfilling rate called constructional backfilling coal mining(CBCM)is proposed.The "backfilling body-immediate roof" cooperative bearing structure of CBCM is analyzed by establishing the model of the medium thick plate on an elastic foundation.The influence of the backfilling rate on the stability of overlying strata is analyzed by the numerical simulation experiment.The control effect of CBCM is verified by a physic similar simulation test.The economic benefit of CBCM is analyzed.The conclusions are:the deformation characteristics of the immediate roof and critical backfilling spacing in CBCM can be analyzed based on the Hu Haichang’s theory.Exerting the bearing capacity of the immediate roof is beneficial to the stability of the overlying strata.The CBCM has a good control effect on the overburden in Xinyang Mine when the backfilling rate is lower than 25%.The backfilling cost of per ton coal is 37.39 yuan/t when the backfilling rate is 13.7%,with a decrease rate of 56.63%than the full-filling.The research results can provide theoretical support for the application of CBCM in coal mining.
基金the National Natural Science Foundation of China(No.51304207)the Fundamental Research Funds for the Key Laboratory of Coal-based CO2 capture and geological storage,China University of Mining and Technology(No.2016A03).
文摘The increasing anthropogenic CO2 emission and global warming has challenged the China and other countries to seek new and better ways to meet the world’s increasing need for energy while reducing greenhouse gas emissions.The overall proposition of this research is to develop a brand-new CO2 physical and chemical sequestration method by using solid waste of coal mining and cementitious material which are widely used for goaf backfilling in coal mining.This research developed a new testing system(constant temperature pressurized reaction chamber(CTPRC))to study the effects of different initial parameters on mineral carbonation such as different initial water-binder ratio,initial sample porosity and initial carbon dioxide pressure.The experimental results show that the CO2 consumption ratio is 15%,10%and 7%higher with relatively high initial water-binder ratio,initial sample porosity and initial CO2 pressure within 48 h.In addition,some physical and chemical evidence was found through the electron microscope scanning and XRD test to further explain the above test results.This proposed research will provide critical parameters for optimizing CO2 sequestration capacity in this cementitious backfilling material with forming agent.
基金the National Natural Science Foundation of China(Nos.U21A20108,52322403,52174108,and 51974105)the Support Plan for Science&Technology Innovation Talents in Universities of Henan Province(No.21HASTIT024)+1 种基金the Scientific and technological innovation research team of Henan Polytechnic University(No.T2021-5)the Henan Excellent Youth Science Foundation(No.222300420045).
文摘Recovery of the coal buried under buildings,railways and water bodies and the residual coal in irregularly arranged fully mechanized mining faces is a common engineering problem facing underground coal mining.In this study,a mining technology of continuous driving and gangue backfilling(CDGB)was proposed.The technology,which can not only alleviate ground subsidence and gangue discharge,but also release the above-mentioned coals,contributes to green and efficient sustainable development of mining.The stability of the system of the solidified body-reserved coal pillar combination(S-C combination)is crucial to the CDGB technology.Therefore,it is of great significance to explore the mechanical and damage characteristics of S-C combination in the synergistic bearing process.First,four sets of differentshaped S-C combination specimens were fabricated and a S-C combination bearing structure in CDGB was constructed to explore the differences in mechanical characteristics and damage modes of different-shaped S-C combination specimens during CDGB.Subsequently,their surface strain field evolutions and acoustic emission(AE)response characteristics in the load-bearing process were obtained with the aid of the digital image correlation technique and the AE signal monitoring system.Furthermore,a damage evolution model based on AE parameters and mechanical parameters was established to clarify the damage evolution law.The following results were obtained:(1)The free area of S-C combination can serve as a quantitative index to evaluate the stability of the overburden control system;(2)The concept of critical value k of the free area was first proposed.When the free area exceeds the critical value k(free area ratio greater than 1.13),the deformation resistance and the free area changes becomes negatively correlated;(3)As the free area expands,the failure of the S-C combination specimen evolves from tensile failure to shear failure.The distribution characteristics of the axial strain field also verified such a change in the failure mode;(4)When the free area expands,the peak AE count gradually changes from“double peaks”to“a single peak”.In this process,the expansion of free area shortens the time for accumulating and releasing energy during loading.Micro cracks generated in the specimen change from a phased steep growth to a continuous increase,and the process in which micro cracks develop,converge,intersect and connect to form macro cracks accelerates.The damage evolution law concluded based on AE parameters and mechanical parameters can well characterize the damage evolution process of S-C combination,providing certain reference for the study on the synergistic bearing of S-C combination during CDGB.
基金financial assistance provided by the National Natural Science Foundation of China(No.51304206)China Postdoctoral Science Foundation funded project(No.2015M580492)
文摘Through changing the axial load on backfilling material compaction test to reflect different overlying strata pressure on backfilling material, the stress-strain relations in the compaction process of backfilling material under the geological condition can be obtained. Based on the characteristic of overlying strata movement in backfill mining, a model of roof thin plate is established. By introducing the stress-strain relation in compaction process into the model and using RIZT method to analyze the bending deformation of roof, the bending deflection and stress distribution can be obtained. The results show that the maximum roof subsidence and maximum tensile stress occurring at the center are 255 mm and5 MPa, respectively. Tensile fracture of roof under the geological condition of Dongping Mine did not occur. The dynamic measurement results of roof in Dongping Mine verify the theoretical result from the aforementioned model, thereby suggesting the roof mechanical model is reliable. The roof thin plate model based on the compaction characteristic of backfilling material in this study is of importance to research on backfill mining theories and application of backfilling material characteristics.
基金support for this work provided by the National Natural Science Foundation of China (No. 51074165)the major program of the National Natural Science Foundation of China (No. 50834004)the Innovation Project of Graduate Students of Jiangsu Province (No. CXZZ11-0308)
文摘For transportation of solid backfill material such as waste and fly ash from the surface to the bottom of the shaft in a fully mechanized backfilling coal backfilling coal mining technology, we developed a new vertical transportation system to transport this type of solid backfill material. Given the demands imposed on safely in feeding this material, we also investigated the structure and basic parameter of this system. For a mine in the Xingtai mining area the results show that: (1) a vertical transportation system should include three main parts, i.e., a feeding borehole, a maintenance chamber and a storage silo; (2) we determined that 486 mm is a suitable diameter for bore holes, the diameter of the storage silo is 6 m and its height 30 m in this vertical transportation system; (3) a conical buffer was developed to absorb the impact during the feeding process. To ensure normal implementation of fully mechanized backfilling coal mining technology and the safety of underground personnel, we propose a series of security technologies for anti-blockage, storage silo cleaning, high pressure air release and aspiration. This vertical transporting system has been applied in one this particular mine, which has fed about 4 million tons solid material with a feeding depth of 350 m and safely exploited 3 million tons of coal.
基金Financial supports for this work provided by the National Natural Science Foundation of China (No. 51074165)the Key Program of National Natural Science Foundation of China (No.50834004)A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (No.SZBF2011-6-B35)
文摘Based on the principle of fully mechanized backflling and coal mining technology and combined with the Xingtai Coal Mine conditions, we mainly optimized the coal mining equipment and adjusted the coal mining method in the Xingtai Coal Mine 7606 working face for implementation this technology. Firstly, we define the practical backfilling process as the ＂（from backfilling scraper conveyor＇s） head to tail back- filling, step by step swinging up of the tamping arm, gradual compacting, moving formed backfilling scra- per conveyor when the second tamping arm cannot pass and connecting the immediate roof by back material push front material movement＂. Meanwhile, the stress changes of backfill body in coal mined out area was monitored by stress sensors, and the roof caving law was analyzed by monitoring the dynamic subsidence of -210 west roadway of this face. The site tests results show that using this new backfilling and coal mining integrated technology, the production capacity in the 7606 working face can reach to 283,000 ton a year, and 282,000 ton of solid materials （waste and fly ash） is backfilled, which meets the needs of high production and efficiency. The goaf was compactly backfilled with solid material and the strata behavior was quite desirable, with an actual maximum vertical stress of the backfill body of 5.5 MPa. Backfill body control the movement of overburden within a certain range, and there is no col- lapses of major areas in the overlying strata upon backfilled gob. The maximum subsidence and speed were 231 mm and 15.75 mm/d respectively, which proved the practical significance of this integrated technology.
基金supported by the National Natural Science Foundation of China (Nos. 51074163 and 50834005)the Ministry of Education Support Program for New Century Excellent of China(No. NCET-08-0837)the Fundamental Research Funds for the Central Universities of China
文摘We analyzed the deformation characteristics of overlying stratum in backfilling with fully-mechanized and retaining roadways along the gob area coal mining technology, and established a mechanical model for the roof key stratum of retaining roadways along gob under the conditions of backfilling and fully- mechanized coal mining technology. Using Winkler elastic foundation theory, we analyzed a part of the key stratum under the action of elastic foundation coupling problem, and derived deflection analyt- ical expressions. Combined with specific conditions, we obtained the deflection curves for the roof key stratum of retaining roadways along gob under the conditions of backfilling and fully-mechanized coal mining technology. On this basis, we adopted the Coulomb's earth pressure theory to solve the problem of lateral pressure of the gangue filling area on the supporting wall beside the roadway and to provide the theoretical basis for reasonable selection of the distance between gangue concrete wall and roof and fur- ther discussion on the supporting stability of roadway.
基金provided by the National Natural Science Foundation of China(No.51074165)the NationalKey Basic Research Program of China(No.2013CB227905)the Qing-Lan Project of China Scholarship Council
文摘To analyze the overlying strata movement law of recovering room mining standing pillars with solid backfilling.Physical simulation experiments with sponge and wood as the backfilling simulation material were tested.The results show that:(i) The covering-rock mechanics of the overly strata comes from "two-arch structures + hinged girder + bend beam" to "backfilling material + hinged girder + bent beam" by increasing the fill ratio from 0%to 85%,the beginning of overlying strata movement appears later and the total duration of subsidence velocity increased from zero to the highest value increases.The trend of "single polarization" of the subsidence velocity curves becomes noticeable and the velocity variation trend becomes stable,(ii) The equiponderate aeolian sand was added to improve the anti-pressure ability of the loess,and the corresponding ground processing & transportation system was designed.
基金the Qinglan Project,the National Key Basic Research Program of China (No.2013CB227905)the Science Fund for Creative Research Groups of the National Natural Science Foundation of China (No.51421003)
文摘Based on the analysis of the failure characteristics and backfilling effect of the compound roof at 1801 backfilling workface in Taiyuan coal mine, China, we propose a method of controlling the pre- subsidence of a compound roof by using pre-stressed bolts to improve the backfilling ratio of the work- face so as to maintain the global stability of the stope roof. In addition, PHASE simulation software was employed to analyze the influence law of pre-stressing force, length, and interval on roof subsidence at the workface. On the basis of the numerical simulation results, a model for calculating the pre-stressing force and length of the bolts, the interval between the bolts, as well as roof subsidence at the workface, was established by using SPSS regression analysis software. Moreover, the research results were applied successfully to the 1801 filling workface. According to the monitoring data of roof closure, it was found that the final subsidence value for the goal roof was 350 mm and the filling ratio at the workface was 86%, which could fully meet the demand for safety production at the workface. The safe and effective control of the stope roof was therefore realized, which achieves the goal of safe and efficient backfilling mining under a compound roof.
基金sponsored by the National Key Basic Research Program of China (No.2013CB227905)Qinglan Projects of Jiangsu Province
文摘Based on the character of upward slicing backfilling mining and the condition of Gonggeyingzi coal mine in Inner Mongolia,this paper describes the studies of the strata behavior and the stress distribution in the process of backfilling mining in extra-thick coal seams.This was achieved by setting up and analyzing the elastic foundation beam model using the ABAQUS software.The results show that:(1) With the gradual mining of different slices,the roof appears to bend continuously but does not break.The vertical stress in the roof decreases and the decreasing amplitude reduces,while the tensile stress in the roof grows with the mining slices and the maximum tensile stress will not exceed the allowable tensile stress.(2) The front vertical stress at the working face exceeds the rear vertical stress and both show a trend of decrease with decreasing amplitude of decrease.(3) The slices mined early have more influence on the surrounding rock than the later ones.Similarly,the strata behavior experiences the same trend.The field measured data show that the roof does not break during the mining process,which is consistent with the conclusion.
文摘Through analyzing the effects of water consumption, diameter of solid particle, and flow vefority on the fluidity of high water content material slurry, the relatinnship among the fluidity, the isotropy of the slurry, and the pumping facilities applied in getway-side backfilling has been found. And the requirment of fluidity of high water content material for the design of getway-side back filling technique is put forward in the paper.
文摘This paper attempts to quantify the effect of backfilling on pillar strength in highwall mining using numerical modelling. Calibration against the new empirical strength formula for highwall mining was conducted to obtain the material parameters used in the numerical modelling. With the obtained coal strength parameters, three sets of backfill properties were investigated. The results reveal that the behavior of pillars varies with the type and amount of backfill as well as the pillar width to mining height ratio(w/h). In case of cohesive backfill, generally 75% backfill shows a significant increase in peak strength, and the increase in peak strength is more pronounced for the pillars having lower w/h ratios. In case of noncohesive backfill, the changes in both the peak and residual strengths with up to 92% backfill are negligible while the residual strength constantly increases after reaching the peak strength only when 100%backfill is placed. Based on the modelling results, different backfilling strategies should be considered on a case by case basis depending on the type of backfill available and desired pillar dimension.
基金supported by the Qing Lan Project Foundation of Jiangsu Province in 2014,Foundation for Distinguished professor of Jiangsu Province in 2015,Science Fund for Creative Research Groups of the National Natural Science Foundation of China(No.51421003)Project funded by China Postdoctoral Science Foundation(2016M601915)National Key Basic Research Program of China(No.2013CB227905)
文摘Aiming to address the following major engineering issues faced by the Pingdingshan No. 12 mine:(1) difficulty in implementing auxiliary lifting because of its depth(i.e., beyond 1000 m);(2) highly gassy main coal seam with low permeability;(3) unstable overlying coal seam without suitable conditions for implementing conventional mining techniques for protective coal seam; and(4) predominant reliance on ‘‘under three" coal resources to ensure production output. This study proposes an integrated, closed-cycle mining-dressing-gas draining-backfilling-mining(MDGBM) technique. The proposed approach involves the mining of protective coal seam, underground dressing of coal and gangue(UDCG), pressure relief and gas drainage before extraction, and backfilling and mining of the protected coal seam. A system for draining gas and mining the protective seam in the rock stratum is designed and implemented based on the geological conditions. This system helps in realizing pressure relief and gas drainage from the protective seam before extraction. Accordingly, another system, which is connected to the existing production system, is established for the UDCG based on the dense medium-shallow trough process. The mixed mining workface is designed to accommodate both solid backfill and conventional fully mechanized coal mining, thereby facilitating coal mining, USCG, and backfilling. The results show that: The mixed mining workface length for the Ji15-31010 protected seam was 220 m with coal production capacity 1.2 million tons per year, while the backfill capacity of gangue was 0.5 million tons per year. The gas pressure decreased from 1.78 to 0.35 MPa, and the total amount of safely mined coal was 1.34 million tons. The process of simultaneously exploiting coal and draining gas was found to be safe, efficient, and green.This process also yielded significant economic benefits.
文摘Mine waste and process tailings storage is one of important challenge for which mining operations are increasingly confronted. Treatment discharges of plants and main part of waste rock development are generally stored on surface areas. The volume and chemical characteristics of these materials generate serious problem for required storage spaces and mainly environmental degradation. Paste backfill(PBF) is one of ingenious solutions to minimize the quantity of tailings to store. PBF is basically defined as a combination of mine processing tailings, binder, and water mixing. The purpose of this paper is to present backfilling components characterization and formula verification for a waste valorization solution through paste backfilling technology in Imiter operation. Obtained results and realized analysis demonstrate PBF conformity and adequacy with assigned underground functions. However the studied recipe can be more ameliorated to obtain an optimal mixture ensuring the required mechanical strength.
基金the Natural Sciences and Engineering Research Council of Canada (RGPIN)the Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST)the industrial partners of the Research Institute on Mines and the Environment (RIME UQAT-Polytechnique)
文摘Cemented paste backfill （CPB） is gaining popularity in many underground mines worldwide. Sufficient water is added into CPB to make a flowable material for pipe transportation. Barricades are built near the drawpoints to prevent in-rush of the fill slurry. To avoid barricade failures resulting from excessive backfill pressures, backfilling is typically performed with a plug pour followed by a final pour. The interval between the two pours should be shortened or removed to increase mining productivity and avoid pipe clogging. Recently, Li proposed to apply wick drains in backfilled stopes to promote drainage and consolidation. The preliminary simulations by considering an instantaneous filling indicated that the drainage of CPB can be significantly accelerated by using wick drains. Barricade was not considered. Here, some new numerical modeUings are presented with more representative filling sequences, stope geometry, and different draining configurations. The results illustrate that the stope can be backfilled continuously by using wick drains.
基金the support from the National Natural Science Foundation of China (No. 51404024)partially funded by the NIOSH of the Centers for Disease Control and Prevention, USA through Contract No.200-201139886 given to the second author
文摘An underground iron mine in China has been used as a case-study to research the subsidence due to ore extraction and backfilling during open stoping operations. A 3-D discontinuum numerical model was built incorporating geologic complexities including faults and interfaces between different lithologies,and the stoping and backfilling sequence adopted from the mine plans. The stoping was carried out in two vertically stacked horizontal layers, with a total of 16 stopes. Large displacements of up to 50 cm were observed along the roof of the stopes, and a maximum surface subsidence of 22.5 cm was observed.Backfilling was found to eliminate subsequent displacements and subsidence. The extraction of the upper orebody was found to influence displacements in the lower orebody. Finally, a subsidence profile was constructed to show the subsidence at all locations along the length of the surface and region of influence on the surface.
基金financially supported by the National Natural Science Foundation of China(Nos.52274143 and 51874284).
文摘During the process of constructional backfill mining,the cemented paste backfill(CPB)typically exhibits a high degree of brittleness and limited resistance to failure.In this study,the mechanical and damage evolution characteristics of waste tire steel fiber(WTSF)-modified CPB were studied through uniaxial compression tests,acoustic emission(AE)tests,and scanning electron microscopy(SEM).The results showed that the uniaxial compressive strength(UCS)decreased when the WTSF content was 0.5%,1%,and 1.5%.When the WTSF content reached 1%,the UCS of the modified CPB exhibited a minimal decrease(0.37 MPa)compared to that without WTSF.When the WTSF content was 0.5%,1%,and 1.5%,peak strain of the WTSF-modified CPB increased by 18%,31.33%,and 81.33%,while the elastic modulus decreased by 21.31%,26.21%,and 45.42%,respectively.The addition of WTSF enhances the activity of AE events in the modified CPB,resulting in a slower progression of the entire failure process.After the failure,the modified CPB retained a certain level of load-bearing capacity.Generally,the failure of the CPB was dominated by tensile cracks.After the addition of WTSF,a gradual increase in the proportion of tensile cracks was observed upon loading the modified CPB sample to the pore compaction stage.The three-dimensional localization of AE events showed that the WTSF-modified CPB underwent progressive damage during the loading,and the samples still showed good integrity after failure.Additionally,the response relationship between energy evolution and damage development of WTSF-modified CPB during uniaxial compression was analyzed,and the damage constitutive model of CPB samples with different WTSF contents was constructed.This study provides a theoretical basis for the enhancement of CPB modified by adding WTSF,serving as a valuable reference for the design of CPB constructional backfill.
基金supported by the National Natural Science Foundation of China(Nos.52274149 and 52474162)the Fundamental Research Funds for the Central Universities(Nos.2024JCCXNY04 and 2023YQTD02)+1 种基金the Ph.D.Top Innovative Talents Fund of CUMTB(No.BBJ2024013)the Yue Qi Young Scholar Project(No.2020QN03)。
文摘Cementitious gangue-fly ash backfill(CGB)is used as a green mining technology worldwide.However,under the coupled effects of geological stress and groundwater,the metal elements in the CGB tend to migrate into nearby strata,which can consequently result in pollution of the groundwater environment.In this paper,the influence of initial pH and stress damage on the migration behavior of metal elements in CGB is quantitatively studied through the multi-physical field coupling model of stress-permeability-con centration.The enhanced Nemerow index evaluation method is used to comprehensively evaluate the impact of these metal elements migration behaviors on the groundwater environment.The research results show that:(1)When the stress damage of the CGB increases from 0.76 to 0.95,the Darcy velocity at the bottom of the CGB first increases,then decreases,and finally stabilizes at 2.01×10^(-7)m/s.The longest time to reach the maximum Darcy velocity is 3 a.(2)When the damage of the CGB is 0.95,the farthest migration distances of Al,Cr,Mn,Fe,Ba,and Pb are 40.5,34.0,29.8,32.9,38.8 and 32.1 m,respectively.(3)The alkaline environment stimulates the migration of Al,Cr,Fe,Mn,and Pb,whereas Ba migrates farther under acidic conditions.The farthest migration distance of Ba is 31.6 m under pH 3.(4)The enhanced Nemerow index indicates that when stress damage increases from 0.76 to 0.95,the areas with poor water quality increase from 0 to 1.71%,and no area is classified as very poor grade.When the initial pH changes from 3 to 11,100%of the region is classified as fair or above.The initial pH of the CGB has a relatively slight influence on the groundwater environment.This study provides experimental data and theoretical basis for the environmental evaluation of CGB.
文摘Underground mining always create voids.These voids can cause subsidence of surface.So it is always a demand to fill the void in such a manner that the effect of underground mining can be minimized.Void filling using mill tailings especially in metal mining is one of the best techniques.The tailings produced in milling process have traditionally been disposed in tailing ponds creating a waste disposal and environmental problems in terms of land degradation,air and water pollution,etc.This disposal practice is more acute in the metal milling industry where the fine grinding,required for value liberation,results in the production of very fine tailings in large percentage.This paper includes discussions on the effectiveness of different paste mixes with varying cement contents in paste backfilling operations.The results revealed that material composition and use of super plasticizer strongly influenced the strength of cemented backfill.
