The 110-mining method,a rising and revolutionary non-pillar longwall mining method,can obviously expand coal extraction ratio and minimize roadway incidents.However,in case of composite hard roof,problems such as diff...The 110-mining method,a rising and revolutionary non-pillar longwall mining method,can obviously expand coal extraction ratio and minimize roadway incidents.However,in case of composite hard roof,problems such as difficulty in commanding the entry steadiness and insufficient fragmentation and bulking of the goaf gangue are prevalent.In this study,a 110-mining method for roadway surrounding rock stability control technology based on a compensation mechanism was proposed.First,the composite hard roof cutting short cantilever beam(SCB)model was built and the compensation mechanism including stress and space dual compensation was studied.Subsequently,the controllable elements influencing the roadway steadiness were confirmed to consequently put forward a control technology based on stress compensation for entry support and space compensation for the fragmentation and bulking of goaf gangue.The control technology was finally verified through onsite engineering experiments in terms of composite hard roof.The adoption of the 110-mining method with compensation control technology indicated good support effect on the roadway.The initial and residual expansion coefficients of the goaf gangue increased by 0.6 and 0.6,respectively,and the maximum and average working resistances of the working face support decreased by 10.9%and 13.8%,respectively.Consequently,the deformations of reserved entry decreased,and entry steadiness was enhanced.The presented technique and effects got probably have practical values for non-pillar mining functions in comparable field.展开更多
In this paper the thickness of a broken zone, a state parameter of roadway surrounding rock, is used as the index to evaluate the stabi1ity of surrounding rock of a deep roadway. The paper gives a theoretic formula fo...In this paper the thickness of a broken zone, a state parameter of roadway surrounding rock, is used as the index to evaluate the stabi1ity of surrounding rock of a deep roadway. The paper gives a theoretic formula for calculating the thickness of the broken zone. The author points out that not only the ultimate strength of rockmass but its residual strength and strain-softening level all have a great influence on the stability of surrounding rock of a deep roadway. The paper’s results show that to reinforce surrounding rock, raise its residual strength and lower its strain-softening level should be taken as a basic requirement for supports of a deep roadway. In addition, the research also indicates that it is impossible for roadway supports to change surrounding rock states of a deep roadway, so it is certain for them to work in a broken state. For this reason, a sufficient yieldable quantity is necessary for roadway supports used in deep mining.展开更多
The purpose of this research is to study the effect of longwall mining on the stability of main roadway in the underground coal mine. The PT GDM （Gerbang Daya Mandiri） underground coal mine in Indonesia, where the r...The purpose of this research is to study the effect of longwall mining on the stability of main roadway in the underground coal mine. The PT GDM （Gerbang Daya Mandiri） underground coal mine in Indonesia, where the rocks are weak, was selected as a representative study site. To accomplish the objective of the research, the finite difference code software FLAC3D was used as a tool for the numerical simulations. The longwall mining of several panel and barrier pillar widths at various depths was simulated and discussed. Based on the simulation results, it indicates that the effect of coal panel extraction on the main roadway stability depends on the width of panel and barrier pillar. The greatest effect occurs when the large panel width and the small barrier pillar width are applied, whereas the smallest effect happens when the narrow panel width and the large barrier pillar width are adopted. In this paper, therefore, to maintain the stability of the main roadway with the aim of maximizing the coal recovery, the appropriate size of panel and barrier pillar width is proposed for each mining depth for this underground coal mine.展开更多
This study aims to investigate the benefcial efects of surface retaining elements (SREs) on the mechanical behaviors of bolted rock and roadway stability. 3D printing (3DP) technology is utilized to create rock analog...This study aims to investigate the benefcial efects of surface retaining elements (SREs) on the mechanical behaviors of bolted rock and roadway stability. 3D printing (3DP) technology is utilized to create rock analogue prismatic specimens for conducting this investigation. Uniaxial compression tests with acoustic emission (AE) and digital image correlation techniques have been conducted on 3DP specimens bolted with diferent SREs. The results demonstrate that the strength and modulus of elasticity of the bolted specimens show a positive correlation with the area of the SRE;the AE characteristics of the bolted specimens are higher than those of the unbolted specimen, but they decrease with an increase in SRE area, thus further improving the integrity of the bolted specimens. The reinforcement efect of SREs on the surrounding rock of roadways is further analyzed using numerical modelling and feld test. The results provide a better understanding of the role of SREs in rock bolting and the optimization of rock bolting design. Furthermore, they verify the feasibility of 3DP for rock analogues in rock mechanics tests.展开更多
In order to more accurately classify the stability of roadway surrounding rock and identify dangerous areas in a timely manner to prevent roadway collapse and other disasters,this study proposes an Improved Northern G...In order to more accurately classify the stability of roadway surrounding rock and identify dangerous areas in a timely manner to prevent roadway collapse and other disasters,this study proposes an Improved Northern Gok algorithm(INGO)and Random Forest(RF)roadway surrounding rock stability prediction model.This model combines the improved INGO-RF based on the analysis of influencing factors of roadway surrounding rock stability.First,three strategies were employed to enhance the Northern Gob algorithm(NGO):logistic chaotic mapping,refraction reverse learning,and improved sine and cosine.Subsequently,INGO was utilized to optimize the number of decision trees and the minimum number of leaf nodes for RF species in order to improve the prediction accuracy of RF.Secondly,a data set consisting of 34 groups of roadway surrounding rock data is selected.The input indexes of the model include the roof strength,two-wall strength,floor strength,burial depth,roadway pillar width,ratio of direct roof thickness to mining height,and surrounding rock integrity.Meanwhile,surrounding rock stability is considered as the output index.Particle swarm optimization backpropagation neural network(PSO-BPNN),genetic algorithm optimization support vector machine(GA-SVM),Sparrow Search Algorithm optimization RF(SSA-RF)models were introduced to compare the predictive results with the INGO-RF model,and the results showed that:INGO-RF model has the best performance in the comparison of various performance indicators;compared with other models,the accuracy rate(Ac)in the test set has increased by 0.12–0.40,the accuracy rate(Pr)has increased by 0.07–0.65,and the recall rate(Re)has increased by 0.08–0.37;the harmonic mean(F1-Score)of the recall rate increased by 0.08–0.52,the mean absolute error(MAE)decreased by 0.1428–0.4285,the mean absolute percentage error(MAPE)decreased by 7.15%–28.57%,and the root mean square error(RMSE)decreased by 0.1565–0.3779;and finally,the data on surrounding rock conditions of roadways in multiple mining areas in Shanxi Province were collected to test the INGO-RF model.The results indicate that the predicted outcomes closely align with the actual results,demonstrating a certain level of reliability and stability,which can better meet the practical needs of engineering and avoid the occurrence of mine disasters.展开更多
At present,non-pillar entry protection in longwall mining is mainly achieved through either the gob-side entry retaining(GER)procedure or the gob-side entry driving(GED)procedure.The GER procedure leads to difficultie...At present,non-pillar entry protection in longwall mining is mainly achieved through either the gob-side entry retaining(GER)procedure or the gob-side entry driving(GED)procedure.The GER procedure leads to difficulties in maintaining the roadway in mining both the previous and current panels.A narrow coal pillar about 5-7 m must be left in the GED procedure;therefore,it causes permanent loss of some coal.The gob-side pre-backfill driving(GPD)procedure effectively removes the wasting of coal resources that exists in the GED procedure and finds an alternative way to handle the roadway maintenance problem that exists in the GER procedure.The FLAC^(3D) software was used to numerically investigate the stress and deformation distributions and failure of the rock mass surrounding the previous and current panel roadways during each stage of the GPD procedure which requires"twice excavation and mining".The results show that the stress distribution is slightly asymmetric around the previous panel roadway after the"primary excavation".The stronger and stiffer backfill compared to the coal turned out to be the main bearing body of the previous panel roadway during the"primary mining".The highest vertical stresses of 32.6 and 23.1 MPa,compared to the in-situ stress of 10.5 MPa,appeared in the backfill wall and coal seam,respectively.After the"primary mining",the peak vertical stress under the coal seam at the floor level was slightly higher(18.1 MPa)than that under the backfill(17.8 MPa).After the"secondary excavation",the peak vertical stress under the coal seam at the floor level was slightly lower(18.7 MPa)than that under the backfill(19.8 MPa);the maximum floor heave and maximum roof sag of the current panel roadway were 252.9 and 322.1 mm,respectively.During the"secondary mining",the stress distribution in the rock mass surrounding the current panel roadway was mainly affected by the superposition of the front abutment pressure from the current panel and the side abutment pressure from the previous panel.The floor heave of the current panel roadway reached a maximum of 321.8 mm at 5 m ahead of the working face;the roof sag increased to 828.4 mm at the working face.The peak abutment pressure appeared alternately in the backfill and the coal seam during the whole procedure of"twice excavation and mining"of the GPD procedure.The backfill provided strong bearing capacity during all stages of the GPD procedure and exhibited reliable support for the roadway.The results provide scientific insight for engineering practice of the GPD procedure.展开更多
In this study, the characteristics of geological structure at Qingshui coal mine were analyzed. And the hollow inclusion strain cell overcoring method was used to obtain the in situ stress. The effect of in situ stres...In this study, the characteristics of geological structure at Qingshui coal mine were analyzed. And the hollow inclusion strain cell overcoring method was used to obtain the in situ stress. The effect of in situ stress on the stability of soft rock roadway was analyzed. The results show that the maximum principal stress is in the horizontal direction with a northeast orientation and has a value of about 1.2–1.9 times larger than gravity; the right side of roadway roof and floor is easily subject to serious deformation and failure, and the in situ stress is found to be a major factor. This paper presents important information for developing countermeasures against the large deformation of the soft rock roadway at Qingshui coal mine.展开更多
Based on the principle of rock-soil mechanics, the bolt supporting technology of mine roadway were researched, it is pointed out that the roadway’s four corner bolt, the prestressed bolt and the extensible bolt play ...Based on the principle of rock-soil mechanics, the bolt supporting technology of mine roadway were researched, it is pointed out that the roadway’s four corner bolt, the prestressed bolt and the extensible bolt play an important role in keeping road stable; it is also indicated that the walls of roadway safeguarded well is important in keeping road sta- ble, which can make the bolt and surrounding rock load-bearing together; bolt and grount- ing technology can increase anchorage capacity, which is very applicable for soft rock supporting and developing entry.展开更多
基金This work described herein was supported by the Program of China Scholarship Council(202206430008)the National Natural Science Foundation of China(NSFC)(52074300 and 52304111)+1 种基金the Yueqi Young Scholars Project of China University of Mining and Technology Beijing(2602021RC84)the Guizhou province science and technology planning project([2020]3007 and[2020]2Y019).
文摘The 110-mining method,a rising and revolutionary non-pillar longwall mining method,can obviously expand coal extraction ratio and minimize roadway incidents.However,in case of composite hard roof,problems such as difficulty in commanding the entry steadiness and insufficient fragmentation and bulking of the goaf gangue are prevalent.In this study,a 110-mining method for roadway surrounding rock stability control technology based on a compensation mechanism was proposed.First,the composite hard roof cutting short cantilever beam(SCB)model was built and the compensation mechanism including stress and space dual compensation was studied.Subsequently,the controllable elements influencing the roadway steadiness were confirmed to consequently put forward a control technology based on stress compensation for entry support and space compensation for the fragmentation and bulking of goaf gangue.The control technology was finally verified through onsite engineering experiments in terms of composite hard roof.The adoption of the 110-mining method with compensation control technology indicated good support effect on the roadway.The initial and residual expansion coefficients of the goaf gangue increased by 0.6 and 0.6,respectively,and the maximum and average working resistances of the working face support decreased by 10.9%and 13.8%,respectively.Consequently,the deformations of reserved entry decreased,and entry steadiness was enhanced.The presented technique and effects got probably have practical values for non-pillar mining functions in comparable field.
文摘In this paper the thickness of a broken zone, a state parameter of roadway surrounding rock, is used as the index to evaluate the stabi1ity of surrounding rock of a deep roadway. The paper gives a theoretic formula for calculating the thickness of the broken zone. The author points out that not only the ultimate strength of rockmass but its residual strength and strain-softening level all have a great influence on the stability of surrounding rock of a deep roadway. The paper’s results show that to reinforce surrounding rock, raise its residual strength and lower its strain-softening level should be taken as a basic requirement for supports of a deep roadway. In addition, the research also indicates that it is impossible for roadway supports to change surrounding rock states of a deep roadway, so it is certain for them to work in a broken state. For this reason, a sufficient yieldable quantity is necessary for roadway supports used in deep mining.
文摘The purpose of this research is to study the effect of longwall mining on the stability of main roadway in the underground coal mine. The PT GDM （Gerbang Daya Mandiri） underground coal mine in Indonesia, where the rocks are weak, was selected as a representative study site. To accomplish the objective of the research, the finite difference code software FLAC3D was used as a tool for the numerical simulations. The longwall mining of several panel and barrier pillar widths at various depths was simulated and discussed. Based on the simulation results, it indicates that the effect of coal panel extraction on the main roadway stability depends on the width of panel and barrier pillar. The greatest effect occurs when the large panel width and the small barrier pillar width are applied, whereas the smallest effect happens when the narrow panel width and the large barrier pillar width are adopted. In this paper, therefore, to maintain the stability of the main roadway with the aim of maximizing the coal recovery, the appropriate size of panel and barrier pillar width is proposed for each mining depth for this underground coal mine.
基金supported by the Young Scientist Project of National Key Research and Development Program of China(2021YFC2900600)the National Natural Science Foundation of China(52074166)Shandong Province(ZR2021YQ38).
文摘This study aims to investigate the benefcial efects of surface retaining elements (SREs) on the mechanical behaviors of bolted rock and roadway stability. 3D printing (3DP) technology is utilized to create rock analogue prismatic specimens for conducting this investigation. Uniaxial compression tests with acoustic emission (AE) and digital image correlation techniques have been conducted on 3DP specimens bolted with diferent SREs. The results demonstrate that the strength and modulus of elasticity of the bolted specimens show a positive correlation with the area of the SRE;the AE characteristics of the bolted specimens are higher than those of the unbolted specimen, but they decrease with an increase in SRE area, thus further improving the integrity of the bolted specimens. The reinforcement efect of SREs on the surrounding rock of roadways is further analyzed using numerical modelling and feld test. The results provide a better understanding of the role of SREs in rock bolting and the optimization of rock bolting design. Furthermore, they verify the feasibility of 3DP for rock analogues in rock mechanics tests.
基金supported by the National Natural Science Foun-dation of China (No.52174188)the Shanxi Basic Research Program (Free Exploration)Project of China (No.202203021222300).
文摘In order to more accurately classify the stability of roadway surrounding rock and identify dangerous areas in a timely manner to prevent roadway collapse and other disasters,this study proposes an Improved Northern Gok algorithm(INGO)and Random Forest(RF)roadway surrounding rock stability prediction model.This model combines the improved INGO-RF based on the analysis of influencing factors of roadway surrounding rock stability.First,three strategies were employed to enhance the Northern Gob algorithm(NGO):logistic chaotic mapping,refraction reverse learning,and improved sine and cosine.Subsequently,INGO was utilized to optimize the number of decision trees and the minimum number of leaf nodes for RF species in order to improve the prediction accuracy of RF.Secondly,a data set consisting of 34 groups of roadway surrounding rock data is selected.The input indexes of the model include the roof strength,two-wall strength,floor strength,burial depth,roadway pillar width,ratio of direct roof thickness to mining height,and surrounding rock integrity.Meanwhile,surrounding rock stability is considered as the output index.Particle swarm optimization backpropagation neural network(PSO-BPNN),genetic algorithm optimization support vector machine(GA-SVM),Sparrow Search Algorithm optimization RF(SSA-RF)models were introduced to compare the predictive results with the INGO-RF model,and the results showed that:INGO-RF model has the best performance in the comparison of various performance indicators;compared with other models,the accuracy rate(Ac)in the test set has increased by 0.12–0.40,the accuracy rate(Pr)has increased by 0.07–0.65,and the recall rate(Re)has increased by 0.08–0.37;the harmonic mean(F1-Score)of the recall rate increased by 0.08–0.52,the mean absolute error(MAE)decreased by 0.1428–0.4285,the mean absolute percentage error(MAPE)decreased by 7.15%–28.57%,and the root mean square error(RMSE)decreased by 0.1565–0.3779;and finally,the data on surrounding rock conditions of roadways in multiple mining areas in Shanxi Province were collected to test the INGO-RF model.The results indicate that the predicted outcomes closely align with the actual results,demonstrating a certain level of reliability and stability,which can better meet the practical needs of engineering and avoid the occurrence of mine disasters.
基金This research was supported by the National Natural Science Foundation of China(51604126,51974293)the Natural Science Foundation of Jiangsu Province(BK20180658),and the Distinguished Foreign Expert Talent Program funding from the Chinese Government and the Jiangxi Province.
文摘At present,non-pillar entry protection in longwall mining is mainly achieved through either the gob-side entry retaining(GER)procedure or the gob-side entry driving(GED)procedure.The GER procedure leads to difficulties in maintaining the roadway in mining both the previous and current panels.A narrow coal pillar about 5-7 m must be left in the GED procedure;therefore,it causes permanent loss of some coal.The gob-side pre-backfill driving(GPD)procedure effectively removes the wasting of coal resources that exists in the GED procedure and finds an alternative way to handle the roadway maintenance problem that exists in the GER procedure.The FLAC^(3D) software was used to numerically investigate the stress and deformation distributions and failure of the rock mass surrounding the previous and current panel roadways during each stage of the GPD procedure which requires"twice excavation and mining".The results show that the stress distribution is slightly asymmetric around the previous panel roadway after the"primary excavation".The stronger and stiffer backfill compared to the coal turned out to be the main bearing body of the previous panel roadway during the"primary mining".The highest vertical stresses of 32.6 and 23.1 MPa,compared to the in-situ stress of 10.5 MPa,appeared in the backfill wall and coal seam,respectively.After the"primary mining",the peak vertical stress under the coal seam at the floor level was slightly higher(18.1 MPa)than that under the backfill(17.8 MPa).After the"secondary excavation",the peak vertical stress under the coal seam at the floor level was slightly lower(18.7 MPa)than that under the backfill(19.8 MPa);the maximum floor heave and maximum roof sag of the current panel roadway were 252.9 and 322.1 mm,respectively.During the"secondary mining",the stress distribution in the rock mass surrounding the current panel roadway was mainly affected by the superposition of the front abutment pressure from the current panel and the side abutment pressure from the previous panel.The floor heave of the current panel roadway reached a maximum of 321.8 mm at 5 m ahead of the working face;the roof sag increased to 828.4 mm at the working face.The peak abutment pressure appeared alternately in the backfill and the coal seam during the whole procedure of"twice excavation and mining"of the GPD procedure.The backfill provided strong bearing capacity during all stages of the GPD procedure and exhibited reliable support for the roadway.The results provide scientific insight for engineering practice of the GPD procedure.
基金provided by the Beijing Natural Science Foundation(No.8142032)the National Natural Science Foundation of China(No.41040027)+2 种基金the State Key Program of National Natural Science of China(No.5113400)the Research Fund for the Doctoral Program of Higher Education(No.20130023110021)the Special Fund of Basic Research and Operating Expenses of State Key Laboratory of Geomechanics and Deep Underground Engineering,China University of Mining&Technology,Beijing
文摘In this study, the characteristics of geological structure at Qingshui coal mine were analyzed. And the hollow inclusion strain cell overcoring method was used to obtain the in situ stress. The effect of in situ stress on the stability of soft rock roadway was analyzed. The results show that the maximum principal stress is in the horizontal direction with a northeast orientation and has a value of about 1.2–1.9 times larger than gravity; the right side of roadway roof and floor is easily subject to serious deformation and failure, and the in situ stress is found to be a major factor. This paper presents important information for developing countermeasures against the large deformation of the soft rock roadway at Qingshui coal mine.
文摘Based on the principle of rock-soil mechanics, the bolt supporting technology of mine roadway were researched, it is pointed out that the roadway’s four corner bolt, the prestressed bolt and the extensible bolt play an important role in keeping road stable; it is also indicated that the walls of roadway safeguarded well is important in keeping road sta- ble, which can make the bolt and surrounding rock load-bearing together; bolt and grount- ing technology can increase anchorage capacity, which is very applicable for soft rock supporting and developing entry.
