Evaluation of the performance of existing support in underground tunnels is of great importance for production and interests.Based on field investigation,the shape and number of joints and fractures were investigated ...Evaluation of the performance of existing support in underground tunnels is of great importance for production and interests.Based on field investigation,the shape and number of joints and fractures were investigated in the mining area.Then,the stability of each structural blocks is analyzed by 3D wedge stability analysis software(Unwedge).Moreover,a new analysis method based on critical block theory is applied to analyze the stability of excavated laneways in continuous and discontinuous rock and monitor the stress changes in a fractured tunnel rock mass.The test results indicate that the 3D wedge stability analysis software for underground excavation can evaluate deep tunnel support.Besides,there is no direct relation between the size of the block and the instability of the tunnel.The support method,on large and thick key blocks,needs to be improved.In a broken tunnel section,U-shaped steel support can effectively promote the stress state of the surrounding rock.By monitoring the surrounding rock,it is proven that the vibrating string anchor stress monitoring system is an efficient and real-time method for tunnel stability evaluation.展开更多
Bonded blockmodel(BBM)has shownpotential in replicating rockmass behavior aswell as the rockesupport interactionmechanism,but their practical application is limited totwo dimensions due to the high associated computat...Bonded blockmodel(BBM)has shownpotential in replicating rockmass behavior aswell as the rockesupport interactionmechanism,but their practical application is limited totwo dimensions due to the high associated computational demand.To allow for the use of BBM in simulating three-dimensional(3D)problems,this study proposes an integrated 3D continuumetwo-dimensional(2D)discontinuum approach,in context of rock pillars.A cross-section of a granite pillar was simulated using a BBM with a load path from a calibrated mine-scale FLAC^(3D)model.Pillar support as employed in the mine was also incorporated in different stages during the simulation.Themodel was calibrated by varying the input parameters until the displacements at six locations within the pillarmatchedthosemeasuredby amulti-point borehole extensometer(MPBX)inthe field.The calibratedmodel was subsequently used to understand how the support and load path influenced the damage evolution in the pillar.The shear component of the load pathwas found to have amajor effect on the severity and extent of the damaged regions.When the support density was increased in the model,the lateral displacements along the pillar walls were significantly suppressed in a somewhat unpredictable manner.Thiswas explained by the interaction between the supports and the damaged regions at the corners,which ultimately modified the stresses along the pillar periphery.The amount of displacement reduction obtained by increasing the support density illustrates the potential of BBMto be used as a support design tool.展开更多
Using vector-analysis, three kinds of roof blocks at the end face of fully mechanized long wall faces have been studied. Tbe result indicates that with face advancing, the three kinds of blocks may all become key bloc...Using vector-analysis, three kinds of roof blocks at the end face of fully mechanized long wall faces have been studied. Tbe result indicates that with face advancing, the three kinds of blocks may all become key blocks. It is put forward that the key blocks can reach into the scope of angle of fracture through supporting, and the fomulas for calculating supporting force needed for the three key blocks to maintain stadility have been derived.展开更多
A cantilevered block is instable rock which results from a combination of several discontinuities, in interaction with an underground mining excavation giving a mass rocky under-gangway without natural support. Since ...A cantilevered block is instable rock which results from a combination of several discontinuities, in interaction with an underground mining excavation giving a mass rocky under-gangway without natural support. Since the starting of the gold mine of Akka in 1998, 4 deaths and 26 grave accidents happened that are associated to the falling of the cantilevered blocks. However, this study analyzes the causes of apparition of this instability in the underground gold mine of Akka which is in the buttonhole of Tagragra （Anti-Atlas, Morocco） taking into account the geological and geotechnical aspects. The more utilized geotechnical approaches were used to evaluate the quality of rocky mass including RQD, RMR and Q System method besides laboratory tests and geomechanical stations. After development of some classical formulas and using of simulation software and analytical methods, a way of support by bolting is proposed to stabilize the risk of blocks collapse inherent to the mining operations. Also we discuss here other technical solutions and theirs application limits in these cases. Finally, we confirmed the reliability of our conclusions and the type of the support proposed during 2012 and 2013 because we did not register any accident associated to cantilevered block falling.展开更多
Block multiple measurement vectors (BMMV) is a reconstruction algorithm that can be used to recover the support of block K-joint sparse matrix X from Y = ΨX + V. In this paper, we propose a sufficient condition for a...Block multiple measurement vectors (BMMV) is a reconstruction algorithm that can be used to recover the support of block K-joint sparse matrix X from Y = ΨX + V. In this paper, we propose a sufficient condition for accurate support recovery of the block K-joint sparse matrix via the BMMV algorithm in the noisy case. Furthermore, we show the optimality of the condition we proposed in the absence of noise when the problem reduces to single measurement vector case.展开更多
共识机制是区块链技术的重要组成部分,针对委托权益证明(delegated proof of stake,DPoS)共识机制中对恶意节点不能及时有效处理的问题,提出了一种基于支持向量机的DPoS共识机制改进方案(SVM-DPoS)。首先构建基于SVM的节点判别模型,通...共识机制是区块链技术的重要组成部分,针对委托权益证明(delegated proof of stake,DPoS)共识机制中对恶意节点不能及时有效处理的问题,提出了一种基于支持向量机的DPoS共识机制改进方案(SVM-DPoS)。首先构建基于SVM的节点判别模型,通过训练好的模型分析节点的行为动机,根据判别结果及时剔除恶意节点;其次基于固定协商出块顺序优化传统算法的出块流程,提升出块效率,进一步提高了整个区块链网络的运行效率。在公开数据集上的实验结果表明,与已有的几种方法相比,改进后的共识机制能够快速剔除恶意节点,不仅维护了系统稳定性,而且增强了对恶意行为的防范能力,从而在保障区块链网络正常运行的同时,提高了整体共识的安全性。展开更多
基金Projects(51964007,51774101)supported by the National Natural Science Foundation of ChinaProject(2016-4011)supported by the High-level Innovative Talents Training Project in Guizhou Province,ChinaProject(2019-5619)supported by the Guizhou Mining Power Disaster Early Warning and Control Technology Innovation Team,China。
文摘Evaluation of the performance of existing support in underground tunnels is of great importance for production and interests.Based on field investigation,the shape and number of joints and fractures were investigated in the mining area.Then,the stability of each structural blocks is analyzed by 3D wedge stability analysis software(Unwedge).Moreover,a new analysis method based on critical block theory is applied to analyze the stability of excavated laneways in continuous and discontinuous rock and monitor the stress changes in a fractured tunnel rock mass.The test results indicate that the 3D wedge stability analysis software for underground excavation can evaluate deep tunnel support.Besides,there is no direct relation between the size of the block and the instability of the tunnel.The support method,on large and thick key blocks,needs to be improved.In a broken tunnel section,U-shaped steel support can effectively promote the stress state of the surrounding rock.By monitoring the surrounding rock,it is proven that the vibrating string anchor stress monitoring system is an efficient and real-time method for tunnel stability evaluation.
基金The research conducted for this study was funded by the National Institute for Occupational Safety and Health(NIOSH)under Grant No.200-2016-90154.
文摘Bonded blockmodel(BBM)has shownpotential in replicating rockmass behavior aswell as the rockesupport interactionmechanism,but their practical application is limited totwo dimensions due to the high associated computational demand.To allow for the use of BBM in simulating three-dimensional(3D)problems,this study proposes an integrated 3D continuumetwo-dimensional(2D)discontinuum approach,in context of rock pillars.A cross-section of a granite pillar was simulated using a BBM with a load path from a calibrated mine-scale FLAC^(3D)model.Pillar support as employed in the mine was also incorporated in different stages during the simulation.Themodel was calibrated by varying the input parameters until the displacements at six locations within the pillarmatchedthosemeasuredby amulti-point borehole extensometer(MPBX)inthe field.The calibratedmodel was subsequently used to understand how the support and load path influenced the damage evolution in the pillar.The shear component of the load pathwas found to have amajor effect on the severity and extent of the damaged regions.When the support density was increased in the model,the lateral displacements along the pillar walls were significantly suppressed in a somewhat unpredictable manner.Thiswas explained by the interaction between the supports and the damaged regions at the corners,which ultimately modified the stresses along the pillar periphery.The amount of displacement reduction obtained by increasing the support density illustrates the potential of BBMto be used as a support design tool.
文摘Using vector-analysis, three kinds of roof blocks at the end face of fully mechanized long wall faces have been studied. Tbe result indicates that with face advancing, the three kinds of blocks may all become key blocks. It is put forward that the key blocks can reach into the scope of angle of fracture through supporting, and the fomulas for calculating supporting force needed for the three key blocks to maintain stadility have been derived.
文摘A cantilevered block is instable rock which results from a combination of several discontinuities, in interaction with an underground mining excavation giving a mass rocky under-gangway without natural support. Since the starting of the gold mine of Akka in 1998, 4 deaths and 26 grave accidents happened that are associated to the falling of the cantilevered blocks. However, this study analyzes the causes of apparition of this instability in the underground gold mine of Akka which is in the buttonhole of Tagragra （Anti-Atlas, Morocco） taking into account the geological and geotechnical aspects. The more utilized geotechnical approaches were used to evaluate the quality of rocky mass including RQD, RMR and Q System method besides laboratory tests and geomechanical stations. After development of some classical formulas and using of simulation software and analytical methods, a way of support by bolting is proposed to stabilize the risk of blocks collapse inherent to the mining operations. Also we discuss here other technical solutions and theirs application limits in these cases. Finally, we confirmed the reliability of our conclusions and the type of the support proposed during 2012 and 2013 because we did not register any accident associated to cantilevered block falling.
文摘Block multiple measurement vectors (BMMV) is a reconstruction algorithm that can be used to recover the support of block K-joint sparse matrix X from Y = ΨX + V. In this paper, we propose a sufficient condition for accurate support recovery of the block K-joint sparse matrix via the BMMV algorithm in the noisy case. Furthermore, we show the optimality of the condition we proposed in the absence of noise when the problem reduces to single measurement vector case.
文摘共识机制是区块链技术的重要组成部分,针对委托权益证明(delegated proof of stake,DPoS)共识机制中对恶意节点不能及时有效处理的问题,提出了一种基于支持向量机的DPoS共识机制改进方案(SVM-DPoS)。首先构建基于SVM的节点判别模型,通过训练好的模型分析节点的行为动机,根据判别结果及时剔除恶意节点;其次基于固定协商出块顺序优化传统算法的出块流程,提升出块效率,进一步提高了整个区块链网络的运行效率。在公开数据集上的实验结果表明,与已有的几种方法相比,改进后的共识机制能够快速剔除恶意节点,不仅维护了系统稳定性,而且增强了对恶意行为的防范能力,从而在保障区块链网络正常运行的同时,提高了整体共识的安全性。
