锚杆锚固下深部岩爆倾向巷道围岩承载层演化机理及特性分析

锚杆锚固下深部岩爆倾向巷道围岩承载层的演化机理及特性分析表明,围岩内部残余强度和剪胀扩容效应是主要影响因素。高残余强度使承载层厚度减小,提高围岩稳定性,降低变形量;而剪胀角越大,承载层厚度越大,围岩稳定性越差,变形量增大。增大支护阻力能够有效控制围岩变形,优化承载层结构,确保巷道的安全和稳定。

金属矿山锚杆锚固下深部岩爆倾向巷道防控技术分析

金属矿山深部岩爆对巷道安全构成严重威胁。防控措施分为主动和被动两方面:主动包括勘查评估、支护设计、监测预警、工艺优化;被动则涵盖应急支护、安全疏散、事故响应。两者相辅相成,形成完整防控体系,保障矿山生产安全。

深部煤矿灾害机理及监测研究进展

我国煤炭开采以井工、露天两种开采方式为主。随着开采范围和深度的不断增加,工程灾害日益增多,如矿井冲击地压,瓦斯爆炸,矿压显现加剧,巷道围岩大变形,地温升高以及露天深部开挖形成的滑坡等对深部资源的安全高效开采均造成了巨大威胁。针对上述问题,近年来,在深部开采岩爆发生机理、瓦斯突出机理以及深部露天开采形成的高边坡滑坡灾害监测等方面展开了比较系统的研究,取得了一些进展。

Assessing the range of blasting-induced cracks in the surrounding rock of deeply buried tunnels based on the unified strength theory

Blasting-induced cracks in the rock surrounding deeply buried tunnels can result in water gushing and rock mass collapse,posing significant safety risks.However,previous theoretical studies on the range of blasting-induced cracks often ignore the impact of the in-situ stress,especially that of the intermediate principal stress.The particle displacement−crack radius relationship was established in this paper by utilizing the blasthole cavity expansion equation,and theoretical analytical formulas of the stress−displacement relationship and the crack radius were derived with unified strength theory to accurately assess the range of cracks in deep surrounding rock under a blasting load.Parameter analysis showed that the crushing zone size was positively correlated with in-situ stress,intermediate principal stress,and detonation pressure,whereas negatively correlated with Poisson ratio and decoupling coefficient.The dilatancy angle-crushing zone size relationship exhibited nonmonotonic behavior.The relationships in the crushing zone and the fracture zone exhibited opposite trends under the influence of only in-situ stress or intermediate principal stress.As the in-situ stress increased from 0 to 70 MPa,the rate of change in the crack range and the attenuation rate of the peak vibration velocity gradually slowed.

Rockburst proneness criteria for rock materials:Review and new insights

To review the rockburst proneness(or tendency)criteria of rock materials and compare the judgment accuracy of them,twenty criteria were summarized,and their judgment accuracy was evaluated and compared based on the laboratory tests on fourteen types of rocks.This study begins firstly by introducing the twenty rockburst proneness criteria,and their origins,definitions,calculation methods and grading standards were summarized in detail.Subsequently,to evaluate and compare the judgment accuracy of the twenty criteria,a series of laboratory tests were carried out on fourteen types of rocks,and the rockburst proneness judgment results of the twenty criteria for the fourteen types of rocks were obtained accordingly.Moreover,to provide a unified basis for the judgment accuracy evaluation of above criteria,a classification standard(obtained according to the actual failure results and phenomena of rock specimen)of rockburst proneness in laboratory tests was introduced.The judgment results of the twenty criteria were compared with the judgment results of this classification standard.The results show that the judgment results of the criterion based on residual elastic energy(REE)index are completely consistent with the actual rockburst proneness,and the other criteria have some inconsistent situations more or less.Moreover,the REE index is based on the linear energy storage law and defined in form of a difference value and considered the whole failure process,and these superior characteristics ensure its accuracy.It is believed that the criterion based on REE index is comparatively more accurate and scientific than other criteria,and it can be recommended to be applied to judge the rockburst proneness of rock materials.

Prediction and control of rock burst of coal seam contacting gas in deep mining

By analyzing the characteristics and the production mechanism of rock burstthat goes with abnormal gas emission in deep coal seams,the essential method of eliminatingabnormal gas emission by eliminating the occurrence of rock burst or depressingthe magnitude of rock burst was considered.The No.237 working face was selected asthe typical working face contacting gas in deep mining;aimed at this working face,a systemof rock burst prediction and control for coal seam contacting gas in deep mining wasestablished.This system includes three parts:① regional prediction of rock burst hazardbefore mining,② local prediction of rock burst hazard during mining,and ③ rock burstcontrol.

Experimental investigation on influence of loading rate on rockburst in deep circular tunnel under true-triaxial stress condition

To investigate the influence of loading rate on rockburst in a circular tunnel under three-dimensional stress conditions,the true-triaxial tests were conducted on 100 mm×100 mm×100 mm cubic sandstone specimens with d50 mm circular perforated holes,and the failure process of hole sidewall was monitored and recorded in real-time by the microcamera.The loading rates were 0.02,0.10,and 0.50 MPa/s.The test results show that the rockburst process of hole sidewall experienced calm period,pellet ejection period,rock fragment exfoliation period and finally formed the V-shaped notch.The rockburst has a time lag and vertical stress is high when the rockburst occurs.The vertical stress at the initial failure of the hole sidewall increases with loading rate.During the same period after initial failure,the rockburst severity of hole sidewalls increased significantly with increasing loading rate.When the vertical stress is constant and maintains a high stress level,the rockburst of hole sidewall under low loading rate is more serious than that under high loading rate.With increasing loading rate,the quality of rock fragments produced by the rockburst decreases,and the fractal dimension of rock fragments increases.

Opportunities and Challenges in Deep Mining： A Brief Review

Mineral consumption is increasing rapidly as more consumers enter the market for minerals and as the global standard of living increases. As a result, underground mining continues to progress to deeper levels in order to tackle the mineral supply crisis in the 21 st century. However, deep mining occurs in a very technical and challenging environment, in which significant innovative solutions and best practice are required and additional safety standards must be implemented in order to overcome the challenges and reap huge eco- nomic gains. These challenges include the catastrophic events that are often met in deep mining engineering： rockbursts, gas outbursts, high in situ and redistributed stresses, large deformation, squeezing and creeping rocks, and high temperature. This review paper presents the current global status of deep mining and high-lights some of the newest technological achievements and opportunities associated with rock mechanics and geotechnical engineering in deep mining. Of the various technical achievements, unmanned workingfaces and unmanned mines based on fully automated mining and mineral extraction processes have become important fields in the 21 st century.