Apparent-Depth Effects of the Dynamic Failure of Thick Hard Rock Strata on the Underlying Coal Mass During Underground Mining

2018 ◽  
Vol 52 (5) ◽  
pp. 1565-1576 ◽  
Author(s):  
Chao Xu ◽  
Qiang Fu ◽  
Xinyuan Cui ◽  
Kai Wang ◽  
Yixin Zhao ◽  
...  
Keyword(s):  
Hard Rock ◽  
Underground Mining ◽  
Coal Mass ◽  
Apparent Depth ◽  
Dynamic Failure ◽  
Rock Strata ◽  
Depth Effects

scholarly journals Mechanism and Prevention and Control of Mine Earthquake in Thick and Hard Rock Strata considering the Horizontal Stress Evolution of Stope

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Ming Zhang ◽  
Xuelong Hu ◽  
Hongtao Huang ◽  
Guangyao Chen ◽  
Shan Gao ◽  
...  
Keyword(s):  
Hard Rock ◽  
Design Method ◽  
Horizontal Stress ◽  
Prevention Measures ◽  
Stress Concentrations ◽  
Estimation Model ◽  
Working Face ◽  
Mining Design ◽  
And Control ◽  
Rock Strata

This study investigated the mechanism, prevention measures, and control methods for earthquake disasters typically occurring in mines with thick and hard rock strata. A mine stope with large faults and thick hard rock strata in Hebei Province was taken as the background study object. Then, theoretical analysis and numerical simulation methods were adopted in conjunction with field monitoring to explore how horizontal stress evolves in the thick and hard hanging roofs of such mines, potentially leading to mining earthquakes. Then, based on the obtained results, a mining design method was proposed to reduce the horizontal stress levels of earthquake mitigation. The results showed that, under the control of large faults, semiopen and semiclosed stopes with thick hard rock strata are formed, which cause influentially pressurized and depressurized zones during the evolution of the overburden movements and horizontal stress. It was determined that the stress concentrations mainly originated from the release and transfer of horizontal stress during the rock fractures and movements in the roof areas, which were calculated using a theoretical estimation model. The horizontal stress concentrations formed “counter torques” at both ends of the thick and hard strata, which prevented the support ending due to tensile failures. As a result, the limit spans were increased. This study proposed a mining strategy of using narrow working faces, strip mining processes, and reasonable mining speeds, which could effectively reduce horizontal stress concentrations and consequently prevent and control mining earthquakes. This study’s research results were successfully applied to the mining practices in working face 16103.

scholarly journals A Supporting Design Method When Longwall FaceStrides across and Passes through a Roadway

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Weidong Pan ◽  
Xinyuan Li ◽  
YiWei Li ◽  
Xiaobin Li ◽  
Qing Qiao ◽  
...  
Keyword(s):  
Stress Condition ◽  
Underground Mining ◽  
Design Method ◽  
Elastic Model ◽  
Mechanical Behaviours ◽  
Normal Production ◽  
Maximum Subsidence ◽  
Seam Mining ◽  
Rock Strata ◽  
Good Agreement

In coal underground mining, situation of longwall face striding across (SAR) or passing through roadway (PTR) is very common, especially in an inclined coal seam mining. A roadway supporting design method, consisting of a model using to determine the minimal rock strata thickness and a segmental supporting scheme, is developed. In addition, to represent the mechanical behaviour of the caved material authentically, an elastic model was developed. The results showed that the elastic model has a good agreement with the caved material mechanical behaviours at a relatively lower stress condition. By using a FDEM method, a real case in Xutuan coal mine is studied. Compared with the process without backfill, the z-displacement of cross-cut roof decreased shapely after backfilling, with a maximum z-displacement, decreases from 0.76 m to 0.13 m and from 0.39 m to 0.064 m in PTR and SAR section, respectively. Therefore, the possibility of fall of ground (FOG) and crushing accidents can be reduced effectively with backfilling material of wood cribs. And the maximum subsidence (SAR section side) of face floor is 0.16 m, which is small enough to ensure normal production. The results of this study are likely to be useful as a reference for the safe and efficient mining of coal resources under similar conditions.

From Grounded Skills to Sky Qualifications: A Study of Workers Creating and Recreating Qualifications, Identity and Gender at an Underground Iron Ore Mine in Sweden

2006 ◽  
Vol 48 (5) ◽  
pp. 657-676 ◽  
Author(s):  
Lena Abrahamsson ◽  
Jan Johansson
Keyword(s):  
Remote Control ◽  
Iron Ore ◽  
Hard Rock ◽  
Underground Mining ◽  
Workplace Culture ◽  
Physical Work ◽  
Iron Ore Mine ◽  
New Type ◽  
Worker Identity ◽  
And Gender

Over a period of 50 years at Kiruna iron ore mine in the far north of Sweden we can see a transformation of work from underground to remote control at surface level. What characterized the old underground workface was the close relation between man and the hard rock centred on arduous physical work under dangerous conditions. Today, the face miners are located ‘up in the sky’ on the seventh level of an office building close to the mine. The workers leave their job at the end of the shift just as clean as when they arrived. The contact with the hard rock is mediated by machines controlled by remote control technology. The modern technology has created a new type of work - new in terms of competencies and knowledge as well as workload. The purpose of this article is to reflect on the technical development of underground mining in Kiruna and to consider the implications it has had on qualifications, identity and gender. There is an emerging, and in many aspects already evident, knowledge transformation - from the old and obsolete physical and tacit knowledge and skills (for example the ability to ‘read the rock’) to something new which can be described as abstract knowledge. But the old culture still provides an important context for workplace learning and the construction of identity and gender. This is associated with a degree of ‘worker identity lag’ and to difficulties in adapting attitudes and norms to the demands and structures that result from the new technology and the new work tasks. The new forms of work in the mine have less need for the traditional mining competencies, attitudes and ideals. The traditional workplace culture and its ‘macho style’ have also been challenged. Workers have to find new ways to learn and to develop a workplace culture more attuned to a new type of worker identity and masculinity.

Square-form structure failure model of mining-affected hard rock strata: theoretical derivation, application and verification

2016 ◽  
Vol 75 (16) ◽  
Author(s):  
Chao Xu ◽  
Liang Yuan ◽  
Yuanping Cheng ◽  
Kai Wang ◽  
Aitao Zhou ◽  
...  
Keyword(s):  
Hard Rock ◽  
Failure Model ◽  
Theoretical Derivation ◽  
Rock Strata

scholarly journals Roof Failure Mechanism and Control Technology of Large Section Open-Off Cut in Soft Rock Strata with Thin Thickness

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Chen Li ◽  
Jun Li ◽  
Xiaoyong Lian ◽  
Yongen Li ◽  
Qi Xue ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Failure Mechanism ◽  
Underground Mining ◽  
Soft Rock ◽  
Mechanical Analysis ◽  
Field Monitoring ◽  
Surrounding Rock ◽  
Engineering Practice ◽  
Control Effect ◽  
Rock Strata

The open-off cut is used for equipment installation of working face before underground mining, and its sectional size is larger than that of the mining roadway. Therefore, the stability of open-off cut surrounding rock determines whether the panel can be put into operation. To solve the roof instability of open-off cut in the Wanli No.1 coal mine, the roof failure mechanism of open-off cut under weak composite rock strata with thin thickness was studied by field monitoring, theoretical analysis, and numerical simulation. First, the characteristics of surrounding rock and the basic law of strata behaviors were obtained by detailed field monitoring. Afterward, FLAC3D numerical simulation and mechanical analysis were used to obtain the main mechanical control parameters of surrounding rock instability, and the existence of a soft interlayer above the roof is the main cause of roof instability. Based on this, the supporting parameters of the open-off cut were optimized and adjusted. The optimized parameters were applied to the adjacent 31207 open-off cut. The engineering practice showed that the optimized supporting parameters have an ideal control effect on roof stability.

Study on Eccentric Wear Mechanism of Pick-Shaped Cutter in Soft and Hard Interbedded Formation Tunnel

2014 ◽  
Vol 501-504 ◽  
pp. 1668-1671 ◽  
Author(s):  
Dong Peng Wu ◽  
Xin An Yang ◽  
Zhi Si He ◽  
Li Cao
Keyword(s):  
Hard Rock ◽  
Soft Rock ◽  
Tunnel Excavation ◽  
Cutting Resistance ◽  
Cutting Machine ◽  
Resistance Torque ◽  
Rotary Cutting ◽  
Homogeneous Formation ◽  
Rock Strata ◽  
Starting Torque

This paper analyzes the stress of the pick-shaped cutter of rotary cutting machine in process of tunnel excavation in soft and hard interbedded formation, results show that the resistance of pick is obviously jumping fluctuations comparing to that of homogeneous formation. When pick transits from cutting hard rock to soft rock, cutting resistance and driving resistance of pick decrease instantaneously, which leads to momentary decreasing of rotation torque. And mud ball is compacted by high impact force of rotary cutting machine when cutting hard rock strata, as a consequence, resistance torque increases. When the sum of resistance torque and starting torque is greater than rotation torque, pick can`t rotate, leading to eccentric wear of pick. At last, this paper puts forward several improvement suggestions.

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