scholarly journals Study on Mechanism of Influence of Mining Speed on Roof Movement Based on Microseismic Monitoring

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Ke Ma ◽  
Su-jian Wang ◽  
Fu-zhen Yuan ◽  
Yi-lin Peng ◽  
Shi-min Jia ◽  
...  
Keyword(s):  
Load Transfer ◽  
B Value ◽  
Microseismic Monitoring ◽  
Surrounding Rock ◽  
Working Face ◽  
Final Failure ◽  
Variation Characteristics ◽  
Microseismic Events ◽  
Roof Strata ◽  
Rock Strata

Based on the study of the movement rule of the rock strata under the influence of the mining speed in the typical working face of Dongjiahe coal mine, the distribution of microseismic events and the variation characteristics of microseismic parameters in the slow and fast advancing stage are compared and analyzed, and the mechanism of the rock strata activity under the influence of the mining advancing speed is revealed from the perspective of the microfracture. The results show that the movement of the roof strata and the stress adjustment of surrounding rock have certain timeliness. The maximum advanced distance of microseismic events in the slow and fast stages is 185 m and 130 m, respectively, and the maximum lag distance of microseismic events in the goaf is 120 m and 180 m, respectively. The time of stress adjustment of surrounding rock is short, and the load transfer of the roof is insufficient. The advanced distance of microseismic events is increased, and the lag distance decreases. The percentage of microseismic events in the total number of events is 47% and 38%, respectively, in the slow and fast stages of advancing. With the increase of mining speed, the intensity of roof strata activity in the goaf is weakened. The rock failure decreases and the volume of broken block increases, and roof collapse and rotary subsidence are insufficient. During the nonpressure period, the maximum development elevation of microseismic events is +350 m and +300 m, respectively, in the slow and fast stages, while with the development elevation of microseismic events in the roof pressure near +390 m, increasing the mining speed cannot change the final failure height of the overburden. During the analysis period of roof pressure, the concentrated release of microseismic energy in the faster stage is 183% of that in the slower stage. The increase of large moment magnitude event frequency leads to the decrease of b value. The risk of roof instability and strata behavior increases.

scholarly journals Presplitting Blasting the Roof Strata to Control Large Deformation in the Deep Mine Roadway

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Chaowen Hu ◽  
Xiaojie Yang ◽  
Ruifeng Huang ◽  
Xingen Ma
Keyword(s):  
Large Deformation ◽  
Field Tests ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Deep Mine ◽  
Mining Depth ◽  
Working Face ◽  
Support Conditions ◽  
Mine Roadways ◽  
Roof Strata

As the mining depth increases, under the influence of high ground stress, the surrounding rock of deep mine roadways shows soft rock characteristics. Under the influence of mining disturbance at the working face, large deformation of the roadway has occurred. To control the large deformation of the roadway, many mines have adopted the form of combined support, which has continuously increased the support strength and achieved a certain effect. However, since the stress environment of the surrounding rock of the roadway has not been changed, large deformation of the roadway still occurs in many cases. Based on the theoretical basis of academician Manchao He’s “short cantilever beam by roof cutting,” this paper puts forward the plan of “presplitting blasting + combined support” to control the large deformation of the deep mine roadways. Without changing the original support conditions of the roadway, presplitting blasting the roof strata of the roadway, by cutting off the mechanical connection of the roof strata between the roadway and gob, improves the stress distribution of the roadway to control the large deformation. Through field tests, the results show that after presplitting blasting the roadway roof, the roadway roof subsidence is reduced by 47.9%, the ribs displacement is reduced by 45.7%, and the floor heave volume is reduced by 50.8%. The effect is significant.

scholarly journals Full-Stress Anchoring Technology and Application of Bolts in the Coal Roadway

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7475
Author(s):  
Xiaowei Guo ◽  
Xigui Zheng ◽  
Peng Li ◽  
Rui Lian ◽  
Cancan Liu ◽  
...  
Keyword(s):  
Axial Force ◽  
Load Transfer ◽  
Surrounding Rock ◽  
Lagrangian Analysis ◽  
Coking Coal ◽  
Tightening Force ◽  
Coal Roadway ◽  
Working Face ◽  
Relationship Model ◽  
Better Than

The traditional anchoring method of bolts has insufficient control over the surrounding rock of the coal roadway. Based on this background, full-stress anchoring technology of bolts was proposed. Firstly, a mechanical relationship model of a bolt-drawing, anchoring interface was established to obtain the equations of the axial force and obtain shear stress distribution as well as the decreasing-load transfer law of the anchoring section of bolts. Through studying the prestress-loading experimental device of bolts, we found that increasing the initial preload could increase the axial force under the same conditions and the retarded anchoring section could control the axial-force loss of bolts in the middle of the anchoring section. Under the full-stress anchoring mode, the effect of applying a pre-tightening force was better than that of applying a pre-tightening force under traditional anchoring methods. Moreover, FLAC3D (Fast Lagrangian Analysis of Continua 3D; ITASCA (Ita sca International Inc), Minnesota, USA) numerical simulation calculation was performed. Under the full-stress anchoring mode of bolts, the increased anchoring length reduced the damage of the anchoring section, with a wider control range of the rock formation and higher strength of the compressive-stress anchoring zone. Based on the above research, four methods for applying the full-stress anchoring technology of bolts in engineering were proposed. The full-stress anchoring technology of bolts in the coal roadway has been applied in the support project of the return-air roadway at working face 3204 of the Taitou Coking Coal Mine of the Xiangning Coking Coal Group, Shanxi. The maximum moving distance of the roof and floor of the roadway was reduced from 200 to 42 mm, and the maximum moving distance on both coal sides was reduced from 330 to 86 mm. The full-stress anchoring technology of bolts was able to control the surrounding rock in the coal roadway.

scholarly journals Research on the Law of Large-Scale Deformation and Failure of Soft Rock Based on Microseismic Monitoring

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Feng Chen ◽  
Tianhui Ma ◽  
Chun’an Tang ◽  
Yanhong Du ◽  
Zhichao Li ◽  
...  
Keyword(s):  
Monitoring System ◽  
Large Scale ◽  
Failure Process ◽  
Soft Rock ◽  
Microseismic Monitoring ◽  
Surrounding Rock ◽  
Deformation And Failure ◽  
Microseismic Events ◽  
Rock Tunnel ◽  
Microseismic Event

Based on the existing Canadian ESG microseismic monitoring system, a mobile microseismic monitoring system for a soft rock tunnel has been successfully constructed through continuous exploration and improvement to study the large-scale nucleation and development of microfractures in the soft rock of the Yangshan Tunnel. All-weather, continuous real-time monitoring is conducted while the tunnel is excavated through drilling and blasting, and the waveform characteristics of microseismic events are analysed. Through the recorded microseismic monitoring data, the variation characteristics of various parameters (e.g., the temporal, spatial, and magnitude distributions of the microseismic events, the frequency of microseismic events, and the microseismic event density and energy) are separately studied during the process of large-scale deformation instability and failure of the soft rock tunnel. The relationship between the deterioration of the rock mass and the microseismic activity during this failure process is consequently discussed. The research results show that a microseismic monitoring system can be used to detect precursors; namely, the microseismic event frequency and energy both will appear “lull” and “active” periods during the whole failure process of soft rock tunnel. Two peaks are observed during the evolution of failure. When the second peak occurs, it is accompanied by the destruction of the surrounding rock. The extent and strength of the damage within the surrounding rock can be delineated by the spatial, temporal, and magnitude distributions of the microseismic events and a microseismic event density nephogram. The results of microseismic analysis confirm that a microseismic monitoring system can be used to monitor the large-scale deformation and failure processes of a soft rock tunnel and provide early warning for on-site construction workers to ensure the smooth development of the project.

scholarly journals Stability Evaluation on Surrounding Rocks of Underground Powerhouse Based on Microseismic Monitoring

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Feng Dai ◽  
Biao Li ◽  
Nuwen Xu ◽  
Yongguo Zhu ◽  
Peiwei Xiao
Keyword(s):  
Rock Mass ◽  
Microseismic Monitoring ◽  
Surrounding Rock ◽  
Underground Powerhouse ◽  
Multiple Faults ◽  
Routine Monitoring ◽  
Underground Caverns ◽  
Macroscopic Deformation ◽  
Microseismic Events ◽  
The Stability

To study the stability of underground powerhouse at Houziyan hydropower station during excavation, a microseismic monitoring system is adopted. Based on the space-time distribution characteristics of microseismic events during excavation of the main powerhouse, the correlation between microseismic events and blasting construction is established; and the microseismic clustering areas of the underground powerhouse are identified and delineated. The FLAC3D code is used to simulate the deformation of main powerhouse. The simulated deformation characteristics are consistent with that recorded by microseismic monitoring. Finally, the correlation between the macroscopic deformation of surrounding rock mass and microseismic activities is also revealed. The results show that multiple faults between 1# and 3# bus tunnels are activated during excavation of floors V and VI of the main powerhouse. The comprehensive method combining microseismic monitoring with numerical simulation as well as routine monitoring can provide an effective way to evaluate the surrounding rock mass stability of underground caverns.

scholarly journals Study on Microseismic Monitoring, Early Warning, and Comprehensive Prevention of a Rock Burst under Complex Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Ke Ding ◽  
Lianguo Wang ◽  
Mei Yu ◽  
Wenmiao Wang ◽  
Bo Ren
Keyword(s):  
Coal Seam ◽  
Rock Burst ◽  
Large Diameter ◽  
Elastic Strain Energy ◽  
Surrounding Rock ◽  
Control Effect ◽  
Pressure Relief ◽  
Working Face ◽  
Geological Conditions ◽  
Microseismic Events

Rock bursts in coal mines are usually unpredictable. In view of this problem, the energy–frequency relationship and spatial distribution characteristics of microseismic events during the mining of 5305 working face in Xinhe Coal Mine under complex geological conditions were analyzed in this study. Besides, the law and precursors of rock burst occurrence in this working face were discussed. The following research results were obtained. Before the rock burst occurred in 5305 working face, the energy and frequency of microseismic events vary in the following order: “peak-drop-rise-rock burst.” The analysis on spatial characteristics of microseismic events suggests that microseismic events were mainly concentrated at the boundary between the roof and the coal seam or at the hard roof near the coal seam within 0–160 m in front of the working face, and most of the events lay on the goaf side. Moreover, the energy and frequency of microseismic events both decrease in the above region before the rock burst occurred. This “microseismic event absence” phenomenon can be regarded as one of the precursors of rock burst occurrence. In addition, a multilevel antiburst scheme was proposed for the complex conditions: (1) to adopt large-diameter boreholes pressure relief technology and key layer high-level pressure relief technology for adjusting the stress distribution in the surrounding rock of crossheading in front of the working face and dissipating elastic strain energy; (2) to determine the advance speed to be 1.5 m/d for reducing the mining disturbance; (3) to adopt full-section reinforced support of the roadway for enhancing the antiburst capacity of surrounding rock. After the implementation of this scheme, the energy and frequency of microseismic events monitored on-site changed gently, and 5305 working face was safely recovered to the stop line position. The scheme boasts a remarkable rock burst prevention and control effect.

scholarly journals Key Strata Inducing Dynamic Disasters Based on Energy Condition: Criterion and Application

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Chao Xu ◽  
Gang Yang ◽  
Haoshi Sun ◽  
Liangliang Qin ◽  
Kai Wang ◽  
...  
Keyword(s):  
Energy Condition ◽  
Microseismic Monitoring ◽  
Rock Breaking ◽  
Rock Stratum ◽  
Key Strata ◽  
Leading Role ◽  
Coal Rock ◽  
Roof Strata ◽  
Rock Strata ◽  
Great Energy

The thick and hard rock strata (THRS) exist widely in coal measure strata, which control the movements of overlying rock strata in stopes. When THRS break, great energy is released, which could aggravate the risks of coal and gas outburst, rock burst, and other dynamic disasters. Therefore, the foundation and key of preventing dynamic disasters are to distinguish the THRS that could induce coal-rock dynamic disasters and to analyze the laws of rock stratum breaking and energy releasing. The paper proposed the theoretical calculation methods of the energy accumulation and attenuation of rock breaking which is greatly affected by the hanging length of rock strata and the spreading distance. One or more roof strata that play a leading role in inducing dynamic disasters of the underlying coal mass are defined as the key disaster-inducing strata (KDIS). The disaster-inducing coefficient (DIC) is defined and used as the criterion of KDIS. The greater the source energy, the shorter the spreading distance, and the smaller the attenuation coefficient are, the easier the roof strata are to become KDIS. The disaster-inducing ability of the main THRS was analyzed, and the igneous sill was judged as KDIS, taking the Yangliu Coal Mine as project background. The breaking laws of the igneous sill were obtained by the methods of UDEC numerical simulation and microseismic monitoring, which verified the criterion of KDIS.

scholarly journals Comprehensive technical support for safe mining in ultra-close coal seams: A case study

2021 ◽  
pp. 014459872110093
Author(s):  
Wei Zhang ◽  
Jiawei Guo ◽  
Kaidi Xie ◽  
Jinming Wang ◽  
Liang Chen ◽  
...  
Keyword(s):  
Coal Seam ◽  
Technical Support ◽  
Surrounding Rock ◽  
Coal Seams ◽  
Deformation Control ◽  
Hard Roof ◽  
Working Face ◽  
Close Coal Seams ◽  
Safe Mining

In order to mine the coal seam under super-thick hard roof, improve the utilization rate of resources and prolong the remaining service life of the mine, a case study of the Gaozhuang Coal Mine in the Zaozhuang Mining Area has been performed in this paper. Based on the specific mining geological conditions of ultra-close coal seams (#3up and #3low coal seams), their joint systematic analysis has been performed, with the focus made in the following three aspects: (i) prevention of rock burst under super-thick hard roof, (ii) deformation control of surrounding rock of roadways in the lower coal seam, and (iii) fire prevention in the goaf of working face. Given the strong bursting tendency observed in upper coal seam and lower coal seam, the technology of preventing rock burst under super-thick hard roof was proposed, which involved setting of narrow section coal pillars to protect roadways and interleaving layout of working faces. The specific supporting scheme of surrounding rock of roadways in the #3low1101 working face was determined, and the grouting reinforcement method of local fractured zones through Marithan was further proposed, to ensure the deformation control of surrounding rock of roadways in lower coal seams. The proposed fire prevention technology envisaged goaf grouting and spraying to plug leaks, which reduced the hazard of spontaneous combustion of residual coals in mined ultra-close coal seams. The technical and economic improvements with a direct economic benefit of 5.55 million yuan were achieved by the application of the proposed comprehensive technical support. The research results obtained provide a theoretical guidance and technical support of safe mining strategies of close coal seams in other mining areas.

Prediction of rockbursts in a typical island working face of a coal mine through microseismic monitoring technology

2021 ◽  
Vol 113 ◽  
pp. 103972
Author(s):  
Chao Zhang ◽  
Gaohan Jin ◽  
Chao Liu ◽  
Shugang Li ◽  
Junhua Xue ◽  
...  
Keyword(s):  
Coal Mine ◽  
Microseismic Monitoring ◽  
Monitoring Technology ◽  
Working Face

Numerical Simulation on the Effect of Compound Roof Separation Position on Bolting Performance

2014 ◽  
Vol 953-954 ◽  
pp. 1638-1642
Author(s):  
Ai Qing Liu ◽  
Jian Zhang ◽  
Peng Cheng ◽  
Yu Hai Zhang
Keyword(s):  
Numerical Simulation ◽  
Simulation Analysis ◽  
Surrounding Rock ◽  
Cohesive Force ◽  
Roof Strata ◽  
Poor Stability ◽  
Key Parameter

Prestress is a key parameter in bolting, while the cohesive force of layers in the compound roof strata is low and prone to separation, causing the prestress proliferation very poor. With the method of numerical simulation analysis,the location of separation in compound roof to affect the performance of bolting support was researched. It is concluded the roof separation in the edge of anchorage zone, the prestress field superpose, but is away from the deep surrounding rock and shows poor stability,however the role of cable can make up for the defect of rockbolts support. It has been found the highly prestressed strength bolting system adapts to the compound roof.

scholarly journals Determination of Long Horizontal Borehole Height in Roofs and its Application to Gas Drainage

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2647
Author(s):  
Gang Wang ◽  
Cheng Fan ◽  
Hao Xu ◽  
Xuelin Liu ◽  
Rui Wang
Keyword(s):  
Numerical Simulation ◽  
Theoretical Model ◽  
Fracture Zone ◽  
Coalbed Methane ◽  
High Efficiency ◽  
Gas Drainage ◽  
Methane Drainage ◽  
Working Face ◽  
Variation Characteristics

Accurately determining the height of the gas-guiding fracture zone in the overlying strata of the goaf is the key to find the height of the long horizontal borehole in the roof. In order to determine the height, in this study we chose the 6306 working face of Tangkou Coal Mine in China as a research example and used both the theoretical model and discrete element method (DEM) numerical simulation to find the height of the gas-guiding fracture zone and applied the height to drill a long horizontal borehole in the roof of the 6303 working face. Furthermore, the borehole was utilized to deep into the roof for coalbed methane drainage and the results were compared with conventional gas drainage measures from other aspects. The height of the gas-guiding fracture zone was found to be 48.57 m in theoretical model based on the bulk coefficient and the void ratio and to be 51.19 m in the DEM numerical simulation according to the temporal and spatial variation characteristics of porosity. Taking both the results of theoretical analysis and numerical simulation into consideration, we determined that gas-guiding fracture zone is 49.88 m high and applied it to drill a long horizontal borehole deep into the roof in the 6303 working face field. Compared with conventional gas drainage measures, we found that the long horizontal borehole has the high stability, high efficiency and strong adaptability for methane drainage.

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