scholarly journals Study on the spectrum characteristics of rock burst and the stability of the surrounding rock of a roadway in mines under dynamic load

2021 ◽  
Author(s):  
Yang yushun ◽  
Sijiang Wei ◽  
Kui Li
Keyword(s):  
Rock Burst ◽  
Dynamic Load ◽  
Strength Criterion ◽  
Surrounding Rock ◽  
Wave Frequency ◽  
Energy Density Distribution ◽  
Tunnel Section ◽  
Vibration Wave ◽  
Seam Mining ◽  
The Impact

Abstract This study analyzes the impact pressure in the Yuejin and Qianqiu coal mines in the Yimei mine area, and shows that rock bursts may be caused by damage to the overburden gravel strata caused by coal seam mining and unreasonable mining layout. Rock burst microseismic signals from the Yuejin and Qianqiu mines show that the duration of the vibration waveform is greater than 0.06 s. The fast Fourier transform shows that the low-frequency component of the rock burst accounts for a large proportion, with the main frequency being concentrated in the range between 5 and 50 Hz. A numerical simulation scheme was designed, and the extended D-P strength criterion was adopted to select the distributed load of a sinusoidal pulse in the load waveform as the dynamic load. The plastic strain energy density distribution is used to measure the tendency of the surrounding rock to impact the roadway. By changing the shock position, wave frequency, disturbance intensity, tunnel section shape, and buried depth, it is seen that when a (vibration wave amplitude) = 2.0 m/s2, f (vibration wave frequency) = 40 Hz, H (roadway buried depth) = 1000 m, θ (the angle between the impact position of the seismic wave and the center of the roadway) = 180°, and the roadway section is horseshoe-shaped, the tendency of the surrounding rock to impact the roadway is higher. Under the same conditions, the impact tendency of the surrounding rock on the roadway is the smallest and second smallest when the roadway is circular and straight-wall arched, respectively.

scholarly journals Research on Deformation and Failure Evolution of Deep Rock Burst Drivage Roadway Surrounding Rock under Dynamic Disturbance

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Xinggang Xu ◽  
Hao Feng ◽  
Lishuai Jiang ◽  
Tao Guo ◽  
Xingyu Wu ◽  
...  
Keyword(s):  
Rock Burst ◽  
Dynamic Load ◽  
Surrounding Rock ◽  
Rock Deformation ◽  
Dynamic Disturbance ◽  
Deformation And Failure ◽  
Plastic Damage ◽  
Failure Evolution ◽  
Deep Rock ◽  
Surrounding Rock Deformation

In order to explore the deformation and failure evolution characteristics of the surrounding rock during the connection process of the deep rock burst drivage roadway under the dynamic load disturbance, and based on this, the catastrophe mechanism of the roadway is analyzed, taking the rock burst accident of Longyun Coal Industry in Shandong Province on October 20, 2018, as the engineering background. FLAC3D was used to study the distribution evolution law of displacement, plastic zone, and stress field in the whole process of “Roadway Drivage-Deformation and Failure-Instability and Disaster” in the surrounding rock of deep roadway. The research results show that under the conditions of high stress and dynamic load disturbance, the surrounding rock deformation and failure are significant during the connection of the thick-top-coal roadway in deep, the roof is the most, the two ribs are the second, and the roadway top-coal is in an “inverted trapezoid” sag pattern. When the length of the bolts is limited or the anchoring force of the cables is not enough to effectively restrain the roof, the impact of dynamic disturbance on the plastic damage of the roof is greater than that of the two ribs and the floor, and the plastic damage of the coal seam roof affecting the surrounding rock deformation of the roadway drivage played a leading role.

scholarly journals Study on Impact Tendency of Coal and Rock Mass Based on Different Stress Paths

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Chengliang Zhang ◽  
Danyong Ye ◽  
Ping Yang ◽  
Shunchuan Wu ◽  
Chao Wang
Keyword(s):  
Rock Mass ◽  
Rock Burst ◽  
Shear Failure ◽  
Mechanical Test ◽  
Specimen Size ◽  
Necessary Condition ◽  
Energy Index ◽  
Bending Energy ◽  
Seam Mining ◽  
The Impact

With the increased mining depth, the dynamic disaster of rock burst in coal mines has become increasingly prominent, and the impact tendency of coal and rock mass in deep coal seam mining is a necessary condition for the occurrence of rock burst and an important index to measure the failure of coal and rock mass. Laboratory tests and numerical tests were used to study the impact tendency of coal and roof strata, including the deformation characteristics, failure characteristics, and bending energy index of the coal and rock mass of different sizes, the failure law and energy evolution characteristics of tlhe coal and rock mass under the same size, and the unloading characteristics of the coal and rock mass under the same size and different confining pressures. The results are shown as follows: (1) The rock roof was determined to have a weak impact tendency through the mechanical test. (2) With the increased size, the microcracks in the rock samples increased correspondingly, and the increased meso-defect leading to the increased heterogeneity was an essential reason for the size effect. The strength of the rock mass decreased with the increased specimen size. The larger the specimen size was, the lower the bending energy index was. (3) Triaxial loading and unloading were tested for the same size under different surrounding rocks. Under the same loading conditions, with the increased confining pressure, the strength and bending energy index of rock mass increased correspondingly, and the failure of rock mass transformed from tensile to shear failure. The failure form and strength characteristic of rock under the unloading condition are different from those under the loading condition. The failure degree was intense, with a high bending energy index. Compared with the loading situation, the impact tendency caused by unloading was higher, and the dynamic impact disaster was more likely to occur.

scholarly journals Research on Stress Distribution Characteristics for Uniquely Shaped Roadway with Hard Roof in Steeply Inclined Coal Seam and Support Technology of Reducing Vibration Impact

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Junhui Zhang ◽  
Hui Chen ◽  
Xiuzhi Shi ◽  
Weiming Guan ◽  
Xiaolong Sun
Keyword(s):  
Stress Distribution ◽  
Coal Seam ◽  
Rock Burst ◽  
Coal Mine ◽  
Surrounding Rock ◽  
Additional Stress ◽  
The Road ◽  
Hard Roof ◽  
Original Rock ◽  
The Impact

This paper presents a comprehensive study of the stress distribution and stability analysis of a uniquely shaped roadway having a steeply dipping hard roof. The coal seam and its roof have a certain impact tendency, which is the internal condition of rock burst. The syncline tectonic stress causes the original rock stress to reach a higher level. The large amount of coal produced in the coal mine and the large movement range of the upper strata cause the huge mining additional stress around the stope. The impact load caused by “cantilever beam” fracture of hard roof can induce and strengthen rock burst. Its engineering geological setting encompasses the mining process and surrounding rock conditions of No. 6 Coal Seam in the 2130 coal mine of Xinjiang. Numerical simulations with theoretical analysis and field measurements investigated a proposed new truss combined support scheme for implementation. A comparison was made of the differences in the state parameters of the road under the new and old support conditions. The application of the new combined support technology changed the form of the stress distribution around the road. Apart from the displacements of the two coal sidewalls, the new support system notably reduced the displacement of roof and floor by 67.8% and 83.6%, respectively. After the implementation of the new support scheme, the frequency of the original rock burst in the working face is greatly reduced, the surrounding rock control and field application effects also remained good, and personnel and equipment safety and production plan have a good guarantee.

scholarly journals Study on Failure Characteristics and Rock Burst Mechanism of Roadway Roof under Cyclic Dynamic Load

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Chunmei Zheng ◽  
Jiayan Zheng ◽  
Xiaojuan Peng ◽  
Lei Zhou
Keyword(s):  
Rock Mass ◽  
Rock Burst ◽  
Dynamic Load ◽  
Control Function ◽  
Surrounding Rock ◽  
Strong Impact ◽  
Large Area ◽  
Rock Destruction ◽  
Supporting Structure ◽  
Cyclic Dynamic

Rock burst is a catastrophic phenomenon that often occurs in underground rock mass engineering. In order to reveal the essence of rock burst of a hard roof in the process of roadway excavation, the particle discrete element method is used to establish a roadway model and simulate the disturbance of harmonic dynamic load based on the analysis of a rock burst accident in a deep mine. The crack field, stress field, displacement field, and kinetic energy of roadway surrounding rock disturbed by cyclic dynamic load were analyzed, and the disaster mechanism of roadway impacting roof instability was discussed. The results show that, compared with the roadway support structure under static load that can give full play to its control function of surrounding rock, the roadway surrounding rock will collapse and lose stability in a large area under the roof cyclic dynamic load, and the ordinary supporting structure cannot give full play to its control function of surrounding rock, resulting in the surrounding rock destruction and supporting structure failure. In addition, the essence of rock burst in a hard thick roof is due to the instantaneous superposition of static stress and dynamic load, leading to the instantaneous instability and collapse of roadway roof in a large area. The research is of great significance to further understand the deformation and failure mechanism of roadway surrounding rock under strong impact load, to guide the safe production and prevent the occurrence of rock burst hazard in underground rock mass engineering.

scholarly journals Dynamic Response Mechanism of Impact Instability Induced by Dynamic Load Disturbance to Surrounding Rock in High Static Loading Roadway

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 971
Author(s):  
Jiazhuo Li ◽  
Penghui Guo ◽  
Heng Cui ◽  
Shikang Song ◽  
Wentao Zhao ◽  
...  
Keyword(s):  
Rock Mass ◽  
Plastic Zone ◽  
Rock Burst ◽  
Dynamic Load ◽  
Static Loading ◽  
Energy Criterion ◽  
Mining Area ◽  
Surrounding Rock ◽  
Load Disturbance ◽  
Distortion Energy

Deep high static loading roadway is extremely prone to rock burst under dynamic load disturbance. The “force-energy criterion” for the failure of surrounding rock in such deep roadways and the “energy criterion” for the rock burst was established by considering the stress and energy evolution characteristics of rock burst under this circumstance. Under the engineering background of the main roadway in No.1 mining area of Gaojiapu Coal Mine in Binchang Mining Area, Shaanxi Province, China, the partial stress field and distortion energy field of surrounding rock in the main roadway and the spatial-temporal evolution laws under dynamic load disturbance were simulated and analyzed by using a built-in dynamic module of FLAC3D. Results show that after the dynamic load disturbance, the partial stress and distortion energy are concentrated in the shallow part at two walls of the roadway in the early phase. With the continuous propagation of dynamic load stress wave, the partial stress and distortion energy are transferred to the deep part. The sudden high-energy release occurred in the peak zone of partial stress, leading to the plastic failure of coal and rock mass. Subsequently, the distortion energy was fully accumulated in the original plastic zone and transferred from shallow surrounding rocks to the deep surrounding rocks in the roadway, where the partial stress and distortion energy of coal and rock mass reached the yield conditions. Thus, the original plastic zone was sharply expanded, thereby forming a new plastic zone. The coal and rock mass experienced an approximately static failure when no residual energy (ΔU) was found in it. When ΔU > 0, the rock mass experienced dynamic failure, and ΔU was mainly the volume transformation energy, which is approximately one-half of the total elastic strain energy. ΔU was transformed into the initial kinetic energy of broken coal and rock mass. Thus, the coal and rock mass are burst out. In severe cases, this condition was manifested by the rock burst in the main roadway. An optimization scheme of prevention and control measures for rock burst was proposed on the basis of the above conclusions. The microseismic activity laws before and after the unloading were compared, and a good effect was achieved. The research results can lay a theoretical foundation for predicting and preventing rock bursts in coal mines by actively regulating the disaster-pregnant environment and mitigating the disaster-inducing conditions.

Numerical solutions for strain-softening surrounding rock under three-dimensional principal stress condition

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sheng Yu-ming ◽  
Li Chao ◽  
Xia Ming-yao ◽  
Zou Jin-feng
Keyword(s):  
Finite Element ◽  
Principal Stress ◽  
Stress Condition ◽  
Strain Softening ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Strength Criterion ◽  
Surrounding Rock ◽  
Flow Rule ◽  
Finite Element Software

Abstract In this study, elastoplastic model for the surrounding rock of axisymmetric circular tunnel is investigated under three-dimensional (3D) principal stress states. Novel numerical solutions for strain-softening surrounding rock were first proposed based on the modified 3D Hoek–Brown criterion and the associated flow rule. Under a 3D axisymmetric coordinate system, the distributions for stresses and displacement can be effectively determined on the basis of the redeveloped stress increment approach. The modified 3D Hoek–Brown strength criterion is also embedded into finite element software to characterize the yielding state of surrounding rock based on the modified yield surface and stress renewal algorithm. The Euler implicit constitutive integral algorithm and the consistent tangent stiffness matrix are reconstructed in terms of the 3D Hoek–Brown strength criterion. Therefore, the numerical solutions and finite element method (FEM) models for the deep buried tunnel under 3D principal stress condition are presented, so that the stability analysis of surrounding rock can be conducted in a direct and convenient way. The reliability of the proposed solutions was verified by comparison of the principal stresses obtained by the developed numerical approach and FEM model. From a practical point of view, the proposed approach can also be applied for the determination of ground response curve of the tunnel, which shows a satisfying accuracy compared with the measuring data.

scholarly journals The Impact of the Coexistence of Methane Hazard and Rock-Bursts on the Safety of Works in Underground Hard Coal Mines

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 128
Author(s):  
Justyna Swolkień ◽  
Nikodem Szlązak
Keyword(s):  
Rock Burst ◽  
Methane Concentration ◽  
High Energy ◽  
Hard Coal ◽  
Coal Seams ◽  
Safety Level ◽  
Methane Drainage ◽  
Innovative Methods ◽  
Hard Coal Mining ◽  
The Impact

Several natural threats characterize hard coal mining in Poland. The coexistence of methane and rock-burst hazards lowers the safety level during exploration. The most dangerous are high-energy bumps, which might cause rock-burst. Additionally, created during exploitation, safety pillars, which protect openings, might be the reason for the formation of so-called gas traps. In this part, rock mass is usually not disturbed and methane in seams that form the safety pillars is not dangerous as long as they remain intact. Nevertheless, during a rock-burst, a sudden methane outflow can occur. Preventing the existing hazards increases mining costs, and employing inadequate measures threatens the employees’ lives and limbs. Using two longwalls as examples, the authors discuss the consequences of the two natural hazards’ coexistence. In the area of longwall H-4 in seam 409/4, a rock-burst caused a release of approximately 545,000 cubic meters of methane into the excavations, which tripled methane concentration compared to the values from the period preceding the burst. In the second longwall (IV in seam 703/1), a bump was followed by a rock-burst, which reduced the amount of air flowing through the excavation by 30 percent compared to the airflow before, and methane release rose by 60 percent. The analyses presented in this article justify that research is needed to create and implement innovative methods of methane drainage from coal seams to capture methane more effectively at the stage of mining.

Reasonable Entry Layout of Lower Seam in Multi-Seam Mining Based on Numerical Simulation

2013 ◽  
Vol 295-298 ◽  
pp. 2980-2984
Author(s):  
Xiang Qian Wang ◽  
Da Fa Yin ◽  
Zhao Ning Gao ◽  
Qi Feng Zhao
Keyword(s):  
Numerical Simulation ◽  
Stress Distribution ◽  
Coal Seam ◽  
Coal Mine ◽  
Abutment Pressure ◽  
Surrounding Rock ◽  
Geological Conditions ◽  
Seam Mining

Based on the geological conditions of 6# coal seam and 8# coal seam in Xieqiao Coal Mine, to determine reasonable entry layout of lower seam in multi-seam mining, alternate internal entry layout, alternate exterior entry layout and overlapping entry layout were put forward and simulated by FLAC3D. Then stress distribution and displacement characteristics of surrounding rock were analyzed in the three ways of entry layout, leading to the conclusion that alternate internal entry layout is a better choice for multi-seam mining, for which makes the entry located in stress reduce zone and reduces the influence of abutment pressure of upper coal seam mining to a certain extent,. And the mining practice of Xieqiao Coal Mine tested the results, which will offer a beneficial reference for entry layout with similar geological conditions in multi-seam mining.

The Specific Characteristics of Shock and Blast Impacts on Construction Sites

2021 ◽  
pp. 81-88
Author(s):  
A.A. Komarov ◽  
Keyword(s):  
Dynamic Load ◽  
Static Load ◽  
Dynamic Loads ◽  
Potential Hazard ◽  
Construction Sites ◽  
Static Loads ◽  
Equivalent Static Loads ◽  
Plane Crash ◽  
Nuclear Plants ◽  
The Impact

The practices of hazardous and unique facilities’ construction imply that specific attention is paid to the issues of safety. Threats associated with crash impacts caused by moving cars or planes are considered. To ensure safety of these construction sites it is required to know the potential dynamic loads and their destructive capacity. This article considers the methodology of reducing dynamic loads associated with impacts caused by moving collapsing solids and blast loads to equivalent static loads. It is demonstrated that practically used methods of reduction of dynamic loads to static loads are based in schematization only of the positive phase of a dynamic load in a triangle forms are not always correct and true. The historical roots of this approach which is not correct nowadays are shown; such approach considered a detonation explosion as a source of dynamic load, including TNT and even a nuclear weapon. Application of the existing practices of reduction of dynamic load to static load for accidental explosions in the atmosphere that occur in deflagration mode with a significant vacuumization phase may cause crucial distortion of predicted loads for the construction sites. This circumstance may become a matter of specific importance at calculations of potential hazard of impacts and explosions in unique units — for instance, in the nuclear plants. The article considers a situation with a plane crash, the building structure load parameters generated at the impact caused by a plane impact and the following deflagration explosion of fuel vapors are determined.

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