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.

scholarly journals Variation of Rock Mass Pressure during Tunnel Construction in Phyllite Stratum

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Jianxun Chen ◽  
Yanbin Luo ◽  
Yao Li ◽  
Lijun Chen ◽  
Chuanwu Wang ◽  
...  
Keyword(s):  
Rock Mass ◽  
Bearing Capacity ◽  
Logistic Function ◽  
Field Monitoring ◽  
Surrounding Rock ◽  
Tunnel Construction ◽  
Time And Space ◽  
Monitoring Method ◽  
Supporting Structure ◽  
The Face

In this paper, the field monitoring method is used to study the variation of rock mass pressure during the construction of a tunnel in phyllite stratum, and three functions are used to fit and analyze the variation of rock mass pressure with deformation, excavation time, and space. The results show the following (1) When the deformation increases significantly, the rock mass pressure decreases firstly and then increases. This is caused by the insufficient bearing capacity of the rock mass in the arch foot of the supporting structure after the excavation of the upper bench, which leads to a settlement of supporting structure and surrounding rock. (2) Compared with other kinds of fitting functions, the logistic function can better characterize the variation of the pressure of surrounding rock with deformation, excavation time, and distance from the face. This paper provides a reliable reference for the design and construction of the tunnel in phyllite stratum. The logistic function can be used to present and predict the change of rock mass pressure with deformation, excavation time, and space in similar rock mass conditions.

scholarly journals Preliminary Discussion on Comprehensive Research Method for Rock Burst in Coal Mine Based on Newton’s Second Law

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Jianping Zuo ◽  
Hongqiang Song ◽  
Yunqian Jiang ◽  
Shankun Zhao ◽  
Meilu Yu ◽  
...  
Keyword(s):  
Rock Mass ◽  
Rock Burst ◽  
Research Method ◽  
Surrounding Rock ◽  
Research Progress ◽  
Field Energy ◽  
Second Law ◽  
Preliminary Discussion ◽  
Geological Conditions ◽  
Newton's Second Law

Rock burst is one of the major dynamic disasters that directly threaten production safety in coal mines. According to the current research, the occurrence of rock burst can be described by the generalized Newton’s second law with three elements which are research object, force condition, and motion state. These three elements refer to the coal and rock mass in the mining area, concentrated static and dynamic loads, and dynamic instability of surrounding rock, respectively. On this basis, a comprehensive rock burst research method involving the three elements of Newton’s second law was proposed, which especially focuses on the investigation into geological conditions of mining areas. The research procedure of this method specifically includes the detailed exploration of engineering geological bodies, the classification and stability evaluation of surrounding rock, the measurement and inversion of in situ stress, the evolution analysis of mining-induced stress field, energy field, and fracture field, the study of multiscale failure mechanism of coal and rock mass, the establishment of theoretical failure model of coal and rock mass, the real-time monitoring and warning in potentially dangerous areas, and the reasonable prevention and control in key risk zones. As a preliminary discussion, the significant research progress in each aspect mentioned above has been reviewed and the feasible research directions of rock burst are presented in this paper.

scholarly journals Study on Pressure Relief Effect of Rock Mass with Different Borehole Parameters

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Chao Peng ◽  
Wanrong Liu
Keyword(s):  
Acoustic Emission ◽  
Rock Mass ◽  
Rock Burst ◽  
Strength Reduction ◽  
Surrounding Rock ◽  
Reduction Degree ◽  
Occurrence Time ◽  
Pressure Relief ◽  
Research Results ◽  
Relief Effect

Rock burst is one of the disaster accidents that can easily happen in rock cavern engineering. At present, one of the most commonly used methods to control rock burst is borehole pressure relief technology. In this paper, the influence of drilling layout schemes on the pressure relief effect of surrounding rock mass is systematically studied. The research results show that the strength reduction degree, AE evolution characteristics, failure modes of rock samples with different borehole positions, boreholes spacing, boreholes dip angles, and boreholes layout forms are different. The strength reduction degree of rock sample with an inclined arrangement form is the largest, followed by the arrangement form being up three-flower layout or down three-flower layout. Using the inclined layout and three-flower layout can achieve better pressure relief effect of the surrounding rock mass. The research results are beneficial to the rock burst of surrounding rock of the cavern. The acoustic emission can effectively monitor the stability of the surrounding rock of the cavern. However, the threshold value and the occurrence time of the acoustic emission of the cavern instability changed after the cavern surrounding rock is drilled holes. If the borehole is arranged at the surrounding rock mass, the occurrence time of the cavern instability may be advanced.

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 Experimental Study of Blasting Excavation for Large Cross-Section Tunnel in Horizontal Layered Rock Mass

2021 ◽  
Author(s):  
Jie Mei ◽  
Wanzhi Zhang ◽  
Bangshu Xu ◽  
Yongxue Zhu ◽  
Bingkun Wang
Keyword(s):  
Rock Mass ◽  
Cross Section ◽  
Surrounding Rock ◽  
Large Cross Section ◽  
Large Area ◽  
Layered Rock ◽  
Blasting Excavation ◽  
Tunnel Blasting ◽  
Layered Rock Mass ◽  
Upper Face

Abstract The drilling and blasting method is still the main method in mountain tunnel excavation. For large cross-section tunnel in horizontal layered rock mass, tunnel blasting often causes serious overbreak and underbreak. In this study, blasting excavation tests of tunnel upper face were conducted and failure mechanisms of surrounding rocks with weak beddings and joints were analyzed based on the Panlongshan tunnel. Then, the blasthole pattern, the cut mode, a variety of peripheral holes, the charge structure and the maximum single-hole charge were optimized. Compared with the failure characteristics, overbreak and underbreak, and deformations of surrounding rocks before and after optimization, the latter was better in tunnel contour forming and surrounding rock stability. The results show that after optimization, the large-area separation of vault rock mass is solved, the step-like overbreak of spandrel rock mass is reduced and the large-size rock blocks and underbreak are avoided. The maximum linear overbreak of vault, spandrel, and haunch surrounding rocks is decreased by 42.3%, 53.7% and 45.1%, respectively. The underbreak at the bottom of the upper face is reduced from -111.5 to - 16.5 cm. The average overbreak area is decreased by 61.1%. In addition, the displacements after optimization finally converge to the smaller values. The arch crown settlement and the horizontal convergence of haunch are reduced by about 21.6% and 18.3%, respectively. Furthermore, from the completion of blasting excavation to the stabilization of surrounding rock, it takes less time by using the optimized blasting scheme.

scholarly journals Numerical Analysis of the Effect of Heterogeneity on Underground Roadway Stability under Dynamic Loads

2021 ◽  
Vol 2021 ◽  
pp. 1-23
Author(s):  
Tao Guo ◽  
Hao Feng ◽  
Zequan Sun ◽  
Yang Zhao ◽  
Xingyu Wu ◽  
...  
Keyword(s):  
Rock Mass ◽  
Dynamic Load ◽  
Surrounding Rock ◽  
Dynamic Loads ◽  
Loading Conditions ◽  
Deformation And Failure ◽  
Average Value ◽  
Roadway Stability ◽  
Rock Mass Failure ◽  
The Stability

With the increasing depth of coal mining and expanding mining scale, the rocks surrounding deep roadways are in a complex mechanical condition of frequent dynamic disturbance. The heterogeneity has an important influence on rock mass failure under dynamic loads. Therefore, it is necessary to study the deformation and failure of heterogeneous roadway under dynamic load. In this paper, the effect of heterogeneity on stability of roadway under static and different dynamic loads is studied. According to the results, the effect of rock mass heterogeneity on the deformation and failure of surrounding rock varies with different degrees of heterogeneity. Under static loading conditions, the stability of roadway is negatively correlated with the degree of heterogeneity of the rock mass. Under dynamic loading conditions, the change of heterogeneity degree has significant influence on the stability of surrounding rock. With the increase in dynamic load strength, the change in variation difference in the average value of roof sag, stress distribution, and plastic zone caused by variations in heterogeneity will increase. This study contributes to understanding the deformation and failure characteristics of heterogeneous roadways under dynamic loads and can be used to analyze heterogeneous roadways under dynamic loads.

Surrounding Rock Stability Analysis and Rock Burst Prediction of Underground Cavity in High In Situ Stress

2012 ◽  
Vol 594-597 ◽  
pp. 1174-1181
Author(s):  
Hai Yan Zang ◽  
Guang Di Wang
Keyword(s):  
Rock Mass ◽  
Rock Burst ◽  
Plastic Region ◽  
Damage Model ◽  
Average Energy ◽  
Stress Transfer ◽  
Surrounding Rock ◽  
Large Section ◽  
Diversion Tunnel

Based on Sidoroff isotropic elastic damage model, the damage deterioration constitutive equation was constructed for rigid and brittle rock mass. The excavation numerical simulation of a diversion tunnel with large section in Jinping hydro station was carried on. The displacement and stress evolution was analyzed considering stress transfer and dissipation of the tunnel surrounding rock mass. The stability evaluation parameters were put forward such as stress relaxation coefficient of surrounding rock mass, safety factor, the scale and distribution of plastic region of surrounding rock mass. The rock burst predication index was presented in viewpoint of energy such as sub-range statistic average energy release rate and sub-range statistic failure volume. The excavation methods for the diversion tunnel with large section were evaluated with multi criteria and the guideline for large section cavity in high in-situ stress was summarized.

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.

Influence exerted by underground excavation shape and by effective stresses on the formation of a tensile strain zone at a depth greater than 1 km

2020 ◽  
pp. 67-75
Author(s):  
Van Min Nguyen ◽  
V. A. Eremenko ◽  
M. A. Sukhorukova ◽  
S. S. Shermatova
Keyword(s):  
Rock Mass ◽  
Cross Sections ◽  
Tensile Strain ◽  
Rock Fracture ◽  
Strain Analysis ◽  
Surrounding Rock ◽  
Underground Excavation ◽  
Secondary Stress ◽  
Principal Stresses ◽  
Mining Depth

The article presents the studies into the secondary stress field formed in surrounding rock mass around underground excavations of different cross-sections and the variants of principal stresses at a mining depth greater than 1 km. The stress-strain analysis of surrounding rock mass around development headings was performed in Map3D environment. The obtained results of the quantitative analysis are currently used in adjustment of the model over the whole period of heading and support of operating mine openings. The estimates of the assumed parameters of excavations, as well as the calculations of micro-strains in surrounding rock mass by three scenarios are given. During heading in the test area in granite, dense fracturing and formation of tensile strain zone proceeds from the boundary of e ≥ 350me and is used to determine rough distances from the roof ( H roof) and sidewalls ( H side) of an underground excavation to the 3 boundary e = 350me (probable rock fracture zone). The modeling has determined the structure of secondary stress and strain fields in the conditions of heading operations at great depths.

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