scholarly journals Similarities between strong rock bursts with fault-slip mechanism and induced earthquakes

2021 ◽  
Vol 861 (5) ◽  
pp. 052044
Author(s):  
A S Batugin
Keyword(s):  
Fault Slip ◽  
Induced Earthquakes ◽  
Slip Mechanism ◽  
Rock Bursts ◽  
Strong Rock

General features of strong rock bursts and induced earthquakes in critical-stress areas of the Earth’s crust

2021 ◽  
pp. 22-27
Author(s):  
A. S. Batugin ◽  
Keyword(s):  
Critical Stress ◽  
Earth’S Crust ◽  
Induced Earthquakes ◽  
Rock Bursts ◽  
Geodynamic Processes ◽  
Hierarchical Block Structure ◽  
Strong Rock ◽  
Earth's Crust ◽  
Impact Zones ◽  
Mining Regions

The problem connected with rock bursts and induced earthquakes is yet one of the most critical in the mining regions. The manmade nature of disastrous earthquakes induced in the areas of the heaviest impact on the subsoil is being widely discussed. The main argument against the manmade genesis of such earthquakes is their great depths and high energies. The general features of the induced earthquakes are considered. The displacement directions of the walls of large tectonic faults during such events are analyzed. The sizes of focal zones are estimated and related with sizes of geodynamcially active blocks in the Earth’s crust. The location of hypocenters of geodynamic events relative to the manmade impact zones is studied. The found homogeny of strong rock bursts and induced earthquakes is explained by the interaction of local and regional (global) geodynamic processes. The critical stress state of the upper Earth’s crust having hierarchical block structure is considered as the basis of such interaction. When focal zones of rock bursts and induced earthquakes have sizes of hundreds of meters or a few kilometers, the initiation zones of such events reaches many kilometers in size, is commensurable with the Earth’s crust blocks and is larger than the mining impact zone. Therefore, displacements along large faults are the part of a tectonic process, i.e. displacement directions along large faults during strong rock bursts are correlated with the regional stress field.

scholarly journals Mining Stress Distribution and Fault-Slip Behavior: A Case Study of Fault-Influenced Longwall Coal Mining

Energies ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2494 ◽  
Author(s):  
Peng Kong ◽  
Lishuai Jiang ◽  
Jiaming Shu ◽  
Lu Wang
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Coal Seam ◽  
Normal Stress ◽  
Longwall Mining ◽  
Hanging Wall ◽  
Fault Slip ◽  
Lagrangian Analysis ◽  
Slip Mechanism ◽  
3 Dimensional

It is well accepted that faults have significant impacts on the safe production of underground coal mines; however, the fault-slip mechanism during longwall mining through a fault still needs to be investigated. In this study, the distribution of microseismicity events during panel mining through a fault is analyzed, and 3-dimensional fast Lagrangian analysis of continua was used to study the mining stress distribution and fault-slip behavior under the two different mining directions, i.e., mining the panel through the fault from the footwall, or mining the panel through the fault from the hanging wall. The research shows that when the panel is mined through the fault from the footwall, the shear displacement of the fault is significantly greater than those created by mining the panel through the fault from the hanging wall. Under the two mining directions, the variation behaviors of the normal stress and shear stress on the fault are quite different, and fault-slips mainly occur in fault areas where the normal stress decreases. When mining the panel through the fault from the footwall, the slip mainly occurs in the coal-seam roof fault, and when mining the panel through the fault from the hanging wall, the slip mainly occurs in the coal-seam floor fault. According to the variations in the normal stress and shear stress of the fault during the period of mining the panel through the fault, the mechanism of the fault slip can be divided into three categories. 1: Normal stress and shear stress decrease abruptly, but the reduction of the normal stress is greater than that of the shear stress. 2: The normal stress is continuously reduced, the shear strength of the fault is decreased, and the shear stress is suddenly increased. 3: Both the normal stress and the shear stress increase, but the increase in the shear stress is greater than that of the normal stress. These research results can provide a reference for the layout of panels and for fault-slip-induced disaster prevention under similar conditions.

scholarly journals A Numerical Investigation of the Hazardous Injection Area of Induced Earthquake during Hydraulic Fracturing

2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Zhiyong Niu ◽  
Shiquan Wang ◽  
Hongrui Ma ◽  
Songbao Feng ◽  
Hengjie Luan ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Geothermal Energy ◽  
Hanging Wall ◽  
Injection Pressure ◽  
Geothermal Field ◽  
Fault Slip ◽  
Rock Fracturing ◽  
Induced Earthquakes ◽  
Induced Earthquake ◽  
The Stability

Hot dry rock (HDR) geothermal energy has many advantages, such as being renewable, clean, widely distributed, and without time and weather limitations. Hydraulic fracturing is usually needed for the exploitation of HDR geothermal energy. It has many hidden faults in the reservoir/caprock sequences. Injecting fluid into underground formations during hydraulic fracturing often induces fault slip and leads to earthquakes. Therefore, to well understand the induced fault slip and earthquakes is important for the applications and development of HDR geothermal exploitation. In this study, we investigated the hazardous injection area of the induced earthquakes during hydraulic fracturing. The study was based on a hydraulic fracturing test in Qiabuqia geothermal field in China. According to the field, a fault-surrounding rock-fracturing region system was developed to study the influences of fluid injection on the stability of the specific fault. A total of 60 hydraulic fracturing regions and 180 numerical experiments were designed. The results revealed that the hazardous injection regions that threaten the fault’s stability were near to the fault and concentrated on the following four areas: (a) above the top of the fault in underlying strata; (b) above the top of the hanging wall of the fault in underlying strata; (c) near to the fault planes in both footwall and hanging wall; (d) at the bottom of the footwall of the fault in underlying strata. The hazardous injection area can be controlled effectively by adjusting the injection pressure.

Post-limit properties and correlation with spontaneous fracture dynamics in rocks

2021 ◽  
pp. 13-19
Author(s):  
B. G. Tarasov ◽  
Keyword(s):  
Initial Conditions ◽  
Deep Level ◽  
Rock Fracture ◽  
Class Iii ◽  
Induced Earthquakes ◽  
Stick Slip ◽  
Slip Mechanism ◽  
Brittle Rocks ◽  
Spontaneous Fracture ◽  
Fracture Dynamics

Spontaneous rock fracture can only occur beyond the ultimate stress limit. The currently known three classes of the post-limit rock behavior (class I, class II and class III) feature different dynamics of spontaneous fracture at the same initial conditions. This article discusses post-limit properties and fracture energy balances in these classes of the post-limit rock behavior. The author focuses on least-studied class III typical of seismic depths. It is shown that class III features the lowest destructive energy and the highest elastic energy release, which creates conditions for the uppermost dynamics of spontaneous fracture. Class III rocks are most instable at seismic depths and are most susceptible to initiation of both natural and induced earthquakes and deep-level rock bursts. Ideas on the spontaneous fracture conditions in strong and brittle rocks were developed concurrently with techniques of studying post-limit properties of rocks. The techniques were improved with sequential discovery of the three classes of the behavior of rocks having post-limit properties illustrated in this article. The bar chart of typical change in the frequency of earthquakes and aftershocks with depth is explained by the action of the fan mechanism. The depth of rocks having minimal fan strength conforms with the depth of the maximum seismic activity. At shallow depths outside the influence zone of the fan mechanism, the stick–slip mechanism is active. The study was supported by the Ministry of Science and Higher Education of the Russian Federation, Grant No. RFMEFI58418X0034.

scholarly journals Multiparameter Monitoring and Prevention of Fault-Slip Rock Burst

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Shan-chao Hu ◽  
Yun-liang Tan ◽  
Jian-guo Ning ◽  
Wei-Yao Guo ◽  
Xue-sheng Liu
Keyword(s):  
Rock Burst ◽  
Early Warning ◽  
Large Diameter ◽  
Early Warning Systems ◽  
Fault Slip ◽  
Pressure Relief ◽  
Stick Slip ◽  
Research Results ◽  
Rock Bursts ◽  
Induced Stress

Fault-slip rock burst is one type of the tectonic rock burst during mining. A detailed understanding of the precursory information of fault-slip rock burst and implementation of monitoring and early warning systems, as well as pressure relief measures, are essential to safety production in deep mines. This paper first establishes a mechanical model of stick-slip instability in fault-slip rock bursts and then reveals the failure characteristics of the instability. Then, change rule of mining-induced stress and microseismic signals before the occurrence of fault-slip rock burst are proposed, and multiparameter integrated early warning methods including mining-induced stress and energy are established. Finally, pressure relief methods targeting large-diameter boreholes and coal seam infusion are presented in accordance with the occurrence mechanism of fault-slip rock burst. The research results have been successfully applied in working faces 2310 of the Suncun Coal Mine, and the safety of the mine has been enhanced. These research results improve the theory of fault-slip rock burst mechanisms and provide the basis for prediction and forecasting, as well as pressure relief, of fault-slip rock bursts.

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