scholarly journals Directional Hydraulic Fracturing (DHF) of the Roof, as an Element of Rock Burst Prevention in the Light of Underground Observations and Numerical Modelling

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 562
Author(s):  
Marek Jendryś ◽  
Andrzej Hadam ◽  
Mateusz Ćwiękała
Keyword(s):  
Rock Mass ◽  
Hydraulic Fracturing ◽  
Coal Mining ◽  
Rock Burst ◽  
Coal Mine ◽  
Seismic Activity ◽  
Black Coal ◽  
Directional Hydraulic Fracturing ◽  
Before And After ◽  
The Face

The following article analyzes the effectiveness of directional hydraulic fracturing (DHF) as a method of rock burst prevention, used in black coal mining with a longwall system. In order to define changes in seismic activity due to DHF at the “Rydułtowy” Black Coal Mine (Upper Silesia, Poland), observations were made regarding the seismic activity of the rock mass during coal mining with a longwall system using roof layers collapse. The seismic activity was recorded in the area of the longwall itself, where, on a part of the runway, the rock mass was expanded before the face of the wall by interrupting the continuity of the rock layers using DHF. The following article presents measurements in the form of the number and the shock energy in the area of the observed longwall, which took place before and after the use of DHF. The second part of the article unveils the results of numerical modeling using the discrete element method, allowing to track the formation of goafs for the variant that does not take DHF into consideration, as well as with modeled fractures tracing DHF carried out in accordance with the technology used at “Rydułtowy” coal mine.

scholarly journals Controlling Mechanism of Rock Burst by CO2 Fracturing Blasting Based on Rock Burst System

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Tianwei Lan ◽  
Chaojun Fan ◽  
Jun Han ◽  
Hongwei Zhang ◽  
Jiawei Sun
Keyword(s):  
Coal Mining ◽  
Rock Burst ◽  
Coal Mine ◽  
Prevention And Control ◽  
Stress Measurement ◽  
Tectonic Stress ◽  
Microseismic Monitoring ◽  
Time Space ◽  
Controlling Mechanism ◽  
And Control

Rock burst induced by mining is one of the most serious dynamic disasters in the process of coal mining. The mechanism of a rock burst is similar to that of a natural earthquake. It is difficult to accurately predict the “time, space, and strength” of rock burst, but the possibility of rock burst can be predicted based on the results of microseismic monitoring. In this paper, the rock burst system under the tectonic stress field is established based on the practice of coal mining and the result of mine ground crustal stress measurement. According to the magnitude of microseismic monitoring, the amount of the energy and spatial position of the rock burst are determined. Based on the theory of explosion mechanics, aiming at the prevention and control of rock burst in the coal mine, the technique of liquid CO2 fracturing blasting is put forward. By the experiment of blasting mechanics, the blasting parameters are determined, and the controlling mechanism of rock burst of liquid CO2 fracturing blasting is revealed. The application of liquid CO2 fissure blasting technology in the prevention and control of rock burst in Jixian Coal Mine shows that CO2 fracturing blasting reduces the stress concentration of the rock burst system and transfers energy to the deeper part, and there is no open fire in the blasting. It is a new, safe, and efficient method to prevent and control rock burst, which can be applied widely.

Field investigation into directional hydraulic fracturing for hard roof in Tashan Coal Mine

2013 ◽  
Vol 19 (2) ◽  
pp. 153-159 ◽  
Author(s):  
Bing-Xiang Huang ◽  
Bin Yu ◽  
Feng Feng ◽  
Zhao Li ◽  
You-Zhuang Wang ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Coal Mine ◽  
Field Investigation ◽  
Directional Hydraulic Fracturing ◽  
Hard Roof

scholarly journals Development status and Prospect of directional hydraulic fracturing technology for coal mine roof

2020 ◽  
Vol 194 ◽  
pp. 01043
Author(s):  
LI Liangwei
Keyword(s):  
Hydraulic Fracturing ◽  
Coal Mine ◽  
Large Scale ◽  
Evaluation Method ◽  
Field Application ◽  
Control Technology ◽  
Control Methods ◽  
Directional Hydraulic Fracturing ◽  
Hard Roof ◽  
Extension Mechanism

Aiming at the harm and control methods of thick and hard roof in coal mine, the paper firstly analyzes the advanced control methods of thick and hard roof, such as directional shaped charge blasting roof control technology, hydraulic fracturing roof control technology, abrasive water jet directional cutting roof technology, large-scale special roof cutting machine, etc Control hole fracturing, transverse slotting fracturing and longitudinal slotting fracturing are compared and analyzed; finally, the shortcomings of current research are analyzed. According to the current research results, the analysis shows that: the method of controlling roof by blasting in the future will be limited, while the method of hydraulic fracturing, especially directional hydraulic fracturing, has obvious advantages; the longitudinal slotting fracturing has the best control over fractures in the directional hydraulic fracturing technology; the guiding mechanism and fracture extension mechanism of longitudinal slotting hydraulic fracturing in thick and hard roof need to be further studied; lack of field application research and corresponding equipment development, lack of field effect evaluation method after longitudinal slotting fracturing.

scholarly journals Determination of fracture location of double-sided directional fracturing pressure relief for hard roof of large upper goaf-side coal pillars

2019 ◽  
Vol 38 (1) ◽  
pp. 111-136 ◽  
Author(s):  
Jiangwei Liu ◽  
Changyou Liu ◽  
Xuehua Li
Keyword(s):  
Hydraulic Fracturing ◽  
Coal Mine ◽  
High Stress ◽  
Coal Pillar ◽  
Local Stress ◽  
Pressure Relief ◽  
Directional Hydraulic Fracturing ◽  
Fracture Location ◽  
Hard Roof ◽  
Coal Pillars

After mining the upper-goaf side, large coal pillars and part of hard roof exposed above the pillars remain. The hard roof can significantly deform the roadway by transferring high stress through coal pillars to the roadway. This paper reports the use of hydraulic fracturing technology to cut the hard roof on both sides (i.e. the broken roof slides to the goaf) to relieve the pressure. The position of the roof fracture is the key to controlling the pressure relief. The bearing characteristics of the large coal pillars and hard roof are analyzed to establish a mechanical model of the broken-roof sliding instability after directional fracturing and determine the width of the coal pillars that can collapse under maximum overburden load on coal pillars as a reasonable hydraulic fracturing position. The results show that the distance from the mine gateway to the fracture location increases with increasing hard-roof length, coal pillar depth, coal pillar thickness (mining height), and goaf width. In addition, the distance to the mine gateway decreases with increasing coal strength, support of the coal pillar by the anchor rod, cohesive force, and internal friction angle of the coal–rock interface. Engineering tests were applied in coal roadway 5107 of coal seam 5# of the Baidong Coal Mine of the Datong Coal Mine Group. Given the site conditions, a reasonable fracturing length of 8.8 m was obtained. Next, directional hydraulic fracturing was implemented. The comparison of the roof deformation before and after fracturing suggests that this method reduces the local stress concentration in coal pillars, which allows the surrounding rock deformation in roadway 5107 to be controlled.

scholarly journals Directional hydraulic fracturing technology for prefabricated longitudinal guide seams in a coal mine tight sandstone roof

2021 ◽  
pp. 014459872110289
Author(s):  
Liangwei Li ◽  
Wenbin Wu
Keyword(s):  
Acoustic Emission ◽  
Hydraulic Fracturing ◽  
Coal Mine ◽  
Tight Sandstone ◽  
Directional Hydraulic Fracturing ◽  
Working Face ◽  
Secondary Cracks ◽  
Initiation Pressure ◽  
Multi Level ◽  
Fracturing Experiments

Triaxial hydraulic fracturing experiments were used to study the initiation pressure variation and acoustic emission characteristics of different guide seams sizes during roof hydraulic fracturing. Numerical simulations were used to explore the feasibility of multiple boreholes with prefabricated guide seams. An experiment of hydraulic fracturing on a pillar-free working face was also carried out in a coal mine. The results show that the specimens with guide seams reduced the initiation pressure, with the number of acoustic emission events and initiation pressure being inversely proportional to the size of the guide seams. Specimens without guide seams were deflected by stress and produced multi-level cracks, while the specimens with guide seams did not produce large secondary cracks and deflection. When the stress difference was small, three holes penetrated but not under large stress differences. The hydraulic fracturing technology of prefabricated longitudinal guide seams was tested in the Ningtiaota Coal Mine, and the auxiliary transportation roadway of S1201 working face was successfully retained for reuse in adjacent working faces.

scholarly journals Analysis of seismic tomography data for definition of hydraulic fracturing parameters in underground coal mines

2021 ◽  
Vol 315 ◽  
pp. 01021
Author(s):  
Gennadii Rout ◽  
Sergey Sokolov ◽  
Evgeniy Utkaev ◽  
Kolmakova Anastasiya
Keyword(s):  
Rock Mass ◽  
Hydraulic Fracturing ◽  
Seismic Exploration ◽  
Reliable Estimate ◽  
Underground Coal Mines ◽  
Before And After ◽  
Coal Rock ◽  
Definition Of ◽  
Rock Mass Fracturing ◽  
Excavation Site

The article analyzes the issue of reliable estimate of the unloading extent and the variation order of coal-rock massif geomechanical characteristics as a result of hydraulic fracturing undertaken from mine workings. For this purpose it is proposed to use the fracturing value of the studied rock mass. In case the possibility of comparison with geological and actual data doesn’t exist, the option of using the rock mass classification based on the estimated value of geophysical index that specifies rock mass fracturing is considered. To address the issue, a geophysical survey of the active roof at the excavation site in the operating coal mine was implemented with a method of a seismic radioscopy before and after hydraulic fracturing. According to the results of seismic exploration, a massif unloading degree and an extent of roof fracturing has been determined.

scholarly journals Pressure Relief Mechanism of Directional Hydraulic Fracturing for Gob-Side Entry Retaining and Its Application

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Zhang Xiao ◽  
Kang Hongpu
Keyword(s):  
Hydraulic Fracturing ◽  
Soft Rock ◽  
Theoretical Research ◽  
Left Endpoint ◽  
Pressure Relief ◽  
Directional Hydraulic Fracturing ◽  
Working Face ◽  
Cantilever Length ◽  
The Face ◽  
Triangular Block

In order to make clear the pressure relief mechanism and application effect of directional hydraulic fracturing for gob-side entry retaining, the directional hydraulic fracturing was carried out by 400 m in haulage gateway remaining along the goaf in 50108 working face of Hejiata Coal Mine. Taking this as the engineering background, a mechanical model of roof cutting was established and the pressure relief mechanism was clarified. The theoretical research shows that it is the moments of gravity FG of the curved triangular roof plate at the face end, the pressure q of the overlying soft rock, and the transverse force TCB in the “voussoir beam” structure to the left endpoint of the triangular block, that is, M F G , M q , and M T CB , which determines the roadside supporting resistance. Hydraulic fracturing can reduce the lateral cantilever length of the basic roof, thus greatly reducing the values of M F G , M T CB , and M q , and significantly reduce the roadside supporting resistance. The field test shows that the directional hydraulic fracturing technology can effectively improve the stress environment of the face end and reduce the deformation of the roadway, and it has a good application effect on the gob-side entry retaining.

scholarly journals Planning of ore shotpileselective mining by the geoinformation technologies in the condition of the Ferrexpo Eristovo Mining

2021 ◽  
Vol 64 ◽  
pp. 18-29
Author(s):  
B Sobko ◽  
O Lozhnikov ◽  
G Barabitskaya
Keyword(s):  
Rock Mass ◽  
Iron Ore ◽  
Economic Effect ◽  
Planning System ◽  
Low Grade ◽  
Geometric Constructions ◽  
Actual Surface ◽  
Selective Mining ◽  
Before And After ◽  
The Face

Purpose. Develop method for predicting the displacement of ore contours in the shotpile after the explosion to planning the ore raw materials selective mining at the development of iron ore quarries. Research methodology. Actual surface measurements were used to determine the loosening coefficient for individual sections of rock mass collapse. The analytical methods were used to calculate the planes of the face sections before and after the explosion. Determination of the predicted position of the contours of iron ore in the shotpile was performed by the method of graphical selection. The results. It is established that the loosening coefficient of the rock is variable in individual parts of the ore block and can be used to determine the predicted position of the ore contour. The main difference of proposed predicting methods consist in establish the expected position of contact of rocks and geological markers in the field, which will allow in the regular mode to control the development of the face by a pit geologist. Scientific novelty. The dependence of the predicted position of the ore contour in the rock mass shotpile on the method of actual survey of the pit surface "before" and "after" the explosion when performing geometric constructions is established. Determined that the proposed method of prediction allow to minimize costs in the form of insignificant organizational changes at planning observance of qualitative indicators, reduction of risks and dangers at geological works is provided, and also efficiency of works on short-term planning system in rock mass shotpile increases. Practical value. A method for determining the position of the ore contour in the rock mass shotpile has been developed. The possibility of using the predicted position of the ore contour for planning the selective mining of ore shotpile has been established. The expected economic effect of the proposed solutions is achieved by reducing the cost on processing rocks and low-grade ore when they fall on the crusher due to erroneous classification during the selective development of ore deposits.

scholarly journals Stress Distribution in a Coal Seam before and after Bump Initiation

10.14311/260 ◽  
2001 ◽  
Vol 41 (4-5) ◽  
Author(s):  
J. Vacek
Keyword(s):  
Rock Mass ◽  
Stress Distribution ◽  
Coal Seam ◽  
Mathematical Modelling ◽  
Rock Burst ◽  
Open Space ◽  
Longwall Mining ◽  
Time Dependent ◽  
Deep Tunnel ◽  
Before And After

This paper deals with to the behaviour of open rock that occurs, for example, during longwall mining in coal mines, in deep tunnel, or shaft excavation.Longwall instability leads to extrusion of rock mass into an open space. This effect is mostly referred to as a bump, or a rock burst. For bumps to occur, the rock has to possess certain particular rock burst properties leading to accumulation of energy and the potential to release this energy. Such materials may be brittle, or the bumps may arise at the interfacial zones of two parts of the rock, that have principally different material properties.The solution is based on experimental and mathematical modelling. These two methods have to allow the problem to be studied on the basis of three presumptions: – the solution must be time dependent – the solution must allow the creation of crack in the rock mass – the solution must allow an extrusion of rock into an open space (bump effect)

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