Roof Strata Research Articles

Research and application of hydraulic fracturing axial roof cutting technology for gently inclined hard roof based on abrasive jet

In order to explore a new method and mode of gently inclined hard roof treatment, the hydraulic fracturing axial roof cutting technology based on abrasive jet is introduced, and the key technical parameters of abrasive jet axial cutting and fracturing are determined based on indoor experiments and field industrial experiments. Taking the mining of working face under the condition of hard roof in Kuangou Coal Mine as the background, the implementation process and the effect of mining process are tested by means of water pressure gauge, drilling peep and observation well water level observation, mi-croseismic monitoring, support fracture monitoring and coal stress monitoring. The research results show that the key technical parameters of slotting and fracturing are mastered in the axial cutting test of abrasive jet. Wherein the kerf depth is 200 m, the kerf length is 300 m, the kerf pressure is 40–50 mpa, the fracturing pressure is 50–55 mpa, and the fracturing time is 20–30 min. After grooving fracturing, the cracks in the roof strata are effectively generated and expanded, which destroys the integrity of the roof, and the fracturing radius is 10–20 m. During the mining period, compared with the tradi-tional blasting technology, the concentrated area of microseismic events was shifted from 80 m in front of the working face to 130 m after the combined treatment of abrasive jet axial roof cutting and blasting, and the microseismic energy release was mainly small energy events. After the application of abrasive jet axial roof cutting and scour prevention technology in hard roof, the periodic weighting step is obviously reduced, the influence range of mining stress and stress concentration coefficient are obviously reduced, the activity intensity and dynamic load effect of surrounding rock are obviously weakened. The research results provide a basis for effective prevention and control of rockburst disasters under the condition of hard roof.

Research on high‐pressure abrasive water jet slotting and pressure relief technology for hard rock roof

AbstractTo solve the problem of severe rock pressure near coal mining face tunnels, a high‐pressure abrasive water jet slotting and roof breaking pressure relief technology is proposed. First, the laneway deformation mechanism and the process of hard rock slotting using high‐pressure abrasive water jets under long‐distance cantilever conditions are analyzed, and the crack initiation conditions of roof strata are obtained. Second, slotting tests under different slotting pressures, nozzle diameters, abrasive particle sizes and slotting times were carried out, and the slotting parameters of a high‐pressure abrasive water jet on a typical roof rock were obtained. Finally, industrial application was carried out in the 81,403 working face of Huayang No.1 Mine. After the hydraulic roof slotting measures were implemented in the test area, the maximum axial force of the anchor cable was reduced to 67 kN, which was 35.5% lower than that of the comparison. The average stress of the coal seam was 15 MPa, which was approximately 25% lower than that of the comparison. The deformation of the tunnel in the experimental area was significantly controlled, with an average movement of 30.0% toward the roof and floor of the tunnel and an average movement of 23.2% toward the two sides of the tunnel. Compared with the movement in the comparison section, the movement toward the roof and floor of the laneway was 42.3% lower, and the movement toward the two sides was 38.2% lower. The industrial application results show that high‐pressure abrasive water jet roof slotting and pressure relief technology can cut off the stress transmission path between the roof rock on both sides, effectively improve the stress state of the surrounding rock of the laneway, reduce the deformation of the roof, floor and two sides of the working face in the later stage of the mining laneway.

Model test of extreme deformation and failure mechanism of automatically formed roadway under thick-hard roof

Automatically formed roadways (AFR) are highly susceptible to extreme deformation and damage under thick-hard roof geological conditions. Taking the thick-hard roof of the Yushuquan coal mine as a case study, this paper mainly studies the extreme deformation, failure mechanism, and control technology of the AFR. First of all, through on-site monitoring, the maximum vertical convergence rate of the AFR in thick-hard roof reaches 44.8 mm/d. The failure of the AFR mainly focuses on the roof sinking, coal rib rupture, and deformation of gangue prevention structure. Then, a model test was employed to analyze the deformation characteristics of the AFR, including the roadway roof, roadway floor, solid coal rib, and gangue rib. Furthermore, the failure mechanism of the AFR in thick-hard roof is explored. The model test shows that the rotation and subsidence of the roadway roof strata are the main factors causing the AFR damage. In turn, the subsidence of the roadway roof strata is controlled by the movement and distribution characteristics of the hard rock blocks within the cutting range. Eventually, cooperative control technology was proposed, including increasing the gangue volume in the goaf and increasing the coal rib strength to control the extreme deformation of the AFR in thick-hard roof conditions. Field engineering application demonstrates that the deformation of AFR surrounding rock is effectively controlled under thick-hard roof. The research findings can serve as a valuable reference for the prevention and control of the stability of AFR under complex geological conditions.

Study on Critical Width of Semi-Coal Rock Roadway of Shallow-Buried Thin Coal Seam Based on Coal Side Self-Stabilization

In the context of a shallow-buried thin coal seam, the surrounding rock deformation in the semi-coal rock roadway is comparatively small, resulting in self-stabilization of the two sides of the roadway without the need for support when the roadway is below a critical width. This study focuses on the transportation roadway of the 2107 working face in the Anzhe Coal Mine, employing a combination of laboratory tests, field tests, theoretical analyses, and numerical simulations. A mechanical model for the layered roof of the semi-coal rock roadway in a shallow-buried thin coal seam is developed, along with a calculation formula for determining the critical width of such roadways. The study also initially examines the correlation between the critical width and factors such as the tensile strength of the roof, the buried depth of the roadway, and the thickness of the immediate roof strata under conditions where the coal sides of the roadway are self-stabilizing. The results showed the following. (1) The calculation formula has good applicability for typical shallow-buried mine roadways in the Niuwu mining area and shallow-buried semi-coal rock roadways with coal thickness below 0.7 m under similar geological conditions. The critical width is related to the tensile strength of the roof, the buried depth of the roadway, and the thickness of the immediate roof strata. The degree of influence is determined by the thickness of the immediate roof strata > the tensile strength of the roof > the buried depth of the roadway. Among these, the tensile strength of the roof, the thickness of the immediate roof strata, and the critical width are basically in a positive exponentially increasing relationship, and the buried depth of the roadway and the critical width are basically in a negative exponentially decreasing relationship. (2) The on-site measurement of the loose circle on both sides of the roadway revealed that the rock mass loose circle had a thickness of 0.2 m, while the coal loose circle had a thickness ranging from 0.6 m to 0.7 m, aligning closely with the results obtained from theoretical calculations. The thickness of the coal loose circle on both sides served as the basis for determining the critical width of the semi-coal rock roadway in the shallow-buried thin coal seam. The calculated critical width of the roadway was 2.9 m, whereas the actual width measured was 2.4 m. Consequently, the two sides of the roadway are deemed capable of self-stabilization in the unsupported state. (3) Following the optimization of the support scheme, engineering analysis indicates that the roof and floor exhibit a maximum convergence of 46.3 mm, while the two sides show a maximum convergence of 18.4 mm. It is observed that the surrounding rock of the roadway satisfies the safety requirements for production. This study can provide theoretical support and a scientific basis for the stability discrimination of two sides and surrounding rock control of semi-coal rock roadways in shallow-buried thin coal seams under similar conditions.

Failure characteristics of thick hard roof stratum under hydraulic pre-splitting and its application in a coal mine, Dongsheng mining area

Failure characteristics of thick hard roof stratum under hydraulic pre-splitting and its application in a coal mine, Dongsheng mining area

Key parameters of gob-side entry retaining by roof cutting in close-distance seam group

During the process of close-distance seam group mining, the coal pillar in the upper coal seam is a stress-concentrated area, which leads to a loss of stability of the roadway during mining of the lower coal seam. This lack of stability introduces great safety hazards to coal mines. To solve the problem of stress concentration of coal pillars, the method of gob-side entry retaining by roof cutting is proposed to remove the coal pillar. In this study, FLAC3D was used to analyze the depth and angle of pre-split blasting. LS-DYNA was used to analyze the spacing of the blasthole. Using the methods of theoretical analysis and numerical simulation, we determined that the optimal depth of the pre-split blasting was 6 m, the optimal angle for pre-split blasting was 15°, and the optimal spacing of the blasthole was 500 mm. A field test was carried out in the 1010201 ventilation roadway of the Yuwang Coal Mine, China. The on-site peeping results showed that when the spacing of the blasthole is 500 mm, connecting cracks can form under the action of blasting stress. After the working surface is mined, the roof strata could collapse and fill the gob over time when the depth and angle of the pre-split blasting are 6 m and 15°, respectively.

Influence of Mineral Composition on Rock Mechanics Properties and Brittleness Evaluation of Surrounding Rocks in Soft Coal Seams

Influence of Mineral Composition on Rock Mechanics Properties and Brittleness Evaluation of Surrounding Rocks in Soft Coal Seams

Research on the causal mechanism of a rock burst accident in a longwall roadway and its prevention measures

Based on the disaster characteristics and the geo-conditions at the scene, in this study, the occurrence mechanism of a serious rock burst accident that occurred in the Tangshan Coal Mine, China, was analysed. Ground stress measurements showed that the mine is in a high ground stress area dominated by horizontal tectonic stress around 33 MPa. Laboratory testing revealed that the coal was a hard seam of 8.3 MPa over bedded by a thick and hard roof stratum with uniaxial compressive strength of 66 MPa. The calculation results indicated that the accident occurred in the roof rebounding area. It is proposed that the hard roof and the hard coal seam formed a seesaw structure around the working face. The vertical pressure relief caused the rib coal mass to lose its clamping forces from the roof and floor and rush into the roadway, resulting in a rock burst accident. Based on the causality mechanism of the rock burst disaster developed in this study, pertinent coal bump prevention measures have been undertaken in practice. Large-diameter boreholes were drilled to eliminate the pivot effect of the seam. Roof blasting was undertaken to prevent the roof from forming a seesaw plank. To summarize, a new causality mechanism for rock burst in coal mines under hard roof and hard seam geo-conditions was developed.

Research Development and Critical Problems Existing in Strata Movement and Its Control

Under the guidance of green mining and scientific mining ideas, strata movement and its control have achieved a series of research developments in China. Based on the summary of research achievements related to strata movement characteristics, the influences on mining activity and surface environment, and the utilizing and controlling methods, critical problems that need to be solved are identified for a study on strata movement and its control. Mining activities will cause the redistribution of mining stress. The overlying strata incurs deformation, breaking, and movement under this mining stress. During this period, energy accumulation and release will occur in the roof strata, and the initiation and expansion of overburden fractures will occur. This demonstrates the impact of mining activities on underground safety and the ground environment. Thus, strata movement characteristics in longwall faces should be emphasized in the future. At present, the rock movement is still in the stage of qualitative description. Monitoring the movement of overlying strata in the stope and making predictions according to the monitoring results play a great role in ensuring the safety of mining production. Furthermore, system stiffness theory and intelligent control techniques for overburden strata should be developed.

Theoretical Basis and Technical Method of Permeability Enhancement of Tectonic Coal Seam by High Intensity Acoustic Wave In Situ

Tectonic coal seams are characterized by soft, low permeability and high gas outburst. The traditional gas control method is the intensive drilling and extraction in this seam, which is not only large in engineering quantity, high in cost, difficult to form holes and low in extraction efficiency, but also easy to induce coal and gas outburst, which is a difficult problem for global coal mine gas control. To solve this difficult problem, the controllable shockwave equipment developed by the author’s team and successfully applied in the practice of permeability enhancement of coal seam, combined with the principles of shock vibration sound wave generation and shock wave attenuation and evolution in the rock stratum, a new idea of loading a controllable shock wave in the roof and floor of coal seam is proposed. The shock wave first attenuates and evolves into a high-strength sound wave in the roof and floor rock stratum, and then enters and loads into the coal seam to achieve the purpose of increasing permeability without damaging the physical properties of the tectonic coal seam and facilitating the opening of the original fractures. According to the new technical ideas, the implementation scheme and key parameters of the gas pre-extraction models in tectonic coal seam are designed, including the penetration drilling, roof and floor horizontal holes, shield tunneling and the high-strength acoustic wave of the working face, which provides a new technical approach to solve the problem of high efficiency and low cost gas extraction in the tectonic coal seam.

Asymmetrical distribution of roof microseismicity and its application to roof control of a deep longwall panel

Deep mining is widely carried out across the world. Due to large cover depth, both stress magnitude and fracture development are greatly enlarged, increasing the complexity in mining conditions. Correspondingly, a series of ground control problems emerge in deep coal mines, such as face collapsing, roof falling and support jamming. This study mainly focusses on the variation in roof activity along face length direction, which helps to strengthen roof control of a deep longwall panel. Geological radar detection reveals that the development of mining-induced fractures present an increasing trend from the maingate to tailgate side, implying the variation in roof activity along face length direction. Microseismic (MS) monitoring is moreover conducted, with which both spatial distribution and dynamic evolution of MS events in roof strata are thoroughly analyzed. Due to stronger influence provided by fault structures, the concentration of MS number mainly occurs to the tailgate section. Thus, roof microseismicity is brisker in the referred section, accounting for 63.7% of the total events. The sensitivity of MS energy to fault structures is weaker than that of MS number. Energy concentration can be observed in the whole panel width. In the maingate section, the energy proportion reaches 44.1%, indicating stronger roof microseismicity. Such asymmetrical distribution in roof microseismicity is sensitive to fault activation, fracture influence and mining disturbance. The location of fault structures, spatial variation in fracture parameters and the difference in stress rotation characteristics contribute to asymmetrical distribution in roof microseismicity on two sides of the target panel. Based on MS characteristics, a coordinative movement method is innovatively proposed for hydraulic supports, which weakens cyclic disturbance of support movement on roof strata at the face area. The method is proved to be effective by the improvement in roof stability and mining efficiency.

A new insight of water inrush mode and coal (rock) pillars setting in near-fault mining under high confined water

Mining-induced fault water inrush has become the most critical disaster-causing factor of mine water disasters in mines in recent years. In near-fault coal mining, the water flowing fractures caused by mining in the roof (floor) of a coal seam may connect the fault fracture zone and induce fault water inrush. The most effective way to prevent fault water damage is to set waterproof coal (rock) pillars. However, the width of coal (rock) pillars was mainly calculated by empirical formulas in the past, and the calculated results were quite different from the actual ones. This paper determines the safe water blocking zone and inelastic zone by introducing mine pressure and confined water pressure (“double pressure”). Then, the range of the mine pressure failure zone is determined by comprehensively considering the floor strata's peak stress propagation direction and the roof strata's collapse propagation angle. The hydraulic model of roof (floor) water inrush in near-fault coal mining under “double pressure” control is established. A new method for calculating the width of waterproof coal (rock) pillars in coal mining on large normal faults is derived by considering the nature of the fault, mine pressure, and confined water pressure. Finally, the research results are applied to the width calculation of waterproof coal (rock) pillars in the Jiaxiang branch fault of Xinhe Coal Mine, and the FLAC3D software is used to conduct numerical simulation and check the calculation of the pillars' width of coal (rock) under the influence of mining. The formation mode of fracture channels in the roof (floor) of a coal seam in near-fault mining is proposed, and the failure theory of surrounding rock in near-fault mining is perfected. The research results will effectively guide the layout of the near-fault working face on the Ordovician limestone confined aquifer in North China Coalfield, liberate a large number of resources threatened by fault water damage, and provide a theoretical basis for the prevention and control of mine fault water damage under other similar geological conditions.

Experimental investigation into damage and failure process of coal-rock composite structures with different roof lithologies under mining-induced stress loading

Coal burst is essentially a destructive manifestation of stratigraphic structure. Although the failure mechanism of the structure has been extensively studied using experimental and numerical methods, few studies have considered the critical role of the mining stress environment and the roof stratum in structural instabilities. In this paper, uniaxial static-cyclic loading tests were performed on a series of composite specimens with different roof lithologies. The objective is to investigate the damage and failure process of composite specimens under mining-induced stress conditions, particularly the mechanical response and damage evolution to coal and rock under cyclic disturbance. The results indicate that the mechanical behaviour of the composite specimen is closely related to the mechanical properties and interactions of the components, and the coal and rock show various characteristics of deformation and damage under cyclic loading with increasing static stress. A dynamic elastic strain energy (DESE) index based on the energy conversion of the specimen was proposed, which is more consistent with the trend of the P-wave velocity and thereby can well reflect the damage state of the specimen. The variation in the acoustic emission (AE) energy rate implies that the composite specimens experience progressive damage before failure, along with AE events spatially clustered in the failure plane of the weak roof and near the upper and lower boundaries of the coal body. The failure pattern of the composite specimen changes with increasing roof strength from initial structural instability due to tensile splitting or shear failure of the roof to the ejection of localized coal chips near the interface, which is attributed to the lateral tensile stresses on the coal near the interface caused by the mechanical difference and frictional constraint under cyclic unloading.

Numerical simulation of solid-fluid-thermal coupling in the heating stage of in-situ injection of supercritical water for hydrogen production from coal

ABSTRACT Hydrogen production via in-situ injection of supercritical water into underground coal seams is a new coal conversion technology. This study proposes a solid-fluid-heat coupling mathematical model for the heating stage of the injection of supercritical water into the coal seam and studies the evolution law of the temperature distribution, pore pressure, solid deformation, and other aspects of the coal seam, the roof strata, and the floor strata using numerical simulation. The results showed that after the injection of supercritical water, the temperature and flow rate near the injection well increased rapidly, gradually decreased, and expanded outwards. Subsequently, the temperature rose to about 1050°C and the flow rate decreased slightly near the injection well. The flow rate near the production well showed a negative exponential growth pattern six months prior; however, the temperature and flow rate remained constant after six months. The temperature around 700 m from the injection well changed little over one year. A large compression deformation zone may form above the injection well and the maximum uplift displacement of the deformation zone within one year can reach 8 mm. The extreme value of vertical stress was located in the surrounding rock layer closest to the coal seam and its maximum value can be 17 MPa.

The Floor Heave Mechanism and Control Technology of Gob-Side Entry Retaining of Soft Rock Floor

Extensive soft-rock floor heave in gob-side entry retaining considerably restricts the efficient and sustainable production of the mine. The mechanical capacities of roadway roof and floor strata are discussed through laboratory tests by taking the N2301 fully caving surface auxiliary transport gate road of the Ancient City Coal Mine in the Lu’an Mining Area of Shanxi Province as an engineering background. The stress distribution law of gob-side entry in mining the working surface was explored based on numerical simulation. After that, the mechanical mechanism of floor heave was studied through theoretical analysis. High lead abutment pressure and horizontal stress were superimposed in front of the working surface to cause soft-rock floor heave. The bulk weight of the high overburden was unevenly transmitted to the two sides because of the roof cantilever structure of entry retaining in the rear of the working face. The roadway floor produced an asymmetric sliding force, which caused the occurrence of floor heave. The control technology of floor heave combining the pressure relief of floor blasting and roof cutting was proposed taking account of the mechanism of floor heave. Then, the stress environment of the surrounding rock was improved by the deep hole blasting of the floor. Gob-side roof cutting was used to reduce impact of the bulk weight of the overburden on the surrounding rock deformation of the roadway. A test was conducted after verifying the control effect of blasting pressure relief on roadway floor heave through a similar simulation. Field tests indicated that the maximum floor heave was 168 mm at 250 m in the rear of the working surface, and floor heave was controlled. This study offers a more scientifically sound theoretical reference for controlling floor heave in gob-side entry retaining, which can significantly advance the sustainable development of gob-side entry retaining technology in coal mining.

Determination of suitable distance between methane drainage stations in Tabas mechanized coal mine (Iran) based on theoretical calculations and field investigation

A large amount of gas is emitted during underground mining processes, so mining productivity decreases and safety risks increase. Efficient methane drainage from the coal seam and surrounding rocks in underground mines not only improves safety but also leads to higher productivity. Methane drainage must be performed when the ventilation air cannot dilute the methane emissions in the mine to a level below the allowed limits. The cross-measure borehole method is one of the methane drainage methods that involves drilling boreholes from the tailgate roadway to an un-stressed zone in the roof or floor stratum of a mined seam. This is the main method used in Tabas coal mine N 1. One of the effective parameters in this method is the distance between methane drainage stations, which has a direct effect on the length of boreholes required for drainage. This study was based on the measurement of ventilation air methane by methane sensors and anemometers placed at the longwall panel as well as measuring the amount of methane drainage. Moreover, in this study, the obtained and analyzed data were used to determine the suitable distance between methane drainage stations based on the cross-measure borehole method. In a field test, three borehole arrangements with different station distances in Panel E4 of Tabas coal mine N 1 were investigated. Then, the amounts of gas drained from these arrangements were compared with each other. The highest methane drainage efficiency was achieved for distances in the range of 9-12 m between methane drainage stations.

Prototype of Instrumented Rock Bolt for Continuous Monitoring of Roof Fall Hazard in Deep Underground Mines

Roof falls are currently one of the most dangerous threats associated with underground mining at great depth. Every occurrence of such an event poses a significant risk to the mining crew and disturbs the continuity of the mining process, which clearly affects the economy of the exploitation process. The development of a reliable monitoring system may significantly reduce the impact of eventual roof failure and will have a positive effect on the sustainability of the extraction process. Within this research study, a prototype of an instrumented rock bolt developed for continuous stress measurement is presented. The procedure of a 4-groove multilevel instrumented rock bolt is described and the calibration process is shown. Then, preliminary results of long-term in situ monitoring are presented. Based on the continuous monitoring of stress distribution within immediate roof strata, it was concluded that the developed instrumented rock bolt provides reliable results and is a very useful device, ensuring the possibility of early warning for miners about increasing roof fall risk.

Failure Mechanism of Anti-Inclined Karst Slope Induced by Underground Multiseam Mining

There occurred a lot of catastrophic landslides in Southwest China karst areas in recent years. This study numerically simulated the failure process of Pusa landslide by distinct element method (UDEC). The Voronoi diagram algorithm was used to discretize the rock blocks in the upper part of the mining area, and the erosion in sliding source area caused by heavy rainfall was simulated by increasing the block density and reducing the joint strength. Results obtained using UDEC matched the failure process recorded by UAV, and the subsidence of monitoring points on the slope surface was well coincident with the InSAR results. The DEM results are as follows: firstly, under the action of underground coal mining, the overlying strata of the mountain deform toward the goaf and the deformation of the stratum increase significantly with the caving of the roof stratum; and the deep karst fissures in the overlying stratum have an important influence on the deformation of the mountain; the upper strata form a subsidence zone along the fissures, expanding the range of tensile fissures. Secondly, due to the excavation and unloading of the rock masses at the leading edge of the sliding area, the extrusion deformation occurs to the outside of the slope, resulting in the critical instability of sliding area. Finally, with the strength decreasing of rock masses and structural planes by heavy rainfall, the stability of the mountain continues to decrease until the sliding area collapses.

Theoretical research on reasonable shield support capacity in close-multiple coal seams with the coordinated mining: A case study of Qianjiaying coal mine.

In order to assess the rationality of the rated shield support capacity (RSSC) experienced selection and guide the reasonable RSSC selection for the subsequent working faces of each coal seam, the coupling relationship between shield and roof strata was revealed during each coal seams mining. According to whether the fractured rock blocks generated by the main roof are articulated and whether the upper coal seam has been mined and influenced on the lower coal seam, two roof structure mechanical models of the rock blocks generated by the thick main roof and two calculation methods of a given load on the rock blocks are proposed. In addition, a selection method of roof structure model for maximum shield support capacity (MSSC) of close-multiple coal seams with the coordinated mining is put forward. Three roof structures to calculate the MSSC are established. Based on a case study of close-multiple coal seams with the coordinated mining in the Qianjiaying coal mine, the MSSC is calculated and analyzed in each coal seam combined with roof structure characteristics description, theoretical analysis, and field measurement. No.7, No.12-1, and No.5 coal seams mining are applicable to a voussoir beam balanced structure. No.8 coal seam mining is applicable to a balanced structure with a given load of loose body. No.9 coal seam mining is applicable to a voussoir beam balanced structure with a given load of loose body. Through the calculation, the MSSC of No.7, No.8, No.12-1, No.9, and No.5 coal seam is 3948.55kN, 4018.32kN, 4101.63kN, 3560.03kN, and 4015.30kN, respectively. And the RSSC suggested selection of each coal seam is 4500kN, 4300kN, 4300kN, 4000kN, and 4300kN, respectively. By field measurement, the RSSC experienced selection of each coal seam in the Qianjiaying coal mine is unreasonable with low support load utilization. However, after adopting the RSSC suggested selection in each coal seam, the support load utilization increased by 29.07%, 9.6%, 8.57%, 15.33%, and 11.39%.

Mechanism and Numerical Simulation of Vertical Fracture Propagation in Composite Coal Rock

Vertical fracture propagation mechanism is important to understand the effect of hydraulic fracturing on the roof of outburst coal seams. In this paper, the differences in physical parameters and in situ stress between an outburst coal seam and its roof strata were compared, and influencing factors of roof-fracturing fractures connecting coal seams were vertically analyzed. The impact of different fracturing strata and injection rates on fracture propagation was studied by numerical models. Results show that the horizontal principal stress of an outburst coal seam is less than that of roof strata, and the fracture length of roof fracturing is larger than that of an outburst coal seam. Roof-fracturing fracture of an outburst coal seam has the material conditions to communicate downward with the coal seam. The downward propagation height of roof-fracturing fracture is positively correlated with the minimum horizontal stress difference between an outburst coal seam and its roof strata. Soft coal fracturing cannot form a long fracture dominated by tensile failure, so the coal seam can be communicated by transforming the roof strata of soft coal to form vertical fractures. The injection rate affects the failure location, fracture width, and fracture-propagation path of the numerical model. Construction parameters should be reasonably designed in accordance with the physical parameters of coal and rock, construction displacement, and in situ stress. These research results can provide a theoretical basis and data support for the design, and optimization of construction parameters of roof fracturing in outburst coal seams.