Isolated island working face anti-burst method under thick and hard roof of strong impact pressure coal seam
By drilling and fracturing a pre-set fracturing layer under the condition of thick and hard coal seam roof, the T-shaped long cantilever structure is destroyed, which solves the problem of high risk of rockburst in isolated working faces and improves safety and economy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CCTEG COAL MINING RES INST
- Filing Date
- 2026-03-10
- Publication Date
- 2026-06-05
AI Technical Summary
Under conditions of thick, hard roof coal seams prone to rockbursts, isolated working faces are highly susceptible to rockbursts due to their T-shaped long cantilever structure. Traditional depressurization methods cannot effectively alleviate the energy distribution pattern, which can easily lead to rockburst disasters.
By determining a pre-set fracturing layer in the top plate area of the working face to be mined, and setting up boreholes at an upward angle for fracturing, the stability of the T-shaped long cantilever structure is destroyed, the elastic potential energy of the overlying rock layer is pre-fractured, the stress transmission path is cut off, and the compressive strength and elastic modulus of the rock layer are reduced.
It effectively reduces the multi-directional ultra-strong concentrated load on the isolated working face, reduces the dynamic load release intensity when the roof breaks, prevents rock burst disasters, improves coal resource recovery rate and mine safety, and reduces production costs.
Smart Images
Figure CN122148318A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of rockburst prevention and control technology, specifically to a method for preventing rockburst in isolated working faces under conditions of strong rockburst and thick, hard roof. Background Technology
[0002] Many old mining areas in my country (such as Shandong, Henan, Liaoning, and Heilongjiang) have formed a large number of valuable coal resources that are technically "isolated" due to early disorderly mining, multi-seam mining, or unreasonable mining area division. These coal pillars have huge reserves, and their direct and permanent disposal means the waste of tens of millions or even hundreds of millions of tons of resources, seriously shortening the service life of the mines and affecting regional energy supply and economic benefits. Coal seams with strong rockburst have strong energy storage capacity. After the formation of isolated coal pillars, they become the only path for stress transmission. Moreover, the thick and hard overlying rock layers are suspended without collapsing, forming a T-shaped long cantilever structure. The isolated island bears the concentrated load from the overlying rock of the upper and surrounding goaf areas. Its internal stress level can reach several times the original stress. The thick and hard rock layers themselves store huge elastic energy. When they break and become unstable, they will release violent dynamic loads instantly. Therefore, the risk of rockburst is extremely high. Traditional local decompression methods are like "a drop in the ocean" in such a strong stress field. They cannot fundamentally change the energy distribution pattern and are prone to "decompression without relief" or even inducing rockburst. Summary of the Invention
[0003] The present invention aims to at least partially solve one of the technical problems in the related art.
[0004] Therefore, embodiments of the present invention propose a method for preventing rockburst in isolated working faces under conditions of strong rockburst and thick, hard roof, which disrupts the stability of the T-shaped long cantilever structure and pre-fractures the elastic potential energy accumulated in the overlying strata.
[0005] The method for preventing rockburst in an isolated working face under conditions of strong rockburst and thick, hard roof in coal seams, according to embodiments of the present invention, includes:
[0006] The key layers in the top plate area of the working face to be mined that meet the preset thickness range are identified as the preset fracturing layers. The fracturing area of the pre-set fracturing layer is determined by the working face to be mined, and the projection surface of the fracturing area in the direction of gravity covers the working face to be mined. The first borehole is set up at an upward angle from the return airway and transport roadway of the working face to be mined, with the end point of the borehole located at the edge of the area to be fracturing. Fracturing is performed on the pre-set fracturing layer in the area to be fracturing; The compressive strength and elastic modulus of the rock strata before and after fracturing are compared to determine the effect of fracturing.
[0007] The embodiment of the present invention provides a method for preventing rockburst in isolated working faces under conditions of thick, hard roof coal seams under strong rockburst, which disrupts the stability of the T-shaped long cantilever structure and pre-fractures the elastic potential energy accumulated in the overlying strata.
[0008] In some embodiments, the projection surface of the working face to be mined along the gravity direction is located within the pressure zone, and the edge of the projection surface of the working face to be mined along the gravity direction is 5m to 10m away from the edge of the fracturing zone.
[0009] In some embodiments, the angle between the straight line extending from the first borehole and the direction of gravity is 60° to 80°.
[0010] In some embodiments, the radial dimension of the borehole inclined upward from the return airway and transport roadway of the working face to be mined is 30mm~50mm; And / or, there are multiple first boreholes, and the spacing between the multiple first boreholes in the extension direction of the working face to be mined is 5m to 10m.
[0011] In some embodiments, stress sensors are arranged in the coal seam and roof of the working face to be mined to monitor stress changes before and after fracturing.
[0012] In some embodiments, the return airway and transport airway are reinforced with support before the first borehole is drilled.
[0013] In some embodiments, fracturing a pre-defined fracturing layer includes: drilling vertically into the area to be fracturing from the ground, then placing a horizontal wellbore in the area to be fracturing, and finally injecting fracturing fluid to fracture.
[0014] In some embodiments, the compressive strength and elastic modulus of the rock strata before and after fracturing are compared. If the ratios of the compressive strength and elastic modulus of the rock strata before fracturing to those after fracturing are both within a preset range, then the fracturing effect is determined to be satisfactory. If at least one of the ratios of the compressive strength and elastic modulus of the rock strata before fracturing to those after fracturing exceeds a preset range, then the pressure of the injected fracturing fluid is increased within 10m to 20m of the corresponding area.
[0015] In some embodiments, the goaf of the working face is filled.
[0016] In some embodiments, a micro-vibration sensor is installed on the working face for micro-vibration monitoring. Attached Figure Description
[0017] Figure 1 This is a schematic cross-sectional view of the working face to be mined according to an embodiment of the present invention.
[0018] Figure 2This is a cross-sectional view of the working surface after fracturing according to an embodiment of the present invention.
[0019] Figure 3 This is a cross-sectional view of the working face before fracturing according to an embodiment of the present invention.
[0020] Figure 4 This is a schematic flowchart of a method for preventing rockburst in isolated working faces under conditions of thick, hard roof coal seams under strong rockburst conditions, according to an embodiment of the present invention.
[0021] Figure label: 1. Working face to be mined; 2. Surface vertical shaft; 3. Horizontal shaft; 4. Goaf; 5. T-shaped long cantilever structure; 6. Return airway; 7. Transport roadway; 8. Surface; 9. Thick and hard rock strata; 10. First borehole. Detailed Implementation
[0022] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.
[0023] The method for preventing rockburst in an isolated working face under conditions of strong rockburst and thick, hard roof in coal seams, according to embodiments of the present invention, includes: S100: The key layer in the roof area of the working face 1 to be mined, which meets the requirements of being within the hydraulic fracturing range of the distance from the coal seam and meeting the preset thickness range, is determined as the preset fracturing layer. S200: The fracturing area of the preset fracturing layer is determined through the working face 1 to be mined, and the projection surface of the fracturing area in the gravity direction covers the working face 1 to be mined. S300: The first borehole 10 is set up inclined upward from the return airway 6 and the transport roadway 7 of the working face 1 to be mined, and the end point of the borehole is located at the edge of the fracturing area. S400: The fracturing area of the preset fracturing layer is fracturing. S500: The compressive strength and elastic modulus of the rock strata before and after fracturing are compared to determine the effect after fracturing.
[0024] The embodiment of the present invention provides a method for preventing rockburst in isolated working faces under conditions of thick, hard roof coal seams under strong rockburst, which disrupts the stability of the T-shaped long cantilever structure 5 and pre-fractures the elastic potential energy accumulated in the overlying strata.
[0025] Specifically, such as Figures 1 to 4 As shown. In the direction of gravity, due to the limitations of early mining technology, multi-seam mining or unreasonable division of mining areas has resulted in a large number of valuable coal resources that are technically "isolated". Moreover, the thick and hard overlying rock layer 9 is suspended without collapsing, forming a T-shaped long cantilever structure 5, which causes the roof of the working face 1 to be mined to bear pressure, making it easy to form rock bursts during mining.
[0026] Understandably, when multiple layers of rock exist within the overburden of a mining area, the layer that controls all or part of the rock mass movement is called the key layer. The activity of the key layer significantly affects the mine pressure, rock strata movement, and surface subsidence of the entire mining area. Furthermore, microseismic monitoring is used to identify the key layer that plays a dominant role in the occurrence of rockbursts or mine tremors; this is also known as the controlling key layer, the rockburst-controlling rock layer, or the mine tremor-controlling rock layer.
[0027] For example, a rock stratum in the key layer above the remaining coal pillar, whose thickness and hardness are within a certain preset range, can be set as a preset fracturing layer. The preset fracturing layer, corresponding to the area of the remaining coal pillar and the working face 1 to be mined in the vertical direction, is set as the fracturing area. It can be understood that the projection of the fracturing area in the vertical direction, or the gravity direction, covers the working face 1 to be mined, and the projection of the working face 1 in the vertical direction onto the preset fracturing layer is included in the fracturing area. This ensures that the horizontal transmission path of the coal pillar stress to both sides of the working face is blocked. This ensures that the horizontal transmission path of the coal pillar stress to both sides of the working face is blocked after the horizontal well 3 is fracturing. At the same time, before fracturing, boreholes are drilled from the return airway 6 and the transport roadway 7 to the fracturing area. The first borehole 10 extends in the surrounding rock, which can guide the fracturing of the thick and hard rock stratum 9 of the overlying rock layer, so as to minimize the volume or weight of the overlying rock layer on the working face 1 to be mined, or to reduce the gravity force on the working face 1 to be mined, thereby reducing the rockburst.
[0028] Through on-site core sampling tests, the compressive strength and elastic modulus of the rock formation after fracturing were measured. Compared with before fracturing, the compressive strength decreased by 30%-50%, and the elastic modulus decreased by 40%-60%, ensuring a significant reduction in the rock formation's elastic energy storage capacity and reducing the dynamic load release intensity at the time of fracture. Simultaneously, the 30%-50% reduction in compressive strength and 40%-60% reduction in elastic modulus after fracturing directly demonstrates that the rock formation's ability to store elastic energy has been significantly weakened, thereby reducing the dynamic load release intensity at the source of roof fracture.
[0029] This invention, through fracturing, targets the key controlling strata that significantly influence mine pressure in the mining area. It directly disrupts the integrity of the T-shaped long cantilever structure 5 above the isolated coal pillar, changing the traditional operational mode where localized pressure relief can only be performed in the shallow part of the coal seam or roof. This cuts off the horizontal stress path transmitted from the overlying cantilever strata to the isolated coal pillar, fundamentally relieving the multi-directional, high-intensity concentrated loads on the working face 1, reducing the elastic modulus and compressive strength of the key strata. This eliminates the severe dynamic load generated by the sudden fracture of the thick, hard overlying rock strata 9 at the root of energy accumulation, while simultaneously weakening its ability to transmit concentrated static loads to the isolated coal pillar. By targeting the fracturing at the specific thick, hard rock strata 9 that dominates rockburst, engineering waste is avoided, the treatment is more targeted, and costs are reduced. Simultaneously, by drilling upwards from the roadway, a guiding effect is provided for the roof fracture, inducing the rock strata to collapse in segments and in an orderly manner along a predetermined trajectory and step distance. Effectively prevent and control rock burst disasters, improve the overall safety level of mines, increase coal resource recovery rate, reduce production costs, and ensure stable production continuity.
[0030] In some embodiments, the projection plane of the working face 1 to be mined along the gravity direction is located within the pressure zone, and the edge of the projection plane of the working face 1 to be mined along the gravity direction is 5m to 10m away from the edge of the fracturing zone. It can be understood that the projection of the area to be mined or the area to be mined of the working face 1 along the vertical direction onto the pre-fracturing layer is included within the fracturing zone. Alternatively, the pre-fracturing weakened zone of the rock strata is slightly larger than the actual mining range, inducing the roof to fracture orderly along the fracturing boundary first during the mining process. This avoids unexpected and uncontrollable severe fracturing of the rock strata at the boundary due to sudden stress changes when the fracturing zone coincides with the working face boundary, further reducing the risk of inducing rockbursts.
[0031] Specifically, such as Figures 1 to 4 As shown. Due to the strong heterogeneity of the underground rock strata and the energy attenuation during the expansion of the fracture network generated by hydraulic fracturing, the weakening effect at the terminal is often less than that in the core area. By setting a margin of 5m to 10m, it is ensured that the entire outline of the working face 1 to be mined (especially the two ends of the stress concentration area) is located within the core modification zone where the hydraulic fracturing fractures are fully developed. This avoids insufficient weakening of the working face edge area due to the hydraulic fracturing boundary effect, and fundamentally eliminates the dead zone for rockburst prevention.
[0032] In some embodiments, the angle between the straight line extending from the first borehole 10 and the direction of gravity is 60° to 80°.
[0033] Specifically, such as Figures 1 to 4As shown. The first borehole 10 extends from bottom to top, and the borehole climbs from the edge of the working face at a preset angle to ensure that the endpoint of its trajectory is located at the edge of the area to be fracturing, so as to provide a certain degree of guidance for the collapse or deformation of the thick and hard rock layer 9 after fracturing.
[0034] In some embodiments, the radial dimension of the borehole inclined upward from the return airway 6 and transport roadway 7 of the working face to be mined is 30mm~50mm; And / or, there are multiple first boreholes 10, and the spacing between the multiple first boreholes 10 in the extension direction of the working face 1 to be mined is 5m to 10m.
[0035] Specifically, such as Figures 1 to 4 As shown, a borehole diameter of 30mm to 50mm forms an intermittent cavity structure in the thick, hard rock stratum 9. This size creates a stress concentration zone around the borehole, inducing the rock stratum to preferentially fracture along the borehole direction during mining. If the borehole diameter is too small, such as <30mm, it is difficult to form an effective stress disturbance, resulting in a weak guiding effect; if the borehole diameter is too large, such as >50mm, it may cause excessive fracturing around the borehole, which in turn affects the overall controllability of the roof. A borehole diameter of 30mm to 50mm ensures that the drill rod has sufficient rigidity to control the trajectory accuracy, while avoiding the risk of borehole wall collapse caused by an excessively large borehole diameter, ensuring that the guide borehole can stably extend to the preset target position. The spacing of 5m to 10m is an empirical value based on the stress disturbance range of the thick, hard rock stratum 9 (such as sandstone and conglomerate). At this spacing, the stress concentration zones generated by adjacent boreholes can overlap, and the original micro-fractures in the rock mass between the boreholes will preferentially expand and connect along the borehole connection direction under the influence of mining, forming a continuous artificial weak surface. If the spacing is greater than 10m, the rock bridge between boreholes will not be effectively disturbed, and the rock strata may cross the borehole to form a new fracture surface, leading to guidance failure. If the spacing is less than 5m, it will result in engineering waste and may cause excessive fragmentation of the roof. Under the influence of mining and the self-weight of the overlying strata, the thick and hard rock strata 9 will fracture in an orderly manner along this pre-set weak surface grid, avoiding the rockburst induced by random fracture locations and excessive fracture spacing under natural conditions. The borehole diameter of 30mm~50mm avoids excessive rock cutting and improves drilling efficiency. The spacing of 5m~10m minimizes the amount of drilling work while ensuring the guiding effect, achieving a balance between technical effectiveness and economic cost.
[0036] In some embodiments, stress sensors are arranged in the coal seam and roof of the working face 1 to monitor stress changes before and after fracturing.
[0037] Specifically, such as Figures 1 to 4 As shown. After fracturing, the maximum principal stress of the coal body in the working face 1 to be mined should be reduced to 0.4-0.6 times the original stress, and the stress distribution should be uniform with no obvious stress concentration areas, ensuring that the stress transmission channel of the T-shaped long cantilever structure 5 is cut off.
[0038] The maximum principal stress of the coal body should be reduced to 0.4 to 0.6 times the original stress. If the stress reduction is too small (>0.6 times), it indicates that the stress transmission path has not been fully cut off by fracturing. If the stress reduction is too large (<0.4 times), it may mean that the roof is excessively weakened and there is a risk of instability.
[0039] Furthermore, when the stress decreases excessively, such as to less than 0.4 of the original stress, it is necessary to strengthen the roof support, such as through grouting support, anchoring support, or increasing the number of hydraulic single-unit columns in the roadway, in order to support the roof as much as possible.
[0040] In some embodiments, the return airway 6 and transport airway 7 are reinforced before the construction of the first borehole 10. This prevents the construction of the first borehole 10 from affecting the roadways and improves roadway stability.
[0041] In some embodiments, fracturing a pre-defined fracturing layer includes: drilling vertically into the area to be fracturing from the surface 8, then positioning a horizontal well 3 axis in the area to be fracturing, and finally injecting fracturing fluid for fracturing. Using the surface 8 drilling method, first drilling vertically from the surface 8 to the center of the T-shaped long cantilever structure, then adjusting the well axis to align with the direction of the T-shaped long cantilever structure 5 rock formation, and drilling the horizontal well 3 axis into the area to be fracturing. After the well axis is positioned, fracturing fluid is injected from the surface 8 to weaken the T-shaped long cantilever structure 5. High-viscosity fracturing fluid is used, and quartz sand proppant is added to improve fracture propagation.
[0042] In some embodiments, the compressive strength and elastic modulus of the rock strata before and after fracturing are compared. If the ratios of the compressive strength and elastic modulus of the rock strata before fracturing to those after fracturing are both within a preset range, then the fracturing effect is determined to be satisfactory. If at least one of the ratios of the compressive strength and elastic modulus of the rock strata before fracturing to those after fracturing exceeds a preset range, then the pressure of the injected fracturing fluid is increased within 10m to 20m of the corresponding area.
[0043] Specifically, such as Figures 1 to 4 As shown in the figure. Through in-situ core sampling tests, the compressive strength and elastic modulus of the rock formation after fracturing were measured. Compared with before fracturing, the compressive strength decreased by 30%-50%, and the elastic modulus decreased by 40%-60%, ensuring a reduction in the rock formation's elastic energy storage capacity and decreasing the dynamic load release intensity upon fracture. Simultaneously, the 30%-50% decrease in compressive strength and 40%-60% decrease in elastic modulus after fracturing demonstrates that the rock formation's ability to store elastic energy has been significantly weakened, thereby reducing the dynamic load release intensity upon roof fracture at the source.
[0044] If at least one of the ratios of the compressive strength and elastic modulus of the rock strata before fracturing to the compressive strength and elastic modulus of the rock strata after fracturing exceeds a preset range, the pressure of the injected fracturing fluid will be increased within 10m to 20m of the corresponding area to improve the fracturing effect.
[0045] In some embodiments, the goaf 4 of the working face is filled. The filling material directly supports the roof, significantly reducing the exposed span and subsidence of the roof, so as to support the roof as much as possible and improve the stability of the roof support. At the same time, the filling of the goaf 4 provides artificial support for the overlying rock, controls its settlement range, and avoids uncontrollable collapse of the fractured rock layers after fracturing.
[0046] In some embodiments, micro-vibration sensors are installed on the working face for micro-vibration monitoring. By locating the spatial distribution of micro-vibration events on the working face, the fracture location and extent of the thick, rigid roof slab can be dynamically determined. In the description of this invention, it should be understood that the terms "center," "longitudinal," "transverse," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.
[0047] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.
[0048] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0049] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.
[0050] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0051] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.
Claims
1. A method for preventing rockburst in an isolated working face under conditions of strong rockburst and thick, hard roof, characterized in that, include: The key layers in the top plate area of the working face to be mined that meet the preset thickness range are identified as the preset fracturing layers. The fracturing area of the pre-set fracturing layer is determined by the working face to be mined, and the projection surface of the fracturing area in the direction of gravity covers the working face to be mined. The first borehole is set up at an upward angle from the return airway and transport roadway of the working face to be mined, with the end point of the borehole located at the edge of the area to be fracturing. Fracturing is performed on the pre-set fracturing layer in the area to be fracturing; The compressive strength and elastic modulus of the rock strata before and after fracturing are compared to determine the effect of fracturing.
2. The method for preventing rockburst in an isolated working face under conditions of thick, hard roof coal seam in strong rockburst, as described in claim 1, is characterized in that... The projection surface of the working face to be mined along the gravity direction is located within the pressure zone, and the edge of the projection surface of the working face to be mined along the gravity direction is 5m to 10m away from the edge of the fracturing zone.
3. The method for preventing rockburst in an isolated working face under conditions of thick, hard roof coal seam under strong rockburst conditions, as described in claim 1, is characterized in that... The angle between the straight line extending from the first borehole and the direction of gravity is 60°~80°.
4. The method for preventing rockburst in an isolated working face under conditions of thick, hard roof coal seam under strong rockburst conditions, as described in claim 3, is characterized in that... The radial dimension of the boreholes inclined upward from the return airway and transport roadway of the working face to be mined is 30mm~50mm; And / or, there are multiple first boreholes, and the spacing between the multiple first boreholes in the extension direction of the working face to be mined is 5m to 10m.
5. The method for preventing rockburst in an isolated working face under conditions of thick, hard roof coal seam in strong rockburst, as described in claim 1, is characterized in that... Stress sensors are placed in the coal seam and roof of the working face to be mined to monitor stress changes before and after fracturing.
6. The method for preventing rockburst in an isolated working face under conditions of thick, hard roof coal seam under strong rockburst conditions, as described in claim 1, is characterized in that... Before drilling the first borehole, reinforce the support for the return airway and transport roadway.
7. The method for preventing rockburst in an isolated working face under conditions of thick, hard roof coal seam under strong rockburst conditions, as described in claim 1, is characterized in that... Fracturing a pre-set fracturing layer includes: drilling vertically into the area to be fracturing from the ground, then placing a horizontal wellbore in the area to be fracturing, and finally injecting fracturing fluid to fracture.
8. The method for preventing rockburst in an isolated working face under conditions of thick, hard roof coal seam under strong rockburst, as described in claim 1, is characterized in that... The compressive strength and elastic modulus of the rock strata before and after fracturing are compared. If the ratios of the compressive strength and elastic modulus of the rock strata before and after fracturing are both within the preset range, the fracturing effect is considered to be satisfactory. If at least one of the ratios of the compressive strength and elastic modulus of the rock strata before and after fracturing exceeds the preset range, the pressure of the fracturing fluid is increased within 10m to 20m of the corresponding area.
9. The method for preventing rockburst in an isolated working face under conditions of thick, hard roof coal seam in strong rockburst, as described in claim 1, is characterized in that... The goaf in the working face is filled.
10. The method for preventing rockburst in an isolated working face under conditions of thick, hard roof coal seam in strong rockburst, as described in claim 1, is characterized in that... Micro-vibration sensors are installed at the working face for micro-vibration monitoring.