A method and system for fracturing and modifying surrounding rock in coal mine erosion prevention roadways

Abstract

This application provides a method and system for fracturing and modifying the surrounding rock in coal mine erosion control roadways. In this method, the surrounding rock of the roadway is radially divided into a grouting reinforcement zone and a fracture weakening zone from the inside out. Multiple radially extending boreholes are drilled into the surrounding rock until reaching the fracture weakening zone, and a hydraulic rock fracturing device is placed at the bottom of a predetermined portion of the boreholes. The fracture weakening zone is then divided into multiple layers radially, and from the outer layer to the inner layer of the fracture weakening zone, the hydraulic rock fracturing device sequentially and cyclically damages and fractures the intact area of ​​the surrounding rock within the fracture weakening zone layer by layer until the damage and fracture range reaches the thickness of the fracture weakening zone. The surrounding rock mass in the grouting reinforcement zone is then sealed and grouted. This method effectively controls the damage and fracturing of the surrounding rock in roadways, overcoming the limitations of traditional drilling and blasting methods and hydraulic fracturing methods in the damage and fracturing of surrounding rock in mine roadways, and achieving controllability of the degree, direction, and distance of fracturing of the surrounding rock.

Description

Technical Field

[0001] This application relates to the field of roadway protection technology, and in particular to a method and system for fracturing and modifying the surrounding rock of coal mine anti-scour roadways. Background Technology

[0002] Rockburst is a sudden and violent destructive dynamic phenomenon caused by the instantaneous release of elastic deformation energy in the rock mass surrounding a mine shaft or working face. It typically occurs during underground mining and tunnel excavation, manifesting as the ejection of coal blocks, the movement of a few coal masses as a whole, accompanied by loud noises, rock vibrations, and shock waves, as well as roof and floor collapses, caving, and gas outbursts.

[0003] In order to effectively prevent damage to the roadway during rockburst accidents, the inner and outer rings of the roadway surrounding rock are reinforced and fractured respectively, transforming passive support into active support, making full use of the fractured zone to absorb and transfer the energy transmitted to the roadway during rockburst, thereby achieving the purpose of rockburst prevention.

[0004] Therefore, it is essential to conduct relevant research and take effective preventive measures. Summary of the Invention

[0005] The purpose of this application is to provide a method and system for fracturing and modifying the surrounding rock of coal mine anti-scour roadways, so as to solve or alleviate the problems existing in the prior art.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] This application provides a method for fracturing and modifying the surrounding rock of a coal mine erosion prevention roadway, comprising: dividing the surrounding rock of the roadway radially from the inside out into a grouting reinforcement zone and a fracture weakening zone; drilling multiple radially extending boreholes into the fracture weakening zone, and placing a rock hydraulic fracturing device at the bottom of a predetermined portion of the boreholes; dividing the fracture weakening zone into multiple layers radially, and sequentially damaging and fracturing the intact area of ​​the surrounding rock within the fracture weakening zone layer by layer from the outer layer to the inner layer using the rock hydraulic fracturing device until the damage and fracturing range reaches the thickness of the fracture weakening zone; sealing and grouting the surrounding rock mass of the grouting reinforcement zone.

[0008] Preferably, the drilling depth is not less than the distance between the stress concentration area of ​​the surrounding rock of the roadway and the coal face; the density of the drilling is determined according to the geological conditions of the mine; multiple drilling holes are arranged in a quincunx pattern on the surrounding rock of the roadway.

[0009] Preferably, according to the formula:

[0010]

[0011] Determine the spacing between two adjacent boreholes In the formula, This is the risk correction factor for borehole spacing; The diameter of the drill bit used for drilling; The elastic modulus of the surrounding rock of the tunnel before the peak value; The softening modulus of the surrounding rock in the roadway after the peak value of the stress-strain curve is given; wherein, based on the comprehensive index method, the impact hazard level of the surrounding rock in the roadway is classified to determine the borehole spacing hazard correction coefficient. .

[0012] Preferably, the classification of the impact hazard level of the surrounding rock of the roadway based on the comprehensive index method includes:

[0013] According to the formula:

[0014]

[0015] Determine the powder removal mass ratio of the borehole In the formula, The actual powder discharge mass per unit length of a single borehole; Coal seam density; The diameter of the drill bit used for drilling;

[0016] Based on the dust removal mass ratio of the surrounding rock in the tunnel, the surrounding rock in the tunnel is divided into different impact hazard zones.

[0017] Preferably, based on the predetermined shape of the fracture surface, the initiation direction and initiation force of the multiple rock hydraulic fracturing devices in the borehole are adjusted to form different types of fracture surfaces in the fractured and weakened zone, so as to damage and break the surrounding rock of the fractured and weakened zone to different degrees.

[0018] Preferably, the energy consumption and impact reduction simulations of different degrees are performed on the fractured and weakened zone of the surrounding rock of the roadway, and the shape of the fracture surface is determined based on the simulation results.

[0019] Preferably, the borehole into which the rock hydraulic fracturing device is inserted is determined according to the shape of the predetermined fracture surface, and the fracturing direction and fracturing force of the inserted rock hydraulic fracturing device are adjusted.

[0020] Preferably, according to the formula:

[0021]

[0022] Determine the thickness of the grouting reinforcement zone and the thickness of the fractured and weakened zone ;

[0023] in, The average gravity density of the overlying rock strata; The depth of the surrounding rock of the tunnel; The cohesion of the surrounding rock of the tunnel; The friction angle of the surrounding rock of the tunnel; The radius of the alleyway.

[0024] Preferably, based on the thickness of the fractured and weakened zone The degree of coal and rock mass fragmentation in the fractured and weakened zone is adjusted, and the influence of changes in the degree of coal and rock mass fragmentation on energy absorption and resistance to impact loads is analyzed to determine the thickness of the fractured and weakened zone. The optimal degree of fragmentation is determined; based on the optimal degree of fragmentation of the coal and rock mass in the fractured and weakened zone, the thickness of the coal and rock mass in the fractured and weakened zone is adjusted, the influence of the change in the thickness of the coal and rock mass on the absorption of energy and resistance to impact load is analyzed, and the optimal thickness of the coal and rock mass in the fractured and weakened zone is determined.

[0025] This application embodiment also provides a coal mine erosion prevention roadway surrounding rock fracturing and modification system, including: a partitioning unit, configured to divide the roadway surrounding rock radially from the inside out into grouting reinforcement zone and fracturing and weakening zone; a drilling unit, configured to drill multiple radially extending holes into the fracturing and weakening zone of the roadway surrounding rock, and to place a rock hydraulic fracturing device at the bottom of a predetermined portion of the holes; and a modification unit, configured to divide the fracturing and weakening zone into multiple layers radially, and to sequentially perform layer-by-layer cyclic damage and fracturing on the intact area of ​​the surrounding rock within the fracturing and weakening zone from the outer layer to the inner layer using the rock hydraulic fracturing device, until the damage and fracturing range reaches the thickness of the fracturing and weakening zone, and to seal and grout the grouting reinforcement zone.

[0026] Beneficial effects:

[0027] The method for fracturing and modifying the surrounding rock of a coal mine erosion prevention roadway provided in this application embodiment firstly divides the surrounding rock of the roadway radially from the inside out into a grouting reinforcement zone and a fracture weakening zone; then, multiple radially extending boreholes are drilled into the surrounding rock of the roadway until the fracture weakening zone is reached, and a rock hydraulic fracturing device is placed at the bottom of a predetermined portion of the boreholes; next, the fracture weakening zone is divided into multiple layers radially, and from the outer layer to the inner layer of the fracture weakening zone, the rock hydraulic fracturing device is used to sequentially and cyclically damage and fracture the intact area of ​​the surrounding rock in the fracture weakening zone layer by layer until the damage and fracture range reaches the thickness of the fracture weakening zone; finally, the surrounding rock mass of the grouting reinforcement zone is sealed and grouted. Therefore, by controlling the initiation direction and initiation force of the rock hydraulic fracturing device, combined with a predetermined partial borehole layout, and utilizing the mutual cooperation of multiple rock hydraulic fracturing devices, the damage and fracturing of the surrounding rock in the roadway can be effectively controlled. This breaks through the limitations of traditional borehole blasting and hydraulic fracturing methods in the damage and fracturing of the surrounding rock in mine roadways, and achieves controllability of the degree, direction, and distance of fracturing of the surrounding rock in the roadway. Attached Figure Description

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. Wherein:

[0029] Figure 1 This is a schematic flowchart of a method for fracturing and modifying the surrounding rock of a coal mine anti-scour roadway according to some embodiments of this application;

[0030] Figure 2 This is a schematic diagram of the structure for fracturing and modifying the surrounding rock of a coal mine erosion prevention roadway according to some embodiments of this application;

[0031] Figure 3 This is a schematic diagram of a structure for drilling holes and inserting a hydraulic rock fracturing device in the surrounding rock of a roadway, according to some embodiments of this application.

[0032] Figure 4 This is a schematic diagram of the structure of the outer layer of the fracture weakening zone after damage and breakage according to some embodiments of this application;

[0033] Figure 5 This is a schematic diagram of a structure for performing layer-by-layer cyclic damage and fracturing on an intact area of ​​the surrounding rock within a fractured and weakened zone, according to some embodiments of this application.

[0034] Figure 6 This is a schematic diagram of a structure for sealing and grouting a grouting-reinforced area according to some embodiments of this application;

[0035] Figure 7 A schematic cross-sectional view of a borehole in the surrounding rock of a roadway is provided according to some embodiments of this application;

[0036] Figure 8 A cross-sectional schematic diagram of a borehole within a fractured and weakened zone is provided according to some embodiments of this application;

[0037] Figure 9 A planar unfolded schematic diagram of a borehole is provided according to some embodiments of this application;

[0038] Figure 10 This is a schematic diagram of a horizontal fracture surface provided according to some embodiments of this application;

[0039] Figure 11 This is a schematic diagram of an inclined fracture surface provided according to some embodiments of this application;

[0040] Figure 12 This is a schematic diagram of a conical fracture surface provided according to some embodiments of this application;

[0041] Figure 13This is a structural schematic diagram of a coal mine anti-scour roadway surrounding rock crushing and modification system provided according to some embodiments of this application. Detailed Implementation

[0042] The present application will now be described in detail with reference to the accompanying drawings and embodiments. Various examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present application without departing from the scope or spirit thereof. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present application encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0043] Mine roadways achieve safe mining by dissipating and transferring the enormous energy brought to the roadway by the loss and fracturing of the surrounding rock and transferring the impact of rock bursts. The main methods include: mining protective layers, coal seam water injection, coal seam decompression blasting, large borehole decompression, deep hole roof breaking blasting, hydraulic fracturing, floor grooving, etc. Currently, the most common methods for damaging and fracturing the surrounding rock in mine roadways are borehole blasting and hydraulic fracturing.

[0044] The borehole blasting method has significant limitations. Firstly, it is unsuitable for high-gas mines or mines with combustible coal dust. In high-gas outburst mines, the large number of boreholes and blasts, coupled with issues like insufficient sealing of blast holes, can easily trigger a mine gas explosion. Secondly, the fracture path caused by blasting is difficult to control, and the resulting impact energy affects the surrounding rock, impacting its stability. Multiple blasts can also disturb the roadway, affecting its overall stability.

[0045] Hydraulic fracturing utilizes high-pressure fluid to fracture rocks. When the fluid pressure injected into the well exceeds the formation stress and the tensile strength of the rock, the rock breaks apart, releasing stress at the working face. However, due to geological conditions and its inherent characteristics, hydraulic fracturing also has significant limitations in mine operations. When the surrounding rock of the roadway contains sandstone, conglomerate, limestone, or other high-strength rock layers with underdeveloped joints and fractures, the confining pressure of hydraulic fracturing is insufficient to break the rock. If the applied water pressure is too high, the fractures generated by the water pressure in the borehole and their orientation become difficult to control, increasing the instability of the rock formation.

[0046] Based on this, the applicant proposed a method for fracturing and modifying the surrounding rock of coal mine anti-scour roadways. By controlling the fracturing direction and fracturing force of the hydraulic rock fracturing device, and combining different borehole arrangements, multiple hydraulic rock fracturing devices are used in coordination to directionally fracture the rock strata in the area to be fractured, causing damage of different degrees and ranges. Different types of fracture surfaces are formed in the surrounding rock of the roadway, realizing the controllability of the degree, direction, and distance of fracturing of the surrounding rock. It is also applicable to high-gas mines, combustible coal dust mines, and when there are sandstone, conglomerate, limestone and other high-strength rock strata with poor joints and fractures in the surrounding rock of the roadway, effectively solving the problems existing in the borehole blasting method and hydraulic fracturing method.

[0047] like Figures 1 to 12 As shown, the method for fracturing and modifying the surrounding rock of the coal mine's anti-scour roadway includes:

[0048] Step S101: Divide the surrounding rock of the tunnel radially from the inside out into a grouting reinforcement zone and a fracture weakening zone.

[0049] After the tunnel is excavated, the stress in the surrounding rock is redistributed. Theoretically, this is determined by the tunnel radius. Determine the thickness of the grouting reinforcement zone and the thickness of the fractured and weakened zone Specifically, according to the formula:

[0050]

[0051] Determine the thickness of the grouting reinforcement zone and the thickness of the fractured and weakened zone .

[0052] in, The average gravity density of the overlying rock strata; The depth of the surrounding rock in the tunnel; The cohesion of the surrounding rock in the tunnel; The friction angle of the surrounding rock in the tunnel; The radius of the alleyway.

[0053] Step S102: Drill multiple radially extending boreholes into the surrounding rock of the tunnel until the fractured and weakened zone is reached, and place a rock hydraulic fracturing device at the bottom of a predetermined portion of the boreholes.

[0054] In this application, the stress distribution characteristics of the surrounding rock in the roadway are analyzed using drill cuttings analysis or stress monitoring methods to determine the stress peak area of ​​the roadway sidewall. The drilling depth is not less than the distance from the stress concentration area of ​​the surrounding rock to the coal wall; that is, the drilling depth must be greater than or equal to the distance from the stress peak location to the coal wall. Simultaneously, the drilling depth is adjusted according to the stress concentration degree of the surrounding rock; the higher the stress concentration degree, the deeper the drilling.

[0055] When drilling radially from the interior of the tunnel into the fractured and weakened zone of the surrounding rock, the density of boreholes is controlled according to the mine's geological conditions, specifically the different types and geological structures of the surrounding rock strata. If the surrounding rock is hard, such as siltstone or shale, a large number of boreholes are drilled; if the surrounding rock is mostly softer, such as mudstone or sandy mudstone, the boreholes can be sparser. Specifically, the higher the uniaxial compressive strength and elastic modulus of the surrounding rock, the more boreholes are drilled. When determining the borehole density based on the uniaxial compressive strength of the surrounding rock, if the uniaxial compressive strength is greater than 60 MPa, the borehole density is increased. Specifically, based on the softening modulus method, the stress-strain curve of the surrounding rock is obtained; according to the formula:

[0056]

[0057] Determine the spacing between two adjacent boreholes .in, This is the risk correction factor for borehole spacing; The diameter of the drill bit used for drilling; The elastic modulus of the surrounding rock in the roadway before the peak value of the stress-strain curve; This represents the softening modulus of the surrounding rock in the tunnel after the peak value of the stress-strain curve. Typically, it is the spacing between two adjacent boreholes. The range is Here, the peak value of the stress-strain curve represents the uniaxial compressive strength of the surrounding rock in the tunnel, and the softening modulus is equal to the ratio of stress to strain after the uniaxial compressive strength point on the stress-strain curve.

[0058] Among them, based on the comprehensive index method, the impact hazard level of the surrounding rock of the roadway is classified into different impact hazard zones (weak impact hazard zone, medium impact hazard zone, and strong impact hazard zone) to determine the borehole spacing hazard correction coefficient. Specifically, based on the dust removal ratio from the borehole, the surrounding rock of the roadway is divided into different impact hazard zones, whereby, according to the formula:

[0059]

[0060] Determine the powder removal mass ratio of the borehole In the formula, The actual powder discharge mass per unit length of a single borehole; Coal seam density; The diameter of the drill bit used for drilling.

[0061] when At that time, it was a low-impact danger zone; when At that time, it was a medium-risk area for impact; when At that time, it is a high-impact hazard zone. For a low-impact hazard zone, the borehole spacing hazard correction factor is... For areas with moderate impact risk, the borehole spacing risk correction factor is... For areas with high impact risk, the borehole spacing risk correction factor is... .

[0062] In a specific example, multiple boreholes are arranged in a quincunx pattern on the surrounding rock of the tunnel. That is, the spacing between adjacent boreholes is the same, the row spacing between two rows of boreholes is the same, and adjacent rows of boreholes are arranged in an inward staggered pattern. Specifically, the row spacing between adjacent rows of boreholes is determined based on the tunnel radius, the thickness of the fractured and weakened zone, and the hardness of the surrounding rock. The quincunx arrangement of multiple boreholes on the surrounding rock allows for the formation of different types of fracture surfaces through the coordinated operation of the hydraulic rock fracturing devices within different boreholes, thereby improving the utilization rate of the hydraulic rock fracturing devices.

[0063] In this application, an energy-consuming and impact-reducing model is used to simulate different degrees of fracture and weakening in the surrounding rock of a roadway. Based on the simulation results, the shape of the fracture surface is determined. Specifically, a numerical model is established or a similar model experiment is conducted based on the actual geological conditions of the mine site to simulate the energy-consuming and impact-reducing effects of different degrees of fracture in the fractured and weakened zone (i.e., simulation results). Then, based on the determined shape of the fracture surface, the borehole for inserting a hydraulic rock fracturing device is determined, and the fracturing direction and fracturing force of the inserted hydraulic rock fracturing device are adjusted. By inserting hydraulic rock fracturing devices into corresponding boreholes and controlling and adjusting the fracturing direction and fracturing force of the hydraulic rock fracturing devices, combined with a pre-determined partial borehole layout, the coordinated operation of multiple hydraulic rock fracturing devices achieves controllability of the degree, direction, and distance of fracture of the surrounding rock in the roadway, effectively controlling the damage and fracture of the surrounding rock.

[0064] Not every drill hole needs to be equipped with a hydraulic rock fracturing device. Instead, the device is placed in the corresponding hole based on the shape of the determined fracture surface. The number of fracturing devices can be adjusted according to the required degree of fracturing in the weakened area. More fracturing devices result in a higher degree of rock fragmentation. The fracturing devices are placed and fracturing occurs simultaneously. If the initial fracturing degree in a certain area is insufficient, secondary fracturing can be performed by placing fracturing devices in nearby holes.

[0065] After fracturing, different types of failure modes are formed, resulting in the required fracture surfaces, such as horizontal, inclined, and conical fracture surfaces. This achieves different degrees of damage and fracturing in the weakened and fractured zone, overcoming the limitations of traditional drilling and blasting methods and hydraulic fracturing methods in the fracturing of surrounding rock in mine roadways. For higher required fracturing levels, the borehole density can be increased or the fracturing direction of the hydraulic fracturing device can be controlled to form a conical fracture surface (under the same borehole arrangement, a conical fracture surface results in a higher degree of fracturing than a horizontal fracture surface).

[0066] Step S103: Divide the fractured and weakened zone into multiple layers along the radial direction, and sequentially damage and break up the intact area of ​​the surrounding rock in the fractured and weakened zone layer by layer from the outer layer to the inner layer using a rock hydraulic fracturing device until the damage and breakage range reaches the thickness of the fractured and weakened zone.

[0067] In this application, when dividing the fractured and weakened zone, the number of layers needs to be adjusted according to the thickness of the fractured and weakened zone. A thicker fractured and weakened zone requires more fracture layers. The thickness of the fractured and weakened zone varies depending on the surrounding rock and geological conditions of each mine roadway. Specifically, the required number of fracture layers is determined based on the initiation force of the hydraulic rock fracturing device, the thickness of the fractured and weakened zone, and the strength of the surrounding rock in the roadway. If the surrounding rock strength is high, under the same initiation force of the hydraulic rock fracturing device, the fractured zone formed around the roadway will be smaller, and correspondingly, more fracture layers will be required.

[0068] During this process, based on the thickness of the fractured and weakened zone Adjusting the degree of coal and rock fragmentation in the fractured and weakened zone, analyzing the impact of changes in the degree of coal and rock fragmentation on energy absorption and resistance to impact loads, and determining the thickness of the fractured and weakened zone. The optimal degree of fragmentation is determined; then, based on the optimal degree of fragmentation of the coal and rock mass in the fractured and weakened zone, the thickness of the coal and rock mass in the fractured and weakened zone (i.e., the thickness of the fractured and weakened zone) is adjusted, and the influence of the change in the thickness of the coal and rock mass on the absorption of energy to resist impact loads is analyzed to determine the optimal thickness of the coal and rock mass in the fractured and weakened zone.

[0069] In a specific example, when analyzing the impact of changes in the degree of coal and rock mass fragmentation on energy absorption and resistance to impact loads, numerical simulations were performed on the impact dynamic load response of the surrounding rock in the roadway under different damage levels (e.g., 30%, 60%, 90%) in the fractured and weakened coal and rock mass. The results show that the higher the degree of fragmentation of the coal and rock mass in the fractured and weakened zone, the more significant the anti-impact modification effect. Based on the dynamic stress changes at different locations in the roadway surrounding rock, the dynamic stress response at the top and bottom of the roadway is most significant, while the impact on the dynamic stress of the roadway sidewalls is relatively small. Therefore, increasing the degree of damage to the surrounding rock of the roadway roof and floor is more beneficial for maintaining the overall stability of the roadway.

[0070] When analyzing the impact of changes in coal and rock mass thickness on energy absorption and resistance to impact loads, numerical simulations were conducted on different grouting reinforcement zone thicknesses (e.g., 1 meter, 3 meters, and 5 meters). The results show that the presence of fractured and weakened zones causes stress in the surrounding rock of the roadway to shift deeper. Furthermore, the greater the thickness of the fractured and weakened zone, the lower the stress in the surrounding rock near the roadway, and the smaller the area affected by dynamic loads on the surrounding rock. In other words, the greater the thickness of the fractured and weakened zone, the better the anti-impact modification effect. However, when the thickness of the fractured and weakened zone increases to a certain value, the impact of changes in the thickness of the fractured and weakened zone on the reduction of dynamic stress weakens. For example, when the thickness of the fractured and weakened zone increases from 1 meter to 3 meters, the peak dynamic stress decreases significantly; however, when the thickness of the fractured and weakened zone increases from 3 meters to 5 meters, the peak dynamic stress decreases significantly.

[0071] During the damage fracturing process, based on the predetermined fracture surface shape, the initiation direction and force of multiple hydraulic rock fracturing devices within the borehole are adjusted to create different types of fracture surfaces in the fractured and weakened zone, thereby causing varying degrees of damage and fracturing to the surrounding rock. Specifically, the hydraulic rock fracturing devices are first placed on the periphery of the fractured and weakened zone. By controlling the initiation direction of the hydraulic rock fracturing devices, the devices in different boreholes cooperate to create different types of fracture surfaces in the surrounding rock, achieving the required damage and fracturing. After fracturing the deep surrounding rock, the hydraulic rock fracturing devices are moved and placed in the shallower area to be fracturing, further fracturing the surrounding rock. This fracturing process is repeated cyclically to achieve layered destruction of the surrounding rock in the tunnel until the fracturing area reaches the reinforced zone, i.e., the thickness of the fractured and weakened zone.

[0072] After the fractured and weakened zone is damaged and broken, the surrounding rock mass in the grouting and reinforcement zone is sealed and grouted to strengthen and reinforce the surrounding rock, increase the integrity of the surrounding rock, and improve the energy absorption capacity of the support system. At the same time, micro-vibration, stress monitoring, drill cuttings method and other methods can be used to monitor and analyze the stress and deformation of the surrounding rock in the roadway, comprehensively predict the impact risk, and achieve the synergistic dual effect of hydraulic breaking and support reinforcement to release the impact.

[0073] In this application, when sealing the surrounding rock mass in the grouting reinforcement zone, the surrounding rock mass in the shallow area of ​​the borehole is first sealed. Concrete is then sprayed onto the surface of the surrounding rock to seal any cracks, thus preventing grout leakage and rock cracking during the grouting process. The thickness of the sprayed concrete on the surrounding rock surface is generally 50 mm to 100 mm, and grouting is performed after the surrounding rock mass in the shallow area of ​​the borehole is sealed.

[0074] During grouting, cement mortar can be used as the grout. The grouting pressure gradually increases with the drilling depth, with the grouting pressure in the shallower areas of the borehole being [specific pressure value would be missing here]. The grouting pressure in the deep borehole region is greater than The amount of grout injected is generally determined by factors such as the stress state and the degree of fracture development of the surrounding rock in the roadway, and the diffusion radius of the grout must be ensured. In coal and rock mass areas with incomplete fracture development, the surrounding rock absorbs the grout more slowly, so the grouting time should be extended and the amount of grout injected should be increased.

[0075] In this application, by controlling the initiation direction and the magnitude of the initiation force of the rock hydraulic fracturing device, and combining different borehole arrangements, multiple rock hydraulic fracturing devices are used in coordination to directionally break the rock strata in the area to be broken, causing damage of different degrees and ranges, forming different types of fracture surfaces in the surrounding rock of the roadway, and realizing the controllability of the degree, direction and distance of the roadway surrounding rock fracturing.

[0076] At the same time, it is also applicable in high-gas, combustible coal dust mines and in roadway surrounding rocks with sandstone, conglomerate, limestone and other joints and fissures that are not well developed and have high strength. It effectively solves the problems existing in drilling and blasting methods and hydraulic fracturing methods. It is suitable for transferring and reducing the stress of the surrounding rock and dissipating the impact load intensity in different types of mines, thereby enhancing the integrity of the surrounding rock and the anti-scour performance of the support system.

[0077] This application also provides a coal mine erosion prevention roadway surrounding rock fracturing and modification system, such as... Figure 13 As shown, the coal mine anti-scour roadway surrounding rock crushing and modification system includes: partition unit 1301, drilling unit 1302, and modification unit 1303.

[0078] The partition unit 1301 is configured to divide the surrounding rock of the roadway into a grouting reinforcement zone and a fracture weakening zone in a radial direction from the inside to the outside; the drilling unit 1302 is configured to drill multiple radially extending holes into the fracture weakening zone of the surrounding rock of the roadway, and to place a rock hydraulic fracturing device at the bottom of a predetermined portion of the holes.

[0079] The modified unit 1303 is configured to divide the fractured and weakened zone into multiple layers along the radial direction, and from the outer layer to the inner layer of the fractured and weakened zone, the rock hydraulic fracturing device sequentially performs layer-by-layer cyclic damage and fracturing on the intact area of ​​the surrounding rock in the fractured and weakened zone until the damage and fracturing range reaches the thickness of the fractured and weakened zone, and then seals and grouts the grouting reinforcement area.

[0080] The coal mine scour prevention roadway surrounding rock crushing and modification system provided in this application embodiment can realize the steps and processes of any of the above-mentioned coal mine scour prevention roadway surrounding rock crushing and modification methods, and achieve the same technical effect, which will not be described in detail here.

[0081] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for fracturing and modifying the surrounding rock of a coal mine erosion prevention roadway, characterized in that, include: The surrounding rock of the tunnel is divided radially from the inside out into a grouting reinforcement zone and a fracture weakening zone. Multiple radially extending boreholes are drilled into the surrounding rock of the tunnel until the fractured and weakened zone is reached. Rock hydraulic fracturing devices are placed at the bottom of a predetermined portion of the boreholes. Different levels of energy consumption and impact reduction simulations are performed on the fractured and weakened zone. The shape of the fracture surface is determined based on the simulation results. The fracturing direction and fracturing force of the multiple rock hydraulic fracturing devices in the boreholes are adjusted according to the shape of the fracture surface to form different types of fracture surfaces in the fractured and weakened zone, thereby causing different degrees of damage and fracturing to the surrounding rock in the fractured and weakened zone. The fractured and weakened zone is divided into multiple layers radially. From the outer layer to the inner layer of the fractured and weakened zone, the rock hydraulic fracturing device sequentially damages and breaks up the intact area of ​​the surrounding rock in the fractured and weakened zone layer by layer until the damage and breakage range reaches the thickness of the fractured and weakened zone. The surrounding rock mass of the grouting and reinforcement zone is then sealed and grouted.

2. The method for fracturing and modifying the surrounding rock of coal mine erosion prevention roadways according to claim 1, characterized in that, The drilling depth shall not be less than the distance from the stress concentration area of ​​the surrounding rock of the roadway to the coal face; The density of boreholes is determined based on the geological conditions of the mine. Multiple boreholes are arranged in a quincunx pattern on the surrounding rock of the tunnel.

3. The method for fracturing and modifying the surrounding rock of coal mine erosion prevention roadways according to claim 1, characterized in that, According to the formula: Determine the spacing between two adjacent boreholes ; In the formula, This is the risk correction factor for borehole spacing; The diameter of the drill bit used for drilling; The elastic modulus of the surrounding rock of the tunnel before the peak value; The softening modulus of the surrounding rock in the roadway after the peak value of the stress-strain curve is given; wherein, based on the comprehensive index method, the impact hazard level of the surrounding rock in the roadway is classified to determine the borehole spacing hazard correction coefficient. .

4. The method for fracturing and modifying the surrounding rock of coal mine anti-scour roadways according to claim 3, characterized in that, The classification of the impact hazard level of the surrounding rock of the roadway based on the comprehensive index method includes: According to the formula: Determine the powder removal mass ratio of the borehole ; In the formula, The actual powder discharge mass per unit length of a single borehole; Coal seam density; The diameter of the drill bit used for drilling; Based on the dust removal mass ratio of the surrounding rock in the tunnel, the surrounding rock in the tunnel is divided into different impact hazard zones.

5. The method for fracturing and modifying the surrounding rock of coal mine anti-scour roadways according to claim 1, characterized in that, According to the formula: Determine the thickness of the grouting reinforcement zone and the thickness of the fractured and weakened zone ; in, The average gravity density of the overlying rock strata; The depth of the surrounding rock of the tunnel; The cohesion of the surrounding rock of the tunnel; The friction angle of the surrounding rock of the tunnel; The radius of the alleyway.

6. The method for fracturing and modifying the surrounding rock of coal mine anti-scour roadways according to claim 5, characterized in that, Based on the thickness of the fractured and weakened zone The degree of coal and rock mass fragmentation in the fractured and weakened zone is adjusted, and the influence of changes in the degree of coal and rock mass fragmentation on energy absorption and resistance to impact loads is analyzed to determine the thickness of the fractured and weakened zone. The optimal degree of fragmentation at that time; Based on the optimal degree of fracturing of the coal and rock mass in the fractured and weakened zone, the thickness of the coal and rock mass in the fractured and weakened zone is adjusted, the influence of the change in the thickness of the coal and rock mass on the absorption of energy and resistance to impact load is analyzed, and the optimal thickness of the coal and rock mass in the fractured and weakened zone is determined.

7. A coal mine scour prevention roadway surrounding rock fracturing and modification system, characterized in that, The method for fracturing and modifying the surrounding rock of a coal mine scour prevention roadway according to any one of claims 1-6 is used to fracture and modify the surrounding rock, wherein the system comprises: The partitioning unit is configured to divide the surrounding rock of the tunnel radially from the inside out into grouting reinforcement zone and fracture weakening zone; The drilling unit is configured to drill multiple radially extending boreholes into the fractured and weakened zone of the surrounding rock of the roadway, and to place a rock hydraulic fracturing device at the bottom of a predetermined portion of the boreholes. The modified unit is configured to divide the fractured and weakened zone into multiple layers along the radial direction, and from the outer layer to the inner layer of the fractured and weakened zone, the rock hydraulic fracturing device sequentially performs layer-by-layer cyclic damage and fracturing on the intact area of ​​the surrounding rock within the fractured and weakened zone until the damage and fracturing range reaches the thickness of the fractured and weakened zone, and then seals and grouts the grouting reinforcement area.

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