Method and system for reinforcing and grouting top plate of withdrawing channel of coal mine working face

Abstract

The invention discloses a coal mine working face retracement channel roof reinforcement grouting method and system, and relates to the technical field of coal mine roof reinforcement grouting. The method comprises the following steps: acquiring engineering information of a to-be-reinforced retracement channel, wherein the engineering information comprises a roof empty roadway and a fracture distribution condition; based on the roof empty roadway and fracture distribution condition, a ground and underground combined drilling and grouting scheme is designed, and the drilling and grouting scheme comprises the arrangement mode of a ground drilling group and an underground measure roadway drilling group, a drilling structure and grouting parameters; and drilling construction is conducted according to the drilling construction scheme, drilling arrangement is dynamically adjusted based on the actually disclosed geological condition in the construction process, supplementary drilling construction is implemented, and a grouting channel is formed. According to the method, ground drilling and underground drilling are organically combined, a three-dimensional grouting reinforcement network is constructed, the limitation of a single grouting mode on space coverage is overcome, all-directional exploration and filling of hidden empty roadways and cracks are achieved, and systematicness and integrity of reinforcement engineering are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of coal mine roof reinforcement grouting technology, specifically a method and system for grouting reinforcement of the roof of a coal mine working face retreat passage. Background Technology

[0002] The stability of the roof in the retreat passage of a coal mine working face is directly related to the safe retreat of equipment, the safety of personnel, and the efficient recovery of coal resources. During coal seam mining, especially in areas that have undergone overlying coal seam mining or are affected by geological structures, the roof often has gaps, fissures, or fracture zones. These geological defects are highly susceptible to roof collapse and coal wall spalling under the influence of dynamic pressure during mining, seriously threatening the safety of retreat operations.

[0003] Currently, the main treatment for such roof hazard is grouting reinforcement technology. This involves injecting grout into tunnels and fissures, which solidifies to form a solidified body with a certain strength, thereby improving the integrity and load-bearing capacity of the roof. Common grouting reinforcement methods include surface drilling grouting and underground tunnel drilling grouting. While surface grouting has the advantages of a wide construction range and large drilling depth, it is constrained by factors such as surface topography, overlying goaf, and hydrogeological conditions, resulting in a long construction period, high cost, and difficulty in implementation in complex mountainous or steep slope areas. Underground grouting, while highly targeted and responsive, is limited by underground space, ventilation, and safety conditions, resulting in lower flexibility in the design of borehole layout and grouting process, making it difficult to comprehensively control the distribution of hidden tunnels and fissures within the roof.

[0004] In actual engineering projects, due to insufficient accuracy of preliminary exploration, changes in geological conditions, or tight production schedules, the original design of borehole locations, quantities, and grouting parameters often do not match the actual conditions, resulting in problems such as grouting blind spots, grout leakage, and uneven reinforcement effects.

[0005] Therefore, this invention proposes a method and system for reinforcing the roof of a coal mine working face retreat passage through grouting. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for reinforcing the roof of a coal mine working face retreat channel by grouting, so as to solve the problems mentioned in the background art.

[0007] According to a first aspect of the present invention, in order to achieve the above-mentioned objective, the present invention provides the following technical solution: a method for reinforcing the roof of a coal mine working face retreat passage by grouting, comprising the following steps: S1. Obtain engineering information on the retreat passage to be reinforced, including the distribution of roof voids and cracks. S2. Based on the distribution of roof tunnels and fissures, design a drilling and grouting scheme that combines surface and underground operations, including the arrangement of surface drilling groups and underground measure tunnel drilling groups, drilling structure and grouting parameters; S3. Drilling is carried out according to the drilling construction plan, and the drilling layout is dynamically adjusted based on the actual geological conditions revealed during the construction process. Supplementary drilling is carried out to form grouting channels. S4. Based on the grouting channel, a downward grouting method is adopted for grouting construction. The grouting construction includes grouting sequence control and grouting pressure control. The grouting sequence control is to grout the downstream boreholes first and then the upstream boreholes, and to grout the low-level holes first and then the high-level holes. S5. After the grouting construction is completed, the grouting effect is verified to confirm that the filling density of voids and cracks in the top slab meets the design requirements.

[0008] Furthermore, in step S2, the surface drilling group is designed as a multi-branch structure, including at least two well sites, each well site corresponding to multiple target points. A two-stage drilling structure is adopted. In the first stage, the casing is run down to below the bottom interface of the goaf and cement slurry is used for well cementing. In the second stage, the drilling is carried out to the coal seam tunnel or fracture zone for grouting. After grouting, the entire hole is sealed.

[0009] Furthermore, in step S2, the underground measures roadway drilling group is arranged outside the outer protection line of the retreat channel, along the roof of the coal seam, including multiple drilling sites, each drilling site has multiple exploration directions, each direction has multiple exploration branches arranged in the vertical direction, and inspection holes are provided.

[0010] Furthermore, the downhole drilling adopts a two-stage structure: the first stage involves running the casing to a set depth, and the second stage involves directional drilling to the coal seam cavity or fracture zone, followed by grouting and sealing of the entire borehole.

[0011] Further, in step S3, drilling is carried out according to the drilling construction plan, and the drilling layout is dynamically adjusted based on the actual geological conditions revealed during the construction process. Supplementary drilling is carried out to form grouting channels, as detailed below: During the drilling process, the integrity of the coal seam structure and the location of the goaf are determined based on the lithological analysis results revealed by the borehole and the actual exploration of the goaf. Based on the assessment results, additional exploration holes were added to the original design. The azimuth, inclination, and depth of the additional holes were determined based on the backwater conditions and locations of voids encountered in the previous drilling, in order to cover the void areas not explored in the original design.

[0012] Furthermore, in step S4, based on the grouting channel, a downward grouting method is used for grouting construction, specifically including: The grouting pipeline is lowered to the designed depth of the borehole, and a micro-pressure grouting method is used to control the grouting pressure within the initial pressure range; During the grouting process, when the grouting pressure is detected to rise to the preset pressure value, the grouting of that hole is immediately stopped, where the preset pressure value is greater than the initial pressure value. After the initial grouting is completed, a second grouting test is conducted. If the grouting pressure does not meet the design requirements during the second grouting, supplementary grouting measures are taken until the grouting is full.

[0013] Furthermore, during the grouting process, if grout leakage is detected in the conveyor belt roadway of the working face, the following measures shall be taken: Adjust the slurry mix ratio, increase the concentration of the mixed slurry, and reduce the slurry flow radius; Intermittent grouting is adopted. After the initial grouting material has set for 8-12 hours, a second grouting is performed to replenish the grouting space caused by shrinkage. Polymer sealing materials are used to form a sealing wall at the leakage point.

[0014] Furthermore, the grouting material used in the grouting construction is a mixture of PO42.5 silicate cement and Class III fly ash, and the proportion of the mixture is determined according to the changes in grouting pressure and grouting volume.

[0015] Furthermore, after the grouting construction is completed, the grouting effect is verified, as follows: Anchor cable support construction was carried out on the roof of the retreat roadway; A number of anchor cables were randomly selected for pull-out tests to verify that the average anchoring force of the anchor cables was not lower than the preset value. During the hydraulic support retraction process, the integrity of the roof and the stability of the coal wall are monitored to confirm that there is no delamination or voids in the roof and no bulging, cracks or water seepage in the coal wall.

[0016] According to a second aspect of the present invention, the present invention provides a grouting system for reinforcing the roof of a coal mine working face retreat passage, used to implement a grouting method for reinforcing the roof of a coal mine working face retreat passage as described in the first aspect, comprising: Ground grouting station, used for storing and mixing fly ash and cement slurry; Drilling equipment used for drilling on the surface and in wells; Grouting pumps and delivery pipelines are used to inject grout into boreholes; Monitoring equipment is used to detect grouting pressure and roof condition in real time; The ground grouting station includes a vertical tank, a primary mixing tank, a secondary mixing tank, and a pump room. The grout is transported to the mixing tank by an air pump and then injected into the borehole by a grouting pump.

[0017] The present invention has at least the following beneficial effects: 1. This invention uses underground tunneling boreholes instead of traditional surface drilling, avoiding the constraints of steep mountain terrain on large drilling equipment and eliminating the need for arduous mountain relocation and site leveling operations. At the same time, underground construction can be synchronized with tunnel excavation, significantly reducing the preparation cycle of drilling projects and effectively solving the contradiction of tight schedule under the background of rapid working face advancement.

[0018] 2. During the construction process, this invention adjusts the layout, number, and grouting parameters of boreholes in a timely manner based on real-time geological exploration results, making the treatment plan closer to the actual geological conditions. This effectively avoids grouting blind spots or grout waste caused by inaccurate geological information, and improves the adaptability of the project and the efficiency of resource utilization.

[0019] 3. By clearly defining the grouting sequence, pressure control, and grout leakage handling mechanism, this invention ensures that the grout effectively diffuses and solidifies within a predetermined range, reduces interference to non-target areas, lowers the risk of roof disturbance or roadway damage caused by improper grouting pressure, and safeguards the safety of underground construction and subsequent mining operations.

[0020] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the method described in this invention; Figure 2 This is a schematic diagram of the ground drilling arrangement of the present invention; Figure 3 This is a three-dimensional perspective view of the ground borehole of the present invention; Figure 4 This is a cross-sectional view of the coal seam, goaf, and surface elevation along the direction of the cessation of mining, as described in this invention. Figure 5 This is a schematic diagram showing the layout of boreholes in the underground tunnel and the surface tunnel of the present invention. Figure 6 This is a cross-sectional view of the design and construction of the borehole group for the downhole measures of this invention; Figure 7 This is a flow chart of the grouting process of the present invention; Figure 8 This is a design drawing for grouting boreholes for reinforcing the top plate of the 8205 working face in this invention. Figure 9 This is a cross-sectional view of the design and construction of the grouting borehole group for the reinforcement of the top plate of the 8205 working face of the present invention. Figure 10 This is a plan view of the actual construction of the grouting drilling for the reinforcement of the top plate of the 8205 working face of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0023] Please see Figures 1-10 This invention provides a technical solution: a method for reinforcing the roof of a coal mine working face retreat passage through grouting, comprising the following steps: S1. Obtain engineering information on the retreat passage to be reinforced, including the distribution of roof voids and cracks. S2. Based on the distribution of roof tunnels and fissures, design a drilling and grouting scheme that combines surface and underground operations, including the arrangement of surface drilling groups and underground measure tunnel drilling groups, drilling structure and grouting parameters; S21. Ground Drilling Construction Plan The surface borehole group is designed as a multi-branch structure, including at least two well sites, each well site corresponding to multiple target points, and the total drilling depth is not less than 1800m; Specifically, the treatment area includes three well sites with a total of seven target points. A passage between the surface and coal seam cavities will be established through surface drilling. Grouting will then be used to fill and reinforce the cavities and coal seam fractures, such as... Figure 2 and Figure 3 As shown, there are 3 borehole groups designed on the ground, with borehole numbers Well 1, Well 2, and Well 3. Well 1 has radiation target points D1-1, D1-2, and D1-3, Well 2 has radiation target points D2-1 and D2-2, and Well 3 has radiation target points D3-1 and D3-2. The total drilling volume is approximately 1800m. The ground above the treatment area of ​​the working face is a hillside with varying slopes of approximately 25-45°, and some areas are undulating. According to topographic data, the elevation of well sites 1, 2, and 3 is approximately 1637m, and the elevation of the target coal seam is approximately 1225m. (See the surface and coal seam cross-sections along the working stop line within the designated treatment area). Figure 4 ); like Figure 4 As shown, because there is a goaf about 150m above the 19-22 coal seam, the surface grouting borehole is designed as a two-stage structure, as follows: A 177.8×8.05mm (20#) casing with a 216mm diameter hole is installed, which is required to be installed at least 30m below the bottom interface of the goaf (approximately 320m deep). Cement slurry is used for well cementing to ensure the cementing quality and prevent water from the goaf from entering the mining face. Second, a 152mm diameter borehole is drilled to the coal seam's internal tunnel or fractured roof coal zone for grouting; After grouting, the cement well is sealed to the second casing, and a side-drilling branch is then performed. After grouting is completed, the entire borehole is sealed to avoid the risk of casing breakage and water conduction caused by mining activities after extraction. S22. Downhole Drilling Construction Plan The underground safety roadway is located 10m south of the outer protection line of the retreat passage, along the roof of the coal seam. Within the roadway, one set of boreholes is designed at 20m intervals. Given the average coal seam thickness of 14m, four horizontal boreholes are designed at vertical intervals to investigate potential voids within the coal seam. These voids are then grouted and reinforced. (See attached diagram.) Figure 5 As shown.

[0024] S22.1 Downhole Drilling Layout Nine drilling sites (Z1-Z9) are set up in the underground access roadway. Z1 contains two exploration directions (each direction has four vertical branches, each branch spaced approximately 4m apart vertically). Z2-Z9 contain three exploration directions. Two of these directions have the same borehole layout as Z1 (marked in blue on the diagram). The remaining direction (marked in red on the diagram) is designed as an inspection hole to check the grouting filling effect; this direction has only one branch. See [link to details]. Figure 5 and Figure 6 ; S22.2 Design Workload and Construction Scheme for Downhole Drilling There are nine borehole groups, Z1-Z9, each containing two exploration directions, and each exploration direction containing four exploratory boreholes. According to the profile design, the total drilling volume for the four exploratory boreholes in each exploration direction is approximately 156 meters, for a total exploratory borehole drilling volume of 2808 meters. Borehole groups Z2-Z9 each contain one inspection borehole, with a single borehole design of 45 meters, for a total inspection borehole drilling volume of 360 meters. The total downhole drilling volume is approximately 3168 meters. The specific design is shown in Table 1. Nine drilling sites were initially set up in the underground measures roadway, and multiple exploration branches were used for construction. During construction, exploratory holes could be added as appropriate for grouting based on the actual situation of the grouted area to ensure the grouting treatment effect of the grouted area. Table 1. Drilling design parameters for downhole measures roadways in working face 8205 S22.3 Downhole Drilling Structure Design The downhole drilling design is a two-section structure. The two-section structure design is as follows: A 108×4.5mm (20#) casing is installed with a borehole diameter of 113mm. Based on the grouting pressure of 1-2MPa, the design depth of the casing is 10 meters.

[0025] Second-stage 94mm diameter directional drilling to the coal seam cavity or fractured roof coal zone, followed by grouting; After grouting is completed, the entire borehole is sealed to avoid the risk of casing breakage and water conduction caused by mining activities after extraction. S3. Drilling is carried out according to the drilling construction plan, and the drilling layout is dynamically adjusted based on the actual geological conditions revealed during the construction process. Supplementary drilling is carried out to form grouting channels. Due to the needs of mine production, the following adjustments have been made to the overall project: 1. Grouting station construction project: Given the rapid progress of the 8205 working face and the upcoming preparation stage for the cessation of mining and relocation, the construction period was tight. Therefore, the grouting station construction project was implemented ahead of schedule and was successfully completed in November 2024.

[0026] 2. Surface drilling project: Given the dangerous terrain of the surface drilling location, the difficulty of construction and the long period of time, in order to ensure construction safety and reduce construction time, the mine decided to abandon the surface drilling project and change to the interception drilling project underground. 3. Underground Drilling Engineering: During the excavation of the 8205 measures roadway, the mine conducted advanced geological exploration drilling according to regulations. Lithological analysis of the boreholes revealed that the coal seam structure within the control area of ​​groups Z1-Z4 was intact, and the exposed lithology consisted entirely of solid coal, with no hidden access roads revealed. Based on the above geological exploration results, and after technical demonstration, the original borehole design plan was optimized and adjusted, and the mine was instead responsible for the construction. The specific adjustments are as follows: A total of 18 sets of in-seam boreholes were designed in the 8205 working face roadway. Given the average coal seam thickness of 20m, each set of boreholes had 3-5 exploration branches constructed vertically (see borehole design for details). The vertical distance between each branch was approximately 6-8m (see...). Figure 8 and Figure 9 A total of 67 boreholes were designed, with a total drilling workload of 2360m. Specific design parameters are shown in Table 2.

[0027] Table 2 Design parameters for grouting boreholes for top plate reinforcement of working face 8205 S4. Based on the grouting channel, a downward grouting method is adopted for grouting construction. The grouting construction includes grouting sequence control and grouting pressure control. The grouting sequence control is to grout the downstream boreholes first and then the upstream boreholes, and to grout the low-level holes first and then the high-level holes. S41. Process Flow Fly ash from the power plant is transported to the ground grouting station via cement tanker trucks and stored in vertical tanks. The fly ash in the vertical tanks is then pumped under high pressure to the primary mixing tank of the grouting station for mixing and slurry preparation. It then flows into the secondary mixing tank for secondary mixing. Finally, the slurry in the secondary mixing tank is pumped into the delivery pipeline by the grouting pump in the pump house, and then injected through the ground and underground boreholes. S42. Grouting parameters (1) Grouting materials 1) Cement: P.O42.5 silicate cement shall be used, and its quality shall meet the national standard GB175-2007. Cement that has become damp and lumpy or expired shall not be used. 2) Fly ash: Grade III, fineness not greater than 45%, water requirement not greater than 130%, loss on ignition not greater than 15%; 3) Water for slurry preparation: The water quality must meet the national standards for concrete mixing water quality, and its SO4 content must be within a certain range. 2- The content should be <1%, and the pH value should be >4; 4) Grout mix ratio: Select the appropriate grout concentration and adjust it promptly according to changes in grout flow rate and grouting pressure; (2) Grouting method Grouting and filling adopts a downward grouting method. If the design standard cannot be achieved in one grouting process, the hole can be swept multiple times and grouting can be repeated to ensure the grouting effect. The full-hole grouting method is used for injection grouting to ensure the quality of roadway grouting and filling reinforcement and underground safety, and to improve construction efficiency. (3) Grouting pressure 1) Grouting of the overlying empty tunnel in the retreat passage of the 8205 working face. Since the existence of the empty tunnel may cause grout to seep into the well, the surface drilling is mainly for filling with grout, and no pressure requirement is placed. 2) For downhole exploration boreholes, micro-pressure grouting is adopted, with a pressure within 1-2 MPa. The final grouting pressure is determined according to the site conditions. 3) If leakage occurs during grouting, timely grouting should be carried out to ensure that the grout does not penetrate into the upper strata or working face during grouting in the roadway; 4) Monitor the downhole conditions. If leakage is detected, stop grouting immediately. The following measures can be taken to deal with it: First, appropriately increase the concentration of the mixed grout to reduce the flow radius of the grout; Second, adopt intermittent grouting. After the initial grouting material has set (8-12 hours), perform a second grouting and repeat the above grouting operation to replenish the shrinkage grouting space until the cavity is filled. (4) Grouting volume The estimated backfill volume is 12,000 tons. S5. After the grouting construction is completed, the grouting effect is verified to confirm that the filling density of voids and cracks in the top slab meets the design requirements.

[0028] The technical solution of the present invention will be further described below with reference to specific embodiments: A company implemented a roof reinforcement project for the 8205 working face retreat passage. The project included surface drilling and grouting, underground drilling and grouting, and the construction and installation of a surface grouting station. The surface drilling consisted of 3 borehole groups with 7 branches, totaling approximately 1800m of drilling. The underground drilling consisted of 80 boreholes, totaling approximately 3168m of drilling. The grouting volume was approximately 12000t. The main objective was to reinforce the open roadway and fractured roof coal fissures through grouting from the surface or underground, ensuring the stability of the surrounding rock in the 8205 working face retreat passage, enabling the company to safely and smoothly retreat the 8205 working face, and maximizing the recovery of coal resources. In this drilling operation, a total of 75 boreholes were completed, with a total length of 2623m. Compared to the revised design, the number of boreholes increased by 8, and the total length increased by 263m. After the completion of each borehole, the data was promptly analyzed and used to scientifically and rationally design supplementary boreholes, ensuring the smooth progress of the project and quality control. Specific details of the actual borehole construction are shown in Table 3 and... Figure 10 .

[0029] Table 3. Construction details of grouting holes for the reinforcement of the top slab of working face 8205. (II) Grouting situation 1. Grouting material: The grouting material is PO42.5 silicate cement and Class III fly ash.

[0030] 2. Grouting pressure 1) Actual grouting pressure is 1-2 MPa.

[0031] During the grouting process, leakage occurred in the conveyor belt tunnel of the working face. The following measures were taken to deal with it: First, the concentration of the mixed grout was appropriately increased to reduce the flow radius of the grout. Second, the void in the roof of the conveyor belt tunnel was filled with polymer sealing material to form a sealing wall. Third, intermittent grouting was adopted. After the initial grouting material had set (8-12 hours), a second grouting was carried out. The above grouting operation was repeated to replenish the shrinkage grouting space until the void was filled.

[0032] 3. Grouting sequence 1) Grout the downstream borehole first, then grout the upstream borehole. The purpose is to avoid the formation of a "reverse slope", that is, when grouting the downstream borehole, the grout flows downstream, which affects the grouting effect.

[0033] 2) Grout the lower holes first, then grout the higher holes. Grouting the lower holes first can prevent the grout from flowing directly to the lower area due to gravity when grouting the higher holes, thus preventing grout loss. Secondly, grouting the lower holes can provide a foundation for grouting the higher holes, ensuring that the grout can fully fill the voids and improve the density of the grout.

[0034] 4. Actual grouting situation A total of 16,933.8 tons of grouting material was used in this embodiment.

[0035] During the initial grouting of a single hole, a micro-pressure grouting method is adopted to ensure that the grout can fully fill the voids and cracks. During the grouting process, the grouting pressure is strictly monitored, and grouting is stopped immediately when the grouting pressure rises to 4MPa.

[0036] To further verify the grouting effect of the single hole, a second grouting test was conducted 24 hours after the initial grouting. The second grouting was used to check whether the initial grouting was full and to ensure that there were no omissions or under-grouting. If the grouting pressure was found to be insufficient during the second grouting, supplementary grouting measures were taken according to the specific situation to ensure the grouting quality.

[0037] Evaluation of major achievements and engineering effects Main achievements 1. The original design for this project included 67 boreholes, with a total designed drilling depth of 2360 meters. The actual completed underground drilling depth was 2623.1 meters. All boreholes were designed and supervised by our company, while the mine was responsible for the entire construction process. Compared to the revised design, the number of boreholes increased by 8, and the total drilling depth increased by 263 meters. After each borehole was completed, the data was promptly analyzed and used to scientifically and rationally design additional boreholes, ensuring the smooth progress and quality control of the project.

[0038] 2. The estimated grouting volume for this project was 12,000 tons, while the actual grouting volume was 16,933.8 tons. The amount of grouting material used exceeded the estimated value. This was mainly because the empty roadway above the retreat channel of the 8205 working face was larger than the previously explored and estimated space. Moreover, during the grouting process, by reasonably adjusting the grouting parameters, it was ensured that the grout could fully fill the voids, thereby improving the density and effect of the grouting.

[0039] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0040] For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances. When an element is referred to as being "assembled on," "mounted on," "fixed to," or "set on" another element, it may be directly on the other element or there may be an intermediate element present. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible embodiments.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0042] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. 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.

Claims

1. A method for reinforcing the roof of a coal mine working face retreat passage using grouting, characterized in that, Includes the following steps: S1. Obtain engineering information on the retreat passage to be reinforced, including the distribution of roof voids and cracks; S2. Based on the distribution of roof tunnels and fissures, design a drilling and grouting scheme that combines surface and underground operations, including the arrangement of surface drilling groups and underground measure tunnel drilling groups, drilling structure and grouting parameters; S3. Drilling is carried out according to the drilling construction plan, and the drilling layout is dynamically adjusted based on the actual geological conditions revealed during the construction process. Supplementary drilling is carried out to form grouting channels. S4. Based on the grouting channel, a downward grouting method is adopted for grouting construction. The grouting construction includes grouting sequence control and grouting pressure control. The grouting sequence control is to grout the downstream boreholes first and then the upstream boreholes, and to grout the low-level holes first and then the high-level holes. S5. After the grouting construction is completed, the grouting effect is verified to confirm that the filling density of voids and cracks in the top slab meets the design requirements.

2. The grouting method for reinforcing the roof of a coal mine working face retreat passage according to claim 1, characterized in that: In step S2, the surface drilling group is designed as a multi-branch structure, including at least two well sites, each well site corresponding to multiple target points. It adopts a two-stage drilling structure. In the first stage, the casing is run down to below the bottom interface of the goaf and cement slurry is used for well cementing. In the second stage, the drilling is carried out to the coal seam tunnel or fracture zone for grouting. After grouting, the entire hole is sealed.

3. The grouting method for reinforcing the roof of a coal mine working face retreat passage according to claim 2, characterized in that: In step S2, the drilling group in the underground measures roadway is arranged outside the outer protection line of the retreat channel and along the roof of the coal seam. It includes multiple drilling sites, each drilling site has multiple exploration directions, and each direction has multiple exploration branches arranged in the vertical direction, and inspection holes are provided.

4. The grouting method for reinforcing the roof of a coal mine working face retreat passage according to claim 3, characterized in that: The downhole drilling adopts a two-stage structure. The first stage involves running the casing to a set depth, and the second stage involves directional drilling to the coal seam cavity or fracture zone. After grouting, the entire borehole is sealed.

5. A method for reinforcing the roof of a coal mine working face retreat passage according to claim 3, characterized in that: Step S3: Drilling is carried out according to the drilling construction plan, and the drilling layout is dynamically adjusted based on the actual geological conditions revealed during the construction process. Supplementary drilling is carried out to form grouting channels, as detailed below: During the drilling process, the integrity of the coal seam structure and the location of the goaf are determined based on the lithological analysis results revealed by the borehole and the actual exploration of the goaf. Based on the assessment results, additional exploration holes were added to the original design. The azimuth, inclination, and depth of the additional holes were determined based on the backwater conditions and locations of voids encountered in the previous drilling, in order to cover the void areas not explored in the original design.

6. The grouting method for reinforcing the roof of a coal mine working face retreat passage according to claim 5, characterized in that: In step S4, based on the grouting channel, a downward grouting method is used for grouting construction, specifically including: The grouting pipeline is lowered to the designed depth of the borehole, and a micro-pressure grouting method is used to control the grouting pressure within the initial pressure range; During the grouting process, when the grouting pressure is detected to rise to the preset pressure value, the grouting of that hole is immediately stopped, where the preset pressure value is greater than the initial pressure value. After the initial grouting is completed, a second grouting test is conducted. If the grouting pressure does not meet the design requirements during the second grouting, supplementary grouting measures are taken until the grouting is full.

7. A method for reinforcing the roof of a coal mine working face retreat passage according to claim 6, characterized in that: When grout leakage is detected in the conveyor belt roadway of the working face during grouting construction, the following measures shall be taken: Adjust the slurry mix ratio, increase the concentration of the mixed slurry, and reduce the slurry flow radius; Intermittent grouting is adopted. After the initial grouting material has set, a second grouting is performed to fill the shrinkage grouting space. Polymer sealing materials are used to form a sealing wall at the leakage point.

8. A method for reinforcing the roof of a coal mine working face retreat passage according to claim 7, characterized in that: The grouting material used in the grouting construction is a mixture of PO42.5 silicate cement and Class III fly ash. The proportion of the mixture is determined according to the changes in grouting pressure and grouting volume.

9. A method for reinforcing the roof of a coal mine working face retreat passage according to claim 7, characterized in that: After the grouting construction is completed, the grouting effect is verified as follows: Anchor cable support construction was carried out on the roof of the retreat roadway; A number of anchor cables were randomly selected for pull-out tests to verify that the average anchoring force of the anchor cables was not lower than the preset value. During the hydraulic support retraction process, the integrity of the roof and the stability of the coal wall are monitored to confirm that there is no delamination or voids in the roof and no bulging, cracks or water seepage in the coal wall.

10. A grouting system for reinforcing the roof of a coal mine working face retreat passage, used to implement the grouting method for reinforcing the roof of a coal mine working face retreat passage as described in any one of claims 1 to 9, characterized in that, include: Ground grouting station, used for storing and mixing fly ash and cement slurry; Drilling equipment used for drilling on the surface and in wells; Grouting pumps and delivery pipelines are used to inject grout into boreholes; Monitoring equipment is used to detect grouting pressure and roof condition in real time; The ground grouting station includes a vertical tank, a primary mixing tank, a secondary mixing tank, and a pump room. The grout is transported to the mixing tank by an air pump and then injected into the borehole by a grouting pump.

Images