Mining roadway gob-side entry retaining method suitable for soft broken roof

Abstract

The invention provides a gob-side entry retaining method suitable for a mining roadway of a soft broken roof, and relates to the technical field of soil layer or rock drilling and mine safety. The method specifically comprises the following steps: determining the area range of the soft broken roof, constructing an anchor net cable or a shed frame in a roadway to reinforce and support the area of the soft broken roof, constructing an anchor cable on one side of solid coal to exert horizontal constraint on surrounding rock after top cutting and roadway retaining, and arranging two paths of unit brackets to be connected with an anchor cable beam during stoping; wherein a directional kerf blasting pre-splitting mode is adopted for roof cutting, and large-diameter drilling pre-splitting blasting roof breaking is constructed in an overlying shear roof while blasting roof cutting is conducted on a lower rock stratum; after mining, retaining and protecting measures are taken beside the roadway in the dynamic pressure roadway, a retained roadway withdrawing scheme is determined in a stable area, a non-withdrawing area, a withdrawing area and an observation area are divided, cyclic utilization of supporting materials is guaranteed through ordered withdrawing of temporary supports, the cost can be saved, the carrying distance can be saved, and the production efficiency can be improved.

Description

Technical Field

[0001] The invention relates to the field of soil layer or rock drilling and mine safety technology, and in particular provides a method for retaining a lane along a gob in a mining tunnel suitable for a soft and broken roof. Background Art

[0002] With the acceleration of the industrialization process, the intensity and scale of coal resource development have increased significantly, the mining depth has increased year by year, the self-weight stress has increased, the strength and integrity of the roof rock have decreased, the tunnel surrounding rock conditions have deteriorated, and the coal rock mass is in an environment of high ground stress, high geothermal temperature, and high karst water pressure. After experiencing multiple strong mining impacts, the high plateau rock stress and mining stress are superimposed, resulting in large deformation of the tunnel surrounding rock during mining, and the difficulty of tunnel stability control has increased significantly.

[0003] The technology of retaining lanes along the goaf is a major revolution in pillarless mining technology. It can fully recover coal resources, improve the recovery rate of coal resources, extend the service life of the mine, reduce the amount of tunnel excavation, alleviate the contradiction between mining and excavation succession, prevent the occurrence of isolated working faces, and realize "Y"-type ventilation. It is an effective way to control the problem of excessive gas in the working face, and has brought huge economic benefits to coal mine production.

[0004] However, at present, if the traditional mining roadway is left for the next working face to continue using under the condition of soft and broken roof, it often faces problems such as difficult roof control, poor safety, and high cost. In order to solve the problems faced by soft and broken roof, it is necessary to further improve the existing method of leaving roadways along the goaf. Summary of the invention

[0005] In order to solve the problems of difficult control of the soft and broken roof along the goaf, poor safety and high cost, save support costs, save transportation distance and improve production efficiency, the present invention provides a method for retaining goaf in a mining tunnel suitable for soft and broken roof, and the specific technical scheme is as follows.

[0006] A method for retaining a gob-side entry in a mining tunnel suitable for a weak and broken roof, comprising the following steps:

[0007] S1. Determine the scope of the weak and broken roof area based on the on-site monitoring of the mining face and the engineering conditions of the retained roadway section;

[0008] S2. Construct anchor nets or scaffolding in the tunnel to reinforce and support the weak and broken roof area;

[0009] S3. After cutting the top and retaining the tunnel, anchor cables are constructed on the solid coal side to impose horizontal constraints on the surrounding rock;

[0010] S4. During mining, two unit supports are set up to connect with anchor beam supports;

[0011] S5. After mining, protection measures are taken along the sides of the dynamic pressure tunnels, and a withdrawal plan for the remaining tunnels is determined in the stable area. The non-withdrawal area, withdrawal area and observation area are divided, and temporary supports are withdrawn in an orderly manner.

[0012] Preferably, the construction of pre-cracking and pressure relief by directional slot blasting includes:

[0013] The design of blasting construction parameters includes blasthole angle, blasthole depth, blasthole diameter, blasthole spacing, charge density, charge structure, and sealing length; when blasting and cutting the top of the lower rock layer, large-diameter drilling and pre-cracking blasting measures are taken to break the top of the hard sandstone roof overlying the tunnel; the drilling and blasting effects are detected using an automatic drilling imager, and the blasting construction parameters are optimized; the construction process and construction efficiency are determined based on the construction drilling and charge blasting effects.

[0014] It is also preferred that the sealing length in the blasting parameters affects the pre-splitting effect, and when deep hole blasting is adopted, the sealing length of the blast hole is greater than or equal to 1 / 3 of the blast hole length.

[0015] It is also preferred that during the optimization of the blasting construction parameters, a test borehole is set, the charge structure and charge amount are adjusted according to the sealing length, the blasting gap development is detected after the test blasting, and the charge structure and charge amount are selected and determined.

[0016] It is also preferred that the methods for inspecting the blasting effect include microseismic monitoring, online stress monitoring and drill cuttings monitoring.

[0017] It is also preferred that the protection measures beside the mining back roadway include:

[0018] S511. Temporary support design is based on the number of unit supports supplied in the leading area. The lagging support section adopts a two-way arrangement, with single hydraulic props interspersed in the middle to coordinate support;

[0019] S512. A combined bar support structure consisting of retractable U-shaped steel and steel mesh is used in the dynamic pressure area;

[0020] S513. Take fire prevention and extinguishing measures including hanging steel mesh, arranging air ducts, and erecting U-shaped steel;

[0021] S514. The tunnel floor is reinforced and supported by cast concrete floor and cable leg anchor rods.

[0022] It is also preferred that the steel mesh is hung on the side of the U-shaped steel, the width of the steel mesh is set according to the height of the tunnel, one end of the steel mesh overlaps the top of the tunnel wall, and the other end penetrates into the bottom plate by not less than 300mm; the overlapping positions between the steel meshes are tied with wire.

[0023] It is also preferred that the retractable U-shaped steels are fixedly connected by connecting rods; an air duct is arranged in the steel mesh interlayer, and the U-shaped steel is erected after the air duct is arranged.

[0024] It is also preferred that the temporary support and withdrawal steps of the stable area include:

[0025] S521. Determine the dynamic pressure range after mining based on the mine pressure observation results;

[0026] S522. Determine the non-retreat area, retreat area and observation area based on the integrity of the working face roof, changes in tunnel structure and deformation of surrounding rock;

[0027] S523. Temporary support shall be set up in the non-retreat area, including the intersection of the chamber, the water sprinkling area, the fault fracture zone, and the 5m range before and after the height change section of the tunnel;

[0028] S524. The withdrawal zone includes the area where the roof is intact and the rate of approach of the roof in the mine pressure observation is less than or equal to 2mm / d. When the length of the withdrawal zone is greater than 40m, the temporary support shall be withdrawn at intervals;

[0029] S525. The observation area includes the area where the roof is intact and the rate of roof approach for mine pressure observation is greater than 2mm / d. The withdrawal area changes into the observation area after the withdrawal.

[0030] The beneficial effects of the method for retaining lanes along the goaf of a mining tunnel suitable for a soft and broken roof provided by the present invention include: the method can reinforce the soft and broken roof of the tunnel, ensure the stability of the roof of the mining tunnel, and avoid large-scale sinking of the lanes along the goaf; the construction safety during directional pre-splitting blasting can be ensured by supporting the roof of the empty roof area on the mining side with hydraulic supports; after the support work is completed, directional pre-splitting blasting construction can be carried out, so as to ensure the stress concentration caused by mining and retaining lanes in front of the working face, which is beneficial to the stability of the surrounding rock during the secondary reuse of the mining tunnel; after the blasting work is completed, temporary support can be carried out behind the working face to ensure the stability of the lane and the requirements of gangue blocking, ventilation and fire prevention; after the temporary support is completed, the temporary support can be withdrawn, which can ensure the recycling of support materials, save costs, and save transportation distance, thereby improving production efficiency.

[0031] In addition, this method is more stable and safe through tunnel roof reinforcement, advanced directional pre-splitting blasting and roadside protection in the post-mining dynamic pressure zone, avoiding the lack of sufficient support strength in the tunnel and possible unpredictable large-scale collapse; after directional pre-splitting blasting, the roof of the goaf collapses in time, and the cut and broken rock can fill the goaf, supporting the overlying rock strata in the mining area and saving support costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a zoning diagram for the method of retaining lanes along the gob in mining tunnels with soft and broken roof;

[0033] Figure 2 It is the layout diagram of the advanced support method;

[0034] Figure 3 It is a schematic diagram of the advanced support arrangement;

[0035] Figure 4 It is a schematic diagram of the spatial arrangement of the concentrated energy blasting holes;

[0036] Figure 5 It is a schematic diagram of the arrangement of drilling holes for preventing top thrust and retaining the lane and cutting the top;

[0037] Figure 6 It is a schematic diagram of temporary support design;

[0038] Figure 7 It is a schematic diagram of the retractable U-shaped steel connection structure;

[0039] In the figure: 1- auxiliary drift, 2- advance support area, 3- post-mining dynamic pressure area, 4- tunnel stability area, 5- working face, 6- reinforcement anchor cable, 7- anchor cable, 8- top cutting hole, 9- reinforcement anchor rod, 10- anchor rod, 11- wind tube, 12- energy gathering hole, 13- energy gathering pipe, 14- tunnel, 15- coal seam, 16- roof, 17- anti-impact blasting and top breaking drilling hole, 18- top cutting and tunnel retaining blasting drilling hole, 19- retractable gangue retaining U-shaped steel, 20- steel mesh, 21- U-shaped steel cable, 22- wind tube. DETAILED DESCRIPTION

[0040] Combination Figures 1 to 7 As shown, a specific implementation method of a method for retaining a lane along the goaf of a mining tunnel suitable for a soft and broken roof provided by the present invention is described.

[0041] A method for retaining lanes along the gob in mining tunnels suitable for weak and broken roofs adopts a construction scheme of "anchor cable reinforcement support in the advanced area + directional slit blasting pre-cracking pressure relief + roadside protection in the post-mining dynamic pressure area + temporary support withdrawal in the stable area". The specific steps include:

[0042] S1. Determine the scope of the weak and broken roof area based on on-site monitoring of the mining face and engineering conditions of the retained tunnel section.

[0043] S2. Construct anchor nets or scaffolding in the tunnel to reinforce the weak and broken roof area; specifically, reinforce the weak and broken roof of the tunnel that is originally supported by anchor nets or scaffolding to fix the weak and broken roof in the hard rock area outside the crushing range.

[0044] S3. After cutting the top and leaving the roadway, anchor cables are constructed on one side of the solid coal to impose horizontal constraints on the surrounding rock. After leaving the roadway, due to the increase in stress of the coal rock on the side of the coal pillar, there is asymmetric stress during mining, which can easily cause roadway deformation. Therefore, anchor cables in the solid coal are used to impose horizontal constraints on the surrounding rock, which greatly improves the stability and bearing capacity of the solid coal and controls the deformation of the roadway surrounding rock.

[0045] S4. During mining, two unit supports are set up to connect with the anchor beam with beam supports.

[0046] S5. After mining, protection measures are taken along the sides of the dynamic pressure tunnels, and a withdrawal plan for the remaining tunnels is determined in the stable area. The non-withdrawal area, withdrawal area and observation area are divided, and temporary supports are withdrawn in an orderly manner.

[0047] The protection measures beside the mining back road include:

[0048] S511. Temporary support design is based on the number of unit supports supplied in the leading area. The lagging support section adopts a two-way arrangement, with single hydraulic props interspersed in the middle for supporting. The lagging support distance is determined according to the stable distance of roof movement monitored by mine pressure;

[0049] The stable distance of roof movement refers to the distance that the roof reaches a relatively stable state after a certain period of time after being disturbed by mining. The determination of this distance needs to consider many factors, including geological conditions, mining technology, support methods, etc. Among them, the lag distance is comprehensively analyzed based on the deformation of the surrounding rock of the roadway after the roadway is retained, the deformation rate of the surrounding rock, the separation of the roof, and the stress of the anchor bolts and cables. At the same time, it is closely related to the distance between the working face and the measuring station, that is, the closer the distance, the greater the tension on the anchor bolts and cables, the greater the deformation of the surrounding rock, and the faster the deformation. Under normal circumstances, within 200m behind the advancement of the working face, due to the greater impact of mining and the periodic collapse of the overburden, the monitored data has a peak value. When the working face advances 200m away from the measuring station, the monitoring data gradually stabilizes. Therefore, in order to ensure that the roadway after the roadway is not affected by mining and periodic collapse of the overburden, the lag support distance is dynamically adjusted according to the mine pressure monitoring data. Combined with historical data and empirical formulas, the lag support distance is usually selected to be 200-300m.

[0050] S512. A combined bar support structure is formed by retractable U-shaped steel and steel mesh in the dynamic pressure area. Two U-shaped steels are fixed and overlapped with U-shaped steel cables to form a retractable rock-blocking U-shaped steel. In order to enhance the overall rock-blocking strength of the retractable rock-blocking U-shaped steel, connecting rods are used to connect the retractable rock-blocking U-shaped steels.

[0051] Among them, a steel mesh is hung on the side of the retractable U-shaped steel. The width of the steel mesh should be set according to the height of the lane. One end of the steel mesh overlaps the top of the lane, and the other end penetrates into the bottom plate column hole to a depth of not less than 300mm. The steel mesh uses a 6.5mm diameter steel welded mesh. The top plate steel mesh is tied together. The steel mesh is φ6mm, the mesh width is 1700×900mm, and the grid spacing is 100mm. The steel mesh overlaps 100mm and is tied with wire. The steel mesh overlaps the original support steel mesh.

[0052] S513. Take fire prevention and extinguishing measures including hanging steel mesh, arranging air ducts, and erecting U-shaped steel;

[0053] S514. The tunnel floor is reinforced and supported by a cast concrete floor and cable-leg anchor rods. The tunnel floor is reinforced and supported by a "cast concrete floor + cable-leg anchor rod" solution. The construction time is determined based on the deformation and damage of the floor during mining and the erection of the legs of the rock shed.

[0054] Among them, before mining, through comprehensive analysis of geological conditions, coal seam occurrence, mining technology and other factors, the possibility and degree of deformation and damage of the floor can be preliminarily predicted. During the mining process, through point monitoring, data analysis and other means, the actual situation of deformation and damage of the floor can be grasped in real time, providing a basis for adjusting the construction time. When the amount of bottom drum in the tunnel is large and the deformation and damage are beyond expectations, and the high-stress roof during the tunnel retention period squeezes the retractable U-shaped steel into the goaf or into the tunnel, the cable leg anchor rods are constructed first to control the tunnel floor to ensure safe production. On the contrary, if the deformation and damage of the floor are relatively stable, normal mining operations can be carried out to shorten the construction time.

[0055] The steel mesh is hung on the side of the U-shaped steel. The width of the steel mesh is set according to the height of the lane. One end of the steel mesh overlaps the top of the lane wall, and the other end penetrates into the bottom plate by no less than 300mm. The overlapping positions between the steel meshes are tied with wire. The retractable U-shaped steels are fixedly connected by connecting rods. A wind tube is set in the steel mesh interlayer, and the U-shaped steel is erected after the wind tube is arranged.

[0056] Temporary support and evacuation steps in the stable area include:

[0057] S521. Determine the dynamic pressure range after mining based on the mine pressure observation results;

[0058] S522. Determine the non-retreat area, retreat area and observation area based on the integrity of the working face roof, changes in tunnel structure and deformation of surrounding rock;

[0059] S523. Temporary support shall be provided in the non-withdrawal area, including the intersection of the chamber, the water sprinkling area, the fault fracture zone, and the 5m range before and after the height change section of the tunnel;

[0060] S524. The withdrawal area includes the area where the roof is intact and the rate of approach of the roof for mine pressure observation is less than or equal to 2 mm / d. When the length of the withdrawal area is greater than 40 m, the temporary support is withdrawn at intervals. After the withdrawal, it becomes the observation area and waits for the next step of withdrawal.

[0061] S525. The observation area includes the area where the roof is intact and the rate of approach of the roof for mine pressure observation is greater than 2mm / d. The withdrawal area changes into the observation area after withdrawal. The withdrawal area and the observation area change dynamically and may be both the withdrawal area and the observation area, which requires continuous observation and dynamic adjustment.

[0062] The construction of pre-cracking and pressure relief by directional slot blasting includes:

[0063] According to the on-site monitoring data of deep-well working face mining and the engineering conditions of the lane-retaining section, the blasting construction parameters are designed, including blasthole angle, blasthole depth, blasthole diameter, blasthole spacing, charge density, charge structure, and sealing length; when blasting and cutting the top of the lower rock layer, large-diameter drilling pre-splitting and blasting measures are taken for the hard sandstone roof overlying the lane to achieve the effect of "upper splitting and lower cutting" coordinated top cutting and pressure relief to retain the lane. The drilling and blasting effect is detected by the automatic imaging instrument, and the blasting construction parameters are optimized. For example, the drilling and blasting charging method is optimized and adjusted with the changes in the top lithology and the detection results of the drilling and blasting effect by the automatic imaging instrument; the construction process and construction efficiency are determined according to the construction drilling, charging and blasting effects.

[0064] Among them, the sealing length in the blasting parameters affects the pre-splitting effect. When deep hole blasting is used, the sealing length of the blasthole is greater than or equal to 1 / 3 of the blasthole length.

[0065] Among them, the appropriate length of the blasthole plugging helps to prolong the action time of the explosive gas in the blasthole, so that the explosive energy can act more fully on the rock, thereby improving the energy utilization rate of the explosives, reducing the amount of explosives, and thus reducing the blasting cost. At the same time, the plugging material (blasthole mud or bladder, etc.) can slow down the speed of the explosive gas rushing out of the blasthole, making the shock wave and stress wave propagating more evenly in the rock, which is conducive to the crushing of the rock and the development of cracks. Secondly, it can reduce the energy loss of the shock wave at the mouth of the blasthole, avoid the waste of explosive energy, and at the same time reduce the intensity of the air shock wave and the throwing distance of the flying rocks, thereby improving the safety of the blasting operation.

[0066] During the optimization of blasting construction parameters, a test borehole is set up, and the charging structure and charging amount are adjusted according to the sealing length. After the test blasting, the development of the blasting gap is detected, and the charging structure and charging amount are selected and determined.

[0067] The methods for testing blasting effects include microseismic monitoring, online stress monitoring and drill cuttings monitoring.

[0068] (1) Microseismic monitoring: Extract vibration events from microseismic data using specific thresholds. Utilize the earthquake source location system and combine vibration data recorded by multiple seismographs to calculate the exact location of the event. Perform amplitude analysis, spectrum analysis, time-frequency analysis, etc. on the extracted events to verify their authenticity and reliability. At the same time, compare the monitoring results with geological exploration data, historical records, etc. to further confirm the accuracy of the monitoring results.

[0069] Taking a coal mine as an example, a microseismic monitoring system was implemented to monitor the stability of the rock layer above the working face and predict the risk of rock burst. Multiple seismometers are arranged around the tunnel and at key locations above it to receive rock vibration signals. Vibration data is analyzed through a specific algorithm to extract vibration events, and the exact location of the event is determined using earthquake source location technology. The monitored events are compared with geological exploration data and historical records to verify the authenticity and reliability of the events. At the same time, the nature of the event is further confirmed through amplitude analysis, spectrum analysis and other means to judge the blasting effect.

[0070] This method has strong real-time monitoring capabilities and can capture tiny earthquake dynamics. It also has obvious advantages in obtaining earthquake source information and the impact range of energy events. It has good early warning effects for rock bursts induced by tectonic stress, hard roof and other conditions. However, the specific location of rock bursts is not accurate enough and is greatly affected by factors such as geological conditions and the accuracy of monitoring equipment.

[0071] (2) Online stress monitoring: The stress changes of the rock mass are monitored in real time through stress sensors, and the data are transmitted to the data processing center. The collected stress data are processed and analyzed, including drawing stress curves and identifying stress change trends. The monitoring results are compared with theoretical calculation values, historical records, etc. to verify the accuracy and reliability of the monitoring results.

[0072] Taking the advancement process of a coal mine working face as an example, in order to monitor the stress changes of coal pillars and roofs and prevent the occurrence of rock burst, an online stress monitoring system was implemented. Stress sensors are arranged at key positions of coal pillars and roofs to monitor stress changes. Stress data is collected in real time, processed and analyzed by system software, and stress curves are drawn. The monitored stress data is compared with theoretical calculation values ​​and historical records to verify the accuracy and reliability of the data, so as to judge the blasting effect.

[0073] This method can realize stress monitoring of specific working faces, and the data is accurate and reliable; it has a good early warning effect on rock burst induced by high stress and disturbance caused by mining. However, there are deficiencies in monitoring rock burst induced by tectonic stress in a larger range, and the monitoring results are affected by factors such as the density of monitoring point layout and sensor accuracy.

[0074] (3) Drill cuttings monitoring: Drill holes are arranged in areas where impact hazards are predicted, and the amount of drill cuttings discharged is measured. Dynamic phenomena during the drilling process are observed, such as drill rod bounce, drill sticking, splitting sounds, etc. The location, time, amount of drill cuttings discharged, and dynamic phenomena of the drilling are recorded, and a comprehensive analysis is conducted to determine the stability of the rock mass.

[0075] Taking a coal mine as an example, in order to evaluate the stability of the tunnel surrounding rock and predict the risk of rock burst, the drill cuttings method monitoring was implemented. Multiple boreholes were arranged on both sides of the tunnel and on the roof, and the drilling depth generally ranged from a few meters to more than ten meters. The amount of drill cuttings discharged was recorded during the drilling process, and the dynamic phenomenon during the drilling process was observed. The amount of drill cuttings was compared with the empirical value or standard value, and the stability of the tunnel surrounding rock was judged in combination with the dynamic phenomenon, thereby judging the blasting effect.

[0076] This method has high monitoring accuracy, relatively mature technology, and can directly reflect the degree of rock fragmentation and stress state. However, the monitoring results are greatly affected by the construction conditions, such as drilling depth, hole diameter, drilling speed, etc. The monitoring process may cause certain disturbance and damage to the rock mass.

[0077] This method can reinforce the soft and broken roof of the tunnel, ensure the stability of the roof of the mining tunnel, and avoid large-scale sinking of the empty tunnel along the goaf; by supporting the roof of the empty roof area on the mining side with hydraulic supports, the construction safety during directional pre-splitting blasting can be guaranteed; after the support work is completed, directional pre-splitting blasting construction can be carried out to ensure the stress concentration caused by mining and leaving the tunnel in front of the working face, which is beneficial to the stability of the surrounding rock during the secondary reuse of the mining tunnel; after the blasting work is completed, temporary support can be carried out behind the working face to ensure the stability of the tunnel and the requirements of gangue blocking, ventilation and fire prevention; after the temporary support is completed, the temporary support can be withdrawn to ensure the recycling of support materials, save costs, and save transportation distance, thereby improving production efficiency.

[0078] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for retaining a lane along the gob in a mining tunnel suitable for a weak and broken roof, characterized in that the steps include: S1. Determine the scope of the weak and broken roof area based on the on-site monitoring of the mining face and the engineering conditions of the retained roadway section; S2. Construct anchor nets or scaffolding in the tunnel to reinforce and support the weak and broken roof area; S3. After cutting the top and retaining the tunnel, anchor cables are constructed on the solid coal side to impose horizontal constraints on the surrounding rock; S4. During mining, two unit supports are set up to connect with anchor beam supports; S5. After mining, protection measures are taken along the sides of the dynamic pressure tunnels, and a withdrawal plan for the remaining tunnels is determined in the stable area. The non-withdrawal area, withdrawal area and observation area are divided, and temporary supports are withdrawn in an orderly manner.

2. A method for retaining a gob-side entry in a mining tunnel suitable for a weak and broken roof according to claim 1, characterized in that: Pre-cracking and pressure relief construction by directional slot blasting includes: The design of blasting construction parameters includes blasthole angle, blasthole depth, blasthole diameter, blasthole spacing, charge density, charge structure, and sealing length; when blasting and cutting the top of the lower rock layer, large-diameter drilling and pre-cracking blasting measures are taken to break the top of the hard sandstone roof overlying the tunnel; the drilling and blasting effects are detected using an automatic drilling imager, and the blasting construction parameters are optimized; the construction process and construction efficiency are determined based on the construction drilling and charge blasting effects.

3. A method for retaining a lane along the gob in a mining roadway suitable for a weak and broken roof according to claim 2, characterized in that: The sealing length in the blasting parameters affects the pre-splitting effect. When deep hole blasting is adopted, the sealing length of the blast hole is greater than or equal to 1 / 3 of the blast hole length.

4. The method for retaining a lane along the gob in a mining roadway suitable for a weak and broken roof according to claim 2, characterized in that: During the optimization of the blasting construction parameters, a test borehole is set, the charge structure and charge amount are adjusted according to the sealing hole length, the blasting gap development is detected after the test blasting, and the charge structure and charge amount are selected and determined.

5. The method for retaining a lane along the gob in a mining roadway suitable for a weak and broken roof according to claim 2, characterized in that: The methods for testing the blasting effect include microseismic monitoring, online stress monitoring and drill cuttings monitoring.

6. The method for retaining a roadway along the gob in a mining roadway suitable for a weak and broken roof according to claim 1, characterized in that: The protection measures beside the mining back road include: S511. Temporary support design is based on the number of unit supports supplied in the leading area. The lagging support section adopts a two-way arrangement, with single hydraulic props interspersed in the middle to coordinate support; S512. A combined bar support structure consisting of retractable U-shaped steel and steel mesh is used in the dynamic pressure area; S513. Take fire prevention and extinguishing measures including hanging steel mesh, arranging air ducts, and erecting U-shaped steel; S514. The tunnel floor is reinforced and supported by cast concrete floor and cable leg anchor rods.

7. A method for retaining a gob-side entry in a mining tunnel suitable for a weak and broken roof according to claim 6, characterized in that: The steel mesh is hung on the side of the U-shaped steel, the width of the steel mesh is set according to the height of the tunnel, one end of the steel mesh overlaps with the top of the tunnel wall, and the other end penetrates into the bottom plate by no less than 300mm; the overlapping positions between the steel meshes are tied with wire.

8. The method for retaining a roadway along the gob in a mining roadway suitable for a weak and broken roof according to claim 6, characterized in that: The retractable U-shaped steels are fixedly connected by connecting rods; a wind tube is arranged in the steel mesh interlayer, and the U-shaped steel is erected after the wind tube is arranged.

9. The method for retaining a lane along the gob in a mining roadway suitable for a weak and broken roof according to claim 1, characterized in that: The temporary support and withdrawal steps of the stable area include: S521. Determine the dynamic pressure range after mining based on the mine pressure observation results; S522. Determine the non-retreat area, retreat area and observation area based on the integrity of the working face roof, changes in tunnel structure and deformation of surrounding rock; S523. Temporary support shall be set up in the non-retreat area, including the intersection of the chamber, the water sprinkling area, the fault fracture zone, and the 5m range before and after the height change section of the tunnel; S524. The withdrawal zone includes the area where the roof is intact and the rate of approach of the roof in the mine pressure observation is less than or equal to 2mm / d. When the length of the withdrawal zone is greater than 40m, the temporary support shall be withdrawn at intervals; S525. The observation area includes the area where the roof is intact and the rate of roof approach for mine pressure observation is greater than 2mm / d. The withdrawal area changes into the observation area after the withdrawal.

Images