Design method of flexible die pumping strut supporting system in impact environment

Abstract

The invention discloses a method for designing a flexible formwork pumping strut support system in an impact environment, which comprises the following steps of: acquiring strut design parameters in a static load environment: acquiring stoping roadway size information, stoping roadway surrounding rock information and stoping roadway anchoring design information in a working face stoping range, and finishing strut design under the action of a roadway roof load; the result comprises pillar height, pillar diameter, pillar design quantity and supporting area of a single pillar to a roadway roof; an anti-impact test block is manufactured for an impact test, and the dynamic load strength of the supporting column and the dynamic load supporting strength of the roadway roof are obtained; the supporting strength of the hydraulic support on the working face is obtained and compared with the dynamic load supporting strength, the optimal set size and number of the flexible formwork pumping supporting columns can be accurately determined, the supporting effect of the flexible formwork pumping supporting columns is guaranteed, excessive design is avoided, the supporting cost of a stoping roadway is saved, and the working efficiency is improved. And the balance between safety and economy is realized.

Description

Technical Field

[0001] The present invention relates to the field of advanced support for fully mechanized mining operations, and more specifically, to a design method for a flexible mold pumping support system in an impact environment. Background Art

[0002] In the current comprehensive mining operations, the mining tunnel is a tunnel excavated for coal mining during the coal mining process. The mining tunnel is mainly used for transporting coal, ventilation, pedestrians, and arranging coal mining equipment. According to its position and function in the mining face, it can be divided into transport tunnels, return air tunnels, etc. When the mining face advances forward, the roof of the mining tunnel will be affected by mining and deformed and damaged. Setting up advanced support in the mining tunnel can effectively support the roof before the roof deforms significantly, prevent sudden collapse of the roof, avoid roof falls, and avoid safety hazards.

[0003] It is very important for the advance support of mining tunnels. In the current support technology for mining tunnels, flexible mold pumping pillars, as a new type of supporting component, have the advantages of low cost, low construction difficulty and good mechanical properties. They are gradually applied to related projects and have achieved good application effects. At present, there has been a relatively sufficient study on the design method of flexible mold pumping pillars under the static load of the roof. Among them, in the Chinese authorized patent CN110397448B and the document "Research and Application of Support Parameter Optimization of Pumping Pillars for Coal Pillar Recovery in Comprehensive Mining Working Face Tunnel", the author proposed a design optimization method for flexible mold pumping pillars. On the basis of ensuring effective support of the tunnel, the design of pumping pillar size and pumping pillar spacing is completed scientifically and effectively, and good support effect and cost saving effect are achieved. However, this parameter optimization method is suitable for the design of flexible mold pumping pillars under static load conditions, and lacks consideration of the bearing capacity of flexible mold pumping pillars under the impact of ground pressure.

[0004] In a working environment where rock burst may occur, and in a mining method that uses direct collapse, the advance support of the mining tunnel will be subject to the impact load when the roof collapses. Without targeted design, the flexible formwork pumping pillars that only meet the static load are prone to collapse when sudden pressure comes, posing a major safety hazard to the mining tunnel. Currently, there is an urgent need for a parameter optimization method that can effectively guide the size and layout design of flexible formwork pumping pillars under impact environments. Summary of the invention

[0005] One object of the present invention is to provide a design method for a flexible mold pumping pillar support system in an impact environment. The method can calculate the optimal setting size and number of flexible mold pumping pillars in an impact environment based on the stress characteristics of the flexible mold pumping pillars, thereby avoiding safety risks and saving costs.

[0006] In order to achieve these purposes and other advantages according to the present invention, the present invention provides a method for designing a flexible mold pumping support system for an impact environment, comprising the following steps: S1. Obtaining pillar design parameters for static load environment: Obtaining the size information of the mining tunnel within the mining range of the working face, the surrounding rock information of the mining tunnel, and the anchor design information of the mining tunnel, and completing the pillar design under the tunnel roof load. The design results include pillar height h, pillar diameter W, pillar design number N, and the support area S of a single pillar on the tunnel roof; S2. Obtaining the dynamic load support strength of the pillar: Using the same material as the pillar to make an impact-resistant test block, and conducting an impact test on the impact-resistant test block to obtain the dynamic load strength σ of the pillar t , and the dynamic load support strength q of the support to the tunnel roof a , where the calculation formula for dynamic load support strength is: ; S3. Correct the design parameters of the support under impact environment: Obtain the support strength q of the hydraulic support on the working surface t , if q a >q t The design results meet the requirements of dynamic load support for mining tunnels. a ≤q t , then increase the number of pillars until q a >q t .

[0007] Preferably, the pillar comprises a filling bag and a plurality of annular ribs spaced apart on the inner surface of the filling bag, wherein the pillar filling material is filled and solidified in the filling bag to form a support body.

[0008] Preferably, the surrounding rock information of the mining roadway includes rock mass density γ, roadway caving width B, and roadway caving height H; the anchoring design information of the mining roadway includes anchor cable row spacing a, anchor cable anchoring force p', number of anchor cables in each row n, and roadway support length L; the pillar design under the roof load includes the following steps: A1. Determine the pillar diameter W according to the size information of the mining tunnel and the working space requirements; A2. Calculate the design value of the bearing capacity of a single pillar P a , the calculation formula is , where r is the pillar radius, σ is the axial compression test strength of the pillar filling material specimen, and f s is the Gooch coefficient of structural strength; A3. Calculate the design number of pillars N under the most unfavorable roof load condition. The calculation formula is: , where f is the anchor force weakening coefficient; A4. Calculate the support area S of a single pillar for the tunnel roof.

[0009] Preferably, said S2 comprises the following steps: S21. Using the same material as the pillar, make a plurality of impact-resistant test blocks with a cylindrical size of 50 mm × 50 mm; S22. Using the Hopkinson bar test system, impact the impact test blocks one by one at different impact speeds and record the data. The data includes the corresponding transmission wave intensity σ for each test. ’ t ; S23. Observe the damage of the impact test block under different striking speeds, and use the transmitted wave intensity σ corresponding to the impact test block when a through crack is about to appear ’ t As the dynamic strength of the test block; S24. According to the height-to-diameter ratio of a single pillar in the pillar design results, the dynamic strength of the test block is corrected to obtain the dynamic load strength σ t , and the dynamic load support strength q is obtained a .

[0010] Preferably, said A1 comprises the following steps: A11. Using the same material as the pillar, make multiple groups of height-to-diameter ratio test pieces with increasing height-to-diameter ratios; A12. Load the height-to-diameter ratio specimens with axial compression from high to low and record the compressive strength and the relative increase in the bearing capacity of the specimens compared with the previous set of height-to-diameter ratio specimens to obtain the height-to-diameter ratio when the relative increase in the bearing capacity of the height-to-diameter ratio specimens is the largest; A13. Take the height-to-diameter ratio corresponding to the height-to-diameter ratio test block with the largest relative increase in bearing capacity as the design height-to-diameter ratio of the pillar, take the tunnel height as the pillar height h, and calculate the pillar diameter W.

[0011] Preferably, the calculation formula for correcting the dynamic strength of the test block is: .

[0012] Preferably, the calculation formula of the design value of the bearing capacity of the single pillar is: , where σ c is the modified axial compressive strength, σ c The calculation formula is: ; ; ; Where d is the diameter of the annular reinforcement, s' is the spacing of the annular reinforcement, σ1 is the radial restraint stress of the circular section, k e is the effective constraint coefficient, P sv is the volumetric stirrup ratio of the annular reinforcement, σ yh is the yield strength of the annular reinforcement, d sIt is the diameter of the support section surrounded by the annular reinforcement.

[0013] Preferably, S3 further includes: S4, according to the calculation results obtained in S3, the pillars are arranged in the mining tunnel of the first mining, and monitoring points are set to monitor the pillar pressure in real time; S5, recalculating the pillar construction parameters according to the pillar pressure variation law obtained in S4; S6. Arrange pillars in the mining tunnel of the later mining according to the calculation results of S5.

[0014] Preferably, a hydraulic pillow is used to monitor the strut pressure.

[0015] Preferably, the diameter of the hydraulic pillow is equal to the diameter of the pillar.

[0016] The present invention has at least the following beneficial effects: First, the present invention is based on the design of the flexible formwork pumping pillar under the static load of the roof, and conducts in-depth design according to the stress characteristics of the flexible formwork pumping pillar under the impact load, fully considering the stress characteristics of the advance support in the environment with impact load, and solving the limitation of the flexible formwork pumping pillar parameter design relying only on the static load-bearing condition, which effectively improves the applicability of the advance support system using the flexible formwork pumping pillar in the impact environment. The design result meets the safety requirements of the support system and ensures the safe mining of the working face.

[0017] Second, through multi-step calculations and tests, the present invention can accurately determine the optimal setting size and number of flexible mold pumping pillars in the presence of impact loads, which not only ensures the support effect of the flexible mold pumping pillars, but also avoids over-design, saves support costs in the tunnel, and achieves a balance between safety and economy.

[0018] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a flow chart of a method for optimizing the design of a flexible mold pumping support in a technical solution of the present invention; Figure 2 A structural diagram of a flexible mold pumping support in a technical solution of the present invention; Figure 3 This is a schematic diagram of the working surface 13128 in an embodiment of the present invention; Figure 4 It is a cross-sectional view and an expanded view of the anchor cable support of the return air lane 13128 in the embodiment of the present invention; Figure 5 The relative increase value curve of the bearing capacity of the height-to-diameter ratio specimen in the embodiment of the present invention; Figure 6 The stress wave curve corresponding to the impact test block at an impact speed of 10.16 m in the embodiment of the present invention; Figure 7 This is a design diagram of the arrangement position of the flexible mold pumping support in an embodiment of the present invention; Figure 8 This is a curve showing the relationship between the stress at the monitoring point and the distance from the working surface in an embodiment of the present invention.

[0020] Description of the drawings: 1-pillar, 2-filling bag, 3-circumferential reinforcement, 4-hanging ear, 5-wooden support, 6-expansion hook, 7-grouting port, 8-inclined support. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can implement the invention with reference to the description.

[0022] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0023] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial sources unless otherwise specified; in the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "set" should be understood in a broad sense, for example, they can be fixedly connected, set, or detachably connected, set, or connected and set in one piece. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood in specific circumstances. The orientation or position relationship indicated by the terms "lateral", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0024] like Figure 1-6 As shown, the present invention provides a design method for a soft mold pumping support system in an impact environment, comprising the following steps: S1. Obtain the size information of the mining tunnel, the surrounding rock information of the mining tunnel, and the anchor design information of the mining tunnel within the mining range of the working face, and complete the pillar design under the tunnel roof load. The design results include the pillar height h, the pillar diameter W, the pillar design number N, and the support area S of a single pillar 1 on the tunnel roof; specifically, under the static load of the roof, the axial bearing capacity of the pillar 1 is evaluated by mechanical calculation and static mechanical property test of the material used, and the bearing capacity design value of the pillar 1 under static load is estimated by multiplying the compressive strength obtained from the test by the cross-sectional area of ​​the pillar 1. The pillar 1 is a flexible mold pumping pillar. The support height h in the design parameters of the pillar 1 is equivalent to the height of the mining tunnel. The pillar diameter can be determined according to the empirical formula of the optimal height-to-diameter ratio or by the test results of the optimal height-to-diameter ratio. The design number of pillars 1 is obtained according to the calculation results of the tunnel roof load and the bearing capacity design value of the single pillar 1. The design parameters also include the pillar spacing and the pillar row spacing. The design parameters need to meet the space requirements for the passage of pedestrians and transportation equipment and the installation of facilities such as ventilation ducts and cables.

[0025] S2. Use the same material as the pillar 1 to make an impact-resistant test block, conduct an impact test on the impact-resistant test block, and obtain the dynamic load strength σ of the pillar 1. t , and the dynamic load support strength q of pillar 1 on the tunnel roof a , where the calculation formula for dynamic load support strength is: Specifically, in the mining process using the complete caving method and in the working face with rock burst, the pillar 1 must effectively resist the impact without failure. In order to determine the dynamic load capacity of the pillar 1, impact tests such as the Hopkinson bar test system, the drop hammer impact test, and the pendulum impact test are used. In accordance with the relevant test specifications and the principle of scaled specimen production, an impact-resistant test block is produced, and an impact test is performed on the impact-resistant test block to obtain the dynamic strength. When judging the dynamic strength of the impact-resistant test block, the impact-resistant test block can be judged based on the fact that it does not produce through cracks under a certain intensity of impact and still maintains a good static load bearing capacity after the impact. It can be considered that the impact-resistant test block will be crushed when subjected to an impact higher than this. Then, based on the support area S of the single pillar 1 on the tunnel roof obtained in step S1, the dynamic load support strength q of the pillar 1 on the roof can be calculated. a .

[0026] S3. Obtain the hydraulic support strength q on the working surface t , if q a >q t , then the design result meets the requirements of dynamic load support for mining tunnels. If q a ≤q t , then increase the number of pillars until q a >q tSpecifically, the mining process of the mining face will cause the stress of the surrounding rock strata to be redistributed, and the mine pressure will be transmitted to the direction of the mining roadway. Therefore, the support strength of the mining roadway cannot be lower than the support strength of the hydraulic support on the working face. a The hydraulic support strength q t For comparison, if q a ≥q t , it means that the pillar 1 designed according to the static load bearing requirements of the top plate can meet the force requirements of the dynamic load of the top plate, and the design result of step S1 can be used. a ≤q t When , it means that although the existing pillar 1 design can meet the static load requirements of the roof, it cannot withstand the impact load when the roof collapses. Pillar 1 is crushed when under pressure, and the mining tunnel is damaged when under impact. Therefore, it is necessary to increase the number of pillars 1 in the mining tunnel calculation area.

[0027] In another technical solution, the pillar 1 includes a filling bag 2 and a plurality of annular ribs 3 arranged at intervals on the inner surface of the filling bag 2, wherein the pillar filling material is filled and solidified in the filling bag 2 to form a support body, wherein a grouting port 7 is arranged on the upper part of the filling bag 2 and an exhaust hole is arranged on the top, the pillar 1 also includes a lifting ear 4 and a wooden strip support 5, and an anchoring section with expansion hooks 6 corresponding to the number of the lifting ears 4 is fixed on the top plate of the tunnel, the filling bag 2 is connected to the expansion hook 6 through the lifting ear 4, the wooden strip support 5 is fixedly connected to the steel bar ring arranged outside the filling bag 2, and an inclined support 8 is arranged at the bottom of the filling bag 2 to stabilize and reinforce the pillar 1. When constructing the pillar 1, the filling bag 2 is first hung by the lifting ear 4, and then the prepared pillar filling material is injected. After the pillar filling material is poured and solidified, it plays a supporting role. In this technical solution, although the filling bag 2 and the annular ribs 3 do not directly bear weight, they play a restraining role for the internally solidified pillar filling material in the subsequent force-bearing process of the pillar 1, and improve the bearing capacity and energy consumption capacity of the pillar 1 to a certain extent.

[0028] In another technical solution, the surrounding rock information of the mining roadway includes rock density γ, roadway caving width B, and roadway caving height H. The anchoring design information of the mining roadway includes anchor cable row spacing a, anchor cable anchoring force, number of anchor cables in each row n, and roadway support length L. The pillar design under the roof load includes the following steps: A1. Determine the pillar diameter according to the size information of the mining tunnel and the requirements of the working space. Specifically, the pillar diameter can be determined based on the empirical formula of the optimal height-to-diameter ratio, or by conducting a height-to-diameter ratio test. Under the optimal height-to-diameter ratio, pillar 1 can withstand relatively high axial pressure while ensuring stability. In addition to considering the optimal height-to-diameter ratio, it is also necessary to consider that pillar 1 does not affect the passage of personnel and equipment transportation in the mining tunnel under this diameter design.

[0029] A2. Calculate the design value p of the bearing capacity of a single pillar 1 a , the calculation formula is , where σ is the axial compression test strength of the pillar filling material specimen, f s is the Goodyear coefficient of structural strength; specifically, the same pillar filling materials and filling bags 2 as those used in actual projects are used to make several full-size pillars and conduct axial compression tests. The pressure test results are used to obtain the design value of the single pillar bearing capacity through regression analysis. Optionally, the same pillar filling materials as those used in actual projects can be used to make axial compression test blocks that meet the axial compression test standards, and multiple groups of axial compression tests are conducted in accordance with the test specifications to obtain the axial compression test strength σ, f s The value is 0.9~1.

[0030] A3. Calculate the design number of pillars N under the most unfavorable roof load condition. The calculation formula is: , where f is the anchor force weakening coefficient; specifically, for the mining roadway with anchor cable reinforcement support, the most unfavorable roof load situation is that all the rock layers within the anchor cable anchoring range are delaminated and the anchor cable fails completely. At this time, pillar 1 is in a given load working state, and the support load required by pillar 1 can be determined, and then its specific parameters can be determined, where the roadway caving width can be the mining roadway width, the roadway caving height can be the anchor cable length, and the rock mass density can be Obtained through on-site collection or through experience.

[0031] A4. Calculate the spacing between the pillars 1 and obtain the supporting area S of a single pillar 1 for the tunnel roof. Specifically, the double rows of pillars 1 may be arranged side by side or in a staggered manner.

[0032] In another technical solution, the S2 comprises the following steps: S21. Use the same material as pillar 1 to make multiple impact-resistant test blocks with a cylindrical size of Ф50mm×50mm. Specifically, use the same material as pillar 1 to carry out scaled design of the impact-resistant test blocks. A separate impact-resistant test block is a cylindrical test block filled with pillar filling material in a filling bag 2. The impact-resistant test block coated with the material of the filling bag 2 can fully simulate the damage of the pillar 1 when it is impacted.

[0033] S22. Using the Hopkinson bar test system, impact the impact test blocks one by one at different impact speeds and record the data, including the transmitted wave intensity σ' corresponding to each test tSpecifically, when actually subjected to stress, the pillar 1 is subjected to a short-term and large impact dynamic load in the axial direction. Compared with other impact tests, the Hopkinson bar test can better simulate the actual stress condition of the pillar 1. The Hopkinson bar test system consists of an impact rod, an incident rod, a transmission rod and an impact-resistant specimen. Based on the propagation principle of stress waves in elastic rods, the dynamic strength corresponding to the destruction of the impact-resistant specimen can be obtained more accurately. When the impact rod hits the incident rod at a certain speed, a stress wave will be generated in the incident rod. The stress wave propagates along the incident rod to the impact-resistant specimen. The impact-resistant specimen is deformed under the action of the stress wave, and a part of the stress wave is transmitted to the transmission rod through the specimen. By measuring the incident stress wave in the incident rod and the transmitted stress wave in the transmission rod, the stress-strain relationship of the impact-resistant specimen at a high strain rate can be calculated according to the one-dimensional stress wave theory. In this technical solution, the impact rod is made to hit each group of impact-resistant specimens at different speeds, and the corresponding transmission wave amplitude and transmission wave intensity under each impact are recorded.

[0034] S23. Observe the damage of the impact test block at different impact speeds, and use the transmitted wave intensity σ' corresponding to the impact test block when a through crack is about to appear t As the dynamic strength of the test block; specifically, dynamic strength refers to the ability of a material or component to resist destruction under dynamic loads, and is usually measured by the maximum stress when the impact test block reaches destruction or yield. In the Hopkinson bar test, as the intensity of the incident wave gradually increases, the stress inside the impact test block also increases. When the impact test block reaches the dynamic strength, that is, the impact test block is about to yield, plastically deform or destroy. In this critical state, the stress reflected by the transmitted wave is close to the maximum stress that the specimen can withstand. The occurrence of through cracks in the impact test block can be used as a criterion for judging whether the specimen has failed, and the intensity of the corresponding transmitted waves before the occurrence of through cracks in the impact test block is used as the dynamic strength of the test block.

[0035] S24. According to the height-to-diameter ratio of a single pillar in the pillar design results, the dynamic strength of the test block is corrected to obtain the dynamic load strength σ t , and the dynamic load support strength q is obtained a Specifically, since the impact test block in the Hopkinson bar test is a standard cylindrical specimen with a height-to-diameter ratio of 1:1, and the height-to-diameter ratio of the pillar 1 actually used is different, it is necessary to select an appropriate dynamic strength-height-to-diameter ratio calculation curve to correct the dynamic strength of the test block obtained in step S23 to obtain the dynamic load strength σ of the pillar 1 under the corresponding height-to-diameter ratio. t .

[0036] In another technical solution, A1 comprises the following steps: A11. Using the same material as the pillar, make multiple groups of height-to-diameter ratio test pieces with increasing height-to-diameter ratios; A12. Load the height-to-diameter ratio specimens with axial compression from high to low and record the compressive strength and the relative increase in the bearing capacity of the specimens compared with the previous set of height-to-diameter ratio specimens to obtain the height-to-diameter ratio when the relative increase in the bearing capacity of the height-to-diameter ratio specimens is the largest; A13. Take the height-to-diameter ratio corresponding to the height-to-diameter ratio test block with the largest relative increase in bearing capacity as the design height-to-diameter ratio of pillar 1, take the tunnel height as the pillar height h, and calculate the pillar diameter.

[0037] Specifically, a series of height-to-diameter ratio specimens with different height-to-diameter ratios are prepared. The pillar filling materials and filling bags 2 inside are the same as those in the actual project. The height-to-diameter ratios can be selected as 3, 3.5, 4, 4.5, and 5. The height-to-diameter ratio specimens are subjected to axial loading tests using an axial pressure testing machine. During the loading process, the loading speed is ensured to be uniform and other relevant test standards are met to obtain the maximum bearing capacity of the height-to-diameter ratio specimens with different height-to-diameter ratios, calculate the relative increase in bearing capacity, and observe the changing trend of the relative increase in bearing capacity. When the relative value of bearing capacity gradually increases with the decrease in the height-to-diameter ratio, it indicates that reducing the height-to-diameter ratio has a positive effect on improving the pillar bearing capacity. When the height-to-diameter ratio reaches a certain value, the relative increase in bearing capacity begins to decrease, indicating that the effect of continuing to reduce the height-to-diameter ratio on improving the bearing capacity of pillar 1 begins to weaken. At this time, the height-to-diameter ratio corresponding to the inflection point and the relative increase in the maximum bearing capacity can be considered as the optimal height-to-diameter ratio, and the diameter of pillar 1 is designed with this height-to-diameter ratio.

[0038] In another technical solution, the calculation formula for correcting the dynamic strength of the test block is: , where the pillar diameter and pillar height are both optimal values, and the obtained σ t That is the dynamic load strength of pillar 1 under the optimal size.

[0039] In another technical solution, the calculation formula of the design value of the bearing capacity of a single pillar 1 is: , where σ c is the modified axial compressive strength, σ c The calculation formula is: ; ; ; Where d is the diameter of the annular reinforcement, s' is the spacing of the annular reinforcement, σ1 is the radial restraint stress of the circular section, k e is the effective constraint coefficient, P sv is the volumetric stirrup ratio of the annular reinforcement, σ yh is the yield strength of the annular reinforcement, d sis the cross-sectional diameter of the pillar surrounded by the annular reinforcement. Since the pillar 1 with the annular reinforcement 3 has a significantly higher axial compressive bearing capacity than the same pillar without the annular reinforcement 3, it is believed that during the static load process of the pillar 1, the annular reinforcement 3 plays a horizontal constraint role on the support body formed by the pillar filling material in the pillar 1, and improves the axial bearing capacity of the support body. In order to obtain the true axial compressive strength of the pillar 1, it is necessary to correct the axial compressive test strength σ of the test block obtained from the axial compressive test. In the elastic stress stage, the support body can be regarded as a plain concrete body or a mortar body. Each annular reinforcement 3 set at intervals has an uneven constraint effect on the inside of the support body. The effective constraint coefficient k e To represent the effective restraint of the annular reinforcement 3, k e It is the ratio of the effective restraint area of ​​the cross section of the support body between the adjacent annular ribs 3 to the core area of ​​the support body. The comparative experiment shows that the modified axial compressive strength σ after correction based on the axial compressive test strength σ of the test block is c , and the calculation error between the axial compressive strength of the scaled test block simulating the constraint effect of the annular reinforcement 3 does not exceed 5%. The present technical solution can further accurately obtain the bearing capacity of a single pillar 1. Optionally, in the design, the axial compressive test strength σ of the test block of the same material as the pillar 1 can be directly used to calculate the bearing capacity of a single pillar 1, and the constraint and lifting effect of the annular reinforcement 3 is used as the bearing capacity design redundancy.

[0040] In another technical solution, S3 also includes: S4. According to the calculation results obtained in S3, pillar 1 is arranged in the mining tunnel of the first mining, and monitoring points are set to monitor the pillar pressure in real time. Specifically, the monitoring equipment used to monitor the pillar pressure can be a hydraulic pillow, or other monitoring equipment that can accurately record the stress and strain of the pillar. The observation starts within a range of 40 to 80 meters from the working face and ends when the working face is mined to the monitoring point.

[0041] S5. Recalculate the pillar construction parameters according to the pillar pressure variation law obtained in S4. Specifically, optimize the design of the goaf of the later mining in combination with the obtained detection data. When the supporting effect of pillar 1 in the mining tunnel of the earlier mining is better and the measured data show that the force on pillar 1 is smaller, the calculation result of the mining tunnel of the later mining can be appropriately optimized, and the total number of pillars 1 can be appropriately reduced to reduce the overall cost. When the collected data shows that the pillar force is much greater than the design value, the construction parameters of pillar 1 in the later mining tunnel are recalculated based on the collected values ​​to ensure the support safety of the mining tunnel.

[0042] S6. Arrange pillars in the mining tunnel of the later mining according to the calculation results of S5.

[0043] In another technical solution, a hydraulic pillow is used to monitor the pillar pressure. The hydraulic pillow has significant advantages in monitoring the axial pressure of pillar 1, including high-precision measurement, uniform loading, real-time monitoring, easy operation and high safety. It can accurately feedback pressure data, simulate actual working conditions, avoid local stress concentration, and record pressure changes in real time through the data acquisition system, providing a reliable basis for the mechanical performance analysis of pillar 1.

[0044] In another technical solution, the diameter of the hydraulic pillow is equal to the diameter of the pillar 1. The hydraulic pillow of the same diameter can completely cover the end face of the pillar 1, ensuring uniform distribution of axial pressure and avoiding stress concentration or edge effect, thereby more realistically simulating the actual stress state; at the same time, the contact area is maximized to improve the measurement accuracy, reduce pressure loss and error, and make the monitoring results more representative. The hydraulic pillow of the same diameter can more scientifically and efficiently detect the axial pressure performance of the pillar and provide accurate data support.

[0045] The following is a specific on-site implementation example: Taking the 13218 mining face of XJH Coal Mine as an example, the 13218 mining face adopts a single-strike longwall mining method, comprehensive mechanized coal mining technology, and all caving methods to deal with the goaf. During the excavation of the 13218 working face, the rubber conveyor drift, auxiliary transport lane, return air lane and connecting lane are all excavated along the coal seam floor. The shape of the lane is a rectangular section. The height of the 13218 return air lane is 3.8m and the width is 5.3m. The roof support design diagram of the 13218 return air lane is as follows: Figure 4 As shown in the figure, the anchor cable diameter is Φ21.6mm steel strand, the length is 6000mm, the layout is 2×2, the spacing between rows is 3000mm×2700mm, according to the calculation of the working face support strength and the mine pressure observation data of the adjacent working face, the ZY15000 / 28 / 58D hydraulic support is selected as the working face support equipment, and the support strength design value of the hydraulic support is 1Mpa. The design of the 13218 return air lane adopts flexible mold pumping pillars for advance support. A relatively independent section of the 13218 return air lane is selected as a calculation example, and the length of the calculation example is 105m.

[0046] The specific steps of the design method of the impact environment flexible mold pumping support system include: The rock density of the roof of S1 and 13218 return air lanes is 2.56×9.8kN / m 3 The pillar filling material is prepared according to the water-cement ratio of 1:1. The axial compression test strength σ of the same material test block after curing for 28 days is 15MPa. Considering the space requirements for mechanical transportation and construction in the 13218 return air lane, the pillar diameter needs to be controlled between 700mm and 1100mm. The annular reinforcement on the filling bag used in the design is HPB235 steel bars with a diameter of 10mm and an interval of 200mm. Four specimens with the same size and material and the same height of 3.8m were made. The diameters of the four specimens were 700mm, 800mm, 900mm and 1000mm respectively. The relative increase curve of bearing capacity was obtained by carrying out axial compression tests on the four specimens with the same height and diameter. Figure 5 As shown in the figure, 800 mm corresponding to the maximum relative increase in bearing capacity is selected as the pillar diameter value, and the effective constraint coefficient k of the annular reinforcement on the pillar to the support body is e =0.765, volume stirrup ratio P sv =0.0079, the yield strength of the annular reinforcement σ yh =235Mpa, circular section radial constraint stress σ1=0.711Mpa, modified axial compressive strength σ c =19.43Mpa. In this calculation example, in order to retain a certain amount of bearing capacity design redundancy, the axial compression test strength of the test block 15Mpa is still used for subsequent single pillar bearing capacity calculation; the single pillar bearing capacity design value P a The calculation formula is 1662.4KN, of which the structural strength Goodyear coefficient f s The value is 0.97; Calculate the design number of pillars N under the most unfavorable roof load. In this calculation section, the anchor cable spacing is 3m, with 2 anchors in each row. The anchor force of the anchor cable is 180KN, and the anchor force weakening coefficient f is 0.66. The calculation formula is: 45.39. In this calculation section, a double-row pillar design is adopted. The total number of pillars is rounded up to 46. The support area S of a single pillar on the tunnel roof is 12.10 m2. The pillar design position is as follows: Figure 7 As shown, there are 2 pillars in a row with a row spacing of 4.77m. In order to facilitate the passage of personnel and equipment transportation, the distance between the pillar axis and the near side of the tunnel is set to 0.9m, and the distance between the pillar axes in the same row is 3.5m.

[0047] S2. Make several impact test blocks with a cylindrical size of 50mm×50mm. Cover the impact test blocks with a layer of filling bags. Place the impact test blocks in the Hopkinson bar test system in turn and conduct impact tests at different impact speeds. The test results show that when the impact speed is 10.16m / s, the filling bags of the corresponding impact test blocks remain intact, and the internal pumping support filling material produces axial cracks and circumferential cracks with a certain angle to the axial cracks. Multiple cracks have a tendency to penetrate. At this time, the stress wave curve of the impact test block is as follows: Figure 6 As shown, the corresponding transmitted wave intensity σ' t It is 32.67Mpa. 32.67Mpa is used as the dynamic strength of the impact test block. In step S1, the diameter of the pillar is 800mm and the height of the pillar is 3.8m. The dynamic strength of the test block needs to be corrected to obtain the dynamic load strength of the pillar. The calculation formula is: , dynamic load support strength 32.67=1.356Mpa.

[0048] S3. Obtain the hydraulic support strength q on the working surface t =1Mpa, 13218 Dynamic load support strength q of the return air lane calculation section a >q t It can be considered that the parameters of the flexible mold pumping support based on static load design meet the requirements of dynamic load calculation and can ensure the stability of the support when pressure comes. 46 supports are evenly spaced in the calculation section of the 13218 return air lane. The design position of the support is as follows Figure 7 As shown, the bearing capacity requirements of the static load and dynamic load of the top plate of this calculation section can be met.

[0049] S4. According to the above design results, several large hydraulic pillows with the same diameter as the pillars are processed and customized on site, and installed at the bottom of the pumping pillars at the designed position to monitor the pillar resistance in real time. Figure 7 As shown in the figure, monitoring data is collected as the working face advances.

[0050] S5. The collected data is as follows Figure 7 As shown in the figure, when the working face is 62m, 45m, and 27m away from the monitoring point, the corresponding pressure values ​​are 0.2Mpa, 0.4MPa, and 2.8MPa respectively. When the working face is 22m away from the monitoring point, it reaches the highest value of 3.4Mpa. After that, the value of the monitoring point gradually decreases as the working face advances. The pillar performance is excellent in the overall force-bearing process, and according to the monitoring results, it is believed that the advance support range of the working face is 40m. According to the on-site monitoring results, the actual maximum bearing pressure of a single column is 1708KN, which is 2.7% lower than the design bearing capacity of 1662.4KN of a single column in the previous steps. There has been no situation where the actual monitoring data is too lower than the design value or too higher than the design value, indicating that the pillar size and spacing adopted according to the design method can effectively control the number while playing a supporting effect, and the design parameters can continue to be used in the mining tunnel of the later mining.

[0051] It should be noted that, although the above describes the various steps in a specific order, it does not mean that the various steps must be performed in the above specific order. In fact, some of these steps can be performed concurrently or even in a different order, as long as the required functions can be achieved. The number of devices and processing scales described here are used to simplify the description of the present invention, and the application, modification and variation of the present invention are obvious to those skilled in the art.

[0052] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A design method for a flexible pumping support system in an impact environment, characterized in that: The following steps are involved: S1. Obtaining pillar design parameters for static load environment: Obtaining the size information of the mining roadway within the mining range of the working face, the surrounding rock information of the mining roadway, and the anchor design information of the mining roadway, and completing the pillar design under the roadway roof load. The design results include the pillar height h, the pillar diameter W, the pillar design number N, and the support area S of a single pillar on the roadway roof; S2. Obtaining the dynamic load support strength of the pillar: Using the same material as the pillar to make an impact-resistant test block, and conducting an impact test on the impact-resistant test block to obtain the dynamic load strength σ of the pillar t , and the dynamic load support strength q of the support to the tunnel roof a , where the calculation formula for dynamic load support strength is: ; S3. Correct the design parameters of the support under impact environment: Obtain the support strength q of the hydraulic support on the working surface a , if q a >q t , then the design result meets the requirements of dynamic load support for mining tunnels. If q a ≤q t , then increase the number of pillars until q a >q t .

2. The method for designing a flexible mold pumping support system for an impact environment as claimed in claim 1, characterized in that: The pillar comprises a filling bag and a plurality of annular ribs spaced apart on the inner surface of the filling bag, wherein the pillar filling material is filled and solidified in the filling bag to form a support body.

3. The method for designing a flexible mold pumping support system for an impact environment as claimed in claim 2, characterized in that: The surrounding rock information of the mining tunnel includes the rock density γ, the tunnel caving width B, and the tunnel caving height H. The anchor design information of the mining tunnel includes the anchor cable spacing a, the anchor cable anchoring force p', the number of anchor cables in each row n, and the tunnel support length L. The pillar design under the roof load includes the following steps: A1. Determine the pillar diameter W according to the size information of the mining tunnel and the working space requirements; A2. Calculate the design value of the bearing capacity of a single pillar p a , the calculation formula is , where σ is the axial compression test strength of the test block of the same material as the support, f s is the Gooch coefficient of structural strength; A3. Calculate the design number of pillars N under the most unfavorable roof load condition. The calculation formula is: , where is the anchor force weakening coefficient; A4. Calculate the support area S of a single pillar for the tunnel roof.

4. The method for designing a flexible mold pumping support system for an impact environment as claimed in claim 2, characterized in that: The S2 comprises the following steps: S21. Using the same material as the pillar, make a plurality of impact-resistant test blocks with a cylindrical size of 50 mm × 50 mm; S22. Using the Hopkinson bar test system, impact the impact test blocks one by one at different impact speeds and record the data, including the transmitted wave intensity σ' corresponding to each test t ; S23. Observe the damage of the impact test block at different impact speeds, and use the transmitted wave intensity σ' corresponding to the impact test block when a through crack is about to appear t As the dynamic strength of the test block; S24. According to the height-to-diameter ratio of a single pillar in the pillar design results, the dynamic strength of the test block is corrected to obtain the dynamic load strength σ t , and the dynamic load support strength q is obtained a .

5. The method for designing a flexible mold pumping support system for an impact environment as claimed in claim 3, characterized in that: The A1 comprises the following steps: A11. Using the same material as the pillar, make multiple groups of height-to-diameter ratio test pieces with increasing height-to-diameter ratios; A12. Load the height-to-diameter ratio specimens with axial compression from high to low and record the compressive strength and the relative increase in the bearing capacity of the specimens compared with the previous set of height-to-diameter ratio specimens to obtain the height-to-diameter ratio when the relative increase in the bearing capacity of the height-to-diameter ratio specimens is the largest; A13. Take the height-to-diameter ratio corresponding to the height-to-diameter ratio test block with the largest relative increase in bearing capacity as the design height-to-diameter ratio of the pillar, take the tunnel height as the pillar height h, and calculate the pillar diameter W.

6. The method for designing a flexible mold pumping support system for an impact environment as claimed in claim 4, characterized in that: The calculation formula for correcting the dynamic strength of the test block is: .

7. The method for designing a flexible mold pumping support system for an impact environment as claimed in claim 3, characterized in that: The calculation formula for the design value of the bearing capacity of a single pillar is: , where σ c is the modified axial compressive strength, σ c The calculation formula is: ； ； ； Where d is the diameter of the annular reinforcement, s' is the spacing of the annular reinforcement, σ1 is the radial restraint stress of the circular section, k e is the effective constraint coefficient, P sv is the volumetric stirrup ratio of the annular reinforcement, σ yh is the yield strength of the annular reinforcement, d s It is the diameter of the support section surrounded by the annular reinforcement.

8. The method for designing a flexible mold pumping support system for an impact environment as claimed in claim 1, characterized in that: S3 also includes: S4, according to the calculation results obtained in S3, the pillars are arranged in the mining tunnel of the first mining, and monitoring points are set to monitor the pillar pressure in real time; S5, recalculating the pillar construction parameters according to the pillar pressure variation law obtained in S4; S6. Arrange pillars in the mining tunnel of the later mining according to the calculation results of S5.

9. The method for designing a flexible mold pumping support system for an impact environment as claimed in claim 8, characterized in that: A hydraulic pillow is used to monitor the pillar pressure.

10. The method for designing a flexible mold pumping support system for impact environments according to claim 9, characterized in that: The diameter of the hydraulic pillow is equal to the diameter of the pillar.

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