Coal wall spalling coordinated control method for fully mechanized working face with large mining height

Abstract

The application provides a coal wall spalling cooperative control method for a large-mining-height fully-mechanized working face, and the method comprises the following steps: before mining of the working face, a regional fracturing is performed on a hard roof in a target layer by using an underground large-flow horizontal long-hole regional fracturing mode; according to the mining height of the large-mining-height working face, a proper hydraulic support supporting strength and a support plate form are selected; the large-mining-height fully-mechanized hydraulic support adopts a support plate support structure with multiple levels, which is used for protecting the coal wall spalling generated in the mining of the coal mining working face under the hard roof. Through the application, the strong mine pressure appearance and the coal wall spalling and roof falling problems of the large-mining-height working face are effectively relieved, and the treatment effect of the coal wall spalling of the large-mining-height working face is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mining, and in particular to a method for collaboratively controlling coal wall spalling in a fully mechanized mining face with a large mining height. Background Art

[0002] The fully mechanized high-mining (HMM) full-height, single-stage mining technology is currently one of the primary mining techniques for thick and extra-thick coal seams in my country. Currently, the maximum single-stage mining height has reached 10 meters. As mining height increases, the difficulty of controlling the surrounding rock mass at the working face increases significantly. Coal wall spalling is becoming increasingly prominent, becoming a major geological hazard threatening safe production at these HMMs. Large pieces of coal can obstruct the passage of shearers. Extensive spalling within a short period of time can easily overload the scraper conveyor or cause congestion at the transfer port, leading to face shutdown and potentially inducing roof collapse. Furthermore, the high-speed ejection of coal from the coal wall poses a threat to fully mechanized mining equipment such as hydraulic supports and the safety of operators.

[0003] Currently, areas with ultra-high mining heights exceeding 6.0 m feature stable coal seam conditions, brittle coal, and a lack of fractures. Furthermore, the presence of a hard roof and high mining intensity in these areas result in intense mining pressure. The pressure during mining is a major cause of coal wall spalling and instability in these high-height mining faces. To address the surrounding rock control challenges associated with spalling in fully mechanized mining faces, high-resistance hydraulic supports are widely used in these areas. Currently, the maximum operating resistance of hydraulic supports has reached 29,000 kN. However, this high-resistance support alone cannot fundamentally address the surrounding rock control issues caused by intense mining pressure and instead leads to new challenges such as high equipment investment and increased tonnage. Grouting reinforcement has also been proposed to address spalling in these hard coal seams with few fractures. However, this approach is ineffective in addressing spalling, disrupting normal operations, and slowing down mining advances, which is inconsistent with the current high-intensity and high-speed mining practices of large mines in this region. Summary of the Invention

[0004] The present invention provides a method for collaboratively controlling coal wall spalling in a fully-mechanized mining face with a large mining height, which effectively alleviates the problems of strong mine pressure and coal wall spalling and roof collapse in the working face with a large mining height, and improves the control effect of coal wall spalling in the working face with a large mining height.

[0005] The present invention provides a method for collaboratively controlling coal wall spalling in a fully-mechanized mining face with a large mining height, the method comprising the following steps:

[0006] Before mining in a fully mechanized mining face with a large mining height, when unloading and weakening the thick hard rock layer above the hard roof, a downhole high-flow horizontal long-hole regional fracturing method is used to regionally fracture the hard roof;

[0007] According to the mining height of the large mining height fully mechanized mining working face, the large mining height fully mechanized mining hydraulic support is reasonably selected. The large mining height fully mechanized mining hydraulic support is used to support the hard roof when the large mining height fully mechanized mining working face is mined. The large mining height fully mechanized mining hydraulic support adopts a side guard structure of multi-level side guard plates. The side guard structure of the multi-level side guard plates is used to protect the coal wall fragments generated by the large mining height fully mechanized mining working face under the hard roof when the large mining height fully mechanized mining working face is mined.

[0008] In some embodiments, the method further comprises:

[0009] The target layer for regional fracturing of the hard roof is determined based on the height range of the thick hard rock layer. The process of determining the height range of the thick hard rock layer includes:

[0010] Determine the average expansion coefficient in the hard roof collapse space of the goaf;

[0011] The height range of thick hard rock formations is calculated according to the following formula:

[0012]

[0013] Among them, M represents the mining height of the fully mechanized mining face with large mining height, Represents the average coefficient of expansion.

[0014] In some embodiments, the construction project of regional fracturing of the hard roof is carried out outside the influence range of the advance support pressure of the large mining height fully mechanized mining face.

[0015] Furthermore, the influence range of the advanced support pressure is the distance between the starting point and the installation position of the drilling stress gauge, and the judgment standard of the starting point is the position point when the drilling stress rise value reaches 5% of the initial stress.

[0016] In some embodiments, the downhole high-flow horizontal long-hole regional fracturing method adopts a retreat-type staged composite fracturing process, and corresponding fracturing process parameters are designed.

[0017] In some embodiments, the method of reasonably selecting a large mining height fully-mechanized mining hydraulic support according to the mining height of the large mining height fully-mechanized mining working face includes:

[0018] For large mining height fully mechanized mining working faces with a mining height of more than 3.5m, two-column shielding hydraulic supports are preferred as large mining height fully mechanized mining hydraulic supports.

[0019] Furthermore, the support strength that the large mining height fully mechanized mining hydraulic support needs to meet is , M represents the mining height of the large mining height fully mechanized mining face.

[0020] In some embodiments, the method further comprises:

[0021] When mining a fully-mechanized mining face with a large mining height, the mine pressure monitoring system is used to monitor the initial support force of the fully-mechanized hydraulic support and the pressure status of the fully-mechanized mining face in real time;

[0022] Dynamically adjust the initial support force of the hydraulic support for large mining height fully mechanized mining according to the pressure state of the large mining height fully mechanized mining working face;

[0023] Among them, when the large mining height fully mechanized mining working face is in a non-pressure state, the initial support force requirement of the large mining height fully mechanized hydraulic support is set to no less than 80% of the rated initial support force;

[0024] When the large mining height fully mechanized mining working face is in a pressure state, start the booster pump installed on the large mining height fully mechanized mining hydraulic support and set the initial support force requirement of the large mining height fully mechanized mining hydraulic support to no less than 90% of the rated initial support force.

[0025] In some embodiments, when mining a fully mechanized mining face with a large mining height, the method further includes:

[0026] When the pressure of the fully mechanized mining face with a large mining height is lower than the preset pressure threshold, the number of multi-level side guards to be retracted in groups shall be set to no more than 5;

[0027] When the pressure of the fully mechanized mining face with a large mining height is greater than the preset pressure threshold, the number of racks for retracting the multi-level side guards in groups is set to 2 or 3.

[0028] Furthermore, the retraction method of the multi-stage side guard plate includes:

[0029] When the depth of the coal wall spalling in the fully mechanized mining face with large mining height is greater than 0.8m, the multi-level side guard plates are recovered in two steps;

[0030] Before the upper cutting drum of the coal mining machine passes through, the retraction degree of the multi-stage side guard plate is set to be at a 45-degree angle to the horizontal ground;

[0031] When the coal mining machine passes through the current large-mining-height fully-mechanized mining hydraulic support, the multi-level side guard plates at a 45-degree angle to the horizontal ground will be completely retracted into place.

[0032] The large-mining-height fully-mechanized working face coal wall spalling cooperative control method provided by the application adopts a downhole large-flow horizontal long-hole regional fracturing mode to perform regional fracturing on a hard roof, uses a large-mining-height fully-mechanized hydraulic support to protect the hard roof during the regional fracturing, and uses a multi-stage spalling protection plate of the hydraulic support to mutually protect the coal wall during mining. Thus, the fracturing pressure relief and the support force of the support are cooperated, the spalling is controlled by using the spalling protection structure, the scientific control of the roof and the coal wall is realized, the strong mine pressure appearance of the large-mining-height working face and the coal wall spalling and roof falling problems are effectively relieved, and compared with the traditional method, the coal wall spalling treatment effect of the large-mining-height working face is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description one by one. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0034] Figure 1 is a flowchart of the large-mining-height fully-mechanized working face coal wall spalling cooperative control method provided by the application.

[0035] Figure 2 is a target horizon diagram of the regional fracturing provided by the application.

[0036] Figure 3 is a relationship diagram of the mining height and the support strength provided by the application.

[0037] Figure 4 is one of the spalling protection diagrams of the multi-stage spalling protection plate provided by the application.

[0038] Figure 5 is another of the spalling protection diagrams of the multi-stage spalling protection plate provided by the application.

[0039] Figure 6 is a third of the spalling protection diagrams of the multi-stage spalling protection plate provided by the application.

[0040] Reference signs:

[0041] 1: support top beam; 2: upper telescopic beam; 3: lower telescopic beam; 4: first-stage spalling protection plate; 5: second-stage spalling protection plate; 6: third-stage spalling protection plate; 7: upper cutting drum of the coal mining machine. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0043] The large-mining-height fully-mechanized working face coal wall spalling coordinated control method of the present application will be described below in combination with the drawings. Figure 1 is a flowchart of the large-mining-height fully-mechanized working face coal wall spalling coordinated control method provided by the present application. As shown in Figure 1 , the method comprises the following steps 101 to 102.

[0044] Step 101, before mining in the large-mining-height fully-mechanized working face, regional fracturing of the hard roof is performed by using an underground large-flow horizontal long-hole regional fracturing method.

[0045] In coal mining operations, before mining in the large-mining-height fully-mechanized working face, the thick hard rock layer of the hard roof above the coal mine needs to be surveyed and pressure relieved. The pressure relief is generally achieved by regional fracturing of the thick hard rock layer, which reduces the length of the hard roof overhang and promotes effective filling of the goaf after the roof collapses. In the present embodiment, regional fracturing of the hard roof is performed by using an underground large-flow horizontal long-hole regional fracturing method to achieve pressure relief of the thick hard rock layer on the upper layer of the hard roof. The fracturing process and fracturing process parameters of the underground large-flow horizontal long-hole regional fracturing method are generally determined according to parameters such as the maximum horizontal principal stress distribution of the hard rock layer above the hard roof, the uniaxial compressive strength of the hard roof, etc. By using the underground large-flow horizontal long-hole regional fracturing method, the stress environment of the mining field is improved, and the dynamic load impact of multi-layer hard roof breakage instability on the coal wall working face is reduced.

[0046] Step 102, according to the mining height of the large-mining-height fully-mechanized working face, a large-mining-height fully-mechanized hydraulic support is reasonably selected. The large-mining-height fully-mechanized hydraulic support is used to support the hard roof during mining in the large-mining-height fully-mechanized working face. The large-mining-height fully-mechanized hydraulic support adopts a multi-stage rib support structure, which is used to protect the coal wall spalling generated in the large-mining-height fully-mechanized working face during mining in the large-mining-height fully-mechanized working face under the hard roof.

[0047] When unloading and weakening the thick hard rock layer above the hard roof, hydraulic supports are required to protect the hard roof in the working area of ​​the large mining height fully-mechanized mining face. Therefore, a reasonable selection of the large mining height fully-mechanized mining hydraulic supports is required. This includes reasonable support types, support strengths, and side protection forms of the hydraulic supports. The selection of the hydraulic supports is determined based on the mining height M of the large mining height fully-mechanized mining face. Because the initial support force level and support strength of the large mining height fully-mechanized mining hydraulic supports are different for large mining height fully-mechanized mining faces with different mining heights, the higher the mining height, the higher the initial support force level and support strength of the hydraulic supports. The large-mining-height fully-mechanized mining hydraulic support is used to support the hard roof during mining in the large-mining-height fully-mechanized mining working face. The ultra-high support resistance of the hydraulic support is used to suppress the sinking and separation of the near-field hard roof, thereby improving the overall stiffness of the support-surrounding rock system. By acting on the hard roof with an ultra-high cutting force, the cutting line of the hard roof is moved backward, changing the broken position and hanging roof state near the hard roof, and reducing the pressure of the hard roof rotation on the coal wall.

[0048] In addition, the large-mining height fully-mechanized mining hydraulic support adopts a side protection structure with a multi-level side protection plate, which is used to protect the coal wall spalling generated in the working face when the large-mining height fully-mechanized mining face under the hard roof is mined. In the embodiment of the present invention, the selected large-mining height fully-mechanized mining hydraulic support is designed with a side protection structure with a multi-level side protection plate. This side protection structure with a multi-level side protection plate is used to protect the side of the large-mining height fully-mechanized mining face, that is, to protect the coal wall when the large-mining height fully-mechanized mining face produces coal wall spalling, and to prevent flying coal blocks from the coal wall spalling from hitting the hydraulic support or the operator. By optimizing the side protection structure, the protection area of ​​the coal wall is increased, the side protection force and the timeliness of the side protection response are improved, and the deformation and damage of the coal wall and the sliding of the spalled coal are suppressed.

[0049] The present invention uses underground high-flow horizontal long-hole regional fracturing to regionally fracture the hard roof before mining in a fully-mechanized mining face with a large mining height. During mining in the face, a fully-mechanized hydraulic support with a large mining height is used to protect the hard roof. Furthermore, the hydraulic support employs multi-stage sidewall protection plates to protect the coal wall during mining. This method achieves scientific control of the roof and coal wall by synergizing the pressure relief of fracturing with the support's support force, and by using a sidewall protection structure to control sidewall spalling. This effectively alleviates the problems of high mine pressure and coal wall spalling and roof caving in large mining height working faces, significantly improving the effectiveness of coal wall spalling control in large mining height working faces compared to traditional methods.

[0050] In some embodiments, before regional fracturing of the hard roof using underground high-flow horizontal long-hole regional fracturing, the target stratum for regional fracturing of the hard roof needs to be determined based on the height range of the thick hard rock stratum. This is because after mining in a high-mining height fully-mechanized mining face, the height range of the roof stratum that will have a significant impact needs to be determined to further determine the target stratum for regional fracturing. The height range of the thick hard rock stratum is calculated based on the mining height M of the high-mining height fully-mechanized mining face in the coal mine. The process for determining the height range of the thick hard rock stratum is described below.

[0051] To reduce the effect of hard roof pressure on the coal wall, it is necessary to reduce the hanging length of the hard roof and promote the effective filling of the goaf after the hard roof collapses. Therefore, the target layer for regional fracturing should be determined based on this purpose. First, the average expansion coefficient within the collapsed space of the hard roof in the goaf is determined. This coefficient can be estimated by actually measuring the rock formation data. The average expansion coefficient is generally between 1.15 and 1.2. Then, the height range of the thick hard rock layer is calculated according to the following formula:

[0052]

[0053] Among them, M represents the mining height of the fully mechanized mining face with large mining height, It represents the average expansion coefficient. According to the above formula, the rock layer height range can be calculated to be 5M or 6M.

[0054] After calculating the rock layer height range that is significantly affected by mining in the large-height fully-mechanized mining face, regional fracturing is then carried out on the target layer within the rock layer height range. Specifically, fracturing is carried out on the target layer surface of the hard roof with a thickness of more than 10m and a uniaxial compressive strength of more than 30MPa. When the number of target layers to be fractured is more than one, the vertical spacing between the target fracturing layers shall not be less than 10m, and the vertical spacing between the lowest fracturing layer and the coal seam shall not be less than 10m.

[0055] For example, Figure 2 As shown in the figure, taking geological drilling hole 58 of a fully mechanized high-mining face in a certain region as an example, analysis of the hard coal seam roof revealed that within 50 meters above the coal seam at the working face, the thick hard rock layers, from bottom to top, are 22.64 meters thick medium-grained sandstone and 12.9 meters thick siltstone. This determined that two target rock layers were targeted for regional fracturing in this area of ​​the working face, with target levels of 15 meters and 35 meters, respectively.

[0056] The embodiment of the present invention performs regional fracturing within the rock layer height range that is significantly affected by mining in a large-height fully-mechanized mining face, thereby reducing the effect of hard roof pressure on the coal wall and promoting effective filling of the goaf after the hard roof collapses.

[0057] To minimize the impact of fracturing on coal face production, regional fracturing of the hard roof is performed outside the influence range of the advanced support pressure in fully mechanized mining faces with large mining heights. The influence range of the advanced support pressure is determined based on actual measurements with borehole stress gauges during fracturing or based on coal mine production experience.

[0058] In some embodiments, the influence range of the advance support pressure is the distance between the starting point and the installation position of the drilling stress gauge, and the judgment criterion of the starting point is the position point when the drilling stress rise value reaches 5% of the initial stress. This position point is recorded as P1, and then the distance between point P1 and the installation position of the drilling stress gauge is the influence range of the advance support pressure.

[0059] Taking the actual implementation situation of a coal mine in a certain area as an example, the measured influence range of the advanced support pressure of the working face is about 100m, that is, the distance between the starting point and the installation position of the borehole stress gauge is 100m. In order to reduce the impact of fracturing construction on the production operations of the working face, the construction project of regional fracturing of the hard roof can be set to be carried out 200 meters away from the advanced large-mining height fully-mechanized mining working face.

[0060] In the embodiment of the present invention, the advance distance of the regional fracturing construction is determined to be a distance outside the influence range according to the influence range of the advance support pressure of the working face, which can effectively reduce the impact of the fracturing construction on the production operation of the coal wall working face.

[0061] In some embodiments, the specific implementation process of regional fracturing can be determined by the mechanical properties of the hard rock formation to be fractured, specifically selected based on the results of in-situ stress tests and roof rock mechanical parameter tests in the actual mining area. Here, a downhole large-flow horizontal long-hole regional fracturing method is adopted, a retreat-type segmented composite fracturing process is adopted, and corresponding fracturing process parameters are designed. The process parameters of regional fracturing include: crack radius, borehole diameter, fracturing borehole depth, horizontal hole depth, horizontal borehole spacing, etc. In order to achieve a good fracturing unloading effect, these fracturing process parameters must be reasonably designed according to the mechanical properties of the rock formation to be fractured.

[0062] Taking the actual implementation of a coal mine in a certain region as an example, based on the results of in-situ stress testing and roof rock mechanical parameter testing, the maximum horizontal principal stress of the sandstone roof of the 2-2 coal seam in the mining area is distributed between 3.3 and 20.5 MPa. The average uniaxial compressive strength of the hard sandstone roof is approximately 50 MPa, and the maximum tensile strength is 3.12 MPa. Based on this, it is calculated that the fracture initiation pressure of the hard roof rock stratum is no less than 15 MPa, and the required pumping pressure is 15 to 32 MPa. Based on this, a retreating staged composite fracturing process is adopted, and the process parameters of regional fracturing are set as follows: single pump flow rate of 1.5 m³ / min; pump station pressure of 70 MPa; fracture radius greater than 40 m; drill hole diameter of 120 mm; fracturing borehole depth not exceeding 800 m; horizontal hole depth of 400 m to 650 m, and horizontal borehole spacing of 80 m.

[0063] In an embodiment of the present invention, underground high-flow horizontal long-hole regional fracturing is used to achieve active pressure relief and weakening of the hard roof above the coal wall. The process parameters of the regional fracturing are determined based on the actual stress data of the rock strata in the mining area. This can effectively improve the stress environment of the mining area, reduce the dynamic load impact on the coal wall caused by the breaking and instability of multiple layers of thick hard roof, and achieve a good fracturing pressure relief effect.

[0064] In some embodiments, when performing regional fracturing, it is necessary to select a suitable large-mining-height fully-mechanized mining hydraulic support to provide roof and side protection. Here, it is necessary to select a large-mining-height fully-mechanized mining hydraulic support with multi-level side protection plates based on the actual mining height M of the large-mining-height fully-mechanized mining working face. In embodiments of the present invention, the hydraulic support is selected based on the support type, support strength, and side protection form, as described in detail below.

[0065] Generally speaking, working faces with higher mining heights are prone to coal wall spalling problems. Here, for fully mechanized mining working faces with a mining height of more than 3.5m, two-column shielding hydraulic supports are preferred as large-mining-height fully mechanized mining hydraulic supports.

[0066] In a certain coal mining area, when the mining height of the large-mining-height fully-mechanized mining face reaches 10m, a two-column shielding hydraulic support is selected as the large-mining-height fully-mechanized mining hydraulic support. The specific hydraulic support model that can be selected is the ZY29000 / 45 / 100D hydraulic support with a rated working resistance of 29000kN.

[0067] Regarding support strength, it is necessary to ensure that the support strength of the large-height fully-mechanized mining hydraulic support is not less than 1.8Mpa, and the rated initial support force is 37.5Mpa, thereby ensuring that the hydraulic support has sufficient initial support force level.

[0068] In terms of the side protection form, the side protection structure of the large-mining height fully-mechanized mining hydraulic support is set as a multi-level side protection plate, specifically a three-level side protection plate. The total length of the three-level side protection plate is 5.5m. Flexible protective wings are set between the frame side protection plates of each large-mining height fully-mechanized mining hydraulic support to prevent coal wall collapse blocks from escaping from between the frames.

[0069] In the embodiment of the present invention, based on the mining height, a reasonable selection of large mining height comprehensive mining hydraulic supports is carried out from the perspective of support type, support strength and side protection form. A two-column shielding hydraulic support is selected for side and top protection during working face mining. The ultra-high support resistance of the hydraulic support suppresses the sinking and separation of the near-field roof, and improves the overall stiffness of the support-surrounding rock system. The ultra-high cutting force acting on the roof causes the roof cutting line to move backward, changes the broken position and suspended roof state of the near-field roof, and effectively reduces the pressure of the roof rotation on the coal wall.

[0070] In some embodiments, the specific support strength of the large mining height fully-mechanized mining hydraulic support can be reasonably and accurately set according to the mining height of the large mining height fully-mechanized mining working face. In the embodiment of the present invention, the empirical formula method is used to determine the reasonable support strength of the large mining height fully-mechanized mining hydraulic support. By collecting the statistical results of the support strength and mining height of the large mining height working face hydraulic support, it is determined that the support strength is positively correlated with the mining height (referred to as mining height), such as Figure 3 As shown, Figure 3 The positive correlation coordinate diagram of support strength (unit: MPa) and mining height (unit: m) is shown. After fitting this positive correlation, the fitting straight line is obtained. , and then we can determine that the support strength that the large mining height fully mechanized hydraulic support needs to meet is , M represents the mining height of the fully mechanized mining face with large mining height. Therefore, based on the actual mining height in a certain coal mining area, the support strength of the two-column shield hydraulic support can be determined to be 1.88~1.95MPa.

[0071] The embodiment of the present invention accurately calculates the support strength of the large-mining-height fully-mechanized mining hydraulic support by mining height, which can improve the support function in actual mining operations and provide a good working environment for controlling the risk of coal wall spalling in actual mining operations.

[0072] In some embodiments, when mining a large-mining-height fully-mechanized mining face, a mine pressure monitoring system is used to monitor in real time the initial support force of the large-mining-height fully-mechanized mining hydraulic support and the pressure status of the large-mining-height fully-mechanized mining face. Therefore, during mining, the hard roof above the large-mining-height fully-mechanized mining face will produce periodic pressure, causing the large-mining-height fully-mechanized mining face to produce periodic pressure. Here, the periodic pressure of the large-mining-height fully-mechanized mining face refers to the periodic mine pressure caused by the periodic breaking of the hard roof on the coal mining face. By monitoring this periodic pressure status and issuing an early warning, the initial support force of the large-mining-height fully-mechanized mining hydraulic support can be dynamically adjusted according to the pressure status of the large-mining-height fully-mechanized mining face.

[0073] When the large mining height fully mechanized mining working face is in a non-pressure state, the initial support force requirement of the large mining height fully mechanized mining hydraulic support is set to no less than 80% of the rated initial support force. When the large mining height fully mechanized mining working face is in a pressure state, the booster pump installed on the large mining height fully mechanized mining hydraulic support is started, and the initial support force requirement of the large mining height fully mechanized mining hydraulic support is set to no less than 90% of the rated initial support force.

[0074] For example, the rated initial support force of a large mining height fully mechanized mining hydraulic support is 37.5Mpa. When the large mining height fully mechanized mining working face is in a non-pressure state, the initial support force of the large mining height fully mechanized mining hydraulic support is set to no less than 30Mpa. When the large mining height fully mechanized mining working face is in a pressure state, the booster pump installed in the large mining height fully mechanized mining hydraulic support is started to increase the initial support force of the large mining height fully mechanized mining hydraulic support to more than 34Mpa to relieve the hard roof pressure of the large mining height fully mechanized mining working face.

[0075] According to the embodiment of the present invention, when mining in a large mining height fully mechanized mining face, by real-time monitoring the initial support force of the large mining height fully mechanized mining hydraulic support and the pressure status of the large mining height fully mechanized mining face, the initial support force level of the support can be adjusted in real time according to the pressure status of the large mining height fully mechanized mining face, thereby achieving accurate control of the pressure of the large mining height fully mechanized mining face and ensuring the normal and safe progress of the mining operation process.

[0076] In some embodiments, after coal is cut in a high-mining height working face, the telescopic beams and side guards of the high-mining height fully-mechanized hydraulic support are controlled to extend and retract multiple levels of side guards to protect against coal wall spalling. When mining a high-mining height working face, workers operate a shearer to cut coal. After cutting, the working face may experience coal wall spalling, and the pressure of the hard roof on the working face may also change. At this time, the telescopic beams of the high-mining height fully-mechanized hydraulic support are controlled to promptly extend and retract multiple levels of side guards to protect the roof and sides.

[0077] like Figure 4 As shown, Figure 4A schematic diagram shows the normal operation of multi-level sidewall guards during mining in a high-mining-height working face. During mining in a fully-mechanized mining face, an upper telescopic beam 2 and a lower telescopic beam 3 are extended from the top beam 1 of the fully-mechanized hydraulic support. The lower telescopic beam 3 connects three levels of sidewall guards: the first, second, and third levels. After mining and coal cutting, the multi-level sidewall guards are extended and retracted by controlling the lower telescopic beam 3 of the fully-mechanized hydraulic support, closely adhering to the coal wall of the working face for protection.

[0078] During mining in a fully-mechanized high-mining face, severe coal wall spalling may occur. To prevent this, embodiments of the present invention monitor the depth of the coal wall spalling in real time. When the depth of the coal wall spalling is detected to be greater than 0.8m, it indicates severe spalling, and the fully-mechanized high-mining face hydraulic supports are deployed in advance. Because severe spalling in a high-mining face requires minimizing the open roof area of ​​the end face to prevent roof collapse, the supports are deployed in advance.

[0079] In this embodiment of the present invention, after coal is cut in a fully-mechanized mining face with a large mining height, the telescopic beams of the fully-mechanized hydraulic supports are controlled to extend and retract multi-stage sidewall guards for sidewall protection. Furthermore, when severe coal wall spalling occurs, the fully-mechanized hydraulic supports are advanced. By rationally operating the supports and multi-stage sidewall guards, effective control of coal wall spalling can be achieved, preventing damage to mining equipment and workers caused by severe spalling, thereby improving the safety of coal cutting operations.

[0080] Furthermore, when mining a large mining height working face, the large mining height fully-mechanized hydraulic support extends and retracts multiple levels of side guards to provide side protection. To ensure that the shearer can cut coal, the multiple levels of side guards need to be recovered. Since the side guards between the large mining height fully-mechanized hydraulic supports are all equipped with flexible protective wings, it is impossible to recover the multiple levels of side guards of a large mining height fully-mechanized hydraulic support alone. The recovery of the multiple levels of side guards is done in groups according to the number of large mining height fully-mechanized hydraulic supports. Since the large mining height fully-mechanized hydraulic supports play a role in protecting the hard roof and the large mining height fully-mechanized working face in real time, the number of recovered supports needs to be reasonably set according to the pressure borne by the hydraulic supports and the working face.

[0081] Coal cutting can only be carried out after the side guard plates of the large-mining-height fully-mechanized mining hydraulic support are recovered. The number of recovered frames is determined according to the pressure of the hydraulic support of the working face. The mine pressure monitoring system can be used to monitor the pressure status of the large-mining-height fully-mechanized mining working face and measure the pressure of the hydraulic support of the working face, that is, the pressure of the large-mining-height fully-mechanized mining working face.

[0082] When the pressure of the large-mining-height fully-mechanized mining working face is lower than the preset pressure threshold, the number of multi-level side guards that are retracted in groups is set to no more than 5. When the pressure of the large-mining-height fully-mechanized mining working face is higher than the preset pressure threshold, the number of multi-level side guards that are retracted in groups is set to 2 or 3.

[0083] Here, when the pressure of the working face support is less than the preset pressure threshold, it means that the mine pressure of the working face is relatively weak at this time, and the number of racks for group-retracting multi-level side guards is set to no more than 5, that is, the number of large-mining height comprehensive mining hydraulic supports for group-retracting side guards is no more than 5. When the pressure of the working face support is greater than the preset pressure threshold, it means that the mine pressure of the working face is relatively strong, and it is still necessary to ensure that there are a certain number of side guards to protect part of the working face coal wall, and the number of racks for group-retracting multi-level side guards is set to 2 or 3, that is, the number of large-mining height comprehensive mining hydraulic supports for group-retracting side guards is 2 or 3, and the remaining unrecovered side guards in the large-mining height comprehensive mining hydraulic supports continue to cling to the coal wall to prevent the generation of coal wall spalling after coal cutting on the part of the working face coal wall where the side guards have been recovered.

[0084] In addition, in order to ensure that the coal mining machine can cut coal, when the operating personnel operate the guard plates of the two large-mining height comprehensive mining hydraulic supports behind the coal mining machine, the large-mining height comprehensive mining hydraulic supports are extended with multiple levels of guard plates to ensure that the guard plates are close to the coal wall. Then, according to the pressure of the hydraulic supports on the working face, the corresponding number of guard plates are recovered.

[0085] According to the embodiment of the present invention, when the pressure on the working face is relatively low, the recovery speed of the multi-level side guards can be accelerated by reasonably controlling the number of multi-level side guards that are retracted in groups, thereby ensuring that the coal mining machine can pass through in time to cut coal. When the pressure on the working face is relatively high, in order to avoid serious coal wall spalling on the working face where the side guards have been retracted, a certain number of side guards are retained and only a certain number of side guards are retracted, thereby ensuring the safe passage of operators operating the coal mining machine.

[0086] In some embodiments, after coal is cut on the working face, the corresponding number of multi-level side guards must be retrieved in groups. However, the method of recovering the side guards needs to be selected based on the actual situation and cannot be recovered all at once. Here, when the coal wall spalling is serious in a fully mechanized mining working face with a large mining height, the multi-level side guards are recovered in two stages.

[0087] Generally speaking, a coal wall spalling depth greater than 0.8m in a fully mechanized mining face with a large mining height indicates severe spalling, while a less severe spalling is considered mild. Therefore, the present invention utilizes this criterion to select a method for recovering the sidewall guard plates. The following describes the process of recovering multiple levels of sidewall guard plates twice when the coal wall spalling depth exceeds 0.8m.

[0088] First, when the upper drum of the coal mining machine passes, the recovery degree of the multi-stage rib support is set to 45 degrees with the horizontal ground, which is the first recovery, and when the coal mining machine passes the large mining height fully mechanized hydraulic support, the multi-stage rib support at 45 degrees with the horizontal ground is fully recovered.

[0089] As shown in Figure 5 When the upper cutting drum of the coal mining machine passes, the recovery degree of the multi-stage rib support is set to 45 degrees with the horizontal ground. Because when the multi-stage rib support is close to the coal wall, the main body of the multi-stage rib support extends in a direction nearly perpendicular to the ground, and before the upper cutting drum of the coal mining machine passes, the first stage recovery is performed, and the recovery degree of the multi-stage rib support is set to 45 degrees with the horizontal ground.

[0090] As shown in Figure 6 When the coal mining machine passes the large mining height fully mechanized hydraulic support, the upper cutting drum 7 of the coal mining machine has finished cutting the coal mine of the hydraulic support, and the multi-stage rib support at 45 degrees with the horizontal ground is fully recovered. Because when the upper cutting drum 7 of the coal mining machine passes the hydraulic support, the coal cutting in the working face is finished, and the second stage recovery is performed, and the multi-stage rib support at 45 degrees with the horizontal ground after the first stage recovery is fully recovered.

[0091] In the embodiment of the present application, the movement of the coal mining machine performs two-stage recovery on the multi-stage rib support, which can well block the coal blocks flying out of the coal wall spalling, avoid the coal blocks entering the large foot of the large mining height fully mechanized hydraulic support, greatly reduce the risk of the personnel in the support being hit by the spalling coal, thus improving the management effect of the large mining height working face coal wall spalling, and ensuring the recovery safety of the large mining height working face.

[0092] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for collaboratively controlling coal wall spalling in a fully mechanized mining face with a large mining height, characterized in that: The method comprises: Before mining in a fully mechanized mining face with a large mining height, when unloading and weakening the thick hard rock layer above the hard roof, a downhole high-flow horizontal long-hole regional fracturing method is used to regionally fracture the hard roof; According to the mining height of the large mining height fully mechanized mining working face, the large mining height fully mechanized mining hydraulic support is reasonably selected. The large mining height fully mechanized mining hydraulic support is used to support the hard roof when the large mining height fully mechanized mining working face is mined. The large mining height fully mechanized mining hydraulic support adopts a multi-level side guard structure. The support strength that the large mining height fully mechanized mining hydraulic support needs to meet is , M represents the mining height of the large-mining-height fully-mechanized mining face, the unit of the mining height is m, the unit of the support strength is MPa, and the multi-level side guard structure is used to protect the coal wall spalling generated in the large-mining-height fully-mechanized mining face under the hard roof when mining; The regional fracturing of the hard roof is carried out outside the influence range of the advanced support pressure of the fully-mechanized mining face with a large mining height. The influence range of the advanced support pressure is the distance between the starting point and the installation location of the borehole stress gauge. The starting point is determined by the point where the borehole stress rise value reaches 5% of the initial stress. When the pressure of the fully mechanized mining face with a large mining height is lower than the preset pressure threshold, the number of multi-level side guards to be retracted in groups shall be set to no more than 5; When the pressure of the fully mechanized mining face with a large mining height exceeds the preset pressure threshold, the number of multi-level side guards to be retracted in groups is set to 2 or 3; The retraction method of the multi-level side guard plate includes: When the depth of the coal wall spalling in the fully mechanized mining face with large mining height is greater than 0.8m, the multi-level side guard plates are recovered in two steps; Before the upper cutting drum of the coal mining machine passes through, the retraction degree of the multi-stage side guard plate is set to be at a 45-degree angle to the horizontal ground; When the coal mining machine passes through the current large-height fully-mechanized mining hydraulic support, the multi-level side guard plates at a 45-degree angle to the horizontal ground will be completely retracted into place.

2. The method for collaboratively controlling coal wall spalling in a fully mechanized mining face with large mining height according to claim 1 is characterized in that: The method further comprises: The target layer for regional fracturing of the hard roof is determined based on the height range of the thick hard rock layer. The process of determining the height range of the thick hard rock layer includes: Determine the average expansion coefficient in the hard roof collapse space of the goaf; The height range of thick hard rock formations is calculated using the following formula: ； Among them, M represents the mining height of the fully mechanized mining face with large mining height, Represents the average coefficient of expansion.

3. The method for controlling coal wall spalling in a fully mechanized mining face with large mining height according to claim 1 is characterized in that: The downhole high-flow horizontal long-hole regional fracturing method adopts a retreat-type staged composite fracturing process, and corresponding fracturing process parameters are designed.

4. The method for collaboratively controlling coal wall spalling in a fully mechanized mining face with large mining height according to claim 1 is characterized in that: According to the mining height of the large mining height fully-mechanized mining working face, reasonable selection of large mining height fully-mechanized mining hydraulic support is carried out, including: For large mining height fully mechanized mining working faces with a mining height of more than 3.5m, two-column shielding hydraulic supports are preferred as large mining height fully mechanized mining hydraulic supports.

5. The method for collaboratively controlling coal wall spalling in a fully mechanized mining face with large mining height according to claim 1 is characterized in that: The method further comprises: When mining a fully-mechanized mining face with a large mining height, the mine pressure monitoring system is used to monitor the initial support force of the fully-mechanized hydraulic support and the pressure status of the fully-mechanized mining face in real time. Dynamically adjust the initial support force of the hydraulic support for large mining height fully mechanized mining according to the pressure state of the large mining height fully mechanized mining working face; Among them, when the large mining height fully mechanized mining working face is in a non-pressure state, the initial support force requirement of the large mining height fully mechanized hydraulic support is set to no less than 80% of the rated initial support force; When the large mining height fully mechanized mining working face is in a pressure state, start the booster pump installed on the large mining height fully mechanized mining hydraulic support and set the initial support force requirement of the large mining height fully mechanized mining hydraulic support to no less than 90% of the rated initial support force.

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