Method for calculating working resistance of hydraulic support and method for selecting hydraulic support

Abstract

The application provides a method for calculating working resistance of hydraulic support and a method for selecting hydraulic support, and the method for calculating working resistance of hydraulic support comprises the following steps: if high-stage top coal caving mining method is used to mine 35-55 or 80-90 steeply inclined thick coal seam, the following steps are performed: calculating first hydraulic support load when the working face normally advances and the top coal protection has not been broken, the first hydraulic support load comprising: coal body self weight and additional load applied by top coal cantilever beam; calculating second hydraulic support load when the working face cycle operation stops and top coal caving starts, the second hydraulic support load comprising: coal body self weight and impact load of large coal body on the support; comparing the first hydraulic support load and the second hydraulic support load, and taking the larger one as the working resistance of the hydraulic support. The application solves the phenomenon that the support is crushed, tilted, slides and bites in the actual production process according to the general top coal caving support selection theory in the prior art.

Description

Technical Field

[0001] This invention relates to the field of coal mining, and more particularly to a method for calculating the working resistance of hydraulic supports and a method for selecting hydraulic supports. Background Technology

[0002] Steeply inclined, extra-thick coal seams mostly employ high-stage top-coal caving mining methods, achieving a mining-to-caving ratio of 1:7, while the general top-coal caving process only achieves a ratio of 1:3. During high-stage top-coal caving, due to the maximum caving height reaching 22m, some large coal or rock masses fall freely onto the top of the hydraulic supports, exerting a significant dynamic load impact. If the working resistance of some hydraulic supports is insufficient or the coal and rock masses are large, accidents such as hydraulic support crushing, damage, collapse, and overturning at the fully mechanized caving face can occur. Currently, the selection and design of hydraulic supports for high-stage top-coal caving processes are still based on the selection and design of supports for general top-coal caving processes or on actual mining experience, lacking a complete theoretical framework for the selection and design of high-stage top-coal caving supports. Summary of the Invention

[0003] Based on the above problems, this invention proposes a method for calculating the working resistance of hydraulic supports and a method for selecting hydraulic supports. This invention solves the technical problems encountered in existing technologies, where, based on general top-coal caving support selection theory, phenomena such as support collapse, toppling, lateral slippage, and support jamming frequently occur during actual production. Furthermore, the top coal recovery rate is low, severely impacting normal operation and production at the working face, significantly reducing work efficiency, leading to high maintenance and labor costs, short support lifespan, and increased unit costs. The method for calculating the working resistance of hydraulic supports proposed in this invention enables the selection of suitable hydraulic supports for steeply inclined, extra-thick coal seams of 35°-55° or 80°-90°, preventing collapse, toppling, lateral slippage, and support jamming during coal seam mining.

[0004] This invention proposes a method for calculating the working resistance of a hydraulic support, comprising:

[0005] When using the high-stage top-coal caving mining method to mine extra-thick coal seams with steep inclinations of 35°-55° or 80°-90°, the following procedures apply:

[0006] Calculate the load of the first hydraulic support when the working face is advancing normally and the roof coal has not yet broken. The load of the first hydraulic support includes: the weight of the coal body and the additional load applied by the roof coal cantilever beam.

[0007] Calculate the load on the second hydraulic support when the working face cycle stops and top coal venting begins. The load on the second hydraulic support includes: the weight of the coal body and the impact load of large coal pieces on the support.

[0008] Compare the loads of the first hydraulic support and the second hydraulic support, and take the larger one as the working resistance of the hydraulic support.

[0009] In addition, the first hydraulic support load calculation formula is:

[0010] P1=(h1+h2)lyB+lh1yB,

[0011] In the formula, l is the length of the top coal suspension roof; y is the coal bulk density; h1 is the thickness of the top coal; h2 is the thickness of the pre-split coal; B is the width of the hydraulic support; and P1 is the first hydraulic support load.

[0012] In addition, the second hydraulic support load calculation formula is:

[0013] P2=(h1+h2)lyB+P3,

[0014] In the formula, l is the length of the top coal suspension roof; y is the coal bulk density; h1 is the thickness of the top coal; h2 is the thickness of the pre-split coal; B is the width of the hydraulic support; and P3 is the impact load of the large coal body on the hydraulic support.

[0015] In addition, P3 is calculated according to the law of conservation of momentum: 3 γ(h1+h2)=P3t,

[0016] y is the coal bulk density; P3 is the impact load of the large coal body on the hydraulic support; t is the extremely short action time of the coal body impacting the hydraulic support; and a 3 is the volume of the maximum block size after the top coal is pre-split.

[0017] In addition, if the high-stage top coal caving mining method is used to mine the 35°-55° steeply inclined special thick coal seam, then

[0018] The working resistance of the hydraulic support = max (the first hydraulic support load, the second hydraulic support load) + the impact potential energy of the broken rock stratum rotation;

[0019] The impact potential energy of the broken rock stratum rotation = mgh, wherein m is the mass of the broken rock stratum, g is the gravitational acceleration, and h is the height of the broken rock stratum collapse.

[0020] The application further provides a method for selecting a hydraulic support, comprising:

[0021] calculating the hydraulic support load for each coal seam section, and determining the working resistance of the hydraulic support to be selected according to the plurality of hydraulic support loads;

[0022] calculating the hydraulic support load for each coal seam section comprises:

[0023] If the high-stage top coal caving mining method is used to mine the 35°-55° or 80°-90° steeply inclined special thick coal seam, then the following processing is performed:

[0024] The first hydraulic support load is calculated when the working face is normally advanced and the top coal is not broken, and the first hydraulic support load includes the self weight of the coal body and the additional load applied by the cantilever beam of the top coal.

[0025] The second hydraulic support load is calculated when the working face is stopped and the top coal is started to be caved, and the second hydraulic support load includes the self weight of the coal body and the impact load of the large coal body on the support.

[0026] The first hydraulic support load and the second hydraulic support load are compared, and the larger one is taken as the working resistance of the hydraulic support.

[0027] In addition, the first hydraulic support load calculation formula is:

[0028] P1 = (h1 + h2) l γ B + l h1 γ B,

[0029] In the formula, l is the length of the top coal cantilever; γ is the volume weight of the coal body; h1 is the thickness of the top coal; h2 is the thickness of the pre-split coal body; B is the width of the hydraulic support; and P1 is the first hydraulic support load.

[0030] In addition, the second hydraulic support load calculation formula is:

[0031] P2 = (h1 + h2) l γ B + P3,

[0032] In the formula, l is the length of the top coal cantilever; γ is the volume weight of the coal body; h1 is the thickness of the top coal; h2 is the thickness of the pre-split coal body; B is the width of the hydraulic support; and P3 is the impact load of the large coal body on the hydraulic support.

[0033] In addition, P3 is calculated according to the law of conservation of momentum: 3 γ (h1 + h2) = P3 t,

[0034] γ is the volume weight of the coal body; P3 is the impact load of the large coal body on the hydraulic support; t is the extremely short action time of the coal body impacting the hydraulic support; and 3 a is the volume of the maximum block size of the top coal after pre-splitting.

[0035] In addition, if the high-stage top coal caving mining method is used to mine the 35°-55° steeply inclined thick coal seam, then

[0036] The working resistance of the hydraulic support = max (the first hydraulic support load, the second hydraulic support load) + the impact potential energy of the broken rock stratum rotation.

[0037] The impact potential energy of the broken rock stratum rotation = mgh, wherein m is the mass of the broken rock stratum, g is the acceleration of gravity, and h is the height of the broken rock stratum collapse.

[0038] The present application solves the technical problems of the prior art, such as the frequent phenomena of the support being crushed, falling, side-sliding and biting in the actual production process according to the general top coal caving support selection theory, the low top coal recovery rate, the serious influence on the normal operation production of the working face, the serious reduction of the working efficiency, the high maintenance and manpower cost, the short service life of the support and the high unit cost. The method for calculating the working resistance of the hydraulic support provided by the present application can select the suitable hydraulic support for the 35°-55° or 80°-90° steeply inclined and super-thick coal seam, so that the hydraulic support will not appear the phenomena of being crushed, falling, side-sliding and biting in the coal seam mining. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 The flow chart of the method for calculating the working resistance of the hydraulic support provided by an embodiment of the present application is provided;

[0040] Figure 2 The schematic diagram of the load estimation method provided by the prior art is provided;

[0041] Figure 3 The schematic diagram of the support load when the working face normally advances provided by an embodiment of the present application is provided;

[0042] Figure 4 The schematic diagram of the support load when the working face caving provided by an embodiment of the present application is provided;

[0043] Figure 5 The schematic diagram of the mining layout of the steeply inclined working face provided by an embodiment of the present application is provided. DETAILED DESCRIPTION

[0044] The present application is further described in detail below in combination with the specific implementation and the drawings. The specific implementation of the present application is only intended to elaborate the present application in detail, and does not have any limitation on the present application, and the protection scope of the present application is subject to the claims.

[0045] Reference Figure 1 The present application provides a method for calculating the working resistance of the hydraulic support, comprising:

[0046] In step S001, if the high-stage top coal caving mining method is used to mine the 35°-55° or 80°-90° steeply inclined and super-thick coal seam, the following processing is performed:

[0047] In step S002, the first hydraulic support load when the working face normally advances and the top coal is not broken is calculated, and the first hydraulic support load comprises the self-weight of the coal body and the additional load applied by the top coal cantilever beam;

[0048] In step S003, the second hydraulic support load when the working face stops and starts to caving is calculated, and the second hydraulic support load comprises the self-weight of the coal body and the impact load of the large coal body on the support.

[0049] Step S004, comparing the first hydraulic support load and the second hydraulic support load, taking the greater as the hydraulic support working resistance.

[0050] The hydraulic support is also simply written as support herein.

[0051] Referring to Figure 2 The original hydraulic support working resistance determination method mainly includes: load estimation method and actual measurement statistical method.

[0052] The load estimation method considers that the reasonable working resistance P should not only bear the entire direct roof weight Q1 of the overburden rock hanging roof part, but also bear the additional load Q2 formed when the main roof comes under pressure.

[0053] P = Q1 + Q2,

[0054] After calculation and derivation, the reasonable support strength p of the working face is obtained as (4-8)Mγ1, that is, the roof pressure is equivalent to the weight of 4-8 times the overburden roof. However, the total thickness of the high-stage top coal mining technology reaches 25m. This calculation method not only does not consider the particularity of the high-stage top coal mining height of the thick coal seam, but also does not reflect the influence of the dynamic load impact on the working resistance of the hydraulic support. Therefore, the traditional hydraulic support working resistance determination method is not suitable for the determination of the working resistance of the hydraulic support of the high-stage fully mechanized caving face which needs to consider the impact.

[0055] For the characteristics of the high-stage top coal mining method, when selecting the type of hydraulic support, not only the weight of the top coal and the additional load of the roof structure should be considered, but also the impact of the top coal during the caving and the dynamic load of the hydraulic support caused by the rotation instability of the 45° thick hard roof should be considered. Through the improvement of the existing top coal caving hydraulic support selection and design method, the load bearing state of the support under different working conditions should be considered comprehensively when calculating the working resistance. When mining 35°-55° or 80°-90° steeply inclined thick coal seam by using the high-stage top coal mining method, there is no rock roof above the support, and the coal seam acts as the direct roof. Because the density of the coal seam is smaller and the strength is lower than that of the rock mass, the support load is smaller when the roof comes under pressure. However, the support needs to bear the weight of the thick broken coal mass above it, and also needs to consider the impact of the top coal on the hydraulic support during the caving process. Through the calculation of the support load before caving, during caving and when the top coal comes under pressure, the maximum load is selected as the basis for determining the working resistance of the hydraulic support.

[0056] From the above analysis, when facing 35°-55° or 80°-90° steeply inclined extremely thick coal seam, the load of the hydraulic support is different in different operation stages, when the working face normally advances and the top coal has not been broken, the load of the hydraulic support includes: the self weight of the coal body and the additional load applied by the cantilever beam of the top coal; when the working face stops and starts to release the top coal, the load of the hydraulic support includes: the self weight of the coal body and the impact load of the large coal body on the support. Comparing the size of the first hydraulic support load and the second hydraulic support load, the larger one is taken as the working resistance of the hydraulic support.

[0057] The application innovatively proposes a top coal impact considering top coal releasing hydraulic support selection design method, and optimizes the original unreasonable support selection scheme. The existing support selection design method is improved for the high stage top coal releasing mining method, and the working resistance of the hydraulic support is recalculated.

[0058] The application solves the technical problems in the prior art that according to the general top coal releasing support selection theory, in the actual production process, the support is often crushed, tilted, side-slipped, and bitten, and the top coal recovery rate is low, which seriously affects the normal operation production of the working face, the working efficiency is seriously reduced, the maintenance and labor cost are high, the support service life is short, and the unit cost is increased. The method for calculating the working resistance of the hydraulic support can select suitable hydraulic supports for 35°-55° or 80°-90° steeply inclined extremely thick coal seams, so that the hydraulic support will not appear the phenomena of crushing, tilting, side-slipping, and biting in the coal seam mining.

[0059] In one embodiment, the first hydraulic support load calculation formula is:

[0060] P1=(h1+h2)lγB+lh1γB,

[0061] In the formula, l is the length of the top coal suspension roof, γ is the coal body volume weight, h1 is the thickness of the top coal, h2 is the thickness of the pre-split coal body, B is the width of the hydraulic support, and P1 is the first hydraulic support load.

[0062] In the mining of 35°-55° or 80°-90° steeply inclined extremely thick coal seams, the mining thickness of the high stage fully mechanized caving face is divided into three parts, the normal working face recovery height is M, the top coal thickness is h1, and the upper pre-split coal body is h2. When the working face normally advances, the top coal has not been broken, at this time, the support load is P1, P1 is the weight of the upper (h1+h2) coal body and the additional load applied by the cantilever beam of the top coal, as shown in the formula (1). Figure 3

[0063] In the formula, l is the length of the top coal suspension roof, unit m; γ is the coal body volume weight, unit kN / m 3 ​; h1 is the thickness of the top coal, unit m; h2 is the thickness of the pre-split coal, unit m; B is the width of the hydraulic support, unit m; P1 is the first hydraulic support load.

[0064] The embodiment ensures that the hydraulic support still provides stability and reliability under the impact of the large coal and rock mass.

[0065] In one of the embodiments, the second hydraulic support load calculation formula is:

[0066] P2 = (h1 + h2) l y B + P3,

[0067] In the formula: l is the length of the top coal hanging roof; y is the bulk density of the coal; h1 is the thickness of the top coal; h2 is the thickness of the pre-split coal; B is the width of the hydraulic support; P3 is the impact load of the large coal mass on the hydraulic support.

[0068] When the working face cycle operation stops and the top coal starts to be released, the support resistance is recorded as P2, P2 is the weight of the coal above (h1 + h2) and the impact load of the large coal mass on the support, as shown in Figure 4 . Among them, the weight of the coal above the support takes the maximum value; the impact load of the coal on the support is calculated according to the law of conservation of momentum. Through field investigation, the maximum size of the top coal after pre-splitting is a*a*a (m 3 ), assuming that the large coal mass is located at the top of the coal seam, that is, the height of the coal mass from the support is (h1 + h2), the large coal mass falls and impacts on the top of the support, and the support deforms Ah under the impact load. According to the law of conservation of energy, the potential energy and kinetic energy of the large coal mass are converted into the strain energy of the support. Among them, t can be obtained according to the monitoring parameters of the support on the site.

[0069] In one of the embodiments, P3 is calculated according to the law of conservation of momentum: a 3 y (h1 + h2) = P3t,

[0070] y is the bulk density of the coal, unit kN / m 3 ; P3 is the impact load of the large coal mass on the hydraulic support, unit kN; t is the extremely short action time of the coal impacting the hydraulic support, unit s; a 3 is the volume of the maximum size of the top coal after pre-splitting, unit m 3 .

[0071] In one of the embodiments, if the high-stage top coal caving mining method is used to mine the 35°-55° steeply inclined thick coal seam, then

[0072] The working resistance of the hydraulic support = max (the first hydraulic support load, the second hydraulic support load) + the impact potential energy of the broken rock stratum rotation;

[0073] The impact potential energy of the broken rock stratum rotation is mgh, wherein m is the mass of the broken rock stratum, g is the gravity acceleration, and h is the height of the broken rock stratum collapse.

[0074] When the high-stage top coal caving method is used to mine the 35°-55° steeply inclined thick coal seam, there is no big difference in the calculation of the weight of the coal body above the support and the cantilever beam attached load. It needs to be noted that the rock stratum at the roof of the working face is prone to rotation instability, which exerts additional load on the support. At the floor of the working face, there is a large amount of un-caved coal body, and the support bears a large load, as shown in FIG. 1. Figure 5

[0075] As can be seen from Figure 5 , when the high-stage top coal caving method is used to mine the 35°-55° steeply inclined thick coal seam, the broken rock stratum rotation instability at the roof exerts load on the support, the un-caved residual coal body at the floor exerts load on the support, and the middle support bears the weight of the coal body above and the impact load of the large coal body. Therefore, when the support is selected, the support load should be calculated in different zones, and used as the basis for determining the support working resistance.

[0076] The broken rock stratum rotation instability has a certain impact force on the hydraulic support. The impact force of the broken rock stratum rotation is determined as follows:

[0077] Firstly, according to the buried depth of the high-stage top coal caving and the analysis of the previous mining history, the height, block size and rotation angle of the broken rock stratum of the top coal caving face are determined. The main method is to use the physical similar simulation experiment method to simulate and analyze the broken rule of the overburden stratum of the current top coal caving face, and test and calculate the height, block size and rotation angle of the broken rock stratum after mining.

[0078] Secondly, according to the impact force of the broken rock stratum rotation, the stress characteristics of the hydraulic support are evaluated. Since the lengths of the working faces are different, the impact forces on the working face caused by the broken rock stratum are not the same in different regions. The size of the impact force on the roof side, the middle and the floor side of the working face should be determined comprehensively according to the collapse mode, height and block size of the broken rock stratum, i.e. the impact load is calculated by the gravitational potential energy formula, and the impact potential energy is equal to mgh, wherein m is the mass of the broken rock stratum, g is the gravity acceleration, and h is the height of the broken rock stratum collapse.

[0079] The influence of the broken rock stratum on different regions of the working face is determined. Generally speaking, the roof side and the floor side of the working face of the steeply inclined thick coal seam are relatively large in pressure, and the middle of the working face is relatively stable. When the working resistance of the hydraulic support is determined, the support at the roof side, the middle support and the support at the floor side of the working face can be determined according to the characteristics.

[0080] ​Finally, the larger value between the first hydraulic support load and the second hydraulic support load and the impact potential energy of the broken stratum rotation are taken as the working resistance of the hydraulic support.

[0081] Optionally, for the phenomenon of inverted support and support biting, it is concluded that it is caused by low support stability, and in the design of the support, the width of the support is appropriately widened, and the soft connection mode is adopted between adjacent supports to prevent the inverted support phenomenon.

[0082] The application provides a method for selecting a hydraulic support, comprising:

[0083] The hydraulic support load of the coal seam is calculated in sections, and the working resistance of the hydraulic support to be selected is determined according to the plurality of hydraulic support loads.

[0084] The hydraulic support load of the coal seam is calculated in sections, and the working resistance of the hydraulic support to be selected is determined according to the plurality of hydraulic support loads.

[0085] If the high-stage top coal caving mining method is used to mine the 35°-55° or 80°-90° steeply inclined thick coal seam, the following processing is performed:

[0086] The first hydraulic support load when the working face normally advances and the protective top coal has not been broken is calculated, and the first hydraulic support load comprises the self weight of the coal body and the additional load applied by the cantilever beam of the protective top coal.

[0087] The second hydraulic support load when the working face stops and starts to release top coal in the cycle operation is calculated, and the second hydraulic support load comprises the self weight of the coal body and the impact load of the large coal body on the support.

[0088] The first hydraulic support load and the second hydraulic support load are compared, and the larger one is taken as the working resistance of the hydraulic support.

[0089] When facing the 35°-55° or 80°-90° steeply inclined thick coal seam, the load of the hydraulic support is different in different operation stages, when the working face normally advances and the protective top coal has not been broken, the load of the hydraulic support comprises the self weight of the coal body and the additional load applied by the cantilever beam of the protective top coal, when the working face stops and starts to release top coal in the cycle operation, the load of the hydraulic support comprises the self weight of the coal body and the impact load of the large coal body on the support. The first hydraulic support load and the second hydraulic support load are compared, and the larger one is taken as the working resistance of the hydraulic support.

[0090] The application innovatively provides a top coal caving hydraulic support selection design method considering the impact of top coal, and optimizes the original unreasonable support selection scheme. For the high-stage top coal caving mining method, the existing support selection design method is improved, and the working resistance of the hydraulic support is recalculated.

[0091] The present application solves the technical problems in the prior art that according to the general top coal caving support selection theory, in the actual production process, the support is often crushed, tilted, side-slipped, and the like, and the top coal recovery rate is low, which seriously affects the normal operation production of the working face, the working efficiency is seriously reduced, the maintenance and labor cost are high, the support service life is short, and the unit cost is increased. The method for calculating the working resistance of the hydraulic support provided by the present application can select suitable hydraulic supports for 35°-55° or 80°-90° steeply inclined and thick coal seams, so that the hydraulic support will not be crushed, tilted, side-slipped, and the like when the coal seam is mined.

[0092] In one of the embodiments, the first hydraulic support load calculation formula is:

[0093] P1=(h1+h2)lγB+lh1γB,

[0094] In the formula, l is the length of the top coal suspension roof, γ is the coal bulk density, h1 is the thickness of the top coal, h2 is the thickness of the pre-split coal, B is the width of the hydraulic support, and P1 is the first hydraulic support load.

[0095] When the 35°-55° or 80°-90° steeply inclined and thick coal seam is mined, the mining thickness of the high-stage fully mechanized caving working face is divided into three parts, the normal working face recovery height is M, the top coal thickness is h1, and the upper pre-split coal thickness is h2. When the working face normally advances, the top coal has not been broken, at this time, the support load is recorded as P1, P1 is the weight of the upper (h1+h2) coal body and the additional load applied by the top coal cantilever beam, as shown in the following formula. Figure 3

[0096] In the formula, l is the length of the top coal suspension roof, unit: m; γ is the coal bulk density, unit: kN / m 3 ; h1 is the thickness of the top coal, unit: m; h2 is the thickness of the pre-split coal, unit: m; B is the width of the hydraulic support, unit: m; and P1 is the first hydraulic support load.

[0097] The embodiment ensures that the hydraulic support still provides stable reliability under the impact of the large coal rock body.

[0098] In one of the embodiments, the second hydraulic support load calculation formula is:

[0099] P2=(h1+h2)lγB+P3,

[0100] In the formula, l is the length of the top coal suspension roof, γ is the coal bulk density, h1 is the thickness of the top coal, h2 is the thickness of the pre-split coal, B is the width of the hydraulic support, and P3 is the impact load of the large coal body on the hydraulic support.

[0101] ​When the working face cycle operation stops and the top coal caving starts, the support resistance is recorded as P2, P2 is the weight of the coal above (h1+h2) and the impact load of the large coal mass on the support, as shown in Figure 4 . Among them, the weight of the coal above the support takes the maximum value; the impact load of the coal on the support is calculated according to the law of conservation of momentum. Through field investigation, the maximum size of the top coal after pre-splitting is a*a*a (m 3 ), assuming that the large coal mass is located at the top of the coal seam, that is, the height of the coal mass from the support is (h1+h2), the large coal mass falls and impacts on the top of the support, and the support deforms Δh under the impact load. According to the law of conservation of energy, the potential energy and kinetic energy of the large coal mass are converted into the strain energy of the support. Among them, t can be obtained according to the monitoring parameters of the support on the site.

[0102] In one of the embodiments, P3 is calculated according to the law of conservation of momentum: a 3 γ(h1+h2) = P3t,

[0103] γ is the unit weight of the coal, unit kN / m 3 ; P3 is the impact load of the large coal mass on the hydraulic support, unit kN; t is the extremely short action time of the coal impacting the hydraulic support, unit s; a 3 is the volume of the maximum size of the top coal after pre-splitting, unit m 3 .

[0104] In one of the embodiments, when the high-stage top coal caving mining method is used to mine the 35°-55° steeply inclined and thick coal seam, then

[0105] The working resistance of the hydraulic support = max (first hydraulic support load, second hydraulic support load) + impact potential energy of broken rock stratum rotation;

[0106] The impact potential energy of broken rock stratum rotation = mgh, where m is the mass of the broken rock stratum, g is the acceleration of gravity, and h is the height of the broken rock stratum collapse.

[0107] When the high-stage top coal caving mining method is used to mine the 35°-55° steeply inclined and thick coal seam, there is no big difference in the calculation of the weight of the coal above the support and the cantilever beam additional load. It needs to be noted that the rock stratum at the roof of the working face is prone to rotation instability, which exerts additional load on the support; at the floor of the working face, due to the existence of a large amount of un-released coal, the load on the support is large, as shown in Figure 5 .

[0108] From Figure 5It can be seen that when the high stage top coal caving method is used to mine the 35°-55° steeply inclined thick coal seam, the load of the support at the roof rock is caused by the broken rock mass rotation instability, the load of the support at the floor rock is caused by the residual coal body not caved, and the support in the middle part needs to bear the weight of the upper coal body and the impact load of the large coal body, so when the support is selected, the support load should be calculated in different zones, and used as the basis for determining the working resistance of the support.

[0109] Alternatively, for the support to appear to be inverted and to bite, etc., it is concluded that it is caused by the low stability of the support, and when the support is designed, the width of the support is appropriately widened, and the soft connection mode is adopted between the adjacent supports to prevent the support from appearing to be inverted.

[0110] The above only describes the principles and preferred embodiments of the present application. It should be noted that for those skilled in the art, on the basis of the principles of the present application, a number of other variations can also be made, which should be considered as the protection scope of the present application.

Claims

1. A method for calculating the working resistance of a hydraulic support, characterized in that, include: When using the high-stage top-coal caving mining method to mine extra-thick coal seams with steep inclinations of 35°-55° or 80°-90°, the following procedures apply: Calculate the load of the first hydraulic support when the working face is advancing normally and the roof coal has not yet broken. The load of the first hydraulic support includes: the weight of the coal body and the additional load applied by the roof coal cantilever beam. Calculate the load on the second hydraulic support when the working face cycle stops and top coal venting begins. The load on the second hydraulic support includes: the weight of the coal body and the impact load of large coal pieces on the support. Compare the loads of the first hydraulic support and the second hydraulic support, and take the larger one as the working resistance of the hydraulic support. The formula for calculating the load of the first hydraulic support is: P1=(h1+h2)lγB+lh1γB, In the formula: l is the length of the roof support coal; γ is the bulk density of the coal body; h1 is the thickness of the roof support coal; h2 is the thickness of the pre-splitting coal body; B is the width of the hydraulic support; P1 is the load of the first hydraulic support.

2. The method for calculating the working resistance of a hydraulic support according to claim 1, characterized in that, The formula for calculating the load of the second hydraulic support is: P2=(h1+h2)lγB+P3, In the formula: l is the length of the roof support coal; γ is the bulk density of the coal; h1 is the thickness of the roof support coal; h2 is the thickness of the pre-splitting coal body; B is the width of the hydraulic support; P3 is the impact load of the large coal block on the hydraulic support.

3. The method for calculating the working resistance of a hydraulic support according to claim 2, characterized in that, Calculate P3 based on the law of conservation of momentum: a 3 γ(h1+h2)=P3t, γ is the bulk density of the coal; P3 is the impact load of the large coal mass on the hydraulic support; t is the extremely short duration of the coal mass impacting the hydraulic support; a 3 This refers to the volume of the largest piece of top coal after pre-splitting.

4. The method for calculating the working resistance of a hydraulic support according to any one of claims 1-3, characterized in that, When using the high-stage top-coal caving mining method to mine 35°-55° steeply inclined extra-thick coal seams, the following calculation formula can also be used to calculate the working resistance of the hydraulic support and the impact potential energy of the rock strata rotation: The working resistance of the hydraulic support = max(load of the first hydraulic support, load of the second hydraulic support) + impact potential energy of the fractured rock layer rotating; The impact potential energy of the fractured rock layer is mgh, where m is the mass of the fractured rock layer, g is the gravitational acceleration, and h is the height of the fractured rock layer when it collapses.

5. A method for selecting a hydraulic support, characterized in that, include: Calculate the hydraulic support load for coal seam zoning, and determine the working resistance of the selected hydraulic support based on the loads of multiple hydraulic supports. The calculation of hydraulic support load for coal seam zoning includes: When using the high-stage top-coal caving mining method to mine extra-thick coal seams with steep inclinations of 35°-55° or 80°-90°, the following procedures apply: Calculate the load of the first hydraulic support when the working face is advancing normally and the roof coal has not yet broken. The load of the first hydraulic support includes: the weight of the coal body and the additional load applied by the roof coal cantilever beam. Calculate the load on the second hydraulic support when the working face cycle stops and top coal venting begins. The load on the second hydraulic support includes: the weight of the coal body and the impact load of large coal pieces on the support. Compare the loads of the first hydraulic support and the second hydraulic support, and take the larger one as the working resistance of the hydraulic support. The formula for calculating the load of the first hydraulic support is: P1=(h1+h2)lγB+lh1γB, In the formula: l is the length of the roof support coal; γ is the bulk density of the coal body; h1 is the thickness of the roof support coal; h2 is the thickness of the pre-splitting coal body; B is the width of the hydraulic support; P1 is the load of the first hydraulic support.

6. The method for selecting a hydraulic support according to claim 5, characterized in that, The formula for calculating the load of the second hydraulic support is: P2=(h1+h2)lγB+P3, In the formula: l is the length of the roof support coal; γ is the bulk density of the coal; h1 is the thickness of the roof support coal; h2 is the thickness of the pre-splitting coal body; B is the width of the hydraulic support; P3 is the impact load of the large coal block on the hydraulic support.

7. The method for selecting a hydraulic support according to claim 6, characterized in that, Calculate P3 based on the law of conservation of momentum: a 3 γ(h1+h2)=P3t, γ is the bulk density of the coal; P3 is the impact load of the large coal mass on the hydraulic support; t is the extremely short duration of the coal mass impacting the hydraulic support; a 3 This refers to the volume of the largest piece of top coal after pre-splitting.

8. The method for selecting a hydraulic support according to any one of claims 5-7, characterized in that, When using the high-stage top-coal caving mining method to mine 35°-55° steeply inclined extra-thick coal seams, the following calculation formula can also be used to calculate the working resistance of the hydraulic support and the impact potential energy of the rock strata rotation: The working resistance of the hydraulic support = max(load of the first hydraulic support, load of the second hydraulic support) + impact potential energy of the fractured rock layer rotating; The impact potential energy of the fractured rock layer is mgh, where m is the mass of the fractured rock layer, g is the gravitational acceleration, and h is the height of the fractured rock layer when it collapses.

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