A method and system for designing a cutting height of a self-formed roadway mining without a coal pillar

Abstract

The application discloses a kind of coal pillar-free self-lane mining top cutting height design method and system, belong to coal mining technical field, method includes the following steps: according to the size of stope, working face advancing length and overburden roof thickness, the crushing and swelling characteristics of top cutting caving rock mass are analyzed by numerical simulation and similar simulation test;Based on the crushing and swelling characteristics of top cutting caving rock mass, the crushing and swelling amount of caving gangue within the range of double-side top cutting is calculated;When the actual mining amount reaches the crushing and swelling amount of caving gangue, the mining height at this time is taken as the optimal top cutting height.The application can improve the caving thickness of overburden, produce more crushing and swelling gangue, can completely fill the goaf, realize overburden crushing and swelling balance, use crushing and swelling gangue to compensate coal seam mining space, slow down the deformation of overburden, relieve the damage of surface ecological environment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coal mining, and particularly relates to a method and system for designing a cutting height for self-lane mining without coal pillars. BACKGROUND

[0002] At present, the commonly used method for coal mining in China is the longwall mining 121 method. After the working face of the longwall mining is mined, the overburden roof is not easy to collapse, the thickness of the collapsed rock stratum is insufficient, and the goaf cannot be completely filled, which leads to deformation and breakage of the overburden, and causes serious surface subsidence and deformation, especially in shallow coal seams, which easily causes ecological problems such as surface subsidence and soil erosion. Based on this, the method of cutting roof pressure relief self-lane mining without coal pillars is proposed by Academician He Manchao, which cuts off the connection between the roof of the roadway and the roof of the goaf, solving the problem of the overburden roof not being easy to collapse. However, the design of the cutting height and the cutting angle is not accurate at present. SUMMARY

[0003] The present application aims to solve the problems of the prior art, and provides a method and system for designing a cutting height for self-lane mining without coal pillars, which can improve the collapse thickness of the overburden, produce more broken and expanded gangue, completely fill the goaf, achieve overburden broken and expanded balance, compensate for the coal mining space with broken and expanded gangue, slow down the deformation of the overburden, and alleviate the damage to the ecological environment of the surface.

[0004] To achieve the above-mentioned purpose, the present application provides the following solutions:

[0005] A method for designing a cutting height for self-lane mining without coal pillars, comprising the following steps:

[0006] According to the size of the stope, the working face advance length and the overburden roof thickness, the broken and expanded characteristics of the cutting roof collapse rock mass are analyzed through numerical simulation and similar simulation tests;

[0007] Based on the broken and expanded characteristics of the cutting roof collapse rock mass, the broken and expanded amount of the collapse gangue within the range of the double-side cutting roof is calculated;

[0008] When the actual mining amount reaches the broken and expanded amount of the collapse gangue, the mining height at this time is taken as the optimal cutting height.

[0009] Preferably, the broken and expanded characteristics of the cutting roof collapse rock mass include the stress-strain relationship of the collapse rock mass, the initial broken and expanded coefficient of the collapse rock mass and the residual broken and expanded coefficient of the collapse rock mass;

[0010] The stress-strain relationship of the collapse rock mass is:

[0011]

[0012] Among them, σ1 represents the vertical stress of the collapsed rock mass, E1 represents the initial elastic modulus of the rock mass, ε1 represents the axial strain of the collapsed rock mass when the stress is σ1, and ε m represents the maximum possible axial strain of the collapsed rock mass, σ c Indicates rock mass strength;

[0013] The calculation method of the initial expansion coefficient of the collapsed rock mass includes:

[0014]

[0015] Among them, K1 represents the initial expansion coefficient of the collapsed rock mass, t1 represents the initial expansion height of the collapsed rock mass, and t represents the initial height of the rock mass;

[0016] The calculation method of the residual expansion coefficient of the collapsed rock mass includes:

[0017]

[0018] Among them, K2 represents the residual expansion coefficient of the collapsed rock mass, γ represents the average bulk density of the overlying rock strata, and h represents the burial depth of the coal seam / rock stratum.

[0019] Preferably, the method for calculating the amount of expansion of the collapsed gangue within the double-sided cutting range includes:

[0020] Calculate the amount of rock expansion in layer i:

[0021]

[0022] in, represents the amount of rock expansion in the i-th layer, h i represents the thickness of the i-th rock layer, h n represents the thickness of the nth rock layer, represents the elastic modulus of the i-th rock layer, represents the initial expansion coefficient of the i-th rock layer, Q represents the load from the top rock layer to the surface, represents the bulk density of the i-th rock layer, represents the bulk density of the nth rock layer, and m represents the number of rock layers within the range of the double-sided top cutting;

[0023] The overburden within the double-sided cutting range is calculated to obtain the final amount of collapse and expansion of the gangue:

[0024]

[0025] Among them, F (y)总 Indicates the final amount of collapsed gangue and rock fragments.

[0026] The present invention also provides a system for designing the top cutting height of coal pillar-free self-forming roadway mining, wherein the system applies any of the above-mentioned methods and comprises: a crushing expansion characteristic analysis module, a crushing expansion amount calculation module and a top cutting height confirmation module;

[0027] The expansion characteristics analysis module analyzes the expansion characteristics of the top-cut rock mass through numerical simulation and similar simulation tests according to the size of the stope, the length of the working face advancement and the thickness of the overburden roof;

[0028] The crushing expansion amount calculation module calculates the crushing expansion amount of collapsed gangue within the double-side cutting range based on the crushing expansion characteristics of the cutting top collapsed rock mass;

[0029] When the actual mining volume reaches the amount of collapsed gangue expansion, the top cutting height confirmation module uses the mining height at this time as the optimal top cutting height.

[0030] Preferably, the collapse expansion characteristics of the top-cut rock mass include: stress-strain relationship of the collapse rock mass, initial collapse expansion coefficient of the collapse rock mass and residual collapse expansion coefficient of the collapse rock mass;

[0031] The stress-strain relationship of the collapsed rock mass is:

[0032]

[0033] Among them, σ1 represents the vertical stress of the collapsed rock mass, E1 represents the initial elastic modulus of the rock mass, ε1 represents the axial strain of the collapsed rock mass when the stress is σ1, and ε m represents the maximum possible axial strain of the collapsed rock mass, σ c Indicates rock mass strength;

[0034] The calculation method of the initial expansion coefficient of the collapsed rock mass includes:

[0035]

[0036] Among them, K1 represents the initial expansion coefficient of the collapsed rock mass, t1 represents the initial expansion height of the collapsed rock mass, and t represents the initial height of the rock mass;

[0037] The calculation method of the residual expansion coefficient of the collapsed rock mass includes:

[0038]

[0039] Among them, K2 represents the residual expansion coefficient of the collapsed rock mass, γ represents the average bulk density of the overlying rock strata, and h represents the burial depth of the coal seam / rock stratum.

[0040] Preferably, the method for calculating the amount of expansion of the collapsed gangue within the double-sided cutting range includes:

[0041] Calculate the amount of rock expansion in layer i:

[0042]

[0043] wherein, represents the i-th layer of rock strata, h i represents the thickness of the i-th layer of rock strata, h n represents the thickness of the n-th layer of rock strata, represents the elastic modulus of the i-th layer of rock strata, represents the initial heave coefficient of the i-th layer of rock strata, Q represents the load within the range from the topmost layer of the top cut to the surface, represents the unit weight of the i-th layer of rock strata, represents the unit weight of the n-th layer of rock strata, m represents the number of rock layers within the range of the double-side top cut;

[0044] The overburden rock within the range of the double-side top cut is calculated to obtain the final caving gangue heave:

[0045]

[0046] wherein, F (y)总 represents the final caving gangue heave.

[0047] Compared with the prior art, the present application has the following beneficial effects:

[0048] The present application can improve the caving thickness of the overburden rock, produce more heaved gangue, can completely fill the goaf, realize the overburden rock heave balance, utilize the heaved gangue to compensate the coal seam mining space, slow down the overburden rock deformation, and relieve the surface ecological environment destruction. BRIEF DESCRIPTION OF DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the present application, the following briefly introduces the drawings needed to be used in the embodiments, obviously, the drawings in the following description only some embodiments of the present application, for those skilled in the art, without paying the creative labor, can also obtain other drawings according to these drawings.

[0050] Figure 1 The method flowchart of the embodiment of the present application;

[0051] Figure 2 The method flowchart of the embodiment of the present application;

[0052] Figure 3 The mechanical calculation model of the overburden rock heave of the embodiment of the present application;

[0053] Figure 4 The mechanical calculation model of the overburden rock heave of the thin coal seam top cut of the embodiment of the present application;

[0054] Figure 5A schematic diagram of a mechanical calculation model of a broken and expanded amount of overburden rock under complex conditions of an embodiment of the present application. DETAILED DESCRIPTION

[0055] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present application.

[0056] In order to make the above-mentioned objects, characteristics and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0057] Embodiment one

[0058] In the present embodiment, as shown in Figure 1 , Figure 2 a cutting height design method for pillarless self-formed roadway mining and top cutting, comprising the following steps:

[0059] S1. According to the size of the stope, the length of the working face and the thickness of the overburden roof, the broken and expanded characteristics of the cutting top caving rock mass are analyzed by numerical simulation and similar simulation test. The broken and expanded characteristics of the cutting top caving rock mass include: stress-strain relationship of the caving rock mass, initial broken and expanded coefficient of the caving rock mass and residual broken and expanded coefficient of the caving rock mass.

[0060] In the present embodiment, when cutting top pressure relief pillarless self-formed roadway mining is carried out, the connection between the roadway roof and the goaf roof is cut off at this time, and the overburden rock is more prone to caving. The volume of the caved rock mass will increase due to its broken and expanded characteristics, which can partially fill the goaf, improve the caving thickness of the overburden rock, produce more broken and expanded gangue, and theoretically fill the goaf completely, realize the broken and expanded balance of the overburden rock, compensate for the coal mining space with the broken and expanded gangue, and slow down the deformation of the overburden rock.

[0061] Based on the distribution of the overburden rock, the broken and expanded characteristics of the caving gangue under different conditions are determined. Because the mechanical properties of different lithology are quite different, when the distribution of the overburden rock is different, the broken and expanded degree of the caving gangue is also different. When the lithology of the overburden rock is relatively hard, the broken and expanded characteristics of the caving gangue are small, at this time, the cutting height can be appropriately increased to increase the stress, thereby indirectly improving the broken and expanded characteristics of the caving gangue. When the lithology of the overburden rock is relatively soft, the broken and expanded characteristics of the caving gangue are large, at this time, the cutting height can be appropriately reduced. In order to maximize the broken and expanded degree of the caving gangue, the cutting height is adjusted according to different lithology to improve the broken and expanded characteristics of the caving gangue as much as possible. The common rock broken and expanded coefficient is shown in Table 1.

[0062] Table 1

[0063]

[0064] Based on the state of the collapsed and swelled rock mass, the rock mass expansion coefficient is divided into the initial expansion coefficient and the residual expansion coefficient. The expansion coefficient at the initial collapse of the rock mass is called the initial expansion coefficient, and the expansion coefficient at the final stabilization of the rock mass collapse is called the residual expansion coefficient. The residual expansion coefficient determines the filling of the goaf and the collapse state of the overburden. In this embodiment, based on the study of the deformation characteristics of the broken rock mass, the stress-strain relationship of the collapsed rock mass is:

[0065]

[0066] Among them, σ1 represents the vertical stress of the collapsed rock mass, in Pa; E1 represents the initial elastic modulus of the rock mass, in Pa; ε1 represents the axial strain of the collapsed rock mass when the stress is σ1; ε m Indicates the maximum possible axial strain of the collapsed rock mass; σ c Indicates rock mass strength, unit is Pa.

[0067] The initial expansion coefficient of collapsed rock mass and the residual expansion coefficient of collapsed rock mass can be calculated as:

[0068]

[0069] Among them, t1 represents the initial crushing height of the collapsed rock mass, in m; t2 represents the residual crushing height of the collapsed rock mass, in m; t represents the initial height of the rock mass, in m; K1 represents the initial crushing coefficient of the collapsed rock mass; K2 represents the residual crushing coefficient of the collapsed rock mass.

[0070] The relationship between the stress and strain of the rock mass and the coefficient of expansion can be calculated as follows:

[0071]

[0072] The vertical stress on the rock mass can be calculated according to the burial depth of the rock mass:

[0073] σ1=γh,

[0074] Where γ represents the average bulk density of the overlying rock layer, and the unit is kg / m 3 ; h represents the burial depth of coal seam / rock layer, in m.

[0075] According to the above formula, the calculation method of the residual expansion coefficient of collapsed rock mass can be obtained as follows:

[0076]

[0077] According to the formula of formula K2, the residual dilatancy coefficient of the rock mass is mainly related to the elastic modulus of the rock mass itself, the initial dilatancy coefficient and the buried depth. When the geological conditions are determined, the rock mass and the buried depth can be determined. Therefore, in order to improve the dilatancy coefficient and the dilatancy amount of the rock mass, the caving height of the rock stratum can be increased by using the top cutting, so that more dilatancy amount of the rock stratum can be generated, the mining space can be better filled, the damage of the overlying rock stratum can be reduced, and then the surface deformation can be slowed down. More dilatancy amount can also support the side of the roadway goaf, reduce the pressure of the roadway roof, and improve the stability and safety of the roadway.

[0078] S2. Based on the dilatancy characteristics of the caving rock mass of the top cutting, the dilatancy amount of the caving gangue in the range of the double-side top cutting is calculated.

[0079] In this embodiment, based on the distribution of the overlying rock stratum and the relationship between the height of the roadway and the thickness of the coal seam, the top cutting height of the caving gangue of the overlying rock stratum under different conditions is determined, and the dilatancy amount of the caving gangue is improved. Based on the relative position relationship between the roadway and the coal thickness, the top cutting height under different conditions is determined. The mechanical model for calculating the dilatancy amount when the double-side top cutting is used or not is the same, and the mechanical model when the double-side top cutting is selected is calculated. In the calculation, it is assumed that the working face has been fully mined, the caving rock mass follows the stress-strain relationship of the broken rock mass, the rock mass is fully dilated, and since the double-side top cutting goaf is basically filled, there is no separation between the rock strata, and the load of the overlying rock stratum is completely transferred to the goaf. The mechanical model is as shown in Figure 3 Under the influence of the double-side top cutting, the rock strata in the range of the double-side top cutting are completely caved, and the calculation formula of the dilatancy amount is as follows:

[0080]

[0081] Wherein, h represents the buried depth of the coal seam / rock stratum, and the unit is m; y represents the top cutting height; l represents the top cutting depth, and the unit is m; θ represents the top cutting angle, and the unit is °.

[0082] Based on the relative position relationship between the roadway and the coal thickness, the top cutting height under different conditions is determined. When the thin / ultra-thin coal seam is mined, since the height of the roadway is higher than the thickness of the coal seam, a part of the roof has been cut during the roadway forming process. However, the dilatancy amount generated by the caving of this part of the roof is generally insufficient to completely fill the goaf, so the double-side top cutting technology is still needed for top cutting. The mechanical model is as shown in Figure 4 However, when calculating the dilatancy amount, this part of the top cutting during the roadway forming process needs to be calculated, so the dilatancy amount calculation formula for thin / ultra-thin coal seams is:

[0083]

[0084] Wherein, l1 represents the height of the roadway exceeding the coal seam.

[0085] For different thickness of coal seam, the space of goaf after coal seam mining is different, and the caving condition of rock mass is different. Under the same other test conditions, the initial dilatancy coefficient of sandstone caving from different height is distributed in 1.794~2.110, and the dilatancy coefficient is greatly affected by the caving height, so the dilatation of rock mass under different coal seam thickness (mining height) needs to be considered in the field engineering, and the full caving coefficient η of rock mass is introduced, combined with the caving data of overburden rock, the actual dilatation amount of rock mass is calculated as follows:

[0086]

[0087] Wherein, η represents the full caving coefficient of rock mass, 0.7~1.0 for medium and back coal seam, 0.4~0.7 for thin coal seam, and 0~0.4 for very thin coal seam.

[0088] According to the above formula, the required dilatation amount of rock mass can be calculated according to the mining height under the condition of obtaining the average unit weight of overburden rock, so as to determine the parameters of top cutting, which can provide calculation basis for field engineering and is suitable for simple geological conditions. In order to make the model more close to the field and suitable for complex conditions, the mechanical model as shown in Figure 5 is established to calculate the dilatation amount of each layer of rock mass in the range of double side top cutting. For thin coal seam, the top cutting part of roadway can also be calculated according to this formula.

[0089] The method for calculating the dilatation amount of caving gangue in the range of double side top cutting includes:

[0090] Based on the dilatation characteristics of overburden caving gangue, the dilatation coefficients of caving gangue of different lithology are different. Because the dilatation coefficients of each lithology are different, the distribution of overburden rock has a crucial influence on the dilatation degree of caving gangue. According to the distribution of overburden rock, the top cutting height needs to be adjusted accordingly. The rock mass in this area is called dilatation rock mass after adopting double side top cutting technology, and the dilatation amount of the i layer of rock mass in the range of double side top cutting is:

[0091]

[0092]

[0093] According to the above two formulas, the dilatation amount of the i layer of rock mass is:

[0094]

[0095] Wherein, represents the dilatation amount of the i layer of rock mass, h i represents the thickness of the i layer of rock mass, h n represents the thickness of the n layer of rock mass, represents the elastic modulus of the i-th rock layer, represents the initial expansion coefficient of the i-th rock layer, Q represents the load from the top rock layer to the surface, represents the bulk density of the i-th rock layer, It represents the bulk density of the nth rock layer, and m represents the number of rock layers within the range of double-sided cutting top.

[0096] The overburden within the double-sided cutting range is calculated to obtain the final amount of collapsed gangue expansion:

[0097]

[0098] Among them, F (y)总 Indicates the final amount of collapsed gangue and rock fragments.

[0099] S3. When the actual mining volume reaches the amount of collapsed gangue and expansion, the mining height at this time will be taken as the optimal top cutting height.

[0100] Example 2

[0101] In this embodiment, a system for designing the top cutting height of coal pillar-free self-forming roadway mining includes: a crushing expansion characteristic analysis module, a crushing expansion amount calculation module, and a top cutting height confirmation module.

[0102] The expansion characteristics analysis module analyzes the expansion characteristics of the top-cut rock mass through numerical simulation and similarity testing based on the stope size, working face advance length, and overburden roof thickness. These expansion characteristics include the stress-strain relationship, the initial expansion coefficient, and the residual expansion coefficient.

[0103] The stress-strain relationship of collapsed rock mass is:

[0104]

[0105] Among them, σ1 represents the vertical stress of the collapsed rock mass, E1 represents the initial elastic modulus of the rock mass, ε1 represents the axial strain of the collapsed rock mass when the stress is σ1, and ε m represents the maximum possible axial strain of the collapsed rock mass, σ c Indicates rock mass strength.

[0106] The calculation methods of the initial expansion coefficient of collapsed rock mass include:

[0107]

[0108] Among them, K1 represents the initial expansion coefficient of the collapsed rock mass, t1 represents the initial expansion height of the collapsed rock mass, and t represents the initial height of the rock mass.

[0109] The calculation methods of the residual expansion coefficient of collapsed rock mass include:

[0110]

[0111] wherein, gamma represents the average bulk density of overburden, and h represents the depth of coal seam / rock layer.

[0112] The fragmentation volume calculation module calculates the fragmentation volume of the caving gangue within the double-side top cutting range based on the fragmentation characteristics of the top cutting caving rock mass.

[0113] The fragmentation volume of the ith layer of rock mass is calculated as follows:

[0114]

[0115] wherein, represents the fragmentation volume of the ith layer of rock mass, h i represents the thickness of the ith layer of rock mass, h n represents the thickness of the nth layer of rock mass, represents the elastic modulus of the ith layer of rock mass, represents the initial fragmentation coefficient of the ith layer of rock mass, Q represents the load within the range from the uppermost rock layer of the top cutting to the surface, represents the bulk density of the ith layer of rock mass, represents the bulk density of the nth layer of rock mass, and m represents the number of rock layers within the double-side top cutting range.

[0116] The overburden within the double-side top cutting range is calculated to obtain the final fragmentation volume of the caving gangue:

[0117]

[0118] wherein, F (y)总 represents the final fragmentation volume of the caving gangue.

[0119] The top cutting height confirmation module takes the mining height at the time when the actual mining amount reaches the fragmentation volume of the caving gangue as the optimal top cutting height.

[0120] The above-described embodiments are merely descriptions of the preferred modes of the present application and are not intended to limit the scope of the present application. Various modifications and improvements to the technical solutions of the present application made by those of ordinary skill in the art without departing from the design spirit of the present application shall fall within the protection scope of the present application as defined by the claims.

Claims

1. A method for designing the top cutting height of coal pillar-free self-forming roadway mining, characterized in that: The following steps are involved: Based on the size of the stope, the length of the working face advancement, and the thickness of the overburden roof, numerical simulation and similarity simulation tests are used to analyze the expansion characteristics of the top-cut rock mass. The expansion characteristics include the stress-strain relationship of the collapse rock mass, the initial expansion coefficient of the collapse rock mass, and the residual expansion coefficient of the collapse rock mass. Based on the crushing and swelling characteristics of the top-cutting collapsed rock mass, the crushing and swelling amount of the collapsed waste rock within the top-cutting range on both sides is calculated; When the actual mining volume reaches the amount of collapsed gangue expansion, the mining height at this time is taken as the optimal top cutting height; The stress-strain relationship of the collapsed rock mass is: ， ， in, σ 1 represents the vertical stress on the collapsed rock mass, E 1 represents the initial elastic modulus of the rock mass, ε 1 means the stress is σ The axial strain of the collapsed rock mass at 1, ε m represents the maximum possible axial strain of the collapsed rock mass, σ c Indicates rock mass strength; The calculation method of the initial expansion coefficient of the collapsed rock mass includes: ， in, K 1 represents the initial expansion coefficient of collapsed rock mass, t 1 represents the initial expansion height of the collapsed rock mass, t represents the initial height of the rock mass; The calculation method of the residual expansion coefficient of the collapsed rock mass includes: ， in, K 2 represents the residual expansion coefficient of collapsed rock mass, γ It represents the average bulk density of the overlying rock layers of the rock mass. h Indicates the depth of coal seam / rock layer; The method for calculating the amount of expansion of collapsed gangue within the double-sided cutting range includes: Calculate the i Layer rock fragmentation and expansion: ， in, Indicates the i The amount of rock layer expansion, h i Indicates the i The thickness of the rock layer, h n Indicates the n The thickness of the rock layer, Indicates the i The elastic modulus of the rock layer, Indicates the i The initial expansion coefficient of the rock layer, Q Indicates the load from the topmost rock layer to the surface. Indicates the i The bulk density of the rock layer, Indicates the n The bulk density of the rock layer, m Indicates the number of rock layers within the range of bilateral cutting top; The overburden within the double-sided cutting range is calculated to obtain the final amount of collapse and expansion of the gangue: ， in, F (y)总 Indicates the final amount of collapsed gangue and rock fragments.

2. A system for designing the top cutting height of coal pillar-free self-forming roadway mining, the system applying the method of claim 1, characterized in that: include: Crushed expansion characteristic analysis module, crushed expansion amount calculation module and top cutting height confirmation module; The expansion characteristics analysis module analyzes the expansion characteristics of the top-cut rock mass through numerical simulation and similar simulation tests according to the size of the stope, the length of the working face advancement and the thickness of the overburden roof. The expansion characteristics of the top-cut rock mass include: the stress-strain relationship of the collapse rock mass, the initial expansion coefficient of the collapse rock mass and the residual expansion coefficient of the collapse rock mass; The crushing expansion amount calculation module calculates the crushing expansion amount of collapsed gangue within the double-side cutting range based on the crushing expansion characteristics of the cutting top collapsed rock mass; When the actual mining volume reaches the amount of collapsed gangue expansion, the top cutting height confirmation module uses the mining height at this time as the optimal top cutting height.

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