A large-span roadway asynchronous tunneling method and a method for determining key parameters

Abstract

The present invention provides a method for asynchronous tunneling in large-span roadways and a method for determining key parameters, which relates to the technical field of coal mining, and includes: Step 1, a single-shot bolting operation; Step 2, an asynchronous continuous mining operation; The present invention also provides a method for determining key parameters for asynchronous tunneling in large-span roadways, including: The construction width 2b' of the single-shot bolting operation is calculated according to the dimensions of the existing equipment required for this operation; A roof mechanical model is established, and the expression for the length 2a' of the tunneling unsupported roof area is obtained by using the tensile failure criterion as the judgment condition, and the limit length 2a' is calculated by using this expression; Through FLAC numerical simulation, the distribution of the plastic zone, the vertical displacement distribution, and the vertical stress distribution of the roadway surrounding rock under different lag distances are calculated. When the vertical displacement and the vertical stress are the smallest, it is used as the condition for selecting the lag distance L. The present invention can achieve one-time roadway formation and determine its key parameters to facilitate the smooth progress of construction.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mining, and in particular to a method for asynchronous tunneling of large-span roadways and a method for determining key parameters. Background Art

[0002] Coal resources are the most abundant and widely distributed fossil energy on the earth. China is the country with the highest coal output. At present, coal still has an irreplaceable position in China's energy industry and is an important driving force for economic development. The reserves of medium-thick coal seams account for about 45% of China's coal reserves. As the Shenfu-Dongsheng coalfield, which is rich in coal resources in the western region of China, is located in the Jurassic coalfield. In this area, the coal seams are shallowly buried, occur stably, have simple geological structures, are thick, and have superior mining conditions. There are 1 - 14 workable coal seams, with a total workable thickness of 0.7 - 26.89 m, and the maximum single-layer thickness is 12.5 m. For the extra-thick coal seams in this area, layered mining is mainly adopted. Due to the limitations of the early fully-mechanized mining manufacturing level and mining technology, the lower layers were not mined after the upper layers were mined, resulting in serious waste of coal resources.

[0003] With the slogan of "using scientific and technological means to rescue wasted coal resources", the coal resources left in the lower layers are urgently recovered. With the development of fully-mechanized mining technology and the need for intelligent mine construction, the equipment is gradually becoming larger, and the span of the working face roadways is also getting larger and larger. The large-span roadways meet the requirements of the current large mining height and top coal caving fully-mechanized mining face for arranging large tunneling and supporting equipment. When arranging roadways in thick coal seams, the cross-section span is larger than that of thin and medium-thick coal seams, making the stress state and deformation characteristics of the roadway surrounding rock different from those of ordinary roadways. For large-span roadways, compared with the return airway and the transportation roadway, the cross-section span is larger, and it is more likely to cause roof fall and rib spalling accidents. As a result, it needs to be repaired many times during its service period, seriously affecting the normal production of the mine and the lives of the workers. How to select a suitable tunneling method has become a key factor restricting the production capacity of fully-mechanized mining in thick coal seams. The traditional large-span roadway tunneling method generally adopts the secondary roadway formation method, that is, first tunnel a certain width, and then expand the roadway to the designed width. In this way, the roof of the cut-through roadway needs to experience 2 times of stress redistribution, seriously affecting the stability of the roadway surrounding rock.

[0004] Based on this, there is an urgent need for a new coal mining method to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for asynchronous tunneling of large-span roadways and a method for determining key parameters to solve the problems existing in the above-mentioned prior art, and to achieve one-time roadway formation. One-time roadway formation can not only shorten the construction period, reduce the procedures of withdrawing the roadheader and disassembling the equipment during secondary roadway formation, effectively reducing the labor intensity of workers; but also can avoid the roof safety problems caused by the redistribution of surrounding rock stress caused by secondary rib expansion.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a large-span roadway asynchronous tunneling method, including:

[0008] Step 1: One-time tunneling and bolting operation

[0009] During roadway construction, first use a roadheader to construct and mine the coal seam on one side close to the secondary rib, and the construction width is , and at the same time, use the roof bolting drill box on the roadheader to complete the roof support of the roadway, and use two side drill boxes to complete the rib support of the roadway;

[0010] Step 2: Asynchronous continuous mining operation

[0011] When the advanced distance of the roadheader construction reaches a reasonable lag distance L, use a continuous miner and its supporting equipment to cut the coal seam of the remaining width on the positive rib side of the roadway to complete asynchronous construction, and carry out the support work on this roadway.

[0012] The present invention also provides a method for determining the key parameters of large-span roadway asynchronous tunneling, including: the construction width of the one-time tunneling and bolting operation Calculate according to the existing equipment dimensions required for this process, and the width needs to be as narrow as possible on the premise of meeting the normal operation of the existing equipment;

[0013] The calculation method for the length of the one-time tunneling empty roof area of 2a is as follows: establish a roof mechanical model, use the tensile failure criterion as the judgment condition to find the expression of the tunneling empty roof area length 2a, and use this expression to calculate the limit length ;

[0014] The judgment method for the lag distance L is as follows: through FLAC numerical simulation, calculate the distribution of the plastic zone, vertical displacement distribution, and vertical stress distribution of the roadway surrounding rock under different lag distances, and select the condition when the vertical displacement and vertical stress are the smallest as the condition for selecting the lag distance L.

[0015] Preferably, regard the roof as a thin plate structure with three sides fixed and one side simply supported, and accordingly establish a roof mechanical model; use the basic equations of elasticity, displacement boundary conditions, and Galerkin variational equations to obtain the deflection equation and the expression of the stress component; on this basis, use the tensile failure criterion as the judgment condition to find the expression of the empty roof area length.

[0016] Preferably, through derivation, the expression of the limit length is:

[0017]

[0018] In the formula, b′ is the tunneling width2b′ Half of; h It is half of the thickness 2h of the roadway roof; q It is to apply a uniform load on the overlying strata of the roof; μ It is the Poisson's ratio of the roadway roof; It is the tensile strength of the roadway roof.

[0019] The present invention has achieved the following technical effects compared with the prior art:

[0020] 1. Shorten the construction period.

[0021] 2. Reduce the procedures of withdrawing the roadheader and disassembling the equipment during the secondary roadway formation.

[0022] 3. Effectively reduce the labor intensity of workers.

[0023] 4. Avoid the roof safety problems caused by the redistribution of surrounding rock stress due to secondary rib expansion. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0025] Figure 1 It is a schematic diagram of roadway driving;

[0026] Figure 2 It is a model with four sides of the roof fixed before roadway driving;

[0027] Figure 3 It is a model with four sides of the roof fixed before roadway driving;

[0028] Figure 4(a) Roadway driving model;

[0029] Figure 4(b) Force analysis of the thin plate in the empty roof area during roadway driving;

[0030] Figures 5(a) to 5(c) It is a numerical model with different lag distances;

[0031] Figure 6 It is a schematic diagram of equipment layout;

[0032] Figure 7 It is a relationship diagram between different driving widths and the length of the empty roof area of the roadway;

[0033] Figure 8(a) is a driving model with a lag of 20 m;

[0034] Figure 8(b) is a driving model with a lag of 40 m;

[0035] Figure 8(c) shows the tunneling model with a lag of 50 m;

[0036] Figure 9 are the roof subsidence and the maximum stress of the remaining coal pillar at the heading face under different lag distances;

[0037] Figure 10(a) shows the relationship between the roof subsidence of measuring point 1 and the roadway driving length in the example;

[0038] Figure 10(b) shows the relationship between the roof subsidence of measuring point 2 and the roadway driving length in the example. Specific implementation manners

[0039] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0040] The purpose of the present invention is to provide a method for asynchronous tunneling of large-span roadways and a method for determining key parameters to solve the problems existing in the above-mentioned prior art, and to achieve one-time roadway formation. One-time roadway formation can not only shorten the construction period, reduce the procedures of withdrawing the roadheader and disassembling the equipment during the second roadway formation, and effectively reduce the labor intensity of workers; but also can avoid the roof safety problems caused by the redistribution of surrounding rock stress caused by the secondary rib expansion.

[0041] To make the above objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0042] Embodiment 1

[0043] This embodiment provides a method for asynchronous tunneling of large-span roadways, as Figures 1 to 3 shown, including:

[0044] Step 1, one-time bolting and tunneling process

[0045] During roadway construction, first use a roadheader to construct and mine the coal seam on the side close to the secondary rib, and the construction width is , and at the same time, use the top anchor drill box on the roadheader to complete the roadway roof support, and use two side drill boxes to complete the roadway rib support;

[0046] Step 2, asynchronous continuous mining process

[0047] When the advanced distance of the tunneling and bolting machine construction reaches the reasonable lag distance L, a continuous miner and its supporting equipment are used to cut the coal seam of the remaining width on one side of the positive side of the roadway to complete asynchronous construction, and the roadway is supported.

[0048] Embodiment 2

[0049] This embodiment provides a method for determining key parameters for asynchronous tunneling of large-span roadways, including: the construction width of one tunneling and bolting operation Calculated according to the existing equipment dimensions required for this process, the width Needs to be as narrow as possible on the premise of meeting the normal operation of the existing equipment;

[0050] The calculation method of the length of the first tunneling roof-free area of 2a is as follows: establish a roof mechanical model, use the tensile failure criterion as the judgment condition to obtain the expression of the tunneling roof-free area length 2a, and use this expression to calculate the limit length ;

[0051] The judgment method of the lag distance L is as follows: through FLAC numerical simulation, calculate the distribution of the plastic zone, vertical displacement distribution, and vertical stress distribution of the roadway surrounding rock under different lag distances, and select the condition when the vertical displacement and vertical stress are the smallest as the condition for selecting the lag distance L.

[0052] Among them, the roof is regarded as a thin plate structure with three sides fixed and one side simply supported, and a roof mechanical model is established accordingly; using the basic equations of elasticity, displacement boundary conditions, and Galerkin variational equations, the deflection equation and stress component expressions can be obtained; on this basis, using the tensile failure criterion as the judgment condition, the expression of the roof-free area length can be obtained. After derivation, the expression of the limit roof-free area length is:

[0053]

[0054] In the formula, b′ is half of the tunneling width 2b′ ; h is half of the roadway roof thickness 2h; q is the uniform load applied by the overlying strata of the roof; μ is the Poisson's ratio of the roadway roof; is the tensile strength of the roadway roof.

[0055] The asynchronous tunneling method and key parameter determination method for large-span roadways provided by the present invention can achieve one-time roadway formation. One-time roadway formation can not only shorten the construction period, reduce the procedures of withdrawing the tunneling machine and disassembling the equipment during the second roadway formation, effectively reduce the labor intensity of workers; but also avoid the roof safety problems caused by the redistribution of surrounding rock stress caused by the second sidewall expansion.

[0056] The specific calculation process of the required parameters is as follows:

[0057] 1) Establishment of the mechanical model for the roof caving area during one-time tunneling

[0058] A thin plate refers to an object with a thickness much smaller than its length and width. The roof of the roadway is solid coal, and the coal-bearing strata belong to a layered structure, which belongs to the category of thin plates; the suspended roof after roadway excavation is a rectangular section, conforming to the structure of a rectangular thin plate. As the roadway working face advances forward, the suspended roof of the roadway will break when it is suspended to a certain extent, and the back of the roadway will lose effective restraint. At this time, the roof caving area of one-time tunneling can be regarded as a thin plate with three sides fixed and one side simply supported. As shown in Figure 4(a). Take its middle surface ( Figure 4a middle plane) for mechanical analysis, as shown in Figure 4(b).

[0059] Conduct mechanical analysis on its middle surface, according to the basic assumptions of elasticity and the displacement boundary conditions of a thin plate with three sides fixed and one side simply supported. In Figure 4, corresponds to the secondary side of the roadway, corresponds to the primary side of the roadway, corresponds to the coal wall of the roadway working face, corresponds to the coal wall on the advancing side of the roadway.

[0060] 2) Solution of the mechanical model

[0061] 、 、 are fixed edges, is a simply supported edge. Substitute into the Galerkin variational equation to obtain the expression of the deflection of the thin plate. According to the obtained deflection expression, substitute into the basic equations of elasticity to obtain the expression of the stress components of each boundary in 1), providing a basis for the breakage of the roadway roof boundary.

[0062] According to the displacement boundary conditions that should be satisfied by the structure of a thin plate with three sides fixed and one side simply supported, set the deflection equation of the elastic thin plate with three sides fixed and one side simply supported as:

[0063] (1)

[0064] Substitute equation (1) into the Galerkin variational equation to get:

[0065] (2)

[0066] In the formula: c are undetermined constants;

[0067] D is the bending stiffness of the thin plate, , E is the elastic modulus of the thin plate, is the Poisson's ratio of the thin plate, and h is the thickness of the thin plate. Substituting Equation (2) into Equation (1), the deflection equation can be obtained as follows;

[0068] (3)

[0069] In the formula: q is the overlying load.

[0070] When the thin plate undergoes flexural deformation and shear stress is not considered, the three principal stress components on it are:

[0071] (4)

[0072] Substituting the deflection formula (3) into (4), the expression of the principal stress components of the elastic thin plate with three sides fixed and one side simply supported can be obtained:

[0073] (5)

[0074] 3) Determination conditions for the length of the limit roofless area in one-pass tunneling

[0075] Since the tensile strength of coal and rock mass is much smaller than its strength, the tensile failure criterion is selected as the judgment standard when judging the roof. That is, the maximum tensile strength of the roof is equal to the maximum tensile stress that the fixed boundaries on both sides of the roof can withstand When this occurs, the fixed boundaries on both sides of the roadway roof will crack first. The boundary conditions of the roof change, and the roadway roof becomes a thin plate with one side fixed and three sides simply supported, only restricted by the coal wall in front, and the tensile stress of the coal wall in front will also quickly increase to the ultimate tensile strength of the roof , resulting in the roadway roof becoming a thin plate with four free sides, and the roof is completely damaged. According to the expression of the stress conditions at the fixed boundaries on both sides obtained in step 2) , through solving, 2a` is obtained. See formulas (6) and (7).

[0076] (6)

[0077] By simplifying Equation (6), the limit roofless area length of the roadway roof can be obtained as:

[0078] (7)

[0079] 4) Determination of influencing factors for the limit roofless area in one-pass tunneling

[0080] According to the above step 3), the limit breaking length of the roofless area in one-pass tunneling is obtained as 2a`. The factors affecting 2a` in formula (6) are the one-pass tunneling width 2b′ , the thickness 2 of the roadway roof h , the uniform load applied by the overlying rock layer on the roof q, Poisson's ratio of the roadway roof μ and tensile strength of the roadway roof .

[0081] For a determined roadway working face, the thickness of its roadway roof is 2 h , a uniform load is applied by the overlying strata of the roof q , Poisson's ratio of the roadway roof μ and tensile strength of the roadway roof are generally fixed values. Based on this, when determining the size of the open roof area of the roadway, only the one-time driving width 2b′ needs to be considered.

[0082] (2) Determination of the reasonable lag distance for secondary asynchronous driving

[0083] During the actual driving process of the roadway, for the convenience of construction, a certain stagger distance must be maintained between the roadheader and the continuous miner during roadway driving for asynchronous construction.

[0084] The roadheader on the side close to the secondary rib is driven first, and after a certain distance, the continuous miner drives to form a complete large-span roadway. Through FLAC numerical simulation, the distribution of the plastic zone, vertical displacement, and vertical stress of the roadway surrounding rock under different lag distances (Figure 5) is calculated. When the vertical displacement and vertical stress are the smallest, it is used as a reference for determining the lag distance, and a data table can be established for comparison. As shown in Table 1.

[0085] Table 1 Determination of the reasonable lag distance for secondary asynchronous driving Lag distance

[0086]

[0087] (4) Specific construction process

[0088] During the driving process of the roadway, the "roadheader + continuous miner asynchronous driving and one-time roadway formation" technology is used. First, the roadheader is used to construct on the side of the cut-eye secondary rib. When the leading distance of the roadheader construction reaches the above-mentioned reasonable lag distance, the continuous miner starts to construct.

[0089] The equipment layout is as Figure 6 shown. The specific construction process is as follows:

[0090] 1) Roadheader operation

[0091] During roadway construction, the roadheader is first used to construct on the side close to the secondary rib. The one-time driving width 2b′ is the key parameter determined in the above step (1). At the same time, the roof support of the roadway is completed by the top anchor drill box on the roadheader, and the rib support of the roadway is completed by two side drill boxes.

[0092] 2) Continuous miner operation

[0093] When the advanced distance of the roadheader construction reaches the reasonable lag distance obtained in the above step (2), a continuous miner and its supporting equipment are used to cut coal on the remaining width of the positive side of the roadway to complete the asynchronous construction of the roadway. One bolter is selected to complete the support work of the roadway.

[0094] Example: (1) Project overview

[0095] Taking a certain mine in the shallow-buried coal seam in northern Shaanxi as a test case, the main coal seam mined in this mine is Coal 1 -2 Coal. The coal seam is a nearly horizontal coal seam with a thickness of 9.5 - 10.6 m and an average burial depth of 77 m. The lithology of the coal seam floor is mainly siltstone and fine sandstone, and calcareous siltstone is interspersed in some areas. The uniaxial compressive strength of the top coal in the roadway ranges from 3.9 - 14.5 MPa; the average compressive strength Rc is 9.2 MPa; the average elastic modulus is 1.8 GPa; the Poisson's ratio is 0.27; the tensile strength ranges from 0.8 - 2.2 MPa, and the average strength is 1.4 MPa. The test roadway is located below the goaf 200 m southeast of the overlying roadway. According to the elevation of the coal seam floor, it is predicted that the remaining coal seam thickness after the upper slice of Coal 1 -2 is 6.4 - 7.1 m. The designed length of the roadway is 251.4 m, the height is 3.9 m, the width is 9 m, and the average thickness of the top coal is 4 m.

[0096] (2) Calculation of key parameters for roadway driving

[0097] 1) Calculation of driving width

[0098] Combined with the limitations of existing equipment, 5 driving schemes are designed, as shown in Table 2.

[0099] Table 2 Roadway driving schemes

[0100]

[0101] According to Equation (7), the lengths of the unsupported roof areas for the 5 schemes are calculated respectively as Figure 7 shown.

[0102] From Figure 7 it can be seen that before the driving width of the roadheader is less than 5.4 m, the length of the unsupported roof area in the roadway roof is inversely proportional to the driving width of the roadheader, that is, the larger the one-time driving width, the smaller the length of the unsupported roof area. When the driving width of the roadheader is greater than 5.4 m, the length of the unsupported roof area in the roadway roof remains almost unchanged.

[0103] 2) Determination of the lag distance for asynchronous driving

[0104] Through FLAC numerical simulation, the deformation and stress distribution of the surrounding rock of the roadway under different lag distances are calculated to provide a reference for determining the lag distance.

[0105] Compare the roof subsidence of the roadway and the stress of the remaining coal pillar at the heading position under 3 kinds of lag distances as Figure 9 shown. When the lag distance increases from 20 m to 40 m, the models are shown in Figures 8(a) - 8(c). Both the roof subsidence and the maximum stress of the remaining coal pillar at the heading position first decrease and then increase. The stress value of the remaining coal pillar is the lowest when the asynchronous tunneling lags by 40 m, which is beneficial to roof control. Considering factors such as on-site construction conditions, safety, procedures, and construction period comprehensively, if the distance between two tunneling faces is too close, the construction will be affected, and if the distance is too far, the normal tunneling construction period will be affected. It is determined that the lag distance of asynchronous tunneling remains 40 m.

[0106] (3) On-site verification of the tunneling method

[0107] Taking the roof-to-floor displacement during tunneling as the judgment criterion, on-site industrial tests are carried out. The monitoring results are shown in Figure 10. During the roadway tunneling, a total of 7 measuring stations are arranged, and the roof subsidence of each measuring station during the roadway tunneling is used as the judgment index to illustrate the stability of the surrounding rock of the roadway. After the roadway working face passes each measuring station, the roof subsidence first increases and then remains unchanged. In measuring stations 6# and 7#, the roof subsidence of measuring point 1 is 0; in measuring station 5#, the roof subsidence of measuring point 2 is 0. Except for measuring station 1#, the maximum roof subsidence of the remaining measuring stations during the whole tunneling period is 4 mm, which is not much different from the roof deformation during tunneling in the numerical simulation results. During the whole monitoring period, the maximum roof subsidence of the roadway occurs at measuring station 1#. Analyze the reasons for the roof subsidence at measuring station 1#. Since measuring station 1# is at the tunneling head of the roadway working face, the undercutting amount during tunneling is 1.5 m, and the distance between the roof layers is only 2.5 m. The distance between the roof layers is relatively small, and measuring station 1# is at the headstock gear socket, with a cross-sectional size of 10.5 m. And due to the influence of the upper slice mining, the floor is damaged to a certain extent, resulting in the top coal of the lower slice being relatively broken and local subsidence occurring. However, the overall deformation amount is small, indicating that the surrounding rock deformation of the roadway roof under this tunneling method is small.

[0108] A "roadheader + continuous miner asynchronous tunneling and one-time roadway formation" technology for large-span roadways is proposed. The key tunneling parameters analyzed are the size of the unsupported roof area for one-time tunneling and the reasonable lag distance for secondary asynchronous tunneling. By establishing a mechanical model to analyze the size of the unsupported roof area for one-time tunneling, it is concluded that the key factor affecting it is the one-time tunneling width of the roadway. It is proposed that numerical simulation can be used to analyze the deformation and stress distribution of the surrounding rock of the roadway under different lag distances, providing a reference for determining the lag distance.

[0109] According to the above analysis results and on-site industrial test verification, the method for determining the key parameters of an asynchronous tunneling method for large-span roadways proposed in this patent has certain feasibility and on-site practicality.

[0110] In the present invention, specific examples are used to illustrate the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation on the present invention.

Claims

1. A method for determining key parameters of asynchronous tunneling in large-span roadways, characterized in that: Including: Construction width of one tunneling and bolting operation Calculated according to the equipment dimensions required for this operation; The length of the unsupported roof area during one-time tunneling is 2a calculated as follows: establish a mechanical model of the roof, and use the tensile failure criterion as the judgment condition to obtain the expression of the length 2a of the unsupported roof area during tunneling, and use this expression to calculate the limit length ; The judgment method of the lag distance L is as follows: Through FLAC numerical simulation, calculate the distribution of the plastic zone, vertical displacement, and vertical stress of the roadway surrounding rock at different lag distances. When the vertical displacement gauge and the vertical stress are the smallest, it is used as the condition for selecting the lag distance L; Regard the roof as a thin plate structure with three sides fixed and one side simply supported, and establish a mechanical model of the roof accordingly; Using the basic equations of elasticity, displacement boundary conditions, and Galerkin variational equations, the deflection equation and the expression of stress components can be obtained; On this basis, using the tensile failure criterion as the judgment condition, the expression of the length of the empty roof area can be obtained; The expression for the derived ultimate length is as follows: In the formula, b′ is half of the width 2b′ ; h is half of the thickness 2h of the roadway roof; q is the uniformly distributed load applied by the overlying strata of the roof; μ is the Poisson's ratio of the roadway roof; is the tensile strength of the roadway roof.

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