Design method of dynamic pressure bearing support in self-forming roadway mining without coal pillar

Abstract

The present invention discloses a design method for dynamic pressure bearing support in self-forming tunnel mining without coal pillars, which relates to the field of mining technology and includes the following steps: S1, combining the movement process and fracture characteristics of the short arm beam roof to determine the action mechanism of dynamic pressure bearing support in self-forming tunnel without coal pillars, and further determine the temporary support range according to the action mechanism of dynamic pressure bearing support; S2, establishing a fracture mechanics model of the short arm beam roof under the action of dynamic pressure bearing support and considering the influencing factors, wherein the influencing factors include at least the rock properties of the roof and asymmetric support; S3, according to the nonlinear strength failure criterion of rock mass and the upper limit analysis theory, combined with the fracture mechanics model of the short arm beam roof, a dynamic pressure bearing support design method is proposed. The present invention can explore the influence of different factors on the dynamic pressure bearing support force, which is of great significance to the theory and technical system of self-forming tunnel mining without coal pillars.

Description

Technical Field

[0001] The invention relates to the technical field of mining, and in particular to a design method for dynamic pressure bearing support for self-forming tunnel mining without coal pillars. Background Art

[0002] The technology of self-forming lanes without coal pillars by cutting the roof and unloading pressure is a new method of coal mining that does not require advance lane digging and does not require the establishment of coal pillars. It uses the roof directional cutting technology to cut off the stress transmission between the roadway roof and the goaf roof, effectively improving the stress environment of the roadway surrounding rock. At the same time, it uses the mining pressure work and the rock mass crushing and expansion characteristics to fill the goaf and automatically form a mining lane. The technology of self-forming lanes without coal pillars can greatly improve the resource recovery rate, eliminate the harm caused by the surrounding rock stress concentration caused by the establishment of coal pillars, and has a significant positive effect on the sustainable development of coal mining.

[0003] When mining without coal pillars, the roof and gravel wall of the self-forming roadway in the area where the roadway is not yet stable behind the working face are continuously affected by the movement of overburden and the disturbance of gangue falling in the goaf. This stage is the dynamic pressure bearing zone, which is the key support section for the roadway. Many scholars have studied and applied the dynamic pressure bearing support technology and forms under different geological conditions. Existing research and application have greatly promoted the development of coal pillar-free mining theory and technology, but the design of temporary support schemes for dynamic pressure bearing zones lacks a specific theoretical basis, and the support form and parameters are usually determined based on field experience.

[0004] Therefore, a novel design method for dynamic pressure bearing support in self-forming tunnel mining without coal pillars is provided to solve the above problems existing in the prior art. Summary of the invention

[0005] The purpose of the present invention is to provide a design method for dynamic pressure bearing support in self-forming tunnel mining without coal pillars, so as to solve the above-mentioned problems existing in the prior art. It can explore the influence of different factors on the dynamic pressure bearing support force, which is of great significance to the theoretical and technical system of self-forming tunnel mining without coal pillars.

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

[0007] The present invention provides a method for designing dynamic pressure bearing support for self-forming tunnel mining without coal pillars, comprising the following steps:

[0008] S1. Combined with the movement process and fracture characteristics of the short arm beam roof, determine the dynamic pressure bearing support mechanism of the self-forming tunnel without coal pillars, and further determine the temporary support range based on the dynamic pressure bearing support mechanism of the self-forming tunnel without coal pillars;

[0009] S2. Establish a fracture mechanics model of the short arm beam top plate under the action of dynamic pressure bearing support and taking into account the influencing factors, wherein the influencing factors at least include the vertical stress of the overlying rock formation, the mining stress concentration coefficient, the thickness of the short arm beam top plate, the width of the roadway, the anchor cable support in the roadway, the crushed and expanded waste rock support coefficient, the lithology of the short arm beam top plate and the asymmetric support;

[0010] S3. According to the nonlinear strength failure criterion of rock mass and the upper limit analysis theory, combined with the fracture mechanics model of the top plate of the short arm beam, the dynamic pressure bearing support force is calculated.

[0011] Preferably, in step S1, the mechanism of the dynamic pressure bearing support for the self-forming lane without coal pillars includes the control of the fracture position of the top plate of the short arm beam. If the dynamic pressure bearing support strength is insufficient or the support is not timely, the top plate of the short arm beam will fracture along the position above the lane; when the dynamic pressure bearing support strength in the lane is sufficient, the top cut short arm beam will fracture above the lateral coal body, which is the target state that the dynamic pressure bearing support strength design should achieve.

[0012] Preferably, in step S1, determining the temporary support range according to the mechanical model and theoretical calculation analysis includes the following steps:

[0013] S101: Based on the rock samples obtained on site, the residual expansion coefficient K after the rock block collapses and stabilizes is measured. 1 ;

[0014] S102: According to formula h s =h+h 1 -K 1 h determines the rotational sinking amount h of the key block B s ; where h 1 is the coal mining height, h is the thickness of the top cutting short arm beam, h s is the rotational sinking of the key block B, K 1 is the residual expansion coefficient of gangue measured in the laboratory;

[0015] S103: According to the formula Determine the length of the key block B; where L is the length of the key block B, K 2 is the rock fracture coefficient (related to the thickness, lithology and mining speed of the key layer, which can be obtained through numerical simulation and model test), L s is the periodic pressure step, h k is the thickness of the key rock layer, R T is the tensile strength of the rock mass in the key layer to control the pressure, and q is the overburden load borne by the rock beam in the key layer;

[0016] S104: The rock mass within the range of rotational deformation failure is regarded as a rigid body, and α is approximately equal to α′. According to the formula Determine the deformation h of the side tunnel roof in the goaf under the stable state of rock collapse s ′, when the actual deformation monitored on site reaches h s ′, remove the temporary support, and use this as the criterion for the timing of temporary support withdrawal;

[0017] Among them, α is the rotation angle of the basic top key block B, α′ is the rotation angle of the tunnel roof deformation, and h s ′ is the deformation of the side tunnel roof of the goaf under the stable state of rock collapse, and l is the tunnel width.

[0018] Preferably, in the step S2, when establishing the fracture mechanics model of the short arm beam top plate, the mining stress concentration coefficient and the crushed and expanded gangue support coefficient are determined.

[0019] Preferably, the mining stress concentration factor is λ 1 , and λ 1 >1;

[0020] When the rock mass in the goaf has not yet produced reliable support for the roof of the goaf, the load q on the key block will be completely borne by the short arm beam structure. The upper bearing length of the short arm beam structure is L b , L b =l+htanθ, Where θ is the cutting angle.

[0021] Preferably, the support coefficient of the crushed gangue is λ 2 , and 0<λ 2 <1;

[0022] Among them, λ 2 =λ 1 K 3 cosθ,K 3 It is the lateral pressure conversion coefficient of crushed and expanded gangue (affected by the physical and mechanical properties of rock mass, shape, gradation and arrangement of collapsed rock mass, and can be obtained through numerical simulation of crushed and expanded rock mass and physical model compression test).

[0023] Preferably, in step S3, based on the nonlinear strength failure criterion of rock mass and the upper limit analysis theory, combined with the fracture mechanics model of the top plate of the short arm beam, the internal energy dissipation rate of the surrounding rock is solved, the work power of the external force of the fracture mechanics model is determined, the dynamic pressure bearing support force is calculated, and a dynamic pressure bearing support design method is proposed.

[0024] Preferably, the dynamic pressure bearing support force is calculated based on the dynamic pressure bearing support parameters; wherein the dynamic pressure bearing support parameters include the vertical stress of the overlying rock strata, the mining stress concentration coefficient, the thickness of the short arm beam top plate, the tunnel width, the rock mass density, the cohesion of the rock mass, the friction angle in the rock mass, the support coefficient of the crushed and expanded gangue, and the asymmetry coefficient.

[0025] Preferably, the formula for calculating the dynamic pressure bearing support force is:

[0026]

[0027] Among them, F is the dynamic pressure bearing support force, Pa is the preload required for a single anchor cable, l is the tunnel width, c is the rock mass cohesion, h is the thickness of the top cut short arm beam, γ is the weight of the rock mass, is the internal friction angle of the rock mass, θ is the cutting angle, q is the vertical stress of the overlying rock layer, n is the number of anchor cables, k is the asymmetry coefficient, λ 1 is the mining stress concentration factor, λ 2 Support coefficient of crushed and expanded rock.

[0028] Preferably, according to the upper limit analysis theory, the judgment criterion is determined as when the tunnel width l is equal to the falling body width b, the dynamic pressure bearing support force under the critical condition is determined.

[0029] Preferably, the dynamic pressure bearing support force is arranged asymmetrically in the tunnel.

[0030] Preferably, the asymmetric coefficient of the dynamic pressure bearing support force is k, which is obtained from the monitoring of the force and deformation of the support structure in actual engineering, and is 1-1.4.

[0031] Compared with the prior art, the present invention has achieved the following technical effects:

[0032] Based on the movement process and fracture characteristics of the roof of a self-forming tunnel without coal pillars, this paper clarifies the mechanism of dynamic pressure bearing support. By establishing a fracture mechanics model of the roof of a short-arm beam, and applying the nonlinear strength failure criterion and upper limit analysis theory of rock mass, this paper proposes a design method for dynamic pressure bearing support parameters. The research results are of great significance to the selection of support equipment, the design of tunnel parameters, the optimization of tunnel technology, and the improvement of the theoretical and technical system of self-forming tunnel mining without coal pillars. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 It is a mechanical model diagram of the roof structure of self-forming roadway mining without coal pillars in an embodiment of the present invention;

[0035] Description of the accompanying drawings: A, B, C are basic top blocks. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The purpose of the present invention is to provide a design method for dynamic pressure bearing support in self-forming tunnel mining without coal pillars, so as to solve the above-mentioned problems existing in the prior art. It can explore the influence of different factors on the dynamic pressure bearing support force, which is of great significance to the theoretical and technical system of self-forming tunnel mining without coal pillars.

[0038] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] like Figure 1 As shown, this embodiment provides a method for designing dynamic pressure bearing support for self-forming tunnel mining without coal pillars, including the following steps:

[0040] S1. Based on the test (physical model test of the N00 mining process) and on-site monitoring, combined with the movement process and fracture characteristics of the short arm beam roof, the dynamic pressure bearing support mechanism of the self-forming tunnel without coal pillars is determined, and the temporary support range is further determined based on the dynamic pressure bearing support mechanism of the self-forming tunnel without coal pillars;

[0041] S2. Establish a fracture mechanics model of the short arm beam top plate under the action of dynamic pressure bearing support and taking into account the influencing factors, wherein the influencing factors at least include the vertical stress of the overlying rock formation, the mining stress concentration coefficient, the thickness of the short arm beam top plate, the width of the roadway, the anchor cable support in the roadway, the crushed and expanded waste rock support coefficient, the lithology of the short arm beam top plate and the asymmetric support;

[0042] S3. According to the nonlinear strength failure criterion of rock mass and the upper limit analysis theory (① Hoek proposed the internationally famous Hoek-Brown criterion in view of the nature of nonlinear failure of rock mass, which is a basic theory known in this field; ② Upper limit analysis theory: In plastic mechanics, the displacement state of the plastic deformation zone is assumed to be a dynamically admissible velocity field. Since the velocity field only needs to satisfy the dynamically admissible conditions and the stress conditions should not be considered, the velocity field is not necessarily a real velocity field. The load obtained is always greater than the real load, so it is called the upper limit method, which is a basic mechanics theory known in this field), combined with the fracture mechanics model of the short arm beam top plate, the dynamic pressure bearing support force is calculated, and a dynamic pressure bearing support design method is proposed.

[0043] In this embodiment, in step S1, the mechanism of the dynamic pressure bearing support of the self-forming roadway without coal pillars includes the control of the fracture position of the top plate of the short arm beam. If the dynamic pressure bearing support strength is insufficient or the support is not timely, the top plate of the short arm beam will fracture along the position above the roadway; when the dynamic pressure bearing support strength in the roadway is sufficient, the top cut short arm beam will fracture above the lateral coal body, which is the target state that the dynamic pressure bearing support strength design should achieve.

[0044] In this embodiment, in step S1, determining the temporary support range according to the mechanical model and theoretical calculation analysis includes the following steps:

[0045] S101: Based on the rock samples obtained on site, the residual expansion coefficient K after the rock block collapses and stabilizes is measured. 1 ;

[0046] S102: According to formula h s =h+h 1 -K 1 h determines the rotational sinking amount h of the key block B s ; where h 1 is the coal mining height, h is the thickness of the top cutting short arm beam, h s is the rotational sinking of the key block B, K 1 is the residual expansion coefficient of gangue measured in the laboratory;

[0047] S103: According to the formula Determine the length of the key block B; where L is the length of the key block B, K 2 is the rock fracture coefficient (related to the thickness, lithology and mining speed of the key layer, which can be obtained through numerical simulation and model test), L s is the periodic pressure step, h k is the thickness of the key rock layer, R T is the tensile strength of the rock mass in the key layer to control the pressure, and q is the overburden load borne by the rock beam in the key layer;

[0048] S104: The rock mass within the range of rotational deformation failure is regarded as a rigid body, and α is approximately equal to α′. According to the formula Determine the deformation h of the side tunnel roof in the goaf under the stable state of rock collapse s ′, when the actual deformation monitored on site reaches h s ′, remove the temporary support, and use this as the criterion for the timing of temporary support withdrawal;

[0049] Among them, α is the rotation angle of the basic top key block B, α′ is the rotation angle of the tunnel roof deformation, and h s ′ is the deformation of the side tunnel roof of the goaf under the stable state of rock collapse, and l is the tunnel width.

[0050] In this embodiment, in step S2, when establishing the fracture mechanics model of the top plate of the short arm beam, the mining influence of the working face is taken into consideration to determine the mining stress concentration coefficient, and the supporting effect of the goaf gangue on the short arm beam is taken into consideration to determine the crushed and expanded gangue support coefficient.

[0051] In this embodiment, the mining stress concentration factor is λ 1 , and λ 1 >1;

[0052] When the rock mass in the goaf has not yet produced reliable support for the roof of the goaf, the load q on the key block will be completely borne by the short arm beam structure. The upper bearing length of the short arm beam structure is L b , L b =l+htanθ, Where θ is the cutting angle.

[0053] In this embodiment, the support coefficient of the crushed and expanded gangue is λ 2 , and 0<λ 2 <1;

[0054] Among them, λ 2 =λ 1 K 3 cosθ,K 3 It is the lateral pressure conversion coefficient of crushed and expanded gangue (affected by the physical and mechanical properties of rock mass, shape, gradation and arrangement of collapsed rock mass, and can be obtained through numerical simulation of crushed and expanded rock mass and physical model compression test).

[0055] In this embodiment, in step S3, based on the nonlinear strength failure criterion of rock mass and the upper limit analysis theory, combined with the fracture mechanics model of the short arm beam top plate, the internal energy dissipation rate of the surrounding rock is solved, the work power of the external force of the fracture mechanics model is determined, the dynamic pressure bearing support force is calculated, and a dynamic pressure bearing support design method is proposed.

[0056] Among them, solving the internal energy dissipation rate of the surrounding rock includes:

[0057] According to the nonlinear Hoek-Brown strength criterion of rock mass and its associated flow law, the plastic normal strain rate and plastic shear strain rate on the fracture surface of rock mass, as well as the normal stress and tangential stress on the thin deformation layer of the fracture surface can be obtained;

[0058] According to the above parameters, the internal energy dissipation rate per unit volume at the fracture surface of the surrounding rock is obtained.

[0059] Determining the working power of the external force of the model includes six parts: determining the working power of the deadweight of the short arm beam roof rock mass, the working power of the tunnel surrounding rock stress, the working power of the dynamic pressure bearing support force, the working power of the roof anchor preload force, the working power of the lateral coal body support force, and the working power of the crushed and expanded gangue support force.

[0060] In this embodiment, the dynamic pressure bearing support force is calculated based on the dynamic pressure bearing support parameters; wherein the dynamic pressure bearing support parameters include the vertical stress of the overlying rock strata, the mining stress concentration coefficient, the thickness of the short arm beam top plate, the tunnel width, the rock mass density, the cohesion of the rock mass, the friction angle of the rock mass, the support coefficient of the broken and expanded gangue, the asymmetry coefficient, etc.

[0061] In this embodiment, the formula for calculating the dynamic pressure bearing support force is:

[0062]

[0063] Among them, F is the dynamic pressure bearing support force, Pa is the preload required for a single anchor cable, l is the tunnel width, c is the rock mass cohesion, h is the thickness of the top cut short arm beam, γ is the weight of the rock mass, is the internal friction angle of the rock mass, θ is the cutting angle, q is the vertical stress of the overlying rock layer, n is the number of anchor cables, k is the asymmetry coefficient, λ 1 is the mining stress concentration factor, λ 2 Support coefficient of crushed and expanded rock.

[0064] In this embodiment, according to the upper limit analysis theory, the judgment criterion is determined as when the tunnel width l is equal to the falling body width b, and the dynamic pressure bearing support force under the critical condition is determined.

[0065] In this embodiment, the dynamic pressure bearing support force is arranged asymmetrically in the tunnel, wherein the asymmetry coefficient of the dynamic pressure bearing support force is k.

[0066] In this embodiment, the asymmetry coefficient is 1-1.4.

[0067] The present specification uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A design method for dynamic pressure bearing support in self-forming lane mining without coal pillars, characterized in that: The following steps are involved: S1. Combined with the movement process and fracture characteristics of the short arm beam roof, determine the dynamic pressure bearing support mechanism of the self-forming tunnel without coal pillars, and further determine the temporary support range based on the dynamic pressure bearing support mechanism of the self-forming tunnel without coal pillars; In step S1, the mechanism of the dynamic pressure bearing support of the self-forming roadway without coal pillars includes the control of the fracture position of the top plate of the short arm beam. If the dynamic pressure bearing support strength is insufficient or the support is not timely, the top plate of the short arm beam will fracture along the position above the roadway; when the dynamic pressure bearing support strength in the roadway is sufficient, the top cut short arm beam will fracture above the lateral coal body, which is the target state to be achieved by the dynamic pressure bearing support strength design; S2. Establish a fracture mechanics model of the short arm beam top plate under the action of dynamic pressure bearing support and taking into account the influencing factors, wherein the influencing factors at least include the vertical stress of the overlying rock formation, the mining stress concentration coefficient, the thickness of the short arm beam top plate, the width of the roadway, the anchor cable support in the roadway, the crushed and expanded waste rock support coefficient, the lithology of the short arm beam top plate and the asymmetric support; S3. Calculate the dynamic pressure bearing support force according to the nonlinear strength failure criterion of rock mass and the upper limit analysis theory, combined with the fracture mechanics model of the top plate of the short arm beam; The dynamic pressure bearing support force is calculated according to the dynamic pressure bearing support parameters; wherein the dynamic pressure bearing support parameters include the vertical stress of the overlying rock strata, the mining stress concentration coefficient, the thickness of the short arm beam top plate, the tunnel width, the rock mass density, the cohesion of the rock mass, the friction angle in the rock mass, the support coefficient of the crushed and expanded waste rock, and the asymmetry coefficient; The formula for calculating the dynamic pressure bearing support force is: Among them, F is the dynamic pressure bearing support force, Pa is the preload required for a single anchor cable, l is the tunnel width, c is the rock mass cohesion, h is the thickness of the top cut short arm beam, γ is the weight of the rock mass, is the internal friction angle of the rock mass, θ is the cutting angle, q is the vertical stress of the overlying rock, n is the number of anchor cables, k is the asymmetry coefficient, λ1 is the mining stress concentration coefficient, and λ2 is the support coefficient of the broken and expanded gangue.

2. The method for designing dynamic pressure bearing support for self-forming tunnel mining without coal pillars according to claim 1 is characterized in that: In step S1, determining the temporary support range includes the following steps: S101: Based on the rock samples obtained on site, the residual expansion coefficient K1 of the rock block after collapse and stabilization is measured; S102: According to formula h s =h+h1-K1h to determine the rotation sinking amount h of the key block B s ; where h1 is the coal mining height, h is the thickness of the top cutting short arm beam, and h s is the rotational settlement of the key block B, K1 is the residual expansion coefficient of the gangue measured in the laboratory; S103: According to the formula Determine the length of the key block B; where L is the length of the key block B, K2 is the rock fracture coefficient, and L s is the periodic pressure step, h k is the thickness of the key rock layer, R T is the tensile strength of the rock mass in the key layer to control the pressure, and q is the overburden load borne by the rock beam in the key layer; S104: The rock mass within the range of rotational deformation failure is regarded as a rigid body, and α is approximately equal to α′. According to the formula Determine the deformation h of the side tunnel roof in the goaf under the stable state of rock collapse s ′, when the actual deformation monitored on site reaches h s ′, remove the temporary support, and use this as the criterion for the timing of temporary support withdrawal; Among them, α is the rotation angle of the basic top key block B, α′ is the rotation angle of the tunnel roof deformation, and h s ′ is the deformation of the side tunnel roof of the goaf under the stable state of rock collapse, and l is the tunnel width.

3. The method for designing dynamic pressure bearing support for self-forming tunnel mining without coal pillars according to claim 2 is characterized in that: In the step S2, when establishing the fracture mechanics model of the short arm beam top plate, the mining stress concentration coefficient and the crushed and expanded gangue support coefficient are determined.

4. The method for designing dynamic pressure bearing support for self-forming tunnel mining without coal pillars according to claim 3 is characterized in that: The mining stress concentration factor is λ1, and λ1>1; When the rock mass in the goaf has not yet produced reliable support for the roof of the goaf, the load q on the key block will be completely borne by the short arm beam structure. The upper bearing length of the short arm beam structure is L b , L b =l+htanθ, Where θ is the cutting angle.

5. The method for designing dynamic pressure bearing support for self-forming tunnel mining without coal pillars according to claim 4 is characterized in that: The support coefficient of the crushed and expanded gangue is λ2, and 0<λ2<1; Among them, λ2=λ1K3cosθ, K3 is the lateral pressure conversion coefficient of crushed and expanded gangue.

6. The method for designing dynamic pressure bearing support for self-forming tunnel mining without coal pillars according to claim 1 or 2, characterized in that: In step S3, based on the nonlinear strength failure criterion of rock mass and the upper limit analysis theory, combined with the fracture mechanics model of the top plate of the short arm beam, the internal energy dissipation rate of the surrounding rock is solved, the work done by the external force of the fracture mechanics model is determined, the dynamic pressure bearing support force is calculated, and a dynamic pressure bearing support design method is proposed.

7. The method for designing dynamic pressure bearing support for self-forming tunnel mining without coal pillars according to claim 1 is characterized in that: According to the upper limit analysis theory, the judgment criterion is to determine the dynamic pressure bearing support force under critical conditions when the tunnel width l is equal to the falling body width b.

8. The method for designing dynamic pressure bearing support for self-forming tunnel mining without coal pillars according to claim 7 is characterized in that: The dynamic pressure bearing support force is arranged asymmetrically on the top plate of the short arm beam in the lane; The asymmetric coefficient of the dynamic pressure bearing support force is k, which is obtained based on the monitoring of the force and deformation of the support structure in actual engineering, and k is 1-1.4.

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