Optimization method of yielding support under influence of partial weakening of hard rock mining section

Abstract

The application discloses a method for optimizing yielding support under the influence of local weakening of a hard rock mining section, comprising the following steps: based on rock sample compression test, constructing a joint weakening zone damage relationship to obtain rock mass mechanical parameters; through a finite element analysis method combined with the rock mass mechanical parameters, constructing a hard rock stope local weakening surrounding rock roadway numerical model to analyze the influence law of hard rock stope weakening on surrounding rock roadway deformation and stress; through a FLAC3D numerical simulation software combined with a support system theoretical formula, constructing a surrounding rock-support interaction balance model; based on the surrounding rock-support interaction balance model, determining the lower limit of the initial support stress of the support according to the Mohr-Coulomb criterion, determining the upper limit of the initial support stress of the support according to the support bearing capacity, analyzing the control effect of the plastic deformation of the surrounding rock by changing the size of the initial support stress of the support, selecting the optimal initial support stress, realizing the yielding balance of the rigid support of the support and the energy release of the surrounding rock, and obtaining the optimized support mode.

Description

Technical Field

[0001] The present invention relates to the technical field of surrounding rock mining, and in particular to a yield support optimization method under the influence of local weakening of a hard rock mining section. Background Art

[0002] With the advancement of deep mineral resource mining, the problem of surrounding rock instability in hard rock mines, caused by the coupling of high ground stress and rock mass weakening, has become increasingly prominent. This problem is one of the major unresolved issues in my country's major disaster research. Research on the progressive failure mechanism of surrounding rock in hard rock roadways and efficient support and control technologies is crucial. Currently, there is little analysis of the weakening mechanism of surrounding rock in hard rock mines. Support is commonly used as a ground pressure control measure to control ground pressure in mines. Pillars are an important tool in this support measure. Determining the initial support force of active steel pillars plays a crucial role in maintaining the stability of the surrounding rock and controlling deformation in weakened roadways. Typically, with the duration of mining operations and the increase in the span of the mine, the mine roof undergoes significant deformation. Increased roof deformation requires the support system to provide more support force. At the same time, due to the gradual release of roof stress, the support force required to maintain roof stability decreases. Therefore, setting the initial support force in the early stages of mining can play a crucial role in controlling roof deformation, effectively limiting the early displacement of the mine roof. However, although the initial support stress of the pillar is too high to limit the deformation of the roof, as the excavation progresses, the axial force of the pillar increases, which requires high strength and stiffness of the pillar. Similarly, too low support force will also cause problems. Larger deformation will cause the roof to separate from the direct top and basic top, the interlayer friction resistance will decrease, and the pillar will easily overturn, causing damage and safety problems.

[0003] At present, the research on active support is limited to the mechanical properties, and there is no research on how to determine the support position and perform active support initial support stress (initial support stress). The initial support stress can limit the deformation of the mining site roof in the early stage of mining. As time or the span of the mining site increases, the deformation of the roof increases, which increases the support stress. At the same time, the release of the roof stress reduces the support stress that maintains the stability of the roof. How to determine the position and size of the initial support stress and explore its relationship with the stress distribution of the mining site roof and the internal force value during the use of active support to obtain the optimal support method is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of the present invention is to address the problems existing in the prior art and provide a yield support optimization method under the influence of local weakening of hard rock mining sections, thereby providing quantitative theoretical support for the support design of deep hard rock tunnels.

[0005] To achieve the above objectives, the present invention adopts the following technical solutions:

[0006] This paper establishes a surrounding rock-support interaction equilibrium model through indoor testing, FLAC3D numerical simulation software, and theoretical formulas for the support system. The model analyzes the mechanical properties of the surrounding rock and the evolution of the plastic zone at different depths as the location of the weakened rock layer changes. The paper determines the location and boundary of the initial support stress of the support and changes the magnitude of the initial support stress based on the boundary. The paper analyzes the control effect of the initial support stress on the plastic deformation of the surrounding rock and proposes an optimal solution for active steel support yielding support for weakened surrounding rock reinforcement. The specific technical solution is as follows:

[0007] A method for optimizing yield support under the influence of local weakening of a hard rock mining section comprises the following steps:

[0008] Based on the axial compression test of weakened rock, the stress-strain relationship of the joint weakening zone under different loads is analyzed, the damage relationship of the joint weakening zone is constructed, and the mechanical parameters of the rock mass are obtained;

[0009] By combining the finite element analysis method with rock mass mechanical parameters, a numerical model of the surrounding rock tunnel with local weakening in a hard rock stope was constructed to analyze the influence of the weakening of the hard rock stope on the deformation and stress of the surrounding rock tunnel.

[0010] Based on the influence of weakening of hard rock stope on deformation and stress of surrounding rock tunnel, the support position is determined, and the surrounding rock-support interaction equilibrium model is constructed by combining FLAC3D numerical simulation software with the theoretical formula of pillar support system.

[0011] Based on the surrounding rock-support interaction equilibrium model, the lower limit of the initial support stress of the pillar is determined by the Mohr-Coulomb criterion, and the upper limit of the initial support stress of the pillar is determined by the pillar bearing capacity. By changing the magnitude of the initial support stress of the pillar, the control effect of the plastic deformation of the surrounding rock is analyzed, and the optimal initial support stress is selected to achieve the pressure balance between the rigid support of the pillar and the energy release of the surrounding rock, thereby obtaining the optimized support method.

[0012] As a further technical solution, the initial support stress The size satisfies the following formula:

[0013] ;

[0014] Where P0 is the original rock stress, is the internal friction angle, For cohesion, is the ultimate bearing capacity of a single pillar; A is the support density.

[0015] As a further technical solution, a surrounding rock-support interaction equilibrium model is constructed, including:

[0016] The cable unit is used to simulate the pillar support and analyze the axial pressure performance of the pillar support, ignoring the shear resistance of the pillar support. The cable unit includes several cable units, and each two cable units are connected by a node. When the pillar is in tension, under the action of axial tensile stress, the cable units are connected by spring stiffness and provide corresponding support reaction force for the surrounding rock through sliding elements.

[0017] Among them, cablesel adopts the ideal elastic-plastic constitutive model and sets the compressive strength limit of the pillar. After exceeding the limit, the axial pressure of the pillar will remain unchanged with the displacement. The stiffness K of the pillar is calculated as follows:

[0018] ;

[0019] Where L is the length of the cablesel, A' is the cross-sectional area of ​​the support, and E is the elastic modulus.

[0020] As a further technical solution, a numerical model of the locally weakened surrounding rock tunnel in a hard rock mine is constructed to analyze the influence of the weakening of the hard rock mine on the deformation and stress of the surrounding rock tunnel, including: constructing numerical models of tunnels with different mining depths under different weakening states, the different weakening states include four states: the rock layer is intact, the weakened layer is located above, the weakened layer runs through the tunnel, and the weakened layer is located below; analyzing the effect of the tunnel mining depth under different weakening states on the surrounding rock deformation and stress distribution including roof displacement and side displacement.

[0021] As a further technical solution, constructing a surrounding rock-support interaction equilibrium model also includes: simulating the initial stress field distribution of the surrounding rock in an unexcavated and unsupported state.

[0022] As a further technical solution, the rock mass mechanical parameters include elastic modulus, Poisson's ratio, internal friction angle, and strength.

[0023] As a further technical solution, the above method also includes constructing a pillar support-sprayed concrete reinforcement collaborative support system and analyzing the synergistic effect of pillar support and sprayed concrete reinforcement.

[0024] As a further technical solution, the above-mentioned construction of the pillar support-sprayed concrete reinforcement coordinated support system includes establishing a three-dimensional grouting sprayed concrete reinforcement numerical simulation calculation model that is the same as the actual project based on FLAC3D numerical simulation software.

[0025] As a further technical solution, the above method also includes: a water immersion and saturation test to establish an optimization method for yielding support under the weakening influence of the coexistence of joints and a moist environment.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention establishes a surrounding rock-support interaction equilibrium model through indoor experiments, FLAC3D numerical simulation software and the theoretical formula of the pillar support system, analyzes the mechanical properties of the surrounding rock and the evolution law of the plastic zone at different depths as the position of the weakened rock layer changes, determines the position and boundary of the pillar initial support stress and changes the size of the initial support stress based on the boundary, analyzes the control effect of the pillar initial support stress on the plastic deformation of the surrounding rock, and proposes the optimal solution of active steel pillar yielding support for weakened surrounding rock reinforcement.

[0028] (2) Based on the control effect of initial support stress on tunnel deformation, the present invention adds sprayed concrete reinforcement to reduce the displacement of the side, constructs a pillar support-sprayed concrete reinforcement collaborative support system, and effectively improves the stability of the surrounding rock tunnel.

[0029] (3) The yield support optimization method of the present invention provides quantitative theoretical support for the support design of deep hard rock tunnels and provides technical guarantee for the safe mining of deep hard rock mines. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flow chart of the yield support mechanism under the influence of local weakening of the hard rock mining section of the present invention;

[0031] Figure 2 This is a schematic diagram of the numerical model of the local weakened surrounding rock tunnel in the hard rock stope of the present invention, wherein: Figure 2 (a) is the geometric model, Figure 2 (b) The finite element model designed according to the different states of the rock formations around the tunnel;

[0032] Figure 3 Schematic diagram of the support geological model of the surrounding rock-support interaction equilibrium model of the present invention;

[0033] Figure 4 This is a mechanical model diagram of the support system of the present invention. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] An embodiment of the present invention provides a method for optimizing yield support under the influence of local weakening of a hard rock mining section, comprising the steps of:

[0036] S1. Based on axial compression tests on weakened rock, analyze the stress-strain relationship in the joint-weakened zone under different loads, construct a damage relationship for the joint-weakened zone, and obtain rock mass mechanical parameters such as elastic modulus, Poisson's ratio, internal friction angle, and strength;

[0037] S2. Using finite element analysis combined with rock mass mechanics parameters, a numerical model of a hard rock stope with locally weakened surrounding rock tunnels was constructed to analyze the effects of weakening in the hard rock stope on deformation and stress in the surrounding rock tunnels.

[0038] S3. Based on the influence of weakening in hard rock stopes on deformation and stress in surrounding rock tunnels, the support locations are determined. A surrounding rock-support interaction equilibrium model is constructed using FLAC3D numerical simulation software combined with theoretical formulas for pillar support systems.

[0039] S4. Based on the surrounding rock-support interaction equilibrium model, the lower limit of the pillar's initial support stress is determined by the Mohr-Coulomb criterion, and the upper limit of the pillar's initial support stress is determined by the pillar's bearing capacity. By varying the pillar's initial support stress, the control effect on the plastic deformation of the surrounding rock is analyzed, and the optimal initial support stress is selected to achieve a compressive balance between the pillar's rigid support and the surrounding rock's energy release, thereby obtaining an optimized support method.

[0040] The embodiment of the present invention takes the working face of a gold deposit in a certain place as the research object for analysis, and the specific yield support mechanism is as follows: Figure 1 As shown:

[0041] The specific steps of step S1 are as follows:

[0042] 1.1 Axial compression test of weakened rock

[0043] The experiment was divided into 7 groups. The red sandstone specimens (with rock properties similar to those of the gold deposit working face) were processed to a size of Φ5cm×10cm. The structural planes were present. The variables were different structural plane inclinations. The surrounding rock was prepared intact, and the angle (joint inclination) between the prepared structural plane and the horizontal plane (the major principal stress action surface, similar to the subsequent ones) was prepared. Specimens with 0°, 30°, and 60° joints were used to analyze the weakening effects of the same filling medium and different structural surface inclinations on rock mechanical properties and deformation characteristics. In actual engineering projects, the range of joint inclination values ​​can be set according to actual working conditions.

[0044] In this embodiment of the present invention, a uniaxial compression test was conducted on each group using a uniaxial compression machine. This experimental study revealed the effects of varying structural inclination angles on the ultimate bearing capacity (including compressive strength) of the specimens, as well as the weakening patterns of the entire stress-strain process under load, known as the stress-strain relationship. The specimens were loaded using a vertical displacement control method.

[0045] Using the stress-strain relationship, the average elastic modulus and Poisson's ratio of red sandstone, the relationship between confining pressure and peak strength q are obtained. The specific expression is:

[0046]

[0047] Cohesion (c) and internal friction angle ( ) can be expressed by the Mohr-Coulomb strength criterion, which can be expressed as a functional relationship between and as follows:

[0048]

[0049] in, represents the maximum principal stress, which is the maximum normal stress that red sandstone can withstand under stress; Represents the minimum principal stress, that is, the minimum normal stress when a force is applied.

[0050] Refer to the cohesion c and internal friction angle of rock , the parameters C0 and q in the above formula can be derived:

[0051]

[0052] By comparing equations (1-1) and (1-2) and combining them with (1-3), we can derive the following expression:

[0053]

[0054]

[0055] Solving the equation group (1-4), we obtain the results c = 14.95MPa, φ = 41.25°, see Table 1 below.

[0056] Table 1 Basic mechanical parameters of intact red sandstone

[0057]

[0058] The stress-strain relationship curve obtained from the loading of the uniaxial compression testing machine found that the uniaxial compressive strength of the single-joint weakened rock mass decays exponentially with the increase of the joint inclination angle. The 60° inclination angle is the most unfavorable weakening condition, and the strength is less than 15% of the intact rock mass. This shows that the most serious weakening deformation occurs at 60°.

[0059] Step S2: Through axial compression testing of weakened rock, the weakened structural plane with the most severe (most unfavorable) weakening and deformation is determined based on the stress-strain relationship curve. A numerical model of a locally weakened surrounding rock roadway in a hard rock mine is constructed. Using the FLAC3D finite element analysis method, the damage mechanism and development evolution during overburden mining under the most unfavorable weakening conditions, i.e., the most unfavorable weakened structural plane, are simulated. The model is set at different excavation locations, different excavation inclinations, and different rock mass in-situ stresses to analyze the effects of different weakening locations and mining depths on the stress and deformation of the roadway surrounding rock. In an embodiment of the present invention, numerical models of roadways at different mining depths under different weakening states are constructed. The different weakening states include four states: intact rock formation, weakened layer located above, weakened layer penetrating the roadway, and weakened layer located below. The effects of roadway mining depth under different weakening states on surrounding rock deformation, including roof displacement and side displacement, and stress distribution are analyzed.

[0060] 2.1 Selection of constitutive model and parameters

[0061] The Mohr-Coulomb constitutive model, based on shear strength theory and using cohesion and internal friction angle as key parameters, is used to characterize the mechanical characteristics and failure morphology of weak surrounding rock. The Mohr-Coulomb constitutive model can also be used to numerically simulate the entire process of rock flow, from elasticity to plasticity and then to instability, by adjusting parameters such as cohesion and internal friction angle. Furthermore, the mechanical model established by this invention can be used to analyze rock tensile failure and characterize its tensile failure characteristics.

[0062] For a gold deposit working face in a certain place in the embodiment, the physical properties and mechanical parameters of each key layer are corrected in combination with the on-site detection report. The specific mechanical parameters are shown in Table 2 from bottom to top.

[0063] Table 2 Rock mass mechanics parameters

[0064]

[0065] Since the average peak strength at 60° is only 7.90 MPa, the strength of the angled structural test specimen is most significantly affected by the weakened surface, which is 84.8% lower than that of the intact specimen. At the same time, the ultimate strain is reduced by more than 80%. The corrected weakened layer parameters are as follows:

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072] 2.2 Establishment of tunnel models at different weakening locations

[0073] The first step in numerical simulation of tunnels at different weakening locations is to construct a numerical model of tunnels with local weakening of surrounding rock in hard rock stopes. The numerical model used in this paper is based on Figure 2 (a) shows the geometric model. To minimize the impact of boundary conditions on the calculation results, the model adopts a rectangular structure with dimensions set to 100m × 100m × 50m. The width and height of the mining roadway are set to 6m and 3m respectively. The initial ground stress is varied to simulate high stress at depth, and different principal stress values ​​σ are set. zz , σ xx , σ yy , the next step is excavation. The four sides are horizontally constrained, and the bottom boundary is fully constrained. At the same time, the finite element model is designed according to the different states of the rock layer around the tunnel, that is, the rock layer is complete, the weakened layer is located above, the weakened layer runs through the tunnel, and the weakened layer is located below. Figure 2 (b).

[0074] Combining the most unfavorable structural surfaces in engineering practice and experiments, the movement patterns of the surrounding rock and the most unfavorable structural surfaces at different locations at different mining depths are studied. For example, in an embodiment of the present invention, the displacement, deformation, and stress variation patterns of different weakened locations, plastic zones of surrounding rock in different roadways, and surrounding rock (roof and side) at a mining depth of 300m are analyzed; the displacement, deformation, and stress variation patterns of surrounding rock plastic zones at different weakened locations in roadways at a mining depth of 500m; and the displacement, deformation, and stress variation patterns of surrounding rock plastic zones at different weakened locations in roadways at a mining depth of 1000m. Based on the displacement, deformation, and stress variation patterns of surrounding rock at different weakened locations and mining depths, the weakened locations and mining depths (deep, high-stress roadways) that pose the greatest threat to roadway stability are determined, and targeted roof and side support is strengthened to optimize the reinforcement strategy for the weakened areas. In the embodiment of the present invention, according to the influence of weakening of hard rock mine on the deformation and stress of surrounding rock tunnels, a deep high-stress tunnel with a weakening inclination of 60° and a mining depth of 1000m is selected for support, as this place poses the greatest threat to tunnel stability.

[0075] Step S3: Based on the influence of the weakening of hard rock stope on the deformation and stress of surrounding rock tunnel, the support position is determined, and the surrounding rock-support interaction balance model is constructed by combining the theoretical formula of the pillar support system with the FLAC3D numerical simulation software, such as Figure 3Specifically, based on the analysis results of step S2, support is provided at the weakened surrounding rock locations and mining depths (deep high-stress roadways) that pose the greatest threat to roadway stability. In this embodiment of the present invention, active steel support is used for optimization. Using FLAC3D numerical simulation software, the active steel support and roadway connection are first numerically modeled. Based on the active steel support settings, the initial support stress is varied to analyze the control effect of the active steel support system on surrounding rock deformation in deep high-stress roadways, specifically the surrounding rock stress and deformation under the initial support stress.

[0076] Among them, the theoretical formula of the active steel pillar support system is as follows:

[0077] Assuming that the tunnel surrounding rock is an axisymmetric elastic medium, the support structure (active steel pillars) provides uniform radial support force. According to the thick-walled cylinder theory of elastic mechanics, the surrounding rock stress distribution satisfies:

[0078]

[0079] Where:

[0080] P0: In-situ rock stress (varies with mining depth, );

[0081] r0: roadway radius;

[0082] r: radius of any point of surrounding rock;

[0083] : radial stress;

[0084] : Hoop stress.

[0085] Derivation of the critical value (boundary) of initial support stress

[0086] 1) Lower limit (minimum initial support stress )

[0087] To prevent the surrounding rock from entering a plastic state, the Mohr-Coulomb strength criterion must be met:

[0088]

[0089] Substituting into the stress expression we get:

[0090]

[0091] After simplification, we get the lower limit formula:

[0092]

[0093] After considering the safety factor of surrounding rock:

[0094] ; Wherein, k1 is the safety factor of surrounding rock;

[0095] 2) Upper limit (maximum initial support stress )

[0096] In order to avoid overload failure of the support structure, the support bearing capacity limit must be met:

[0097]

[0098] Where:

[0099] : The ultimate bearing capacity of a single steel pillar (determined by the material strength);

[0100] A: support density (number of pillars per unit area × cross-sectional area of ​​a single pillar);

[0101] After considering the safety of the support structure in actual projects:

[0102] ; Wherein, k2 is the safety factor of the support structure;

[0103] Based on the surrounding rock-support interaction equilibrium model, the lower limit of the initial support stress is determined by the Mohr-Coulomb criterion, and the upper limit is determined by the bearing capacity of the support structure. This ensures that the surrounding rock does not enter plasticity under the optimal initial support stress, prevents support overload, and provides space for compressive energy release.

[0104] Take a gold mine -1000m stope as an example, the mining depth is H 1000m, the rock density is 2700kg / m³, the surrounding rock strength parameter c=14.95MPa, and the original rock stress is , =41.25° (Table 2), surrounding rock safety factor k1=1.5, support structure safety factor k2=3.5.

[0105] 1) Determine the lower limit

[0106]

[0107] After considering the safety factor:

[0108]

[0109] 2) Determine the upper limit

[0110] Assuming the ultimate bearing capacity of a single steel support =3000kN, support density is A=0.8m 2 :

[0111]

[0112] Considering structural safety in actual engineering:

[0113]

[0114] In the embodiment of the present invention, the upper limit is taken as 10 MPa.

[0115] In the embodiment of the present invention, the magnitude of the initial support stress should satisfy the following formula: .

[0116] As a specific embodiment of the present invention, a surrounding rock-support interaction equilibrium model is constructed, including:

[0117] The cable unit is used to simulate the pillar support and analyze the axial pressure performance of the pillar support. The shear resistance of the pillar support is ignored. The cable unit includes several cable units. Every two cable units are connected by a node. When the steel is subjected to axial tensile load, the cables are connected by spring stiffness and provide corresponding support reaction force for the surrounding rock through sliding elements. Figure 4 The mechanical model diagram of the support system of the present invention is shown;

[0118] Among them, cablesel adopts the ideal elastic-plastic constitutive model and sets the ultimate compressive strength value of the pillar. After exceeding the limit, the axial force of the pillar rod will remain unchanged with the displacement. The stiffness K of the pillar rod is calculated as follows:

[0119] ;

[0120] Where L is the length of the cablesel, A' is the cross-sectional area of ​​the rod, and E is the elastic modulus.

[0121] Step S4: Based on the surrounding rock-support interaction balance model and the critical range of the pillar initial support stress, the pillar initial support stress is changed (adjusted according to the steel support initial support stress boundary determined in step S3, specifically adjusted between 3.2-10 MPa). The stress field under no support conditions and the displacement distribution, stress distribution, and plastic zone change characteristics of the surrounding rock of the locally weakened mine tunnel in the hard rock mine under different support conditions are analyzed, and the control effect of the initial support stress on the plastic deformation of the surrounding rock is analyzed; the optimal initial support stress is selected according to the control effect to achieve the pressure balance between the pillar rigid support and the energy release of the surrounding rock, and the optimal support scheme for single column support under weak surrounding rock conditions is obtained.

[0122] In the actual case of the gold mine mining field of the present invention, support was applied to the tunnel through the weakened area to control the deformation of the tunnel. Under the action of the support, the vertical displacement of the roof was reduced from the original -21.64mm to -10.86mm. The drop was reduced by 9.78mm, and the drop was reduced by 47.38%. On this basis, the initial support stress was applied again. The displacement of the 2MPa initial support stress was reduced by 2.21%, the initial support stress of 4MPa was reduced by 5.71%, and when the initial support stress was 6MPa: the displacement was reduced by 20.90%, the initial support stress of 8MPa was reduced by 7.09%, and the initial support stress of 10MPa was reduced by 8.20%. When the initial support stress was 6MPa, the displacement of the roof was reduced the most, the displacement of the roof was effectively curbed, and the reduction was the largest. Its displacement contour gradually contracted towards the center area of ​​the roof, indicating that the support and initial support stress had a significant supporting effect on the roof, so that the deformation of the roof was more reasonably controlled. Because yield support has the greatest displacement restriction at an initial support stress of 6 MPa, although it causes stress concentration in the roof and the maximum stress reaches 15 MPa, it can reduce the evolution range of the plastic zone of the tunnel surrounding rock by 3 to 5 m. The plastic zone of the mine tunnel surrounding rock has undergone significant changes. Compared with the unsupported condition, the area of ​​the plastic zone is greatly reduced. The results show that the support force of the active steel pillar with a yield stress of 6 MPa can effectively control the development of the plastic zone and significantly inhibit its deformation and damage, thereby improving the stability of the tunnel. When the initial support stress is further increased, the roof stress shows a double peak, indicating that the appropriate increase in the initial support stress effectively activates the secondary bearing zone, resulting in an expansion of the stress diffusion range. Therefore, both in the present invention and in actual working conditions, it is necessary to optimize the initial support stress according to the specific geological conditions and surrounding rock characteristics. The higher the initial support stress, the better.

[0123] As one embodiment of the present invention, the method also includes constructing a synergistic support system of pillar support and shotcrete reinforcement, analyzing the synergistic effects of pillar support and shotcrete reinforcement. Specifically, based on actual project conditions, concrete of varying thicknesses is sprayed around the roadway, followed by pillar support, to achieve a combined support effect, further optimizing the support pattern and reducing roadway deformation and concentrated stress.

[0124] In the above-mentioned implementation, it specifically includes establishing a three-dimensional grouting sprayed concrete reinforcement numerical simulation calculation model that is the same as the actual project based on the FLAC3D numerical simulation software. For deep mining tunnel excavation, sprayed concrete reinforcement schemes of different thicknesses are adopted to achieve effective protection. The deformation of the tunnel under the conditions of sprayed concrete reinforced pillar support is compared with the conditions of non-sprayed concrete pillar support, and the influence of sprayed concrete reinforced tunnel deformation stability is analyzed. The results show that the reasonable use of sprayed concrete reinforcement scheme can improve the support performance of weakened tunnels, improve the strength and stiffness of the rock formations around the tunnels, effectively reduce the roof settlement and horizontal displacement of the side caused by tunnel excavation, and improve the stability of the tunnel.

[0125] As an embodiment of the present invention, the above method also includes: a immersion and saturation test to establish an optimization method for yielding support under the weakening influence of the coexistence of joints and a moist environment, so that the model of the present invention is closer to reality and the support effect is better.

[0126] In summary, the present invention establishes a surrounding rock-support interaction equilibrium model through indoor experiments, FLAC3D numerical simulation software combined with the theoretical formula of the pillar support system, performs dynamic simulation and mechanical simulation on the support system under the condition of weakened surrounding rock, analyzes the mechanical properties of the surrounding rock and the evolution law of the plastic zone at different depths as the position of the weakened rock layer changes, determines the boundary of the initial support stress of the pillar and changes the size of the initial support stress based on the boundary, analyzes the control effect of the initial support stress of the pillar on the plastic deformation of the surrounding rock, and proposes the optimal distribution scheme of the active steel pillar pressure-yielding support for the weakened surrounding rock reinforcement, providing important quantitative theoretical support for the support design of the hard rock mining working face and the stability of the roadway under high stress weakening conditions. In addition, according to the control effect of the initial support stress on the roadway deformation, sprayed concrete reinforcement is added to reduce the displacement of the side, and a pillar support-sprayed concrete reinforcement collaborative support system is constructed, which effectively improves the stability of the roadway and provides technical guarantee for the safe mining of deep hard rock mines.

[0127] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. The yield support optimization method under the influence of local weakening of hard rock mining section is characterized by: Including steps: Based on the axial compression test of weakened rock, the stress-strain relationship of the joint weakening zone under different loads is analyzed, the damage relationship of the joint weakening zone is constructed, and the mechanical parameters of the rock mass are obtained; By combining the finite element analysis method with rock mass mechanical parameters, a numerical model of the surrounding rock tunnel with local weakening in a hard rock stope was constructed to analyze the influence of the weakening of the hard rock stope on the deformation and stress of the surrounding rock tunnel. Based on the influence of weakening of hard rock stope on deformation and stress of surrounding rock tunnel, the support position is determined, and the surrounding rock-support interaction equilibrium model is constructed by combining FLAC3D numerical simulation software with the theoretical formula of pillar support system. Based on the surrounding rock-support interaction equilibrium model, the lower limit of the initial support stress of the pillar is determined by the Mohr-Coulomb criterion, and the upper limit of the initial support stress of the pillar is determined by the pillar bearing capacity. By changing the initial support stress of the pillar, the control effect of the plastic deformation of the surrounding rock is analyzed, and the optimal initial support stress is selected to achieve the pressure balance between the pillar rigid support and the energy release of the surrounding rock, thereby obtaining the optimized support method. Among them, the theoretical formula of the pillar support system is: Assuming that the tunnel surrounding rock is an axisymmetric elastic medium and the support structure provides uniform radial support force, according to the thick-walled cylinder theory of elastic mechanics, the surrounding rock stress distribution satisfies: ； Where: P0: original rock stress; r0: roadway radius; r: radius of any point in the surrounding rock; : radial stress; : hoop stress; Initial support stress The size satisfies the following formula: ； Where P0 is the original rock stress, is the internal friction angle, For cohesion, is the ultimate bearing capacity of a single pillar, A is the support density, k1 is the safety factor of the surrounding rock, and k2 is the safety factor of the support structure.

2. The yield support optimization method under the influence of local weakening of hard rock mining section according to claim 1 is characterized by: Construct a surrounding rock-support interaction equilibrium model, including: The cable unit is used to simulate the pillar support and analyze the axial pressure performance of the pillar support, ignoring the shear resistance of the pillar support. The cable unit includes several cable units, and each two cable units are connected by a node. When the pillar is in tension, under the action of axial tensile stress, the cable units are connected by spring stiffness and provide corresponding support reaction force for the surrounding rock through sliding elements. Among them, cablesel adopts the ideal elastic-plastic constitutive model and sets the ultimate compressive strength value of the pillar. After exceeding the limit, the axial pressure of the pillar will remain unchanged with the displacement. The stiffness K of the pillar is calculated as follows: ； Where L is the length of the cablesel, A' is the cross-sectional area of ​​the support, and E is the elastic modulus.

3. The yield support optimization method under the influence of local weakening of hard rock mining section according to claim 1 is characterized in that: A numerical model of a hard rock stope with locally weakened surrounding rock tunnels was constructed to analyze the effects of weakening in the hard rock stope on the deformation and stress of the surrounding rock tunnels, including: Numerical models of tunnels with different mining depths under different weakening states are constructed. The different weakening states include four states: intact rock strata, weakened layer located above, weakened layer running through the tunnel, and weakened layer located below. The effects of tunnel mining depth under different weakening states on surrounding rock deformation, including roof displacement and side displacement, and stress distribution are analyzed.

4. The yield support optimization method under the influence of local weakening of hard rock mining section according to claim 1 is characterized in that: Constructing a surrounding rock-support interaction equilibrium model also includes: simulating the initial stress field distribution of the surrounding rock in the unexcavated and unsupported state.

5. The yield support optimization method under the influence of local weakening of hard rock mining section according to claim 1 is characterized in that: The rock mass mechanical parameters include elastic modulus, Poisson's ratio, internal friction angle, and strength.

6. The yield support optimization method under the influence of local weakening of hard rock mining section according to claim 1 is characterized in that: It also includes constructing a pillar support-sprayed concrete reinforcement collaborative support system and analyzing the synergistic effect of pillar support and sprayed concrete reinforcement.

7. The yield support optimization method under the influence of local weakening of hard rock mining section according to claim 6 is characterized in that: Construct a pillar support-spray-mix reinforcement collaborative support system. Including, based on FLAC3D numerical simulation software, establishing a three-dimensional grouting shotcrete reinforcement numerical simulation calculation model that is the same as the actual project.

8. The yield support optimization method under the influence of local weakening of hard rock mining section according to claim 1 is characterized in that: Also includes: Through immersion and saturation tests, an optimization method for yielding support under the weakening influence of joints and moist environment is established.

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