A control method for the surrounding rock stability of gob-side entry with small coal pillars

Abstract

The present invention relates to the technical field of surrounding rock reinforcement in coal mine roadways, and particularly to a method for controlling the stability of the surrounding rock of a gob-side entry with a small coal pillar, which comprises the following steps: establishing four mechanical models of direct roof fracture; calculating the correlation between the shear force, bending moment and deflection of the direct roof; judging the type of mechanical model to which the gob-side entry with a small coal pillar belongs; calculating the mathematical relationship between the maximum deflection of the direct roof and the supporting force of the small coal pillar; subjecting multiple rock samples, coal samples and consolidated specimens of multiple groups of grouting reinforcement materials to a single loading, and subjecting the grouting coupling test body to a secondary loading by using an orthogonal test; obtaining the optimal grouting reinforcement materials, consolidation time and injection rate; establishing a numerical model of grouting reinforcement for the small coal pillar of the gob-side entry by FLAC3D and simulating; obtaining the optimal grouting layout scheme by using the simulated annealing algorithm; determining the optimal grouting reinforcement scheme; the present invention combines experiments with simulation, scientifically evaluates the support reinforcement parameters, realizes the effective control of the stability of the surrounding rock of the gob-side entry with a small coal pillar, and has the advantages of simple method and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of surrounding rock reinforcement in coal mine roadways, and particularly to a method for controlling the stability of surrounding rocks in gob-side entry with small coal pillars. Background Art

[0002] As the main energy source and important chemical raw material in China, coal, as the basis of China's energy production and consumption, the exploitation of coal resources is inseparable from the service of roadways. As the passage of the coal mine production system, the stability and maintenance quality of underground roadways directly affect whether the mine can achieve safe and efficient production. The western region will be the key area for China's coal industry production in the future. The geological conditions in the northwest region mainly show the following characteristics: the surface layer is mostly sedimentary sand layer; the bedrock layer is mostly composed of mudstone layer, sand layer, and interbedded rock mass of mudstone and sandstone. Affected by the mining disturbance, the surrounding rock deformation of gob-side entry with small coal pillars is one of the main problems plaguing coal mine production and construction in China and even the world, posing higher requirements for coal mining equipment, technology, etc. Gob-side entry with small coal pillars often suffers from large deformation of surrounding rocks, roof caving, floor heaving, and rib spalling due to the loose and unstable small coal pillars, directly affecting the safe and efficient exploitation of coal. Moreover, the residual small coal pillars generally cannot be recovered, greatly wasting coal resources. Mining roadways in the high-gravity area of residual small coal pillars is prone to rock burst accidents, as well as coal seam gas outburst and gas explosion accidents. At the same time, the ventilation in the goaf caused by the force failure of the reserved small coal pillar for protecting the roadway is also prone to gas and fire accidents.

[0003] In the prior art, when retaining roadways, generally, the original roadway roof is supported by a combined support of bolts, meshes, cables, and spraying in advance. However, for the complex conditions in western mining areas, the combined roof rock strata are complex. Improper support measures are prone to bedding separation or roof caving. Moreover, the deformations of different rock strata during mining are inconsistent, easily leading to roadway deformation. Traditional support methods are difficult to meet the requirements of roadway stability under the conditions of combined roof, and the overall strength of the surrounding rock is low, greatly affected by mining disturbances, and the spatial structure form of the overlying rock caving in adjacent working faces is complex, etc. The above problems all pose a serious threat to the safety and stability of roadways.

[0004] The present invention proposes a method for controlling the stability of surrounding rocks in gob-side entry with small coal pillars. By combining methods such as theoretical analysis, indoor rock mechanics experiments, and numerical calculations, a grouting reinforcement plan for the deformation of the surrounding rocks in gob-side entry with small coal pillars is obtained, which is of great significance for the development of the grouting reinforcement technology of the surrounding rocks in gob-side entry with small coal pillars and the safe and efficient exploitation of coal mines. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for controlling the stability of surrounding rocks in gob-side entry with small coal pillars to solve the problems raised in the above background art.

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

[0007] A method for controlling the surrounding rock stability of a gob-side entry with small coal pillars includes the following steps:

[0008] Step S1: Divide four fracture structure forms according to the fracture line position between the main roof rock blocks, and correspondingly establish four mechanical models of the immediate roof of the gob-side entry with small coal pillars;

[0009] Step S2: According to the four mechanical models, calculate the correlation of the immediate roof shear force, the immediate roof bending moment, and the immediate roof deflection respectively through the static equilibrium condition of the immediate roof;

[0010] Step S3: Use the borehole optical imaging method and the roof separation monitoring method to monitor the surrounding rock of the gob-side entry with small coal pillars, obtain the gob-side entry environmental parameters, judge the type of mechanical model to which the gob-side entry with small coal pillars belongs, and calculate the support loads of the rock blocks and the coal wall;

[0011] Step S4: Input the gob-side entry environmental parameters and the loads applied by the coal wall and the coal pillar to the immediate roof into the corresponding mechanical model, and calculate the mathematical relationship between the maximum value of the immediate roof deflection and the support load of the small coal pillar;

[0012] Step S5: Obtain multiple groups of initial intact rock samples of the gob-side entry roof and initial intact coal samples of the side roadway of the small coal pillar, make consolidated specimens of the grouting reinforcement material, conduct a primary loading test and obtain its corresponding mechanical properties and related parameters; use the orthogonal test method for the secondary loading test of the grouting-coupled reinforcement test body after failure;

[0013] Step S6: Obtain the test results, and obtain the grouting reinforcement material, the consolidation time of the grouting reinforcement material, and the injection rate of the grouting reinforcement material in the optimal small coal pillar grouting reinforcement plan;

[0014] Step S7: Use FLAC3D to establish a numerical model for grouting reinforcement of the small coal pillar of the gob-side entry, calculate and simulate the deformation data of the surrounding rock of the gob-side entry without grouting and count them;

[0015] Step S8: Use the simulated annealing algorithm to obtain the optimal grouting layout plan, obtain the grouting hole positions and determine the row and column spacing between grouting holes, calculate and simulate the deformation data of the surrounding rock of the gob-side entry after grouting reinforcement and count them;

[0016] Step S9: Analyze the stress, strain and plastic zone development and evolution characteristics of the gob-side entry and the small coal pillar before and after grouting, and determine the optimal grouting reinforcement plan.

[0017] Preferably, the four mechanical models are established according to the fracture line position of the main roof and the relative position between the roadway and the solid coal wall. The four mechanical models include that the main roof fracture line is located inside the solid coal wall, the main roof fracture line is located above the roadway, the main roof fracture line is located above or outside the small coal pillar, and the main roof does not form a structure.

[0018] Preferably, the environmental parameters include the length of the overhanging roof of the immediate roof, the thickness of the immediate roof, the elastic modulus E of the immediate roof, the depth of the gob-side entry, the width of the gob-side entry, the length of the small coal pillar, and the length of the coal wall.

[0019] Preferably, the secondary loading test on the grouting-coupled reinforcement test body after failure using the orthogonal test method includes the following steps: determining three key factors, namely the grouting reinforcement material, the consolidation time, and the grouting volume, and selecting relevant parameters for the key factors.

[0020] Preferably, step S5 includes the following steps:

[0021] Fabricating multiple groups of consolidated specimens of the grouting reinforcement material, and respectively conducting multiple primary loading tests on multiple groups of initially intact roof rock samples of the gob-side entry and initially intact coal samples of the side wall of the small coal pillar, and the consolidated specimens of the grouting reinforcement material according to the support load conditions of the small coal pillar; for each group of crushed rock samples and damaged coal samples after uniaxial compression, coupling with the corresponding grouting reinforcement material for different consolidation times to obtain the grouting-coupled reinforcement test body of the post-peak crushed rock sample and the grouting-coupled reinforcement test body of the post-peak damaged coal sample after the primary loading, and adjusting the relevant parameters according to the orthogonal test table, and respectively conducting secondary loading tests.

[0022] Preferably, the orthogonal test arrangement is 16 tests, including three factors and four parameters for each factor, and the generated orthogonal test table has 16 rows and 3 columns. Each row is one test, each column is a different factor, and each test takes different parameters of each factor.

[0023] Preferably, step S8 includes the following steps:

[0024] Step S81: Selecting the layout parameters of the grouting interval and row spacing as the design variables, setting the target function value as the total deformation after the extraction of the upper panel working face, randomly obtaining a layout parameter of the grouting interval and row spacing as the initial solution T0, and simulating to obtain the initial target function F(T0);

[0025] Step S82: Generating a new layout parameter of the grouting interval and row spacing T k in the neighborhood of the current layout parameter of the grouting interval and row spacing T k+1 ;

[0026] Step S83: Evaluating the grouting reinforcement effect of the new layout parameter of the grouting interval and row spacing T k+1 and calculating the new target function value F(T k+1 );

[0027] Step S84: Accepting the new layout parameter of the grouting interval and row spacing T k+1 according to the Metropolis criterion;

[0028] Step S85: According to the exponential cooling strategy, i.e., Tk+2 = α * T k+1 decreases in the order of, where α is the temperature reduction coefficient and 0 < α < 1, k is the number of iterations and k > 1;

[0029] Step S86: Repeat steps S82 to S85 until k reaches the set number of iterations.

[0030] Preferably, step S83 includes the following steps:

[0031] Input the obtained optimal grouting reinforcement material, its corresponding optimal consolidation time, and grouting injection rate, and input the obtained new layout parameters of grouting interval and row spacing into the established numerical model of grouting reinforcement to obtain the statistical data of the surrounding rock deformation of the gob-side entry after grouting. Without changing other parameters, compare the strength of the gob-side entry before and after grouting with the statistical data of the surrounding rock deformation of the gob-side entry before grouting to evaluate the effect of the strength recovery of the gob-side entry.

[0032] Preferably, the Metropolis criterion is: the objective function value of the current layout parameter of grouting interval and row spacing is F(T k ), if the new objective function value F(T k+1 ) is less than the current objective function value F(T k ), then directly accept the new layout parameter T of grouting interval and row spacing k+1 ; if the new objective function value F(T k+1 ) is greater than the current objective function value F(T k ), then accept the new layout parameter T of grouting interval and row spacing with a set probability P k+1 ; where the set probability P = exp(-Δf / Tk), and Δf is the difference between the objective function value F(T k+1 ) of the new layout parameter of grouting interval and row spacing and the objective function value F(T k ) of the current layout parameter of grouting interval and row spacing.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] A method for controlling the stability of the surrounding rock of a gob-side entry with a small coal pillar provided by the present invention analyzes and establishes a mechanical model of the immediate roof of the gob-side entry with a small coal pillar, studies the internal factors of the instability and deformation of the surrounding rock of the gob-side entry with a small coal pillar, and uses FLAC3D to establish a numerical model of grouting reinforcement for the small coal pillar of the gob-side entry. Based on the strength characteristics of the coupled reinforcement of the broken surrounding rock obtained from the rock samples, coal samples, grouting reinforcement materials and their coupling, the optimal grouting reinforcement plan is determined, and the control effect is evaluated with the changes of the surrounding rock stress, strain and plastic zone as the evaluation indexes; finally, the control of the surrounding rock deformation of the gob-side entry with a small coal pillar in the western mining area and the optimization of the grouting reinforcement parameters are obtained, which has positive social and economic benefits and great technical significance for the safe and efficient coal mining.

[0035] A method for controlling the surrounding rock stability of gob-side entry with small coal pillars provided by the present invention determines the relevant mechanical properties of the in-situ geology through the coupling reinforcement strength characteristic test of the broken surrounding rock, and uses conventional support materials in the test to determine the optimal grouting reinforcement material and the grouting reinforcement time, reducing the waste of the grouting reinforcement material and saving the support cost. It can also optimize the support and grouting reinforcement parameters according to the actual geological conditions of the engineering site, realizing the practical application of one mine, one strategy.

[0036] A method for controlling the surrounding rock stability of gob-side entry with small coal pillars provided by the present invention uses the simulated annealing algorithm to analyze the stability of the surrounding rock of the stope under the grouting reinforcement of the small coal pillar body of the gob-side entry for different grouting volumes, scientifically evaluates the support reinforcement parameters, and effectively controls the stability of the surrounding rock of the gob-side entry with small coal pillars. The method is simple and has low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic flow chart of a method for controlling the surrounding rock stability of gob-side entry with small coal pillars according to an embodiment of the present invention;

[0038] Figure 2 It is a schematic flow chart of the uniaxial compression test of the rock sample, coal sample and different grouting reinforcement materials consolidated according to an embodiment of the present invention;

[0039] Figure 3 It is a schematic diagram of the overlying strata structure of the gob-side entry with small coal pillars according to an embodiment of the present invention;

[0040] Figure 4 It is a schematic diagram of the mechanical model of the immediate roof of the gob-side entry with small coal pillars according to an embodiment of the present invention;

[0041] Figure 5 It is a schematic diagram of the structure of the numerical calculation model for grouting reinforcement of the small coal pillar of the gob-side entry according to an embodiment of the present invention;

[0042] Figure 6 It is a sectional view of the support of the return airway according to an embodiment of the present invention;

[0043] Figure 7 It is a developed plan view of the support of the return airway according to an embodiment of the present invention;

[0044] Figure 8 It is a schematic sectional view of the layout of the grouting scheme according to an embodiment of the present invention;

[0045] Figure 9 It is a schematic plan view of the layout of the grouting scheme according to an embodiment of the present invention;

[0046] Figure 10 It is a schematic diagram of the anchor cable structure according to an embodiment of the present invention;

[0047] Figure 11 It is a relationship diagram between the maximum value of the deflection of the immediate roof and the support load of the small coal pillar according to an embodiment of the present invention. Detailed implementation manners

[0048] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to 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. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] In the following description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation. The term "connection" only represents the connection between devices and has no special meaning.

[0050] In addition, as long as there is no conflict between the technical fields and installation manners involved in the embodiments of the present invention described below, they can be combined with each other.

[0051] Specific embodiment: Please refer to Figure 1 and Figure 2 , a method for controlling the surrounding rock stability of a gob-side entry with a small coal pillar, comprising the following steps:

[0052] Step S1: Divide four fracture structure forms according to the fracture line position between the main roof rock blocks, and correspondingly establish four mechanical models of the immediate roof of the gob-side entry with a small coal pillar.

[0053] Specifically, as shown in Figure 3 , according to the main roof, the roadway, the coal wall C, the small coal pillar D and the fracture line position of the main roof, it is divided into 4 fracture structure forms. After the main roof fractures, rock blocks A and B are formed on both sides. The established overlying strata structure model of the gob-side entry with a small coal pillar corresponds to Figure 3 the four mechanical models of (a), (b), (c) and (d) respectively. The lengths of the rock block A, the rock block B, the coal wall C and the small coal pillar D are respectively expressed as l A , l B , l C and l D , the width of the gob-side entry is expressed as l, and the length of the studied immediate roof is expressed as L.

[0054] Specifically, Figure 3 in (a) of A ≤l C , it means that the fracture line position of the main roof is located inside the solid coal wall C; in (b), l C <l A≤l + l C , indicating that the position of the basic roof fracture line is above the roadway; in (c), l + l C < l A < L, indicating that the position of the basic roof fracture line is above or outside the small coal pillar; in (d), l A ≥ L, indicating that the basic roof basically does not form a structure.

[0055] Step S2: According to the four mechanical models, calculate the correlations of the shear force, bending moment, and deflection of the immediate roof through the static equilibrium conditions of the immediate roof respectively.

[0056] Among them, based on the force relationships among the immediate roof, coal wall C, small coal pillar D, and basic roof, a mechanical model of the immediate roof is constructed as Figure 4 shown, where q A , q B (x), q C and q D (x) represent the loads applied to the immediate roof by rock block A, rock block B, coal wall C, and small coal pillar D respectively. The deformations of rock block B and the small coal pillar are different at different positions. According to Hooke's law, the loads applied by rock block B and the small coal pillar are uneven, and they are respectively expressed as functions of the horizontal axis x in turn.

[0057] Specifically, through the static equilibrium conditions of the immediate roof, the parameter expressions of the shear force, bending moment, and deflection of the immediate roof are calculated to judge the stability of the immediate roof of the gob-side entry with a small coal pillar:

[0058] (1) When the mechanical model is that the basic roof fracture line is inside the solid coal wall, the roof deflections of the gob-side entry and the small coal pillar satisfy the following relationships

[0059]

[0060] Among them, E represents the elastic modulus, I represents the interface moment of inertia, and ω represents the deflection.

[0061] (2) When the mechanical model is that the basic roof fracture line is above the roadway, the roof deflections of the gob-side entry and the small coal pillar satisfy the following relationships

[0062]

[0063] (3) When the mechanical model is that the basic roof fracture line is above or outside the small coal pillar, the roof deflections of the gob-side entry and the small coal pillar satisfy the following relationships

[0064]

[0065] (4) When the mechanical model is that the basic roof does not form a structure, the roof deflections of the gob-side entry and the small coal pillar satisfy the following relationships

[0066]

[0067] Step S3: Monitor the surrounding rock of the gob-side entry with small coal pillar by using the borehole optical imaging method and the roof separation monitoring method, obtain the environmental parameters of the gob-side entry, judge the type of mechanical model to which the gob-side entry with small coal pillar belongs, and calculate the support loads of the rock block and the coal wall.

[0068] Specifically, use the borehole optical imaging method to observe the surrounding rock of the roadway, obtain geological information such as the deformation and cracks of the surrounding rock of the roadway, use the roof separation monitoring method to monitor the roof separation of the roadway in real time, and obtain the environmental parameters of the gob-side entry; among them, the environmental parameters include the depth of the gob-side entry, the width l of the gob-side entry, the overhanging length of the immediate roof, the thickness of the immediate roof, the elastic modulus E of the immediate roof, the length l of rock block A A 、the length l of rock block B B 、the length l of coal wall C C 、the length l of small coal pillar D D , the overhanging length of the immediate roof refers to the length that the immediate roof extends into the goaf protruding from the small coal pillar D, and the length L of the immediate roof is obtained by summing the width l of the gob-side entry, the length l of coal wall C C 、the length l of small coal pillar D D and the overhanging length of the immediate roof. According to the environmental parameters and the obtained length of the main roof, the type of mechanical model to which the gob-side entry with small coal pillar belongs can be judged; combining the stress monitoring data of the surrounding rock of the roadway, analyze the stress distribution of the surrounding rock of the roadway, and calculate the loads q A 、q D applied by rock block A and coal wall C to the immediate roof according to the load monitoring data of the roadway support structure and the stress monitoring data of the surrounding rock of the roadway.

[0069] Step S4: Input the environmental parameters of the gob-side entry and the loads applied by the rock block and the coal wall to the immediate roof into the corresponding mechanical model, and calculate the mathematical relationship between the maximum deflection of the immediate roof and the support load of the small coal pillar.

[0070] In this embodiment, taking the roof rock stratum structure where the main roof does not form a structure as an example, the acting load q D (x) of the small coal pillar on the immediate roof is regarded as a uniformly distributed load q D :

[0071] At this time, the static condition of roof stability is

[0072] F Oy +q C l C +q D l D -q A L = 0

[0073]

[0074] Among them, F Oy and M O respectively represent the vertical force and bending moment borne by the coal wall C.

[0075] It can be obtained that

[0076] F Oy = q A L - q C l C - q D l D

[0077]

[0078] At this time, when 0 < x ≤ l C the immediate roof deflection satisfies

[0079]

[0080] From the initial conditions of the cantilever beam

[0081]

[0082] ω x＝0 = 0

[0083] it can be obtained that E1 = 0 and F1 = 0.

[0084] Through the above calculations, it can be obtained that

[0085]

[0086] At this time, x = l C the rotation angle and deflection at this position are

[0087]

[0088] At this time, when l C < x ≤ l + l C that is, the immediate roof deflection above the roadway satisfies

[0089]

[0090] When x = l C it can be obtained that

[0091]

[0092] From this, it can be obtained that

[0093]

[0094] From this, the relationship between the rotation angle and deflection of the roof deformation of the gob-side entry retaining with small coal pillar can be obtained

[0095]

[0096] Let Then there exists \(x = x_0(0 \lt x_0 \leq l\) C ), such that holds, and the direct roof deflection satisfies

[0097] \(\omega\) max =\(\omega\) x＝x0

[0098] Since \(E\), \(I\), \(x_0\), \(q\) A , \(q\) C , \(l\) A , \(l\) B , \(l\) C , \(l\) D , and \(l\) is equal to \(L\) and both are constants, thus we can obtain

[0099]

[0100] At this time, the maximum value of the direct roof deflection and the support load \(q\) of the small coal pillar D satisfy the following relationship

[0101] \(\omega\) max = \(aq\) D + \(b\) (\(a\) and \(b\) are both constants)

[0102] Where

[0103]

[0104] According to the geological conditions of the example mine, the thickness of the direct roof \(H = 17.01m\), the elastic modulus \(E = 4.61GPa\). When the main roof does not form a structure, \(l\) A = \(L\), take \(l\) C = \(10m\), the roadway width \(l = 5.4m\), the small coal pillar \(l\) D = \(6.0m\); assume that the direct roof on the goaf side has a cantilever roof of \(5m\), then the length \(L\) of the direct roof under study is \(L = l + l\) C + \(l\) D + \(5 = 26.4m\), the roadway burial depth is \(309.4m\), then \(q\) A ≈ \(q\) C = \(7.5MPa\). Therefore, the moment of inertia \(10m \lt x_0 \leq 15.4m\); substituting the data, we can get \(a \lt 0\), \(b \gt 0\). Therefore, it can be obtained that the maximum subsidence of the direct roof and the support force of the small coal pillar show a monotonically decreasing linear function. As Figure 11 shown, the deformation of the direct roof is closely related to the support strength of the small coal pillar. Therefore, grouting reinforcement measures can be taken to restore and improve the strength of the broken small coal pillar.

[0105] Specifically, the relationship diagram between the maximum value of the direct roof deflection and the support load of the small coal pillar is shown in Figure 11 , where the maximum critical value of the roof subsidence for safe production corresponds to the maximum deflection of ω3, and the corresponding support load of the small coal pillar is q D2 , q D4 is the support load of the small coal pillar before crushing, corresponding to the maximum roof deflection of ω1; q D1 is the support load of the coal pillar after crushing, corresponding to the maximum roof deflection of ω4; q D3 is the support load after grouting reinforcement of the crushed small coal pillar, corresponding to the maximum roof deflection of ω2.

[0106] Furthermore, the maximum critical value of the roof subsidence for safe production needs to be determined by combining the specific engineering actual situation and the relevant data obtained in step S3.

[0107] When the goaf is formed during the mining of the upper section working face, the internal structure of the small coal pillar is damaged, and its support performance decreases from q D4 to q D1 . The corresponding maximum roof deformation increases from ω1 to ω4. At this time, the roof deformation amount seriously exceeds the maximum deformation critical value of the roof for safe production, that is, the maximum value allowed for roof separation within the safe range. Therefore, it is necessary to improve the strength of the coal pillar. Generally, grouting reinforcement measures are taken to restore the strength of the crushed small coal pillar. After grouting reinforcement, the support load of the coal pillar after strength recovery increases from q D1 to q D3 , where q D2 <q D3 <q D4 . The maximum roof deflection also decreases from ω4 to ω2, and its deformation amount is less than the maximum value of the surrounding rock deformation for safe production, meeting the requirements of normal production.

[0108] Substitute the obtained relevant parameters into the corresponding formula of the mechanical model to which the gob-side entry belongs obtained in step S3, and calculate the mathematical relationship between the maximum value of the direct roof deflection and the support load of the small coal pillar, and obtain the maximum deflection of the roof corresponding to the grouting reinforcement of the crushed small coal pillar and the data of the small coal pillar support force, so that the strength and stability of the small coal pillar after crushing grouting reinforcement, and the maximum deflection of the roof corresponding to the small coal pillar after crushing grouting reinforcement is lower than the maximum deflection of the roof corresponding to the maximum critical value of the roof subsidence for safe production, meeting the requirements of safe production.

[0109] Step S5: Obtain multiple groups of initial intact rock samples of the gob-side entry roof and initial intact coal samples of the side roadway of the small coal pillar, make consolidated specimens of the grouting reinforcement material, conduct a primary loading test and obtain their corresponding mechanical properties and relevant parameters; use the orthogonal test method for the secondary loading test of the grouting coupling reinforcement test body after failure.

[0110] Specifically, roof rock samples and small coal pillar coal samples are collected in the field, and multiple rock sample test bodies and coal sample test bodies are made. The loading pressure is adjusted according to the support load situation of the small coal pillar, and a single loading test is carried out on multiple rock sample test bodies and coal sample test bodies respectively to obtain the mechanical properties and related parameters of the rock samples and coal samples.

[0111] Among them, the setting of the loading pressure can be carried out by combining the gradual change of the load with the setting of the maximum load. First, the gradual change of the load is used to observe the deformation process of the rock sample or coal sample or the consolidated sample of the grouting reinforcement material, and then after reaching the preset maximum load, it is maintained for a period of time to observe the failure situation of the rock sample or coal sample or the consolidated sample of the grouting reinforcement material. This method can more comprehensively understand the mechanical properties of the coal sample and measure the key mechanical parameters such as the compressive strength of the rock sample or coal sample or the consolidated sample of the grouting reinforcement material; the mechanical properties and related parameters of the rock sample, coal sample and consolidated test bodies of various grouting reinforcement materials include compressive strength, elastic modulus, Poisson's ratio, strain and deformation, etc.

[0112] Further, cement slurry grouting reinforcement materials that are often widely used in the grouting reinforcement project of mine roadway surrounding rock in the prior art are selected. The consolidated samples of the grouting reinforcement materials are proportioned according to the water-cement ratio of 1:2, and additives are added at 8% of the material to obtain consolidated test bodies of various grouting reinforcement materials. The loading pressure is adjusted to be the same as the above test, and a single loading test is carried out to obtain the mechanical properties and related parameters of the consolidated test bodies of various grouting reinforcement materials.

[0113] For the broken rock samples and damaged coal samples after each single loading test, the corresponding grouting reinforcement materials are used for coupling with different consolidation times to obtain the post-peak broken rock sample coupled grouting reinforcement test bodies and post-peak broken coal sample coupled grouting reinforcement test bodies, and the secondary loading tests are carried out respectively according to the support load situation of the small coal pillar.

[0114] Specifically, the broken rock samples and broken coal samples after the single loading test are collected, and they are cemented with different grouting reinforcement materials respectively, and at different consolidation times, multiple post-peak broken rock sample coupled grouting reinforcement test bodies and multiple post-peak broken coal sample coupled grouting reinforcement test bodies are prepared; the obtained post-peak broken rock sample coupled grouting reinforcement test bodies and post-peak broken coal sample coupled grouting reinforcement test bodies are subjected to the secondary loading test, and both the single loading test and the secondary loading test are uniaxial compression tests.

[0115] Further, the orthogonal test design method is adopted in this embodiment for the secondary loading test. By selecting some representative points for the test, the number of tests is greatly reduced, and the required test materials and time costs are reduced. At the same time, it can clarify the influence of each factor on the test results and provide a basis for optimizing the test conditions.

[0116] Select at least three factors from the factors affecting the compressive strength of the grouting coupling test body as key factors. In this embodiment, three key factors are selected, namely, the grouting reinforcement material, the consolidation time of the coupling material, and the grouting injection rate.

[0117] Set parameters for the selected key factors, generate an orthogonal experimental table based on the selected factors and their parameters. Each key factor takes n values. Determine the orthogonal test plan according to the three key factors and the n values of each factor. In this embodiment, n takes 4, and 16 groups of orthogonal test plans are determined; conduct a secondary loading test according to the test parameters corresponding to the orthogonal test plan, obtain the mechanical properties and related parameters corresponding to different parameter combinations, and determine the primary and secondary order of the influence of each factor on the compressive strength according to the test results, and design the optimal plan for improving the compressive strength of the small coal pillar by grouting reinforcement.

[0118] Among them, the grouting reinforcement materials include high-performance cement-based grouting materials, ordinary cement grouting materials, fly ash cement grouting materials, and portland cement grouting materials. The consolidation times of the coupling materials are set to 3 days, 7 days, 14 days, and 28 days respectively, and the injection rates are selected as 20%, 25%, 30%, and 35% respectively.

[0119] Step S6: Obtain the test results, and obtain the grouting reinforcement material, the consolidation time of the grouting reinforcement material, and the injection rate of the grouting reinforcement material in the optimal grouting reinforcement plan for the small coal pillar.

[0120] Step S7: Use FLAC3D to establish a numerical model for grouting reinforcement of the small coal pillar along the gob-side roadway, calculate and simulate the deformation data of the surrounding rock of the gob-side roadway without grouting and count them.

[0121] Specifically, combined with the actual background of the grouting reinforcement of the small coal pillar along the gob-side roadway of the example working face, use FLAC 3D Establish a numerical model for grouting reinforcement of the small coal pillar along the gob-side roadway with a length×width×height = 280m×60m×60m. The simulated return airway is a coal roadway with a buried depth of 309.4m. Apply a fixed load of 7.5MPa on the top of the whole model; the upper section of the return airway is the working face being mined, and a 6m protective small coal pillar is left between them. According to the grouting reinforcement design plan and the grouting slurry diffusion law, determine a grouting reinforcement area on the side of the small coal pillar roadway. The specific numerical calculation simulation is as follows Figure 5 shown.

[0122] Set support reinforcement in the above roadway model. The support plan is shown in Figure 6 and Figure 7 , and conduct calculation simulation without grouting to obtain the stress, strain, and plastic zone development and evolution characteristics of the gob-side roadway and the small coal pillar before grouting.

[0123] Step S8: Use the simulated annealing algorithm to obtain the optimal grouting layout plan, obtain the positions of grouting holes and determine the row and column spacing between grouting holes, calculate the surrounding rock deformation data of the gob-side entry after simulated grouting reinforcement and conduct statistics.

[0124] Step S81: Select the layout parameters of the row and column spacing of grouting that affect the stress and deformation of the small coal pillar as design variables, set the objective function value as the total deformation after the mining of the upper panel working face, randomly obtain a layout parameter of the row and column spacing of grouting as the initial solution T0, and simulate to obtain the initial objective function F(T0);

[0125] Furthermore, the diffusion radius of the grouting hole can be preliminarily determined according to the fragmentation condition of the small coal pillar and relevant grouting experience, usually in the range of 1 to 3 meters; according to the technological requirements of the grouting reinforcement material and the actual situation, determine the constraint conditions and the objective function value when optimizing the grouting reinforcement effect;

[0126] Specifically, randomly generate a solution as the current layout parameter of the row and column spacing of grouting. In this embodiment, it can be set that the cooling strategy adopts exponential cooling, which can usually be expressed as T k+1 = α * T k , where α is the cooling coefficient, and 0 < α < 1, T is the current temperature, k is the number of iterations, and k > 1; set the objective function value as the total deformation after the mining of the upper panel working face, set the algorithm termination condition that k reaches the set number of iterations, etc.; randomly obtain a relatively large layout parameter of the row and column spacing of grouting as the initial solution T0, and simulate to obtain the initial objective function value F(T0).

[0127] Step S82: Generate a new layout parameter of the row and column spacing of grouting T k in the neighborhood of the current layout parameter of the row and column spacing of grouting T k+1 ;

[0128] Step S83: Evaluate the grouting reinforcement effect of the new layout parameter of the row and column spacing of grouting T k+1 , calculate the new objective function value F(T k+1 );

[0129] Input the optimal grouting reinforcement material obtained in Step S6, its corresponding optimal consolidation time, and the injection rate of the grouting reinforcement material, input the obtained new layout parameter of the row and column spacing of grouting T k+1 into the grouting reinforcement numerical model established in Step S7, without changing other parameters, obtain the statistics of the surrounding rock deformation data of the gob-side entry after grouting, and compare the strength of the gob-side entry before and after grouting with the statistics of the surrounding rock deformation data of the gob-side entry before grouting obtained in Step S7 to evaluate the strength recovery effect of the gob-side entry.

[0130] Step S84: According to the Metropolis criterion, accept the new layout parameter of the row and column spacing of grouting T k+1 ;

[0131] If the new objective function value F(T k+1 ) is less than the current objective function value F(T k ), then directly accept the new grouting interval layout parameter T k+1 ; if the new objective function value F(T k+1 ) is greater than the current objective function value F(T k ), then accept the new grouting interval layout parameter T with the set probability P k+1 ;

[0132] where P = exp(-Δf / T), and Δf is the difference between the new objective function value F(T k+1 ) and the current objective function value F(T k ).

[0133] Step S85: Continue to decrease according to the cooling strategy, that is, in the order of T k+2 = α * T k+1 .

[0134] Step S86: Repeat Step S82 to Step S85 until k reaches the set number of iterations.

[0135] After the algorithm terminates, the obtained optimal solution is the optimal grouting interval layout parameter.

[0136] Step S9: Analyze the stress, strain and plastic zone development and evolution characteristics of the gob-side entry and small coal pillar before and after grouting, and determine the optimal grouting reinforcement plan.

[0137] This embodiment discloses a set of simulation test results (see Table 1) to illustrate that grouting reinforcement improves the strength of the gob-side entry. In the simulation comparison and verification of this set of slurries, it is obtained from the analysis of the roadway surrounding rock deformation data before and after grouting reinforcement that the grouting reinforcement reduces the plastic zone range of the roadway to 1.2 m, and an elastic zone of 2.00 - 3.00 m appears in the center of the entire small coal pillar; the reinforcement and support effect makes the stress values of the support bodies on both sides approach each other continuously, making the stress distribution of the roadway surrounding rock more balanced. The grouting reinforcement plays a role in maintaining the stability of the roadway, and it can be verified that the grouting-related parameters obtained by simulating with the deep learning model have a good effect on coal sample reinforcement.

[0138] Table 1 Statistical data of roadway surrounding rock deformation before and after grouting reinforcement

[0139]

[0140]

[0141] Obtain the optimal value of the row and column spacing of the grouting holes obtained in step S8, and determine the grouting reinforcement plan based on the optimal grouting reinforcement material, the consolidation time of the grouting reinforcement material, and the injection rate of the grouting reinforcement material obtained in step S7; the optimal grouting reinforcement plan disclosed in this embodiment is: the optimal grouting reinforcement material is a high-performance cement-based grouting material, the consolidation time of the optimal grouting reinforcement material is 14 days, the injection rate of the grouting reinforcement material is 25%, the spacing of the grouting holes is 3.0 m, the row spacing between the bottom row of grouting bolts and the middle row of grouting cables is 400 mm, and the row spacing between the middle row of grouting cables and the top row of grouting cables is 800 mm.

[0142] On the basis of the combined support of bolts, wire meshes, cables, and shotcreting in this embodiment, a grouting reinforcement process is carried out. Among them, the combined support of bolts, wire meshes, cables, and shotcreting includes the following steps:

[0143] During the roadway excavation process, φ22×2500 mm deformed steel bolts are used for the full section. Each deformed steel bolt is filled with 2 sections of MSK2370 resin cartridges, and the anchoring force is not less than 190 kN (28.5 MPa). The pre-tightening torque of the deformed steel bolt is not less than 250 N·m. The tray specification is a 150×150×10 mm dish-shaped tray, and the row and column spacing is 800×1000 mm; two single-point cables are installed in every other row at the top of the roadway. The specific structure of the cable is shown in Figure 10 , and the row and column spacing between the two cables is 1600×2000 mm; another three rows of cable beams are arranged in a "five-flower type" stepping layout, and the row and column spacing is 2000×1600 mm; the top cable specification is φ21.8×7300 mm steel strand. Each cable is filled with 2.5 sections of MSK2370 type resin cartridges. The tray specification is 300×300×16 mm. The cable beam is made of 11# miner steel with L = 2400 mm, and the hole spacing is 2000 mm;

[0144] Two single-point cables are installed in every other row on the side roadway of the coal mining side of the roadway, arranged in the same row as the deformed steel bolts, and the row and column spacing is 1600×2000 mm. The upper cable uses φ21.8×5500 mm steel strand, and each cable is filled with 2 sections of MSK2370 type resin anchoring agent. The lower cable uses φ21.8×3500 mm steel strand, and each cable is filled with 2 sections of MSK3535 type resin anchoring agent;

[0145] On the side roadway of the small coal pillar of the roadway, three rows of cable beams are arranged in a "five-flower type" stepping layout along the strike. The first row and the second row of cables both use φ21.8×3500 mm steel strands, and each cable is filled with 2 sections of MSK3535 type resin anchoring agent. The third row of cables uses 21.8×5500 mm steel strand, and each cable is filled with 2 sections of MSK2370 type resin anchoring agent;

[0146] One diagonal single-point anchor cable is installed between every two rows of supports at the shoulder socket on the side of the small coal pillar in the roadway. Steel strands with a diameter of φ21.8×7300mm are used. Each anchor cable is filled with 2.5 sections of MSK2370 resin anchoring agents. All anchor cables (except the bottom feet) in the water-inflow section are changed to full-anchor shear-resistant devices. The full-anchor shear-resistant device includes an anchor head, supporting steel strands (φ21.8mm), steel pipes, grout stop plugs, bolts (screw plugs); the anchoring force of the side anchor cables of the full-anchor shear-resistant device is not less than 200kN (24MPa), and the anchoring force of the top anchor cables is not less than 300kN (38MPa).

[0147] During the roadway driving process, double-layer nets (one diamond-shaped net and one steel bar net, with the diamond-shaped net on the inner layer) are hung at the two shoulder sockets, and the length of the diamond-shaped net is 2m; a metal net made of φ6.5mm round steel is hung across the entire roadway section, and the steel belt uses a φ16×6480×80-800-9 round steel belt; a hooked-edge steel bar net welded with φ6.5mm round steel is hung across the entire section, with a length×width of 3000×1000mm, the hooked edge is exposed 80mm, and the mesh size is 100×100mm; the top and side nets are all connected by hooking the edges. Where hooking the edges for networking is not possible, two strands of 14# lead wires are used to connect every 100mm with no less than three turns of kinking; at the top, a φ16×6480×80-800-9 round steel belt is used, and the threaded steel bolts and anchor cables are arranged in the same way as the steel belt.

[0148] The floor thickness is 200mm, the concrete strength grade is C25, the shotcrete thickness is 100mm, and the concrete strength is C20. The roadway drainage ditch is arranged on the left hand side in the driving direction. In this embodiment, the support structure is an existing technology, and the specific support schematic diagram is shown in Figure 6 and Figure 7 .

[0149] On the basis of the above combined support, grouting reinforcement is carried out. A grouting reinforcement area is established on the side of the small coal pillar roadway. A total of 3 rows of drill holes are arranged on the side of the small coal pillar. The upper row is a 5.1m grouting anchor cable hole, with a hole depth of 4.8m, 1.6m from the top, a spacing of 3.0m, and an elevation angle of 32°. About 1.4m of the hole body in the roof rock formation can prevent the displacement of the small coal pillar. The lower row is a grouting bolt hole, about 0.4m from the floor, anchored into the floor at a 15° depression angle, with a spacing of 3.0m. The middle row is a 5.1m grouting anchor cable, arranged between the upper row of grouting anchor cables, about 0.8m from the floor, with an elevation angle of 18°, and a spacing of 3.0m. The middle row of grouting anchor cables can be lengthened to be anchored and combined with the original support body on the goaf side; the specific grouting reinforcement plan is shown in Figure 8 and Figure 9 .

[0150] Among them, for the grouting bolt construction, a φ43mm borehole is drilled and 2 sections of 3535 resin cartridges are installed. When installing, stop-grouting cotton yarn is wound at the orifice section, and a tray is installed with a stop-grouting plug; for the grouting cable bolt hole, the first 2 sections of the cable bolt (2.4m) are used to drill a φ32mm borehole, and the inner section (2.4 - 4.8m) is drilled with a 032mm borehole. One section of 2370 resin cartridge is installed in each hole. When constructing the grouting cable bolt, first insert a 0.7m long 16mm aluminum-plastic tube into the grouting cable bolt hole as the grouting pipe, with 0.2m of the aluminum-plastic tube exposed outside the hole. The hole is sealed with the resin cartridges stirred well at the orifice, and then the cable bolt tray of the grouting cable bolt is installed. When grouting, a connector is installed at the hole of the aluminum-plastic tube and connected to the grouting pipeline through the connector.

[0151] The grouting branch pipes are arranged according to the positions of the reserved grouting holes. A control gate valve is set for each grouting port branch pipe. The grouting reinforcement material uses high-performance cement-based grouting material. The grouting sequence is to grout one by one from bottom to top. The grouting pressure is controlled at 2 - 4MPa. When the pressure reaches 4MPa, keep the pressure stable for grouting for 5 minutes. If the grouting pressure is less than 4MPa (2 - 4MPa), the grouting time can be adjusted to 5 - 10 minutes; when local leakage occurs on the sidewall during the grouting process, stop grouting in time, and then grout again after 10 - 15 minutes; after grouting, wait for the slurry to initially set, then remove the grouting device and seal the hole in time; the overall grouting reinforcement time is maintained for 14 days, and the injection rate during the grouting process is maintained at 25%.

[0152] A method for controlling the surrounding rock stability of gob-side entry with small coal pillars provided by the present invention analyzes and establishes a mechanical model of the immediate roof of the gob-side entry with small coal pillars, studies the internal factors of the instability and deformation of the surrounding rock of the gob-side entry with small coal pillars, and uses FLAC3D to establish a numerical model for grouting reinforcement of the small coal pillar in the gob-side entry. Based on the strength characteristics of the broken surrounding rock coupling obtained after coupling the rock samples, coal samples, grouting reinforcement materials and their breakage, the optimal grouting reinforcement plan is determined, and the control effect is evaluated with the changes of surrounding rock stress, strain and plastic zone as the evaluation indexes; finally, the control of the surrounding rock deformation of the gob-side entry with small coal pillars in the western mining area and the optimization of grouting reinforcement parameters are obtained, which has positive social and economic benefits and great technical significance for the safe and efficient coal mining.

[0153] A method for controlling the surrounding rock stability of gob-side entry with small coal pillars provided by the present invention determines the relevant mechanical properties of the in-situ geology through the test of the strength characteristics of the broken surrounding rock coupling, and uses conventional support materials in the test to determine the optimal grouting reinforcement materials and grouting reinforcement time, reducing the waste of grouting reinforcement materials and saving the support cost; it can also optimize the support and grouting reinforcement parameters according to the actual geological conditions of the engineering site, realizing the practical application of one mine, one strategy.

[0154] A method for controlling the surrounding rock stability of gob-side entry with small coal pillars provided by the present invention analyzes the surrounding rock stability of the stope under the grouting reinforcement of the small coal pillar body of the gob-side entry with different grouting volumes by using the simulated annealing algorithm, scientifically evaluates the support reinforcement parameters, realizes the effective control of the surrounding rock stability of the gob-side entry with small coal pillars, and has the advantages of simple method and low cost.

Claims

1. A method for controlling the stability of surrounding rock in a small coal pillar gob-side roadway, characterized in that: The steps include: Step S1: four types of fracture structures are divided according to the positions of the fracture lines between the basic roof rock blocks, and four types of direct roof mechanical models of small coal pillars along the gob are established accordingly; Step S2: According to the four mechanical models, the correlation between the shear force, bending moment and deflection of the top is calculated respectively through the static equilibrium conditions of the top; Step S3: using the borehole optical camera method and the roof separation monitoring method to monitor the surrounding rock of the gob-side roadway with small coal pillars, obtain the environmental parameters of the gob-side roadway, determine the type of mechanical model to which the gob-side roadway with small coal pillars belongs, and calculate the support load of rock blocks and coal walls; Step S4: inputting the environmental parameters of the gob-side tunnel and the loads applied by the coal wall and coal pillars to the immediate roof into the corresponding mechanical model, and calculating the mathematical relationship between the maximum deflection of the immediate roof and the supporting load of the small coal pillars; Step S5: obtaining multiple groups of initial complete rock samples of the roof of the gob-side tunnel and initial complete coal samples of the side tunnel of the small coal pillar, making consolidation samples of grouting reinforcement materials, conducting a loading test and obtaining the corresponding mechanical properties and related parameters; and conducting a secondary loading test on the post-destruction grouting coupling reinforcement test body using an orthogonal test method; Step S6: Obtain test results to obtain the grouting reinforcement materials, the consolidation time of the grouting reinforcement materials, and the injection rate of the grouting reinforcement materials in the optimal small coal pillar grouting reinforcement scheme; Step S7: using FLAC3D corresponding to the numerical model of grouting reinforcement of small coal pillars in gob-side tunnels, calculating and simulating the deformation data of surrounding rock in gob-side tunnels without grouting, and making statistics; Step S8: using simulated annealing algorithm to obtain the optimal grouting layout scheme, obtain the grouting hole positions and determine the row spacing between grouting holes, calculate and count the deformation data of the surrounding rock of the gob-side tunnel after simulated grouting reinforcement; Step S9: Analyze the stress, strain and plastic zone development and evolution characteristics of the gob-side tunnel and small coal pillars before and after grouting to determine the optimal grouting reinforcement scheme.

2. The method for controlling surrounding rock stability of a small coal pillar gob-side roadway according to claim 1, characterized in that: The four mechanical models are established based on the position of the basic top fracture line and the relative position between the roadway and the solid coal wall. The four mechanical models include the basic top fracture line located on the inner side of the solid coal wall, the basic top fracture line located above the roadway, the basic top fracture line located above or outside the small coal pillar and the basic top does not constitute a structure.

3. The method for controlling surrounding rock stability of a small coal pillar gob-side roadway according to claim 1, characterized in that: The environmental parameters include the length of the immediate roof hanging roof, the thickness of the immediate roof, the elastic modulus E of the immediate roof, the buried depth of the gob-side tunnel, the width of the gob-side tunnel, the length of the small coal pillar and the length of the coal wall.

4. The method for controlling surrounding rock stability of a small coal pillar gob-side roadway according to claim 1, characterized in that: The secondary loading test of the post-destruction grouting coupling reinforcement test body using the orthogonal test method includes the following steps: determining three key factors: grouting reinforcement material, consolidation time, and grouting amount, which are related parameters for selecting the key factors.

5. The method for controlling the surrounding rock stability of a small coal pillar gob-side roadway according to claim 4 is characterized in that: The step S5 comprises the following steps: Multiple groups of grouting reinforcement material consolidation specimens were made, and multiple primary loading tests were carried out on multiple groups of initial intact rock samples of gob-side tunnel roofs, initial intact coal samples of small coal pillar side tunnels, and grouting reinforcement material consolidation specimens according to the small coal pillar support load conditions. For each group of broken rock samples and damaged coal samples after uniaxial compression, the corresponding grouting reinforcement materials were used to couple different consolidation times to obtain the post-peak broken rock sample coupled grouting reinforcement test bodies and the post-peak broken coal sample coupled grouting reinforcement test bodies after primary loading. The relevant parameters were adjusted according to the orthogonal test table, and secondary loading tests were carried out respectively.

6. A method for controlling surrounding rock stability of a small coal pillar gob-side roadway according to claim 5, characterized in that: The orthogonal experiment arranges 16 experiments, including three factors and four parameters for each factor. The generated orthogonal experiment table has 16 rows and 3 columns. Each row is an experiment, each column is a different factor, and each experiment takes different parameters of each factor.

7. The method for controlling surrounding rock stability of a small coal pillar gob-side roadway according to claim 1, characterized in that: The step S8 comprises the following steps: Step S81: Select the spacing layout parameter between grouting as the design variable, set the objective function value as the total deformation of the upper section working face after mining, randomly obtain a spacing layout parameter between grouting as the initial solution T0, and simulate to obtain the initial objective function F(T0); Step S82: Setting the spacing parameter T in the current grouting room k The neighborhood generates a new grouting spacing layout parameter T k+1 ; Step S83: Setting the parameters T for the new grouting spacing k+1 Evaluate the grouting reinforcement effect and calculate the new objective function value F(T k+1 ); Step S84: Accept the new grouting spacing layout parameter T according to the Metropolis criterion k+1 ; Step S85: According to the exponential cooling strategy, T k+2 =α*T k+1 The order of decrease is, where α is the temperature reduction coefficient, and 0<α<1, k is the number of iterations, and k>1; Step S86: Repeat steps S82 to S85 until k reaches the set number of iterations.

8. The method for controlling the surrounding rock stability of a small coal pillar gob-side roadway according to claim 7, characterized in that: The step S83 comprises the following steps: The obtained optimal grouting reinforcement material and its corresponding optimal consolidation time and grouting injection rate, and the obtained new grouting spacing layout parameters are input into the established grouting reinforcement numerical model, and the deformation data statistics of the surrounding rock of the goaf tunnel after grouting are obtained. Without changing other parameters, the strength of the goaf tunnel before and after grouting is compared with the deformation data statistics of the surrounding rock of the goaf tunnel before grouting, so as to evaluate the strength recovery effect of the goaf tunnel.

9. The method for controlling the surrounding rock stability of a small coal pillar gob-side roadway according to claim 7, characterized in that: The Metropolis criterion is: the current grouting spacing layout parameter objective function value is F(T k ), if the new objective function value F(T k+1 ) is less than the current objective function value F(T k ), then directly accept the new grouting spacing layout parameter T k+1 ; If the new objective function value F(T k+1 ) is greater than the current objective function value F(T k ), then the new grouting spacing layout parameter T is accepted with the set probability P k+1 ; Where, the probability P is set to be exp(-Δf / T k ), Δf is the new grouting spacing layout parameter F(T k+1 ) and the objective function value F(T k ) difference.

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