Coal mine overburden strata separation grouting subsidence effect comprehensive evaluation method

Abstract

The application discloses a kind of coal mine overburden separation layer grouting subsidence reduction effect comprehensive evaluation method, comprising the following steps: S1, the ratio of injected fly ash wet ash volume and coal volume is taken as injection-production ratio, and injection-production ratio is calculated and analyzed, to make from separation layer space filling whether to be evaluated whether sufficient;S2, the measured surface deformation value is calculated, and compared with surface deformation target value, to obtain surface deformation difference value, to evaluate grouting effect;S3, the compaction degree of filling compaction area after grouting is tested by rock mass density, and after being compared with original stratum rock mass density, obtain rock mass density reduction rate, to evaluate the filling compaction degree of filling compaction area;S4, the evaluation results of S1 to S3 are combined, and the target separation layer grouting subsidence reduction effect is comprehensively evaluated.The application uses injection-production ratio, surface deformation value and rock mass density test respectively to carry out comprehensive evaluation on the effect of grouting subsidence reduction from multiple aspects.

Description

Technical Field

[0001] This invention relates to the field of coal mine overburden separation grouting and filling technology, and in particular to a comprehensive evaluation method for the settlement reduction effect of coal mine overburden separation grouting. Background Technology

[0002] The traditional evaluation method first predicts the surface deformation value without grouting, then measures the surface deformation value after grouting, and calculates the settlement reduction rate to evaluate the settlement reduction effect. (Settlement reduction rate calculation formula: r=(S1-S0) / S0, where r-settlement reduction rate, S1-measured surface deformation after grouting, S0-predicted stratum deformation value without grouting.)

[0003] However, the deformation values ​​obtained from theoretical calculations or empirical values ​​before grouting often differ from the actual deformation values. Furthermore, in order to enhance the effect of grouting in reducing settlement, the predicted surface deformation values ​​under non-grouting conditions have often been overestimated in past engineering cases.

[0004] Using measured deformation values ​​after grouting as an evaluation index is too simplistic and lacks theoretical support, making it difficult to scientifically define a reasonable deformation value as an evaluation index before grouting. Therefore, developing evaluation indicators for delamination grouting is crucial for the application of delamination grouting settlement reduction technology.

[0005] Because the abscess space is in a dynamic development state during the working face mining period, it cannot be evaluated by calculating the goaf filling rate and remaining voids, unlike the evaluation of grouting effects in goaf areas. The abscess space filling rate is dynamically changing and has no practical significance. To improve the abscess grouting and settlement reduction effect, high-pressure grouting is often used to promote the development of the abscess space. The filling grout acts as a support, "lifting" the key strata upwards and compressing the weak rock strata downwards, thereby expanding the abscess space.

[0006] This invention proposes a comprehensive evaluation method for the settlement reduction effect of delamination grouting, which uses multiple indicators to scientifically evaluate the settlement reduction effect. The settlement reduction effect of delamination grouting is comprehensively evaluated based on indicators such as injection-production ratio, surface deformation, and density reduction rate of rock mass in compacted zone. Summary of the Invention

[0007] The present invention aims to at least partially solve one of the technical problems in the related art.

[0008] To achieve the above objectives, this invention proposes a comprehensive evaluation method for the settlement reduction effect of grouting for coal mine overburden separation, comprising the following steps:

[0009] S1. The ratio of the volume of wet fly ash injected to the volume of coal extracted is taken as the injection-production ratio, and the injection-production ratio is calculated and analyzed to evaluate whether the filling of the separation space is sufficient.

[0010] S2. Calculate the measured surface deformation value and compare it with the target value of surface deformation to obtain the surface deformation difference, which is used to evaluate the grouting effect.

[0011] S3. The density of the rock mass is tested to assess the compaction degree of the grouting compaction zone after grouting. The density of the rock mass is compared with that of the original stratum rock mass to obtain the rock mass density reduction rate, which is used to evaluate the compaction degree of the grouting compaction zone.

[0012] S4. Based on the evaluation results of S1 to S3, a comprehensive evaluation of the target delamination grouting and settlement reduction effect is conducted.

[0013] This invention comprehensively evaluates the effect of grouting on reducing settlement by using injection-production ratio, surface deformation value, and rock mass density test, and obtains the most comprehensive evaluation by comprehensively evaluating the effect of grouting on reducing settlement of overburden separation from multiple aspects.

[0014] Optionally, in step S1, when using the injection-production ratio for calculation and analysis, the injection-production ratio affects the compaction zone range of the overburden grouting filling. A larger compaction zone range is more conducive to surface subsidence control. Let V1 be the volume of wet fly ash injected into the separation space, V2 be the volume of coal extracted from the working face filling area, and n be the injection-production ratio. .

[0015] Furthermore, in S1, different thresholds are set for the injection-production ratio for working faces with different mining methods:

[0016] For fully mined longwall longwall faces, the injection-production ratio threshold is set at 0.45. When the injection-production ratio is ≥0.45, it indicates that the separation space is fully filled and the filling effect is good. When the injection-production ratio is <0.45, it indicates that the separation space is not fully filled and a single index indicates that the filling effect is not ideal.

[0017] For shortwall longwall mining faces and strip mining faces that are not fully mined, the injection-production ratio threshold is set at 0.25. When the injection-production ratio is ≥0.25, it indicates that the separation space is fully filled and the filling effect is good. When the injection-production ratio is <0.25, it indicates that the separation space is not fully filled and the single index indicates that the filling effect is not ideal.

[0018] When conducting a comprehensive evaluation in step S4, if the results of this indicator combined with those of indicators S2 and S3 are both unsatisfactory, then the grouting and filling effect can be evaluated as poor.

[0019] Furthermore, in S1, V1 is equal to the sum of the volumes of fly ash after water has been released from fly ash slurries with different proportions. Affected by changes in grouting pressure and formation pressure, the compacted wet ash volume of fly ash slurries with different proportions varies under different pressures. Therefore, a standard for calculating V1 is set in a laboratory environment:

[0020] V1= ;

[0021] Where α represents the percentage of wet fly ash volume to slurry volume after water separation in fly ash slurries with different proportions under the designed grouting pressure conditions; V i The injection volume of fly ash slurry with different proportions.

[0022] Furthermore, in S2, when comparing the measured surface deformation value with the target value of surface deformation, the difference between the measured and target values ​​of surface deformation is obtained, thereby evaluating the grouting effect. Then:

[0023] ΔS=S l -S m ;

[0024] In the formula: ΔS --The difference between the measured value and the target value of surface deformation;

[0025] S m --Target value for surface deformation due to delamination grouting, vector value, negative for downward settlement, positive for upward lift;

[0026] S l --Measured surface deformation values ​​after delamination grouting, vector values; downward settlement is negative, and upward uplift is positive.

[0027] when ΔS If the value is less than 0, it indicates that the grouting reduction target has not been achieved, and the grouting effect is considered unsatisfactory; when... ΔS ≥0, and satisfy S l If the result is ≤10mm, it indicates that the grouting and sedimentation reduction target has been achieved, and the grouting effect is considered to be relatively ideal.

[0028] Furthermore, the target value of the surface deformation amount of the delamination grouting S m The calculation process includes the following steps:

[0029] S21. Establish a probabilistic integral mathematical model based on the equivalent coal mining height, and calculate the theoretical target value of surface deformation after delamination grouting under the designed filling volume. S m1 ;

[0030] S22. Based on the measured surface deformation of similar previous delamination grouting and settlement reduction projects. S m2 As a reference value for the target value of surface deformation;

[0031] S23. To meet the needs of engineering construction, data on the allowable surface deformation corresponding to different damage levels for different building structures were reviewed, and target values ​​for the allowable surface deformation corresponding to acceptable damage levels were formulated accordingly. S m3 ;

[0032] S24, to S m1 、S m2 、S m3 A comprehensive analysis is conducted to determine the most suitable approach for the specific project. S m .

[0033] Furthermore, calculations are performed in S21. S m1 The filling volume of the infill material is designed based on the coal mining height. After the filling volume design is completed, the equivalent coal mining height is calculated. Finally, the surface subsidence is calculated using the equivalent coal mining height. S m1 Perform the calculation.

[0034] Furthermore, when calculating the design filling rate α, the design filling rate α = design compacted volume of filling body / coal mining volume. The compacted volume of filling body under pressure for different slurry ratios can be obtained from laboratory tests.

[0035] Furthermore, in S3, the grouting-filled boreholes that have completed grouting are reopened or new inspection boreholes are constructed. Through in-hole sonic logging, the rock mass density of the strata below the delamination filling location is tested, with a focus on the fracture zone and caving zone. The density reduction rate is calculated compared to the original strata rock mass density before mining.

[0036] ;

[0037] In the formula, ε -- rock mass density reduction rate; --Rock mass density after delamination grouting; --Density of the original strata and rock mass;

[0038] Evaluation method: When ε > 0, the grouting settlement reduction effect is considered good; when -0.1 < ε < 0, the grouting settlement reduction effect is considered qualified; when ε < -0.1, the grouting settlement reduction effect is considered unqualified and supplementary grouting is required.

[0039] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0040] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0041] Figure 1 This is a schematic diagram illustrating the overall steps of a comprehensive evaluation method for the sediment reduction effect of grouting for coal mine overburden separation according to the present invention;

[0042] Figure 2 This is a detailed schematic diagram illustrating the steps for obtaining the difference in surface deformation using a comprehensive evaluation method for the settlement reduction effect of grouting for coal mine overburden separation according to the present invention.

[0043] Figure 3 This is a chart of surface deformation values ​​corresponding to different damage levels of brick-concrete structures in step S23 of a comprehensive evaluation method for the settlement reduction effect of grouting for coal mine overburden separation according to the present invention.

[0044] Figure 4 This is a schematic diagram of overburden separation grouting according to a comprehensive evaluation method for the sediment reduction effect of coal mine overburden separation grouting based on the present invention. Detailed Implementation

[0045] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0046] This application provides a comprehensive evaluation method for the settlement reduction effect of grouting for coal mine overburden separation, including the following steps:

[0047] S1. The ratio of the volume of wet fly ash injected to the volume of coal extracted is taken as the injection-production ratio, and the injection-production ratio is calculated and analyzed to evaluate whether the filling of the separation space is sufficient.

[0048] S2. Calculate the measured surface deformation value and compare it with the target value of surface deformation to obtain the surface deformation difference, which is used to evaluate the grouting effect.

[0049] S3. The density of the rock mass is tested to assess the compaction degree of the grouting compaction zone after grouting. The density of the rock mass is compared with that of the original stratum rock mass to obtain the rock mass density reduction rate, which is used to evaluate the compaction degree of the grouting compaction zone.

[0050] S4. Based on the evaluation results of S1 to S3, a comprehensive evaluation of the target delamination grouting and settlement reduction effect is conducted.

[0051] This invention comprehensively evaluates the effect of grouting on reducing settlement by using injection-production ratio, surface deformation value, and rock mass density test, and obtains the most comprehensive evaluation by comprehensively evaluating the effect of grouting on reducing settlement of overburden separation from multiple aspects.

[0052] The delamination space develops dynamically. Based on the developmental patterns of delamination spaces, the fundamental purpose of grouting is to maximize the amount of grout injected, injecting more fly ash to fundamentally eliminate the delamination space, inhibit the upward transmission of overburden movement, and control surface deformation. Grouting only changes surface movement parameters, not the shape of the settlement curve. The most important parameter determining the settlement reduction effect of grouting is the settlement coefficient, which depends on the amount of grout injected. Therefore, the amount of fly ash injected can be used as an evaluation factor for the delamination grouting effect. In this embodiment, the injection-to-production ratio is the ratio of the volume of wet fly ash injected to the volume of coal extracted. In other embodiments, the injection-to-production ratio is the ratio of the weight of dry fly ash injected to the weight of coal extracted.

[0053] In S1, the injection-production ratio affects the compaction zone range of the overburden grouting filling; obviously, a larger compaction zone range is more beneficial to surface subsidence control. From the perspective of improving the injection-production ratio to ensure the surface subsidence control effect, this invention, during the grouting filling process, uses the injection-production ratio to evaluate the subsidence reduction effect of overburden separation grouting. Let V1 be the volume of wet fly ash injected into the separation space, V2 be the volume of coal extracted from the filling area of ​​the working face, and n be the injection-production ratio. ;

[0054] For working faces using different mining methods, different thresholds are set for the injection-production ratio. In under-mined working faces, the separation space is insufficiently developed, resulting in a generally smaller grouting volume. In fully mined working faces, the overlying strata undergo greater movement and deformation, leading to a more developed separation space and generally a larger grouting volume. Based on extensive engineering experience, the following threshold standards are derived:

[0055] For fully mined longwall longwall faces, the injection-production ratio threshold is set at 0.45. When the injection-production ratio is ≥0.45, it indicates that the separation space is fully filled and the filling effect is good. When the injection-production ratio is <0.45, it indicates that the separation space is not fully filled and a single index indicates that the filling effect is not ideal.

[0056] For shortwall longwall mining faces and strip mining faces that are not fully mined, the injection-production ratio threshold is set at 0.25. When the injection-production ratio is ≥0.25, it indicates that the separation space is fully filled and the filling effect is good. When the injection-production ratio is <0.25, it indicates that the separation space is not fully filled and the single index indicates that the filling effect is not ideal.

[0057] When conducting a comprehensive evaluation in step S4, if the results of this indicator combined with those of indicators S2 and S3 are both unsatisfactory, then the grouting and filling effect can be evaluated as poor.

[0058] The volume of wet fly ash injected into the delamination space, V1, is equal to the sum of the volumes of fly ash after water has been released from fly ash slurries with different proportions. Affected by changes in grouting pressure and formation pressure, the compacted wet ash volume of fly ash slurries with different proportions varies under different pressures. Therefore, a calculation standard for V1 is established. To facilitate the measurement of the wet fly ash volume V1, in a laboratory environment:

[0059] V1= ;

[0060] Where α represents the percentage of wet fly ash volume to slurry volume after water separation in fly ash slurries with different proportions under the designed grouting pressure conditions; V i The injection volume of fly ash slurry with different proportions.

[0061] The injection-production ratio concept in this application differs from the traditional concept. Traditional injection-production ratios have problems: the volume of compacted wet ash is affected by pressure, but the actual stress on the filling material within the delamination space is difficult to determine due to the pressure from the grouting at the borehole, the pressure of the liquid column inside the borehole, and the formation pressure. This makes it difficult to calculate the volume of the compacted wet ash formed within the delamination. Traditional methods for calculating the volume of wet lime rely on simple estimations of the compacted fly ash density based on past experience, combined with the weight of injected dry fly ash, to calculate the volume of the wet ash. However, this method of back-calculating from empirical values ​​is relatively crude, resulting in low accuracy of the injection-production ratio calculation. The injection-production ratio in this application is defined as the ratio of the sum of the volumes of compacted wet ash with different proportions tested in the laboratory to the corresponding volume of coal space extracted from the mine. Currently, the most commonly used evaluation index for delamination grouting effectiveness is the settling reduction rate. The following analysis of the relationship between the injection-production ratio and the settling reduction rate in this application demonstrates the effectiveness of using the injection-production ratio to evaluate the settling reduction effect.

[0062] In the concept of settlement reduction rate, the ratio of the reduction in maximum surface subsidence during grouting to the maximum surface subsidence without grouting is called the settlement reduction rate. The settlement reduction rate can also be defined using subsidence volume and subsidence coefficient, that is:

[0063] r=ΔV / V 0; ΔV=V 0 -V g ; r=Δq / q 0; Δq=q 0 -q g ;

[0064] In the formula, r --Sinking reduction rate; V 0 -- Surface subsidence volume without grouting, m 3 ; V g--The volume of surface subsidence during grouting for settlement reduction, in m³ 3 ; ΔV -- Grouting reduction volume, m 3 ; q 0 -- Settlement coefficient without grouting; q g --Settlement coefficient during grouting for settlement reduction; Δq - The reduction in the settling coefficient during grouting.

[0065] Settlement reduction rate can be divided into two categories: stage settlement reduction rate and final settlement reduction rate. Stage settlement reduction rate refers to the settlement reduction rate of the surface after grouting under conditions of insufficient surface mining; final settlement reduction rate refers to the settlement reduction rate after grouting under conditions of full surface mining.

[0066] The reduction volume coefficient and the collapse volume coefficient are introduced. The reduction volume coefficient refers to the ratio of the surface reduction volume to the compacted ash volume in the delamination layer during grouting reduction, while the collapse volume coefficient refers to the ratio of the surface subsidence volume to the corresponding underground extracted space volume under non-grouting conditions.

[0067] The formula for calculating the volumetric efficiency of sediment reduction is: f = ΔV / V a ,in, f --Sinking volume coefficient, ΔV -- Grouting reduction volume, m 3 ; V a - Compacted coal ash volume, m 3 Furthermore, it can be deduced from the formula for calculating the sediment reduction volume factor: ΔV = φ V a .

[0068] The formula for calculating the collapse volume factor is: K s = V 0 / V e ,in, K s -- Collapse volume coefficient; V 0 -- Surface subsidence volume without grouting, m 3 ; V e --Volume of the space where coal is extracted, m 3 Furthermore, it can be deduced from the formula for calculating the collapse volume coefficient: V 0= K s ·V e .

[0069] Will ΔV = φ Va as well as V 0= K s ·V e Substitute into the sedimentation rate formula r=ΔV / V 0, we can get:

[0070] r = ΔV / V 0= ( φ V a ) / ( K s ·V e );

[0071] Wherein, according to the injection-production ratio concept of this application, the injection-production ratio n = V a / V e That is, we have: r = f·n / K s .

[0072] The above formula shows that the subsidence reduction rate is directly proportional to the injection-production ratio, and its proportionality coefficient depends on the subsidence reduction coefficient and the collapse coefficient. This is an important calculation formula in the grouting subsidence reduction theory. In the formula for calculating the grouting subsidence reduction rate from the injection-production ratio, the injection-production ratio is calculated from the grouting volume and the volume of the mined coal body, which is relatively easy to determine. From the above analysis, it can be seen that to improve the subsidence reduction rate, that is, to control surface subsidence to the greatest extent, it is necessary to increase the injection-production ratio and the subsidence volume coefficient, that is, to increase the amount of grouting (ash).

[0073] In step S2, when comparing the measured surface deformation value with the target value of surface deformation, the difference between the measured and target values ​​of surface deformation is obtained, thereby evaluating the grouting effect.

[0074] ΔS=S l -S m ;

[0075] In the formula: ΔS --The difference between the measured value and the target value of surface deformation;

[0076] S m --Target value for surface deformation due to delamination grouting, vector value, negative for downward settlement, positive for upward lift;

[0077] S l --Measured surface deformation values ​​after delamination grouting, vector values; downward settlement is negative, and upward uplift is positive.

[0078] when ΔS If the value is less than 0, it indicates that the grouting reduction target has not been achieved, and the grouting effect is considered unsatisfactory; when... ΔS ≥0, and satisfy S l If the result is ≤10mm, it indicates that the grouting and sedimentation reduction target has been achieved, and the grouting effect is considered to be relatively ideal.

[0079] Furthermore, in cases of delamination grouting, improper selection of grouting pressure often leads to surface uplift. Surface heave can easily cause surface cracks, resulting in secondary damage to surface structures and increasing the risk of grout leakage accidents. Therefore, when evaluating the effectiveness of delamination grouting, surface uplift should be avoided as much as possible. S l If the measured surface deformation is greater than 0, and the positive difference between the measured surface deformation and the target value is large, it should also be judged as poor grouting effect, or even unqualified.

[0080] However, scientifically and rationally determining the target value for surface deformation presents significant technical challenges. In past engineering projects, this target value was often set based on project needs or the allowable deformation of surface structures. This resulted in some projects setting a target of 10cm while others set it at 100cm, leading to vastly different allowable deformations, even when using the same or similar delamination grouting techniques. Some projects were even deemed "failures" because the delamination grouting failed to meet the predetermined targets due to unreasonable target setting. Therefore, the setting of target values ​​for surface deformation in traditional engineering cases often lacked scientific basis and was not calculated based on the delamination grouting technology used. This invention comprehensively determines the target value for surface deformation after delamination grouting based on theoretical calculations, engineering analogies, and the needs of engineering construction.

[0081] The target value of surface deformation during delamination grouting S m The calculation process includes the following steps:

[0082] S21. Establish a probabilistic integral mathematical model based on the equivalent coal mining height, and calculate the theoretical target value of surface deformation after delamination grouting under the designed filling volume. S m1 ;

[0083] S22. Based on the measured surface deformation of similar previous delamination grouting and settlement reduction projects. S m2 As a reference value for the target value of surface deformation;

[0084] S23. To meet the needs of engineering construction, data on the allowable surface deformation corresponding to different damage levels for different building structures were reviewed, and target values ​​for the allowable surface deformation corresponding to acceptable damage levels were formulated accordingly. Sm3 ;

[0085] S24, to S m1 、S m2 、S m3 A comprehensive analysis is conducted to determine the most suitable approach for the specific project. S m .

[0086] In S21, calculation S m1 The filling volume of the infill material is designed based on the coal mining height. After the filling volume design is completed, the equivalent coal mining height is calculated. Finally, the surface subsidence is calculated using the equivalent coal mining height. S m1 The calculations were performed using the calculation methods and formulas for the movement and deformation of the goaf recommended in Appendix H of GB51044.

[0087] The equivalent mining height can be understood as the actual mining height of the working face minus the height of the compacted backfill, i.e., the final settlement of the roof after backfilling and compaction. It is inversely proportional to the design filling rate, and the calculation formula is as follows:

[0088] ;

[0089] In the formula, --Equivalent coal mining height; --Actual coal mining height; —Designed filling rate.

[0090] And in calculating the design fill rate At that time, design fill rate =Designed compacted backfill volume / coal mining volume. The compacted backfill volume of different slurry ratios under pressure can be obtained from laboratory tests.

[0091] In S22, based on the measured surface deformation of similar previous delamination grouting settlement reduction projects... S m2 As a reference value for the target value of surface deformation, similar projects refer to those with similar engineering geological conditions, similar mining methods, and consistent grouting technology.

[0092] In S23, the purpose of delamination grouting for settlement reduction is to decrease surface deformation and protect surface structures within the mining impact area. Therefore, meeting the needs of engineering construction is the primary consideration in setting the target value for surface deformation. However, surface structures of different structural forms have different sensitivities to surface deformation. Even for the same building, the allowable surface deformation varies depending on the damage level. Referring to Table 3, the surface deformation values ​​corresponding to different damage levels for brick-concrete structures should be consulted. For different structures, the allowable surface deformation corresponding to the acceptable damage level should be specifically determined. S m3 .

[0093] Reference Figure 4 Based on the mechanism of overburden grouting for settlement reduction, the overburden grouting filling technology utilizes high-pressure grouting to form a filling and compaction zone in the middle of the working face. This zone, together with the isolation coal pillars deployed underground, supports the overlying strata. Simultaneously, it leverages the bearing characteristics of the key strata to support the strata above them, ultimately forming a "coal pillar – filling and compaction zone – key strata" bearing structure. This inhibits the transmission of overburden movement and deformation to the surface, reduces surface deformation, and protects surface structures from mining damage. Therefore, the ability to form a stable and reliable filling and compaction zone to bear the weight of the overlying strata on the working face is a crucial factor affecting the settlement reduction effect of overburden grouting; and the degree of compaction of the filling and compaction zone can be determined by testing the rock density of the compacted zone.

[0094] In step S3, the grouting-filled borehole that has been completed is reopened or a new inspection borehole is constructed. Using in-hole sonic logging, the rock mass density of the strata below the delamination filling location is tested, with a focus on the fracture zone and caving zone. The density reduction rate is calculated compared to the original rock mass density before mining.

[0095] ;

[0096] In the formula, ε -- rock mass density reduction rate; --Rock mass density after delamination grouting; --Density of the original strata and rock mass;

[0097] Evaluation method: When ε > 0, the grouting settlement reduction effect is considered good; when -0.1 < ε < 0, the grouting settlement reduction effect is considered qualified; when ε < -0.1, the grouting settlement reduction effect is considered unqualified and supplementary grouting is required.

[0098] The evaluation is based on the following: the degree of density reduction in the rock mass within the water-conducting fracture zone determines whether the filled and compacted zone can form a stable load-bearing structure. To form a stable load-bearing structure and transfer the load of the overlying strata to the goaf floor and coal pillars, the density reduction rate of the filled and compacted zone should not exceed 10%. This 10% density reduction threshold is based on the requirement in GB51180 that the void filling rate in goaf reduction grouting projects should not be less than 90%. If the rock mass density still decreases by 10% after grouting, it indicates that there are still many mining-induced fractures in the overlying strata of the compacted zone, making it impossible to form a stable load-bearing structure.

[0099] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0100] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0101] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A comprehensive evaluation method for the settlement reduction effect of grouting for coal mine overburden separation, characterized in that, Includes the following steps: S1. The ratio of the volume of wet fly ash injected to the volume of coal extracted is taken as the injection-production ratio, and the injection-production ratio is calculated and analyzed to evaluate whether the filling of the separation space is sufficient. S2. Calculate the measured surface deformation value and compare it with the target value of surface deformation to obtain the surface deformation difference, which is used to evaluate the grouting effect. S3. The density of the rock mass is tested to assess the compaction degree of the grouting compaction zone after grouting. The density of the rock mass is compared with that of the original stratum rock mass to obtain the rock mass density reduction rate, which is used to evaluate the compaction degree of the grouting compaction zone. S4. Based on the evaluation results of S1 to S3, a comprehensive evaluation of the target delamination grouting settlement reduction effect is conducted. In S1, different thresholds are set for the injection-production ratio for working faces with different mining methods: For fully mined longwall longwall faces, the injection-production ratio threshold is set at 0.

45. When the injection-production ratio is ≥0.45, it indicates that the separation space is fully filled and the filling effect is good. When the injection-production ratio is <0.45, it indicates that the separation space is not fully filled and a single index indicates that the filling effect is not ideal. For shortwall longwall mining faces and strip mining faces that are not fully mined, the injection-production ratio threshold is set at 0.

25. When the injection-production ratio is ≥0.25, it indicates that the separation space is fully filled and the filling effect is good. When the injection-production ratio is <0.25, it indicates that the separation space is not fully filled and the single index indicates that the filling effect is not ideal. When conducting a comprehensive evaluation in step S4, the evaluation results of the index on whether the delamination space is adequately filled, combined with the results of the two indexes S2 and S3, are all unsatisfactory, indicating that the grouting filling effect of this grouting is poor. In S2, when comparing the measured surface deformation value with the target surface deformation value, the difference between the measured and target surface deformation values ​​is obtained, thereby evaluating the grouting effect. Therefore: ΔS=S l -S m ； In the formula: ΔS --The difference between the measured value and the target value of surface deformation; S m --Target value for surface deformation due to delamination grouting, vector value, negative for downward settlement, positive for upward lift; S l --Measured surface deformation values ​​after delamination grouting, vector values; downward settlement is negative, and upward uplift is positive. when ΔS If the value is less than 0, it indicates that the grouting reduction target has not been achieved, and the grouting effect is considered unsatisfactory; when... ΔS ≥0, and satisfy S l If the grouting thickness is ≤10mm, it indicates that the grouting reduction target has been achieved, and the grouting effect is considered to be relatively ideal. In S3, the grouting-filled boreholes that have finished grouting are reopened or new inspection boreholes are constructed. Through in-hole sonic logging, the rock strata below the delamination filling location are tested, with a focus on the rock mass density of fracture zones and caving zones. The rock mass density reduction rate is calculated compared to the original rock mass density before mining. ； In the formula, ε -- rock mass density reduction rate; --Rock mass density after delamination grouting; --Density of the original strata and rock mass; Evaluation method: When ε > 0, the grouting settlement reduction effect is considered good; when -0.1 < ε < 0, the grouting settlement reduction effect is considered qualified; when ε < -0.1, the grouting settlement reduction effect is considered unqualified and supplementary grouting is required.

2. The comprehensive evaluation method for the settlement reduction effect of grouting for coal mine overburden separation as described in claim 1, characterized in that, In S1, when using the injection-production ratio for calculation and analysis, the injection-production ratio affects the compaction zone range of the overburden grouting filling. A larger compaction zone range is more conducive to surface subsidence control. Let V1 be the volume of wet fly ash injected into the separation space, V2 be the volume of coal extracted from the working face filling area, and n be the injection-production ratio. .

3. The comprehensive evaluation method for the settlement reduction effect of grouting for coal mine overburden separation as described in claim 2, characterized in that, In S1, V1 equals the sum of the volumes of fly ash after water has been released from fly ash slurries with different proportions. Affected by changes in grouting pressure and formation pressure, the compacted wet ash volume of fly ash slurries with different proportions varies under different pressures. Therefore, a standard for calculating V1 is set in a laboratory environment: ； Where α represents the percentage of wet fly ash volume to slurry volume after water separation in fly ash slurries with different proportions under the designed grouting pressure conditions; V i The injection volume of fly ash slurry with different proportions.

4. The comprehensive evaluation method for the settlement reduction effect of grouting for coal mine overburden separation as described in claim 1, characterized in that, The target value of surface deformation due to delamination grouting S m The calculation process includes the following steps: S21. Establish a probabilistic integral mathematical model based on the equivalent coal mining height, and calculate the theoretical target value of surface deformation after delamination grouting under the designed filling volume. S m1 ; S22. Based on the measured surface deformation of similar previous delamination grouting and settlement reduction projects. S m2 As a reference value for the target value of surface deformation; S23. To meet the needs of engineering construction, data on the allowable surface deformation corresponding to different damage levels for different building structures will be reviewed, and target values ​​for the allowable surface deformation corresponding to acceptable damage levels will be formulated accordingly. S m3 ; S24, to S m1 、S m2 、S m3 A comprehensive analysis is conducted to determine the most suitable approach for the specific project. S m .

5. The comprehensive evaluation method for the settlement reduction effect of grouting for coal mine overburden separation as described in claim 4, characterized in that, Calculation in S21 S m1 The filling volume of the infill material is designed based on the coal mining height. After the filling volume design is completed, the equivalent coal mining height is calculated. Finally, the surface subsidence is calculated using the equivalent coal mining height. S m1 Perform the calculation.

6. The comprehensive evaluation method for the settlement reduction effect of grouting for coal mine overburden separation as described in claim 5, characterized in that, The equivalent mining height can be understood as the actual mining height of the working face minus the height of the compacted backfill, i.e., the final settlement of the roof after backfilling and compaction. It is inversely proportional to the design filling rate, and the calculation formula is as follows: ； In the formula, --Equivalent coal mining height; --Actual coal mining height; —Designed filling rate; Among them, the design fill rate is calculated. At that time, design fill rate =Designed compacted backfill volume / coal mining volume. The compacted backfill volume of different slurry ratios under pressure was obtained from laboratory tests.

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