Engineering geology rock mass quality grade evaluation method considering roof water disaster risk

Abstract

The invention relates to an engineering geological rock mass quality grade evaluation method considering roof water disaster danger. Taking the water-bearing stratum water yield evaluation index A, the near-field immediate roof stratum disintegration index B, the water-resisting stratum water-resisting evaluation index C, the structure danger evaluation index D, the working face mining stability evaluation index E and the water-bearing stratum structure evolution evaluation index F as engineering geological rock mass quality grade evaluation indexes; on the basis of the mining overlying strata separation layer water disaster key indexes, working face mining overlying strata roof water disaster risk grades are divided, and a mining overlying strata roof water disaster risk evaluation index G is obtained; and based on the obtained index value A, index value B, index value C, index value D, index value E, index value F and index value G, calculating a comprehensive index value I of the working face engineering geological rock mass quality, and according to a set grade evaluation rule, obtaining an evaluation result of the engineering geological rock mass quality grade. According to the method, the roof water disaster risk can be evaluated more accurately.

Description

Technical Field

[0001] The present application belongs to the technical field of mine water hazard prevention and control, and specifically relates to an engineering geological rock mass quality grade evaluation method taking into account the risk of roof water hazard. Background Art

[0002] In the process of coal mining in my country, roof water damage is one of the main problems that pose a serious threat to mine safety. However, the currently widely used rock mass quality grade evaluation methods, such as geological strength index (GSI), rock mass quality index (RMR) and rock mass classification (Q value), are mainly aimed at the original geological conditions and focus on the evaluation of slopes, tunnels and other projects. These traditional methods mainly evaluate the stability of rock mass in its natural state, ignoring the changes in rock mass structure and mechanical properties during coal mining, as well as complex hydrogeological conditions. Especially in coal mining, the roof rock mass is affected by multiple factors such as engineering disturbance, overburden characteristics and groundwater seepage, and its stability and quality are significantly different from those of slope and tunnel projects.

[0003] For coal mines, it is crucial to scientifically evaluate the quality grade of the roof rock mass. However, there are relatively few rock mass quality grade evaluation methods for surrounding rocks in the coal mining field. Although some rock mass quality grade evaluation methods have been proposed in terms of roof support, rock burst, floor drum and floor water damage, these existing methods are not suitable for the rock mass quality grade evaluation of roof water damage. Directly applying the above methods to the rock mass quality grade evaluation of roof water damage will directly lead to greater blindness and uncertainty in the process of working face water damage control.

[0004] Therefore, how to accurately assess the danger level of roof water inrush from the perspective of rock mass quality grade evaluation, so as to formulate and implement effective control measures to ensure safe production in coal mines, is a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of the above analysis, an embodiment of the present invention aims to provide a method for evaluating the quality grade of engineering geological rock mass taking into account the risk of roof water damage, so as to solve the above technical problems existing in the prior art.

[0006] The object of the present invention is achieved in that:

[0007] A method for evaluating the quality grade of engineering geological rock mass considering the risk of roof water damage comprises the following steps:

[0008] S1. Survey the engineering geology and hydrogeology of coal mines and obtain basic data and information;

[0009] S2. The water-richness evaluation index A of the aquifer, the disintegration index B of the near-field direct top rock layer, the water-proofness evaluation index C of the aquiclude, the structural hazard evaluation index D, the working face mining stability evaluation index E, and the aquifer structural evolution evaluation index F are used as the engineering geological rock mass quality grade evaluation indexes, and the index values ​​A, B, C, D, E, and F are calculated;

[0010] S3. Based on the key indicators of overburden stratum water hazard caused by mining, the risk level of overburden stratum water hazard caused by mining is divided; according to the type of water inrush at the working face and the comprehensive level of water hazard caused by stratum water hazard caused by mining, the risk evaluation index G of overburden stratum water hazard caused by mining is obtained, and the index value G is obtained according to the set scoring rules;

[0011] S4. Based on the obtained index value A, index value B, index value C, index value D, index value E, index value F, and index value G, calculate the comprehensive index value I of the engineering geological rock mass quality of the working face, and according to the set grade evaluation rules, obtain the evaluation result of the engineering geological rock mass quality grade of the roof water hazard.

[0012] Furthermore, based on the thickness, permeability, unit water yield, water pressure and mudstone proportion of the aquifer, the index value A is calculated according to the following formula:

[0013]

[0014] In the above formula, T1 is the standardized aquifer thickness; T2 is the standardized permeability coefficient of the Cretaceous aquifer; T3 is the standardized unit water yield of the target formation; T4 is the standardized water pressure; T5 is the standardized mudstone proportion of the aquifer.

[0015] Further, the preliminary calculation result value B' of the near-field direct top rock layer disintegration index B is scored according to a scoring rule to obtain the index value B;

[0016] The preliminary calculation result value B' is obtained by calculating according to the following formula:

[0017]

[0018] In the above formula, is the cumulative thickness of the mudstone layer, m; is the proportion of mudstone on the immediate roof; Ω is the average collapse coefficient of the immediate roof rock layer, φ is the average porosity of the immediate roof rock layer; ∑α i is the distance between the direct roof interface and the coal seam roof, m; σ and τ are the average uniaxial compressive strength and average shear strength of the direct roof rock stratum, MPa, respectively.

[0019] Further, the index value C is determined based on the preliminary calculation result C' of the water-proof property evaluation index C of the water-proof layer and the scoring rule three;

[0020] The preliminary calculation result C' is calculated according to the following formula:

[0021] C' = C1 × C2;

[0022] Among them, the waterproof layer water-proofing evaluation value C1 and the water-proofing evaluation value C2 are obtained according to the set scoring rule two.

[0023] Furthermore, the index value D is calculated according to the following formula:

[0024] D = D1 + D2;

[0025] Among them, the fault evaluation value D1 and the fold evaluation value D2 are obtained according to the set scoring rule four.

[0026] Furthermore, the index value E is calculated according to the following formula:

[0027] E = E1 + E2;

[0028] Among them, according to the set scoring rule five, the working face inclination evaluation value E1 and the overburden rheological degradation degree evaluation value E2 are obtained.

[0029] Furthermore, the index value F is calculated according to the following formula:

[0030] F = F1 + F2;

[0031] Among them, according to the set scoring rule six, the evaluation value F1 of the aquifer structure stability and the evaluation value F2 of the risk of abscission inside the aquifer are obtained.

[0032] Further, step S3 includes:

[0033] S31. Determine the type of water damage in the coal mine working face and identify the working face with the risk of delamination water damage;

[0034] S32, determining the abscission layer water source evaluation index S, the abscission layer water channel evaluation index P, and the abscission layer water power source evaluation index T as key indicators of the abscission layer water hazard caused by mining, and calculating the values ​​of each key indicator;

[0035] S33. Based on the key indicator values ​​of overburden stratum water hazards caused by mining, the comprehensive risk level of overburden stratum water hazards caused by mining is divided.

[0036] Furthermore, the water source evaluation index S of the abscission layer water hazard is calculated according to the following formula:

[0037]

[0038] In the above formula, Λ is the mining height, m; K pis the expansion coefficient of the rock formation in the collapse zone, T1 is the thickness of the immediate top, m; L is the width of the working face, m; w is the surface subsidence, m; T1 is the standardized aquifer thickness; T2 is the standardized permeability coefficient of the Cretaceous aquifer; T3 is the standardized unit water yield of the target formation; T4 is the standardized water pressure of the aquifer; T5 is the standardized mudstone proportion of the aquifer;

[0039] The evaluation index P of the delamination water hazard channel is calculated according to the following formula:

[0040]

[0041] In the above formula, Γ is the average buried depth of the coal seam mined by the working face, m; H1 is the distance from the bottom of the aquifer to the top of the coal seam, m; V is the advancement speed of the working face (m / d); n is the proportion of overburden sandstone lithology within the range from the bottom of the aquifer to the top of the coal seam; χ1 is the distance from the bottom of the aquifer to the top of the coal seam, m; ζ1 is the thickness of the aquifer, m;

[0042] Calculate the evaluation index T of the power source of delamination water damage according to the following formula:

[0043]

[0044] In the above formula, χ2 is the distance from the bottom of the aquifer to the top of the coal seam, m; ζ2 is the thickness of the aquifer, m.

[0045] Further, step S4 includes:

[0046] S41, based on the obtained index value A, index value B, index value C, index value D, index value E, index value F, index value G, calculate the comprehensive index value I of the engineering geological rock mass quality of the working face according to the following formula;

[0047]

[0048] S42. Based on the obtained comprehensive index I and in accordance with the set grade evaluation rules, an evaluation result of the engineering geological rock mass quality grade of the roof water hazard is obtained.

[0049] Compared with the prior art, the engineering geological rock mass quality grade evaluation method taking into account the roof water hazard risk provided by the present invention comprehensively considers the hydrogeological characteristics of the aquifer (impermeable) layer, the dynamic changes of the rock mass structure and the stability of the rock layer during coal mining, the engineering mining disturbance, the roof water inrush type and the disaster-causing mechanism, and constructs a rock mass quality grade evaluation system with multi-factor analysis. Specifically, the aquifer water-richness evaluation index A, the near-field direct top rock layer disintegration index B, the impermeable layer water-impermeability evaluation index C, the structural hazard evaluation index D, the working face mining stability evaluation index E, the aquifer structure evolution evaluation index F and the mining-induced overburden roof water hazard risk evaluation index G are used as engineering geological rock mass quality grade evaluation indicators, so that the roof water hazard risk can be evaluated more accurately, providing scientific guidance and decision-making support for the safe production of coal mines. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of this specification. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0051] Figure 1 It is a schematic diagram of the mining-induced overburden stratum separation structure;

[0052] Figure 2 A flow chart for determining the comprehensive level of water hazard risk of overburden separation caused by mining provided in an embodiment of the present invention;

[0053] Figure 3 The present invention provides an operational flow chart of the engineering geological rock mass quality grade evaluation method considering the roof water hazard risk. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. It should be noted that, in the absence of conflict, the embodiments in the present disclosure and the features in the embodiments can be combined, separated, interchanged and / or rearranged with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0055] In the accompanying drawings, the size and relative size of components may be exaggerated for clarity and / or descriptive purposes. When the exemplary embodiments may be implemented differently, the specific process sequence may be performed in a different order than described. For example, two consecutively described steps may be performed substantially simultaneously or in an order opposite to the order described.

[0056] The terms used here are for the purpose of describing specific embodiments, and are not intended to be restrictive. As used here, unless the context clearly indicates otherwise, the singular forms "one (kind, person)" and "said (the)" are also intended to include plural forms. In addition, when the terms "comprise" and / or "include" and their variations are used in this specification, it is explained that there are stated features, integral bodies, steps, operations, parts, assemblies and / or their groups, but it is not excluded that there are or add one or more other features, integral bodies, steps, operations, parts, assemblies and / or their groups. It should also be noted that, as used here, the terms "substantially", "approximately" and other similar terms are used as approximate terms and not as degree terms, so that they are used to explain the inherent deviations of the measured values, calculated values ​​and / or the values ​​provided that will be recognized by those of ordinary skill in the art.

[0057] Example 1

[0058] A specific embodiment of the present invention discloses a method for evaluating the quality grade of engineering geological rock mass considering the risk of roof water damage. The operation process is as follows: Figure 3 As shown, the evaluation method comprises the following steps:

[0059] S1. Conduct surveys on the engineering geology and hydrogeology of coal mines to obtain basic data and information.

[0060] First, collect and study the existing geological reports, geological maps, exploration data, mining history and other information in the mining area, conduct a detailed investigation of the geological structure of the mining area, and determine the structural features such as faults, folds, and joints. Investigate the exposure of rock strata on the surface and profile of the mining area, record the rock type, bedding, degree of weathering, and rock mass fragmentation, and draw an engineering geological map of the mining area, including the distribution of strata, structural characteristics, and spatial distribution of geological phenomena. Obtain core samples through drilling and describe the core in detail, including lithology, structure, physical and mechanical properties, etc. Conduct geological surveys of the tunnels of existing mines, record the contact relationship of rock strata, the geological characteristics of the roof and floor, and the occurrence conditions of coal seams, draw geological profiles, and analyze the impact of geological conditions on mine stability and roof water damage. Collect and analyze historical water damage event records in the mining area and adjacent mining areas, and summarize the causes, occurrence patterns, and impact range of water damage.

[0061] S2. Take the water-richness evaluation index A of the aquifer, the disintegration index B of the near-field direct top rock layer, the water-impermeability evaluation index C of the aquiclude, the structural hazard evaluation index D, the working face mining stability evaluation index E, and the aquifer structure evolution evaluation index F as the engineering geological rock mass quality grade evaluation indexes, and calculate the index value A, index value B, index value C, index value D, index value E and index value F.

[0062] S21. The index value A of the water-richness evaluation index A of the aquifer is calculated based on the aquifer thickness, permeability, unit water yield, water pressure, and mudstone ratio.

[0063] Aquifer thickness (m), permeability (m / d), unit water yield (L / (s·m)), water pressure (MPa), and mudstone proportion were selected as evaluation indicators to obtain a comprehensive evaluation index of aquifer water richness. The above evaluation factors are positively correlated with the water richness of the roof aquifer, so the formation data are standardized according to the following formula:

[0064]

[0065] In the formula, x N represents the normalized value of the indicator, x is the initial value of the indicator, and x max is the maximum value of the indicator, x min is the minimum value of the indicator.

[0066] The index value A of the water-richness evaluation index A of the aquifer is calculated according to the following formula:

[0067]

[0068] Wherein, T1 is the standardized aquifer thickness; T2 is the standardized permeability coefficient of the Cretaceous aquifer; T3 is the standardized unit water yield of the target formation; T4 is the standardized water pressure; T5 is the standardized mudstone proportion of the aquifer. When the standardized T5 is ≤ 0.1, it is taken as 0.1.

[0069] S22, determining the range of the rock layer on the immediate top of the working face, and obtaining an index value B of the disintegration index B of the immediate top rock layer in the near field based on the proportion of mudstone on the immediate top;

[0070] The rock layer range of the working face is as follows: Figure 1 The proportion of mudstone in the near-field direct top rock layer and its disintegration are selected as evaluation indicators for the danger of mud, sand and water inrush from the roof. First, the range of the direct top rock layer of the working face is determined based on the following formula:

[0071] First, determine the distance from the basic roof and bottom plate of the coal mining face to the roof of the coal seam. Starting from the coal seam, determine from bottom to top whether the following relationship is met:

[0072] α i+(χ - 1)∑α i-1 ≤Λ

[0073] If it is satisfied, then this rock stratum belongs to the immediate roof. Continue to discriminate the next layer until a certain rock stratum satisfies:

[0074] α i+1 +(χ - 1)∑α i >Λ

[0075] In the formula, α i is the thickness of the i-th rock stratum, m; Λ is the mining height, m; χ is the average swelling coefficient of the caving zone rock strata, taking 1.1 - 1.15; ∑α i is the cumulative thickness of the i - 1 rock strata above the coal seam roof, m.

[0076] Then, the range from the floor of this rock stratum to the coal seam roof is regarded as the immediate roof, that is, the distance from the top interface of the immediate roof to the coal seam roof is ∑α i . Obtain the preliminary calculated result value B' of the disintegration index B of the near - field immediate roof rock stratum according to the following formula:

[0077]

[0078] In the formula, is the cumulative thickness of the mudstone layer, m; is the proportion of mudstone in the immediate roof; Ω is the average disintegration coefficient of the immediate roof rock stratum, φ is the average porosity of the immediate roof rock stratum; ∑α i is the distance from the top interface of the immediate roof to the coal seam roof, m; σ and τ are the average uniaxial compressive strength and average shear strength of the immediate roof rock stratum, MPa.

[0079] According to the scoring rule one in Table 1, score the preliminary calculated result value B' of the disintegration index B of the near - field immediate roof rock stratum to obtain the index value B.

[0080] Table 1 Scoring table for the disintegration index B of the near - field immediate roof rock stratum

[0081] Preliminary calculation result value B' 0＜B’≤0.001 0.001＜B’≤0.005 0.005＜B’≤0.01 B’>0.01 Rating index value B 1 2 3 4

[0082] S23. Obtain the water - isolation evaluation value C1 and water - isolation evaluation value C2 of the water - isolation layer according to the set scoring rule two; and based on the product of the water - isolation evaluation value C1 and the water - isolation evaluation value C2 and the set scoring rule three, obtain the index value C of the water - isolation evaluation index C of the water - isolation layer.

[0083] Referring to the scoring rule two in Table 2, assuming the mining height is Λ, determine the water - isolation evaluation value C1 based on the thickness of the water - isolation layer. Then, classify the water - isolation property according to the occurrence conditions of the water - isolation layer lithology to determine the water - isolation evaluation value C2. The numerical values a1 and a2 are constants greater than 0, determined according to the actual stratum distribution situation, with a1 < a2 and a 2-a1≤20m. For example, if a1 is 20 and a2 is 40m, the aquiclude can be divided into: complete mudstone layer, interlayers of mudstone greater than 40m and sandstone less than 20m, interlayers of mudstone 20-40m and sandstone 20-40m, and interlayers of mudstone less than 20m and sandstone greater than 40m.

[0084] Table 2 Waterproof layer water-proof evaluation index C score table

[0085]

[0086] According to the evaluation values ​​of C1 and C2 determined by the scoring rule 2 in Table 2 above, the preliminary calculation result C' of the water-insulating evaluation index C of the water-insulating layer is calculated according to the following calculation formula. Based on the size of the preliminary calculation result C', the index value C of the water-insulating evaluation index C of the water-insulating layer is determined according to the scoring rule 3 in Table 3:

[0087] C'=C1×C2

[0088] Table 3 Waterproof layer water-proof evaluation index C score table

[0089] Preliminary calculation results C' C’<8 8≤C’<24 24≤C’<40 40≤C’≤64 Scoring index value C 2 4 6 8

[0090] S24, obtaining the fault evaluation value D1 and the fold evaluation value D2 according to the set scoring rule 4, and obtaining the index value D of the structural hazard evaluation index D based on the sum of the fault evaluation value D1 and the fold evaluation value D2.

[0091] According to Table 4, each fault inside the working face is scored, and all fault scores are accumulated as the final fault evaluation value D1; each fold inside the working face is scored, and all fold scores are accumulated as the final fold evaluation value D2.

[0092] Table 4 Structural hazard assessment index D score table

[0093]

[0094] Based on the evaluation value D1 and the evaluation value D2 obtained by the scoring rule 4 in Table 4, the index value D of the structural hazard evaluation index D is calculated according to the following formula:

[0095] D=D1+D2

[0096] S25. Obtain the working face inclination evaluation value E1 and the overburden rheological degradation degree evaluation value E2 according to the set scoring rule five, and calculate the index value E of the working face mining stability evaluation index E based on the working face inclination evaluation value E1 and the overburden rheological degradation degree evaluation value E2.

[0097] According to the scoring rule 5 in Table 5, the inclination of the working face is scored. If the coal seam of the working face is undulating, the maximum inclination is taken as the evaluation value E1 of the working face inclination; the evaluation value E2 of the degree of rheological degradation of the overburden is determined based on the working face suspension time.

[0098] Table 5 Working face mining stability evaluation index E score table

[0099]

[0100] Based on the evaluation values ​​E1 and E2 obtained by the bisection rule 5 in Table 5, the index value E of the working face mining stability evaluation index E is calculated according to the following formula:

[0101] E=E1+E2

[0102] S25. According to the set scoring rule six, the aquifer structure stability evaluation value F1 and the evaluation value F2 of the risk of forming a delamination inside the aquifer are obtained, and based on the aquifer structure stability evaluation value F1 and the evaluation value F2 of the risk of forming a delamination inside the aquifer, the index value F of the aquifer structure evolution evaluation index F is calculated.

[0103] like Figure 1 As shown in Table 6, based on the thickness of the first single rock layer from bottom to top of the aquifer, the structural stability of the aquifer is classified according to the scoring rule 6 in Table 6 to determine the evaluation value F1 of the structural stability of the aquifer. Then, according to the thickness ratio of the upper rock layer to the lower rock layer of the adjacent rock layer of the aquifer (n = H i+1 / H i , H i+1 is the thickness of the aquifer layer i+1, H i is the maximum value n of the thickness of the i-th layer of the aquifer max , determine the evaluation value F2 of the risk of aquifer formation inside the aquifer. Assume that the thickness of the aquifer is H.

[0104] Table 6 Aquifer structure evolution evaluation index F score table

[0105]

[0106] Based on the evaluation values ​​F1 and F2 obtained by the bisection rule 6 in Table 6, the index value F of the aquifer structure stability evaluation index F is calculated according to the following formula:

[0107] F=F1+F2

[0108] S3. Based on the key indicators of overburden stratum water hazard caused by mining, the risk level of overburden roof water hazard caused by mining is divided; according to the type of water inrush at the working face and the comprehensive level of water hazard caused by stratum water hazard, the risk evaluation index G of overburden roof water hazard caused by mining is obtained, and the index value G is obtained according to the set scoring rule seven.

[0109] S31. Determine the type of water hazard in the coal mine working face and identify the working face at risk of delamination water hazard.

[0110] Based on the working face mining height and the distance between the aquifer floor and the coal seam roof, the risk judgment formula for separation water damage is determined:

[0111] a×Λ-b≤J <a×Λ+c

[0112] In the formula, Λ is the working face mining height, m, J is the distance between the bottom plate of the aquifer and the top plate of the coal seam, m, and the coefficients a, b, c, d are constants, which are determined by the actual engineering geological conditions and water inrush types of each working face in the mine. In general, there are at least four Λ and J values ​​of working faces that have experienced delamination water inrush, and the unknowns a, b, c are solved by linear fitting. In the absence of data, a=14.14,b=46.38;c=14.14,d=85 can be taken.

[0113] If the distance between the bottom plate of the aquifer and the top plate of the coal seam satisfies the above formula, there is a risk of delamination water damage, and the risk level of delamination water damage needs to be further determined.

[0114] S32. Determine the delamination water source evaluation index S, the delamination water channel evaluation index P, and the delamination water power source evaluation index T as key indicators of delamination water damage caused by mining, and calculate the values ​​of each key indicator.

[0115] Calculate the water source evaluation index S of the abscission layer water hazard according to the following formula:

[0116]

[0117] Where Λ is the mining height, m; K p is the expansion coefficient of the rock strata in the collapse zone, T1 is the thickness of the direct top, m; L is the width of the working face, m; w is the surface subsidence, m; T1 is the standardized aquifer thickness; T2 is the standardized permeability coefficient of the Cretaceous aquifer; T3 is the standardized unit water yield of the target stratum; T4 is the standardized water pressure of the aquifer; T5 is the standardized mudstone proportion of the aquifer.

[0118] The evaluation index P of the delamination water hazard channel is calculated according to the following formula:

[0119]

[0120] Wherein, Γ is the average buried depth of the coal seam mined by the working face, m; H1 is the distance from the bottom of the impermeable layer to the top of the coal seam, m; V is the advancing speed of the working face (m / d); n is the proportion of overlying sandstone lithology within the range from the bottom of the aquifer to the top of the coal seam; χ1 is the distance from the bottom of the impermeable layer to the top of the coal seam, m; ζ1 is the thickness of the impermeable layer, m.

[0121] Calculate the evaluation index T of the power source of delamination water damage according to the following formula:

[0122]

[0123] Where, χ2 is the distance from the bottom of the aquifer to the top of the coal seam, m; ζ2 is the thickness of the aquifer, m.

[0124] S33. Based on the key indicator values ​​of overburden stratum water hazards caused by mining, the comprehensive risk level of overburden stratum water hazards caused by mining is divided.

[0125] Calculate the water source evaluation index, channel evaluation index and power source evaluation index of all working faces in the entire mining area, standardize them according to the formula in step S21, and obtain the standardized evaluation index value. According to the standardized water source evaluation index value, channel evaluation index value and power source evaluation index value, they are graded. The grade classification rules of the three are shown in Table 7.

[0126] Table 7 Standardized classification of water source, channel and power source evaluation indicators

[0127] grade powerful middle weak Standardized evaluation indicators S, P, T 0.6<S,P,T≤1 0.3<S,P,T≤0.6 0<S,P,T≤0.3

[0128] After determining the water source, channel and power source level, follow Figure 2 The judgment process shown divides the comprehensive level of abscission water hazard risk into four categories: extremely high risk, high risk, medium risk and low risk. The judgment principle is: if the water source level is weak, the comprehensive level of abscission water hazard risk must be weak. When the water source level is strong and the channel or power source level is also strong, the comprehensive level of abscission water hazard risk must be strong.

[0129] S34. According to the type of water inrush at the working face and the comprehensive level of water hazard at the absorptive layer, obtain the risk evaluation index G of water hazard at the overburden roof caused by mining. Score the index G according to the scoring rule 7 in Table 8 to obtain the index value G.

[0130] Table 8 Score table of risk assessment index G for water damage in overburden roof caused by mining

[0131] Types of water inrush and comprehensive levels of delamination water damage G-score Non-detachment water damage 1 Delamination water damage-very high risk 8 Delamination Water Damage-High Risk 4 Delamination Water Damage-Medium Risk 2 Delamination water damage-low risk 1

[0132] S4. Based on the index values ​​A, B, C, D, E, F and G obtained in steps 2 and 3, calculate the comprehensive index value I of the engineering geological rock mass quality of the working face, and obtain the evaluation result of the engineering geological rock mass quality grade of the roof water hazard according to the set grade evaluation rules.

[0133] S41. Calculate and obtain the comprehensive index value I of the engineering geological rock mass quality of the working face.

[0134] Specifically, based on the index values ​​A, B, C, D, E, F, and G obtained in step 2 and step 3, the comprehensive index value I of the engineering geological rock mass quality of the working face is calculated according to the following formula:

[0135]

[0136] S42. Classification of engineering geological rock mass quality levels for water hazards in the roof of coal mine working faces.

[0137] Specifically, based on the comprehensive index I, according to the set grade evaluation rules in Table 9, the evaluation results of the engineering geological rock mass quality grade of the roof water hazard are obtained.

[0138] Table 9 Classification of engineering geological rock mass quality for roof water hazards

[0139] Comprehensive Index I I<200 200≤I＜400 400≤I＜600 600≤I＜800 I≥800 Rock mass quality grade excellent good middle Difference Very bad

[0140] Compared with the prior art, the engineering geological rock mass quality grade evaluation method taking into account the risk of roof water hazard provided in this embodiment constructs a rock mass quality grade evaluation system with multi-factor analysis, specifically using the aquifer water-richness evaluation index A, the near-field direct roof rock layer disintegration index B, the aquiclude water-impermeability evaluation index C, the structural hazard evaluation index D, the working face mining stability evaluation index E, the aquifer structure evolution evaluation index F and the mining-induced overburden roof water hazard risk evaluation index G as engineering geological rock mass quality grade evaluation indicators, thereby being able to more accurately assess the risk of roof water hazard and provide scientific guidance and decision-making support for the safe production of coal mines.

[0141] Actual project cases

[0142] Taking Cuimu Coal Mine in Yonglong Mining Area of ​​Ordos Basin as an example, the engineering geological rock mass quality grade evaluation method for roof water hazard in the above mining area was applied to the 22306 working face of 22 panel area of ​​Cuimu Coal Mine.

[0143] 1. Survey of coal mine engineering geology and hydrogeological conditions

[0144] Collect and study the existing geological reports, geological maps, exploration data, mining history and other information in the mining area, conduct a detailed investigation of the geological structure of the mining area, and determine the structural features such as faults, folds, and joints. Clarify the stratum distribution, structural characteristics, spatial distribution of aquifers and aquicludes in the mining area. Obtain core samples through drilling and test the physical and mechanical properties of the cores. Collect and analyze the records of historical water disasters in the mining area. Determine the comprehensive geological conditions of the 22306 working face as shown in Table 10.

[0145] Table 10 Comprehensive stratigraphic conditions of the 21 and 22 panels of Cuimu Coal Mine

[0146]

[0147] 2. Calculation of engineering geological rock mass quality grade evaluation indicators

[0148] Statistics of various indicators of 22307 working face, as shown in Table 11

[0149] Table 11 Statistics of evaluation index information of 22307 working face

[0150]

[0151] 3. Scoring and grading of comprehensive indicators of coal mine engineering geological rock mass quality

[0152] The calculation of the scores of various indicators of the 22307 working face is shown in Table 12:

[0153] Table 12 Scores of various indicators of 22307 working face

[0154] A B C D E F G I Index value 1.2 3 8 5 9 5 4 2460.6

[0155] Based on the calculation formula of the comprehensive index value I of the engineering geological rock mass quality of the working face, the comprehensive index I was calculated to be 2460.6, and the engineering geological rock mass quality grade of the roof water hazard was judged to be extremely poor. The average water inflow during the actual mining period of the 22307 working face reached 700m 3 / h, resulting in the crushing of supports and clogging of tunnels, which has a serious adverse impact on the production. This proves that the engineering geological rock mass quality grade evaluation method proposed in this patent can be effectively used in the assessment and prediction of roof water hazard risks.

[0156] The specific implementation methods described above further illustrate the purpose, technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only the specific implementation method of the present application and is not intended to limit the scope of protection of the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A method for evaluating the quality grade of engineering geological rock mass considering the risk of roof water damage, characterized in that: The steps include: S1. Survey the engineering geology and hydrogeology of coal mines and obtain basic data and information; S2. The water-richness evaluation index A of the aquifer, the disintegration index B of the near-field direct top rock layer, the water-proofness evaluation index C of the aquiclude, the structural hazard evaluation index D, the working face mining stability evaluation index E, and the aquifer structural evolution evaluation index F are used as the engineering geological rock mass quality grade evaluation indexes, and the index values ​​A, B, C, D, E, and F are calculated; S3. Based on the key indicators of overburden stratum water damage caused by mining, the risk level of overburden roof water damage caused by mining of the working face is divided; According to the type of water inrush at the working face and the comprehensive level of water damage in the abscission layer, the risk evaluation index G of water damage in the overburden roof caused by mining is obtained, and the index value G is obtained according to the set scoring rules; S4. Based on the obtained index value A, index value B, index value C, index value D, index value E, index value F, and index value G, calculate the comprehensive index value I of the engineering geological rock mass quality of the working face, and according to the set grade evaluation rules, obtain the evaluation result of the engineering geological rock mass quality grade of the roof water hazard.

2. The engineering geological rock mass quality grade evaluation method considering the roof water hazard risk according to claim 1 is characterized in that: Based on the thickness, permeability, unit water yield, water pressure and mudstone proportion of the aquifer, the index value A is calculated according to the following formula: In the above formula, T1 is the standardized aquifer thickness; T2 is the standardized permeability coefficient of the Cretaceous aquifer; T3 is the standardized unit water yield of the target formation; T4 is the standardized water pressure; T5 is the standardized mudstone proportion of the aquifer.

3. The engineering geological rock mass quality grade evaluation method considering the roof water hazard risk according to claim 1 is characterized in that: Scoring the preliminary calculated result value B' of the near-field direct top rock layer disintegration index B according to the scoring rule to obtain the index value B; The preliminary calculation result value B' is obtained by calculating according to the following formula: In the above formula, is the cumulative thickness of the mudstone layer, m; υ is the proportion of mudstone on the immediate top; Ω is the average collapse coefficient of the immediate top rock layer, φ is the average porosity of the immediate top rock layer; ∑α i is the distance between the direct roof interface and the coal seam roof, m; σ and τ are the average uniaxial compressive strength and average shear strength of the direct roof rock stratum, MPa, respectively.

4. The engineering geological rock mass quality grade evaluation method considering the roof water hazard risk according to claim 1 is characterized in that: Determine the index value C based on the preliminary calculation result C' of the water-proofing evaluation index C of the water-proofing layer and the scoring rule three; The preliminary calculation result C' is calculated according to the following formula: C' = C1 × C2; Among them, the waterproof layer water-proofing evaluation value C1 and the water-proofing evaluation value C2 are obtained according to the set scoring rule two.

5. The engineering geological rock mass quality grade evaluation method considering the roof water hazard risk according to claim 1 is characterized in that: The index value D is calculated according to the following formula: D = D1 + D2; Among them, the fault evaluation value D1 and the fold evaluation value D2 are obtained according to the set scoring rule four.

6. The engineering geological rock mass quality grade evaluation method considering roof water hazard according to claim 1 is characterized in that: The index value E is calculated according to the following formula: E = E1 + E2; Among them, according to the set scoring rule five, the working face inclination evaluation value E1 and the overburden rheological degradation degree evaluation value E2 are obtained.

7. The engineering geological rock mass quality grade evaluation method considering roof water hazard according to claim 1 is characterized in that: The index value F is calculated according to the following formula: F = F1 + F2; Among them, according to the set scoring rule six, the evaluation value F1 of the aquifer structure stability and the evaluation value F2 of the risk of abscission inside the aquifer are obtained.

8. The engineering geological rock mass quality grade evaluation method considering roof water hazard risk according to claim 1 is characterized in that: Step S3 includes: S31. Determine the type of water damage in the coal mine working face and identify the working face with the risk of delamination water damage; S32, determining the abscission layer water source evaluation index S, the abscission layer water channel evaluation index P, and the abscission layer water power source evaluation index T as key indicators of the abscission layer water hazard caused by mining, and calculating the values ​​of each key indicator; S33. Based on the key indicator values ​​of overburden stratum water hazards caused by mining, the comprehensive risk level of overburden stratum water hazards caused by mining is divided.

9. The engineering geological rock mass quality grade evaluation method considering roof water hazard risk according to claim 1 is characterized in that: Calculate the water source evaluation index S of the abscission layer water hazard according to the following formula: In the above formula, Λ is the mining height, m; K p is the expansion coefficient of rock strata in the collapse zone, T1 is the thickness of the immediate roof, m; L is the width of the working face, m; w is the surface subsidence, m; T1 is the standardized aquifer thickness; T2 is the standardized permeability coefficient of the Cretaceous aquifer; T3 is the standardized unit water yield of the target formation; T4 is the standardized water pressure of the aquifer; T5 is the standardized mudstone proportion of the aquifer; The evaluation index P of the delamination water hazard channel is calculated according to the following formula: In the above formula, Γ is the average buried depth of the coal seam mined by the working face, m; H1 is the distance from the bottom of the aquifer to the top of the coal seam, m; V is the advancement speed of the working face (m / d); n is the proportion of overburden sandstone lithology within the range from the bottom of the aquifer to the top of the coal seam; χ1 is the distance from the bottom of the aquifer to the top of the coal seam, m; ζ1 is the thickness of the aquifer, m; Calculate the evaluation index T of the power source of delamination water damage according to the following formula: In the above formula, χ2 is the distance from the bottom of the aquifer to the top of the coal seam, m; ζ2 is the thickness of the aquifer, m.

10. The engineering geological rock mass quality grade evaluation method considering roof water hazard risk according to claim 1, characterized in that: Step S4 includes: S41, based on the obtained index value A, index value B, index value C, index value D, index value E, index value F, index value G, calculate the comprehensive index value I of the engineering geological rock mass quality of the working face according to the following formula; S42. Based on the obtained comprehensive index I and in accordance with the set grade evaluation rules, an evaluation result of the engineering geological rock mass quality grade of the roof water hazard is obtained.

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