Hidden danger identification and grading method for separated seam water disaster in overlying strata based on rock mass acoustic wave stiffness

Abstract

The present invention discloses a method for identifying potential hidden dangers of separated strata water hazards in overlying strata based on the acoustic wave stiffness of rock masses. First, in-situ testing of acoustic waves in rock masses is carried out; secondly, the acoustic wave stiffness of rock masses is calculated; then, the ratio of the acoustic wave stiffness of adjacent strata rock masses is calculated; then, in-situ discrimination and scale grading of potential hidden dangers of separated strata water hazards in overlying strata are carried out, and finally, the risk grading of potential hidden dangers of separated strata water hazards in overlying strata is carried out. The present invention comprehensively uses the strata structure revealed by boreholes and the borehole acoustic wave test data, without the need to carry out complex indoor tests to obtain physical and mechanical parameters, and can quickly identify and grade potential hidden dangers of separated strata water hazards in the mining area in-situ, providing a scientific basis for formulating prevention and control plans for separated strata water hazards and ensuring the safe mining of coal mines.

Description

Technical Field

[0001] The invention belongs to the technical field of overburden movement in coal mining, and relates to a method for identifying and grading hidden dangers of separated seam water disaster based on the acoustic wave stiffness of rock mass. Background Technique

[0002] With the advancement of coal seam mining in the working face, the separated seam in the overburden gradually develops, and the water in the aquifer in the overburden continuously replenishes the separated space; as the water accumulation in the separated space and the deformation of the overburden gradually increase, under certain conditions, the lower rock layer of the separated seam breaks, and the water body in the separated cavity gushes out, resulting in separated seam water inrush. The separated seam water disaster is a special type of water disaster. Such disasters have the characteristics of a large amount of water inrush instantaneously, unclear water inrush signs, and periodic roof water inrush, often causing great harm.

[0003] Accurately predicting the location of hidden dangers of separated seam water disaster is the premise for evaluating and preventing separated seam water disaster. Currently, the prediction of the location of hidden dangers of separated seam water disaster is mainly divided into the following types: (1) theoretical prediction; (2) numerical analysis and similar material simulation; (3) empirical analogy. Most of the judgment methods are computationally cumbersome, complex, and require many parameters, lacking a method for quickly identifying hidden dangers of separated seam water disaster based on in-situ rock mass test results. The invention identifies hidden dangers of separated seam water disaster by in-situ acoustic wave test, introduces the acoustic wave stiffness parameter of rock mass, and fills this gap. In addition, there is a lack of research on grading the scale and danger of overburden separated seam water disaster at home and abroad. Based on the identification of the location of hidden dangers of separated seam water disaster, the invention realizes the grading of the scale and danger of separated seam water disaster by introducing the thickness of the coal seam being mined and the vertical height of the hidden danger of separated seam water disaster from the coal seam, considering the response of the hidden danger of separated seam water disaster to the coal seam mining effect. Summary of the Invention

[0004] The purpose of the invention is to provide a method for identifying and grading hidden dangers of overburden separated seam water disaster based on the acoustic wave stiffness of rock mass, which solves the problem of insufficient research on grading the scale and danger of overburden separated seam water disaster in the prior art.

[0005] The technical solution adopted by the invention is as follows:

[0006] A method for identifying and grading hidden dangers of overburden separated seam water disaster based on the acoustic wave stiffness of rock mass, used to identify and grade hidden dangers of water disaster between two adjacent rock masses above the coal seam, includes the following steps:

[0007] Step 1, through surface drilling, obtain the coal seam thickness m, the lithology of the strata above the coal seam, and the strata thickness M; conduct in-situ rock mass acoustic wave test in the borehole to obtain the rock mass wave velocity V;

[0008] Step 2, for two adjacent rock masses above the coal seam, calculate the rock mass acoustic wave stiffness R according to the strata thickness M and the rock mass wave velocity V;

[0009] Step 3: Calculate the ratio K of the rock mass acoustic wave stiffness of adjacent strata based on the calculation result of the rock mass acoustic wave stiffness.

[0010] Step 4: Determine the location of the hidden danger of separated seam water disaster in overlying strata and classify the scale based on the ratio K of the rock mass acoustic wave stiffness.

[0011] Step 5: For the locations where the hidden danger of water disaster has been determined, classify the risk of the separated seam water disaster according to the thickness m of the mined coal seam, the vertical distance H from the interface of adjacent strata to the coal seam, and the ratio K of the acoustic wave stiffness.

[0012] The features of the present invention also lie in:

[0013] In the said Step 2, the specific calculation formula of the rock mass acoustic wave stiffness R is: R = V 2 ·M 3 .

[0014] In the said Step 3, the calculation method of the ratio K of the rock mass acoustic wave stiffness of adjacent strata is: K = R 上 / R 下 , where R 上 is the rock mass acoustic wave stiffness of the upper stratum, and R 下 is the rock mass acoustic wave stiffness of the lower stratum.

[0015] The said Step 4 is specifically:

[0016] When K > 1, it is determined that there is a hidden danger of separated seam water disaster at the interface of strata;

[0017] When 1 < K ≤ 10, it is determined that the scale classification of the hidden danger of separated seam water disaster is level three; when 10 < K ≤ 100, it is determined that the scale classification of the hidden danger of separated seam water disaster is level two; when K > 100, it is determined that the scale classification of the hidden danger of separated seam water disaster is level one.

[0018] The said Step 5 is as follows:

[0019] First, calculate the risk classification index S of the separated seam water disaster, and the calculation formula is: S = K × m / H;

[0020] Second, when S < 1, it is determined that the risk level of the separated seam water disaster is level three; when 1 ≤ S < 10, it is determined that the risk level of the separated seam water disaster is level two; when S ≥ 10, it is determined that the risk level of the separated seam water disaster is level one.

[0021] The beneficial effects of the present invention are:

[0022] The method for identifying the hidden danger of separated seam water disaster in overlying strata based on the rock mass acoustic wave stiffness provided by the present invention is a method for predicting the layer position of the hidden danger of separated seam water disaster before mining by using the results of borehole acoustic logging for the first time. The mining area can design a prevention and control plan for separated seam water disaster according to the prediction results to ensure the safe coal mining. Description of the Drawings

[0023] Figure 1 This is the flow chart of the implementation of the method of the present invention;

[0024] Figure 2 This is the in-situ test result diagram of a local stratum in a coal mine in the northwest. Detailed Implementation Modes

[0025] The present invention will be described in detail below in conjunction with the drawings and specific implementation modes.

[0026] As Figure 1 , a hidden danger identification and grading method for separated seam water disaster in overlying strata based on rock mass acoustic wave stiffness is used to identify and grade the hidden danger of water disaster between two adjacent rock masses above the coal seam, and includes the following steps:

[0027] Step 1: Through surface drilling, obtain the formation structure information and conduct in-situ acoustic wave test on the rock mass in the borehole to obtain the rock mass wave velocity V; the formation structure information includes the formation lithology above the coal seam, the formation thickness M, the coal seam thickness m, and the vertical distance H from the interface of adjacent formations to the coal seam;

[0028] Step 2: For two adjacent rock masses above the coal seam, calculate the rock mass acoustic wave stiffness R according to the formation thickness M and the rock mass wave velocity V; the specific calculation formula is: R = V 2 ·M 3 .

[0029] Step 3: Based on the calculation result of the rock mass acoustic wave stiffness, calculate the rock mass acoustic wave stiffness ratio K of adjacent formations; the specific calculation method is: K = R 上 / R 下 , where R 上 is the rock mass acoustic wave stiffness of the upper formation, and R 下 is the rock mass acoustic wave stiffness of the lower formation.

[0030] Step 4: Based on the rock mass acoustic wave stiffness ratio K, determine the location of the hidden danger of separated seam water disaster in overlying strata and grade the scale; specifically:

[0031] When K > 1, it is determined that there is a hidden danger of separated seam water disaster at the formation interface;

[0032] When 1 < K ≤ 10, it is determined that the scale of the hidden danger of separated seam water disaster is graded as level three; when 10 < K ≤ 100, it is determined that the scale of the hidden danger of separated seam water disaster is graded as level two; when K > 100, it is determined that the scale of the hidden danger of separated seam water disaster is graded as level one.

[0033] Step 5: For the locations that have been determined to be hidden dangers of water disaster, according to the coal seam thickness m of the mined coal seam, the vertical distance H from the interface of adjacent formations to the coal seam, and the acoustic wave stiffness ratio K, conduct a risk grading of the hidden danger of separated seam water disaster, specifically:

[0034] First, calculate the risk classification index S of the hidden danger of separated seam water disaster. The calculation formula is: S = K × m / H;

[0035] Secondly, when S < 1, determine that the risk level of the hidden danger of separated seam water disaster is level three; when 1 ≤ S < 10, determine that the risk level of the hidden danger of separated seam water disaster is level two; when S ≥ 10, determine that the risk level of the hidden danger of separated seam water disaster is level one.

[0036] Example 1

[0037] The example uses the method for identifying and grading hidden dangers of separated seam water disaster in overlying strata based on the acoustic stiffness of rock mass of the present invention to identify and grade the hidden dangers of separated seam water disaster in a local stratum of a certain coal mine in the northwest. The steps are as follows:

[0038] Step 1: Through surface boreholes, obtain the formation structure information and conduct in-situ acoustic wave tests on the rock mass in the boreholes. The specific results are as Figure 2 shown. According to the borehole data, there are two strata above the coal seam. The upper layer is medium sandstone with a thickness of 30.5 m, and the lower layer is sandy mudstone with a thickness of 6.06 m. For the test results of the rock mass wave velocity of the above two layers, the average value is taken to obtain 6071.7 m / s for the upper layer and 6864.8 m / s for the lower layer. The thickness m of the coal seam is 8.9 m, and the vertical distance H from the interface of adjacent strata to the coal seam is 337.1 m;

[0039] Step 2: Calculate the acoustic stiffness R of the rock mass according to the formation thickness M and the rock mass wave velocity V. The specific calculation formula is: R = V 2 ·M 3 , and after calculation, R 上 = 1.04597×10 12 m 5 / s, R 下 = 10435707597 m 5 / s;

[0040] Step 3: Based on the calculation result of the acoustic stiffness of the rock mass, calculate the ratio K of the acoustic stiffness of the rock mass between adjacent strata. The specific calculation formula is: K = R 上 / R 下 , where R 上 is the acoustic stiffness of the upper stratum, and R 下 is the acoustic stiffness of the lower stratum.

[0041] Step 4: Based on the ratio K of the acoustic stiffness of the rock mass, determine the location of the hidden danger of separated seam water disaster and classify the scale of the separated seam water disaster. The specific calculation results are shown in Table 1.

[0042] Step 5: According to the thickness m of the mined coal seam, the vertical distance H from the hidden danger of separated seam water disaster to the coal seam, and the ratio K of the acoustic stiffness, conduct a risk classification of the hidden danger of separated seam water disaster. Specifically:

[0043] According to the mining plan and the stratum structure, here m = 8.9 m and H = 337.1 m. Therefore:

[0044] S = K × m / H = 2.65

[0045] It is determined that the risk level of the hidden danger of separated seam water disaster here is grade two.

[0046] Table 1 Discrimination results of hidden dangers of separated seam water disaster

[0047]

[0048] The present invention comprehensively adopts the stratum structure revealed by boreholes and the borehole acoustic test data, without the need to carry out complex indoor tests to obtain physical and mechanical parameters, and can quickly identify and classify the hidden dangers of separated seam water disaster in the overlying strata of the mining area, providing a scientific basis for the formulation of the prevention and control plan for separated seam water disaster and ensuring the safe mining of coal mines.

Claims

1. A method for identifying and grading hidden dangers of separated layer water disaster in overlying strata based on the acoustic wave stiffness of rock mass, characterized in that, To identify and classify the hidden dangers of water disasters between two adjacent rock masses above the coal seam, the following steps are included: Step 1: Through surface drilling, obtain the coal seam thickness m, the lithology of the strata above the coal seam, and the stratum thickness M; conduct in-situ acoustic wave tests on the rock mass in the borehole to obtain the rock mass wave velocity V; Step 2: For two adjacent rock masses above the coal seam, calculate the rock mass acoustic stiffness R according to the stratum thickness M and the rock mass wave velocity V; Step 3: Based on the calculation results of the rock mass acoustic stiffness, calculate the rock mass acoustic stiffness ratio K of the adjacent strata; Step 4: Based on the rock mass acoustic stiffness ratio K, determine the location and scale classification of the hidden dangers of separated strata water disasters; Step 5: For the locations that have been determined as hidden dangers of water disasters, conduct a risk classification of the hidden dangers of separated strata water disasters according to the coal seam thickness m of the mined coal seam, the vertical distance H from the interface of the adjacent strata to the coal seam, and the acoustic stiffness ratio K.

2. The hidden danger identification and grading method for overlying strata separation water disaster based on the rock mass acoustic wave stiffness according to claim 1, characterized in that In the said step 2, the specific calculation formula for the rock mass acoustic wave stiffness R is: R = V 2 ·M 3 .

3. The method for identifying and grading hidden dangers of separated seam water disaster in overlying strata based on the acoustic wave stiffness of rock mass according to claim 1, characterized in that In the said step 3, the calculation method of the rock mass acoustic wave stiffness ratio K between adjacent strata is: K = R 上 / R 下 , where R 上 is the rock mass acoustic wave stiffness of the upper stratum, and R 下 is the rock mass acoustic wave stiffness of the lower stratum.

4. The method for identifying and grading potential hidden dangers of separated seam water disaster in overlying strata based on the acoustic wave stiffness of rock mass as claimed in claim 1, wherein The specific content of Step 4 is as follows: When K﹥1, it is determined that there is a hidden danger of separated strata water disaster at the stratum interface; When 1<K≤10, it is determined that the scale classification of the hidden danger of separated strata water disaster is grade three; when 10<K≤100, it is determined that the scale classification of the hidden danger of separated strata water disaster is grade two; when K﹥100, it is determined that the scale classification of the hidden danger of separated strata water disaster is grade one.

5. The hidden danger identification and grading method for overburden separation water disaster based on rock mass acoustic wave stiffness according to claim 1, characterized in that The content of Step 5 is as follows: First, calculate the risk classification index S of the hidden danger of separated strata water disaster. The calculation formula is: S = K×m / H; Second, when S<1, it is determined that the risk level of the hidden danger of separated strata water disaster is grade three; when 1≤S<10, it is determined that the risk level of the hidden danger of separated strata water disaster is grade two; when S≥10, it is determined that the risk level of the hidden danger of separated strata water disaster is grade one.

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