Coal seam outburst risk prediction index sensitivity analysis method

Abstract

The invention discloses a coal seam outburst risk prediction index sensitivity analysis method, and belongs to the technical field of coal mine safety. According to the method, regional outburst prediction indexes (including gas pressure and gas content) and local outburst prediction indexes (including a drilling cutting gas desorption index K1 and a drilling cutting gas desorption index delta h2) are adopted to predict the coal and gas outburst risk of a coal seam; if a certain index value of the regional outburst prediction index reaches the index critical value and other index values do not reach the index critical value, the index is relatively sensitive; and if the error between the measured value of the local outburst prediction index and the local outburst prediction index value reversely deduced from the laboratory coal sample desorption data is smaller, the index is more sensitive. According to the method, the coal and gas outburst risk of the coal seam is predicted by adopting the coal seam outburst risk prediction index with high sensitivity, so that the coal and gas outburst risk can be predicted accurately with high sensitivity, and the life safety of workers and the safety production of a coal mine are effectively guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mine safety, and in particular relates to a sensitivity analysis method for coal seam outburst hazard prediction indicators. Background Art

[0002] Coal and gas outburst (hereinafter referred to as "outburst") is one of the major disasters that seriously threaten coal mine safety production around the world. 95% of my country's coal mines are underground mining, of which high-gas mines and coal and gas outburst mines account for more than 40%. The scale of outbursts can be tens of tons, hundreds of tons, or even more than 10,000 tons, which is related to the safety of underground workers and the economic benefits of mines.

[0003] Coal and gas outburst is the result of the combined effects of multiple factors such as ground stress, gas pressure and physical and mechanical properties of coal. In areas where the gas pressure is higher, the ground stress is greater and the coal body is more severely damaged, the greater the risk of outburst. To determine the size of the risk of coal seam outburst, it is necessary to predict the risk of coal seam outburst to guide the scientific application of anti-outburst measures. Since coal and gas outburst is a complex dynamic phenomenon, the types of outburst are different, the risk factors causing outburst are different, and the sensitivity of its outburst risk prediction index is also different. Therefore, selecting appropriate outburst risk prediction indicators and their critical values, and studying reliable outburst risk prediction means and methods to achieve accurate prediction of outburst risk are the key foundations for effectively preventing and controlling outburst disasters and efficiently developing and utilizing coal seam gas (coalbed methane) resources. It has also been a key problem and major research topic in the field of mine safety.

[0004] The "Detailed Rules for Preventing and Controlling Coal and Gas Outbursts" clearly puts forward the principle of "regional outburst prevention measures first, local outburst prevention measures supplementary". Among them, the regional outburst prediction indicators are mainly gas pressure and gas content, and the local outburst prediction indicators are mainly drill cuttings gas desorption index K1 and drill cuttings gas desorption index Δh2.

[0005] Since the critical values ​​of outburst hazard prediction indicators in different mines or coal seams are different, in the actual application process, a large number of laboratory studies and field tests are needed to find out the outburst hazard prediction indicators and their critical values ​​applicable to this mine or coal seam; and the critical values ​​used in the prediction indicators are all reference critical values ​​in the "Detailed Rules for Preventing and Controlling Coal and Gas Outbursts", and the sensitivity of the indicators is unknown. With the increase of mining depth in the mining area and the change of coal seam occurrence conditions, there is a possibility of low-index outbursts. Therefore, the sensitivity analysis of outburst hazard prediction indicators and the determination of critical values ​​are the key to outburst hazard prediction.

[0006] In summary, in order to ensure the life safety of employees and safe production of coal mines, it is necessary to study the sensitivity and critical values ​​of coal seam outburst hazard prediction indicators and provide a sensitivity analysis method for coal seam outburst hazard prediction indicators. Summary of the invention

[0007] The present invention aims to solve one of the technical problems in the above-mentioned related art at least to a certain extent.

[0008] To this end, the purpose of the present invention is to provide a coal seam outburst hazard prediction index sensitivity analysis method, which can highly sensitively and accurately predict the gas outburst hazard.

[0009] In order to solve the above-mentioned technical problems, the present invention is achieved as follows:

[0010] The embodiment of the present invention provides a method for analyzing the sensitivity of coal seam outburst hazard prediction indicators, wherein the coal seam outburst hazard prediction indicators of the method include regional outburst prediction indicators and local outburst prediction indicators;

[0011] The regional outburst prediction index includes gas pressure and gas content, and the local outburst prediction index includes drill cuttings gas desorption index Δh2 and drill cuttings gas desorption index K1;

[0012] The drill cuttings gas desorption index K1 means the total amount of gas desorbed per gram of coal exposed to the atmosphere for 1 minute under the gas adsorption equilibrium pressure, which can reflect the attenuation degree of the gas content and desorption rate of the coal sample;

[0013] The drill cuttings gas desorption index Δh2 means the gas desorption amount of 10 grams of coal sample at the 4th and 5th minutes after it falls off from the coal body and is exposed to the atmosphere;

[0014] The analysis process of the method includes:

[0015] First, the measured values ​​of coal seam regional outburst prediction indicators are obtained, and the sensitivity of the indicators is determined according to the measured values ​​of each indicator and the indicator critical value; the sensitivity of the regional outburst prediction indicator means that when a certain indicator value reaches the indicator critical value, while other indicator values ​​have not reached the indicator critical value, the indicator is relatively sensitive;

[0016] Secondly, obtain the measured values ​​of the local coal outburst prediction index; inversely deduce the inverse value of the local coal outburst prediction index based on the laboratory coal sample desorption data; determine the sensitivity of the index based on the error between the measured value and the inverse value of each index; the smaller the error, the more sensitive the index;

[0017] Conduct sensitivity analysis on sensitivity indicators.

[0018] In addition, the coal seam outburst hazard prediction index sensitivity analysis method according to the present invention may also have the following additional technical features:

[0019] In some embodiments, the critical value of the gas pressure is 0.74 MPa, and the critical value of the gas content is 8 m3 / t, the critical value of the drilling cuttings gas desorption index K1 is 0.5mL / (g·min 0.5 ), the critical value of the drill cuttings gas desorption index Δh2 is 200Pa.

[0020] In some of the embodiments, the values ​​of the drill cuttings gas desorption index K1 and the drill cuttings gas desorption index Δh2 can be determined by reverse deduction based on coal body desorption amount data;

[0021] The sensitivity of the drill cuttings gas desorption index K1 and the drill cuttings gas desorption index Δh2 is determined according to the error between the measured value and the inverse value inferred according to the coal body desorption amount data; the smaller the error, the more sensitive the index.

[0022] In some embodiments, the relationship between the drill cuttings gas desorption index K1 and the coal sample desorption amount is:

[0023]

[0024] Where Q1 is the gas desorption amount per unit mass of coal sample from the exposure time to time t, m 3 / t;

[0025] t is the exposure time of coal sample, min.

[0026] In some embodiments, the relationship between the drill cuttings gas desorption index Δh2 and the coal sample desorption amount is:

[0027] Q2=0.0083Δh2 / 10;

[0028] Where Q2 is the gas desorption amount per unit mass of coal sample in the 4th and 5th minutes, m 3 / t.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects:

[0030] In an embodiment of the present invention, a sensitivity analysis method for coal seam outburst hazard prediction indicators is provided, which uses highly sensitive coal seam outburst hazard prediction indicators to predict coal seam outburst hazard, and can effectively protect the lives of employees and safe production in coal mines.

[0031] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A graph showing the change trend of gas desorption over time of soft coal in the No. 3 coal seam of a coal mine at different gas adsorption equilibrium pressures disclosed in one embodiment of the present invention;

[0033] Figure 2 A graph showing the change trend of gas desorption over time of hard coal in the No. 3 coal seam of a coal mine at different gas adsorption equilibrium pressures disclosed in one embodiment of the present invention;

[0034] Figure 3 A graph showing a trend of gas desorption index of soft coal cuttings in No. 3 coal seam of a coal mine as a function of pressure disclosed in one embodiment of the present invention;

[0035] Figure 4 A graph showing a trend of gas desorption index of hard coal drill cuttings in No. 3 coal seam of a coal mine as a function of pressure disclosed in one embodiment of the present invention;

[0036] Figure 5 A relationship diagram between gas pressure and gas content of soft coal in No. 3 coal seam of a coal mine disclosed in one embodiment of the present invention;

[0037] Figure 6 A relationship diagram between gas pressure and gas content of hard coal in No. 3 coal seam of a coal mine disclosed in one embodiment of the present invention;

[0038] Figure 7 This is a graph showing the results of measuring the desorption index value of drill cuttings gas in the No. 3 coal seam of a coal mine according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The embodiments of the present invention are described in detail below through specific embodiments and application scenarios in conjunction with the accompanying drawings.

[0041] In order to ensure the life safety of employees and the safe production of coal mines, it is necessary to study the sensitivity and critical value of coal seam outburst prediction indicators in coal mines. Based on the gas occurrence and geological structure conditions of coal seams in a coal mine, this paper investigates and analyzes regional outburst prediction indicators and local outburst prediction indicators, and combines laboratory analysis to determine the sensitivity and critical value of regional outburst prediction indicators and local outburst prediction indicators to guide the safe mining of coal.

[0042] The coal seam outburst hazard prediction index in the present invention includes a regional outburst prediction index (including gas pressure and gas content) and a local outburst prediction index (including a drill cuttings gas desorption index Δh2 and a drill cuttings gas desorption index K1). When predicting the coal seam outburst hazard, the above four indexes all have index critical values. If the index values ​​obtained from actual research in the coal seam exceed these critical values, it is determined that there is an outburst hazard. When performing a sensitivity analysis of the outburst hazard prediction index, all four indexes need to be considered.

[0043] For regional outburst prediction indicators, if one indicator reaches the critical value while another indicator has not reached the critical value, it means that the indicator is relatively sensitive. For example, when the gas pressure reaches the critical value but the gas content is lower than the critical value, it means that the gas pressure indicator is relatively sensitive; conversely, if the gas content reaches the critical value but the gas pressure is lower than the critical value, it means that the gas content is relatively sensitive.

[0044] For local outburst prediction indicators, the drill cuttings gas desorption index Δh2 and the drill cuttings gas desorption index K1 are both related to the coal body desorption amount, so Δh2 and K1 can be inferred from the desorption amount, and then their sensitivity can be judged according to the error between the measured value and the inferred value. For example, if the error between the Δh2 and K1 values ​​inferred from the desorption amount and the actual measured values ​​is small, it means that the indicator is more sensitive, otherwise, it is insensitive.

[0045] There is another method to determine the sensitivity of local outburst prediction indicators, that is, when a dynamic phenomenon occurs in a coal seam, it happens that one or some indicator values ​​are measured to exceed the critical value, while other indicators do not exceed the critical value. At this time, these indicators that exceed the critical value can be determined as more sensitive. For example, in a coal seam, dynamic phenomena occurred in 5 boreholes where the K1 value actually measured was greater than the indicator critical value, while no dynamic phenomenon occurred in other boreholes where the K1 value was less than the indicator critical value. It can be considered that the sensitivity of the K1 value is relatively high.

[0046] In some embodiments of the present invention, a method for analyzing the sensitivity of coal seam outburst hazard prediction indicators is provided, and the method includes two major parts: laboratory investigation of gas desorption laws and sensitivity analysis of coal seam outburst prediction indicators.

[0047] Part I: Laboratory Investigation of Gas Desorption Laws

[0048] 1.1 Experimental results

[0049] 1.1.1 Industrial analysis, adsorption constants and outstanding prediction index determination results

[0050] The collected coal samples were subjected to industrial analysis in the laboratory and their moisture content (M ad )、Ash content (A ad ), volatile matter (Vdaf ) content, and the solidity coefficient (f), initial gas emission velocity (Δp) and adsorption constants (a, b) of the coal samples were determined. The results are shown in Table 1.

[0051] Table 1 Industrial analysis, adsorption constant and outburst index determination results of coal samples

[0052]

[0053] 1.1.2. Results of determination of drilling cuttings gas desorption index

[0054] The present invention measured the drilling cuttings gas desorption index on the soft and hard coal samples selected from the No. 3 coal seam of a certain coal mine, and the results are shown in Table 2.

[0055] Table 2 Determination results of drilling cuttings gas desorption index of No. 3 coal seam in a coal mine

[0056]

[0057]

[0058] 1.1.3 Effect of gas adsorption equilibrium pressure on gas desorption law

[0059] In the laboratory, using coal samples with a particle size range of 1 to 3 mm, the relationship between the gas desorption amount and time of soft and hard coal samples in the No. 3 coal seam of a coal mine under different gas adsorption equilibrium pressure conditions was studied. Figure 1 and Figure 2 shown.

[0060] Depend on Figure 1 and Figure 2 It can be seen that whether it is soft coal or hard coal, the desorption curves of the coal samples are different but still have certain regularity. Under a certain gas adsorption equilibrium pressure, the gas desorption amount of the coal sample is positively correlated with time. The curves with high gas adsorption equilibrium pressure at different desorption times are all above the curves with low gas adsorption equilibrium pressure. The gradient of the curve with high gas adsorption equilibrium pressure at the initial moment is relatively large, that is to say, the initial gas desorption rate of the coal sample is large under a higher gas adsorption equilibrium pressure. The common feature of each curve is that the amount of desorbed gas gradually increases with time, and the desorption rate gradually decreases. At the initial moment, the gas desorption rate is very large, but it decays quickly.

[0061] In terms of the comparison between soft coal and hard coal, the initial desorption amount of soft coal is larger than that of hard coal, the desorption rate is also faster than that of hard coal, and the time when the desorption curve of soft coal tends to relax is shorter than that of hard coal.

[0062] 1.1.4. Investigation and analysis of initial gas desorption amount of coal body

[0063] From the results of coal sample desorption law determination, it can be seen that the coal body has the characteristics of large initial gas desorption rate and fast desorption rate decay. The initial gas desorption amount accounts for a considerable part of the total desorption amount, as shown in Tables 3 and 4.

[0064] Table 3 Relationship between initial desorption and cumulative desorption of soft coal in No. 3 coal seam of a coal mine

[0065]

[0066] Table 4 Relationship between initial desorption and cumulative desorption of hard coal in No. 3 coal seam of a coal mine

[0067]

[0068] It can be seen from Table 3 and Table 4 that the desorption amount is large in the initial stage of desorption, and the desorption amount increases more slowly in the later stage. For soft coal, the gas desorption amount in the first minute accounts for 18.156-21.259% of the cumulative gas desorption amount in 120 minutes, with an average of 19.414%; the gas desorption amount in the first ten minutes accounts for 68.136-74.104% of the cumulative desorption amount in 120 minutes, with an average of 71.566%, and the maximum value exceeds 70%; for hard coal, the gas desorption amount in the first minute accounts for 8.544-15.553% of the cumulative gas desorption amount in 120 minutes, with an average of 12.300%; the gas desorption amount in the first ten minutes accounts for 32.225-45.236% of the cumulative desorption amount in 120 minutes, with an average of 37.600%, and the maximum value exceeds 45%. It can be found that the initial desorption amount of the coal sample accounts for a large part of the total desorption amount, and the change of soft coal is much more obvious than that of hard coal, and the desorption amount in the early stage is also much larger than that of hard coal.

[0069] 1.2 Analysis of the relationship between drill cuttings gas desorption index and gas adsorption equilibrium pressure

[0070] The desorption characteristics of drill cuttings gas in coal are related to the gas content, gas pressure, degree of coal damage and coal structure of the coal seam. The drill cuttings gas desorption index is a prominent predictive index reflecting the adsorption and desorption characteristics of coal and the structural characteristics of coal, and has been widely used in coal mine production. The commonly used drill cuttings gas desorption indexes are K1 and Δh2. The following will explore the relationship between the two indicators Δh2 and K1, and analyze their relationship with gas pressure.

[0071] The present invention has measured the desorption index of drilling cuttings gas of soft and hard coal in the No. 3 coal seam of a selected coal mine, and the results are shown in Table 2. According to the data in Table 2, a curve diagram of the change of the desorption index of drilling cuttings gas of the experimental coal sample with pressure is made, as shown in FIG. Figure 3 and Figure 4 shown.

[0072] Depend on Figure 3 and Figure 4It can be seen that, no matter it is soft coal or hard coal, with the increase of gas adsorption equilibrium pressure, the drill cuttings gas desorption index Δh2 and K1 values ​​gradually increase; and the growth trend of Δh2 with gas pressure is consistent with the growth trend of K1 with gas pressure. This is because Δh2 and K1 both represent the desorption amount of coal samples over a period of time, reflecting the desorption characteristics of the coal body. The same coal body has the same desorption law, and the influence on Δh2 and K1 is the same.

[0073] Part II: Sensitivity analysis of coal seam outburst prediction indicators

[0074] 2.1 Research on regional prominence prediction indicators

[0075] 2.1.1 Determination of relative sensitivity of outburst prediction indicators in No. 3 coal seam of a coal mine

[0076] According to the field measured gas pressure and gas content results, combined with industrial analysis and adsorption constant determination, the relationship between the gas pressure and gas content of the soft and hard coal in the No. 3 coal seam of a coal mine is made, such as Figure 5 and Figure 6 shown.

[0077] from Figure 5 It can be seen that the gas content of soft coal in the No. 3 coal seam of a coal mine is 8.00m 3 / t, the corresponding gas pressure is 0.3MPa, and when the gas pressure is 0.74MPa, the corresponding coal seam gas content is 13.62m 3 / t; and from Figure 6 It can be seen that the gas content of the hard coal in the No. 3 coal seam of a coal mine is 8.00m 3 / t, the corresponding gas pressure is 0.23MPa, and when the gas pressure is 0.74MPa, the corresponding coal seam gas content is 16.14m 3 / t.

[0078] Comparison shows that both soft coal and hard coal in the No. 3 coal seam of a coal mine are highly sensitive to gas content. 3 / t is safer as the critical value of regional protrusion prediction indicator.

[0079] During the tunneling work face construction of the No. 3 coal seam in the coal mine, the measured gas pressure was 0.71 MPa, which was less than the critical value of 0.74 MPa, and the measured gas content was 10.71 m 3 / t, greater than the critical value 8m 3 / t, it can also be seen that with a gas content of 8.00m 3 / t is safer as the critical value of regional protrusion prediction indicator.

[0080] 2.1.2 Relative sensitivity analysis of regional prominent prediction indicators

[0081] According to statistical analysis, the corresponding relationship between the gas pressure and gas content of the No. 3 coal seam in a coal mine under their respective critical value conditions is shown in Table 5.

[0082] Table 5 Corresponding relationship between gas pressure and gas content in No. 3 coal seam of a coal mine under critical value conditions

[0083]

[0084] From Table 5, we can know that the gas content of No. 3 coal seam in a coal mine is 8.00m 3 / t, the corresponding gas pressure is 0.35MPa; and when the gas pressure is 0.74MPa, the corresponding coal seam gas content is 10.97m 3 / t, it can be seen that the sensitivity of gas content is higher than that of gas pressure.

[0085] 2.2 Research on local protrusion prediction indicators

[0086] In the area where the regional outburst hazard prediction or regional effect inspection determines that there is no outburst hazard area, the local outburst prediction index should be used to predict the local outburst hazard during the working face mining process. The local outburst hazard prediction of the No. 3 coal seam in a coal mine mainly uses the drill cuttings gas desorption index Δh2 and K1.

[0087] 2.2.1. Principle of determination of drilling cuttings gas desorption index

[0088] 1) K1 measurement principle

[0089] The K1 index is measured by a WTC gas outburst parameter instrument. Under the action of gas adsorption equilibrium pressure, the granular coal sample is exposed to the atmosphere, and the gas in the coal sample is rapidly desorbed. Through experiments, it is found that the gas desorption amount and desorption time of the coal sample have the following relationship:

[0090]

[0091] Where: Q1 is the gas desorption amount per unit mass of coal sample from the exposure time to time t, m 3 / t;

[0092] t is the exposure time of coal sample, min.

[0093] Therefore, the gas-containing coal sample is exposed instantaneously to the atmosphere or an instrument with similar atmospheric environmental conditions, and the gas desorption amount of unit mass of coal sample in different time periods is measured according to the isochoric, isobaric and variable volume and variable pressure desorption principles. Then, the relationship between the measured data and the coal sample exposure time is subjected to corresponding mathematical processing to obtain the drill cuttings gas desorption index K1 value.

[0094] 2) Principle of Δh2 determination

[0095] Nowadays, the determination of the drilling cuttings gas desorption index Δh2 is mainly carried out by the MD-2 gas desorption instrument, which is a variable volume and pressure instrument. The basic principle of the instrument is that under the condition of no coal sample degassing and gas filling, the residual gas in the coal cuttings desorbs and releases gas into a closed space, causing changes in the volume and pressure of the space, and the amount of gas desorbed from the coal cuttings is indicated by the water gauge pressure difference.

[0096] The physical meaning of Δh2 is the amount of gas desorption at 4 and 5 minutes after 10 grams of coal sample falls off from the coal body and is exposed to the atmosphere;

[0097] For the MD-2 gas desorption instrument, the gas desorption amount of the unit mass coal sample at the 4th and 5th minutes and Δh2 have the following relationship:

[0098] Q2=0.0083Δh2 / 10 (2)

[0099] Where: Q2 is the gas desorption amount of the unit mass coal sample at the 4th and 5th minutes, m 3 / t.

[0100] Experiments have shown that the size of Δh2 is closely related to the exposure time before measurement, coal sample particle size, coal damage type, coal seam gas pressure, etc.

[0101] 2.2.2 Reliability analysis of drilling cuttings gas desorption index

[0102] According to the principle of drill cuttings gas desorption index, the drill cuttings gas desorption index K1 reflects the gas desorption amount of the coal sample in the first minute, while Δh2 corresponds to the gas desorption amount of the coal sample in the fourth and fifth minutes. Here, the K1 and Δh2 obtained by actual measurement are compared with the values ​​inferred from the gas desorption amount of the coal sample to analyze their sensitivity.

[0103] 1) Reliability analysis of the Δh2 value of the drilling cuttings gas desorption index

[0104] According to the MD-2 gas desorption instrument, the drilling cuttings gas desorption index Δh2 of each coal sample under different gas adsorption equilibrium pressures can be measured. According to the desorption data of coal samples under different gas adsorption equilibrium pressures, the actual desorption amount Q of the coal sample in the 4th and 5th minutes can be calculated. 4～5 , and then according to formula (2), the reverse value of the drill cuttings gas desorption index Δh2 can be inferred. The results are shown in Table 6.

[0105] Table 6 Comparison results of measured and inferred values ​​of gas desorption index Δh2 of cuttings of coal sample from No. 3 coal seam in a coal mine

[0106]

[0107] It can be seen from Table 6 that, regardless of soft coal or hard coal, the actual measured drill cuttings gas desorption index Δh2 converted into desorption amount has a large error compared with the actual desorption amount of the coal sample at the 4th and 5th minutes, and the relative error exceeds 50%. This shows that the drill cuttings gas desorption index Δh2 value of the No. 3 coal seam in a coal mine obtained based on calculation is inappropriate, and the measured drill cuttings gas desorption index Δh2 value is much larger than the value deduced from the actual desorption amount of the experimental coal sample at the 4th and 5th minutes after adsorption equilibrium.

[0108] 2) Reliability analysis of the K1 value of the drilling cuttings gas desorption index

[0109] According to the WTC gas outburst parameter measuring instrument, the drill cuttings gas desorption index K1 of each coal sample under different gas adsorption equilibrium pressures can be measured. According to the desorption data of the coal samples under different gas adsorption equilibrium pressures, the actual desorption amount Q1 of the coal sample in the first minute can be calculated. Then, according to formula (1), the inverse value of the drill cuttings gas desorption index K1 can be inferred. The results are shown in Table 7.

[0110] Table 7 Comparison of the measured K1 value and the actual desorption amount in the first minute of the No. 3 coal seam in a coal mine

[0111]

[0112] It can be seen from Table 7 that the difference between the measured value of the drill cuttings gas desorption index K1 of the soft coal in the No. 3 coal seam of a coal mine and the value inferred from the actual desorption amount in the first minute after the adsorption equilibrium of the coal sample is small, with an average error of about 2.079%. The average error between the measured value of the drill cuttings gas desorption index K1 of the hard coal in the No. 3 coal seam of a coal mine and the value inferred from the actual desorption amount in the first minute after the adsorption equilibrium of the coal sample is about 1.6%, which is much smaller than the error between the measured value and the inferred value of the drill cuttings gas desorption index Δh2.

[0113] It can be seen that the error between the inferred value and the measured value of the drill cuttings gas desorption index Δh2 of the coal sample of the No. 3 coal seam of a coal mine is large, and it cannot accurately reflect the drill cuttings gas desorption characteristics of the No. 3 coal seam, indicating that the Δh2 index is insensitive and unreliable, and cannot be used to predict the outburst hazard of the coal seam. Compared with the Δh2 index, the error between the measured value and the inferred value of the drill cuttings gas desorption index K1 is small, and it can accurately reflect the drill cuttings gas desorption characteristics of the No. 3 coal seam, indicating that the K1 index is more sensitive and reliable, and can be used to predict the outburst hazard of the coal seam.

[0114] 2.2.3. Field application effect of drilling cuttings gas desorption index sensitivity

[0115] According to the actual situation on site, the measured data of the drill cuttings gas desorption index K1 value measured in the No. 3 coal seam of a coal mine were statistically analyzed, such as Figure 7 shown.

[0116] according to Figure 7 It can be seen that the desorption index K1 and Δh2 of drill cuttings gas were measured 69 times during the mine production. The actual measured desorption index K1 of the drill cuttings gas in the No. 3 coal seam of a coal mine ranged from 0.02 to 0.68 mL / (g·min 0.5 ) -1 Among the K1 values ​​actually measured, 5 data values ​​are greater than 0.5mL / (g·min 0.5 ) -1 The rest were less than the critical value of 0.5mL / (g·min 0.5 ) -1 The actual measured value of K1 for gas desorption in drilling cuttings is 62-178 Pa, which is less than the critical value of 200 Pa. According to the relevant data of drilling construction in No. 3 coal seam, the actual measured K1 value is greater than 0.5 mL / (g·min 0.5 ) -1 Gas dynamic phenomena occurred in all five boreholes. It can be seen that the sensitivity of the K1 value is relatively high, and it is reasonable to use the drill cuttings gas desorption index K1 value to predict the danger of gas outburst.

[0117] Parts of the present invention that are not described in detail are well known to those skilled in the art.

[0118] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A method for sensitivity analysis of coal seam outburst hazard prediction indicators, characterized in that: The coal seam outburst hazard prediction index of the method includes a regional outburst prediction index and a local outburst prediction index; The regional outburst prediction index includes gas pressure and gas content, and the local outburst prediction index includes drill cuttings gas desorption index K1 and drill cuttings gas desorption index Δh2; The drill cuttings gas desorption index K1 means the total amount of gas desorbed per gram of coal exposed to the atmosphere for 1 minute under the gas adsorption equilibrium pressure, which can reflect the attenuation degree of the gas content and desorption rate of the coal sample; The drill cuttings gas desorption index Δh2 means the gas desorption amount of 10 grams of coal sample at the 4th and 5th minutes after it falls off from the coal body and is exposed to the atmosphere; The analysis process of the method includes: First, the measured values ​​of coal seam regional outburst prediction indicators are obtained, and the sensitivity of the indicators is determined according to the measured values ​​of each indicator and the indicator critical value; the sensitivity of the regional outburst prediction indicator means that when a certain indicator value reaches the indicator critical value, while other indicator values ​​have not reached the indicator critical value, the indicator is relatively sensitive; Secondly, obtain the measured values ​​of the local coal outburst prediction index; inversely deduce the inverse value of the local coal outburst prediction index based on the laboratory coal sample desorption data; determine the sensitivity of the index based on the error between the measured value and the inverse value of each index; the smaller the error, the more sensitive the index; Conduct sensitivity analysis on sensitivity indicators.

2. The method for sensitivity analysis of coal seam outburst hazard prediction indicators according to claim 1, characterized in that: The critical value of the gas pressure index is 0.74MPa, and the critical value of the gas content index is 8m 3 / t, the critical value of the drilling cuttings gas desorption index K1 is 0.5mL / (g·min 0.5 ), the critical value of the drill cuttings gas desorption index Δh2 is 200Pa.

3. The method for sensitivity analysis of coal seam outburst hazard prediction indicators according to claim 1, characterized in that: The relationship between the drill cuttings gas desorption index K1 and the coal sample desorption amount is: Where Q1 is the gas desorption amount per unit mass of coal sample from the exposure time to time t, t is the exposure time of coal sample; The relationship between the drilling cuttings gas desorption index Δh2 and the coal sample desorption amount is: Q2=0.0083Δh2 / 10; Where Q2 is the gas desorption amount per unit mass of coal sample in the 4th and 5th minutes.

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