CN114109506A - Coal mine earthquake risk assessment method - Google Patents

Coal mine earthquake risk assessment method Download PDF

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CN114109506A
CN114109506A CN202111427685.4A CN202111427685A CN114109506A CN 114109506 A CN114109506 A CN 114109506A CN 202111427685 A CN202111427685 A CN 202111427685A CN 114109506 A CN114109506 A CN 114109506A
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earthquake
mine
mine earthquake
key layer
energy
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CN114109506B (en
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曹安业
李振雷
窦林名
宋大钊
王桂峰
何学秋
巩思园
彭雨杰
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China University of Mining and Technology CUMT
University of Science and Technology Beijing USTB
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China University of Mining and Technology CUMT
University of Science and Technology Beijing USTB
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
    • E21F17/00—Methods or devices for use in mines or tunnels, not covered elsewhere
    • E21F17/18—Special adaptations of signalling or alarm devices
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
    • E21F17/00—Methods or devices for use in mines or tunnels, not covered elsewhere

Abstract

The invention relates to the field of mine earthquake risk assessment in a coal mining process, in particular to an assessment method for assessing mine earthquake risk caused by breakage of a overburden rock key layer in the coal mining process, which comprises the following steps: calculating theoretical breaking step distance and release energy of the key layer; evaluating whether the key layer can be broken; evaluating the mine earthquake intensity caused by the breakage of the key layer; evaluating the potential influence of the mine earthquake on the earth surface; and evaluating the potential influence of the mine earthquake on the underground. The method provides a technical means for scientifically evaluating the mine earthquake risk for the mine, can effectively identify the mine earthquake risk source and the risk level, further pertinently makes mine earthquake disaster prevention and treatment measures, reduces the mine earthquake risk to the maximum extent, weakens or even eliminates the rock burst disaster induced by the mine earthquake, and ensures the safe production of the mine.

Description

Coal mine earthquake risk assessment method
Technical Field
The invention relates to the field of mine earthquake risk assessment in a coal mining process, in particular to an assessment method for assessing mine earthquake risk caused by breakage of a overburden rock key layer in the coal mining process.
Background
Coal is an important guarantee for energy safety in China. Rock burst disasters can instantaneously destroy roadway equipment, cause casualties, and also can induce secondary disasters such as outburst and gas explosion, which is one of the most serious disasters of coal mines. By 2020, the high-risk rock burst mine 123 exists in China, the productivity of the mine accounts for more than 10% of the total production capacity of coal in China, and the rock burst disaster situation is more severe as the coal mining depth is increased. Rock burst prevention and control are worldwide problems which need to be solved urgently. The mine earthquake is a vibration event generated in mine excavation engineering and is a dynamic phenomenon generated in a coal rock body. Rock burst is an expression form of mine earthquake, is a type of mine earthquake which causes destructiveness and disastrous in a mining space, and is a destruction result generated in a supporting working space by a dynamic phenomenon. Each occurrence of rock burst is accompanied by a mine shake.
In addition to rock burst disasters caused by mine earthquake, frequent mine earthquake can also have adverse effects on the health of underground workers, and in addition, in the mining process of shallow-buried deep mines, mine earthquake occurring underground can also cause sensitive vibration on the earth surface to cause troubles to local residents, strong mine earthquake even causes damage to earth surface buildings, and the disaster-causing risk of mine earthquake is increasingly prominent. Therefore, accurate evaluation of the mine earthquake risk is an inevitable choice for effectively preventing and controlling mine earthquake disasters, and is also a precondition and guarantee for predicting and preventing rock burst disasters and ensuring mine safe production.
Aiming at the problems, the invention provides a coal mine earthquake risk assessment method, which can effectively solve the problems and help coal mine enterprises to scientifically assess the mine earthquake risk so as to realize accurate management and safe production.
Disclosure of Invention
The embodiment of the invention provides a coal mine earthquake risk assessment method, which is used for assessing the risk of inducing mine earthquake by breaking a overburden rock key layer in the coal mining process. The technical scheme is as follows:
s1: calculating theoretical breaking step distance and release energy of the key layer;
s2: evaluating whether the key layer can be broken;
s3: evaluating the mine earthquake intensity caused by the breakage of the key layer;
s4: evaluating the potential influence of the mine earthquake on the earth surface;
s5: and evaluating the potential influence of the mine earthquake on the underground.
Further, the step of calculating the theoretical breaking step distance and the release energy of the key layer comprises the following steps:
b1: judging and identifying a key layer above a mined coal seam according to a key layer theory;
b2: calculating the first breaking step distance of the key layer
Figure BDA0003377487280000021
And periodic breaking step
Figure BDA0003377487280000022
Wherein h is the thickness (m) of the key layer, RtThe key layer has tensile strength (Pa), and q is the overburden load (N/m) borne by the key layer2)；
B3: calculating the energy released when the key layer is broken for the first time and broken periodically,
Figure BDA0003377487280000023
wherein, U0Release energy (J), U for initial rupturepReleasing energy (J) for periodic fracture, b is the fracture width (m) of the key layer, l is the fracture step distance (m) of the key layer, E is the elastic modulus (Pa) of the key layer, I is the inertia moment of the cross section of the key layer to the neutral axis, and I is bh3/12，(m4)。
Further, the evaluating whether the key layer can be broken comprises the following steps:
c1: estimating the maximum development height of a fractured zone, and h when the top plate is a weak rock stratump＝9～12hcWhen the roof is a medium hard rock layer hp＝12～18hcWhen the roof is a hard rock layer hp＝18～28hcWherein h ispThe maximum development height (m), h of fissure zonecThe coal seam mining height (m);
c2: evaluating whether the critical layer in the maximum development height range of the fissure zone can be broken, and when the critical layer is Lc≥L0The critical layer of the layer is broken at +2d/tan theta, wherein LcAnd taking small values (m) of the strike length and the dip length of the goaf, wherein d is the distance (m) between the key layer and the coal bed, and theta is the rock stratum collapse angle (°).
Further, the evaluation of the mine earthquake intensity caused by the breakage of the key layer comprises the following steps:
evaluating mine earthquake energy caused by the breakage of the key layer, wherein E is the mine earthquake energy (J), U is the breaking release energy (J) of the key layer, and eta is the earthquake efficiency which is generally 0.26-3.6%;
evaluation of the seismic magnitude, log, of the mineral caused by the rupture of the critical zone10E＝a+bMLWherein M isLAnd a and b are constants, and mine seismic energy monitored by the coal mine microseismic monitoring system is related to the seismic level monitored by a local seismic station.
Further, the evaluation of the potential impact of the mine earthquake on the earth surface comprises:
mine earthquake with an earthquake magnitude of about 3 can be sensed by people on the earth surface, mine earthquake with an earthquake magnitude of more than 4.5 can cause earth surface damage, mine earthquake with an earthquake magnitude of more than 6 can cause great earth surface damage, and mine earthquake with an earthquake magnitude of more than 7 can cause severe earth surface damage.
Further, the evaluating the potential effect of the mine earthquake on the underground comprises:
estimating the minimum mine earthquake energy inducing the rock burst according to the historical rock burst and the statistical result of the microseismic monitoring data;
estimate switchThe residual mine earthquake energy when the key layer is broken to induce the mine earthquake to be spread to the mining area,
Figure BDA0003377487280000031
wherein E iscIs the residual mine earthquake energy (J), diThe propagation distance (m) of the vibration wave in the ith medium; lambda [ alpha ]iThe attenuation coefficient of the ith medium is generally 1.15-2.13;
and evaluating the potential underground influence of the mine earthquake, wherein if the residual mine earthquake energy is less than the minimum mine earthquake energy for inducing rock burst, the influence of the key layer induced mine earthquake on the underground is small, otherwise, if the residual mine earthquake energy is more than or equal to the minimum mine earthquake energy for inducing rock burst, the influence of the key layer induced mine earthquake on the underground is large.
Further, the evaluating the potential effect of the mine earthquake on the underground further comprises:
d1, estimating the dynamic load disturbance intensity caused by the propagation of the mine earthquake induced by the breaking of the key layer to the mining area,
Figure BDA0003377487280000032
wherein d isiThe propagation distance (m) of the vibration wave in the ith medium; lambda [ alpha ]iThe attenuation coefficient of the ith medium; sigmadFor propagation to distance source boundary dnDynamic load disturbance (MPa); rhonTo propagate to dnDensity of medium (kg/m)3)；CnTo propagate to dnThe medium wave velocity (m/s); v. of0Is the peak velocity of vibration (m/s) of the particles at the source boundary,
Figure BDA0003377487280000033
d2: estimating the degree of static load concentration, σ, around the excavation areasK γ H, where k is the stress concentration coefficient and γ is the overburden bulk density (N/m)3) H is the coal seam burial depth (m);
d3: estimating critical intensity sigma of coal body generating rock burstbminSigma when uniaxial compressive strength of coal is more than 20MPabminTaking 50MPa of uniaxial compressive strength of coalSigma when the degree is less than 16MPabminTaking 70MPa, and when the uniaxial compressive strength of the coal is 16-20 MPa, obtaining the sigmabminTaking 50-70 MPa;
d4: evaluating the potential effect of the mine earthquake on the underground when the sigma isd+σs≥σbminThe key layer induces the ore shock to have larger influence on the underground, has higher possibility of inducing rock burst, and has higher possibility of inducing rock burst when the sigma is largerd+σs＜σbminThe key layer induces the mineral earthquake to have small influence on the underground.
The technical scheme provided by the embodiment of the invention has the beneficial effects that at least: the mine earthquake disaster prevention and treatment method provides a technical means for scientifically evaluating mine earthquake risks for mines, effectively identifies the mine earthquake risk source and the risk level, further pertinently formulates mine earthquake disaster prevention and treatment measures, reduces the mine earthquake risks to the greatest extent, weakens or even eliminates rock burst disasters induced by mine earthquake, and ensures the safe production of mines.
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In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic flow chart of a coal mine earthquake risk assessment method provided by an embodiment of the invention;
FIG. 2 is a plan view of a mine face excavation project provided by an embodiment of the present invention;
FIG. 3 is a plot of critical interval break versus face extraction provided by an embodiment of the present invention;
fig. 4 is a graph showing the relationship between the number of occurrences of mine earthquake and rock burst and the energy thereof according to the embodiment of the present invention.
Detailed Description
The burial depth of a certain mine working face is about 380m, the inclined length is 255m, and the pushing length is 1256m, as shown in figure 2, the top coal is adopted for mining, the mining and laying height is 27m, the uniaxial compressive strength of roof rock is 22.8MPa, the uniaxial tensile strength is 3MPa, the elastic modulus is 9GPa, and the drilling column of the working face is shown in Table 1. There is a need to assess the risk of mine quake during the face propulsion.
TABLE 1 drilling column for certain working face
Number of rock formation Lithology Stratum bottom board buried depth (m) Thickness of rock layer h (m) Distance coal bed d (m)
/ 6 coal bottom 519.19 / /
/ 6 coal top 492.19 27.00 /
1 Coarse sandstone 487.89 4.10 4.30
2 Coarse sandRock (A. B. E 475.57 6.60 16.62
3 Coarse sandstone 459.82 7.24 32.37
4 Coarse sandstone 444.45 25.41 47.74
5 Coarse sandstone 412.42 5.14 79.77
6 Fine sandstone 387.55 21.28 104.64
7 Coarse sandstone 366.27 17.30 125.92
8 Fine sandstone 348.97 19.74 143.22
9 Fine sandstone 325.53 19.54 166.66
10 Fine sandstone 300.03 19.91 192.16
11 Coarse sandstone 280.12 38.93 212.07
12 Fine sandstone 241.19 17.85 251.00
13 Coarse sandstone 223.34 40.79 268.85
14 Coarse sandstone 175.55 37.48 316.64
15 Coarse sandstone 130.25 37.84 361.94
16 Coarse sandstone 83.57 58.83 408.62
17 Surface soil 24.74 24.74 467.45
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
As shown in fig. 1, an embodiment of the present invention provides a coal mine earthquake risk assessment method, including:
s1, calculating the theoretical breaking step pitch and the release energy of the key layer;
s2, evaluating whether the key layer can be broken;
s3, evaluating the mine earthquake intensity caused by the breakage of the key layer;
s4, evaluating the potential influence of the mine earthquake on the earth surface;
and S5, evaluating the potential influence of the mine earthquake on the underground.
The coal mine earthquake risk assessment method provided by the embodiment of the invention provides a technical means for scientifically assessing mine earthquake risks for a mine, can effectively identify a mine earthquake risk source and a risk grade, further pertinently makes a mine earthquake prevention and treatment measure, reduces the mine earthquake risks to the greatest extent, weakens or even eliminates rock burst disasters induced by the mine earthquake, and ensures the safe production of the mine.
In this embodiment, the calculating the theoretical breaking step size and the releasing energy of the key layer in S1 includes:
identifying key layers above the mined coal seam according to the key layer theory, wherein the key layers comprise rock layers 1, 2, 3, 4, 6, 8, 9, 10, 11, 13, 15 and 16;
calculating the first breaking step distance of the key layer
Figure BDA0003377487280000051
And periodic breaking step
Figure BDA0003377487280000052
Wherein h is the thickness (m) of the key layer, RtThe key layer has tensile strength (Pa), and q is the overburden load (N/m) borne by the key layer2) The method is obtained by a key layer theory;
calculating the energy released when the key layer is broken for the first time and broken periodically,
Figure BDA0003377487280000053
wherein, U0Release energy (J), U for initial rupturepReleasing energy (J) for periodic fracture, b is the fracture width (m) of the key layer, l is the fracture step distance (m) of the key layer, E is the elastic modulus (Pa) of the key layer, I is the inertia moment of the cross section of the key layer to the neutral axis, and I is bh3/12，(m4) The calculation results are shown in Table 2, taking the critical layer breaking width to be about half of the inclined length of the working face, namely 180 m.
TABLE 2 theoretical breaking step and released energy of key layer
Figure BDA0003377487280000054
Figure BDA0003377487280000061
In this embodiment, the evaluating whether the key layer can be broken in S2 includes:
estimating the maximum development height of a fractured zone, and h when the top plate is a weak rock stratump＝9～12hcWhen the roof is a medium hard rock layer hp＝12～18hcWhen the roof is a hard rock layer hp＝18～28hcWherein h ispThe maximum development height (m), h of fissure zonecThe coal seam mining height (m) is determined, the uniaxial compressive strength of a roof is 22.8MPa, the coal seam mining height is 27m, and the maximum development height of a fracture zone is 324 m-486 m calculated according to a medium hard rock stratum;
assessing whether the critical layer within the maximum development height of the fissure zone will break, as shown in FIG. 3, when Lc≥L0The critical layer of the layer is broken at +2d/tan theta, wherein LcAnd (3) taking small values of the run length and the dip length of the goaf, wherein 255m is taken, d is the distance (m) between the key layer and the coal seam, theta is the collapse angle of the rock stratum, and 70 degrees is taken, so that the key layers 1, 2, 3, 4, 6, 8, 9, 10 and 11 can be judged to meet the conditions and can be broken.
In this embodiment, the evaluating the earthquake intensity caused by the breaking of the key layer in S3 includes:
the key layers 1, 2, 3, 4, 6, 8, 9, 10 and 11 meet the conditions and can be broken, so that the mine earthquake intensity caused by the broken key layers is calculated;
evaluating mine earthquake energy caused by the breakage of the key layer, wherein E is mine earthquake energy (J), U is release energy (J) of the breakage of the key layer, eta is earthquake efficiency and is generally 0.26-3.6%, no goaf is arranged at the periphery of the working face, and eta is 3.6% according to the most adverse factor;
evaluation of the seismic magnitude, log, of the mineral caused by the rupture of the critical zone10E＝a+bMLWherein M isLIs the Lee's magnitude, a and b are constants, the mine earthquake energy monitored by the coal mine microseismic monitoring system is related to the magnitude monitored by the local earthquake table, and the log is taken for the mine10E＝1.8+1.9MLThe results of the calculations thus obtained are shown in Table 3, where E0And EpMine earthquake energy, M, caused by primary and periodic breaking of key layerL0And MLpThe mine earthquake magnitude caused by the primary breaking and the periodic breaking of the key layer is respectively.
TABLE 3 mine earthquake intensity caused by breaking of key layer
Figure BDA0003377487280000062
Figure BDA0003377487280000071
In this embodiment, the evaluating the potential impact of the mine earthquake on the earth surface in S4 includes:
the mineral earthquake with the earthquake magnitude of about 3 levels can be sensed by people on the earth surface, the mineral earthquake with the earthquake magnitude of more than 4.5 levels can cause earth surface damage, the mineral earthquake with the earthquake magnitude of more than 6 levels can cause greater earth surface damage, the mineral earthquake with the earthquake magnitude of more than 7 levels can cause severe earth surface damage, the mineral earthquake magnitude caused by the breakage of the key layer is below 3.0 levels and belongs to the microseismic level by referring to table 4 and table 3, and the influence of the mineral earthquake generated by the breakage of the key layer on the earth surface can be judged to be small.
TABLE 4 division of the impact of mine vibrations on the earth's surface
Figure BDA0003377487280000072
In this embodiment, the evaluating the potential downhole impact of the mineral earthquake in S5 includes:
estimating minimum ore shock energy inducing the rock burst according to the statistical results of the rock burst history and the microseismic monitoring data, wherein the mine is not provided with a microseismic monitoring system, has no microseismic monitoring data and has no over-rock burst, so the mine is determined by adopting the empirical relationship between the rock burst and the microseismic energy under similar conditions, as shown in fig. 4, the horizontal axis in the graph represents the energy of the ore shock and the rock burst, the vertical axis represents the occurrence times of the ore shock and the rock burst, the minimum ore shock energy inducing the rock burst can be determined to be E +04J grade, and the higher the ore shock energy is, the higher the possibility of inducing the rock burst is;
estimating the residual mine earthquake energy when the key layer is broken to induce the mine earthquake to propagate to the mining area,
Figure BDA0003377487280000073
wherein E iscIs the residual mine earthquake energy (J), diThe propagation distance (m) of the vibration wave in the ith medium; lambda [ alpha ]iThe attenuation coefficient of the ith medium is generally 1.15-2.13, no goaf is arranged at the periphery of the working surface, and lambda is taken according to the most adverse factoriIs 1.15, and the calculation results are shown in Table 5, wherein Ec0And EcpResidual energy is respectively generated when the mine earthquake caused by the primary breaking and the periodic breaking of the key layer is transmitted to the mining area;
TABLE 5 residual mine seismic energy as it propagates to the mining area
Figure BDA0003377487280000074
Figure BDA0003377487280000081
And (3) evaluating the potential influence of the mine earthquake on the underground, if the residual mine earthquake energy is less than the minimum mine earthquake energy inducing the rock burst, the influence of the key layer inducing the mine earthquake on the underground is small, otherwise, if the residual mine earthquake energy is more than or equal to the minimum mine earthquake energy inducing the rock burst, the influence of the key layer inducing the mine earthquake on the underground is large, and as can be seen from the table 5, the residual mine earthquake energy is less than the E +04J grade, which indicates that the influence of the key layer inducing the mine earthquake on the underground is small.
In this embodiment, the evaluating the potential effect of the mineral earthquake on the downhole in S5 further includes:
d1, estimating the dynamic load disturbance intensity caused by the propagation of the mine earthquake induced by the breaking of the key layer to the mining area,
Figure BDA0003377487280000082
wherein d isiThe propagation distance (m) of the vibration wave in the ith medium; lambda [ alpha ]iThe attenuation coefficient of the ith medium; sigmadFor propagation to distance source boundary dnDynamic load disturbance (MPa); rhonTo propagate to dnDensity of medium (kg/m)3)；CnTo propagate to dnThe medium wave velocity (m/s); v. of0Is the peak velocity of vibration (m/s) of the particles at the source boundary,
Figure BDA0003377487280000083
the dynamic load disturbance intensity caused by the mine earthquake with different energy can be calculated, see table 6, and the comparison table 5 shows that the residual mine earthquake energy generated by the key rupture is generally in the grade of E +03J, and the corresponding dynamic load disturbance intensity is 2 MPa-10 MPa;
TABLE 6 dynamic load disturbance intensity Range due to mine earthquake
Figure BDA0003377487280000084
Figure BDA0003377487280000091
D2, estimating the static load concentration degree, sigma, of the periphery of the mining areasK γ H, where k is the stress concentration factor, the face is the face of the lead, k is 2, γ is the overburden bulk density, and 2.5E +04N/m is preferred3H is the coal seam buried depth, 380m is taken, and the static load concentration degree is calculated to be 19 MPa;
d3, estimating the critical strength sigma of the coal body generating rock burstbminSigma when uniaxial compressive strength of coal is more than 20MPabminTaking 50MPa, and sigma when the uniaxial compressive strength of the coal is less than 16MPabminTaking 70MPa, and when the uniaxial compressive strength of the coal is 16-20 MPa, obtaining the sigmabminTaking 50-70 MPa;
the workThe uniaxial compressive strength of the surface coal is about 17MPa, and the sigma is takenbmin50 to 70 MPa;
d4, evaluating the potential effect of the mine earthquake on the underground when the sigma isd+σs≥σbminThe key layer induces the ore shock to have larger influence on the underground, has higher possibility of inducing rock burst, and has higher possibility of inducing rock burst when the sigma is largerd+σs＜σbminThe key layer induces the ore earthquake to have small influence on the underground;
calculating to obtain sigmad+σsAbout 21MPa to 29MPa, less than sigmabminAnd judging that the influence of the key layer induced ore shock on the underground is small.
In conclusion, the coal mine earthquake risk assessment method provided by the embodiment of the invention provides a technical means for scientifically assessing mine earthquake risks for the mine, effectively identifies the mine earthquake risks, is beneficial to the mine to make mine earthquake disaster prevention and treatment measures in a targeted manner, reduces the mine earthquake risks to the greatest extent, weakens or even eliminates rock burst disasters induced by mine earthquake, and ensures the safe production of the mine.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (7)

1. A coal mine earthquake risk assessment method is characterized by comprising the following steps:
s1: calculating theoretical breaking step distance and release energy of the key layer;
s2: evaluating whether the key layer can be broken;
s3: evaluating the mine earthquake intensity caused by the breakage of the key layer;
s4: evaluating the potential influence of the mine earthquake on the earth surface;
s5: and evaluating the potential influence of the mine earthquake on the underground.
2. The coal mine earthquake risk assessment method according to claim 1, wherein the step of calculating the theoretical breaking step distance and the release energy of the key layer comprises the following steps:
b1: judging and identifying a key layer above a mined coal seam according to a key layer theory;
b2: calculating the first breaking step distance of the key layer
Figure FDA0003377487270000011
And periodic breaking step
Figure FDA0003377487270000012
Wherein h is the thickness (m) of the key layer, RtThe key layer has tensile strength (Pa), and q is the overburden load (N/m) borne by the key layer2)；
B3: calculating the energy released when the key layer is broken for the first time and broken periodically,
Figure FDA0003377487270000013
wherein, U0Release energy (J), U for initial rupturepReleasing energy (J) for periodic fracture, b is the fracture width (m) of the key layer, l is the fracture step distance (m) of the key layer, E is the elastic modulus (Pa) of the key layer, I is the inertia moment of the cross section of the key layer to the neutral axis, and I is bh3/12，(m4)。
3. The coal mine earthquake risk assessment method according to claim 1, wherein said assessing whether the key layer can be broken comprises the following steps:
c1: estimating the maximum development height of a fractured zone, and h when the top plate is a weak rock stratump＝9～12hcWhen the roof is a medium hard rock layer hp＝12～28hcWhen the roof is a hard rock layer hp＝18～28hcWherein h ispThe maximum development height (m), h of fissure zonecThe coal seam mining height (m);
c2: evaluating whether the critical layer in the maximum development height range of the fissure zone can be broken, and when the critical layer is Lc≥L0The critical layer of the layer is broken at +2d/tan theta, wherein LcTaking small values (m) of the strike length and the dip length of the goaf, wherein d is the distance (m) between the key layer and the coal seam,θ is the formation collapse angle (°).
4. The coal mine earthquake risk assessment method according to claim 1, wherein the assessment of the earthquake intensity caused by the breakage of the key layer comprises:
evaluating mine earthquake energy caused by the breakage of the key layer, wherein E is the mine earthquake energy (J), U is the breaking release energy (J) of the key layer, and eta is the earthquake efficiency which is generally 0.26-3.6%;
evaluation of the seismic magnitude, log, of the mineral caused by the rupture of the critical zone10E＝a+bMLWherein M isLAnd the mine earthquake energy monitored by the coal mine micro-earthquake monitoring system is related to the earthquake magnitude monitored by the local earthquake table.
5. The coal mine earthquake risk assessment method according to claim 1, wherein said assessing the potential impact of the mine earthquake on the earth's surface comprises:
mine earthquake with an earthquake magnitude of about 3 can be sensed by people on the earth surface, mine earthquake with an earthquake magnitude of more than 4.5 can cause earth surface damage, mine earthquake with an earthquake magnitude of more than 6 can cause great earth surface damage, and mine earthquake with an earthquake magnitude of more than 7 can cause severe earth surface damage.
6. The coal mine earthquake risk assessment method according to claim 1, wherein the assessment of the potential downhole impact of the mine earthquake comprises:
estimating the minimum mine earthquake energy inducing the rock burst according to the historical rock burst and the statistical result of the microseismic monitoring data;
estimating the residual mine earthquake energy when the key layer is broken to induce the mine earthquake to propagate to the mining area,
Figure FDA0003377487270000021
wherein E iscIs the residual mine earthquake energy (J), diThe propagation distance (m) of the vibration wave in the ith medium; lambda [ alpha ]iThe attenuation coefficient of the ith medium is generally 1.15-2.13;
and evaluating the potential underground influence of the mine earthquake, wherein if the residual mine earthquake energy is less than the minimum mine earthquake energy for inducing rock burst, the influence of the key layer induced mine earthquake on the underground is small, otherwise, if the residual mine earthquake energy is more than or equal to the minimum mine earthquake energy for inducing rock burst, the influence of the key layer induced mine earthquake on the underground is large.
7. The coal mine earthquake risk assessment method according to claim 1, wherein the assessment of the potential downhole impact of the mine earthquake further comprises:
d1: estimating the dynamic load disturbance intensity caused when the breaking of the key layer induces the mine earthquake to propagate to the mining area,
Figure FDA0003377487270000022
wherein d isiThe propagation distance (m) of the vibration wave in the ith medium; lambda [ alpha ]iThe attenuation coefficient of the ith medium; sigmadFor propagation to distance source boundary dnDynamic load disturbance (MPa); rhonTo propagate to dnDensity of medium (kg/m)3)；CnTo propagate to dnThe medium wave velocity (m/s); v. of0Is the peak velocity of vibration (m/s) of the particles at the source boundary,
Figure FDA0003377487270000023
m；
d2: estimating the degree of static load concentration, σ, around the excavation areasK γ H, where k is the stress concentration coefficient and γ is the overburden bulk density (N/m)3) H is the coal seam burial depth (m);
d3: estimating critical intensity sigma of coal body generating rock burstbminSigma when uniaxial compressive strength of coal is more than 20MPabminTaking 50MPa, and sigma when the uniaxial compressive strength of the coal is less than 16MPabminTaking 70MPa, and when the uniaxial compressive strength of the coal is 16-20 MPa, obtaining the sigmabminTaking 50-70 MPa;
d4: evaluating the potential effect of the mine earthquake on the underground when the sigma isd+σs≥σbminThe key point ofThe stratum induced ore shock has larger influence on the underground, and the possibility of inducing rock burst is higher when the sigma is largerd+σs＜σbminThe key layer induces the mineral earthquake to have small influence on the underground.
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