CN112861068A - Method for determining mining overburden rock damage height - Google Patents
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Abstract
The invention discloses a method for determining mining overburden failure height, which comprises the following steps: s1, determining the bearing load and the layer position of the hard rock stratum; s2, determining the height wi of the cavity below the hard rock stratum; s3, calculating the maximum deflection sinking deformation omega before each hard rock layer is damagedmax(ii) a S4, judging whether the hard rock stratum is broken or not; when the hard rock layer is not broken, the distance between the hard rock layer and the coal bed, namely the breaking height of the mining overburden rock; when the hard rock stratum is broken, starting next hard rock stratum judgment until the hard rock stratum which is not broken is judged; when the hard rock layer is damaged up to the uppermost part, the damage height of the overlying strata is the buried depth of the coal bed. The method disclosed by the invention determines that the hard rock layer is taken as a research object, and performs mechanical analysis and breakage judgment on the hard rock layer, so that the damage height of the mining overburden rock is more accurately determined, and further, the safe and efficient stoping of a working face, the reasonable design of a gas extraction drill hole and the evaluation of the stability of a surface building of the goaf after the stoping of the working face are completed are realized.
Description
Technical Field
The invention relates to the technical field of coal mining, in particular to a method for determining the damage height of mining overburden rock.
Background
The mining of the coal seam can cause the damage and the collapse of the upper rock stratum, and the overlying rock stratum of the stope begins to move under the mining influence of the working face along with the propulsion of the working face. The apparent characteristics of stope overburden migration are separation, breakage, collapse of rock stratum and movement deformation of earth surface, and overburden movement damage gradually develops from bottom to top. It is well known that the presence of partially hard formations (hard formations) in the overburden affects the overall migration destruction process of the formation. It is because overburden migration is affected by hard rock formations that mining overburden presents the characteristic of a group migration failure.
In the coal production process, the determination of the overburden failure height relates to safe and efficient stoping of a working face, and has important significance on actual production activities such as gas extraction, water body underground coal mining and stability judgment of an old goaf.
The existing method for determining the damage height of the overlying strata comprises an engineering analogy method, a theoretical calculation method and a field actual measurement method.
The engineering analogy method obtains the damage height of the overlying strata through engineering analogy according to the existing field actual measurement result. This method has a problem in that it is necessary to have the same or similar working face being produced and already obtain the overburden failure height of this working face; the method is therefore not suitable for use in mines where no face extraction activity is being performed during the early stages of the design or development.
The theoretical calculation method is to calculate the damage height of the overlying strata by adopting an empirical formula, and the empirical formula is obtained by measuring the damage height of the overlying strata through long-term actual production through statistical analysis. Because the method belongs to an empirical formula and has certain guiding significance on the calculation of the damage height of the overlying strata, the calculation result of partial geological conditions is greatly different from the actual result.
And (3) a field actual measurement method, namely detecting the damage height of the overburden rock by a drilling fluid leakage method, a double-end water plugging method, a drilling television and other methods after the working face is recovered. The method cannot be used for mines which do not have stoping activities on the working face, and the implementation process of the method is time-consuming and labor-consuming.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for determining the mining overburden failure height, which is used for overcoming the defects of poor applicability, complex operation and the like commonly existing in the process of determining the mining overburden failure height before coal seam mining. The method has the advantages of simple operation, high efficiency and strong applicability.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for determining the failure height of mining overburden rock comprises the following steps:
the first step is as follows: the hard rock layer bearing load and the layer position of the hard rock layer in the overlying rock layer of the mining field are determined, and the ith hard rock layer is named sequentially from bottom to top (i is 1,2 and 3 …).
The second step is that: determining the height wi of a cavity below a hard rock stratum according to the following formula by combining the mining height of the coal seam, the distance between the hard rock stratum and the coal seam and the crushing and swelling characteristics of the rock stratum;
wi＝M-∑hi((Kp)i-1)
in the formula: m is the thickness of a mining coal seam, (Kp) i is the crushing expansion coefficient of each rock stratum between the ith hard rock stratum and the coal seam, hi is the thickness of each rock stratum between the ith hard rock stratum and the coal seam, and wi is the height of a cavity below the ith hard rock stratum;
the third step: before the rock stratum is subjected to primary fracture, the rock stratum is regarded as a clamped beam model with a rectangular section;
in the formula: lc is the length of the primary breaking block body, b is the width of the rectangular section of the beam, and I is the inertia moment of the rectangular section;
the relationship between the maximum subsidence deformation of the rock stratum and the height of the cavity at the lower part of the rock stratum determines whether the rock stratum is damaged or not; and (3) calculating a deflection equation of the rock stratum and the maximum subsidence of the rock stratum under the damage critical state by taking the tensile strength criterion as the damage criterion of the rock stratum:
when the rectangular cross section of the rock formation is a unit width, i.e. b 1,
in the formula: omega is the deflection of the beam, E is the elastic modulus of the rock stratum;
when x is 0, the bending deflection of the clamped beam reaches a maximum value:
the fourth step: and starting from the 1 st hard rock stratum, judging whether the hard rock stratum can be broken or not. When the hard rock layer is not broken, the distance between the hard rock layer and the coal bed, namely the breaking height of the mining overburden rock; when the hard rock stratum is broken, starting next hard rock stratum judgment until the hard rock stratum which is not broken is judged; when the hard rock layer is damaged up to the uppermost part, the damage height of the overlying strata is the buried depth of the coal bed.
As an improvement to the above technical solution, in step S1, the level and the bearing load of the hard rock layer at the upper part of the stope are calculated by the following formula:
(qn)i＞(qn+1)i
in the formula: q is the rock stratum bearing load, E is the elastic modulus of the rock stratum, h is the thickness of each rock stratum between the hard rock stratum and the coal bed, gamma is the rock stratum volume weight, n is the bearing rock stratum, and i is the number of layers of the upper load rock stratum of the bearing rock stratum;
the hard formation is calculated from the first formation above the coal seam, n is also counted from the current formation, and when:
(qn)i＞(qn+1)i
and (5) the n +1 stratum is the (i + 1) th hard stratum, n starts counting from the i +1 th stratum again, and the steps are repeated until the surface is calculated.
Preferably, in the third step, the length of the primary broken block of the hard rock stratum on the upper part of the stope is solved by adopting a clamped beam model to obtain Lc：
In the formula, LcFor the first time breaking the block length, q is the hard rock loading, h is the hard rock thickness, σtIs the tensile strength of hard rock formations.
When the height of the lower cavity of the hard rock layer is larger than the maximum deflection bending deformation of the hard rock layer, the hard rock layer is broken, otherwise, the hard rock layer is not broken.
Starting from 1 hard rock stratum, whether the hard rock stratum is broken or not is judged. When a certain hard rock stratum is judged to be broken, the hard rock stratum and a load rock stratum thereof belong to the damage range of the overlying strata; until the unbroken hard rock layer is judged, the distance from the hard rock to the coal bed is the breaking height of the mining overburden rock
Compared with the prior art, the invention has the following beneficial effects:
the method for determining the mining overburden rock damage height solves the problem that the mining overburden rock damage height is difficult to accurately determine before coal seam mining, and provides theoretical support for the work of safe and efficient stoping of a working face, reasonable design of gas extraction drill holes, evaluation of the stability of a surface building of a goaf after the stoping of the working face and the like. The method for determining the mining overburden rock damage height provided by the invention considers that when the rock stratum exceeds the ultimate deflection sinking value, the rock stratum is broken, so that whether the rock stratum is damaged or not is determined according to the relation between the maximum sinking deformation of the rock stratum and the height of a cavity at the lower part of the rock stratum, and the hard rock stratum is used as a main influence rock stratum in the mining overburden rock migration process, so that the hard rock stratum is determined to be used as a research object, and the mechanical analysis and breakage judgment are carried out on the hard rock stratum, so that the mining overburden rock damage height is determined more accurately, the safe and efficient stoping of a working face, the reasonable design of a gas extraction drill hole and the evaluation of the stability of a ground surface building of a goaf after the stoping of the working face are finished.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic illustration of a hard formation space for producing overburden;
FIG. 2 is a model of hard formation horizon and load calculation;
FIG. 3 is a mechanical model of an initial fracture of a hard rock formation;
fig. 4 is a flow chart of overburden failure height determination.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived from the embodiments of the present invention by a person skilled in the art without any creative effort, should be included in the protection scope of the present invention.
As shown in figures 1-4, the method for determining the damage height of the mining overburden rock comprises the following operation steps:
the first step is as follows: hard rock layer bearing load and the layer position of the hard rock layer in the overlying rock layer of the stope are determined, the ith hard rock layer (i is 1,2 and …) is named sequentially from bottom to top, and the spatial relative positions of different hard rock layers in the overlying rock are shown in fig. 1.
The position and the bearing load of the hard rock stratum are determined and obtained by calculation, analysis and determination of geological data such as a histogram and the like near a working face and rock stratum mechanical parameters. The specific process can be preliminarily determined by adopting the following method, wherein the position and the bearing load of the hard rock layer above the coal bed are determined by the method:
in the formula: q is the formation bearing load (q)n)iLoading the upper n rock stratums of the i hard rock stratums to the i hard rock stratums; h is the thickness of each rock layer between the hard rock layer and the coal layer, hiIs the thickness of each formation; eiThe elastic modulus of each rock stratum, and gamma is the volume weight of the rock stratum; n is a bearing rock stratum, and i is the number of layers of an upper load rock stratum of the bearing rock stratum;
the hard formation is calculated from the first formation above the coal seam, n is also counted from the current formation, and when:
(qn)i＞(qn+1)i
and (5) the n +1 stratum is the (i + 1) th hard stratum, n starts counting from the i +1 th stratum again, and the steps are repeated until the surface is calculated.
The second step is that: determining the height wi of a cavity below the hard rock stratum according to the mining height of the coal seam, the distance between the hard rock stratum and the coal seam and the crushing and swelling characteristics of the rock stratum;
wi＝M-∑hi((Kp)i-1)
in the formula: m is the thickness of the mined coal seam, (Kp) i is the coefficient of crushing and expansion of each rock stratum between the ith hard rock stratum and the coal seam, and hi is the coefficient of crushing and expansion of the ith hard rock stratum to the coal seam.
The third step: adopting a clamped beam model to calculate the maximum deflection sinking deformation omega before each hard rock layer is damagedmax。
In the formula, LcFor the first time the block length is broken, q is the hard rock layer load, E is the hard rock layer modulus of elasticity, I is the moment of inertia of the rectangular section per unit width.
The i-th hard formation can be loaded by (q)n)iCalculated to obtain the length L of the primary breaking block bodycThe clamped beam model can be adopted for calculation:
in the formula, LcFor the first time breaking the block length, q is the hard rock loading, h is the hard rock thickness, σtIs the tensile strength of hard rock formations.
The fourth step: and starting from the 1 st hard rock stratum, judging whether the hard rock stratum can be broken or not. When the hard rock layer is not broken, the distance between the hard rock layer and the coal bed, namely the breaking height of the mining overburden rock; when the hard rock stratum is broken, starting next hard rock stratum judgment until the hard rock stratum which is not broken is judged; when the hard rock layer is damaged up to the uppermost part, the damage height of the overlying strata is the buried depth of the coal bed.
The method for determining the mining overburden rock damage height solves the problem that the mining overburden rock damage height is difficult to accurately determine before coal seam mining, and provides theoretical support for the work of safe and efficient stoping of a working face, reasonable design of gas extraction drill holes, evaluation of the stability of a surface building of a goaf after the stoping of the working face and the like. The method for determining the mining overburden rock damage height provided by the invention considers that when the rock stratum exceeds the ultimate deflection sinking value, the rock stratum is broken, so that whether the rock stratum is damaged or not is determined according to the relation between the maximum sinking deformation of the rock stratum and the height of a cavity at the lower part of the rock stratum, and the hard rock stratum is used as a main influence rock stratum in the mining overburden rock migration process, so that the hard rock stratum is determined to be used as a research object, and the mechanical analysis and breakage judgment are carried out on the hard rock stratum, so that the mining overburden rock damage height is determined more accurately, the safe and efficient stoping of a working face, the reasonable design of a gas extraction drill hole and the evaluation of the stability of a ground surface building of a goaf after the stoping of the working face are finished.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
Claims (5)
1. A method for determining the failure height of mining overburden is characterized by comprising the following steps:
s1, determining the bearing load and the layer position of the hard rock stratum in the overburden stratum of the stope, and sequentially naming the ith hard rock stratum from bottom to top (i is 1,2 and …);
s2, determining the height wi of a cavity below the hard rock stratum by combining the mining thickness of the coal seam, the distance between the hard rock stratum and the coal seam and the crushing and swelling characteristics of the rock stratum:
wi＝M-∑hi((Kp)i-1)
wherein M is the thickness of a mining coal seam, (Kp) i is the crushing expansion coefficient of each rock stratum between the ith hard rock stratum and the coal seam, (hi) is the thickness of each rock stratum between the ith hard rock stratum and the coal seam, and (wi) is the height of a cavity below the ith hard rock stratum;
s3, calculating the maximum deflection sinking deformation omega before each hard rock layer is damaged by adopting a clamped beam modelmaxTo obtain
In the formula, LcThe length of a primary broken block is q, the load of the hard rock stratum is q, the elastic modulus of the hard rock stratum is E, and I is the inertia moment of a rectangular section with unit width;
s4, starting from the 1 st hard rock stratum, judging whether the hard rock stratum is broken or not; when the hard rock layer is not broken, the distance between the hard rock layer and the coal bed, namely the breaking height of the mining overburden rock; when the hard rock stratum is broken, starting next hard rock stratum judgment until the hard rock stratum which is not broken is judged; when the hard rock layer is damaged up to the uppermost part, the damage height of the overlying strata is the buried depth of the coal bed.
2. The method for determining the mining overburden destruction height as recited in claim 1, wherein in the step S1, the level and the bearing load of the hard rock layer at the upper part of the stope are calculated by using the following formula:
(qn)i＞(qn+1)i
in the formula: q is the rock stratum bearing load, E is the elastic modulus of the rock stratum, h is the thickness of each rock stratum between the hard rock stratum and the coal bed, gamma is the rock stratum volume weight, n is the bearing rock stratum, and i is the number of layers of the upper load rock stratum of the bearing rock stratum;
the hard rock formation is calculated from the first rock formation above the coal seam, n is also counted from the hard rock formation, and when the following conditions are met:
(qn)i＞(qn+1)i
and (5) the n +1 stratum is the (i + 1) th hard stratum, n starts counting from the i +1 th stratum again, and the steps are repeated until the surface is calculated.
3. The method for determining a damage height of a mining overburden as claimed in claim 1, wherein in step S3, a clamped beam model is used to calculate a critical value L of a suspended span length of an initial fracture of a hard rock formationcObtaining the length of the first broken block and the inertia moment of the rectangular section
In the formula, LcFor the first time breaking the block length, q is the hard rock loading, h is the hard rock thickness, σtThe tensile strength of the hard rock layer, and b is the width of the rectangular section of the beam;
when the rectangular cross section of the rock formation is a unit width, i.e. b 1,
in the formula: omega is the deflection of the beam, E is the elastic modulus of the rock stratum; when x is 0, the bending deflection deformation of the clamped beam reaches a maximum value.
4. The method of determining a mining overburden destruction height as claimed in claim 1, wherein in step S4, when it is determined whether the hard rock layer is broken in the third step, the determination is made using a ω -value,
ω＝ωi-ωmax
when omega is more than 0, the rock stratum is broken; when omega is less than or equal to 0, the rock stratum is not broken.
5. The method of determining a mining overburden failure height as recited in claim 1, wherein tan Φ is 0.3.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115130311A (en) * | 2022-07-04 | 2022-09-30 | 河南大学 | Method for judging water inrush disaster of coal seam overlying strata separation layer |
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| CN104933266A (en) * | 2015-07-09 | 2015-09-23 | 西安科技大学 | Method for determining height of overlying stratum water guiding crack zone |
| CN107060761A (en) * | 2017-06-19 | 2017-08-18 | 内蒙古科技大学 | A kind of nearly horizontal mining in combined mining thick coal seam stope base object model first breaking space computing method |
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- 2020-12-29 CN CN202011599798.8A patent/CN112861068A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104484713A (en) * | 2014-11-24 | 2015-04-01 | 辽宁工程技术大学 | Prediction method for height of filling and mining water flowing fracture zone |
| CN104933266A (en) * | 2015-07-09 | 2015-09-23 | 西安科技大学 | Method for determining height of overlying stratum water guiding crack zone |
| CN107060761A (en) * | 2017-06-19 | 2017-08-18 | 内蒙古科技大学 | A kind of nearly horizontal mining in combined mining thick coal seam stope base object model first breaking space computing method |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115130311A (en) * | 2022-07-04 | 2022-09-30 | 河南大学 | Method for judging water inrush disaster of coal seam overlying strata separation layer |
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