CN110130895B - Coal pillar destruction method for weakening potential destruction surface of left coal pillar - Google Patents
Coal pillar destruction method for weakening potential destruction surface of left coal pillar Download PDFInfo
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- CN110130895B CN110130895B CN201910443568.3A CN201910443568A CN110130895B CN 110130895 B CN110130895 B CN 110130895B CN 201910443568 A CN201910443568 A CN 201910443568A CN 110130895 B CN110130895 B CN 110130895B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C41/00—Methods of underground or surface mining; Layouts therefor
- E21C41/16—Methods of underground mining; Layouts therefor
- E21C41/18—Methods of underground mining; Layouts therefor for brown or hard coal
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/24—Investigating strength properties of solid materials by application of mechanical stress by applying steady shearing forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0025—Shearing
Abstract
The invention belongs to the field of coal mines, and particularly relates to a coal pillar destruction method for weakening a potential destruction surface of a left coal pillar, which comprises the following steps: drilling a rock core on the upper-layer left coal pillar, processing the rock core into a test piece with the same height-diameter ratio as the left coal pillar, performing a uniaxial compression test, determining whether the failure mode of the test piece meets the shearing failure mode, and if so, entering the next step; the test piece is subjected to a variable angle shear test, and the internal friction angle of the test piece is measuredφThe method comprises the steps of measuring the position of a coal pillar on a coal seam, calculating an included angle α between a failure surface of a test piece and bearing pressure, calculating the position and the length of a weakened drill hole according to the measurement result of the test piece and the parameters of the remaining coal pillar and the coal seam roadway, wherein the starting point of the weakened drill hole is the side wall of the coal seam roadway, close to the coal pillar, and the weakened drill hole passes through the centroid of the remaining coal pillar, and drilling the weakened drill hole according to the calculation result to enable the remaining coal pillar to be damaged under the action of mine pressure.
Description
Technical Field
The invention belongs to the field of coal mines, and particularly relates to a coal pillar destruction method for weakening a potential destruction surface of a left coal pillar.
Background
Due to the limitation of factors such as mining level, equipment conditions, geological factors and the like, a large number of various coal pillars are reserved in the coal seam mining process and are used for supporting a top plate and protecting an upper coal seam roadway to ensure safe production. These coal pillars will be left in the ground permanently and cannot be extracted, resulting in a great waste of resources. More importantly, the existence of the coal pillar can cause stress concentration, so that the mining pressure of the lower coal seam is abnormal, and accidents such as frame pressing, roof caving, rock burst and the like are easy to happen. The reserved size of the lower coal seam protection coal pillar can be increased, the recovery rate is reduced, and resources are further wasted.
At present, resources are increasingly exhausted, energy supply is increasingly tense, and coal is taken as a high-quality non-renewable resource, so that the influence of coal pillars on mining is reduced as far as possible, the recovery rate is improved, and the accident rate is reduced. Aiming at the problem, experts, scholars and engineering technicians do a great deal of work with great efficiency and obtain better effect. E.g. by blasting means, hydraulic fracturing, supercritical CO2The method of pre-cracking, low-temperature liquid nitrogen pre-cracking and the like damages the upper coal pillar, plays a role in reducing the stress concentration of the coal pillar, and achieves the purposes of reducing the mining accidents of the lower coal seam and reducing the size of the coal pillar. However, these methods do not utilize the action of mine pressure, and are not designed for the form and characteristics of pillar destruction, so that the implementation effect is not ideal. The concrete points are as follows:
(1) the cost is high. The existing method does not fully utilize the acting force of the top and bottom plates on the coal pillar, and the integral crushing of the coal pillar is realized only by increasing the using amounts of explosive, fracturing fluid and low-temperature liquid nitrogen, so that the using amount of materials required by the coal pillar damage is too large, and the cost is increased.
(2) The technical difficulty is high. No treatment is performed according to the destruction form and destruction characteristics of the coal pillar. In the prior art, the integrity of the coal pillar is damaged by external force, so that the coal pillar can be damaged only by large external force, and the technical difficulty is increased.
(3) Low safety and poor effect. The prior art does not consider the factors, so that the goaf gas accumulation explosion is easy to explode, and a large potential safety hazard exists; in the hydraulic fracturing process, fracturing liquid easily flows into a goaf through a coal pillar crack, and the damage effect is poor.
Disclosure of Invention
The invention overcomes the defects of the prior art, and solves the technical problems that: the coal pillar destruction method is used for weakening the potential destruction surface of the coal pillar so as to reduce the mining accident rate of the lower coal seam and improve the resource recovery rate.
In order to solve the technical problems, the invention adopts the technical scheme that: a pillar failure method for weakening a potential failure face of a remaining pillar, comprising the steps of:
s1, drilling a rock core on the upper-layer left coal pillar, processing the rock core into a test piece with the same height-diameter ratio as the left coal pillar, performing a uniaxial compression test, and determining whether the failure mode of the test piece meets the shearing failure mode, if so, entering the next step;
s2, carrying out a variable angle shearing test on the test piece, and measuring the internal friction angle of the test pieceφCalculating an included angle α between the damage surface of the test piece and the supporting pressure;
s3, calculating the position and the length of the weakened drill hole according to the test piece measurement result and the parameters of the left coal pillar and the lower coal seam roadway; the starting point of the weakened drill hole is that the side wall of the coal seam roadway close to one side of the coal pillar is arranged, and the weakened drill hole passes through the centroid of the remaining coal pillar;
and S4, drilling the weakened drill hole according to the calculation result, so that the remaining coal pillar after drilling the weakened drill hole is damaged under the action of the mine pressure.
In step S2, an included angle α between the fracture surface of the test piece and the bearing pressure is calculated as:
α=(45°-0.5φ)。
in step S3, the calculation formula of the location and the length of the weakened hole is:
c 1=(H-0.5d)/tanα-0.5a-h；
L=(H-0.5d)/sinα；
wherein the content of the first and second substances,c 1to weaken the distance from the initial position of the drill hole to the top plate of the lower coal seam;Lin order to weaken the length from the initial position of the drilling hole to the centroid of the remaining coal pillar;Hthe horizontal distance from the centroid of the left coal pillar to the centroid of the roadway of the lower coal seam;athe height of the left coal pillar;bthe width of the left coal pillar;canddthe height and the width of a lower coal seam roadway are respectively;hthe vertical distance between the coal pillar bottom plate and the lower coal seam top plate is adopted;αis the angle between the fracture surface and the supporting pressure under the action of the supporting pressure.
In step S3, before calculating the location and length of the weakened borehole, the method further includes the following steps: calculating whether the parameters of the left coal pillars and the lower coal seam roadway meet the conditions:
(0.5a+h)*tanα+0.5d＜H＜(0.5a+h+c)*tanα+0.5d；
wherein the content of the first and second substances,athe height of the left coal pillar;Hthe horizontal distance from the centroid of the left coal pillar to the centroid of the roadway of the lower coal seam;canddthe height and the width of a lower coal seam roadway are respectively;hthe vertical distance between the coal pillar bottom plate and the lower coal seam top plate is adopted;αis the angle between the fracture surface and the supporting pressure under the action of the supporting pressure.
Compared with the prior art, the invention has the following beneficial effects:
the invention can realize the damage of the coal pillar by only depending on the supporting pressure acting on the coal pillar without additional technical measures, fully utilizes the mine pressure, reduces the material usage amount and reduces the cost.
The invention reduces the critical strength required by the coal pillar damage by weakening the potential damage surface of the left coal pillar, and does not need to wholly damage the coal pillar, thereby reducing the technical difficulty.
Compared with the method for mining the coal pillar by blasting and penetrating, the method for mining the coal pillar has the advantages that the potential damage surface of the coal pillar is weakened, the coal pillar is damaged, and the method has the advantages of being high in safety and good in effect. The potential safety hazard of gas accumulation and explosion in the goaf is eliminated; the method solves the problem that when a hydraulic fracturing method is used, fracturing liquid easily flows into a goaf through a coal pillar crack, and the damage effect is poor.
Drawings
FIG. 1 is a schematic sectional view showing the positional relationship between a remaining coal pillar and a lower coal seam stoping roadway.
FIG. 2 is a schematic cross-sectional view of a calculation of the distance from the location of a weakened borehole to the roof in a lower seam roadway.
FIG. 3 is an enlarged partial cross-sectional view of the calculation of the distance from the location of a weakened borehole to the roof in the lower seam roadway.
FIG. 4 is a schematic view of a pillar failure after weakening of the potentially destructive face.
In the figure: 1. a coal seam is laid; 2. leaving the coal pillars; 3. a coal seam roof is arranged; 4. a coal layer roadway is arranged; 5. a lower coal seam stoping roadway; 6. weakening the bore.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments; all other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention provides a coal pillar destruction method for weakening a potential destruction face of a left coal pillar, which has the occurrence conditions that the left coal pillar 2 exists above a lower coal seam 1, the left coal pillar 2 is used for supporting an upper coal seam roof 3 and protecting an upper coal seam roadway 4, and toxic and harmful gases such as gas, CO and the like exist on two sides of the left coal pillar 2. The coal pillar of this embodiment destroys, it establishes the shape to reserve of the clearly left-over coal pillar 2 in the benefit exploration, size, leave over the vertical distance between the bottom plate of coal pillar 2 and the roof of lower coal seam 1, leave over the distance of the centroid of coal pillar 2 to the centroid of lower coal seam stoping tunnel 5 and leave over behind the poisonous, harmful gas in 2 both sides of coal pillar, it gets the core to leave over coal 2 post drilling in the upper coal seam, carry out the uniaxial compression test after processing the core into the test piece with the same height-diameter ratio of coal pillar, confirm whether its destruction form accords with the shearing destruction form, if accord with this form, then carry out the angle-changing shearing test, record the internal friction angleφCalculating an included angle α between the fracture surface and the supporting pressure under the action of the supporting pressure, and selecting the proper position and sum of the weakened drill holes 6 in the mining roadway 5 of the lower coal seam according to the included angle αAnd (3) drilling an angle, so that the fracture surface of the remaining coal pillar 2 is weakened, and the weakened remaining coal pillar 2 is damaged along the potential fracture surface under the action of mine pressure.
On the basis of the above embodiment:
as shown in fig. 1, the method is performed under the conditions that a left coal pillar 2 is present above a lower coal seam 1 for supporting an upper coal seam roof 3 and protecting an upper coal seam roadway 4, and toxic and harmful gases such as gas and CO are present on both sides of the left coal pillar. Coal is mainly characterized by coal seam groups, and generally mined from top to bottom in sequence, so a large amount of residual coal pillars mined from the upper coal seam exist. After the coal layer is mined, a large amount of toxic and harmful gases such as gas, CO and the like exist in the goaf at the two sides of the remaining coal pillar.
The invention is suitable for the left coal pillar and is provided with a cuboid or cube in shape, firstly, a core needs to be drilled on the upper coal layer left coal pillar 2, and the core needs to be processed into a test piece with the same height-diameter ratio as the coal pillar after the core is processed into a test piece with the same height-diameter ratio as the coal pillar in consideration of the larger influence of the height-diameter ratio on the damage form of the left coal pillar 2, and then a uniaxial compression test is carried out, and whether the damage form of the test piece accords with the shearing damage form is determined from the angle of the; if the form is satisfied, a variable angle shearing test is carried out, and the internal friction angle is measuredφAnd calculating an included angle α between the bearing pressure and a fracture surface of a test piece with the same height-diameter ratio as the left coal pillar 2 under the action of the bearing pressure, wherein the calculation formula is as follows:
α=(45°-0.5φ)； （1）
as shown in fig. 2 and 3, in combination with actual working conditions, a weakened borehole 6 starts to be drilled in the lower coal seam mining roadway, the starting point of the weakened borehole 6 is that the lower coal seam roadway 5 is close to the side wall of the coal pillar, and the weakened borehole 6 passes through the centroid of the remaining coal pillar 2;
the included angle α is obtained from the experimental results and equation (1), and the location and length of the appropriate weakened borehole are calculated as follows:
c 1=(H-0.5d)/tanα-0.5a-h； （2）
L=(H-0.5d)/sinα； （3）
in the formula:c 1to weaken the distance from the position of the drill hole 6 to the top plate in the lower coal seam roadway 5; L the borehole 6 is obliquely long for weakening;Hthe horizontal distance from the centroid of the left coal pillar 2 to the centroid of the lower coal layer roadway 5 is obtained;athe height of the left coal pillar 2; b is the width of the left coal pillar 2;canddthe height and the width of the lower coal seam roadway 5 are respectively;hthe vertical distance between the bottom plate of the remaining coal pillar 2 and the top plate of the lower coal seam, and α the included angle between the damaged surface and the supporting pressure under the action of the supporting pressure.
Considering that the starting position of the weakened borehole 6 should be located between the roof and the floor of the lower coal seam, the calculation formula for the position and length of the weakened borehole 6 should satisfy the following condition:
(0.5a+h)*tanα+0.5d＜H＜(0.5a+h+c)*tanα+0.5d （4）
according to the result obtained by the formula calculation, holes are drilled in the lower coal seam roadway 5 in the direction of the center of the left coal pillar, the potential fracture surface of the left coal pillar 2 above the lower coal seam mining roadway 5 in the inclined direction is weakened, and the weakened left coal pillar 2 is broken along the potential fracture surface under the action of mine pressure, as shown in fig. 4.
Example (b):
the height a and the width b of a certain rectangular coal pillar 2 are respectively 3m and 5m, the height c and the width d of a lower coal seam stoping roadway 5 are respectively 3m and 4.5m, the vertical distance H between a bottom plate of the coal pillar 2 and a top plate of a lower coal seam 1 is 20m, and the horizontal distance H from the centroid of the coal pillar 2 to the centroid of the lower coal seam stoping roadway 5 is 15 m.
Drilling a core for the upper coal bed remaining coal pillar 2, considering that the height-diameter ratio has larger influence on the damage form of the remaining coal pillar 2, processing the core into a test piece with the same height-diameter ratio as the coal pillar, performing a uniaxial compression test, and determining that the damage form of the test piece conforms to the shear damage form from the angle of the test; further carrying out a variable angle shearing test to measure the internal friction angleφCalculating an included angle α (45-0.5) between the fracture surface of the sample with the same height-diameter ratio as the left coal pillar 2 and the supporting pressure under the action of the supporting pressure according to the formula (1)φ)=30°。
In order to ensure the weakening of the fracture surface of the remaining coal pillar, the remaining coal pillar is broken along the potential fracture surface under the action of mine pressure. The following calculation was performed using calculation formulas (2) to (3):
c 1=(H-0.5d)/tanα-0.5a-h=0.58m；
L=(H-0.5d)/sinα=25.5m；
calculating formula (4) according to the position and the length of the weakened drilling hole, and meeting the following conditions:
(0.5a+h)*tanα+0.5d＜H＜(0.5a+h+c)*tanα+0.5d；
substituting the mine-related parameters into the above formula, one can obtain:
14.6(m)＜H＜16.4m；
through verification, the horizontal distance H =15m from the centroid of the mine remaining coal pillar 2 to the centroid of the lower coal seam stoping roadway 5 meets the applicable conditions of the method.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (4)
1. A coal pillar destruction method for weakening a potential destruction surface of a remaining coal pillar, comprising the steps of:
s1, drilling a rock core on the upper-layer left coal pillar, processing the rock core into a test piece with the same height-diameter ratio as the left coal pillar, performing a uniaxial compression test, and determining whether the failure mode of the test piece meets the shearing failure mode, if so, entering the next step;
s2, carrying out a variable angle shearing test on the test piece, and measuring the internal friction angle of the test pieceφCalculating an included angle α between the damage surface of the test piece and the supporting pressure;
s3, calculating the position and the length of the weakened drill hole (6) according to the test piece measurement result and the parameters of the left coal pillar (2) and the lower coal seam roadway (5); the starting point of the weakened drilling hole (6) is that the side wall of the coal seam roadway (5) close to one side of the coal pillar, and the weakened drilling hole (6) passes through the centroid of the left coal pillar (2);
and S4, drilling the weakened drill hole (6) according to the calculation result, and enabling the remaining coal pillar (2) drilled with the weakened drill hole (6) to be damaged under the action of mine pressure.
2. The coal pillar destruction method for weakening a potential destruction surface of a remaining coal pillar as claimed in claim 1, wherein in the step S2, the included angle α between the destruction surface of the test piece and the bearing pressure is calculated as follows:
α=(45°-0.5φ)。
3. the coal pillar destruction method for weakening the potential destruction surface of the remaining coal pillar as claimed in claim 1, wherein in the step S3, the calculation formula of the position and the length of the weakened drilling hole (6) is:
c 1=(H-0.5d)/tanα-0.5a-h；
L=(H-0.5d)/sinα；
wherein the content of the first and second substances,c 1in order to weaken the distance from the initial position of the drilling hole (6) to the top plate of the lower coal seam;Lin order to weaken the length from the initial position of the drill hole (6) to the centroid of the remaining coal pillar (2);Hthe horizontal distance from the centroid of the left coal pillar (2) to the centroid of the lower coal seam roadway;athe height of the left coal pillar;bthe width of the left coal pillar;canddthe height and the width of the lower coal seam roadway (5) are respectively;hthe vertical distance between the coal pillar bottom plate and the lower coal seam top plate is adopted;αis the angle between the fracture surface and the supporting pressure under the action of the supporting pressure.
4. The coal pillar destruction method for weakening the potential destruction surface of the remaining coal pillar as claimed in claim 1, wherein the step S3 further comprises the following steps before calculating the position and length of the weakened drilling hole (6): calculating whether the parameters of the left coal pillars (2) and the lower coal layer roadway (5) meet the conditions:
(0.5a+h)*tanα+0.5d＜H＜(0.5a+h+c)*tanα+0.5d；
wherein the content of the first and second substances,athe height of the left coal pillar;Hthe horizontal distance from the centroid of the left coal pillar (2) to the centroid of the lower coal seam roadway;canddthe height and the width of the lower coal seam roadway (5) are respectively;hthe vertical distance between the coal pillar bottom plate and the lower coal seam top plate is adopted;αis the angle between the fracture surface and the supporting pressure under the action of the supporting pressure.
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| CN110714764B (en) * | 2019-12-10 | 2020-10-13 | 山西工程技术学院 | Short-distance overlying residual coal pillar pressure relief method |
| CN113266356A (en) * | 2021-06-17 | 2021-08-17 | 天地科技股份有限公司 | Hydraulic weakening method for upper coal pillar supporting pressure in short-distance coal seam mining |
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