AU2015387618B2 - Method for fracturing filler wall left behind in adjacent coal-mining face - Google Patents

Method for fracturing filler wall left behind in adjacent coal-mining face Download PDF

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Publication number
AU2015387618B2
AU2015387618B2 AU2015387618A AU2015387618A AU2015387618B2 AU 2015387618 B2 AU2015387618 B2 AU 2015387618B2 AU 2015387618 A AU2015387618 A AU 2015387618A AU 2015387618 A AU2015387618 A AU 2015387618A AU 2015387618 B2 AU2015387618 B2 AU 2015387618B2
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AU
Australia
Prior art keywords
mining
filler
coal
behind
fracturing
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Ceased
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AU2015387618A
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AU2015387618A1 (en
Inventor
Changliang HAN
Chuangxin LV
Dongjiang PAN
Fei Xue
Nong Zhang
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China University of Mining and Technology CUMT
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China University of Mining and Technology CUMT
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Priority to CN201510134567.2A priority Critical patent/CN104847406B/en
Priority to CN201510134567.2 priority
Application filed by China University of Mining and Technology CUMT filed Critical China University of Mining and Technology CUMT
Priority to PCT/CN2015/095914 priority patent/WO2016150188A1/en
Publication of AU2015387618A1 publication Critical patent/AU2015387618A1/en
Application granted granted Critical
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Classifications

    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21FSAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
    • E21F15/00Methods or devices for placing filling-up materials in underground workings
    • E21F15/02Supporting means, e.g. shuttering, for filling-up materials
    • E21F15/04Stowing mats; Goaf wire netting; Partition walls

Abstract

A method for fracturing a filler wall left behind in an adjacent coal-mining face, applicable in continuous pressure-relief mining of a coal seam group at a great depth. A drill hole (2) distribution scheme, parameters, and a volume of an explosive charge are designed on the basis of the size of a filler wall (1), a construction scheme for same, and a state of earlier damages of same; one to three rows of downward tilted drill holes are constructed by an advancing coal-mining face (3) on a filler wall left behind and reused by an adjacent coal-mining face (4) in a tunnel; one to two rows of the drill holes in the rear within an extremity hydraulic frame (6) are filled with the explosive charge and sealed; as the coal-mining face advances, the drill holes filled with the explosive charge in the rear within the extremity hydraulic frame enter the rear side of the coal-mining face, microcracks on the filler wall caused by earlier mining pressure are utilized to intensify cracking of the filler wall, and, combined with the effect of a lagging mining-induced stress, the filler wall left behind is ultimately fractured. The method allows fracturing of the filler wall left behind in a goaf by the adjacent coal-mining face, thus effectively eliminating an effect of stress concentration posed by the filler wall to upper and lower adjacent coal seams, implementing the goal of continuous pressure relief, and solving safety risks of adjacent coal seam mining.

Description

Description
METHOD FOR FRACTURING FILLER WALL LEFT BEHIND IN ADJACENT COAL-MINING FACE
I Field of the Invention
The present invention relates to a method for fracturing a filler wall left behind in an adjacent coal-mining face, which is especially applicable to continuous pressure relief mining of coal seam groups at a great depth.
II Background of the Invention
Gob-side entry retaining is to construct a wall with certain bearing capacity along edge of a gob to retain a stoping roadway at the adjacent coal-mining face for stoping of the current coal-mining face. It is one of key techniques for continuous pressure relief mining of coal seam group at a great depth, and is developed to overcome safety difficulties, such as rock burst, coal and gas outburst, high gas, and high ground pressure, etc.
Presently, constructing a wall for gob-side entry retaining with cement-based materials is applied more and more, especially in deep mining areas. A cement-based wall becomes hardened quickly and has high early strength. Assisted with reinforcing means such as shear-resistant anchor rods and three-dimensional reinforcing ribs, etc., such a cement-based wall can essentially ensure normal use of the stoping roadways at the two coal-mining faces. Though a cement-based wall may have micro-fractures under twice mining disturbances, it still builds up resistance continuously, and its load bearing capacity cannot be destructed automatically; hence, a concentrated stress area is formed between upper and lower adjacent coal seams, and the purpose of continuous pressure relief cannot be attained, still resulting in a potential safety hazard in the mining of adjacent coal seams. Therefore, there is an urgent need for a method for fracturing the filler wall left behind in a gob of an adjacent coal-mining face more effectively to destruct the bearing capacity of the retained filler wall, for stoping at the current coal-mining face.
Throughout the specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.
Modifications and variations such as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.
The preceding discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge of the person skilled in the art in any jurisdiction as at the priority date of the application.
2015387618 07 Sep 2018
III Contents of the Invention
Technical problem: To overcome the drawbacks in the prior art, the present invention provides a method for fracturing a filler wall left behind in an adjacent coal-mining face.
Technical scheme: The method for fracturing a filler wall left behind in an adjacent coal-mining face provided in the present invention comprises:
a. Designing distribution scheme and parameters of drilled holes and a volume of an explosive charge according to the size, construction scheme and earlier-stage breakage state of the filler wall;
b. One to three rows of downward tilted drill holes at an inclination of about 10-25° are constructed by an advancing coal-mining face on a filler wall left behind and reused by an adjacent coal-mining face in a roadway;
c. Executing coal mining while loading the explosive at an explosive loading interval not greater than the pushing interval of an end hydraulic support, and grouting slurry and filling the explosive into one to two columns of drilled holes formed in the rear portion of the interior of the end hydraulic support; wherein, the slurry is made of SCA-I or SCA-II static fracturing agent mixed with water, and the orifices of the drilled holes are sealed with yellow mud or polyurethane foams;
d. Advancing the coal-mining face, so that the drilled holes loaded with the explosive in the rear portion of the interior of the end hydraulic support are left behind the coal-mining face and expansion pressure is generated in the drilled holes after 3 to 8 hours, enhancing the fracturing of the filler wall with micro-fractures generated under earlier-stage mine pressure on the filler wall, and finally fracturing the filler wall left behind under the influence of lagged mining-induced stress;
e. Repeating the steps b and c, till the fracturing of the filler wall left behind in the adjacent coal-mining face is finished.
The inclination angle of the downward-inclined drilled holes is 10-25°, the hole diameter is 40-100mm, the pitch-row of the drilled holes is 0.4-0.8m, the array pitch is 0.3-0.7m, the distance of the orifices of the drilled holes from the roof or floor is 0.5~1.0m, the distance of the bottoms of the drilled holes to the filler wall at the side of the gob is 20-30cm.
The water/agent ratio of the slurry is 0.25-0.35, the volume of an explosive charge of the static fracturing agent per unit volume of filler wall is 10~25kg.
Beneficial effects: With the above-mentioned technical scheme, compared with the prior art, the method provided in the present invention attains a good fracturing effect, is low in cost, easy to operate, and safe and reliable. Specifically, the method has the following advantages:
) The static fracturing agent has high expansion force, the fracturing of the filler wall left behind in the adjacent coal-mining face in the gob is enhanced with the micro-fractures generated under earlier-stage mine pressure on the filler wall, and the filler wall is fractured finally with the assistance of the lagged mining-induced stress. The overlaying strata can subside adequately,
2015387618 13 Jun2017 and the influence of stress concentration of the wall on the upper and lower adjacent coal seams is effectively eliminated, the purpose of continuous pressure relieving is attained, and a potential safety hazard in mining of the adjacent coal seam is eliminated.
) The static fracturing process does not produce slungshot, dust, or waste gas, and is highly safe.
) Since the leading drilled holes are inclined at 10-25°, the workers can operate conveniently; in addition, a characteristic that the wall tends to have tensile failure owing to its brittleness along a 45° oblique section is partially used, the fracturing power is effectively saved, and the fracturing cost is reduced.
) The workers can operate safely at the leading coal face or in the end hydraulic support.
) The procedures are simple and easy to operate, the labor intensity of the workers is lowered, and the operation time is reduced.
IV Brief Description of the Drawings
Fig. 1 is a schematic diagram of a top view of stoping at a coal-mining face according to the present invention;
Fig. 2 is a schematic diagram of the distribution of the drilled holes near an end hydraulic support according to the present invention;
Fig. 3 is a sectional view of the drilled holes of the wall according to the present invention.
Among the figures: 1 - filler wall; 2 - drilled hole; 3 - coal-mining face; 4 - adjacent coal-mining face; 5 - static fracturing agent; 6 - end hydraulic support; 7 - yellow mud or polyurethane foam.
V Detailed Description of the Embodiments
Hereunder the present invention will be further detailed in an embodiment with reference to the accompanying drawings.
The method for fracturing a filler wall left behind in an adjacent coal-mining face provided in the present invention comprises the following steps:
a. Designing distribution scheme and parameters of drilled holes 2 and a volume of an explosive charge according to the size, construction mode and earlier-stage breakage state of the filler wall 1;
b. One to three rows of downward tilted drill holes 2 are constructed by an advancing coal-mining face 3 on a filler wall 1 left behind and reused by an adjacent coal-mining face 4 in a roadway; wherein, the inclination angle of the downward-inclined drilled holes 2 is 10-25°, the hole diameter is 40-100mm, the pitch-row of the drilled holes is 0.4-0.8m, the array pitch is 0.3-0.7m, the distance of the orifices of the drilled holes from the roof or floor is 0.5~1.0m, the distance of the bottoms of the drilled holes from the filler wall 1 at the side of the gob is 20~30cm;
2015387618 13 Jun2017
c. Executing coal mining while loading the explosive at an explosive loading interval not greater than the pushing interval of an end hydraulic support 6, and grouting slurry and filling the explosive into one to two columns of drilled holes 2 formed in the rear portion of the interior of the end hydraulic support 6; wherein, the slurry is made of SCA-I or SCA-II static fracturing agent 5 mixed with water, and the orifices of the drilled holes are sealed with yellow mud or polyurethane foams 7; the water/agent ratio of the slurry is 0.25-0.35, the volume of an explosive charge of the static fracturing agent 5 per unit volume of filler wall 1 is 10~25kg.
d. Advancing the coal-mining face 3, so that the drilled holes 2 loaded with the explosive in the rear portion of the interior of the end hydraulic support 6 are left behind the coal-mining face 3 and expansion pressure is generated in the drilled holes 2 after 3 to hours, enhancing the fracturing of the filler wall 1 with micro-fractures generated under earlier-stage mine pressure on the filler wall 1, and finally fracturing the filler wall 1 left behind under the influence of lagged mining-induced stress;
e. Repeating the steps b and c, till the fracturing of the filler wall left behind in the adjacent coal-mining face is finished.
Embodiment 1: The dimensions of a filler wall 1 left behind for reuse at an adjacent coal-mining face 4 are 3m X 2.6m (W XH), the filler wall left behind is constructed with C30 paste material pumped via a pump, and is assisted with shear-resistant anchor rod. When the current coal-mining face 3 is stoped, a stress concentration peak occurs at 13m leading the coal-mining face, the stress concentration factor is 1.67. At that point, the overall quality of the nearby filler wall 1 is good, and the filler wall 1 has a small quantity of fractures.
The leading coal-mining face 3 is at 30m distance from the current coal-mining face, two rows of downward-inclined drilled holes 2 at 15° inclination angle are constructed in the roadway towards the filler wall 1, the hole diameter is 50mm, the pitch-row is 0.6m, the array pitch is 0.6m, the distance from the orifices of the drilled hole to the roof is 1.0m, the distance from the orifices of the drilled hole to the floor is 1.0m, and the distance from the bottom of the drilled hole to the other side of the filler wall 1 is 25 cm.
Coal mining and explosive loading are executed synchronously. Under a principle that the explosive loading interval is not greater than the pushing interval (0.6m here) of the end hydraulic support 6, it is determined that one column of drilled holes in the rear portion of interior of the end hydraulic support 6 will be loaded with the explosive. A SCA-II static fracturing agent 5 is used, and the water/agent ratio is about 0.3, about 10cm length is reserved at the orifice of the drilled hole, and the orifice of the drilled hole is sealed with yellow mud 7. The volume of an explosive charge of the static fracturing agent 5 per unit volume of the filler wall 1 is 10~25kg.
As the coal-mining face 3 is advanced, the drilled holes 2 loaded with the explosive are left behind the coal-mining face 3, expansion pressure is generated in the drilled holes 2 after 3 to 8 hours, and the fracturing of the filler wall 1 is enhanced by utilizing micro-fractures generated under earlier-stage mine pressure on the filler wall 1. The filler wall 1 left behind is finally fractured under the influence of lagged mining-induced stress.
Please see Figs. 1, 2, and 3.
2015387618 07 Sep 2018

Claims (3)

  1. Claims
    1 A method for fracturing a filler wall left behind in an adjacent coal-mining face, comprising the following steps:
    a. designing distribution scheme and parameters of drilled holes and a volume of an explosive charge according to the size, construction mode and earlier-stage breakage state of the filler wall;
    b. one to three rows of downward tilted drill holes at an inclination of 10-25° are constructed by an advancing coal-mining face on a filler wall left behind and reused by an adjacent coal-mining face in a roadway;
    c. executing coal mining while loading the explosive at an explosive loading interval not greater than the pushing interval of an end hydraulic support, and grouting slurry and filling the explosive into one to two columns of drilled holes formed in the rear portion of the interior of the end hydraulic support; wherein, the slurry is made of SCA-I or SCA-II static fracturing agent mixed with water, and the orifices of the drilled holes are sealed with yellow mud or polyurethane foams;
    d. advancing the coal-mining face , so that the drilled holes loaded with the explosive in the rear portion of the interior of the end hydraulic support are left behind the coal-mining face and expansion pressure is generated in the drilled holes after 3 to 8 hours, enhancing the fracturing of the filler wall with micro-fractures generated under earlier-stage mine pressure on the filler wall, and finally fracturing the filler wall left behind under the influence of lagged mining-induced stress;
    e. repeating the steps b and c, till the fracturing of the filler wall left behind in the adjacent coal-mining face is finished.
  2. 2 The method for fracturing a filler wall left behind in an adjacent coal-mining face according to claim 1, wherein: the inclination angle of the downward-inclined drilled holes is 10-25°, the hole diameter is 40~100mm, the pitch-row of the drilled holes is 0.4-0.8m, the array pitch is 0.3-0.7m, the distance from the orifices of the drilled holes to the roof or floor is 0.5~1.0m, the distance from the bottoms of the drilled holes to the filler wall at the side of the gob is 20~30cm.
  3. 3 The method for fracturing a filler wall left behind in an adjacent coal-mining face according to claim 1, wherein: the water/agent ratio of the slurry is 0.25-0.35, the volume of an explosive charge of the static fracturing agent per unit volume of the filler wall is 10~25kg.
    1/2
    Fig. 1
    Fig. 2
    2/2
    Fig. 3
AU2015387618A 2015-03-25 2015-11-30 Method for fracturing filler wall left behind in adjacent coal-mining face Ceased AU2015387618B2 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
CN201510134567.2A CN104847406B (en) 2015-03-25 2015-03-25 Method for fracturing retained filled wall of adjacent coal face
CN201510134567.2 2015-03-25
PCT/CN2015/095914 WO2016150188A1 (en) 2015-03-25 2015-11-30 Method for fracturing filler wall left behind in adjacent coal-mining face

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AU2015387618A1 AU2015387618A1 (en) 2017-07-06
AU2015387618B2 true AU2015387618B2 (en) 2018-11-01

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AU (1) AU2015387618B2 (en)
WO (1) WO2016150188A1 (en)
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Publication number Priority date Publication date Assignee Title
CN104847406B (en) * 2015-03-25 2017-04-12 中国矿业大学 Method for fracturing retained filled wall of adjacent coal face
CN106761543B (en) * 2016-12-02 2019-07-19 淮北矿业股份有限公司 A method of drilling misses section by goaf
CN107035370A (en) * 2017-05-05 2017-08-11 太原理工大学 One kind cuts top pressure relief method for gob side entry retaining static crushing

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ZA201701756B (en) 2019-06-26
WO2016150188A1 (en) 2016-09-29
CN104847406A (en) 2015-08-19
CN104847406B (en) 2017-04-12
AU2015387618A1 (en) 2017-07-06

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