METHOD FOR OVER-PIT AND UNDER-PIT COOPERATIVE CONTROL OF ROOFS OF FAR AND NEAR FIELDS OF AN EXTRA-LARGE STOPING SPACE

Abstract

The invention relates to a control method for a hard roof of a coal mine, specifically to a method for over-pit and under-pit cooperative control of roofs of far and near fields of an extra-large stoping space. The method provided by the invention overcomes the problem of lack of comprehensive and cooperative control methods for hard roofs of far and near fields of an extra-large stoping space in the prior art. According to a technical scheme in the invention, the method comprises an over-pit vertical hole hydraulic fracturing method, an over-pit L-shaped hole hydraulic fracturing method, an over-pit highly-energy-gathered repetition pulse strong shock wave method, an under-pit water injection method, an under-pit layered blasting method and an under-pit hydraulic fracturing method. The method has the advantages that 1) the problem of great mine pressure of the extra-large stoping space is effectively controlled through over-pit and under-pit cooperative control of the hard roofs of far and near fields; 2) advantages of the variety of methods are given to full play and disadvantages of the variety of methods are mutually compensated, so weakening effect on the hard roofs is substantially improved; and 3) all the over-pit and under-pit holes can be used independently or be used in a shared way, so time, manpower, material resources and money used for hole perforation can be greatly reduced.

Claims

1. A method for over-pit and under-pit cooperative control of roofs of far and near fields of an extra-large stoping space, including a method for controlling a hard roof by means of hydraulic fracturing via an over-pit vertical bore of a far field of an extra-large stoping space, a method for controlling a hard roof by means of hydraulic fracturing via an over-pit L-shaped bore of a far field of an extra-large stoping space, a method for controlling a hard roof via an over-pit strong repeating impact pulse of high energy density of a far field of an extra-large stoping space, a method for controlling a hard roof via down-pit water injection of a near field of an extra-large stoping space, a method for controlling a hard roof via down-pit stratified blasting of a near field of an extra-large stoping space, and a method for controlling a hard roof via weakening by hydraulic fracturing of a near field of an extra-large stoping space; characterized in that the method comprises following steps: firstly, the hard roof of the far field is controlled by adopting the method for controlling a hard roof by means of hydraulic fracturing via an over-pit vertical bore of a far field of an extra-large stoping space; secondly, the hard roof of each target stratum is controlled by adopting the method for controlling a hard roof by means of hydraulic fracturing via an over-pit L-shaped bore of a far field of an extra-large stoping space; then, the weakened hard roof of each target stratum is further controlled by adopting the method for controlling a hard roof via an over-pit strong repeating impact pulse of high energy density of a far field of an extra-large stoping space; so far, the over-pit constructive control of the hard roof of the far field of the extra-large stoping space has been completed, simultaneously or successively, the down-pit constructive control of the hard roof of the near field of the extra-large stoping space is conducted, firstly, the near-field hard roof is preliminary controlled by adopting the method for controlling a hard roof via down-pit water injection of a near field of an extra-large stoping space; then, the near-field hard roof is controlled and weakened in layers by adopting the method for controlling a hard roof via down-pit stratified blasting of a near field of an extra-large stoping space; finally, the near-field hard roof is controlled by adopting the method for controlling a hard roof via weakening by hydraulic fracturing of a near field of an extra-large stoping space.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0019] FIG. 1 is the schematic constructional view of the far-field over-pit vertical bore hydraulic fracturing hard roof control method for extra-large stoping space and the far-field over-pit L-shaped bore hydraulic fracturing hard roof control method for extra-large stoping space.

[0020] FIG. 2 is the schematic structural view of blast bore and hydraulic fracturing bore;

LIST OF REFERENCE MARKS

[0021] 1-Lshaped bore, 2vertical bore, 3perforating slots, 4ground, 5far-field hard roof, 6near-field hard roof, 7working face, 8blast bore, 9hydro-fracturing bores, 10wedge pre-splitting crack.

DETAILED DESCRIPTION

[0022] The method for over-pit and under-pit cooperative control of a roofs of far and near fields of an extra-large stoping space includes a method for controlling a hard roof by means of hydraulic fracturing via an over-pit vertical bore of far field of an extra-large stoping space, a method for controlling a hard roof by means of hydraulic fracturing via an over-pit L-shaped bore of far field of an extra-large stoping space, a method for controlling a hard roof via an over-pit strong repeating impact pulse of high energy density of far field of an extra-large stoping space, a method for controlling a hard roof via down-pit water injection of near field of an extra-large stoping space, a method for controlling a hard roof via down-pit stratified blasting of near field of an extra-large stoping space, and a method for controlling a hard roof via weakening by hydraulic fracturing of near field of an extra-large stoping space;

[0023] firstly, the hard roof of far field is controlled by adopting the method for controlling a hard roof by means of hydraulic fracturing via an over-pit vertical bore of far field of an extra-large stoping space, which specifically includes the following steps:

[0024] a. drilling a vertical hydraulic-fracturing bore 2 from the ground 4 towards the far-field hard roof 5 overlying a working face 7, with the distance from the end of the fracturing bore to the working face being 100-350 m;

[0025] b. injecting fracturing fluid from a fracturing string into the vertical hydraulic-fracturing bore 2 and a guidance fracturing bore by means of a high pressure water perforator and a fracturing device, and slotting the stratum of the far-field hard roof 5 via a perforator gun;

[0026] c. after the formation of perforating slots 3 by perforating the target stratum, continuing to inject the fracturing fluid from the fracturing string, and simultaneously injecting proppant into the annulus between the fracturing string and a sleeve to finish the hydraulic fracturing work of vertical hydraulic-fracturing bore 2, after which performing a reverse circulation purge via a perforated tube and a check valve, and then lifting the fracturing string to conduct the work of the next target stratum; after the completion of this work of all the target strata, lifting the fracturing string from the sleeve out of the fracturing bore.

[0027] secondly, the hard roof of each target stratum is controlled by adopting the method for controlling a hard roof by means of hydraulic fracturing via an over-pit L-shaped bore of far field of an extra-large stoping space, which specifically includes the following steps:

[0028] d. drilling an L-shaped hydraulic-fracture bore 1 from the ground 4 towards the far-field hard roof 5 overlying the working face 7, with the vertical distance from the horizontal bore to the working face 7 being 100-350 m;

[0029] e. injecting fracturing fluid into the L-shaped hydraulic-fracturing bore 1 from a fracturing string by means of a high pressure water perforator and a fracturing device, and perforating and slotting the stratum of the hard roof at high level via a perforator gun;

[0030] f. after the formation of perforating slots 3 by perforating the target stratum in segments, continuing to inject fracturing fluid from a fracturing string, and simultaneously injecting proppant into the annulus between the fracturing string and a sleeve to finish the hydraulic fracturing work of the target stratum having horizontal bore in segments via the L-shaped hydraulic-fracturing bore; after the completion of this work, lifting the fracturing string from the sleeve out of the fracturing bore;

[0031] then, the weakened hard roof of each target stratum is further controlled by adopting the method for controlling a hard roof via an over-pit strong repeating impact pulse of high energy density of far field of an extra-large stoping space, which specifically includes the following steps:

[0032] g. drilling a vertical impact bore from the ground 4 towards the far-field hard roof 5 overlying the working face 7, with the vertical distance from the end of the vertical impact bore to the working face being 100-350 m;

[0033] h. injecting clean water into the vertical impact bore until it is saturated;

[0034] i. inserting the probe of strong repeating impact pulse generator into the vertical impact bore, and submerging it into the clean water; energizing the probe of strong repeating impact pulse generator, so that it can create impulsed high-voltage discharge towards the target stratum of the hard roof at high level, so as to form a crack and widen it to finish the impact and weakening work of the target stratum at the vertical bore via strong repeating impact pulse of high energy density; after the completion of this work, lifting the probe of strong repeating impact pulse generator from the vertical bore out of the impact bore;

[0035] so far, the over-pit constructive control of the hard roof of far field of an extra-large stoping space has been completed, simultaneously or successively, the down-pit constructive control of the hard roof of near field of an extra-large stoping space is conducted; firstly, the near-field hard roof is preliminary controlled by adopting the method for controlling a hard roof via down-pit water injection of near field of an extra-large stoping space, which specifically includes the following steps:

[0036] j. forming a plurality of water injection bores at down-pit space towards the near-field hard roof 6 overlying the working face 7, and injecting cement slurry into the ports of the individual water injection bores to seal the bores;

[0037] k. injecting dynamic and static pressure water into the water injection bores via the high-pressure water injection pump, with the quantity of the injected water being determined by an empirical moistening radius;

[0038] l. repeating the above steps to inject water into each water injection bores, so as to complete the preliminary softening work of the near-field hard roof 6.

[0039] then, the near-field hard roof is controlled and weakened in layers by adopting the method for controlling a hard roof via down-pit stratified blasting of near field of an extra-large stoping space, which specifically includes the following steps:

[0040] m. forming a plurality of blasting bores 8 at down-pit space towards the near field hard roof 6 overlying the working face 7, and drill a pre-crack 10 in the form of a wedge-shaped groove in each of the blasting segments along each blasting bore 8;

[0041] n. placing the primary explosive, taphole clay and wooden wedge into the blasting segment of the blasting bore 8 in sequence, clamping the wooden wedge tightly to complete the loading of the first blasting segment in the blasting bore 8, and then repeating the above steps to complete the loading of all the blasting segments;

[0042] o. repeating the above steps to complete the loading of all the blasting bores, sealing all the blasting bores with taphole clay, and then connecting a detonator to a detonating cord and stemming; at last, connecting the blasting network to initiate the blast;

[0043] finally, the near-field hard roof is controlled by adopting the method for controlling a hard roof via weakening by hydraulic fracturing of near field of an extra-large stoping space, which specifically includes the following steps:

[0044] p. forming a plurality of hydraulic fracturing bores 9 at down-pit space towards the near-field hard roof 6 overlying the working face 7, and drill a pre-crack 10 in the form of a wedge-shaped groove in each of the fracturing segments along the drilled bore;

[0045] q. pushing a bore packer having a hydraulic-fracturing mounting bar into the hydraulic fracturing segment, and pressurizing the bore packer to seal the hydraulic fracturing segment;

[0046] r. injecting high-pressure water into the hydraulic fracturing bore via fracturing pump to fracture the hydraulic fracturing segment;

[0047] s. as each hydraulic fracturing bore has a plurality of hydraulic fracturing segments, repeating the above steps to conduct the fracturing work in segments and complete the work of all the hydraulic fracturing segments of each hydraulic fracturing bore.