CN108361011B

CN108361011B - Method for controlling mining influence range from underground roadway directional hydraulic fracturing

Info

Publication number: CN108361011B
Application number: CN201810191325.0A
Authority: CN
Inventors: 郭文兵; 冯占杰; 谭毅; 杨达明; 徐飞亚
Original assignee: Henan University of Technology
Current assignee: Henan University of Technology
Priority date: 2018-03-08
Filing date: 2018-03-08
Publication date: 2020-06-23
Anticipated expiration: 2038-03-08
Also published as: CN108361011A

Abstract

The invention relates to a method for controlling mining influence range from underground roadway directional hydraulic fracturing, which comprises the following steps: 1) acquiring geological mining conditions of a working face and geological conditions of overlying strata of a pre-splitting roadway, and analyzing the boundary of a ground surface moving basin; 2) determining the width of an enclosure belt and controlling the boundary of a ground surface moving basin according to the level of a ground surface construction needing protection; 3) controlling the surface mobile basin boundary to determine the pre-splitting height and position of the overburden according to the step 2); 4) performing a hydraulic fracturing operation on a roof of the overburden according to the pre-fracture height and location of the overburden determined in step 3). The method of the invention can reduce the mining influence range, thereby eliminating mining damage to the surface construction and achieving the purpose of protecting the surface construction.

Description

Method for controlling mining influence range from underground roadway directional hydraulic fracturing

Technical Field

The invention particularly relates to a method for controlling mining influence range from underground roadway directional hydraulic fracturing, and belongs to the technical field of mining methods.

Background

Coal is a main energy source in the current society, and with the development of the society and the progress of production technology, the demand of people for energy sources is more and more large. After the coal is mined from the underground, the overlying strata above the coal is not supported, the original stress balance state in the rock mass is damaged, the redistribution of the internal stress of the rock mass is caused, and the rock mass around the goaf is displaced, deformed and damaged. When the area of the goaf reaches a certain range, the earth surface above the goaf is caused to move and deform. The movement and deformation of the earth's surface affects the foundation of the structure, resulting in movement and deformation of the structure and even destruction.

In the prior art, there are methods for controlling and mitigating ground subsidence through goaf filling. The goaf filling is to fill the goaf area by using peripheral materials, and the method needs to use a large amount of filling materials, is expensive and complex and has less practical application. In actual production, the boundary of the earth surface moving basin is mostly defined according to the angle of the earth surface moving basin boundary. The method can only estimate and delimit the mining influence range, can not actively control the ground surface mining influence range, and can not play an active protection role on the building in the ground surface subsidence area.

Disclosure of Invention

The invention aims to provide a method for controlling the mining influence range from the directional hydraulic fracturing of an underground roadway, which comprises the following specific steps:

a method for controlling the mining influence range from directional hydraulic fracturing of a downhole roadway comprises the following steps:

1) acquiring working face geological mining conditions and pre-splitting roadway overburden geological conditions, and analyzing earth surface moving basin boundaries, wherein the working face geological mining conditions and the pre-splitting roadway overburden geological conditions comprise overburden layer positions, rock layer thicknesses, rock layer strengths and ground stresses;

2) determining the width of an enclosure belt and controlling the boundary of a ground surface moving basin according to the level of a ground surface construction needing protection;

3) determining the horizontal movement distance S of the boundary of the earth surface moving basin according to the geological mining conditions of the working face and the geological conditions of the overburden of the pre-splitting roadway in the step 1) and the geological conditions of the earth surface moving basin in the step 2) and controlling the boundary of the earth surface moving basin, and determining the pre-splitting height H = S tan of the overburden

₀；

4) Performing a hydraulic fracturing operation on the overburden according to the pre-fracture height H of the overburden determined in the step 3).

The hydraulic fracturing operation in step 4) comprises the following steps:

41) determining drilling parameters according to the pre-splitting height and the geological condition of the overlying strata;

42) drilling holes on the top plate of the pre-splitting roadway in sequence according to the drilling parameters determined in the step 41);

43) according to the geological condition of the overlying rock stratum and the hole depth of the drilled hole, slotting at a preset distance of the drilled hole to obtain a plurality of slots;

44) sealing holes at the front and rear positions of each cutting groove, injecting high-pressure water into the drill hole, and enabling the high-pressure water to act on the cutting groove to crack the two sides of the cutting groove to form a through crack; cutting the fracture to cut off the roadway overlying rock stratum and forming a large weak surface in the rock stratum;

45) along with the working face is recovered to a pre-splitting roadway area, the overall strength of the broken overlying strata is weakened, the broken overlying strata slide along the weak face, are layered and orderly collapsed, and a ground surface moving basin is formed outside the building enclosure zone.

Further, the drilling parameters in step 41) include drilling position, drilling depth, drilling distance and drilling angle.

The hydraulic fracturing technology is applied to weakening the rock strength and controlling the mining influence range, namely, the rock strength is weakened through directional hydraulic fracturing to form a through crack, and the transmission of overburden rock fracture to the mining direction of a working face is cut off, so that the aim of controlling the mining influence range is fulfilled. The weakening of rock mass by hydraulic fracturing is mainly embodied in two aspects: firstly, the macroscopic and microscopic structure of the rock mass is reformed through the initiation and expansion of hydraulic fractures, and the mechanical property of the rock mass is weakened; and secondly, the mechanical property of the rock is reduced through the physical and chemical action of water on the rock. The two act together to weaken the mechanical property of the rock mass, reduce the overall strength of the overlying strata and enable the broken overlying strata to slip, delaminate and collapse orderly along the weak face. The method and the device can effectively increase the crushing degree of the overlying rock stratum of the top plate of the working face and the collapse height, and the boundary angle of the basin is moved due to the earth surface₀The mining influence range is reduced, so that mining damage to the earth surface construction is eliminated, and the earth surface construction is protected.

Drawings

FIG. 1 is a schematic diagram of the present invention for determining the pre-crack height;

FIG. 2 is a schematic view of a drilling arrangement according to the present invention;

FIG. 3 is a schematic cross-sectional view B-B of FIG. 2;

fig. 4 is a schematic cross-sectional view of a drilling arrangement.

Detailed Description

To select a mineral 53041The lanes are the test areas. As shown in fig. 1-4, by obtaining the horizon of the overburden stratum, the thickness of the stratum, the strength of the stratum and the ground stress, taking a point sinking 10mm as a boundary point A of the earth surface moving basin, determining a boundary angle of the earth surface moving basin

₀. Further, dividing the buildings into levels according to the protection grades of the buildings in the mining area according to the condition that the buildings are brick-wood or brick-mixed village civil houses, obtaining the horizontal moving distance S of the boundary of the earth surface moving basin according to the width of the enclosure belt being 10m, and finally determining the pre-splitting height H of the overlying strata.

The fracturing drill holes are arranged in a single row, as shown in figures 1-4, the distance between the drill holes is calculated according to the wetting radius R of the water injection hole, so that the formed through crack is determined to be 10 m. The pre-splitting drill hole is arranged on a top plate 0.5-1 m away from the coal pillar side, the diameter of the drill hole is 56(75) mm, and the elevation angle is 70-90 degrees.

A KZ54 type grooving drill bit is adopted, a transverse grooving is prefabricated in a rock stratum, a reverse fracturing method is adopted for hydraulic fracturing holes, and fracturing is carried out once every 1.5-2 m from the bottom of a drilled hole to the outside.

The whole strength of the overburden broken in the fracturing area weakens, the layering is orderly collapsed, and a surface moving basin is formed outside the building enclosure zone A'.

Claims

1. A method for controlling mining influence range from directional hydraulic fracturing of an underground roadway is characterized by comprising the following steps:

1) obtaining geological mining conditions of a working face and geological conditions of overlying strata of a pre-splitting roadway, analyzing the boundary of a ground surface moving basin, and determining the boundary angle delta of the ground surface moving basin₀The working face geological mining conditions and the geological conditions of the overlying strata of the pre-split roadway comprise stratum horizons, stratum thicknesses, stratum strengths and ground stress of the overlying strata;

3) according to the step 1) geological mining conditions of the working face and geological conditions of overlying rock strata of the pre-splitting roadway and the step 2) controlMaking a surface moving basin boundary, determining the horizontal moving distance S of the surface moving basin boundary, and determining the pre-splitting height H = S tan delta of the overburden₀；

4) Performing a hydraulic fracturing operation on the overburden according to the pre-fracture height H of the overburden determined in the step 3), wherein the hydraulic fracturing operation comprises the following steps:

42) drilling holes in the overburden rock of the pre-splitting roadway according to the drilling parameters determined in the step 41) in sequence; the method comprises the following steps that the drill holes are arranged in a single row, the distance between the drill holes is calculated according to the wetting radius R of water injection holes to form a through crack, the drill holes are arranged on a top plate 0.5-1 m away from the coal pillar side, the diameter of each drill hole is 56mm, and the angle of elevation is 70-90 degrees;

43) according to the geological condition of the overlying rock stratum and the hole depth of a drilled hole, grooving at a preset distance of the drilled hole by adopting a KZ54 type grooving drill bit, and prefabricating a plurality of transverse grooving in the rock stratum;

44) sealing holes at the front and rear positions of each cutting groove, injecting high-pressure water into the drill hole, performing hydraulic fracturing operation by adopting a backward fracturing method, fracturing once every 1.5-2 m from the bottom of the drill hole to the outside, and allowing the high-pressure water to act on the cutting groove to crack two sides of the cutting groove to form a through crack; cutting the roadway overburden rock stratum through the through cracks, and forming a large weak surface in the rock stratum;

2. The method of directional hydraulic fracturing from a downhole roadway to control the extent of mining impact of claim 1, wherein: the drilling parameters in the step 41) comprise drilling positions, drilling hole depths, drilling intervals and drilling angles.