Tunnel tunneling construction method for locally passing through goaf

Abstract

The invention discloses a roadway tunneling construction method for locally passing a goaf, which comprises the following steps of: firstly, drilling a hole in the goaf, introducing inert gas nitrogen, and calculating the actual carbon monoxide concentration in the goaf through a specific formula, so that the carbon monoxide concentration in the goaf can be accurately known; meanwhile, the concentration of carbon monoxide and oxygen in the goaf can be diluted; by comparing the carbon monoxide concentration of other drill holes with the carbon monoxide concentration extracted by the gas injection hole and combining the hole depth of the drill holes and the water return condition, data is provided for the water-cement ratio of the injected paste quick-setting material, different measures are taken under different conditions, and the goaf can be rapidly and accurately filled. After grouting, the grouting effect is detected through air exhaust of hole sites of different layers and different depths, whether roadway tunneling can be carried out or not is judged, or thickened slurry or paste quick-setting materials need to be further injected or not, and finally the safety of roadway tunneling can be guaranteed.

Description

Technical Field

[0001] The invention relates to a construction method for tunnel excavation through a goaf area, in particular to a construction method for tunnel excavation through a local goaf area. Background Art

[0002] Coal resources are the pillar energy. Years of coal mining have led to the depletion of shallow coal resources. After the upper coal is mined, the lower coal is mined to solve the problem of insufficient coal mining reserves, reduce the waste of coal resources and extend the production time of the mine. However, in layered mining, after the upper coal is mined, a goaf is formed. When the lower layer is excavated or mined through the goaf, it will face the following threats: roof collapse or top rock coal falling, water inrush, and coal seam spontaneous combustion. Especially when the excavation working face exposes the goaf, air will enter the goaf, causing the coal in the goaf to spontaneously combust. Therefore, when the tunnel is excavated through the goaf, corresponding measures need to be taken in advance to prevent accidents.

[0003] Tunnel excavation through goafs is mainly divided into two situations: all through goafs and part through goafs. The measures taken for all through goafs are: knocking on the walls and asking the top, drilling holes, checking gas, roof, water accumulation, initial spraying, temporary support, slag removal and permanent support; such as the patent with publication number CN114837697A, which proposes a method for controlling the entire process of tunnels passing through goafs, injecting grouting pipes into the cavity of the goaf in front before excavation, and using resistance-enhanced pressure-relieving grouting anchors to support the roof and perform secondary grouting after excavation. This patent takes measures of advance grouting and roof reinforcement before passing through the goaf, but does not detect harmful gases, and cannot avoid accidents caused by excessive concentrations of harmful gases. However, if it is dealt with in the same way as all through goafs, it will greatly increase the cost, and if it is not handled, it will greatly increase the danger of construction.

[0004] For local goafs, the situation of the goafs must be explored first. In order to accurately explore the distribution of the goafs, the method of collecting and detecting CO is usually adopted. Therefore, how to accurately monitor the concentration of CO is particularly important. At present, the detection of CO is mainly to directly pump out the concentration of CO, but this method will cause inaccurate gas detection results due to factors such as gas leakage during gas extraction or uneven gas distribution, which will cause hidden dangers in construction. For example, in 2013, a gas explosion occurred in the Babao Coal Mine in Jilin. The cause of the accident was air leakage in the goaf of the working face of the goaf of the Babao Coal Mine, which caused the coal to spontaneously ignite and cause a gas explosion in the goaf. The main reason for the accident was that when the goaf was passed locally, the gas and slurry materials were not used together, and the effect data after gas treatment was not analyzed and reasoned, which eventually led to the accident.

[0005] Based on this, there is an urgent need for a tunnel excavation construction method that does not require the entire goaf area to be treated in the same way, but can carry out targeted treatment of local goaf areas. Summary of the invention

[0006] In view of the problems existing in the above-mentioned prior art, the present invention provides a tunnel excavation construction method for local goaf areas, which uses gas to control and detect goaf areas. The gas can be used to fully fill every corner of the cracks, which can not only make the detected carbon monoxide concentration more accurate, but also effectively reduce the concentrations of carbon monoxide and oxygen, greatly reducing the risk of explosion and spontaneous combustion of coal.

[0007] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a tunnel excavation construction method for partially passing through the goaf area, the specific steps are: A. Determine the drilling arrangement plan based on relevant geological data and the distribution of underground construction locations and drill according to the plan to preliminarily determine the situation of the goaf; B. Select any borehole from the boreholes constructed in step A as a gas injection hole, inject a certain amount of inert gas into the borehole, mix the inert gas with the gas in the vicinity of the borehole terminal, wait for a period of time, extract gas from the borehole and surrounding boreholes that have not been injected with gas, and detect the concentration of carbon monoxide in the gas extracted from each borehole; C. Calculate the actual concentration of carbon monoxide around each borehole based on the carbon monoxide concentration in the gas extracted from each borehole and the amount of inert gas introduced in step B; D. Compare the actual carbon monoxide concentration of the surrounding boreholes with that of the gas injection holes, and determine the boreholes that need grouting according to the depth of the boreholes into the goaf and the water return situation, and then determine the amount of paste quick-setting material to be injected into each borehole, the grouting time and the water-cement ratio of the slurry; E. Re-extract gas from boreholes at different levels and depths for testing. If no carbon monoxide is detected, start tunnel excavation construction; if the carbon monoxide concentration is 0-24ppm, there are small cracks at that location, and thickened slurry needs to be injected for plugging; if the carbon monoxide concentration is greater than 24ppm, it is necessary to re-inject paste quick-setting material into the borehole required for grouting in step D until no carbon monoxide is detected, and then proceed with tunnel excavation work.

[0008] Furthermore, the drilling arrangement scheme in step A is specifically as follows: Drill holes are constructed on the top plate and both sides of the tunnel excavation surface. Five holes are arranged in a single construction, of which two holes are arranged in the first row. The hole depth is a, and the inclination angle between this row of holes and the excavation direction is Ɵ°. According to the width of the tunnel, the hole spacing of the first row of holes is 1 to 2 m; the second row is below the first row of holes. The two holes in this row are respectively facing the outside of the two side walls. The hole depth is a, and the inclination angle between each hole and the excavation direction is Ɵ° and they are inclined to the outside of the corresponding side walls. The hole spacing of the second row of holes is b; one hole is arranged in the middle of the excavation face, which is arranged in a plum blossom shape with the above four holes. The hole depth is a, and the inclination angle between this hole and the excavation direction is Ɵ°. The aperture of each hole is c.

[0009] Furthermore, the inclination angle Ɵ is specifically: when the goaf is above the tunnel excavation, the value range of Ɵ is 30° to 90°; when the goaf is in front of the tunnel excavation, the range of Ɵ is -20° to 30°.

[0010] Furthermore, the actual concentration of carbon monoxide in the area calculated in step C is specifically: in: is the actual carbon monoxide concentration in the goaf, %; is the carbon monoxide concentration detected after nitrogen injection, %; is the nitrogen injection flow rate, Nm 3 / h; t is the nitrogen injection time, h; is the nitrogen concentration detected after nitrogen injection, %; is the nitrogen concentration in the original goaf before nitrogen injection, %.

[0011] Furthermore, in step D, the grouting parameters of the paste quick-setting material are determined according to the concentration, the depth of drilling into the goaf and the return water conditions. Specifically, if the actual carbon monoxide concentration of any borehole is lower than that of the gas injection hole, the grouting amount of the borehole is reduced accordingly; if the actual carbon monoxide concentration of any borehole is higher than that of the gas injection hole, the grouting amount of the borehole is increased accordingly; if the depth of drilling into the goaf is large or the return water is small, it means that the internal cracks are large, and it is necessary to increase the grouting amount and time, and reduce the slurry water-cement ratio; if the drilling depth is small or the return water is large, it means that the internal cracks are small, and it is necessary to reduce the grouting amount and time, and increase the slurry water-cement ratio to increase fluidity.

[0012] Furthermore, the inert gas in step B is nitrogen. Nitrogen is used because it is easy to prepare and transport and has low cost.

[0013] Furthermore, the quick-setting paste material in step D is a fast-strength quick-setting paste material.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention first drills a hole into the goaf and introduces inert gas nitrogen, and calculates the actual carbon monoxide concentration in the goaf through a specific formula. This method of first injecting inert gas and then extracting to determine the carbon monoxide concentration, first, because the injection of inert gas increases the internal air pressure of the goaf, thus reducing the air leakage in the goaf during the sampling process; second, by injecting inert gas, the gas in the goaf can be mixed evenly to prevent gas stratification due to long-term standing, thus overcoming the existing problem of directly extracting gas from the goaf when sampling, directly extracting gas from a certain layer after stratification, ultimately resulting in inaccurate detected concentration; therefore, this method of the present invention can not only accurately understand the carbon monoxide concentration in the goaf, but also dilute the carbon monoxide and oxygen concentrations in the goaf.

[0015] 2. The present invention can provide data for the water-cement ratio of the injected paste quick-setting material by comparing the carbon monoxide concentration of other boreholes with the carbon monoxide concentration extracted from the gas injection holes according to the concentration, thereby improving the pertinence of grouting and ensuring the filling effect after grouting.

[0016] 3. The paste quick-setting material selected in the present invention can adjust its fluidity by adjusting the water-cement ratio according to the actual situation of the goaf, so as to adopt different measures in different situations, and can quickly and accurately fill the goaf, saving time for the construction process.

[0017] 4. The present invention detects the grouting effect by pumping air from holes at different layers and depths, thereby realizing accurate monitoring of the goaf after grouting. Based on the monitoring results, it is determined whether tunnel excavation can be carried out or whether thickened slurry or paste quick-setting material needs to be further injected, thereby ultimately ensuring the safety of tunnel excavation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a front view of the arrangement of the grouting holes in the present invention; Figure 2 It is a top view of the arrangement of grouting holes in the present invention; Figure 3 is a cross-sectional view of the arrangement of grouting holes in the present invention; Figure 4 It is a diagram of the terminal hole position and the slurry diffusion range in the present invention; Figure 5 It is a construction flow chart of the present invention; Figure 6 Schematic diagram of the distribution of the excavation position and goaf area in this embodiment; Figure 7 Schematic diagram of the distribution of drilling holes on the excavation face of this embodiment; Figure 8 Schematic diagram of the grouting hole position distribution selected in this embodiment; Fig. 9It is a schematic diagram of the goaf area being located above the heading tunnel in the present invention; Fig.10 It is a schematic diagram of the goaf area in front of the excavation tunnel in the present invention.

[0019] In the figure: 1. Grouting hole; 2. Tunnel roof; 3. Tunnel floor; 4. Slurry diffusion range; 5. Grouting end hole; 6. Excavation working face; 7. Goaf. DETAILED DESCRIPTION

[0020] The present invention will be further described below.

[0021] The following is a description of the specific implementation steps of the present invention by taking the 6301 track drift working face of Luwa Coal Mine as the research object: A. According to the situation of the goaf of the 6301 track drift in Luwa Coal Mine, Figure 6 As shown, and in accordance with Fig. 9 and 10 It is determined that the goaf 7 in this embodiment is in front of the tunnel, and then the position of the drill hole is determined. The track chute 6301 of Luwa Coal Mine obliquely passes through the goaf, so the selected drilling angles are 3° and 19°, -8° and -12°; Figure 6 As shown in the figure, according to the distance between the excavation position and the goaf 7, drilling holes in different directions and depths of 0.1m to 1.5m are selected. During each drilling process, when the drilling pressure becomes significantly smaller and the drilling speed becomes significantly faster, it means that the final hole position of the drilling hole has reached the goaf 7. At this time, the current drilling is stopped. The final distribution of the positions of the various drilling holes is as follows: Figure 7 As shown; B. Select any drill hole as the air injection hole and inject 800Nm into the air injection hole. 3 After nitrogen was injected for 10 minutes, gas was extracted from the injection hole and surrounding holes for testing. The carbon monoxide concentration in the gas extracted from the injection hole was measured: =51ppm; nitrogen concentration =86%, substitute into the formula Among them =800Nm 3 / h; t=10min, calculate the actual concentration of carbon monoxide in the goaf =80ppm; C. Through the detection and calculation of the gas extracted from other boreholes in step B, it can be seen that the borehole pressure below 0.8m is significantly increased and the carbon monoxide concentration is significantly reduced, so the grouting hole 1 is selected as Figure 8As shown, a paste quick-setting material is injected into each grouting hole 1 to seal the cracks. The carbon monoxide concentration in the goaf is detected before grouting, so that the cracks in the goaf can be quickly and targetedly sealed to prevent carbon monoxide. The nitrogen introduced can reduce the oxygen concentration, thereby reducing the risk of coalfield fire. D. After a period of time after grouting, drill again at different layers and depths of the goaf 7, extract gas to detect the carbon monoxide concentration. After the detection, no carbon monoxide gas is found in the goaf 7 after grouting, which indicates that the grouting effect of the present invention is significant and the carbon monoxide concentration in the goaf is greatly reduced. Subsequently, each borehole is sealed and the tunnel excavation construction work can be carried out normally.

[0022] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A tunnel excavation construction method for partially passing through a goaf area, characterized in that: The specific steps are: A. Determine the drilling arrangement plan based on relevant geological data and the distribution of underground construction locations and drill according to the plan to preliminarily determine the situation of the goaf; B. Select any borehole from the boreholes constructed in step A as a gas injection hole, inject a certain amount of inert gas into the borehole, mix the inert gas with the gas in the vicinity of the borehole terminal, wait for a period of time, extract gas from the borehole and surrounding boreholes that have not been injected with gas, and detect the concentration of carbon monoxide in the gas extracted from each borehole; C. Calculate the actual concentration of carbon monoxide around each borehole based on the carbon monoxide concentration in the gas extracted from each borehole and the amount of inert gas introduced in step B; D. Compare the actual carbon monoxide concentration of the surrounding boreholes with that of the gas injection holes, and determine the boreholes that need grouting according to the depth of the boreholes into the goaf and the water return situation, and then determine the amount of paste quick-setting material to be injected into each borehole, the grouting time and the water-cement ratio of the slurry; E. Re-extract gas from boreholes at different levels and depths for testing. If no carbon monoxide is detected, start tunnel excavation construction; if the carbon monoxide concentration is 0-24ppm, there are small cracks at that location, and thickened slurry needs to be injected for plugging; if the carbon monoxide concentration is greater than 24ppm, it is necessary to re-inject paste quick-setting material into the borehole required for grouting in step D until no carbon monoxide is detected, and then proceed with tunnel excavation work.

2. The tunnel excavation construction method for partially passing through the goaf area according to claim 1 is characterized in that: The drilling arrangement scheme in step A is specifically as follows: Drill holes are constructed on the top plate and both sides of the tunnel excavation surface. Five holes are arranged in a single construction, of which two holes are arranged in the first row. The hole depth is a, and the inclination angle between this row of holes and the excavation direction is Ɵ°. According to the width of the tunnel, the hole spacing of the first row of holes is 1 to 2 m; the second row is below the first row of holes. The two holes in this row are respectively facing the outside of the two side walls. The hole depth is a, and the inclination angle between each hole and the excavation direction is Ɵ° and they are inclined to the outside of the corresponding side walls. The hole spacing of the second row of holes is b; one hole is arranged in the middle of the excavation face, which is arranged in a plum blossom shape with the above four holes. The hole depth is a, and the inclination angle between this hole and the excavation direction is Ɵ°. The aperture of each hole is c.

3. The tunnel excavation construction method for partially passing through the goaf area according to claim 2 is characterized in that: The inclination angle Ɵ is specifically: when the goaf is above the tunnel excavation, the value range of Ɵ is 30° to 90°; when the goaf is in front of the tunnel excavation, the range of Ɵ is -20° to 30°.

4. The tunnel excavation construction method for partially passing through the goaf area according to claim 1 is characterized in that: The actual concentration of carbon monoxide in the area calculated in step C is specifically: Where: is the actual carbon monoxide concentration in the goaf, %; is the carbon monoxide concentration detected after nitrogen injection, %; is the nitrogen injection flow rate, Nm 3 / h; is the nitrogen injection time, h; is the nitrogen concentration detected after nitrogen injection, %; is the nitrogen concentration in the original goaf before nitrogen injection, %.

5. The tunnel excavation construction method for partially passing through the goaf area according to claim 1 is characterized in that: In the step D, the grouting parameters of the paste quick-setting material are determined according to the concentration, the depth of drilling into the goaf and the return water conditions. Specifically, if the actual carbon monoxide concentration of any borehole is lower than that of the gas injection hole, the grouting amount of the borehole is reduced accordingly; if the actual carbon monoxide concentration of any borehole is higher than that of the gas injection hole, the grouting amount of the borehole is increased accordingly; if the depth of drilling into the goaf is large or the return water is small, it means that the internal cracks are large, and it is necessary to increase the grouting amount and time, and reduce the slurry water-cement ratio; if the drilling depth is small or the return water is large, it means that the internal cracks are small, and it is necessary to reduce the grouting amount and time, and increase the slurry water-cement ratio to increase fluidity.

6. The tunnel excavation construction method for partially passing through the goaf area according to claim 1 is characterized in that: The inert gas in step B is nitrogen.

7. The tunnel excavation construction method for partially passing through the goaf area according to claim 1 is characterized in that: The quick-setting paste material in step D is a fast-strength quick-setting paste material.

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