A method for preventing and controlling water hazards in tunneling under complex hydrogeological conditions

Abstract

The present invention provides a method for proactively preventing and controlling water hazards in tunneling under complex hydrogeological conditions. The method comprises four steps: constructing a first long-distance directional drilling hole, forming a frozen layer, constructing a second long-distance directional drilling hole, and continuing construction. By combining the hydrogeological conditions of the sandstone aquifer in the tunneling roof, the present invention constructs a horizontal long-distance directional drilling hole to freeze the sandstone aquifer in the roof. The resulting frozen layer serves as an aquiclude, and long-distance directional drilling is then conducted to explore and drain water from the sandstone aquifer above the frozen layer. This releases the static reserves of the aquifer, effectively reducing water inflow from the tunnel. The method also locally reinforces the sandstone aquifer in the roof, thereby preventing water hazards in tunneling tunnels directly above the aquifer in the roof.

Description

Technical Field

[0001] The present invention belongs to the technical field of mine disaster prevention and control, relates to mine disaster prevention and control during coal mine tunneling, and specifically relates to an advanced prevention and control method for water hazards in tunneling tunnels under complex hydrogeological conditions. Background Art

[0002] my country's Jurassic coal resources are primarily distributed in western mining areas, accounting for over 60% of the nation's total reserves. With the gradual westward shift of my country's coal resource development strategy, the development of western Jurassic coal resources has become a crucial pillar of national economic development and energy security. Because Jurassic coal-bearing strata formed later than the Carboniferous and Permian coal-bearing strata, the sandstone aquifers overlying these coal seams are less mature and poorly cemented. Furthermore, many coal seams are directly roofed in sandstone aquifers. This results in significant water inflow during tunneling and is also prone to water inrush and sand bursts.

[0003] Before tunneling, the roof aquifer in front must be explored and drained. However, when the hydrogeological conditions of the tunnel are complex, especially when the direct roof of the tunnel is a sandstone aquifer or the direct roof aquifer is thin, conventional drilling for water exploration and drainage will cause a large amount of water to gush out of the borehole before the water-stop casing is installed due to the lack of a sufficiently thick roof aquifer. Without the control of water-stop casings and gate valves, a large amount of water gush out of the borehole will not only seriously deteriorate the working environment of the tunnel, but may even lead to water disasters. Failure to drain the static reserves of the tunnel roof aquifer means that the tunnel cannot be excavated normally, seriously restricting the normal construction and production of the mine.

[0004] To prevent flooding and ensure smooth tunneling, the coal seam roof must be reinforced and modified. However, since the main mining seam roof in Jurassic coalfields is typically composed of a sandstone aquifer, grouting to reinforce and modify the sandstone aquifer in the roadway roof is difficult due to the low porosity and small pore throats of the sandstone, making it difficult to inject large amounts of large-particle cement slurry into the aquifer. Using chemical slurry to grout the sandstone aquifer in the roof is not only expensive but also contaminates the groundwater in the aquifer. Summary of the Invention

[0005] In view of the defects and shortcomings of the existing technology, the purpose of the present invention is to provide an advanced prevention and control method for water disasters in tunneling tunnels under complex hydrogeological conditions, so as to solve the technical problem that it is difficult to reinforce the sandstone aquifer on the roof of the coal seam under complex hydrogeological conditions in the existing technology, which makes water disasters prone to occur.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for preventing and controlling water hazards in tunneling under complex hydrogeological conditions, the method comprising the following specific steps:

[0008] Step 1: Construction of the first long distance directional drilling:

[0009] A drilling site is set up in the excavated tunnel, and the first long-distance directional drilling is carried out according to the pre-designed location of the tunnel to be excavated.

[0010] Step 2: Forming a frozen layer:

[0011] A cooling chamber is constructed next to the drilling site in the excavated tunnel. The cooling device is connected to the freezing pipe and then installed in the cooling chamber. Then, the first long-distance directional drilling described in step 1 is performed, and the cooling device and the freezing pipe are used to freeze the water-bearing layer below the top plate of the tunnel to be excavated, and a frozen layer is formed. Then, the tunnel to be excavated is excavated forward, and an advance distance is reserved during excavation.

[0012] Step 3: Construction of the second long distance directional drilling:

[0013] Construct a second long-distance directional drill hole on the top plate of the tunnel to be excavated, and construct two second long-distance directional drill holes in each drilling site. Drill a hole in the frozen layer described in step 2, and set a water-stop casing in the second long-distance directional drill hole, and then drain the water from the aquifer above the frozen layer.

[0014] Step 4: Continue construction:

[0015] Repeat steps one to three at the head of the excavated tunnel until the tunnel to be excavated reaches the designed position.

[0016] The present invention also has the following technical features:

[0017] Specifically, in step 1, the length of the first long-distance directional drilling hole is 500 m, and the inner hole diameter of the first long-distance directional drilling hole is 165 mm.

[0018] Specifically, the number of the first long-distance directional drilling holes is five, and the number of the first long-distance directional drilling holes is calculated and determined according to the following formula I:

[0019] n=W / (0.7r)Formula Ⅰ.

[0020] Where:

[0021] n represents the number of long-distance directional drilling holes.

[0022] w represents the width of the tunnel to be excavated.

[0023] r represents the freezing radius of a single first long-distance directional drilling hole.

[0024] Specifically, in step one, the specific process of constructing the first long-distance directional drilling hole is as follows: before constructing the first long-distance directional drilling hole, the top plate of the drilling site is raised by 3m to form multiple drilling operation spaces, and then the long-distance directional drilling rig is fixed on the bracket, and the operation space is used to construct multiple groups of first long-distance directional drilling holes in the top plate of the tunnel to be excavated, and a water-stop casing is set when constructing the first long-distance directional drilling hole.

[0025] Specifically, in step one, multiple groups of first long-distance directional drill holes are arranged in a fan-shaped structure, and the distance between the centers of adjacent first long-distance directional drill holes is 1.4 m.

[0026] Specifically, in step 2, the length of the refrigeration chamber is 3m, the width is 2.5m, and the height is 2.4m. The multiple refrigeration chambers are arranged at equal intervals, and the distance between adjacent refrigeration chambers is 500m.

[0027] Specifically, in step 2, a calcium chloride solution is used to freeze the lower part of the aquifer. The freezing time is 10 to 30 days, and the temperature of the calcium chloride solution is -32°C to -30°C.

[0028] Specifically, in step 2, the total length of the freezing pipe is 500m.

[0029] Specifically, in step three, the length of the second long-distance directional drilling is 500m.

[0030] Specifically, in step three, the second long-distance directional drilling hole is located 1 m above the bottom plate of the aquifer and 6 m away from the center line of the tunnel to be excavated.

[0031] Compared with the prior art, the present invention has the following beneficial technical effects:

[0032] (I) The method for proactively preventing and controlling water hazards in tunneling under complex hydrogeological conditions of the present invention combines the hydrogeological conditions of the sandstone aquifer on the roof of the tunneling, constructs horizontal long-distance directional drilling to freeze the sandstone aquifer on the roof, utilizes the formed frozen layer as an aquifer to construct long-distance directional drilling to explore and drain water from the sandstone aquifer above the frozen layer, and drains the static reserve of the aquifer, which can effectively reduce the amount of water gushing from the tunnel and simultaneously locally reinforce the sandstone aquifer on the roof, thereby avoiding the occurrence of water hazard accidents in tunneling with the roof as the aquifer.

[0033] (II) The method for proactively preventing and controlling water hazards in tunneling under complex hydrogeological conditions of the present invention forms a frozen layer of a certain thickness below the sandstone aquifer on the roof before tunneling, which not only effectively blocks the recharge of groundwater in the aquifer to the tunnel, but also effectively consolidates the weakly cemented sandstone aquifer on the roof of the tunnel. After the static reserves of the aquifer above the frozen layer are effectively drained by long-distance directional drilling, and after freezing of the aquifer directly on the roof of the tunnel is stopped, the long-distance directional drilling in the original frozen layer can also supplement and drain the static reserves after the frozen layer is converted into an aquifer, thereby completely eliminating the influence and threat of the sandstone aquifer on the roof of the tunnel on the safe tunneling.

[0034] (III) The method for proactively preventing and controlling water hazards in tunneling under complex hydrogeological conditions of the present invention uses long-distance directional drilling to treat water hazards in the tunnel roof of about 500 m at a time. While the frozen layer on the roof of the preceding tunnel is thawing, water hazards on the roof of the subsequent tunnel to be excavated can be treated, thereby significantly improving the efficiency of water hazard treatment in tunneling.

[0035] (IV) The method for proactively preventing and controlling water hazards in tunneling under complex hydrogeological conditions of the present invention only freezes the aquifer on the tunnel roof, and no other materials are used to transform the aquifer during the process of preventing and controlling water hazards on the roof, thus avoiding pollution and achieving green prevention and control of water hazards on the tunnel roof. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a cross-sectional diagram of the drilling operation space and cooling chamber.

[0037] Figure 2 This is a schematic plan view of the drilling operation space and cooling chamber.

[0038] Figure 3 This is a plan view of the first long-distance directional drilling of the first group to freeze the aquifer in the roof of the tunnel to be excavated.

[0039] Figure 4 This is a cross-sectional schematic diagram of the second group and the subsequent first long-distance directional drilling to freeze the aquifer in the roof of the tunnel to be excavated.

[0040] Figure 5 A schematic plan view of the second and subsequent first long-distance directional drilling to freeze the aquifer in the roof of the tunnel to be excavated.

[0041] The meanings of the numbers in the figure are: 1-excavated tunnel, 2-tunnel to be excavated, 3-first long-distance directional drilling hole, 4-refrigeration chamber, 5-refrigeration device, 6-aquifer, 7-frozen layer, 8-second long-distance directional drilling hole, 9-drilling operation space, 10-anchor rod.

[0042] The technical solution of the present invention is further described below in conjunction with embodiments. DETAILED DESCRIPTION

[0043] In the present invention:

[0044] It should be noted that all devices used in the present invention, unless otherwise specified, are devices known in the art. For example, the refrigeration chamber (4) is a conventional underground refrigeration chamber known in the prior art. The refrigeration device (5) is a conventional refrigeration device known in the prior art.

[0045] In accordance with the above technical solution, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0046] Example:

[0047] This embodiment provides a method for preventing and controlling water hazards in tunneling under complex hydrogeological conditions. The method specifically includes the following steps:

[0048] Step 1: Construction of the first long distance directional drilling:

[0049] like Figure 1 、 Figure 2 and Figure 3 As shown, according to the actual conditions underground, a suitable location is selected in the excavated tunnel 1 as a drilling site, and the first long-distance directional drilling 3 is constructed according to the pre-designed location of the tunnel 2 to be excavated.

[0050] In this embodiment, the first long-distance directional drilling hole 3 completely covers the tunnel to be excavated 2 in the plane, and the first long-distance directional drilling hole 3 is located above the top plate of the tunnel to be excavated 2 in the vertical direction to ensure that the lower part of the aquifer 5 on the top plate of the tunnel to be excavated is frozen to form a frozen layer 6 of a certain thickness.

[0051] In this embodiment, the first long-distance directional drilling hole 3 is used to freeze the lower part of the aquifer 5. On the one hand, the first long-distance directional drilling hole 3 is relatively long, and a small number of drilling holes can be used to cover the tunnel to be excavated 2, effectively reducing the number of drilling sites and cooling chambers 4. On the other hand, the trajectory of the first long-distance directional drilling hole 3 is controllable, and the distance between the first long-distance directional drilling hole 3 and the top plate of the tunnel to be excavated can be accurately controlled.

[0052] As a specific scheme of this embodiment, in step one, the specific process of constructing the first long-distance directional drilling hole 3 is: before constructing the first long-distance directional drilling hole 3, the top plate of the drilling site is raised by 3m to form multiple drilling work spaces 9, and then the long-distance directional drilling rig is fixed on the bracket, and the work space 4 is used to construct multiple groups of first long-distance directional drilling holes 3 towards the top plate of the tunnel 2 to be excavated, and a water stop casing is set when constructing the first long-distance directional drilling hole 3.

[0053] In this embodiment, the inclination angle of the first long-distance directional drilling hole 3 is consistent with the inclination angle of the roadway 2 to be excavated. The length of the first long-distance directional drilling hole 3 is 500 m, the inner hole diameter of the first long-distance directional drilling hole 3 is 165 mm, and the number of the first long-distance directional drilling holes 3 is five. The number of the first long-distance directional drilling holes 3 is calculated and determined according to the following formula I:

[0054] n=W / 0.7r Formula Ⅰ.

[0055] Where:

[0056] n represents the number of long-distance directional drilling holes.

[0057] w represents the width of the tunnel to be excavated, and the width w of the tunnel to be excavated usually does not exceed 6m.

[0058] r represents the freezing radius of the single first long-distance directional drilling hole 3, and the freezing radius r is generally 2 m.

[0059] In this embodiment, the roof of the excavated tunnel 1 for the construction of the first group of first long-distance directional drilling holes 3 must have a complete waterproof layer with a thickness of more than 4m, and there is no requirement for the thickness of the waterproof layer for the roof of the tunnel 2 to be excavated in the subsequent first long-distance directional drilling holes 3.

[0060] In this embodiment, multiple groups of first long-distance directional drill holes 3 are arranged in a fan-shaped structure, and the distance between the centers of adjacent first long-distance directional drill holes 3 is 1.4 m.

[0061] In this embodiment, the length L of the water-stop sleeve is determined according to the original water head height of the roof aquifer. During construction, the distance between the first long-distance directional drilling hole 3 and the roof of the tunnel to be excavated 2 is always maintained at 2m.

[0062] Step 2: Forming a frozen layer:

[0063] like Figure 4 and Figure 5 As shown, a cooling chamber 4 is constructed next to the drilling site in the excavated tunnel 1, and the cooling device 5 is connected to the freezing pipe and placed in the cooling chamber 4. Then, through the first long-distance directional drilling 3 in step one, the cooling device 5 and the freezing pipe are used to freeze the lower part of the aquifer 5 on the roof of the tunnel to be excavated, and a frozen layer 6 of a certain thickness is formed. Then, the tunnel to be excavated 2 is excavated forward 480m, and a 20m advance distance is reserved during excavation.

[0064] In this embodiment, the permeability coefficient of the frozen layer 7 is very low, and its strength is significantly improved. The frozen layer 7 has three functions: first, it creates conditions for the installation of the water-stop casings in the next set of first long-distance directional boreholes 3; second, the formed frozen layer 7 blocks groundwater recharge from the aquifer 6 above the frozen layer 7 to the tunnel 2 to be excavated, effectively reducing the amount of water inflow during excavation of the tunnel 2 to be excavated; and third, the formation of a certain thickness of frozen layer 7 provides the required anchoring force for the anchor rod 10 and prevents groundwater in the aquifer 5 from entering the tunnel 2 to be excavated along the annular space between the anchor rod 10 and the aquifer 5.

[0065] In this embodiment, the refrigeration chamber 4 is 3 meters long, 2.5 meters wide, and 2.4 meters high. Multiple refrigeration chambers 4 are evenly spaced, with a spacing of 500 meters between adjacent refrigeration chambers 4. The size of the refrigeration chamber 4 is determined based on the size of the refrigeration unit 5 and can meet the space requirements of the refrigeration unit 5.

[0066] In this embodiment, the freezing pipe is composed of multiple freezing pipe short sections, and the total length of the freezing pipe is 500m. The freezing pipe short section adopts No. 20 high-quality low-carbon seamless steel pipe known in the prior art. The length of the freezing pipe short section is 133mm and the inner diameter is 6mm.

[0067] In this embodiment, a calcium chloride solution is used to freeze the lower portion of the aquifer 5 in the roof of the roadway to be excavated. The freezing period is 10 to 30 days, and the temperature of the calcium chloride solution is -32°C to -30°C. The freezing radius of the aquifer 5 is approximately 2 meters, centered at the center of the first long-distance directional borehole 3. If the mine has not implemented freezing methods before and lacks relevant parameters and experience, a verification borehole can be constructed at the outer edge of the freezing radius of the aquifer 5. The freezing status of the aquifer surrounding the first long-distance directional borehole 3 can be verified by coring or drilling.

[0068] Step 3: Construction of the second long distance directional drilling:

[0069] like Figure 5 As shown, a second long-distance directional drill hole 8 is constructed on the top plate of the tunnel 2 to be excavated, two second long-distance directional drill holes 8 are constructed in each drilling site, a hole is opened in the frozen layer 7 in step 2, and a water-stop casing is set in the second long-distance directional drill hole 8, and then the water-bearing layer 6 above the frozen layer 7 is drained.

[0070] In this embodiment, first, the static reserves of the aquifer 6 above the frozen layer 7 are effectively drained by using the first long-distance directional drilling hole 3; second, when the freezing of the lower part of the aquifer 6 is stopped, the small amount of static reserves after the frozen layer 7 thaws and becomes the aquifer 6 again can be effectively drained at the same time.

[0071] In this embodiment, the casing length L is determined according to the original water head height of the roof aquifer 5. The length of the second long-distance directional drilling hole 8 is 500m, and the angle between the azimuth and the excavation direction of the tunnel to be excavated 2 is 0°, which can ensure that the water-stop casing is solidified in the frozen layer 6, effectively avoiding the problem of uncontrollable water discharge in the event of large water gushing when the second long-distance directional drilling hole 8 reveals the roof aquifer 6 of the tunnel to be excavated and the water-stop casing has not yet been installed.

[0072] In this embodiment, the second long-distance directional drill hole 8 is located 1 m above the bottom plate of the aquifer 5 on the roof of the tunnel to be excavated and 6 m away from the center line of the tunnel to be excavated 2 .

[0073] In this embodiment, when the water volume in the second long-distance directional drilling hole 8 drops to less than 5% of the maximum water volume of the aquifer 5 exposed by the drilling hole or the water pressure drops to less than 0.05 MPa, it is considered that the static reserve of the aquifer 6 above the frozen layer 7 has been released, and at this time, the freezing of the aquifer 6 on the top plate of the tunnel is stopped.

[0074] In this embodiment, after stopping the freezing of the aquifer 5 on the roof of the tunnel to be excavated by the second long-distance directional drilling 8, the static reserve of the aquifer 5 converted from the thawed frozen layer 7 can be supplemented and drained by the first long-distance directional drilling 3.

[0075] Step 4: Continue construction:

[0076] Repeat steps 1 to 3 at the head of the excavated tunnel 1 until the tunnel to be excavated 2 is excavated to the designed position.

[0077] In this embodiment, the length of the aquifer 6 and the frozen layer 7 on the roof of the tunnel to be excavated along the excavation direction of the tunnel 2 to be excavated is 500 m, and the tunnel can be excavated for 480 m.

Claims

1. A method for preventing and controlling water hazards in tunneling under complex hydrogeological conditions, characterized in that: The method comprises the following specific steps: Step 1: Construction of the first long distance directional drilling: A drilling site is set up in an excavated tunnel (1), and a first long-distance directional drilling hole (3) is constructed according to a pre-designed position of a tunnel to be excavated (2); Step 2: Forming a frozen layer: A cooling chamber (4) is constructed next to the drilling site in the excavated tunnel (1), and a cooling device (5) is connected to a freezing pipe and then placed in the cooling chamber (4). Then, the first long-distance directional drilling (3) described in step 1 is performed, and the water-bearing layer (6) below the top plate of the tunnel to be excavated (2) is frozen using the cooling device (5) and the freezing pipe to form a frozen layer (7). Then, the tunnel to be excavated (2) is excavated forward, and a lead distance is reserved during excavation. Step 3: Construction of the second long distance directional drilling: Constructing a second long-distance directional drill hole (8) on the top plate of the tunnel to be excavated (2), constructing two second long-distance directional drill holes (8) in each drilling site, drilling a hole in the frozen layer (7) described in step 2, and setting a water-stop casing in the second long-distance directional drill hole (8), and then draining water from the aquifer (6) above the frozen layer (7); Step 4: Continue construction: Repeat steps 1 to 3 at the head of the excavated tunnel (1) until the tunnel to be excavated (2) is excavated to the designed position.

2. The method for preventing and controlling water hazards in tunneling under complex hydrogeological conditions according to claim 1, characterized in that: In step 1, the length of the first long-distance directional drilling hole (3) is 500m, and the inner hole diameter of the first long-distance directional drilling hole (3) is 165mm.

3. The method for preventing and controlling water hazards in tunneling under complex hydrogeological conditions according to claim 1, characterized in that: The number of the first long-distance directional drilling holes (3) is five, and the number of the first long-distance directional drilling holes (3) is calculated and determined according to the following formula I: n=W / (0.7r) Formula Ⅰ; Where: n represents the number of long-distance directional drilling holes; w represents the width of the tunnel to be excavated; r represents the freezing radius of the single first long-distance directional drilling hole (3).

4. The method for preventing and controlling water hazards in tunneling under complex hydrogeological conditions according to claim 1, characterized in that: In step 1, the specific process of constructing the first long-distance directional drilling hole (3) is as follows: before constructing the first long-distance directional drilling hole (3), the top plate of the drilling site is elevated by 3 meters to form multiple drilling operation spaces (9), and then the long-distance directional drilling rig is fixed on the bracket, and the drilling operation space (9) is used to construct multiple groups of first long-distance directional drilling holes (3) in the top plate of the tunnel to be excavated (2), and a water stop casing is set when constructing the first long-distance directional drilling hole (3).

5. The method for preventing and controlling water hazards in tunneling under complex hydrogeological conditions according to claim 4, characterized in that: In step one, multiple groups of first long-distance directional drill holes (3) are arranged in a fan-shaped structure, and the distance between the centers of adjacent first long-distance directional drill holes (3) is 1.4m.

6. The method for preventing and controlling water hazards in tunneling under complex hydrogeological conditions according to claim 1, characterized in that: In step 2, the length of the refrigeration chamber (4) is 3m, the width is 2.5m, and the height is 2.4m. The multiple refrigeration chambers (4) are arranged at equal intervals, and the interval between adjacent refrigeration chambers (4) is 500m.

7. The method for preventing and controlling water hazards in tunneling under complex hydrogeological conditions according to claim 1, characterized in that: In step 2, the lower part of the water-bearing layer (6) is frozen using a calcium chloride solution. The freezing time is 10 to 30 days, and the temperature of the calcium chloride solution is -32°C to -30°C.

8. The method for preventing and controlling water hazards in tunneling under complex hydrogeological conditions according to claim 1, characterized in that: In step 2, the total length of the freezing pipe is 500m.

9. The method for preventing and controlling water hazards in tunneling under complex hydrogeological conditions according to claim 1, wherein: In step 3, the second long distance directional drilling (8) is 500m long.

10. The method for preventing and controlling water hazards in tunneling under complex hydrogeological conditions according to claim 1, wherein: In step three, the second long-distance directional drilling hole (8) is located 1m above the bottom plate of the aquifer (6) and 6m away from the center line of the tunnel to be excavated (2).

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