Karst tunnel construction period gushing well flooding accident treatment method

Abstract

A karst tunnel construction period water gushing well flooding accident treatment method, comprising the following steps, 1) predicting the maximum water inflow of the well flooding section; 2) setting the reserved safety rock disc thickness according to the overall stability of the surrounding rock; 3) forming upper, middle and lower three steps according to the step design parameters; 4) according to the design parameters of the advanced drill hole, the advanced drill hole drainage is made in the middle step; 5) reinforcing the reserved safety rock disc; 6) when the well flooding water level drops to the middle step drainage hole, the upper step of the tunnel is excavated; 7) after the upper step is completely penetrated, the well flooding water body of the tunnel is directly pumped out. The karst tunnel construction period water gushing well flooding accident treatment method can maintain the overall stability of the safety rock disc surrounding rock, efficiently pump out the water of the karst tunnel construction period water gushing well flooding, restore the site construction as soon as possible, and ensure the construction safety.

Description

Technical Field

[0001] This invention relates to the field of disaster management technology during tunnel construction, and in particular to a method for handling water inrush and well flooding accidents during the construction of karst tunnels. Background Technology

[0002] In southwestern my country, karst formations are extremely common. Constructing tunnels in karst areas presents significant challenges due to the complex and varied forms and scale of karst development, coupled with well-developed underground karst conduits and underground river systems. Sudden water inrushes are an unavoidable threat. Mountain tunnel construction often involves multiple work faces in sections, including inclined shafts and tunnel entrances at both ends. When underground rivers, fault water-conducting zones, and water-rich karst cavities are exposed during reverse slope construction, water inrushes and flooding accidents can easily occur in the constructed sections.

[0003] Currently, drainage control during the construction of karst water-rich tunnels is difficult. When a tunnel floods due to water inrush, there is a lack of systematic and reasonable treatment methods, which forces the tunnel construction to be interrupted and may even lead to instability of the surrounding rock and structural damage, resulting in huge economic losses. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for handling water inrush and well flooding accidents during the construction of karst tunnels. This method employs an overall approach of advanced drilling for drainage and a three-stage excavation method to facilitate rapid resumption of construction and ensure construction safety.

[0005] To achieve the above objectives, the present invention provides a method for handling water inrush and well flooding accidents during the construction of karst tunnels, comprising the following steps:

[0006] 1) Predict the maximum water inflow in the flooded section;

[0007] 2) Set the reserved safety rock mass thickness according to the overall stability of the surrounding rock;

[0008] 3) According to the stair design parameters, three levels of steps are formed: upper, middle, and lower.

[0009] 4) Drill drainage holes in the middle bench according to the design parameters of the advanced drilling;

[0010] 5) Reinforce the reserved safety rock base;

[0011] 6) When the water level in the flooded well drops to the drainage hole of the middle bench, excavation of the upper bench of the tunnel will begin;

[0012] 7) After the upper steps are fully connected, the water in the tunnel wells will be directly pumped out.

[0013] Furthermore, step 1) further includes determining the integrity and water pressure of the surrounding rock ahead of the tunnel face, investigating the direction, development level, elevation, and flow rate of the underground river in the tunnel, and predicting the maximum water inflow in the flooded section.

[0014] Furthermore, step 2) further includes using whether the tunnel excavation deformation and failure zone is connected as a criterion for judging the overall stability of the surrounding rock of the safe rock mass. When the surrounding rock mass of the safe rock mass is level IV and karst is not locally developed, the reserved thickness of the safe rock mass is greater than or equal to 15 meters; when the surrounding rock mass of the safe rock mass is level IV and karst has developed a certain scale of solution pipes or cavities in front, the reserved thickness of the safe rock mass is greater than or equal to 25 meters; when the surrounding rock mass of the safe rock mass is level V and karst is not locally developed, the reserved thickness of the safe rock mass is greater than or equal to 20 meters; when the surrounding rock mass of the safe rock mass is level V and karst has developed a certain scale of solution pipes or cavities in front, the reserved thickness of the safe rock mass is greater than or equal to 30 meters.

[0015] Furthermore, step 3) further includes, and includes, the step design parameters, including, the step height; the length of each of the upper, middle, and lower steps is less than one times the diameter of the opening.

[0016] Furthermore, in step 4), the advanced drilling design parameters include the number of holes and the hole diameter.

[0017] Furthermore, step 5) further includes using advanced small guide pipes to perform advanced grouting reinforcement on the reserved safety rock mass to control the stability of the surrounding rock.

[0018] Furthermore, step 6) further includes, during the excavation of the upper step, increasing the density of monitoring points and monitoring frequency for the construction of the through section, and measuring data such as displacement around the tunnel, crown subsidence, and surface subsidence.

[0019] Furthermore, step 6) further includes the following: the density of monitoring and measurement points and the monitoring frequency of the construction monitoring of the through section refers to the density of each cross section of the Class V and Class IV surrounding rock being increased to 5m, with 5 monitoring and measurement points set up for each cross section.

[0020] Furthermore, step 7) further includes, after the upper step is fully connected, using a pumping and drainage device configured on the upper step to directly pump out the water from the flooded well in the tunnel.

[0021] The method for handling water inrush and well flooding accidents during the construction of karst tunnels according to the present invention has the following advantages compared with the prior art:

[0022] Maintain the overall stability of the surrounding rock of the safe rock mass;

[0023] Efficiently pump out water to restore on-site construction as soon as possible and ensure construction safety.

[0024] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0025] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0026] Figure 1 The present invention provides a flowchart for the treatment of water inrush and well flooding accidents during the construction of karst tunnels.

[0027] Figure 2 This is a schematic diagram of tunnel segmented multi-face construction according to the present invention;

[0028] Figure 3 This is a schematic diagram of the flooded well section, safety rock bed, pumping and drainage operation face, and water-adjacent surface according to the present invention;

[0029] Figure 4 This is a schematic diagram of the three-step excavation method according to the present invention;

[0030] Figure 5 This is a schematic diagram of the arrangement of encrypted measurement points for the through section monitoring according to the present invention;

[0031] Figure 6 This is a schematic diagram of the pre-drilling arrangement for the drainage operation face according to the present invention. Detailed Implementation

[0032] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0033] Figure 1 To illustrate the flowchart of the method for handling water inrush and well flooding accidents during karst tunnel construction according to the present invention, the following will refer to... Figure 1 The present invention provides a detailed description of the method for handling water inrush and well flooding accidents during the construction of karst tunnels.

[0034] First, in step 101, the maximum possible water inflow in the flooded section is predicted.

[0035] In this embodiment of the invention, the integrity of the surrounding rock and the water pressure in front of the tunnel face are determined, the direction, development level, elevation and flow rate of the underground river in the tunnel are investigated, and the maximum possible water inflow in the flooded section is predicted.

[0036] In step 102, the thickness of the reserved safety rock mass is set according to the overall stability of the surrounding rock.

[0037] In this embodiment of the invention, a reserved safety rock mass thickness is determined to prevent rock mass cracking and damage caused by insufficient rock mass thickness during the pumping and drainage process, while also preventing excessive rock mass thickness from causing excessive resistance in the pumping and drainage boreholes and drainage.

[0038] Whether the deformation and failure zone of the tunnel excavation is connected is used as a criterion for judging the overall stability of the surrounding rock of the safe rock mass. According to the "Design Specifications for Highway Tunnels, Volume 1: Civil Engineering" (JTG3370.1—2018), the level of the surrounding rock of the safe rock mass is determined.

[0039] If the safety rock mass is of grade IV and the karst is not locally developed, the reserved rock mass thickness shall be greater than or equal to 15 meters.

[0040] If the safety rock mass is of grade IV and the karst in front has developed a certain scale of solution tubes or cavities, the thickness of the safety rock mass should be greater than or equal to 25 meters.

[0041] If the surrounding rock of the safety rock mass is of grade V and the karst is not locally developed, the thickness of the reserved safety rock mass shall be greater than or equal to 20 meters.

[0042] If the safety rock mass is of grade V and the karst in front has developed a certain scale of solution tubes or cavities, the reserved safety rock mass thickness should be greater than or equal to 30 meters.

[0043] In step 103, according to the step design parameters, three levels of steps are formed: upper, middle and lower.

[0044] In this embodiment of the invention, the design parameters of the steps mainly involve the step height (H). Considering that the water head height h0 continuously decreases during the pumping and drainage process, and the single-hole drainage capacity q continuously decreases, the step height should be reasonably calculated and determined to achieve the drainage target, while ensuring the operating space of large machinery. The height of the upper step should not exceed 4m. In this embodiment of the invention, the three-step method is used to excavate the adjacent unflooded well section. The three-step method of excavation refers to dividing the entire cross-section into three sections from top to bottom. The upper section is excavated first, and after excavating to a certain length, the middle and lower sections are excavated in sequence to form upper, middle, and lower steps. Finally, the upper, middle, and lower sections are constructed simultaneously. The step length is less than one tunnel diameter.

[0045] In step 104, according to the design parameters of the advance drilling, advance drilling for drainage is carried out in the middle step.

[0046] The main design parameters for advanced drilling include the number of holes (n) and the hole diameter. Before large-scale drainage of flooded wells, the water level in the flooded wells is basically stable, and it can be assumed that the water pressure of the flooded wells and the main water inflow points are in equilibrium. Pre-drilling to drain the flooded wells will disrupt the equilibrium between the flooded well water and the surrounding rock water, resulting in a situation of "drainage and replenishment simultaneously." Therefore, during the actual drainage process, the reservoir capacity within the tunnel is dynamically controlled by the replenishment and drainage volumes. To reduce the effective reservoir capacity of the water inflow within the tunnel, the drainage capacity (Q) of the drainage system must effectively exceed the groundwater replenishment volume (P) within the tunnel.

[0047] The drainage capacity (Q) of the drainage system is the product of the single-hole drainage capacity (q) and the number of boreholes, i.e., Q = q × n.

[0048] The single-orifice drainage capacity q, assuming it conforms to Bernoulli's equation, is calculated using the following formula:

[0049]

[0050] Where: u is the flow coefficient, h0 is the head height, and A is the borehole cross-sectional area.

[0051] Since the flow coefficients of boreholes with different diameters are approximately equal, a test borehole can be set up on site first, and the flow coefficient u can be calculated back based on the actual flow rate measured at the test borehole.

[0052] To improve the effectiveness of water exploration and release, the advance drilling should penetrate as many fissures as possible and reach the water-facing surface of the safe rock bed.

[0053] In step 105, the reserved safety rock mass is reinforced.

[0054] In this embodiment of the invention, the reserved safety rock mass is reinforced by advanced grouting using advanced small guide pipes to control the stability of the surrounding rock.

[0055] In step 106, when the water level in the flooded well drops to the drainage hole of the middle step, the upper step of the tunnel is excavated.

[0056] In this embodiment of the invention, when the water level in the flooded well drops to near the drainage hole of the middle step, the upper step is excavated to connect to the water-facing surface. During the excavation of the upper step, the number of monitoring points and the monitoring frequency of the construction monitoring of the connected section are increased to measure data such as displacement around the tunnel, crown settlement, and surface settlement. When abnormal data is detected, corresponding measures should be taken in a timely manner to reinforce the surrounding rock and inject grout to plug the water.

[0057] In step 107, after the upper step is fully connected, the water in the flooded well is directly pumped out.

[0058] In this embodiment of the invention, after the upper step is fully connected, drainage equipment is installed on the upper step to directly pump out the water in the tunnel wells. After the water in the wells is pumped out, normal tunnel construction is resumed.

[0059] Figure 2 This is a schematic diagram of tunnel segmented multi-face construction according to the present invention. Figure 2 As shown, it includes: 1. Inclined shaft; 2. Main water inflow point; 3. Tunnel excavation direction; 4. Completed excavation section; 5. Unexcavated section.

[0060] In this embodiment of the invention, a multi-face construction method combining inclined shafts is adopted to expose the main water inflow points located in the internal construction section during construction.

[0061] Figure 3 The schematic diagram of the flooded well section, safety rock bed, pumping and drainage working face, and water-adjacent surface according to the present invention is as follows: Figure 3 As shown, it includes: a reserved safety rock bed 6; a drainage working face 7; a water-facing face 8; and a section of the well flooded by water inrush 9.

[0062] Figure 4 This is a schematic diagram of the three-step excavation method according to the present invention, as shown below. Figure 4 As shown, it includes: a step height of 10; a step 11 on the pumping operation surface; a step 12 in the middle of the pumping operation surface; and a step 13 below the pumping operation surface.

[0063] Figure 5 A schematic diagram of the arrangement of monitoring and measurement densification points for the through section according to the present invention is shown below. Figure 5 As shown, it includes 14 monitoring measurement points.

[0064] In this embodiment of the invention, the monitoring points and monitoring frequency of the construction of the through section are increased. For Class V and Class IV surrounding rock, the monitoring points are increased to 5m for each section, and 5 monitoring points are set up for each section (1 for the arch crown, 1 for each of the two arch waists, and 1 for each of the two side walls).

[0065] Figure 6 This is a schematic diagram of the pre-drilling arrangement for the drainage operation face according to the present invention, as shown below. Figure 6 As shown, it includes a water head height of 15 and a pre-drilled hole of 16.

[0066] In this embodiment of the invention, the drilling construction requirements are as follows:

[0067] (1) Drilling must be carried out strictly according to the marked azimuth and inclination. The azimuth and inclination of the borehole must be checked every shift to ensure that the borehole and the final borehole reach the designed stratum. The azimuth and inclination errors are to be controlled within 1° to be considered qualified;

[0068] (2) During the drilling process, the drilling tool should be carefully recorded and the depth error should not exceed 0.15 meters. During the drilling process, the situation inside the hole should be closely monitored. If the water flow in the hole is large, the drilling should be stopped immediately, and the drilling tool should be pulled out after taking measures.

[0069] (3) While controlling the release of water, decide whether to conduct a water release test based on the water inflow situation, but it is necessary to observe hydrogeological parameters such as water pressure, water quality, and water inflow.

[0070] (4) During the drilling process, if the strata soften or water surges, the hole depth should be accurately recorded, and the changes in depth between soft rock and hard rock should be carefully recorded.

[0071] It will be understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for handling water inrush and well flooding accidents during the construction of karst tunnels, characterized in that, Includes the following steps: 1) Predict the maximum water inflow in the flooded section; 2) Set the reserved safety rock mass thickness based on the overall stability of the surrounding rock; 3) According to the step design parameters, three levels of steps are formed: upper, middle and lower. The step design parameters include the step height. The three-step method is used to excavate the adjacent unflooded well section, dividing the entire cross section into three sections from top to bottom, forming three steps with a length of less than one tunnel diameter: upper, middle and lower. 4) Drilling for drainage in the middle bench according to the design parameters of the advanced drilling; the design parameters of the advanced drilling include the number of boreholes and the borehole diameter; the drainage capacity of the advanced drilling for drainage in the middle bench is the product of the drainage capacity of a single borehole and the number of boreholes; the drainage capacity of a single borehole is calculated as follows: ， Where q is the drainage capacity of a single borehole, u is the flow coefficient, h0 is the head height, and A is the cross-sectional area of ​​the borehole. 5) Reinforce the reserved safety rock base; 6) When the water level in the flooded well drops to the drainage hole of the middle bench, excavation of the upper bench of the tunnel will commence; 7) After the upper steps are fully connected, the water in the tunnel wells will be directly pumped out.

2. The method for handling water inrush and well flooding accidents during karst tunnel construction according to claim 1, characterized in that, Step 1) includes determining the integrity and water pressure of the surrounding rock ahead of the tunnel face, investigating the direction, development level, elevation, and flow rate of the underground river in the tunnel, and predicting the maximum water inflow in the flooded section.

3. The method for handling water inrush and well flooding accidents during karst tunnel construction according to claim 1, characterized in that, Step 2) includes using whether the tunnel excavation deformation and failure zone is connected as a criterion for judging the overall stability of the surrounding rock of the safe rock mass. When the surrounding rock mass of the safe rock mass is level IV and karst is not locally developed, the reserved thickness of the safe rock mass is greater than or equal to 15 meters; when the surrounding rock mass of the safe rock mass is level IV and karst has developed a certain scale of solution pipes or cavities in front, the reserved thickness of the safe rock mass is greater than or equal to 25 meters; when the surrounding rock mass of the safe rock mass is level V and karst is not locally developed, the reserved thickness of the safe rock mass is greater than or equal to 20 meters; when the surrounding rock mass of the safe rock mass is level V and karst has developed a certain scale of solution pipes or cavities in front, the reserved thickness of the safe rock mass is greater than or equal to 30 meters.

4. The method for handling water inrush and well flooding accidents during karst tunnel construction according to claim 1, characterized in that, Step 5) includes using advanced small guide pipes to perform advanced grouting reinforcement on the reserved safety rock mass to control the stability of the surrounding rock.

5. The method for handling water inrush and well flooding accidents during karst tunnel construction according to claim 1, characterized in that, Step 6) also includes, during the excavation of the upper step, increasing the number of monitoring points and the frequency of monitoring the construction of the through section, and measuring data such as displacement around the tunnel, crown subsidence, and surface subsidence.

6. The method for handling water inrush and well flooding accidents during karst tunnel construction according to claim 5, characterized in that, Step 6) also includes the densification of the on-site construction monitoring and measurement points and the monitoring frequency of the connected section, which means that the density of each cross section of the Class V and Class IV surrounding rock is increased to 5m, and 5 monitoring and measurement points are set up for each cross section.

7. The method for handling water inrush and well flooding accidents during karst tunnel construction according to claim 1, characterized in that, Step 7) includes, after the upper step is fully connected, using a pumping and drainage device configured on the upper step to directly pump out the water from the flooded well in the tunnel.

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