Segmented and layered pressure reduction system for long-distance pressure tunnel and water filling and draining control method

Abstract

The invention discloses a segmented and layered pressure reduction system and a water filling and draining control method for a long-distance pressure tunnel, the pressure tunnel comprises a pressure tunnel front section and a pressure tunnel rear section, an inlet of the pressure tunnel front section is connected with an upstream reservoir, and an outlet of the pressure tunnel rear section is connected with a downstream water receiving reservoir or a river channel; the pressure reduction system is arranged between the pressure tunnel front section and the pressure tunnel rear section; the surge shaft is arranged at an outlet of the front section of the pressure tunnel and communicated with the outlet, the pressure stabilizing chamber is arranged between the surge shaft and the rear section of the pressure tunnel and communicated with the surge shaft and the rear section of the pressure tunnel, a rock stem dividing a flow channel into an upper layer and a lower layer is arranged in the middle of the joint of the pressure stabilizing chamber and the surge shaft, and the control gate is used for controlling the water delivery flow of the upper-layer flow channel and the lower-layer flow channel respectively. A traditional pressure tunnel tail end control mode is broken through, the problem that the water pressure in the rear section of the tunnel is high is solved, the problems of submerged outflow of an arc-shaped gate and high-water-head opening and closing of a plane gate are avoided, and the problem that the water hammer pressure is high when the gate is closed is relieved.

Description

Technical Field

[0001] The invention relates to the field of hydraulic engineering construction in civil engineering, and in particular to a segmented and layered pressure reduction system for a long-distance pressurized tunnel and a filling and drainage control method. Background Art

[0002] Invention patent CN114635398A discloses a mid-section control rear section pressure relief system and a filling and drainage control method for an ultra-long pressurized tunnel. The pressure relief system includes: a control gate, which is arranged in the middle section of the pressurized tunnel and divides it into two sections, front and back, for connecting or isolating the front and back sections of the pressurized tunnel; a pressure stabilizing chamber, which is arranged behind the control gate and connected to the rear section of the pressurized tunnel, for stabilizing the water surface fluctuation after the water jump and replenishing water to the rear section of the pressurized tunnel when it is in a negative pressure state; and two inspection gates, which are respectively arranged at the entrance and exit of the pressurized tunnel. The invention patent breaks through the traditional idea of ​​end control of pressurized tunnels, and adopts a mid-section control scheme to greatly reduce the maximum internal water pressure of the rear section of the tunnel, reducing engineering risks, construction difficulties and engineering investment. However, the patent still has the following defects: (1) When the radial gate is closed, the patent will cause higher water hammer pressure, resulting in a larger maximum pressure envelope, a higher design pressure of the tunnel lining, and a significant increase in the lining cost; (2) The patent adopts a single radial gate control, and the operation of the radial gate should try to avoid flooding the outflow. The layout of the patent cannot avoid the radial gate flooding the outflow. Summary of the invention

[0003] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a segmented and layered pressure reduction system and a filling and drainage control method for high-head free outflow and low-head submerged outflow in a long-distance pressurized water transfer tunnel, breaking through the traditional terminal control method of a pressurized tunnel, solving the problem of high water pressure in the rear section of the tunnel, avoiding the problems of submerged outflow of arc gates and high-head opening and closing of plane gates, and alleviating the problem of higher water hammer pressure when closing the gates.

[0004] In order to solve the above technical problems, the present invention is implemented by the following technical solutions:

[0005] On the one hand, the present invention provides a segmented and layered pressure reduction system for a long-distance pressurized tunnel, wherein the pressurized tunnel comprises a front section of the pressurized tunnel and a rear section of the pressurized tunnel, the inlet of the front section of the pressurized tunnel is connected to an upstream reservoir, and the outlet of the rear section of the pressurized tunnel is connected to a downstream receiving reservoir or a river, and the pressure reduction system is arranged between the front section of the pressurized tunnel and the rear section of the pressurized tunnel; it is characterized in that the pressure reduction system comprises a pressure regulating well, a pressure stabilizing chamber and a control gate, the pressure regulating well is arranged at the outlet of the front section of the pressurized tunnel and is connected thereto, the pressure stabilizing chamber is arranged between the pressure regulating well and the rear section of the pressurized tunnel and is connected to each other, a rock stem is arranged in the middle of the connection between the pressure stabilizing chamber and the pressure regulating well, which divides the flow channel into an upper and lower layer, and the control gate is used to control the water delivery flow of the upper flow channel and the lower flow channel respectively.

[0006] As a further optimization scheme of the present invention, the control gate includes an upper arc gate and a lower plane gate. The upper arc gate can control the water flow rate of the upper flow channel under the control of the arc gate opening and closing machine room, and the lower plane gate can control the water flow rate of the lower flow channel under the control of the plane gate opening and closing machine.

[0007] As a further optimization scheme of the present invention, the plane gate opening and closing machine is arranged at the top of the pressure regulating shaft, and a bottom hole gate chamber is arranged in the rock stem, and the bottom hole gate chamber is used to control the opening and closing of the lower plane gate through the plane gate opening and closing machine.

[0008] As a further optimization solution of the present invention, the arc gate opening and closing machine room is arranged on the top of the pressure stabilizing chamber.

[0009] As a further optimization scheme of the present invention, the rear section of the pressurized tunnel adopts a reverse slope design, and the bottom elevation of the pressure stabilizing chamber needs to be lower than the bottom elevation of the terminal end of the rear section of the pressurized tunnel.

[0010] As a further optimization scheme of the present invention, the elevation of the top of the pressure regulating well needs to be higher than the maximum water hammer pressure head.

[0011] As a further optimization scheme of the present invention, the elevation of the top of the pressure stabilizing chamber needs to be higher than the normal water level of the downstream river.

[0012] As a further optimization solution of the present invention, the entrance of the front section of the pressurized tunnel and the exit of the rear section of the pressurized tunnel are both provided with inspection gates.

[0013] On the other hand, the present invention provides a method for controlling the filling and drainage of a segmented and layered pressure reduction system with high-head free outflow and low-head submerged outflow in a long-distance pressurized tunnel, the method comprising:

[0014] When the tunnel is filled with water, the control gate is kept closed, and water is filled into the front section and the rear section of the pressurized tunnel from the entrance and exit of the pressurized tunnel respectively. After the filling is completed, the upper radial gate is slowly opened first, and then the lower plane gate is slowly opened (to prevent the radial gate from flooding the outflow and reduce the working pressure of the plane gate). The water flow in the front section of the pressurized tunnel flows into the plenum through the control gate. As the water level in the plenum rises, the water flow in the rear section of the pressurized tunnel begins to accelerate to the downstream outlet. The water level in the plenum fluctuates and then tends to stabilize. The amount of water flowing into the plenum from the front section of the pressurized tunnel and the amount of water flowing into the plenum from the plenum to the rear section of the pressurized tunnel reach a balance, which is the water delivery flow of the entire tunnel system. The tunnel filling process is completed, and the tunnel enters a normal operating state.

[0015] When draining the tunnel, first slowly close the lower flat gate, and then slowly close the upper arc gate (to prevent the arc gate from submerging the outflow, reduce the working pressure of the flat gate, and relieve water hammer pressure), block the water flow in the front section of the pressurized tunnel, and the water in the pressure chamber is replenished into the rear section of the pressurized tunnel. The water in the rear section of the pressurized tunnel continues to flow downstream, and the water level in the pressure chamber drops; as the water level in the pressure chamber drops, the water flow in the rear section of the pressurized tunnel slows down until the water flow stops; after fluctuations, the water level in the pressure chamber is the same as the water level of the river or reservoir at the outlet of the rear section of the pressurized tunnel. The rear section of the pressurized tunnel only bears the internal water pressure brought by the water level of the downstream river or reservoir. After the water level in the tunnel stabilizes, close the inspection gates at the inlet and outlet of the tunnel, and use a water pump to pump out the remaining water in the tunnel to complete the tunnel drainage process.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] (1) The double-layer gate + pressure regulating well + pressure stabilizing chamber design adopted by the present invention, in which a pressure regulating well is arranged in front of the double-layer gate, can effectively relieve the water hammer pressure. The working pressure of the double-layer gate is reduced, and the construction cost is reduced. It can not only effectively relieve the water hammer pressure when the system is closed, but also effectively improve the flow state of the tunnel behind the gate, avoid the problem of alternating open and full flow, and enable the downstream tunnel to maintain a stable pressurized flow state.

[0018] (2) The double-layer gate design adopted by the present invention avoids the problem of the radial gate being submerged and the plane gate being opened and closed at high water head, reducing the design difficulty and safety risks of the gate. The specific advantages are: ① During the opening of the water supply system, when the water level in the pressure regulating well in front of the gate is higher than the bottom elevation of the radial gate, the radial gate is opened first to ensure the free outflow of the radial gate. When the water level is lower than the bottom elevation of the radial gate, the plane gate is opened and the water flows through the plane gate; ② During the closing of the water supply system, the radial gate is closed first, the water level in the pressure regulating well rises, and the water flows through the radial gate, and then the radial gate is closed, which can effectively alleviate the water hammer pressure, reduce the maximum pressure envelope, and reduce the lining cost; ③ The double-layer arrangement scheme makes the working design pressure of the plane gate also smaller. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the arrangement and operating conditions of the pressure reducing system of the present invention; in the figure, A is the tunnel entrance, B is the control gate, C is the tunnel exit, H1 is the water supply level of the upstream reservoir, H2 is the normal water level of the downstream outlet river, D1 is the highest total water head line from the tunnel entrance to the control system under normal operating conditions, and D2 is the highest total water head line from the tunnel entrance through the double-layer gate to the tunnel exit under normal operating conditions.

[0020] Figure 2 Detailed structural diagram of the pressure reducing system of the present invention.

[0021] Numbers in the figure: 1. Upper radial gate; 2. Lower flat gate; 3. Pressure regulating well; 4. Pressure stabilizing chamber; 5. Maintenance gate; 6. Rock stem; 7. Radial gate opening and closing machine room; 8. Flat gate opening and closing machine; 9. Bottom hole gate chamber. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solution of the present invention, the preferred implementation scheme of the present invention is described below in conjunction with specific embodiments. However, it should be understood that the drawings are only used for exemplary description and cannot be understood as a limitation on this patent. In order to better illustrate this embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted. The positional relationship described in the drawings is only for exemplary description and cannot be understood as a limitation on this patent.

[0023] For the traditional terminal control method of pressurized tunnels, when the gate is closed, the water flow can be quickly cut off, and a positive pressure water hammer will appear in front of the gate. Behind the gate is the open water receiving river channel downstream. However, the segmented and layered pressure reduction system can avoid the possibility of negative pressure caused by the water in the pressure stabilizing chamber continuing to flow downstream due to inertia when the system is closed.

[0024] The technical solution of the present invention is to reduce the maximum internal water pressure of the rear section of the tunnel by moving the control building of the long pressurized tunnel forward to the middle section, and at the same time set up a segmented and layered pressure reduction system to avoid the problem of radial gate flooding outflow and plane gate opening and closing with high water head, and alleviate the maximum water hammer pressure of the tunnel when the system is closed. The specific solution is as follows:

[0025] like Figure 1 and Figure 2As shown, the present invention provides a segmented and layered pressure reduction system for high-head free outflow and low-head submerged outflow of a long-distance pressurized water transfer tunnel, the pressurized tunnel comprises a front section of the pressurized tunnel and a rear section of the pressurized tunnel, the entrance of the front section of the pressurized tunnel is connected to an upstream reservoir, the outlet of the rear section of the pressurized tunnel is connected to a downstream receiving reservoir or a river, and both the entrance of the front section of the pressurized tunnel and the outlet of the rear section of the pressurized tunnel are provided with inspection gates 5; the pressure reduction system is arranged between the front section of the pressurized tunnel and the rear section of the pressurized tunnel; the pressure reduction system comprises a pressure regulating well 3, a pressure stabilizing chamber 4 and a control gate.

[0026] Among them, the pressure regulating well 3 is arranged at the outlet of the front section of the pressurized tunnel and is connected thereto. The pressure regulating well 3 is used to stabilize the pressure fluctuations during the closing process of the upper radial gate 1 and to relieve the water hammer pressure. At the same time, the pressure regulating well 3 can also serve as a ventilation well to balance the air pressure in the pressure stabilizing chamber 4.

[0027] Among them, the pressure-stabilizing chamber 4 is arranged between the pressure-regulating well 3 and the rear section of the pressurized tunnel and is interconnected. The pressure-stabilizing chamber 4 is used to stabilize the water surface fluctuations that cause water jumps when opening and closing the control gate, and to prevent the gas that may be generated when opening the control gate from entering the downstream tunnel.

[0028] Among them, a rock stem 6 is arranged in the middle of the connection between the pressure-stabilizing chamber 4 and the pressure-regulating well 3, which divides the flow channel into upper and lower layers, and the control gate is used to control the water flow of the upper flow channel and the lower flow channel respectively. Specifically, the control gate includes an upper radial gate 1 and a lower plane gate 2. The upper radial gate 1 can control the water flow of the upper flow channel under the control of the radial gate opening and closing machine room 7, and the lower plane gate 2 can control the water flow of the lower flow channel under the control of the plane gate opening and closing machine 8. The plane gate opening and closing machine is arranged at the top of the pressure-regulating well 3, and a bottom hole gate chamber 9 is arranged in the rock stem 6. The bottom hole gate chamber 9 is used to control the opening and closing of the lower plane gate 2 through the plane gate opening and closing machine 8. The radial gate opening and closing machine room 7 is arranged at the top of the pressure-stabilizing chamber 4. Among them, the control radial gate is arranged above the control plane gate, which avoids the problem of the radial gate flooding outflow and the plane gate opening and closing at high water head, and reduces the design difficulty and safety risk of the gate.

[0029] Among them, the rear section of the pressurized tunnel adopts a reverse slope design, and the elevation of the bottom of the stabilizing chamber must be lower than the elevation of the bottom of the rear end of the pressurized tunnel. Under the condition that the tunnel exit position and elevation are fixed, the reverse slope is adopted to reduce the elevation of the entire tunnel line, which is conducive to ensuring the pressurized operation state of the rear section of the tunnel. The slope of the reverse slope should be determined after comprehensive consideration of the geological conditions and operation scheduling conditions, because when the tunnel exit position and elevation are fixed, the larger the reverse slope, the easier it is to ensure the pressurized operation state of the rear section of the tunnel, but the greater the buried depth of the control gate and the stabilizing chamber, the more additional support engineering work may be required.

[0030] from Figure 1It can be seen that the maximum internal water pressure of the AB section tunnel occurs when the control system is closed at B, and the maximum internal water pressure of the BC section tunnel occurs under normal water delivery operation conditions. Since the control system has been moved forward to the middle section B, the connection between the BC section tunnel and the upstream reservoir is cut off, and the maximum internal water pressure borne by the rear section of the tunnel is much smaller than the terminal control solution. For the shallow buried tunnel section, since the maximum internal water pressure is greatly reduced, there is no need to set up a steel lining, which significantly saves project investment and construction period.

[0031] In order to better illustrate the technical effects of the present invention, a detailed description is now given in conjunction with specific implementation cases.

[0032] Taking the Yangtze River to Han River Diversion Project as an example, according to the traditional pressure tunnel end control method, the entire tunnel has to withstand the maximum hydrostatic pressure of 102m brought by the water supply level of the upstream Three Gorges Reservoir of up to 173.3m under static water. This is not a control condition for deep buried tunnels with good surrounding rock and large external water pressure, but for shallow buried sections with broken surrounding rock, it is necessary to greatly strengthen the tunnel support measures. According to calculations, about 14km long of the shallow buried tunnel in the rear section needs to be equipped with a steel lining. After adopting the double-layer gate joint control scheme, the maximum internal water pressure of the 30km tunnel in the rear section corresponds to the water level of the Three Gorges Reservoir of 173.3m. At this time, the highest operating water level of the tunnel is about 103.4m, and it decreases to the downstream river water level of about 88m towards the tunnel exit. The highest water level in the transient stabilizing chamber when the gate is opened is about 104.8m. Considering that the bottom plate elevation of the rear section tunnel is 65-76m reverse slope, the maximum internal water pressure of the rear section tunnel is 39.8m, which is about 60m lower than the terminal control scheme. According to structural calculations, the steel lining of the rear section tunnel can be basically eliminated by adopting the segmented and layered pressure reduction system, which saves more than 1 billion yuan in direct engineering investment, greatly speeds up the construction progress, and reduces engineering risks.

[0033] For pressurized tunnels, cavitation, erosion, vibration and other problems caused by alternating open and full flow will seriously threaten the durability of the tunnel structure. This is a situation that is not allowed to occur in the form of mandatory provisions of the "Specifications for the Design of Hydraulic Tunnels" (SL 279-2016). Taking the Yangtze River to Han River Diversion Project as an example, the control system was moved forward to the pile number 164km, and the approximately 194km long pressurized tunnel was divided into two sections, 164km and 30km long respectively. According to the engineering layout and scheduling method of the initial design research stage of the Yangtze River to Han River Diversion Project, the closed-door transient minimum water level in the stabilizing chamber is 80.21m, which can maintain the stable pressurized flow state of the rear section of the tunnel and the transient minimum water head line of the rear section of the tunnel is not lower than the cave top elevation by 2m.

[0034] The above is only a preferred embodiment of the present invention, but the present invention is not limited to the above specific embodiments. Those skilled in the art may make some modifications, supplements or use similar methods instead without departing from the principle of the present invention, which should also be regarded as the protection scope of the present invention.

Claims

1. A segmented and layered decompression system for a long-distance pressurized tunnel, wherein the pressurized tunnel comprises a front section of the pressurized tunnel and a rear section of the pressurized tunnel, wherein the entrance of the front section of the pressurized tunnel is connected to an upstream reservoir, and the outlet of the rear section of the pressurized tunnel is connected to a downstream receiving reservoir or river, and the decompression system is arranged between the front section of the pressurized tunnel and the rear section of the pressurized tunnel; characterized in that: The pressure reducing system comprises a pressure regulating well (3), a pressure stabilizing chamber (4) and a control gate. The pressure regulating well (3) is arranged at the outlet of the front section of the pressure tunnel and is in communication with the outlet. The pressure stabilizing chamber (4) is arranged between the pressure regulating well (3) and the rear section of the pressure tunnel and is in communication with each other. A rock stem (6) is arranged in the middle of the connection between the pressure stabilizing chamber (4) and the pressure regulating well (3) to divide the flow channel into upper and lower layers. The control gate is used to control the water flow of the upper flow channel and the lower flow channel respectively.

2. The segmented and layered decompression system for a long-distance pressurized tunnel according to claim 1 is characterized in that: The control gate comprises an upper radial gate (1) and a lower plane gate (2); the upper radial gate (1) can control the water flow rate of the upper flow channel under the control of the radial gate opening and closing machine room (7); and the lower plane gate (2) can control the water flow rate of the lower flow channel under the control of the plane gate opening and closing machine (8).

3. The segmented and layered decompression system for a long-distance pressurized tunnel according to claim 2 is characterized in that: The plane gate opening and closing machine (8) is arranged at the top of the pressure regulating shaft (3), and a bottom hole gate chamber (9) is arranged in the rock stem (6). The bottom hole gate chamber (9) is used to control the opening and closing of the lower plane gate (2) through the plane gate opening and closing machine (8).

4. The segmented and layered decompression system for a long-distance pressurized tunnel according to claim 2 is characterized in that: The arc gate opening and closing machine room (7) is arranged on the top of the pressure stabilizing chamber (4).

5. The segmented and layered decompression system for a long-distance pressurized tunnel according to claim 1 is characterized in that: The rear section of the pressurized tunnel adopts a reverse slope design, and the bottom elevation of the pressure stabilizing chamber (4) needs to be lower than the bottom elevation of the end of the rear section of the pressurized tunnel.

6. The segmented and layered decompression system for a long-distance pressurized tunnel according to claim 1 is characterized in that: The top elevation of the pressure regulating well (3) needs to be higher than the maximum water hammer pressure head.

7. The segmented and layered decompression system for a long-distance pressurized tunnel according to claim 1 is characterized in that: The top elevation of the stabilizing chamber (4) needs to be higher than the normal water level of the downstream river channel.

8. The segmented and layered decompression system for a long-distance pressurized tunnel according to claim 1 is characterized in that: The entrance of the front section of the pressurized tunnel and the exit of the rear section of the pressurized tunnel are both provided with inspection gates (5).

9. A method for controlling the filling and drainage of a segmented and layered pressure reduction system of a long-distance pressure tunnel according to any one of claims 1 to 8, characterized in that: The filling and drainage control method comprises: When the tunnel is filled with water, the control gate is kept closed, and water is filled into the front section and the rear section of the pressurized tunnel from the entrance and exit of the pressurized tunnel respectively. After the water filling is completed, the upper arc gate (1) is slowly opened first, and then the lower plane gate (2) is slowly opened. The water flow in the front section of the pressurized tunnel flows into the stabilizing chamber (4) through the control gate. As the water level in the stabilizing chamber (4) rises, the water flow in the rear section of the pressurized tunnel begins to accelerate toward the downstream outlet. The water level in the stabilizing chamber (4) fluctuates and then tends to stabilize. The amount of water flowing into the stabilizing chamber (4) from the front section of the pressurized tunnel and the amount of water flowing into the stabilizing chamber (4) from the stabilizing chamber (4) into the rear section of the pressurized tunnel reach a balance, which is the water delivery flow of the entire tunnel system. The tunnel water filling process is completed, and the tunnel enters a normal operating state. When draining the tunnel, the lower plane gate (2) is first slowly closed, and then the upper arc gate (1) is slowly closed to block the water flow in the front section of the pressurized tunnel. The water in the pressure chamber (4) is replenished and enters the rear section of the pressurized tunnel. The water in the rear section of the pressurized tunnel continues to flow downstream, and the water level in the pressure chamber (4) decreases. As the water level in the pressure chamber (4) decreases, the water flow in the rear section of the pressurized tunnel slows down until the water flow stops. After fluctuations, the water level in the pressure chamber (4) is the same as the water level of the river or reservoir at the outlet of the rear section of the pressurized tunnel. The rear section of the pressurized tunnel only bears the internal water pressure brought by the water level of the downstream river or reservoir. After the water level in the tunnel stabilizes, the inspection gates (5) at the inlet and outlet of the tunnel are closed, and the remaining water in the tunnel is pumped out by a water pump to complete the tunnel drainage process.

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