A diversion tunnel construction adit plugging body and plugging method

Abstract

This invention discloses a sealing body and sealing method for a construction adit of a diversion tunnel, comprising an outlet sealing body located at the outlet of the construction adit and an inlet sealing body located at the inlet of the construction adit. The inlet sealing body is constructed of micro-expansion concrete, and its cross-sectional shape matches the cross-section of the construction adit. The inlet sealing body also includes a water pressure balancing system and a surrounding rock bonding system. The water pressure balancing system includes at least one row of drainage holes located at the bottom of the inlet sealing body and penetrating the inlet sealing body along the axis of the construction adit. The surrounding rock bonding system includes system reinforcing bars arranged around the perimeter of the inlet sealing body in contact with the surrounding rock, and backfill grouting pipes pre-embedded in the top arch of the inlet sealing body. This invention can significantly optimize the structural dimensions of the outlet sealing body and significantly enhance the stability of the inlet slope of the construction adit.

Description

Technical Field

[0001] This invention relates to the field of water conservancy and hydropower engineering construction technology, specifically to a sealing body and sealing method for a diversion tunnel construction branch. Background Technology

[0002] In water conservancy and hydropower projects, after the diversion tunnel construction adit (hereinafter referred to as the construction adit) has completed its auxiliary mission, it needs to be sealed before the gate is closed for water impoundment. Based on the premise that the overall surrounding rock conditions of the construction adit are good, the conventional design of the sealing body at the outlet of the construction adit is as follows: when the diversion tunnel is flowing, the total head pressure of the construction adit is not water inside, but the diversion tunnel is full of water. It mainly relies on the friction and cohesion between the outlet concrete and the bedrock to resist slippage.

[0003] However, for the inlet section of the construction adit, especially the weathered slope with poor surrounding rock stability at the entrance and the construction adit with tight schedule and no reinforcement, the traditional outlet sealing body design faces two major challenges: (1) Insufficient stability at the entrance: The surrounding rock at the entrance of the construction adit is poor and the slope is prone to instability due to the lack of lining inside the tunnel and high pressure water seepage after water storage; (2) Poor economy: After water storage, due to the inlet water flow rate and the seepage rate of the diversion tunnel inlet gate being inconsistent, the outlet sealing body of the construction adit will bear huge water thrust. The designed outlet sealing body is long and large in volume, resulting in high cost and long construction period.

[0004] Current technology lacks an effective means to simultaneously ensure the stability of the inlet slope of the construction adit and the economic efficiency of the sealing body at the outlet of the construction adit. Summary of the Invention

[0005] In view of this, the present invention provides a sealing body and sealing method for a construction adit of a diversion tunnel. Based on the existence of an outlet sealing body in the construction adit of the diversion tunnel, an inlet sealing body is set up, which can significantly optimize the structural dimensions of the outlet sealing body and significantly enhance the stability of the inlet slope of the construction adit.

[0006] The technical solution adopted in this invention is as follows: A sealing body for a diversion tunnel construction adit includes an outlet sealing body located at the outlet of the construction adit and an inlet sealing body located at the inlet of the construction adit. The inlet sealing body is cast from micro-expansion concrete, and its cross-sectional shape matches the cross-section of the construction adit. The inlet sealing body is further provided with: a water pressure balancing system, including at least one row of drainage holes located at the bottom of the inlet sealing body and penetrating the inlet sealing body along the axis of the construction adit; a surrounding rock bonding system, including system reinforcing bars arranged around the perimeter of the inlet sealing body in contact with the surrounding rock, and a backfill grouting pipe pre-embedded in the top arch of the inlet sealing body.

[0007] Furthermore, the backfill grouting pipe includes a grout inlet pipe, a grout outlet pipe, and an exhaust pipe.

[0008] Furthermore, the inlet sealing body is divided into a first sealing body and a second sealing body along the axis of the construction adit. The structural joint between the first sealing body and the second sealing body is provided with a number of connecting reinforcing bars that connect the first sealing body and the second sealing body; the connecting reinforcing bars are arranged in a crisscross pattern.

[0009] Furthermore, the system's reinforcing bars are HPB300 steel bars, arranged in a quincunx pattern.

[0010] Furthermore, the strength grade of the micro-expansion concrete is C20.

[0011] A method for sealing a construction adit of a diversion tunnel includes: based on an outlet sealing body at the outlet of the construction adit, casting micro-expansion concrete at the inlet of the construction adit to form an inlet sealing body matching the cross-section of the construction adit; during the casting of the micro-expansion concrete, pre-embedding sleeves at designated locations to form at least one row of drainage holes penetrating the inlet sealing body; arranging systematic reinforcing bars at the contact surface between the inlet sealing body and the surrounding rock, and pre-embedding backfill grouting pipes in the top arch of the inlet sealing body; and after the micro-expansion concrete reaches its strength, backfilling and grouting the gaps in the top arch through the backfill grouting pipes.

[0012] Furthermore, when the length of the inlet sealing body exceeds the set value, the inlet sealing body is divided into a first sealing body and a second sealing body, which are cast separately, and connecting reinforcing bars are arranged crosswise in the structural joint between the first sealing body and the second sealing body.

[0013] Furthermore, the number and diameter of the drainage holes are calculated and determined based on the water inflow rate after the diversion tunnel is sealed. This is to ensure that the amount of water entering the construction adit through the drainage holes can change synchronously during the process of the diversion tunnel being filled with seepage water, thereby achieving a balance of water pressure between the construction adit and the diversion tunnel.

[0014] Beneficial effects: 1. On the one hand, the present invention utilizes the bottom drainage hole to achieve real-time water pressure balance between the construction adit and the diversion tunnel after water storage, avoiding the outlet sealing body from bearing the full head pressure. On the other hand, the system reinforces the integrity of the inlet sealing body and the surrounding rock through reinforcement and backfill grouting, effectively solving the slope instability problem under fragile surrounding rock conditions such as the weathered slope at the inlet of the construction adit, while significantly optimizing the structural dimensions of the outlet sealing body.

[0015] 2. The backfill grouting pipe of this invention adopts a combination structure of grout inlet pipe, grout outlet pipe and vent pipe to ensure that the grouting of the top arch gap is dense. Combined with the quincunx arrangement of the system reinforcement bars, it further improves the bonding strength between the inlet sealing body and the surrounding rock, ensures the long-term stability of the sealing body and avoids structural hazards caused by high-pressure water seepage.

[0016] 3. The present invention involves the segmented casting of the imported sealing body and the setting of intersecting connecting ribs at the structural joints. This not only solves the problem of temperature control and crack prevention during the construction of long-length sealing bodies, but also transfers stress through the connecting ribs, making the segmented sealing bodies form a cohesive whole that bears the load, thereby improving the structural bearing capacity and adapting to the sealing needs of construction tunnels of different lengths.

[0017] 4. This invention uses C20 micro-expansion concrete to pour the imported sealing body. Its micro-expansion characteristics can compensate for concrete shrinkage, enhance the density and impermeability of the sealing body, and reduce the risk of leakage in the gaps by matching the design with the cross-section of the construction adit. At the same time, the C20 strength grade takes into account both structural load-bearing capacity and economy, reducing construction costs.

[0018] 5. This invention achieves precise control of water pressure balance by pre-embedding the drain hole in the sleeve and calculating the drain hole parameters based on the water inlet rate. This avoids the outlet sealing body from being designed to be bulky due to excessive head difference, significantly optimizes the structural dimensions of the outlet sealing body, shortens the construction period, and improves the overall economic efficiency of the project. Attached Figure Description

[0019] Figure 1 This is a longitudinal section view of the adit for the diversion tunnel construction.

[0020] Figure 2 This is a longitudinal sectional view of the inlet sealing body of the present invention.

[0021] Figure 3 This is a cross-sectional view of the inlet sealing body of the present invention.

[0022] Among them, 1-construction adit; 21-inlet sealing body; 22-outlet sealing body; 3-drainage hole; 4-grout inlet pipe; 5-grout outlet pipe; 6-vent pipe; 7-system reinforcing bar; 8-structural joint; 9-diversion tunnel; 10-surrounding rock; 11-connecting reinforcing bar. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] Example 1 The construction adit 1 of the diversion tunnel 9 of a certain hydropower station has a cross-section shaped like a city gate (width × height = 7m × 8m). Due to the tight construction schedule, the second-stage lining was not carried out. The inlet of the construction adit 1 ( Figure 1 The left end of the tunnel is a downward-facing weathered slope with poor stability. The bottom elevation of the inlet of construction adit 1 is 2365m, the bottom elevation of the outlet of construction adit 1 is 2356m, and an outlet sealing body 22 is provided at the outlet of construction adit 1. The designed normal water level of the reservoir is 2372m. Before impoundment, the diversion tunnel 9 was overflowing, with a water level of 2364m, and there was no water accumulation in the construction adit 1. After impoundment, the reservoir water level reached 2372m, and seepage occurred after the gate at the entrance of diversion tunnel 9 was closed, eventually filling diversion tunnel 9. If the diversion tunnel inlet sealing body 21 is not installed, the seepage during the impoundment process will be too fast compared to the inlet gate of diversion tunnel 9, resulting in the construction adit 1 of the diversion tunnel being full of water while diversion tunnel 9 is empty. The highest head of the diversion tunnel construction adit outlet sealing body 22 is 2372m, forming a head difference of 16m.

[0025] The most unfavorable working condition is that there is no water in the diversion tunnel 9 but there is water in the construction adit 1 of the diversion tunnel. At this time, the outlet sealing body 22 bears the maximum water thrust in the construction adit 1 of the diversion tunnel. The existing technology calculates the length of the outlet sealing body 22, which needs to take this working condition into account, resulting in the outlet sealing body 22 being too large.

[0026] This embodiment provides a sealing body for a diversion tunnel construction adit, such as... Figure 1 As shown, the system includes an outlet sealing body 22 located at the outlet of construction adit 1 and an inlet sealing body 21 located at the inlet of construction adit 1. The inlet sealing body 21 is constructed of C20 micro-expansion concrete, and its cross-sectional shape matches the cross-section of construction adit 1. The inlet sealing body 21 significantly enhances the stability of the inlet slope of construction adit 1. The inlet sealing body 21 also includes a water pressure balance system and a surrounding rock bonding system.

[0027] like Figure 2 As shown, the water pressure balancing system includes at least one row of drainage holes 3 located at the bottom of the inlet sealing body 21 and extending through the axis of the construction adit 1. The bottom drainage holes 3 can actively guide and balance the internal and external water pressure, avoiding the situation where the diversion tunnel 9 is full of water while the construction adit 1 is empty, thereby optimizing the design length of the outlet sealing body 22 of the construction adit 1.

[0028] In other words, during the seepage process of the diversion tunnel 9, water enters the construction adit 1 through the drainage hole 3 from the outside, ensuring that the water pressure on the inside of the outlet sealing body 22 from the construction adit 1 and the water pressure on the outside of the outlet sealing body 22 from the diversion tunnel 9 are balanced in real time, thereby significantly reducing the design length of the outlet sealing body 22.

[0029] like Figure 3 As shown, the surrounding rock bonding system includes system reinforcing bars 7 arranged around the perimeter of the inlet sealing body 21 and the contact surface with the surrounding rock 10, as well as backfill grouting pipes pre-embedded in the top arch of the inlet sealing body 21. The backfill grouting pipes include an inlet pipe 4, an outlet pipe 5, and an exhaust pipe 6. In this embodiment, several sets of backfill grouting pipes are evenly arranged in the top arch of the inlet sealing body 21, wherein the inlet pipe 4 and the outlet pipe 5 in each set of backfill grouting pipes are respectively arranged on both sides of the exhaust pipe 6.

[0030] like Figure 2 As shown, when the length of the inlet sealing body 21 is large, considering the concrete pouring capacity and to avoid cold joints, the inlet sealing body 21 is divided into a first sealing body and a second sealing body along the axis of the construction support tunnel 1. The structural joint 8 between the first sealing body and the second sealing body is provided with a number of connecting reinforcing bars 11 that connect the first sealing body and the second sealing body; the connecting reinforcing bars 11 are arranged in a cross pattern.

[0031] The inlet sealing body 21 provided in this embodiment actively enhances the bond between the sealing body and the fragile surrounding rock 10 through the combination of micro-expansion concrete, system reinforcing bars 7, backfill grouting, structural joints 8, and connecting reinforcing bars 11, forming a unified whole that shares the load. This ensures the slope stability of the tunnel entrance, even if the surrounding rock 10 of the construction adit 1 has poor conditions, after external flow or water impoundment at the power station. Simultaneously, the water pressure balancing system can actively balance water pressure and significantly optimize the structural dimensions of the outlet sealing body 22.

[0032] Example 2 This embodiment provides a method for sealing a construction adit of a diversion tunnel. Based on the presence of an outlet sealing body 22 at the outlet of the construction adit 1, C20 micro-expansion concrete is poured at the inlet of the construction adit 1 to form an inlet sealing body 21 that matches the arch-shaped cross-section of the construction adit 1.

[0033] When pouring C20 micro-expansion concrete, a sleeve is pre-embedded at a designated location (bottom of the outlet sealing body 22) to form at least one row of drainage holes 3 penetrating the inlet sealing body 21. The number and diameter of the drainage holes 3 are calculated and determined based on the water inflow rate after the diversion tunnel 9 is sealed. This ensures that the amount of water entering the construction adit 1 through the drainage holes 3 changes synchronously during the process of seepage filling the diversion tunnel 9, thereby achieving water pressure balance between the construction adit 1 and the diversion tunnel 9. In this embodiment, a row of seven drainage holes 3 with a diameter of 60mm is formed, which can keep the water pressure inside and outside the outlet sealing body 22 as synchronously as possible during the flood season, ensuring the stability of the sealing body and the inlet slope, and fully achieving the design expectations.

[0034] System reinforcing bars 7 are arranged at the contact surface between the inlet sealing body 21 and the surrounding rock 10, and backfill grouting pipes are pre-embedded in the top arch of the inlet sealing body 21. In this embodiment, HPB300 system reinforcing bars 7 with a diameter of 25mm and a length of 3m are arranged in a quincunx pattern at the contact surface between the inlet sealing body 21 of the construction adit 1 and the surrounding rock 10, with a spacing of 2m between each row of system reinforcing bars 7. Backfill grouting inlet pipe 4, grout outlet pipe 5, and exhaust pipe 6 are pre-embedded in the top arch of the inlet sealing body 21. After the micro-expansion concrete reaches its strength, backfill grouting is performed on the gaps in the top arch through the backfill grouting pipes.

[0035] When the length of the inlet sealing body 21 exceeds the set value, the inlet sealing body 21 is divided into a first sealing body and a second sealing body and cast separately, and connecting reinforcing bars 11 are arranged crosswise in the structural joint 8 between the first sealing body and the second sealing body.

[0036] In this embodiment, the length of the inlet sealing body 21 is L=18m. A structural joint 8 is set in the middle of the inlet sealing body 21. When pouring the concrete of the first sealing body on one side, a template is installed at the preset joint position. After the concrete of the first sealing body reaches a certain strength, the template is removed, and then the concrete of the second sealing body on the other side is poured. During the construction process, HPB300 connecting dowel bars 11 with a length of 3m are intersected in the structural joint 8, and the spacing between each group of adjacent intersecting connecting dowel bars 11 is 2m.

[0037] This invention addresses the issue of poor geological conditions at the inlet slope of construction adit 1, which are further exacerbated by rising water levels after reservoir impoundment. By employing an inlet sealing body 21 to permanently seal the inlet of construction adit 1, the stability problem of the inlet slope of construction adit 1 is effectively solved. Simultaneously, by incorporating drainage holes 3 into the inlet sealing body 21, this invention achieves a combination of active water pressure balance and comprehensive structural reinforcement. While ensuring the long-term stability of the inlet slope of construction adit 1, it significantly optimizes the design dimensions of the outlet sealing body 22, eliminating the need for the bulky outlet sealing body 22 found in existing technologies. This effectively solves the engineering safety and economic problems of the outlet sealing body 22 under high external water pressure conditions.

[0038] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A sealing body for a diversion tunnel construction adit, characterized in that, It includes an outlet sealing body installed at the exit of the construction adit and an inlet sealing body installed at the inlet of the construction adit; the inlet sealing body is made of micro-expansion concrete, and its cross-sectional shape matches the cross-section of the construction adit; the inlet sealing body also includes: The water pressure balancing system includes at least one row of drainage holes located at the bottom of the inlet sealing body and extending through the inlet sealing body along the axis of the construction adit; The surrounding rock bonding system includes system reinforcing bars arranged around the perimeter of the inlet sealing body and the contact surface with the surrounding rock, as well as backfill grouting pipes pre-embedded in the top arch of the inlet sealing body.

2. The sealing body for the construction adit of the diversion tunnel as described in claim 1, characterized in that, The backfill grouting pipe includes an inlet pipe, an outlet pipe, and an exhaust pipe.

3. The sealing body for the construction adit of the diversion tunnel as described in claim 1, characterized in that, The inlet sealing body is divided into a first sealing body and a second sealing body along the axis of the construction adit. The structural joint between the first sealing body and the second sealing body is provided with a number of connecting reinforcing bars that connect the first sealing body and the second sealing body; the connecting reinforcing bars are arranged in a crisscross pattern.

4. The sealing body for the construction support tunnel of the diversion tunnel as described in claim 1, characterized in that, The system's reinforcing bars are HPB300 steel bars, arranged in a quincunx pattern.

5. The sealing body for the construction adit of the diversion tunnel as described in any one of claims 1-4, characterized in that, The strength grade of the micro-expansion concrete is C20.

6. A method for sealing an adit during the construction of a diversion tunnel, characterized in that, include: Based on the outlet sealing body at the exit of the construction adit, micro-expansion concrete is poured at the inlet of the construction adit to form an inlet sealing body that matches the cross-section of the construction adit. When pouring micro-expansion concrete, sleeves are pre-embedded at designated locations to form at least one row of drainage holes penetrating the inlet sealing body; system reinforcing bars are arranged at the contact surface between the inlet sealing body and the surrounding rock, and backfill grouting pipes are pre-embedded in the top arch of the inlet sealing body; After the micro-expansion concrete reaches its strength, the voids in the top arch are filled with grout through the backfill grouting pipe.

7. The method for sealing the construction adit of the diversion tunnel as described in claim 4, characterized in that, When the length of the inlet sealing body exceeds the set value, the inlet sealing body is divided into a first sealing body and a second sealing body, which are cast separately, and connecting reinforcing bars are arranged crosswise in the structural joint between the first sealing body and the second sealing body.

8. The sealing method according to claim 6 or 7, characterized in that, The number and diameter of the drainage holes are calculated and determined based on the water inflow rate after the diversion tunnel is sealed. This is to ensure that the amount of water entering the construction adit through the drainage holes can change synchronously during the process of the diversion tunnel being filled with seepage water, so as to achieve water pressure balance between the construction adit and the diversion tunnel.

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