Confluence construction method and convergence system for intersection of water conveyance tunnel

Abstract

The invention relates to the technical field of water conservancy and hydropower engineering, in particular to a water conveyance tunnel intersection confluence construction method and a confluence system. The construction method comprises the steps that a main hole is excavated, a main adit intersection is excavated on the main hole, a straight-going central axis of the adit is established at the main adit intersection, the straight-going central axis of the adit and the straight-going central axis of the main hole are arranged at an angle, the adit is excavated according to the established straight-going central axis, and the straight-going central axis at the tail end of the adit is reconstructed to be an arc-shaped central axis. And flow guide piers with the same radian are arranged in the tail ends of the branch holes and are used for guiding water flow in the branch holes into the downstream of the main hole. The water flow direction in the branch hole is at the intersection of the main and branch holes, and the included angle between the water flow direction in the branch hole and the water flow direction in the main hole is reduced, so that the top flushing effect of branch hole water flow on the inner side wall of the main hole is greatly improved, and the stability of the side wall structure of the main hole is improved.

Description

Technical Field

[0001] The invention relates to the technical field of water conservancy and hydropower engineering, in particular to a water conveyance tunnel intersection confluence construction method and a confluence system. Background Art

[0002] The water transfer tunnel is an important part of the hydropower station project. It is an artificial tunnel excavated and lined in the mountain, which has the functions of water transfer and flood discharge. The water transfer tunnel is usually a single tunnel. As the technology continues to mature, more and more water transfer tunnels adopt the form of a combination of main and branch tunnels. The outlet of the branch tunnel is arranged in the main tunnel, and the water in the branch tunnel flows into the main tunnel through the intersection of the main and branch tunnels.

[0003] However, due to geological conditions, the closer the axis of the branch tunnel is to 90°, the more severe the impact of the branch tunnel water flow on the side walls of the main tunnel when it merges into the main tunnel. In addition, the surge waves generated by the branch tunnel water flow hitting the side walls of the main tunnel will roll to the top of the tunnel, causing water capping at the tunnel intersection, seriously affecting the tunnel's water supply, flood discharge and safe operation of buildings. Summary of the invention

[0004] The technical problem to be solved by the embodiments of the present invention is to provide a water conveyance tunnel intersection confluence construction method and confluence system to solve the problem of water flow capping easily occurring at tunnel intersections in the prior art.

[0005] The invention discloses a water conveyance tunnel intersection confluence construction method, comprising: According to the actual conditions of the project, a main tunnel was excavated for water delivery and flood discharge; Excavating a first side wall located on one side of the main tunnel to form a main-branch tunnel intersection, and establishing a straight central axis of the branch tunnel from the main-branch tunnel intersection, so that the straight central axis of the branch tunnel and the straight central axis of the main tunnel are arranged at an angle; According to the straight central axis established by the branch tunnel, the branch tunnel is excavated upstream from the intersection of the main and branch tunnels; Based on the straight central axis established by the branch tunnel, at the end of the branch tunnel where it connects to the intersection of the main tunnel and the branch tunnel, the straight central axis of the end of the branch tunnel is reconstructed as an arc central axis until the arc central axis of the end of the branch tunnel is tangent to the straight central axis of the main tunnel; According to the arc-shaped central axis reconstructed at the end of the branch tunnel, a diversion pier with the same arc is arranged at the end of the branch tunnel to divert the water flow in the branch tunnel into the downstream of the main tunnel.

[0006] Optionally, the reconstructing the straight central axis of the end of the branch hole as an arc-shaped central axis includes: Determining the width of the branch tunnel excavation; According to the excavation width determined by the branch tunnel, the radius of the arc-shaped central axis of the end of the branch tunnel is determined. The function expression of the radius of the arc-shaped central axis of the end of the branch tunnel is:

[0007] In the formula, R represents the radius of the arc centerline at the end of the branch tunnel. Indicates the width of the branch tunnel excavation.

[0008] Optionally, the excavating the branch tunnel upstream from the intersection of the main branch tunnel includes: Excavating the branch tunnel upstream from the intersection of the main and branch tunnels, and using the side wall of the branch tunnel located downstream of the intersection of the main and branch tunnels as the second side wall; At the beginning of the excavation of the branch tunnel, according to the arc-shaped central axis reconstructed at the end of the branch tunnel, an arc-shaped lining line concentric with the arc-shaped central axis at the end of the branch tunnel is established at the edge downstream of the intersection of the main branch tunnel, so that the arc-shaped lining line is tangent to the first side wall of the main tunnel; According to the established arc lining line, a straight lining line parallel to the central axis of the branch tunnel is established, so that the straight lining line is tangent to the arc lining line, and the arc lining line and the straight lining line are connected at the tangent point to establish a side wall lining line; The second side wall is lined along the established side wall lining line.

[0009] Optionally, the arc-shaped central axis reconstructed according to the end of the branch tunnel and the diversion piers with the same arc are arranged in the end of the branch tunnel, including: According to the arc-shaped central axis reconstructed at the end of the branch tunnel, the diversion piers are respectively arranged on both sides of the arc-shaped central axis, so that an arc-shaped diversion area tangent to the water flow direction in the main tunnel is formed between the two diversion piers and between the diversion piers and the adjacent branch tunnel side walls.

[0010] Optionally, the method for arranging the diversion piers includes: Establishing a first arc curve and a second arc curve in parallel along the width direction of the branch hole, and making the first arc curve and the second arc curve concentric with the arc center axis of the end of the branch hole; The guide walls on both sides of the guide pier are constructed according to the connected first arc curve and the second arc curve.

[0011] Optionally, the method for arranging the guide piers further includes: Establishing a third arc curve upstream of the first arc curve, making the third arc curve tangent to the first arc curve and the second arc curve respectively, and connecting the third arc curve with the first arc curve and the second arc curve respectively at the tangent point; The diversion wall of the diversion pier facing the upstream water flow is built according to the connected third arc curve.

[0012] Optionally, the method for arranging the guide piers further includes: Establishing a fourth arc curve downstream of the second arc curve, making the fourth arc curve tangent to the second arc curve, and making the fourth arc curve tangent to the extension line of the first side wall of the main hole, and connecting the fourth arc curve with the second arc curve at the tangent point; According to the connected fourth arc curve, the diversion pier is built to merge the water flow in the branch tunnel into the diversion wall downstream of the main tunnel through tangency.

[0013] Optionally, the method for arranging the guide piers further includes: Establishing a straight construction line perpendicular to the water flow direction of the main tunnel downstream of the first arc curve, and extending the first arc curve and the fourth arc curve downstream to connect with the straight construction line; The diversion pier is built according to the connected straight construction line to respectively merge the water flows on both sides into the interception wall downstream of the main tunnel.

[0014] Optionally, the excavation method of the main tunnel and the branch tunnel includes: According to the actual conditions of the project, the excavation point of the main hole is selected in the target area; According to the selected main hole excavation point, the main hole is excavated, and during the excavation process, the side wall, bottom plate and arch of the main hole are temporarily supported; After the excavation of the main hole is completed, the side walls, bottom plate and vault of the main hole are permanently supported and lined; According to the confluence requirement, the side wall on one side of the main tunnel is selected as the first side wall, and the intersection of the main and branch tunnels is excavated on the first side wall; According to the straight central axis of the branch tunnel, the branch tunnel is excavated in an upstream direction along the straight central axis, and during the excavation process, the side wall, bottom plate and arch of the branch tunnel are temporarily supported; After the excavation of the branch tunnel is completed, the side walls, bottom plate and arch of the branch tunnel are permanently supported and lined.

[0015] The present invention also discloses a confluence system, which adopts the above-mentioned water conveyance tunnel intersection confluence construction method. The confluence system includes a main tunnel, a branch tunnel and a diversion pier. The branch tunnel is connected to the main tunnel, and the central axis of the branch tunnel is set at an angle to the central axis of the main tunnel. The diversion pier is an arc-shaped pier set at the intersection of the branch tunnel and the main tunnel, and the diversion direction of the diversion pier is tangent to the water flow direction of the main tunnel.

[0016] Compared with the prior art, the water diversion tunnel intersection confluence construction method and confluence system provided by the embodiment of the present invention have the following beneficial effects: By establishing the straight central axis of the branch tunnel during the excavation of the branch tunnel, the precise excavation position of the branch tunnel is ensured, deviation is avoided, and the relative position of the branch tunnel and the main tunnel is correct. By arranging the straight central axis of the branch tunnel and the straight central axis of the main tunnel at an angle, the angle between the branch tunnel and the main tunnel can be accurately controlled, which is conducive to the control of the confluence direction of the main tunnel and the branch tunnel, and can reduce the impact of the branch tunnel on the internal water pressure of the main tunnel. On this basis, by establishing the arc central axis at the end of the branch tunnel tangent to the straight central axis of the main tunnel, and arranging the diversion pier with the same arc as the arc central axis, the water flow in the branch tunnel is introduced into the downstream of the main tunnel in a direction tangent to the water flow in the main tunnel, so that the angle between the water flow direction in the branch tunnel and the water flow direction in the main tunnel becomes smaller at the intersection of the main and branch tunnels, thereby greatly improving the top impact of the branch tunnel water flow on the inner side wall of the main tunnel, which is conducive to improving the stability of the side wall structure of the main tunnel. At the same time, the water flow from the branch tunnel into the main tunnel will not hit the side wall, climb to the top of the side wall and then roll down, which effectively improves the flow state at the intersection of the main and branch tunnels and avoids obstacles to water supply and flood discharge in the main tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments, in which: Figure 1 A schematic diagram of the intersection structure of the main tunnel and the branch tunnel of the water diversion tunnel intersection confluence construction method provided by an embodiment of the present invention; Figure 2 A schematic diagram of the distribution of the central axis of the main tunnel and the branch tunnel provided in an embodiment of the present invention; Figure 3 A schematic structural diagram of a guide pier provided in an embodiment of the present invention.

[0018] The reference numerals in the figures are: 1. Main tunnel; 11. First side wall; 2. Branch tunnel; 21. Second side wall; 3. Arc-shaped central axis; 4. Diversion pier; 41. First arc curve; 42. Second arc curve; 43. Third arc curve; 44. Fourth arc curve; 45. Straight construction line. DETAILED DESCRIPTION

[0019] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. Now, in conjunction with the accompanying drawings, a preferred embodiment of the present invention is described in detail.

[0020] The present invention discloses a water conveyance tunnel intersection confluence construction method, such as Figure 1 and Figure 2 As shown, including: According to the actual conditions of the project, a main tunnel 1 is excavated for water delivery and flood discharge; The first side wall 11 located on one side of the main tunnel 1 is excavated to form an intersection of the main and branch tunnels 2, and the straight central axis of the branch tunnel 2 is established at the intersection of the main and branch tunnels 2, so that the straight central axis of the branch tunnel 2 and the straight central axis of the main tunnel 1 are arranged at an angle; According to the straight central axis established by branch tunnel 2, branch tunnel 2 is excavated upstream from the intersection of main branch tunnel 2; Based on the straight central axis established by the branch tunnel 2, located at the end of the branch tunnel 2 where it connects to the intersection of the main branch tunnel 2, the straight central axis of the end of the branch tunnel 2 is reconstructed as the arc central axis 3, until the arc central axis 3 of the end of the branch tunnel 2 is tangent to the straight central axis of the main tunnel 1; According to the arc-shaped central axis 3 reconstructed at the end of the branch tunnel 2, a diversion pier 4 with the same arc is arranged at the end of the branch tunnel 2 to divert the water flow in the branch tunnel 2 into the downstream of the main tunnel 1.

[0021] Through the implementation of the above-mentioned water diversion tunnel intersection confluence construction method embodiment, in the process of excavating the branch tunnel 2, a main tunnel 1 for water diversion and flood discharge is first excavated, and the intersection of the main and branch tunnels 2 is excavated on the main tunnel 1 as the confluence entrance for the water flow of the branch tunnel 2 to merge into the water flow of the main tunnel 1. Then, the straight central axis of the branch tunnel 2 is established to ensure the precise position of the excavation of the branch tunnel 2, avoid deviation, and ensure that the relative position of the branch tunnel 2 and the main tunnel 1 is correct. And by arranging the straight central axis of the branch tunnel 2 and the straight central axis of the main tunnel 1 at an angle, the angle between the branch tunnel 2 and the main tunnel 1 can be accurately controlled, which is conducive to the control of the confluence direction of the main tunnel 1 and the branch tunnel 2, and can reduce the influence of the water confluence of the branch tunnel 2 on the internal water pressure of the main tunnel 1. On this basis, by establishing the arc-shaped central axis 3 at the end of the branch tunnel 2 to be tangent to the straight central axis of the main tunnel 1, and laying out the diversion pier 4 with the same arc as the arc-shaped central axis 3, after the branch tunnel 2 is excavated, the water flow in the branch tunnel 2 is introduced into the downstream of the main tunnel 1 in a direction tangent to the water flow in the main tunnel 1, so that the angle between the water flow direction in the branch tunnel 2 and the water flow direction in the main tunnel 1 becomes smaller at the intersection of the main and branch tunnels 2, thereby greatly improving the top impact of the water flow in the branch tunnel 2 on the inner wall of the main tunnel 1, which is conducive to improving the stability of the side wall structure of the main tunnel 1. At the same time, the water flow in the branch tunnel 2 that flows into the main tunnel 1 will not top impact the side wall, climb to the top of the side wall and then roll down, which effectively improves the flow state of the water flow at the intersection of the main and branch tunnels 2 and avoids the situation of hindering the water supply and flood discharge of the main tunnel 1. In addition, since the water flow of the traditional branch tunnel 2 hits the side wall of the main tunnel 1, it is more obvious, and in order to meet the requirements of the specification on the side wall height, it is necessary to raise the overall side wall of the intersection of the main and branch tunnels 2, which requires a large amount of excavation work and is difficult to support. The embodiment of the present invention utilizes the setting of the diversion pier 4 to avoid raising the overall side wall of the main tunnel 1, which has the beneficial effects of convenient construction and saving investment.

[0022] Furthermore, the straight central axis at the end of the branch tunnel 2 is reconstructed into an arc-shaped central axis 3, including: Determine the width of branch tunnel 2 excavation; According to the excavation width determined by the branch tunnel 2, the radius of the arc-shaped central axis 3 at the end of the branch tunnel 2 is determined. The function expression of the radius of the arc-shaped central axis 3 at the end of the branch tunnel 2 is:

[0023] Where R represents the radius of the arc centerline 3 at the end of the branch hole 2, Indicates the width of branch tunnel 2 excavation.

[0024] By implementing the above-mentioned embodiment of the water diversion tunnel intersection confluence construction method, the width of the branch tunnel 2 is proportionally set to the radius of the arc-shaped central axis 3 at the end of the branch tunnel 2, so as to fully consider the water flow in the branch tunnel 2, thereby ensuring that the diversion pier 4 at the end of the branch tunnel 2 can have a diversion arc that matches the passing water flow, so as to fully introduce the water flow in the branch tunnel 2 into the downstream of the main tunnel 1 in a direction tangent to the water flow in the main tunnel 1, thereby ensuring that the resistance of the water flow is reduced, the diversion efficiency of the water flow in the branch tunnel 2 is improved, and the formation of vortices and backflows in the branch tunnel 2 during confluence is avoided.

[0025] Further, excavating a branch tunnel 2 upstream from the intersection of the main branch tunnel 2 includes: The branch tunnel 2 is excavated upstream from the intersection of the main branch tunnel 2, and the side wall of the branch tunnel 2 located downstream of the intersection of the main branch tunnel 2 is used as the second side wall 21; At the beginning of the excavation of the branch tunnel 2, according to the arc-shaped central axis 3 reconstructed at the end of the branch tunnel 2, an arc-shaped lining line concentric with the arc-shaped central axis 3 at the end of the branch tunnel 2 is established at the edge downstream of the intersection of the main branch tunnel 2, so that the arc-shaped lining line is tangent to the first side wall 11 of the main tunnel 1; According to the established arc lining line, a straight lining line parallel to the central axis of branch tunnel 2 is established, so that the straight lining line is tangent to the arc lining line, and the arc lining line and the straight lining line are connected at the tangent point to establish the side wall lining line; The second side wall 21 is lined along the established side wall lining line.

[0026] Through the implementation of the above-mentioned water diversion tunnel intersection confluence construction method embodiment, since the water flow in the branch tunnel 2 is downstream of the water flow in the main tunnel 1 when converging, and the traditional main and branch tunnels 2 side wall joints are all formed corners, under the scouring and shearing effect of the water flow flowing downstream, this area is prone to negative pressure, which will cause cavitation damage to the side wall. Therefore, the present invention lines the second side wall 21 by establishing a side wall lining line composed of an arc lining line and a straight lining line, that is, the side wall of the branch tunnel 2 located downstream of the intersection of the main and branch tunnels 2, so that the end of the second side wall 21 is tangent to the first side wall 11 of the main tunnel 1, so that the connection between the side walls of the main tunnel 1 and the branch tunnel 2 is an arc structure, avoiding the generation of sharp corners, and when the water flow in the main tunnel 1 or the branch tunnel 2 passes through the intersection of the main and branch tunnels 2, it is smoother, and the generation of cavitation damage is also avoided.

[0027] Furthermore, according to the arc-shaped central axis 3 reconstructed at the end of the branch tunnel 2, a diversion pier 4 with the same arc is arranged at the end of the branch tunnel 2, including: According to the arc-shaped central axis 3 reconstructed at the end of the branch tunnel 2, diversion piers 4 are respectively arranged on both sides of the arc-shaped central axis 3, so that an arc-shaped diversion area tangent to the water flow direction in the main tunnel 1 is formed between the two diversion piers 4 and between the diversion piers 4 and the side walls of the adjacent branch tunnel 2.

[0028] Furthermore, combined with Figure 3 As shown, the layout method of the guide pier 4 is as follows: A first arc curve 41 and a second arc curve 42 are established in parallel along the width direction of the branch hole 2, and the first arc curve 41 and the second arc curve 42 are concentric with the arc center axis 3 at the end of the branch hole 2; The guide walls on both sides of the guide pier 4 are constructed according to the connected first arc curve 41 and the second arc curve 42 .

[0029] Furthermore, the method for arranging the guide pier 4 also includes: Establish a third arc curve 43 upstream of the first arc curve 41, so that the third arc curve 43 is tangent to the first arc curve 41 and the second arc curve 42 respectively, and connect the third arc curve 43 with the first arc curve 41 and the second arc curve 42 at the tangent point; The diversion wall of the diversion pier 4 facing the upstream water flow is built according to the connected third arc curve 43.

[0030] Furthermore, the method for arranging the guide pier 4 also includes: A fourth arc curve 44 is established downstream of the second arc curve 42, so that the fourth arc curve 44 is tangent to the second arc curve 42, and the fourth arc curve 44 is tangent to the extension line of the first side wall 11 of the main hole 1, and the fourth arc curve 44 is connected with the second arc curve 42 at the tangent point; According to the connected fourth arc curve 44, a diversion pier 4 is built to connect the water flow in the branch tunnel 2 to the diversion wall downstream of the main tunnel 1 through tangency.

[0031] Furthermore, the method for arranging the guide pier 4 also includes: A straight construction line 45 perpendicular to the water flow direction of the main tunnel 1 is established downstream of the first arc curve 41, and the first arc curve 41 and the fourth arc curve 44 are extended downstream to the straight construction line 45 for connection; According to the connected straight construction line 45, a diversion pier 4 is built to respectively merge the water flows on both sides into the interception wall downstream of the main tunnel 1.

[0032] Through the implementation of the above-mentioned water diversion tunnel intersection confluence construction method embodiment, the shape of the diversion pier 4 is composed of multiple arc curves and a straight construction line 45. The diversion walls on both sides of the diversion pier 4 are constructed by using the first arc curve 41 and the second arc curve 42, which helps the water flow on both sides of the diversion pier 4 to smoothly transition at the end of the branch tunnel 2, reduce the resistance and energy loss of the water flow, and provide a clear flow path for the water flow, prevent the water flow from scouring and eroding the wall of the branch tunnel 2, and enhance the structural stability of the branch tunnel 2; the diversion wall of the diversion pier 4 facing the upstream water flow is constructed by using the third arc curve 43, so that when the water flow upstream of the branch tunnel 2 enters the end of the branch tunnel 2, it can smoothly transition to both sides of the diversion pier 4 along the diversion wall of the diversion pier 4 facing the upstream water flow, so as to reduce the impact force of the water flow on the diversion pier 4. And through the tangent design, the eddy current and resistance when the water flow contacts the diversion pier 4 can be reduced, and the flow efficiency of the water flow can be improved; the diversion pier 4 is built by using the fourth arc curve 44 to merge the water flow in the branch hole 2 into the diversion wall downstream of the main hole 1 through tangency, so that the water flow in the branch hole 2 directly merges into the main hole 1 after passing through the diversion pier 4, and ensures that it can smoothly transition when merging into the main hole 1 to reduce the impact force. And through the tangent design, it is ensured that the water flow flows along the predetermined path to reduce the erosion of the side wall of the main hole 1; the diversion pier 4 is built by using the straight construction line 45 to merge the water flow on both sides into the interception wall downstream of the main hole 1, and the water flow on both sides of the diversion pier 4 is guided and merged into the downstream of the main hole 1, and the water flow on both sides of the diversion pier 4 is avoided. The confluence before merging into the main hole 1, thereby greatly improving the top impact of the water flow of the branch hole 2 on the inner wall of the main hole 1, is conducive to improving the stability of the side wall structure of the main hole 1. Therefore, the arrangement of the diversion pier 4 can not only make the angle between the water flow in the branch tunnel 2 and the water flow in the main tunnel 1 smaller, but also ensure that the end of the diversion pier 4 will not interfere with the water flow in the main tunnel 1.

[0033] Furthermore, the excavation method of the main tunnel 1 and the branch tunnel 2 is as follows: According to the actual conditions of the project, the excavation point of the main tunnel 1 is selected in the target area; According to the selected excavation point of the main tunnel 1, the main tunnel 1 is excavated, and during the excavation process, the side walls, bottom plate and arch of the main tunnel 1 are temporarily supported; After the excavation of the main tunnel 1 is completed, the side walls, floor and vault of the main tunnel 1 are permanently supported and lined; According to the confluence requirements, the side wall on one side of the main tunnel 1 is selected as the first side wall 11, and the intersection of the main and branch tunnels 2 is excavated on the first side wall 11; According to the straight central axis established by the branch tunnel 2, the branch tunnel 2 is excavated in the upstream direction along the straight central axis, and during the excavation process, the side wall, bottom plate and arch of the branch tunnel 2 are temporarily supported; After the excavation of branch tunnel 2 is completed, the side walls, bottom plate and arch of branch tunnel 2 are permanently supported and lined.

[0034] The present invention also discloses a confluence system, which adopts the above-mentioned water conveyance tunnel intersection confluence construction method. The confluence system includes a main tunnel 1, a branch tunnel 2 and a diversion pier 4. The branch tunnel 2 is connected to the main tunnel 1, and the central axis of the branch tunnel 2 is set at an angle to the central axis of the main tunnel 1. The diversion pier 4 is an arc-shaped pier set at the intersection of the branch tunnel 2 and the main tunnel 1, and the diversion direction of the diversion pier 4 is tangent to the water flow direction of the main tunnel 1.

[0035] Through the implementation of the above-mentioned confluence system, by arranging the diversion pier 4 at the intersection of the branch tunnel 2 and the main tunnel 1, the water flow in the branch tunnel 2 is directed to the downstream of the main tunnel 1, and the angle between the water flow direction in the branch tunnel 2 and the side wall of the main tunnel 1 is reduced, which greatly improves the top impact of the water flow in the branch tunnel 2 on the side wall of the main tunnel 1, which is beneficial to the structural stability of the side wall of the main tunnel 1. At the same time, the water flow in the branch tunnel 2 will no longer top-impact the side wall, climb to the top of the side wall and then roll down, which effectively improves the flow state of the water flow at the intersection of the main and branch tunnels 2, and no longer hinders the water delivery and flood discharge of the main tunnel 1.

[0036] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. For those skilled in the art, the technical solutions described in the above embodiments can be modified, or some of the technical features therein can be replaced by equivalents; and all these modifications and replacements should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A water diversion tunnel intersection confluence construction method, characterized in that: The water conveyance tunnel intersection confluence construction method comprises: According to the actual conditions of the project, a main tunnel was excavated for water delivery and flood discharge; Excavating a first side wall located on one side of the main tunnel to form a main-branch tunnel intersection, and establishing a straight central axis of the branch tunnel from the main-branch tunnel intersection, so that the straight central axis of the branch tunnel and the straight central axis of the main tunnel are arranged at an angle; According to the straight central axis established by the branch tunnel, the branch tunnel is excavated upstream from the intersection of the main and branch tunnels; Based on the straight central axis established by the branch tunnel, at the end of the branch tunnel where it connects to the intersection of the main tunnel and the branch tunnel, the straight central axis of the end of the branch tunnel is reconstructed as an arc central axis until the arc central axis of the end of the branch tunnel is tangent to the straight central axis of the main tunnel; According to the arc-shaped central axis reconstructed at the end of the branch tunnel, a diversion pier with the same arc is arranged at the end of the branch tunnel to divert the water flow in the branch tunnel into the downstream of the main tunnel.

2. The water diversion tunnel intersection confluence construction method according to claim 1, characterized in that: The reconstruction of the straight central axis of the end of the branch tunnel into an arc-shaped central axis includes: Determining the width of the branch tunnel excavation; According to the excavation width determined by the branch tunnel, the radius of the arc-shaped central axis of the end of the branch tunnel is determined. The function expression of the radius of the arc-shaped central axis of the end of the branch tunnel is: In the formula, R represents the radius of the arc centerline at the end of the branch tunnel. Indicates the width of the branch tunnel excavation.

3. The water diversion tunnel intersection confluence construction method according to claim 1 or 2, characterized in that: The excavation of the branch tunnel upstream from the intersection of the main branch tunnel comprises: Excavating the branch tunnel upstream from the intersection of the main and branch tunnels, and using the side wall of the branch tunnel located downstream of the intersection of the main and branch tunnels as the second side wall; At the beginning of the excavation of the branch tunnel, according to the arc-shaped central axis reconstructed at the end of the branch tunnel, an arc-shaped lining line concentric with the arc-shaped central axis at the end of the branch tunnel is established at the edge downstream of the intersection of the main branch tunnel, so that the arc-shaped lining line is tangent to the first side wall of the main tunnel; According to the established arc lining line, a straight lining line parallel to the central axis of the branch tunnel is established, so that the straight lining line is tangent to the arc lining line, and the arc lining line and the straight lining line are connected at the tangent point to establish a side wall lining line; The second side wall is lined along the established side wall lining line.

4. The water diversion tunnel intersection confluence construction method according to claim 1, characterized in that: The method of arranging a diversion pier with the same curvature at the end of the branch tunnel according to the arc-shaped central axis reconstructed at the end of the branch tunnel comprises: According to the arc-shaped central axis reconstructed at the end of the branch tunnel, the diversion piers are respectively arranged on both sides of the arc-shaped central axis, so that an arc-shaped diversion area tangent to the water flow direction in the main tunnel is formed between the two diversion piers and between the diversion piers and the adjacent branch tunnel side walls.

5. The water diversion tunnel intersection confluence construction method according to claim 1, characterized in that: The method for laying out the diversion pier includes: Establishing a first arc curve and a second arc curve in parallel along the width direction of the branch hole, and making the first arc curve and the second arc curve concentric with the arc center axis of the end of the branch hole; The guide walls on both sides of the guide pier are constructed according to the connected first arc curve and the second arc curve.

6. The water diversion tunnel intersection confluence construction method according to claim 5, characterized in that: The method for arranging the guide pier further includes: Establishing a third arc curve upstream of the first arc curve, making the third arc curve tangent to the first arc curve and the second arc curve respectively, and connecting the third arc curve with the first arc curve and the second arc curve respectively at the tangent point; The diversion wall of the diversion pier facing the upstream water flow is built according to the connected third arc curve.

7. The water diversion tunnel intersection confluence construction method according to claim 6, characterized in that: The method for arranging the guide pier further includes: Establishing a fourth arc curve downstream of the second arc curve, making the fourth arc curve tangent to the second arc curve, and making the fourth arc curve tangent to the extension line of the first side wall of the main hole, and connecting the fourth arc curve with the second arc curve at the tangent point; According to the connected fourth arc curve, the diversion pier is built to merge the water flow in the branch tunnel into the diversion wall downstream of the main tunnel through tangency.

8. The water diversion tunnel intersection confluence construction method according to claim 7, characterized in that: The method for arranging the guide pier further includes: Establishing a straight construction line perpendicular to the water flow direction of the main tunnel downstream of the first arc curve, and extending the first arc curve and the fourth arc curve downstream to connect with the straight construction line; The diversion pier is built according to the connected straight construction line to respectively merge the water flows on both sides into the interception wall downstream of the main tunnel.

9. The water diversion tunnel intersection confluence construction method according to claim 1, characterized in that: The excavation method of the main tunnel and the branch tunnel includes: According to the actual conditions of the project, the excavation point of the main hole is selected in the target area; According to the selected main hole excavation point, the main hole is excavated, and during the excavation process, the side wall, bottom plate and arch of the main hole are temporarily supported; After the excavation of the main hole is completed, the side walls, bottom plate and vault of the main hole are permanently supported and lined; According to the confluence requirement, the side wall on one side of the main tunnel is selected as the first side wall, and the intersection of the main and branch tunnels is excavated on the first side wall; According to the straight central axis of the branch tunnel, the branch tunnel is excavated in an upstream direction along the straight central axis, and during the excavation process, the side wall, bottom plate and arch of the branch tunnel are temporarily supported; After the excavation of the branch tunnel is completed, the side walls, bottom plate and arch of the branch tunnel are permanently supported and lined.

10. A confluence system, characterized in that: The water diversion tunnel intersection confluence construction method according to any one of claims 1 to 9 is adopted, wherein the confluence system includes a main tunnel, a branch tunnel and a diversion pier, the branch tunnel is connected to the main tunnel, and the central axis of the branch tunnel is arranged at an angle to the central axis of the main tunnel, the diversion pier is an arc-shaped pier arranged at the intersection of the branch tunnel and the main tunnel, and the diversion direction of the diversion pier is tangent to the water flow direction of the main tunnel.

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