Longitudinal cofferdam structure

Abstract

The present invention belongs to the technical field of water conservancy and hydropower engineering, and specifically relates to a longitudinal cofferdam structure. The longitudinal cofferdam structure includes a longitudinal cofferdam body made of concrete structure. A U-shaped groove is arranged in the middle of the longitudinal cofferdam body along its length direction, and a slag backfill structure is arranged in the U-shaped groove. The U-shaped groove is located at the center position in the width direction of the longitudinal cofferdam body; the width of the U-shaped groove is not greater than 50% of the width of the longitudinal cofferdam body; the depth of the U-shaped groove is not greater than 60% of the height of the longitudinal cofferdam body. The two side walls at the top of the U-shaped groove are connected by horizontally arranged precast concrete beams, and the precast concrete beams are arranged at intervals along the length direction of the U-shaped groove. The top of the U-shaped groove is closed by a clay sandwiched geomembrane structure. The longitudinal cofferdam structure in the present invention can be used as a conventional longitudinal cofferdam for normal diversion during the construction period, and can be rebuilt into a permanent flood discharge sluice for flood discharge during the operation period; the required engineering quantity is relatively small, and the construction period is also shortened.

Description

Technical Field

[0001] The present invention belongs to the technical field of water conservancy and hydropower engineering, and particularly relates to a longitudinal cofferdam structure. Background Art

[0002] When constructing a water conservancy and hydropower project on a river channel with large flow and wide river valley, due to reasons such as the large transverse width of the project, large diversion flow, and construction difficulty, the project construction generally adopts a construction plan of staged construction on the left and right sides. As the main part of the two-way water retaining of the diversion project, the longitudinal cofferdam has a long service life during the staged construction process, and has a greater impact on the progress and safety. Among the longitudinal cofferdams on the bedrock foundation, gravity concrete cofferdams are mostly used. The cofferdam occupies the flow-through section and reduces the flow-through capacity. At the same time, the following problems exist in its construction: a large amount of concrete is required for the pouring of the cofferdam. As a temporary building, the subsequent demolition and blasting workload of the longitudinal cofferdam is large; the adjacent gates, dams, factories and other buildings and the foundation anti-seepage curtain have high requirements for blasting vibration, and the blasting difficulty is large; a large number of blasting slag removal and other treatment processes will also occupy a certain amount of economic cost and construction period. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a longitudinal cofferdam structure, which can be conveniently rebuilt into a permanent flood discharge sluice during the operation period, can reduce the subsequent blasting workload and blasting difficulty of the longitudinal cofferdam, and save project investment.

[0004] The technical solution adopted by the present invention to solve its technical problems is: a longitudinal cofferdam structure, including a longitudinal cofferdam body of concrete structure, a U-shaped groove is arranged in the middle of the longitudinal cofferdam body along its length direction, and a stone slag backfill structure is arranged in the U-shaped groove.

[0005] In order to ensure the stability of the longitudinal cofferdam structure on the premise that the cofferdam shape is as small as possible, a further preferred solution is: the U-shaped groove is arranged at the center position in the width direction of the longitudinal cofferdam body; the width of the U-shaped groove is not greater than 50% of the width of the longitudinal cofferdam body; the depth of the U-shaped groove is not greater than 60% of the height of the longitudinal cofferdam body.

[0006] In order to better ensure the stability of the longitudinal cofferdam structure, a further preferred solution is: cross-section transition sections are arranged at both ends in the length direction of the U-shaped groove, and in the direction from the center of the U-shaped groove to the end of the U-shaped groove, the transverse cross-sectional area of the cross-section transition section shows a decreasing trend.

[0007] In order to better ensure the stability of the longitudinal cofferdam structure, a further preferred solution is: the two side walls at the top of the U-shaped groove are connected by a horizontally arranged precast concrete beam, and the precast concrete beams are arranged at intervals along the length direction of the U-shaped groove. The precast concrete beam can improve the overall stress of the side walls on both sides of the longitudinal cofferdam.

[0008] To better ensure the stability of the longitudinal cofferdam structure, a further optimized solution is as follows: The top of the U-shaped groove is closed by a structure of clay sandwiched with geomembrane. The geomembrane can play a role in preventing seepage at the top.

[0009] To better ensure the stability of the cofferdam structure, a further optimized solution is as follows: The longitudinal cofferdam body includes an upstream first-stage cofferdam section, an upstream first- and second-stage cofferdam section, a reconstructible permanent flood discharge sluice section, a downstream first- and second-stage cofferdam section, and a downstream first-stage cofferdam section arranged in sequence along its length direction; the upstream first- and second-stage cofferdam section, the reconstructible permanent flood discharge sluice section, and the downstream first- and second-stage cofferdam section are arranged along the axis direction of the longitudinal cofferdam body. The axis of the upstream first-stage cofferdam section has a set included angle relative to the axis of the longitudinal cofferdam body, and the upstream first-stage cofferdam section is inclined towards the direction close to the first-stage upstream transverse cofferdam. The axis of the downstream first-stage cofferdam section has a set included angle relative to the axis of the longitudinal cofferdam body, and the downstream first-stage cofferdam section is inclined towards the direction close to the first-stage downstream transverse cofferdam. The upstream first-stage cofferdam section and the downstream first-stage cofferdam section of the longitudinal cofferdam body are both arranged in an inclined manner, which can better protect the ends of the first-stage upstream and downstream transverse cofferdams, avoid the direct scouring of the transverse cofferdam ends, and at the same time play a role in smoothing the water flow.

[0010] To facilitate the later reconstruction construction, a further optimized solution is as follows: A flat gate slot is reserved on the side wall of the U-shaped groove of the reconstructible permanent flood discharge sluice section.

[0011] The structural design principles of the front toe, rear heel, and axil angle of the longitudinal cofferdam are the same as those of the conventional longitudinal cofferdam. The principles of setting joints to adapt to the uneven settlement deformation of the foundation and the layout of consolidation grouting to improve the foundation bearing capacity are the same as those of the conventional longitudinal cofferdam. That is: Longitudinal cofferdam joints are arranged at intervals along the length direction of the longitudinal cofferdam body, water stops are set at the longitudinal cofferdam joint parts, and consolidation grouting is arranged on both sides at the bottom of the longitudinal cofferdam body.

[0012] As the first optimized structure of the present invention, when the uplift pressure at the foundation is large and the stability cannot meet the specification requirements, a grouting drainage gallery is arranged at the foundation part of the longitudinal cofferdam body close to the water-retaining side. Curtain grouting is arranged on the outer side at the bottom of the grouting drainage gallery, and deep drainage holes are arranged on the inner side at the bottom of the grouting drainage gallery to reduce the uplift pressure at the longitudinal cofferdam foundation, thereby increasing the safety of lateral anti-sliding and anti-overturning stability.

[0013] As the second optimized structure of the present invention, when the uplift pressure at the longitudinal cofferdam foundation is large and the stability cannot meet the specification requirements, prestressed anchor cables are arranged at the foundation part of the longitudinal cofferdam body close to the water-retaining side to increase the lateral anti-sliding and anti-overturning loads.

[0014] When the above longitudinal cofferdam structure of the present invention is applied and implemented, it mainly includes the following steps:

[0015] Step 1: Use the longitudinal cofferdam body, the first-stage upstream transverse cofferdam, the first-stage downstream transverse cofferdam and the riverbank to enclose the first-stage construction foundation pit, complete the construction of the first-stage construction buildings, and divert the river through the river channel outside the longitudinal cofferdam body during the construction period of the first-stage construction buildings.

[0016] Step 2: After the completion of the first-stage construction buildings, the side close to the longitudinal cofferdam body and the longitudinal cofferdam body form a second-stage diversion structure. Use the longitudinal cofferdam body, the second-stage upstream transverse cofferdam, the second-stage downstream transverse cofferdam and the other riverbank to enclose the second-stage construction foundation pit, complete the construction of the second-stage construction buildings, and divert the river through the above-mentioned second-stage diversion structure during the construction period of the second-stage construction buildings.

[0017] Step 3: After the completion of the second-stage construction buildings, reconstruct the longitudinal cofferdam body into a permanent flood discharge sluice, and the flow passage of the permanent flood discharge sluice corresponds to the U-shaped groove of the longitudinal cofferdam body.

[0018] The beneficial effects of the present invention are as follows: The longitudinal cofferdam structure in the present invention can be used as a conventional longitudinal cofferdam for normal diversion during the construction period and can be reconstructed into a permanent flood discharge sluice for flood discharge during the operation period; this structure increases the flood discharge capacity of the project, reduces the engineering quantity of blasting and demolishing the longitudinal cofferdam, reduces the adverse impact of blasting vibration on adjacent buildings and the foundation anti-seepage curtain, reduces the workload and difficulty of handling blasting slag, and shortens the construction period; when implementing the present invention, only the pouring of the upper permanent structure needs to be increased during the process of reconstructing the permanent flood discharge sluice. Compared with the construction method of demolishing the cofferdam as a whole and then reconstructing the permanent building structure, the required engineering quantity is relatively small, and the construction period is also shortened, having certain engineering benefits and promotion value. Description of the Drawings

[0019] Figure 1 It is a schematic plan view of the longitudinal cofferdam structure during the construction period of the present invention.

[0020] Figure 2 It is a schematic diagram of a typical cross-section of the longitudinal cofferdam of the present invention.

[0021] Figure 3 It is a schematic plan view of the first-stage diversion layout of the present invention.

[0022] Figure 4 It is a schematic plan view of the second-stage diversion layout of the present invention.

[0023] Figure 5 It is a schematic plan view of the hub layout during the operation period of the present invention.

[0024] Figure 6 It is a schematic side view of the reconstructed permanent flood discharge sluice during the operation period of the present invention.

[0025] Figure 7 It is a schematic sectional view of the first preferred structure of the longitudinal cofferdam of the present invention.

[0026] Figure 8 This is a schematic cross-sectional view of the second preferred structure of the longitudinal cofferdam of the present invention.

[0027] Figure 9 This is a schematic plan layout during the construction period of the first and second preferred structures of the longitudinal cofferdam of the present invention.

[0028] The markings in the figure are: upstream first-phase cofferdam section 101, upstream first- and second-phase cofferdam section 102, reconstructible permanent flood discharge sluice section 103, downstream first- and second-phase cofferdam section 104, downstream first-phase cofferdam section 105, first-phase construction foundation pit 201, second-phase construction foundation pit 202, first-phase upstream transverse cofferdam 301, first-phase downstream transverse cofferdam 302, second-phase upstream transverse cofferdam 303, second-phase downstream transverse cofferdam 304, first-phase construction buildings 401, second-phase construction buildings 402; longitudinal cofferdam body 1, U-shaped groove 2, longitudinal cofferdam joint 3, precast concrete beam 4, flat gate slot 5, water stop 6, rockfill backfill structure 7, consolidation grouting 8, clay sandwich geomembrane structure 9, upper permanent structure of the reconstructed sluice section 10, upper auxiliary structure of the reconstructed sluice section 11, steel gate 12, blasting demolition bottom elevation of the upstream first-phase cofferdam section 13, blasting demolition bottom elevation of the downstream first-phase cofferdam section 14, blasting demolition bottom elevation of the upstream first- and second-phase cofferdam section 15, blasting demolition bottom elevation of the downstream first- and second-phase cofferdam section 16, grouting and drainage gallery 17, deep drainage holes 18, curtain grouting 19, prestressed anchor cable 20. Specific embodiments

[0029] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0030] Combined Figures 1 to 9 As shown, the longitudinal cofferdam structure in the present invention includes a longitudinal cofferdam body 1 made of concrete structure. A U-shaped groove 2 is arranged in the middle of the longitudinal cofferdam body 1 along its length direction, and a rockfill backfill structure 7 is arranged in the U-shaped groove 2.

[0031] In order to ensure the stability of the longitudinal cofferdam structure on the premise that the cofferdam shape is as small as possible, the preferred scheme is: the U-shaped groove 2 is arranged at the central position in the width direction of the longitudinal cofferdam body 1; the width of the U-shaped groove 2 is not greater than 50% of the width of the longitudinal cofferdam body 1; the depth of the U-shaped groove 2 is not greater than 60% of the height of the longitudinal cofferdam body 1.

[0032] In order to better ensure the stability of the longitudinal cofferdam structure, the preferred scheme is: cross-section gradual change sections are arranged at both ends in the length direction of the U-shaped groove 2, and in the direction from the center of the U-shaped groove 2 to the end of the U-shaped groove 2, the transverse cross-sectional area of the cross-section gradual change section shows a decreasing trend. Here, the "transverse cross-section" refers to the cross-section perpendicular to the axis of the longitudinal cofferdam body 1.

[0033] According to different diversion functions, the longitudinal cofferdam body 1 generally includes an upstream first-stage cofferdam section 101, an upstream first- and second-stage cofferdam section 102, a reconstructible permanent flood discharge sluice section 103, a downstream first- and second-stage cofferdam section 104, and a downstream first-stage cofferdam section 105 arranged in sequence along its length direction. The U-shaped groove 2 in this embodiment is arranged in the upstream first- and second-stage cofferdam section 102, the reconstructible permanent flood discharge sluice section 103, and the downstream first- and second-stage cofferdam section 104. Cross-section transition sections of the U-shaped groove 2 are respectively arranged at the upstream end of the upstream first- and second-stage cofferdam section 102 and the downstream end of the downstream first- and second-stage cofferdam section 104. The preferred layout scheme of the axis of the longitudinal cofferdam body 1 is as follows: the upstream first- and second-stage cofferdam section 102, the reconstructible permanent flood discharge sluice section 103, and the downstream first- and second-stage cofferdam section 104 are arranged along the axis direction of the longitudinal cofferdam body 1. The axis of the upstream first-stage cofferdam section 101 has a set included angle relative to the axis of the longitudinal cofferdam body 1, and the upstream first-stage cofferdam section 101 is inclined towards the direction close to the first-stage upstream transverse cofferdam 301. The axis of the downstream first-stage cofferdam section 105 has a set included angle relative to the axis of the longitudinal cofferdam body 1, and the downstream first-stage cofferdam section 105 is inclined towards the direction close to the first-stage downstream transverse cofferdam 302. The upstream first-stage cofferdam section and the downstream first-stage cofferdam section of the longitudinal cofferdam body are both arranged in an inclined manner, which can better protect the ends of the first-stage upstream and downstream transverse cofferdams, avoid direct scouring of the ends of the transverse cofferdams, and play a role in smoothing the water flow at the same time.

[0034] To better ensure the stability of the longitudinal cofferdam structure, the preferred scheme is that the two side walls at the top of the U-shaped groove 2 are connected by a horizontally arranged precast concrete beam 4, and the precast concrete beams 4 are arranged at intervals along the length direction of the U-shaped groove 2. The precast concrete beams can improve the overall stress of the side walls on both sides of the longitudinal cofferdam.

[0035] To better ensure the stability of the longitudinal cofferdam structure, the top of the U-shaped groove 2 is closed by a clay sandwich geomembrane structure 9. The geomembrane can play a role in preventing seepage at the top. The "clay sandwich geomembrane structure 9" means that a geomembrane is arranged between the upper clay layer and the lower clay layer.

[0036] To facilitate the later reconstruction construction, the preferred scheme is that a flat gate slot 5 is reserved on the side wall of the U-shaped groove 2 in the reconstructible permanent flood discharge sluice section 103, which can reduce the difficulty of later blasting construction.

[0037] The structural design principles of the front toe, rear heel, and axillary angle of the longitudinal cofferdam are the same as those of the conventional longitudinal cofferdam. The layout principles of the joints provided to adapt to the uneven settlement deformation of the foundation and the consolidation grouting carried out to improve the foundation bearing capacity are the same as those of the conventional longitudinal cofferdam. That is, longitudinal cofferdam joints 3 are arranged at intervals along the length direction of the longitudinal cofferdam body 1, water stops 6 are arranged at the longitudinal cofferdam joint 3 positions, and consolidation grouting 8 is arranged on both sides at the bottom of the longitudinal cofferdam body 1.

[0038] Such as Figure 7 AndFigure 9 As shown in the figure, as the first preferred structure of the present invention, when the uplift pressure of the longitudinal cofferdam foundation is large and the stability cannot meet the specification requirements, a grouting drainage gallery 17 is arranged at the foundation part of the longitudinal cofferdam body 1 close to the water retaining side. A curtain grouting 19 is arranged at the outer side of the bottom of the grouting drainage gallery 17, and deep drainage holes 18 are arranged at the inner side of the bottom of the grouting drainage gallery 17 to reduce the uplift pressure of the longitudinal cofferdam foundation, thereby increasing the safety of lateral anti-sliding and anti-overturning stability.

[0039] As Figure 8 and Figure 9 shown in the figure, as the second preferred structure of the present invention, when the uplift pressure of the longitudinal cofferdam foundation is large and the stability cannot meet the specification requirements, prestressed anchor cables 20 are arranged at the foundation part of the longitudinal cofferdam body 1 close to the water retaining side to increase the lateral anti-sliding and anti-overturning loads. The prestressed anchor cables 20 can be arranged vertically or at a certain inclination angle according to the actual situation.

[0040] The specific parameters of the longitudinal cofferdam structure can be selected according to the actual situation and the requirements of the engineering construction specifications.

[0041] For example, in order to make the longitudinal cofferdam have sufficient self-weight, the bulk density of the backfilled stone slag should be greater than 1.8t / m 3 . The concrete grade of the reconstructible permanent flood discharge sluice section 103 should not be lower than C25 and should also meet the requirements for the concrete strength of the permanent structure. The structural and casting material selection principles of the upstream first-stage cofferdam section 101 and the downstream first-stage cofferdam section 105 are the same as those of the common concrete longitudinal cofferdam. The casting material selection principles of the upstream first- and second-stage cofferdam sections 102 and the downstream first- and second-stage cofferdam sections 104 are the same as those of the common concrete longitudinal cofferdam.

[0042] When the longitudinal cofferdam structure of the present invention is applied and implemented, it mainly includes the following steps:

[0043] Step 1, use the longitudinal cofferdam body 1, the first-stage upstream transverse cofferdam 301, the first-stage downstream transverse cofferdam 302 and the river bank to enclose the first-stage construction foundation pit 201, and complete the construction of the first-stage construction building 401. During the construction period of the first-stage construction building 401, the river channel outside the longitudinal cofferdam body 1 is used for diversion.

[0044] Among them, the length of the upstream first-stage cofferdam section 101 should ensure that the first-stage diversion does not directly scour the slope of the first-stage upstream transverse cofferdam 301. Its length is determined according to the width of the contact part with the first-stage upstream transverse cofferdam 301 on the basis of the length of the upstream first- and second-stage cofferdam section 102, and its top elevation should be higher than the elevation of the first-stage upstream transverse cofferdam 301 body in contact with it;

[0045] The length of the downstream first-phase cofferdam section 105 should ensure that the first-phase diversion does not directly scour the slope of the first-phase downstream transverse cofferdam 302, and its length is determined based on the width of the contact part with the first-phase downstream transverse cofferdam 302 on the basis of the length of the downstream first- and second-phase cofferdam section 104.

[0046] In Step 2, after the construction of the first-phase construction building 401 is completed, the side close to the longitudinal cofferdam body 1 and the longitudinal cofferdam body 1 form a second-phase diversion structure in combination. The longitudinal cofferdam body 1, the second-phase upstream transverse cofferdam 303, and the second-phase downstream transverse cofferdam 304 are used to enclose the second-phase construction foundation pit 202 with the other side of the river bank, and the construction of the second-phase construction building 402 is completed. The second-phase construction building 402 is diverted by the above-mentioned second-phase diversion structure during the construction period.

[0047] Among them, during the formation of the second-phase diversion structure, the longitudinal cofferdam body 1 can be rebuilt according to the actual situation. In this embodiment, after the first-phase diversion is completed, the upstream first-phase cofferdam section 101 and the downstream first-phase cofferdam section 105 need to be demolished by blasting.

[0048] The length of the upstream first- and second-phase cofferdam section 102 is determined according to the width of the contact part with the second-phase upstream transverse cofferdam 303, and its top elevation should not be lower than the higher value of the elevation of the first-phase upstream transverse cofferdam 301 and the second-phase upstream transverse cofferdam 303 in contact with it.

[0049] The length of the downstream first- and second-phase cofferdam section 104 is determined according to the width of the contact part with the second-phase downstream transverse cofferdam 304, and its top elevation should not be lower than the higher value of the elevation of the first-phase downstream transverse cofferdam 302 and the second-phase downstream transverse cofferdam 304 in contact with it.

[0050] In Step 3, after the construction of the second-phase construction building 402 is completed, the longitudinal cofferdam body 1 is rebuilt into a permanent flood discharge sluice, and the flow passage of the permanent flood discharge sluice corresponds to the U-shaped groove 2 of the longitudinal cofferdam body 1. It can be understood that according to the specific structural form of the longitudinal cofferdam body 1 provided by the present invention and the well-known structural form of the permanent flood discharge sluice, the reconstruction project can be implemented by using conventional processes. Specifically, before blasting demolition, generally, the backfilled rock and slag in the U-shaped groove 2 should be cleaned first. The upper permanent building part is poured on the upper part of the reconstructible permanent flood discharge sluice section 103 until it is flush with the top elevation of the adjacent permanent building. After the bent frames are arranged and the portal cranes and gates are installed, it is rebuilt into a permanent flood discharge sluice.

[0051] Preferred embodiment:

[0052] In the project, generally, certain protective measures are taken during the dry season to carry out the foundation pit excavation of the longitudinal cofferdam body 1. After excavation, each section of the longitudinal cofferdam body 1 is poured according to the design of the longitudinal cofferdam joints 3, and one water stop 6 is arranged at each longitudinal cofferdam joint 3 part.

[0053] When the longitudinal cofferdam body 1 is poured to form a U-shaped groove 2 of a certain height, rockfill backfilling can be carried out to form a rockfill backfilling structure 7. The unit weight of the rockfill backfilling structure 7 should be greater than 1.8 t / m 3 , and its height should be kept lower than the side walls on both sides by 4 m, and at the same time its height should not be greater than 50% of the net height of the U-shaped groove 2; when the longitudinal cofferdam body 1 is poured to 2.5 m from the crest, install the precast concrete beam 4. After the side walls on both sides and the precast concrete beam 4 at the top are poured and reach the 7-day design age, then carry out the rockfill backfilling in the U-shaped groove 2 to the design height; after the rockfill is filled to the design height, the top is closed with a clay sandwich geomembrane structure 9. The filled clay should have a slope of 2% - 5% from the longitudinal axis of the longitudinal cofferdam to both sides. The thickness of the clay below the geomembrane is 50 cm, the thickness of the clay above the geomembrane is 20 cm, the thickness of the composite geomembrane is 0.1 mm, and the composite geomembrane is fixedly connected to the top of the longitudinal cofferdam by a pressing strip.

[0054] After the longitudinal cofferdam body 1 has the water retaining condition, the first-stage river closure can be carried out, and then the construction of the first-stage upstream transverse cofferdam 301 and the first-stage downstream transverse cofferdam 302 is carried out, that is, the first-stage construction foundation pit 201 is formed. After the first-stage construction foundation pit 201 is pumped and drained to reach the dry construction condition, the construction of the first-stage construction buildings 401 can be carried out.

[0055] After the construction of the first-stage construction buildings 401 is completed, the first-stage upstream transverse cofferdam 301, the first-stage downstream transverse cofferdam 302, the upstream first-stage cofferdam section 101 and the downstream first-stage cofferdam section 105 are demolished. The upstream first-stage cofferdam section 101 is demolished by blasting, and the demolition reaches the blasting demolition bottom elevation 13 of the upstream first-stage cofferdam section. The downstream first-stage cofferdam section 105 is demolished by blasting, and the demolition reaches the blasting demolition bottom elevation 14 of the downstream first-stage cofferdam section.

[0056] After the flood discharge buildings in the first-stage construction buildings 401 have the flow-through condition, the second-stage river closure is carried out, and then the construction of the second-stage upstream transverse cofferdam 303 and the second-stage downstream transverse cofferdam 304 is carried out, that is, the second-stage construction foundation pit 202 is formed. After the second-stage construction foundation pit 202 is pumped and drained to reach the dry construction condition, the construction of the second-stage construction buildings 402 can be carried out.

[0057] After the construction of the second-stage construction buildings 402 is completed, the second-stage upstream transverse cofferdam 303, the second-stage downstream transverse cofferdam 304, the upstream first- and second-stage cofferdam section 102 and the downstream first- and second-stage cofferdam section 104 are demolished. They are respectively demolished to the blasting demolition bottom elevation 15 of the upstream first- and second-stage cofferdam section and the blasting demolition bottom elevation 16 of the downstream first- and second-stage cofferdam section.

[0058] Before blasting and demolishing the upstream first- and second-stage cofferdam section 102 and the downstream first- and second-stage cofferdam section 104, first clean the rockfill backfilling structure 7 in the U-shaped groove 2.

[0059] After the second-phase blasting demolition is completed, the reconstructed permanent flood discharge sluice section 103 can be retained as part of the permanent flood discharge sluice. The upper permanent building part (i.e., the upper permanent structure 10 of the reconstructed sluice section) is poured to the top elevation, and the auxiliary structure (i.e., the upper auxiliary structure 11 of the reconstructed sluice section) above the upper permanent building part and the installation of the steel gate 12 are completed. Thus, the construction of the reconstructed permanent flood discharge sluice of the longitudinal cofferdam body 1 is completed.

[0060] After the application of the first and second preferred structural combination embodiments of the present invention in a certain navigation and hydropower project, the first-phase and second-phase diversion construction of the project is successfully completed. As the permanent flood discharge sluice, it has been used for normal flood discharge for more than 10 years, and the project benefits are obvious.

Claims

1. Longitudinal cofferdam structure, including the longitudinal cofferdam body (1) made of concrete structure, characterized in that: In the middle of the longitudinal cofferdam body (1), a U-shaped groove (2) is arranged along its length direction, and a slag backfill structure (7) is arranged in the U-shaped groove (2). The U-shaped groove (2) is arranged at the center position in the width direction of the longitudinal cofferdam body (1); the width of the U-shaped groove (2) is not greater than 50% of the width of the longitudinal cofferdam body (1); the depth of the U-shaped groove (2) is not greater than 60% of the height of the longitudinal cofferdam body (1). Both ends of the U-shaped groove (2) in the length direction are provided with cross-section gradual change sections, and in the direction from the center of the U-shaped groove (2) to the end of the U-shaped groove (2), the cross-sectional area of the cross-section gradual change section shows a decreasing trend. Between the two side walls at the top of the U-shaped groove (2), they are connected by a horizontally arranged precast concrete beam (4), and the precast concrete beams (4) are arranged at intervals along the length direction of the U-shaped groove (2). The top of the U-shaped groove (2) is closed by a clay sandwich geomembrane structure (9). The longitudinal cofferdam body (1) includes an upstream first-phase cofferdam section (101), an upstream first and second-phase cofferdam section (102), a reconstructible permanent flood discharge sluice section (103), a downstream first and second-phase cofferdam section (104), and a downstream first-phase cofferdam section (105) arranged in sequence along its length direction; the upstream first and second-phase cofferdam section (102), the reconstructible permanent flood discharge sluice section (103), and the downstream first and second-phase cofferdam section (104) are arranged along the axis direction of the longitudinal cofferdam body (1), the axis of the upstream first-phase cofferdam section (101) has a set included angle relative to the axis of the longitudinal cofferdam body (1), the upstream first-phase cofferdam section (101) is inclined and arranged towards the direction close to the first-phase upstream transverse cofferdam (301), the axis of the downstream first-phase cofferdam section (105) has a set included angle relative to the axis of the longitudinal cofferdam body (1), and the downstream first-phase cofferdam section (105) is inclined and arranged towards the direction close to the first-phase downstream transverse cofferdam (302). A flat gate slot (5) is reserved on the side wall of the U-shaped groove (2) of the reconstructible permanent flood discharge sluice section (103). A grouting and drainage gallery (17) is arranged at the foundation part of the longitudinal cofferdam body (1) close to the water retaining side, curtain grouting (19) is arranged at the outer side of the bottom of the grouting and drainage gallery (17), and deep drainage holes (18) are arranged at the inner side of the bottom of the grouting and drainage gallery (17).

2. The longitudinal cofferdam structure according to claim 1, characterized in that: Prestressed anchor cables (20) are arranged at the foundation part of the longitudinal cofferdam body (1) close to the water retaining side.

3. Implementation method of longitudinal cofferdam structure, characterized in that: Adopt the longitudinal cofferdam structure as described in claim 1 or 2, and include the following steps: Step 1, use the longitudinal cofferdam body (1), the first-phase upstream transverse cofferdam (301), the first-phase downstream transverse cofferdam (302) and the river bank to enclose a first-phase construction foundation pit (201), complete the construction of the first-phase construction building (401), and during the construction period of the first-phase construction building (401), divert the river through the river channel outside the longitudinal cofferdam body (1). Step 2: After the construction of the first-phase construction buildings (401) is completed, the side of the first-phase construction buildings (401) close to the longitudinal cofferdam body (1) and the longitudinal cofferdam body (1) form a second-phase diversion structure together. The longitudinal cofferdam body (1), the second-phase upstream transverse cofferdam (303), the second-phase downstream transverse cofferdam (304) and the other river bank enclose a second-phase construction foundation pit (202), and the construction of the second-phase construction buildings (402) is completed. During the construction period of the second-phase construction buildings (402), the above-mentioned second-phase diversion structure is used for diversion; Step 3: After the construction of the second-phase construction buildings (402) is completed, the longitudinal cofferdam body (1) is rebuilt into a permanent flood discharge sluice, and the flow passage of the permanent flood discharge sluice corresponds to the U-shaped groove (2) of the longitudinal cofferdam body (1).

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