Cofferdam water retaining structure and dismantling method thereof

Abstract

The invention belongs to the technical field of water-power engineering diversion design, and particularly discloses a cofferdam water retaining structure which comprises a water retaining rock bank and a sub-weir, a foundation surface of the sub-weir is arranged at the top of the water retaining rock bank, and gaps are reserved between the foundation surface of the sub-weir and the edge of the upstream side and the edge of the downstream side of the top of the water retaining rock bank. According to the dismantling method of the cofferdam water retaining structure, the cofferdam water retaining structure is dismantled, and the water retaining rock ridge and the sub-weir are dismantled in a layering and partitioning blasting mode according to the sequence from top to bottom and from inside to outside. According to the method, dry land construction conditions can be ensured when the water inlet and the water outlet of the mixed pumped storage hydropower station are built in the existing hydropower station reservoir with the annual regulation capacity.

Description

Technical Field

[0001] The invention relates to the technical field of diversion design for hydropower projects, and in particular to a cofferdam water retaining structure and a dismantling method thereof. Background Art

[0002] Hybrid pumped storage hydropower stations often use existing reservoirs as upper or lower reservoirs. They can be developed and constructed simultaneously with conventional hydropower stations, or they can be expanded or continued on existing conventional hydropower stations. If the reservoir of an existing hydropower station is used, the operation and storage capacity of the existing reservoir cannot be interfered with. When the existing reservoir has the ability to regulate for many years, since the power station is mainly for power generation and takes flood control into consideration, it does not have the conditions to empty the reservoir for a long time or significantly reduce the operating water level for inlet / outlet construction. In addition, the reservoir water level fluctuates greatly, the water depth greatly exceeds other similar cofferdams, and the working conditions are extremely complex. The reservoir bank slope terrain is usually steep, the geological structure is complex, the weathering unloading is serious, and most of the surrounding rocks are Class IV to V, which makes construction difficult.

[0003] During the construction period, the natural terrain is often used to excavate and reserve rock ridges as temporary cofferdams to retain water. However, when the water level of the reservoir is high, it is easy to cause sliding damage due to seepage. At the same time, the blasting volume and demolition scale will also increase accordingly, and it is inevitable to carry out blasting and slag removal under deep water conditions. The following cofferdam water retaining technologies are disclosed in the prior art:

[0004] Technology 1: A water retaining cofferdam structure for a deep river valley hydropower project with application number 201420139872.1 in the prior art. The purpose is to provide a water retaining cofferdam structure for a deep river valley hydropower project with a simple structure and convenient construction to improve the anti-sliding stability of the water retaining cofferdam and ensure the safety during the foundation pit construction period. The structure has a concrete water retaining cofferdam cast on a rock platform on one side of the riverbed, a grouting curtain is set in the rock platform and at the axis position of the water retaining cofferdam, drainage holes are drilled on the backwater side of the rock platform, a rock ridge is reserved on the rock platform at the bottom of the concrete water retaining cofferdam, and the water-facing side of the rock ridge is excavated in steps, the top of the rock head on the backwater side of the concrete upper water retaining cofferdam is reinforced with anchor cables or anchor reinforcement bundles, a platform is reserved on the rock platform on the riverbed side of the concrete water retaining cofferdam and reinforced with anchor cables or anchor reinforcement bundles, and the anchor cables or anchor reinforcement bundles pass through a gently inclined structural surface 1 to 2m that has a controlling effect on the stability of the cofferdam.

[0005] Technology 2: A reinforcement system for a reserved rock ridge water retaining cofferdam for water intake under the operating water level of the reservoir area with application number 201910696344.3 in the prior art. The reserved rock ridge water retaining cofferdam is reinforced by a reinforcement system including steel pipe piles, consolidation grouting, membrane bag concrete, glass fiber reinforced concrete slabs on the inner side of the cofferdam, and inner support beams. By adopting a scientific cofferdam reinforcement, consolidation and support system, the conditions for creating dry land construction for water intake construction under the operating water level of the reservoir area are met. This invention is suitable for reservoir areas, beside rivers, where the geological conditions are poor and it is not possible to cast underwater concrete cofferdams.

[0006] Technology 3: A construction method for the inlet of an emergency water discharge tunnel of an existing reservoir with an application number of 202210308461.X in the prior art. The method is to divide the inlet excavation into two stages, including the following steps: Phase I construction: According to the water level elevation guaranteed by reservoir irrigation + the water retaining elevation of the lower limit of 0.5m of the weir top safety heightening, the first phase slope excavation dry land operation elevation of the water inlet is calculated, and the slope excavation is carried out and the construction platform is excavated at the elevation position; Phase II construction: The cofferdam is set up by using the rock ridge reserved by the original landform on the shore, and the steel sheet pile + grouting anti-seepage technology is adopted to ensure the dry land operation of the second phase lock chamber foundation excavation. The invention uses the natural boundary conditions such as reservoir hydrology and landform to excavate the water inlet in two phases, overcomes the technical disadvantages of the water inlet being excavated in one go to the designed foundation elevation without stages, reduces the difficulty of filling earth and stone cofferdams, reduces the damage to the surrounding soil and water conservation and ecological environment, and reduces the excavation depth of the base surface.

[0007] Among them, the disadvantages of technology 1 are: when constructing inlets and outlets in existing reservoirs, the operation and storage capacity of the existing reservoirs cannot be interfered with. When the existing reservoir has a multi-year regulation capacity, since the power station is mainly used for power generation, it does not have the conditions to empty the reservoir for a long time or significantly reduce the operating water level for inlet / outlet construction, so the reservoir can maintain a low water level for a limited time. This solution requires reserved rock ridge excavation, curtain grouting, anchor rod and anchor cable construction during the water level drawdown period, which takes a long time. When the rock ridge is high, scaffolding needs to be set up when constructing anchor cables or anchor tendons on the backwater side. This solution does not reserve a construction channel and is only applicable to the case of low rock ridges. In addition, this solution does not take slag accumulation measures. When the rock ridge is removed, the slag will damage the diversion tunnel structure.

[0008] Among them, the disadvantages of technology 2 are: the invention uses a reinforcement system such as steel pipe piles, consolidation grouting, membrane bag concrete, glass fiber reinforced concrete slabs on the inner side of the cofferdam, and inner support beams to reinforce the reserved rock ridge water retaining cofferdam. When the rock ridge is high, if the above reinforcement system is continued to be used for reinforcement, due to the long vertical calculation length of the steel pipe piles, its stability performance is reduced, and support measures need to be taken to prevent it from becoming unstable, and measures need to be taken both in the plane and out of the plane, and the support system engineering is large. And anti-slip stability is difficult to ensure.

[0009] Among them, the disadvantages of technology 3 are: the invention is mainly aimed at a construction method for building an emergency water discharge tunnel in an existing reservoir. The design is mainly for reservoirs in water conservancy projects. During construction, the water level of the reservoir can be lowered to the water level elevation guaranteed by reservoir irrigation. However, in water conservancy and hydropower projects, in order to ensure that the operation of the reservoir is not affected by power generation needs, the water level cannot be actively lowered. In addition, it introduces the water inlet construction method, which is mainly divided into two phases. The second phase is to carry out excavation and dry land construction of the gate chamber foundation under the protection of the reserved rock ridge, but it does not introduce how to remove the rock ridge. Summary of the invention

[0010] The invention provides a cofferdam water retaining structure, which aims to ensure dry land construction conditions when constructing a water inlet and outlet of a hybrid pumped storage hydropower station in an existing hydropower station reservoir with annual regulation capacity.

[0011] The present invention is achieved through the following technical scheme: a cofferdam water retaining structure, including a water retaining rock sill and a sub-weir, the base surface of the sub-weir is placed on the top of the water retaining rock sill, and there is a distance between the base surface of the sub-weir and the edge of the water-facing side and the edge of the water-retaining side of the top of the water retaining rock sill.

[0012] Furthermore, the top of the water retaining rock sill is 1.5-2m higher than the water level during the reservoir operation period.

[0013] Furthermore, a plurality of anchor rods are inserted on the backwater side of the water retaining rock sill for support.

[0014] Furthermore, the height of the sub-weir is not greater than 20m.

[0015] Furthermore, the distance between the construction base surface of the sub-weir and the edge of the water-facing side of the top of the water-retaining rock sill is not less than 5m, and the distance between the construction base surface of the sub-weir and the edge of the water-retaining side of the top of the water-retaining rock sill is not less than 10m.

[0016] Furthermore, a plurality of deep holes are opened on the top of the water retaining rock sill, and the plurality of deep holes are sequentially spaced and distributed along the length direction of the water retaining rock sill, and grouting is performed in the deep holes to form the foundation of the bottom of the sub-weir.

[0017] Furthermore, a row of main anti-seepage curtains is arranged on the sill of the water retaining rock sill, and the axes of the main anti-seepage curtains extend toward the upstream and downstream directions of the axis of the water retaining rock sill respectively.

[0018] Furthermore, a row of auxiliary anti-seepage curtains is arranged on one side of the main anti-seepage curtain, and the axes of the auxiliary anti-seepage curtains extend toward the upstream and downstream directions of the axis of the water retaining rock sill, respectively.

[0019] A method for dismantling a cofferdam water retaining structure is provided. The cofferdam water retaining structure is dismantled. The water retaining rock sill and sub-weir are blasted in layers and blocks in a top-down and inside-out order.

[0020] Furthermore, the water retaining rock sill and sub-dam are demolished as a whole from top to bottom in three stages. The first stage is the concrete surrounding rock blasting zone I, the second stage is the rock sill blasting zone II, the rock sill blasting zone II is divided into multiple layers, and each layer of the rock sill blasting zone II is divided into at least two blasting blocks; the third stage is the rock sill blasting zone III, the rock sill blasting zone III is divided into at least two blasting blocks.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] The cofferdam water retaining structure of the present invention can ensure dry land construction conditions when constructing the water inlet and outlet of a hybrid pumped storage hydropower station in an existing hydropower station reservoir with annual regulation capacity. An anti-seepage system is formed by constructing anti-seepage curtain grouting in the structure and the mountain; and anchor rods are arranged on the backwater side of the water retaining rock sill to improve the stability of the slope.

[0023] In order to reduce the amount of underwater blasting demolition and the difficulty of engineering demolition, the demolition progress matches the water level drop rate, and ensures that the reserved rock sill is always 1.5 to 2 meters above the water level line. In a demolition method of a cofferdam water retaining structure in the present invention, the rock sill is demolished from top to bottom, from inside to outside, and is blasted in layers and blocks, which can ensure that the structure is demolished by blasting in one water level drawdown period, while reducing underwater blasting and slag removal. The construction and demolition of the water retaining structure in the present invention does not interfere with the operation and storage capacity utilization of the existing reservoir, and is safer and more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0025] Figure 1 This is a structural schematic diagram of a cofferdam water retaining structure embodiment 1 of the present invention;

[0026] Figure 2 It is a schematic diagram of layered and block dismantling in Embodiment 2 of a cofferdam water retaining structure of the present invention;

[0027] Figure 3 It is a schematic diagram of dismantling in layers and blocks in Embodiment 3 of a cofferdam water retaining structure of the present invention;

[0028] Figure 4 It is a structural schematic diagram of a cofferdam water retaining structure embodiment 4 of the present invention;

[0029] Figure 5 It is a structural schematic diagram of a cofferdam water retaining structure of the present invention in actual engineering application;

[0030] Figure 6 It is a schematic diagram of the layered and block-by-block dismantling of a cofferdam water retaining structure of the present invention in actual engineering application.

[0031] Marks and corresponding parts names in the attached drawings:

[0032] Sub-weir 1, deep hole 2, water retaining rock sill 3, main anti-seepage curtain 4, anti-seepage curtain 401, auxiliary anti-seepage curtain 5, slag collection pit 6. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0034] Example 1

[0035] like Figure 1 As shown, this embodiment 1 provides a cofferdam water retaining structure, including a water retaining rock sill 3 and a sub-weir 1, the sub-weir 1 is a concrete sub-weir cast in concrete, the water retaining structure in this embodiment takes the form of a reserved rock sill + concrete sub-weir, the concrete sub-weir 1 structure is a gravity type, and the height should be determined comprehensively according to the bedrock conditions and the water retaining height. In this embodiment, the height of the concrete sub-weir 1 should not be greater than 20m. The top elevation of the water retaining rock sill 3 should take into account the influence of factors such as safety heightening. In this embodiment, the top of the water retaining rock sill 3 is 1.5 to 2m higher than the water level of the power station reservoir during operation under the design standard.

[0036] In this embodiment, the foundation surface of the sub-weir 1 is placed on the top of the water-retaining rock sill 3, and there is a distance between the foundation surface of the sub-weir 1 and the edge of the water-facing side and the edge of the water-retaining side of the top of the water-retaining rock sill 3. Specifically: in this embodiment, the foundation surface of the sub-weir 1 is not less than 5m away from the edge of the water-facing side of the top of the water-retaining rock sill 3, and the foundation surface of the sub-weir 1 is not less than 10m away from the edge of the water-retaining rock sill 3.

[0037] The bottom of the reserved water retaining rock sill 3 is the elevation of the bottom plate of the water inlet and outlet, and the top elevation of the water retaining rock sill 3 is the elevation of the foundation surface of the concrete sub-weir 1. The width of the top platform of the water retaining rock sill 3 should be able to ensure the reserved width requirements of the concrete sub-weir 1 on both sides. If the width is insufficient, concrete can be backfilled on the water-facing side.

[0038] In this embodiment, a plurality of deep holes 2 are opened on the top of the water retaining rock sill 3, the depth of the deep holes 2 is 10m, and the plurality of deep holes 2 are sequentially spaced along the length direction of the water retaining rock sill 3. Grouting is performed in the deep holes 2 to form the foundation of the bottom of the sub-weir 1 as the sub-weir foundation. In this embodiment, the sub-weir foundation adopts 10m deep consolidation grouting, and the spacing between rows is 3m.

[0039] A number of anchor rods are inserted on the backwater side of the water retaining rock step 3 for support. Specifically: the excavation slope ratio of the backwater side of the water retaining rock step 3 should be determined according to the geological conditions, and the elevation and width of the horseway should be considered according to the on-site traffic planning. The slope surface is supported by shallow sprayed anchors (using 10cm thick C20 sprayed concrete, with an anchor spacing of 3m×3m).

[0040] In this embodiment, a row of main anti-seepage curtains 4 are arranged on the sill of the water retaining rock sill 3, and the axes of the main anti-seepage curtains 4 extend respectively in the upstream and downstream directions of the axis of the water retaining rock sill 3. A row of auxiliary anti-seepage curtains 5 are also arranged on one side of the main anti-seepage curtains 4, and the axes of the auxiliary anti-seepage curtains 5 extend respectively in the upstream and downstream directions of the axis of the water retaining rock sill 3.

[0041] Specifically: According to the drilling water pressure conditions, in order to reduce the amount of drainage from the foundation pit and improve the stability of the rock sill cofferdam, a main anti-seepage curtain is set on the sill body of the water retaining rock sill 3. The depth of the curtain is determined according to the geological seepage conditions. At the same time, in order to reduce upstream and downstream bypass seepage, the axis of the main anti-seepage curtain 4 extends 100m upstream and downstream of the axis of the water retaining rock sill respectively, and the spacing between the curtain grouting holes is 1.5m.

[0042] In addition, in combination with the need to remove the rock sill, an auxiliary anti-seepage curtain 5 is arranged outside the main anti-seepage curtain 4. The depth is determined according to the geological seepage conditions. The axis of the auxiliary anti-seepage curtain 5 extends 50.0m upstream and downstream respectively, arranged in a single row, and the hole spacing is 1.5m. At the same time, the bottom of the foundation pit side of the water retaining rock sill is not less than 10m away from the hydraulic structure, wherein the bottom of the foundation pit side of the water retaining rock sill in this embodiment refers to the bottom slope foot of the water retaining rock sill facing the trash rack side, and the hydraulic structure refers to the trash rack section of the water intake.

[0043] like Figure 1 As shown, a slag collecting pit 6 is provided at the bottom of the water retaining rock sill 3. One side of the backwater side of the water retaining rock sill 3 is a trash rack.

[0044] Example 2

[0045] like Figure 2 As shown, the difference between this embodiment and embodiment 1 is that: this embodiment discloses a method for dismantling a cofferdam water retaining structure, and a cofferdam water retaining structure as described in embodiment 1 is dismantled. The demolition of the water retaining structure should be completed by blasting and dismantling the concrete cofferdam and the water retaining rock sill 3 during a water level drawdown period.

[0046] In this embodiment, the demolition of the water-retaining rock sill 3 and the sub-weir 1 is carried out in layers and blocks by blasting (blasting demolition) in the order from top to bottom and from inside to outside (wherein the inside refers to the backwater side of the rock sill, and the outside refers to the frontwater side of the rock sill). In this embodiment, blasting is carried out from inside to outside, so that the blasting blocks facing the frontwater side can play a role in retaining water. In this way, blasting can be carried out in the backwater side area of ​​the rock sill in advance, and there is no need to wait for the water level on the frontwater side to be completely lowered before starting construction, thereby improving the blasting efficiency.

[0047] Specifically: the water retaining rock sill 3 and the sub-weir 1 are demolished as a whole from top to bottom in three stages, the first stage is the concrete surrounding rock blasting zone I, the second stage is the rock sill blasting zone II, the rock sill blasting zone II is divided into multiple layers, in this embodiment, the rock sill blasting zone II has four layers, and each layer of the rock sill blasting zone II is divided into at least two blasting blocks, in this embodiment, each layer of the rock sill blasting zone II is divided into 2-3 blasting blocks, the first layer has 2 blasting blocks, the second layer, the third layer and the fourth layer each have 3 blasting blocks; the third stage is the rock sill blasting zone III, the rock sill blasting zone III is divided into at least two blasting blocks, in this embodiment, the rock sill blasting zone III is divided into 3 blasting blocks.

[0048] like Figure 2 As shown, in this embodiment, each blasting block in the rock ridge blasting zone II and the rock ridge blasting zone III is represented by serial numbers ①, ②, and ③, wherein block ① is the thinning of the inner side of the main anti-seepage curtain, block ② is the thinning of the outer side of the main anti-seepage curtain, and block ③ is the last one-time blasting.

[0049] In this embodiment, the rock ridge blasting II area is divided into four layers, and the lower layer is blasted after the upper layer is blasted. At the same time, each layer is blasted in sequence from the backwater side to the frontwater side according to the sequence number ①, ②, ③.

[0050] In another embodiment, the blasting block with serial number ③ in the rock step blasting III zone is located in the middle position. When the rock step blasting III zone is blasted and demolished, the blasting block with serial number ① and the blasting block with serial number ② are blasted and demolished simultaneously toward the blasting block with serial number ③, and finally the blasting block with serial number ③ is blasted and demolished. This can save construction time and ensure the construction of the hydraulic structure below in the later stage. Figure 1 The shape of the ramp shown in .

[0051] Example 3

[0052] like Figure 3 As shown, the difference between this embodiment and embodiment 2 is that in order to reduce the amount of underwater blasting demolition and the difficulty of engineering demolition, match the demolition progress with the water level drop rate, and ensure that the reserved water retaining rock sill 3 is always 1.5 to 2 meters above the water level line, the last blasting construction period for demolition of the water retaining rock sill 3 should be arranged in May to June.

[0053] The water-retaining rock sill in this embodiment is similar to a triangular shape, and the rock sill is blasted in a top-down, inside-out order. In this embodiment, when blasting the rock sill blasting area II, after the first layer of the rock sill blasting area II is blasted, the second layer, the third layer and the fourth layer of the rock sill blasting area II are blasted in the order shown in the figure, that is, a blasting block located on the water-facing side in the upper blasting area is blasted before a blasting block located on the water-receiving side in the lower blasting area is blasted.

[0054] Since it takes a certain amount of time for the water level to drop, if the method of Example 2 is followed, it is necessary to wait until the water level corresponding to each blasting area drops completely to the next layer before the blasting blocks on the water-facing side can be blasted. When the blasting sequence in this embodiment is adopted, the blasting blocks on the water-facing side of the previous layer can play a water-blocking role. In this way, there is no need to wait for the water level of the previous layer to drop completely to the water level of the next layer before the blasting blocks on the water-retaining side of the next layer can be blasted. In this way, the demolition progress can be effectively matched with the water level drop rate, and it can be ensured that the reserved water-retaining rock sill 3 is always 1.5 to 2 meters above the water level line, and the blasting construction efficiency is effectively improved.

[0055] Specifically, Figure 3 As shown, the rock ridge blasting II area is divided into ①, ②, ③, ④, ⑤, ⑥, ⑦, ⑧, ⑨, ①0, The first layer of rock sill blasting zone II consists of two blasting blocks: ①) and ②; the second layer consists of three blasting blocks: ③, ④, and ⑥; the third layer consists of three blasting blocks: ⑤, ⑦, and ⑨; the fourth layer consists of three blasting blocks: ⑧, ⑩, When blasting in Zone II, follow ①, ②, ③, ④, ⑤, ⑥, ⑦, ⑧, ⑨, ①0, blasting in the order of .

[0056] Compared with the prior art, the water retaining structure of the present invention has a more complete anti-seepage system and better structural stability. The present invention can effectively ensure the dry land construction of the water inlet and outlet, and when the water retaining structure of the present invention is dismantled, the dismantling progress matches the water level drop rate, reducing the amount of underwater blasting and slag removal work, and can ensure that it is completely dismantled in a water level drop period, which is safer.

[0057] Example 4

[0058] like Figure 4 As shown, the difference between this embodiment and embodiment 3 is that in this embodiment, an anti-seepage curtain 401 is additionally provided on the right side of the main anti-seepage curtain 4 and located on the upper part of the main anti-seepage curtain 4. The main anti-seepage curtain 4 and the anti-seepage curtain 401 are arranged side by side, and the anti-seepage curtain 401 can further improve the anti-seepage effect.

[0059] Such as 5 and Figure 6As shown, the present invention is introduced by taking the design of the upper reservoir water retaining structure of a hybrid pumped storage hydropower station in the southwest region as an example.

[0060] This project uses the existing hydropower station reservoir as the upper reservoir. The water retaining structure of the upper reservoir inlet / outlet adopts the form of reserved rock sill + concrete sub-weir. The elevation of the bottom plate of the upper reservoir inlet / outlet is 2772.50m. The design standard of the cofferdam adopts the 10-year flood recurrence period throughout the year. After flood control calculation, the water level in front of the cofferdam during the 10-year flood recurrence period during the operation of the power station is 2865.00m. Considering the influence of factors such as safety heightening, the top elevation of the concrete sub-weir is taken as 2867.00m, the elevation of the construction base is taken as 2847m, the height of the concrete sub-weir is 20m, and the sub-weir foundation adopts 10m deep consolidation grouting with a spacing of 3m.

[0061] The reserved water retaining rock step is about 77.1m high. According to the geological conditions revealed by the drilling, the excavation slope ratio of the reserved water retaining rock step on the back water side at an elevation of 2772.50m to 2800.00m is 1:0.3, the excavation slope ratio at an elevation of 2800.00m to 2825.00m is 1:0.5, and the excavation slope ratio at an elevation of 2800.00m to 2825.00m is 1:0.75. A horseway with a width of 2m is reserved for each level, and the slope is supported by shallow sprayed anchors.

[0062] According to the drilling water pressure situation, in order to reduce the amount of drainage from the foundation pit and improve the stability of the rock cofferdam, a main anti-seepage curtain is set on the cofferdam body. The curtain is 110m deep and has a bottom elevation of 2737.00m, which is 33.5m lower than the lowest point of the water inlet foundation surface. The axis length of the concrete sub-weir is 203m. In order to reduce the upstream and downstream bypass seepage, the axis of the main anti-seepage curtain is extended 100m upstream and downstream respectively. The total length of the main anti-seepage curtain axis is 403m, and the spacing between the curtain grouting holes is 1.5m. A row of curtain grouting holes is added to the upper 50m of the main anti-seepage curtain 4 to form an anti-seepage curtain 401.

[0063] In addition, in view of the need to remove the rock sill, an auxiliary anti-seepage curtain is arranged outside the main anti-seepage curtain. The top elevation of the auxiliary anti-seepage curtain is 2830.00m, the depth is 77.0m, and the axis of the auxiliary anti-seepage curtain extends 50.0m upstream and downstream respectively. The total length of the axis is 303.0m. It is arranged in a single row with a hole spacing of 1.5m.

[0064] According to the construction schedule, the concrete cofferdam and rock sill will be demolished by blasting in one water level drawdown period. In order to reduce the amount of underwater demolition and the difficulty of engineering demolition, the demolition progress is matched with the rate of water level drop, and the reserved water retaining rock sill is always 1.5 to 2 meters above the water level. The best construction period for the last blasting of the water retaining rock sill is from May to June. In summary, combined with the relationship between the monthly upstream water level of the Lianghekou Reservoir over the years and the construction schedule, the reserved water retaining rock sill demolition period is from January to June of the fifth year.

[0065] The removal of the water retaining rock sill and concrete sub-weir at the inlet / outlet of the upper reservoir is carried out from top to bottom and from inside to outside, layer by layer and block by block. Generally, it is divided into three stages: the first stage is the blasting of the concrete cofferdam area I, the second stage is the blasting of the rock sill area II, the rock sill blasting area II is divided into 4 layers, each layer is divided into 2 to 3 blocks, and the third stage is the blasting of the rock sill area III, which is divided into 3 blocks. Block ① is the thinning of the inner side of the anti-seepage curtain, block ② is the thinning of the outer side of the anti-seepage curtain, and block ③ is the last one-time blasting. The specific zoning and block demolition plan is as follows: Figure 5 shown.

[0066] It should be noted that the above description of the disclosed embodiments enables professionals and technicians in the field to implement or use the present application. Various modifications to these embodiments will be apparent to professionals and technicians in the field, and the general principles defined herein can be implemented in other embodiments without departing from the scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but should conform to the widest scope consistent with the principles and novel features disclosed herein.

[0067] In the description of the present invention, it should be noted that the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0068] In the description of this document, terms such as "up", "down", "left", "right", "front", "back", "top", "bottom", "inside", "outside", "middle", "vertical", "horizontal", "lateral", and "longitudinal" indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only used to illustrate the relative positional relationships between the various components or components, and do not particularly limit the specific installation orientations of the various components or components.

[0069] In the description of this document, some terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to the specific circumstances.

[0070] In the description of this document, the terms "installed", "set", "provided with", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0071] The structures, proportions, sizes, etc. drawn in the drawings in this application are only used to match the contents disclosed in this technical briefing book for technical personnel in this field to understand and read, and are not used to limit the restrictive conditions for the implementation of this application. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in this application without affecting the effects and purposes that can be achieved by this application.

[0072] The terms used in this document are those common terms currently widely used in the art in consideration of the functions of the present disclosure, but these terms may vary according to the intention of a person of ordinary skill in the art, precedents, or new technologies in the art. In addition, specific terms may be selected by the applicant, and in this case, their detailed meanings will be described in the detailed description of the present disclosure. Therefore, the terms used in the document should not be understood as simple names, but rather as an overall description based on the meaning of the terms and the present disclosure.

[0073] Flowcharts or text are used in this document to illustrate the operating steps performed according to the embodiments of the present application. It should be understood that the operating steps in the embodiments of the present application are not necessarily accurately performed in the order of recording. On the contrary, various steps can be processed in reverse order or simultaneously as needed. At the same time, other operations can also be added to these processes, or a certain step or several steps can be removed from these processes.

[0074] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A cofferdam water retaining structure, It is characterized in that It comprises a water retaining rock sill and a sub-weir, wherein the foundation surface of the sub-weir is placed on the top of the water retaining rock sill, and there is a distance between the foundation surface of the sub-weir and the edge of the water-facing side and the edge of the water-retaining side of the top of the water retaining rock sill.

2. A cofferdam water retaining structure according to claim 1, It is characterized in that The top of the water retaining rock sill is 1.5-2m higher than the water level line during the reservoir operation period.

3. A cofferdam water retaining structure according to claim 1, It is characterized in that A plurality of anchor rods are inserted into the backwater side of the water retaining rock sill for support.

4. A cofferdam water retaining structure according to claim 1, It is characterized in that The height of the sub-weir is not more than 20m.

5. A cofferdam water retaining structure according to claim 1, It is characterized in that The construction base surface of the sub-weir is not less than 5m away from the edge of the water-facing side of the top of the water-retaining rock sill, and the construction base surface of the sub-weir is not less than 10m away from the edge of the water-retaining rock sill top.

6. A cofferdam water retaining structure according to claim 1, It is characterized in that A plurality of deep holes are opened on the top of the water retaining rock sill, and the plurality of deep holes are sequentially spaced and distributed along the length direction of the water retaining rock sill. Grouting is poured into the deep holes to form the foundation of the bottom of the sub-weir.

7. A cofferdam water retaining structure according to claim 1, It is characterized in that A row of main anti-seepage curtains are arranged on the sill of the water retaining rock sill, and the axes of the main anti-seepage curtains extend toward the upstream and downstream directions of the axis of the water retaining rock sill respectively.

8. A cofferdam water retaining structure according to claim 7, It is characterized in that A row of auxiliary anti-seepage curtains is also arranged on one side of the main anti-seepage curtain, and the axes of the auxiliary anti-seepage curtains extend toward the upstream and downstream directions of the axis of the water retaining rock sill respectively.

9. A method for dismantling a cofferdam water retaining structure, It is characterized in that The cofferdam water retaining structure according to any one of claims 1 to 8 is demolished, and the water retaining rock sill and sub-weir are demolished in layers and blocks in a top-down and inside-out order by blasting.

10. A method for dismantling a cofferdam water retaining structure according to claim 9, It is characterized in that The water retaining rock sill and sub-weir are demolished as a whole from top to bottom in three stages. The first stage is the concrete surrounding rock blasting zone I, the second stage is the rock sill blasting zone II, the rock sill blasting zone II is divided into multiple layers, and each layer of the rock sill blasting zone II is divided into at least two blasting blocks; the third stage is the rock sill blasting zone III, the rock sill blasting zone III is divided into at least two blasting blocks.

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