Cofferdam structure suitable for seasonal river in mountainous area

Abstract

The cofferdam structure suitable for the seasonal river in the mountainous area comprises a grouting platform and a closure embankment which are arranged on the upstream side and the downstream side respectively, and a cofferdam body structure is formed between the grouting platform and the closure embankment by backfilling rock ballast mixtures. The cofferdam main body structure covers the top of the closure embankment; the grouting platform comprises a backfill layer, a water-resisting layer and a protective layer; an anti-seepage body is arranged in the grouting platform, and the bottom of the anti-seepage body is embedded into the bed rock; a geotechnical cloth layer, a transition material layer and a steel bar gabion are sequentially arranged at the top of the cofferdam main body structure from bottom to top, and the steel bar gabion extends towards the two sides to the top of the grouting platform and the downstream side of the closure embankment correspondingly; a drainage pipeline is arranged on the reinforced gabion at the top of the cofferdam body structure, and the two ends of the drainage pipeline extend below the water level of the upstream side and the downstream side of the cofferdam body structure respectively. The stability of the cofferdam structure is improved, and the construction cost is reduced.

Description

Technical Field

[0001] This utility model relates to the field of cofferdam engineering technology. More specifically, this utility model relates to a cofferdam structure suitable for seasonal rivers in mountainous areas. Background Technology

[0002] In water conservancy and hydropower projects, cofferdams are often used to block water and tunnels to allow flow, so as to create a dry working environment for the construction of the dam foundation pit. The quality of the cofferdam seepage prevention body and the safety of its own structure are crucial to the subsequent construction.

[0003] Cofferdams, used as water-retaining and waterproofing structures, have traditionally been constructed using concrete cutoff walls, clay core walls, or high-pressure jet grouting piles. High-pressure jet grouting piles use high-pressure rotating nozzles to inject cement slurry into the soil layer, mixing it to form a continuously overlapping cement-reinforced body. This method is suitable for sandy strata but not for gravel layers. Concrete cutoff walls and clay core walls require excavation of foundation trenches. In deep gravel strata, underwater excavation involves large volumes of excavation, and drilling or trenching with washing machines carries the risk of borehole collapse, resulting in high construction difficulty and cost. Furthermore, the cutoff body is typically embedded in bedrock, with its bottom elevation below the control line. All three methods present significant challenges in addressing bedrock excavation during the construction of the cutoff body.

[0004] During engineering construction, projects are often difficult to complete in a single dry season. Therefore, cofferdams designed for dry seasons need to be used to impound water across multiple dry seasons. When using flood-season-only cofferdams on rivers with significant flood and dry periods, meeting design standards often requires constructing tall cofferdams and large diversion structures, resulting in substantial costs. While using dry-season cofferdams can lower the standards for diversion structures, the repeated water flow during the flood season causes dynamic changes in the head difference before and after the cofferdam. High head differences and reverse drainage within the cofferdam can impact structural stability. Ensuring the cofferdam's stability during flood overflow, high head differences, and dewatering during foundation pit construction is crucial. Utility Model Content

[0005] One object of this invention is to solve at least the problems described above and to provide at least the advantages that will be explained later.

[0006] To achieve these objectives and other advantages according to this utility model, a cofferdam structure suitable for seasonal rivers in mountainous areas is provided, comprising: a grouting platform and a cutoff dike respectively disposed on the upstream and downstream sides, wherein the grouting platform and the cutoff dike are connected by backfilling with a mixture of stone and gravel to form the main cofferdam structure, the main cofferdam structure covering the top of the cutoff dike; the grouting platform includes a backfill layer and a waterproof layer and a protective layer sequentially disposed on the upstream side of the backfill layer; an impermeable body is disposed within the grouting platform, the bottom of the impermeable body being embedded in the bedrock; the top of the main cofferdam structure is provided with a geotextile layer, a transition material layer and a reinforced gabion sequentially disposed from bottom to top, the reinforced gabion extending to the top of the grouting platform and the downstream side of the cutoff dike respectively; a drainage pipe is disposed on the reinforced gabion at the top of the main cofferdam structure, the two ends of the drainage pipe extending below the water level on the upstream and downstream sides of the main cofferdam structure respectively.

[0007] Preferably, the water-facing side of the intercepting dike is provided with a gravel drainage layer.

[0008] Preferably, the backfill layer is fine mudstone aggregate, and the height of the grouting platform exceeds the normal water level by 0.5m.

[0009] Preferably, the waterproof layer is clay and the protective layer is large stones.

[0010] Preferably, the main structure of the cofferdam is backfilled with a mixture of stone chips, and the transition material layer is a sand and gravel transition material.

[0011] Preferably, the grouting platform has three rows of grouting holes arranged sequentially from upstream to downstream corresponding to the location of the seepage barrier, with the bottom of each grouting hole extending at least 2m into the bedrock; the seepage barrier is formed by grouting into the grouting holes.

[0012] This utility model has at least the following beneficial effects:

[0013] This utility model provides a cofferdam structure suitable for seasonal rivers in mountainous areas, applicable to earth-rock cofferdam construction in geological conditions with deep sand and gravel layers. The flow is cut off by a dike, and a grouting platform is set up as a construction platform for the seepage prevention body to ensure water-stopping effect. A waterproof layer is laid on the upstream side to reduce the flow of water in the downstream area, providing less dynamic water conditions for subsequent grouting. A drainage pipe, utilizing the inverted siphon principle, balances the water head difference on both sides of the cofferdam structure during the flood season, reducing electricity consumption and further ensuring the stability of the cofferdam structure. A reinforced gabion is installed on the downstream side of the cofferdam structure to further ensure the overall structural stability.

[0014] Other advantages, objectives and features of this invention will be partly apparent from the following description, and partly understood by those skilled in the art through study and practice of this invention. Attached Figure Description

[0015] Figure 1 This is a side view of the cofferdam structure applicable to seasonal rivers in mountainous areas as described in this utility model;

[0016] Figure 2 This is a schematic diagram illustrating the process of drainage from the upstream side to the downstream side of the cofferdam structure using the drainage pipe described in this utility model.

[0017] Figure 3 This is a schematic diagram illustrating the process of drainage from the downstream side to the upstream side of the cofferdam structure using the drainage pipe described in this utility model. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0019] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified. In the description of this utility model, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0020] like Figure 1As shown, this utility model provides a cofferdam structure suitable for seasonal rivers in mountainous areas, comprising: a grouting platform 6 and a diversion dam 1 respectively set on the upstream and downstream sides, wherein the grouting platform 6 and the diversion dam 1 are connected by backfilling with a mixture of stone and gravel to form the main cofferdam structure 3, and the main cofferdam structure 3 covers the top of the diversion dam 1; the grouting platform 6 includes a backfill layer and a waterproof layer 8 and a protective layer 9 sequentially set on the water-facing side of the backfill layer; an impermeable body is provided inside the grouting platform 6, the bottom of which is embedded in the bedrock; the top of the main cofferdam structure 3 is provided with a geotextile layer, a transition material layer 4 and a reinforced gabion 5 sequentially from bottom to top, the reinforced gabion 5 extending to the top of the grouting platform 3 and the backwater side of the diversion dam 1 respectively; a drainage pipe 10 is provided on the reinforced gabion 5 at the top of the main cofferdam structure 3, and the two ends of the drainage pipe 10 extend below the water level on the upstream and downstream sides of the main cofferdam structure 3 respectively.

[0021] In this technical solution, the intercepting dike 1 is constructed first, followed by the grouting platform 6, to avoid the grouting platform material encroaching on the dike opening and ensure successful diversion. The impermeable layer 8 is laid on the upstream side of the grouting platform 6 to reduce the flow of water in its downstream area, providing less dynamic water conditions for subsequent grouting. The impermeable body within the grouting platform 6 prevents seepage, and its bottom is embedded in the bedrock to increase stability. The drainage pipe 10 utilizes the inverted siphon principle to balance the head difference on both sides of the cofferdam structure, reducing power consumption and further ensuring the stability of the cofferdam structure. The reinforced gabion 5 extends to the downstream side of the intercepting dike 1; that is, the installation of a reinforced gabion slope protection behind the dam further ensures the stability of the cofferdam structure.

[0022] The specific construction process of the cofferdam structure suitable for seasonal rivers in mountainous areas is as follows:

[0023] Step 1: First, the intercepting dike 1 is pre-occupied on the upstream side to complete the riverbed interception. A gravel drainage layer 2 is provided on the upstream side of the intercepting dike 1.

[0024] Step Two: Clean the loose surface layer of the original riverbed in the seepage prevention area, such as... Figure 1 The gravel cover layer shown in the figure; the backfill layer is filled, which is fine mudstone aggregate and can be selected locally; the height of the grouting platform 6 is filled to exceed the normal water level by 0.5m, and the grouting platform 6 is compacted by a rammer to ensure the compaction of the backfill material below the normal water level and the junction of the backfill material and the riverbed, reduce the porosity, and ensure the subsequent grouting effect.

[0025] Step 3: Lay the waterproof layer 8 on the water-facing side of the grouting platform 6. The waterproof layer 8 is made of clay to reduce the flow of water in the downstream area, so as to ensure that the subsequent grouting is carried out under conditions of less water flow. Then lay the protective layer 9 to protect the waterproof layer 8. The protective layer 9 is made of large stones with a particle size of 0.5-1.0m.

[0026] Step 4: Layered filling and compaction of the grouting platform 6 to the design elevation, and testing the compacted soil to ensure that the unit weight and porosity meet the design requirements; at the same time, backfill part of the main structure 3 of the cofferdam.

[0027] Step 5: Construct the controlled grouting seepage barrier. Three rows of grouting holes are sequentially opened on the grouting platform 6 from upstream to downstream, corresponding to the location of the seepage barrier. The bottom of each grouting hole extends at least 2 meters into the bedrock. The seepage barrier is formed by grouting into these holes. Grouting is carried out in the following order: first the upstream row, then the downstream row, and finally the middle row, to improve the quality of the cofferdam seepage barrier. For areas where grouting does not create pressure, a combination of crushed stone / sand grouting, low-pressure grouting, and paste-like grout is used to gradually seal the pore channels. Inspection holes are increased to check the seepage barrier's effectiveness and ensure its quality, thus completing the construction of the controlled grouting seepage barrier. During the grouting process, a graded sedimentation tank is set up downstream of the grouting platform 6 to ensure that the water does not cause environmental pollution.

[0028] Step Six: Layered backfilling, compaction, and heightening of the main cofferdam structure 3. The main cofferdam structure 3 is backfilled with a mixture of stone and rubble, and the transition layer is a sand and gravel transition material. After the main cofferdam structure 3 is backfilled to the design height, the geotextile layer is laid, and the reinforced gabion slope protection on the backwater side of the main cofferdam structure 3 is constructed simultaneously to ensure the structural stability of the cofferdam during flood season, high water head difference, and pumping during the foundation pit construction period.

[0029] Step 7: Install the drainage pipe 10.

[0030] During the flood season, such as Figure 2 and Figure 3 As shown, in order to adjust the head difference between the water-facing and back-facing sides of the cofferdam structure in a timely manner, the drainage pipe 10 and the pumping equipment are used to balance the head difference on both sides by utilizing the inverted siphon principle, thereby reducing the power consumption.

[0031] During the construction of the foundation pit, the pumping rate is controlled to ensure that the reverse drainage of the cofferdam structure is balanced with the pumping speed of the foundation pit, thereby ensuring structural stability.

[0032] Although the embodiments of this utility model have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for this utility model. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, this utility model is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A cofferdam structure suitable for seasonal rivers in mountainous areas, characterized in that, include: The cofferdam includes a grouting platform and a diversion dam, respectively located on the upstream and downstream sides. The grouting platform and the diversion dam are connected by backfilling with a mixture of stone and gravel to form the main structure of the cofferdam, which covers the top of the diversion dam. The grouting platform includes a backfill layer and a waterproof layer and a protective layer sequentially arranged on the upstream side of the backfill layer. An impermeable body is installed within the grouting platform, with its bottom embedded in the bedrock. The top of the main cofferdam structure consists of a geotextile layer, a transition material layer, and a reinforced gabion, arranged sequentially from bottom to top. The reinforced gabion extends to the top of the grouting platform and the downstream side of the diversion dam, respectively. A drainage pipe is installed on the reinforced gabion at the top of the main cofferdam structure, with both ends extending below the water level on the upstream and downstream sides of the main cofferdam structure.

2. The cofferdam structure suitable for seasonal rivers in mountainous areas as described in claim 1, characterized in that, The intercepting dike has a gravel drainage layer on its water-facing side.

3. The cofferdam structure suitable for seasonal rivers in mountainous areas as described in claim 1, characterized in that, The backfill layer is composed of fine mudstone aggregate, and the height of the grouting platform exceeds the normal water level by 0.5m.

4. The cofferdam structure suitable for seasonal rivers in mountainous areas as described in claim 1, characterized in that, The waterproof layer is clay, and the protective layer is large stones.

5. The cofferdam structure suitable for seasonal rivers in mountainous areas as described in claim 1, characterized in that, The main structure of the cofferdam is backfilled with a mixture of stone and slag, and the transition material layer is a sand and gravel transition material.

6. The cofferdam structure suitable for seasonal rivers in mountainous areas as described in claim 1, characterized in that, The grouting platform has three rows of grouting holes arranged sequentially from upstream to downstream, corresponding to the location of the seepage barrier. The bottom of each grouting hole extends at least 2m into the bedrock. The seepage barrier is formed by grouting into the grouting holes.

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