A construction method for an anti-seepage cofferdam structure combined with interception and drainage

Abstract

The invention relates to a construction method for an anti-seepage cofferdam structure combined with interception and drainage, which comprises the following steps: forming a lower filling component at the bottom of a reservoir, paving a lower water-facing surface slope protection on the water-facing slope of the lower filling component; inserting and constructing a tensile steel sheet pile on the top surface of the lower filling component, arranging a water-blocking curtain in the lower filling component by curtain grouting; pouring a sealing layer on the top surface of the lower filling component at the position of the tensile steel sheet pile and the water-blocking curtain; filling an upper filling component on the lower filling component, arranging a water-passing box culvert during the filling of the upper filling component, and pouring an anti-scouring wall and a drop chute at the outlet of the water-passing box culvert; installing a working well connected to the outlet of the interception and drainage ditch on the reservoir bank at the inlet of the water-passing box culvert; completing the filling of the upper filling component; paving an upper water-facing surface slope protection on the water-facing slope of the upper filling component, pouring a sealing layer on the top surface of the upper filling component, and paving a water-retaining surface slope protection on the water-retaining slope of the cofferdam.

Description

Technical Field

[0001] The present invention relates to a construction method for an anti-seepage cofferdam structure combined with interception and drainage, and is applicable to the technical field of cofferdam construction. Background Art

[0002] Currently, the application of cofferdam technology in water conservancy project construction mostly occurs within reservoirs or rivers, with low-lying terrain and concentrated construction areas. During the construction period, drainage interception requirements are high, and the cofferdam must meet the requirements of water retention and anti-seepage during the construction period. On the one hand, the layout of intercepting drainage ditches is important. During site layout, intercepting drainage ditches are often arranged on high terrain on mountain ridges. Unless special circumstances occur, water flows by gravity to the reservoir outside the weir. For large-scale water collection, forced drainage measures are used, and water must bypass the cofferdam. If the cofferdam is located at a higher elevation than the inner and outer contours of the site, it is difficult to achieve self-drainage requirements. This not only makes construction difficult and expensive, but also increases the land area and the number of seedlings to be relocated. On the other hand, the choice of cofferdam type is also important. Cofferdam construction generally adopts two forms, double-row Larsen steel sheet piles and earth-rock cofferdams, which are more widely used. The former is filled with clay as a seepage-proof and water-stopping measure. Construction requires the establishment of an overwater construction platform, which is difficult to construct and has a long construction period. It cannot be implemented under geological conditions such as rounded gravel and shallow bedrock. The latter uses local materials and makes full use of excavated waste as cofferdam filling. It has the advantages of simple structure, convenient construction, easy dismantling and low project cost. However, the filling materials of its main earth-rock cofferdam basically have the problem of large permeability coefficient. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: In order to solve the above technical problem, the present invention provides a construction method of an anti-seepage cofferdam structure combined with intercepting and draining water.

[0004] The technical solution adopted by the present invention is: a construction method of an anti-seepage cofferdam structure combined with interception and drainage, characterized in that:

[0005] When the water level of the reservoir drops to a low level, the bottom of the reservoir is dredged and the bottom of the reservoir is excavated into a step shape;

[0006] Fill the bottom of the reservoir to form a lower filling component, and lay a lower layer of water-facing slope protection on the water-facing slope of the lower filling component;

[0007] On the top surface of the lower filling structure, tensile steel sheet piles extending into the reservoir bottom are driven along the length of the cofferdam body. A water-blocking curtain is arranged in the lower filling structure on the back side of the tensile steel sheet piles through curtain grouting.

[0008] Cast a sealing layer on the top surface of the lower filling member at the location of the tensile steel sheet piles and the water-blocking curtain;

[0009] The upper filling component is filled on the top surface of the lower filling component. When the upper filling component is filled to the position of the water box culvert, the water box culvert is arranged on the upper filling component, and the anti-scouring wall and the drop chute are cast below the water box culvert on the water-facing slope of the upper filling component;

[0010] A vertically arranged working well is installed on the water box culvert on the back slope of the upper filling component, and the inlet of the working well is connected to the outlet of the intercepting drainage ditch on the reservoir bank;

[0011] Complete the filling of the upper filling components;

[0012] The upper water-facing slope protection is paved on the water-facing slope of the upper filling component, the sealing layer is poured on the top surface of the upper filling component, and the back-facing slope protection is paved on the back-facing slopes of the upper filling component and the lower filling component.

[0013] The water box culvert is provided with a concave notch at the non-fill interface, and a clay sealing layer is provided at the concave notch of the water box culvert for fully fitting the water box culvert with the upper filling component.

[0014] A filter body is arranged in the working well, and supporting screen plates are fixedly installed in the working wells on the upper and lower sides of the filter body.

[0015] The filter body comprises a coarse aggregate layer arranged in a working well, fine aggregate layers are arranged in the working wells on the upper and lower sides of the coarse aggregate layer, and a supporting screen plate is arranged between the coarse aggregate layer and the fine aggregate layer.

[0016] The lower filling member includes a first filling member arranged on the waterfront side and a second filling member arranged on the waterback side.

[0017] The first filling component is composed of soil and stone, the second filling component is composed of fine stone slag, and the upper filling component is composed of stone slag.

[0018] An anti-skid sill is provided on the water-facing slope of the upper filling component above the outlet of the water culvert to prevent water from seeping into the upper filling component through the gap between the water culvert and the upper filling component.

[0019] The lower water-facing slope protection is a large stone slope protection, the upper water-facing slope protection has an upper water-facing surface protection, a transition layer, a cushion layer and a composite geomembrane sequentially paved on the slope surface of the upper filling component, and the back water slope protection is a waterproof layer composed of a mixture of clay and silt solidifier.

[0020] The working well is connected to a position on the intercepting and draining ditch at a certain distance from the end of the intercepting and draining ditch, and the water culvert is connected to a position on the working well at a certain distance from the bottom of the working well.

[0021] The elevation H2 of the top of the lower filling component is higher than the low water level line H1 of the reservoir, the elevation of the bottom of the water culvert is higher than the normal water level line H3 of the reservoir, the elevation H5 of the top of the cofferdam body is higher than the high water level line H4 of the reservoir, and the elevation of the top of the working well is higher than the elevation H5 of the top of the cofferdam body.

[0022] The beneficial effects of the present invention are as follows: the present invention arranges the water-passing box culvert inside the cofferdam during the cofferdam filling process, and connects the water-passing box culvert with the intercepting drainage ditch on the reservoir bank through a working well, so that the accumulated water on the reservoir bank can be quickly discharged into the reservoir through the working well and the water-passing box culvert. At the same time, the arrangement of the water-passing box culvert only needs to be arranged on the cofferdam during the cofferdam filling process. The construction difficulty of the cofferdam is low, the construction period is short, and the construction cost is low. It can also avoid the subsequent arrangement of forced drainage equipment in the cofferdam to drain the cofferdam. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a side sectional view of the present invention;

[0024] Figure 2 It is a front structural schematic diagram of the present invention;

[0025] Figure 3 is a top view of the present invention;

[0026] In the figure: 1. Cofferdam body; 1-1. First filling component; 1-2. Second filling component; 1-3. Upper filling component; 1-4. Upper water-facing surface protection; 1-5. Composite geomembrane; 1-6. Cushion layer; 1-7. Transition layer; 1-8. Sealing layer; 1-9. Water-blocking curtain; 1-10. Tensile steel sheet piles; 1-11. Lower water-facing surface slope protection; 1-12. Backwater surface slope protection; 2. Intercepting ditch; 3. Working pit: 3-1. Supporting screen plate; 3-2. Fine aggregate layer; 3-3. Coarse aggregate layer; 4. Water culvert; 4-1. Anti-slip sill; 4-2. Clay seal layer; 5. Scour wall; 6. Drop chute. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and through examples. The following examples are intended to explain the present invention but the present invention is not limited to the following examples.

[0028] This embodiment describes a construction method for an anti-seepage cofferdam structure combined with an intercepting and draining system. This method is used to construct a cofferdam body 1 within a reservoir, effectively draining water from the reservoir bank. The cofferdam body 1 is located within the reservoir, with an intercepting and draining ditch 2 arranged on the reservoir bank. The outlet of the intercepting and draining ditch 2 is located at a higher elevation than the elevation H5 of the top of the cofferdam body 1. A vertically arranged working well 3 is connected to the outlet of the intercepting and draining pipe. A water culvert 4 is connected to the outlet of the working well 3, which extends through the cofferdam body 1. Runoff from the reservoir bank is discharged into the reservoir through the intercepting and draining ditch 2, the working well 3, and the water culvert 4, preventing runoff from the reservoir bank from flowing into the cofferdam area and affecting drainage within the cofferdam.

[0029] In this embodiment, the cross section of the intercepting and draining ditch 2 is trapezoidal, and has good water storage capacity and pressure bearing capacity.

[0030] In this embodiment, the working well 3 is a square reinforced concrete structure. The working well 3 is connected to the intercepting drainage ditch 2 at a certain distance from the end of the intercepting drainage ditch 2. In this way, a buffer zone is formed at the end of the intercepting drainage ditch 2, which has a force-dissipating effect on the water flow in the intercepting drainage ditch 2. A filter body is set in the working well 3, and a supporting screen plate 3-1 is set in the working well 3 above and below the filter body. The filter body has a fine aggregate layer 3-2, a coarse aggregate layer 3-3, and a fine aggregate layer 3-2 arranged in sequence from top to bottom. The supporting screen plate 3-1 is set between the fine aggregate layer 3-2 and the coarse aggregate layer 3-3. In this way, the water flow entering the water box culvert 4 in the cofferdam body 1 from the intercepting drainage ditch 2 is filtered, preventing impurities from clogging the water box culvert 4 in the cofferdam body 1 and making it inconvenient to repair. The supporting screen plate 3-1 provides good support for the filter body.

[0031] In this embodiment, a water culvert 4 is connected to the outlet of the working well 3 , and the bottom of the working well 3 is lower than the connection between the working well 3 and the water culvert 4 , which also plays a certain force dissipation role.

[0032] In this embodiment, a water culvert 4 is installed within and through the cofferdam 1. Its outlet extends outward from the slope of the cofferdam 1, facing the reservoir. This allows runoff from the reservoir bank to be discharged into the reservoir via the intercepting drainage ditch 2, the working well 3, and the water culvert 4. This prevents runoff from flowing into the cofferdam and affecting drainage within the cofferdam.

[0033] In this embodiment, the water culvert 4 adopts a square reinforced concrete structure. An inward-concave notch is provided at the non-filled interface of the water culvert 4 to prevent damage to the water culvert 4 under pressure. At the same time, clay is filled in the inward-concave notch of the water culvert 4 to form a clay seal layer. The clay seal layer 4-2 is used to bond the water culvert 4 and the cofferdam body 1, so that the water culvert 4 and the cofferdam body 1 are fully fitted together, thereby enhancing the anti-seepage ability of the cofferdam body 1.

[0034] In this embodiment, an anti-skid sill 4-1 is provided on the water-facing slope of the cofferdam body 1 above the outlet of the water culvert 4. The anti-skid sill 4-1 is used to prevent water from seeping into the cofferdam body 1 through the gap between the water culvert 4 and the cofferdam body 1.

[0035] In this embodiment, a scouring wall 5 and a drop chute 6 are provided on the water-facing slope of the cofferdam body 1 below the outlet of the water culvert 4. The scouring wall 5 and the drop chute 6 are used to dissipate the energy of the water flow discharged from the outlet of the water culvert 4, thereby reducing the scouring of the slope of the cofferdam body 1 by the water flow.

[0036] The cofferdam 1 in this embodiment comprises a lower filling member arranged within the reservoir and an upper filling member 1-3 arranged above the lower filling member. The lower filling member comprises a first filling member 1-1 on the upstream side and a second filling member 1-2 on the downstream side. The first filling member 1-1 is composed of soil and stone, the second filling member 1-2 is composed of fine stone slag, and the upper filling member 1-3 is composed of stone slag.

[0037] In this embodiment, a lower water-facing slope protection 1-11 is provided on the slope of the lower filling member of the cofferdam body 1 facing the reservoir, an upper water-facing slope protection is provided on the slope of the upper filling member 1-3 facing the reservoir, and a backwater slope protection 1-12 is provided on the slope of the cofferdam body 1 away from the reservoir. A sealing layer 1-8 is provided on the top surfaces of both the upper filling member 1-3 and the lower filling member. The upper water-facing slope protection comprises an upper water-facing surface protection 1-4, a transition layer 1-7, a cushion layer 1-6, and a composite geomembrane 1-5, which are sequentially laid on the water-facing slope of the upper filling member 1-3. The lower water-facing slope protection 1-11 comprises a large stone slope protection laid on the water-facing slope of the lower filling member. The backwater slope protection 1-12 is a waterproof layer composed of a mixture of clay and a silt solidifier. Among them, the upper water-facing slope protection is a woven bag-filled soil protection with a thickness of 50cm; the composite geomembrane 1-5 is a 400g / 0.8mm / 400g HDEP geomembrane, and the thickness of the transition layer 1-7, cushion layer 1-6, large stone slope protection and waterproof layer are all 50cm; the waterproof layer is formed by mixing clay and silt curing agent in a certain proportion and brushing the slope and then fully curing; the sealing layer 1-8 is made of plain concrete.

[0038] In this embodiment, all debris and sharp stones on the slope surface should be removed before laying the composite geomembrane 1-5 to ensure that it is laid on a flat surface of sand-free concrete without any protruding or concave parts.

[0039] In this embodiment, tensile steel sheet piles 1-10 are anchored to the top surface of the lower fill member at the toe of the upstream slope of the upper fill member 1-3. These are Type IV tensile steel sheet piles, with their bottoms extending 5 meters into the reservoir bottom cover. An expansion joint is installed at the junction of the tensile steel sheet piles 1-10 and the composite geomembrane 1-5. The overlapped portion of the folded expansion joint must be greater than 0.5 meters to ensure good extensibility.

[0040] In this embodiment, a water-blocking curtain 1-9 is provided in the lower filling member of the tensile steel sheet pile 1-10 away from the reservoir. The water-blocking curtain 1-9 is formed by pouring grout into the cofferdam body 1 through curtain grouting.

[0041] In this embodiment, the elevation H2 of the top of the lower filling member is higher than the reservoir's low water mark H1, the elevation of the bottom of the water culvert 4 is higher than the reservoir's normal water mark H3, the elevation H5 of the top of the cofferdam body 1 is higher than the reservoir's high water mark H4, and the elevation of the top of the working well 3 is higher than the elevation H5 of the top of the cofferdam body 1. Thus, as long as the water in the reservoir does not overflow, the working well 3 not only serves as a buffer and filter, but also forms an interconnecting pipe inside and outside the cofferdam body, reducing bias pressure instability of the cofferdam body. Furthermore, when the water level in the reservoir is too high, the filter inside the working well 3 acts as a high-water backflow filter, protecting the water source from pollution.

[0042] The specific construction method of this embodiment is as follows:

[0043] When the water level in the reservoir drops to the minimum, the bottom of the reservoir is desilted and the bottom of the reservoir is excavated into a step-like shape;

[0044] After completion, the first filling component 1-1, the second filling component 1-2 and the lower water-facing slope protection 1-11 are constructed simultaneously using the advance occupation method. The lower water-facing slope protection 1-11 uses large stone slope protection. The first filling component 1-1 and the second filling component 1-2 are compacted by layered vibration rolling and filled to the top of the lower filling component.

[0045] At the toe of the upper filling member 1-3, tensile steel sheet piles 1-10 are driven in. The tensile steel sheet piles 1-10 extend 5 meters into the reservoir bottom cover layer. Curtain grouting is performed in the lower filling member on the back side of the tensile steel sheet piles 1-10 to form a water-blocking curtain 1-9. Plain concrete is poured on the top surface of the lower filling member above the tensile steel sheet piles 1-10 and the water-blocking curtain 1-9 to form a sealing layer 1-8.

[0046] After the lower fill elements have settled, the upper fill elements 1-3 are placed. When the fill reaches the elevation of the water box culvert 4 below the upper fill elements 1-3, the water box culvert 4 is constructed. An inward-concave notch is provided at the non-fill interface to ensure interlocking with the surrounding fill. Simultaneously with the construction of the water box culvert 4, the anti-scouring wall 5 and the water chute 6 are cast in situ, and the working well 3 is also constructed.

[0047] After the construction of the water box culvert 4 is completed, the remaining upper filling components 1-3 are filled. A clay seal layer 4-2 is set on the outer circle of the concave notch of the water box culvert 4 for clay sealing and protection, which is combined with the soil and stone materials of the dam body. The cushion layer 1-6, transition layer 1-7, composite geomembrane 1-5 and water-facing surface protection are constructed simultaneously with the filling of the upper filling component 1-3. The upper filling component 1-3 is compacted by vibration rolling, and then the top sealing layer 1-8 of the upper filling component 1-3 is constructed;

[0048] The main body of cofferdam 1 is essentially complete. After post-construction settlement is complete, the seepage condition of cofferdam 1 will be inspected. The final anti-seepage measure involves covering the backwater side with slope protection 1-12. This backwater side slope protection 1-12 is a waterproof layer made of a specific mixture of clay and silt solidifier, which provides excellent bonding, stability, and anti-seepage effects.

[0049] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A construction method for an anti-seepage cofferdam structure combined with interception and drainage, characterized by: When the water level of the reservoir drops to a low level, the bottom of the reservoir is dredged and the bottom of the reservoir is excavated into a step shape; Filling the bottom of the reservoir to form a lower filling component, and paving the lower water-facing surface slope protection (1-11) on the water-facing slope of the lower filling component; On the top surface of the lower filling component, a tensile steel sheet pile (1-10) extending into the bottom of the reservoir is driven in along the longitudinal direction of the cofferdam body (1); and a water-blocking curtain (1-9) is arranged in the lower filling component on the back surface of the tensile steel sheet pile (1-10) through curtain grouting construction; Casting a sealing layer (1-8) on the top surface of the lower filling member at the tensioned steel sheet pile (1-10) and the water-blocking curtain (1-9); The upper filling component (1-3) is filled on the top surface of the lower filling component. When the upper filling component (1-3) is filled to the position of the water box culvert (4), the water box culvert (4) is arranged on the upper filling component (1-3), and the anti-scouring wall (5) and the drop chute (6) are cast on the water-facing slope of the upper filling component (1-3) at a position below the water box culvert (4); A vertically arranged working well (3) is installed on the water box culvert (4) on the back slope of the upper filling component (1-3), and the inlet of the working well (3) is connected to the outlet of the intercepting drainage ditch (2) on the reservoir bank; Complete the filling of the upper filling components (1-3); An upper layer of water-facing slope protection is laid on the water-facing slope of the upper filling component (1-3), a sealing layer (1-8) is poured on the top surface of the upper filling component (1-3), and a water-retaining slope protection (1-12) is laid on the water-retaining slopes of the upper filling component (1-3) and the lower filling component.

2. The construction method of a combined anti-seepage cofferdam structure with interception and drainage according to claim 1, characterized in that: The water box culvert (4) is provided with a concave notch at the non-filling interface, and a clay sealing layer (4-2) is provided at the concave notch of the water box culvert (4) for fully fitting the water box culvert (4) with the upper filling component (1-3).

3. The construction method of a combined anti-seepage cofferdam structure with interception and drainage according to claim 1, characterized in that: A filter body is provided in the working well (3), and supporting screen plates (3-1) are fixedly installed in the working well (3) on the upper and lower sides of the filter body.

4. The construction method of a combined anti-seepage cofferdam structure with interception and drainage according to claim 3, characterized in that: The filter body comprises a coarse aggregate layer (3-3) arranged in a working well (3), fine aggregate layers (3-2) are arranged in the working well (3) on the upper and lower sides of the coarse aggregate layer (3-3), and a supporting screen plate (3-1) is arranged between the coarse aggregate layer (3-3) and the fine aggregate layer (3-2).

5. The construction method of a combined anti-seepage cofferdam structure with interception and drainage according to claim 1, characterized in that: The lower filling member comprises a first filling member (1-1) arranged on the waterfront side and a second filling member (1-2) arranged on the waterback side.

6. The construction method of a combined anti-seepage cofferdam structure with interception and drainage according to claim 5, characterized in that: The first filling component (1-1) is composed of soil and stone, the second filling component (1-2) is composed of fine stone slag, and the upper filling component (1-3) is composed of stone slag.

7. The construction method of a combined anti-seepage cofferdam structure with interception and drainage according to claim 1, characterized in that: An anti-slip sill (4-1) for preventing water from seeping into the upper filling component (1-3) through a gap between the water culvert (4) and the upper filling component (1-3) is provided on the water-facing slope of the upper filling component (1-3) at a position above the outlet of the water culvert (4).

8. The construction method of a combined anti-seepage cofferdam structure with interception and drainage according to claim 1, characterized in that: The lower water-facing slope protection (1-11) is a large stone slope protection, the upper water-facing slope protection comprises an upper water-facing surface protection (1-4), a transition layer (1-7), a cushion layer (1-6) and a composite geomembrane (1-5) sequentially paved on the slope surface of the upper filling component (1-3), and the backwater slope protection (1-12) is a waterproof layer composed of a mixture of clay and a silt solidifier.

9. The construction method of a combined anti-seepage cofferdam structure with interception and drainage according to claim 1, characterized in that: The working well (3) is connected to the intercepting drainage ditch (2) at a position a certain distance from the end of the intercepting drainage ditch (2), and the water culvert (4) is connected to the working well (3) at a position a certain distance from the bottom of the working well (3).

10. The construction method of the anti-seepage cofferdam structure combined with interception and drainage according to claim 1, characterized in that: The elevation H2 of the top of the lower filling member is higher than the low water level H1 of the reservoir, the elevation of the bottom of the water culvert (4) is higher than the normal water level H3 of the reservoir, the elevation H5 of the top of the cofferdam body (1) is higher than the high water level H4 of the reservoir, and the elevation of the top of the working well (3) is higher than the elevation H5 of the top of the cofferdam body (1).

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