Steel pipe pile earth rock cofferdam structure of sandy gravel layer and construction method of steel pipe pile earth rock cofferdam structure

Abstract

The invention relates to the field of sandy gravel layer cofferdam design, and particularly discloses a sandy gravel layer steel pipe pile earth rock cofferdam structure and a construction method thereof. The earth rock cofferdam is arranged on the bank side near the river, and a gap is formed in the right upper part of one side near the river; the boulder presser foot is arranged on one side, close to a river, of the earth rock cofferdam; the concrete retaining wall is arranged at the vacancy of the earth rock cofferdam, and the bottom of the concrete retaining wall is connected to the upper part of the boulder presser foot; the steel pipe penetrates through the concrete retaining wall and the earth rock cofferdam and then extends downwards. The anti-seepage structure is arranged between the concrete retaining wall and the earth rock cofferdam. The form that the steel pipe piles are combined with the concrete retaining wall is adopted on the river side, the slope ratio of the river side is reduced, the requirements of environmental water conservation approval are met, the construction safety in the flood season is guaranteed, the investment of an anti-seepage system is effectively reduced through the anti-seepage structure, the foundation pit water seepage project amount is reduced, and the concrete construction quality is guaranteed.

Description

Technical Field

[0001] The invention relates to the field of sand and gravel layer cofferdam design, and in particular to a sand and gravel layer steel pipe pile earth and rock cofferdam structure and a construction method thereof. Background Art

[0002] In water conservancy and hydropower projects, the existing cofferdam types include earth-rock cofferdam, concrete cofferdam and other types of cofferdam. Other types of cofferdams mainly include mortar-made stone, wooden cage, bamboo cage, grass-soil cofferdam and other types, which are suitable for projects with abundant local material sources.

[0003] Water and environmental conservation refers to the comprehensive science and technology of preventing and controlling soil erosion, protecting, improving and rationally utilizing water and soil resources in mountainous areas, hilly areas and sandy areas, maintaining and improving land productivity, so as to give full play to the economic and social benefits of water and soil resources and establish a good ecological environment. The sand and gravel foundation cofferdam is the most common cofferdam on the river side, but due to comprehensive problems such as water and environmental conservation and river channel encroachment, the design and construction of the cofferdam on this basis is more difficult. For a gravel riverbed like the one in a hydropower station site, the scheme recommended by the riverbed cofferdam specification is the earth-rock cofferdam scheme. The earth-rock cofferdam can make full use of local soil and engineering excavation materials, has strong adaptability to the foundation, simple construction technology, easy to dismantle, and convenient for flood prevention and rescue, so it should be used first. However, the earth-rock cofferdam is greatly restricted by the terrain. The slope of the waterside and back slope of the conventional cofferdam is generally greater than 1:1.5. If the cofferdam is higher, the earth-rock cofferdam is more likely to encroach on the river channel, which is not conducive to environmental and water conservation assessment and demonstration, and its approval risk is extremely high. Summary of the invention

[0004] The purpose of the present invention is to provide a sand and gravel layer steel pipe pile earth and rock cofferdam structure and a construction method thereof, so as to solve the problem that when the basic river channel is restricted, the earth and rock cofferdam alone occupies a large river channel and does not meet the environmental and water conservation approval requirements.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a sand and gravel layer steel pipe pile earth and rock cofferdam structure, including an anti-seepage structure, an earth and rock cofferdam, steel pipe piles, a large stone pressure foot and a concrete retaining wall; The earth-rock cofferdam is set on the bank facing the river, with a gap in the upper right part of the side close to the river; Large stone pressure feet are set on the side of the earth-rock cofferdam close to the river; A concrete retaining wall is set in the gap of the earth-rock cofferdam, and the bottom is connected to the upper part of the large stone pressure foot; Steel pipe piles are set vertically and extend downward after passing through the concrete retaining wall and earth-rock cofferdam; The anti-seepage structure is set between the concrete retaining wall and the earth-rock cofferdam.

[0006] As a further technical solution of the above-mentioned solution, the anti-seepage structure includes an anti-seepage wall, a rice stone sand pile and a composite geomembrane; the rice stone sand pile is arranged on the left side of the concrete retaining wall, and the composite geomembrane covers the left part of the rice stone sand pile; the anti-seepage wall is arranged vertically, with the upper end connected to the left part of the rice stone sand pile and the lower end extending downward.

[0007] The present invention also provides a construction method for a sand-pebble layer steel pipe pile earth-rock cofferdam structure, comprising the following steps: Step S1, after dumping and filling, the underwater weir body is layered and rolled to form an earth-rock cofferdam, and large stone pressure feet are laid on the river side with a slope ratio of 1:1.75; Step S2, setting a base of a concrete retaining wall on the upper part of the large stone pressure foot, and the slope ratio of the river-facing side of the base is 1:0.3; Step S3, constructing steel pipe piles, passing through the base of the concrete retaining wall, extending downward, and setting reinforcing ribs in the steel pipe piles; Step S4, setting an anti-seepage structure between the earth-rock cofferdam and the concrete retaining wall.

[0008] As a further technical solution of the above scheme, in step S4, including an anti-seepage wall, a stone sand pile and a composite geomembrane, the anti-seepage wall is first set up, and consolidation grouting is performed at the lower part of the concrete retaining wall and the right side of the anti-seepage wall to form a bottom support; reinforced gabions are used for protection above the base of the concrete retaining wall, retaining wall protection is used in the middle, and a composite geomembrane is laid on the concrete retaining wall.

[0009] Compared with the prior art, the present invention has the following advantages and beneficial effects: the present invention reduces the riverside slope ratio by adopting steel pipe piles combined with concrete retaining walls on the riverside, meets the environmental and water conservation approval requirements, and ensures construction safety during the flood season. The use of an anti-seepage structure effectively reduces the investment in the anti-seepage system, reduces the amount of foundation pit seepage work, and ensures the quality of concrete construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a side structural schematic diagram of the present invention.

[0011] Figure 2 This is a schematic diagram of the bottom construction of the earth-rock cofferdam.

[0012] Figure 3 Schematic diagram of the structure of the consolidation grouting area.

[0013] Figure 4 Schematic diagram of steel pipe pile construction.

[0014] Figure 5 This is the process flow chart of anti-seepage wall construction.

[0015] The meanings of the numbers in the figure are: earth-rock cofferdam-1; steel pipe pile-2; large stone pressure foot-3; concrete retaining wall-4; anti-seepage wall-51; rice stone sand pile-52; composite geomembrane-53. DETAILED DESCRIPTION

[0016] The technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention, so as to have a further understanding of the concept of the present invention, the technical problems solved, the technical features constituting the technical scheme and the technical effects brought about.

[0017] like Figure 1~Figure 5 As shown, a sand and gravel layer steel pipe pile earth and rock cofferdam structure and its construction method are specifically implemented as follows: Step S1, construction platform filling and protection construction; The filling elevation of the cofferdam construction platform is EL.2571.0m, the filling height is about 5m, and the filling width is not less than 12m. The filling of the underwater part of the construction platform should be carried out by 25t dump truck end throwing, bulldozer leveling, and the weir surface should be controlled to be about 1.0m above the water surface, and 25t vibrating roller compaction should be used. After completing the underwater weir filling, the water weir filling is carried out. Due to site restrictions, the water filling is rolled by overlapping method, and the rolling layer thickness is 50cm. It must be implemented in accordance with the provisions of DL / T5129-2013 (Construction Specifications for Rolled Earth-Rock Dams), and the following requirements should be met: ① The dry capacity of the underwater weir after dumping and compaction shall not be less than 1.65t / m3.

[0018] ② After the water is dumped out of the weir body, it should be compacted layer by layer. The compaction parameters and control standards must meet the parameters and control standards of the corresponding dam body compaction.

[0019] ③ The direction of the vibratory roller should be parallel to the axis of the cofferdam. It can run along the slope where the roller cannot reach the side slope, but the number of rolling times should be appropriately increased.

[0020] The construction method of the water part of the construction platform is 25t dump truck + bulldozer + PC360 backhoe + 25t vibratory roller. The filling materials need to be screened from the waste slag yard and can only be used after meeting the requirements of the specifications. For details of the specific construction process, please refer to Figure 2 .

[0021] After the construction platform is completed, in order to ensure the safety of the riverside construction, it is necessary to add enclosure measures on the outer edge of the platform before the construction of the anti-seepage wall; because the plant phase I is in the excavation stage, there is a large amount of rock blasting. In order to reduce the impact of blasting on the cofferdam construction, 2 rows of reinforced gabions are added inside to prevent flying stones from damaging the cofferdam machinery and equipment. For details of the specific structure, see Figure 3 .

[0022] Step S2, cofferdam foundation consolidation grouting construction; After the cofferdam construction platform is filled, in order to prevent the cofferdam foundation from being washed away, the outer foundation is constructed with large stones for footing + slope protection. For specific measures, please refer to the river dredging plan. The outer filling material above EL.2567m is consolidated and grouting is carried out. The consolidation grouting pressure of the I sequence hole is controlled below 0.3Mpa, the grouting pressure of the II sequence hole is controlled below 0.5Mpa, and the hole spacing is controlled at 2m×2m. For specific construction technology, please refer to Figure 3 .

[0023] Step S3, steel pipe pile construction; Steel pipe piles are made of hot-rolled seamless steel pipes made of P110 with an outer diameter of 299mm and a wall thickness of 14mm. The steel pipe piles are constructed 2m away from the outer filling edge line. In principle, the depth of the steel pipe piles should not be less than 15m, but at least 2m deep into the third layer of gravel. C30 concrete is used for pouring inside the steel pipe piles. When constructing the EL.2571m platform, a temporary bracket with 18mm threaded steel bars welded on the top is required to fix a 12m anchor bar bundle (specification: 3 36mm steel bars), and the exposed length of the anchor bar bundle is 3m. HM-90A drilling rig is used for drilling holes in steel pipe pile construction. In order to ensure that the drilling rig can smoothly pass through the lower boulder, a concentric drilling process is adopted. For specific construction methods, see Figure 4 .

[0024] Step S4, construction of anti-seepage wall; The main construction procedures of the anti-seepage wall include site leveling, guide trough pouring, mud preparation, trench excavation, hole cleaning and slurry replacement, and concrete pouring under mud. The construction process is conventional and will not be explained in detail. For the specific process flow, see Figure 5 .

[0025] Step S5, concrete retaining wall construction; The top elevation of the seepage wall adopts a protection scheme of concrete retaining wall + reinforced gabion, the upstream and downstream are protected by reinforced gabion, and the middle is protected by retaining wall. The concrete retaining wall is cast with C30 concrete, and the PC360 backhoe is used for warehousing. The P3015+P1015 steel formwork is used for erection, and the layer height is not more than 2m. For details of the retaining wall structure, please see the attached Figure 1 .

[0026] Step S6, laying of geomembrane; The composite geomembrane is made of 350g / 0.8mmHDPE / 350g, and fine sand with small particle size is laid as a protective layer. The thickness of the protective layer is not less than 1m. A layer of rice stone is filled outside the fine sand layer with a thickness of not less than 50cm. At the connection between the geomembrane, rock mass and concrete anti-seepage wall, C25 backfill concrete and cap concrete are used to complete the connection between the geomembrane and the lower part. The geomembrane is laid from the anti-seepage construction platform to 50cm below the top of the weir. When laying the membrane, pay attention to moderate tension and relaxation to avoid stress concentration and man-made damage. When laying, the joint surface of the geomembrane and the foundation cushion must be matched and flat, and there must be no protruding wrinkles in the upstream and downstream directions. The parameters are shown in the table below: Composite geomembrane parameter table .

[0027] The present invention adopts the type of steel pipe piles + concrete retaining wall on the river side, which effectively reduces the slope ratio of the river side, ensures that the outside of the cofferdam is basically perpendicular to the river channel, effectively ensures the flow section of the river channel, and ensures the construction safety during the flood season. Compared with the traditional construction method, this type of cofferdam can realize the conditions for the parallel construction of the anti-seepage wall and the concrete retaining wall, which can effectively reduce the construction time of the cofferdam and ensure the construction safety of the factory foundation pit excavation. The cofferdam adopts an anti-seepage system of suspended concrete anti-seepage wall + concrete retaining wall + composite geomembrane, which can effectively reduce the investment in the anti-seepage system, reduce the amount of foundation pit seepage engineering, and ensure that the quality of concrete construction meets the specification requirements. This type of cofferdam can be applied to soft foundations not limited to sand and gravel foundations, and can be extended to other similar foundations. It has a wide range of uses and can provide corresponding construction experience for other projects.

[0028] The terms “connection” and “fixation” mentioned in the description of the present invention may refer to fixed connection, processing and forming, welding or mechanical connection. The specific meanings of the above terms in the present invention shall be understood according to the specific circumstances.

[0029] In the description of the present invention, the terms "center", "upper", "lower", "horizontal", "inside", "outside", etc., which indicate the orientation or position relationship, are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying a specific orientation that the device or element referred to must have, and therefore cannot be understood as a limitation on the present invention.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sand and gravel layer steel pipe pile earth and rock cofferdam structure, characterized by: It comprises an anti-seepage structure, an earth-rock cofferdam (1), steel pipe piles (2), a large stone pressure foot (3) and a concrete retaining wall (4); The earth-rock cofferdam (1) is arranged on the bank facing the river, and a gap is provided at the upper right part of the side close to the river; A large stone pressure foot (3) is arranged on a side of the earth-rock cofferdam (1) close to the river; A concrete retaining wall (4) is arranged in the gap of the earth-rock cofferdam (1), and the bottom is connected to the upper part of the large stone pressure foot (3); The steel pipe pile (2) is vertically arranged, passes through the concrete retaining wall (4) and the earth-rock cofferdam (1) and then extends downward; The anti-seepage structure is arranged between the concrete retaining wall (4) and the earth-rock cofferdam (1).

2. A sand and gravel layer steel pipe pile earth and rock cofferdam structure as claimed in claim 1, characterized in that: The anti-seepage structure comprises an anti-seepage wall (51), a stone-sand pile (52) and a composite geomembrane (53); the stone-sand pile (52) is arranged on the left side of the concrete retaining wall (4), and the composite geomembrane (53) covers the left part of the stone-sand pile (52); the anti-seepage wall (51) is arranged vertically, with the upper end connected to the left part of the stone-sand pile (52) and the lower end extending downward.

3. A construction method for the sand and gravel layer steel pipe pile earth and rock cofferdam structure as claimed in claim 1, characterized in that: The following steps are involved: Step S1, after the underwater weir body is dumped and filled, it is layered and rolled to form an earth-rock cofferdam (1), and a large stone pressure foot (3) is laid on the river side, with a slope ratio of 1:1.75; Step S2, setting a base of a concrete retaining wall (4) on the upper part of the large stone pressure foot (3), wherein the slope ratio of the inclined side of the base facing the river is 1:0.3; Step S3, constructing the steel pipe pile (2), passing through the base of the concrete retaining wall (4), extending downward, and providing reinforcing ribs inside the steel pipe pile (2); Step S4, providing an anti-seepage structure between the earth-rock cofferdam (1) and the concrete retaining wall.

4. The construction method of the sand and gravel layer steel pipe pile earth and rock cofferdam structure as claimed in claim 3, characterized in that: In step S4, an anti-seepage wall (51), a stone-sand pile (52) and a composite geomembrane (53) are provided. First, the anti-seepage wall (51) is provided, and consolidation grouting is performed at the lower part of the concrete retaining wall (4) and the right side of the anti-seepage wall (51) to form a bottom support. A reinforced gabion is used for protection above the base of the concrete retaining wall (4), a retaining wall is used for protection in the middle, and the stone-sand pile (52) and the composite geomembrane (53) are laid on the concrete retaining wall (4).

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