Prestressed cantilever retaining wall and construction method thereof

Abstract

The present invention relates to a prestressed cantilever retaining wall and a construction method thereof. A plurality of steel casings extending from a concrete vertical plate to a concrete bottom plate are arranged inside the cantilever retaining wall, and a plurality of high-tension steel cables are introduced into the steel casings. The two ends of the high-tension steel cables in a stretched state are respectively locked and fixed to the cantilever retaining wall by a locking component, so that the cantilever retaining wall is in a prestressed state before filling, which can effectively offset part of the tension in the concrete cantilever retaining wall due to the bending of the vertical plate after the retaining wall is filled, thereby improving the overall bending resistance and anti-overturning performance of the retaining wall. The construction method of the prestressed cantilever retaining wall of the present invention can be applied to any area, especially in soft soil areas, to build a cantilever retaining wall with a height greater than 6m, and can reduce the flexural deformation, increased bending, and potential fracture and breakage risks of the concrete vertical plate as the height of the retaining wall increases.

Description

Technical Field

[0001] The invention relates to the fields of civil engineering and geological engineering, and in particular to a prestressed cantilever retaining wall and a construction method thereof which can effectively improve the flexural deformation or bending resistance of a concrete vertical slab. Background Art

[0002] The cantilever retaining wall is mainly composed of a base plate (including a toe plate and a heel plate) and a vertical plate fixed on the base plate. It mainly relies on the weight of the backfill on the base plate to maintain its stability. Cantilever retaining walls are widely used in civil engineering and geological engineering because of their simple structure and light weight, and can adapt to relatively soft foundation soil layers. However, the current specification "Design Specifications for Railway Roadbed Support Structures" and the document "Design and Engineering Examples of New Support Structures" require that the height of a cantilever retaining wall should generally not be greater than 6m. This is because when the height of the vertical plate of the retaining wall exceeds 6m, as the height of the retaining wall increases, after the backfill is completed, the flexural deformation and bending moment of the vertical plate will increase rapidly, resulting in a rapid decrease in the anti-overturning stability of the retaining wall, or due to insufficient bending resistance of the vertical plate, it may cause the reinforced concrete vertical plate to break.

[0003] Therefore, in areas with high foundation bearing capacity, if the height of a cantilever retaining wall needs to exceed 6m, the problem of flexural deformation and excessive bending moment can generally be reduced by increasing the amount of reinforced concrete, adjusting the thickness of the retaining wall slab, or adding buttresses on the outside of the slab (forming a buttress retaining wall). However, this method will cause the amount of reinforced concrete used in the cantilever retaining wall to increase, and its overall weight will increase sharply, and this will put higher requirements on the foundation bearing capacity at the bottom of the retaining wall. However, the foundation bearing capacity of some other soft soil areas is generally not large, and if soft soil foundation treatment is to be carried out, the cost is usually high. Therefore, the above method of increasing the construction height of the cantilever retaining wall is obviously not suitable for soft soil areas. Summary of the invention

[0004] Based on the above-mentioned defects existing in the prior art when constructing a cantilever retaining wall to increase its height, the present invention provides a prestressed cantilever retaining wall and a construction method, which can be applicable to any various areas, especially can greatly improve the construction height of the cantilever retaining wall in soft soil areas, and can also significantly reduce the problems of flexural deformation and excessive bending moment of the vertical plate of the cantilever retaining wall.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a prestressed cantilever retaining wall, comprising a concrete bottom plate and a concrete vertical plate arranged on the concrete bottom plate, wherein a plurality of prestressing components are arranged inside the prestressed cantilever retaining wall, and the prestressing components are composed of a steel casing, a high-tension steel cable and a locking component, wherein:

[0006] The steel casing is hollow inside and has openings at both ends. One end of the steel casing is opened at the top of the concrete slab, and the other end is opened at the side of the concrete bottom slab.

[0007] The high-tension steel cables are provided in plurality, and are respectively inserted into the opening at one end of the steel casing and led out from the opening at the other end of the steel casing;

[0008] The locking components are respectively arranged at the two openings of the steel casing and are used to lock and fix a plurality of high-tensile steel cables in a stretched state to the cantilever retaining wall.

[0009] In the above scheme, the locking component is composed of a steel backing plate and a clamp, and the steel backing plate and the clamp are both made of steel material; wherein: the thickness of the steel backing plate is 6-8 cm, and the thickness of the clamp is 12-15 cm.

[0010] In the above scheme, the steel casing is a galvanized spiral corrugated casing with a wall thickness of 10-14 mm and a diameter of 8-15 cm. The steel casing is arranged inside the cantilever retaining wall at equal longitudinal intervals.

[0011] In the above scheme, the high-tensile strength steel cable is composed of 3-5 high-strength, low-relaxation, non-bonded prestressed steel strands.

[0012] The present invention also provides a construction method of the above-mentioned prestressed cantilever retaining wall, which specifically comprises the following steps:

[0013] S1, on-site construction preparation;

[0014] S2, construction of the main body of the cantilever retaining wall;

[0015] After the site is excavated and leveled, the steel bars of the concrete slab and concrete base are tied according to the design drawings; then multiple steel casings with hollow channels are pre-installed at the center left of the concrete slab and concrete base; finally, the scaffolding is erected and the steel formwork is installed, and the wall concrete is poured;

[0016] S3, prestressing the cantilever retaining wall;

[0017] After the cantilever retaining wall in step S2 reaches more than 75% of the design strength, 3-5 high-tensile steel cables are inserted into the hollow channels reserved in the steel casing, and then the high-tensile steel cables are stretched by an external stretching machine. After being clamped with a steel pad and a clamp, the tension of the stretching machine is relaxed, and the pre-tensioning force of the high-tensile steel cables is transmitted to the concrete by means of the clamp set at the end of the high-tensile steel cables, so that the concrete structure generates axial pre-compression stress; finally, cement slurry is poured into the steel casing through the pores at the top of the clamp to form a whole with the prestressed tendons and the concrete member.

[0018] S4, backfilling of soil after construction of cantilever retaining wall;

[0019] Backfill the filling layer between the concrete slab and the slope soil; complete the entire retaining wall construction by backfilling in layers and compacting it with a small compactor.

[0020] Compared with the prior art, the present invention has the following advantages and effects:

[0021] 1. The present invention arranges a plurality of steel casings extending from the concrete vertical plate to the concrete bottom plate inside the cantilever retaining wall, introduces a plurality of high-tensile steel cables into the steel casings, and then uses locking components to lock and fix the two ends of the high-tensile steel cables in a stretched state to the cantilever retaining wall respectively, thereby making the cantilever retaining wall in a prestressed state before filling, which can effectively offset part of the tension generated in the concrete retaining wall due to the bending of the vertical plate after the retaining wall is filled, thereby improving the overall bending resistance and anti-overturning stability of the retaining wall.

[0022] 2. The prestressed cantilever retaining wall of the present invention has a stronger crack resistance, greater rigidity and higher shear strength than the existing ordinary cantilever retaining wall due to the arrangement of the prestressing components inside the structure, on the basis of the same thickness of the vertical plate and without the need to set the vertical plate buttresses. It is also easy to construct, has clear force transmission, is economical and reliable, and can be applied to geological disaster control and slope support in various areas (especially soft soil areas).

[0023] 3. The construction method of the prestressed cantilever retaining wall of the present invention can be applied to any area, especially in soft soil areas, to build cantilever retaining walls with a height greater than 6m, and can reduce the flexural deformation, increased bending and potential fracture and break risks of the concrete slab as the height of the retaining wall increases.

[0024] 4. Compared with the existing process of increasing the thickness of the concrete slab or setting slab buttresses to improve the bending and overturning resistance of the retaining wall, the construction method of the prestressed cantilever retaining wall of the present invention can greatly save the amount of reinforced concrete (saving 40% to 50% of steel and 20% to 40% of concrete) under the condition of the same height of the cantilever retaining wall, reduce the cross-sectional size of the slab, reduce the overall deadweight of the structure, and effectively prevent cracking and reduce deflection, so that the cantilever retaining wall structure can be designed to be more economical, lightweight and beautiful.

[0025] 5. In the construction method of the cantilever prestressed retaining wall described in the present invention, a steel casing is reserved inside the cantilever retaining wall. After the concrete reaches the designed strength, a high-tensile steel cable is inserted into the steel casing to apply prestress to the expected tensile position. This can overcome the weakness of low tensile strength of the concrete slab and achieve a prestressed cantilever retaining wall structure in which the slab will not crack or overturn after the prestress is used. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0027] Figure 1 It is a schematic diagram of the three-dimensional structure of the prestressed cantilever retaining wall in an embodiment of the present invention.

[0028] Figure 2 for Figure 1 A magnified schematic diagram of the structure at A in the middle.

[0029] Figure 3 Schematic diagram of the cross section of the prestressed cantilever retaining wall after the filling is completed in the embodiment of the present invention.

[0030] Explanation of numbers: 1. Concrete slab; 2. Concrete bottom plate; 21. Toe plate; 22. Heel plate; 3. Steel casing; 4. Steel pad; 5. Clamp; 6. High-tensile steel cable; 7. Slope soil; 8. Filling layer. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with embodiments. The following embodiments are for explanation of the present invention but the present invention is not limited to the following embodiments.

[0032] Example 1: Figures 1 to 3 As shown, a prestressed cantilever retaining wall comprises a concrete bottom plate 2 and a concrete vertical plate 1 arranged on the concrete bottom plate 2. A plurality of prestressing components are arranged inside the prestressed cantilever retaining wall. The prestressing components are composed of a steel casing 3, a high-tension steel cable 6 and a locking component, wherein:

[0033] like Figure 3 As shown, the interior of the steel casing 3 is a hollow structure with openings at both ends. One end of the steel casing 3 is opened at the top of the concrete slab 1, and the other end is opened at the side end of the concrete bottom slab 2.

[0034] The high-tension steel cables 6 are provided in plurality, and are respectively inserted into the opening at one end of the steel casing 3 and led out from the opening at the other end of the steel casing 3;

[0035] The locking components are respectively arranged at the two openings of the steel casing 3, and are used to lock and fix the multiple high-tensile steel cables 6 in a stretched state to the cantilever retaining wall.

[0036] In the prestressed cantilever retaining wall described in Example 1, the concrete bottom plate 2 is composed of a toe plate 21 and a heel plate 22, and the toe plate 21, the heel plate 22 and the concrete slab 1 are cast in one piece. The design parameters are as follows: the height of the concrete slab 1 is 5m, and the length of the concrete bottom plate 2 is 3.5m; the slope of the slab surface is 1:0.06, the back slope is vertical, and the top width of the slab is 0.3m; the concrete bottom plate 2 has a gradual thickness, which is 0.5m thick near the slab and slightly thinner by 0.05-0.1m near the end. The wall of the cantilever retaining wall is made of C30 reinforced concrete, with an elastic modulus E of 30000MPa, a Poisson's ratio μ of 0.15, and a specific gravity γ of 23.5kN / m 3 .

[0037] Furthermore, if Figure 2 As shown, in this embodiment 1, the locking component is composed of a steel plate 4 and a clamp 5, and the steel plate 4 and the clamp 5 are both made of steel material; wherein: the thickness of the steel plate 4 is 6-8cm, preferably 6cm, and the thickness of the clamp is 12-15cm, preferably 12cm; Figure 3 As shown, the steel casing 3 is a galvanized spiral corrugated casing with a wall thickness of 10-14 mm, preferably 12 mm, a diameter of 8-15 cm, a uniform, smooth and continuous wall surface, and no small holes, spaces, pores, cracks, peeling and other defects that can be distinguished by the naked eye, and the steel casing 3 is arranged inside the cantilever retaining wall at equal longitudinal intervals.

[0038] In addition, in this embodiment 1, the high-tensile steel cable 6 is composed of 3-5 high-strength, low-relaxation, non-bonded prestressed steel strands, and the connection strength of a single steel strand is greater than 200KN. The high-tensile steel cable 6 can be stretched by an external stretching machine, clamped with a steel pad 4 and a clamp 5, and then the tension of the stretching machine is relaxed, so that the cantilever retaining wall of the concrete structure can generate axial prestress.

[0039] Embodiment 2: A construction method for constructing the prestressed cantilever retaining wall described in Embodiment 1, comprising the following steps:

[0040] S1, on-site construction preparation;

[0041] Before the formal construction on site, the location, direction, length, elevation, etc. are checked in combination with the actual terrain and geological conditions of the site; then the site is cleaned and the materials (cement, sand, pebbles, graded crushed stone) are prepared for stacking, and according to the configuration of the construction equipment, the construction roads in and out of the site are ensured to be unobstructed; finally, before construction, the construction personnel are organized to familiarize themselves with the construction process and master the construction operation skills.

[0042] S2, construction of the main body of the cantilever retaining wall;

[0043] After the site is excavated and leveled, the steel bars of the concrete slab 1 and the concrete bottom slab 2 are tied according to the design drawings; then a plurality of steel casings 3 with hollow channels are pre-installed at the left center of the concrete slab 1 and the concrete bottom slab 2; finally, the scaffolding is erected and the steel formwork is installed to ensure that the components are firm and the joints do not leak after the formwork is installed, and the wall concrete is poured;

[0044] S3, prestressing the cantilever retaining wall;

[0045] After 25 days of curing, when the cantilever retaining wall in step S2 reaches more than 75% of the design strength, 3-5 high-tension steel cables 6 are inserted into the hollow channels reserved in the steel casing 3, and then the high-tension steel cables 6 are stretched by an external stretching machine. After being clamped with a steel pad 4 and a clamp 5, the tension of the stretching machine is relaxed, and the pre-tensioning force of the high-tension steel cables is transmitted to the concrete by the clamp at the end of the high-tension steel cables, so that the concrete structure generates axial pre-compression stress; finally, cement slurry is poured into the steel casing 3 through the pores at the top of the clamp, so that the prestressed tendons and the concrete components form a whole, and the prestressed cantilever retaining wall is completed.

[0046] Example 3: Figure 3 As shown, an application of a prestressed cantilever retaining wall constructed by the construction method described in Example 2 in slope support, the specific support method is as follows:

[0047] When the cement slurry poured and the poured concrete in Example 2 have expired, a filler layer 8 is backfilled between the concrete slab 1 and the slope soil 7; the entire construction content is completed by backfilling in layers and compacting with a small compactor.

[0048] Among them, the slope soil 7 in this embodiment 3 is the slope accumulation Q2 old loess, the cohesion c is 28.0kPa, and the internal friction angle is is 18.0°, elastic modulus E is 24MPa, Poisson's ratio μ is 0.30, and gravity γ is 18.0kN / m 3 , with a slope of 60°.

[0049] In this embodiment 3, the filler layer 8 is made of yellow sand, which is determined to be medium sand by particle analysis test. The maximum and minimum dry densities of the yellow sand are 1.65 and 1.44 g / cm3 respectively. During construction, the relative density of the filler is controlled to be 85%, the compaction degree is 97%, and the corresponding density is 1.62 g / cm 3 The internal friction angle of the filler was found to be 42° through direct shear test.

[0050] In addition, it should be noted that the shapes and names of the parts and components of the specific embodiments described in this specification may be different. Any equivalent or simple changes made based on the structure, features and principles described in the patent concept of the present invention are included in the protection scope of the patent of the present invention. The technicians in the technical field of the present invention can make various modifications or supplements to the specific embodiments described or replace them in a similar manner, as long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A prestressed cantilever retaining wall, comprising a concrete base plate and a concrete vertical plate arranged on the concrete base plate, characterized in that: The prestressed cantilever retaining wall is provided with a plurality of prestressing components inside, and the prestressing components are composed of a steel casing, a high-tension steel cable and a locking component, wherein: The steel casing is hollow inside and has openings at both ends. One end of the steel casing is opened at the top of the concrete slab, and the other end is opened at the side of the concrete bottom slab. The high-tension steel cables are provided in plurality, and are respectively inserted into the opening at one end of the steel casing and led out from the opening at the other end of the steel casing; The locking components are respectively arranged at the two openings of the steel casing, and are used to lock and fix the multiple high-tension steel cables in a stretched state to the cantilever retaining wall; The locking component is composed of a steel plate and a clamp, and both the steel plate and the clamp are made of steel material; wherein: the thickness of the steel plate is 6-8cm, and the thickness of the clamp is 12-15cm; The steel casing is a galvanized spiral corrugated casing with a wall thickness of 10-14 mm and a diameter of 8-15 cm. The steel casing is arranged inside the cantilever retaining wall in a longitudinally equidistant manner.

2. The prestressed cantilever retaining wall according to claim 1, characterized in that: The high-tension steel cable is composed of 3-5 high-strength, low-relaxation, non-bonded prestressed steel strands.

3. A construction method for a prestressed cantilever retaining wall according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1, on-site construction preparation; S2, construction of the main body of the cantilever retaining wall; After the site is excavated and leveled, the steel bars of the concrete slab and concrete base are tied according to the design drawings; then multiple steel casings with hollow channels are pre-installed at the center left of the concrete slab and concrete base; finally, the scaffolding is erected and the steel formwork is installed, and the wall concrete is poured; S3, prestressing the cantilever retaining wall; After the cantilever retaining wall in step S2 reaches more than 75% of the design strength, 3-5 high-tensile steel cables are inserted into the hollow channels reserved in the steel casing, and then the high-tensile steel cables are stretched by an external stretching machine. After being clamped with a steel pad and a clamp, the tension of the stretching machine is relaxed, and the pre-tensioning force of the high-tensile steel cables is transmitted to the concrete by means of the clamp set at the end of the high-tensile steel cables, so that the concrete structure generates axial pre-compression stress; finally, cement slurry is poured into the steel casing through the pores at the top of the clamp to form a whole with the prestressed tendons and the concrete member.

4. The construction method of the prestressed cantilever retaining wall according to claim 3 is characterized in that: The following steps are also included: S4, backfilling of soil after construction of cantilever retaining wall; Backfill the filling layer between the concrete slab and the slope soil; complete the entire retaining wall construction by backfilling in layers and compacting it with a small compactor.

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