Abutment structure of a sea-crossing bridge and construction method thereof

Abstract

The application discloses a bridge abutment structure of a cross-sea bridge and a construction method thereof, characterized in that the bridge abutment is located on the water surface outside a seawall, a circle of prefabricated concrete sheet piles are arranged in front of and on the two sides of the bridge abutment, and the sheet piles are connected to form a closed scour-preventing structure; and light foam soil and block stones are used for filling soil behind the bridge abutment, and a filter structure is arranged. The bridge abutment of the application is located on the water surface outside the seawall and directly bears the scour of ocean waves, the bridge abutment has the functions of scour prevention and anti-voiding, and the problem that the bridge abutment is not suitable to be arranged on the seaward side is solved through comprehensive measures. Meanwhile, the bridge abutment is suitable to be applied to complex sites with high filling soil and soft ground.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cross-sea bridge, in particular to a new type of abutment structure of cross-sea bridge and a construction method thereof. BACKGROUND

[0002] With the development of economy and society, a large number of cross-sea bridges have been built in China. The conventional cross-sea bridge will cross the seawall, and the abutment is arranged on the land in the seawall, which is not much different from the abutment of the conventional bridge. However, in the road network of the coastal city, the coastal road is built along the seawall, and the cross-sea bridge needs to cross the coastal road, so the abutment can only be arranged on the outside of the seawall and needs to withstand the action of ocean wave force and scouring.

[0003] On the one hand, the abutment is located on the outside of the seawall and faces the problem of soil scouring. The huge ocean current may hollow out the fill soil in front of the abutment and erode the fill soil behind the abutment, causing the land to be hollowed out, the road surface to collapse and the abutment to be unstable, which may cause serious accidents and casualties. On the other hand, the strong wave suction force and the soft soil foundation in the coastal area pose a severe challenge to the settlement control of the abutment. The superposition of the wave suction force and the soil pressure behind the abutment, as well as the soft underlying layer commonly existing in the coastal area, are very unfavorable factors for the design of the abutment friction pile. SUMMARY

[0004] The purpose of the present application is to solve the problem that the conventional abutment is only arranged in the seawall, and to provide an abutment structure of cross-sea bridge. The abutment is located on the water surface outside the seawall and directly withstands the scouring and wave suction force of the ocean wave. The abutment has the functions of preventing scouring and hollowing out. The problem of unsuitable abutment arrangement on the seaside is solved by comprehensive measures. At the same time, the abutment is suitable for complex sites with high fill soil and soft foundation.

[0005] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows: an abutment structure of cross-sea bridge, characterized in that the abutment is located on the water surface outside the seawall, a circle of prefabricated concrete sheet piles is arranged in front of and on both sides of the abutment, the sheet piles are connected to form a closed scouring prevention structure, and the fill soil behind the abutment is filled with light foam soil and block stones and is provided with a filter structure.

[0006] Further, fine stone concrete is poured into the double grooves between the ends of adjacent prefabricated concrete sheet piles, and high-pressure rotary jet piles are used to seal the space between the sheet piles and the retaining wall of the adjacent project.

[0007] The space between the prefabricated concrete sheet piles and the abutment is filled with gravel and concrete post-poured layer. The fill soil is filled after the abutment is constructed, and the post-poured layer is constructed, so as to avoid the sheet piles from bearing the soil pressure behind the abutment. The front of the sheet piles is filled with block stones to prevent the front of the sheet piles from being hollowed out.

[0008] The sheet piles are constructed to be about 4 meters higher than the ground level, which plays the role of construction cofferdam. After the abutment is constructed, the sheet piles protruding above the ground are knocked down. One pile is used for multiple purposes, which saves the engineering cost and construction period.

[0009] The backfilling soil behind the abutment adopts light foam soil above the water level line to reduce the earth pressure, and adopts block stone below the water level line, and two pieces of stone, a mixed inverted filter layer and a filter soil cloth are sequentially arranged below the block stone, so that a complete inverted filter structure is formed to prevent soil loss, and the internal friction angle of the filling soil is increased and the earth pressure is reduced; and the abutment is provided with a water drain hole and a gravel filter bag above the water level line.

[0010] To meet the requirement of durability, the abutment adopts high-performance marine concrete, a concrete surface coating, a rust inhibitor and an increased steel reinforcement protective layer and other measures.

[0011] A construction method of an abutment structure of a sea-crossing bridge, characterized in that the method comprises the following steps:

[0012] A, leveling the site, dry land construction;

[0013] B, construction of precast sheet piles, fine stone concrete is poured into the double grooves between the end sheet piles, and high-pressure rotary jet piles are used to seal between the sheet piles and the adjacent engineering retaining wall;

[0014] C, construction of bored piles and abutments;

[0015] D, construction of an inverted filter structure behind the abutment, then filling block stone to the water level line elevation, and then construction of the upper structure;

[0016] E, filling light foam soil behind the abutment;

[0017] F, knocking down the sheet piles above the ground, bending the steel reinforcement, and filling gravel and concrete post-poured layer between the abutment and the sheet piles.

[0018] The present application has the following obvious technical features: first, the sealed structure formed by the precast concrete sheet piles can effectively prevent erosion; second, the sheet piles and the abutment are independent of each other, and after the backfilling soil behind the abutment is completed, the gap between the sheet piles and the abutment is filled with concrete; third, the filling soil above the water level line behind the abutment adopts light foam concrete, and the filling soil below the water level line adopts block stone, which can greatly reduce the earth pressure behind the abutment and reduce the overall settlement of the abutment; fourth, the block stone and the inverted filter layer behind the abutment form an inverted filter structure to prevent land soil loss; and fifth, the abutment adopts a complete set of anti-corrosion measures to ensure the durability requirement. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a schematic diagram of the present application as a whole;

[0020] Figure 2 is a schematic diagram of the anti-erosion construction elevation of the present application;

[0021] Figure 3 is a schematic diagram of the anti-erosion construction plane of the present application;

[0022] Figure 4 Fig. 1 is a schematic view of a sheet pile;

[0023] Fig. 1 is a schematic view of a sheet pile; DETAILED DESCRIPTION

[0024] The prefabricated concrete sheet pile 1 is arranged in front of the abutment, and the prefabricated concrete sheet pile and the abutment are filled with gravel 18 and C40 concrete post-poured layer, which are independent of each other, so as to avoid that the sheet pile 1 bears the soil pressure behind the abutment. The 200-400 kg block stone 17 is filled in front of the sheet pile to prevent the front of the sheet pile from being hollowed out.

[0025] The light foam soil 9 is used on the water level line to reduce the soil pressure, and the 10-100 kg block stone 11 is used below the water level line, and the two-piece stone 12, the mixed inverted filter layer 13 and the filter geotextile 14 are sequentially arranged below the block stone, so as to form a complete inverted filter structure to prevent soil loss and increase the internal friction angle of the fill and reduce the soil pressure. The water discharge hole 5 and the sand gravel filter bag 7 are arranged on the water level line.

[0026] The specific implementation method is as follows:

[0027] 1) Level the site and construct on dry land. Fill the soil to the designed road surface height, and after preloading, excavate the abutment construction surface.

[0028] 2) Construct the prefabricated sheet pile. The sheet pile is not allowed to appear loose tenon phenomenon during construction. The end sheet pile is filled with fine stone concrete in the double concave groove. The sheet pile and the retaining wall of the adjacent project are sealed with high-pressure jet grouting pile. It is necessary to ensure that a sealed space is formed in front of the abutment to prevent soil leakage under the abutment. The sheet pile is constructed to be about 4 meters above the ground line, which plays the role of construction cofferdam. The distance between the prefabricated sheet pile and the abutment is 1000-1500 mm.

[0029] 3) Construct the bored pile and the abutment. The abutment concrete pouring must take measures to avoid cracks caused by large temperature difference on the inner surface due to hydration heat. Pouring should be carried out when the air temperature is low in a day, and measures such as reducing the amount of cement, using low hydration heat cement, reducing the pouring layer thickness, and embedding cooling pipes (horizontal and vertical) in the concrete should be taken to reduce the temperature difference on the inner surface.

[0030] The temperature of the concrete is strictly controlled by methods such as water cooling, etc. The temperature of the surface and the interior of the concrete is measured after pouring, and the temperature difference is controlled within the range required by the specification.

[0031] The bridge abutment concrete strength reaches 100% of the design strength, and the upper structure can be erected not less than 14 days later.

[0032] 4) The inverted filter structure is constructed behind the abutment, and then the stone is filled to the water level elevation, and then the upper structure is constructed.

[0033] 5) The light foam soil is filled behind the abutment. The light foam soil of D1000 grade is used to increase the anti-floating performance of the filled soil. Before the pouring construction of the foam light soil subgrade, there should be no obvious accumulated water and sundries on the base, and the base compaction degree index

[0034] ≥85%. The single-layer pouring thickness of the foam light soil is controlled at 0.3m-1.0m; the pouring construction time of a single pouring area should not exceed the initial setting time of the cement paste; the pouring interval time of the upper and lower adjacent two pouring layers should not be less than 8 hours. A single pouring layer should be poured at one time, and if necessary, it can be poured at most twice, and the interval time of the two times of pouring should be controlled at 6 hours-24 hours. After the pouring of the foam light soil at the roadbed position is completed, the plastic film or non-woven geotextile should be covered for moisture curing; after pouring to the design elevation, the curing time should not be less than 7 days.

[0035] 6) Knock off the sheet piles that are higher than the ground, bend the reinforcement. Fill 800mm high concrete between the abutment and the sheet piles.

[0036] The cross-sea bridge faces serious seawater corrosion problems, and the durability requirements of the abutment are as follows:

[0037] 1) Thickness of protective layer

[0038] The thickness of the concrete protective layer in the marine environment should be larger than that of the general concrete protective layer due to the presence of chloride salt. In addition to meeting the minimum protective layer thickness determined in the bridge design specification, the minimum protective layer of this project is determined by referring to similar projects: the minimum protective layer thickness of the main reinforcement of the pier column and the abutment is 70mm; the minimum protective layer thickness of the main reinforcement of the pile is 85mm.

[0039] 2) High-performance marine concrete

[0040] The difference between high-performance marine concrete and ordinary concrete is that one or more of fly ash, blast furnace slag, and micro-silica powder are mixed to improve the specific performance of the concrete under specific conditions, such as high elastic modulus, low permeability, and resistance to certain types of damage.

[0041] High performance concrete, from the index, relative to ordinary concrete, the maximum particle size of aggregate, the highest water-cement ratio, etc. have made more stringent requirements.

[0042] 3) concrete surface coating system. The outer surface of the abutment is painted with anticorrosive paint and silane impregnation.

[0043] 4) concrete mixed with rust inhibitor.

[0044] The application will be further described below in combination with a specific example.

[0045] A new bridge is built between two artificial islands in a city, and the bridge head is located at a cross intersection. The abutment can only be set on the outer sea side. The foundation bearing layer is silty clay, and the soil performance is poor. The abutment fill height is 12 meters, which is a kind of high fill abutment with poor foundation conditions. When the project is designed, a circle of precast concrete is set in front of the abutment and on both sides

[0046] The soil plate piles are connected to each other to form a closed anti-scour structure; the fill soil behind the abutment adopts light foam concrete and block stone with small internal friction angle, which better solves the problems of anti-scour and soil pressure of high fill.

Claims

1. A construction method of a bridge abutment structure of a sea-crossing bridge, characterized by The abutment is located on the water surface outside the seawall, a circle of precast concrete sheet piles are arranged in front of and on both sides of the abutment, the sheet piles are connected to form a closed scour-preventing structure; the backfill soil of the abutment is made of light foam soil and block stones, and a filter structure is arranged; the precast concrete sheet piles and the abutment are filled with gravel and concrete post-poured layers; the sheet piles are 4m higher than the ground line during construction, and play the role of construction cofferdam; after the abutment is constructed, the sheet piles higher than the ground are knocked down, and the reinforcement is bent; the sheet piles and the abutment are independent of each other, and after the backfill soil behind the abutment is completed, the gap between the sheet piles and the abutment is filled with concrete; the abutment is made of high-performance marine concrete, a concrete surface coating, a rust inhibitor and an increased reinforcement protective layer to meet the durability requirements; The construction method comprises the following steps: A. Level the site and construct on dry ground; B. Construct precast sheet piles, pour fine concrete into the double grooves between the ends of adjacent precast concrete sheet piles, and use high-pressure rotary jet piles to seal between the sheet piles and the retaining wall of the adjacent project; C. Construct bored piles and abutments; D. Construct a filter structure behind the abutment, fill block stones to the water level elevation, and then construct the upper structure; E. Fill light foam soil behind the abutment; F. Knock down the sheet piles that are higher than the ground, bend the reinforcement, and fill gravel and concrete post-poured layers between the abutment and the sheet piles.

2. The method of constructing the abutment structure of a sea-crossing bridge according to claim 1, characterized in that The backfill soil behind the abutment is made of light foam soil on the water level line to reduce the soil pressure, and block stones are used below the water level line, two pieces of stone, a mixed filter layer and a filter geotextile are arranged in turn below the block stones, which can form a complete filter structure to prevent soil loss, and can also increase the internal friction angle of the fill and reduce the soil pressure; the abutment is provided with a drain hole and a gravel filter bag on the water level line.

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