A method and structure for backfilling bridge abutments of urban bridges

Abstract

This invention relates to a method and structure for backfilling bridge abutments in urban bridges, specifically to a method and structure for backfilling bridge abutments in urban bridges. The method includes the following steps: Before backfilling, the foundation pit within the area to be backfilled, enclosed by the abutment, two retaining walls, and the approach road, is cleaned to ensure the site is dry, free of sewage, garbage, and other debris; Measurement and layout are conducted, using a total station to mark the backfill area based on the backfill soil and lightweight foamed concrete, and a level to mark the backfill height, marking the retaining walls and the back of the abutment; This invention eliminates uneven settlement of the abutment backfill by using lightweight foamed concrete for backfilling the back of the abutment and the back of the retaining walls, transitioning layer by layer outwards, and by setting crossbeams, approach slabs, and plain concrete transition zones on the top surface of the foamed concrete.

Description

Technical Field

[0001] This invention relates to the field of urban bridge construction technology, specifically to a method and structure for backfilling bridge abutments in urban bridges. Background Technology

[0002] The connection between the main body of an urban bridge and the ground road is generally achieved through approach roads, which are typically roads with backfilled soil between retaining walls on both sides. The bridge abutment back is the main body of the bridge, and one side of it connects to the roadbed.

[0003] Backfilling of bridge abutments and approach road retaining walls is a crucial aspect of engineering quality control, serving as a transition between the roadbed fill and the bridge structure. In practice, numerous quality issues arise due to inadequate compaction of the backfill behind abutments and retaining walls, low stiffness of the backfill material, high compressibility, or limited coverage of rigid or semi-rigid materials. These issues lead to uneven transitions between the bridge and approach roads, road subsidence, and negatively impact driving safety, pedestrian comfort, and road lifespan. These problems stem from both design flaws and non-standard construction practices. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a bridge abutment backfilling method and backfilling structure for urban bridges that can solve the problems of vehicle bouncing and unstable driving caused by inadequate backfilling and large settlement.

[0005] This invention discloses a method for backfilling bridge abutments in urban bridges, comprising the following steps:

[0006] 1) Before backfilling, clean the foundation pit within the area to be backfilled, which is enclosed by the bridge abutment, two retaining walls, and bridge approach road, and keep the foundation dry, free of sewage, garbage, and debris.

[0007] 2) Surveying and setting out: Based on the backfill range of the backfill soil and lightweight foamed concrete, use a total station to survey and set out the backfill area of ​​the backfill soil and lightweight foamed concrete, and use a level to survey and set out the backfill height, and make marks at the retaining wall and abutment.

[0008] 3) Take backfill soil samples on site and send them to a qualified laboratory to test the natural moisture content, standard compaction and strength values ​​of the backfill soil, and control the moisture content of the backfill soil within ±2% of the optimum moisture content;

[0009] 4) Mark the boundaries of the backfill soil and lightweight foamed concrete backfill within the area to be backfilled, and begin backfilling the lightweight foamed concrete and backfill soil layer by layer.

[0010] In each backfill layer, the backfill area of ​​the backfill soil is a T-shaped backfill area, and the backfill area of ​​the lightweight foamed concrete is a U-shaped backfill area. The central extension area of ​​the T-shaped backfill area extends into the U-shaped backfill area to form a rectangular backfill area.

[0011] When backfilling, please use the following method:

[0012] Backfilling construction: Backfill soil that meets the requirements is backfilled in layers into the backfilling area. After each layer of backfill soil is backfilled, it is compacted. The compaction degree after compaction is tested according to the standard compaction test. The compaction degree is not less than 95%. Then the next layer of backfill soil is backfilled. When the backfill soil height reaches 1-1.2m, the backfilling construction is stopped, and the backfill soil is allowed to settle naturally before the lightweight foamed concrete backfilling construction is carried out.

[0013] Backfilling construction of lightweight foamed concrete: The end of the backfill area extending into the lightweight foamed concrete backfill area is excavated using machinery at a slope of 1:0.3, according to the boundary markings. The lightweight foamed concrete backfill areas on both sides of the backfill area extending into the lightweight foamed concrete backfill area are then excavated using machinery, according to the boundary markings, and shaped into stepped steps 0.5m high, 0.5m wide, and with a slope of 1:1. Lightweight foamed concrete is then backfilled in layers within the lightweight foamed concrete backfill area. After each layer of lightweight foamed concrete backfill is completed, it is covered and kept moist for curing. After moist curing, the next layer of lightweight foamed concrete is backfilled until the backfill height is reached, and then the backfilling construction is repeated.

[0014] Repeat the backfilling construction of the soil and the backfilling construction of the lightweight foamed concrete until the backfill reaches the bottom surface of the subgrade or the bottom surface of the superstructure.

[0015] A ramp is set on the bottom surface of the subgrade or the bottom surface of the superstructure. The bottom surface of the ramp is connected to the crossbeam. When backfilling to the bottom of the crossbeam, formwork is set on both sides of the crossbeam to reserve the construction area of ​​the crossbeam. Then, lightweight foamed concrete is used to backfill to the design elevation.

[0016] Check the scope and top elevation of the backfill soil and lightweight foamed concrete. After it is qualified, carry out the construction of the slab cushion concrete. On the side of the slab away from the back of the platform, construct the plain concrete transition zone. The plain concrete transition zone extends into the lightweight foamed concrete backfill with a width of 0.8-1.2m.

[0017] A 60cm thick layer of 8% lime-soil was constructed under the outer side of the lightweight foamed concrete roadbed as the subbase of the road; an asphalt concrete surface layer was directly laid on top of the approach slab and plain concrete transition zone to complete the bridge abutment backfilling construction.

[0018] Preferably, the lightweight foamed concrete is lightweight foamed concrete with a dry density grade of A07 and a compressive strength of CF1.0.

[0019] Preferably, the thickness of each backfill layer is no more than 30cm.

[0020] Preferably, the height of each layer of lightweight foamed concrete backfill is no more than 50cm.

[0021] The backfill structure obtained by using a bridge abutment backfilling method for urban bridges.

[0022] This invention eliminates uneven settlement of the abutment backfill by using lightweight foamed concrete for backfilling the abutment and retaining wall backfill and transitioning it outward layer by layer, and by setting crossbeams, slabs and plain concrete transition zones on the top surface of the lightweight foamed concrete.

[0023] The present invention uses lightweight foamed concrete backfill for the back of the retaining wall, which can reduce the weight of the backfill soil behind the retaining wall and achieve the effects of water isolation and weight reduction. Therefore, there is no need to leave drainage holes on the retaining wall.

[0024] The invention employs alternating layered backfilling, which allows the backfill soil time to settle naturally, thus eliminating subsidence caused by backfill soil settlement during construction.

[0025] This invention, by using lightweight foamed concrete for backfilling and setting a reinforced concrete slab and plain concrete transition zone on top, and applying 8% lime-soil on top of the backfill, can effectively prevent water seepage from the road surface into the backfill subgrade and reduce the impact of external factors on the moisture content of the roadbed backfill.

[0026] The lightweight foamed concrete in this invention has good fluidity, high material strength and high rigidity. During construction, the fluidity of the material can be used to fill all corners, avoiding the settlement problems caused by small backfill space and insufficient compaction of backfill material near bridge abutments and the back of retaining walls.

[0027] This invention allows for rapid backfilling. The lightweight foamed concrete is mixed on-site with cement, water, and foaming agent, and then poured in layers. Compared to traditional earthwork backfilling and compaction, this method can significantly shorten construction time and save on the project duration.

[0028] This invention reduces the infiltration of surface water into the roadbed fill and reduces uneven settlement of the backfill soil by filling the bridge abutment and retaining wall with lightweight foamed concrete and applying a 60cm thick 8% lime-soil seal layer on the inner side of the lightweight foamed concrete and the top surface of the plain soil backfill. Attached Figure Description

[0029] Figure 1 This is a plan view of the bridge abutment backfill.

[0030] Figure 2 for Figure 1 Section 1-1.

[0031] Figure 3 for Figure 1 Section 2-2.

[0032] Attached reference numerals: 1-bridge abutment, 2-backfill area of ​​backfill soil, 3-backfill area of ​​lightweight foamed concrete, 4-subbase of road, 5-plain concrete transition zone, 6-crossbeam, 7-plain concrete cushion layer of approach slab, 8-approach slab, 9-retaining wall. Detailed Implementation

[0033] This invention discloses a method for backfilling abutment 1 of an urban bridge, comprising the following steps:

[0034] 1) Before backfilling, clean the foundation pit in the area to be backfilled, which is enclosed by the bridge abutment 1, the two retaining walls 9 and the bridge approach road, and keep the foundation dry, free of sewage, garbage and debris.

[0035] 2) Surveying and setting out: Based on the backfill range of the backfill soil and lightweight foamed concrete, use a total station to survey and set out the backfill area 3 of the backfill soil and lightweight foamed concrete, and use a level to survey and set out the backfill height, and make marks at the retaining wall 9 and the back of the abutment.

[0036] 3) Take backfill soil samples on site and send them to a qualified laboratory to test the natural moisture content, standard compaction and strength values ​​of the backfill soil, and control the moisture content of the backfill soil within ±2% of the optimum moisture content;

[0037] 4) Mark the boundaries of the backfill soil and lightweight foamed concrete backfill within the area to be backfilled, and begin backfilling the lightweight foamed concrete and backfill soil layer by layer.

[0038] In each backfill layer, the backfill area 2 of the backfill soil is a T-shaped backfill area, and the backfill area 3 of the lightweight foamed concrete is a U-shaped backfill area. The central extension area of ​​the T-shaped backfill area extends into the U-shaped backfill area to form a rectangular backfill area.

[0039] When backfilling, please use the following method:

[0040] Backfilling construction: Backfill soil that meets the requirements is backfilled in layers into backfilling area 2. After each layer of backfill soil is backfilled, it is compacted. The compaction degree after compaction is tested according to the standard compaction test. The compaction degree is not less than 95%. Then the next layer of backfill soil is backfilled. When the height of the backfill soil is 1-1.2m, the backfilling construction is stopped, and the backfill soil is allowed to settle naturally before the lightweight foamed concrete backfilling construction is carried out.

[0041] Backfilling construction of lightweight foamed concrete: The backfill area 2 extends into the lightweight foamed concrete backfill area 3 at one end, and is excavated using machinery at a slope of 1:0.3 according to the boundary markings. The lightweight foamed concrete backfill area 3, located on both sides of the backfill area 2 extending into the lightweight foamed concrete backfill area 3, is also excavated using machinery according to the boundary markings, and shaped into a stepped platform 0.5m high, 0.5m wide, and with a slope of 1:1. Then, lightweight foamed concrete is backfilled in layers in the lightweight foamed concrete backfill area 3. After each layer of lightweight foamed concrete backfill is completed, it is covered and kept moist. After moist curing, the next layer of lightweight foamed concrete is backfilled until the backfill height is reached, and then the backfilling construction is repeated.

[0042] Repeat the backfilling construction of the soil and the backfilling construction of the lightweight foamed concrete until the backfill reaches the bottom surface of the subgrade or the bottom surface of the superstructure.

[0043] A slab 8 is provided on the bottom surface of the subgrade or the bottom surface of the superstructure. The bottom surface of the slab 8 is connected to the crossbeam 6. When backfilling to the bottom of the crossbeam 6, formwork is set up on both sides of the crossbeam 6 to reserve the construction area of ​​the crossbeam 6. Then, lightweight foamed concrete is used for backfilling to the design elevation.

[0044] After inspecting the backfill soil and the area and top elevation of the lightweight foamed concrete, and confirming that they are qualified, proceed with the concrete construction of the plain concrete cushion layer 7 of the slab. Construct the plain concrete transition zone 5 on the side of the slab 8 away from the back of the platform. The plain concrete transition zone 5 extends into the lightweight foamed concrete backfill with a width of 0.8-1.2m.

[0045] A 60cm thick layer of 8% lime-soil was constructed under the outer side of the lightweight foamed concrete roadbed as the subbase 4 of the road; an asphalt concrete surface layer was directly laid on top of the approach slab 8 and the plain concrete transition zone 5, and the backfilling construction of the bridge abutment 1 was completed.

[0046] Lightweight foamed concrete is a type of lightweight foamed concrete with a dry density grade of A07 and a compressive strength of CF1.0.

[0047] The thickness of each backfill layer shall not exceed 30cm.

[0048] The height of each layer of lightweight foamed concrete backfill should not exceed 50cm.

[0049] The backfill structure obtained by using a bridge abutment 1 backfilling method for urban bridges.

[0050] Implementation example:

[0051] 1) Before backfilling, clean up the garbage, water, etc. in the area of ​​the back of the bridge abutment 1 and the retaining walls on both sides 9;

[0052] 2) Based on the backfill range of the backfill soil and lightweight foamed concrete, mark out the backfill area 3 of the backfill soil and lightweight foamed concrete, and use a level to mark out the backfill control height, and make marks at the retaining wall 9 and the back of the abutment.

[0053] 3) After the purchased soil arrives on site, soil samples are taken and sent to the laboratory to test the natural moisture content, standard compaction strength (CBR) value. At the same time, the construction mix ratio of lightweight foamed concrete is determined, cement:water:foaming agent = 400:240:0.6. Before backfilling and compaction, the moisture content of the backfill soil is tested and controlled within ±2% of the optimum moisture content.

[0054] 4) Mark the boundaries of the backfill soil and lightweight foamed concrete backfill in the area to be backfilled. Start backfilling the soil first, with each layer being 250-300mm thick. After each layer of backfill soil is leveled, compacted, and has a compaction degree of not less than 95%, and passes the test, proceed with the next layer of backfill soil. When backfilling each layer of backfill soil, backfill 1m beyond the boundary of the lightweight foamed concrete. After backfilling 3-4 layers to a thickness of about 1m, use machinery and manual labor to remove the backfill soil that has crossed the boundary of the lightweight foamed concrete. On the side of the abutment 1, manually trim it into a step with a width of 0.5m and a height of 1m and a 1:1 slope. On the side of the retaining wall, manually trim it into a 1:0.3 slope. Then, backfill the lightweight foamed concrete in layers with a thickness of 300-500mm.

[0055] In each backfill layer, the backfill area 2 of the backfill soil is a U-shaped backfill area, and the backfill area 3 of the lightweight foamed concrete is a T-shaped backfill area. The central extension area of ​​the U-shaped backfill area extends into the T-shaped backfill area to form a rectangular backfill area.

[0056] When backfilling, please use the following method:

[0057] Backfilling construction: Backfill soil that meets the requirements is backfilled in layers into backfilling area 2. After each layer of backfill soil is backfilled, it is compacted. The compaction degree after compaction is tested according to the standard compaction test. The compaction degree is not less than 95%. Then the next layer of backfill soil is backfilled. When the height of the backfill soil is 1-1.2m, the backfilling construction is stopped, and the backfill soil is allowed to settle naturally before the lightweight foamed concrete backfilling construction is carried out.

[0058] Backfilling construction of lightweight foamed concrete: The backfill area 2 extends into the lightweight foamed concrete backfill area 3 at one end, and is excavated using machinery at a slope of 1:0.3 according to the boundary markings. The lightweight foamed concrete backfill area 3, located on both sides of the backfill area 2 extending into the lightweight foamed concrete backfill area 3, is also excavated using machinery according to the boundary markings, and shaped into a stepped platform 0.5m high, 0.5m wide, and with a slope of 1:1. Then, lightweight foamed concrete is backfilled in layers in the lightweight foamed concrete backfill area 3. After each layer of lightweight foamed concrete backfill is completed, it is covered and kept moist. After moist curing, the next layer of lightweight foamed concrete is backfilled until the backfill height is reached, and then the backfilling construction is repeated.

[0059] Repeat the backfilling construction of the soil and the backfilling construction of the lightweight foamed concrete until the backfill reaches the bottom surface of the subgrade or the bottom surface of the superstructure.

[0060] A slab 8 is provided on the bottom surface of the roadbed or the bottom surface of the superstructure. A crossbeam 6 is provided on the bottom surface of the slab 8. When backfilling reaches the bottom of the crossbeam 6, formwork is erected on both sides of the crossbeam 6 to reserve the construction area of ​​the crossbeam 6. Then, lightweight foamed concrete is used for backfilling to the design elevation.

[0061] Check the backfill soil and the range and top elevation of the lightweight foamed concrete. After it is qualified, carry out the concrete construction of the plain concrete cushion layer 7 of the slab. On the side of the slab 8 away from the back of the platform, construct the plain concrete transition zone 5. The plain concrete transition zone 5 extends into the lightweight foamed concrete backfill with a width of about 1m.

[0062] A 60cm thick layer of 8% lime-soil was constructed under the roadbed outside the lightweight foamed concrete backfill area as the subbase 4 of the road; an asphalt concrete surface layer was directly laid on top of the approach slab 8 and the plain concrete transition zone 5 to complete the backfilling construction of the bridge abutment 1.

[0063] The present invention eliminates uneven settlement of the abutment backfill by using lightweight foamed concrete backfill on the back of the abutment and the back of the retaining wall 9 and transitioning it outward layer by layer, and by setting a crossbeam 6, a slab 8 and a plain concrete transition zone 5 on the top surface of the lightweight foamed concrete.

[0064] The use of lightweight foamed concrete backfill on the back of the retaining wall 9 in this invention can reduce the weight of the backfill soil behind the retaining wall, thus achieving the effects of water isolation and weight reduction. Therefore, there is no need to leave drainage holes on the retaining wall 9.

[0065] The invention employs alternating layered backfilling, which allows the backfill soil time to settle naturally, thus eliminating subsidence caused by backfill soil settlement during construction.

[0066] The present invention, by using lightweight foamed concrete for backfilling and setting a reinforced concrete slab 8 and a plain concrete transition zone 5 on top, and by applying 8% lime-soil on top of the backfill, can effectively prevent water from seeping into the backfill soil and reduce the impact of external factors on the moisture content of the roadbed backfill soil.

[0067] The lightweight foamed concrete in this invention has good fluidity, high material strength and high rigidity. During construction, the fluidity of the material can be used to fill all corners, avoiding the settlement problem caused by small backfill space and insufficient compaction of backfill material near the bridge abutment 1 and the back of the retaining wall 9.

[0068] This invention allows for rapid backfilling. The lightweight foamed concrete is mixed on-site with cement, water, and foaming agent, and then poured in layers. Compared to traditional earthwork backfilling and compaction, this method can significantly shorten construction time and save on the project duration.

[0069] This invention reduces the infiltration of surface water into the roadbed fill and reduces uneven settlement of the backfill soil by filling the bridge abutment 1 and retaining wall 9 with lightweight foamed concrete and applying a 60cm thick 8% lime-soil sealing layer on the inner side of the lightweight foamed concrete and the top surface of the plain soil backfill.

Claims

1. A method for backfilling bridge abutments in urban bridges, characterized in that, Includes the following steps: 1) Before backfilling, clean the foundation pit within the area to be backfilled, which is enclosed by the bridge abutment, two retaining walls, and bridge approach road, and keep the foundation dry, free of sewage and garbage; 2) Surveying and setting out: Based on the backfill range of the backfill soil and lightweight foamed concrete, use a total station to survey and set out the backfill area of ​​the backfill soil and lightweight foamed concrete, and use a level to survey and set out the backfill height, and make marks at the retaining wall and abutment. 3) Take backfill soil samples on site and send them to a qualified laboratory to test the natural moisture content, standard compaction and strength values ​​of the backfill soil, and control the moisture content of the backfill soil within ±2% of the optimum moisture content; 4) Mark the boundaries of the backfill soil and lightweight foamed concrete backfill within the area to be backfilled, and begin backfilling the lightweight foamed concrete and backfill soil layer by layer. In each backfill layer, the backfill area of ​​the backfill soil is a T-shaped backfill area, and the backfill area of ​​the lightweight foamed concrete is a U-shaped backfill area. The central extension area of ​​the T-shaped backfill area extends into the U-shaped backfill area to form a rectangular backfill area. When backfilling, please use the following method: Backfilling construction: Backfill soil that meets the requirements is backfilled in layers into the backfilling area. After each layer of backfill soil is backfilled, it is compacted. The compaction degree after compaction is tested according to the standard compaction test. The compaction degree is not less than 95%. Then the next layer of backfill soil is backfilled. When the backfill soil height reaches 1-1.2m, the backfilling construction is stopped, and the backfill soil is allowed to settle naturally before the lightweight foamed concrete backfilling construction is carried out. Backfilling construction of lightweight foamed concrete: The end of the backfill area extending into the lightweight foamed concrete backfill area is excavated using machinery at a slope of 1:0.3, according to the boundary markings. The lightweight foamed concrete backfill areas on both sides of the backfill area extending into the lightweight foamed concrete backfill area are then excavated using machinery, according to the boundary markings, and shaped into stepped steps 0.5m high, 0.5m wide, and with a slope of 1:

1. Lightweight foamed concrete is then backfilled in layers within the lightweight foamed concrete backfill area. After each layer of lightweight foamed concrete backfill is completed, it is covered and kept moist for curing. After moist curing, the next layer of lightweight foamed concrete is backfilled until the backfill height is reached, and then the backfilling construction is repeated. Repeat the backfilling construction of the soil and the backfilling construction of the lightweight foamed concrete until the backfill reaches the bottom surface of the subgrade or the bottom surface of the superstructure. A ramp is set on the bottom surface of the subgrade or the bottom surface of the superstructure. The bottom surface of the ramp is connected to the crossbeam. When backfilling to the bottom of the crossbeam, formwork is set on both sides of the crossbeam to reserve the construction area of ​​the crossbeam. Then, lightweight foamed concrete is used to backfill to the design elevation. Check the scope and top elevation of the backfill soil and lightweight foamed concrete. After it is qualified, carry out the construction of the slab cushion concrete. On the side of the slab away from the back of the platform, construct the plain concrete transition zone. The plain concrete transition zone extends into the lightweight foamed concrete backfill with a width of 0.8-1.2m. A 60cm thick layer of 8% lime-soil was constructed under the outer side of the lightweight foamed concrete roadbed as the subbase of the road; an asphalt concrete surface layer was directly laid on top of the approach slab and plain concrete transition zone to complete the bridge abutment backfilling construction.

2. The method for backfilling bridge abutments of urban bridges as described in claim 1, characterized in that, The lightweight foamed concrete is a lightweight foamed concrete with a dry density grade of A07 and a compressive strength of CF1.

0.

3. The method for backfilling bridge abutments of urban bridges as described in claim 2, characterized in that, The thickness of each backfill layer shall not exceed 30cm.

4. The method for backfilling bridge abutments of urban bridges as described in claim 3, characterized in that, The height of each layer of lightweight foamed concrete backfill should not exceed 50cm.

5. The backfill structure obtained by using the bridge abutment backfilling method for urban bridges as described in any one of claims 1-4.

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