A comprehensive treatment method for solving the hazard of vehicle bump at bridge heads with low roadbeds in soft soil areas

Abstract

The present invention belongs to the technical field of geotechnical engineering, and discloses a comprehensive treatment method for solving the harm of vehicle bumping at the bridgehead with low subgrade in soft soil areas. First, determine the treatment area, clean the pavement structure layer in this area, and arrange the positions of pile holes; then drill and take soil, and separately make the subgrade soil and foundation soil into fluidized solidified soil; then pour the fluidized solidified soil in the foundation section into the pile holes, insert the core piles, and then pour the fluidized solidified soil in the subgrade section into the pile holes until they are filled, forming a solidified soil cast-in-place composite pile; finally, lay a honeycomb pavement strengthening panel and asphalt mixture until the pavement is flush with the bridge deck. The present invention considers the foundation, subgrade and pavement structure layer as a whole, strengthens the foundation through the solidified soil cast-in-place pile, strengthens the subgrade through the solidified soil cast-in-place composite pile, and then forms an overall strengthening structure by connecting with the pavement strengthening structure, fundamentally controlling the vertical deformation of the foundation and subgrade, and solving the disease of vehicle bumping at the bridgehead.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical engineering, and particularly relates to a comprehensive treatment method for solving the hazard of vehicle bump at bridgeheads with low subgrades in soft soil areas. Background Technique

[0002] Vehicle bump at bridgeheads in areas with thick silty soft soil is a common disease of low subgrades, which is caused by the uneven settlement of the bridge deck and road surface due to the stiffness difference between the bridge and road structures and materials. In order to prevent such diseases, during the road construction process, the subgrade of the transition section is strengthened and the foundation is reinforced for treatment. However, the existing treatment methods have no obvious effect on low subgrades on soft soil foundations lacking a bearing layer in areas with thick silty soft soil. Vehicle bump at bridgeheads has become one of the most difficult engineering problems to control in areas with thick silty soft soil.

[0003] In order to control such diseases, the main methods adopted in China at present are to set up lapping plates on the road surface and add asphalt concrete materials to fill the loss of the road surface structure caused by uneven settlement. These can only relieve the vehicle bump disease at bridgeheads and cannot fundamentally solve such diseases. Some people have also proposed the method of obliquely grouting to form a strengthened subgrade and partially strengthen the foundation. Such methods also cannot fundamentally solve the differential settlement between the bridge and road under the condition of low subgrades.

[0004] Chinese Patent CN206090284U discloses an asphalt pavement repair layer for treating vehicle bump at bridgeheads. The idea of this patent for treating the uneven settlement of the bridge deck and road surface is to lay a mixture layer of steel fiber layer, tack coat layer and asphalt on the damaged surface of the road surface. This patent temporarily treats the uneven settlement of the subgrade at the vehicle bump at bridgeheads, but cannot fundamentally solve the uneven settlement caused by the rigid body difference in the bridge - road transition section, because the uneven settlement in the transition section is caused by the uneven deformation of the foundation, subgrade and road surface base. This patent only relieves the road surface damage caused by the uneven settlement of the road surface base and cannot solve the uneven settlement of the subgrade and foundation under the road surface base. Chinese Patent CN114508015A discloses a reinforcement method for strengthening the vehicle bump at bridgeheads on the road surface. The idea of this patent is to use the high temperature of the thermite reaction to melt the subgrade material into a vitreous substance to reinforce the subgrade. Similarly, it only treats the road surface foundation and does not treat the subgrade and foundation. The stiffness difference between the bridge and road at the transition section still exists, and with the operation of the highway, uneven settlement will appear again.

[0005] Therefore, there is an urgent need for a method to solve the vehicle bump disease at bridgeheads with low subgrades in soft soil areas, which not only needs to strengthen the subgrade and road surface structures, but also needs to strengthen the soft soil foundation structure to fundamentally solve the vehicle bump disease problem. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a comprehensive treatment method for solving the hazard of vehicle bumping at the bridgehead of low embankments in soft soil areas in view of the deficiencies existing in the prior art. The foundation, embankment and pavement structure layer are considered as a whole. The foundation is strengthened by soil-cement piles, the embankment is strengthened by soil-cement pile composite piles, and then a whole strengthening structure is formed by connecting with the pavement strengthening structure, so as to fundamentally control the vertical deformation of the foundation and embankment and solve the disease of vehicle bumping at the bridgehead.

[0007] To solve the technical problems proposed by the present invention, the present invention provides a comprehensive treatment method for solving the hazard of vehicle bumping at the bridgehead of low embankments in soft soil areas, including the following steps:

[0008] 1) Determine the treatment area

[0009] Carry out geological exploration on the road-bridge transition section where vehicle bumping at the bridgehead occurs, determine the area to be treated, clean the pavement structure layer in this area, and evenly arrange the positions of pile holes;

[0010] 2) Drill and take soil

[0011] Drill and take soil according to the positions of pile holes to form pile holes, and place the soil taken from the embankment and foundation separately to obtain embankment soil and foundation soil;

[0012] 3) Prepare fluid soil-cement

[0013] Mix the embankment soil with cement and water to prepare fluid soil-cement for the embankment section, and mix the foundation soil with a dispersant and a curing agent to prepare fluid soil-cement for the foundation section;

[0014] 4) Pour and insert cores to form piles

[0015] Pour the fluid soil-cement for the foundation section into the pile holes, then insert precast reinforced concrete core piles into the pile holes. The top surface of the core piles is flush with the hole openings, keep the core piles vertical, and pour the fluid soil-cement for the embankment section into the pile holes until they are filled to form soil-cement pile composite piles;

[0016] 5) Reconstruct the pavement structure layer

[0017] Lay a honeycomb-shaped pavement strengthening panel made of reinforced concrete casting. The panel is connected with the top of the soil-cement pile composite piles to form a whole strengthening structure, and then lay asphalt mixture until the pavement is flush with the bridge deck.

[0018] In the above solution, the cross-sectional structure of the road-bridge transition section includes a pavement structure layer, an embankment and a foundation from top to bottom, and the thickness of the embankment does not exceed 3.5 m.

[0019] In the above solution, in step 1), when cleaning the pavement structure layer, 0.05 - 1.05 m thickness of the pavement structure layer is reserved, and the rest is removed.

[0020] In the above solution, step 1) also includes arranging a cement-soil mixing pile waterproof curtain at the bottom of the embankment slope. 1-3 rows of waterproof curtains are arranged on each side, and the row spacing is 1.5-2m to prevent the subgrade instability caused by the flow around the piles.

[0021] In the above solution, the aperture of the pile hole is 0.6-0.8m, the hole depth reaches 8-10m below the subgrade, and the hole spacing is 2-3m.

[0022] In the above solution, the fluidized solidified soil in the subgrade section comprises the following raw materials in parts by weight: 60-80 parts of subgrade soil, 20-40 parts of cement, and 12-20 parts of water, and the water-cement ratio is 50-60%.

[0023] In the above solution, the foundation soil is silty clay, the dispersant is the dispersant for premixed fluidized solidified soil disclosed in CN115108751A, and the fluidized solidified soil in the foundation section is the premixed fluidized solidified soil prepared from the foundation soil according to the technical solution disclosed in CN115108751A.

[0024] In the above solution, the fluidized solidified soil in the foundation section is poured to a depth of 1-1.5m below the subgrade.

[0025] In the above solution, the bottom surface of the precast reinforced concrete core pile reaches 1-1.5m below the subgrade.

[0026] In the above solution, the solidified soil cast-in-place pile is cured naturally for 15-40d and then the road surface structure layer is reconstructed.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1) The present invention proposes a comprehensive treatment solution for the pavement structure layer, subgrade and foundation for the problem of vehicle bump at low subgrade transition sections with a thickness of no more than 3.5m in the treatment of deep soft soil foundations without pipe piles lacking a bearing layer. By using the solidified soil cast-in-place pile as the bearing layer of the precast reinforced concrete core pile, the defect of the deep soft soil foundation lacking a stable bearing layer is made up; the composite structure composed of the precast reinforced concrete core pile and the solidified soil cast-in-place pile strengthens the subgrade body, improves the strength and stiffness of the subgrade body, and effectively restricts the deformation of the subgrade body itself; by arranging the cement-soil mixing pile waterproof curtain, the pavement settlement caused by the subgrade structure instability caused by the flow around the piles is prevented; by repairing the pavement, the loss of the pavement structure layer caused by differential settlement is filled; the cast-in-place pile, the reinforced concrete core pile and the pavement base repair structure together constitute a reinforced overall structure, fundamentally controlling the vertical deformation of the foundation and subgrade, and perfectly solving the problem of vehicle bump at the bridgehead.

[0029] 2) All raw materials required for the present invention are taken from the in-situ soil, without the need for additional coarse and fine aggregates. The particle size distribution of the subgrade soil obtained from the pile holes meets the permeability requirements for subgrade drainage, and its particle size distribution is good, and it can be directly mixed with cement to make fluidized solidified soil for backfilling. The foundation soil obtained from the pile holes is silty clay, with poor particle size distribution, high clay content, and high organic matter content. Under the action of ordinary cement solidification slurry, fluidized solidified soil cannot be formed. By adding a patented dispersant, fluidized solidified soil that meets the requirements of injectability is formed. In this way, the soil taking is utilized, which has good environmental protection and economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a longitudinal sectional view of the treatment area of Embodiment 1 of the present invention.

[0031] Figure 2 It is a transverse sectional view of the treatment area of Embodiment 1 of the present invention.

[0032] In the figure: 1, bridge deck; 2, bridge; 3, bridge pier; 4, asphalt mixture; 5, pavement structure layer; 6, subgrade; 7, foundation; 8, pile hole; 9, precast reinforced concrete core pile; 10, embankment slope; 11, waterproof curtain. DETAILED DESCRIPTION OF THE INVENTION

[0033] In order to better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments, but the content of the present invention is not limited to the following embodiments.

[0034] Embodiment 1

[0035] For a mountain-crossing river bridge approach section with the disease of bridge approach bump, the technical solution of the present invention is adopted for treatment, including the following steps:

[0036] 1) Determine the treatment area

[0037] After investigation, the profile structure of the road-bridge transition section with the disease of bridge approach bump includes a pavement structure layer, a subgrade and a foundation from top to bottom. The thickness of the subgrade is 3.2 m, belonging to a deep soft soil foundation with a low subgrade. There is an obvious settlement of about 5 cm on the pavement 10 m away from the bridge head position. Therefore, it is determined to treat the area within 15 m from the bridge head;

[0038] Clean the pavement structure layer in this area, retain 1 m thickness of the pavement structure layer, and remove the rest; at the same time, arrange 2 rows of cement-soil mixing pile waterproof curtains on each side of the bottom of the embankment slope. The first row is arranged at a horizontal distance of 10 m from the top of the slope pavement, and the first row is between the second row and the bottom of the slope. The row spacing between the second row and the first row is 1.5 m; then evenly arrange the pile hole positions in this area, determine the hole diameter to be 0.8 m, the hole depth reaches 10 m below the subgrade, the hole spacing is 3 m, and each row of hole piles is arranged in a nested manner;

[0039] 2) Boring and soil extraction

[0040] Bore and extract soil according to the pile hole positions to form pile holes, and separately place the soil extracted from the subgrade and foundation to obtain subgrade soil and foundation soil;

[0041] 3) Preparation of fluidized solidified soil

[0042] Mix the subgrade soil with cement and water to prepare fluidized solidified soil for the subgrade section. The specific raw material composition is: 80 parts of subgrade soil, 20 parts of cement, and 12 parts of water. The water-cement ratio is 60%. The specific preparation method is: mix the subgrade soil, cement, and water evenly to obtain fluidized solidified soil for the subgrade section;

[0043] Mix the foundation soil with a dispersant and a curing agent to prepare fluidized solidified soil for the foundation section, which is prepared according to the technical solution disclosed in CN 115108751A. The specific preparation method is: mix the foundation soil with the dispersant evenly to obtain a modified muddy cohesive soil slurry; mix the modified muddy cohesive soil slurry with HAS soil curing agent evenly to obtain pre-mixed fluidized solidified soil, which is the fluidized solidified soil for the foundation section. The dispersant is composed of the following raw materials in parts by weight: 9 parts of anti-sticking water agent, 0.6 part of stabilizer, and 90.4 parts of water. The anti-sticking water agent is compounded by sodium pyrophosphate and amino sulfonic acid-based water reducer ASP in a ratio of 2:1, and the stabilizer is phosphite; the dosage of the dispersant is 6% of the mass of the foundation soil; the dosage of HAS soil curing agent is 20% of the mass of the modified muddy cohesive soil slurry;

[0044] 4) Grouting and inserting core piles to form piles

[0045] Pour the fluidized solidified soil for the foundation section into the pile holes. Stop pouring when it reaches 1.5 m below the subgrade. Then insert a precast reinforced concrete core pile with a diameter of 0.2 m into the pile hole. The bottom surface of the core pile reaches 1.5 m below the subgrade, and the top surface of the core pile is flush with the hole opening. Keep the core pile vertical, and pour the fluidized solidified soil for the subgrade section into the pile hole until it is full to form a solidified soil grouting composite pile;

[0046] 5) Reconstruct the pavement structure layer

[0047] After the solidified soil grouting composite pile is naturally cured for 28 d, lay a honeycomb-shaped pavement strengthening panel made of reinforced concrete casting. The panel is connected to the top of the solidified soil grouting composite pile to form an integral strengthening structure, and then lay asphalt mixture until the pavement is flush with the bridge deck.

[0048] After the pavement and bridge deck are leveled, the vehicle can pass. Subsequently, detect the pavement settlement every three days to observe whether the pavement settles. After 40 days of detection, the bridge head bumping disease no longer occurs.

[0049] Example 2

[0050] A bridgehead bumping disease occurred in the transition section of a river-crossing bridge in a certain area of Hunan. The technical solution of the present invention was adopted for treatment, including the following steps:

[0051] 1) Determine the treatment area

[0052] After investigation, the profile structure of the road and bridge transition section where the bridgehead bumping disease occurred includes a pavement structure layer, a subgrade, and a foundation from top to bottom. The thickness of the subgrade is 2.8m, belonging to a deep soft soil foundation with a low subgrade. Obvious settlement occurred on the pavement 8m away from the bridgehead position, and the settlement height is about 6cm. Therefore, it was determined to treat the area within 10m from the bridgehead;

[0053] Clean the pavement structure layer in this area, retain a thickness of 0.65m of the pavement structure layer, and remove the rest; at the same time, arrange 1 row of cement-soil mixing pile waterproof curtains on each side at the bottom of the embankment slope, which are arranged at a horizontal distance of 8m from the top of the slope pavement; then evenly arrange the pile hole positions in this area, determine the hole diameter to be 0.6m, the hole depth to reach 8m below the subgrade, the hole spacing to be 2.5m, and each row of hole piles is arranged in a nested manner;

[0054] 2) Drill and take soil

[0055] Drill and take soil according to the pile hole positions to form pile holes, and place the soil taken from the subgrade and the foundation separately to obtain subgrade soil and foundation soil;

[0056] 3) Prepare fluidized solidified soil Mix the subgrade soil with cement and water to prepare subgrade-section fluidized solidified soil. The specific raw material composition is: 70 parts of subgrade soil, 30 parts of cement, and 16.5 parts of water, and the water-cement ratio is 55%. The specific preparation method is: mix the subgrade soil, cement, and water evenly to obtain subgrade-section fluidized solidified soil;

[0057] Mix the foundation soil with a dispersant and a curing agent to prepare foundation-section fluidized solidified soil, which is prepared according to the technical solution disclosed in CN 115108751A. The specific preparation method is: mix the foundation soil with the dispersant evenly to obtain the improved silt-like cohesive soil slurry; mix the improved silt-like cohesive soil slurry with HAS soil curing agent evenly to obtain the premixed fluidized solidified soil, which is the foundation-section fluidized solidified soil; the dispersant is composed of the following raw materials in parts by weight: 9 parts of anti-sticking water agent, 0.6 parts of stabilizer, and 90.4 parts of water; the anti-sticking water agent is compounded by sodium pyrophosphate and amino sulfonic acid-based water reducer ASP in a ratio of 2:1, and the stabilizer is phosphite; the dosage of the dispersant is 6% of the mass of the foundation soil; the dosage of HAS soil curing agent is 20% of the mass of the improved silt-like cohesive soil slurry;

[0058] 4) Pour and insert cores to form piles

[0059] Pour the fluidized solidified soil in the foundation section into the pile hole. Stop pouring when it reaches 1.3 m below the subgrade. Then insert a precast reinforced concrete core pile with a diameter of 0.15 m into the pile hole. The bottom surface of the core pile reaches 1.3 m below the subgrade, and the top surface of the core pile is flush with the hole opening. Keep the core pile vertical. Pour the fluidized solidified soil in the subgrade section into the pile hole until it is full to form a solidified soil poured composite pile.

[0060] 5) Reconstruct the pavement structure layer

[0061] After the solidified soil poured composite pile is naturally cured for 28 days, lay a honeycomb pavement strengthening panel made of reinforced concrete casting. The panel is connected to the top of the solidified soil poured composite pile to form an integral strengthening structure. Then lay asphalt mixture until the pavement is flush with the bridge deck.

[0062] After the pavement and the bridge deck are leveled, the road can be opened to traffic. Subsequently, detect the pavement settlement every three days to observe whether the pavement settles. After 40 days of detection, the disease of bump at bridge head does not occur again.

[0063] The above embodiments are merely examples clearly described and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. Therefore, the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A comprehensive treatment method for solving the hazard of vehicle bumping at the bridgehead with low subgrade in soft soil areas, characterized in that, The following steps are involved: 1) Determine the governance area Conduct geological surveys on the road-bridge transition section where the bridgehead jump disease occurs, determine the area that needs to be treated, clean the pavement structure layer in the area, and evenly arrange the pile hole positions; 2) Drilling and soil extraction Drill holes and take soil according to the pile hole positions to form pile holes, and separate the soil taken from the roadbed and the foundation to obtain roadbed soil and foundation soil; 3) Make fluidized solidified soil The roadbed soil is mixed with cement and water to form fluidized solidified soil for the roadbed section, and the foundation soil is mixed with a dispersant and a solidifying agent to form fluidized solidified soil for the foundation section; 4) Casting and inserting piles The fluidized solidified soil of the foundation section is poured into the pile hole, and then the prefabricated reinforced concrete core pile is inserted into the pile hole, the top surface of the core pile is flush with the hole mouth, the core pile is kept vertical, and the fluidized solidified soil of the roadbed section is poured into the pile hole until it is filled, forming a solidified soil poured composite pile; 5) Reconstruction of pavement structure layer A honeycomb pavement reinforcement panel made of reinforced concrete is laid, and the panel is connected to the top of the solidified soil cast-in-place composite pile to form an overall reinforced structure. Then asphalt mixture is laid until the road surface is flush with the bridge deck.

2. The comprehensive treatment method for solving the problem of vehicle bump at bridgeheads with low roadbeds in soft soil areas according to claim 1, characterized in that, The cross-sectional structure of the road-bridge transition section includes a pavement structure layer, a roadbed and a foundation from top to bottom, and the thickness of the roadbed does not exceed 3.5m.

3. The comprehensive treatment method for solving the problem of vehicle bump at bridgeheads with low roadbeds in soft soil areas according to claim 1, characterized in that, In step 1), when cleaning the pavement structure layer, retain 0.05-1.05m thickness of the pavement structure layer and remove the rest.

4. The comprehensive treatment method for solving the problem of vehicle bumping at the bridgehead with low subgrade in soft soil areas according to claim 1, characterized in that, Step 1) also includes laying out cement-soil mixing pile waterproof curtains at the bottom of the embankment slope, with 1-3 rows of waterproof curtains arranged on each side, with a row spacing of 1.5-2m, to prevent roadbed instability caused by flow around the piles.

5. The comprehensive treatment method for solving the problem of vehicle bump at bridgeheads with low roadbeds in soft soil areas according to claim 1, characterized in that, The diameter of the pile hole is 0.6-0.8m, the hole depth reaches 8-10m below the roadbed, and the hole spacing is 2-3m.

6. The comprehensive treatment method for solving the problem of vehicle bump at bridgeheads with low roadbeds in soft soil areas according to claim 1, characterized in that, The fluidized solidified soil of the roadbed section comprises the following raw materials in parts by weight: 60-80 parts of roadbed soil, 20-40 parts of cement, 12-20 parts of water, and a water-cement ratio of 50-60%.

7. The comprehensive treatment method for solving the problem of vehicle bump at bridgeheads with low roadbeds in soft soil areas according to claim 1, characterized in that, The foundation soil is silty clay soil, and the foundation section fluidized solidified soil is premixed fluidized solidified soil prepared by preparing the foundation soil according to the technical solution disclosed in CN115108751A.

8. The comprehensive treatment method for solving the problem of vehicle bump at bridgeheads with low roadbeds in soft soil areas according to claim 1, characterized in that, The fluidized solidified soil of the foundation section is poured to 1-1.5 m below the roadbed.

9. The comprehensive treatment method for solving the problem of vehicle bump at bridgeheads with low subgrades in soft soil areas according to claim 1, characterized in that, The bottom surface of the prefabricated reinforced concrete core pile reaches 1-1.5m below the roadbed.

10. The comprehensive treatment method for solving the problem of vehicle bumping at the bridgehead with low subgrade in soft soil areas according to claim 1, characterized in that, The pavement structure layer is reconstructed after the solidified soil cast-in-place composite piles are naturally cured for 15-40 days.

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