Steep slope abutment foam light soil structure and construction method thereof

Abstract

The invention relates to a steep slope abutment foam light soil structure and a construction method thereof. The construction method comprises the following steps that S1, abutment body construction of a frame type abutment is completed on a steep slope site; s2, excavation is conducted on the original slope surface below the frame type bridge abutment to form multiple stages of steps; s3, a panel foundation is constructed on the multiple steps, a concrete panel which is enclosed in the circumferential direction is poured upwards on the panel foundation, and an under-platform space with the top open is formed; the foam light soil is converted into a structural bearing component from a common filler, meanwhile, the concrete panel serves as a permanent supporting structure, a stress system of the abrupt slope bridge abutment is reconstructed, traditional complex and expensive anti-sliding measures such as anti-sliding piles and back pressure protection ways are fundamentally replaced, and the construction cost is reduced through the simple and efficient technology. The core problem of slippage instability of the abrupt slope bridge abutment is economically and reliably solved, and support-free construction is achieved.

Description

Foamed lightweight soil structure for steep slope bridge abutments and its construction method Technical Field

[0001] This invention relates to the field of bridge engineering construction technology, specifically to a foamed lightweight soil structure for steep slope bridge abutments and its construction method. Background Technology

[0002] In the construction of bridges in mountainous areas, it is often necessary to build frame-type bridge abutments on steep slopes.

[0003] Traditional construction methods face severe challenges on steep slopes (slope > 30°): the backfill behind the abutment generates enormous horizontal earth pressure in an unfavorable direction on the steep slope, which can easily cause the abutment structure located on the steep slope to slide and become unstable along the slope. To resist this sliding force, the conventional approach is to deepen or strengthen the abutment pile foundation, set up a huge anti-sliding structure behind the abutment (such as counterweight retaining wall or earthwork), or carry out complex treatment of the foundation. These measures are not only large in scale, expensive, and have a long construction period, but their long-term anti-sliding reliability is still questionable on steep slopes with complex soil and rock conditions (such as the presence of weak interlayers), and cannot fundamentally, economically, and effectively solve the core problem of sliding stability of bridge abutments on steep slopes. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art and provide a foamed lightweight soil structure for steep slope bridge abutments and its construction method, thereby solving the problem of slope slippage and instability of frame bridge abutments on steep slopes caused by soil pressure behind the abutment.

[0005] To achieve the above objectives, this invention provides a construction method for a foamed lightweight soil structure for steep slope bridge abutments, applicable to steep slope sites with a slope greater than 30°. The construction method includes the following steps: S1, completing the abutment body construction of a frame-type bridge abutment on the steep slope site; S2, excavating to form multi-level steps on the original slope surface below the frame-type bridge abutment; S3, constructing a panel foundation on the multi-level steps, and pouring a circumferentially enclosed concrete panel upwards on the panel foundation to form an open-topped space under the abutment; S4, pouring foamed lightweight soil in layers into the space under the abutment until its top surface reaches the design bottom elevation of the cast-in-place bridge panel; S5, using the solidified foamed lightweight soil as a permanent load-bearing foundation, directly constructing the cast-in-place bridge panel on its top surface; S6, backfilling the abutment back area.

[0006] By adopting this technical solution, foamed lightweight soil is transformed from ordinary filler into structural load-bearing components. At the same time, concrete panels are used as permanent retaining structures, reconstructing the stress system of steep slope bridge abutments. This fundamentally replaces traditional complex and expensive anti-slip measures such as anti-slip piles and counterweight retaining walls. With a simple and efficient process, it economically and reliably solves the core problem of slippage and instability of steep slope bridge abutments and realizes scaffold-free construction.

[0007] Furthermore, step S2 also includes laying geotextile materials in the multi-step area formed by excavation.

[0008] By adopting this technical solution, the integrity between the excavated step surface and the newly poured concrete panel foundation is enhanced, preventing the problem of local spalling of the soil and rock mass on the step surface during construction or use.

[0009] Furthermore, in step S3, a gap is reserved between the concrete panel and the abutment body of the frame bridge.

[0010] By adopting this technical solution, the gap allows for relative displacement between the two under load and temperature changes, avoiding the direct transmission of the deformation or settlement of the abutment itself to the concrete panel, thereby effectively preventing the concrete panel from cracking and being damaged due to forced deformation.

[0011] Furthermore, in step S3, the circumferentially enclosed concrete panel as a whole spans at least two pile foundations under the frame abutment body.

[0012] By adopting this technical solution, the concrete panel is transformed from an isolated baffle into a lateral connection structure that connects multiple abutment pile foundations. This effectively disperses the soil pressure behind the abutment to multiple support points, significantly improving the stability and integrity of the entire abutment-panel composite against lateral slippage.

[0013] Furthermore, in step S4, when pouring the foamed lightweight soil in layers, the pouring height of a single layer shall not exceed 1 meter.

[0014] By adopting this technical solution, the internal quality and uniformity of the foamed lightweight soil casting body are ensured.

[0015] Furthermore, in step S6, the filler material for backfilling the abutment is tightly adhered to and compacted against the back of the concrete panel.

[0016] By adopting this technical solution, it is ensured that the backfill soil is in close contact with the back of the concrete panel and forms a stable support.

[0017] The present invention also provides a construction method for a foamed lightweight soil structure for a steep slope bridge abutment, comprising: a frame abutment built on a steep slope foundation; a concrete panel disposed on the slope side below the frame abutment, enclosing an open-topped space below the abutment; a foamed lightweight soil filler filling the space below the abutment, with a flat top surface; and a cast-in-place bridge deck directly cast on the top surface of the foamed lightweight soil filler; wherein the foamed lightweight soil filler serves as the permanent load-bearing foundation for the cast-in-place bridge deck.

[0018] By adopting this technical solution, the traditional external load is transformed into an internally controllable transmission path, and the heavy foundation is replaced with a lightweight load-bearing body, thus permanently eliminating the risk of steep slope landslides from a physical structure perspective.

[0019] Furthermore, a gap is provided between the concrete panel and the frame abutment.

[0020] By adopting this technical solution, it is ensured that no harmful internal forces are transmitted between the bridge abutment and the concrete panel during long-term use of the finished structure. This is a key structural feature that maintains the long-term durability and functional independence of the composite structure.

[0021] Furthermore, the back of the concrete panel forms the support surface for the backfill soil of the abutment.

[0022] By adopting this technical solution, it was confirmed that the concrete panel is not only a retaining formwork, but also an active load-bearing component. It directly bears and transmits the lateral pressure of the backfill soil to the stable foundation. It is the physical carrier and functional embodiment of the core idea of ​​using support to resist sliding, making the anti-sliding mechanism of the entire structure clear and reliable.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. The soil behind the abutment, which is traditionally used as a load, is replaced by a combination of lightweight materials with structural functions and concrete panels. The concrete panels not only enclose the pouring space, but also directly serve as a retaining structure to resist the soil pressure behind the abutment, thereby significantly reducing the active load that pushes the abutment to slide from the root. At the same time, the solidified foamed lightweight soil serves as the permanent foundation of the bridge panel. Its self-weight is extremely light, which further reduces the sliding force and forms an integral whole with the bridge panel, enhancing the overall stability of the abutment area.

[0024] 2. No need to add large anti-slide piles or complex counter-pressure structures. The construction is simple, the cycle is short and the cost is low. It fundamentally and economically solves the problem of anti-slide stability of steep slope bridge abutments, and also solves the problems of difficult traditional support erection and poor adaptability to uneven foundation settlement. Attached Figure Description

[0025] Figure 1 is a flowchart illustrating the construction method of the foamed lightweight soil structure for steep slope bridge abutments according to the present invention; Figure 2 is a front sectional view of the foamed lightweight soil structure for steep slope bridge abutments according to the present invention; Figure 3 is a partial structural diagram of the foamed lightweight soil structure for steep slope bridge abutments according to the first side view direction according to the present invention; Figure 4 is a partial structural diagram of the foamed lightweight soil structure for steep slope bridge abutments according to the second side view direction according to the present invention.

[0026] Explanation of the attached diagram labels: 1. Original slope; 2. Pile foundation; 3. Abutment; 4. Cast-in-place bridge deck; 5. Multi-level steps; 6. Panel foundation; 7. Concrete panel; 8. Foamed lightweight soil. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0028] Please refer to Figures 1-4. This invention provides a foamed lightweight soil structure for steep slope bridge abutments, and its construction method is as follows: S1. On a steep slope site with a slope greater than 30°, the foundation construction of the frame bridge abutment is completed according to the design. The foundation construction includes the construction of the abutment body 3. It should be noted that the frame bridge abutment is usually composed of three parts: the abutment body 3, the pile foundation 2, and the cast-in-place bridge deck 4. The foundation construction includes the construction of the pile foundation 2 and the abutment body 3.

[0029] S2. On the original slope 1 below the frame abutment, excavation is carried out to form multi-level steps 5; the size of the multi-level steps 5 is determined according to the soil quality and stability calculation; in another preferred embodiment, in order to enhance the bonding between the old and new soil and prevent local peeling of the step surface, geogrids and other geotechnical materials can be laid on the formed multi-level steps 5.

[0030] S3. Concrete strip foundations are poured on the prepared multi-level steps 5 as panel foundations 6. Based on this, concrete panels 7 are poured upwards using formwork. The concrete panels 7 are poured around the inner side of the abutment body 3 in a circumferential manner, ultimately forming a container-shaped space under the abutment with its top open to the predetermined direction of the cast-in-place bridge panel 4. To ensure clear structural stress, the top of the concrete panels 7 should be poured to a height close to the predetermined bottom surface of the cast-in-place bridge panel 4. Crucially, a certain width (e.g., 5cm) of gap should be reserved between the concrete panels 7 and the abutment body 3 of the frame abutment. This gap can be filled with flexible material. Its purpose is to allow the concrete panels 7 to bear the load independently, avoiding the direct transfer of the load of the frame abutment to the concrete panels 7, which would cause cracking. It should be noted that, to enhance the overall integrity, the design of the concrete panels 7 should ensure that its overall structure spans at least the two pile foundations 2 under the abutment body 3, forming an effective lateral connection and a thrust-resistant plane.

[0031] S4. After the space under the abutment is formed, foamed lightweight soil 8 can be poured into it in layers. Foamed lightweight soil 8 is made of cement, foaming agent, water and other materials. It has the characteristics of light density (usually 5-12kN / m³), good fluidity and strong self-support. When pouring, the thickness of a single layer should be controlled, preferably not exceeding 1 meter, to ensure the pouring quality and curing effect. Pour in layers until the top surface of the foamed lightweight soil 8 filler reaches the bottom surface elevation of the designed cast-in-place bridge deck 4, and then level it.

[0032] S5. Once the foamed lightweight soil 8 filler has cured to the design strength, it will have sufficient load-bearing capacity. At this point, there is no need to build complex temporary supports on the steep slope. Reinforcing bars can be tied directly on the flat top surface of the foamed lightweight soil 8 filler, formwork can be erected, and concrete can be poured to form the cast-in-place bridge deck 4. In this system, the cured foamed lightweight soil 8 filler serves as the permanent load-bearing foundation of the cast-in-place bridge deck 4.

[0033] S6. Backfill the abutment back area. During backfilling, qualified fill material should be selected, and it should be ensured that the fill material is tightly adhered to the back of the concrete panel 7 and compacted in layers. At this time, the back of the concrete panel 7 directly constitutes a permanent support surface for the abutment backfill, actively bearing the earth pressure behind the abutment and transferring it to the stable step foundation and the panel itself, thereby effectively preventing the earth pressure from pushing the frame abutment down the slope. The present invention has been described in detail above with reference to the accompanying drawings and embodiments. Those skilled in the art can make various modifications to the present invention based on the above description. Therefore, certain details in the embodiments should not be construed as limiting the present invention, and the scope of protection of the present invention shall be defined by the appended claims.

Claims

1. A construction method for a foamed lightweight soil structure for steep slope bridge abutments, applicable to steep slope sites with a slope greater than 30°, characterized in that, The construction method includes the following steps: S1, completing the abutment body construction on a steep slope site; S2, excavating the original slope surface below the frame abutment to form multi-level steps; S3, constructing the panel foundation on the multi-level steps, and pouring a circumferentially enclosed concrete panel upwards on the panel foundation to form an open-top space under the abutment; S4, pouring foamed lightweight soil in layers into the space under the abutment until its top surface reaches the design bottom elevation of the cast-in-place bridge panel; S5, using the solidified foamed lightweight soil as a permanent load-bearing foundation, directly constructing the cast-in-place bridge panel on its top surface; S6, backfilling the abutment back area.

2. The construction method of the foamed lightweight soil structure for steep slope bridge abutments according to claim 1, characterized in that: Step S2 also includes laying geotextile materials in the multi-step area formed by excavation.

3. The construction method of the foamed lightweight soil structure for steep slope bridge abutments according to claim 1, characterized in that: In step S3, a gap is reserved between the concrete panel and the abutment body of the frame bridge.

4. The construction method of the foamed lightweight soil structure for steep slope bridge abutments according to claim 1, characterized in that: In step S3, the circumferentially enclosed concrete panel as a whole spans at least two pile foundations under the frame abutment.

5. The construction method of the foamed lightweight soil structure for steep slope bridge abutments according to claim 1, characterized in that: In step S4, when pouring the foamed lightweight soil in layers, the pouring height of a single layer shall not exceed 1 meter.

6. The construction method of the foamed lightweight soil structure for steep slope bridge abutments according to claim 1, characterized in that: In step S6, the filler material for backfilling the abutment is tightly adhered to and compacted against the back of the concrete panel.

7. A foamed lightweight soil structure for steep slope bridge abutments constructed using the construction method described in any one of claims 1-6, characterized in that, include: The frame abutment is built on a steep slope foundation; the concrete panel is set on the slope side below the frame abutment and encloses an open-top space below the abutment. Foamed lightweight soil filler is used to fill the space under the platform, and its top surface is flat. The cast-in-place bridge deck is directly poured onto the top surface of the foamed lightweight soil filler; the foamed lightweight soil filler serves as the permanent load-bearing foundation of the cast-in-place bridge deck.

8. The foamed lightweight soil structure for steep slope bridge abutments according to claim 7, characterized in that: There is a gap between the concrete panel and the frame abutment.

9. The foamed lightweight soil structure for steep slope bridge abutments according to claim 7, characterized in that: The back of the concrete panel forms the support surface for the backfill soil.

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