A composite retaining wall structure of foamed lightweight soil and reinforced grid

Abstract

This utility model discloses a combined retaining wall structure of foamed lightweight soil and reinforced geogrid, belonging to the field of geotechnical support technology. The structure includes: a foamed lightweight soil wall structure located on the free side, and a reinforced geogrid reinforcement zone located behind it. The foamed lightweight soil wall structure is cast-in-place and can be vertical; the reinforced geogrid reinforcement zone consists of multiple layers of horizontally laid reinforced geogrids and interlayer filler, with the reinforced geogrids connected to the foamed lightweight soil wall structure. This utility model utilizes the self-supporting and plasticity of foamed lightweight soil to achieve steep or vertical walls, solving the problem of limited slope in traditional reinforced soil retaining walls; simultaneously, its lightweight and low compressibility significantly reduces the structure's self-weight and wall compression, effectively controlling wall top settlement. This utility model features a stable structure and convenient construction, making it particularly suitable for projects with limited land and high requirements for settlement control.

Description

Technical Field

[0001] This utility model belongs to the field of geotechnical engineering and building engineering technology, specifically relating to a new type of retaining wall structure, particularly a combined reinforced retaining wall that can achieve steep or vertical walls and effectively control top settlement. Background Technology

[0002] Against the backdrop of my country's ongoing infrastructure construction, the performance requirements for slope protection structures in fields such as construction, highways, railways, municipal works, and water conservancy are constantly increasing. Reinforced soil retaining walls, as a classic form of slope protection, have long been widely used in various projects due to their core advantages, including relatively low cost, simple construction process, regular appearance, and good adaptability to foundation deformation. Their structural system mainly consists of three parts: a panel for load-bearing and enclosure, reinforcing materials providing tensile bearing capacity (common types include steel strips, geogrids, and polymer synthetic reinforcing strips), and backfill material. The basic working principle involves laying high-tensile-strength, durable reinforcing materials within the soil. Through the friction and interlocking effect between the reinforcing materials and the backfill particles, as well as the tensile constraint of the reinforcing materials themselves, the dispersed soil particles are integrated into a composite soil structure with overall load-bearing capacity, thereby effectively resisting lateral earth pressure and achieving stable slope protection.

[0003] However, with the accelerated pace of urbanization, land resources in urban built-up areas are becoming increasingly scarce. Various engineering projects are gradually extending to mountainous and hilly areas, as well as areas for the renovation and expansion of existing projects. The technical limitations of traditional reinforced soil retaining walls are becoming increasingly apparent in practical applications, making it difficult to meet the engineering needs under complex conditions. Firstly, regarding wall slope design, due to the structural mechanical characteristics of traditional panel types (such as precast concrete modules, gabion boxes, and geotextile-wrapped panels) and the physical and mechanical parameters of the fill material itself, such as the internal friction angle and cohesion, it is generally difficult to achieve a steep slope in traditional reinforced soil retaining walls. According to current industry standards and engineering practice, the recommended slope ratio is generally controlled within 70 degrees, and under special geological conditions, it may even need to be reduced to below 60 degrees, making it almost impossible to achieve the design goal of a 90-degree vertical or near-vertical wall. This deficiency greatly limits the engineering applicability of reinforced soil retaining walls in road widening and reconstruction (where slope protection needs to be achieved within a limited space to avoid occupying existing buildings or road land), mountain highway and railway construction (where the terrain is narrow and the limited space needs to be maximized for the layout of lines and support structures), and urban municipal engineering (such as underground utility tunnel perimeter support, temporary support for building foundation pits, and other scenarios where land height is limited). It even prevents them from being applied in some key projects.

[0004] Secondly, regarding settlement control performance, reinforced soil retaining walls, as typical flexible support structures, have always faced significant challenges and concerns in the engineering field regarding post-construction settlement and uneven settlement. From the perspective of settlement mechanisms, the main causes are two core aspects: Firstly, under long-term self-weight loads and additional loads from above (such as vehicle loads and building loads), the backfill material undergoes continuous compaction and creep deformation. This is especially true when using granular backfill materials such as sandy soil or gravelly soil, where the pores between particles gradually compress, leading to overall wall subsidence. Secondly, the weight of the entire retaining wall structure and the load from above are transferred to the foundation, generating additional stress. If the foundation soil is soft soil, silty clay, or other highly compressible soil layers, it easily triggers consolidation settlement, and the settlement process is prolonged and difficult to control effectively. When the top area of ​​a retaining wall is used in settlement-sensitive scenarios such as high-grade highways (e.g., expressways, urban expressways), urban arterial roads, large parking lots, or building foundations, significant post-construction settlement (generally requiring post-construction settlement of the roadbed of high-grade highways to not exceed 15cm, and uneven settlement not exceeding 1%) and uneven settlement can directly damage the integrity and performance of the top structure. For example, it can lead to defects such as road surface cracks, settlement depressions, and bridge approach slabs, as well as cracks in building walls and tilting of foundations. This not only seriously affects traffic safety and building safety but also requires high post-construction maintenance costs for repair, significantly increasing the economic cost of the entire project lifecycle.

[0005] To address the aforementioned shortcomings of traditional reinforced soil retaining walls, the engineering community has experimented with rigid retaining walls as an alternative in some projects. Common types include gravity retaining walls, cantilever retaining walls, and buttress retaining walls. These rigid retaining walls, leveraging the mechanical advantages of their rigid structure, can easily achieve 90-degree vertical wall designs, effectively solving land use constraints and demonstrating superior settlement control. However, rigid retaining walls have significant drawbacks: firstly, gravity retaining walls rely on their massive self-weight for stability, resulting in large wall cross-sectional dimensions and high material consumption; while cantilever and buttress retaining walls, although reducing material consumption through structural optimization, still require a heavy foundation structure. Both types of retaining walls have extremely high requirements for the bearing capacity of the foundation. If the bearing capacity of the foundation soil is insufficient, it is necessary to set up enlarged foundations, replacement layers, or even pile foundations for treatment, which leads to a significant increase in project cost (usually 30%-50% higher than the cost of traditional reinforced soil retaining walls). Secondly, the construction process of rigid retaining walls is complex, requiring a large amount of formwork support, concrete pouring and curing work, resulting in a long construction cycle (20%-40% longer than the construction cycle of traditional reinforced soil retaining walls). Moreover, the construction difficulty is significantly increased under complex terrain conditions, making it difficult to meet the requirements of economic efficiency and timeliness in engineering construction.

[0006] In summary, given the current comprehensive demands of infrastructure construction for support structures that offer "high space utilization, precise settlement control, excellent economy, and convenient construction," developing a new type of retaining wall technology that can overcome the slope limitations of traditional reinforced soil retaining walls to achieve steep or even vertical wall designs, while retaining the core advantages of flexible retaining walls—such as affordability and strong adaptability to foundation deformation—and possessing excellent settlement control performance, has become a key technical challenge that urgently needs to be solved in the field of geotechnical engineering. This technology is of great significance for promoting high-quality development of infrastructure construction. Utility Model Content

[0007] The purpose of this invention is to provide a combined retaining wall structure of foamed lightweight soil and reinforced grid to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, this utility model provides the following technical solution: A combined retaining wall structure of foamed lightweight soil and reinforced grid includes: a foamed lightweight soil wall structure 1 and a reinforced grid reinforcement zone 9; The foamed lightweight soil wall structure 1 is located on the outermost side of the entire retaining wall structure, i.e., the side facing the open space. The side of the foamed lightweight soil wall structure 1 facing the open space has one or more steps, which increase from bottom to top, forming an inverted trapezoid. The foamed lightweight soil wall structure 1 also includes: foundation 4 and transverse gravel drainage ditch 8 inside the retaining wall. The foundation 4 is located at the bottom of the foamed lightweight soil wall structure 1. The transverse gravel drainage ditch 8 inside the retaining wall is distributed in multiple layers throughout the entire combined retaining wall structure and penetrates the reinforced grid reinforcement area 9 of the foamed lightweight soil wall structure 1. The reinforced grid reinforcement zone 9 is located behind the foamed lightweight soil wall structure and forms a close contact with it; the reinforced grid reinforcement zone 9 also includes: reinforced grid 2 and filler 3, wherein the reinforced grid 2 is laid horizontally within the reinforced grid reinforcement zone 9; The filler 3 is filled between the layers of reinforced grids in the reinforced grid reinforcement zone.

[0009] Preferably, the foamed lightweight earthen wall structure 1 is an inverted right trapezoid, and its free surface is formed into a plane perpendicular to the ground.

[0010] Preferably, the end of the reinforced grid 2 near the free surface extends to and is anchored at the interface between the foamed lightweight soil wall structure 1 and the reinforced grid reinforcement zone 9; the end near the soil extends to and is anchored in the stable soil, and its setting direction is horizontal with the ground.

[0011] Preferably, the end of the reinforced grid 2 near the free surface extends into the interior of the foamed lightweight soil wall structure to ensure effective connection and mechanical transfer between the two; the end near the soil extends and is anchored in the stable soil, with its setting direction horizontal to the ground.

[0012] Preferably, the transverse gravel drainage ditch 8 inside the retaining wall is oriented horizontally to the ground, and the multi-layered and uniformly penetrating foam lightweight soil wall structure 1 is reinforced with a grid reinforcement zone 9.

[0013] Preferably, it also includes: a top wall load 5, a bottom wall 7, and a ground surface at the top of the slope behind the wall 6; the bottom wall 7 is the part of the combined retaining wall structure that extends to the ground; the top wall load 5 and the ground surface at the top of the slope behind the wall are located at the top of the entire combined retaining wall structure and serve as an enclosure.

[0014] A composite retaining wall structure of foamed lightweight soil and reinforced geogrid, the construction method of which includes: Perform foundation treatment and construct foundation 4; The construction method is carried out in layers. The construction of each layer includes: first, pouring the foam lightweight soil wall structure 1 of the thickness of the layer, and then laying a layer of reinforced grid 2 behind the foam lightweight soil wall structure 1. c) Backfill material 3 above the reinforced grid 2 laid in this layer and compact it so that the height of the fill material is flush with the height of the foamed lightweight soil wall structure 1 in this layer. d) Repeat steps b) and c) until the total height of the retaining wall design is reached.

[0015] Preferably, the construction method also includes, after the total height of the retaining wall design is reached, using a concrete capping beam to enhance the overall integrity, forming the wall top load 5 and the ground surface 6 at the top of the slope behind the wall.

[0016] Preferably, in step b), when pouring the foamed lightweight soil, a template is set on one side of its free face, and the template is removed or retained after the foamed lightweight soil reaches the predetermined strength.

[0017] Preferably, the height of each step of the foamed lightweight soil wall structure 1 is 1.0 m to 3.5 m, and the width of the step is 1.0 m to 3.5 m; the dry bulk density of the foamed lightweight soil used is preferably 500 kg / m³ to 1000 kg / m³.

[0018] Compared with the prior art, the beneficial effects of this utility model are: 1. Overcoming Slope Limitations and Saving Valuable Land: This utility model utilizes the excellent self-supporting properties and construction flexibility of foamed lightweight soil to easily achieve steep or even vertical walls that are difficult to achieve with traditional reinforced soil retaining walls. This is revolutionary for projects with limited land, such as those in urban centers and mountain roads, and can maximize the use of land resources.

[0019] 2. Eradicates persistent settlement and reduces maintenance costs: This invention significantly reduces the self-weight of the retaining wall by using lightweight foamed soil, thereby substantially reducing the additional stress on the foundation and long-term consolidation settlement. Simultaneously, the foamed lightweight soil itself, after hardening, becomes a rigid material with extremely low compressibility, eliminating the wall's own compressive settlement. This dual effect effectively ensures the long-term smoothness and stability of the road or building atop the wall, greatly reducing subsequent maintenance and repair costs.

[0020] 3. The structure boasts a rational stress distribution and ensures safety and reliability: The foamed lightweight soil wall structure features multiple inverted trapezoidal steps from bottom to top, precisely opposite to the direction of soil sloping downhill. This stepped geometry enhances the vertical shielding against soil slumping, reducing horizontal and downward forces on the combined foamed lightweight soil and reinforced grid retaining wall structure, resulting in greater structural stability. The foamed lightweight soil wall primarily serves to enclose, constrain, and construct the geometric shape, while the main soil pressure is borne by the reinforced grid-fill composite behind it. This clear and rational stress distribution pattern, with its internal and external separation and coordinated operation, guarantees the safety and stability of the entire structure.

[0021] 4. Optimized construction process, high efficiency and environmental protection: The pumping and pouring process of foamed lightweight soil achieves mechanization and automation of construction, resulting in high speed and low labor intensity. Its assembly line operation mode with reinforcement and filling processes can significantly shorten the overall project duration. Furthermore, the production process of foamed lightweight soil can utilize a large amount of industrial waste such as fly ash, aligning with green and environmentally friendly engineering concepts. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the combined retaining wall structure of foamed lightweight soil and reinforced grid of this utility model.

[0023] Figure 2 This is a horizontal cross-sectional view of the combined retaining wall structure of foamed lightweight soil and reinforced grid of this utility model.

[0024] Figure 3 This is a functional area division diagram of the combined retaining wall structure of foamed lightweight soil and reinforced grid of this utility model.

[0025] In the diagram: 1-Foam lightweight soil structure; 2-Reinforced grid; 3-Fill material; 4-Foundation; 5-Roof load; 6-Ground surface at the top of the slope behind the wall; 7-Bottom of the retaining wall; 8-Transverse gravel drainage ditch inside the retaining wall; 9-Reinforced grid reinforcement zone. Detailed Implementation

[0026] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0027] A construction method for a combined retaining wall structure of foamed lightweight soil and reinforced geogrid includes the following core steps: (a) Foundation Treatment: Excavate the foundation trench according to the design requirements, remove debris, level the foundation and compact it to the specified compaction degree. If the bearing capacity of the foundation is insufficient, necessary foundation treatments such as replacement and dynamic compaction are required. Then pour a layer of concrete or crushed stone as the foundation of the retaining wall.

[0028] (b) Construction of the first layer structure: On the foundation, erect formwork of the first layer pouring height along the open side of the retaining wall. Then, pour foamed lightweight soil into the formwork by pumping or on-site mixing to form the first layer wall structure. After the foamed lightweight soil reaches a certain initial strength, such as being able to stand on its own after initial setting, lay the first layer of reinforced grid horizontally behind it along the design elevation.

[0029] (c) Backfilling of the first layer of fill material: On top of the first layer of reinforced grid that has been laid, backfill material is backfilled in layers and compacted to the specified density using small compaction machinery until the backfill height is flush with the top surface of the first layer of foamed lightweight soil wall. Usually, well-graded and easy-to-compact conventional road construction materials such as sandy soil and gravelly soil are used to fill between the layers of reinforced grid in the reinforced grid reinforcement zone, forming a tight interlock with the reinforced grid and working together.

[0030] (d) Repeated construction: On the top surface of the completed first layer of structure, repeat steps (b) and (c), that is, erect the next layer of formwork, pour foamed lightweight soil, lay reinforced grid, backfill and compact the fill material, and so on, layer by layer upwards, until the total design height of the retaining wall is reached.

[0031] (e) Top Treatment and Maintenance: After the retaining wall is constructed to the top surface, top treatment is carried out according to design requirements, such as installing reinforced concrete capping beams to enhance the overall integrity, or directly laying the road base and surface layers. At the same time, the exposed foamed lightweight soil wall surface is watered for curing to ensure its normal strength development, and surface beautification treatment can be carried out as needed.

[0032] The dry bulk density of the foamed lightweight soil is preferably between 500 kg / m³ and 1000 kg / m³. This density range ensures both significant lightweight effect (approximately one-third that of ordinary fill) and sufficient material strength. Its unconfined compressive strength at 28 days is preferably between 0.8 MPa and 3.0 MPa. This strength range is sufficient for the foamed lightweight soil wall structure to withstand its own stress and certain external loads, and provides reliable end restraint for the reinforced grid.

[0033] The reinforced geogrid is preferably made of unidirectional or bidirectional geogrids made of high-density polyethylene (HDPE) or other high-molecular polymer materials with excellent creep resistance and durability. Its ultimate tensile strength is preferably not less than 80 kN / m to meet the safety and long-term stability requirements of permanent retaining wall structures.

[0034] This invention specifies the geometric dimensions of the stepped wall. When the structure of the foamed lightweight soil adjacent wall is designed as stepped, the height of each step is preferably 1.0 meter to 3.5 meters, and the width of each step is preferably 1.0 meter to 3.5 meters. This dimensional design comprehensively considers construction convenience, structural stability, and aesthetic harmony. Example

[0035] Please see Figure 1 This embodiment provides a combined retaining wall structure of foamed lightweight soil and reinforced grid, which is applied to a city expressway widening project, with a total retaining wall height of 12 meters.

[0036] The combined retaining wall structure, from the open side to the interior, includes: a foamed lightweight soil stepped wall structure 1 and a reinforced grid reinforcement zone 9.

[0037] Foamed lightweight soil stepped wall structure 1 is located on the outermost side of the retaining wall. Due to land constraints, the overall slope of the wall is nearly vertical. To facilitate construction and enhance stability, it is designed as a stepped structure. Specifically, it consists of four steps, each 3.0 meters high and 3.0 meters wide. This wall structure 1 is made of foamed lightweight soil pumped and cast on-site. The proportions of the foamed lightweight soil used are carefully designed to control its final dry bulk density at approximately 700 kg / m³, and its 28-day unconfined compressive strength reaches 1.5 MPa to meet the requirements for structural self-support and panel strength.

[0038] The reinforced geogrid reinforcement zone 3, located behind the foamed lightweight soil wall structure 1, is the main load-bearing area. Multiple layers of reinforced geogrid 2 are laid horizontally within this zone and filled and compacted by filler material 3.

[0039] The reinforced geogrid 2 is made of high-density polyethylene (HDPE) unidirectional geogrid with an ultimate tensile strength of 110 kN / m, exhibiting excellent creep resistance and making it suitable as a permanent support structure. The vertical spacing of the reinforced geogrid 2 is 0.5 meters, meaning two layers are laid per meter of height. The length of the reinforced geogrid 2 is determined based on Rankine earth pressure theory and stability calculations (anti-slip, anti-overturning, overall stability, etc.), with a maximum length of 6.0 meters at the bottom and a minimum length of 5.0 meters at the top. During construction, the front end of the reinforced geogrid 2 is tightly fitted to the foamed lightweight soil wall structure 1, and anchored through the wrapping effect of the foamed lightweight soil during pouring.

[0040] Filler 3 is made of well-graded crushed stone soil, spread in layers (50cm each), and compacted with a small vibratory roller. The compaction degree is required to be no less than 95%.

[0041] The entire retaining wall structure sits on a reinforced concrete strip foundation 4, which is 1.0 meter deep and rests on the treated ground. After the retaining wall is completed, the top of the wall will serve as a new driveway, bearing a load 5 on the top of the wall.

[0042] Drainage ditches should be installed at the bottom of the retaining wall (7), waterproofing and seepage prevention measures should be installed on the ground at the top of the slope behind the wall (6), and transverse gravel drainage channels (8) should be evenly installed in the middle of the retaining wall.

[0043] The construction method in this embodiment is as follows: 1. First, excavate the foundation trench and treat the ground, then pour the reinforced concrete foundation 4.

[0044] 2. On foundation 54, erect the outer wooden formwork of the first level (3.0 meters high) wall 1.

[0045] 3. Pump and pour 3.0-meter-high foamed lightweight soil. During the pouring process, reinforced grid 2 is laid behind it in four stages (every 0.5-meter elevation). Specifically, pour 0.5 meters of foamed lightweight soil, lay a layer of grid, pour another 0.5 meters, lay another layer, and so on.

[0046] 4. After each layer of reinforced grid 2 is laid, backfill and compact the fill material 3 immediately behind it, always keeping the working surface of the fill material roughly level with the foamed lightweight soil pouring surface.

[0047] 5. After completing the construction of the first 3.0-meter-high wall, repeat the above steps on the formed steps to construct the second, third, and fourth levels of the wall until a total height of 12 meters is reached.

[0048] 6. Finally, remove all formwork, water-cur the foamed lightweight soil wall for at least 7 days, and construct the road structure layer on top of the wall.

[0049] By adopting the technical solution of this embodiment, a near-vertical high retaining wall was successfully constructed in a narrow space. According to the subsequent settlement observation data, the total settlement at the top of the wall was reduced by more than 70% compared with the design prediction value of the traditional reinforced soil retaining wall scheme, which effectively ensured the smoothness and durability of the road surface and achieved excellent technical and economic benefits.

[0050] In the description of this utility model, it should be noted that the terms "vertical", "up", "down", "horizontal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0051] The above description is merely a preferred embodiment of this utility model, but the scope of protection of this utility model is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in this utility model, based on the technical solution and inventive concept of this utility model, should be included within the scope of protection of this utility model. It is obvious to those skilled in the art that this utility model is not limited to the details of the above exemplary embodiments, and that it can be implemented in other specific forms without departing from the spirit or basic characteristics of this utility model. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of this utility model is defined by the appended claims rather than the foregoing description, and therefore all variations falling within the meaning and scope of equivalent elements of the claims are intended to be included within this utility model. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A retaining wall structure combining foamed lightweight soil and reinforced grid, characterized in that, include: A foamed lightweight earth wall structure (1) and a reinforced grid reinforcement zone (9); The foamed lightweight soil wall structure (1) is located on the outermost side of the entire retaining wall structure, that is, the side facing the open. The side of the foamed lightweight soil wall structure (1) facing the open has one or more steps, which increase from bottom to top, presenting an inverted trapezoidal shape. The foam lightweight soil wall structure (1) also includes: foundation (4) and transverse gravel drainage ditch (8) inside the retaining wall; the foundation (4) is located at the bottom of the foam lightweight soil wall structure (1), and the transverse gravel drainage ditch (8) inside the retaining wall is distributed in multiple layers throughout the entire combined retaining wall structure and runs through the reinforced grid reinforcement area (9) of the foam lightweight soil wall structure (1). The reinforced grid reinforcement zone (9) is located behind the foamed lightweight soil wall structure and forms a close contact with it; the reinforced grid reinforcement zone (9) also includes: a reinforced grid (2) and filler (3), wherein the reinforced grid (2) is laid horizontally in the reinforced grid reinforcement zone (9); The filler (3) is filled between the layers of reinforced grids in the reinforced grid reinforcement zone.

2. The combined retaining wall structure of foamed lightweight soil and reinforced grid according to claim 1, characterized in that, The foamed lightweight earthen wall structure (1) is an inverted right trapezoid, and its open surface forms a plane perpendicular to the ground.

3. The combined retaining wall structure of foamed lightweight soil and reinforced grid according to claim 1, characterized in that, The reinforced grid (2) extends to and is anchored at the interface between the foamed lightweight soil wall structure (1) and the reinforced grid reinforcement area (9) at one end near the free surface; the end near the soil extends to and is anchored in the stable soil, and its setting direction is horizontal with the ground.

4. The combined retaining wall structure of foamed lightweight soil and reinforced grid according to claim 1, characterized in that, The reinforced grid (2) extends into the interior of the foam lightweight soil wall structure at one end near the free surface to ensure effective connection and mechanical transmission between the two; the end near the soil extends and is anchored in the stable soil, and its setting direction is horizontal with the ground.

5. The combined retaining wall structure of foamed lightweight soil and reinforced grid according to claim 1, characterized in that, The transverse gravel drainage ditch (8) inside the retaining wall is set horizontally to the ground, and the multi-layered and uniformly penetrating foam lightweight soil wall structure (1) reinforced grid reinforcement area (9).

6. The combined retaining wall structure of foamed lightweight soil and reinforced grid according to claim 1, characterized in that, Also includes: The top load (5), the bottom of the retaining wall (7), and the ground at the top of the slope behind the wall (6); the bottom of the retaining wall (7) is the part of the combined retaining wall structure that extends to the ground; the top load (5) and the ground at the top of the slope behind the wall (6) are located at the top of the entire combined retaining wall structure and serve as an enclosure.

Images