Latticed rigid stiffening surface layer structure for soft soil foundation and construction method of latticed rigid stiffening surface layer structure

Abstract

The invention provides a latticed rigid stiffening surface layer structure for a soft soil foundation. The latticed rigid stiffening surface layer structure comprises a geotechnical cloth layer laid on the surface of the soft soil foundation; the latticed rigid stiffening frame is arranged on the geotechnical cloth layer, the rigid stiffening frame is composed of cylindrical fabric sleeves arranged in a latticed mode and early strength mortar filled in the fabric sleeves, and the three-day compressive strength of the early strength mortar is larger than or equal to 20 MPa; and the aggregate layer is paved on the latticed rigid stiffening frame. The invention further provides a construction method of the latticed rigid stiffening surface layer structure. According to the space grid beam structure formed by compounding the flexible sleeve and the rigid mortar, high rigidity far higher than that of a traditional geosynthetic material is provided, loads can be effectively diffused, and differential settlement is remarkably restrained. The whole structure is of a temporary assembly type, can be completely dismantled after construction of a corresponding area is completed, is extremely small in disturbance to an original foundation, can be quickly recovered to a cultivated land or an original appearance, meets the high-standard environment-friendly requirement, and is high in construction efficiency and low in comprehensive manufacturing cost.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering technology, specifically relating to a grid-like rigid stiffened surface structure for soft soil foundations and its construction method. Background Technology

[0002] When constructing temporary works such as access roads and heavy machinery operation platforms on soft soil foundations, it is necessary to reinforce the surface soil to improve the bearing capacity of the soft soil foundation. Grid-based foundation treatment is widely used in soft soil foundation reinforcement due to its advantages of ease of construction and dismantling. For example, Chinese patent CN206109901U discloses a highway soft soil foundation reinforcement structure, which includes several piles embedded in the soft soil foundation. The piles are buried 160cm into the bottom of the weak stratum of the soft soil foundation, and multiple sets of reinforcing bars are installed inside the piles. A permeable geomembrane is installed on the outer wall of the piles, and a 60cm thick gravel cushion layer is installed at the top of the piles. A 6mm thick geogrid layer is installed inside the gravel cushion layer. This foundation reinforcement structure is simple, efficient, and has a deep reinforcement depth, short construction period, and low cost. However, this foundation reinforcement structure mainly relies on the friction between the pile pipe and the soil to function, and its own rigidity is limited. Under heavy equipment loads, it is prone to large deformation and it is difficult to effectively control uneven settlement.

[0003] Another Chinese patent with publication number CN117286860A discloses a rapid gridded foundation treatment construction method under soft plastic geological conditions. The steps are as follows: S1: Draw lines on the soft plastic ground and divide it into several grid squares of the same size.

[0004] S2: Two grid partition walls are set at the edges of the grid squares, and the foundation pit is constructed for replacement. S3: Slag replacement is carried out in the middle of the grid squares. S4: A layer of high-strength geogrid is constructed on top of the grid partition walls. S5: Overall compaction is carried out. This construction method forms a shell structure by replacing the internal filling of the grid partition walls, and through the connection of high-strength geogrid, it forms an integral whole with the grid partition wall structure, thus forming a grid-type composite foundation that meets specific bearing capacity requirements. However, it is essentially still a planar reinforcement achieved through high-strength geogrid, and fails to form a spatial grid beam structure with overall rigidity.

[0005] Neither of the two aforementioned solutions can quickly and completely restore the original appearance of the soft soil foundation after completing the corresponding tasks, resulting in the soft soil foundation failing to fully regain its original functionality and causing damage. Therefore, there is an urgent need in this field for a new soft soil foundation surface treatment technology that can balance high stiffness, rapid construction, and easy post-construction restoration to solve the technical bottlenecks faced by traditional methods in temporary engineering applications. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this application first proposes a grid-like rigid stiffened surface structure for soft soil foundations, comprising:

[0007] Geotextile layer laid on the surface of soft soil foundation;

[0008] A grid-like rigid stiffening frame is installed on the geotextile layer. The rigid stiffening frame consists of a grid-like arranged cylindrical fabric sleeve and early-strength mortar filled in the fabric sleeve. The 3-day compressive strength of the early-strength mortar is ≥20MPa. The cylindrical fabric sleeve includes warp tubes and weft tubes arranged at intervals. The warp tubes and weft tubes are arranged to cross each other to form a grid.

[0009] A granular layer is laid on the rigid, mesh-like frame. The tubular fabric sleeve is made of materials such as nylon, polyester fiber, PET fiber, and PPS fiber. Specifically, to facilitate the laying of the tubular fabric sleeve, the mesh formed by the intersection of the warp and weft tubes is plain weave, twill weave, or satin weave.

[0010] This application utilizes a spatial grid beam structure formed by a combination of flexible sleeves and rigid mortar, providing significantly higher stiffness than traditional geosynthetics. This effectively diffuses loads and significantly suppresses uneven settlement. The entire structure is a temporary prefabricated form, which can be completely dismantled after the completion of construction in the corresponding area, causing minimal disturbance to the original foundation. Utilizing the geotextile layers, it can be quickly restored to farmland or its original state, meeting high environmental protection standards. Furthermore, it boasts high construction efficiency, reaching up to 400m. 2 / day, the overall cost is lower than that of cement-soil mixing piles and other construction methods that require full-area reinforcement.

[0011] Furthermore, the grid layout of this rigid stiffening frame can be either uniform or non-uniform. When the grid layout is non-uniform, the grid spacing is denser in areas of concentrated load than in areas of low load. This design allows for the application of different grid densities to different load areas, thereby reducing construction costs.

[0012] Furthermore, to improve the bending stiffness and local compressive strength of the node area, the cylindrical fabric sleeve uses reinforced sleeves at grid intersections, structural boundaries, and stress concentration areas, while ordinary sleeves are used in other areas except for grid intersections, structural boundaries, and stress concentration areas. The wall thickness of the reinforced sleeve is 1.5-2 times that of the ordinary sleeve.

[0013] Alternatively, annular stiffening ribs may be provided at the grid intersections of the tubular fabric sleeve.

[0014] Reinforced sleeves achieve increased wall thickness by increasing braiding density or using composite lamination processes.

[0015] Furthermore, to enhance the adhesion and mechanical interlocking force between the tubular fabric sleeve and the early-strength mortar, the inner surface of the tubular fabric sleeve is roughened or modified with a coating.

[0016] Secondly, in order to successfully realize the above-mentioned grid-like rigid stiffened surface structures, this application also proposes a construction method for the grid-like rigid stiffened surface structure described in any of the above-mentioned claims, which includes the following steps:

[0017] (1) Level the ground and lay geotextile layers in the designated area;

[0018] (2) Lay the tubular fabric sleeve in a grid pattern;

[0019] (3) Inject early-strength mortar into the tubular fabric sleeve until the grouting pressure reaches the set pressure;

[0020] (4) Spreading and compaction of the granular layer.

[0021] Specifically, in order to ensure the strength of the early-strength mortar after solidification, the grouting pressure in step (3) is set to 0.3-0.8 MPa.

[0022] Furthermore, to improve the rheological properties, strength, or toughness of the early-strength mortar, at least one of nano-silica powder, polypropylene fiber, and water-reducing agent is added to the early-strength mortar, with nano-silica powder accounting for 1-3% of the weight of the cementitious material and polypropylene fiber accounting for 0.5-1.5% of the weight of the cementitious material. Attached Figure Description

[0023] Figure 1 A schematic diagram showing the plain weave arrangement of tubular fabric sleeves.

[0024] Figure 2 for Figure 1 Enlarged view of section A.

[0025] Figure 3 for Figure 1 Enlarged view of section B. Detailed Implementation

[0026] The following section first describes the grid-like rigid stiffened surface structure for soft soil foundations in this application. Please refer to [link to relevant documentation]. Figure 1 , Figure 1Arrow X in the diagram indicates the weft direction, and arrow Y indicates the warp direction. The structure includes a geotextile layer 60 laid on the soft soil foundation surface, a grid-like rigid reinforcing frame 100 disposed on the geotextile layer, and a granular layer laid on the grid-like rigid reinforcing frame. The granular layer is not shown in the accompanying drawings. In this embodiment, the granular layer uses stone with a particle size of 5-30 mm and a thickness of 250 mm. The rigid reinforcing frame 100 consists of a cylindrical fabric sleeve and early-strength mortar filled within the fabric sleeve. The early-strength mortar has a 3-day compressive strength ≥25 MPa and a 28-day strength ≥40 MPa. The cylindrical fabric sleeve includes spaced-apart warp tubes 20 and spaced-apart weft tubes 10, which are perpendicular to each other. The grid formed by the intersecting warp and weft tubes is plain weave. It is understood that in other embodiments, the grid may also be twill or satin weave.

[0027] In this embodiment, the grid layout of the rigid stiffening frame is a uniform grid. The distance between the center lines of adjacent warp tubes is 1.5 meters, and the distance between the center lines of adjacent weft tubes is 1.5 meters, i.e., the grid spacing is 1.5 meters × 1.5 meters, resulting in a uniformly arranged square grid layout. In this embodiment, both the warp and weft tubes are 1.5 mm thick PET fiber braided tubes, and the outer diameter of both the warp and weft tubes is 150 mm.

[0028] It is understood that, in another embodiment, the grid layout of the rigid stiffening frame can be non-uniform, for example, in the vehicle traffic area, the grid spacing can be set to 1 meter × 1.5 meters. That is, a denser grid spacing is used in the load-concentrated area than in the non-concentrated area. To improve the load-bearing capacity, in yet another embodiment, in the high-load area of ​​vehicle traffic, the thickness of the corresponding warp and weft tubes can be increased, for example, the thickness of the warp and weft tubes can be increased to 2.5 mm. The 1.5 mm thick PET fiber braided tube is called the ordinary sleeve, while the 2.5 mm thick PET fiber braided tube is called the reinforced sleeve.

[0029] In this embodiment, since the intersection of the radial and latitudinal tubes, i.e., the grid intersection point, bears a greater load, a 2mm thick PET fiber braided short tube is fitted onto the tube segment located in the grid intersection area of ​​the radial and latitudinal tubes. The length of the PET fiber braided short tube is 300mm, and this PET fiber braided short tube serves as an annular stiffening rib. It can be understood that, to save materials, three 50mm long and 2mm thick PET fiber braided short tubes can be used to replace the aforementioned 300mm long PET fiber braided short tube, thereby forming three annular stiffening ribs.

[0030] In this embodiment, the inner surface of the tubular fabric sleeve is roughened by sanding to improve the adhesion and mechanical bonding force between the tubular fabric sleeve and the early-strength mortar. It is understood that in other embodiments, a coating modification can also be applied to the inner wall of the tubular fabric sleeve to improve the adhesion and mechanical bonding force between the tubular fabric sleeve and the early-strength mortar. Both the sanding treatment and the coating modification utilize existing mature technologies.

[0031] The following describes the construction method for the aforementioned grid-like rigid stiffened surface structure, which includes the following steps:

[0032] (1) Level the ground and lay the geotextile layer 60 in the designated area;

[0033] (2) Lay the tubular fabric sleeve in a grid pattern. Please refer to [link / reference]. Figures 1-3 One end of each meridional pipe is connected to the first grouting main pipe 40 via the first connecting pipe 45, and one end of each latitudinal pipe is connected to the second grouting main pipe 30 via the second connecting pipe 35.

[0034] For each first connecting pipe, a first grouting branch pipe 41 is provided on the first grouting main pipe, and a first on / off valve 42 is installed on each first grouting branch pipe 41. The first branch pipe is connected to the corresponding first connecting pipe. A first grout inlet valve 21 is installed at the end of each radial pipe adjacent to the first connecting pipe, and a first vent valve 22 is installed at the end of each radial pipe away from the first connecting pipe.

[0035] For each second connecting pipe, a second grouting branch pipe 31 is provided on the second grouting main pipe, and a second on / off valve 32 is installed on each second grouting branch pipe 31. The second branch pipe is connected to the corresponding second connecting pipe. A second grout inlet valve 11 is installed at the end of each latitudinal pipe adjacent to the second connecting pipe, and a second vent valve 12 is installed at the end of each latitudinal pipe away from the second connecting pipe.

[0036] (3) Inject early-strength mortar into the tubular fabric sleeve until the grouting pressure reaches the set pressure of 0.5 MPa. In this embodiment, the grouting of the warp tube is completed first, and then the grouting of the weft tube is completed.

[0037] In this embodiment, ten meridional pipes and ten latitudinal pipes are provided. During grouting of the meridional pipes, the ten meridional pipes are divided into two groups of five pipes each. Early-strength mortar enters the first group of meridional pipes through the first grouting main pipe. The first vent valve remains open until the early-strength mortar flows out, at which point the first vent valve is closed. The grouting continues until the grouting pressure reaches 0.5 MPa, at which point the first grout inlet valve is closed. The same steps are then followed to complete the grouting of the second group of meridional pipes. Each first connecting pipe is disassembled from the meridional pipe and connected to the first grouting main pipe for cleaning and recycling. The first on / off valve serves as a backup valve for the first grout inlet valve.

[0038] During grouting into the latitudinal pipes, the ten latitudinal pipes are divided into two groups of five. Early-strength mortar enters the first group of latitudinal pipes through the second grouting main pipe. The second vent valve remains open until the early-strength mortar flows out, at which point the second vent valve is closed. The grouting pressure is then increased to 0.5 MPa, and the second grout inlet valve is closed. The same procedure is followed to complete the grouting of the second group of latitudinal pipes. Each second connecting pipe is disassembled from the latitudinal pipes and connected to the second grouting main pipe for cleaning and recycling. The second on / off valve serves as a backup valve for the second grout inlet valve.

[0039] In this embodiment, the proportions of the early-strength mortar are as follows: 25 parts water-reducing agent, 300 parts cement, 70 parts 40-70 mesh quartz sand, 70 parts 20-40 mesh quartz sand, 50 parts 12-20 mesh quartz sand, 70 parts 8-12 mesh quartz sand, 75 parts expansion agent, 2 parts cement mortar defoamer, 130 parts fly ash admixture, 70 parts early-strength agent, 120 parts water-quenched blast furnace slag powder, 240 parts water, 5.5 parts polypropylene fiber, and the gel material includes cement, fly ash admixture and water-quenched blast furnace slag powder, with polypropylene fiber accounting for 1% of the weight of the gel material.

[0040] (4) Spreading and compaction of the granular layer.

[0041] Tests after construction showed that the foundation reaction coefficient K 30 ≥110MN / m 3 It fully meets the usage requirements. After the project was completed, the structure was successfully dismantled, and the site was restored to its original state.

[0042] Table 1 compares this embodiment with other construction schemes in the prior art.

[0043] Table 1

[0044] index This invention Option B Option C Bearing capacity characteristic value (kPa) 120 60 >150 Construction period (days) 5 7 15 <![CDATA[Total cost (yuan / m 2 )]]> 280 200 450 Post-construction recovery difficulty Extremely easy Relatively difficult (cleaning up gravel) Unrecoverable

[0045] Table 1 shows that both Scheme B and Scheme C were constructed using existing technologies under the same geological conditions as the above embodiments. Scheme B is the traditional crushed stone replacement method, and Scheme C is the cement mixing pile method. As can be seen from Table 1, although the overall cost of Scheme B is lower than that of this application, its bearing capacity characteristic value is lower, and foundation restoration is difficult. Although Scheme C has a higher bearing capacity characteristic value than this application, its overall cost is higher, and the foundation cannot be restored to its original state.

Claims

1. A grid-like rigid stiffened surface structure for soft soil foundations, characterized in that, include: Geotextile layer laid on the surface of soft soil foundation; A grid-like rigid stiffening frame is installed on the geotextile layer. The rigid stiffening frame consists of a grid-like arranged cylindrical fabric sleeve and early-strength mortar filled in the fabric sleeve. The 3-day compressive strength of the early-strength mortar is ≥20MPa. The cylindrical fabric sleeve includes warp tubes and weft tubes arranged at intervals. The warp tubes and weft tubes are arranged to cross each other to form a grid. A layer of granules laid on the grid-like rigid stiffened frame.

2. The mesh-like rigid stiffened surface structure according to claim 1, characterized in that, The grid layout of the grid-like rigid stiffening frame can be uniform or non-uniform. When the grid layout of the grid-like rigid stiffening frame is non-uniform, the grid spacing in the load-concentrated area is denser than that in the non-concentrated area.

3. The grid-like rigid stiffened surface structure according to claim 1, characterized in that, The tubular fabric sleeve uses reinforced sleeves at grid intersections, structural boundaries, and stress concentration areas, while ordinary sleeves are used in other areas. The wall thickness of the reinforced sleeve is 1.5-2 times that of the ordinary sleeve.

4. The mesh-like rigid stiffened surface structure according to claim 1, characterized in that, Annular stiffening ribs are provided at the grid intersections of the tubular fabric sleeve.

5. The mesh-like rigid stiffened surface structure according to claim 1, characterized in that, The grid pattern formed by the intersection of the warp and weft tubes can be plain, twill, or satin.

6. The mesh-like rigid stiffened surface structure according to claim 1, characterized in that, The inner surface of the tubular fabric sleeve is roughened or modified with a coating.

7. A construction method for the grid-like rigid stiffened surface structure according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Level the ground and lay geotextile layers in the designated area; (2) Lay the tubular fabric sleeve in a grid pattern; (3) Inject early-strength mortar into the tubular fabric sleeve until the grouting pressure reaches the set pressure; (4) Spreading and compaction of the granular layer.

8. The construction method according to claim 7, characterized in that, In step (3), the grouting pressure is set to 0.3-0.8 MPa.

9. The construction method according to claim 7, characterized in that, The early-strength mortar contains at least one of nano-silica powder, polypropylene fiber, and water-reducing agent. The nano-silica powder accounts for 1-3% of the weight of the cementitious material, and the polypropylene fiber accounts for 0.5-1.5% of the weight of the cementitious material.

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