Composite foundation and broadened road for reconstruction and extension project in coastal soft soil area

Abstract

The invention discloses a composite foundation and a broadened road for reconstruction and extension engineering in a coastal soft soil area, belongs to the technical field of road engineering, and aims to solve the problem that fine-particle soil in a soft soil foundation in the prior art invades a drainage channel along with water flow to form clogging. The composite foundation comprises composite piles, warp-knitted composite layers, foundation gabions, an anti-clogging gravel hardcore and a soft soil layer, the composite piles are located in the soft soil layer and arranged in the vertical direction, containing grooves are formed in the upper surface of the soft soil layer and between every two adjacent composite piles, and the continuous warp-knitted composite layers are laid on the upper surface of the soft soil layer and the groove walls and the groove bottoms of the containing grooves. The foundation gabion is arranged on the warp-knitted composite layer in the containing groove, and the anti-clogging broken stone hardcore is laid on the foundation gabion and the warp-knitted composite layer located on the surface of the foundation gabion. The method can be used for reconstruction and extension projects in coastal soft soil areas.

Description

Technical Field

[0001] This invention belongs to the field of road engineering technology, and in particular to a composite foundation and road widening method for reconstruction and expansion projects in coastal soft soil areas. Background Technology

[0002] With the surge in travel demand, the existing two-way four-lane expressways are insufficient in terms of capacity, and congestion and rear-end collisions occur frequently during peak hours. Therefore, it is necessary to promote the reconstruction and expansion project of four lanes to six / eight lanes.

[0003] Coastal soft soil areas are key and challenging areas for reconstruction and expansion projects. The foundations in these areas are characterized by shallow groundwater levels and high water content. Due to capillary action, the water in the foundation continuously migrates to the roadbed, leading to increased water content and reduced shear strength in the embankment, which can easily cause roadbed settlement, pavement cracking, and other defects.

[0004] Existing technologies often employ a drainage system consisting of a "crushed stone drainage layer + blind drain" to address water migration issues, removing excess water from the foundation by constructing drainage channels. However, fine-grained soil in soft soil foundations can infiltrate the drainage channels with the water flow, causing blockages that are irreversible. As the operating time increases, drainage efficiency decreases significantly, eventually rendering the system ineffective. Summary of the Invention

[0005] Based on the above analysis, the embodiments of the present invention aim to provide a composite foundation and road widening for reconstruction and expansion projects in coastal soft soil areas, in order to solve at least one of the following problems in the prior art: fine-grained soil in soft soil foundations can intrude into drainage channels with water flow and cause siltation; the widened composite foundation experiences large settlement and large lateral deformation; the connection stability between the vertical panel and the micropile geocell is poor; and the soft soil between piles undergoes excessive deformation due to excessive load.

[0006] The objective of this invention is mainly achieved through the following technical solutions.

[0007] This invention provides a composite foundation for reconstruction and expansion projects in coastal soft soil areas, comprising composite piles, a warp-knitted composite layer, a foundation gabion, an anti-siltation crushed stone cushion layer, and a soft soil layer. The composite piles are located in the soft soil layer and are arranged vertically. A receiving groove is provided on the upper surface of the soft soil layer and between two adjacent composite piles. A continuous warp-knitted composite layer is laid on the upper surface of the soft soil layer and on the walls and bottom of the receiving groove. The foundation gabion is placed on the warp-knitted composite layer in the receiving groove. The anti-siltation crushed stone cushion layer is laid on the foundation gabion and the warp-knitted composite layer on the surface.

[0008] Furthermore, the composite pile is a cement-fly ash-gravel pile.

[0009] Furthermore, the height of the foundation gabion is equal to the depth of the receiving trench.

[0010] Furthermore, the stiffness of the composite foundation is greater than that of the original foundation.

[0011] Furthermore, the number of composite piles is multiple, and the multiple composite piles are arranged in a rectangular pattern.

[0012] Furthermore, the diameter of the composite pile is 400mm~600mm, and the spacing between the composite piles is 1200mm~3000mm.

[0013] Furthermore, the thickness of the anti-clogging crushed stone cushion layer is 200mm~500mm.

[0014] Furthermore, the foundation gabion includes a cage body, filled crushed stone inside the cage body, and grouting material filling the gaps between the filled crushed stone.

[0015] Furthermore, the warp-knitted composite layer comprises alternating layers of geotextile and geogrid.

[0016] The present invention also provides a road widening project for coastal soft soil area reconstruction and expansion projects, including the composite foundation mentioned above for coastal soft soil area reconstruction and expansion projects.

[0017] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: A) The road widening project for coastal soft soil area reconstruction and expansion provided by this invention is a multi-stage reinforced seepage-proof cement fly ash gravel pile composite foundation (i.e., multi-stage reinforced seepage-proof CFG composite foundation). A continuous warp-knitted composite layer is laid on the upper surface of the soft soil layer and the walls and bottom of the receiving trench. The foundation gabion is placed on the warp-knitted composite layer in the receiving trench. With its high strength and good mechanical transmission characteristics, the warp-knitted composite layer can further and orderly transfer the gravity load it bears to the composite pile, forming a relay load transmission path of foundation gabion, warp-knitted composite layer and composite pile, which alleviates the excessive deformation of the soft soil between the piles due to excessive load, and ensures the stability of the composite foundation bearing system.

[0018] B) The anti-siltation crushed stone cushion layer for road widening and expansion projects in coastal soft soil areas provided by this invention serves as a filter layer, effectively intercepting fine-particle soil, significantly reducing the siltation risk of the anti-siltation crushed stone cushion layer, extending the service life of the anti-siltation crushed stone cushion layer, and solving the problem in the prior art that fine-particle soil in soft soil foundations will invade drainage channels with water flow and form siltation.

[0019] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained through the embodiments described and the accompanying drawings, which are particularly pointed out. Attached Figure Description

[0020] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. Figure 1 This is a schematic diagram of a composite foundation for a coastal soft soil area reconstruction and expansion project provided in Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the structure of a road widening project for coastal soft soil area reconstruction and expansion, provided in Embodiment 2 of the present invention. Figure 3 This is a schematic diagram of the structure of the double-layer grid cage connector in the road widening project for the reconstruction and expansion of coastal soft soil areas, provided in Embodiment 2 of the present invention. Figure 4 This is a schematic diagram of the structure of a turning axis in a widened road for a coastal soft soil area reconstruction and expansion project, provided in Embodiment 2 of the present invention.

[0021] Figure label: 1-Composite foundation; 11-Composite pile; 12-Warp-knitted composite layer; 13-Foundation gabion; 14-Anti-silting crushed stone cushion layer; 15-Soft soil layer; 2-Reinforced widening zone; 21-Vertical panel; 211-Concrete component; 212-Gabion between components; 22-Micropile geocell; 23-Widening fill layer; 24-Double-stage gabion connector; 241-Connecting base; 242-Gabion insertion slot; 243-Gabion insertion slot; 244-Rotating shaft; 245-Ratchet; 246-Pawl; 247-Connecting bolt; 248-Axial groove; 3-Widening pavement; 4-Connecting layer; 5-Gabion reinforcement layer; 6-Existing roadbed; 7-Existing foundation. Detailed Implementation

[0022] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0023] Example 1 This embodiment provides a composite foundation for reconstruction and expansion projects in coastal soft soil areas. See [link to relevant documentation]. Figure 1 It includes composite piles 11, warp-knitted composite layer 12, foundation gabion 13, anti-siltation crushed stone cushion layer 14, and soft soil layer 15.

[0024] Among them, the composite pile 11 is located in the soft soil layer 15 and is set in the vertical direction. A receiving groove is provided on the upper surface of the soft soil layer 15 and between two adjacent composite piles 11. A continuous warp-knitted composite layer 12 is laid on the upper surface of the soft soil layer 15, as well as the groove wall and bottom of the receiving groove. The foundation gabion 13 is placed on the warp-knitted composite layer 12 in the receiving groove. The anti-siltation crushed stone cushion layer 14 is laid on the foundation gabion 13 and the warp-knitted composite layer 12 on the surface.

[0025] It should be noted that the height of the foundation gabion 13 is equal to the depth of the receiving groove, so that the upper surface of the foundation gabion 13 and the warp-knitted composite layer 12 form a complete plane.

[0026] Compared with the prior art, the road widening project for coastal soft soil area reconstruction and expansion provided in this embodiment is a multi-level reinforced seepage-proof cement fly ash gravel pile composite foundation. On the one hand, a continuous warp-knitted composite layer 12 is laid on the upper surface of the soft soil layer 15 and the walls and bottom of the receiving trench. The foundation gabion 13 is placed on the warp-knitted composite layer 12 in the receiving trench. With its high strength and good mechanical transmission characteristics, the warp-knitted composite layer 12 can further and orderly transfer the gravity load it bears to the composite pile 11, forming a relay load transfer path of foundation gabion 13, warp-knitted composite layer 12 and composite pile 11, which alleviates the excessive deformation of the soft soil between the piles due to excessive load, and ensures the stability of the composite foundation bearing system.

[0027] On the other hand, the anti-clogging crushed stone cushion layer 14, as a filter layer, effectively intercepts fine soil particles, significantly reduces the risk of clogging of the anti-clogging crushed stone cushion layer 14, extends the service life of the anti-clogging crushed stone cushion layer 14, and solves the problem in the prior art that fine soil particles in soft soil foundations will invade the drainage channel with water flow and form clogging.

[0028] To address the settlement issue arising from the widened composite foundation, the stiffness of the composite foundation is greater than that of the original foundation 7. Thus, after the road widening construction is completed, the greater stiffness of the composite foundation effectively resists deformation caused by the superstructure load, thereby reducing differential settlement between the old and new roadbeds. Simultaneously, this stiffness difference also guides more of the superstructure load to the composite foundation area, further enhancing the foundation's stability.

[0029] For example, the diameter of the composite pile 11 is 400mm~600mm, and the pile length is determined according to the thickness of the soft soil layer 15 and the design bearing capacity; the pile spacing of the composite pile 11 is 1200mm~3000mm, and multiple composite piles 11 are arranged in a rectangular shape.

[0030] Specifically, the structure of the anti-clogging crushed stone cushion layer 14 includes graded crushed stone and filling material filling the gaps between the graded crushed stone. The composition of the filling material by mass parts includes 1-2 parts of N,N′methylenebisacrylamide (crosslinking agent), 22-25 parts of acrylamide monomer (AM), 3-6 parts of bentonite (reinforcing agent), 0.05-0.2 parts of potassium ferricyanide (retarder), and 0.5-1.5 parts of potassium persulfate (KP, thermal initiator).

[0031] In this way, the above-mentioned anti-clogging crushed stone cushion layer 14 is mainly composed of graded crushed stone, and the gaps between the graded crushed stone are filled with a mixture mainly composed of acrylamide monomer and N,N′methylenebisacrylamide. The raw materials of the filling material undergo chemical reaction in the gaps between the graded crushed stone to form a three-dimensional complex in-situ gel network, which can efficiently intercept fine soil particles, significantly reduce the clogging risk of the anti-clogging crushed stone cushion layer 14, and extend the service life of the anti-clogging crushed stone cushion layer 14.

[0032] Meanwhile, due to the porosity and incomplete filling of the three-dimensional complex in-situ gel network, the overall permeability of the silted gravel cushion layer is guaranteed, and the drainage capacity is not fundamentally affected.

[0033] In addition, because the gel network is elastic, it can adapt to the deformation of the composite foundation and maintain its barrier function after deformation, making it less prone to brittle failure.

[0034] For example, the thickness of the anti-clogging crushed stone cushion layer 14 is 200mm~500mm, and the particle size of the graded crushed stone is 20mm~40mm.

[0035] Specifically, the structure of the foundation gabion 13 includes a cage body, crushed stone filling inside the cage body, and grouting material filling the gaps between the crushed stone. The cage body has dimensions of no less than 15000mm × 1000mm × 500mm (length × width × height). The grouting material is a high-strength, high-adhesion special cement-based material, which, after curing, can tightly bind the crushed stone into a whole, significantly enhancing the overall strength and stability of the foundation gabion 13. Simultaneously, the grouting material also has good permeability, allowing it to fully penetrate the gaps between the crushed stone, ensuring no voids or weak areas, further improving the load-bearing capacity and deformation resistance of the foundation gabion 13.

[0036] Specifically, the structure of the warp-knitted composite layer 12 includes alternating layers of geotextile and geogrid, exemplarily having a width of 3000~6000mm and a weight of 100~150g.

[0037] Example 2 This embodiment provides a road widening project for reconstruction and expansion in coastal soft soil areas. See [link to relevant documentation]. Figure 2It includes a composite foundation 1, a reinforced widening zone 2 and a widened road surface 3 stacked from bottom to top. The composite foundation 1 is located outside the original foundation 7, and the reinforced widening zone 2 is located outside the original roadbed 6. The composite foundation 1 is the composite foundation provided in Example 1 for the reconstruction and expansion project in coastal soft soil areas.

[0038] Compared with the prior art, the widened road provided in this embodiment for the reconstruction and expansion project in coastal soft soil areas has basically the same beneficial effects as the composite foundation provided in Embodiment 1 for the reconstruction and expansion project in coastal soft soil areas, and will not be described in detail here.

[0039] For reinforced and widened zone 2, see Figure 2 Its cross-sectional shape along the line is rectangular, and the interface between the reinforced widening layer and the original roadbed 6 is set in the vertical direction.

[0040] Specifically, it includes a vertical panel 21, a micropile geocell 22, and a widened fill layer 23. The multi-layer micropile geocell 22 and the multi-layer widened fill layer 23 are stacked alternately to form a reinforced laminated structure. The vertical panel 21 is located on the outside of the reinforced laminated structure in the vertical direction, and multiple vertical panels 21 are arranged continuously along the longitudinal direction of the road.

[0041] To address the issue of lateral deformation, the vertical panel 21 is a prefabricated semi-rigid gabion panel. Specifically, it includes concrete components 211 and inter-component gabions 212. In two adjacent concrete components 211, the upper surface of the lower concrete component 211 has a lower groove, and the lower surface of the upper concrete component 211 has an upper groove. The lower and upper grooves are positioned correspondingly to form a receiving cavity for accommodating the inter-component gabions 212, which are placed in the receiving cavity.

[0042] To address the issue of poor connection stability between the vertical panel 21 and the micropile geocell 22, the aforementioned reinforced widening zone 2 also includes a double-layer geocell connector 24. (See [link]). Figure 3 The micropile geocell 22 is detachably connected to the inter-component gabion 212 via a double-stage gabion connector 24. The double-stage gabion connector 24 is manufactured and installed on-site, which can efficiently complete the connection between the micropile geocell 22 and the inter-component gabion 212.

[0043] Specifically, the double-stage gabion connector 24 includes a connector base 241 and a rotating tensioning shaft. A long strip-shaped gabion insertion slot 242 is opened on one side of the connector base 241, and a hexagonal gabion insertion slot 243 is opened on the other side of the connector base 241. A tensioning shaft insertion hole is opened longitudinally inside the connector base 241. The rotating tensioning shaft is inserted into the tensioning shaft insertion hole and is rotatably connected to the connector base 241. The gabion insertion slot 242 is connected to the tensioning shaft insertion hole.

[0044] To achieve a fixed connection between the rotating tensioning shaft and the sheet-like structure at the end of the micropile geocell 22, for the structure of the rotating tensioning shaft, see [link to relevant documentation]. Figures 3 to 4 It includes a pivot 244, a ratchet 245, a pawl 246, and a connecting bolt 247.

[0045] The rotating shaft 244 has an axial groove 248 along the axial direction. One end of the connecting bolt 247 is fixedly connected to one side of the axial groove 248, and the other end of the connecting bolt 247 is suspended and has a gap with the other side of the axial groove 248. The ratchet 245 is sleeved on one end of the rotating shaft 244, and the pawl 246 is provided on the connecting base 241. The ratchet 245 and the pawl 246 are connected in cooperation.

[0046] Correspondingly, bolt holes are made on the sheet-like structure at the end of the micropile geocell 22.

[0047] The sheet-like structure at the end of the micropile geocell 22 passes through the geocell insertion groove 242 and is inserted into the gap between the connecting bolt 247 and the wall of the axial groove 248. The bolt hole and the connecting bolt 247 are positioned correspondingly. At this time, rotating the shaft 244 will insert the connecting bolt 247 into the bolt hole, thus fixing the rotating tensioning shaft of the sheet-like structure at the end of the micropile geocell 22. Continuing to rotate the shaft 244 will cause the sheet-like structure at the end of the micropile geocell 22 to wrap around the shaft 244, thus tensioning the micropile geocell 22. When the micropile geocell 22 reaches the preset tension force, the pawl 246 is inserted into the ratchet 245 to fix the tension of the micropile geocell 22.

[0048] In this way, the rotating tensioning shaft with the above-described structure can achieve a stable and fixed connection between the sheet-like structure at the end of the micropile geocell 22 and the rotating tensioning shaft. During the rotation of the shaft 244, the connecting bolt 247 is precisely inserted into the bolt hole, which not only completes the initial positioning and connection, but also, as the shaft 244 continues to rotate, the sheet-like structure at the end of the micropile geocell 22 gradually wraps around the shaft 244, realizing the gradual tensioning of the micropile geocell 22. When the tension force reaches the preset value, the pawl 246 quickly inserts into the ratchet 245, forming a reliable mechanical lock, thereby ensuring the stability of the micropile geocell 22 under tension.

[0049] In order to solve the transition between the original roadbed 6 and the reinforced widening zone 2 and reduce the settlement difference between the two, the widening road used for the reconstruction and expansion project in the coastal soft soil area also includes a dual-medium connection zone in the original roadbed 6. Specifically, it includes a multi-layer connection component, which includes a connection layer 4 and a gabion reinforcement layer 5 stacked from bottom to top, and the two are in close contact.

[0050] To address the issue of unreasonable length settings for connecting components, in the aforementioned multi-layer connecting components, the i-th layer connecting component is defined as the connecting component to be determined, where i is any positive integer from 1 to n, and the minimum anchorage length of the connecting layer to be determined is specified. The calculation formula is as follows: ; ; In the formula: The unit weight of the original roadbed fill material, kN / m 3 ; The unit weight of the filler in the reinforced and widened zone is kN / m. 3 ; The additional load acting on the connection layer to be determined is kN / m 2 ; The friction coefficient of the upper surface of the bonding layer to be determined; The friction coefficient of the lower surface of the bonding layer to be determined; The embedment depth of the connecting layer to be determined is in meters (m). The ratio of the maximum deflection of the micro-pile geocell in the reinforced and widened zone after flexural deformation to half the width of the reinforced and widened zone; l is the width of the geocell along the cross section of the line in the reinforced and widened area, in meters; E represents the elastic modulus of the geocell in the reinforced and widened zone, in kPa; h represents the thickness of the bonding layer to be determined, in meters. h c The height of the geocell in the reinforced and widened area is given in meters. D represents the node spacing of geocells in the reinforced and widened zone, in meters. d 50 The median particle size (m) of the geocell filler in the reinforced and widened zone; Q i The vertical stress at the joint layer under vehicle load, in kPa, is to be determined. L c The width of the load arrangement used in structural calculations, in meters; L ci For depth z i The stress diffusion width at the point, in meters, is calculated using the following formula; When Z i +H'≤2b c At that time, L ci =L c +H'+zi When Z i +H'>2b c At that time, L ci =L c +b c +(H'+z i ) / 2 H' is the height from the topmost connecting layer to the widened road surface, in meters; b c The distance from the back of the vertical panel to the edge of the original roadbed is in meters (m).

[0051] Thus, the minimum anchorage length precisely calculated using the above formula ensures the stability of the connecting components under various loads, effectively solving the settlement difference problem caused by unreasonable length settings of the connecting components. In practical applications, based on specific engineering parameters and geological conditions, various values ​​are substituted into the formula for calculation to obtain the minimum anchorage length of each layer of connecting components, thereby guiding precise laying during construction. This scientific and reasonable calculation method not only improves the stability and safety of the project but also avoids resource waste and engineering hazards caused by over-design or under-design. Furthermore, the formula considers various influencing factors, such as the unit weight, additional load, friction coefficient, and burial depth of the original roadbed fill material (6 fill material) and the reinforced widening zone fill material (2 fill material), making the calculation results more accurate and reliable, providing strong technical support for road widening projects in coastal soft soil areas.

[0052] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite foundation for reconstruction and expansion projects in coastal soft soil areas, characterized in that, It includes composite piles, warp-knitted composite layers, foundation gabions, anti-siltation crushed stone cushion layers, and soft soil layers. The composite piles are located in the soft soil layers and are set vertically. A receiving trench is provided on the upper surface of the soft soil layers and between two adjacent composite piles. A continuous warp-knitted composite layer is laid on the upper surface of the soft soil layers and on the walls and bottom of the receiving trenches. The foundation gabions are placed on the warp-knitted composite layers in the receiving trenches. The anti-siltation crushed stone cushion layers are laid on the foundation gabions and the warp-knitted composite layers on the surface.

2. The composite foundation for coastal soft soil area reconstruction and expansion projects according to claim 1, characterized in that, The composite pile is a cement-fly ash-gravel pile.

3. The composite foundation for coastal soft soil area reconstruction and expansion projects according to claim 1, characterized in that, The height of the foundation gabion is equal to the depth of the receiving trench.

4. The composite foundation for coastal soft soil area reconstruction and expansion projects according to claim 1, characterized in that, The stiffness of the composite foundation is greater than that of the original foundation.

5. The composite foundation for coastal soft soil area reconstruction and expansion projects according to claim 1, characterized in that, The composite piles consist of multiple piles arranged in a rectangular pattern.

6. The composite foundation for coastal soft soil area reconstruction and expansion projects according to claim 5, characterized in that, The composite pile has a diameter of 400mm to 600mm and a pile spacing of 1200mm to 3000mm.

7. The composite foundation for coastal soft soil area reconstruction and expansion projects according to claim 1, characterized in that, The thickness of the anti-clogging crushed stone cushion layer is 200mm~500mm.

8. The composite foundation for coastal soft soil area reconstruction and expansion projects according to any one of claims 1 to 7, characterized in that, The foundation gabion includes a cage body, filled gravel inside the cage body, and grouting material filling the gaps between the filled gravel.

9. The composite foundation for coastal soft soil area reconstruction and expansion projects according to any one of claims 1 to 7, characterized in that, The warp-knitted composite layer comprises alternating layers of geotextile and geogrid.

10. A road widening project for reconstruction and expansion in coastal soft soil areas, characterized in that, Includes the composite foundation for coastal soft soil area reconstruction and expansion projects as described in any one of claims 1 to 9.

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