Soft foundation subgrade pavement structure and construction method

Abstract

The application relates to the technical field of soft foundation roadbed road construction, in particular to a soft foundation roadbed pavement structure which comprises, from bottom to top, a bearing layer, a soft foundation layer, a floating box layer, a roadbed layer and a pavement layer, a floating cavity is excavated in the soft foundation layer, the floating box layer is arranged in the floating cavity, a plurality of pipe piles are arranged below the floating box layer, the lower ends of the pipe piles are vertically inserted into the soft foundation layer and the bearing layer, the upper ends of the pipe piles are fixedly connected with the floating box layer, and the roadbed layer is arranged on the upper surface of the floating box layer; the pipe piles are used for providing the floating box layer with anti-pulling force. The application also relates to a construction method of the soft foundation roadbed pavement structure. The application has the effect of prolonging the service life of the road in the soft foundation area.

Description

Technical Field

[0001] This application relates to the technical field of soft soil subgrade road construction, and in particular to a soft soil subgrade pavement structure and construction method. Background Technology

[0002] The main characteristic of soft soil subgrade road construction is that the road is located in a soft soil area. Due to the groundwater level, the soil layer in the soft soil area has poor stability. Therefore, in order to carry out road construction in the soft soil area, it is necessary to replace the soft soil first, and then lay the subgrade and pavement.

[0003] A related technology discloses a soft soil treatment process for composite foundations in low-fill road sections, including leveling the ground surface, pressing prefabricated positioning rings into the foundation, forming an annular cavity above the positioning rings; then using pipe piles to press into the ground below the corresponding positioning rings, allowing the pipe piles to enter the bearing layer of the foundation, forming a chamber above the pipe piles; the soil in the annular cavity is cleaned into the inner cavity of the pipe piles, and the annular cavity and the chambers are connected to form a cylindrical cavity; a limiter is installed on the top of the pipe pile, connecting the pipe pile and the positioning ring; lightweight flexible filler is filled into the cylindrical cavity; loose filler is filled on top of the lightweight flexible filler to the original ground surface, forming a flexible support structure at the top of the pile; the cylindrical cavity is formed by the sequential pressing of the positioning rings and pipe piles, and lightweight flexible filler and loose filler are placed in the cylindrical cavity, thereby forming a soil arch effect and reducing road settlement.

[0004] However, the cylindrical cavity of the above structure is easily deformed by pressure due to the lightweight flexible filler, which in turn causes damage to the road surface and reduces the service life of the road. Summary of the Invention

[0005] In order to extend the service life of roads in soft soil areas, this application provides a soft soil subgrade pavement structure and construction method.

[0006] This application provides a soft soil subgrade pavement structure, which adopts the following technical solution:

[0007] A soft soil subgrade pavement structure includes a bearing layer, a soft base layer, a floating box layer, a road base layer, and a pavement layer arranged sequentially from bottom to top. A floating cavity is excavated in the soft base layer, and the floating box layer is disposed in the floating cavity. Multiple pipe piles are disposed below the floating box layer, with the lower end of the pipe piles vertically inserted into the soft base layer and the bearing layer, and the upper end of the pipe piles fixedly connected to the floating box layer. The road base layer is laid on the upper surface of the floating box layer. The pipe piles are used to provide pull-out resistance to the floating box layer.

[0008] By adopting the above technical solution, during use, the pipe piles are inserted into the soft base layer and bearing layer through the floating cavity. At the same time, the floating box layer is set in the floating cavity. The floating box layer has buoyancy, and the pipe piles connected to the floating box layer are used to provide the pull-out force of the floating box layer to resist the buoyancy of the floating box layer. Then, the road base layer and the pavement layer are laid on the floating box layer. Thus, the downward force on the pavement layer is transmitted to the floating box layer through the road base layer. It is first used to resist the buoyancy of the floating box layer to reduce the pull-out force of the pipe piles. Then, when the pull-out force is greater than zero, it can ensure that the floating box layer has high stability, reduce the deformation of the road base layer and the pavement layer, and thus enable the road in the soft soil area to have a longer service life.

[0009] Preferably, the upper end of the pipe pile is provided with a connecting bar, the floating box layer includes multiple concrete floating boxes, the concrete floating boxes are provided with embedded bars, and the embedded bars and connecting bars are fixedly connected by connecting sleeves.

[0010] By adopting the above technical solution, connecting bars are set at the upper end of the pipe pile, and the pontoon layer includes multiple concrete pontoons. The concrete pontoons have high strength and service life, and are fixed by setting connecting sleeves between the pre-embedded bars and the connecting bars, thereby improving the connection firmness of the concrete pontoons.

[0011] Preferably, the concrete pontoon is provided with lightweight filler, and a waterproof layer is provided between the lightweight filler and the inner wall of the concrete pontoon, the waterproof layer being adhered to the lightweight filler and the concrete pontoon.

[0012] By adopting the above technical solution, lightweight filler is set inside the concrete pontoon, which allows the concrete pontoon to be supported during construction. The waterproof layer is first applied to the lightweight filler and then adhered to the inner layer of the concrete pontoon, which facilitates the construction of the hollow concrete pontoon. At the same time, the waterproof layer is supported by the lightweight filler, resulting in higher connection strength, reduced detachment, and higher waterproof performance.

[0013] Preferably, a connecting chamber is provided between the bottom of the concrete pontoon and the pontoon cavity, and a casting chamber is provided between the two sides of the concrete pontoon and the inner wall of the pontoon cavity. The casting chamber is connected to the connecting chamber, and foamed concrete is poured in the casting chamber and the connecting chamber to form a blocking part and a connecting part, respectively.

[0014] By adopting the above technical solution, concrete is poured into the connecting chamber and the pouring chamber, so that the pouring chamber and the connecting chamber form an integrated connecting part and a blocking part. The blocking part is located on both sides of the concrete pontoon, which further improves the strength of the concrete.

[0015] Preferably, a stepped groove is formed at the upper part of the blocking part, the stepped groove is located on the side of the blocking part close to the concrete pontoon, a precast block is connected to the upper side of the blocking part, and a plug is provided at the lower part of the precast block, the plug being slidably inserted into the stepped groove; a prestressed tie rod for connecting the two precast blocks is provided between the precast blocks on both sides of the concrete pontoon.

[0016] By adopting the above technical solution, the precast blocks are connected in the stepped groove through the plug joint, so that the precast blocks can be stuck on both sides of the concrete pontoon under the action of the stepped groove, which further improves the stability of the concrete pontoon. At the same time, it is more convenient to directly install the precast blocks during construction. Furthermore, the prestressed tie rods between the precast blocks make the two precast blocks better at preventing the lateral movement of the concrete pontoon.

[0017] Preferably, the prestressed tie rod includes an end and a rod portion, the diameter of the end being larger than the diameter of the rod portion, and a vertical connecting groove is provided on the upper part of the precast block, the cross-section of the connecting groove being T-shaped, and the end being placed in the connecting groove.

[0018] By adopting the above technical solution, the diameter of the end is larger than the diameter of the rod. When connecting the prestressed tie rod, the end of the prestressed tie rod is directly placed into the connecting groove, which makes the connection between the prestressed tie rod and the precast block more convenient. At the same time, the prestressed tie rod can have a higher tensile strength and improve its service life.

[0019] Preferably, a prestressed steel bar is provided at the center of the rod, and a spiral-shaped reinforcing bar is provided on the outside of the prestressed steel bar. The outside of the prestressed steel bar is wrapped with concrete to form the prestressed tie rod.

[0020] By adopting the above technical solution, the prestressed steel bars are placed at the center of the rod, and the strength of the prestressed tie rod of the concrete structure is increased by setting spiral reinforcement on the outside.

[0021] Preferably, the road base layer includes a sand layer, a gravel layer, and a modified soil layer, wherein the sand content of the sand layer is 90%-95%; the sand layer is laid on the floating box layer; the gravel layer is laid on the sand layer; and the modified soil layer has a ratio of hydrated lime to soil of 3:40-50.

[0022] By adopting the above technical solutions, the road base formed by the sand layer, crushed stone layer and modified soil layer reduces the damage to the floating box layer due to the contact between the sand layer and the floating box layer, and the crushed stone layer is laid on the sand layer, which improves the support strength of the road surface layer.

[0023] Preferably, after the upper surface of the sand layer is compacted, cement slurry is sprayed to form a transition layer, and the water-cement ratio of the cement slurry is 0.8-1.2.

[0024] By adopting the above technical solution, the transition layer formed by spraying cement slurry on the upper surface of the sand layer has the function of preventing loosening. On the one hand, it can enable the gravel and the sand layer to make good contact and firmly connect. On the other hand, it can prevent the gravel layer from entering the sand layer and reduce the occurrence of hollowing in the gravel layer.

[0025] This application also provides a construction method for soft soil subgrade pavement structure, which adopts the following technical solution:

[0026] A construction method for a soft subgrade and pavement structure includes excavating a floating cavity on the soft subgrade, inserting pipe piles into the bottom of the floating cavity, fixing the upper end of the pipe piles to a floating box layer, and then laying the subgrade and pavement layers sequentially on the floating box layer.

[0027] By adopting the above technical solution, a floating cavity is excavated in the soft base layer, and then pipe piles are inserted into the bottom of the floating cavity. This allows the pipe piles to fix the floating box layer to the pipe piles within the soft base layer. The pipe piles can provide pull-out resistance, which resists the buoyancy of the floating box layer. This makes the floating box layer more stable when subjected to upward and downward forces, thereby enabling the road in the soft base area to have a longer service life.

[0028] In summary, this application includes at least one of the following beneficial technical effects:

[0029] 1. By first using the buoyancy of the floating box layer to reduce the pull-out force of the pipe pile, the floating box layer can be guaranteed to have high stability when the pull-out force is greater than zero, reducing the deformation of the subgrade and pavement layers, thereby enabling roads in soft soil areas to have a longer service life.

[0030] 2. The casting chamber and the connecting chamber form an integrated connecting part and a blocking part, with the blocking part located on both sides of the concrete pontoon, further improving the strength of the concrete;

[0031] 3. By setting prestressed steel bars at the center of the rod and setting spiral reinforcement bars on the outside of the prestressed steel bars, the strength of the prestressed tie rod in the concrete structure is increased. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall cross-sectional structure of an embodiment of this application;

[0033] Figure 2 This is a schematic diagram of the structure of the floating cavity in an embodiment of this application;

[0034] Figure 3 yes Figure 2 Enlarged view of section A;

[0035] Figure 4 This is a schematic diagram of the internal structure of the concrete pontoon in an embodiment of this application;

[0036] Figure 5This is a schematic diagram showing the location of the tie rod in an embodiment of this application;

[0037] Figure 6 This is a schematic diagram of the installation position of the prefabricated block in an embodiment of this application;

[0038] Figure 7 This is a schematic diagram of the reinforcing bar structure in an embodiment of this application.

[0039] Explanation of reference numerals in the attached drawings: 1. Bearing layer; 2. Soft base layer; 21. Floating cavity; 22. Connecting chamber; 23. Casting chamber; 24. Tie bar; 3. Floating box layer; 31. Concrete floating box; 311. Embedded bar; 32. Lightweight filler; 4. Road base layer; 41. Sand layer; 42. Crushed stone layer; 43. Modified soil layer; 44. Transition layer; 5. Pavement layer; 6. Pipe pile; 61. Connecting bar; 62. Connecting sleeve; 71. Connecting part; 72. Blocking part; 721. Step groove; 8. Precast block; 81. Insert joint; 82. Connecting groove; 9. Prestressed tie rod; 91. End; 92. Rod part; 93. Prestressed steel bar; 94. Reinforcing bar wrapping. Detailed Implementation

[0040] The following is in conjunction with the appendix Figure 1-7 This application will be described in further detail.

[0041] This application discloses a soft soil subgrade pavement structure, with reference to... Figure 1 and Figure 2 The structure includes a bearing layer 1, a soft base layer 2, a floating box layer 3, a road base layer 4, and a pavement layer 5 arranged from bottom to top. The soft base layer 2 is formed from soft soil below the ground. The bearing layer 1 is a soil layer below the soft soil where the geological structure is suitable for the construction of pipe piles 6. A portion of the soft soil is excavated inside the soft base layer 2 along the design direction of the road to form a floating cavity 21. The floating box layer 3 is constructed inside the floating cavity 21. Then, the road base layer 4 is laid on the floating box layer 3, and the pavement layer 5 is constructed on the road base layer 4.

[0042] During construction, after excavating the floating cavity 21, drainage is required if water is present within it. Multiple pipe piles 6 are vertically inserted downwards into the floating cavity 21, with the piles located at the bottom and their upper ends extending at least 30cm beyond the top of the cavity. The lower ends of the pipe piles 6 penetrate the soft base layer 2 and enter the bearing layer 1. The depth of the pipe piles 6 into the bearing layer 1 is determined according to road design requirements. The pipe piles 6 are designed to resist pull-out; the friction between the pipe piles 6 and the bearing layer 1 and soft base layer 2, along with the weight of the pipe piles 6, provide pull-out resistance. When the pipe piles 6 are located within the bearing layer 1, their movement is reduced by the influence of the bearing layer 1. The depth of the pipe piles 6 within the bearing layer 1 is at least 50m. When the length of the pipe piles 6 within the soft base layer 2 is longer, the weight of the pipe piles 6 is greater, thus reducing the depth of the pipe piles 6 within the bearing layer 1.

[0043] refer to Figure 2 and Figure 3 Above the pipe pile 6 is the construction site for the floating box layer 3, which is connected to the upper end of the pipe pile 6. During construction, the upper end of the pipe pile 6 is first removed as needed to expose the connecting rib 61, which is vertically installed. Embedded ribs 311 are installed on the lower surface of the floating box layer 3, with the exposed portion of the ribs 311 pointing vertically downwards. A connecting sleeve 62 is installed between the upper end of the connecting rib 61 and the lower end of the embedded rib 311, fixing the pipe pile 6 to the floating box layer 3.

[0044] refer to Figure 2 and Figure 4 The floating box layer 3 includes multiple concrete floating boxes 31, which are hollow structures to provide buoyancy. Lightweight filler 32, such as polystyrene foam, is filled inside each floating box 31. The inner wall of the floating box 31 is coated with a waterproof layer. During construction, the lightweight filler 32 can be made into rectangular blocks. The waterproof layer is first applied to the outer surface of the lightweight filler 32, and then the concrete floating box 31 is poured, allowing the waterproof layer to adhere to the inner surface of the floating box 31. Simultaneously, the lightweight filler 32 supports the floating box 31. Using concrete floating boxes 31 improves load-bearing capacity. Furthermore, after construction, the floating boxes 31 are located within the soft base layer 2 and will experience buoyancy from the soft base layer 2, especially when the soft base layer 2 contains a high amount of water. Since the concrete pontoon 31 is fixed on the pipe pile 6, the pipe pile 6 can stably keep the concrete pontoon 31 within the soft base layer 2. When a vehicle lightly passes over the road surface layer 5, the concrete pontoon 31 bears the downward force transmitted by the road surface layer 5. Since the anti-buoyancy force provided by the pipe pile to the concrete pontoon 31 can offset the force transmitted by the road surface layer 5, the concrete pontoon 31 is stably placed within the soft base layer 2.

[0045] refer to Figure 4 and Figure 5The embedded reinforcing bars 311 are L-shaped and can be fixedly connected to the reinforcing bars inside the concrete pontoon 31. In this embodiment, two concrete pontoons 31 are arranged along the width of the road, and three pipe piles 6 are arranged along the width of the road, so that the upper end of the middle pipe pile 6 is below the two concrete pontoons 31, connecting the middle pipe pile 6 to the two concrete pontoons 31, thereby making the relative position of the two concrete pontoons 31 more stable; at the same time, two adjacent concrete pontoons 31 along the length of the road are also connected to the same pipe pile 6. Each pipe pile 6 has multiple connecting reinforcing bars 61 at its upper end, with one embedded reinforcing bar 311 corresponding to one connecting reinforcing bar 61. When the concrete pontoon 31 is placed on the upper end of the pipe pile 6, a connection chamber 22 of at least 15cm is formed between the lower surface of the concrete pontoon 31 and the bottom surface of the pontoon cavity 21. Workers can pour concrete into the connecting sleeve 62 from the connection chamber 22 to firmly connect the concrete pontoon 31 to the pipe pile 6.

[0046] refer to Figure 5 and Figure 6 A casting chamber 23 is provided between the side wall of the floating cavity 21 and the corresponding side wall of the concrete pontoon 31. The casting chamber 23 is connected to the connecting chamber 22. A tie rod 24 is provided in the connecting chamber 22, extending from the casting chamber 23 on one side of the concrete pontoon 31 through the connecting chamber 22 to the casting chamber 23 on the other side of the concrete pontoon 31. Foamed concrete is poured in the connecting chamber 22 and the casting chamber 23, forming a connecting part 71 in the connecting chamber 22 and a blocking part 72 in the casting chamber 23. The connecting part 71 and the blocking part 72 are integrally set. Since the two blocking parts 72 are located on both sides of the concrete pontoon 31, and the distance between the two blocking parts 72 is limited by the connecting part 71, the lateral slippage of the concrete pontoon 31 can be reduced.

[0047] refer to Figure 6 A stepped groove 721 is formed above the blocking part 72, located on the side of the blocking part 72 near the concrete pontoon 31. Multiple precast blocks 8, made of concrete, are arranged along the length of the blocking part 72, spaced apart. A connector 81 is formed at the lower part of each precast block 8, which is slidably inserted into the stepped groove 721. A prestressed tie rod 9 is provided at the upper end of the connector 81, connecting two connectors 81 on both sides of the concrete pontoon 31. This allows the connectors 81 and the prestressed tie rod 9 to restrict the position of the upper sides of the concrete pontoon 31. Simultaneously, combined with the blocking part 72 at the lower part of the concrete pontoon 31, it stably confines the concrete pontoon 31 within the soft base layer 2.

[0048] refer to Figure 6 and Figure 7The prestressed tie rod 9 includes an end 91 and a rod 92. The diameter of the end 91 is larger than the diameter of the rod 92. A prestressed steel bar 93 is provided at the center of the rod 92. A reinforcing bar 94 is provided on the outside of the prestressed steel bar 93. The reinforcing bar 94 has a spiral structure. The prestressed tie rod 9 is then formed by pouring concrete to wrap the reinforcing bar 94. A connecting groove 82 is provided at the upper end of the precast block 8. The connecting groove 82 has a T-shaped cross-section and is vertically opened so that the two ends of the prestressed tie rod 9 are respectively located in the connecting groove 82 of the two precast blocks 8. This allows the prestressed tie rod 9 to connect the two precast blocks 8, which is convenient to operate. At the same time, the use of the prestressed tie rod 9 can improve the service life and reduce the damage of the prestressed tie rod 9.

[0049] refer to Figure 1 The road base layer 4 includes a sand layer 41, a crushed stone layer 42, and a modified soil layer 43. The sand layer 41 has a sand content of 90%-95%. The sand layer 41, crushed stone layer 42, and modified soil layer 43 are arranged sequentially from bottom to top. During construction, the sand layer 41 is first laid on the floating box layer 3 and extends to the top of the soft base layer 2 on both sides, so that the sand layer 41 completely covers the floating cavity 21. At the same time, the sand layer 41 can stably transfer the force of the road surface to the floating box layer 3, reducing damage to the floating box layer 3. When laying the sand layer 41, it is compacted using a subgrade roller. Then, cement slurry with a water-cement ratio of 0.8-1.2 is sprayed onto the upper surface of the sand layer 41, allowing the slurry to penetrate into the compacted sand layer 41 and form a transition layer 44 on top. After the cement slurry solidifies, a crushed stone layer 42 is laid. The crushed stone layer 42 can transfer the force to the sand layer 41 through the transition layer 44. Furthermore, because the transition layer 44 forms clumps, it reduces the risk of voids in the crushed stone layer 42 caused by movement into the sand layer 41. After the crushed stone layer 42 is laid and leveled, a modified soil layer 43 is laid on top of it and compacted in layers. The modified soil layer 43 has a lime-to-soil ratio of 3:40-50. The pavement layer 5 is an asphalt structure, laid on top of the modified soil layer 43 and then leveled.

[0050] This embodiment also discloses a construction method for a soft soil subgrade pavement structure. The construction of the above-mentioned soft soil pavement structure includes excavating a floating cavity 21 in the soft base layer 2, constructing pipe piles 6 at the bottom of the floating cavity 21, fixing the upper end of the pipe piles 6 to the concrete floating box 31 of the floating box layer 3, then pouring foamed concrete to fill the gap between the inner wall of the floating cavity 21 and the floating box, then connecting precast blocks 8 to both sides of the floating box layer 3, and then laying a sand layer 41, a crushed stone layer 42, a modified soil layer 43 and a pavement layer 5 in sequence.

[0051] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A soft soil subgrade pavement structure, characterized in that: The structure includes, from bottom to top, a bearing layer (1), a soft base layer (2), a floating box layer (3), a road base layer (4), and a road surface layer (5). A floating cavity (21) is excavated in the soft base layer (2). The floating box layer (3) is located in the floating cavity (21). Multiple pipe piles (6) are installed below the floating box layer (3). The lower ends of the pipe piles (6) are vertically inserted into the soft base layer (2) and the bearing layer (1). The upper ends of the pipe piles (6) are fixedly connected to the floating box layer (3). The road base layer (4) is laid on the upper surface of the floating box layer (3). The pipe piles (6) are used to provide pull-out resistance to the floating box layer (3). The upper end of the pipe pile (6) is provided with a connecting bar (61), the floating box layer (3) includes multiple concrete floating boxes (31), the concrete floating boxes (31) are provided with embedded bars (311), and the embedded bars (311) and the connecting bars (61) are fixedly connected by connecting sleeves (62). A connecting chamber (22) is provided between the bottom of the concrete pontoon (31) and the pontoon (21). A casting chamber (23) is provided between the two sides of the concrete pontoon (31) and the inner wall of the pontoon (21). The casting chamber (23) is connected to the connecting chamber (22). Foamed concrete is poured in the casting chamber (23) and the connecting chamber (22) to form a blocking part (72) and a connecting part (71) respectively. A stepped groove (721) is formed at the upper part of the blocking part (72). The stepped groove (721) is located on the side of the blocking part (72) close to the concrete pontoon (31). A precast block (8) is connected to the upper side of the blocking part (72). A plug-in joint (81) is provided at the lower part of the precast block (8). The plug-in joint (81) is slidably inserted into the stepped groove (721). A prestressed tie rod (9) for connecting the two precast blocks (8) is provided between the precast blocks (8) on both sides of the concrete pontoon (31).

2. The soft soil subgrade pavement structure according to claim 1, characterized in that: The concrete pontoon (31) is provided with lightweight filler (32), and a waterproof layer is provided between the lightweight filler (32) and the inner wall of the concrete pontoon (31). The waterproof layer is adhered to the lightweight filler (32) and the concrete pontoon (31).

3. The soft soil subgrade pavement structure according to claim 1, characterized in that: The prestressed tie rod (9) includes an end (91) and a rod (92). The diameter of the end (91) is larger than the diameter of the rod (92). A vertical connecting groove (82) is provided on the upper part of the precast block (8). The cross-section of the connecting groove (82) is T-shaped. The end (91) is placed in the connecting groove (82).

4. A soft soil subgrade pavement structure according to claim 3, characterized in that: The center of the rod (92) is provided with a prestressed steel bar (93), and the outside of the prestressed steel bar (93) is provided with a wrapping bar (94). The wrapping bar (94) is spiral in shape, and the outside of the prestressed steel bar (93) is wrapped with concrete to form the prestressed tie rod (9).

5. A soft soil subgrade pavement structure according to claim 1, characterized in that: The road base (4) includes a sand layer (41), a crushed stone layer (42) and a modified soil layer (43). The sand content of the sand layer (41) is 90%-95%. The sand layer (41) is laid on the floating box layer (3). The crushed stone layer (42) is laid on the sand layer (41). The modified soil layer (43) has a ratio of hydrated lime to soil of 3:40-50.

6. A soft soil subgrade pavement structure according to claim 5, characterized in that: After the upper surface of the sand layer (41) is compacted, cement slurry is sprayed to form a transition layer (44), and the water-cement ratio of the cement slurry is 0.8-1.2.

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