Vacuum preloading soft soil foundation reinforcement device with floating raft type cushion and method thereof

Abstract

This invention relates to a vacuum preloading device and method for reinforcing soft soil foundations using a floating raft cushion. The reinforcement device includes a sealing wall surrounding the soft soil foundation, with a floating raft cushion covering the soft soil foundation within the sealing wall. A drainage board is installed below the floating raft cushion, vertically inserted into the soft soil foundation with its upper end penetrating into the floating raft cushion. A vacuum sealing membrane covers the floating raft cushion, and a vacuum loading system is connected to the outside of the floating raft cushion. The vacuum loading system generates a vacuum negative pressure within the floating raft cushion to draw water from the soft soil foundation through the drainage board. This reinforcement device can be used on general soft soil foundations, extremely soft soil foundations, and suspended silt foundations. The construction process does not require the accumulation of large amounts of sand cushion layers, and reinforcement can be completed without multiple treatments, saving a significant amount of sand resources. It provides good preloading effect, a short construction cycle, and high efficiency. Furthermore, the floating raft cushion can be reused without damaging or polluting the environment, thus reducing construction costs and effectively protecting the environment.

Description

Technical Field

[0001] This invention relates to the field of soft soil foundation reinforcement technology, specifically to a vacuum preloading soft soil foundation reinforcement device and method using a floating raft cushion layer. Background Technology

[0002] Soft soil refers to fine-grained soil deposited in coastal areas, lakes, valleys, and riverbanks, characterized by high natural water content, large void ratio, high compressibility, and low shear strength. It is characterized by high natural water content, large natural void ratio, high compressibility, low shear strength, small consolidation coefficient, long consolidation time, high sensitivity, high disturbance, poor permeability, complex layered distribution, and significant differences in physical and mechanical properties between layers. Soft soil foundations refer to weak soil layers with low strength and high compressibility, often containing some organic matter. Due to its low strength and large settlement, soft soil often poses significant hazards to road engineering; improper handling can greatly affect construction and use.

[0003] Traditional methods for treating soft soil foundations include vacuum preloading. Vacuum preloading involves installing sand wells or plastic drainage boards within the soft soil foundation to be reinforced, then laying a sand cushion layer on the ground, which is covered with an airtight sealing membrane to isolate it from the atmosphere. Through suction pipes buried in the sand cushion layer, a vacuum device is used to extract air from the membrane, creating a pressure difference between the inside and outside of the membrane. This pressure difference is converted into a load acting on the foundation, preventing shear failure, which is advantageous for soft soil foundations. This method does not require surcharges, eliminating loading and unloading processes, shortening preloading time, and saving a large amount of surcharge materials. The equipment and construction technology used are relatively simple, requiring no large-scale equipment, and facilitating large-scale construction.

[0004] It has the following technical problems:

[0005] Vacuum preloading using sand cushion layers has high requirements for soft soil foundations and is only applicable to general soft soil foundations. It is not suitable for extremely soft soil foundations or suspended silt foundations. Furthermore, it is prone to uneven settlement, which can lead to sand layer fractures, requiring multiple treatments and resulting in low construction efficiency. At the same time, as the area of ​​the soft soil foundation increases, the amount of sand required for the sand cushion layer also increases exponentially. The scarcity of sand resources makes the implementation cost of vacuum preloading increasingly high, and the sand cannot be recycled and reused, resulting in significant waste. Summary of the Invention

[0006] To address the problems existing in the prior art, one of the objectives of this invention is to provide a vacuum preloading soft soil foundation reinforcement device with a floating raft cushion layer, which can adapt to the construction environment of ultra-soft soil or suspended silt foundation, can complete the reinforcement without multiple treatments, and can be reused, thereby reducing construction costs and improving construction efficiency.

[0007] The second objective of this invention is to provide a method for reinforcing a soft soil foundation using a floating raft cushion layer under vacuum preloading.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A vacuum preloading soft soil foundation reinforcement device with a floating raft cushion includes a sealing wall surrounding the soft soil foundation, a floating raft cushion covering the soft soil foundation inside the sealing wall, a drainage board installed below the floating raft cushion, the drainage board being vertically inserted into the soft soil foundation with its upper end penetrating into the floating raft cushion, a vacuum sealing membrane covering the floating raft cushion, and a vacuum loading system connected to the outside of the floating raft cushion. The vacuum loading system is used to generate a vacuum negative pressure inside the floating raft cushion to draw out water from the soft soil foundation through the drainage board.

[0010] Furthermore, the floating raft cushion layer includes a top plate, a bottom plate, and side plates enclosed within a sealing wall. The upper and lower ends of the side plates are connected to the top plate and the bottom plate, respectively. The bottom plate covers the soft soil foundation, and a vacuum sealing membrane covers the top plate. The space enclosed by the side plates, top plate, and bottom plate is filled with geotextile filter material. A drainage board is installed through the bottom plate, and the upper end of the drainage board is located between the top plate and the bottom plate.

[0011] Furthermore, a pad filter screen is attached to the bottom of the base plate, and a drainage board is inserted through the pad filter screen.

[0012] Furthermore, the bottom plate has an flared opening with a cross-section that gradually increases from top to bottom, and the minimum outer diameter of the flared opening matches the outer diameter of the drainage board.

[0013] Furthermore, a sand cushion layer is provided around the perimeter of the side plate, and the sand cushion layer is located between the top plate and the bottom plate, with the height of the sand cushion layer being adapted to the height of the floating raft cushion layer.

[0014] Furthermore, multiple partitions are provided between the top slab and the bottom slab. The upper and lower ends of each partition are connected to the top slab and the bottom slab respectively, and the left and right ends of each partition are connected to the side slab respectively. The multiple partitions intersect to form multiple grids, and the geotextile filter material is placed in each of the multiple grids.

[0015] Furthermore, the vacuum loading system is equipped with multiple vacuum tubes; these multiple vacuum tubes pass through the vacuum sealing membrane and are connected to multiple grids one by one.

[0016] Furthermore, both the base plate and the partition plate are provided with multiple through holes at intervals.

[0017] A method for reinforcing a vacuum preloaded soft soil foundation using a floating raft cushion includes the following steps:

[0018] A sealing wall is built around the soft soil foundation. A floating raft cushion layer is installed on the soft soil foundation inside the sealing wall. A drainage board is installed below the floating raft cushion layer. The drainage board is vertically inserted into the soft soil foundation with its upper end penetrating into the floating raft cushion layer. A vacuum sealing membrane is covered on the floating raft cushion layer. A vacuum loading system is used to generate a vacuum negative pressure in the floating raft cushion layer so that water from the soft soil foundation is drawn out through the drainage board and the floating raft cushion layer.

[0019] Furthermore, a sand pad layer is set between the top plate and the bottom plate around the side plate, and the friction between the sand pad layer and the bottom plate is used to eliminate the indentation deformation caused by the vacuum pressure acting on the side plate of the floating raft pad layer.

[0020] In summary, the present invention has the following advantages:

[0021] During construction, this reinforcement device involves first building a sealing wall around the soft soil foundation, then installing drainage boards on the surface. Next, a floating raft-type cushion layer is placed on the foundation surface, with drainage boards inserted one-to-one into the cushion layer. A vacuum sealing membrane is then placed over the cushion layer, and the cushion layer is connected to the vacuum loading system. After connection, vacuum preloading can be performed. This reinforcement device can be used on general soft soil foundations, extremely soft soil foundations, and suspended silt foundations. The construction process eliminates the need for large sand cushion layers, preventing sand layer fractures and eliminating the need for multiple treatments, thus saving significant sand resources. It offers excellent preloading results, a short construction cycle, and high efficiency. Furthermore, the floating raft-type cushion layer is reusable, preventing environmental damage or pollution, thereby reducing construction costs and effectively protecting the environment. Attached Figure Description

[0022] Figure 1 This is a schematic cross-sectional view of the middle section of a vacuum preloading soft soil foundation reinforcement device for a floating raft cushion layer.

[0023] Figure 2 A schematic diagram of the edge profile of a vacuum preloading soft soil foundation reinforcement device for a floating raft cushion layer.

[0024] Figure 3 This is a grid distribution diagram of the vacuum loading system of the present invention.

[0025] Figure 4 This is a schematic diagram of the floating raft structure of the present invention.

[0026] Figure 5 This is a schematic diagram of the bottom structure of the floating raft-type cushion layer of the present invention.

[0027] Figure 6 for Figure 5 A schematic diagram of AA.

[0028] Figure 7 for Figure 6 A magnified view of part C.

[0029] Figure 8 This is a schematic diagram of the raft bottom plate structure of the present invention.

[0030] Figure 9 for Figure 8 A schematic diagram of BB.

[0031] Figure 10 for Figure 9 A magnified view of part D.

[0032] Figure 11 This is a schematic diagram of the floating raft partition structure of the present invention.

[0033] The attached diagram includes:

[0034] 1-Side plate, 2-Top plate, 3-Partition plate, 4-Geotechnical filter material, 5-Bottom plate, 6-Cushion layer filter screen, 7-Vacuum sealing membrane, 8-Vacuum pipe, 9-Drainage board, 10-Sealing wall, 11-Sand cushion layer, 12-Filtration trench, 13-Soft soil foundation, 14-Through hole, 15-Flanged opening, 16-Drainage board hole, 17-Vacuum loading system, 18-Floating raft, 19-Floating raft cushion layer. Detailed Implementation

[0035] This device is connected to the floating raft cushion layer 19 through the vacuum loading system 17. A vacuum degree is generated in the floating raft cushion layer 19, and then the vacuum degree is diffused into the soft soil foundation 13 through the floating raft cushion layer 19, so that a water head gradient is formed between the floating raft cushion layer 19 and the soft soil, which draws out the pore water in the soft soil foundation 13, thereby improving the hardness and strength of the soft soil foundation 13 and achieving the purpose of reinforcing the soft soil.

[0036] The present invention will now be described in further detail.

[0037] like Figure 1 , Figure 2 As shown, a vacuum preloading soft soil foundation reinforcement device with a floating raft cushion includes a sealing wall 10 surrounding a soft soil foundation 13. A floating raft cushion 19 covers the soft soil foundation 13 inside the sealing wall 10. A drainage board 9 is provided below the floating raft cushion 19. The drainage board 9 is vertically inserted into the soft soil foundation 13 and its upper end penetrates into the floating raft cushion 19. A vacuum sealing membrane 7 covers the floating raft cushion 19. A vacuum loading system 17 is connected to the outside of the floating raft cushion 19. The vacuum loading system 17 is used to generate a vacuum negative pressure inside the floating raft cushion 19 so as to draw out water from the soft soil foundation 13 through the drainage board 9.

[0038] Specifically, the floating raft cushion layer 19 includes a top plate 2, a bottom plate 5, and side plates 1 enclosed within the sealing wall 10. The upper and lower ends of the side plates 1 are connected to the top plate 2 and the bottom plate 5, respectively. The bottom plate 5 covers the soft soil foundation 13. The vacuum sealing membrane 7 covers the top plate 2. The space enclosed by the side plates 1, the top plate 2, and the bottom plate 5 is filled with geotextile filter material 4. The drainage board 9 passes through the bottom plate 5, and the upper end of the drainage board 9 is located between the top plate 2 and the bottom plate 5.

[0039] Multiple top plates 2, bottom plates 5 and side plates 1 are arranged to form multiple floating rafts 18. The multiple floating rafts 18 are assembled in sections on the foundation surface to form an integral floating raft cushion layer 19.

[0040] Preferably, the raft 18 is rectangular in shape, with a length of 10-15m, a width of 0.5-1.5m, and a height of 0.3-0.5m; the top plate 2, bottom plate 5, and side plates 1 are made of composite materials or plastics.

[0041] The geotextile filter material 4 filling the floating raft 18 is a geotextile filter material 4 formed by one or more combinations of filter grid, sponge rubber, and geotextile sponge.

[0042] like Figure 6 , Figure 7 As shown, a cushion filter 6 is attached to the bottom of the base plate 5, and a drainage board 9 is inserted through the cushion filter 6; the cushion filter 6 is preferably a filter geotextile.

[0043] like Figure 8 , Figure 9 , Figure 10 As shown, the base plate 5 has a flared opening 15 with a cross-section that gradually increases from top to bottom, and the minimum outer diameter of the flared opening 15 matches the outer diameter of the drainage plate 9.

[0044] Drainage plate holes 16 are provided on the base plate 5 at certain intervals (usually 1m) to allow the drainage plates 9 to pass through. The diameter of the drainage plate holes 16 matches the outer diameter of the drainage plates 9. The lower end of the drainage plate holes 16 is set with a flared opening 15 to facilitate the insertion of the drainage plates 9.

[0045] like Figure 2 As shown, a sand cushion layer 11 is provided around the side plate 1. The sand cushion layer 11 is located between the top plate 2 and the bottom plate 5. The height of the sand cushion layer 11 is adapted to that of the floating raft cushion layer 19.

[0046] A sand pad 11 is set between the top plate 2 and the bottom plate 5 around the side plate 1. The friction between the sand pad 11 and the bottom plate 5 is used to eliminate the depression deformation caused by the vacuum pressure acting on the side plate 1 of the floating raft pad 19, thereby improving the overall stability of the reinforcement device and enhancing the drainage efficiency.

[0047] like Figure 4 , Figure 5As shown, multiple partitions 3 are provided between the top plate 2 and the bottom plate 5. The upper and lower ends of each partition 3 are connected to the top plate 2 and the bottom plate 5 respectively, and the left and right ends of each partition 3 are connected to the side plate 1 respectively. Multiple partitions 3 intersect to form multiple grids, and geotextile filter material 4 is placed in multiple grids respectively.

[0048] The partition 3 is located between the bottom plate 5 and the top plate 2, and mainly serves to support the top plate 2, preventing it from denting and deforming under vacuum pressure, thus improving the overall stability of the reinforcement device.

[0049] like Figure 3 As shown, the vacuum loading system 17 is provided with multiple vacuum tubes 8; the multiple vacuum tubes 8 pass through the vacuum sealing membrane 7 and are respectively connected to multiple grids one by one.

[0050] One end of the vacuum tube 8 is connected to the center of the floating raft 18, and the other end of the vacuum tube 8 is connected to the vacuum loading system 17, which provides the vacuum degree for drainage of the soft foundation. Each vacuum tube 8 is connected to a row of floating raft cushion layers 19; the vacuum tubes 8 can be further interconnected to form a mesh-like arrangement of vacuum tubes 8, so that the vacuum degree distribution is more uniform and it is beneficial to improve drainage efficiency.

[0051] like Figure 2 As shown, pressure grooves 12 are provided around the perimeter of the vacuum tube 8 along its extension direction. The edge of the vacuum sealing membrane 7 is buried in the pressure grooves 12 around the perimeter and filled with clay. A sealing wall 10 is provided below the pressure grooves 12 to form a sealing area reinforced by the soft soil foundation 13, so as to ensure the overall vacuum sealing of the reinforcement device.

[0052] like Figure 8 , Figure 11 As shown, both the base plate 5 and the partition plate 3 are provided with multiple through holes 14 at intervals.

[0053] Multiple through holes 14 evenly distributed on the base plate 5 and partition plate 3 serve to transmit vacuum pressure, making the overall vacuum degree of the floating raft pad 19 more uniform and effective, and avoiding vacuum pressure concentration.

[0054] A method for reinforcing a soft soil foundation using a vacuum preloading system with a floating raft cushion includes the following steps: constructing a sealing wall 10 around the soft soil foundation 13; setting a floating raft cushion 19 on the soft soil foundation 13 within the sealing wall 10; setting a drainage board 9 below the floating raft cushion 19; vertically inserting the drainage board 9 into the soft soil foundation 13 with its upper end penetrating into the floating raft cushion 19; covering the floating raft cushion 19 with a vacuum sealing membrane 7; and using a vacuum loading system 17 to generate a vacuum negative pressure within the floating raft cushion 19 to draw water out of the soft soil foundation 13 through the drainage board 9 and the floating raft cushion 19.

[0055] The specific steps are as follows:

[0056] Step 1: Clear and level the soft soil foundation 13 that needs to be reinforced; dig a membrane trench 12 around the soft soil foundation 13, and set a sealing wall 10 below the membrane trench 12 to form a sealed area for the reinforcement of the soft soil foundation 13.

[0057] Step 2: Measure and mark the distance of the drainage board holes 16 on the surface of the soft soil foundation 13 according to the distance of the drainage board holes 16 on the base plate 5, and then install a number of drainage boards 9 at the set distance.

[0058] Step 3: According to the distribution of drainage boards 9, place the bottom plate 5 of the floating raft cushion layer 19 on the surface of the soft soil foundation 13 that needs to be reinforced, and then pass several drainage boards 9 through the drainage board holes 16.

[0059] Step 4: Assemble the side plate 1 and partition plate 3 on the bottom plate 5, and fill the assembled and separated floating raft cushion layer 19 with geotextile filter material 4; among them, fill the outermost floating raft 18 with sand.

[0060] Step 5: After filling is completed, cover the top plate 2 on top of the floating raft cushion layer 19, and then cover the top plate 2 with a vacuum sealing film 7. The edges of the vacuum sealing film 7 are buried in the surrounding pressure trench 12 and filled with clay.

[0061] Step 6: Pass the vacuum tubes 8 through the vacuum sealing membrane 7 and the top plate 2 in sequence, and connect them to the center of the floating raft 18. Several floating rafts 18 are respectively equipped with vacuum tubes 8 at their centers. The vacuum tubes 8 are interconnected to form a mesh-like vacuum tube network 8.

[0062] Step 7: Connect the vacuum tube 8 to the vacuum loading system 17 for pre-compression; during pre-compression, check the integrity of the vacuum sealing membrane 7 and repair any leaks in time.

[0063] Step 8: After pre-compression is completed, the floating raft cushion layer 19 is recovered and cleaned for reuse.

[0064] This device uses a floating raft-type cushion layer 19 to replace the traditional sand cushion layer 11 for construction. Compared with the traditional vacuum preloading reinforcement method using a sand cushion layer 11, it can be applied not only to the reinforcement of general soft soil foundations 13, but also to the reinforcement of extremely soft soil foundations and environmental protection fields such as the dewatering treatment of waste soil from waterway dredging and river dredging. Its application range is wider. For example, for suspended silt foundations filled by hydraulic filling, the traditional vacuum preloading reinforcement method cannot be reinforced because a sand cushion layer 11 cannot be laid on it. However, this floating raft-type cushion layer 19 vacuum preloading method can be conveniently applied to reinforce suspended silt foundations filled by hydraulic filling. In addition, the water content of waste soil from waterway dredging and river dredging often exceeds 200%. This device and method can be used to efficiently and cost-effectively dewater the soil. During the treatment process, a large amount of sand resources are saved, sand stratification and fracture do not occur, multiple treatments are not required, the preloading effect is good, and it can be reused to avoid waste and is beneficial to environmental protection.

[0065] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A vacuum preloading soft soil foundation reinforcement device with a floating raft-type cushion layer, characterized in that: It includes a sealing wall built around the soft soil foundation, a floating raft cushion layer covering the soft soil foundation inside the sealing wall, a drainage board installed below the floating raft cushion layer, the drainage board being vertically inserted into the soft soil foundation with its upper end penetrating into the floating raft cushion layer, a vacuum sealing membrane covering the floating raft cushion layer, and a vacuum loading system connected to the outside of the floating raft cushion layer. The vacuum loading system is used to generate a vacuum negative pressure inside the floating raft cushion layer so as to draw out water from the soft soil foundation through the drainage board. The floating raft cushion layer includes a top plate, a bottom plate, and side plates enclosed within a sealing wall. The upper and lower ends of the side plates are connected to the top plate and the bottom plate, respectively. The bottom plate covers the soft soil foundation, and a vacuum sealing membrane covers the top plate. The space enclosed by the side plates, top plate, and bottom plate is filled with geotextile filter material. A drainage board is installed through the bottom plate, and the upper end of the drainage board is located between the top plate and the bottom plate. A sand cushion layer is provided around the side plate, and the sand cushion layer is located between the top plate and the bottom plate. The height of the sand cushion layer is adapted to the height of the floating raft cushion layer.

2. The vacuum preloading soft soil foundation reinforcement device with a floating raft cushion layer according to claim 1, characterized in that: A pad filter screen is attached to the bottom of the base plate, and a drainage board is inserted through the pad filter screen.

3. The vacuum preloading soft soil foundation reinforcement device with a floating raft cushion layer according to claim 1, characterized in that: The base plate has an flared opening with a cross-section that gradually increases from top to bottom, and the minimum outer diameter of the flared opening matches the outer diameter of the drainage board.

4. The vacuum preloading soft soil foundation reinforcement device with a floating raft cushion layer according to claim 1, characterized in that: Multiple partitions are provided between the top slab and the bottom slab. Each partition is connected to the top slab and the bottom slab at its upper and lower ends, respectively, and to the side slab at its left and right ends, respectively. The multiple partitions intersect to form multiple grids, and the geotextile filter material is placed in each of the multiple grids.

5. The vacuum preloading soft soil foundation reinforcement device with a floating raft cushion layer according to claim 4, characterized in that: Both the base plate and the partition plate have multiple through holes spaced apart.

6. The vacuum preloading soft soil foundation reinforcement device with a floating raft cushion layer according to claim 4, characterized in that: The vacuum loading system is equipped with multiple vacuum tubes; each vacuum tube passes through a vacuum sealing membrane and is connected to a corresponding grid.

7. A method for reinforcing a vacuum preloaded soft soil foundation with a floating raft cushion layer, characterized in that, The vacuum preloading soft soil foundation reinforcement device using a floating raft cushion layer as described in any one of claims 1-6 includes the following steps: A sealing wall is built around the soft soil foundation. A floating raft cushion layer is installed on the soft soil foundation inside the sealing wall. A drainage board is installed below the floating raft cushion layer. The drainage board is vertically inserted into the soft soil foundation with its upper end penetrating into the floating raft cushion layer. A vacuum sealing membrane is covered on the floating raft cushion layer. A vacuum loading system is used to generate a vacuum negative pressure in the floating raft cushion layer so that water from the soft soil foundation is drawn out through the drainage board and the floating raft cushion layer.

8. The method for reinforcing a vacuum preloaded soft soil foundation with a floating raft cushion layer according to claim 7, characterized in that: A sand pad layer is set between the top plate and the bottom plate on the periphery of the side plate. The friction between the sand pad layer and the bottom plate is used to eliminate the indentation deformation caused by the vacuum pressure acting on the side plate of the floating raft pad layer.

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