A new type of pipe pile raft foundation capable of self-reinforcement and a construction method thereof

Abstract

The present application belongs to the technical field of pile raft foundation, and discloses a novel pipe pile raft slab foundation capable of self-reinforcing, which comprises a pipe pile, a pile top block, a rubber slab layer arranged on the pile top block, a full-steel slab layer arranged on the rubber slab layer, and a jack, wherein the jack is located above the pipe pile, the bottom of the jack is pressed on the full-steel slab layer, and the top end of the jack is connected with a steel bar, the steel bar passes through the rubber slab layer and the full-steel slab layer and is connected to the pile top block, the full-steel slab layer comprises a steel slab corresponding to the pipe pile, the steel slab is arranged in the foundation area, the edges of the steel slabs on the top of adjacent pipe piles are sealed by filling the gaps therebetween, the jack is used for pre-pressing the full-steel slab layer downward in the state that the steel bar is tensioned, and a sand cushion layer is arranged below the full-steel slab layer and outside the pile top block, and a device pipeline for vacuum extraction is connected. The present application avoids the time-consuming repair and replacement of the film in the prior art, and effectively improves the construction efficiency.

Description

Technical Field

[0001] This invention belongs to the field of pile-raft foundation technology, specifically relating to a novel self-reinforcing pipe pile raft foundation and its construction method. Background Technology

[0002] In riverside and coastal sedimentary areas, loose sandy soil layers often have low consolidation, high water content, and low bearing capacity due to the shallow natural soil layers. When piles are laid under the raft foundation, the load is almost entirely borne by the piles, resulting in a large number of piles. Loose sandy soil layers often exhibit significant negative skin friction affecting the pile foundation's bearing capacity. Sandy soil also has a liquefaction effect, which is detrimental to the structural foundation's safety. Traditional vacuum preloading methods use surface covering membranes, but current vacuum preloading methods require a large-scale, separate installation of sealing membranes. Uneven site surfaces and the risk of gravel and construction machinery puncturing the membranes lead to delays in repair, and most membranes are damaged and unusable after excavation, resulting in low reuse rates and increased project costs. Furthermore, current technologies require the installation of vertical drainage systems, complicating the process; backfilling requires layered transport and spreading, resulting in large earthwork volumes, limited on-site transportation, and subsequent unloading and removal costs. Summary of the Invention

[0003] The purpose of this invention is to provide a novel self-reinforcing pipe pile raft foundation to solve the technical problems of existing technologies that use surface coating technology, where the film is easily punctured and damaged, and is difficult to reuse after excavation, resulting in high costs.

[0004] The aforementioned novel self-reinforcing pipe pile raft foundation includes pipe piles and a pile top block, as well as a rubber sheet layer on the pile top block, a full-coverage steel plate layer on the rubber sheet layer, and jacks. The jacks are located above the pipe piles, with their bottoms pressing against the full-coverage steel plate layer and their tops connected to reinforcing bars. The reinforcing bars pass through the rubber sheet layer and the full-coverage steel plate layer and connect to the pile top block. The full-coverage steel plate layer includes steel plates corresponding one-to-one with the pipe piles, and the steel plates are fully distributed throughout the foundation area. The gaps between the edges of the steel plates at the top of adjacent pipe piles are filled and sealed. The jacks are used to pre-press the full-coverage steel plate layer downwards when the reinforcing bars are tensioned. A sand cushion layer is laid below the full-coverage steel plate layer outside the pile top block, and a vacuum equipment pipeline is connected to it.

[0005] Preferably, the rubber sheet layer includes a perforated rubber sheet corresponding to a pipe pile, the perforated rubber sheet having through holes, and a steel plate having reserved openings, the reserved openings corresponding to the through holes; a reserved steel pipe corresponding to and communicating with the reserved openings is welded to the steel plate, and the reinforcing bars pass through the through holes, the reserved openings and the steel pipes in sequence.

[0006] Preferably, an integral steel plate plane is formed on the surface within the pipe pile area, and a film is connected to the bottom perimeter of the steel plate. The edges of the film are fixed by a sealing trench method. The film is used to seal the gaps between the edges of the steel plate. Above the film, the gaps between the edges of the steel plate are filled with asphalt hemp fiber.

[0007] Preferably, the sidewall of the pipe pile is provided with a drainage hole, and the central hole of the pipe pile is provided with a water inlet pipe for a drainage device.

[0008] Preferably, the size of the gap between the edges of the steel plates is 10~20mm.

[0009] The present invention also provides a construction method for a novel self-reinforcing pipe pile raft foundation as described above, comprising the following steps: Step 1: After the pipe pile construction is completed, connect the reinforcing bars, pour the pile top block, and install the perforated rubber plate and steel plate in sequence on the top of each pile. Before installing the steel plate, set a sand cushion layer on the soil surface outside the pile top block, and then let the reinforcing bars pass through the pile top block, the perforated rubber plate and the steel plate. Step 2: Install jacks on the steel plate and fix the upper end of the reinforcing bar to the top of the jacks; Step 3: Pre-install the air inlet pipe of the vacuum device in the sand pad layer under the steel plate, and draw a vacuum until the vacuum pressure reaches the design requirements and stabilizes. Step 4: While maintaining vacuum pressure, use a compensating jack to apply pressure to the foundation soil under the steel plate through the steel plate. Step 5: During the vacuum preloading process, water in the soil enters the pipe pile through the drainage holes on the side wall of the pipe pile and is pumped out from the pipe pile through the drainage device. Step 6: After vacuum preloading is completed, the steel plates and jacks are removed and recycled. The pressurized foundation soil and piles are tested. Once the design foundation target value is reached, the next step of construction can be carried out.

[0010] Preferably, in step 1, after the pipe pile construction is completed, a hole is opened in the side wall of the pipe pile for drainage.

[0011] Preferably, in step 1, the edges of the steel plates are joined together on the plane of the sand cushion layer, and a film is reliably connected to the edges of the steel plates. The edges of the film are fixed by means of sealing grooves, etc., and the gaps between the edges of the steel plates are filled with asphalt hemp fiber to achieve sealing.

[0012] Preferably, in step 4, the jack generates a vertical upward pulling force on the pipe pile through the connecting steel bars, and the applied load is controlled at 1 / 2 of the limit value of the friction force of the soil around the pile.

[0013] This invention has the following advantages: Since it uses a steel plate instead of a membrane, it is less prone to damage during construction, avoiding the time-consuming repairs and replacements of membranes in existing technologies, thus effectively improving construction efficiency. Furthermore, the steel plate remains largely intact after use, allowing for multiple reuses and significantly reducing construction material costs. The perforated rubber sheet is plastic, enabling effective compression of the steel plate during the extrusion process, avoiding the problem of rigid structures being unable to achieve vacuum pre-compression.

[0014] This invention utilizes pipe piles as vertical drainage bodies, eliminating the need for separate installations and saving on engineering work and construction time. Applying this invention reduces negative skin friction in pile foundations, increases the design value of pile bearing capacity, and significantly improves the bearing capacity of the pile foundation after considering the interaction between piles and soil. This effectively reduces the number of piles, saves investment, and reduces carbon emissions. Attached Figure Description

[0015] Figure 1 This is a partial plan view of a novel self-reinforcing pipe pile raft foundation according to the present invention, which is fully covered with steel plate layers. Figure 2 for Figure 1 A cross-sectional view along the AA direction in the structure shown; Figure 3 This is a schematic diagram of the pipe pile installation in this invention; Figure 4 This is a comparison diagram of the number of piles after the foundation was reinforced using existing technology and the present invention in the embodiments.

[0016] The markings in the attached diagram are as follows: 1 Pipe pile, 2 Pile top block, 3 Jack, 4 Reinforcing bar, 5 Steel plate, 6 Sand cushion, 7 Perforated rubber sheet, 8 Reserved steel pipe, 9 Drainage hole, 10 Center hole, 11 Asphalt hemp fiber. Detailed Implementation

[0017] The following detailed description of the embodiments, with reference to the accompanying drawings, will further illustrate the specific implementation of the present invention, in order to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention.

[0018] like Figures 1-4As shown, this invention provides a novel self-reinforcing pipe pile raft foundation, including pipe piles 1 and pile top blocks 2, as well as a rubber sheet layer on the pile top blocks 2, a full-coverage steel plate layer 5 on the rubber sheet layer, and a jack 3. The jack 3 is located above the pipe piles 1, with its bottom pressing on the full-coverage steel plate layer 5 and its top connected to a reinforcing bar 4. The reinforcing bar 4 passes through the rubber sheet layer and the full-coverage steel plate layer 5 and connects to the pile top blocks 2. The full-coverage steel plate layer 5 includes steel plates 5 corresponding one-to-one with the pipe piles 1, and the steel plates 5 are fully distributed in the foundation area. The gaps between the edges of the steel plates 5 at the top of adjacent pipe piles 1 are filled and sealed. The jack 3 is used to pre-press the full-coverage steel plate layer 5 downward when the reinforcing bar 4 is tensioned. A sand cushion layer 6 is laid on the part of the full-coverage steel plate layer outside the pile top blocks 2 and connected to the equipment pipeline for vacuuming.

[0019] Through the structure of the raft foundation described above, the jack 3 can press down the steel plate 5 and the loose sand layer under the steel plate 5, and at the same time, it can also perform vacuuming through the equipment pipeline, thereby realizing the vacuum preloading method based on the full layer of steel plate 5, thus effectively realizing the combined preloading of the loose sand layer, causing the water in it to be forced out, making the soil denser, and improving the consolidation degree of the original foundation soil.

[0020] Furthermore, since this invention uses a steel plate 5 instead of a thin film, it is not easily damaged during construction, avoiding the time spent on repairing and replacing the film in existing technologies, thus effectively improving construction efficiency. At the same time, the steel plate 5 remains largely intact after use, allowing for multiple reuses and significantly reducing construction material costs. The perforated rubber sheet 7 is plastic, allowing the steel plate 5 to be effectively pressed down during the extrusion process, avoiding the problem of rigid structures being unable to achieve vacuum pre-compression.

[0021] The rubber sheet layer includes perforated rubber sheets 7 corresponding to the pipe piles 1 one-to-one. Each perforated rubber sheet 7 has through holes for the reinforcing bars 4 to pass through. A steel plate 5 has pre-drilled openings, each corresponding to one of the through holes for the reinforcing bars 4 to pass through. A pre-drilled steel pipe 8, corresponding to one of the pre-drilled openings, is welded to the steel plate 5. The upper end of the steel pipe extends straight towards the output end of the jack 3, and the reinforcing bars 4 pass through the pre-drilled steel pipe 8. Through the pre-drilled holes and steel pipes, the reinforcing bars 4 are allowed to pass through the end connecting to the jack 3 while maintaining the direction of extension, facilitating the fixed connection between the reinforcing bars 4 and the top of the jack 3. The pre-drilled steel pipe 8 and the reinforcing bars 4 are sealed with grease.

[0022] The reinforcing bar 4 passes through the top of the pile top block 2, with its lower end connected to the lower side of the pile top block 2. This allows the reinforcing bar 4 to almost pass through the pile top block 2, ensuring reliable fixation between the pile top block 2 and the reinforcing bar 4 after its formation, thus preventing displacement of the reinforcing bar 4 when the jack 3 applies excessive pressure. The jack 3 is positioned perpendicular to the steel plate 5, and several reinforcing bars 4 are symmetrically arranged around the jack 3 to ensure a stable pressure direction applied by the jack 3 to the steel plate 5. The top of the reinforcing bar 4 extends diagonally upwards from the outside of the jack 3 and is fixedly connected to it.

[0023] A monolithic steel plate 5 is formed on the surface of the pipe pile 1. A membrane is connected to the bottom perimeter of the steel plate 5, and the edges of the membrane are fixed using a sealing trench method. The membrane is used to seal the gaps between the edges of the steel plate 5. The size of the gaps between the edges of the steel plate 5 is 10~20mm. Above the membrane, asphalt-impregnated hemp fibers 11 can also be used to fill the gaps between the edges of the steel plate 5. In this way, the gaps between the edges of the steel plate 5 can be effectively filled by the above method, preventing air and water leakage. The membrane and asphalt-impregnated hemp fibers 11 can still ensure a good sealing effect when the height or gap between adjacent steel plates 5 changes slightly.

[0024] The pipe pile 1 has drainage holes 9 on its sidewalls, and a water inlet pipe for a drainage device is installed in the central hole 10 of the pipe pile 1. In this way, the present invention utilizes the pipe pile 1 as a vertical drainage body without the need for separate installation, saving engineering work and construction time. A sleeve is fitted over the pipe pile 1, and the sleeve also has water flow holes corresponding to the drainage holes 9. The sand cushion layer 6 serves as a drainage layer in the vacuum preloading method and can continue to be used as the lower cushion layer of the raft foundation after construction is completed.

[0025] This invention also provides a construction method for a novel self-reinforcing pipe pile raft foundation, comprising the following steps: Step 1: After the pipe pile 1 is constructed, connect the reinforcing bars 4, pour the pile top block 2, and arrange the perforated rubber plate 7 and steel plate 5 in sequence on the top of each pile. Before setting the steel plate 5, set a sand cushion layer 6 on the soil surface outside the pile top block 2, and then let the reinforcing bars 4 pass through the pile top block 2, the perforated rubber plate 7 and the steel plate 5.

[0026] In this step, after the pipe pile 1 is constructed, a hole is drilled in the side wall of the pipe pile 1 to form a natural vertical drainage body. Following step 1, steel plates 5 are fully distributed in the foundation area. On the plane of the sand cushion layer 6, the edges of each steel plate 5 are joined together, and the gap between the edges of the steel plates 5 is 10~20mm.

[0027] In this step, a film is reliably connected to the edge of the steel plate 5, and the edge of the film is fixed by means of sealing grooves, etc. The gaps between the edges of the steel plate 5 are filled with asphalt hemp fiber 11 to achieve sealing, which facilitates subsequent vacuuming.

[0028] Step 2: Install jacks 3 on steel plate 5 and fix the upper end of steel bar 4 to the top of jacks 3.

[0029] Except for the 1m×1m area at the top of the pile (the area of ​​the pile top block 2), the steel plate 5 is covered by a sand cushion layer 6, which serves as a drainage layer during the preloading process and can be used as a cushion layer under the raft foundation after construction is completed.

[0030] Step 3: Pre-install the air inlet pipe of the vacuum device in the sand pad layer 6 under the steel plate 5, and draw a vacuum until the vacuum pressure reaches the design requirements and stabilizes.

[0031] Step 4: While maintaining vacuum pressure, use the compensating jack 3 to apply pressure to the foundation soil under the steel plate 5.

[0032] In this invention, the jack 3, through the connecting steel bar 4, generates a vertically upward pulling force on the pipe pile 1. The load is controlled at 1 / 2 of the limit value of the friction force of the soil around the pile. The pipe pile 1 will generate the same vertically downward reverse force through the connecting steel bar 4 and transmit it to the steel plate 5 under the jack 3. The steel plate 5 pressurizes the foundation soil under the steel plate 5, achieving the effect of traditional soil loading preloading.

[0033] Step 5: During the vacuum preloading process, water in the soil enters the pipe pile 1 through the drainage hole 9 on the side wall of the pipe pile 1, and is pumped out of the pipe pile 1 through the drainage device.

[0034] The preloading process, combined with water pump drainage, improves the consolidation of the loose sand layer of the original foundation under vacuum preloading, thereby increasing the bearing capacity of the foundation, reinforcing the soil between piles, enabling the piles and rafts to jointly bear the design load of the superstructure, reducing the number of engineering piles, saving costs, and reducing carbon emissions; for sandy soil foundations, it can effectively mitigate the liquefaction effect of sandy soil.

[0035] Step 6: After vacuum preloading is completed, steel plate 5 and jack 3 are dismantled and recycled. The pressurized foundation soil and piles are tested. After the design foundation target value is reached, the next construction step is carried out.

[0036] After preloading, pipe pile 1 itself becomes an engineering pile. This method allows for the reuse of steel plate 5 and jack 3, saving costs, simplifying procedures, and improving the bearing capacity of the soil under the raft foundation. By using pipe pile 1 and steel bar 4 to tighten jack 3, no additional pressure objects are needed. Pipe pile 1 plays a role in self-reinforcing the bearing soil, effectively reducing the number of piles and leveraging the combined effect of piles and raft.

[0037] The specific implementation method is as follows: An 18-story high-rise building in a waterfront sandy area uses a pile-raft foundation. The raft slab area is A = 26m² * 30m² = 780m². 2The foundation is 1 meter thick, consisting of loose sandy soil with high water content, poorly consolidated, and liquefiable. The soil beneath the raft slab is also liquefiable and poorly consolidated; the pile cap effect is not considered. One φ500PRC-AB type pipe pile is selected, with a pile length of 20m. The characteristic value of the vertical bearing capacity of a conventional single pile, R, is used. a =1700kN. Due to the low bearing capacity of the foundation, the vertical load borne by the raft foundation is usually not considered. Assuming 1.5 tons per floor (approximately 15 kN), the total is 15 * 18 * 780 = 210600 kN. The self-weight of the raft foundation is approximately 780 * 1 * 24 = 18720 kN. The total is 210600 + 18720 = 229320 kN. The number of piles n1 = G / R a =229320 / 1700=135.

[0038] After adopting the scheme of this invention, a steel plate 5 is arranged on the top of the pile. A vacuum is created by drawing a vacuum under the steel plate 5, achieving vacuum preloading. The steel plate 5 pressurizes the foundation soil, consolidating the loose sand and compacting it, expelling pore water, improving bearing capacity, and reducing the hazards of liquefaction. According to Section 5.2.5 of the "Code for Design of Building Pile Foundations," considering the interaction between piles and soil, according to Table 5.2.5, sa / d=4.6, BC / l>0.8, η c Take 0.28, f ak Reaching 120 kPa, the pile foundation bearing capacity R = R a +η c *f ak *(A-nA PS ) / n=1700+0.28*120*(780-120*0.196) / 120=1911 kN, number of piles n2=G / R a =229320 / 1911=120 piles, reducing the number of piles by approximately 11%. See details below. Figure 4 .

[0039] As can be seen from the above specific embodiments, by adopting the present invention, the negative skin friction of the pile foundation is reduced, the design value of the pile foundation bearing capacity is increased, and the bearing capacity of the pile foundation after considering the soil action between piles is significantly improved. This can effectively reduce the number of piles, save investment, and reduce carbon emissions.

[0040] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A novel self-reinforcing pipe pile raft foundation, comprising pipe piles and pile cap blocks, characterized in that, It also includes a rubber sheet layer on the pile top block, a full steel plate layer on the rubber sheet layer, and a jack. The jack is located above the pipe pile, with its bottom pressing on the full steel plate layer and its top connected to a reinforcing bar. The reinforcing bar passes through the rubber sheet layer and the full steel plate layer and connects to the pile top block. The full steel plate layer includes steel plates corresponding to the pipe piles one by one. The steel plates are fully installed in the foundation area, and the gaps between the edges of the steel plates at the top of adjacent pipe piles are filled and sealed. The jack is used to pre-press the full steel plate layer downwards when the reinforcing bar is tensioned. A sand cushion layer is laid on the part of the full steel plate layer outside the pile top block and connected to the equipment pipeline for vacuuming.

2. The novel self-reinforcing pipe pile raft foundation according to claim 1, characterized in that, The rubber sheet layer includes a perforated rubber sheet corresponding to a pipe pile. The perforated rubber sheet has through holes, and the steel plate has reserved openings that correspond to the through holes. The reserved openings correspond to the through holes. Reserved steel pipes that correspond to and communicate with the reserved openings are welded to the steel plate. Reinforcing bars pass through the through holes, the reserved openings, and the steel pipes in sequence.

3. The novel self-reinforcing pipe pile raft foundation according to claim 1, characterized in that, An integral steel plate plane is formed on the surface within the pipe pile area. A film is connected to the bottom perimeter of the steel plate. The edges of the film are fixed using a sealing trench method. The film is used to seal the gaps between the edges of the steel plate. Above the film, the gaps between the edges of the steel plate are filled with asphalt hemp fiber.

4. The novel self-reinforcing pipe pile raft foundation according to claim 1, characterized in that, The sidewall of the pipe pile is provided with a drainage hole, and the central hole of the pipe pile is provided with a water inlet pipe for a drainage device.

5. The novel self-reinforcing pipe pile raft foundation according to claim 1, characterized in that, The gap between the edges of the steel plates is 10~20mm.

6. A construction method for a novel self-reinforcing pipe pile raft foundation according to claim 1, characterized in that, Includes the following steps: Step 1: After the pipe pile construction is completed, connect the reinforcing bars, pour the pile top block, and install the perforated rubber plate and steel plate in sequence on the top of each pile. Before installing the steel plate, set a sand cushion layer on the soil surface outside the pile top block, and then let the reinforcing bars pass through the pile top block, the perforated rubber plate and the steel plate. Step 2: Install jacks on the steel plate and fix the upper end of the reinforcing bar to the top of the jacks; Step 3: Pre-install the air inlet pipe of the vacuum device in the sand pad layer under the steel plate, and draw a vacuum until the vacuum pressure reaches the design requirements and stabilizes. Step 4: While maintaining vacuum pressure, use a compensating jack to apply pressure to the foundation soil under the steel plate through the steel plate. Step 5: During the vacuum preloading process, water in the soil enters the pipe pile through the drainage holes on the side wall of the pipe pile and is pumped out from the pipe pile through the drainage device. Step 6: After vacuum preloading is completed, the steel plates and jacks are removed and recycled. The pressurized foundation soil and piles are tested. Once the design foundation target value is reached, the next step of construction can be carried out.

7. The construction method of the novel self-reinforcing pipe pile raft foundation according to claim 6, characterized in that, In step 1, after the pipe pile construction is completed, holes are made in the side wall of the pipe pile for drainage.

8. The construction method of the novel self-reinforcing pipe pile raft foundation according to claim 6, characterized in that, In step 1, the edges of the steel plates are joined together on the plane of the sand cushion layer, and the film is reliably connected to the edges of the steel plates. The edges of the film are fixed by means of sealing grooves, etc., and the gaps between the edges of the steel plates are filled with asphalt hemp fiber to achieve sealing.

9. The construction method of the novel self-reinforcing pipe pile raft foundation according to claim 6, characterized in that, In step 4, the jack generates an upward vertical tension on the pipe pile through the connecting steel bars, and the applied load is controlled at 1 / 2 of the limit value of the friction force of the soil around the pile.

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