Construction method of pile combined structure with bearing platform

Abstract

This invention discloses a construction method for a pile cap composite structure, comprising the following steps: S1: Based on the structural characteristics of the pile cap composite structure, the pouring sequence is divided into a first pouring layer and a second pouring layer; the first pouring layer includes the pile foundation and the first pile cap slab of the pile cap composite structure, and the second pouring layer includes the second pile cap slab and the cantilever of the pile cap composite structure; S2: The first pouring layer is poured as a whole first; then, the second pouring layer is poured as a whole on the basis of the first pouring layer, completing the pouring construction of the pile cap composite structure. Compared with the traditional method of "three pouring layers with two construction joints", this construction method realizes the rapid pouring construction of the pile cap composite structure with "one joint and three structures", and sets the construction joint generated during pouring inside the pile cap, thereby significantly improving the bearing capacity and overall quality of the pile cap composite structure, which has a positive effect on the large-scale promotion and application of pile cap composite structures.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering technology, and in particular to a construction method for a pile cap composite structure. Background Technology

[0002] Reinforced piles are widely used in geotechnical engineering. However, because traditional reinforced piles typically have a single cross-sectional dimension, when subjected to significant external forces (such as strong earthquakes or high embankments), larger cross-sectional dimensions or longer pile lengths are required, leading to higher project costs and increased construction risks, especially when foundation conditions are poor. To address these issues, existing technologies have proposed solutions using pile cap structures (such as Chinese Patent Publication No. CN113502841A – Integral Cast-in-Place Construction Method for Pile Caps).

[0003] The pile cap structure is a new type of composite structure, consisting of a lower pile foundation, a middle pile cap plate, and an upper cantilever section. It is formed by adding a pile cap at the anchor point of the traditional reinforced pile. It uses the overburden on the pile cap to offset the upper bending moment, which significantly improves the structural stress of the reinforced pile, reduces the pile foundation cross-sectional size and pile length, and reduces construction safety risks.

[0004] Studies have found that pile cap structures must be constructed using reasonable methods to achieve overall structural load-bearing capacity and meet design requirements. Traditional construction methods have two main problems: (1) the lower pile foundation uses manually excavated bored piles, resulting in low construction efficiency and high safety risks; (2) the lower pile foundation, middle pile cap, and upper cantilever section are constructed in segments, creating construction joints between the pile cap and the lower pile foundation, as well as between the upper cantilever section, thus reducing the overall load-bearing capacity of the structure. Therefore, a reasonable construction method for pile cap composite structures is proposed to achieve overall structural load-bearing capacity, which will have a positive effect on the large-scale application of pile cap composite structures and improving project quality. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing construction methods that create construction joints between the pile cap slab and the lower pile foundation, as well as between the upper cantilever section, thus reducing the overall bearing capacity of the pile cap structure. This invention proposes a construction method for a pile cap composite structure. This method enables rapid casting of the pile cap composite structure with one joint and three structural elements, and places the construction joint inside the pile cap, thereby significantly improving the bearing capacity and overall quality of the pile cap composite structure. This method has a positive effect on the large-scale promotion and application of pile cap composite structures.

[0006] To achieve the above-mentioned objectives, this invention provides a construction method for a pile cap composite structure, comprising the following steps:

[0007] S1: Based on the structural characteristics of the pile cap composite structure, the pile cap composite structure is divided into a first pouring layer and a second pouring layer according to the pouring sequence; the first pouring layer includes the pile foundation and the first pile cap plate of the pile cap composite structure, and the second pouring layer includes the second pile cap plate and the cantilever of the pile cap composite structure.

[0008] S2: First, carry out the overall pouring construction of the first pouring layer; then, on the basis of the first pouring layer, carry out the overall pouring construction of the second pouring layer to complete the pouring construction of the pile cap structure.

[0009] This invention discloses a construction method for a pile cap composite structure. The pile cap composite structure is poured in layers, achieving not only the pouring of the three structures (pile foundation, pile cap slab, and cantilever) within a single construction joint, but also ensuring that the construction joint generated during secondary pouring is located inside the pile cap. This improves the load-bearing capacity of the pile cap composite structure while maintaining the construction progress and workload, significantly enhancing the overall quality of the structure. This method is suitable for large-scale application in the pouring of pile cap composite structures and promotes their widespread adoption.

[0010] Preferably, the thickness of the second support plate is 20cm to 50cm.

[0011] Preferably, before step S2, pile well construction is also included; specifically, it is carried out in accordance with the "Technical Specification for Construction of Railway Concrete Engineering" (Q / CR 9207-2017).

[0012] Preferably, the pile well construction includes:

[0013] (1) Wells are excavated using rotary drilling or impact drilling methods depending on the geological conditions;

[0014] (2) Set up a slurry discharge trough and a guide pipe; the guide pipe is placed in the slurry discharge trough and the pile well is connected to the sedimentation tank through the guide pipe.

[0015] Preferably, the bottom surface of the slurry discharge trough is 40-60cm below the top surface of the pile well, and the bottom slope is not less than 4%; this facilitates the discharge of slurry.

[0016] Preferably, the guide pipe is a PE pipe or a steel pipe, with one end connected to the steel casing of the pile well through a drilled hole, and the other end connected to the sedimentation tank.

[0017] Preferably, the guide pipe is equipped with a valve, which can control the discharge of mud and concrete.

[0018] Preferably, the integral pouring construction of the first pouring layer in step S2 includes:

[0019] (1) Install the pile foundation reinforcement cage and excavate the foundation pit of the slab simultaneously; install the side formwork of the slab and the reinforcement cage of the slab in the foundation pit of the slab, and fix the pile foundation reinforcement cage and the slab reinforcement cage into one piece.

[0020] (2) Inject concrete into the pile well where the pile foundation reinforcement cage is installed, and vibrate it simultaneously; when the concrete liquid level is close to the guide channel, reduce the injection speed to ensure that the mud in the pile well can flow smoothly out to the sedimentation tank through the guide pipe.

[0021] (3) After the mud is discharged and the floating slurry at the pile head is removed, continue to inject concrete and vibrate it simultaneously until the first pile cap is poured.

[0022] Preferably, the pile foundation reinforcement cage is provided with reserved anchoring steel bars; this facilitates connection and fixation with the cantilever reinforcement cage, thereby ensuring the mechanical performance of the pile cap composite structure.

[0023] Preferably, during the pouring of the first foundation plate, support members are installed at the four corner points where the cantilever connects to the foundation plate; this facilitates the erection of the cantilever formwork; more preferably, the support members are steel sections.

[0024] Preferably, the support should be positioned and installed after the concrete of the first pier plate has been poured and before the concrete has initially set.

[0025] Preferably, if work needs to be temporarily suspended during the pouring process due to special circumstances, the pouring interval between the pile foundation and the first bearing plate must not exceed 1 hour; construction joints should be avoided to prevent affecting the pouring quality.

[0026] Preferably, the integral pouring construction of the second pouring layer in step S2 includes:

[0027] (1) Install the cantilever steel cage, cantilever formwork and top formwork of the foundation; the top formwork of the foundation is hinged to the side formwork of the foundation, and the top formwork of the foundation is in the open state at this time;

[0028] (2) After the concrete of the first foundation slab has set, continue to pour concrete and vibrate it simultaneously until the second foundation slab is poured; close the formwork on the top surface of the foundation slab.

[0029] (3) Continue to inject concrete and vibrate it simultaneously until the cantilever is completed.

[0030] Preferably, a hinge is provided between the top template of the foundation and the side template of the foundation; this ensures that the template can be opened or closed freely.

[0031] Preferably, the bottom of the cantilever template is fixedly connected to the support member; most preferably, the bottom of the cantilever template is welded to the support member.

[0032] Preferably, if work needs to be temporarily suspended during the pouring process due to special circumstances, the pouring interval between the cantilever and the second bearing plate must not exceed 1 hour; construction joints should be avoided to prevent affecting the pouring quality.

[0033] Preferably, after the casting of the pile cap structure is completed in step S2, the maintenance of the pile cap structure is also included; the maintenance is carried out in accordance with the "Technical Specification for Construction of Railway Concrete Engineering" (Q / CR 9207-2017).

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. The present invention provides a construction method for a pile cap composite structure, which involves layered pouring of the pile cap composite structure. This transforms the traditional three-stage pouring with two construction joints into two-stage pouring with one construction joint, thereby achieving the pouring construction of three structures (pile foundation, pile cap slab, and cantilever) in one joint (construction joint), thus improving the construction efficiency of the pile cap composite structure.

[0036] 2. The present invention provides a construction method for a pile cap composite structure, which involves layered pouring of the pile cap composite structure and setting the construction joint generated during the secondary pouring inside the pile cap, transforming the traditional exposed construction joint into an embedded construction joint, thereby improving the bearing capacity of the pile cap composite structure and significantly improving the overall quality of the pile cap structure.

[0037] 3. The present invention provides a construction method for a pile cap structure, which adopts a trench-embedded low-level slurry discharge method to avoid slurry leakage, effectively improves the level of on-site safety and civilized construction, and has less environmental pollution and better environmental protection.

[0038] 4. The construction method of the pile cap composite structure of the present invention is simple to operate and has stable pouring quality. It is suitable for large-scale application in the pouring construction of pile cap composite structures and is conducive to the promotion and application of pile cap composite structures. Attached image description:

[0039] Figure 1 This is a schematic diagram of a pile cap structure formed by casting using existing casting construction method (a) and the construction method of the present invention (b).

[0040] Figure 2 This is a schematic diagram illustrating the preparations before pouring the first pouring layer in Embodiment 1 of the present invention.

[0041] Figure 3 This is a schematic diagram of the pouring construction of the first pouring layer in Embodiment 1 of the present invention.

[0042] Figure 4 This is a schematic diagram illustrating the preparations before pouring the second pouring layer in Embodiment 1 of the present invention.

[0043] Figure 5 This is a schematic diagram of the pouring construction of the second pouring layer in Embodiment 1 of the present invention.

[0044] Attached reference numerals: 1-Pile foundation; 101-Pile foundation reinforcement cage; 102-Pile well; 2-Pile cap slab; 201-Pile cap slab reinforcement cage; 202-Pile cap side formwork; 203-Supporting component; 204-Pile cap top formwork; 205-First pile cap slab; 206-Second pile cap slab; 3-Cantilever; 301-Cantilever reinforcement cage; 302-Reserved anchoring reinforcement; 303-Cantilever formwork; 4-Construction joint; 5-Groove drainage channel; 6-Sedimentation tank; 7-First pouring layer; 8-Second pouring layer. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to experimental examples and specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of this invention to the following embodiments; all technologies implemented based on the content of this invention fall within the scope of this invention.

[0046] Example 1:

[0047] Table 1. List of Main Materials for Construction Method

[0048] Serial Number Material Name Specifications and Technical Indicators 1 C45 concrete C45 2 Reinforcing steel HRB400 3 gravel Particles larger than 20cm do not exceed 50% 4 Supporting foundation I500×158×12 5 steel formwork Thick 8mm 6 steel casing 12mm thick, 2m high

[0049] Table 2. List of Main Equipment for Construction Methods

[0050] Serial Number Equipment Name Specifications, power, and capacity unit Subtotal 1 Concrete mixing plant HZS180 tower 3 2 Concrete transport truck 10m3 tower 3 3 Internal combustion generator 300KVA tower 2 4 Loader ZL50C tower 1 5 excavator PC200-6 tower 1 6 Impact drill or rotary drilling rig CF20 tower 1 7 mud pump BW-160 tower 2 8 truck crane QY25 tower 1 9 sprinkler 10m3 tower 1 10 electric welding machine BX-251 tower 2

[0051] The team is composed of skilled workers as the backbone, with a reasonable and complete configuration of job types, as follows: 4 pile drivers, 1 electrician, 3 steelworkers, 4 formwork and concrete workers, 1 safety officer, 1 technician, 1 environmental protection officer, and 1 surveyor.

[0052] Construction methods should strictly comply with national and local (industry) standards. The national / industry standards to be implemented are as follows:

[0053] (1) Code for Design of Concrete Structures (GB 50010-2010);

[0054] (2) Technical Specification for Construction of Railway Concrete Engineering (Q / CR 9207-2017)

[0055] (3) Railway Concrete Engineering Construction Quality Acceptance Standard (TB10424-2010)

[0056] (4) "Standards for Acceptance of Construction Quality of Railway Subgrade Engineering" (TB 0414-2003);

[0057] (5) Specification for Testing Railway Subgrade Retaining Structures (TB 10450-2020);

[0058] (6) Design Specification for Railway Subgrade Retaining Structure (TB 10025-2019).

[0059] The specific pouring construction steps are as follows:

[0060] (1) Based on the structural characteristics of the pile cap composite structure, the pile cap composite structure is divided into a first pouring layer 7 and a second pouring layer 8 according to the pouring sequence; the first pouring layer 7 includes the pile foundation 1 and the first pile cap 205 of the pile cap composite structure, and the second pouring layer 8 includes the second pile cap 206 and the cantilever 3 (see Figure 5 );

[0061] 2) Excavation of pile well 102 below ground level (pile foundation 1). Traditional construction methods will be adopted, in accordance with the provisions of the "Technical Specification for Construction of Railway Concrete Engineering" (Q / CR 9207-2017), and rotary drilling or impact drilling will be used depending on the geological conditions.

[0062] 3) A mud diversion pipe is reserved, which is connected to sedimentation tank 6, such as... Figure 2 As shown. After the excavation of pile well 1 is completed, a rectangular slurry discharge channel 5 is excavated in the direction of the toe plate (short side) of the pile cap. The slurry discharge channel 5 is about 50cm below the top surface of pile well 102, with a bottom slope of 4%. A guide pipe is laid along the slope. The guide pipe is made of φ50PE pipe. One end of the guide pipe is connected to the steel casing through a drilled hole, and the other end is connected to the sedimentation tank 6. The discharge of mud and concrete is controlled by a valve.

[0063] 4) Hoist the pile foundation reinforcement cage 101 and simultaneously excavate the foundation pit for the pile cap slab. Hoist and position the pile foundation reinforcement cage 101 according to design requirements. The pile head is equipped with pre-reserved anchoring steel bars 302. Excavate the foundation pit for the pile cap and install the side formwork 202 of the pile cap. Install the pile cap slab reinforcement cage 201. Figure 3 As shown.

[0064] 5) Grouting of Pit 1. Grouting is performed on Pit 1 below ground level. The concrete is vibrated, and when the grout level approaches the discharge trough 5, the grouting speed is reduced to ensure the slurry can flow smoothly through the guide pipe to the sedimentation tank 5. Figure 3 ).

[0065] 6) Pour the first pile cap 205. After the mud has been discharged and the laitance at the pile head has been removed, continue grouting up to the first pile cap 205. The first pile cap 205 should be constructed in the same step as the pile foundation grouting. At the same time, insert support members 203 (steel sections, as load-bearing supports for the cantilever formwork 303) at the four corners of the cantilever formwork 303 until the concrete reaches its final set state. Figure 3 As shown.

[0066] 7) Construct the cantilever formwork 303 and the top formwork 204 of the foundation. A hinge is installed between the top formwork 204 and the side formwork 202 of the foundation to allow the formwork to open or close freely. First, with the top formwork 202 in the open state, install the cantilever top formwork and weld the bottom of the formwork to the support 203. Figure 4 ).

[0067] 8) Cast the second foundation slab 206. After the first foundation slab 205 has been cast and reached its final set, continue casting the second foundation slab 206, as follows: Figure 5 As shown, the concrete is vibrated until the vibration requirements are met, and then the top surface formwork 204 of the foundation is quickly sealed to ensure that all formwork is in a sealed state.

[0068] 9) Pour cantilever concrete. Immediately after the top formwork 204 of the foundation cap is closed, grout the cantilever concrete, ensuring that the grouting of the second foundation cap slab 206 and the cantilever section concrete are performed in the same construction step. Figure 5 As shown, the construction of the pile cap has been completed, and the concrete is now being cured.

[0069] Practical application in projects such as the Mimeng Railway shows that this construction method, compared with traditional methods, ( Figure 1 This method has achieved good results in terms of economic, environmental, energy conservation and social benefits, and meets the requirements of green construction and energy conservation and emission reduction. It is conducive to promoting the development and utilization of renewable energy and belongs to the construction method cultivation work carried out in conjunction with the new type of pile cap structure.

[0070] Taking the pile cap construction site of the Mimeng Railway as an example:

[0071] 1) Economic benefits:

[0072] (1) Compared with the traditional construction method, the construction site has a total of 516 pile caps. According to the new construction method, each pile saves 9 hours of time, for a total of 4644 hours. Each pile requires 5 people (1 pile driver, 1 electrician, 1 steelworker, and 1 formwork and concrete worker) to work for 580.5 days (8 hours per day). At 500 yuan / day, the new construction method saves a total of 1.452 million yuan in costs.

[0073] (2) Compared with traditional reinforcement piles, the cost of pile cap piles is reduced by 5% to 45% depending on the geological conditions from hard rock to soft soil. Based on the average cost reduction of 20% for sandy gravel soil, and assuming an average cost of 100,000 yuan per pile, the cost reduction for 516 piles is 100,000 yuan / pile × 20% × 516 piles = 10.32 million yuan.

[0074] 2) Construction efficiency: The traditional construction method adopts a three-stage segmented pouring process, constructing the foundation piles, pile caps and cantilever separately. The specific construction period is shown in Table 3.

[0075] Table 3. Summary of Construction Period Statistics for Traditional Construction Methods (per pile)

[0076]

[0077] The new construction method adopts a two-stage segmented pouring process, constructing the anchoring section and the lower layer of the foundation plate, and the cantilever section and the upper layer of the foundation plate separately. The specific construction period is shown in Table 4.

[0078] Table 4: Summary of Construction Period Statistics for New Construction Methods

[0079]

[0080]

[0081] The new construction method improves construction efficiency by 22.5% compared to the traditional method.

[0082] 3) Environmental benefits: Traditional pile wells use open discharge of mud, which easily leads to mud leakage and spillage, polluting the site environment. This method uses trench-embedded low-level mud discharge, avoiding mud leakage and effectively improving the level of safe and civilized construction on site.

[0083] 4) Construction Safety: The new structure has significantly smaller cross-sectional dimensions and pile lengths compared to traditional structures, reducing the requirements for mechanical equipment used in drilling, hoisting, and formwork erection during construction, thus enhancing safety. The new structure allows for mechanical drilling, significantly reducing safety risks compared to the manual drilling required for traditional piles.

[0084] 5) Social benefits: The pile cap combined structure is a new type of retaining structure suitable for high embankment retaining projects under soft geological conditions. The new construction method is conducive to improving the application of the new structure and will be promoted and applied in high embankment projects such as airport hubs, large spoil heaps, and station yards. It has broad prospects and good social benefits.

[0085] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A construction method for a pile cap composite structure, characterized in that, Includes the following steps: S1: Based on the structural characteristics of the pile cap composite structure, the pouring sequence of the pile cap composite structure is divided into a first pouring layer and a second pouring layer; the first pouring layer includes the pile foundation and the first pile cap plate of the pile cap composite structure, and the second pouring layer includes the second pile cap plate and the cantilever of the pile cap composite structure. S2: First, carry out the overall pouring construction of the first pouring layer; then, on the basis of the first pouring layer, carry out the overall pouring construction of the second pouring layer to complete the pouring construction of the pile cap structure.

2. The construction method according to claim 1, characterized in that, The thickness of the second support plate is 20cm to 50cm.

3. The construction method according to claim 1 or 2, characterized in that, Before step S2, the process also includes pile well construction; the pile well construction includes: (1) Wells are excavated using rotary drilling or impact drilling methods depending on the geological conditions; (2) Set up a slurry discharge trough and a guide pipe; the guide pipe is placed in the slurry discharge trough and the pile well is connected to the sedimentation tank through the guide pipe.

4. The construction method according to claim 3, characterized in that, The bottom of the slurry drainage trough is 40-60cm below the top surface of the pile well, and the bottom slope is not less than 4%.

5. The construction method according to claim 3, characterized in that, Step S2, the integral pouring construction of the first pouring layer includes: (1) Install the pile foundation reinforcement cage and excavate the foundation pit of the slab simultaneously; install the side formwork of the slab and the reinforcement cage of the slab in the foundation pit of the slab, and fix the pile foundation reinforcement cage and the slab reinforcement cage into one piece; (2) Inject concrete into the pile well where the pile foundation reinforcement cage has been installed, and vibrate it simultaneously; when the concrete liquid level is close to the guide channel, reduce the injection speed to ensure that the mud in the pile well can flow smoothly out to the sedimentation tank through the guide pipe. (3) After the mud is discharged and the floating slurry at the pile head is removed, continue to inject concrete and vibrate it simultaneously until the first pile cap is poured.

6. The construction method according to claim 5, characterized in that, While the first foundation plate is being poured, support components are installed at the four corner points where the cantilever connects to the foundation plate.

7. The construction method according to claim 6, characterized in that, The support should be positioned and installed after the first pier plate concrete is poured and before the concrete has initially set.

8. The construction method according to claim 5, characterized in that, The integral pouring construction of the second pouring layer in step S2 includes: (1) Install the cantilever steel cage, cantilever formwork and top surface formwork of the foundation; the top surface formwork of the foundation is hinged to the side formwork of the foundation, and the top surface formwork of the foundation is in the open state at this time; (2) After the concrete of the first foundation slab has set, continue to pour concrete and vibrate it simultaneously until the second foundation slab is poured; close the formwork on the top surface of the foundation slab. (3) Continue to inject concrete and vibrate it simultaneously until the cantilever is completed.

9. The construction method according to claim 8, characterized in that, A hinge is provided between the top template of the foundation and the side template of the foundation.

10. The construction method according to claim 1, characterized in that, During the pouring of the first and second pouring layers, the pouring interval between the pile foundation and the first abutment slab, and the pouring interval between the cantilever and the second abutment slab, shall not exceed 1 hour.

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