Comprehensive construction method of large-diameter tubular pile for supporting deep rock-filled sand layer foundation pit

Abstract

The invention provides a comprehensive construction method of a large-diameter tubular pile for supporting a foundation pit in a deep and thick rock-filled sand layer, which adopts a double-machine cooperation segmented construction mode and comprises the following construction steps: deploying a while-drilling tubular pile machine A equipped with a down-the-hole hammer and a steel casing at a target pile position; steel casing synchronous hole guiding; transferring the pile machine A; backfilling a soil body in the steel casing in which the hole is led; the steel casing is pulled out through hoisting equipment; in a hole section formed by backfill soil, the large-diameter tubular pile is driven by a while-drilling and tubular pile machine B to follow up and sink along with drilling; forming a pile; the pile machine A is used for hole guiding and steel casing supporting, the pile machine B is used for pipe pile forming, and the pile machine A and the pile machine B work independently in parallel. According to the construction method, the down-the-hole hammer leads the hole to be matched with the steel casing to follow up to the bottom of the rock-fill layer to effectively control the drilling quality and efficiency of the rock-fill layer, the large-diameter while-drilling pipe pile effectively controls hole collapse of the sand layer, and the construction method effectively solves the problems that pile forming is difficult, the construction efficiency is low, and the pile forming quality is poor in the construction process of foundation pit supporting piles in deep and thick rock-fill and sand layer areas.

Description

Technical Field

[0001] The invention belongs to pile foundation construction technology, and in particular relates to a large-diameter pipe pile construction method for supporting a foundation pit in a thick stone-filled sand layer. Background Art

[0002] With the continuous development of land reclamation projects, existing sea areas, lakes, or riverbanks are being artificially transformed into land. Land reclamation plays a crucial role in accommodating limited urban space, particularly in mountainous coastal cities with limited land. Many major coastal cities, such as Hong Kong, Macao, Shenzhen, Dalian, Tianjin, and Huizhou, often create new land through methods such as sandblasting and island filling, or rock dumping and backfilling. Consequently, construction projects on this newly created land often require pile foundation construction through deep layers of artificial rock and sand. The characteristics of these strata significantly limit the effectiveness of traditional pile foundation construction techniques, primarily in the following three areas.

[0003] First, traditional rotary drilling pile technology suffers from extremely poor borehole stability and a significant risk of hole collapse. Deep backfill rock layers present a loose structure, large variations in particle size, and poor gradation, resulting in numerous overhead voids. Conventional rotary drilling or percussion drilling can easily lead to severe slurry leakage, extensive hole wall collapse, and even drill tool deflection and sticking. Deep sand layers (especially saturated sand layers) exhibit poor self-stability and are susceptible to sand flow and surge under dynamic disturbances or groundwater action. Traditional slurry wall protection is limited in effectiveness, and failure to promptly install casing can lead to hole collapse and drill burial.

[0004] Second, the traditional rotary pile drilling process suffers from low pile quality and construction efficiency. First, the repeated handling of incidents such as hole collapse and grout leakage significantly prolongs the construction cycle of individual piles, resulting in low equipment utilization. Second, hole collapse frequently leads to defects such as mud inclusion, diameter shrinkage, and segregation in the pile concrete, making it difficult to ensure pile integrity and bearing capacity. Third, to cope with complex strata, conservative methods such as multi-stage casing or repeated backfilling and re-drilling are often employed, resulting in cumbersome processes and poor quality control.

[0005] Third, traditional rotary-drilled pile construction solutions are costly. To ensure borehole wall stability, full-depth steel casing (also known as the full-sleeve process) is often required. While this method effectively protects the borehole wall, it requires extremely powerful equipment, and the casing placement and removal are extremely time-consuming. This consumes significant amounts of steel, leading to skyrocketing equipment rental and material costs, making it uneconomical. Furthermore, pile foundations constructed in this type of stratum often require rework and additional piling due to inconsistent quality, further increasing overall costs and delaying the project.

[0006] Therefore, faced with complex geological conditions characterized by overlapping thick rockfill and sand layers, efficiently and economically traversing these layers while ensuring both borehole and pile quality and construction safety has become a core challenge facing foundation pit support pile construction. The market urgently needs an innovative construction process that can effectively address these geological challenges while also offering excellent practicality and cost competitiveness. Summary of the Invention

[0007] In order to solve the problems of difficult pile formation, low efficiency, poor quality and high cost in the existing traditional rotary drilling pile construction technology when faced with complex geological conditions where deep stone-filled layers and sand layers are superimposed, the purpose of the present invention is to provide a large-diameter pipe pile construction method for supporting foundation pits in deep stone-filled sand layers.

[0008] The present invention achieves the above technical effects through the following technical solutions:

[0009] A method for constructing large-diameter pipe piles for supporting foundation pits in deep stone-filled sand layers adopts a dual-machine collaborative segmented construction mode and includes the following construction steps:

[0010] S1: Pile driver A is deployed at the target pile location. The pile driver A equipped with a down-the-hole hammer and steel casing is deployed at the target pile location.

[0011] S2: Synchronous drilling with steel casing: The down-the-hole hammer is driven by pile driver A, while the steel casing and drill bit are controlled to follow synchronously to the designed depth;

[0012] S3: Pile driver A moves to the next pile position and continues the boring operation after the steel casing reaches the designed depth;

[0013] S4: Backfill in the hole: backfill the soil in the steel casing of the bored hole;

[0014] S5: Steel casing removal: Use lifting equipment to remove the steel casing;

[0015] S6: Pile driver B construction: In the hole section formed by backfill soil, the large-diameter pipe pile is driven by the pile driver B to sink while drilling;

[0016] S7: Pile formation: The final pile body is formed after the pipe pile reaches the designed elevation;

[0017] Among them, pile driver A is used for boring and steel casing support, and pile driver B is used for pipe pile driving. The two operate independently and in parallel.

[0018] Furthermore, in step S1, the drill rod of the pile driver power head of the pile driver A is connected to a down-the-hole hammer.

[0019] Furthermore, in step S2, during the construction process, a pile controller is used to clamp the bottom of the steel casing, and the top of the steel casing is connected to the clamp of the drill head of the pile driver A.

[0020] Furthermore, in step S1, the diameter of the drill bit of the pile driver A is 1 cm larger than the diameter of the steel casing, ensuring that the steel casing can follow without resistance.

[0021] Furthermore, in step S2, the length of the steel casing is greater than or equal to the thickness of the rock filling layer.

[0022] Furthermore, the thick stone-filled sand layer comprises an upper stone-filled layer and a lower sand layer.

[0023] Furthermore, in step S4, the particle size of the backfill soil is not greater than 15 cm, so as to facilitate the pile sinking by the pile driver B while drilling.

[0024] Furthermore, in step S6, pile driver B independently constructs at the hole-guiding position completed by pile driver A, and its operation progress is asynchronously matched with the hole-guiding progress of pile driver A. In step S6, the follow-up pile construction adopts a drilling-one-jump-two spacing construction.

[0025] Furthermore, in step S7, the length of a single pile can be up to 15-16 meters. Specifically, the pile connection can be controlled according to the design and specifications.

[0026] The large-diameter pipe pile construction method for supporting deep stone-filled sand layers provided by the present invention has the following significant beneficial effects compared to the existing technology:

[0027] 1. Different from the traditional mud wall pile-forming process, this process adopts steel casing to solve the problem of hole collapse; at the same time, it adopts a pile-driving machine to solve the problem of synchronous follow-up of steel casing during drilling; compared with the full-rotation process, the pile-driving machine adopts a long drill rod + large air volume blowing method to efficiently blow out the backfill stone, which is different from the traditional rotary drilling bucket that is difficult to remove loose backfill stone.

[0028] 2. Solve the problem of hole collapse and significantly improve the quality of hole and pile formation:

[0029] (1) Precise control of the rock fill layer: The use of a down-the-hole hammer with high-efficiency crushing combined with the immediate rigid follow-up of the steel casing has completely overcome the stubborn problems of grout leakage, collapse, and drill sticking in the rock fill layer. The steel casing reaches directly to the bottom of the rock fill layer, forming a stable hole wall, laying a solid foundation for subsequent processes, and effectively avoiding quality defects such as mud inclusion, diameter reduction, and segregation in the pile body.

[0030] (2) High-efficiency sand layer retaining wall: Within the stable environment created by the steel casing, a large-diameter drill-and-drill pipe pile driver is used to drill and follow the piles. The piles themselves serve as both permanent retaining wall and the final pile body, sinking synchronously to the designed elevation. This process perfectly solves the problem of hole collapse in the sand layer (especially quicksand and gushing sand), ensures the density and integrity of the pile concrete, and significantly improves the bearing capacity and reliability of the retaining piles.

[0031] 3. Significantly improve construction efficiency and shorten construction period:

[0032] (1) Collaborative work processes and efficient equipment utilization: The "dual-machine collaboration, segmented construction" model is adopted. Pile driver A (down-the-hole hammer + steel casing) specializes in drilling holes in high-risk rockfill layers. After completion, it can quickly move to the next hole location, achieving continuous equipment operation. At the same time, pile driver B (drilling and pipe pile driver) focuses on pipe pile construction in the stable hole section where the drilling has been completed. The two work in parallel, significantly reducing equipment idle waiting time.

[0033] (2) Reduce accident handling time: Through the dual wall protection of steel casing and permanent pipe piles, serious accidents such as collapsed holes and buried drills are basically eliminated, and time-consuming steps such as repeated accident handling, backfilling and re-drilling in traditional processes are avoided. The construction period of a single pile is significantly shortened, and the overall construction speed is greatly improved.

[0034] 4. Outstanding comprehensive cost advantages and significant economic benefits:

[0035] (1) Equipment cost optimization: Compared with the traditional full-casing method that requires a large full-casing drilling rig, the main equipment of the present invention (down-the-hole hammer drill, pile-driving machine, crawler crane) is more common, with lower purchase or rental costs and relatively loose site requirements.

[0036] (2) Material and energy saving: The steel casing is only used as a temporary hole wall protection, and its length only needs to cover the stone filling layer. It can be pulled out and reused after use, with little material loss. Compared with the full sleeve method that requires burying and pulling out an extra-long and extra-heavy full sleeve in deep strata, the energy consumption and mechanical loss in pulling out the casing are greatly reduced in this invention.

[0037] (3) Reduced maintenance and labor costs: The construction process is smooth and the accident rate is low, which reduces equipment maintenance and additional labor input. The efficient construction speed also reduces project management costs.

[0038] (4) The comprehensive cost is significantly lower than that of traditional solutions: It has been verified through engineering practice that under the same complex formation conditions, the comprehensive construction cost of the present invention can be reduced by about 20% compared with the traditional full-sleeve process, and the economic benefits are extremely considerable.

[0039] 5. The process is highly universal, safe and environmentally friendly:

[0040] (1) This method can effectively deal with deep, complex and interactive rock-fill and sand layers, solving the problem of foundation pit support pile construction under such extremely adverse geological conditions and has a wide range of applications.

[0041] (2) The construction process causes little disturbance and the hole wall is stable, which significantly improves the safety of the operation.

[0042] (3) The amount of mud used is reduced (or dry drilling can be used), which reduces the impact on the surrounding environment and meets the requirements of green construction.

[0043] In summary, the construction method provided by the present invention utilizes a steel casing to drill a hole while drilling with a down-the-hole hammer, then fills the steel casing with soil, removes the casing, and finally, drills and installs piles while drilling. On the one hand, the down-the-hole hammer drilling combined with the steel casing to the bottom of the rockfill effectively controls drilling quality and efficiency within the rockfill layer. On the other hand, the large-diameter piles drilled while drilling effectively control sand layer collapse, successfully achieving the goal of high-quality, high-efficiency, and low-cost foundation pit support pile construction in deep rockfill sand layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a flow chart of the construction method of large-diameter pipe piles for supporting a deep stone-filled sand layer foundation pit according to the present invention. DETAILED DESCRIPTION

[0045] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the embodiments described herein are part of the embodiments of the present invention, rather than all of the embodiments, and are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0046] In order to make the technical problems solved by the present invention, the technical solutions adopted, and the technical effects achieved more clear, the technical solutions of the embodiments of the present invention are described in further detail below.

[0047] The present invention discloses a method for constructing large-diameter pipe piles for supporting a deep stone-filled sand layer foundation pit, which adopts a dual-machine collaborative segmented construction mode and includes the following construction steps:

[0048] S1: Pile driver A is deployed at the target pile location. The pile driver A equipped with a down-the-hole hammer and steel casing is deployed at the target pile location.

[0049] S2: Synchronous drilling with steel casing: The down-the-hole hammer is driven by pile driver A, while the steel casing and drill bit are controlled to follow synchronously to the designed depth;

[0050] S3: Pile driver A moves to the next pile position and continues the boring operation after the steel casing reaches the designed depth;

[0051] S4: Backfill in the hole: backfill the soil in the steel casing of the bored hole;

[0052] S5: Steel casing removal: Use lifting equipment to remove the steel casing;

[0053] S6: Pile driver B construction: In the hole section formed by backfill soil, the large-diameter pipe pile is driven by the pile driver B to sink while drilling;

[0054] S7: Pile formation: The final pile body is formed after the pipe pile reaches the designed elevation;

[0055] Among them, pile driver A is used for boring and steel casing support, and pile driver B is used for pipe pile driving. The two operate independently and in parallel.

[0056] Specifically, in step S1, the drill rod of the pile driver power head of the pile driver A is connected to a down-the-hole hammer.

[0057] In some specific embodiments, in step S2, during the construction process, a pile controller is used to clamp the bottom of the steel casing, and the top of the steel casing is connected to the clamp of the drill head of the pile driver A.

[0058] In some specific embodiments, in step S1, the diameter of the drill bit of the pile driver A is 1 cm larger than the diameter of the steel casing, ensuring that the steel casing can follow without resistance.

[0059] In some specific embodiments, in step S2, the length of the steel casing is greater than or equal to the thickness of the rock fill layer.

[0060] In some specific embodiments, the thick stone-filled sand layer comprises an upper stone-filled layer and a lower sand layer.

[0061] In some specific embodiments, in step S4, the particle size of the backfill soil is not greater than 15 cm, so as to facilitate the pile sinking by the pile driver B while drilling.

[0062] In some specific embodiments, in step S6, pile driver B independently constructs at the hole-drilling position completed by pile driver A, and its operation progress is asynchronously matched with the hole-drilling progress of pile driver A; in step S6, the follow-up pile construction adopts a drilling-one-jump-two spacing construction.

[0063] In some specific embodiments, in step S7, the maximum length of a single pile can be 15-16 meters. Specifically, the pile connection can be controlled according to the design and specifications.

[0064] In some specific embodiments, pile driver A integrates a down-the-hole hammer drill, a steel casing clamping system, a high-pressure air blowing system, and a real-time tracking control module; pile driver B integrates a large-diameter pipe pile tracking device and a depth synchronization control system. The operating locations and construction sequence of pile drivers A and B can be dynamically allocated. Pile driver A's operating locations include the hole-guiding location, while pile driver B's operating locations include the pile-driving location. The specific construction sequence can be such that pile driver A operates before pile driver B or that pile drivers A and B operate simultaneously.

[0065] Specifically, take typical application geological conditions as an example:

[0066] The site is backfilled with medium to slightly weathered tuff compacted boulders, with a small amount of coarse gravel and silty clay mixed on the surface. The stone content is generally greater than 50%, and the stone particle size varies from 5 to 50 cm. Some particle sizes are greater than 100 cm and are sub-angular, making it difficult to sink support pipe piles.

[0067] Large-diameter pipe drilling rig A, equipped with a down-the-hole hammer, pilots the hole. Large-diameter pipe drilling rig B then proceeds to drill and pile the pipes at the piloted location. Piling is done with a one-drill-two-drill interval to prevent hole collapse and cross-drilling. Equipped with one construction machine, the system uses single large-diameter pipe piles for support, constructing six piles per day, each 15-16 meters long.

[0068] like Figure 1 The specific construction steps are as follows:

[0069] S1. Determine the pile position and put the large diameter pile driver A into position;

[0070] S2, drilling and steel casing construction based on down-the-hole hammer drilling;

[0071] S3: The steel casing passes through the rockfill layer and reaches the design elevation, and the pile driver A moves to the next hole location to start drilling;

[0072] S4. Backfill soil in the steel casing;

[0073] S5. Crawler crane cooperates with pile puller to remove steel casing;

[0074] S6: Piling machine B is put into position while drilling, and large-diameter pipe piles are piled while drilling;

[0075] S7. The large-diameter pipe piles reach the designed elevation and are finally formed.

[0076] In step S1 , the drill bit of the pile driver A is provided with a down-the-hole hammer.

[0077] In step S2, during the construction process, a pile controller is used to clamp the bottom of the steel casing, and the top of the steel casing is connected to the clamp of the drill head of the pile driver A.

[0078] In step S1, the drill bit diameter of pile driver A is larger than the diameter of the steel casing. Preferably, the drill bit diameter of pile driver A is 1 cm larger than the diameter of the steel casing. This allows the steel casing to be simultaneously advanced to the designed elevation during drilling.

[0079] In step S2, the length of the steel casing is greater than or equal to the thickness of the rock fill layer.

[0080] The above-mentioned thick stone-filled sand layer is an upper stone-filled layer and a lower sand layer.

[0081] The rock filling content of the upper rock filling layer is greater than 50%; the rock filling particle size of the upper rock filling layer is 5-100 cm.

[0082] In step S4, the particle size of the backfill soil is not greater than 15 cm, so as to facilitate the pile sinking by the pile driver B while drilling.

[0083] In step S6, follow-up piling is carried out using a drilling-one-jump-two spacing. Specifically, pile driver A and pile driver B are constructed simultaneously at a distance of at least two pile positions to prevent disturbance of adjacent holes.

[0084] In step S7, the length of a single pile can be up to 15-16m, and the pile connection can be controlled according to the design and specifications.

[0085] The present invention is further described above with the aid of specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the essence and scope of the present invention. Various modifications made to the above embodiments by ordinary technicians in this field after reading this specification are all within the scope of protection of the present invention.

Claims

1. A method for constructing large-diameter pipe piles for supporting foundation pits in deep stone-filled sand layers, characterized in that: The dual-machine collaborative segmented construction mode is adopted, including the following construction steps: S1: Pile driver A is deployed at the target pile location. The pile driver A equipped with a down-the-hole hammer and steel casing is deployed at the target pile location. S2: Synchronous drilling with steel casing: The down-the-hole hammer is driven by pile driver A, while the steel casing and drill bit are controlled to follow synchronously to the designed depth; S3: Pile driver A moves to the next pile position and continues the boring operation after the steel casing reaches the designed depth; S4: Backfill in the hole: backfill the soil in the steel casing of the bored hole; S5: Steel casing removal: Use lifting equipment to remove the steel casing; S6: Pile driver B construction: In the hole section formed by backfill soil, the large-diameter pipe pile is driven by the pile driver B to sink while drilling; S7: Pile formation: The final pile body is formed after the pipe pile reaches the designed elevation; Among them, pile driver A is used for boring and steel casing support, and pile driver B is used for pipe pile driving. The two operate independently and in parallel.

2. The method for constructing large-diameter pipe piles for supporting a deep stone-filled sand foundation pit according to claim 1, characterized in that: In step S1, a down-the-hole hammer is connected to the drill rod of the pile driver power head of the pile driver A.

3. The method for constructing large-diameter pipe piles for supporting a deep stone-filled sand layer foundation pit according to claim 1, characterized in that: In step S2, during the construction process, a pile controller is used to clamp the bottom of the steel casing, and the top of the steel casing is connected to the clamp of the drill head of the pile driver A.

4. The method for constructing large-diameter pipe piles for supporting a foundation pit in a thick stone-filled sand layer according to claim 1, characterized in that: In step S1 , the diameter of the drill bit of the pile driver A is 1 cm larger than the diameter of the steel casing.

5. The method for constructing large-diameter pipe piles for supporting a foundation pit in a thick stone-filled sand layer according to claim 1, characterized in that: In step S2, the length of the steel casing is greater than or equal to the thickness of the rock-fill layer.

6. The large-diameter pipe pile construction method for supporting a deep stone-filled sand foundation pit according to claim 1 is characterized in that: The thick stone-filled sand layer comprises an upper stone-filled layer and a lower sand layer.

7. The method for constructing large-diameter pipe piles for supporting a foundation pit in a deep stone-filled sand layer according to claim 1, characterized in that: In step S4, the particle size of the backfill soil is no more than 15 cm.

8. The method for constructing large-diameter pipe piles for supporting a foundation pit in a thick stone-filled sand layer according to claim 1, characterized in that: In step S6, pile driver B independently constructs at the hole-guiding position completed by pile driver A, and its operation progress is asynchronously matched with the hole-guiding progress of pile driver A. In step S6, the follow-up pile construction adopts a drilling-one-jump-two spacing construction.

9. The method for constructing large-diameter pipe piles for supporting a deep stone-filled sand foundation pit according to claim 1, characterized in that: In step S7, the length of a single pile can be up to 15-16m.

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