Composite pile pulling construction method based on pile casing isolation and pile side soil body cutting

Abstract

The invention discloses a composite pile pulling construction method based on pile casing isolation and pile side soil body cutting, which is characterized in that technicians selectively execute the following process paths according to site construction conditions: 1, a pile casing physical isolation pile pulling process: a resonance-free vibratory hammer is used for driving a long steel pile casing to wrap an old pile; the old pile and the pile casing are integrally pulled out after being connected; 2, a hydraulic girdling antifriction pile pulling process, namely performing high-pressure clear water jet grouting cutting around the old pile to form a soft belt, and then directly hoisting out the old pile after hoisting point reinforcement is performed on the old pile; and thirdly, a combined pile pulling process is carried out, namely, the cutting step in the hydraulic ring cutting antifriction pile pulling process is firstly carried out to preliminarily reduce friction, and then the pile casing physical isolation pile pulling process is carried out to finish final pulling. According to the method, three technical paths aiming at different working conditions are provided, and a standardized and replicable solution is provided for technicians to safely and efficiently deal with various complex old pile pulling-out tasks.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering construction technology, and in particular to a composite pile extraction construction method based on casing isolation and pile side soil cutting. Background Technology

[0002] In urban renewal and underground space development projects, the removal of old pile foundations (such as driven piles and precast piles) of existing buildings is an unavoidable step. Traditional pile extraction methods mainly rely on large cranes and vibratory hammers for direct removal, which has the following significant drawbacks: First, the frictional resistance between the pile and the surrounding soil is enormous, especially in dense soil layers. Direct extraction requires ultra-large lifting equipment, which is costly and carries the risk of pile breakage or equipment overturning. Second, the strong vibrations pose a safety threat to nearby buildings, subway tunnels, underground pipelines, and other sensitive structures. Third, the pile holes left after extraction are prone to collapse, which may cause ground subsidence.

[0003] There are also some improved pile extraction techniques in the existing technology, such as:

[0004] High-pressure jet cutting can be used to assist in cutting the soil, but its effectiveness may be poor in hard soil layers or when there are obstacles in the pile body. Mechanical devices such as sliding pin-type steel boots can be used, but their applicability may be limited by the condition of the old pile bottom. Casing isolation can be used, but its application is mostly focused on frictional isolation of newly built pile foundations, rather than the removal of existing old piles.

[0005] The most prominent problem at present is not the lack of a single technical means, but the lack of a clear and operational selection standard and methodology to systematically guide technicians on "when to use which technology" when facing complex and ever-changing on-site conditions. Currently, process selection relies heavily on the personal experience of project managers or technical leaders. This "experience-driven" model has high decision-making risks, poor replicability, and is prone to leading to mismatched solutions, cost overruns, or safety accidents. In particular, for old piles with extremely long and high frictional resistance, a single pile extraction process often proves inadequate, becoming a technical challenge on construction sites.

[0006] Therefore, there is an urgent need for a comprehensive pile extraction method that can integrate multiple effective process systems and provide technicians with clear decision-making basis and operating procedures. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this invention provides a composite pile extraction method based on casing isolation and pile side soil cutting. By providing technical paths for different working conditions, it offers a standardized and replicable solution for technicians to safely and efficiently handle various complex old pile extraction tasks.

[0008] To achieve the above objectives, this invention provides a composite pile extraction construction method based on casing isolation and pile side soil cutting. The construction method is implemented by technicians selectively following the process path according to the on-site construction conditions:

[0009] The first process path includes the following steps:

[0010] S1a: A vibrating device is used to drive the long steel casing into the soil around the old pile, so that the old pile is completely enclosed in the long steel casing.

[0011] S2a: The top of the old pile is rigidly connected to the top of the long steel casing to form a whole;

[0012] S3a: Start the vibration equipment and coordinate with the lifting equipment to lift the long steel casing in sync, thereby removing the whole formed by the long steel casing and the old pile;

[0013] The second process path includes the following steps:

[0014] S1b: Multiple high-pressure jet grouting holes are symmetrically arranged in the soil around the old pile;

[0015] S2b: High-pressure water jetting is used to cut the soil on the sidewall of the old pile to reduce friction and form a ring-shaped weak zone.

[0016] S3b: Insert reinforcing bars at the top of the old pile and connect the original main bars of the old pile with the reinforcing bars to form a lifting point;

[0017] S4b: Install double lifting rings at the lifting point and use the double lifting rings to lift the old pile out;

[0018] The third process path includes the following steps:

[0019] S1c: Execute steps S1b and S2b in the second process path in sequence to cut and reduce friction on the soil of the old pile sidewall;

[0020] S2c: Execute steps S1a, S2a and S3a in the first process path in sequence to complete the removal of the old pile.

[0021] Preferably, when technicians selectively execute different process paths based on on-site construction conditions, the technicians make judgments based on geological conditions, sensitivity to the surrounding environment, and parameters of existing piles. The judgment methods include:

[0022] When the surrounding environment is sensitive to vibration, the second process path is selected;

[0023] When an old pile is adjacent to an important underground structure or there are obstacles around the old pile, the first process path shall be selected.

[0024] When the length of the old pile and the estimated frictional resistance exceed the economic or technical processing capacity of a single process path, a third process path is selected.

[0025] Preferably, in the first process path, the lifting equipment is a crawler crane, and a portion of the counterweight of the crawler crane is replaced by a hydraulic power station for providing power to the vibrating equipment.

[0026] Preferably, in the second process path, the jet pressure of high-pressure clean water is ≥20 MPa, and the influence radius of the annular weak zone is ≥500 mm.

[0027] Preferably, in step S1c of the third process path, the depth of the high-pressure water cutting is 1 / 2 to 2 / 3 of the length of the old pile.

[0028] By adopting the above technical solution, the present invention has the following beneficial effects:

[0029] 1) Scientific and standardized decision-making: The decision-making process that relies on personal experience is transformed into a standardized process based on clear technical logic, which reduces decision-making risks and uncertainties and makes the selection of solutions based on evidence.

[0030] 2) It provides an effective means to overcome extreme problems: The innovative combined process solves the problem of removing ultra-long and ultra-large frictional old piles that cannot be handled by a single technical approach through the strategy of "soft first and then hard".

[0031] 3) Greatly improves environmental adaptability: By dividing the two processes, it can accurately address the two core challenges of urban construction, namely "vibration sensitivity" and "pipeline protection", and significantly reduce the impact of construction on the surrounding environment.

[0032] 4) Optimization of technical and economic benefits: The combined process allows the use of smaller equipment to complete the work that originally required super-large equipment, or reduces construction risks through step-by-step processing, achieving the best balance between technology and economy.

[0033] 5) High standardization and replicability: Each process has its standardized construction procedures and clear applicable scenarios, which facilitates promotion and application in different projects and different technical teams. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is the overall process selection and flowchart of the composite pile extraction construction method based on casing isolation and pile side soil cutting in the embodiments of the present invention.

[0036] Figure 2 This is a construction flowchart of the physical isolation pile extraction process using a casing in an embodiment of the present invention.

[0037] Figure 3 This is a diagram showing the hole layout in the hydraulic ring cutting and friction reduction pile extraction process in this embodiment of the invention.

[0038] Figure 4 This is a diagram of the lifting point reinforcement structure in the hydraulic ring shearing and friction reduction pile extraction process in this embodiment of the invention.

[0039] Figure 5 This is a construction flowchart of the combined pile extraction process in an embodiment of the present invention.

[0040] The correspondence between the numbers in the attached diagram is as follows:

[0041] 1- High-pressure jet grouting hole; 2- Existing pile; 3- Double lifting ring; 4- Reinforcing lifting rod. Detailed Implementation

[0042] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0043] Please see Figures 1 to 5 As shown, this invention provides a composite pile extraction construction method based on casing isolation and pile side soil cutting, including the following process path selectively executed by technicians according to the on-site construction conditions:

[0044] The first process path includes the following steps:

[0045] S1a: Use a vibrating device to drive the long steel casing into the soil around the old pile, so that the old pile is completely encased in the long steel casing.

[0046] S2a: The top of the old pile is rigidly connected to the top of the long steel casing to form a whole;

[0047] S3a: Start the vibration equipment and coordinate with the lifting equipment to lift the long steel casing in sync, thereby removing the whole formed by the long steel casing and the old pile;

[0048] The second process path includes the following steps:

[0049] S1b: Multiple high-pressure jet grouting holes 1 are symmetrically arranged in the soil around the old pile 2;

[0050] S2b: High-pressure water jetting is used to cut the soil on the sidewalls of the old pile 2, thereby cutting and reducing friction on the soil on the sidewalls of the old pile 2, thus forming a ring-shaped weak zone.

[0051] S3b: Insert reinforcing bars 4 at the top of old pile 2 and connect the original main bars of old pile 2 with reinforcing bars 4 to form a lifting point;

[0052] S4b: Install double lifting rings 3 at the lifting point and use the double lifting rings 3 to lift out the old pile;

[0053] The third process path includes the following steps:

[0054] S1c: Execute steps S1b and S2b in the second process path in sequence to cut and reduce friction on the soil of the old pile sidewall;

[0055] S2c: Execute steps S1a, S2a and S3a in the first process path in sequence to complete the removal of the old pile.

[0056] Furthermore, when technicians selectively execute different process paths based on on-site construction conditions, they make judgments based on geological conditions, sensitivity to the surrounding environment, and parameters of existing piles. These judgment methods include:

[0057] When the surrounding environment is sensitive to vibration, the second process path is selected;

[0058] When an old pile is adjacent to an important underground structure or there are obstacles around the old pile, the first process path shall be selected.

[0059] When the length of the old pile and the estimated skin friction exceed the economic or technical processing capacity of a single process path, a third process path is selected. It should be noted that in this embodiment, the first process path is the physical isolation pile extraction process using a casing, the second process path is the hydraulic ring shearing and skin friction reduction pile extraction process, and the third process path is a combined pile extraction process. The core mechanisms, preferred applicable working conditions, and technical effects of the three process paths are shown in Table 1.

[0060] Table 1

[0061] Process Path Core Mechanism Preferred applicable working conditions Technical effect physical isolation of the casing By using steel casings to form a physical barrier, the side friction of the pile can be completely eliminated. It is located near important underground pipelines; there are obstacles around the pile. Provides reliable physical isolation and protection, with controllable vibration. Hydraulic ring shear friction reduction By actively cutting and softening the soil around the pile using high-pressure water jets, the frictional resistance is greatly reduced. The surrounding environment is sensitive to vibration (such as subway protection zones); the old piles are relatively short. The construction process is virtually vibration-free, protecting sensitive facilities. Combined process First, use hydraulic ring cutting to reduce friction, then install a casing to complete the final removal. The old piles are too long and have huge frictional resistance, making a single mode of operation insufficient or uneconomical. Reduce equipment requirements, balance safety and economy, and cope with extreme working conditions.

[0062] Furthermore, in the first process path, the lifting equipment is a crawler crane, the vibration equipment is a non-resonance vibratory hammer, and part of the counterweight of the crawler crane is replaced by a hydraulic power station to provide power to the vibration equipment.

[0063] It should be noted that in this embodiment, in the second process path, the injection pressure of high-pressure clean water is ≥20 MPa, and the influence radius of the annular weak zone is ≥500 mm. Preferably, in step S1c of the third process path, the cutting depth of the high-pressure clean water is 1 / 2 to 2 / 3 of the length of the old pile. That is, hydraulic ring cutting and friction reduction are performed first, and the cutting depth is optimized (e.g., cutting to 2 / 3 of the pile length). The purpose is to utilize the low disturbance characteristics of hydraulics to proactively and preemptively weaken the most difficult frictional resistance in the upper part of the pile. Then, subsequent casing isolation and protection are implemented. That is, after completing the initial friction reduction, steps S1a, S2a, and S3a in the first process path are executed. Since the pile side frictional resistance has been weakened in advance, the excitation force and lifting force required to drive the casing are significantly reduced. The role of the steel casing is mainly to provide final wrapping of the lower part of the pile, support the pile hole, and provide a stable extraction path.

[0064] The present invention will be described in detail below through specific embodiments. The selection of modes in these embodiments is the result of human judgment by those skilled in the art based on the aforementioned preset decision logic.

[0065] Example 1: Pile extraction in an area adjacent to important underground pipelines (using physical isolation technology with casing)

[0066] Operating conditions: A gas pipeline in use runs parallel to the old pile that needs to be removed, making the environment highly sensitive.

[0067] Process selection: Based on the condition of "adjacent to important underground structures", the technicians determined that the physical isolation pile extraction process with casing should be selected (first process path) to ensure absolute protection of the pipeline.

[0068] Construction process: Refer to Figure 2 A modified crawler crane (with some counterweights replaced by hydraulic stations) was used to lift a non-resonant vibratory hammer, driving a long steel casing into the soil and completely encasing the old pile. After welding the main reinforcement of the old pile to the top of the long steel casing, it was vibrated upwards and pulled out as a whole, removing the long steel casing and the old pile. Throughout the process, the long steel casing effectively isolated the construction from the impact on nearby pipelines.

[0069] Example 2: Pile extraction in a vibration-sensitive area of ​​the subway (using hydraulic ring cutting friction reduction technology)

[0070] Working conditions: The old piles are located within the protection zone of the operating subway tunnel, and the requirements for vibration control are extremely strict.

[0071] Process selection: Based on the condition that "the environment is sensitive to vibration", the technicians determined that the hydraulic ring cutting friction reduction and pull-out pile process (second process path) should be selected to eliminate the vibration source.

[0072] Construction process: Refer to Figure 3High-pressure jet grouting holes were installed around the old pile, and high-pressure water was used to circumferentially cut the soil around the pile, creating a weak zone. Reinforcing bars were then inserted into the top of the old pile and welded to the original main reinforcement bars to form a stable lifting point. Finally, a crane was used to smoothly lift the old pile out. This process was conducted without strong vibrations, meeting the subway protection requirements.

[0073] Example 3: Removal of excessively long old piles (using a combined process)

[0074] Working conditions: The old piles to be removed are cast-in-place concrete piles, 28 meters long and 0.8 meters in diameter, with extremely high estimated frictional resistance.

[0075] Process Selection: Based on the condition of "excessively long old piles with huge frictional resistance," the technicians determined that using a single casing process would require an ultra-large vibratory hammer and crane, resulting in poor economic efficiency; while using a single hydraulic process would result in excessively long piles, low success rates, and a high risk of pile hole collapse. Therefore, the combined pile extraction process (third process path) was deemed the most suitable option.

[0076] Construction process: Refer to Figure 4 First, hydraulic circumferential cutting is performed: high-pressure jet grouting holes are first laid out around the old pile. Using a high-pressure jet grouting drill, clean water is sprayed at a pressure of over 20 MPa, and the cutting depth is controlled to be about 18 meters (about 2 / 3 of the pile length) to fully circumferentially cut the soil above the old pile, thus achieving preliminary friction reduction.

[0077] Subsequent casing removal: A crawler crane was then used in conjunction with a non-resonant vibratory hammer to drive in a steel casing approximately 20 meters long. Because the frictional resistance in the upper section had been significantly reduced, the casing was driven in smoothly, requiring a much lower excitation force than when driving it directly to a depth of 28 meters. After welding the old pile to the casing, the casing and the old pile were successfully pulled out as a whole.

[0078] Technical results: By combining processes, the removal of ultra-long old piles was successfully completed using medium-sized equipment, avoiding the high costs of using ultra-large equipment. At the same time, the use of casing support effectively prevented the collapse of the pile hole, resulting in significant overall benefits.

[0079] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A composite pile extraction construction method based on casing isolation and pile side soil cutting, characterized in that, The construction method is implemented selectively by technicians according to the on-site construction conditions, following the process path: First process route, Includes the following steps: S1a: A vibrating device is used to drive the long steel casing into the soil around the old pile, so that the old pile is completely enclosed in the long steel casing. S2a: The top of the old pile is rigidly connected to the top of the long steel casing to form a whole; S3a: Start the vibration equipment and coordinate with the lifting equipment to lift the long steel casing in sync, thereby removing the whole formed by the long steel casing and the old pile; The second process path includes the following steps: S1b: Multiple high-pressure jet grouting holes are symmetrically arranged in the soil around the old pile; S2b: High-pressure water jetting is used to cut the soil on the sidewall of the old pile to reduce friction and form a ring-shaped weak zone. S3b: Insert reinforcing bars at the top of the old pile and connect the original main bars of the old pile with the reinforcing bars to form a lifting point; S4b: Install double lifting rings at the lifting point and use the double lifting rings to lift the old pile out; The third process path includes the following steps: S1c: Execute steps S1b and S2b in the second process path in sequence to cut and reduce friction on the soil of the old pile sidewall; S2c: Execute steps S1a, S2a and S3a in the first process path in sequence to complete the removal of the old pile.

2. The composite pile extraction construction method based on casing isolation and pile side soil cutting as described in claim 1, characterized in that, When technicians selectively execute different process paths based on on-site construction conditions, they make judgments based on geological conditions, sensitivity to the surrounding environment, and parameters of existing piles. The judgment methods include: When the surrounding environment is sensitive to vibration, the second process path is selected; When an old pile is adjacent to an important underground structure or there are obstacles around the old pile, the first process path shall be selected. When the length of the old pile and the estimated frictional resistance exceed the economic or technical processing capacity of a single process path, a third process path is selected.

3. The composite pile extraction construction method based on casing isolation and pile side soil cutting as described in claim 1, characterized in that, In the first process path, the lifting equipment is a crawler crane, and a portion of the counterweight of the crawler crane is replaced by a hydraulic power station to provide power to the vibrating equipment.

4. The composite pile extraction construction method based on casing isolation and pile side soil cutting as described in claim 1, characterized in that, In the second process path, the jet pressure of high-pressure clean water is ≥20 MPa, and the influence radius of the annular weak zone is ≥500 mm.

5. The composite pile extraction construction method based on casing isolation and pile side soil cutting as described in claim 1, characterized in that, In step S1c of the third process path, the depth of high-pressure water cutting is 1 / 2 to 2 / 3 of the length of the old pile.

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