Hydraulic reclamation foundation treatment method based on cooperation of high-energy-level dynamic compaction and concrete pipe piles

Abstract

The invention provides a hydraulic reclamation foundation treatment method based on cooperation of high-energy-level dynamic compaction and concrete pipe piles, and belongs to the technical field of geotechnical engineering foundation treatment. S2, layered progressive high-energy-level dynamic compaction treatment is carried out; s3, low-disturbance dry-type pneumatic hole forming is adopted; and S4, the PRC pipe pile is hammered and implanted, and a composite foundation is formed. According to the method, the gradient stiffness dynamic compaction layer and the low-disturbance PRC pipe pile are subjected to cooperative treatment, and integrated efficient improvement of a soil shallow layer and a deep base is achieved; a dry-type pneumatic pore-forming technology is adopted, the soil disturbance rate is controlled within 5%, and the disturbance problem of a traditional pore-forming technology on a pretreated soil body is effectively solved; the mechanical property of the hammering implanting technology is matched with that of the PRC pipe pile, it is precisely guaranteed that the pile end enters a bearing stratum through penetration control, meanwhile, the pile-soil interaction is enhanced, collaborative optimization of high crack resistance, high ductility and high durability is achieved through the mixed reinforcement design of the PRC pipe pile, and the PRC pipe pile is suitable for the special environment of coastal dredger fill.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering foundation treatment technology, and relates to a treatment method, particularly a hydraulic filling foundation treatment method based on the synergy of high-energy dynamic compaction and concrete pipe piles. Background Technology

[0002] The foundations of coastal reclamation areas are characterized by high groundwater levels, deep loose fill, and underlying soft, fluid-plastic interlayers, which easily lead to insufficient bearing capacity, excessive post-construction settlement of buildings and structures, and uneven settlement. Current technologies, such as high-energy dynamic compaction alone, can only improve shallow foundations and have limited effectiveness in treating deep, soft soil layers. Using pile foundations alone can generate negative skin friction due to the high compressibility of the soil around the piles, reducing the actual bearing capacity of the pile foundation. Furthermore, traditional pile driving techniques (such as hammer driving) exacerbate soil disturbance, further aggravating uneven settlement and stability problems. Summary of the Invention

[0003] The purpose of this invention is to address the aforementioned problems in existing technologies by proposing a method for treating dredged fill foundations that can simultaneously achieve shallow soil compaction and deep foundation reinforcement, reduce pile-soil settlement differences, and significantly reduce negative skin friction.

[0004] The objective of this invention can be achieved through the following technical solution: a method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles, comprising:

[0005] Including the following steps:

[0006] S1: Construction site pretreatment;

[0007] S2: Layered and progressive high-energy dynamic compaction treatment;

[0008] S3: Low-disturbance dry pneumatic drilling is adopted;

[0009] S4: PRC pipe piles are driven in and a composite foundation is formed.

[0010] In the above-mentioned method for treating dredged fill foundation based on the synergy of high-energy dynamic compaction and concrete pipe piles, step S2 includes main compaction treatment, secondary compaction treatment, and full compaction treatment, and the energy level of the main compaction during the main compaction treatment, the energy level of the secondary compaction during the secondary compaction treatment, and the energy level of the full compaction during the full compaction treatment decrease by a multiple.

[0011] In the above-mentioned method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles, step S2 includes the following steps:

[0012] S21: Main tamping treatment, and the main tamping adopts an energy level of 8000kN·m. The number of single-point tamping blows is 10-12. Among them, the average settlement of the last two blows is ≤150mm as the standard for stopping the hammer.

[0013] S22: Secondary compaction treatment, and the secondary compaction adopts an energy level of 4000kN·m. The number of single-point compaction blows is 6-8. Among them, the average settlement of the last two blows is ≤100mm as the standard for stopping the hammer.

[0014] S23: Full compaction treatment, with full compaction using an energy level of 2000kN·m, two adjacent compaction marks overlapping by 1 / 3, each point being compacted twice, and the average settlement of the two compaction marks being controlled to be ≤50mm.

[0015] In the above-mentioned method for treating dredged and filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles, for step S2, the main compaction points are arranged in a quincunx pattern, and the secondary compaction points are located at the center between any two adjacent main compaction points.

[0016] In the above-mentioned method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles, for step S2, the main compaction process is performed twice, including the following steps:

[0017] S211, the first main compaction, in which multiple main compaction points are arranged in an array. In the horizontal direction, the distance between any two adjacent main compaction points is 8m; in the vertical direction, the distance between any two adjacent main compaction points is 8m.

[0018] S212: Second round of main compaction, in which multiple main compaction points are arranged in an array. In the horizontal direction, the distance between any two adjacent main compaction points is 8m; in the vertical direction, the distance between any two adjacent main compaction points is 8m, and any one of the main compaction points in the second round is the center of the grid formed by the four adjacent main compaction points in the first round.

[0019] In the above-mentioned method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles, step S3 includes the following steps:

[0020] S31: After step S1 is completed, rest for a preset number of days and monitor the degree of soil strength recovery after the preset number of days;

[0021] S32: Dry pneumatic drilling equipment is used for pile hole construction, with the rotation speed controlled at 30-60 r / min and the hole diameter at 800±20 mm.

[0022] In the above-mentioned method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles, step S3 further includes the following steps:

[0023] S33: Acceptance of borehole quality, including a depth of ≥1.2m into the bearing stratum, a borehole wall verticality deviation of ≤1%, and a soil disturbance rate of ≤5%.

[0024] In the aforementioned method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles, the PRC pipe piles in step S4 have an outer diameter of 800 mm, a wall thickness of 130 mm, and a pile length of 18 m; the concrete strength grade is C80, the impermeability grade is P12, and the chloride ion permeability coefficient is ≤1.0×10⁻⁶. 12 m / s.

[0025] In the above-mentioned method for treating dredged and filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles, the PRC pipe piles include prestressed main reinforcement, non-prestressed structural reinforcement, and spiral stirrups wrapped around the prestressed main reinforcement and non-prestressed structural reinforcement. The prestressed main reinforcement is made of spiral channel steel bar; the non-prestressed structural reinforcement is made of threaded steel; and the spiral stirrups are made of cold-drawn low-carbon steel wire.

[0026] In the above-mentioned method for treating dredged and filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles, for step S4, the average penetration of the last three hammer blows is ≤50mm as the standard for stopping the hammer blows, wherein the pile tip penetrates into the bearing layer by no less than 2.5m.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] This invention provides a method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles. It integrates gradient stiffness dynamic compaction layers with low-disturbance PRC pipe piles, achieving efficient and unified improvement of both shallow and deep soil layers. The dry pneumatic drilling technology controls soil disturbance to within 5%, effectively solving the problem of disturbance to pretreated soil caused by traditional drilling processes. The hammer-driven implantation process is matched with the mechanical properties of the PRC pipe piles, ensuring precise penetration control to ensure the pile tip enters the bearing layer while enhancing pile-soil interaction. The hybrid reinforcement design of the PRC pipe piles achieves synergistic optimization of "high crack resistance, high ductility, and high durability," adapting to the special environment of coastal hydraulically filled soils. Attached Figure Description

[0029] Figure 1 This is a block diagram of a method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles according to the present invention.

[0030] Figure 2 This is a schematic diagram of material property settings and mesh generation during the three-dimensional numerical simulation of this invention.

[0031] Figure 3 This is a schematic diagram of the boundary conditions and load conditions set during the three-dimensional numerical simulation of this invention.

[0032] Figure 4 This is a comparison diagram of pile side friction resistance during dynamic compaction and non-dynamic compaction in the three-dimensional numerical simulation of this invention.

[0033] Figure 5This is a graph showing the relationship between processing depth and pull-down load during the three-dimensional numerical simulation of this invention. Detailed Implementation

[0034] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0035] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0036] like Figures 1 to 5 As shown, the present invention provides a method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles, comprising the following steps:

[0037] S1: Construction site pretreatment;

[0038] S2: Layered and progressive high-energy dynamic compaction treatment;

[0039] S3: Low-disturbance dry pneumatic drilling is adopted;

[0040] S4: PRC pipe piles are driven in and a composite foundation is formed.

[0041] It is worth mentioning that, through the above treatment methods, the characteristic value of the bearing capacity of the composite foundation after treatment is ≥200kPa; the vertical ultimate bearing capacity of a single pile is ≥10000kN; post-construction settlement is controllable, with an average annual settlement of ≤15mm and differential settlement of ≤1.5‰; and the durability of the pile body is significantly improved, making it suitable for harsh corrosive environments.

[0042] This invention provides a method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles. It integrates gradient stiffness dynamic compaction layers with low-disturbance PRC pipe piles, achieving efficient and unified improvement of both shallow and deep soil layers. The dry pneumatic drilling technology controls soil disturbance to within 5%, effectively solving the problem of disturbance to pretreated soil caused by traditional drilling processes. The hammer-driven implantation process is matched with the mechanical properties of the PRC pipe piles, ensuring precise penetration control to ensure the pile tip enters the bearing layer while enhancing pile-soil interaction. The hybrid reinforcement design of the PRC pipe piles achieves synergistic optimization of "high crack resistance, high ductility, and high durability," adapting to the special environment of coastal hydraulically filled soils.

[0043] Preferably, step S2 includes the following steps:

[0044] S21: One to two main compaction passes, with the main compaction point using an energy level of 8000kN·m, 10-12 blows per point, and the average settlement of the last two blows ≤150mm as the standard for stopping the hammer.

[0045] S22: One round of secondary compaction, wherein the secondary compaction point uses an energy level of 4000kN·m, and each point is compacted 6-8 times, and the average settlement of the last two blows is ≤100mm as the standard for stopping the hammer.

[0046] S23: Full compaction treatment, using 2000kN·m energy level, with adjacent compaction marks overlapping by 1 / 3, each point being compacted twice, and the average settlement of the two compaction blows being controlled to be ≤50mm.

[0047] It is worth mentioning that when a shallow reinforced zone with a gradient stiffness distribution is formed after dynamic compaction, its mechanical properties must meet the following requirements:

[0048] 0-4m soil layer: compression modulus Es≥18MPa, standard penetration test blow count N63.5≥18 blows;

[0049] 4-6m soil layer: compression modulus Es≥16MPa, standard penetration test blow count N63.5≥15 blows;

[0050] 6-8m soil layer: compression modulus Es≥12MPa, standard penetration test blow count N63.5≥12 blows.

[0051] The compression modulus Es describes the relationship between vertical stress and corresponding vertical strain when soil is under fully confined compression. It reflects the soil's ability to resist compressive deformation under pressure. The standard penetration test blow count N is an in-situ test index used in geotechnical engineering investigation to evaluate the physical and mechanical properties of soil layers (especially sand, silt, and general cohesive soil).

[0052] It is worth mentioning that the standard penetration test is a field test method conducted in a borehole, and its process is as follows:

[0053] Step 1: Place a standard probe (called a standard penetrator, which consists of a split tube and a specially made boot cap) into the bottom of the borehole;

[0054] Step 2: Use a 63.5kg hammer to drop it freely from a height of 76cm (30 inches) to impact the drill rod;

[0055] Step 3: Record the number of hammer blows required to drive the penetrator into the soil to a depth of 30cm. The number of blows in the first 15cm is not counted. Only the number of blows in every 10cm of the last 30cm is recorded. Finally, the total number of blows in the last 30cm is taken as the standard penetration blow count N value at that depth.

[0056] More preferably, the main compaction points are arranged in an 8m×8m quincunx pattern, that is, the distance between any two adjacent main compaction points is 8m; the secondary compaction points are located at the midpoint between any two adjacent main compaction points.

[0057] More preferably, step S21 includes the following steps:

[0058] S211: First pass of main compaction, in which multiple main compaction points are arranged in an array. In the horizontal direction, the distance between any two adjacent main compaction points is 8m; in the vertical direction, the distance between any two adjacent main compaction points is 8m.

[0059] S212: Second round of main compaction, in which multiple main compaction points are arranged in an array. In the horizontal direction, the distance between any two adjacent main compaction points is 8m; in the vertical direction, the distance between any two adjacent main compaction points is 8m, and any one of the main compaction points in the second round is the center of the grid formed by the four adjacent main compaction points in the first round.

[0060] Preferably, step S3 includes the following steps:

[0061] S31: After step S1 is completed, rest for a preset number of days, which is generally 14 days, and monitor the degree of soil strength recovery after the preset number of days.

[0062] S32: Dry pneumatic drilling equipment is used for pile hole construction. The hole diameter is 800±20mm. The hole depth needs to penetrate the dredged fill layer and the underlying soft soil layer, and the depth into the lower dense bearing layer should not be less than 1.2m. The rotation speed is controlled at 30-60r / min to ensure that the verticality deviation of the hole wall is ≤1%.

[0063] It is worth mentioning that the pipe pile should be implanted within 24 hours after the hole is drilled, and the soil disturbance rate should be calculated by monitoring the change of the soil void ratio within 1m around the hole, and controlled to be ≤5%.

[0064] Preferably, in step S4, the PRC pipe pile has an outer diameter of 800 mm, a wall thickness of 130 mm, and a pile length of 18 m; the concrete strength grade is C80, the impermeability grade is P12, and the chloride ion permeability coefficient is ≤1.0×10⁻⁶. 12 m / s;

[0065] Furthermore, it is pointed out that PRC pipe piles include prestressed main reinforcement, non-prestressed structural reinforcement, and spiral stirrups wrapped around the prestressed main reinforcement and non-prestressed structural reinforcement. Among them, the prestressed main reinforcement uses 24 spiral channel steel bars with a diameter of 12.6mm for low-relaxation prestressed concrete, with a tensile strength design value ≥1000N / mm2; the non-prestressed structural reinforcement uses 24 hot-rolled ribbed HRB400 grade steel bars with a diameter of 14mm, with a tensile strength design value ≥360N / mm2; the spiral stirrups use cold-drawn low-carbon steel wire with a diameter of 5mm, with a spacing of 80mm in the non-reinforced zone and 50mm in the reinforced zone (within the pile top and pile end range), with a tensile strength design value ≥320N / mm2.

[0066] It is worth mentioning that, regarding the requirements for hammer driving construction: a 16t diesel hammer is used for pile driving construction, and the average penetration of the last three sets (10 blows per set) is ≤50mm as the standard for stopping the hammer, ensuring that the pile tip enters the dense silt or gravel bearing layer to a depth of not less than 2.5m.

[0067] In this embodiment, high-energy dynamic compaction significantly improves the density of shallow soil through dynamic consolidation and densification, forming a "stiffness gradient layer." This increases the compression modulus of the soil around the pile from 3-5 MPa to 12-18 MPa, and the gradient stiffness layer effectively reduces the settlement difference between the pile and the soil. Three-dimensional numerical simulation analysis shows that dynamic compaction optimizes the load transfer mode, transforming the pile foundation from a "primarily end-bearing" to a "combined end-bearing and friction" stress state. As the depth of dynamic compaction increases, the neutral point of the pile shifts downward, and the peak negative skin friction significantly decreases. Specifically, compared to the case without dynamic compaction, at a 10m dynamic compaction depth, the peak negative skin friction decreases from -96.1 kPa to -53.4 kPa (a decrease of 44.4%), the neutral point shifts from approximately 20m to approximately 30m (a decrease of 50%), and the downward load decreases from 3225 kN to 2272 kN (a decrease of 29.6%).

[0068] Dry pneumatic drilling avoids disturbance to the dynamic compaction reinforcement layer, with a hole wall stability coefficient ≥0.95, ensuring the bonding performance of the pile-soil interface;

[0069] The hybrid reinforcement design of PRC pipe piles takes into account the high crack resistance of prestressed tendons (the bending moment design value of its flexural bearing capacity is ≥1215kN·m) and the high ductility of non-prestressed tendons (ultimate elongation rate ≥7%), enabling them to better adapt to the complex stress state of "vertical bearing + horizontal constraint" in composite foundations.

[0070] The combination of C80 high-strength concrete and P12 high impermeability grade greatly improves the pile's resistance to chloride ion erosion and durability in the high-salt coastal environment, with an expected service life of no less than 50 years.

[0071] During the hammer-driven implantation method, the controlled penetration index ensures that the pile tip enters the designed bearing layer. At the same time, the hammer energy can further compact the soil around the pile and increase the positive skin friction of the pile side.

[0072] It should be noted that in this invention, the use of terms such as "first," "second," and "a" is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. The terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise explicitly specified. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0073] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0074] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles, characterized in that, Including the following steps: S1: Construction site pretreatment; S2: Layered and progressive high-energy dynamic compaction treatment; S3: Low-disturbance dry pneumatic drilling is adopted; S4: PRC pipe piles are driven in and a composite foundation is formed.

2. The method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles as described in claim 1, characterized in that, Step S2 includes main tamping treatment, secondary tamping treatment, and full tamping treatment, and the energy level of the main tamping treatment, the energy level of the secondary tamping treatment, and the energy level of the full tamping treatment decrease by a multiple.

3. The method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles as described in claim 2, characterized in that, For step S2, the steps include: S21: Main tamping treatment, and the main tamping adopts an energy level of 8000kN·m. The number of single-point tamping blows is 10-12. Among them, the average settlement of the last two blows is ≤150mm as the standard for stopping the hammer. S22: Secondary compaction treatment, and the secondary compaction adopts an energy level of 4000kN·m. The number of single-point compaction blows is 6-8. Among them, the average settlement of the last two blows is ≤100mm as the standard for stopping the hammer. S23: Full compaction treatment, with full compaction using an energy level of 2000kN·m, two adjacent compaction marks overlapping by 1 / 3, each point being compacted twice, and the average settlement of the two compaction marks being controlled to be ≤50mm.

4. The method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles as described in claim 3, characterized in that, For step S2, the main tamping points are arranged in a quincunx pattern, and the secondary tamping points are located at the center between any two adjacent main tamping points.

5. The method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles as described in claim 4, characterized in that, For step S2, the main compaction process is performed twice, including the following steps: S211, the first main compaction, in which multiple main compaction points are arranged in an array. In the horizontal direction, the distance between any two adjacent main compaction points is 8m; in the vertical direction, the distance between any two adjacent main compaction points is 8m. S212: Second round of main compaction, in which multiple main compaction points are arranged in an array. In the horizontal direction, the distance between any two adjacent main compaction points is 8m; in the vertical direction, the distance between any two adjacent main compaction points is 8m, and any one of the main compaction points in the second round is the center of the grid formed by the four adjacent main compaction points in the first round.

6. The method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles as described in claim 1, characterized in that, For step S3, the steps include: S31: After step S1 is completed, rest for a preset number of days and monitor the degree of soil strength recovery after the preset number of days; S32: Dry pneumatic drilling equipment is used for pile hole construction, with the rotation speed controlled at 30-60 r / min and the hole diameter at 800±20 mm.

7. The method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles as described in claim 6, characterized in that, For step S3, the following steps are also included: S33: Acceptance of borehole quality, including a depth of ≥1.2m into the bearing stratum, a borehole wall verticality deviation of ≤1%, and a soil disturbance rate of ≤5%.

8. The method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles as described in claim 1, characterized in that, For the PRC pipe pile in step S4, its outer diameter is 800mm, wall thickness is 130mm, and pile length is 18m; the concrete strength grade is C80, the impermeability grade is P12, and the chloride ion permeability coefficient is ≤1.0×10⁻⁻¹. 12 m / s.

9. The method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles according to claim 1, characterized in that, PRC pipe piles include prestressed main bars, non-prestressed structural bars, and spiral stirrups wrapped around the prestressed main bars and non-prestressed structural bars. The prestressed main bars are made of spiral channel steel bars; the non-prestressed structural bars are made of threaded steel bars; and the spiral stirrups are made of cold-drawn low-carbon steel wire.

10. The method for treating hydraulically filled foundations based on the synergy of high-energy dynamic compaction and concrete pipe piles according to claim 1, characterized in that, For step S4, the hammering standard is to use an average penetration depth of ≤50mm for the last three hammering passes, where the pile tip penetrates the bearing layer by no less than 2.5m.

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