Method for buckling prevention of pile foundation reinforced with partially deep liquefied soil between piles

Abstract

The application discloses a kind of pile foundation buckling prevention methods for reinforcing local depth liquefied soil between piles, the method comprises the following steps: step one, reinforcement scheme theoretical calculation;Step two, site construction.The application uses buckling-restrained brace to connect foundation pile to form a reinforcing body, which constrains lateral deformation of foundation pile, improves overall lateral stiffness and reduces differential settlement of foundation pile;Combined jack is used to transmit force to segmented pressure rod, and buckling-restrained brace is segmented and gradually driven into fixed depth, with lower resistance from soil body and accurate positioning.The application does not require large construction equipment, solves the problem of narrow space and unsuitable construction for existing buildings, and does not produce waste residue, waste, noise pollution and other environmental pollution, and is environmentally friendly construction.The void left by buckling-restrained brace construction is backfilled with gravel and injected with reinforcement slurry, which can improve the bearing capacity of foundation soil and speed up the drainage speed of liquefied soil layer, finally achieving simultaneous reinforcement of pile foundation and foundation soil, achieving two goals at once.

Description

Technical Field

[0001] This invention belongs to the field of bridge engineering technology and relates to a pile foundation buckling-resistance device and its construction method, specifically to a pile foundation buckling-resistance device and its construction method for reinforcing locally deep inter-pile liquefiable soil. Background Technology

[0002] Due to their advantages of high bearing capacity, good stability, small differential settlement, and suitability for soft soil foundations, pile foundation-pile cap-superstructure structure has been widely used in transportation construction such as bridges, highways, and overpasses. However, past earthquake damage has shown that a large number of pile foundations have been damaged during earthquakes, with failure modes including pile foundation settlement caused by liquefaction, bending failure, and buckling failure. Summary of the Invention

[0003] To address the aforementioned problems in the background art, this invention provides a method for reinforcing pile foundations with locally deep inter-pile liquefiable soil to prevent buckling. This invention targets the reinforcement of existing pile foundations, calculates the reinforcement location based on the pile's slenderness ratio and Euler's formula, and utilizes precast steel supports to locally reinforce the target depth. It offers advantages such as convenient construction, reliable reinforcement performance, and low cost, and has broad application prospects.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A method for buckling prevention of pile foundations with locally deep inter-pile liquefiable soil includes the following steps:

[0006] Step 1: Theoretical Calculation of Reinforcement Scheme

[0007] The theoretical calculations for the reinforcement scheme include the calculation of the slenderness ratio and effective length of the pile foundation based on the pile foundation stability theory, and the determination of the reinforcement location of the pile foundation;

[0008] Step 2: On-site construction

[0009] Step 21: Geological condition survey to determine the depth of unfavorable soil layers, and based on this, determine the location for pile foundation reinforcement;

[0010] Step 22: Based on the layout and cross-sectional type of the pile foundation, determine the type and length of the buckling-restrained brace and the type and size of the steel clamp, and prefabricate them accordingly;

[0011] Steps 2 and 3: Fix the steel clamps to the pile body and weld the buckling-resistance beams between two adjacent steel clamps;

[0012] Step 24: According to the reserved holes of the buckling-resistance support beam, position the fixed end of the pressing device and fix the bottom end of the combined jack to the fixed end of the pressing device.

[0013] Step 25: Connect the pressure rod. One end of the pressure rod is connected to the reserved hole in the anti-buckling support beam, and the other end of the pressure rod is connected to the top of the combined jack.

[0014] Step 26: Use a combination jack to drive the buckling-restrained brace into the foundation soil along the pile body. Since the displacement of the jack is limited, it is driven in segment by segment using pressure bars. When the maximum range is reached, a new pressure bar is connected until the target depth is reached.

[0015] Step 27: Remove the pressure bar from the soil and remove the combined jack and pressure bar;

[0016] Step 28: Fill the voids left during the buckling brace compression process by backfilling or grouting.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. Based on the stability theory of pile foundations, the reinforcement requirements are determined, which can maximize the efficiency of improving the performance of existing pile foundations and increase their bearing capacity.

[0019] 2. Buckling-restrained bracing beams in soft soil sites reduce the slenderness ratio of the original piles and increase the vertical bearing capacity of the piles, thus achieving the purpose of preventing buckling failure.

[0020] 3. The present invention utilizes buckling-resistance braces to connect the foundation piles to form a reinforced body, which constrains the lateral deformation of the foundation piles, improves the overall lateral stiffness, and reduces the differential settlement of the foundation piles.

[0021] 4. This invention can use a combination jack to transmit force to the segmented pressure rods, and drive the buckling restraint brace into a fixed depth segment by segment. The lower end of the buckling restraint brace is triangular prism-shaped, which has low soil resistance and can be accurately positioned.

[0022] 5. This invention does not require large construction equipment, solving the problem of limited space and unsuitability for construction in existing buildings. It also avoids generating waste residue, debris, and noise pollution, making it an environmentally friendly construction method. The pores left by the buckling-resistance brace construction can be filled with crushed stone and reinforced with grout, which can improve the bearing capacity of the foundation soil and accelerate the drainage of liquefied soil layers, ultimately achieving simultaneous reinforcement of the pile foundation and the foundation soil – a win-win situation. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the pile foundation buckling prevention device of the present invention;

[0024] Figure 2 This is a schematic diagram of the pressing device;

[0025] Figure 3 This is a structural schematic diagram of a buckling-restrained brace;

[0026] Figure 4 This is a structural schematic diagram of a buckling-restrained brace beam;

[0027] Figure 5 This is a structural schematic diagram of the steel clamp;

[0028] Figure 6 This is a schematic diagram of the construction process;

[0029] In the diagram: 1-Pile cap; 2-Foundation pile; 3-Pressing device; 4-Fixing end of pressing device; 5-Combined jack; 6-Pressure rod; 7-Buckling brace; 8-Buckling brace beam; 9-Steel clamp; 10-Rubber air spring; 11-Steel clamp bolt hole; 12-Reserved hole; 13-Steel clamp plate. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0031] Example 1

[0032] This embodiment provides a pile foundation buckling-resistance device for reinforcing locally deep liquefiable soil between piles, such as... Figures 1-5 As shown, the pile foundation buckling-restraint device includes an insertion device 3 and a buckling-restraint brace 7, wherein:

[0033] The pressing device 3 includes a pressing device fixed end 4, a combined jack 5, and a pressure rod 6;

[0034] The buckling brace 7 includes a buckling brace beam 8, a steel clamp 9, and a rubber air spring 10;

[0035] The fixed end 4 of the pressing device is fixedly connected to the pile cap 1 or the pile foundation 2;

[0036] The bottom end of the combined jack 5 is connected to the fixed end 4 of the pressing device, the top end of the combined jack 5 is connected to one end of the pressure rod 6, and the other end of the pressure rod 6 is connected to the anti-buckling support beam 8.

[0037] The steel clamp 9 is welded to the end of the buckling-resistance beam 8;

[0038] The rubber air spring 10 is bolted between the steel clamp 9 and the anti-buckling support beam 8.

[0039] In this embodiment, the pressure rod 6 is segmented, with each segment being 0.5–1.0 m in length. The rods are connected by threaded rings, and the actual number of segments required should be determined based on the preset position of the buckling-restrained brace. During construction, the combined jacks 5 transmit force to the pressure rod 6, gradually driving the buckling-restrained brace 7 into the foundation soil. When the pressure rod 6 is completely embedded in the foundation soil, a new pressure rod 6 is added on top of the pressure rod 6 until the buckling-restrained brace 7 is driven to the target depth.

[0040] In this embodiment, the steel clamp 9 is composed of two steel clamp pieces 13 connected by bolts. The size should be determined according to the size of the pre-reinforced pile foundation, and the diameter 9 (side length) of the steel clamp should be 5 to 20 cm larger than the diameter (side length) of the pile foundation. Before pressing, the steel clamp 9 surrounds the pile body, and the buckling-resistance brace 7 is gradually driven into the target depth using the pressing device 3.

[0041] In this embodiment, the upper part of the buckling-restrained brace beam 8 is rectangular, and the lower part is triangular prism to reduce soil resistance during compression. During construction, the upper rectangular part has a pre-drilled hole 12 that can contact the bottom end of the pressure rod 6, while the lower triangular prism contacts the foundation soil, facilitating the driving of the buckling-restrained brace 7 into the foundation soil.

[0042] In this embodiment, the type of buckling-restrained brace 8 can be determined according to the actual pile foundation layout and reinforcement requirements, and can generally be a single-brace type, a cross-shaped type, etc.

[0043] In this embodiment, the height of the rubber air spring 10 should not exceed 15cm to prevent excessive resistance during the pressing process.

[0044] Example 2

[0045] This embodiment provides a method for reinforcing locally deep inter-pile liquefiable soil using the pile foundation buckling-resistance device described in Embodiment 1. Figure 6 As shown, the method includes the following steps:

[0046] Step 1: Theoretical Calculation of Reinforcement Scheme

[0047] The theoretical calculations for the reinforcement scheme include the calculation of the slenderness ratio and effective length of the pile foundation based on the pile foundation stability theory, and the determination of the reinforcement location of the pile foundation;

[0048] The stability theory of the pile foundation is Euler column stability, i.e., linear eigenvalue buckling theory. The linear eigenvalue can be calculated based on differential equilibrium equations or energy methods.

[0049] The location for pile foundation reinforcement can be determined using the following methods:

[0050] λ>50

[0051]

[0052]

[0053] L = L' + 3D

[0054] Where λ is the slenderness ratio of the pile; μL is the effective length of the pile; μ is the length factor: μ = 2 when there is no hard clay layer at the top of the soil layer, and μ = 0.5 when there is a hard clay layer at the top of the soil layer; i is the radius of gyration of the pile; I is the moment of inertia of the pile; A is the cross-sectional area of ​​the pile; L is the effective length of the pile; L' is the thickness of the liquefiable soil layer; and D is the diameter of the pile.

[0055] When λ > 50, buckling-resistance reinforcement of the pile foundation is required, and the primary reinforcement location is below the ground surface. If λ is still greater than 50 after one reinforcement, the reinforcement location should be changed to below the ground surface. and The determination was made at two locations until λ was less than 50 after reinforcement.

[0056] Special note: If λ≤50, reinforcement is not necessarily required. Whether reinforcement is needed can be determined based on the owner's requirements, and the reinforcement depth can be determined using the method described above.

[0057] Step 2: On-site construction process

[0058] Step 2: 1. Geological survey to determine the depth of unfavorable soil layers such as soft soil and liquefiable soil layers, and based on this, determine the location for pile foundation reinforcement. Multiple reinforcement locations can be set as needed.

[0059] Step 2: Based on the layout and cross-sectional type of the pile foundation, determine the type and length of the buckling-restrained brace 7 and the type and size of the steel clamp 9, and prefabricate them respectively.

[0060] Steps 2 and 3: Fix the steel clamps 9 to the pile body and weld the buckling-resistance beam 8 between two adjacent steel clamps 9, with the lower triangular prism of the buckling-resistance beam 8 facing the foundation soil.

[0061] Step 24: Based on the reserved hole 12 of the anti-buckling support beam 8, position the pressing device fixing end 4, and fix the bottom end of the combined jack 5 to the pressing device fixing end 4.

[0062] Step 25: Connect the pressure rod 6. One end of the pressure rod 6 is connected to the reserved hole 12 in the anti-buckling support beam, and the other end of the pressure rod 6 is connected to the top of the combined jack 5.

[0063] Step 26: Using the combined jack 5, drive the buckling-resistance brace 7 into the foundation soil along the pile body 2. Since the displacement of the jack is limited, it is driven in segment by segment through the pressure bar 6. When the maximum range is reached, a new pressure bar 6 is connected until the target depth is reached.

[0064] Step 27: Remove the pressure bar 6 from the soil and remove the combined jack 5 and pressure bar 6.

[0065] Step 28: Fill the voids left during the pressing process of buckling-restrained brace 7 by backfilling with soil or grouting. For liquefiable sites, it is recommended to backfill the buckling-restrained brace beams 8 with crushed stone to accelerate soil drainage and reduce liquefaction hazards.

Claims

1. A buckling-restrained method of pile foundation for reinforcing partially deep liquefied soil between piles, characterized by The method comprises the following steps: Step one, theoretical calculation of reinforcement scheme The theoretical calculation of reinforcement scheme comprises calculation of slenderness ratio and effective length of pile foundation based on pile foundation stability theory, and determination of pile foundation reinforcement position; Step two, field construction process Step two one, geological condition survey to determine the depth of poor soil layer, and accordingly determine the pile foundation reinforcement position; Step two two, according to the arrangement form and cross section type of pile foundation, determine the type and length of buckling-restrained brace, the type and size of steel hoop, and respectively pre-process; Step two three, fix the steel hoop to the pile body, and weld the buckling-restrained brace beam between two adjacent steel hoops; Step two four, according to the reserved hole of buckling-restrained brace beam, position the fixed end of pressing device, and fix the bottom end of combined jack to the fixed end of pressing device; Step two five, connect the pressure rod, one end of which is connected to the reserved hole of buckling-restrained brace beam, and the other end of which is connected to the top end of combined jack; Step two six, use the combined jack to press the buckling-restrained brace into the ground along the pile body, the displacement of jack is limited, so the pressure rod is pressed in section by section, and a new pressure rod is connected every time the maximum range is reached until the target depth is reached; Step two seven, remove the pressure rod in the soil, and remove the combined jack and pressure rod; Step two eight, fill the hole left by the pressing process of buckling-restrained brace with soil or grouting.

2. The buckling-restrained pile foundation method for partially liquefied soil between piles according to claim 1, characterized in that The length of the pressure rod is 0.5-1.0m, and the rods are connected by thread rings.

3. The buckling-restrained pile foundation method for partially liquefied soil between piles according to claim 1, characterized in that The steel hoop is composed of two steel hoop pieces connected by bolts.

4. The buckling-restrained pile foundation method for partially liquefied soil between piles according to claim 1 or 3, characterized in that The diameter of the steel hoop is 5-20cm larger than the diameter of the pile foundation.

5. The buckling-restrained pile foundation method for partially liquefied soil between piles according to claim 1, characterized in that The upper part of the buckling-restrained brace beam is cuboid, and the lower part is triangular prism.

6. The buckling-restrained pile foundation method for partially liquefied soil between piles according to claim 1 or 5, characterized in that The buckling-restrained brace beam is single support type or cross type.

7. The buckling-restrained pile foundation method for partially liquefied soil between piles according to claim 1 or 3, characterized in that The rubber air spring is connected between the steel hoop and the buckling-restrained brace beam.

8. The buckling-restrained pile foundation method for partially liquefied soil between piles according to claim 7, characterized in that The height of the rubber air spring is not more than 15cm.

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