A method for lifting pile foundation grouting reinforcement on large-thickness island filling ground

Abstract

This invention discloses a lifting method for grouting reinforcement of pile foundations on thick island fill foundations, comprising the following steps: Step 1: Measure settlement data and arrange first grouting holes around the outer ring of the pile cap; arrange second grouting holes inside the pile cap; arrange third grouting holes between pile caps; Step 2: Simultaneously grout through the first and second grouting holes to form a first-class bearing layer; Step 3: Grout through the third grouting hole to form a second-class bearing layer; Step 4: Perform low-pressure slow grouting on the foundation soil at the bottom of the pile cap, stopping grouting when the lifting data of the pile cap reaches more than half of the initial settlement data; Step 5: Perform low-pressure slow grouting on the pile fill around the pile at the bottom of the pile cap until a pile-soil bond is formed; wherein, a lifting zone is formed between the first-class bearing layer and the pile-soil bond; Step 6: Simultaneously grout the lifting zone through the first and second grouting holes until it is lifted to a preset height, thus completing the pile foundation grouting reinforcement lifting.

Description

Technical Field

[0001] This invention relates to the field of pile foundation grouting reinforcement and lifting technology, and in particular to a lifting method for pile foundation grouting reinforcement on a thick island fill foundation. Background Technology

[0002] In the industrial development and construction of islands, due to terrain limitations, large-scale backfilling using materials such as excavated soil and slag fill is commonly used to create thick artificial fill foundations. These fills are characterized by their large thickness, loose structure, and high porosity. For pile foundations on these thick fill foundations on islands that have already experienced settlement, conventional remediation techniques are mainly divided into two categories: the first is simple pile tip grouting, which only reinforces the soil below the pile tip; the second is simple foundation cap grouting, which only involves shallow grouting and lifting below the foundation cap. However, simple pile tip grouting only reinforces a localized area at the pile tip and does not address the entire pile. Treating long stretches of fill makes it impossible to form a coordinated load-bearing system. When simply grouting the bottom of the pile cap for lifting, the grouting pressure acts directly on the bottom of the pile cap, and the lifting force needs to forcibly overcome the side friction resistance of the entire pile length. During the lifting process, excessive shear stress and bending moment are easily generated at the connection between the pile head and the pile cap, which seriously affects the structural safety and durability. Therefore, there is an urgent need for a lifting method for grouting reinforcement of pile foundations on thick island fill foundations to solve the technical problems such as the inability of traditional single pile end grouting to achieve synchronous lifting of pile, soil and pile cap, insufficient safety and durability of traditional pile cap bottom grouting structures, high porosity of island fill, and easy grout leakage during the grouting lifting process. Summary of the Invention

[0003] This invention provides a lifting method for pile foundation reinforcement using grouting on thick island fill foundations, addressing technical problems such as the inability of traditional single pile end grouting to achieve simultaneous lifting of the pile and soil cap, insufficient safety and durability of traditional cap bottom grouting structures, high porosity of island fill, and grout leakage during the lifting process. To achieve the above objectives, this invention adopts the following technical solution: A lifting method for pile foundation grouting reinforcement on a thick island fill foundation, characterized by comprising the following steps: Step 1: Measure the settlement data of each pier cap and arrange the grouting hole positions: Arrange multiple first grouting holes around the outer ring of each pier cap; arrange multiple second grouting holes inside each pier cap; arrange multiple third grouting holes in the area between each pier cap. Step 2: Construct a bearing layer: A raised zone is set at the bottom of the pile foundation, and grouting is carried out through the first grouting hole and the second grouting hole. The grouting depth starts from the bottom of the raised zone and extends to the bottom of the rock layer to form a bearing layer. Step 3: Constructing the second type of bearing layer: In the area between the pile caps, grouting is carried out through the third grouting hole. The grouting depth starts from the bottom of the pile foundation and extends down to below the rock stratum to form the second type of bearing layer. The lifting zone is located between the first-class bearing layer and the bottom of the pile foundation. The second-class bearing layer is higher than the first-class bearing layer. The height difference corresponds to the thickness of the lifting zone. The second-class bearing layer is located around the first-class bearing layer to form a circumferential constraint. Step 4, Shallow grouting and lifting of the foundation: Based on the foundation settlement data measured in Step 1, grout the foundation soil at the bottom of the foundation. The grouting method is low-pressure slow grouting. Grouting is stopped when the lifting data of the foundation reaches more than half of the initial settlement data. Step 5: Constructing the pile-soil composite: Grouting is performed on the backfill around the piles at the bottom of the pile cap. The grouting method is low-pressure slow injection until the piles and the surrounding soil are consolidated into a single rigid column, forming the pile-soil composite. The range of the raised zone corresponds to the range of the pile-soil composite structure. Step 6: Secondary grouting and lifting of the lifting zone: Grouting is carried out simultaneously through the first and second grouting holes in the lifting zone to achieve the synchronous and unidirectional overall lifting of the pile-soil bond and the pile cap until it is lifted to the preset height. At this point, the pile foundation grouting reinforcement and lifting is completed.

[0004] Furthermore, in step 1, the first grouting holes are spaced apart along the outer ring of the foundation, and the distance between adjacent first grouting holes is 3m; The second grouting holes are arranged in a rectangular interval within the pier cap area, with a spacing of 3-6m between adjacent second grouting holes; The third grouting holes are arranged in a quincunx pattern in the area between the foundations, and the distance between adjacent second grouting holes is 6m.

[0005] Furthermore, the design grout diffusion radius is 3.5m, and the reinforcement range of any two adjacent grouting holes is hinged and interlocked with each other.

[0006] Furthermore, in step 3, the grouting pressure when forming the second type of bearing layer is lower than the grouting pressure when forming the first type of bearing layer in step 2, in order to prevent excessive intrusion of grout into the uplift zone.

[0007] Furthermore, before shallow grouting and lifting in step 4, quick-setting grout is injected into the foundation soil under the pier through the second grouting hole to adapt to the construction environment of high porosity, abundant groundwater, and easy grout leakage in the island fill.

[0008] Furthermore, in step 5, the component pile-soil composite is constructed in sections, with each section being 5m deep, and slag powder resistant to seawater corrosion is added to the grouting slurry.

[0009] Furthermore, during the lifting process in steps 4 and 6, the settlement and horizontal displacement of the pier are monitored in real time by displacement sensors installed on the pier, and the lifting rate is controlled by adjusting the grouting pressure and flow rate, so as to achieve coordinated grouting and lifting among multiple piers.

[0010] Furthermore, it also includes step 7, arranging the foundation vibration damping ring: after the lifting is completed, grouting is performed on the first grouting hole around the outer edge of the foundation to form an annular foundation vibration damping ring with a depth of 5m.

[0011] Furthermore, the vibration damping ring is made of flexible grouting material, and its elastic modulus after solidification is lower than that of the pile-soil bond and the surrounding reinforced soil.

[0012] Furthermore, when arranging the grouting hole positions in step 1, the spacing and number of grouting holes are adjusted according to the amount of settlement of each pier. In areas with large settlement, the density of grouting holes is increased accordingly.

[0013] The beneficial effects of this invention are reflected in: 1) This invention constructs a first-class bearing layer and a second-class bearing layer in stages to form a bottom constraint system at the pile bottom, which effectively avoids the problem of disorderly downward diffusion of grout and grout leakage to the surrounding area caused by the high porosity and loose soil of island fill, so that the boundary of the lifting zone is clear and the energy of grout is concentrated. 2) This invention forms a pile-soil composite by low-pressure slow injection along the entire length of the pile, transforming the discrete pile and loose fill into a rigid column, changing the load transfer path, and transforming the pile side friction resistance that needs to be forcibly overcome in the traditional lifting method into a cohesive whole, which is beneficial to subsequent overall lifting and long-term cohesive load. 3) This invention adopts a distributed construction sequence of first shallow lifting and then overall lifting. The former improves construction efficiency and reduces construction costs, while the latter improves lifting accuracy and structural stability. Through the secondary lifting of the pile-soil combination, the pile, soil and pile cap are lifted synchronously and in the same direction, and the lifting process is stable and controllable.

[0014] Therefore, this application solves the technical problems of traditional single pile end grouting being unable to achieve synchronous lifting of the pile and soil cap, insufficient safety and durability of traditional cap bottom grouting structures, high porosity of island fill, and easy grout leakage during the grouting and lifting process; other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention; the main objectives and other advantages of the invention can be realized and obtained by means of the methods particularly pointed out in the description. Attached Figure Description

[0015] Figure 1 This is a vertical cross-sectional schematic diagram of a lifting method for grouting reinforcement of pile foundations on a thick island fill foundation; Figure 2This is a top view of the first grouting hole, the second grouting hole, and the third grouting hole; Figure 3 This is a schematic diagram of the cross-sections of a Class I bearing layer and a Class II bearing layer; Figure 4 This is a schematic diagram of the cross-section of the pile-soil composite structure; Figure 5 This is a top view of the vibration damping ring.

[0016] Attached reference numerals: 1-Pile cap, 2-First grouting hole, 3-Second grouting hole, 4-Third grouting hole, 5-Class I bearing layer, 6-Class II bearing layer, 7-Pile-soil combination, 8-Uplift zone, 9-Vibration damping ring. Detailed Implementation

[0017] The technical solutions of the present invention will be described in detail below through embodiments. The following embodiments are merely exemplary and can only be used to explain and illustrate the technical solutions of the present invention, and should not be construed as limiting the technical solutions of the present invention.

[0018] Taking a construction project in a coastal area as an example, the site elevation is equivalent to the local elevation of 146m. Uneven settlement occurred in the foundations of several rotary kilns. The rotary kilns are located in a slag backfill area, with the slag backfill depth at the foundation bottom ranging from 41m to 52m. The lower foundation is a prestressed concrete pipe pile foundation, and the upper structure is a reinforced concrete structure with pile lengths of 30m. From construction to commissioning, the cumulative uneven settlement of the rotary kiln foundations was 108mm. To achieve simultaneous lifting of the pile-soil cap in the island area with loose soil and high porosity, and to improve the structural safety and durability of traditional grouting methods, a method is proposed... Figure 1-5 The method for lifting pile foundations reinforced by grouting on thick island fill foundations is applied, including the following steps: Step 1: Measure the settlement data of each pier cap 1 and arrange the grouting hole positions: Arrange multiple first grouting holes 2 around the outer ring of each pier cap 1; arrange multiple second grouting holes 3 inside each pier cap 1; arrange multiple third grouting holes 4 in the area between each pier cap 1; first obtain the actual settlement data of each pier cap 1, and then arrange the first grouting holes 2, second grouting holes 3 and third grouting holes 4 in the outer ring, inside and between pier cap 1 in sections. The arrangement of the three types of holes is completed at one time, which reserves grouting channels for all subsequent processes such as bottom constraint, lifting and vibration damping ring 9, reduces the risk of hole wall collapse caused by repeated drilling in the extremely uneven strata of island fill, and the disturbance to the existing pier cap 1 foundation, which greatly improves construction efficiency and safety.

[0019] In this embodiment, in step 1, the first grouting holes 2 are spaced apart along the outer ring of the pile cap 1, with a spacing of 3m between adjacent first grouting holes 2; the second grouting holes 3 are arranged in a rectangular pattern within the pile cap 1, with a spacing of 3-6m between adjacent second grouting holes 3; the third grouting holes 4 are arranged in a quincunx pattern in the area between pile caps 1, with a spacing of 6m between adjacent second grouting holes 3; the designed diffusion radius of the grout is 3.5m, and the reinforcement range of any two adjacent grouting holes is hinged and interlocked with each other; the above hole arrangement fully considers the unfavorable construction conditions of uneven particle gradation and large voids in the island fill soil. The first grouting holes 2 form a reliable circumferential curtain, the rectangular arrangement of the second grouting holes 3 ensures the uniformity of reinforcement, and the quincunx arrangement of the third grouting holes 4 effectively reduces the construction difficulty and drilling workload of densely arranged holes between pile foundations while ensuring the continuity of the second type of bearing layer 6, thus improving construction efficiency.

[0020] Step 2: Constructing a Type I bearing layer 5: A raised zone is set at the bottom of the pile foundation, and grouting is carried out through the first grouting hole 2 and the second grouting hole 3. The grouting depth starts from the bottom of the raised zone 8 and extends to below the rock stratum, forming a Type I bearing layer 5; Step 3: Constructing a Type II bearing layer 6: Located in the area between pile caps 1, grouting is carried out through the third grouting hole 4. The grouting depth starts from the bottom of the pile foundation and extends to below the rock stratum, forming a Type II bearing layer 6; wherein, the raised zone 8 is set in a... Between the first-class bearing layer 5 and the bottom of the pile foundation, the second-class bearing layer 6 is higher than the first-class bearing layer 5. The height difference corresponds to the thickness setting of the uplift zone 8. The second-class bearing layer 6 is set around the first-class bearing layer 5 to form a circumferential constraint. By constructing the first-class bearing layer 5 and the second-class bearing layer 6 in stages, a bottom constraint system is formed at the bottom of the pile, which effectively avoids the problem of disorderly downward diffusion of grout and grout leakage to the surrounding area caused by the high porosity and loose soil of the island fill. This makes the boundary of the uplift zone 8 clear and the grout energy concentrated.

[0021] In this embodiment, in step 3, the grouting pressure when forming the second type of bearing layer 6 is lower than the grouting pressure when forming the first type of bearing layer 5 in step 2, in order to prevent excessive intrusion of grout into the uplift zone 8. This scheme adopts a differentiated grouting pressure control strategy. The first type of bearing layer 5 uses a higher pressure to ensure sufficient reinforcement of the soil directly below the pile end, forming a rigid support. The second type of bearing layer 6 uses a lower pressure to form circumferential constraints while avoiding high-pressure intrusion of grout into the uplift zone 8. For island fill, a stratum that is prone to hydraulic fracturing and grout leakage, this pressure differential control effectively prevents the soil in the uplift zone 8 from being grouted prematurely, retains the appropriate compressibility of the uplift zone 8, and creates a good premise for subsequent low-pressure uplift and controllable grouting, ensuring the smooth implementation of the "first up, then consolidate, then uplift" process.

[0022] Step 4, Shallow Grouting and Lifting of Foundation 1: Based on the settlement data of Foundation 1 measured in Step 1, low-pressure slow grouting is performed on the foundation soil within a 3m depth range of the bottom of Foundation 1. Grouting is stopped when the lifting data of Foundation 1 reaches more than half of the initial settlement data. When the pile backfill has not yet been reinforced and the pile side friction resistance is still weak, low-pressure slow grouting and lifting are performed on the shallow layer of 3m at the bottom of Foundation 1. The island backfill is naturally loose and the soil strength is even lower after being soaked by groundwater. At this time, only a small grouting pressure is needed to easily achieve the initial correction and lifting of the foundation, reducing construction costs. Lifting is stopped when more than half of the settlement is reached, leaving space for subsequent overall reinforcement and fine final lifting, realizing step-by-step controllable precision lifting construction.

[0023] In this embodiment, before shallow grouting and lifting in step 4, quick-setting grout is injected into the foundation soil at the bottom of the foundation 1 through the second grouting hole 3 to adapt to the construction environment of high porosity, abundant groundwater, and easy grout leakage in the island fill. Injecting quick-setting grout before shallow lifting can effectively block the main grout leakage channels, improve the accumulation efficiency of grout pressure during subsequent lifting grouting, achieve the expected initial lifting target with a lower grouting volume, further save grouting materials and shorten the construction period.

[0024] Step 5, Pile-Soil Composite Body 7: Low-pressure slow grouting is applied to the pile perimeter of the pile cap 1 until the pile and the surrounding soil are consolidated into a single rigid column, forming the pile-soil composite body 7; the range of the lifting zone 8 corresponds to the range of the pile-soil composite body 7; by applying low-pressure slow grouting to the entire length of the pile perimeter to form the pile-soil composite body 7, the discrete piles and loose backfill are transformed into a rigid column, changing the load transfer path and transforming the pile side friction resistance that needs to be forcibly overcome in the traditional lifting method into a cohesive whole, creating decisive conditions for the final overall lifting and long-term cohesive load.

[0025] In this embodiment, in step 5, the pile-soil composite component 7 is constructed in segments, with each segment measuring 5m in depth. Seawater-resistant slag powder is incorporated into the grouting slurry. This segmented construction at 5m depths allows for dynamic adjustment of grouting parameters based on the compaction and porosity characteristics of the fill at different depths, ensuring that the soil around each pile segment is fully filled and cemented, thus achieving pile-soil consolidation across the entire pile length. The addition of seawater-resistant slag powder prevents strength reduction due to seawater erosion after grouting reinforcement, ensuring the long-term performance of the pile-soil composite component 7.

[0026] Step 6, Secondary grouting and lifting of lifting zone 8: Grouting is carried out on lifting zone 8 through first grouting hole 2 and second grouting hole 3 at the same time, so as to realize the synchronous and unidirectional overall lifting of pile-soil combination 7 and pile cap 1 until it is lifted to the preset height. At this point, the pile foundation grouting reinforcement and lifting is completed.

[0027] By performing secondary grouting and lifting through the lifting zone 8 reserved between the bearing layer 5 and the pile-soil composite 7, the pile-soil composite 7 and the pile cap 1 can be easily and synchronously lifted upwards as a whole. Since the lifting force is borne and evenly transmitted by the bottom surface of the entire pile-soil composite 7, stress concentration is eliminated, and the pile, soil, and pile cap 1 are lifted smoothly and in the same direction with precision. The first shallow lifting is to save economic costs and lift quickly until it approaches the preset height. The second overall lifting controls the uneven settlement and reset accuracy of the large equipment foundation on the island to the millimeter level, focusing on lifting accuracy and stability.

[0028] In this embodiment, during the lifting process in steps 4 and 6, the settlement and horizontal displacement of the pier 1 are monitored in real time by displacement sensors installed on the pier 1. The lifting rate is controlled by adjusting the grouting pressure and flow rate, so as to achieve coordinated grouting and lifting among multiple piers 1. The lifting amount and horizontal displacement are monitored in real time by displacement sensors, and the data is fed back to the grouting control system. The pressure and flow rate of each grouting hole can be precisely adjusted to ensure that each pier 1 is lifted synchronously and in a coordinated manner, avoiding excessive uneven displacement that may cause additional stress to the superstructure or connecting pipes, and further improving the stability of the construction plan.

[0029] In this embodiment, step 7 is also included: arranging the vibration damping ring 9 of the foundation 1. After the lifting is completed, grouting is performed on the first grouting hole 2 around the outer edge of the foundation 1 to form an annular vibration damping ring 9 of the foundation 1 with a depth of 5m. The material of the vibration damping ring 9 is a flexible grouting material, and its elastic modulus after solidification is lower than that of the pile-soil composite 7 and the surrounding reinforced soil. After the lifting and reinforcement are completed, the annular vibration damping ring 9 is constructed using the existing first grouting hole 2 on the outer ring of the foundation 1. No additional drilling is required, making the construction efficient and economical. In addition, the vibration damping ring 9 is constructed using a flexible grouting material with a low elastic modulus, forming a three-dimensional vibration damping system that combines rigidity and flexibility with the internal high-rigidity pile-soil composite 7.

[0030] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A lifting method for pile foundation grouting reinforcement on a thick island fill foundation, characterized in that, Includes the following steps: Step 1: Measure the settlement data of each pier (1) and arrange the grouting hole positions: Arrange multiple first grouting holes (2) on the outer ring of each pier (1); arrange multiple second grouting holes (3) inside each pier (1); arrange multiple third grouting holes (4) in the area between each pier (1). Step 2, construct a bearing layer (5): A lifting zone is set at the bottom of the pile foundation, and grouting is carried out through the first grouting hole (2) and the second grouting hole (3). The grouting depth starts from the bottom of the lifting zone (8) and extends to the bottom of the rock layer to form a bearing layer (5). Step 3, constructing the second type of bearing layer (6): In the area between the pile cap (1) and the pile cap (1), grouting is carried out through the third grouting hole (4). The grouting depth starts from the bottom of the pile foundation and extends to the bottom of the rock layer to form the second type of bearing layer (6). Among them, the lifting zone (8) is set between the first bearing layer (5) and the bottom of the pile foundation, the second bearing layer (6) is higher than the first bearing layer (5), and the height difference corresponds to the thickness of the lifting zone (8). The second bearing layer (6) is set around the first bearing layer (5) to form a circumferential constraint. Step 4, Shallow grouting and lifting of the foundation (1): Based on the settlement data of the foundation (1) measured in Step 1, grouting is carried out on the foundation soil at the bottom of the foundation (1). The grouting method is low-pressure slow grouting. Grouting is stopped when the lifting data of the foundation (1) reaches more than half of the initial settlement data. Step 5: Constructing the pile-soil composite (7): Grouting is performed on the pile-surrounding soil at the bottom of the pile cap (1). The grouting method is low-pressure slow grouting until the pile and the surrounding soil are consolidated into a rigid column, forming a pile-soil composite. Among them, the range of the lifting zone (8) corresponds to the range of the pile-soil composite (7); Step 6, Secondary grouting and lifting of the lifting zone (8): Grouting is carried out on the lifting zone (8) through the first grouting hole (2) and the second grouting hole (3) to realize the synchronous and unidirectional overall lifting of the pile-soil combination (7) and the pile cap (1) until it is lifted to the preset height. At this point, the pile foundation grouting reinforcement and lifting is completed.

2. The lifting method for pile foundation grouting reinforcement on a thick island reclaimed land foundation according to claim 1, characterized in that, In step 1, the first grouting holes (2) are spaced along the outer ring of the foundation (1), and the distance between adjacent first grouting holes (2) is 3m; The second grouting holes (3) are arranged in a rectangular interval within the area of ​​the foundation (1), and the distance between adjacent second grouting holes (3) is 3-6m; The third grouting hole (4) is arranged in a quincunx pattern in the area between the foundation (1) and the foundation (1), and the distance between adjacent second grouting holes (3) is 6m.

3. The lifting method for pile foundation grouting reinforcement on a thick island reclaimed land foundation according to claim 2, characterized in that, The design grout diffusion radius is 3.5m, and the reinforcement range of any two adjacent grouting holes is hinged and interlocked.

4. The lifting method for pile foundation grouting reinforcement on a thick island reclaimed land foundation according to claim 1, characterized in that, In step 3, the grouting pressure when forming the second type of bearing layer (6) is lower than the grouting pressure when forming the first type of bearing layer (5) in step 2, in order to prevent the grout from excessively intruding into the lifting zone (8).

5. The lifting method for pile foundation grouting reinforcement on a thick island reclaimed land foundation according to claim 1, characterized in that, Before shallow grouting and lifting in step 4, quick-setting grout is injected into the foundation soil within a depth of 3m at the bottom of the foundation (1) through the second grouting hole (3) to adapt to the construction environment of high porosity, abundant groundwater, and easy grout leakage of the island fill soil.

6. The lifting method for pile foundation grouting reinforcement on a thick island reclaimed land foundation according to claim 1, characterized in that, In step 5, the component pile-soil combination (7) is constructed in sections, with each section having a depth of 5m, and slag powder resistant to seawater corrosion is added to the grouting slurry.

7. The lifting method for pile foundation grouting reinforcement on a thick island reclaimed land foundation according to claim 1, characterized in that, During the lifting process in steps 4 and 6, the settlement and horizontal displacement of the pier (1) are monitored in real time by displacement sensors installed on the pier (1), and the lifting rate is controlled by adjusting the grouting pressure and flow rate to achieve coordinated grouting and lifting among multiple piers (1).

8. The lifting method for pile foundation grouting reinforcement on a thick island reclaimed land foundation according to claim 1, characterized in that, It also includes step 7, arranging the vibration damping ring (9) of the foundation (1): After the lifting is completed, the first grouting hole (2) around the outer edge of the foundation (1) is grouted to form a ring-shaped foundation (1) vibration damping ring (9) with a depth of 5m.

9. The lifting method for pile foundation grouting reinforcement on a thick island reclaimed land foundation according to claim 8, characterized in that, The material of the vibration damping ring (9) is a flexible grouting material, and its elastic modulus after solidification is lower than that of the pile-soil composite (7) and the surrounding reinforced soil.

10. The lifting method for pile foundation grouting reinforcement on a thick island reclaimed land foundation according to claim 1, characterized in that, When arranging grouting holes in step 1, the spacing and number of grouting holes are adjusted according to the amount of settlement of each pier (1). In areas with large settlement, the density of grouting holes is increased accordingly.

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