CN115949091A - Pile foundation structure and method suitable for underpinning pile foundation of pile-falling tunnel - Google Patents
Pile foundation structure and method suitable for underpinning pile foundation of pile-falling tunnel Download PDFInfo
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- CN115949091A CN115949091A CN202211454489.0A CN202211454489A CN115949091A CN 115949091 A CN115949091 A CN 115949091A CN 202211454489 A CN202211454489 A CN 202211454489A CN 115949091 A CN115949091 A CN 115949091A
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Abstract
The invention discloses a pile foundation structure and a method suitable for underpinning pile foundations of a pile-up tunnel, belonging to the technical field of underpinning of pile foundations, wherein the pile foundation structure comprises underpinning piles, and the tops of the underpinning piles are fixedly connected with underpinning girders; the underpinning pile is divided into a first section, a middle section and a tail section from top to bottom, a reinforcement cage is arranged at the first section and the middle section of the underpinning pile, and a plurality of through-bottom main reinforcements are arranged at the tail section to support the reinforcement cage; the underpinning girder is provided with underpinning girder main ribs, the underpinning girder main ribs are arranged at the bottom of the underpinning girder and at the top of the girder, underpinning girder distribution ribs are arranged between the bottom of the underpinning girder and the top of the girder, and the underpinning girder main ribs and the underpinning girder distribution ribs are bound through underpinning girder lacing wires. The pile-underpinning reinforcement-arranging method can provide a more precise pile-underpinning reinforcement arrangement scheme for the large-disturbance shield tunnel to penetrate through the existing bridge pile, and ensures that the structure is high in strength and strong in connectivity between the members.
Description
Technical Field
The invention belongs to the technical field of underpinning of pile foundations, and particularly relates to a pile foundation structure and a method suitable for underpinning of pile foundations of a pile-up tunnel.
Background
The statements herein merely provide background information related to the present disclosure and may not necessarily constitute prior art.
With the continuous deepening of underground space development, shallow underground available space is also gradually reduced, so that some subway tunnels can be constructed in a stacking-falling mode. The existing urban overpass bridge piles often invade into the planned subway route, and then the existing bridge piles need to be underpinned. Because the disturbance of the up-and-down stacked structure to the surrounding stratum and the structure is far larger than that of a single-line tunnel, and the stress condition is complex and the stress change of a rock-soil body is difficult to accurately predict, the reinforcement bar for underpinning the pile foundation has higher requirements. And the disturbance to the existing peripheral structure is avoided when underpinning pile foundation engineering is carried out.
The structure and the construction method of the existing underpinning pile foundation mainly have the following defects: 1. the reinforcement cage is not specially designed, and the reinforcement is not encrypted and arranged aiming at a large disturbance area; 2. the existing underpinning bridge pile is only suitable for projects with small disturbance such as a single-line tunnel and the like, but not suitable for projects with large disturbance such as a stacked tunnel and the like; 3. the design and application of the conventional rectangular underpinning crossbeam are limited greatly and cannot adapt to the narrow space of the urban ground.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a pile foundation structure and a method suitable for underpinning pile foundations of a pile-up tunnel, which can provide a more precise underpinning pile reinforcement scheme for a large-disturbance shield tunnel to pass through an existing bridge pile, ensure high structural strength and strong connectivity between members, and simultaneously combine a special-shaped underpinning girder designed in the surrounding environment, thereby meeting the strength requirement, reducing the disturbance to the existing ground and underground structure and saving material resources.
In order to realize the purpose, the invention is realized by the following technical scheme:
in a first aspect, the invention provides a pile foundation structure suitable for underpinning pile foundations of a pile-up tunnel, which comprises underpinning piles, wherein the tops of the underpinning piles are fixedly connected with underpinning girders; the underpinning pile is divided into a first section, a middle section and a tail section from top to bottom, a reinforcement cage is arranged at the first section and the middle section of the underpinning pile, and a plurality of through-bottom main reinforcements are arranged at the tail section to support the reinforcement cage; the underpinning girder is provided with underpinning girder main ribs, the underpinning girder main ribs are arranged at the bottom of the underpinning girder and at the top of the girder, underpinning girder distribution ribs are arranged between the bottom of the underpinning girder and the top of the girder, and the underpinning girder main ribs and the underpinning girder distribution ribs are bound through underpinning girder lacing wires.
As a further technical scheme, the main reinforcement of the underpinning girder, the distribution reinforcement of the underpinning girder and the tie reinforcement of the underpinning girder form a reinforcement cage, and concrete is poured in the reinforcement cage of the underpinning pile and the reinforcement cage of the underpinning girder.
As a further technical scheme, the reinforcement cage adopts segmented reinforcement and comprises a plurality of longitudinal main reinforcements, outer-layer spiral stirrups are arranged on the outer sides of the longitudinal main reinforcements, and inner-layer annular stirrups are arranged on the inner sides of the longitudinal main reinforcements.
As a further technical scheme, the distance between the middle section longitudinal main ribs is larger than the distance between the first section longitudinal main ribs.
As a further technical scheme, the tail part of the middle section of the reinforcement cage is folded inwards.
As a further technical scheme, the longitudinal main reinforcement, the outer layer spiral stirrup and the inner layer ring stirrup all adopt threaded steel bars; main ribs of underpinning girders are arranged in a grid shape in a transverse and longitudinal crossed manner; the underpinning crossbeam lacing wires are arranged according to a quincunx shape, and a reinforcing mesh is formed among the underpinning crossbeam lacing wires; main ribs of the underpinning girder and distribution ribs of the underpinning girder are all thread steel bars; the tension bar of the underpinning crossbeam adopts a smooth steel bar.
As a further technical scheme, the underpinning girder is embedded with an existing bearing platform, main ribs of the underpinning girder on the upper portion invade the existing bearing platform, distribution ribs of the underpinning girder also invade the existing bearing platform, and the length of the main ribs of the underpinning girder invading the existing bearing platform is greater than the length of the distribution ribs of the underpinning girder invading the existing bearing platform.
In a second aspect, the present invention further provides a method for constructing a pile foundation structure suitable for underpinning pile foundations of a stacked tunnel, including the following steps:
carrying out pile hole excavation operation at a preset position; fixing a grouting pipe and a reinforcement cage, putting the grouting pipe into a pile hole, simultaneously starting grouting at the first section, the middle section and the tail section to form a newly-built bridge pile, and reserving a reinforcement joint and a jacking construction space;
placing a slope and excavating, exposing the existing bearing platform and the existing bridge pile, drilling the existing bearing platform, filling structural adhesive into the holes, and starting bar planting operation;
laying main ribs at the bottom of the underpinned girder, arranging temporary supports, laying distribution ribs of the underpinned girder on the layer of reinforcing steel bars, and laying main ribs at the top of the underpinned girder after the distribution ribs are laid; arranging underpinned girder lacing wires, binding main wires and distribution wires, and reserving bridge pile connecting wires to form a steel reinforcement framework;
pouring concrete into the steel reinforcement framework, and embedding a vibrating rod at the edge of the existing bearing platform; embedding grouting pipes at the base of the bearing platform, and filling and grouting the bottom of the bearing platform when the structural strength of the newly-built bearing platform reaches 70% to form a newly-built bearing platform;
continuously excavating the foundation pit downwards, installing a jacking device, and performing pre-jacking operation on the bearing platform structure;
connecting the reinforcing steel bars at the first section of the underpinning pile with the reserved reinforcing steel bars in the underpinning girder, and pouring concrete to enable the bridge pile and the underpinning girder to form a new underpinning pile foundation;
pile cutting operation is carried out on the existing bridge pile; and backfilling the foundation pit and removing the ground support.
As a further technical scheme, after the reinforcement cage is finished, three layers of cooling pipes are arranged in the bearing platform, wherein the first layer of cooling pipe and the second layer of cooling pipe adopt first cooling pipes which are arranged in a snake shape and bypass the existing bearing platform, and the third layer of cooling pipe adopts second cooling pipes which are arranged in a snake shape and bypass the existing bridge piles; after the concrete is poured, cooling water is introduced after the surface is initially set; when the grouting pressure is lower than the normal value for a long time, or grout is blown out from the ground or surrounding pile holes are strung, intermittent grouting is changed, or the water-cement ratio of the grout is reduced.
As a further technical scheme, the existing bearing platform adopts jump drilling operation for drilling, and the bar planting operation avoids damaging the original steel bars; arranging steel base plates at the top of the pile and the bottom of the bearing platform, and anchoring the steel base plates into the pile or the bearing platform by using anchor bars for fixing; the steel backing plate is provided with air outlets to ensure that concrete is poured tightly under the steel backing plate.
The beneficial effects of the invention are as follows:
according to the pile foundation structure, the underpinning pile reinforcement cage adopts segmented reinforcement, and the encrypted reinforcement is adopted for the large disturbance area crossed by the stacked shield tunnel, so that the stability and the safety of the bridge pile are improved when the shield passes through the pile foundation structure.
According to the pile foundation structure, the ground area considers the surrounding practical usable environment, so that the space is saved while the support stability is ensured; the underground area ensures the damage of the newly-built pile foundation caused by the large disturbance when the superposed tunnel passes through the section, and ensures the stability of the underpinned pile foundation.
The pile foundation structure adopts the special-shaped design to be designed into the polygonal diamond beam in order to adapt to the current situation of a specific construction area under the limitation of the existing building, meets the requirement of underpinning pile strength, avoids disturbance to the existing ground and underground structures at the periphery as much as possible, saves resources and reduces the construction cost compared with the conventional design.
The construction method can greatly reduce the time for the concrete to reach the preset strength, and has higher strength.
The construction method of the invention greatly improves the connectivity between the bridge pile and the underpinning girder and has continuity of mechanical and physical properties.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are included to illustrate an exemplary embodiment of the invention and not to limit the invention.
FIG. 1 is a cross-sectional view of a lower section reinforcement underpinning pile of the present invention;
FIG. 2 is a top view of a lower section reinforcement underpinning pile reinforcement area of the present invention;
FIG. 3 is a top view of the upper underpinning girder of the present invention;
FIG. 4 is a long side sectional view of an upper underpinning girder of the present invention;
FIG. 5 is a schematic view of the main reinforcement and the distribution reinforcement of the underpinning girder of the present invention intruding into the existing bearing platform;
FIG. 6 is a first cooling tube distribution pattern within the newly constructed platform of the present invention;
FIG. 7 is a second cooling tube pattern within the newly constructed platform of the present invention;
FIG. 8 is a schematic view of a steel shim plate according to an embodiment of the present invention;
in the figure: the space or size between each other is exaggerated to show the position of each part, and the schematic diagram is only used for illustration;
the novel tunnel comprises a longitudinal main rib 1, an outer layer spiral stirrup 2, an inner layer ring stirrup 3, a first section 4, a middle section 5, a tail section 6, a through bottom main rib 7, an existing bearing platform 8, an existing bridge pile 9, a pier column 10, a newly-built bearing platform 11, a newly-built bridge pile 12, a newly-built bridge pile 13, a main rib of a underpinning girder 14, a distribution rib of the underpinning girder 15, a bracing rib of the underpinning girder 16, a first cooling pipe 17, a second cooling pipe 18, a steel base plate 19, a steel base plate connecting anchor rib 20, a steel base plate vent hole 21 and a newly-built shield pile-up tunnel.
Detailed Description
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
In a typical embodiment of the present invention, as shown in fig. 1, a pile foundation structure suitable for underpinning pile foundations of a pile-up tunnel is provided, which includes underpinning piles located at a lower portion and underpinning girders located at an upper portion, and tops of the underpinning piles are fixedly connected with the underpinning girders.
Underpinning the stake from top to bottom divide into head 4, middle section 5 and tail section 6, and the underpinning stake is equipped with steel reinforcement cage in head and middle section, and this steel reinforcement cage adopts the segmentation arrangement of reinforcement, and wherein, the head arrangement of reinforcement configuration is: adopting an encrypted reinforcement, wherein a plurality of longitudinal main reinforcements 1 are arranged, the longitudinal main reinforcements are arranged at the same fixed distance, an outer-layer spiral stirrup 2 is arranged on the outer side of each longitudinal main reinforcement 1, and an inner-layer annular stirrup 3 is arranged on the inner side of each longitudinal main reinforcement 1; the middle section reinforcement configuration is as follows: the spiral hoop is characterized in that a plurality of longitudinal main ribs are arranged, the distance between the longitudinal main ribs is larger than that between the first section of the longitudinal main ribs, outer-layer spiral hoops are also arranged on the outer sides of the longitudinal main ribs, and inner-layer annular hoops are arranged on the inner sides of the longitudinal main ribs.
The tail section is provided with a plurality of through bottom main reinforcements 7 which are communicated with the bottom to support a reinforcement cage.
The longitudinal main reinforcement, the outer layer spiral stirrup and the inner layer ring stirrup are all made of twisted steel. In this embodiment, the longitudinal main rib interval of the first section is half of the longitudinal main rib interval of the middle section, the arrangement interval of the outer layer spiral stirrup of the first section is half of the arrangement interval of the outer layer spiral stirrup of the middle section, and the intervals of the first section and the inner layer ring stirrup of the middle section are the same. Specifically, the first section of longitudinal main reinforcement adopts three-stage twisted steel, the diameter of the first section of longitudinal main reinforcement is 28mm, and the first section of longitudinal main reinforcement is arranged according to a fixed distance of 130 mm; the middle-section longitudinal main reinforcement adopts three-stage twisted steel, the diameter of the middle-section longitudinal main reinforcement is 28mm, and the middle-section longitudinal main reinforcement is arranged according to the fixed distance of 250 mm; the first section of outer layer spiral stirrup adopts three-stage thread steel bars, the diameter of each thread steel bar is 12mm, and the layers are arranged according to the fixed distance of 100 mm; the middle-section outer-layer spiral stirrup adopts three-stage twisted steel, the diameter of the middle-section outer-layer spiral stirrup is 12mm, and the middle-section outer-layer spiral stirrup is arranged at a fixed distance of 200mm from layer to layer; the first section and middle section inlayer ring stirrup adopt tertiary twisted steel, and the diameter is 25mm, sets up according to fixed distance 2000mm between the inlayer ring stirrup.
The lower part of the encrypted reinforcement area of the first section 4 of the underpinning pile exceeds the bottom 1D of the off-line tunnel (D is the diameter of the tunnel), so that the excavation passing area of the newly-built shield pile-up tunnel 21 is in the encrypted area, the disturbance to a newly-built bearing platform and surrounding buildings and structures is reduced, and the safety of the pile-up tunnel passing through the old bridge pile is greatly improved; the first section of reinforcing bars are correspondingly consistent with the reserved reinforcing bars in the bearing platform; the tail part of the middle section 5 of the reinforcement cage is made into a folded shape inwards according to the length range of 1 mm in order to prevent the end part of the longitudinal reinforcement from rubbing the wall of the reinforcement cage; the horizontal section of the outer layer spiral stirrup 2 is not less than one circle and a half; and the outer layer spiral stirrup 2 and the inner layer ring stirrup 3 of the reinforcement cage are in single-side spot welding with the longitudinal main reinforcement 1.
The transverse section of the underpinning crossbeam is integrally specially shaped, such as a polygonal rhombus; the underpinning girder is provided with reinforcing bars and comprises underpinning girder main bars 13, the underpinning girder main bars are arranged at the bottom and the top of the underpinning girder, the underpinning girder main bars are crosswise arranged in a grid shape in the transverse direction and the longitudinal direction, and the distance between the transverse direction and the longitudinal direction is fixed and the same; the underpinning crossbeam distribution rib 14 is arranged between the bottom of the underpinning crossbeam and the top of the crossbeam, the underpinning crossbeam distribution rib is arranged between the main ribs of the underpinning crossbeam at the bottom of the crossbeam and the top of the crossbeam, the diameter of the main rib is slightly smaller than that of the main rib, and the distance between layers is the same; the main supporting girder ribs 13 and the distribution ribs 14 of the supporting girder are bound through supporting girder tie bars 15 and are arranged according to a quincunx shape, and a reinforcing mesh is formed between the tie bars.
The main ribs 13 and the distribution ribs 14 of the underpinning girder are all threaded steel bars; the supporting and changing crossbeam lacing wire 15 adopts a plain round steel bar.
In the embodiment, the main ribs of the underpinning girder adopt three-level thread steel bars, the diameter of each thread steel bar is 32mm, the distances between the transverse main ribs and the longitudinal main ribs are fixed and the same, and the main ribs and the longitudinal main ribs are all arranged according to 120 mm; the distribution ribs of the underpinning crossbeam adopt three-level thread reinforcing steel bars, the diameter of each three-level thread reinforcing steel bar is 20mm and is slightly smaller than that of the main rib, and the distribution ribs are arranged between layers according to a fixed distance of 200 mm; the underpinning girder lacing wires adopt first-level smooth round steel wires with the diameter of 16mm, are arranged according to a quincunx shape, form a reinforcing mesh between the lacing wires, and are arranged according to the transverse distance of 120mm and the longitudinal distance of 240 mm. Under the limit of the existing building, the underpinning girder is designed into a polygonal diamond beam by adopting a special-shaped design to adapt to the current situation of a specific construction area, so that the requirement on the strength of the underpinning pile is met, the disturbance to the existing ground and underground structures at the periphery is avoided as much as possible, and compared with the conventional design, the underpinning girder can save resources and reduce the construction cost.
And (3) forming a steel reinforcement framework by the reinforcing bars of the underpinned girder, and pouring concrete in a steel reinforcement cage of the underpinned pile and the steel reinforcement framework of the underpinned girder.
The existing bearing platform 8 is embedded into the underpinning girder, the top surface of the existing bearing platform is flush with the top surface of the underpinning girder, the bottom of the existing bearing platform is embedded into the underpinning girder, the main rib 13 of the underpinning girder at the upper part invades the existing bearing platform, the distribution rib 14 of the underpinning girder also invades the existing bearing platform, and the length of the main rib 13 of the underpinning girder, which invades the existing bearing platform, is longer than that of the distribution rib 14 of the underpinning girder, which invades the existing bearing platform. The relative position of the original pier stud 10 and the existing bearing platform 8 is unchanged.
In another exemplary embodiment of the present invention, a method for constructing a pile foundation structure suitable for underpinning pile foundations of a pile-up tunnel is provided, which specifically includes the following steps:
1) Carrying out pile hole excavation operation at a preset position;
2) Fixing the precast concrete grouting pipe and a reinforcement cage together, putting the precast concrete grouting pipe into a pile hole, and simultaneously starting grouting at the first section 4, the middle section 5 and the tail section 6;
3) Stopping grouting when the total grouting amount and the grouting pressure reach the design requirements;
4) When the strength of the pile body concrete reaches the design requirement, a newly-built bridge pile 12 is formed, and a steel bar joint and a jacking construction space are reserved;
5) Slope is set down and excavated, and the existing bearing platform 8 and the existing bridge piles 9 are exposed;
6) Chiseling the surfaces of an existing bearing platform 8 and an existing bridge pile 9, exposing and cleaning an old steel bar structure, and brushing an interface treating agent;
7) Drilling a hole on the existing bearing platform 8, filling structural adhesive into the hole, and starting bar planting operation;
8) Laying main ribs at the bottom of the underpinned girder beam at a preset place, arranging temporary supports, laying distribution ribs 14 of the underpinned girder on the layer of the steel ribs, and laying main ribs at the top of the underpinned girder beam after the distribution ribs are laid;
9) Underpinning girder lacing wires 15 according to a quincunx arrangement, binding main ribs and distribution ribs, and reserving bridge pile connecting ribs at specified positions;
10 After the reinforcing steel bar framework is finished, arranging three layers of cooling pipes in the bearing platform, wherein the first layer of cooling pipes and the second layer of cooling pipes adopt first cooling pipes 16 which are arranged in a snake shape and bypass the existing bearing platform, and the third layer of cooling pipes adopt second cooling pipes 17 which are arranged in a snake shape and bypass the existing bridge piles;
11 Concrete is poured on the steel reinforcement framework, and a vibrating rod is embedded at the edge of the existing bearing platform 8;
12 Pre-burying a grouting pipe at the base of the bearing platform, and timely filling and grouting the bottom of the bearing platform when the structural strength of the newly-built bearing platform reaches 70%;
13 When the strength of the pile body reaches the design strength, a newly-built bearing platform 11 is formed;
14 Continuously excavating the foundation pit downwards, mounting a jacking device, and performing pre-jacking operation on the bearing platform structure;
15 After the bridge pile and the bridge are deformed stably, screwing down a jacking support bolt until a jacking support accurately converts the lifting force of a jack, taking out the jack and installing a steel enclosing plate, connecting a first section 4 steel bar of the underpinning pile with a reserved steel bar in the underpinning girder, and pouring concrete to enable the bridge pile and the underpinning girder to form a new underpinning pile foundation;
16 Carrying out pile cutting operation on the existing bridge piles 9;
17 Backfilling the foundation pit and removing the ground support.
As shown in fig. 1, the rear grouting pipe is bound or welded with the reinforcement cage; the tail section should be not less than 3 main reinforcements penetrating the bottom to support the reinforcement cage; pile bottom slip casting pipe sets up 3 along steel reinforcement cage inboard circumference symmetry, and pile week slip casting pipe sets up 3 along steel reinforcement cage outside circumference symmetry. When the grouting pressure is lower than the normal value for a long time, or the slurry is blown out from the ground or the surrounding pile holes are strung, intermittent grouting is changed, the intermittent time is 30-60min, or the water-cement ratio of the slurry is reduced.
As shown in FIG. 5, the existing bearing platform 8 should be drilled by using a jump drill operation, and the steel bar planting operation should ensure that the original steel bars are prevented from being damaged. The length of the main reinforcement 13 of the upper underpinning girder intruding into the existing bearing platform is 860mm, which is 1.6 times of the length of the distribution reinforcement 14 of the underpinning girder intruding into the existing bearing platform 540 mm; main reinforcement and distribution reinforcement of the bearing platform in a certain area at the lower part meet the old pile, the edge of the pile can be wound around, and the middle part of the pile can be welded with the main reinforcement of the old pile in an L shape.
As shown in fig. 6-7, the first cooling tube 16 is required to bypass the existing cap, and the second cooling tube 17 is required to bypass the existing bridge pier. After the concrete is poured, cooling water is introduced after the surface is initially set, and the water inlet and the water outlet are replaced once every 8 hours, so that the uniform temperature inside the concrete is ensured, and the possibility of temperature cracks is reduced.
As shown in fig. 8, in order to ensure that the concrete at the top of the underpinned pile and at the bottom of the newly-built bearing platform 11 is not crushed during the loading process of the underpinning system, steel backing plates 18 with the thickness of 30mm are arranged at the top of the pile and at the bottom of the bearing platform, and 7 steel backing plates with the diameter of 22mm are connected with anchor bars 19 and anchored into the pile or the bearing platform for fixing; the steel tie plate is provided with 4 steel tie plate air outlets 20 to ensure that concrete under the steel tie plate is poured compactly.
The steel coaming can be used for supporting and protecting during later concrete pouring; the reserved steel bars of the bearing platform and the pile head steel bars are mechanically connected or welded on two sides.
The foundation pit is tamped, backfilled and compacted in a layered mode, and the backfilling is symmetrically carried out, so that the newly-built structure is prevented from settling.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A pile foundation structure suitable for underpinning pile foundations of a pile-up tunnel is characterized by comprising underpinning piles, wherein the tops of the underpinning piles are fixedly connected with underpinning girders; the underpinning pile is divided into a first section, a middle section and a tail section from top to bottom, a reinforcement cage is arranged at the first section and the middle section of the underpinning pile, and a plurality of through-bottom main reinforcements are arranged at the tail section to support the reinforcement cage; the underpinning girder is provided with underpinning girder main ribs, the underpinning girder main ribs are arranged at the bottom of the underpinning girder and at the top of the girder, underpinning girder distribution ribs are arranged between the bottom of the underpinning girder and the top of the girder, and the underpinning girder main ribs and the underpinning girder distribution ribs are bound through underpinning girder lacing wires.
2. A pile substructure suitable for underpinning a pile foundation of a pile-on-tunnel according to claim 1, wherein said main underpinning girder reinforcement, distribution girder reinforcement and tension girder reinforcement form a framework of reinforcement, and concrete is poured into the cages of the underpinning piles and the framework of reinforcement of the underpinning girder.
3. A pile foundation structure suitable for underpinning a pile foundation of a pile-up tunnel according to claim 1, wherein the reinforcement cage adopts a segmented reinforcement comprising a plurality of longitudinal main reinforcements, an outer layer spiral stirrup is arranged outside the longitudinal main reinforcements, and an inner layer ring stirrup is arranged inside the longitudinal main reinforcements.
4. A pile foundation structure adapted for underpinning a pile foundation of a pile-on-tunnel according to claim 3, wherein the distance between the longitudinal cage bars of the intermediate section is greater than the distance between the longitudinal cage bars of the first section.
5. A pile foundation structure adapted for underpinning pile foundations in a pile-erected tunnel as claimed in claim 1, wherein the tail of the middle section of the reinforcement cage is inwardly folded; the transverse section of the underpinning girder is a polygonal rhombus.
6. A pile foundation structure suitable for underpinning a pile foundation of a pile-up tunnel according to claim 1, wherein the longitudinal main reinforcement, the outer spiral stirrups and the inner hoop stirrups are all made of twisted steel; main ribs of underpinning girders are arranged in a grid shape in a transverse and longitudinal crossed manner; the underpinning crossbeam lacing wires are arranged according to a quincunx shape, and a reinforcing mesh is formed among the underpinning crossbeam lacing wires; the main rib of the underpinning girder and the distribution rib of the underpinning girder are both threaded steel bars; the tension bar of the underpinning crossbeam adopts a smooth steel bar.
7. A pile foundation structure adapted for underpinning a pile foundation according to claim 1, wherein said underpin longerons have an existing bolster embedded therein and the upper underpin longeron main tendons penetrate into the existing bolster and the underpin longeron distribution tendons also penetrate into the existing bolster, the length of the underpin longeron main tendons penetrating into the existing bolster being greater than the length of the underpin longeron distribution tendons penetrating into the existing bolster.
8. A method of constructing a pile foundation structure suitable for underpinning pile foundations in a stacked tunnel according to any one of claims 1 to 7, including the steps of:
carrying out pile hole excavation operation at a preset position; fixing a grouting pipe and a reinforcement cage, putting the grouting pipe into a pile hole, simultaneously starting grouting at the first section, the middle section and the tail section to form a newly-built bridge pile, and reserving a reinforcement joint and jacking construction space;
placing a slope and excavating, exposing the existing bearing platform and the existing bridge pile, drilling the existing bearing platform, filling structural adhesive into the holes, and starting bar planting operation;
laying main ribs at the bottom of the underpinned girder, arranging a temporary support, laying distribution ribs of the underpinned girder on the layer of reinforcing steel bars, and laying main ribs at the top of the underpinned girder after the distribution ribs are laid; arranging underpinned girder lacing wires, binding main wires and distribution wires, and reserving bridge pile connecting wires to form a steel reinforcement framework;
pouring concrete into the steel reinforcement framework, and burying a vibrating rod at the edge of the existing bearing platform; embedding grouting pipes at the base of the bearing platform, and filling and grouting the bottom of the bearing platform when the structural strength of the newly-built bearing platform reaches 70% to form a newly-built bearing platform;
continuously excavating the foundation pit downwards, installing a jacking device, and performing pre-jacking operation on the bearing platform structure;
connecting the reinforcing steel bars at the first section of the underpinning pile with the reserved reinforcing steel bars in the underpinning girder, and pouring concrete to enable the bridge pile and the underpinning girder to form a new underpinning pile foundation;
pile cutting operation is carried out on the existing bridge piles; and backfilling the foundation pit and removing the ground support.
9. The construction method as claimed in claim 8, wherein after the reinforcing cage is completed, three layers of cooling pipes are arranged in the bearing platform, wherein the first and second layers of cooling pipes are arranged in a serpentine shape and pass through the existing bearing platform, and the third layer of cooling pipes are arranged in a serpentine shape and pass through the existing bridge piles; after the concrete is poured, cooling water is introduced after the surface is initially set; when the grouting pressure is lower than the normal value for a long time, or the slurry is blown out from the ground or the surrounding pile holes are strung, intermittent grouting is changed, or the water-cement ratio of the slurry is reduced.
10. The construction method according to claim 8, wherein the existing bearing platform is drilled by using a jump drill operation, and the bar planting operation avoids damaging the original steel bars; arranging steel base plates at the top of the pile and the bottom of the bearing platform, and anchoring the steel base plates into the pile or the bearing platform by using anchor bars for fixing; the steel backing plate is provided with air outlets to ensure that concrete is poured tightly under the steel backing plate.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211454489.0A CN115949091A (en) | 2022-11-21 | 2022-11-21 | Pile foundation structure and method suitable for underpinning pile foundation of pile-falling tunnel |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211454489.0A CN115949091A (en) | 2022-11-21 | 2022-11-21 | Pile foundation structure and method suitable for underpinning pile foundation of pile-falling tunnel |
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| CN115949091A true CN115949091A (en) | 2023-04-11 |
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| CN202211454489.0A Pending CN115949091A (en) | 2022-11-21 | 2022-11-21 | Pile foundation structure and method suitable for underpinning pile foundation of pile-falling tunnel |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116356880A (en) * | 2023-04-12 | 2023-06-30 | 中交第四航务工程局有限公司 | Construction method for pipe ditch joist replacement |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116356880A (en) * | 2023-04-12 | 2023-06-30 | 中交第四航务工程局有限公司 | Construction method for pipe ditch joist replacement |
| CN116356880B (en) * | 2023-04-12 | 2023-11-21 | 中交第四航务工程局有限公司 | Construction method for pipe ditch joist replacement |
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