CN111636496A - Combined jacking underpinning structure and method for large-span bidirectional prestressed box type underpinning beam - Google Patents
Combined jacking underpinning structure and method for large-span bidirectional prestressed box type underpinning beam Download PDFInfo
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- CN111636496A CN111636496A CN202010512107.XA CN202010512107A CN111636496A CN 111636496 A CN111636496 A CN 111636496A CN 202010512107 A CN202010512107 A CN 202010512107A CN 111636496 A CN111636496 A CN 111636496A
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D35/00—Straightening, lifting, or lowering of foundation structures or of constructions erected on foundations
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
- E01D22/00—Methods or apparatus for repairing or strengthening existing bridges ; Methods or apparatus for dismantling bridges
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/10—Deep foundations
- E02D27/12—Pile foundations
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/10—Deep foundations
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- E02D27/14—Pile framings, i.e. piles assembled to form the substructure
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Abstract
A combined jacking underpinning structure and method of a large-span bidirectional prestressed box type underpinning beam are suitable for underpinning a pile foundation of a large-span underpinning beam and a rail transit bridge with a structure strictly meeting deformation requirements, the bidirectional prestressed concrete box type underpinning beam comprises a longitudinal prestressed system and a transverse prestressed system, an upper jacking system acts below the underpinned beam and is supported above the bidirectional prestressed concrete box type underpinning beam, and a lower jacking system acts below the bidirectional prestressed concrete box type underpinning beam; the underpinning structure can be suitable for underpinning the pile foundation of the rail transit bridge, effectively increases the adaptability of the underpinning structure, and increases the safety and durability of the underpinning structure. Through the coordination control of the bidirectional prestressed underpinning beam combined jacking system, the deformation of the underpinned structure can be well controlled, the safety requirement of a rail transit operating line is met, and the pile foundation underpinning project is completed under the normal operation condition that rail transit is not stopped and the speed is not limited.
Description
Technical Field
The invention relates to the technical field of rail transit bridges, in particular to a combined jacking underpinning structure and a method of a large-span bidirectional prestress box type underpinning beam, which are suitable for underpinning a large-span underpinning beam and a rail transit bridge pile foundation with a structure with strict deformation requirements.
Background
The pile foundation underpinning technology is an important branch of underpinning technology and mainly comprises two forms of active underpinning and passive underpinning. The passive underpinning is generally used for underpinning structures with relaxed deformation control requirements, the deformation of the underpinned structures can not be adjusted in the construction process of the passive underpinning, the settlement of the underpinned structures depends on the deformation capacity of underpinning beams and the settlement control of underpinned piles, and the passive underpinning belongs to passive adaptation. For underpinning structures with strict deformation control, active underpinning is generally adopted, which means that deformation requirements of underpinned structures are met through deformation adjustment in an active mode, jack loading equipment is generally arranged between underpinned new piles and underpinned beams, and the jacking process is completed through step-by-step loading of the jack loading equipment, so that overlarge settlement of the existing structures is avoided. The deformation control of the active underpinning has certain initiative, but when the pile beam is solidified, the initiative disappears.
For the pile foundation underpinning project of the urban rail transit operation line bridge, the pure active underpinning is still difficult to meet the requirements, and the main expression is as follows:
4.2.1. the deformation control requirements are strict. The deformation requirement of the rail on the rail transit bridge is higher than that of a common structure, so that the deformation control of the rail transit operation line bridge is higher than that of the common bridge.
4.2.2. The construction time is strictly controlled. Due to the characteristics of long operation time and short window period, the construction time of the rail transit operation line bridge for underpinning the pile foundation is strictly controlled, and the underpinning project is usually completed by operation measures such as speed limitation or shutdown.
4.2.3. The underpinning structure has larger span. Due to the characteristic that the rail transit bridge serves a city, the rail transit bridge is generally an important urban traffic main road or an urban dense area along the rail transit bridge, underpinning arrangement and construction space for underpinning a pile foundation are generally limited by municipal traffic or pipelines, and the underpinning structure has large span.
In view of the above characteristics of urban rail transit bridges, pile foundation underpinning is generally difficult to implement, and by taking Beijing as an example, all operation line bridges do not implement pile foundation underpinning until 2019, and when a newly-built underground structure conflicts with the foundation position of the newly-built underground structure, avoidance measures such as route changing and section size reducing are generally adopted, so that the functionality and the economy of a newly-built project are reduced.
Therefore, in view of the above-mentioned drawbacks, the present inventor has made extensive research and design to overcome the above-mentioned drawbacks by designing and developing a combined jacking and underpinning structure and method for a large-span bidirectional prestressed box type underpinning girder, which combines the experience and result of the related industries for many years.
Disclosure of Invention
The invention aims to provide a combined jacking underpinning structure and a method for a large-span bidirectional prestressed box type underpinning beam, which can effectively improve the span and width limitation of the underpinning structure, can also improve the adaptation range, the deformation control capability and the safety of the underpinning construction of a traversing project, expand the application range of the underpinning structure and improve the deformation control capability of the traversing project on a traversed structure.
In order to realize the purpose, the invention discloses a combined jacking underpinning structure of a large-span bidirectional prestressed box type underpinning beam, which comprises an upper layer jacking system, an underpinned structure bearing platform, an underpinned structure pile foundation, a bidirectional prestressed concrete box type underpinning beam structure, a lower layer jacking system and an underpinned beam structure, and is characterized in that:
the bidirectional prestressed box type underpinning beam structure adopts a bidirectional prestressed concrete structure system, is provided with a longitudinal prestressed system and a transverse prestressed system, and has a box-shaped section so as to be suitable for a large-span underpinning structure;
the bidirectional prestressed concrete box type underpinning beam structure is connected with the underpinned structure in a mode of coaction of a tongue-and-groove, interface glue and post-embedded bars;
the upper jacking system is arranged below the underpinned beam and comprises an upper jacking jack group, an upper jacking system supporting surface structure, an upper jacking system supporting column structure, an upper jacking system connecting anchor bolt and an upper jacking foundation structure, wherein the upper jacking jack group is arranged between the underpinned beam and the upper jacking system supporting surface structure, the upper jacking system supporting surface structure adopts a steel structure beam form, the upper jacking system supporting column structure is arranged below the upper jacking system supporting column structure, the column top of the upper jacking system supporting column structure is connected with the upper jacking system supporting surface structure through the anchor bolt or a welding form, and the column bottom of the upper jacking system supporting column structure is connected with the underpinned bearing platform through the upper jacking system connecting anchor bolt and the upper jacking foundation structure.
Wherein: the longitudinal prestressed system and the transverse prestressed system adopt prestressed stranded wires or prestressed thick steel bars, the longitudinal prestressed system is uniformly arranged in a web plate of the bidirectional prestressed concrete box type underpinning beam structure, and the transverse prestressed system is transversely arranged on two sides and the bottom of a bearing platform of the underpinned structure.
Wherein: the upper jacking system connecting anchor bolt is implanted into the underpinned bearing platform in a post-bar planting mode.
Wherein: the horizontal limiting device is of an upper sleeve structure and a lower sleeve structure, the upper sleeve structure and the lower sleeve structure comprise an upper sleeve and a lower sleeve which are small in size at the top and big at the bottom, a gap is reserved between the upper sleeve and the lower sleeve and used for eliminating secondary internal force, and self-compacting concrete is poured and filled through a reserved hole of the bidirectional prestress box type underpinning beam structure after jacking is completed.
Wherein: the underpinned structure bearing platform is connected with the bidirectional prestressed concrete box type underpinning beam structure through the combined action of the tongue-and-groove, the interface glue and the post-embedded steel bar.
Wherein: the lower-layer jacking system comprises a underpinning pile structure, a lower-layer bidirectional hydraulic jack group, a mechanical safety self-locking jack group and a horizontal limiting device, wherein the lower-layer bidirectional hydraulic jack group and the mechanical safety self-locking jack group are located between the underpinning pile foundation and the bidirectional prestressed concrete box type underpinning beam structure, the bidirectional hydraulic jack group is used for adjusting the vertical displacement of the bidirectional prestressed concrete box type underpinning beam structure 7, and the mechanical safety self-locking jack group plays a safety protection role in the working process of the bidirectional hydraulic jack group. The adjustment amount of the bidirectional hydraulic jack group adopts the principle of force and displacement double control, a graded loading distribution adjustment mode is adopted, each grade of loading amount ensures that the vertical displacement change of the underpinned beam is not more than 0.2mm, the transverse displacement difference is not more than 0.1mm, after each grade of adjustment is finished, the bidirectional hydraulic jack group is locked, the manual follow-up mechanical self-locking jack group is locked after being closely attached to the bidirectional prestressed concrete box type underpinned beam structure 7, and the next grade of loading adjustment can be carried out after the deformation is stable.
Wherein: the central position of the pile top of each underpinning pile structure is correspondingly provided with a set of horizontal limiting device, the horizontal limiting device adopts the situation of an upper sleeve and a lower sleeve, the upper sleeve is pre-embedded at the bottom of the bidirectional prestressed box type underpinning beam structure and is smaller than the lower sleeve, and the lower sleeve is pre-embedded at the central position of the underpinning pile structure, so that the upper sleeve and the lower sleeve are vertically overlapped and nested but mutually leave a gap to release the horizontal deformation of the bidirectional prestressed concrete box type underpinning beam structure caused by the prestress and shrinkage creep effect and avoid causing larger secondary internal force.
Wherein: the underpinning pile structure is provided with an underpinning pile cap, a post-cast strip and a horizontal limiting device are arranged between the underpinning pile cap and the bidirectional prestressed concrete box type underpinning beam structure, the underpinning pile cap upwards reserves reinforcing steel bars and extends into the post-cast strip, and the bidirectional prestressed concrete box type underpinning beam structure downwards reserves reinforcing steel bars and extends into the post-cast strip.
Also discloses a combined jacking and underpinning method of the large-span bidirectional prestressed box type underpinning beam, which is characterized by comprising the following steps:
the method comprises the following steps: the construction upper layer jacking system comprises a construction upper layer jacking system supporting surface structure, an upper layer jacking system supporting column structure, an upper layer jacking system connecting anchor bolt and an upper layer jacking foundation structure, and an upper layer jacking jack group is installed. The construction needs to plant a layer jacking system connecting anchor bolt after a bearing platform of a underpinned structure, assemble an upper layer jacking system supporting column structure on the top of the bearing platform of the underpinned structure, hoist the upper layer jacking system supporting surface structure and connect with the layer jacking system supporting column structure by using bolts, arrange each jack group of the upper layer jacking system on the upper layer jacking system supporting surface structure, and tightly attach to the underpinned beam by adjusting the height of the jack group of the upper layer jacking system;
step two: constructing a underpinning pile structure, and reserving connecting steel bars for the bidirectional prestressed box type underpinning beam structure in the underpinning pile structure;
step three: constructing and underpinning a foundation pit;
step four: constructing a underpinning pile cap, wherein a lower layer jacking system is arranged on the top surface of the underpinning pile cap and comprises an underpinning pile structure, a bidirectional hydraulic jack group, a mechanical safety self-locking jack group and a horizontal limiting device, a lower sleeve of the horizontal limiting device is pre-buried in the center of the underpinning pile cap, the bidirectional hydraulic jack and the mechanical safety self-locking jack are uniformly arranged at corresponding positions of the pile top, and connecting reinforcing steel bars with a bidirectional prestressed box type underpinning beam structure are reserved along the peripheral edge of the underpinning pile cap;
step five: pouring a bidirectional prestressed box type underpinning beam structure;
step six: a transverse prestress system and a longitudinal two-way prestress system of a two-way prestress box type underpinning beam structure are tensioned, the tensioning adopts the sequence of batch and symmetrical tensioning, and the displacement condition of the underpinned beam is monitored in real time;
step seven: switching a jacking system;
step eight: cutting off the underpinned structure pile foundation;
step nine: the bidirectional prestressed concrete box type underpinning beam structure is fixedly connected with the underpinning pile structure;
step ten: constructing a crossing structure;
step eleven: and (5) dismantling the upper jacking system.
Wherein: and seventhly, adopting a graded loading mode, ensuring that the vertical displacement change of the underpinned beam is not more than 0.2mm and the transverse displacement difference is not more than 0.1mm by each grade of loading, locking the bidirectional hydraulic jack group after each grade of adjustment is finished, locking the manual follow-up mechanical safety self-locking jack group after the manual follow-up mechanical safety self-locking jack group is closely attached to the bidirectional prestressed box type underpinned beam, and performing next grade of loading adjustment after the structure of the bidirectional prestressed box type underpinned beam is deformed stably.
From the above, the combined jacking underpinning structure and method of the large-span bidirectional prestressed box type underpinning beam has the following effects:
1. the upper jacking system can be continued in the whole construction process, and is dismantled after the whole crossing project is finished and the deformation is stable. When the upper jacking system can be used for excavating a foundation pit, the lower jacking system can be used as a deformation control system before being built, and can also be used for effectively adjusting deformation generated in the later period of creep, construction disturbance and the like of the structure after the lower jacking system is out of work after the pile beam is solidified.
2. The initiative of the upper layer jacking system exists, the lower layer jacking system can adopt consolidation measures earlier than the traditional active underpinning, namely consolidation is carried out before the lower part passes through the project, so that an statically indeterminate system is formed earlier by the underpinning structure, and the construction risk is greatly reduced.
3. The span and width limitation of the underpinning structure are improved, and the adaptation range, the deformation control capability and the crossing construction safety of the crossing project are improved. The self weight of the underpinning beam is effectively reduced through the underpinning beam with the box-shaped section hollowed in the middle, and the deformation of the underpinning structure is reduced; the span and the width of the underpinning structure are increased and the application range of the underpinning structure is expanded through a bidirectional prestress system; the deformation control capability of the crossing engineering on the crossed structure is improved through the mutual coordination and matching of the combined jacking systems.
4. By consolidating the lower jacking system in advance, the crossing risk in the construction process of the lower crossing project is reduced compared with the traditional active underpinning. By means of the active pile foundation underpinning of the large-span bidirectional prestressed concrete box-shaped section combined jacking system, the urban rail system with strict deformation control can be met, and the whole traversing process is not limited in speed and stopped, so that the influence of traversing construction on the traveling of the existing rail transit line is greatly reduced, and the feasibility of traversing rail transit engineering is improved.
The details of the present invention can be obtained from the following description and the attached drawings.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be discussed below, it is obvious that the technical solutions described in conjunction with the drawings are only some embodiments of the present invention, and for those skilled in the art, other embodiments and drawings can be obtained according to the embodiments shown in the drawings without creative efforts.
Fig. 1 shows a schematic view of one embodiment of the combined jacking underpinning structure of the large-span bidirectional prestressed box type underpinning beam of the present invention.
Fig. 2 shows a layout of prestressed reinforcement bars of a bidirectional prestressed box type underpinning beam according to an embodiment of the present invention.
FIG. 3 shows a floor plan of a lower jacking system in an embodiment of the present invention.
Figure 4 shows a floor plan of a lower jacking system in an embodiment of the present invention.
Fig. 5 shows a layout of an upper jacking system in an embodiment of the present invention.
FIG. 6 is a diagram illustrating a relationship between a underpinning structure and a traversing structure in an embodiment of the present invention.
FIG. 7 is a graph showing the vertical displacement time course of an underpinned beam bridge structure in the application of the present invention.
Fig. 8 shows a graph of the vertical displacement time course of the underpinned beam track structure in the application of the present invention.
FIG. 9 is a graph showing the time course of the lateral displacement of the underpinned beam track structure in the application of the present invention.
Figure 10 shows a graph of differential settlement time course of a switch point rail and a stock rail in a underpinned beam applied by the present invention.
Detailed Description
Referring to fig. 1 to 6, there are shown a combined jacking and underpinning structure and method of a large-span bidirectional prestressed box type underpinning beam according to the present invention.
The combined jacking underpinning structure of the large-span bidirectional prestressed box type underpinning beam can comprise an upper jacking system 1, an underpinned structure bearing platform 5, an underpinned structure pile foundation 6, a bidirectional prestressed concrete box type underpinning beam structure 7, a lower jacking system 8 and an underpinned beam structure 10, wherein the bidirectional prestressed concrete box type underpinning beam structure 7 adopts a bidirectional prestressed structure system, the bidirectional prestressed concrete box type underpinning beam structure is provided with a longitudinal prestressed system 12 and a transverse prestressed system 13, the section of the bidirectional prestressed concrete box type underpinning beam structure adopts a box section, and the bidirectional prestressed concrete box type underpinning beam structure is suitable for large-span underpinning structures.
The longitudinal prestressed system 12 and the transverse prestressed system 13 may be prestressed steel strands or prestressed thick steel bars, the longitudinal prestressed system 12 may be uniformly arranged in a web of the bidirectional prestressed concrete box-type underpinning beam structure 7 according to the stress condition, and the longitudinal crack resistance of the bidirectional prestressed concrete box-type underpinning beam structure 7 is mainly controlled, so that the longitudinal bridge is prevented from cracking under the combination of main force, main load and auxiliary load. The transverse prestressed systems 13 are transversely arranged on the two sides and the bottom of the underpinned structure bearing platform 5, and have the functions of improving the transverse crack resistance of the bidirectional prestressed concrete box type underpinning beam structure 7, mainly improving the friction force of the connecting interface of the underpinned structure bearing platform 5 and the bidirectional prestressed concrete box type underpinning beam structure 7 and enhancing the safety of the connecting surface of the underpinning structure.
The upper-layer jacking system 1 and the lower-layer jacking system 8 are combined to adjust the displacement of the underpinned beam structure 10, and the upper-layer jacking system 1 can adjust the vertical displacement of the underpinned beam structure 10.
The upper jacking system 1 is arranged below the underpinned beam 10 and comprises an upper jacking jack group, an upper jacking system supporting surface structure 2, an upper jacking system supporting column structure 3, an upper jacking system connecting anchor bolt 4 and an upper jacking base structure 11, the upper jacking jack group is arranged between the underpinned beam 10 and the upper jacking system supporting surface structure 2, the upper jacking system supporting surface structure 2 adopts a steel structure beam form and can adopt a box-shaped or I-shaped section as required, the upper jacking system jack group is arranged on the upper jacking system supporting surface structure, the upper jacking system supporting column structure 3 is arranged below the upper jacking system supporting surface structure, the column top of the upper jacking system supporting column structure 3 is connected with the upper jacking system supporting surface structure 2 in an anchor bolt or welding form, the column bottom of the upper jacking system connecting anchor bolt 4 is connected with the upper jacking base structure 11, and the underpinned bearing platform 5 are connected, the upper jacking system connecting anchor bolt 4 is implanted into the underpinned bearing platform 5 in a post-bar planting mode. The upper jacking system 1 plays a role in safely assisting the lower jacking system 8 before the underpinning pile foundation 9 is consolidated with the bidirectional prestressed concrete box type underpinning beam structure 7, and plays a role in adjusting the displacement of the underpinned beam structure 10 after the underpinning pile foundation 9 is consolidated with the bidirectional prestressed concrete box type underpinning beam structure 7. The upper jacking system 1 is to be removed after the construction of the traversing structure 15 is completed and stabilized by the deformation of the underpinning beam structure 10.
The upper layer jacking jack group consists of a plurality of jacks, the jacks are lifted synchronously, and the tonnage and the arrangement form of the plurality of upper layer jacks can be determined according to the underpinned beam structure 10.
The lower end of the upper jacking system supporting column structure 3 is anchored on the underpinned structure bearing platform 5 through the post-planting anchor bolt and the post-cast concrete connecting structure 11 of the upper jacking system connecting anchor bolt 4, the post-planting anchor bolt 4 is anchored above the underpinned bearing platform 5 through the post-anchoring technology, and the number and the diameter of the post-planting anchor bolt are determined according to the underpinned beam structure 10.
The underpinned structure bearing platform 5 is connected with a bidirectional prestressed concrete box type underpinning beam structure 7 through a connection mode of coaction of a tongue-and-groove, interface glue and post-embedded bars.
The lower jacking system 8 comprises a underpinned pile structure 9, a lower bidirectional hydraulic jack group, a mechanical safety self-locking jack group and a horizontal limiting device 20, the lower jacking system 8 can adjust the vertical displacement of the underpinned beam structure 10 and the bidirectional prestressed concrete box-shaped underpinned beam structure 7, the horizontal displacement of the underpinned beam structure 10 is limited by the horizontal limiting device 20, the number of the lower bidirectional hydraulic jacks is determined according to the jacking force, the safety coefficient is not less than 2, the lower bidirectional hydraulic jacks are positioned between the underpinned pile foundation 9 and the bidirectional prestressed concrete box-shaped underpinned beam structure 7, the bidirectional hydraulic jack group is used for adjusting the vertical displacement of the bidirectional prestressed concrete box-shaped underpinned beam structure 7, the mechanical safety jack group plays a safety protection role in the working process of the bidirectional hydraulic jack group, and the adjustment amount of the bidirectional hydraulic jack group adopts the self-locking principle of force and displacement double control, by adopting a graded loading distribution adjustment mode, the vertical displacement change of the underpinned beam 10 is not more than 0.2mm and the transverse displacement difference is not more than 0.1mm by each grade of loading capacity. After each stage of adjustment is completed, the bidirectional hydraulic jack group is locked, the manual follow-up mechanical safety self-locking jack is locked after being closely attached to the bidirectional prestressed concrete box type underpinning beam structure 7, and next stage of loading adjustment can be performed after the deformation is stable.
A set of horizontal limiting device 20 is correspondingly arranged at the center of the pile top of each underpinning pile structure 9. The horizontal limiting device 20 adopts the shape of an upper sleeve and a lower sleeve, the upper sleeve is pre-embedded at the bottom of the two-way prestressed concrete box-shaped underpinning beam structure 7 and is slightly smaller than the lower sleeve, and the lower sleeve is pre-embedded at the central position of the underpinning pile structure 9. The upper and lower sleeves of the horizontal limiting device 20 are overlapped and nested up and down, but a gap is reserved between the upper and lower sleeves. The clearance function of the bidirectional prestressed concrete box-type underpinning beam mainly comprises the horizontal deformation of the bidirectional prestressed concrete box-type underpinning beam structure 7 caused by the effects of releasing prestress and shrinking creep, so that larger secondary internal force is avoided.
The bidirectional prestressed concrete box type underpinning beam structure 7 is connected with the underpinned structure 14 in a mode of post-planting bars 18.
The underpinning pile structure 9 is provided with a plurality of underpinning pile caps 16, a post-cast strip 17 and a horizontal limiting device 20 are arranged between the underpinning pile caps 16 and the bidirectional prestressed concrete box type underpinning beam structure 7, the underpinning pile caps 16 are upwards reserved with reinforcing steel bars and extend into the post-cast strip 17, and the bidirectional prestressed concrete box type underpinning beam structure 7 is downwards reserved with reinforcing steel bars and extend into the post-cast strip 17. The underpinning pile structure 9, the underpinning pile cap 16 reserved steel bars and the bidirectional prestressed concrete box type underpinning beam structure 7 reserved steel bars are effectively connected before the consolidation operation of the lower jacking system, before jacking and in-place consolidation, concrete is poured after upper and lower sleeves of the horizontal limiting device 20 pass through the bidirectional prestressed concrete box type underpinning beam structure 7 reserved holes, and construction of the traversing structure 15 is carried out after the underpinning pile structure 9 and the bidirectional prestressed concrete box type underpinning beam structure 7 are consolidated.
The invention also relates to a combined jacking and underpinning method of the large-span bidirectional concrete box type underpinning beam, which comprises the following steps:
the method comprises the following steps: the construction upper layer jacking system comprises a construction upper layer jacking system supporting surface structure 2, an upper layer jacking system supporting column structure 3, an upper layer jacking system connecting anchor bolt 4, an upper layer jacking foundation structure 11 and an upper layer jacking jack group. The construction needs to plant a layer jacking system connecting anchor bolt 4 after a underpinned structure bearing platform 5, assemble an upper layer jacking system supporting column structure 3 on the underpinned structure bearing platform 5, hoist an upper layer jacking system supporting surface structure 2 and connect the layer jacking system supporting column structure 3 by using a bolt, arrange an upper layer jacking jack group on the upper layer jacking system supporting surface structure 2, and tightly attach to the underpinned beam 10 by adjusting the height of the upper layer jacking jack group.
Step two: and constructing the underpinning pile structure 9. The underpinning pile structure 9 needs to reserve connecting steel bars for the bidirectional prestressed concrete box type underpinning beam structure 7. The displacement of the underpinned beam 10 resulting from the construction of the underpinning pile structure 9 can be adjusted by means of the upper jacking system 1.
Step three: and (5) underpinning the foundation pit. The structural deformation generated by the construction foundation pit can be adjusted by the upper jacking system 1.
Step four: and (4) constructing the underpinning pile cap 16. The underpinning pile cap 16 has lower jacking system 8 comprising underpinning pile structure 9, two-way hydraulic jack set, mechanical safety self-locking jack set and horizontal limiting unit 20. The lower sleeve of the horizontal limiting device 20 is embedded in the center of the underpinning pile cap 16, and the bidirectional hydraulic jack group and the mechanical safety self-locking jack group are uniformly arranged at corresponding positions of the pile top. And connecting steel bars are reserved along the peripheral edges of the underpinning pile caps 16 and the bidirectional prestressed concrete box-type underpinning beam structure 7.
Step five: and pouring the bidirectional prestressed concrete box-type underpinning beam structure 7. Connecting steel bars are reserved at the bottom of the bidirectional prestressed concrete box type underpinning beam structure 7 and are connected with the construction underpinning pile cap 16 and the underpinning pile structure 9, an upper sleeve of the horizontal limiting device 20 is pre-embedded at the center of the underpinning pile structure 9, and the displacement of the underpinned beam 10 generated by the construction of the bidirectional prestressed concrete box type underpinning beam structure 7 can be adjusted through the upper jacking system 1.
Step six: and (3) tensioning a transverse prestress system 13 and a longitudinal bidirectional prestress system 12 of the bidirectional prestressed concrete box type underpinning beam structure 7 in a batch and symmetrical tensioning sequence, and monitoring the displacement condition of the underpinned beam 10 in real time. The displacement of the underpinned beam 10 generated by tensioning can be adjusted by the upper layer jacking system 1 and the lower layer jacking system 8 together.
Step seven: and (5) switching the jacking system. The loading needs to be carried out at the night window-free period of subway operation, a graded loading mode is adopted, the loading capacity of each grade ensures that the vertical displacement change of the underpinned beam (10) is not more than 0.2mm, and the transverse displacement difference is not more than 0.1 mm. After each stage of adjustment is completed, the bidirectional hydraulic jack group is locked, the manual follow-up mechanical safety self-locking jack group is locked after being closely attached to the bidirectional prestressed concrete box type underpinning beam structure 7, and next stage of loading adjustment can be performed after the bidirectional prestressed concrete box type underpinning beam structure 7 is stably deformed. And (3) loading step by step until the load is loaded to the jacking conversion load, locking the bidirectional hydraulic jack group of the lower jacking system 8, and manually following the mechanical safety self-locking jack group to be closely attached to the bidirectional prestressed concrete box type underpinning beam structure 7.
Step eight: the underpinned structural pile 6 is cut off. Pile cutting needs to be carried out at the empty window period at night of subway operation, and the underpinned structure pile foundation 6 is cut off one by one, and the underpinned structure pile foundation 6 main rib fracture one by one needs to be guaranteed during the cutting off, and the cutting off process needs to monitor the displacement of the underpinned beam 10 and the deformation value of the bidirectional prestressed concrete box type underpinned beam structure 7 in real time, and the next pile foundation of the underpinned structure pile foundation 6 can be cut off after the deformation is stable. The displacement of the underpinned beam 10 can be adjusted by the lower jacking system 8 and the upper jacking system 1.
Step nine: the bidirectional prestressed concrete box type underpinning beam structure 7 is fixedly connected with the underpinning pile structure 9. Locking the bidirectional hydraulic jack group in the lower jacking system 8, withdrawing the mechanical safety self-locking jack group, connecting the bidirectional prestressed concrete box type underpinning beam structure 7 and the underpinning pile structure 9 to reserve steel bars, pouring the horizontal limiting device 20, pouring the concrete of a post-pouring belt of the underpinning pile cap 16, and solidifying the bidirectional prestressed concrete box type underpinning beam structure 7 and the underpinning pile structure 9. During which the structural deformation is regulated by the upper jacking system 1.
Step ten: a pass-through structure 15 is constructed. The displacement of the underpinned beam 10 during this time is regulated by the upper jacking system 1.
Step eleven: the upper jacking system 1 is dismantled. And after all the constructions are finished and the displacement of the underpinned beam 10 and the structural deformation of the bidirectional prestressed concrete box type underpinned beam structure 7 are stable, the upper jacking system 1 is dismantled.
Compared with the traditional active underpinning structure, the combined jacking active underpinning structure of the large-span bidirectional prestressed concrete box-shaped section underpinning beam provided by the invention has the advantages that:
1. in the traditional active pile foundation underpinning, an underpinning structure generally adopts a reinforced concrete structure, and the spanning capability is limited. The bidirectional prestressed box-shaped section underpinning beam provided by the invention effectively improves the spanning capability of the underpinning structure by arranging the longitudinal prestress, and enlarges the application range of the underpinning structure. The method is more suitable for underpinning projects in terrain and ground object complex areas such as urban rail transit.
2. In the traditional active pile foundation underpinning, underpinning beams have cracks under the normal working condition. The underpinning beam with the bidirectional prestressed box-shaped section effectively controls cracks of the underpinning structure and increases the durability of the underpinning structure by arranging the bidirectional prestress. The friction force of the occlusal surface of the underpinning structure and the underpinned structure is increased by arranging the transverse prestress, and the safety of the underpinning structure is enhanced.
3. The traditional active pile foundation underpins generally lack construction horizontal displacement control. The underpinning beam with the bidirectional prestress box-shaped section provided by the invention forms an underpinning pile cap by connecting the underpinning piles, so that the integrity of the underpinning pile is enhanced, an upper sleeve and a lower sleeve which are horizontally limited are additionally arranged, the horizontal displacement of an underpinning structure during the underpinning and jacking process is effectively limited, and the construction safety is enhanced.
4. In the traditional active pile foundation underpinning, the initiative of deformation control only exists after the underpinning beam is implemented, and the initiative of the pile top after consolidation also disappears in the jacking conversion period. Namely, the construction method has no initiative in the construction stages of underpinning pile foundation construction, underpinning beam construction and pile beam consolidation, the construction process of a lower penetrating structure and the like. The bidirectional prestressed concrete box-section underpinning beam combination jacking underpinning system provided by the invention has initiative in each construction stage.
5. In the traditional active pile foundation underpinning, because the active adjusting device acts below the underpinning beam, the jack has large tonnage, high adjusting difficulty and poor adjusting precision. The active underpinning structure of the bidirectional prestressed concrete box-section underpinning beam combined jacking system provided by the invention has the advantages that the upper jacking system directly acts on the underpinned beam structure, the jacking tonnage is small, and the adjusting precision is high.
6. When the lower part of the traditional active pile foundation underpins is constructed through a penetrating structure, the underpinning system belongs to a simply supported system, and the construction risk is high. The active underpinning method of the bidirectional prestressed box-section underpinning beam combined jacking system provided by the invention has the advantages that before the construction of the lower traversing structure, the pile beam is solidified to form a hyperstatic system, so that the deformation resistance and disturbance resistance of the underpinning structure are improved, and the construction risk and construction influence of the traversing structure are reduced.
7. Traditional active pile underpinning is due to its limited deformation control. The crossing construction process usually requires that the crossed rail transit line takes measures of speed limitation, stop operation and the like. The active underpinning structure of the large-span bidirectional prestress box type combined jacking system provided by the invention has the advantages that due to the effectiveness and long-term property of deformation control, the whole traversing construction process is not limited and is not in continuous operation, and the feasibility of implementation of rail transit traversing engineering is effectively improved.
Fig. 7 to 10 and table 1 show data of monitoring results in the embodiment of the present invention, and under the complex condition that the maximum underpinning tonnage in the current field of rail transit in our country, i.e., a single underpinning beam 4600 tons, and the eccentric load reaches 65855kn.m, the present invention simultaneously acts on 390 jacks, and the jacking precision is controlled to be precise to the micron order. And finally, after construction, the accumulated vertical displacement of the track structure is controlled to be 0.9mm (allowable value is 3mm), the transverse displacement of the track structure is controlled to be 0.7mm (allowable value is 2mm), the vertical displacement of the pier is 1mm (allowable value is 3mm), the transverse displacement of the pier is 0.3mm (allowable value is 2mm), the displacement of the line steel rail is 0.4mm (allowable value is 3mm), and the differential settlement of the switch blade and the stock rail is 0.6mm (allowable value is 1 mm). According to the monitoring result, all monitoring deformation values are far smaller than the strict deformation standard of subway safe operation, and the deformation value of the whole underpinning construction process is accurately controlled. The underpinning of 30 pile foundations in 5 groups is successfully completed under the conditions of no stop of subway transportation and no speed limit, a construction precedent is created for passing through subway projects in the future without stop of subway transportation and no speed limit, the social benefit and the economic benefit are obvious, and the accuracy and the effectiveness of controlling the displacement of the underpinned body and the applicability in the field of underpinning of pile foundations of urban rail transit are powerfully proved.
TABLE 1
Therefore, the underpinning structure can be suitable for underpinning the pile foundation of the rail transit bridge, the adaptability of the underpinning structure is effectively improved through the large-span bidirectional prestressed box type underpinning beam, and the safety and the durability of the underpinning structure are improved. Through the coordination control of the bidirectional prestressed box type underpinning beam combined jacking system, the deformation of the underpinned structure 10 can be well controlled, the safety requirement of a rail transit operating line is met, and the pile foundation underpinning project is completed under the normal operation condition that rail transit is maintained without stopping and speed limitation.
It should be apparent that the foregoing description and illustrations are by way of example only and are not intended to limit the present disclosure, application or uses. While embodiments have been described in the embodiments and depicted in the drawings, the present invention is not limited to the particular examples illustrated by the drawings and described in the embodiments as the best mode presently contemplated for carrying out the teachings of the present invention, and the scope of the present invention will include any embodiments falling within the foregoing description and the appended claims.
Claims (10)
1. The utility model provides a combination jacking underpinning structure of two-way prestressed box type underpinning roof beam of large-span, include upper jacking system, by underpinning structure cushion cap, by underpinning structure pile foundation, two-way prestressed concrete box underpinning roof beam structure, lower floor's jacking system and by underpinning roof beam structure, its characterized in that:
the bidirectional prestressed box type underpinning beam structure adopts a bidirectional prestressed concrete structure system, is provided with a longitudinal prestressed system and a transverse prestressed system, and has a box-shaped section so as to be suitable for a large-span underpinning structure;
the bidirectional prestressed concrete box type underpinning beam structure is connected with the underpinned structure in a mode of coaction of a tongue-and-groove, interface glue and post-embedded bars;
the upper jacking system is arranged below the underpinned beam and comprises an upper jacking jack group, an upper jacking system supporting surface structure, an upper jacking system supporting column structure, an upper jacking system connecting anchor bolt and an upper jacking foundation structure, wherein the upper jacking jack group is arranged between the underpinned beam and the upper jacking system supporting surface structure, the upper jacking system supporting surface structure adopts a steel structure beam form, the upper jacking system supporting column structure is arranged below the upper jacking system supporting column structure, the column top of the upper jacking system supporting column structure is connected with the upper jacking system supporting surface structure through the anchor bolt or a welding form, and the column bottom of the upper jacking system supporting column structure is connected with the underpinned bearing platform through the upper jacking system connecting anchor bolt and the upper jacking foundation structure.
2. The combined jacking and underpinning structure of the large-span bidirectional prestressed box type underpinning beam as claimed in claim 1, wherein: the longitudinal prestressed system and the transverse prestressed system adopt prestressed stranded wires or prestressed thick steel bars, the longitudinal prestressed system is uniformly arranged in a web plate of the bidirectional prestressed concrete box type underpinning beam structure, and the transverse prestressed system is transversely arranged on two sides and the bottom of a bearing platform of the underpinned structure.
3. The combined jacking and underpinning structure of the large-span bidirectional prestressed box type underpinning beam as claimed in claim 1, wherein: the upper jacking system connecting anchor bolt is implanted into the underpinned bearing platform in a post-bar planting mode.
4. The combined jacking and underpinning structure of the large-span bidirectional prestressed box type underpinning beam as claimed in claim 1, wherein: the horizontal limiting device is of an upper sleeve structure and a lower sleeve structure, the upper sleeve structure and the lower sleeve structure comprise an upper sleeve and a lower sleeve which are small in size at the top and big at the bottom, a gap is reserved between the upper sleeve and the lower sleeve and used for eliminating secondary internal force, and self-compacting concrete is poured and filled through a reserved hole of the bidirectional prestress box type underpinning beam structure after jacking is completed.
5. The combined jacking and underpinning structure of the large-span bidirectional prestressed box type underpinning beam as claimed in claim 1, wherein: the underpinned structure bearing platform is connected with the bidirectional prestressed concrete box type underpinning beam structure through the combined action of the tongue-and-groove, the interface glue and the post-embedded steel bar.
6. The combined jacking and underpinning structure of the large-span bidirectional prestressed box type underpinning beam as claimed in claim 1, wherein: the lower-layer jacking system comprises a underpinning pile structure, a lower-layer bidirectional hydraulic jack group, a mechanical safety self-locking jack group and a horizontal limiting device, wherein the lower-layer bidirectional hydraulic jack group and the mechanical safety self-locking jack group are located between the underpinning pile foundation and the bidirectional prestressed concrete box type underpinning beam structure, the bidirectional hydraulic jack group is used for adjusting the vertical displacement of the bidirectional prestressed concrete box type underpinning beam structure 7, and the mechanical safety self-locking jack group plays a safety protection role in the working process of the bidirectional hydraulic jack group. The adjustment amount of the bidirectional hydraulic jack group adopts the principle of force and displacement double control, a graded loading distribution adjustment mode is adopted, each grade of loading amount ensures that the vertical displacement change of the underpinned beam is not more than 0.2mm, the transverse displacement difference is not more than 0.1mm, after each grade of adjustment is finished, the bidirectional hydraulic jack group is locked, the manual follow-up mechanical self-locking jack group is locked after being closely attached to the bidirectional prestressed concrete box type underpinned beam structure 7, and the next grade of loading adjustment can be carried out after the deformation is stable.
7. The combined jacking and underpinning structure of the large-span bidirectional prestressed box type underpinning beam as claimed in claim 1, wherein: the central position of the pile top of each underpinning pile structure is correspondingly provided with a set of horizontal limiting device, the horizontal limiting device adopts the situation of an upper sleeve and a lower sleeve, the upper sleeve is pre-embedded at the bottom of the bidirectional prestressed box type underpinning beam structure and is smaller than the lower sleeve, and the lower sleeve is pre-embedded at the central position of the underpinning pile structure, so that the upper sleeve and the lower sleeve are vertically overlapped and nested but mutually leave a gap to release the horizontal deformation of the bidirectional prestressed concrete box type underpinning beam structure caused by the prestress and shrinkage creep effect and avoid causing larger secondary internal force.
8. The combined jacking and underpinning structure of the large-span bidirectional prestressed box type underpinning beam as claimed in claim 1, wherein: the underpinning pile structure is provided with an underpinning pile cap, a post-cast strip and a horizontal limiting device are arranged between the underpinning pile cap and the bidirectional prestressed concrete box type underpinning beam structure, the underpinning pile cap upwards reserves reinforcing steel bars and extends into the post-cast strip, and the bidirectional prestressed concrete box type underpinning beam structure downwards reserves reinforcing steel bars and extends into the post-cast strip.
9. A combined jacking and underpinning method for a large-span bidirectional prestressed box type underpinning beam is characterized by comprising the following steps:
the method comprises the following steps: the construction upper layer jacking system comprises a construction upper layer jacking system supporting surface structure, an upper layer jacking system supporting column structure, an upper layer jacking system connecting anchor bolt and an upper layer jacking foundation structure, and an upper layer jacking jack group is installed. The construction needs to plant a layer jacking system connecting anchor bolt after a bearing platform of a underpinned structure, assemble an upper layer jacking system supporting column structure on the top of the bearing platform of the underpinned structure, hoist the upper layer jacking system supporting surface structure and connect with the layer jacking system supporting column structure by using bolts, arrange each jack group of the upper layer jacking system on the upper layer jacking system supporting surface structure, and tightly attach to the underpinned beam by adjusting the height of the jack group of the upper layer jacking system;
step two: constructing a underpinning pile structure, and reserving connecting steel bars for the bidirectional prestressed box type underpinning beam structure in the underpinning pile structure;
step three: constructing and underpinning a foundation pit;
step four: constructing a underpinning pile cap, wherein a lower layer jacking system is arranged on the top surface of the underpinning pile cap and comprises an underpinning pile structure, a bidirectional hydraulic jack group, a mechanical safety self-locking jack group and a horizontal limiting device, a lower sleeve of the horizontal limiting device is pre-buried in the center of the underpinning pile cap, the bidirectional hydraulic jack and the mechanical safety self-locking jack are uniformly arranged at corresponding positions of the pile top, and connecting reinforcing steel bars with a bidirectional prestressed box type underpinning beam structure are reserved along the peripheral edge of the underpinning pile cap;
step five: pouring a bidirectional prestressed box type underpinning beam structure;
step six: a transverse prestress system and a longitudinal two-way prestress system of a two-way prestress box type underpinning beam structure are tensioned, the tensioning adopts the sequence of batch and symmetrical tensioning, and the displacement condition of the underpinned beam is monitored in real time;
step seven: switching a jacking system;
step eight: cutting off the underpinned structure pile foundation;
step nine: the bidirectional prestressed concrete box type underpinning beam structure is fixedly connected with the underpinning pile structure;
step ten: constructing a crossing structure;
step eleven: and (5) dismantling the upper jacking system.
10. The combined jacking and underpinning method of the large-span bidirectional prestressed box type underpinning beam as claimed in claim 9, characterized in that: and seventhly, adopting a graded loading mode, ensuring that the vertical displacement change of the underpinned beam is not more than 0.2mm and the transverse displacement difference is not more than 0.1mm by each grade of loading, locking the bidirectional hydraulic jack group after each grade of adjustment is finished, locking the manual follow-up mechanical safety self-locking jack group after the manual follow-up mechanical safety self-locking jack group is closely attached to the bidirectional prestressed box type underpinned beam, and performing next grade of loading adjustment after the structure of the bidirectional prestressed box type underpinned beam is deformed stably.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112942147A (en) * | 2021-02-07 | 2021-06-11 | 上海市政工程设计研究总院（集团）有限公司 | Bridge pile active underpinning method |
| CN114150674A (en) * | 2021-12-09 | 2022-03-08 | 中冶建筑研究总院（深圳）有限公司 | Foundation pit upright post underpinning method |
-
2020
- 2020-06-08 CN CN202010512107.XA patent/CN111636496A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112942147A (en) * | 2021-02-07 | 2021-06-11 | 上海市政工程设计研究总院（集团）有限公司 | Bridge pile active underpinning method |
| CN114150674A (en) * | 2021-12-09 | 2022-03-08 | 中冶建筑研究总院（深圳）有限公司 | Foundation pit upright post underpinning method |
| CN114150674B (en) * | 2021-12-09 | 2023-10-03 | 中冶建筑研究总院（深圳）有限公司 | Foundation pit upright post underpinning method |
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