A pile foundation underpinning structure and underpinning method for shield tunnels passing under buildings

Abstract

This invention discloses a pile foundation replacement structure for buildings and structures passing under a shield tunnel. It is used to replace the pile foundations of existing buildings and structures that conflict with the shield tunnel. The pile foundations include both existing pile foundations that conflict with the shield tunnel and those that do not. The pile foundation replacement structure includes newly constructed replacement pile foundations, a newly constructed cantilever replacement beam cap, a newly constructed cantilever replacement beam, and a jacking structure. The lower end of the newly constructed cantilever replacement beam cap is fixedly connected to several newly constructed replacement pile foundations, which are located on the same side of the shield tunnel. The newly constructed cantilever replacement beam is fixedly installed on the newly constructed cantilever replacement beam cap, and the jacking structure is installed on the newly constructed cantilever replacement beam, with its upper end abutting against a supporting structure. The existing buildings and structures are located on the upper side of the supporting structure. This structure, using a cantilever replacement beam, minimizes the length of the replacement beam, reduces the number of replacement construction steps, and results in a short construction period, low construction cost, and low difficulty.

Description

Technical Field

[0001] This invention relates to the field of pile foundation underpinning technology, and in particular to a pile foundation underpinning structure and method for shield tunnels passing under buildings. Background Technology

[0002] With the construction of subways in major cities across the country, construction techniques have become increasingly mature. Among these, shield tunneling is widely used in urban subway construction. During the planning of rail transit projects, conflicts inevitably arise between the shield tunnel sections and the pile foundations of existing structures. To minimize the impact on existing structures, pile replacement is typically used to protect the pile foundations. The core technology of pile replacement is the conversion of loads between the new and original piles, requiring that the deformation of the replacement structure and the new piles be limited within the allowable range of the superstructure during the conversion process.

[0003] In response to this, the traditional method for replacing the pile foundations of shield tunnels is to use a "portal-type replacement" method, which involves replacing piles and beams to support the existing structure's pile foundations. This involves installing various types of piles at the bottom or sides of the foundation structure, and then placing beams or pile cap systems on the piles, or directly anchoring them to the foundation, to support the structure being replaced. This pile foundation replacement can be done actively or passively. This method requires the placement of replacement piles at specific locations and extensive excavation for the replacement piles and beams, resulting in a long construction period, high costs, and high difficulty. For bridge abutment locations, the limited ground space makes it difficult to implement pile foundation replacement.

[0004] Pile foundation replacement is a complex system engineering project involving the interaction and influence of tunnels, soil, pile foundations, and superstructures, and is fraught with risks. The essence of pile foundation replacement is to disrupt the equilibrium between the old pile foundation and the soil. Through active and passive replacement methods, load transfer is achieved, allowing the replacement beam, new pile foundation, soil, and existing bridge to re-achieve equilibrium through interaction. Based on different pile foundation replacement mechanisms, it can be divided into two technical types: passive replacement and active replacement. Active replacement requires applying loads to the new piles and the replacement structure to eliminate structural deformation. Active replacement is suitable when structural deformation requirements are strict and the replacement load is large. Passive replacement relies primarily on the rigidity of the replacement structure. The replacement piles are removed after the replacement structure is completed. This technique is widely used in tunnel construction.

[0005] When a shield tunnel passes under the pile foundation of an existing building, and the building cannot be demolished but needs to be maintained, the common solution is pile foundation underpinning. The load from the superstructure borne by these pile foundations is transferred to the pile foundations outside the tunnel construction's influence area through a newly constructed underpinning structure.

[0006] Problems with this solution:

[0007] (1) The layout of “portal type underpinning” pile foundation is constrained by factors such as the construction site and surrounding environment, which may make it difficult to avoid setting it, resulting in high construction difficulty, many uncontrollable factors, and high risk.

[0008] (2) As the inner diameter of the shield tunnel increases, the new pile foundations need to be located on both sides of the shield tunnel, the net distance between the new pile foundations increases, the span of the replacement beam is too large, the cross-sectional size of the replacement structure is too large, the replacement construction process is complicated, the construction period is long, and the replacement cost is high.

[0009] (3) The excavation pit for pile foundation replacement and the large area occupied by the ground, which involves influential building structures, pipelines, and traffic connections, need to be dealt with.

[0010] The problems encountered by subway (intercity, etc.) shield tunnels passing under buildings (such as buildings, bridges, box culverts, etc.) are becoming more and more frequent. Common problems include limited construction space, difficulty in pile foundation removal, difficulty in coordinating ground land borrowing, and coordination of pipeline and traffic diversion, which make it impossible to carry out pile foundation replacement in the usual pile foundation replacement structural form. Summary of the Invention

[0011] The purpose of this invention is to overcome the shortcomings of the prior art and provide a pile foundation replacement structure and method for shield tunnels passing under buildings.

[0012] This invention is achieved through the following technical solution: a pile foundation replacement structure for buildings and structures passing under a shield tunnel, used to replace the pile foundations of existing buildings and structures that conflict with the shield tunnel. The existing buildings and structures have a supporting structure underneath them, which is fixed to the pile foundations. The pile foundations include existing pile foundations that conflict with the shield tunnel and existing pile foundations that do not conflict. The pile foundation replacement structure includes newly constructed replacement pile foundations, a newly constructed cantilever replacement beam platform, a newly constructed cantilever replacement beam, and a jacking structure. The lower end of the newly constructed cantilever replacement beam platform is fixedly connected to several newly constructed replacement pile foundations, which are located on the same side of the shield tunnel. The newly constructed cantilever replacement beam is fixedly installed on the platform, and the jacking structure is installed on the newly constructed cantilever replacement beam, with its upper end abutting the supporting structure. The existing buildings and structures are located on the upper side of the supporting structure.

[0013] This structure employs a cantilevered support beam design. Cantilevered support beams are installed and connected to the existing building foundation, and newly constructed support piles are connected and fixed to these beams to support the structure being supported. The jacking structure can apply active jacking force in stages, achieving a "transfer" of the load on the bridge superstructure. This support structure is simple in design and has good stability. It eliminates the need for fixed piles on both sides of the shield tunnel, allowing for pile placement based on site constraints, making it suitable for complex environments. The pile support is achieved through the cantilevered support beam connection, resulting in a clear structural stress distribution. The structure can be supported without the need for large-span support beams, leading to a short construction period, low construction cost, and low difficulty.

[0014] The lifting structure includes jacks and connecting supports. The lower end of the connecting supports is fixed to the upper side of the newly constructed cantilevered support beam, and its upper end abuts against the supporting structure. The jacks are located between the connecting supports, with their lower ends positioned on the upper side of the newly constructed cantilevered support beam and their upper ends abutting against the supporting structure. Several jacks are provided, and the centroid of the combined jacks coincides with the centroid of the lifting structure. This coincidence of the combined centroid of the jacks and the centroid of the lifting structure ensures the stability of the bridge's center of gravity.

[0015] The jack is connected to the upper side of the newly built cantilever support beam and the supporting structure by rebar anchoring; the connecting pier is connected to the upper side of the newly built cantilever support beam and the supporting structure by rebar anchoring or post-anchoring.

[0016] After the shield tunneling pile has passed and the pile settlement has been monitored and stabilized, the gaps around the jacks are backfilled with micro-expansion concrete.

[0017] The newly constructed cantilever support beam shall be a concrete structural beam, a steel composite structural beam, an ultra-high performance structural beam, or a prestressed concrete structural beam.

[0018] One end of the newly constructed cantilevered support beam is fixed to the newly constructed support pile foundation, and the other end is cantilevered. The lifting structure is installed at the cantilever.

[0019] The distance between the newly constructed replacement pile foundation and the planned shield tunnel is ≥1m.

[0020] A repair connection structure is provided between the connecting pier and the supporting structure; the repair connection structure is a steel plate bonding connection structure or a rebar anchoring connection structure.

[0021] The supporting structure is a bridge cap beam, a building's abutment and pile foundation, a telecommunications tower's abutment and pile foundation, or a box culvert foundation structure; the newly built underpinning pile foundation is selected from cast-in-place concrete piles or steel pipe piles.

[0022] A method for replacing the pile foundation underpinning structure of a shield tunnel passing beneath a building or structure includes the following steps:

[0023] Step 1: Enclose the site, provide temporary support for existing buildings and structures, and construct new replacement pile foundations under the existing site conditions;

[0024] Step 2: Under the existing site conditions, construct the retaining structure, new underpinning pile foundation, new cantilever underpinning beam cap, and new cantilever underpinning beam; repair and connect the joints of the supporting structure, and cast it into a square whole; set up a jacking structure between the new cantilever underpinning beam and the supporting structure, the jacking structure including jacks and steel pads;

[0025] Step 3: After the pile foundation replacement structure reaches the design strength, the replacement and jacking structure work is carried out; active jacking force is applied in stages, and the changes in vertical displacement and cracks of the existing building structure are strictly monitored during the loading process; the upper load of the existing building structure is transferred to the newly built cantilever replacement beam through jacks and connecting supports.

[0026] Step 4: After the shield tunnel has passed the pile excavation and the structural test data of the existing buildings and structures have stabilized, the connecting supports are poured, and the gaps around the jacks are backfilled with micro-expansion concrete.

[0027] Step 5: Remove the temporary supports and backfill the foundation pit.

[0028] Compared with existing technologies, the advantages of this invention are as follows: This structure effectively solves the problem of existing buildings encroaching on shield tunnels, and also avoids problems such as bridge stability and safety caused by shield tunnel construction in the later stages. It is suitable for complex construction environments. The replacement of bridge abutments effectively reduces the length (span) of the replacement beam, solves the problem of limited site space, and reduces construction difficulty. The replacement structure is simple, practical, and has good stability. It does not require fixed pile foundations on both sides of the tunnel. Pile foundations can be arranged according to site limitations, making it suitable for complex environments. It overcomes the problems of large excavation pits, high risks, and high construction difficulty of traditional pile foundation replacement. The pile foundation replacement is connected by cantilevered replacement beams, and the structural stress is clear. It can replace buildings without the need for replacement beams with large spans, resulting in short construction period, low construction cost, and low difficulty. Attached Figure Description

[0029] Figure 1 This is a top view of an embodiment of the present invention;

[0030] Figure 2 for Figure 1 Sectional view along the middle AA direction;

[0031] Figure 3 This is a perspective view of an embodiment of the present invention;

[0032] Figure 4 This is a perspective view from another direction of an embodiment of the present invention.

[0033] The meanings of the labels in the attached diagram are as follows: 1. Pile foundation of existing buildings and structures that conflict with the shield tunnel; 2. Pile foundation of existing buildings and structures that do not conflict; 3. Supporting structure; 4. Shield tunnel; 5. Lifting structure; 6. Newly built cantilevered replacement beam; 7. First replacement pile foundation; 8. Second replacement pile foundation; 9. Newly built cantilevered replacement beam cap; 10. Existing buildings and structures; 11. Repair and connection structure; 12. Underground pipelines. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0035] Example

[0036] See Figures 1 to 4 This is a pile foundation replacement structure for a shield tunnel passing under a building, used to replace the existing building pile foundation 1 that conflicts with the shield tunnel 4. The existing building 10 is supported and fixed by a support structure 3 on its lower side. The support structure 3 is fixed to the building pile foundation below. The building pile foundation includes the existing building pile foundation 1 that conflicts with the shield tunnel 4 and the existing building pile foundation 2 that does not conflict. The pile foundation replacement structure includes a newly built replacement pile foundation, a newly built cantilever replacement beam platform 9, a newly built cantilever replacement beam 6, and a jacking structure 5. The lower end of the newly built cantilever replacement beam platform 9 is fixedly connected to several newly built replacement pile foundations, which are located on the same side of the shield tunnel 4. The newly built cantilever replacement beam 6 is fixedly installed on the newly built cantilever replacement beam platform 9, and the jacking structure 5 is installed on the newly built cantilever replacement beam 6, with its upper end abutting the support structure 3. The existing building 10 is set on the upper side of the support structure 3. In this embodiment, two new replacement pile foundations are provided, namely the first replacement pile foundation 7 and the second replacement pile foundation 8.

[0037] This structure employs a cantilevered support beam structure. Cantilevered support beams are installed and connected to the existing foundation structure of building 10. Newly constructed support piles are connected and fixed to the cantilevered support beams to support the supported building. The jacking structure 5 can apply active jacking force in stages, achieving the "transfer" of loads on the bridge superstructure. This support structure is simple in structure and has good stability. It eliminates the need for fixed piles on both sides of the shield tunnel 4, allowing for pile placement based on site constraints, making it suitable for complex environments. The pile foundation support is achieved through the cantilevered support beam connection, ensuring clear structural stress. The support beams do not require large spans, resulting in short construction periods, low construction costs, and low difficulty. Newly constructed support piles and cantilevered support beams 6 can be arranged according to site constraints such as underground pipelines 12, traffic diversion, and clearance under buildings.

[0038] The lifting structure 5 includes jacks and connecting piers. The lower end of the connecting piers is fixed to the upper side of the newly constructed cantilevered replacement beam 6, and its upper end abuts against the supporting structure 3. The jacks are located between the connecting piers, with their lower ends positioned on the upper side of the newly constructed cantilevered replacement beam 6 and their upper ends abutting against the supporting structure 3. Several jacks are provided, and the combined centroid of these jacks coincides with the centroid of the lifting structure 5. This coincidence of the combined centroid of the jacks and the centroid of the lifting structure 5 ensures the stability of the bridge's center of gravity. Depending on the pile foundation replacement mechanism, active or passive replacement can be selected. The connecting piers can be made of cast-in-place concrete.

[0039] The jacks are connected to the upper side of the newly constructed cantilevered replacement beam 6 and the supporting structure 3 via rebar anchoring; the connecting piers are also connected to the upper side of the newly constructed cantilevered replacement beam 6 and the supporting structure 3 via rebar anchoring or post-anchoring. Rebar anchoring, also known as rebar planting, is a connection technology in seismic reinforcement engineering of building structures that utilizes the locking force of structural adhesive for post-anchoring of steel bars. It is the best choice for structural rebar anchoring reinforcement and heavy load fastening applications.

[0040] After the shield tunneling piles have passed and the pile settlement has stabilized, the gaps around the jacks are backfilled with micro-expansion concrete. When the micro-expansion concrete structure is not under load, its physical and mechanical state is as follows: due to the presence of a certain amount of steel reinforcement in the concrete, there is an inevitable constraint effect of the structural boundary in the project, which makes all kinds of deformations in the excavation state. Concrete with admixtures is equivalent to shrinkage-compensating concrete.

[0041] The newly constructed cantilevered replacement beam 6 can be a concrete structural beam, a steel composite structural beam, an ultra-high performance structural beam, or a prestressed concrete structural beam. Depending on the stress conditions, the newly constructed cantilevered replacement beam 6 can be constructed using either a concrete structural beam, a steel composite structural beam, an ultra-high performance structural beam, or a prestressed concrete structural beam, and can be configured in different shapes. The direction and length of the newly constructed cantilevered replacement beam 6 can be adjusted according to site constraints.

[0042] One end of the newly constructed cantilevered support beam 6 is fixed to the newly constructed support pile foundation, and the other end is cantilevered. The lifting structure 5 is installed at the cantilever. The cantilever direction and length of the newly constructed cantilevered support beam 6 can be adjusted according to the actual situation.

[0043] The distance between the newly constructed replacement pile foundation and the planned shield tunnel 4 is ≥1m.

[0044] A repair connection structure 11 is provided between the connecting pier and the supporting structure 3; the repair connection structure 11 is a steel plate bonding connection structure or a rebar anchoring connection structure. The repair connection structure 11 is a rebar anchoring connection or a steel plate bonding connection in this field, and its process is existing technology, so there is no need to elaborate on it.

[0045] Supporting structure 3 includes bridge cap beams, building foundations and pile foundations, telecommunications tower foundations and pile foundations, or box culvert foundation structures; newly constructed replacement piles will use cast-in-place concrete piles or steel pipe piles. The number of newly constructed replacement piles can be determined based on stress calculations.

[0046] A method for replacing the pile foundation underpinning structure of a shield tunnel passing beneath a building or structure includes the following steps:

[0047] Step 1: Enclose the site, provide temporary support for the existing buildings and structures 10, and construct new replacement pile foundations under the existing site conditions;

[0048] Step 2: Under the existing site conditions, construct the retaining structure, new underpinning pile foundation, new cantilever underpinning beam cap 9, and new cantilever underpinning beam 6; repair and connect the connection of the supporting structure 3, and cast it into a square whole; set up a jacking structure between the new cantilever underpinning beam 6 and the supporting structure 3, the jacking structure including jacks and steel pads;

[0049] Step 3: After the pile foundation replacement structure reaches the design strength, the replacement and jacking structure work is carried out; active jacking force is applied in stages, and the changes in vertical displacement and cracks of the existing building structure are strictly monitored during the loading process; the upper load of the existing building structure 10 is transferred to the newly built cantilever replacement beam 6 through jacks and connecting supports.

[0050] Step 4: After the shield tunnel 4 grinding piles are excavated and the structural test data of the existing building 10 is stable, the connecting support piers are poured and the gaps around the jacks are backfilled with micro-expansion concrete.

[0051] Step 5: Remove the temporary supports and backfill the foundation pit.

[0052] In this embodiment, the implementation plan is as follows: When the shield tunnel 4 conflicts with the foundation structure of the existing building 10, a traditional pile foundation replacement method is adopted, namely, a "portal replacement" of replacement piles and replacement beams. The pile foundation layout must maintain a pile foundation height of ≥1m with the planned shield tunnel 4. The layout of the replacement beam is combined with the adjustment of the newly built pile foundation. The overall replacement structure after the layout still conflicts with the underground pipeline 12 (which cannot be temporarily relocated; in this embodiment, the underground pipeline 12 is located below the supporting structure 3 and above the newly built cantilever replacement beam 6). The replacement beam has a long span and occupies a large area of ​​the site, especially for the location of the bridge abutment, where the ground clearance is small, affecting traffic diversion. The traditional pile foundation replacement scheme is difficult to meet. A cantilever replacement beam structure is arranged near the conflicting pile foundation for replacement. The newly built cantilever replacement beam 6 is connected to the supporting structure 3 of the existing building 10. Newly built pile foundations are set at the bottom of the newly built cantilever replacement beam 6, and different construction methods can be selected for the pile foundations. The arrangement of the newly constructed cantilever replacement beam 6 and the newly constructed pile foundations is flexibly adjusted based on the surrounding environment (underground pipelines 12, traffic diversion, etc.) and the safety clearance requirements of the planned shield tunnel 4. For bridge abutment locations with low ground clearance and idle working space under the bridge due to construction equipment, this cantilever beam replacement method can also be referenced. Jacks are placed between the newly constructed cantilever replacement beam 6 and the existing building structure 10. Depending on the pile foundation replacement mechanism, active or passive replacement can be selected. This transfers the load borne by the original pile foundation to the newly constructed cantilever replacement beam 6 and then to the replacement pile foundation. Finally, the shield tunnel 4 is excavated (pile grinding) through. The overall structure of the newly constructed cantilever replacement beam 6 can be flexibly arranged, and the cantilever direction can be adjusted according to the actual situation, reducing the span of the replacement beam and offering high applicability.

[0053] The overlapping parts of each component of this support structure should be poured with the highest grade of concrete among all components.

[0054] This invention uses a support structure to support the building structure, and sets up a cantilevered support beam, which can minimize the length of the support beam and reduce the support construction process, overcoming the problems of large excavation, high risk and high construction difficulty of traditional pile foundation support pits.

[0055] The above detailed description is a specific description of feasible embodiments of the present invention. These embodiments are not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included in the patent scope of this case.

Claims

1. A pile foundation underpinning structure for a shield tunnel underpassing a building, for underpinning an existing building pile foundation in conflict with a shield tunnel, the lower side of the existing building being a support structure fixedly supported thereby, the support structure being fixedly arranged on the building pile foundation below, the building pile foundation comprising an existing building pile foundation in conflict with the shield tunnel, and an existing building pile foundation not in conflict, characterized in that: The pile foundation underpinning structure comprises a newly-built underpinning pile foundation, a newly-built cantilever underpinning beam pile cap, a newly-built cantilever underpinning beam and a jacking structure; the lower end of the newly-built cantilever underpinning beam pile cap is fixedly connected with a plurality of newly-built underpinning pile foundations, and the plurality of newly-built underpinning pile foundations are located on the same side of the shield tunnel; the newly-built cantilever underpinning beam is fixedly installed on the newly-built cantilever underpinning beam pile cap, the jacking structure is installed on the newly-built cantilever underpinning beam, the upper end of the jacking structure bears against a supporting structure, and the existing building structure is arranged on the upper side of the supporting structure; the jacking structure comprises a jack and a connecting buttress, the lower end of the connecting buttress is fixed to the upper side of the newly-built cantilever underpinning beam, and the upper end of the connecting buttress bears against the supporting structure; the jack is located between the connecting buttresses, the lower end of the jack is arranged on the upper side of the newly-built cantilever underpinning beam, and the upper end of the jack bears against the supporting structure; the jack is provided with a plurality of jacks, the combined center of the plurality of jacks coincides with the center of the jacking structure; after the shield tunneling pile passes through and the pile foundation settlement is stable, the gaps around the jack are backfilled with micro-expansive concrete; one end of the newly-built cantilever underpinning beam is fixed on the newly-built underpinning pile foundation, the other end of the newly-built cantilever underpinning beam is cantilevered, the jacking structure is installed at the cantilevered end, and the cantilevered direction and length of the newly-built cantilever underpinning beam can be adjusted according to actual conditions. ​ 2. The pile underpinning structure for shield tunneling under a building according to claim 1, wherein: The jack is connected with the upper side of the newly-built cantilever underpinning beam and the supporting structure through a planted bar respectively; the connecting buttress is connected with the upper side of the newly-built cantilever underpinning beam and the supporting structure through a planted bar or a post-anchoring connection.

3. The pile underpinning structure for shield tunneling under a building according to claim 1, wherein: The newly-built cantilever underpinning beam is selected from a concrete structure beam, a profile steel composite structure beam, an ultra-high performance structure beam or a prestressed concrete structure beam.

4. The pile underpinning structure for shield tunneling under a building according to claim 1, wherein: The distance between the newly-built underpinning pile foundation and the planned shield tunnel is greater than or equal to 1 m.

5. The pile underpinning structure for shield tunneling under a building according to claim 1, wherein: A repairing connection structure is arranged between the connecting buttress and the supporting structure; the repairing connection structure is a steel plate bonding structure or a planted bar connection structure.

6. The pile underpinning structure for shield tunneling under a building according to claim 1, wherein: The supporting structure is a bridge bent cap, a pile foundation of a house, a pile foundation of a telecom tower or a foundation structure of a box culvert; the newly-built underpinning pile foundation is selected from a concrete bored pile or a steel pipe pile.

7. A method for underpinning a pile foundation of a building structure based on the shield tunneling method according to claim 1, characterized by, The method comprises the following steps: Step 1: site enclosure, temporary support of the existing building structure, construction of the newly-built underpinning pile foundation under the existing site conditions; Step 2: construction of the enclosure structure, the newly-built underpinning pile foundation, the newly-built cantilever underpinning beam pile cap, the newly-built cantilever underpinning beam under the existing site conditions, repairing connection of the connecting part of the supporting structure, pouring into a square whole, arrangement of the jacking structure between the newly-built cantilever underpinning beam and the supporting structure, and the jacking structure comprising a jack and a steel pad; Step 3: after the pile foundation underpinning structure reaches the design strength, the underpinning jacking structure is operated; the vertical displacement and crack change of the existing building structure are strictly monitored during the process of applying the active jacking force in stages; the upper load of the existing building structure is transmitted to the newly-built cantilever underpinning beam through the jack and the connecting buttress; Step 4: after the shield tunneling pile passes through, the connecting buttress is poured after the detection data of the existing building structure is stable, and the gaps around the jack are backfilled with micro-expansive concrete; Step 5: removal of the temporary support and backfilling of the foundation pit.

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