CN111395347A - Method for controlling upward floating of existing tunnel striding on foundation pit by adopting prestressed uplift pile - Google Patents
Method for controlling upward floating of existing tunnel striding on foundation pit by adopting prestressed uplift pile Download PDFInfo
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- CN111395347A CN111395347A CN202010106529.7A CN202010106529A CN111395347A CN 111395347 A CN111395347 A CN 111395347A CN 202010106529 A CN202010106529 A CN 202010106529A CN 111395347 A CN111395347 A CN 111395347A
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/02—Foundation pits
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/02—Foundation pits
- E02D17/04—Bordering surfacing or stiffening the sides of foundation pits
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D31/00—Protective arrangements for foundations or foundation structures; Ground foundation measures for protecting the soil or the subsoil water, e.g. preventing or counteracting oil pollution
- E02D31/10—Protective arrangements for foundations or foundation structures; Ground foundation measures for protecting the soil or the subsoil water, e.g. preventing or counteracting oil pollution against soil pressure or hydraulic pressure
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/58—Prestressed concrete piles
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Abstract
The invention relates to the technical field of urban underground engineering construction, and discloses a floating control method for an existing tunnel striding over a foundation pit by adopting a prestressed uplift pile, wherein the floating control method comprises the following construction steps: a, arranging a monitoring system (13) in the tunnel (20); b, constructing a foundation pit enclosure structure and a dewatering well; c, constructing an uplift pile (7); d, excavating the foundation pit to a specified elevation in a layered and sectional manner or in a vertical shaft manner; e, constructing an uplift pile buffer layer (18) and a PVC sleeve for sleeving uplift pile reinforcing steel bars (16), wherein the buffer layer is formed by foamed plastic or rubber; f, constructing a reinforced concrete anti-floating plate (11); g, tensioning the uplift pile (7) in a grading manner; h, locking the uplift pile (7) according to the tunnel deformation monitoring value; and i, carrying out next excavation and subsection construction of the main body structure. The uplift pile pre-stressed tensioning device can reduce the floating deformation of the tunnel through the pre-stressed tensioning of the uplift piles arranged on the two sides of the tunnel.
Description
Technical Field
The invention relates to the technical field of urban underground engineering construction, in particular to a floating control method for an existing tunnel striding on a foundation pit by adopting a prestressed uplift pile.
Background
With the development of subways and the full utilization of underground spaces, construction of some underground projects above a subway tunnel is inevitably needed, but floating deformation of an operation tunnel is generated due to upper unloading when the construction of the underground projects above the tunnel is completed, so that the safety of the tunnel structure is endangered.
14 domestic foundation pit engineering examples are collected in a text of 'actual measurement and analysis of influence of foundation pit excavation on an existing shield tunnel below' published by 'geotechnical' in 2013, the actual measurement data is statistically analyzed, and the result shows that 64% of tunnel floating deformation values exceed an alarm value by 10mm, which indicates that the deformation of a lower lying shield tunnel caused by unloading of foundation pit excavation cannot be ignored.
Liu Tuo Qiang, Dong Tianjun, Zhang Longyun, equal to 2019, in the application research of the uplift pile combined anti-floating plate in the control of the uplift of the horizontal subway tunnel under the foundation pit, which is published by Guangdong building materials, the text introduces that the uplift pile combined anti-floating plate forms a whole to inhibit the vertical uplift of the tunnel. However, the anti-floating plate can be poured only after the foundation pit needs to be excavated to the bottom, so that the tunnel generates certain floating deformation before the anti-floating plate is poured. The anti-floating plate is rigidly connected with the anti-pulling pile, and the anti-pulling pile can exert the stress action only by generating larger upward pulling deformation. Therefore, after the anti-floating plate is poured, the floating deformation amount of the tunnel before pouring cannot be reduced, and the limiting effect of the anti-floating pile and the anti-floating plate system can be exerted only by further increasing the deformation of the tunnel to a certain degree, so that the deformation of the tunnel exceeds a control value, and the anti-floating plate and the anti-floating pile are still stressed less and cannot fully exert the effect.
Therefore, a new control method for floating over the existing tunnel on the foundation pit needs to be designed to overcome or alleviate the above-mentioned defects of the prior art.
Disclosure of Invention
The invention aims to solve the technical problem of providing a floating control method for an existing tunnel striding over a foundation pit by adopting a prestressed uplift pile.
In order to achieve the purpose, the invention provides a floating control method for an existing tunnel spanned on a foundation pit by adopting a prestressed uplift pile, which comprises the following construction steps: a, arranging a monitoring system in a tunnel; b, constructing a foundation pit enclosure structure and a dewatering well; c, constructing uplift piles; d, excavating the foundation pit to a specified elevation in a layered and sectional manner or in a vertical shaft manner; e, constructing a buffer layer of the uplift pile and a PVC sleeve for surrounding and sleeving the steel bars of the uplift pile, wherein the buffer layer is formed by foamed plastic or rubber; f, constructing a reinforced concrete anti-floating plate; g, tensioning the uplift pile in a grading manner; h, locking the uplift pile according to the tunnel deformation monitoring value; and i, carrying out next excavation and constructing the main structure in sections.
Preferably, in step c, the minimum distance between the uplift pile and the tunnel is not less than 1.5m, the pile bottom of the uplift pile is located at a position which is one time of the tunnel diameter from the bottom of the tunnel, the uplift force of the uplift pile is not less than 1.5 times of the upper soil covering weight, and the uplift pile construction is performed by adopting a full-casing rotary drilling machine.
Preferably, in the step d, the excavation of the foundation pit adopts a layered and sectional excavation mode, or a mode of jumping excavation by a vertical shaft and constructing a supporting structure, so as to control the deformation of the tunnel and ensure the self-stability of the foundation pit.
Preferably, in the step e, the thickness of the uplift pile buffer layer is calculated according to 2 times of the rebound deformation of the foundation pit excavation unloading pit bottom, and is not less than 5 cm.
Preferably, in step e, the PVC casing for enclosing the uplift pile steel bars can prevent the uplift pile steel bars from being glued with the anti-floating plate, so as to ensure that the uplift pile steel bars are stressed independently.
Preferably, in step f, the anti-floating plate is a cast-in-place reinforced concrete anti-floating plate or a prefabricated plate, and a groove for installing an anchor is formed on the anti-floating plate, and the depth of the groove is matched with that of the anchor.
Preferably, in the step g, the tension load of each stage of the uplift pile is not more than 0.1 time of the unloaded soil pressure, the deformation value of the tunnel is monitored in real time during each stage of tension, and the next stage of tension is performed when the deformation of the tunnel is stable.
Preferably, in the step h, when the tensile force of the uplift pile reaches the original overlying soil pressure of the tunnel or the floating deformation value of the tunnel reaches 0mm, the uplift pile is locked.
Through the technical scheme, the invention has the following beneficial effects:
the invention adopts the prestressed uplift pile to control the upward floating deformation of the existing tunnel lying below caused by the excavation of the foundation pit, can fully exert the bearing capacity of the uplift pile, compensate the overlying soil pressure of the tunnel reduced by the excavation unloading, effectively reduce the upward floating deformation of the tunnel during the excavation of the foundation pit, and ensure the operation safety of the tunnel in the construction process.
Additional features and more prominent advantages of the invention will be set forth in the detailed description which follows.
Drawings
Fig. 1 is a construction flow chart of a floating control method for striding an existing tunnel on a foundation pit by adopting a prestressed uplift pile.
FIG. 2 is a schematic view of the parallel relative positions of a foundation pit and a tunnel according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of the relative intersection position of a tunnel and a foundation pit in another embodiment of the invention;
fig. 4 is a schematic plan view of a prestressed uplift pile system according to an embodiment of the invention;
fig. 5 is a schematic longitudinal construction view of a foundation pit prestressed uplift pile system in one embodiment of the invention;
fig. 6 is a schematic construction view of a vertical shaft prestressed uplift pile system in one embodiment of the invention;
fig. 7 is a detail view of a prestressed uplift pile system according to an embodiment of the present invention;
fig. 8 is a detail view of the uplift pile locking construction in one embodiment of the present invention;
fig. 9 is a detail view of the final state of the prestressed uplift pile system in one embodiment of the invention.
Description of the reference numerals
1 foundation pit sideline 2 tunnel sidelines
3 tunnel axis 4 steel plate
5 tunnel monitoring point 6 hydraulic cylinder
7 anti-floating pile 8 earth's surface
9 bottom of foundation pit and 10 side slopes of foundation pit
11 anti-floating plate 12 monitoring circuit
13 monitoring system 14PVC sleeve
15 underground structure bottom plate 16 uplift pile reinforcing steel bar
17 reinforcing steel bar anchor head 18 buffer layer
19 supporting structure 20 tunnel
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "mounted," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; either directly or indirectly through intervening media, either internally or in any combination thereof. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
As shown in fig. 1 to 9, the method for controlling floating of an existing tunnel over a foundation pit using a prestressed uplift pile according to a basic embodiment of the present invention includes the following steps:
a, arranging a monitoring system 13 in the tunnel 20;
b, constructing a foundation pit enclosure structure and a dewatering well;
c, constructing an uplift pile 7;
d, excavating the foundation pit to a specified elevation in a layered and sectional manner or in a vertical shaft manner;
e, constructing an uplift pile buffer layer 18 and a PVC sleeve for surrounding and sleeving the uplift pile reinforcing steel bars 16, wherein the buffer layer is formed by foamed plastic or rubber;
f, constructing a reinforced concrete anti-floating plate 11;
g, tensioning the uplift pile 7 in a grading manner;
h, locking the uplift pile 7 according to the tunnel deformation monitoring value;
and i, carrying out next excavation and constructing the main structure in sections.
In a specific embodiment, referring to fig. 7, a buffer layer 18 is formed at the top of the uplift pile 7, uplift pile steel bars 16 extending out of the top of the uplift pile 7 sequentially pass through the buffer layer 18, a PVC protection pipe 14 and two steel plates 4, the PVC protection pipe 9 penetrates through the uplift plate 11, the uplift pile steel bars 16 are further sequentially sleeved with two steel bar anchor heads 17, the two steel bar anchor heads 17 are in one-to-one correspondence with the two steel plates 4, each steel bar anchor head 17 is respectively located above the corresponding steel plate 4, and a hydraulic oil cylinder 6 is installed between the two steel plates 4; in the process of stretching the uplift pile 7 in stages, the steel bar anchor head 17 at the lower part is unlocked, and the steel bar anchor head 17 at the upper part is locked; after the tunnel deformation value is reduced to 0mm and the tunnel 20 is guaranteed not to be settled, the reinforcing steel bar anchor head 17 at the lower part can be locked, the reinforcing steel bar anchor head 17 at the upper part, the steel plate 4 and the hydraulic oil cylinder 6 are removed, referring to fig. 8, the uplift pile reinforcing steel bars 16 are cut off to the top of the uplift plate 11, and finally the main structure is constructed in the coverage area of the uplift plate 11, for example, fig. 9 shows a specific embodiment of the underground structure bottom plate 15 which constructs the main structure in the coverage area of the uplift plate 11;
wherein the designated elevation is a vertical distance from a point on the ground or building to a selected reference level in a construction design.
The thickness of the buffer layer 18 above the uplift pile 7 is estimated according to 2 times of the rebound deformation of the foundation pit excavation unloading pit bottom, and is required to be not less than 5 cm.
Furthermore, in order to prevent the anti-floating pile reinforcing bars 16 from being cemented with the anti-floating slab 11, the diameter of the PVC sleeve 14 is larger than that of the anti-floating pile reinforcing bars 16, so that the anti-floating pile reinforcing bars 16 can be stressed independently.
Generally, the anti-floating plate 11 is a cast-in-place reinforced concrete anti-floating plate or a prefabricated plate, a groove for installing an anchor is reserved on the anti-floating plate 11, the depth of the groove is matched with the height of the anchor, and the anchor can be a reinforced anchor head 17.
Referring to fig. 4, the tunnel is a shield tunnel, a monitoring system 13 arranged in the tunnel is realized by matching a measuring robot with professional monitoring software, a plurality of monitoring sections are arranged in an excavation range, each monitoring section is provided with four tunnel monitoring points 5, namely one tunnel top, one tunnel waist and one track bed, and each tunnel monitoring point 5 is connected to the monitoring system 13 through a monitoring line 12; according to the monitored tunnel deformation value, the output pressure of the hydraulic oil cylinder 6 is controlled, so that the uplift pile 7 can be tensioned in a grading manner, and the overlying soil pressure of the tunnel 20 reduced due to excavation unloading is compensated, so that the tunnel uplift deformation during the excavation of the foundation pit is effectively reduced; wherein, tunnel monitoring point 5 department is provided with pressure monitor, and measuring robot and professional monitoring software all adopt current measuring robot and monitoring software program.
Referring to fig. 7, in step g, the specific process of tensioning the uplift pile 7 in stages is as follows: stretching by extending a piston rod of a hydraulic oil cylinder 6, wherein the upper limit of the tensile force is 0.8-1.2 times of the weight of the overlying soil, 1.0 time of the weight of the overlying soil is taken, monitoring the deformation value of the tunnel in real time in the stretching process, performing next-stage stretching after the tunnel 20 is deformed stably until the deformation value of the tunnel is 0mm or the tensile force reaches 1.0 time of the weight of the overlying soil, and finishing the stretching; the uplift pile 7 is then locked.
From the above, in the process of controlling the upward floating deformation of the lower horizontal existing tunnel caused by the excavation of the foundation pit, the uplift pile 7 is tensioned in a grading manner to compensate the overlying soil pressure of the tunnel 20 reduced by the unloading of the excavation of the foundation pit, and the bearing capacity of the uplift pile 7 is fully exerted, so that the upward floating deformation of the tunnel during the excavation of the foundation pit is effectively reduced, and the operation safety of the tunnel in the construction process is ensured.
In a specific embodiment, referring to fig. 7, in step c, the minimum close distance between the uplift pile 7 and the tunnel 20 is not less than 1.5m, the minimum close distance is a horizontal distance between an edge of an outer contour of the uplift pile 7 on a side close to the tunnel 20 and the tunnel 20, a pile bottom of the uplift pile 7 is located at a position below one time of the hole diameter from the bottom of the tunnel 20, where "below one time of the tunnel hole diameter" is a position where the pile bottom of the uplift pile 7 is one time of the tunnel hole diameter from the bottom of the tunnel 20 or exceeds one time of the tunnel hole diameter, the uplift force of the uplift pile 7 is not less than 1.5 times of the soil weight, and the uplift pile 7 construction should be performed by using a full casing rotary drilling machine.
In addition, referring to fig. 5 and 6, the excavation of the foundation pit can adopt a layered and segmented mode, a foundation pit side slope 10 is formed by adopting a foundation pit slope placing excavation method, and finally the foundation pit bottom 9 is excavated to finish the layered and segmented excavation of the foundation pit; the foundation pit can also be excavated by adopting a mode of jumping excavation of the vertical shaft and constructing the supporting structure 19, so that the deformation of the tunnel can be well controlled and the stability of the foundation pit can be ensured.
Example (b):
in order to better understand the technical scheme of the invention, the method for controlling the upward floating of the foundation pit over the existing tunnel by using the prestressed uplift pile is described below by combining specific data.
The method is characterized in that residual soil, gravelly cohesive soil, granite, thick granite, fully weathered and strongly weathered underground, is coated on a certain site, the coarse granite, which is horizontally laid, is taken as an example, an underground continuous wall is taken as a foundation pit enclosure structure, the size of the foundation pit is 90m × 40m, the ground surface 8 is taken as a reference, the elevation of the bottom of the foundation pit is-13.00 m, the elevation of the underground water level is-2.00 m, a left line of an operated subway tunnel is horizontally laid on the foundation pit, is collinear with the foundation pit in a long distance, the collinear distance reaches 80mm, the relative position relation refers to fig. 2, namely, a tunnel side line 2 is parallel to a tunnel axis 3 and a foundation pit side line 1 and completely enters the range of the foundation pit, the outer diameter of the tunnel is 6.30m, the elevation of the top of the tunnel.
Referring to fig. 4, a monitoring system 13 is arranged inside a tunnel 20, the monitoring system is realized by matching a measuring robot with professional monitoring software, a plurality of monitoring sections are arranged in an excavation range, four tunnel monitoring points 5 are arranged on each monitoring section, the monitoring points are respectively one at the top of the tunnel, one at the waist part of the two sides of the tunnel and one on a track bed, and each tunnel monitoring point 5 is connected into the monitoring system 13 through a monitoring line 12.
Referring to fig. 7, the uplift pile 7 is a cast-in-place pile with a diameter of 1.0m, which is longitudinally arranged at both sides of the tunnel 20, with a safety distance of 1.5m from the tunnel 20, and the uplift pile 7 extends 6.0m below the bottom of the tunnel 20.
The bearing capacity of the uplift pile 7 is not lower than that of:
wherein: a. b is the plane size of the anti-floating plate of the excavation region; h is the excavation depth; gamma' is the effective gravity of the soil in the excavated area; and n is the number of the uplift piles in the excavation area. The effective gravity is also called as floating gravity, the natural gravity of the soil taken out from the underground water level can be used as saturated gravity, when the soil is below the underground water level, the soil is subjected to the buoyancy action of water, the effective gravity of particles in unit soil volume is obtained, and the gravity of the particles in unit soil volume minus the buoyancy is called as the effective gravity of the soil.
Referring to fig. 6, in combination with on-site geological conditions and construction conditions, the foundation pit is excavated in a vertical shaft jump excavation mode, the foundation pit is divided into 11 vertical shafts with the size of 6m × 12m in a collinear range, and the excavation depth is 13 m.
In the specific embodiment, the size of the vertical shaft is 6m × 12m × 13m, the soil layer is granite residual soil, and the gravity gamma is 18.0kN/m3And the underground water level elevation is-2.00 m, four uplift piles 7 are arranged on each uplift plate 11, and the bearing capacity of the uplift pile 7 can be calculated according to the calculation:
referring to fig. 7, the uplift pile buffer layer 18 is made of foam plastic or rubber, the thickness of the uplift pile buffer layer is estimated according to the rebound amount of the foundation pit excavation unloading pit bottom, and the thickness is 8.0 cm.
Referring to fig. 7, the uplift pile reinforcing steel bars 16 are prestressed reinforcing steel bars with a diameter of 22mm, in order to prevent the uplift pile reinforcing steel bars 16 from being cemented with the reinforced concrete anti-floating plate 11, the diameter of the PVC casing 14 is 40mm, and the pipe openings are immediately plugged by sealing plugs after the uplift pile reinforcing steel bars 16 pass through the PVC casing 14, so as to prevent concrete from entering the PVC casing 14.
Referring to fig. 7, the anti-floating plate 11 is a cast-in-place reinforced concrete anti-floating plate, the thickness of the plate is 0.9m, a groove is reserved for installing the steel plate 4 and the steel bar anchor head 17 during casting, and the size of the groove is determined according to the size of the steel bar anchor head 17 and the steel plate 4.
Referring to fig. 7, the steel plate 4 has a diameter of 1.0m and a thickness of 20mm, and is perforated according to the number of exposed reinforcing bars.
After the anti-floating plate 11 and the PVC sleeve 14 are poured, the steel plate 4 positioned below is installed; installing a reinforcing steel bar anchor head 17 positioned below (not locking); installing a hydraulic oil cylinder 6; installing a steel plate 4 positioned above; the rebar anchor head 17 located above is installed (locked).
Referring to fig. 7, the step tensioning process of the uplift pile 7 is as follows: tensioning is carried out by extending a piston rod of the hydraulic oil cylinder 6, in the embodiment applied in fig. 7, for example, the weight of the overlying soil is detected or weighed to be 2232kN, wherein the tensioning force is 1.0 time of the weight of the overlying soil, namely 2232kN, the deformation value of the tunnel is monitored in real time in the tensioning process, the next stage of tensioning is carried out after the deformation of the tunnel is stable, and the tensioning is finished until the deformation value of the tunnel is 0 or the tensioning value reaches 1.0 time of the weight of the overlying soil.
Referring to fig. 9, the step of locking the uplift pile 7 in sections and constructing the main structure is: locking the reinforcing steel bar anchor head 17 positioned below; sequentially removing the steel bar anchor head 17, the steel plate 4 and the hydraulic oil cylinder 6 which are positioned above; cutting off the uplift pile reinforcing steel bars 16 to the top of the anti-floating plate 11; and constructing a main body structure.
According to the invention, the uplift deformation of the existing tunnel lying below caused by excavation of the foundation pit can be controlled by utilizing the prestressed uplift pile 7 according to the uplift deformation condition of the tunnel, the bearing capacity of the uplift pile 7 can be fully exerted, the overlying soil pressure of the tunnel 20 reduced due to excavation unloading is compensated, the uplift deformation of the tunnel during excavation of the foundation pit is effectively reduced, and the operation safety of the tunnel in the construction process is ensured.
It should be noted that the excavation method of the foundation pit is not limited to the jump excavation of the vertical shaft, and a method of excavating the foundation pit in a layered and segmented manner as shown in fig. 5 may also be adopted.
The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, numerous simple modifications can be made to the technical solution of the invention, including combinations of the individual specific technical features in any suitable way. The invention is not described in detail in order to avoid unnecessary repetition. Such simple modifications and combinations should be considered within the scope of the present disclosure as well.
Claims (8)
1. A floating control method for spanning an existing tunnel on a foundation pit by adopting a prestressed uplift pile comprises the following construction steps:
a, arranging a monitoring system (13) in the tunnel (20);
b, constructing a foundation pit enclosure structure and a dewatering well;
c, constructing an uplift pile (7);
d, excavating the foundation pit to a specified elevation in a layered and sectional manner or in a vertical shaft manner;
e, constructing a uplift pile buffer layer (18) and a PVC sleeve (14) for surrounding and sleeving uplift pile steel bars (16), wherein the buffer layer is formed by foamed plastic or rubber;
f, constructing a reinforced concrete anti-floating plate (11);
g, tensioning the uplift pile (7) in a grading manner;
h, locking the uplift pile (7) according to the tunnel deformation monitoring value;
and i, carrying out next excavation and constructing the main structure in sections.
2. The method for controlling upward floating of an existing tunnel on a foundation pit by using the prestressed uplift pile according to claim 1, wherein in the step c, the minimum distance between the uplift pile (7) and the tunnel (20) is not less than 1.5m, the pile bottom of the uplift pile is positioned below one time of the tunnel diameter from the bottom of the tunnel (20), the uplift force of the uplift pile is not less than 1.5 times of the earth covering weight, and the uplift pile construction is performed by using a full-casing rotary drilling machine.
3. The method for controlling the upward floating of the existing tunnel over the foundation pit by using the prestressed uplift pile according to claim 1, wherein in the step d, the excavation of the foundation pit adopts a layered and sectional excavation mode or a mode that a vertical shaft is jumped and excavated and a supporting structure (19) is applied, so that the deformation of the tunnel can be controlled and the self-stability of the foundation pit can be ensured.
4. The method for controlling upward floating of the foundation pit across the existing tunnel by using the prestressed uplift pile according to claim 1, wherein in the step e, the thickness of the uplift pile buffer layer (18) is calculated according to 2 times of the rebound deformation of the bottom of the foundation pit excavation unloading pit and is not less than 5 cm.
5. The method for controlling upward floating of the foundation pit across the existing tunnel by using the prestressed uplift pile according to claim 1, wherein in the step e, the PVC sleeve (14) for enclosing the uplift pile steel bars (16) can prevent the uplift pile steel bars (16) from being bonded with the uplift plate (11) so as to ensure that the uplift pile steel bars (16) are stressed independently.
6. The method for controlling the upward floating of the existing tunnel over the foundation pit by using the prestressed uplift pile according to claim 1, wherein in the step f, the anti-floating plate (11) is a cast-in-place reinforced concrete anti-floating plate or a prefabricated plate, and a groove for installing an anchor is formed in the anti-floating plate (11), and the depth of the groove is matched with that of the anchor.
7. The method for controlling upward floating of the foundation pit across the existing tunnel by using the prestressed uplift pile according to claim 1, wherein in the step g, the tension load of each stage of the uplift pile (7) is not more than 0.1 time of the unloaded soil pressure, the deformation value of the tunnel is monitored in real time during the tension of each stage, and the next stage of the tension is performed when the deformation of the tunnel is stable.
8. The method for controlling upward floating of the existing tunnel on the foundation pit by adopting the prestressed uplift pile according to any one of claims 1 to 7, wherein in the step h, when the tensile force of the uplift pile (7) reaches the original overlying soil pressure of the tunnel (20) or the upward floating deformation value of the tunnel (20) reaches 0mm, the uplift pile (7) is locked.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113186989A (en) * | 2021-04-20 | 2021-07-30 | 广州地铁设计研究院股份有限公司 | Anti-floating construction method for tunnel |
| CN116180768A (en) * | 2023-03-16 | 2023-05-30 | 中国十九冶集团有限公司 | Construction device and construction method for anti-floating anchor rod of building engineering |
| CN117150817A (en) * | 2023-10-26 | 2023-12-01 | 湖南大学 | Combined door type anti-floating frame design method based on soil arch effect |
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| CN117150817A (en) * | 2023-10-26 | 2023-12-01 | 湖南大学 | Combined door type anti-floating frame design method based on soil arch effect |
| CN117150817B (en) * | 2023-10-26 | 2024-02-02 | 湖南大学 | Combined door type anti-floating frame design method based on soil arch effect |
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