CN114809106B

CN114809106B - Construction method of combined protection structure of existing tunnel

Info

Publication number: CN114809106B
Application number: CN202210366164.0A
Authority: CN
Inventors: 张世鑫; 范立军; 李延昌; 张明明; 康胜国; 耿彬; 马强; 赵忠诚; 高亭; 刘世昌
Original assignee: China Railway Construction Group Co Ltd; China Railway Construction Group Southern Engineering Co Ltd
Current assignee: China Railway Construction Group Co Ltd; China Railway Construction Group Southern Engineering Co Ltd
Priority date: 2022-04-08
Filing date: 2022-04-08
Publication date: 2023-06-13
Anticipated expiration: 2042-04-08
Also published as: CN114809106A

Abstract

The invention discloses a construction method of a combined protection structure of an existing tunnel, which comprises the following steps: respectively pouring a crown beam and a pull beam above the existing guard piles on two sides of the existing tunnel; pouring a grouting reinforcement area on the inner side of the existing fender post; constructing a plurality of shafts to the existing tunnel roof in the grouting reinforcement area, and respectively pouring a pressing pier; respectively constructing anti-pulling piles outside the existing guard piles; excavating the outer sides of the existing fender piles along the subway sections to the lower part of a channel foundation pit, and pouring connecting beams respectively; symmetrically sectionally and sectionally excavating a channel foundation pit on two sides of the existing guard pile, constructing a channel structure in time and weighting; excavating foundation pits among the existing guard piles in a segmented and partitioned mode, and chiseling off the existing guard piles; constructing a channel structure in time, connecting the channel structure with channels on two sides, and simultaneously carrying out weighting according to monitoring data; the invention ensures the stability of the existing tunnel and can also ensure the rapid propulsion of the earth excavation construction at the upper part of the subway.

Description

Construction method of combined protection structure of existing tunnel

Technical Field

The invention relates to the technical field of building construction, in particular to a construction method of a combined protection structure of an existing tunnel.

Background

Along with the rapid development of cities, the engineering construction along and around the subway is increasingly increased, the situation that the existing tunnel is covered with a building is frequently required, and the earthwork excavation on the upper part of the subway easily generates great safety risks for the existing tunnel. How to ensure the safety and stability of the operated existing tunnel and ensure the rapid pushing of the earth excavation construction at the upper part of the subway is an urgent need to solve the problem.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a construction method of a combined protection structure of an existing tunnel; the method solves the problems of ensuring the safety and stability of the existing tunnel and ensuring the rapid propulsion of the earth excavation construction on the upper part of the subway.

In order to achieve the above purpose, the present invention provides a construction method of a combined protection structure of an existing tunnel, comprising the following steps:

step S1: crown beams are respectively poured above existing fender piles on two sides of an existing tunnel, and tie beams are poured between the crown beams on two sides;

step S2: pouring a grouting reinforcement area on the inner side of the existing fender post;

step S3: constructing a plurality of shafts to the existing tunnel roof in the grouting reinforcement area, and respectively pouring a pressing pier; the top pressing pier is effectively connected with the existing guard pile;

step S4: respectively constructing anti-pulling piles outside the existing guard piles;

step S5: excavating the outer sides of the existing fender piles along the subway sections to the lower part of a channel foundation pit, and pouring connecting beams respectively; the connecting beam is effectively connected with the existing guard piles;

step S6: symmetrically sectionally and sectionally excavating a channel foundation pit on two sides of the existing guard pile, constructing a channel structure in time and weighting;

step S7: excavating foundation pits among the existing guard piles in a segmented and partitioned mode, and chiseling off the existing guard piles; and constructing a channel structure in time, connecting the channel structure with channels on two sides, and simultaneously carrying out weighting according to the monitoring data.

Preferably, in the step S2, a soil layer above the existing tunnel is reinforced by grouting with a ground sleeve valve pipe between the existing fender piles; and pouring grouting reinforcement areas on the side edges of the existing fender piles.

Preferably, the ground sleeve valve pipe adopts a PVC pipeline with the diameter of 52mm and the wall thickness of 4mm; the length of the ground sleeve valve pipe is equal to the distance between 3m below the pull beam and 0.5m above the top of the existing tunnel; the cement reinforced by grouting adopts sulphoaluminate cement, and the water cement ratio is 1:1; grouting reinforcement width is 2.5m.

Preferably, in the step S3, a top pier is constructed by adopting a reverse wall hanging method; the reverse wall of the well adopts a reinforced bar grating to spray concrete, the thickness is 30cm, grouting anchor pipes are arranged around the wall of the well, the well depth is 9.0-10.5 m, and the clearance size in the well plane is 2m multiplied by 2m.

Preferably, in the step S3, the center-to-center longitudinal spacing of the capping pier is between 5m and 10 m; the width direction is 1.5m, the length along the tunnel direction is between 1.5m and 2m, and the height direction is 2m.

Preferably, in the step S3, before the construction of the capping pier is completed and the backfilling of the shaft, a quick setting rubber asphalt waterproof coating is sprayed in the excavation range of the shaft of the existing tunnel roof, wherein the thickness of the waterproof coating is greater than 2.0mm; and C20 fine stone concrete protective layer of 70mm is applied on the outer layer of the waterproof coating.

Preferably, in the step S4, the uplift pile is immediately adjacent to the existing guard pile, and is constructed by adopting a full-rotation drilling guard cylinder, wherein the diameter of the uplift pile is 1200mm, and the longitudinal spacing is between 5m and 10 m; the pile length of the uplift pile is between 40m and 50m, and the uplift pile enters into middle-weathered or weak-weathered granite.

Preferably, in the step S5, the length direction of the connecting beam is along the tunnel direction, the width is 1.6m, and the vertical height is 2m.

Preferably, in the step S3, the node connection between the jacking pier and the existing fender post is performed by using a bar planting, and the contact surface is roughened and coated with an interface agent layer; in the step S5, the node connection between the existing fender post and the connecting beam is performed by adopting a bar planting method, and the contact surface is roughened and coated with an interfacial agent layer.

Preferably, in the step S7, the existing fender post is cut in segments by rope saw cutting.

Compared with the prior art, the invention has the beneficial effects that:

1. according to the method, the roof pier is constructed on the local temporary vertical shaft, and the roof pier is connected with the existing tunnel roof and the existing guard piles, so that the structure of the existing tunnel is fully utilized for restraining the floating of the subway tunnel structure caused by foundation rebound due to deep foundation pit unloading excavation, and the integral stability of the structure is ensured.

2. The invention further discloses a method for protecting the tunnel structure by re-excavating and pouring the anti-pulling pile, wherein the anti-pulling pile is connected with the existing guard pile through the connecting beam, and the anti-pulling pile and the existing guard pile are used for jointly jacking and protecting the tunnel structure.

3. In order to reduce the influence of tunnel structure deformation caused by excavation of the gallery channel foundation pits at two sides of a tunnel, the gallery foundation pits at two sides are transversely distributed and excavated symmetrically; and (5) carrying out longitudinal sectional partition construction, constructing a corridor structure in time and weighting.

4. According to the invention, the upper part of the existing tunnel is provided with the jacking pier, the jacking pier is connected with the top plate of the existing tunnel and the existing fender post by adopting a method of planting ribs, meanwhile, one side of the existing fender post is additionally provided with the anti-pulling pile, the anti-pulling pile is connected with the existing fender post by adopting a method of planting ribs through the connecting beam, and the stress with the floating of the tunnel is transmitted to a deep soil body through the existing tunnel, the jacking pier, the existing fender post and the anti-pulling pile in sequence, so that the tunnel structure is protected, the floating of the subway tunnel structure caused by foundation rebound due to unloading excavation of a deep foundation pit can be effectively restrained, and the integral stability of the structure is ensured.

5. The protection structure provided by the invention makes it possible to newly build a large building on the existing tunnel, realizes the continuous operation of the train in the existing tunnel while the large engineering construction operation is carried out on the upper part of the existing tunnel, ensures the safety and stability of the existing tunnel structure, the normal operation of the train and the ordered construction of the upper engineering, promotes the development of construction technology to a certain extent in a comprehensive view, and solves the problems that the safety and stability of the existing tunnel can be ensured and the rapid propulsion of the earth excavation construction on the upper part of the subway can be ensured.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic cross-sectional view of a combined protection structure for an existing tunnel according to the present invention;

FIG. 2 is a top view of a modular protective structure for an existing tunnel provided by the present invention;

FIG. 3 is a schematic view of the connection of the reinforcement bars between the press pier, the existing fender post and the connecting beam provided by the invention;

fig. 4 is a schematic view of a multiple shaft construction provided by the present invention;

FIG. 5 is a stepwise symmetrical excavation diagram of a channel foundation pit provided by the invention;

FIG. 6 is a stepwise excavation diagram of a foundation pit right above a tunnel provided by the invention;

FIG. 7 is a construction schematic diagram of a foundation pit with a channel excavated by two symmetrical blocks on two sides of an existing fender pile;

FIG. 8 is a schematic view of the construction of the present invention for removing existing fender piles;

fig. 9 is a cross-sectional view of shaft construction provided by the present invention;

FIG. 10 is a plan view of the social gallery channel pit dividing and excavating sequence provided by the invention;

fig. 11 is a longitudinal bin excavation sequence diagram of the outer side of a tunnel foundation pit.

The drawings include:

1. an existing tunnel; 2. existing guard piles; 5. a crown beam; 7. pulling a beam; 3. grouting reinforcement areas; 4. pressing a top pier; 6. pulling-resistant piles; 8. and connecting the beams.

Description of the embodiments

The technical solutions of the present embodiment of the present invention will be clearly and completely described below with reference to the drawings in the present embodiment of the present invention, and it is apparent that the described present embodiment is one embodiment of the present invention, but not all the present embodiments. All other embodiments, which can be made by those skilled in the art without making any inventive effort, are intended to be within the scope of the present invention.

Referring to fig. 1 to 11, the present invention provides a construction method of a combined protection structure of an existing tunnel.

In the embodiment, the depth of the foundation pit excavation of the main body part of the social corridor to be constructed is deeper, the deepest depth is about 8-10m, the earth covering above the operated subway is unloaded in the excavation process of the corridor channel, the necessary capping protection is needed before construction, and the influence of the foundation pit excavation on the floating of the operated subway interval after the earth above the subway interval is unloaded is avoided. The current ground elevation 22.000 of the north outlet of the social corridor is 15.000 of the planned ground elevation, the unloading earthwork is about 7m high, the necessary capping protection treatment is needed to be carried out on the subway section before construction, and the deformation of the subway section operated below due to the unloading of the soil body is avoided. In order to reduce the influence of peripheral soil unloading on a subway section, special subway protection design should be carried out.

Specifically, the following is a construction method of a combined protection structure of an existing tunnel, which comprises the following steps:

step S1: as shown in fig. 5, the construction site is leveled;

as shown in fig. 4, crown beams 5 are respectively poured above the existing fender piles 2 on two sides of the existing tunnel 1, and tie beams 7 are poured between the crown beams 5 on two sides; the pull beams 7 connect the two side crown beams 5 together to form a temporary support structure.

Step S2: as shown in fig. 1 and fig. 4, the soil layer above the existing tunnel 1 is reinforced by adopting ground sleeve valve pipe grouting between the existing fender piles 2; and pouring grouting reinforcement areas 3 on the side edges.

Specifically, the subway section is a tunnel constructed by an open cut method, soil above the tunnel is backfill soil, and the soil layer parameters are large in difference; the grouting reinforcement of the sleeve valve pipe on the ground can be carried out on the filling soil above the tunnel from the ground, and the stratum characteristic of the sleeve valve pipe is improved, so that the protection is provided for the excavation of a small vertical shaft for the construction of a capping pier.

Further, the ground sleeve valve pipe adopts a PVC pipeline with the diameter of 52mm and the wall thickness of 4mm; the length of the ground sleeve valve pipe is from below 3m below the pull beam 7 to 0.5m at the top of the existing tunnel 1; the grouting reinforcement cement adopts sulphoaluminate cement, and the water cement ratio is 1:1; grouting reinforcement width is 2.5m.

The disturbance to the lower subway open cut tunnel and the depth of the leading hole of the sleeve valve pipe and the grouting pressure should be strictly controlled during grouting. The depth of the pilot hole of the sleeve valve pipe is calculated according to the coordinates of the laid control points, the coordinate position of the pilot hole is calculated, the total station is used for discharging the hole position, the level meter is used for measuring the ground elevation, and the depth of the pilot hole is determined. When grouting, grouting pressure should be strictly controlled, the reinforcement depth is the current situation that the ground surface is below 3m to the top of the subway tunnel, and the vertical distance between the sleeve valve pipe and the top of the subway tunnel is not less than 0.5m. The high-pressure slurry pump, the high-pressure machine and the high-pressure clean water pump must be specially operated by a person, and the pressure gauge should be periodically overhauled and checked. Grouting experiments should be carried out before grouting construction, and parameters such as grouting mixing ratio, pressure, flow and the like are determined.

Step S3: as shown in fig. 9, constructing a plurality of shafts in the grouting reinforcement area 3 to the top plate of the existing tunnel 1, and respectively pouring a capping pier 4; the capping pier 4 is effectively connected with the existing fender post 2; specifically, an open cut tunnel in a subway section is constructed by adopting an open cut method, and the existing fender piles 2 are bored cast-in-place piles. To limit the rising deformation of the subway tunnel in the process of channel foundation pit excavation, the existing fender post 2 can be tightly attached to the tunnel to be used as a vertical shaft, and the pressing pier is poured and connected with the bored pile.

Further, in the step S3, as shown in fig. 3, the node connection between the capping pier 4 and the existing fender post 2 is performed by using a planted bar, and the contact surface is roughened and coated with an interfacial agent layer.

In the step S3, a reverse hanging well wall method is adopted to construct the top pier 4; the reverse wall of the well adopts a reinforced bar grating to spray concrete, the thickness is about 30cm, grouting anchor pipes are arranged around the wall of the well, the depth of the well is about 9.0-10.5 m, and the clearance size in the well plane is 2m multiplied by 2m.

In the step S3, the center-to-center longitudinal distance of the capping piers 4 is between 5m and 10 m; the width direction is 1.5m, the length along the tunnel direction is between 1.5m and 2m, and the height direction is 2m; specifically, the non-deformation joint has a pier size of 1.5m (width direction) ×1.5m (in the tunnel direction) ×2m (height direction), and the deformation joint has a pier size of 1.5m (width direction) ×2m (in the tunnel direction) ×2m (height direction).

In the step S3, before the construction of the capping pier 4 is completed and the backfilling of the shaft, quick setting rubber asphalt waterproof paint is sprayed in the excavation range of the shaft of the top plate of the existing tunnel 1, wherein the thickness of the waterproof paint is more than 2.0mm; and C20 fine stone concrete protective layers with the thickness of 70mm are applied on the outer layer of the waterproof coating, so that the waterproof safety of the subway is ensured.

Step S4: as shown in fig. 1, uplift piles 6 are respectively constructed outside the existing guard piles 2; specifically, the uplift pile 6 is closely adjacent to the existing guard pile 2, a full-rotation drilling guard cylinder is adopted for construction, disturbance to peripheral stratum is reduced as much as possible, the diameter of the uplift pile 6 is 1200mm, and the longitudinal distance is 5m to 10 m; the pile length of the uplift pile 6 is between 40m and 50m, in this embodiment, the pile length of the uplift pile 6 is tentatively set to 40.5m (the pile bottom enters approximately 50m below the ground) and enters medium-weathered or weakly weathered granite.

Step S5: as shown in fig. 1 and 5, the outside of the existing fender post 2 is excavated to the lower part of a channel foundation pit by 2m along the subway section, and connecting beams 8 are respectively poured; the connecting beam 8 is effectively connected with the existing fender post 2; the connecting beam is used for connecting the uplift piles 6 and connecting a plurality of uplift piles 6 together, as shown in fig. 2, the length direction of the connecting beam 8 is along the tunnel direction, the width is 1.6m, and the vertical height is 2m.

In the step S5, as shown in fig. 3, the node connection between the existing fender post 2 and the connecting beam 8 is performed by using a bar planting, and the contact surface is roughened and coated with an interface agent layer.

Step S6: as shown in fig. 7, the channel foundation pit is excavated on two sides of the existing guard pile 2 in a symmetrical sectional and partitioned mode, and the channel structure is constructed in time and weighted;

step S7: as shown in fig. 8, excavating foundation pits between existing fender piles 2 in a segmented and partitioned manner, and chiseling out the existing fender piles 2; and constructing a channel structure in time, connecting the channel structure with channels on two sides, and simultaneously carrying out weighting according to the monitoring data.

In order to protect the safety and stability of the subway structure, the existing fender post 2 should be cut by rope saw cutting and sectionally cut, and the pile head cannot be damaged by methods such as air pick, rotary digging pile excavation and the like. The rope saw cutting method can save the stability and the safety of the existing structure to the greatest extent, improve the working speed, shorten the construction period and further reduce the labor cost.

The influence of underground social gallery construction on the subway tunnel is mainly rebound deformation of the lower subway tunnel caused by excavation and unloading of a foundation pit. In the foundation pit excavation process, sectional and partitioned excavation is performed, the space effect is fully utilized, the main body structure of the social gallery is built back in time, the back pressure on the tunnel below is formed, and the vertical deformation of the tunnel can be effectively reduced theoretically. Sectional excavation and bin excavation of the project; under the precondition of ensuring the operation safety of the subway, the size of the sub-warehouse in the implementation stage can be properly adjusted according to the condition of subway automation monitoring data and construction organization.

The excavation sequence is as follows:

1. the longitudinal excavation book sequence of the tunnel external construction is as follows: outer 1-N- & gt, outer 2-N- & gt, outer 3-N- & gt, outer 4-N;

2. the transverse excavation book sequence of the tunnel outer construction is as follows: extra N-0- & gt extra N-1- & gt extra N-2- & gt extra N-3;

as shown in fig. 5, the excavation cross section steps of the gallery channel foundation pit above the existing tunnel 1 are as follows: outer 1-0 → outer 1-1 → outer 1-2 → outer 1-3 → inner 1-1.

According to the step excavation diagram, soil right above the subway section is reserved until the soil is finally unloaded, excavation of foundation pits of the vestibule channels on the two sides outside the subway section guard piles is required to be constructed step by step and symmetrically, and safety problems of instability of the guard structure and the like caused by uneven unloading of the two sides of the subway section guard piles are avoided.

Soil in the range of 1-1 in the right upper part of the subway is excavated by adopting segmented partition along the longitudinal direction of the subway line, the excavation schematic and sequence are shown in figure 6, a bottom plate is applied in time after each section of excavation is completed, and the weight is balanced according to the monitoring condition.

As shown in fig. 6, the excavation procedure right above the existing tunnel 1 is: inner 1-0 → inner 1-1 → inner 1-2 → inner 1-3.

The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.

Claims

1. A construction method of a combined protection structure of an existing tunnel is characterized by comprising the following steps: the method comprises the following steps:

step S1: crown beams (5) are respectively poured above existing guard piles (2) on two sides of an existing tunnel (1), and tie beams (7) are poured between the crown beams (5) on two sides;

step S2: pouring a grouting reinforcement area (3) on the inner side of the existing fender post (2);

step S3: constructing a plurality of shafts to the top plate of the existing tunnel (1) in the grouting reinforcement area (3), and respectively pouring out a pressing pier (4); the capping pier (4) is effectively connected with the existing guard pile (2);

step S4: respectively constructing anti-pulling piles (6) on the outer sides of the existing guard piles (2);

step S5: excavating the outer sides of the existing fender piles (2) along the subway section to the lower part of a channel foundation pit, and pouring connecting beams (8) respectively; the connecting beam (8) is effectively connected with the existing fender post (2);

step S6: symmetrically sectionally and sectionally excavating a channel foundation pit on two sides of the existing guard pile (2), constructing a channel structure in time and weighting;

step S7: excavating foundation pits among the existing fender piles (2) in a sectional and subarea mode, and chiseling off the existing fender piles (2); and constructing a channel structure in time, connecting the channel structure with channels on two sides, and simultaneously carrying out weighting according to the monitoring data.

2. The construction method of the combined protection structure of the existing tunnel according to claim 1, wherein the construction method comprises the following steps: in the step S2, the soil layer above the existing tunnel (1) is reinforced by adopting ground sleeve valve pipe grouting between the existing fender piles (2); and pouring a grouting reinforcement area (3) on the side edge of the existing fender post (2).

3. The construction method of the combined protection structure of the existing tunnel according to claim 2, wherein the construction method comprises the following steps: the ground sleeve valve pipe adopts a PVC pipeline with the diameter of 52mm and the wall thickness of 4mm; the length of the ground sleeve valve pipe is equal to the distance from 3m below the pull beam (7) to 0.5m above the top of the existing tunnel (1); the cement reinforced by grouting adopts sulphoaluminate cement, and the water cement ratio is 1:1; grouting reinforcement width is 2.5m.

4. The construction method of the combined protection structure of the existing tunnel according to claim 1, wherein the construction method comprises the following steps: in the step S3, a top pier (4) is constructed by adopting a reverse hanging well wall method; the reverse wall of the well adopts a reinforced bar grating to spray concrete, the thickness is 30cm, grouting anchor pipes are arranged around the wall of the well, the well depth is 9.0-10.5 m, and the clearance size in the well plane is 2m multiplied by 2m.

5. The construction method of the combined protection structure of the existing tunnel according to claim 1, wherein the construction method comprises the following steps: in the step S3, the center-to-center longitudinal distance of the capping piers (4) is between 5m and 10 m; the width direction is 1.5m, the length along the tunnel direction is between 1.5m and 2m, and the height direction is 2m.

6. The construction method of the combined protection structure of the existing tunnel according to claim 1, wherein the construction method comprises the following steps: in the step S3, before construction of the capping pier (4) is completed and backfilling of a vertical shaft, quick setting rubber asphalt waterproof paint is sprayed in the excavation range of the vertical shaft of the top plate of the existing tunnel (1), and the thickness of the waterproof paint is more than 2.0mm; and C20 fine stone concrete protective layer of 70mm is applied on the outer layer of the waterproof coating.

7. The construction method of the combined protection structure of the existing tunnel according to claim 1, wherein the construction method comprises the following steps: in the step S4, the uplift pile (6) is closely adjacent to the existing guard pile (2), a full-rotation drilling guard cylinder is adopted for construction, the diameter of the uplift pile (6) is 1200mm, and the longitudinal distance is between 5m and 10 m; the pile length of the uplift pile (6) is between 40m and 50m, and the uplift pile enters into middle-weathered or weak-weathered granite.

8. The construction method of the combined protection structure of the existing tunnel according to claim 1, wherein the construction method comprises the following steps: in the step S5, the length direction of the connecting beam (8) is along the tunnel direction, the width is 1.6m, and the vertical height is 2m.

9. The construction method of the combined protection structure of the existing tunnel according to claim 1, wherein the construction method comprises the following steps: in the step S3, the node connection between the capping pier (4) and the existing fender post (2) is performed by adopting a bar planting mode, and the contact surface is roughened and coated with an interface agent layer; in the step S5, the node connection between the existing fender post (2) and the connecting beam (8) is performed by adopting a bar planting mode, and the contact surface is roughened and is coated with an interface agent layer.

10. The construction method of the combined protection structure of the existing tunnel according to claim 1, wherein the construction method comprises the following steps: in the step S7, the existing fender pile (2) is cut in sections by adopting a rope saw.