CN115450221B

CN115450221B - Construction method for subway crossing river channel

Info

Publication number: CN115450221B
Application number: CN202211283576.4A
Authority: CN
Inventors: 黄昌富; 田书广; 李想; 高佳豪; 伍天华; 裴博文; 董佳琳; 刘汝辉; 李坤; 田峰; 郭迪迪; 王深圳
Original assignee: University of Science and Technology Beijing USTB; Urban Rail Transit Engineering Co Ltd of China Railway 15th Bureau Group Co Ltd
Current assignee: University of Science and Technology Beijing USTB; Urban Rail Transit Engineering Co Ltd of China Railway 15th Bureau Group Co Ltd
Priority date: 2022-10-19
Filing date: 2022-10-19
Publication date: 2024-07-23
Anticipated expiration: 2042-10-19
Also published as: CN115450221A

Abstract

A construction method for subway crossing river course includes the steps: the foundation pit is segmented and partitioned, one section of the subway track crossing the existing river is called a main foundation pit section, and the rest is called a secondary foundation pit section; in the main foundation pit section, at least a planned aqueduct region, an existing river region, and other regions not containing the planned aqueduct region and the existing river region are divided based on the existing river position; constructing a diaphragm wall, namely constructing the diaphragm wall in a planned aqueduct area and other areas in the main foundation pit section, the secondary foundation pit section and the existing river area in the main foundation pit section sequentially based on foundation pit segmentation and partition; draining the existing river channel; plugging an existing river channel and removing an existing river channel bridge; constructing a main body structure of the station; and recovering the existing river channel. The foundation pit partition scheme is adopted, so that disturbance influence among construction procedures can be reduced, construction efficiency is improved, and operation cost is reduced.

Description

Construction method for subway crossing river channel

Technical Field

The disclosure relates to the field of urban rail transit station construction, in particular to a construction method for an open excavation foundation pit to pass through a river channel in subway construction under the condition of no flow cutoff.

Background

Due to the rapid development of urban construction in China, a large number of people are rushed into the city, the subway is taken as a traffic form to effectively relieve the traffic pressure of urban roads, and more cities are in hot tide for construction of the subway. However, when a subway is built in a city with a large number of rivers (for example, in su zhou, hangzhou areas), subway lines may often cross river channels. When the subway line passes through the river channel, the subway line is mainly divided into two conditions: the subway section tunnel passes through the river channel and the subway station foundation pit passes through the river channel, wherein the former is most common in most cases. In either case, in the process that the subway line passes through the river channel, the influence of the seepage effect of water in the river channel on subway construction structural members (such as foundation pit underground continuous walls, tunnel lining segments and the like) is strictly controlled, and under the coupling effect of water flow and subway construction excavation unloading disturbance, the surrounding soil layer is extremely easy to deform, so that the service life and reliability of the surrounding existing structure are further influenced.

So far, most of subway station construction adopts open cut construction, namely, building an enclosure structure (such as underground diaphragm wall, bored pile, steel sheet pile and the like) of a station foundation pit on the ground, and after the design requirement is met, carrying out layered and subsection excavation operation under the open air condition.

Particularly, for the underground railway station open cut foundation pit to pass through the river channel, the importance of the river to the urban landscape and the smooth water channel is considered, and the river channel needs to be protected mainly, so that it is important to ensure that the river is not cut off in the process of the open cut foundation pit passing through. The construction conditions of the subway section tunnel passing through the river channel are rarely considered in terms of river cut-off, because most of subway section tunnel excavation adopts the construction of a hidden excavation method (such as mining method excavation, shield method excavation and the like), most of the route planning process relates to the section tunnel passing through the river channel downwards, and the phenomenon that the river channel is cut-off under the working conditions is rarely considered in terms of the fact that the prior related technical measures for controlling the deformation of the river bottom are mature when the subway section tunnel passes through the river channel downwards. However, differently, the working condition that the underground station open cut foundation pit passes through the river is difficult to meet the condition of the downward-passing river, so how to adopt an effective construction method can ensure the safety of foundation pit construction operation and reduce the influence of foundation pit construction on surrounding environment conditions, and simultaneously ensure that no current cutting phenomenon occurs in the existing river in the foundation pit construction process, thus being a real difficult problem to be solved urgently in the current engineering industry.

Currently, the vast majority of researches on the crossing of a river channel in subway line construction are performed by a construction control method for crossing the river channel (mainly downwards crossing) in a subway tunnel section (mine underground excavation construction and shield tunneling construction).

Li Kui and the construction scheme research of crossing small rivers and bridges under subway tunnels issued by the rock-soil mechanics in 2010 adopt a method combining a field monitoring means and numerical simulation analysis to primarily analyze horizontal jet grouting piles, full-section deep hole grouting, long pipe sheds and encrypted small pipe grouting which are possibly adopted by crossing bridge shield tunnel construction and are assisted with 4 advanced support schemes of temporary inverted arches. The construction method of the shield tunnel crossing river bridge is determined by combining the comparison of multiple aspects of technology, economy and the like, and adopts the encrypted small conduit grouting and the temporary inverted arch as a main construction scheme and adopts the deep hole grouting as a construction scheme.

The first proposal of the method is that advanced geological forecast is adopted to ascertain the geological condition in front of the face in 2017 in the first construction technology simple analysis of the under-river primary support of the shallow underground mining method tunnel published in Jiangsu building; then, in order to prevent leakage phenomenon in the process of penetrating the river channel under the undercut tunnel, series of construction methods such as surface water interception, centralized water leakage, buried pipe drainage of water burst, grouting liquid pressing and the like are suggested. Meanwhile, a water retaining cofferdam is required to be established before the tunnel is penetrated down, and the cofferdam is not removed in time after the tunnel is ensured to pass through smoothly, so that induced seepage cracks are prevented from being generated on the disturbance of a rock-soil layer due to vibration generated in the subsequent mine construction operation.

However, researches on the crossing of a river channel by an open cut foundation pit of a subway station are freshly reported, a surname is continuously used for providing a comprehensive design scheme of a cofferdam, a diversion pipe, an anchor rope and an internal support foundation pit combined supporting system and a box culvert for further bridge construction in a section of a subway station design scheme discussion of a downdraft river channel and a bridge foundation published in a section of a railway standard design in 2016, but the scheme has the advantages of complex construction procedures, high construction control difficulty, high manufacturing cost, greatly reduced water crossing capacity by adopting a diversion mode, incapability of realizing navigation conditions at all, and in addition, the construction in the mode needs to avoid working in rainy seasons, greatly limits construction working conditions and is easy to delay the construction period.

The chinese laid-open patent CN 107059878 proposes a method suitable for a river channel crossing a subway station foundation pit, and the method proposes to apply a box culvert on one side of the river channel as a temporary channel of the river channel, so as to solve the problem of blocking the existing river channel during construction, but the method is only specific to specific projects, lacks general applicability, for example, under the condition of complex traffic lines, the problem of traffic line correction is considered, the construction amount of the box culvert is large, and the difficulty of digging the foundation pit under the box culvert is large, so that the construction cost is high and the construction period is prolonged.

Therefore, how to perform safe, economical and efficient construction of open cut foundation pit river crossing of subway station under the condition that urban traffic lines are complex and smooth and continuous river flow is guaranteed is a technical problem to be solved urgently by those skilled in the art.

Disclosure of Invention

In order to solve at least one technical problem in the prior art, the present disclosure provides a construction method for a subway to pass through a river channel, which is especially suitable for the situations of complex urban traffic lines and high protection level requirements on the river channel, not only ensures that the foundation pit construction passes through the river channel smoothly and strictly, but also solves the technical problem that how to construct on the ultra-soft silt stratum of the river channel, the wall of a ground continuous wall is easy to collapse, and meanwhile, the safety of the foundation pit body needs to be ensured, and the influence and the disturbance degree of the excavation unloading of the foundation pit on the surrounding environment are ensured to be minimum.

In order to solve at least one of the above technical problems, the technical scheme adopted in the present disclosure is as follows:

a construction method for subway crossing river course includes the steps:

The foundation pit is segmented and partitioned, one section of the subway track crossing the existing river is called a main foundation pit section, and the rest is called a secondary foundation pit section; in the main foundation pit section, at least a planned aqueduct region, an existing river region, and other regions not containing the planned aqueduct region and the existing river region are divided based on the existing river position;

Constructing a diaphragm wall, namely constructing the diaphragm wall in a planned aqueduct area and other areas in a main foundation pit section, a secondary foundation pit section and an existing river channel area in the main foundation pit section in sequence based on foundation pit segmentation and partition, wherein the construction of a temporary aqueduct is carried out immediately after the construction of the diaphragm wall in the planned aqueduct area is completed;

the method comprises the steps of draining an existing river channel, building a temporary box culvert and a temporary open channel based on a built temporary aqueduct, and draining water in the existing river channel into the temporary aqueduct;

Plugging an existing river channel, dismantling an existing river channel bridge, and reinforcing the existing river channel bridge by adopting triaxial stirring piles with different cement doping amounts along with different depths in a groove of the underground diaphragm wall of the existing river channel region, wherein the triaxial stirring piles are firstly built before the underground diaphragm wall of the existing river channel region;

digging a foundation pit, constructing the foundation pit in the secondary foundation pit section and the main foundation pit section according to the distance from far to near based on the position of the temporary aqueduct, and installing a maintenance structure while constructing;

constructing a station main body structure, and constructing the station main body structure in each section or each region of foundation pit in a layering manner according to the sequence from bottom to top based on the excavated foundation pit until the top plate pouring is completed;

and restoring the existing river channel, restoring the bridge of the existing river channel, restoring the through flow of the existing river channel, and removing the temporary aqueduct.

Preferably, the planned aqueduct region in the main foundation pit section is arranged at the other side of the existing river channel far from other regions and is positioned at a position which is 2-3 times away from the width of the existing river channel;

a blocking wall between the planned aqueduct area and the existing river area is applied to a central line position between the temporary aqueduct and the existing river width;

The other blocking wall in the planned aqueduct area is applied at a position which is 2-3 times away from the width of the temporary aqueduct;

the blocking wall between the existing river region and other regions is applied at a position 2-3 times away from the width of the existing river.

Preferably, before the plugging wall between the planned aqueduct area and the existing river area is constructed, the inner side and the outer side of the plugging wall at the position are reinforced by adopting triaxial stirring piles;

The cement mixing amount of the triaxial mixing pile used for the plugging wall between the planned aqueduct area and the existing river area does not change along with the change of depth.

Preferably, the drainage of the existing river channel comprises:

Constructing a temporary aqueduct, putting a slope in a planned aqueduct area, excavating a foundation pit, and reinforcing the side slope; after a foundation pit is excavated to the bottom of a groove, mechanically crushing bridge piles in the existing river bridge by using a crusher; anchoring the main ribs of the ground connecting wall into the same side wall in the aqueduct bottom plate and pouring the same; lattice columns are erected at the bottom of the aqueduct and serve as auxiliary bearing structures; when the temporary aqueduct is built, the template is supported by three steps of the bottom plate, the side wall and the anti-collision guardrail in sequence, and then concrete pouring is carried out;

Constructing a temporary box culvert, and excavating a groove required for placing the box culvert; erecting a template for placing the box culvert; pouring a layer of concrete at the bottom of the groove to form a cushion layer; after the concrete in the groove meets the design strength requirement, removing the template; placing a box culvert, and simultaneously backfilling the two sides of the box culvert with ash soil; the construction of pouring the concrete in the formwork erection and the groove can be carried out together with the temporary aqueduct construction process;

After the construction of the aqueduct and the box culvert is finished, excavating a temporary open channel for connecting the existing river channel and the temporary aqueduct, and sequentially transferring water in the existing river channel at one side of the foundation pit to the existing river channel at the other side of the foundation pit through the temporary box culvert, the temporary aqueduct and the temporary open channel, so that the water in the existing river channel is kept continuous in the construction process.

Preferably, the construction of the underground diaphragm wall of the secondary foundation pit section and other areas in the main foundation pit section can be performed synchronously with the drainage construction of the existing river;

Before the construction of the diaphragm wall, the pipeline which influences the construction is relocated and the enclosure is closed.

Preferably, the plugging the existing river and removing the existing river bridge comprises:

Plugging a river channel in the existing river channel region, and after water in the existing river channel is changed to flow, plugging a river channel opening in the existing river channel region by using a steel sheet pile, and constructing a water collecting pit; removing the clear water in the existing river channel area and then removing the sewage in the river channel area; cleaning up sludge in the river bottom, and filling up the river in the existing river area with clay;

Removing bridges in the existing river channel area, and sequentially removing railings, plate girders and caps on the existing river channel bridges; then the bearing platform position is broken by blocks along with the extraction position of the bridge pile foundation; after the bridge pile is pulled out, backfilling bridge pile holes in time and tamping, pulling out residual bridge pile bodies, collecting the residual bridge pile bodies together with the rest concrete fragments, and then transporting the residual bridge pile bodies outside for disposal; wherein, the foundation pit backfill in the existing river channel area adopts the layered compaction of ash soil, and backfills to the bearing platform top surface height.

Preferably, the construction of the underground diaphragm wall of the existing river area is further included after the existing river bridge is plugged and removed, and the construction method comprises the following steps:

Reinforcing the groove walls of the grooves of the underground continuous wall of the existing river channel region by adopting a plurality of groups of triaxial stirring piles, wherein the depth of reinforcing the groove walls of the grooves of the underground continuous wall of the existing river channel region is 2-3m deeper than that of the underground continuous wall;

Taking the first excavation depth of the foundation pit in the existing river channel area and the final depth after excavation as boundaries,

Backfilling soil bodies in the width range of the bottom of the trench of the diaphragm wall step by pseudo-ginseng gray soil and compacting the soil bodies in the area smaller than the first excavation depth of the foundation pit; when the slope is put down and excavated to original soil, the construction of the groove wall of the diaphragm wall groove is started;

for the area which is larger than the first excavation depth of the foundation pit and smaller than the final excavation depth of the foundation pit, adopting triaxial stirring piles with full-section cement mixing amount of 8-10% to laterally reinforce the two sides of the wall of the underground diaphragm wall groove, wherein the area belongs to a weaker reinforcing section;

and (3) laterally reinforcing the region below the final excavation depth of the foundation pit by adopting triaxial stirring piles with the full-section cement doping amount of 20-25% on two sides of the wall of the diaphragm wall groove, wherein the region belongs to a strong reinforcing section.

Preferably, the excavation of the foundation pit is performed before the construction of the station body structure,

The foundation pit excavation is based on the position of a temporary aqueduct, the foundation pits in the secondary foundation pit section and the main foundation pit section are constructed according to the distance from far to near, and the maintenance structure is installed while the construction is performed;

When a foundation pit is excavated, firstly, excavating construction is carried out on the secondary foundation pit section, and then excavating construction is carried out on the main foundation pit section; when the main foundation pit section is constructed, the foundation pit in other areas is excavated firstly, then the foundation pit in the existing river area is excavated, and finally the foundation pit in the aqueduct area is excavated.

Preferably, all foundation pits are constructed by adopting an open excavation forward method, after the foundation pits are excavated, concrete cushion layers, bottom plates, side walls, top plates and top plates of the upper/lower parts of the underground stations are sequentially applied from bottom to top for backfilling, and then corresponding support systems are sequentially removed according to the construction sequence.

Preferably, after the construction of the main structure of the foundation pit in the existing river channel region is finished, the existing river channel and the bridge thereof are reconstructed, the river water in the temporary aqueduct is changed back into the existing river channel, and the structures of the temporary aqueduct and the temporary box culvert are removed after the river channel is unblocked.

By adopting the construction method for the subway to pass through the river course, which is designed by the present disclosure, the construction of the existing river course by the open cut foundation pit is aimed at, and the temporary aqueduct is constructed, so that the original river course is changed into the temporary aqueduct, and the river course is ensured to be continuous; the adopted foundation pit partition scheme ensures the mutual connection of each construction procedure to the greatest extent, reasonably adjusts the foundation pit construction sequence of the temporary aqueduct area and the existing river area, and strictly controls the structure of the temporary aqueduct and the deformation of the foundation pit; the foundation pit diaphragm wall grooving construction of the existing river region adopts combined groove wall reinforcement measures which change along with the depth, and solves the technical problem that the groove wall is easy to collapse during the foundation pit diaphragm wall construction of the section, thereby forming a whole set of construction method for the open excavation foundation pit to penetrate the existing river without cutting off flow.

The method is particularly suitable for construction of the open cut foundation pit crossing the river channel under the condition of no flow break, the continuous flow break of the existing river channel is ensured by constructing the temporary aqueduct for drainage of river water, the mutual connection of the construction procedures of the transition of the existing river channel to the aqueduct, the excavation of the foundation pit and the station construction can be ensured, and the construction efficiency is improved; the foundation pit partition excavation scheme is also provided, disturbance and influence on the foundation pit in the temporary aqueduct area are reduced to a certain extent, and site construction has higher controllability and stability.

The technical problem that the foundation pit of the existing river area is a soft soil stratum and the corresponding diaphragm wall is difficult to construct is solved, and a combined groove wall reinforcing measure which changes along with the depth is provided, namely, in the stratum range of the existing river height, the original silt stratum is compacted and backfilled by pseudo-ginseng ash soil, the compactness of the soil layer is increased, the collapse of the groove wall of the diaphragm wall at the upper part is prevented to a certain extent, and the demolition work of the diaphragm wall range structure during the later river return is facilitated; simultaneously, triaxial mixing piles with different cement doping amounts are adopted in the lower stratum to respectively cope with different stratum conditions, so that a more stable strong foundation wall is obtained, the construction effect is good, and the operation cost is saved.

Aiming at foundation pit construction penetrating through the existing river channel region, after the temporary aqueduct is built, the existing river channel is changed into the temporary aqueduct to ensure that the river is kept smooth; after the internal structure of the foundation pit main body is basically finished, the existing river channel is restored, the river channel water flow is restored to the original position, and other structures such as temporary aqueducts are removed. The river course is changed twice, so that the river course can not flow out in the foundation pit open cut construction process, the original river course and bridge can be restored again, the influence of construction on the surrounding environment is reduced to the greatest extent, and the construction requirements of safety, high efficiency and green are met; and each process is mutually linked in the foundation pit construction process, and is not mutually influenced, so that the construction operation progress is accelerated, and the station engineering is completed in a planned period.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the disclosure and together with the description serve to explain the principles of the disclosure.

Fig. 1 is a flowchart of a construction method of a subway crossing a river channel of the present disclosure;

FIG. 2 is a schematic plan view of a foundation pit section and partition in an engineering example of the present disclosure;

FIG. 3 is a plan view of a temporary aqueduct for water flow diversion in an example of the disclosed project;

FIG. 4 is a cross-sectional view of a new temporary aqueduct for a foundation pit in an example of the disclosed project;

FIG. 5 is a cross-sectional view of a newly constructed temporary aqueduct for a foundation pit in an example of the disclosed project;

FIG. 6 (a) is a cross-sectional view of a foundation pit foundation wall grooving reinforcement measure in an existing river area in an example of the engineering of the present disclosure;

FIG. 6 (b) is a second cross-sectional view of the reinforcement means for foundation pit foundation wall grooving in the river area in the construction example of the present disclosure;

FIG. 7 is a perspective view of the overall structure of the temporary aqueduct and the diaphragm wall in the disclosed construction example;

Fig. 8 is a graph showing the maximum displacement of each monitoring item as a function of the excavation depth in the engineering example of the present disclosure.

In the figure:

100. Main foundation pit section 200, secondary foundation pit section 1 and existing river region

2. Aqueduct zone 3, other zone 10, existing river course

11. Lotus flower river 12, vehicle inclined river 13 and road

20. Blocking wall 21, enclosure 30 and ground connecting wall

31. Groove 32, stirring pile 33 and lime soil backfill layer

40. Temporary aqueduct 41, aqueduct 42 and crown beam

43. Connecting beam 44, cross beam 45 and longitudinal beam

46. First support 47, lattice column 48, second support

49. Third support 410, cover 411, and bottom plate

412. Sedimentation joint 413, concrete cushion layer 50 and temporary box culvert

60. Temporary open channel a, earth surface monitoring point b and underground wall monitoring point

C. Aqueduct bottom plate monitoring point

Detailed Description

The present disclosure is described in detail below with reference to the attached drawings and specific examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant matter and not limiting of the disclosure. It should be further noted that, for convenience of description, only a portion relevant to the present disclosure is shown in the drawings.

It should be noted that, without conflict, the embodiments of the present disclosure and features of the embodiments may be combined with each other. The present disclosure will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

The embodiment provides a construction method for a subway to pass through a river channel, as shown in fig. 1, which specifically comprises the following steps:

S1, segmenting and partitioning the foundation pit.

As shown in fig. 2, based on the foundation pit design data and the actual situation on site, a section of the subway rail intersecting the existing river 10 is referred to as a main foundation pit section 100, and the rest is referred to as a sub-foundation pit section 200. Wherein, in the main foundation pit section 100, based on the position of the existing river 10, at least three areas are divided, respectively: the planned aqueduct region 2, the existing river region 1, and the other regions 3 which do not contain the planned aqueduct region 2 and the existing river region 1; if other special conditions exist in the foundation pit, the foundation pit can be subjected to refined partition. The block wall 20 is constructed by partitioning each region in the main foundation pit section 100, then the foundation pit construction main body of each region is determined, and partition excavation is performed.

Preferably, in the main foundation pit section 100, the planned aqueduct region 2 is disposed at a position that is 2-3 times away from the width of the existing river 10 and away from the other side in the other region 3; the existing river 10 is adjacent to the other zone 3.

Wherein the partition plugging wall 20 between the planned aqueduct area 2 and the existing river area 1 is applied at the center line position between the temporary aqueduct 40 and the width of the existing river 10; the other blocking wall 20 in the planned aqueduct region 2 is applied at a position 2-3 times away from the width of the temporary aqueduct 40. The partition blocking wall 20 between the existing river region 1 and the other region 3 is applied at a position 2-3 times away from the width of the existing river 10.

Furthermore, before the plugging wall 20 between the planned aqueduct area 2 and the existing river area 1 is constructed, the walls of the inner side and the outer side of the trench of the plugging wall 20 at the position are reinforced by adopting a plurality of triaxial stirring piles 32; the cement mixing amount of the triaxial mixing pile 32 used for the plugging wall 20 between the planned aqueduct area 2 and the existing river area 1 does not change along with the depth change, and is the common triaxial mixing pile 32. The triaxial stirring piles 32 are adopted to reinforce the groove walls of the grooves of the plugging wall 20 between the planned aqueduct area 2 and the existing river area 1 so as to improve the wall forming quality of the plugging wall 20 and the joint water stopping effect; other partition walls 20 are normally constructed. The number of the foundation pit partition plugging walls 20 can be determined according to the spatial position relationship between the foundation pit newly built on the actual engineering site and the existing river 10 and the site construction conditions.

S2, constructing the diaphragm wall 30.

Based on foundation pit segmentation and zoning, the foundation wall 30 is constructed in the planned aqueduct zone 2 and other zone 3 in the main foundation pit section 100, the secondary foundation pit section 200, and the existing river zone 1 in the main foundation pit section 100 in sequence.

Specifically, the construction sequence of the diaphragm wall 30 is: firstly, constructing maintenance structures for the planned aqueduct area 2 and other areas 3 in the main foundation pit section 100 in sequence, and constructing the diaphragm wall 30, the upright post piles and the like; then, constructing maintenance structures in the secondary foundation pit section 200, constructing a diaphragm wall 30, upright piles and the like; and finally, performing maintenance structure and construction of the diaphragm wall 30, the upright posts and the like on the existing river channel region 1 in the main foundation pit section 100. Before the existing river channel area 1 is applied to the diaphragm wall 30, the operation must be waited until the existing river channel 10 is changed, namely, the river channel area must be changed to the temporary aqueduct 40 for water supply; wherein the temporary aqueduct 40 must be built immediately after the construction of the diaphragm wall 30 in the aqueduct section 2 is completed.

As shown in fig. 3, the main foundation pit section 100 is arranged across the width of the lotus flower middle river 11 as the existing river 10, and the water in the existing car inclined river 12 directly flows out of the lotus flower middle river 11, and the main foundation pit section 100 crosses the lotus flower middle river 11 and passes through the width of the lotus flower middle river 11. Therefore, before constructing the underground diaphragm wall 30 on the aqueduct area 2, the water flow in the lotus middle river 11 needs to be introduced into the temporary aqueduct 40 from the oblique river 12 on the east of the main foundation pit section 100 through the temporary box culvert 50, and then is transferred into the lotus middle river 11 on the west of the main foundation pit section 100 through the temporary open channel 60.

Preferably, the construction of the underground diaphragm wall 30 of the secondary foundation pit section 200 and the other areas 3 in the main foundation pit section 100 can be synchronously carried out with the drainage construction of the existing river 10, and the construction time is saved and the construction efficiency is improved. Wherein, before constructing the diaphragm wall 30, the pipeline influencing the construction is relocated and the closure of the enclosure 21 is completed.

S3, draining the existing river channel 10.

Based on the constructed temporary aqueduct 40, the temporary box culvert 50 and the temporary open channel 60 are constructed, and water in the existing river channel 10 is drained into the temporary aqueduct 40, namely, the temporary aqueduct 40, the temporary box culvert 50 and the temporary open channel 60 are constructed across the foundation pit in sequence, specifically comprising the following steps:

Constructing a temporary aqueduct 40, firstly placing a slope in a planned aqueduct area 2, excavating a foundation pit, and reinforcing the side slope; after the foundation pit is excavated to the bottom of the pit, a breaker is used for mechanically breaking the bridge piles in the bridge of the existing river 10, namely the bridge piles on the bridge in the river 11 in the lotus. The main tendons of the diaphragm wall 30 are anchored into the same side walls in the bottom plate 411 in the aqueduct 41 and poured together; and lattice columns 47 are erected at the bottom of the aqueduct 41 as supporting structures for assisting in bearing. When the temporary aqueduct 40 is built, the templates are sequentially supported by the bottom plate 411, the side walls and the anti-collision guardrails in three steps, and then concrete pouring is performed.

A temporary box culvert 50 is built, and the box culvert is buried under the road 13 and is communicated with the oblique river 12. Digging grooves required by placing box culverts, and erecting templates for placing the box culverts in the grooves of the box culverts; pouring a layer of concrete at the bottom of the groove to form a concrete cushion layer; after the concrete in the groove meets the design strength requirement, removing the template; placing the box culvert, and backfilling the ash soil on two sides of the box culvert. The construction of concrete in the groove of the box culvert can be performed together with the construction process of constructing the temporary aqueduct 40.

After construction of the aqueduct 41 and the box culvert is finished, a temporary open channel 60 connecting the existing river channel 10 and the temporary aqueduct 40, namely, the temporary open channel 60 connecting the lotus flower middle river 11 and the temporary aqueduct 40 is excavated, firstly, water in the lotus flower middle river 11 of the existing river channel 10 on the east side of the main foundation pit section 100 is changed from the oblique river 12, sequentially passes through the temporary box culvert 50, the temporary aqueduct 40 and the temporary open channel 60, and is introduced into the lotus flower middle river 11 of the existing river channel 10 on the west side of the main foundation pit section 100, so that water in the lotus flower middle river 11 serving as the existing river channel 10 in the construction process is kept continuous.

S4, plugging the existing river channel 10 and removing the bridge on the existing river channel 10.

Blocking the lotus flower middle river 11, removing the bridge on the lotus flower middle river 11, removing pile foundation construction, and then constructing the underground diaphragm wall 30 of the foundation pit in the existing river channel area 1. Before the diaphragm wall 30 is built in the existing river region 1, and the triaxial mixing piles 32 with different cement doping amounts according to different depths are adopted to reinforce the grooves 31 of the diaphragm wall 30 in the existing river region 1.

Plugging a river channel crossing the lotus flower middle river 11 and the main foundation pit section 100 in the existing river channel region 1, after water in the lotus flower middle river 11 serving as the existing river channel 10 is changed and drained to the temporary aqueduct 40, plugging a river channel opening in the existing river channel region 1 by utilizing a steel sheet pile, and constructing a water pit; discharging clear water in the lotus flower river 11, installing a sewage pump, discharging sewage in the lotus flower river 11, settling the lotus flower river in a field settling pond, and discharging the lotus flower river into a sewage pipe network. And (3) cleaning up sludge in the river bottom in the lotus flower middle river 11 by using an excavator before filling the river, and filling the river in the lotus flower middle river 11 in the existing river region 1 by using clay.

Removing the bridge in the existing river region 1, namely removing the bridge on the lotus middle river 11 serving as the existing river 10, specifically removing the railing, the plate girder and the table cap on the bridge in sequence; then the position of the bearing platform connected with the abutment cap can be broken by blocks along with the extraction position of the bridge pile foundation; and after the bridge pile is removed, backfilling bridge pile holes in time, tamping and backfilling, removing the residual bridge pile body, collecting the residual bridge pile body together with the rest concrete fragments, and then transporting and discarding the bridge pile. Wherein, the foundation pit backfill in the existing river channel area 1 adopts the layered compaction of the lime soil and backfills to the height of the top surface of the bearing platform.

Preferably, after the existing river 10 is plugged and the bridge of the existing river 10 is removed, the construction of the underground diaphragm 30 of the existing river area 1 is further included, including: the groove walls of the grooves 31 of the underground diaphragm wall 30 of the existing river region 1 are reinforced by adopting a plurality of groups of triaxial mixing piles 32, and the depth of the reinforcement of the groove walls of the grooves 31 of the underground diaphragm wall 30 of the existing river region 1 is 2-3m deeper than that of the underground diaphragm wall 30.

As shown in fig. 6, the first excavation depth of the foundation pit in the existing river region 1 and the final depth after excavation are taken as boundaries, and the method is specifically divided into:

For the area smaller than the first excavation depth of the foundation pit, backfilling and compacting soil bodies in the width range of the bottom of the groove 31 of the diaphragm wall 30 step by pseudo-ginseng gray soil to form a gray soil backfill layer 33; when the slope is excavated to the original soil, the working of the walls of the grooves 31 of the diaphragm wall 30 is started.

For the area which is larger than the first excavation depth of the foundation pit and smaller than the final excavation depth of the foundation pit, triaxial stirring piles 32 with full-section cement mixing amount of 8-10% are adopted on two sides of the wall of a groove 31 of the diaphragm wall 30 for lateral reinforcement, and the area belongs to weaker reinforcement sections.

For the area below the final excavation depth of the foundation pit, triaxial stirring piles 32 with the full-section cement doping amount of 20-25% are adopted at two sides of the wall of the groove 31 of the diaphragm wall 30 for lateral reinforcement, and the range belongs to a strong reinforcement section, so that the collapse of the wall of the groove is prevented to the greatest extent, and the wall forming quality and joint water stopping effect of the diaphragm wall 30 in the range of the existing river channel area 1 are improved.

S5, excavating a foundation pit.

Based on the position of the temporary aqueduct 40, the foundation pit in the secondary foundation pit section 200 and the main foundation pit section 100 is constructed at a distance from far to near, and the maintenance structure is installed while the construction is being performed. Preferably, when the foundation pit is excavated, firstly, the foundation pit of the secondary foundation pit section 200 is excavated, and then the foundation pit of the main foundation pit section 100 is excavated; during construction of the main foundation pit section 100, the foundation pit in the other area 3 is excavated, then the foundation pit in the existing river area 1 is excavated, and finally the foundation pit in the aqueduct area 2 is excavated.

When the foundation pit of each section is constructed, the corresponding crown beam 42 and the concrete support serving as the first support 46 are firstly constructed; then excavating soil mass to the elevation of the supporting frame in a segmented and layered mode, installing a steel supporting and supporting system, and constructing steel supporting prestress until the soil mass is excavated to the pit bottom; and so on until the enclosure structures of all the foundation pits except the temporary aqueduct 40 are completely constructed, and then the foundation pit of the temporary aqueduct 40 is constructed in a focused manner. Firstly, constructing a foundation pit far away from the temporary aqueduct 40 section, in order to reduce the influence of the foundation pit around the excavation on the aqueduct 41 structure as much as possible, and finally, when constructing the foundation pit of the temporary aqueduct 40 section, the important attention is paid and the deformation of the aqueduct 41 structure and the foundation pit support structure is strictly controlled.

When the foundation pit of the temporary aqueduct 40 is constructed, soil is excavated to the erection elevation of the second support 48 in a layered manner, and a steel support supporting system serving as the second support 48 is installed; and excavating depth according to the design of the foundation pit to be excavated until the foundation pit is excavated to the bottom of the temporary aqueduct 40 section.

S6, constructing a station main body structure.

And (3) based on the excavated foundation pit, constructing the station main body structure in the foundation pit of each section or each region in a layering manner according to the sequence from bottom to top until the top plate pouring is completed.

Preferably, all the foundation pits are constructed by adopting an open excavation forward method, after the foundation pit is excavated, a cushion layer, a bottom plate, a side wall, a top plate and a top plate of the upper/lower part of the underground station are sequentially constructed from bottom to top, and then the corresponding support systems are sequentially removed according to the construction sequence, wherein the concrete cushion layer and the bottom plate which are cast at the bottom of the foundation pit are bottom foundations provided for the internal structure which is built from top to bottom, the top plate on the foundation pit is a concrete structure which is formed by covering the uppermost part of the station after the station is built, and road driving can be performed after the top plate is covered with soil and flattened, and the road driving is different from the cover plate 410, the bottom plate 411 and the concrete cushion 413 when the temporary aqueduct 40 is constructed.

S7, recovering the existing river channel.

The bridge of the existing river 10 is restored and the current of the existing river 10 is restored, and then the temporary aqueduct 40 is removed.

Preferably, after the construction of the main structure of the foundation pit in the existing river channel region 1 is finished, the existing river channel 10 and the bridge thereof are reconstructed, the river water in the temporary aqueduct 40 is redirected back to the existing river channel 10, and the structures of the temporary aqueduct 40 and the temporary box culvert 50 are removed after the river channel is unblocked. That is, the bridge on the lotus middle river 11 is built again, and the water in the oblique river 12 is restored to directly enter the lotus middle river 11 for circulation; and removes the corresponding temporary box culvert 50 and temporary aqueduct 40.

For a clearer understanding of the objects and technical aspects of the present disclosure, reference will now be made in further detail to specific engineering examples and drawings.

The construction method for crossing the river channel by the open excavation foundation pit of the subway under the condition of no flow is introduced by taking the interpenetrating of the east-extension road station foundation pit and the lotus middle river 11 of the Suzhou rail transit No. 8 line 9 standard section as an engineering background. The length 477m and the width 20.7m of the foundation pit of the track traffic No. 8 line east delay station are about 18.0m of the average excavation depth, the foundation pit is narrow and long, and the open excavation forward construction method is adopted. The foundation pit of the main body of the rail transit No. 8 line east extension station is provided with a plurality of shafts which are supported by concrete, namely, a1 shaft, a 30 shaft, a 38 shaft, a 43 shaft, a 46 shaft and a 46 shaft in FIG. 2, and the drawings of other shafts are omitted. The section range from 38 axis to 43 axis is directly crossed and interpenetrating with the lotus flower middle river 11 of the existing river 10, and the position relationship of the two is shown in figure 2. Because the foundation pit passes through the area of the ultra-soft soil layer of the silt in the river 11 of the lotus flower, the weak soil interface has low compactness and poor cementing property, the construction of the diaphragm wall 30 on the area has the technical problem that the groove wall of the groove 31 used for constructing the diaphragm wall 30 is easy to collapse, the foundation pit is required to be ensured to be in an anhydrous environment as much as possible in the construction process, the excessive deformation of the foundation pit structure is prevented, the river water in the river 11 of the lotus flower is required to be strictly ensured to be uninterrupted, the stability of the surrounding water system is maintained, and the influence of the construction on the surrounding environment is reduced to the minimum.

When the method and the device are adopted to realize that the station open cut foundation pit passes through the river channel, the river is strictly guaranteed to be continuous, the safety and stability of the foundation pit underground wall grooving of the ultra-soft soil stratum are guaranteed, and meanwhile, the disturbance and the influence of construction operation on the surrounding environment are guaranteed to be small, and the method and the device specifically comprise the following steps:

S1, segmenting and partitioning the foundation pit.

Before construction, the pipelines around the foundation pit to be excavated are changed, and the enclosing barrier 21 is closed, so that the influence on the surrounding environment is reduced. According to the length of a subway track to be built, namely a newly built 8-wire station foundation pit and the crossing condition of a north foundation pit and a lotus middle river 11, wherein the distance between any two shafts is 7-10m, dividing the foundation pit to be dug of the 8-wire station into a main foundation pit section 100 containing a temporary aqueduct 40 and a secondary foundation pit section 200 not containing the temporary aqueduct 40 from the south to the north by taking a 30 th shaft as a boundary, as shown in fig. 2.

A row of filling stirring piles 32 with the diameter phi of 850mm and the adjacent horizontal center-to-center spacing of 600mm are arranged between the main foundation pit section 100 and the secondary foundation pit section 200 to serve as soft isolation, and foundation pits on two sides of a pile body of the stirring piles 32 are excavated in a slope manner. In the main foundation pit section 100, the partitioning is performed based on the position of the existing river 10, and the partitioning is respectively: the planned aqueduct region 2 between the 43 rd axis and the 46 th axis, the existing river region 1 between the 38 th axis and the 43 rd axis, and the other regions 3 of the existing river 10 are not contained between the 30 th axis and the 38 th axis and between the 46 th axis and the 56 th axis. Between the main foundation pit section 100 and the sub foundation pit section 200, and between the respective areas in the main foundation pit section 100, blocking walls 20 for partitioning are provided, the blocking walls 20 being provided at positions of 30 axis, 38 axis, 43 axis and 46 axis, respectively. And before the plugging wall 20 is applied, triaxial stirring piles 32 are also adopted on the inner side and the outer side of the groove of the plugging wall 20 to reinforce the groove wall of the groove, so that the wall forming quality of the plugging wall 20 and the joint water stopping effect are improved.

S2, constructing the diaphragm wall 30.

Based on the segmentation and partition of the foundation pit, the construction sequence of the diaphragm wall 30 is as follows: firstly, constructing the underground diaphragm wall 30 of the planned aqueduct region 2 in the main foundation pit section 100, then constructing the underground diaphragm wall 30 of other regions 3 in the main foundation pit section 100 and the auxiliary foundation pit section 200, and finally, after the river channel in the river 11 in the lotus is changed into the temporary aqueduct 40 to be filled with water, constructing the underground diaphragm wall 30 in the existing river channel region 1.

As can be seen from fig. 3, the construction fence 21 is provided on the outer side of the foundation pit diaphragm wall 30 due to the ultra-soft soil layer of the foundation pit at the existing river region 1, and the wall of the trench 31 of the diaphragm wall 30 is easily collapsed when the diaphragm wall 30 is constructed. Therefore, the wall reinforcement mode of the combination according to the depth is needed to be carried out by adopting the triaxial mixing piles 32 with different cement doping amounts before the construction of the underground diaphragm wall 30 in the existing river region 1.

As shown in fig. 6 (a) and 6 (B), the grooving process of the diaphragm wall 30 is shown, wherein fig. 6 (a) is a cross-sectional view of A-A in fig. 6 (B), and fig. 6 (B) is a cross-sectional view of B-B in fig. 6 (a). Specifically, during construction of an area with depth less than 3m, pseudo-ginseng ash soil is backfilled and compacted step by step on soil body with the groove bottom width of 1.5m of the groove 31 of the diaphragm wall 30 to form an ash soil backfill layer, 1:1 slope is excavated to original soil, and then the groove wall of the diaphragm wall 30 is constructed. For the construction of the region with the depth of more than 3m and less than 18m, a JB180 type walking full hydraulic pile machine with ultra-deep reinforcement capability is adopted on two sides of the groove wall of the diaphragm wall 30 to respectively construct a row of triaxial cement stirring piles 32 with diameter phi 700mm, adjacent horizontal center-to-center spacing 500mm (abbreviated as phi 700@500 shown in fig. 6 (a) and (b) and with 10% of the total cement mixing amount, so as to reinforce the groove wall. And when the construction is performed for the area larger than 18m and smaller than 38m, a row of triaxial mixing piles 32 with diameter phi 700mm and adjacent horizontal center-to-center spacing 500mm, the full-section cement mixing amount of which is 20%, are adopted on two sides of the groove wall of the diaphragm wall 30 to reinforce the groove wall. So as to prevent the groove wall from collapsing and improve the wall forming quality of the diaphragm wall 30 and the joint water stopping effect.

S3, draining the existing river channel 10.

And constructing a temporary aqueduct 40, a temporary box culvert 50 and a temporary open channel 60 which span the foundation pit in sequence. As shown in fig. 3, the original water flow direction of the water in the lotus flower middle river 11 as the existing river 10 is shown by the solid arrow in fig. 3, and the water flows from the source of the vehicle inclined river 11 through the lotus flower middle river 11. The foundation pit is placed through the width of the lotus flower middle river 11, that is, the main foundation pit section 100 is arranged across the width of the lotus flower middle river 11, so before the foundation pit is applied as the underground diaphragm wall 30 on the planned aqueduct area 2, the water flow in the lotus flower middle river 11 needs to be introduced into the temporary aqueduct 40 from the oblique vehicle river 12 at the east of the main foundation pit section 100 through the temporary box culvert 50, and then is transferred into the lotus flower middle river 11 at the west of the main foundation pit section 100 through the temporary open channel 60, and the water flow is changed as shown by the dotted arrow in fig. 3, thereby ensuring that the water flow in the lotus flower middle river 11 is not interrupted in the track station building process.

The temporary aqueduct 40 is built by firstly using the slope ratio of 1:1.5, a foundation pit of a planned aqueduct area 2 is excavated by slope laying, drainage ditches are arranged at positions 1m away from two sides of the bottom edge of the temporary open channel 60, drainage slopes are outwards arranged at the periphery of the top edge of the foundation pit, and intercepting ditches are arranged at proper distances. And (3) reinforcing the side slope by adopting an HRB400 reinforced anchor rod with the diameter of 20mm and C25 cast-in-place concrete, mechanically crushing the pile head of the bridge pile of the existing bridge of the lotus middle river 11 by using a crusher after the foundation pit is excavated to the bottom of the groove 31, and casting and forming the same side wall in the bottom plate 411 of the aqueduct 41 by the main reinforcement anchor of the diaphragm wall 30, as shown in fig. 4. The bottom of the aqueduct 41 is provided with 8 lattice columns 47, the lattice columns 47 are formed by combining and welding angle steel and steel plates together, namely four angle steel side length x side thickness are 180mm x 18mm to form a column body of the lattice column 47 with the cross section of 450 x 450mm, the top of the column body is welded with a steel plate with the thickness of 20mm and the length x width of 700mm x 600mm, stiffening plates are arranged around the joint of the column body formed by the angle steel and the steel plate and are stably connected, and HRB400 steel bars with the diameter of 20mm and the length of 500mm are arranged through nail penetration welding and anchored on longitudinal beams 45 of the aqueduct 41; the lattice column 47 is used as an auxiliary load-bearing structure, and the specific position distribution is shown in fig. 5 and 7.

As shown in fig. 4 to 5 and 7, in the process of constructing the temporary aqueduct 40, the two ends of the aqueduct 41 are respectively provided with the diaphragm walls 30, the bottom of the inner side of the aqueduct 41 is provided with the longitudinal beams 45 arranged along the length direction thereof, the top of the aqueduct 41 is provided with the connecting beams 43 which span the width thereof, the end part of the aqueduct 41 is provided with the two crown beams 42, the outer side wall of the aqueduct 41 is provided with the concrete support which is used as the first support 46 along the length direction thereof for connecting the crown beams 42 at the two ends, the outer wall surface of the aqueduct 41 is surrounded with the cross beams 44, the lattice columns 47 are propped against the bottom of the aqueduct 41 for supporting, and meanwhile, a row of steel supports which are used as the second support 48 and the steel supports which are used as the third support 49 are sequentially arranged from top to bottom between the diaphragm walls 30 at the two sides and below the aqueduct 41. A concrete cushion layer is further arranged below the bottom plate 411 of the aqueduct 41, and a cover plate 410 is further arranged between the adjacent connecting beams 43. The temporary aqueduct 40 is divided into three steps of a bottom plate, side walls and an anti-collision guardrail, and is subjected to formwork supporting installation and pouring construction. The concrete cushion layer is a common leveling layer in foundation pit engineering, and also plays a role in hardening the working surface of the foundation pit, the strength of the concrete is not high, and the thickness of the concrete cushion layer is generally about 10-20cm. Before pouring concrete, a layer of concrete interfacial agent should be uniformly coated on the surface of the settlement joint 412 as shown in fig. 4, and a water stop steel plate should be disposed along the vertical direction of the settlement joint 412.

Constructing a temporary box culvert 50, excavating a groove for placing the box culvert, and erecting a template for placing the box culvert in the groove of the box culvert; a concrete cushion layer is poured in the groove for placing the box culvert, and the construction of the cushion layer formed by concrete pouring can be carried out together with the construction of the temporary aqueduct 40. After the strength of the concrete cushion layer in the groove of the box culvert reaches the design requirement, the mould is disassembled, and the two sides of the temporary box culvert 50 are backfilled with the lime soil.

After the construction of the temporary open channel 60, the temporary aqueduct 40 and the temporary box culvert 50 is finished, the temporary open channel 60 is excavated, so that the temporary open channel 60 is communicated with the lotus middle river 11 and the temporary aqueduct 40.

The drainage is changed, the water flow in the lotus flower middle river 11 is led into the temporary aqueduct 40 from the oblique river 12 at the east of the foundation pit through the temporary box culvert 50, and then is changed into the lotus flower middle river 11 at the west of the main foundation pit section 100 through the temporary open channel 60, and the changed water flow is shown by a dotted arrow in fig. 3, so that the water flow in the lotus flower middle river 11 can be ensured to be continuous in the track station building process. The river of the lotus flower middle river 11 in the existing river channel 10 is changed, namely, the river is moved into the temporary box culvert 50, the temporary aqueduct 40 and the temporary open channel 60 from the vehicle inclined river 12 and then is led into the lotus flower middle river 11, so that the vehicle inclined river 12 and the lotus flower middle river 11 are kept continuous in the construction process.

S4, plugging the lotus flower middle river 11 and dismantling the bridge on the lotus flower middle river 11.

After the water flow in the lotus flower middle river 11 is changed to the temporary aqueduct 40 to keep the river water smooth, an IV-type Lasen steel sheet pile with the length of 12m is adopted to block the eastern side of the lotus flower middle river 11, a water collecting pit is constructed to drain the clear water in the lotus flower middle river 11, a sewage pump with a bracket and a chain with an adjustable height is arranged to drain the sewage in the existing river channel area 1, and the sewage is deposited by a field sedimentation tank and then is discharged into a sewage pipe network. The mud in the river bottom is cleaned by an excavator before filling the river, and then the river channel in the lotus flower river 11 in the existing river channel area 1 is filled with clay.

When the river bridge is dismantled, the excavator with the hydraulic crushing pliers is firstly adopted to directly pull out and transport the railing, then the excavator is used for dismantling the plate girder opening by the vibration gun hammer, the hydraulic pliers are used for dismantling the bridge along the girder length direction by adopting a girder-by-girder small block crushing method, and finally, the excavator with the vibration gun hammer is respectively arranged at the bridge abutment of the north and south to break the rest of the bridge caps. And then the bearing platform is broken, the bearing platform is pulled out along with the pile foundation and broken by blocks, and after the prefabricated bridge pile is pulled out by adopting a pile pulling machine of 450 Lasen steel sheet piles, the bridge pile holes are backfilled in time after the bridge pile is pulled out, and backfill materials in the bridge pile holes are tamped. In the process of removing all pile foundations, firstly, excavating about 2m of pile top part, crushing an upper pile body, then loosening soil around the pile by using special section steel by a pile remover, clamping reinforcing steel bars at the broken pile by a pile clamp, vibrating and removing the pile, and collecting the residual pile body together with the rest concrete fragments and then transporting the residual pile body outwards for disposal. And backfilling the earthwork of the foundation pit by adopting 6% of gray soil, compacting in a layered manner, and backfilling to the height of the top surface of the bearing platform.

After the original bridge in the lotus flower middle river 11 is dismantled, the diaphragm wall 30 of the foundation pit in the range of the existing river channel region 1 is constructed, and the construction of the diaphragm wall 30 on the range of other foundation pits can be carried out simultaneously with the process of transferring the river channel of the lotus flower middle river 11 into the temporary aqueduct 40, and the diaphragm walls are mutually connected.

S5, excavating a foundation pit.

And dividing the total of the main foundation pit section 100 and the secondary foundation pit section 200 into a plurality of segments according to the length of each segment being 20-30m, and excavating the foundation pit. The crown beam 42 and the first support 46 of the whole foundation pit to be excavated are applied on site, and the first support 46 is a concrete support column and is the same as the first support 46 in the temporary aqueduct 40. When the foundation pit is excavated by the foundation pit connecting wall 30, the crown beams 42 on the foundation pit and the first support 46 on the foundation pit to meet the design strength requirement, the foundation pit of other sections far away from the temporary aqueduct 40 in the main foundation pit section 100 and the secondary foundation pit section 200 is excavated by adopting a sectional layered construction mode, the layered thickness is 3m, and after the excavation of each sectional foundation pit is completed, the support is erected in time and the prestress is applied. The three-channel steel support supporting structure adopted by the whole foundation pit construction is the same as the supporting structure of a first channel support 46, a second channel support 48 and a third channel support 49 in the temporary aqueduct 40, and according to the site construction conditions, the first channel support 46 and the third channel support 49 in the foundation pit construction are all steel supports with the outer diameter of 800mm and the wall thickness of 20 mm; the second support 48 is a steel support with an outer diameter of 609mm and a wall thickness of 16 mm. Finally, constructing the foundation pit within the range of the aqueduct area 2, and adopting sectional construction, wherein the deformation of the structure of the aqueduct 41 and the foundation pit support structure is monitored in the sectional construction process.

S6, constructing a station main body structure.

According to the foundation pit excavation method of the open cut forward method, when the foundation pit in each section is excavated and constructed to the pit bottom, main structures of the station, such as a cushion layer, a bottom plate, upper/lower side walls, a top plate, backfill of the top plate and the like of the station are sequentially applied from bottom to top; and sequentially removing the support systems according to the construction sequence, and after the main structures at the two sides of the blocking wall 20 are capped, chiseling the blocking wall 20 in sections.

S7, dredging lotus flower river 11.

After the foundation pit main structure at the position of the original lotus middle river 11 is capped, a lotus middle river 11 river channel and a bridge are built on a station Fang Fu, and the river channel in the temporary aqueduct 40 is changed back to the lotus middle river 11, namely, the water flow in the oblique river 12 directly flows into the lotus middle river 11, as shown by the solid line direction of the water flow in fig. 3, after the river channel of the lotus middle river 11 is unblocked, the temporary aqueduct 40, the temporary box culvert 50 and other temporary structures are removed.

In the construction process, different positions in the aqueduct area 2 to be constructed are also monitored, namely a ground surface monitoring point a, a diaphragm wall monitoring point b and an aqueduct bottom plate monitoring point c, and the arrangement positions are shown in figure 3. The early warning values of the ground surface settlement, the diaphragm wall offset and the aqueduct bottom plate settlement are respectively 30mm, 35mm and 30mm, and according to the on-site monitoring result, the change curves of the maximum displacement of each monitoring item along with the excavation depth are shown in fig. 8, three groups of curves are obtained, namely the ground surface maximum settlement monitored by a ground surface monitoring point a, the diaphragm wall maximum offset in the foundation pit monitored by a diaphragm wall monitoring point b and the aqueduct maximum settlement monitored by an aqueduct bottom plate monitoring point c. As can be seen from fig. 8, the maximum deformation of the three monitoring projects does not exceed the early warning value after each excavation is finished, and is within the control range, which means that the foundation pit is in a safe and stable state from excavation to finishing, and further indicates the feasibility of the proposal of the disclosure.

It will be appreciated by those skilled in the art that the above-described embodiments are merely for clarity of illustration of the disclosure, and are not intended to limit the scope of the disclosure. Other variations or modifications will be apparent to persons skilled in the art from the foregoing disclosure, and such variations or modifications are intended to be within the scope of the present disclosure.

Claims

1. The construction method for the subway to pass through the river channel is characterized by comprising the following steps:

restoring the existing river channel, restoring the bridge of the existing river channel, restoring the through flow of the existing river channel, and removing the temporary aqueduct;

The planned aqueduct region in the main foundation pit section is arranged at the other side of the existing river channel far from other regions and is positioned at a position which is 2-3 times away from the width of the existing river channel;

the blocking wall between the existing river channel region and other regions is applied at a position which is 2-3 times away from the width of the existing river channel;

plugging the existing river and dismantling the existing river bridge and then constructing the underground diaphragm wall of the existing river area, comprising the following steps:

2. The construction method for the subway to pass through the river course according to claim 1, wherein before constructing the plugging wall between the planned aqueduct area and the existing river course area, the inner side and the outer side of the plugging wall at the position are further reinforced by adopting triaxial stirring piles;

3. The method for constructing a subway crossing river according to any one of claims 1 to 2, wherein the drainage of the existing river comprises:

4. A method of constructing a subway crossing river according to any one of claims 1 to 3 wherein construction of the diaphragm wall of the secondary and primary foundation pit sections and other areas in the primary foundation pit section is synchronized with drainage construction of the existing river;

5. The method for constructing a subway tunnel according to any one of claims 1 to 4, wherein the steps of plugging an existing tunnel and removing an existing tunnel bridge include:

6. A construction method for crossing a river channel in a subway according to any one of claims 1 to 5 wherein excavation of a foundation pit is performed before the construction of a station main structure,

7. The method for constructing a subway tunnel according to any one of claims 1 to 6, wherein all foundation pits are constructed by adopting an open excavation method, and after the foundation pit is excavated, concrete cushion layers, bottom plates, side walls, top plates and top plates of the upper/lower parts of the underground station are sequentially constructed from bottom to top and backfilled, and then corresponding support systems are sequentially removed according to the construction sequence.

8. The construction method for a subway passing through a river according to any one of claims 1 to 7, wherein after the construction of the main structure of the foundation pit in the existing river area is finished, the existing river and the bridge thereof are restored, the river water in the temporary aqueduct is changed back to the existing river, and the structures of the temporary aqueduct and the temporary box culvert are removed after the river is unblocked.