CN113338953A - Construction method for extra-large section tunnel with turnout line led out from railway tunnel - Google Patents
Construction method for extra-large section tunnel with turnout line led out from railway tunnel Download PDFInfo
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- 238000010276 construction Methods 0.000 title claims abstract description 73
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 111
- 239000010959 steel Substances 0.000 claims abstract description 111
- 238000009412 basement excavation Methods 0.000 claims abstract description 92
- 238000000034 method Methods 0.000 claims abstract description 76
- 239000011435 rock Substances 0.000 claims abstract description 47
- 238000005192 partition Methods 0.000 claims abstract description 35
- 238000005422 blasting Methods 0.000 claims description 18
- 230000003014 reinforcing effect Effects 0.000 claims description 16
- 238000005507 spraying Methods 0.000 claims description 6
- 238000005553 drilling Methods 0.000 claims description 5
- 238000005516 engineering process Methods 0.000 claims description 4
- 230000002787 reinforcement Effects 0.000 claims description 3
- 230000007547 defect Effects 0.000 abstract description 6
- 101150054854 POU1F1 gene Proteins 0.000 description 6
- 238000012544 monitoring process Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 2
- 102200157180 rs7997 Human genes 0.000 description 2
- 239000002689 soil Substances 0.000 description 2
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 239000004746 geotextile Substances 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/04—Lining with building materials
- E21D11/10—Lining with building materials with concrete cast in situ; Shuttering also lost shutterings, e.g. made of blocks, of metal plates or other equipment adapted therefor
- E21D11/105—Transport or application of concrete specially adapted for the lining of tunnels or galleries ; Backfilling the space between main building element and the surrounding rock, e.g. with concrete
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/14—Lining predominantly with metal
- E21D11/18—Arch members ; Network made of arch members ; Ring elements; Polygon elements; Polygon elements inside arches
- E21D11/183—Supporting means for arch members, not provided for in E21D11/22
Abstract
The invention discloses a construction method of a tunnel with an extra-large cross section for leading out a turnout line in a railway tunnel, which comprises the following steps: firstly, constructing an auxiliary excavation section of a cavity with an extra-large section; secondly, expanding and digging an auxiliary digging section; thirdly, grouting the medium pipe shed; fourthly, excavating a cavity with an extra-large section. The construction method is flexible and variable, high in applicability and high in construction speed, and by combining the characteristic of good surrounding rock lithology of the construction method, a simple middle partition wall method and two large-diameter steel pipe temporary vertical braces are adopted on the upper half section of the super-large section cavern, and the step method is adopted on the lower half section to excavate, so that large-section shallow-buried and soft rock construction methods such as double side walls and the like are replaced, the steel arch frames can be smoothly connected from the vault to two ends, the stress structure is stable, enough operation space can be provided for large construction operation equipment, the defects of difficulty in unfolding of large equipment, low construction speed and high safety risk in large-section shallow-buried and soft rock tunnel excavation construction methods such as double side walls and the like are overcome, and the application range of the tunnel step method excavation method is expanded.
Description
Technical Field
The invention belongs to the technical field of tunnel engineering construction, and particularly relates to a construction method for a tunnel with an extra-large cross section by leading out a turnout line in a railway tunnel.
Background
With the large-scale construction of high-speed railways and highways in China, the number of large-span tunnels is increasing. In some areas, such as Chongqing mountain city, the construction of tunnels is influenced by terrain conditions, so that station yards or turnouts have to be arranged in the tunnels to form stations or lead out turnout tunnels, and the cross-section span of the tunnels is increased sharply.
The construction technology of the super-large section tunnel at home and abroad is mature day by day, the excavation method mainly comprises a cross middle partition (CRD) method, a double-side-wall pit guiding method (a spectacle method), a middle tunnel method, a hole pile method and the like, and the construction method mainly aims at the shallow buried underground excavation station and the super-large section tunnel with poor geological conditions.
The main line of the Chongqing east railway is connected with a Chongqing east station, two large spans are arranged in a tunnel of a woodman terrace, and left and right connecting lines of the Chongqing east station are led out respectively, wherein the starting and ending mileage of the large span of the right connecting line is DK43+ 150-DK 43+304, and the length is 154 m; the long span beginning-to-end mileage of the left tie line is DK43+ 400-DK 43+584, and the length is 184 m; the total length of the two sections is 338 m. Take the large span of the right tie line as an example: the full length of the large span is 154m, the left side of the position DK43+150 is unchanged, the right side of the position DK43+150 is straightly bent, and the section of the tunnel is suddenly changed from a standard section of 15.12m multiplied by 13.61m to a large section of 19.77m multiplied by 14.33 m; the tunnel section at the DK43+257 is suddenly changed from a large section of 19.77m multiplied by 14.33m to an extra large section of 24.53m multiplied by 16.2 m. Based on the deeply-buried extra-large section tunnel with good surrounding rock lithology and integral rock stratum, the excavation method is not strong in pertinence, and further research and discussion on a new construction method are needed.
Disclosure of Invention
The invention aims to solve the technical problem of providing a construction method of a tunnel with an extra-large cross section for leading out a turnout line in a railway tunnel aiming at the defects in the prior art, the construction is flexible and changeable, the applicability is strong, the construction speed is high, by combining the characteristic of good lithology of surrounding rocks, the upper half section of the cavern with the extra-large section adopts a simple middle partition wall method and two temporary vertical braces with large-diameter steel pipes, the lower half section adopts a step method for excavation to replace large-section shallow-buried and soft rock construction methods such as double side walls and the like, so that the steel arch centering can be smoothly connected from the vault to the two ends, the stress structure is stable, the method can provide enough operation space for large-scale construction operation equipment, overcomes the defects of the double-side-wall and other large-section shallow-buried soft rock tunnel excavation methods that large-scale equipment is difficult to unfold, the construction speed is low and the safety risk is high, and expands the application range of the tunnel 'step method' excavation method.
In order to solve the technical problems, the invention adopts the technical scheme that: a construction method of a tunnel with an extra-large section and leading out a branch line in a railway tunnel is characterized in that the excavation width of a cavity with the extra-large section of a constructed tunnel is 20-26 m, the excavation height of the cavity with the extra-large section is 15-17 m, the constructed tunnel is a deep-buried anhydrous tunnel with the buried depth of 164-253 m, and the surrounding rock grade of the cavity in the constructed tunnel is grade III or grade IV;
the method comprises the following steps:
step one, constructing an auxiliary excavation section of a cavity with an extra-large section: continuously excavating 5 m-10 m forwards from the excavated large-section cavern to form an auxiliary excavation section for constructing the large-section cavern;
step two, expanding and digging an auxiliary digging section: according to the construction drawing of the cavern with the extra-large section, the auxiliary excavation section is directly turned upwards and rightwards along the inner wall of the auxiliary excavation section to perform expanding excavation so as to complete expanding excavation of the auxiliary excavation section and form a primary cavern with the extra-large section;
grouting the medium pipe shed: installing a plurality of middle pipe sheds along the tunnel face of the primary super-large section cavern towards the tunnel excavation direction by using a pipe shed drilling machine, and grouting and reinforcing through the middle pipe sheds;
step four, excavating a cavity with an extra-large section, wherein the process is as follows:
step 401, excavating the left side of the tunnel face of the primary super-large section cavern by adopting a middle partition wall method to form an upper half section advanced pilot tunnel, and synchronously supporting the excavated part on which steel arch frame segments and middle partition wall steel frames are erected in time;
step 402, when the excavation length of the upper half section leading pit reaches 15 m-20 m, blasting excavation on the right side of the upper half section of the extra-large section cavern is carried out by adopting a two-step method based on a smooth blasting technology, supporting the excavated part in time by erecting a steel arch section, and spraying concrete to the erected steel arch section; the method comprises the following steps that (1) with continuous excavation of the right side of the upper half section of a cavern with an extra-large section, vertical supports are timely arranged in the upper half section of the cavern with the extra-large section excavated on the two sides of a middle partition steel frame, and arch tops of the cavern with the extra-large section are supported in a manner of separating trusses;
403, when the excavation length of the lower step on the right side of the upper half section of the cavity with the extra-large section reaches 3-5 m, adopting a step method to excavate the lower half section of the cavity with the extra-large section step by step, erecting steel arch frame segments on the excavated part in time to form a ring in a sealed mode, spraying concrete on the erected steel arch frame segments, filling an inverted arch and the inverted arch following construction, and constructing secondary lining of the arch wall in time; when the lower half section of the cavern with the extra-large section is excavated to the positions of the middle partition steel frame and the vertical supports, grouting and reinforcing the arch crown of the section of the tunnel where the middle partition steel frame and the vertical supports are located by using the small guide pipes, dismantling the middle partition steel frame and the vertical supports, and continuing to excavate forwards.
The construction method for the extra-large section tunnel with the turnout line led out from the railway tunnel is characterized by comprising the following steps: in the third step, when the middle pipe sheds are adopted for grouting the hole body with the extra-large section, the plurality of middle pipe sheds are arranged at equal intervals along the annular direction of the hole body with the extra-large section, the length of each middle pipe shed is not less than 25m, and the annular interval between every two adjacent middle pipe sheds is 0.3-0.5 m.
The construction method for the extra-large section tunnel with the turnout line led out from the railway tunnel is characterized by comprising the following steps: in step 401, when the middle partition wall method is adopted to excavate the upper half section pilot tunnel of the front left side super large section cavern, only the temporary middle partition wall is arranged, the temporary inverted arch is not arranged, and the temporary middle partition wall in the upper half section pilot tunnel is supported by steel pipes at intervals.
The construction method for the extra-large section tunnel with the turnout line led out from the railway tunnel is characterized by comprising the following steps: in step 402, when blasting excavation is performed on the right side of the upper half section of the super large section cavern, the blasting excavation is far away from the middle bulkhead steel frame, loosening blasting is adopted at the middle bulkhead steel frame, and manual auxiliary mechanical excavation is performed.
The construction method for the extra-large section tunnel with the turnout line led out from the railway tunnel is characterized by comprising the following steps: in step 403, when the step method is adopted to carry out excavation on the lower half section of the super-large section cavern in a layered manner step by step, firstly, excavating the inverted trapezoidal lateral rock masses on the two sides of the lower half section of the super-large section cavern in a staggered manner by adopting a two-step method by depending on the vertical supports on the two sides of the middle partition steel frame;
excavating a middle step rock mass between the two side rock masses after the side rock masses are excavated and supported for 3-5 m; when the middle step rock mass is excavated to the position of the middle bulkhead steel frame, the middle bulkhead steel frame is firstly dismantled, and then the middle step rock mass is continuously excavated forwards.
The construction method for the extra-large section tunnel with the turnout line led out from the railway tunnel is characterized by comprising the following steps: in step 403, reinforcing circumferential steel arches by using longitudinal reinforcing rods, wherein a plurality of longitudinal reinforcing rods are arranged between every two adjacent steel arches;
the steel arch is formed by splicing a plurality of steel arch splicing sections, two adjacent steel arch splicing sections are fixedly connected through a connecting plate, and the number of longitudinal reinforcing rods connected between every two adjacent steel arches is equal to that of the steel arch splicing sections in the steel arch.
Compared with the prior art, the invention has the following advantages:
1. according to the invention, the advanced pilot tunnel is excavated on the upper half section of the cavity with the extra-large section, then the upper half section of the cavity with the extra-large section is excavated firstly based on the advanced pilot tunnel by adopting a step method, and then the lower half section of the cavity with the extra-large section is excavated, so that the steel arch frames can be smoothly connected from the arch crown to the two ends, and the stress structure is stable; the hidden danger of safety quality that the two side walls of the steel arch centering of the double-side wall method are firstly arranged and then the arch crown is arranged, the steel arch centering is difficult to be smoothly connected into a whole, and the stress structure is unstable is overcome.
2. The step excavation construction method is adopted for the upper half section and the lower half section of the cavity with the extra-large section, so that the excavation construction of the cavity with the extra-large section is flexible and changeable, the applicability is strong, enough operation space can be provided for large construction operation equipment, and the construction speed is high; the method overcomes the defects that large equipment is difficult to unfold, the construction speed is low and the safety risk is high in a double-side-wall equal large-section shallow-buried soft rock tunnel excavation method.
3. The invention adopts a simple middle partition wall method and two large-diameter steel pipe temporary vertical braces on the upper half section of the extra-large section cavern, and adopts a step method to excavate the lower half section, thereby replacing the large-section shallow-buried and soft rock construction method with double side walls and the like, and expanding the application range of the tunnel step method excavation method.
In conclusion, the construction is flexible and variable, the applicability is strong, the construction speed is high, and by combining the characteristic of good lithology of surrounding rocks, a simple middle partition wall method and two large-diameter steel pipe temporary vertical braces are adopted on the upper half section of a cavity with an extra-large section, and the step method is adopted on the lower half section to replace large-section shallow-buried and soft rock construction methods such as double side walls and the like, so that the steel arch frames can be smoothly connected from the arch top to two ends, the stress structure is stable, enough operation space can be provided for large construction operation equipment, the defects of the large-section shallow-buried and soft rock tunnel excavation methods such as the double side walls and the like are overcome, large equipment is difficult to unfold, the construction speed is low, the safety risk is high, and the application range of the tunnel step method excavation method is expanded.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a block flow diagram of the present invention.
Fig. 2 is a schematic construction plan view of the present invention.
Fig. 3 is a schematic cross-sectional view of the construction of the present invention.
Description of reference numerals:
1, leading a pit on the upper half section in advance; 2-middle bulkhead steel frame; 3, vertical supporting;
4-lateral rock mass; 5-middle step rock mass; 6-large-section cavern;
7-a cavity with super-large section.
Detailed Description
A construction method of a tunnel with an extra-large section and leading out a branch line in a railway tunnel is disclosed, as shown in figures 1 to 3, the excavation width of a chamber 7 with the extra-large section of a constructed tunnel is 24.53m, the excavation height of the chamber 7 with the extra-large section is 16.2m, the constructed tunnel is a deep-buried anhydrous tunnel with the buried depth of 164 m-253 m, and the surrounding rock level of the chamber in the constructed tunnel is III level or IV level;
the method comprises the following steps:
step one, constructing an auxiliary excavation section of a cavity with an extra-large section: continuously excavating 5 m-10 m forwards from the large-section cavern 6 which is already excavated and formed to form an auxiliary excavation section for constructing the large-section cavern;
during specific implementation, the section size of the auxiliary excavation section is the same as that of the large-section cavern 6, before the excavation of the extra-large-section cavern 7 is carried out, firstly, 5 m-10 m of the large-section cavern 6 which is already excavated and formed is continuously excavated forwards to serve as the auxiliary excavation section for the construction of the extra-large-section cavern 7, a certain working space can be provided for the expanding excavation of the extra-large-section cavern 7, and the excavation efficiency and the construction effect of the extra-large-section cavern 7 can be effectively improved.
Step two, expanding and digging an auxiliary digging section: according to the construction drawing of the cavern 7 with the extra-large section, the auxiliary excavation section is directly turned upwards and rightwards along the inner wall of the auxiliary excavation section to perform expanding excavation so as to form a primary cavern with the extra-large section;
in specific implementation, because the tunnel face rock stratum is complete, at the dividing point DK43+257 of the large-section cavern 6 and the extra-large-section cavern 7, firstly, the large-section cavern with the length of 19.77m multiplied by 14.33m is excavated continuously for 5m to 10m, then, the tunnel is directly excavated rightwards and upwards according to design requirements, and the extra-large section with the height mutation of 24.53m multiplied by 16.2m is widened and heightened.
Grouting the medium pipe shed: drilling holes on the body of the primary super-large section cavern 7 along the palm surface of the primary super-large section cavern by using a pipe shed drilling machine, installing a plurality of middle pipe sheds, and grouting and reinforcing the body of the super-large section cavern 7 through the middle pipe sheds;
in specific implementation, 13m is extended behind a starting point DK43+257 of a super-large section cavern 7, DK43+ 270-290 long 20m is used as an assembly trolley section, 5m extends to the front of a palm surface, 13 medium pipe sheds are arranged in total, the circumferential distance between every two adjacent medium pipe sheds is 0.4m, 1 medium pipe shed is arranged at the center line of a vault with a width of 24.53m, and 6 medium pipe sheds are arranged on two sides of the center line of the vault respectively; the middle pipe shed can be a T76S middle pipe shed with the length of 25m, or two T76S middle pipe sheds with the length of 15m are overlapped for 5m to form the middle pipe shed, and the grouting pressure of the middle pipe shed is 1 MPa-2 MPa.
When the tunnel arch wall secondary lining trolley is actually used, the tunnel body of the tunnel 7 with the extra-large section is grouted and reinforced through the middle pipe shed, soil of the tunnel 7 with the extra-large section can be effectively solidified, a simple gantry crane hook is conveniently installed at the arch part of the tunnel, and the tunnel arch wall secondary lining trolley with the extra-large section of 24.53m multiplied by 16.2m is assembled.
During specific implementation, when the middle pipe shed is installed, a hole isolation construction method is adopted, so that the construction efficiency can be improved, meanwhile, the disturbance of a pipe shed drilling machine to the hole body of the hole chamber 7 with the super-large section can be reduced, and the construction safety is ensured.
Step four, excavating a cavity with an extra-large section, wherein the process is as follows:
step 401, excavating the left side of the tunnel face of the preliminary extra-large section cavern by adopting a middle partition wall method from the preliminary extra-large section cavern formed by the expanded auxiliary excavation section to form an upper half section pilot tunnel 1, and synchronously supporting the excavated part on which a steel arch truss segment and a middle partition wall steel frame 2 are erected in time;
in specific implementation, the section width of the upper half section leading pit 1 is 10.5m, and the section height of the upper half section leading pit 1 is 7.61 m; firstly, a leading pit 1 with a smaller section size is excavated, and can be supported by most of unearthed soil in the super-large section cavern 7, so that the construction safety of the super-large section cavern 7 in the excavation process can be ensured.
It should be noted that the steel arch segments and the middle bulkhead steel frame 2 are both made of i 25b steel, in order to ensure the connection quality of the steel arch joints at the top of the first pilot pit 1 and the subsequent pilot pit arch, the annular i 25b steel arch is required to be connected with the gusset plates, the distance between the gusset plates and the vertical middle bulkhead steel arch is not less than 20cm, and the annular connecting joints and the gusset plates are wrapped by geotextile or other braided fabrics.
Step 402, when the excavation length of the upper half section leading pit 1 reaches 15 m-20 m, blasting excavation on the right side of the upper half section of the extra-large section cavern is carried out by adopting a two-step method based on a smooth blasting technology, supporting the excavated part in time by erecting a steel arch section, and spraying concrete to the erected steel arch section;
with continuous excavation of the right side of the upper half section of the cavern with the extra-large section, vertical supports 3 are timely arranged in the upper half section of the cavern with the extra-large section excavated on the two sides of the middle partition steel frame 2, and the arch crown of the steel arch frame of the cavern with the extra-large section is supported at a roof truss; namely, two vertical supports 3 are supported at the bottom of every other steel arch;
in practical use, in order to avoid tunnel collapse caused by insufficient supporting strength of the middle partition steel frame 2, in the excavation process of the super-large section cavern, every interval is 10m, a section is selected to distribute settlement monitoring points, 5 settlement monitoring points are uniformly distributed in each section, one settlement monitoring point is distributed at the vault of the super-large section cavern, two settlement monitoring points are distributed on two sides respectively, according to monitoring measurement data of the settlement monitoring points, once settlement is found, and the settlement amount is not more than 27mm, two rows of large-diameter steel pipe vertical supports 3 supported in the upper half section of the super-large section cavern 7 are strengthened in time, and construction safety is guaranteed.
During the concrete implementation, vertical braces 3 adopt phi 426 steel pipe to support, strengthen vertical braces 3 with phi 609 steel pipe when subsiding, and the bottom of vertical braces 3 is provided with the bottom plate, can effectively increase the area of contact between vertical braces 3 and the lower half section top of super large section cavern 7, and then guarantees that vertical braces 3 supports firmly, prevents that vertical braces 3 atress is too big, and middle step rock mass from taking place to sink, and then leads to the roof of super large section cavern 7 to produce and cave in.
It should be noted that, when the excavation on the right side of the upper half section of the cavity with the extra-large section is started, the excavation of the first pilot pit 1 of the upper half section is not stopped, and the excavation is continued, so that the two processes are not interfered with each other.
403, when the excavation length of the lower step on the right side of the upper half section of the cavity with the extra-large section reaches 3-5 m, adopting a step method to excavate the lower half section of the cavity with the extra-large section step by step, erecting steel arch frame segments on the excavated part in time to form a ring in a sealed mode, spraying concrete on the erected steel arch frame segments, filling an inverted arch and the inverted arch following construction, and constructing secondary lining of the arch wall in time; along with excavation of the lower half section of the cavity with the extra-large section, when the lower half section of the cavity with the extra-large section is excavated to the positions of the middle partition steel frame 2 and the vertical supports 3, grouting reinforcement is firstly carried out on the arch tops of the tunnel sections where the middle partition steel frame 2 and the vertical supports 3 are located by adopting small guide pipes, then the middle partition steel frame 2 and the vertical supports 3 are dismantled, and excavation is continued forwards.
During concrete implementation, the detached middle partition wall steel frame 2 and the detached vertical supports 3 can be timely moved to the front end to be continuously used, the middle partition wall steel frame 2 and the vertical supports 3 can be detached at any time, and the utilization rate of materials is improved.
In the embodiment, the vault of the cavern with the extra-large section is reinforced by grouting through the small guide pipe, so that the vault of the cavern with the extra-large section can be integrally solidified after the middle bulkhead steel frame 2 and the vertical supports 3 are removed, and can be effectively supported through the steel arch frame which is erected into a ring, and the vault of the cavern with the extra-large section is prevented from being partially collapsed.
When the method is used in practice, the step excavation construction method is adopted for the upper half section and the lower half section of the cavity with the extra-large section, so that the excavation construction of the cavity with the extra-large section is flexible and changeable, the applicability is strong, enough operation space can be provided for large construction operation equipment, and the construction speed is high; the method overcomes the defects that large equipment is difficult to unfold, the construction speed is low and the safety risk is high in a double-side-wall equal large-section shallow-buried soft rock tunnel excavation method.
In the third step, when the middle pipe sheds are used for grouting the hole body with the extra-large cross section, the middle pipe sheds are arranged at equal intervals along the annular direction of the hole body with the extra-large cross section, the length of each middle pipe shed is not less than 25m, and the annular interval between every two adjacent middle pipe sheds is 0.3-0.5 m.
In practical use, the length of the middle pipe shed is preferably 25m, the circumferential distance between every two adjacent middle pipe sheds is preferably 0.4m, the middle pipe sheds are adopted for grouting the tunnel body with the extra-large section, and the construction safety of the secondary lining trolley for assembling the arch wall of the tunnel with the extra-large section at the section can be guaranteed.
In this embodiment, in step 401, when the middle partition wall method is used to excavate the first half section pilot tunnel 1 of the front left extra-large section cavern, only the temporary middle partition wall is provided, and the temporary inverted arch is not provided.
In actual use, as the lower part of the upper half section pilot tunnel 1 needs to be excavated continuously, the upper half section pilot tunnel 1 can be excavated by adopting a simple middle partition wall method without constructing a temporary inverted arch, and the construction efficiency can be effectively improved.
In a specific embodiment, the temporary intermediate bulkhead is supported by the steel pipe with a large diameter of phi 426, and is reinforced by a steel pipe with a phi 609 if necessary.
In this embodiment, in step 402, when blasting excavation is performed on the right side of the upper half-section of the super-large section cavern, the blasting excavation is performed far away from the slotted hole of the middle bulkhead steel frame 2, and the loosening blasting and manual auxiliary mechanical excavation are performed on the middle bulkhead steel frame 2.
During actual use, when blasting excavation is carried out on the right side of the upper half section of the extra-large section cavern, the cutting holes are far away from the middle bulkhead steel frame 2 as far as possible, so that the middle bulkhead steel frame 2 cannot be greatly influenced during blasting excavation, and the reliability of support of the middle bulkhead steel frame 2 is further ensured.
In this embodiment, in step 403, when the step method is adopted to perform excavation of the lower half section of the cavern with the extra-large section step by step in step 403, the two-step method is firstly adopted to excavate the inverted trapezoidal lateral rock masses 4 on the two sides of the lower half section of the cavern with the extra-large section in a staggered manner by depending on the vertical supports 3 on the two sides of the middle partition steel frame 2;
after the side rock masses 4 are excavated and supported for 3-5 m, excavating the middle step rock mass 5 between the two side rock masses 4; with the excavation of the middle step rock mass 5, when the middle step rock mass 5 is excavated to the position of the middle bulkhead steel frame 2, the middle bulkhead steel frame 2 is firstly dismantled, and then the excavation is continued forwards.
When the excavating device is used in practice, when the side rock bodies 4 of the inverted trapezoids on two sides of the lower half section of the cavity with the extra-large section are excavated, the side rock body 4 of the inverted trapezoids on the left side and the side rock body 4 of the inverted trapezoids on the right side are excavated in a staggered manner, and the side rock body 4 of the inverted trapezoids on the left side and the side rock body 4 of the inverted trapezoids on the right side are staggered by 2-3 m; in the lower half section excavation process, the effective support of the middle step rock mass 5 and the vertical support 3 is required to be ensured all the time.
When the method is specifically implemented, the lower half section of the cavity with the extra-large section is excavated in a step-by-step and layered mode by adopting a step method, so that the construction space is large, the mechanized construction is convenient, and the parallel operation of multiple operation surfaces can be realized; can adapt to different spans and various section forms; on the basis of the bench method excavation, the two sides are firstly excavated and then the middle is excavated, and the two sides are excavated in a staggered mode, so that the stability of an excavation working surface is facilitated.
In this embodiment, in step 403, circumferential steel arches are reinforced by longitudinal reinforcing rods, and a plurality of longitudinal reinforcing rods are arranged between every two adjacent steel arches;
the steel arch is formed by splicing a plurality of steel arch splicing sections, two adjacent steel arch splicing sections are fixedly connected through a connecting plate, and the number of longitudinal reinforcing rods connected between every two adjacent steel arches is equal to that of the steel arch splicing sections in the steel arch.
In actual use, the longitudinal reinforcing rods are preferably I20 a section steel, and the I25 b section steel arch is adopted in the whole ring of the tunnel with the extra-large section, and I20 a section steel is longitudinally welded and reinforced at the steel arch gusset plates, so that the investment is increased compared with the I22 b section steel arch originally designed by a double-side wall method; but the method reduces the cost of measures such as damage and reinforcement of temporary engineering by temporary engineering of the right side wall and the temporary inverted arch and surrounding rock blasting, and the like, saves 10 to 25 percent of total material cost by preliminary calculation, and greatly enhances the safety performance compared with the I22 b type steel arch center originally designed by a double-side wall method.
When the method is specifically implemented, when the extra-large section hole body is excavated, the I25 b type steel arch frame is adopted in the whole ring of the tunnel, the longitudinal connection is strengthened, the upper half section adopts a simple middle partition wall method and two large-diameter steel pipe temporary vertical supports, the lower half section adopts a step method, the large-section shallow-buried and soft rock construction methods such as double side walls and the like are replaced, and the application range of the tunnel step method excavation method is expanded.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.
Claims (6)
1. A construction method of a tunnel with an extra-large section and leading out a branch line in a railway tunnel is characterized in that the excavation width of a cavity (7) with the extra-large section of a constructed tunnel is 20 m-26 m, the excavation height of the cavity (7) with the extra-large section is 15 m-17 m, the constructed tunnel is a deep-buried anhydrous tunnel with the buried depth of 164 m-253 m, and the surrounding rock level of the cavity in the constructed tunnel is III level or IV level;
the method comprises the following steps:
step one, constructing an auxiliary excavation section of a cavity with an extra-large section: continuously excavating 5 m-10 m forwards from the large-section cavern (6) which is already excavated and formed to form an auxiliary excavation section for the construction of the large-section cavern;
step two, expanding and digging an auxiliary digging section: according to the construction drawing of the cavity (7) with the extra-large section, the cavity is expanded and excavated along the inner wall of the auxiliary excavation section in a straight upward and right turning way, so that the expansion and excavation of the auxiliary excavation section are completed, and a primary cavity with the extra-large section is formed;
grouting the medium pipe shed: installing a plurality of middle pipe sheds along the tunnel face of the primary super-large section cavern towards the tunnel excavation direction by using a pipe shed drilling machine, and grouting and reinforcing through the middle pipe sheds;
step four, excavating a cavity with an extra-large section, wherein the process is as follows:
step 401, excavating the left side of the tunnel face of the primary super-large section cavern by adopting a middle partition wall method to form an upper half section pilot tunnel (1), and synchronously supporting the excavated part on which steel arch frame segments and a middle partition wall steel frame (2) are erected in time;
step 402, when the excavation length of the upper half section pilot tunnel (1) reaches 15 m-20 m, blasting excavation on the right side of the upper half section of the extra-large section cavern is carried out by adopting a two-step method based on a smooth blasting technology, supporting the excavated part in time by erecting steel arch segments, and spraying concrete to the erected steel arch segments; the method comprises the following steps that with continuous excavation of the right side of the upper half section of the cavern with the extra-large section, vertical supports (3) are arranged in the upper half section of the cavern with the extra-large section excavated on the two sides of a middle bulkhead steel frame (2) in time, and arch tops of the cavern with the extra-large section excavated are supported in a truss-separated mode;
403, when the excavation length of the lower step on the right side of the upper half section of the cavity with the extra-large section reaches 3-5 m, adopting a step method to excavate the lower half section of the cavity with the extra-large section step by step, erecting steel arch frame segments on the excavated part in time to form a ring in a sealed mode, spraying concrete on the erected steel arch frame segments, filling an inverted arch and the inverted arch following construction, and constructing secondary lining of the arch wall in time; the method comprises the following steps that along with excavation of the lower half section of the cavity with the extra-large section, when the lower half section of the cavity with the extra-large section is excavated to the positions of the middle bulkhead steel frame (2) and the vertical supports (3), grouting reinforcement is firstly carried out on the arch tops of the tunnel sections where the middle bulkhead steel frame (2) and the vertical supports (3) are located through small guide pipes, then the middle bulkhead steel frame (2) and the vertical supports (3) are dismantled, and then excavation is continued forwards.
2. The construction method of the extra-large-section tunnel with the lead-out turnout line in the railway tunnel according to claim 1, characterized in that: in the third step, when the middle pipe sheds are adopted for grouting the hole body with the extra-large section, the plurality of middle pipe sheds are arranged at equal intervals along the annular direction of the hole body with the extra-large section, the length of each middle pipe shed is not less than 25m, and the annular interval between every two adjacent middle pipe sheds is 0.3-0.5 m.
3. The construction method of the extra-large-section tunnel with the lead-out turnout line in the railway tunnel according to claim 1, characterized in that: in step 401, when the upper half section pilot tunnel (1) of the front left extra-large section cavern is excavated by adopting a middle partition wall method, only a temporary middle partition wall is arranged, a temporary inverted arch is not arranged, and the temporary middle partition wall in the upper half section pilot tunnel (1) is supported by steel pipes at intervals.
4. The construction method of the extra-large-section tunnel with the lead-out turnout line in the railway tunnel according to claim 1, characterized in that: in step 402, when blasting excavation is performed on the right side of the upper half section of the super large section cavern, the blasting excavation is far away from the slotted hole of the middle bulkhead steel frame (2), loose blasting is adopted at the position of the middle bulkhead steel frame (2), and manual auxiliary mechanical excavation is performed.
5. The construction method of the extra-large-section tunnel with the lead-out turnout line in the railway tunnel according to claim 1, characterized in that: in step 403, when the step method is adopted to carry out excavation on the lower half section of the super-large section cavern in a layered mode step by step, the two-step method is firstly adopted to excavate the inverted trapezoidal lateral rock masses (4) on the two sides of the lower half section of the super-large section cavern in a staggered mode by depending on the vertical supports (3) on the two sides of the middle partition steel frame (2);
after the side rock masses (4) are excavated and supported for 3-5 m, excavating the middle step rock mass (5) between the two side rock masses (4); with the excavation of the middle step rock mass (5), when the middle step rock mass (5) is excavated to the position of the middle bulkhead steel frame (2), the middle bulkhead steel frame (2) is firstly dismantled, and then the excavation is continued forwards.
6. The construction method of the extra-large-section tunnel with the lead-out turnout line in the railway tunnel according to claim 1, characterized in that: in step 403, reinforcing circumferential steel arches by using longitudinal reinforcing rods, wherein a plurality of longitudinal reinforcing rods are arranged between every two adjacent steel arches;
the steel arch is formed by splicing a plurality of steel arch splicing sections, two adjacent steel arch splicing sections are fixedly connected through a connecting plate, and the number of longitudinal reinforcing rods connected between every two adjacent steel arches is equal to that of the steel arch splicing sections in the steel arch.
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Application publication date: 20210903 |