CN111997624A - Shallow-buried large-section underground excavation rectangular tunnel construction method - Google Patents

Shallow-buried large-section underground excavation rectangular tunnel construction method Download PDF

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Publication number
CN111997624A
CN111997624A CN202010829595.7A CN202010829595A CN111997624A CN 111997624 A CN111997624 A CN 111997624A CN 202010829595 A CN202010829595 A CN 202010829595A CN 111997624 A CN111997624 A CN 111997624A
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China
Prior art keywords
steel
grouting
pipe
excavation
arch
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CN202010829595.7A
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Chinese (zh)
Inventor
程争民
戴育昕
李旭
陈东东
杨涛
姜新宙
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CCCC SHEC Third Highway Engineering Co Ltd
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CCCC SHEC Third Highway Engineering Co Ltd
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Priority to CN202010829595.7A priority Critical patent/CN111997624A/en
Publication of CN111997624A publication Critical patent/CN111997624A/en
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    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D9/00Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
    • E21D9/001Improving soil or rock, e.g. by freezing; Injections
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/04Lining with building materials
    • E21D11/10Lining 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
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/04Lining with building materials
    • E21D11/10Lining 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
    • E21D11/105Transport 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
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/14Lining predominantly with metal
    • E21D11/18Arch members ; Network made of arch members ; Ring elements; Polygon elements; Polygon elements inside arches

Abstract

The invention provides a construction method of a shallow-buried large-section underground rectangular tunnel, which comprises the following steps of: s1: constructing the tunnel at the underground excavation section by adopting a CRD method, carrying out comprehensive precipitation treatment on an underground excavation area before construction, and reducing the underground water level to 0.5m below the excavation surface of the foundation pit; s2: grouting and reinforcing the ground surface broken rock stratum to prevent the deformation and damage of the peripheral ground surface caused in the excavation construction process; s3: an advanced large pipe shed and an advanced grouting small pipe are adopted for advanced support; s4: the underground excavation section immediately carries out primary spraying after the excavation or the subsection excavation is finished, the exposed surface of the surrounding rock is closed in time, and the support of the profile steel arch frame, the anchor rod and the reinforcing mesh is carried out in cooperation with the excavation circulation footage; s5: re-spraying concrete; s6: grouting the arch back gap in time after primary support. According to the invention, by the technical measures, the effects of reinforcing the surrounding rock of the tunnel and controlling the subsidence of the earth surface are realized, the problem that the deformation of the surrounding rock of the shallow-buried large-section underground rectangular tunnel is difficult to control is solved, and effective safety guarantee is provided for the construction of the shallow-buried large-section underground rectangular tunnel.

Description

Shallow-buried large-section underground excavation rectangular tunnel construction method
Technical Field
The invention belongs to the technical field of tunnel engineering, and particularly relates to a construction method of a shallow-buried large-section underground excavation rectangular tunnel.
Background
With the continuous acceleration of urbanization in China, the construction of urban rail transit (subway) enters a rapid development period, and common urban underground construction methods mainly comprise open excavation methods, underground excavation methods, pipe jacking methods, mine methods and other construction methods. However, the subway station is mainly located in a main urban area, the road traffic of the main urban area is busy, underground pipelines are staggered and arranged vertically and horizontally, and the open cut method has great influence on ground traffic and the underground pipelines, so that the subway station is generally not suitable for the tunnel engineering construction of the main urban area; the pipe jacking method has higher requirement on the linearity of an underground road and has poor applicability to projects with shallow buried depth; the mining method is suitable for tunnel engineering with large buried depth and construction sites in rock strata. The underground excavation method can overcome the defects of the method and has the characteristics of flexible construction and wide application range.
However, the conventional underground excavation method cannot be applied to the construction of underground excavated tunnels in areas with much rainfall, and because the underground excavated tunnels closely traverse communication pipelines, water supply pipelines, sewage pipelines, power pipelines, rainwater pipelines and pipeline maintenance wells, and rainwater culverts traverse the upper parts of the tunnels, the distance between the underground excavated cross sections is short, the underground excavated cross sections are affected by tide, the daily variation of underground water is large, the control requirement on the underground excavation construction process is high, the tunnel structure is complex, and great examination is brought to the construction.
Based on the reasons, a shallow-buried large-section underground rectangular tunnel construction method is urgently needed, and the stability of the excavated surrounding rock and the safety of pipelines in the upper shallow earth are ensured in the construction process.
Disclosure of Invention
The invention provides a construction method of a shallow-buried large-section underground rectangular tunnel, which aims to solve the problems of the existing method and solve the construction problem of the shallow-buried large-section underground rectangular tunnel in a main urban area.
The technical scheme of the invention is as follows: a construction method of a shallow-buried large-section underground rectangular tunnel comprises the following main construction steps:
s1: constructing the tunnel at the underground excavation section by adopting a CRD method, carrying out comprehensive precipitation treatment on an underground excavation area before construction, and reducing the underground water level to 0.5m below the excavation surface of the foundation pit;
s2: broken rock stratum slip casting of earth's surface is consolidated, prevents to arouse among the excavation work progress that peripheral ground warp to destroy, and concrete process includes (1) drilling location: after the on-site cleaning is finished, according to the rechecked control points, measuring and setting a positioning axis to perform pile position lofting, wherein the size of a pile of the loft is required to meet the design and construction requirements, and the allowable deviation is controlled within 10 mm; (2) positioning a drilling machine: after the drilling machine enters a field and is debugged, the drilling machine is installed in place, carefully leveled and firmly supported, so that the drilling machine is ensured not to incline or shift in construction; (3) drilling by a drilling machine: the drilling machine is in place, equipment is leveled, drilling is carried out, steel pipes are installed after the drilling is in place, and the steel pipes are transported to the site for installation after being processed in a processing factory; (4) hole cleaning: before grouting, washing impurities in the seamless steel pipe, and inserting the grouting pipe into the bottom of the hole; (5) grouting: sequentially grouting from bottom to top until thick slurry flows out of the top opening of the seamless steel pipe;
s3: an advanced large pipe shed and an advanced grouting small pipe are adopted for advanced support;
s4: the underground excavation section immediately carries out primary spraying after the excavation or the subsection excavation is finished, the exposed surface of the surrounding rock is closed in time, and the support of the profile steel arch frame, the anchor rod and the reinforcing mesh is carried out in cooperation with the excavation circulation footage;
s5: after the steel arch frame, the anchor rod and the reinforcing mesh are supported, concrete is sprayed again in time;
s6: grouting the arch back gap in time after primary support to prevent gaps from being left in the arch part, so that support and surrounding rock analysis are realized.
In the step S1, the precipitation at the entrance and exit is performed by using large-diameter tube well precipitation, the well points in the foundation pit are arranged at intervals of 8-12 m, the diameter of the well tube is 0.8m, and the insertion depth of the precipitation well steel tube is not less than 5m lower than the bottom of the foundation pit.
Further, in the step S2, the grouting range is 2m outside the excavation contour line, the grouting process adopts sleeve valve pipes for grouting reinforcement, a phi 108 steel pipe is inserted into the jet grouting pile, the steel pipe extends to 2m below the basement, the grouting reinforcement adopts cement-water glass double-fluid slurry, and the water cement ratio is 1: 1, grouting pressure is 1.0 MPa-2.0 MPa.
Further, in the step S3, the construction process of the advanced large pipe shed includes (1) measuring and setting out; (2) laying down a pipe shed operating platform; (3) the drilling machine is in place to drill holes, a down-the-hole drilling machine is adopted to operate according to geological conditions and construction conditions, and construction is carried out according to the foundation pit excavation sequence in the construction sequence; (4) jacking a pipe shed, numbering steel joints of the steel pipes when the steel pipes are processed in order to stagger the joints of the steel pipes, adopting a direct impact method to impact a conduit to a designed position when the wall of the hole is not easy to collapse during pipe descending, and simultaneously drilling the conduit and a drill bit when the wall of the hole is easy to collapse; (5) carry out the slip casting after the comprehensive inspection is qualified, detect after the slip casting is accomplished, adopt a full drilling slip casting, the pipe roof slip casting reaches the grout diffusion radius and is not less than 0.5m, select the slip casting mode according to the rock condition, the slip casting adopts the grout, grout water cement ratio 1: 1, grouting pressure: the initial pressure is 0.5-1 MPa, the final pressure is 2MPa, a grouting field test is performed before grouting, and grouting parameters are adjusted according to actual conditions through the field test.
In the step S3, the construction process of the advanced grouting small conduit includes (1) measuring the hole site of the conduit, designing the advanced grouting small conduit within the arch range of the underground excavation section, wherein the circumferential distance is 30cm, the camber angle of the small conduit is 10-15 degrees, the longitudinal horizontal lap length is 1m, one end of the grouting pipe is made into a conical head, and the other end is welded with an iron hoop; (2) drilling, namely, drilling at a position 1.0m away from the iron hoop, wherein the drill holes are distributed at intervals of 150mm along the pipe wall in a quincunx manner, the hole positions mutually form 90 degrees, the hole diameter is 8mm, and the drill holes can be directly jacked by a wind drill; (3) installing a guide pipe, jacking the small guide pipe by using an air drill, exposing the tail end of the guide pipe for a sufficient length, and welding the tail end of the guide pipe and the steel frame together; (4) spraying concrete to close the grouting surface; (5) and (3) grouting by using a guide pipe, wherein the grouting slurry is cement-water glass double-liquid slurry, and the grouting pressure is set to be 0.4-0.6 MPa.
Furthermore, in the step S4, the construction process of the steel arch includes (1) section inspection and measurement positioning, wherein the steel arch is different according to different designed sections; (2) the steel supports are assembled, erected in place and locked by anchor rods, the primary support steel frames adopt I20a I-shaped steel, the temporary vertical supports and the temporary inverted arches adopt I18I-shaped steel, the distance is 0.5m, two adjacent steel frames are connected by phi 20 steel bars, the circumferential distance of connecting ribs is 0.5m, grooves for mounting steel frame channel steel are reserved at two arch feet and two side wall feet to ensure the arch feet to be solid, wood wedges are driven into the grooves when concrete is sprayed for the first time, connecting plates or channel steel positions are reserved for erecting the steel frames, and the steel frames and the anchor rods are welded together for enhancing the overall stability of the steel frames; (3) arranging longitudinal connecting steel bars and installing steel bar nets, wherein each longitudinal steel arch truss is connected by a phi 8@200 double-layer steel bar net, the inner layer and the outer layer are arranged alternately, and the connecting steel bars are firmly welded with the steel frame; (4) the concrete spraying is fixed, the anchor spraying operation is carried out as soon as possible after the steel frame is erected, the spraying sequence is carried out symmetrically from bottom to top, a gap between the steel frame and surrounding rocks is sprayed firstly, the concrete between the steel frame and the steel frame is sprayed later, the steel frame is covered completely, the thickness of a protective layer of the protective layer is not smaller than 40mm, the steel frame and the spray anchor are stressed together, the spray anchors are carried out in a layered mode, the thickness of each layer is about 50-60 mm, the spray anchors are sprayed upwards from the arch springing or the wall springing position firstly to prevent the upper spray material from covering the arch springing or the wall springing loosely, the strength is insufficient, and the arch spring.
According to the scheme, the sprayed concrete in the preliminary bracing is strength grade C25 concrete with the thickness of 300mm, the construction is carried out by a wet spraying method, the concrete for spraying is mixed on site by a mixing station, the concrete is transported to a working surface, the spraying anchor construction is carried out by a wet spraying machine, the spraying sequence is that a side wall, a rear arch foot and a final arch top are arranged from bottom to top, a spray head spirally and uniformly moves slowly, each circle presses the front half circle, the diameter of each circle is about 30cm, a large concave depression is formed, the concrete is firstly sprayed and filled, and the spray nozzle is vertical to the rock surface and is 1.5-2.0 m away from the sprayed surface. After excavation, early spraying is carried out in time, and after muck is produced, secondary spraying is carried out in time; the re-spraying concrete is carried out after the anchor rods, the hanging net and the steel frames are installed, the whole stress of the anchor spraying support is formed as soon as possible to inhibit the change of surrounding rocks, the steel frames are sprayed with the concrete and are leveled by the concrete, enough protective layers are arranged, the concrete spraying is carried out in a segmentation and fragmentation mode from bottom to top, when the re-spraying concrete is carried out, the concrete between the steel frame support and the arch wall is sprayed firstly, and then the concrete between the two arch frames is sprayed.
Further, in the step S6, during arch back grouting, that is, primary support construction, the embedded Φ 32mm steel of the arch side wall is welded as a grouting pipe, the length of the grouting pipe is generally set in a row of 0.8 according to the lining design requirement, the circumferential distance of each row is 1m, and after the primary support is closed into a ring, the grouting pump is used for grouting in time 1: 1 cement mortar, filling the pores after primary backing.
The invention has the advantages that: the invention provides a construction method for a shallow-buried large-section underground rectangular tunnel, which is characterized in that the construction method is implemented by adopting subsection excavation, adding of a temporary inverted arch, an advanced large pipe shed and small pipe grouting reinforcement, the deformation of surrounding rocks and the earth surface of the tunnel is controlled, the problem that the deformation of the surrounding rocks of the shallow-buried large-section underground rectangular tunnel is difficult to control is solved, and effective safety guarantee is provided for the construction of the shallow-buried large-section underground rectangular tunnel.
Drawings
FIG. 1 is a flow chart of a surface grouting reinforcement construction process of the construction method of the shallow-buried large-section underground excavation rectangular tunnel;
FIG. 2 is a flow chart of an advanced large pipe shed construction process of the construction method of the shallow-buried large-section underground rectangular tunnel;
FIG. 3 is a flow chart of a construction process of a small advanced grouting guide pipe of the construction method of a shallow-buried large-section underground rectangular tunnel;
FIG. 4 is a process flow diagram of a profile steel arch construction method of the shallow-buried large-section underground excavation rectangular tunnel construction method of the invention.
Detailed Description
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which a person skilled in the art can, without any creative effort, fully implement the present invention.
The specific implementation mode of the invention is as follows: as shown in fig. 1-4, a construction method of a shallow-buried large-section underground excavation rectangular tunnel comprises the following main construction steps:
s1: constructing the tunnel at the underground excavation section by adopting a CRD method, carrying out comprehensive precipitation treatment on an underground excavation area before construction, and reducing the underground water level to 0.5m below the excavation surface of the foundation pit;
s2: broken rock stratum slip casting of earth's surface is consolidated, prevents to arouse among the excavation work progress that peripheral ground warp to destroy, and concrete process includes (1) drilling location: after the on-site cleaning is finished, according to the rechecked control points, measuring and setting a positioning axis to perform pile position lofting, wherein the size of a pile of the loft is required to meet the design and construction requirements, and the allowable deviation is controlled within 10 mm; (2) positioning a drilling machine: after the drilling machine enters a field and is debugged, the drilling machine is installed in place, carefully leveled and firmly supported, so that the drilling machine is ensured not to incline or shift in construction; (3) drilling by a drilling machine: the method comprises the following steps that a drilling machine is in place, equipment is leveled, drilling is carried out, steel pipes are installed after the drilling is in place, the steel pipes are transported to the site for installation after being processed in a processing factory, screw threads with the length of 15cm are processed at two ends of each seamless steel pipe, A10mm slurry discharge holes are processed on the steel pipes every 10cm and are arranged in a quincunx mode, and according to the pile length, in order to enable the number of joints of two adjacent piles on the same vertical surface to be not more than 50% of the total pipe number; (4) hole cleaning: before grouting, washing impurities in the seamless steel pipe, and inserting the grouting pipe into the bottom of the hole; (5) grouting: sequentially grouting from bottom to top until thick slurry flows out of the top opening of the seamless steel pipe;
s3: an advanced large pipe shed and an advanced grouting small pipe are adopted for advanced support;
s4: the underground excavation section immediately carries out primary spraying after the excavation or the subsection excavation is finished, the exposed surface of the surrounding rock is closed in time, and the support of the profile steel arch frame, the anchor rod and the reinforcing mesh is carried out in cooperation with the excavation circulation footage;
s5: after the steel arch frame, the anchor rod and the reinforcing mesh are supported, concrete is sprayed again in time;
s6: grouting the arch back gap in time after primary support to prevent gaps from being left in the arch part, so that support and surrounding rock analysis are realized.
Furthermore, in the step S1, the precipitation at the entrance and the exit adopts large-diameter tube well precipitation, well points in the foundation pit are arranged at intervals of 8-12 m, the diameter of the well tube is 0.8m, and the insertion depth of the precipitation well steel tube is not less than 5m lower than the bottom of the foundation pit.
Furthermore, in the step S2, the grouting range is 2m outside the excavation contour line, the grouting process adopts sleeve valve pipes for grouting reinforcement, a phi 108 steel pipe is inserted into the jet grouting pile, the steel pipe extends to 2m below the basement, the grouting reinforcement adopts cement-water glass double-fluid slurry, and the water cement ratio is 1: 1, grouting pressure is 1.0 MPa-2.0 MPa.
Further, in the step S3, the construction process of the advanced large pipe shed includes (1) measuring and setting out; (2) a large pipe shed is made of hot rolled seamless steel pipes with the diameter of 108mm, the wall thickness of the large pipe shed is 9mm, the section length is 4m or 6m, the inclination angle is smaller than 2 degrees upwards, grouting holes with the diameter of 10-16mm are drilled on the periphery of the pipe wall of the steel pipe, the drilling holes are distributed in a quincunx shape at intervals of 150mm along the pipe wall, the hole positions mutually form 90 degrees, and a hole-free grout stopping section with the diameter of 1.5m is reserved at the tail part of the large pipe; a reinforcement cage is additionally arranged in the pipe to improve the bending resistance of the guide pipe, the reinforcement cage is composed of four main reinforcements and a fixing ring, and the circumferential distance of the large pipe shed is 40 cm; (3) the drilling machine is in place to drill holes, a down-the-hole drilling machine is adopted to operate according to geological conditions and construction conditions, construction is carried out according to the excavation sequence of a foundation pit in the construction sequence, the distance between the drilling machine and a working face is not less than 2m in general during drilling, meanwhile, the drilling hole is mainly based on a pneumatic down-the-hole impact drilling method, an alloy pipe drill is used as an auxiliary material, the diameter of the drilled hole is 150mm, the circumferential distance is 40cm, a rock core pipe with the diameter of 108mm is used for hole sweeping, the length of the rock core pipe is not less than 3m, meanwhile, high-pressure air is used for blowing and washing until the hole is cleaned completely, the pipe wall of the steel pipe with the diameter of 108mm is drilled, the hole diameter is 10-16mm, the hole distance is; (4) jacking a pipe shed, in order to stagger steel pipe joints, numbering steel joints of the steel pipes when the steel pipes are processed, when the steel pipes are lowered, impacting a guide pipe to a designed position by adopting a direct impact method when a hole wall is not easy to collapse, and simultaneously drilling the guide pipe and a drill bit when the hole wall is easy to collapse, in order to stagger the steel pipe joints, adopting 4m pipes for constructing first sections of pipes with odd numbers, adopting 6m steel pipes for first sections of pipes with even numbers, later adopting 6m long steel pipes for each section, if the steel pipes are jacked to meet a fault and cannot be jacked, checking reasons, and jacking the steel pipes after hole sweeping is carried out again if necessary; (5) carry out the slip casting after the comprehensive inspection is qualified, detect after the slip casting is accomplished, adopt a full drilling slip casting, the pipe roof slip casting reaches the grout diffusion radius and is not less than 0.5m, select the slip casting mode according to the rock condition, the slip casting adopts the grout, grout water cement ratio 1: 1, grouting pressure: the initial pressure is 0.5-1 MPa, the final pressure is 2MPa, a grouting field test is performed before grouting, grouting parameters are adjusted according to actual conditions through the field test, and cement-water glass slurry can be used if underground water is large. Before grouting, a steel pipe plug is made of a10mm steel plate at the steel pipe opening of the pipe shed, the steel pipe plug is welded with the steel pipe opening of the pipe shed, a grouting pipe is welded at the plug opening through hole burning, and a grouting valve is installed on a grouting pipe screw fastener. A plastic hard pipe with the diameter of 15mm is arranged in the steel perforated pipe along the pipe wall to the bottom of the hole, and a steel pipe is welded on the grouting pipe at the pipe opening (outer end) and is used as a vent hole (provided with a grouting valve). And the grouting is performed at one time from the orifice, so that the grout in the pipe is full and compact, and the grouting is performed at the final pressure until the designed grouting pressure or the designed grouting amount is reached after the grout flows out from the exhaust hole during grouting. And then close the valve.
Furthermore, in the step S3, the construction process of the advanced grouting small guide pipe includes (1) measuring hole positions of the guide pipe, designing the advanced grouting small guide pipe within the arch part range of the underground excavation section, wherein the annular distance is 30cm, the camber angle of the small guide pipe is 10-15 degrees, the longitudinal horizontal lap length is 1m, one end of the grouting pipe is made into a conical head, and an iron hoop is welded at the other end; (2) drilling, namely, drilling at a position 1.0m away from the iron hoop, wherein the drill holes are distributed at intervals of 150mm along the pipe wall in a quincunx manner, the hole positions mutually form 90 degrees, the hole diameter is 8mm, and the drill holes can be directly jacked by a wind drill; (3) installing a guide pipe, jacking the small guide pipe by using an air drill, exposing the tail end of the guide pipe for a sufficient length, and welding the tail end of the guide pipe and the steel frame together; (4) spraying concrete to close the grouting surface; (5) and (3) grouting by using a guide pipe, wherein the grouting slurry is cement-water glass double-liquid slurry, and the grouting pressure is set to be 0.4-0.6 MPa.
Furthermore, in the step S4, the construction process of the steel arch includes (1) section inspection, measurement and positioning, wherein the steel arch is different according to different designed sections; (2) the steel supports are assembled, erected in place and locked by anchor rods, the primary support steel frames adopt I20a I-shaped steel, the temporary vertical supports and the temporary inverted arches adopt I18I-shaped steel, the distance is 0.5m, two adjacent steel frames are connected by phi 20 steel bars, the circumferential distance of connecting ribs is 0.5m, grooves for mounting steel frame channel steel are reserved at two arch feet and two side wall feet to ensure the arch feet to be solid, wood wedges are driven into the grooves when concrete is sprayed for the first time, connecting plates or channel steel positions are reserved for erecting the steel frames, and the steel frames and the anchor rods are welded together for enhancing the overall stability of the steel frames; (3) arranging longitudinal connecting steel bars and installing steel bar nets, wherein each longitudinal steel arch truss is connected by a phi 8@200 double-layer steel bar net, the inner layer and the outer layer are arranged alternately, and the connecting steel bars are firmly welded with the steel frame; (4) the concrete spraying is fixed, the anchor spraying operation is carried out as soon as possible after the steel frame is erected, the spraying sequence is carried out symmetrically from bottom to top, a gap between the steel frame and surrounding rocks is sprayed firstly, the concrete between the steel frame and the steel frame is sprayed later, the steel frame is covered completely, the thickness of a protective layer of the protective layer is not smaller than 40mm, the steel frame and the spray anchor are stressed together, the spray anchors are carried out in a layered mode, the thickness of each layer is about 50-60 mm, the spray anchors are sprayed upwards from the arch springing or the wall springing position firstly to prevent the upper spray material from covering the arch springing or the wall springing loosely, the strength is insufficient, and the arch spring.
The invention further provides that the sprayed concrete in the primary support is strength grade C25 concrete with the thickness of 300mm, the construction is carried out by a wet spraying method, the sprayed concrete is mixed on site by a mixing station, the mixed concrete is transported to a working surface, the spraying anchor construction is carried out by a wet spraying machine, the spraying sequence is from bottom to top, the side wall, the rear arch foot and the final arch crown are arranged, the spray head spirally and uniformly moves, each circle presses the front half circle, the diameter of the circle is about 30cm, a large concave part is arranged, the spraying is firstly carried out to fill, the spray nozzle is vertical to the rock surface and is 1.5-2.0 m away from the sprayed surface. After excavation, early spraying is carried out in time, and after muck is produced, secondary spraying is carried out in time; the re-spraying concrete is carried out after the anchor rods, the hanging net and the steel frames are installed, the whole stress of the anchor spraying support is formed as soon as possible to inhibit the change of surrounding rocks, the steel frames are sprayed with the concrete and are leveled by the concrete, enough protective layers are arranged, the concrete spraying is carried out in a segmentation and fragmentation mode from bottom to top, when the re-spraying concrete is carried out, the concrete between the steel frame support and the arch wall is sprayed firstly, and then the concrete between the two arch frames is sprayed.
Further, in the step S6, during the arch back grouting, that is, the preliminary bracing construction, the pre-buried Φ 32mm steel of the arch side wall is welded as the grouting pipe, the length of the grouting pipe is generally set in a row of 0.8 according to the lining design requirement, the circumferential distance of each row is 1m, after the preliminary bracing is closed to form a ring, the grouting pump is used for grouting 1: 1 cement mortar, filling the pores after primary backing.
While the preferred embodiments of the invention have been described, it is to be understood that the invention is not limited to the precise embodiments described, and that equipment and structures not described in detail are understood to be practiced as commonly known in the art; any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention by those skilled in the art can be made without departing from the technical scope of the present invention, and still fall within the protection scope of the technical solution of the present invention.

Claims (8)

1. A construction method of a shallow-buried large-section underground rectangular tunnel is characterized by comprising the following main construction steps:
s1: constructing the tunnel at the underground excavation section by adopting a CRD method, carrying out comprehensive precipitation treatment on an underground excavation area before construction, and reducing the underground water level to 0.5m below the excavation surface of the foundation pit;
s2: broken rock stratum slip casting of earth's surface is consolidated, prevents to arouse among the excavation work progress that peripheral ground warp to destroy, and concrete process includes (1) drilling location: after the on-site cleaning is finished, according to the rechecked control points, measuring and setting a positioning axis to perform pile position lofting, wherein the size of a pile of the loft is required to meet the design and construction requirements, and the allowable deviation is controlled within 10 mm; (2) positioning a drilling machine: after the drilling machine enters a field and is debugged, the drilling machine is installed in place, carefully leveled and firmly supported, so that the drilling machine is ensured not to incline or shift in construction; (3) drilling by a drilling machine: the drilling machine is in place, equipment is leveled, drilling is carried out, steel pipes are installed after the drilling is in place, and the steel pipes are transported to the site for installation after being processed in a processing factory; (4) hole cleaning: before grouting, washing impurities in the seamless steel pipe, and inserting the grouting pipe into the bottom of the hole; (5) grouting: sequentially grouting from bottom to top until thick slurry flows out of the top opening of the seamless steel pipe;
s3: an advanced large pipe shed and an advanced grouting small pipe are adopted for advanced support;
s4: the underground excavation section immediately carries out primary spraying after the excavation or the subsection excavation is finished, the exposed surface of the surrounding rock is closed in time, and the support of the profile steel arch frame, the anchor rod and the reinforcing mesh is carried out in cooperation with the excavation circulation footage;
s5: after the steel arch frame, the anchor rod and the reinforcing mesh are supported, concrete is sprayed again in time;
s6: grouting the arch back gap in time after primary support to prevent gaps from being left in the arch part, so that support and surrounding rock analysis are realized.
2. The method for constructing a shallow-buried large-section underground rectangular tunnel according to claim 1, wherein in step S1, the precipitation at the entrance and exit is large-diameter well precipitation, the well points in the foundation pit are arranged at intervals of 8-12 m, the diameter of the well pipe is 0.8m, and the insertion depth of the precipitation well steel pipe is not less than 5m lower than the bottom of the foundation pit.
3. The method for constructing a shallow-buried large-section underground rectangular tunnel according to claim 1, wherein in the step S2, the grouting range is 2m outside the excavation contour line, the grouting process adopts sleeve valve pipe grouting reinforcement, a phi 108 steel pipe is inserted into a jet grouting pile, the steel pipe extends to 2m below the basement, the grouting reinforcement adopts cement-water glass double-liquid cement, the water cement ratio is 1: 1, grouting pressure is 1.0 MPa-2.0 MPa.
4. The method for constructing a shallow-buried large-section underground rectangular tunnel according to claim 1, wherein in the step S3, the construction process of the advanced large pipe shed includes (1) measuring and setting-out; (2) laying down a pipe shed operating platform; (3) the drilling machine is in place to drill holes, a down-the-hole drilling machine is adopted to operate according to geological conditions and construction conditions, and construction is carried out according to the foundation pit excavation sequence in the construction sequence; (4) jacking a pipe shed, numbering steel joints of the steel pipes when the steel pipes are processed in order to stagger the joints of the steel pipes, adopting a direct impact method to impact a conduit to a designed position when the wall of the hole is not easy to collapse during pipe descending, and simultaneously drilling the conduit and a drill bit when the wall of the hole is easy to collapse; (5) carry out the slip casting after the comprehensive inspection is qualified, detect after the slip casting is accomplished, adopt a full drilling slip casting, the pipe roof slip casting reaches the grout diffusion radius and is not less than 0.5m, select the slip casting mode according to the rock condition, the slip casting adopts the grout, grout water cement ratio 1: 1, grouting pressure: the initial pressure is 0.5-1 MPa, the final pressure is 2MPa, a grouting field test is performed before grouting, and grouting parameters are adjusted according to actual conditions through the field test.
5. The method for constructing a shallow-buried large-section underground excavation rectangular tunnel according to claim 1, wherein in the step S3, the construction process of the small advanced grouting pipes comprises (1) measuring pipe hole positions, designing the small advanced grouting pipes within the arch part of the underground excavation section, wherein the circumferential distance is 30cm, the camber angle of the small pipes is 10-15 degrees, the longitudinal horizontal lap joint length is 1m, one end of each grouting pipe is made into a conical head, and an iron hoop is welded at the other end; (2) drilling, namely, drilling at a position 1.0m away from the iron hoop, wherein the drill holes are distributed at intervals of 150mm along the pipe wall in a quincunx manner, the hole positions mutually form 90 degrees, the hole diameter is 8mm, and the drill holes can be directly jacked by a wind drill; (3) installing a guide pipe, jacking the small guide pipe by using an air drill, exposing the tail end of the guide pipe for a sufficient length, and welding the tail end of the guide pipe and the steel frame together; (4) spraying concrete to close the grouting surface; (5) and (3) grouting by using a guide pipe, wherein the grouting slurry is cement-water glass double-liquid slurry, and the grouting pressure is set to be 0.4-0.6 MPa.
6. The method for constructing a shallow-buried large-section underground rectangular tunnel according to claim 1, wherein in the step S4, the construction process of the steel arch is (1) section inspection and measurement positioning, and the steel arch is different according to the design section; (2) the steel supports are assembled, erected in place and locked by anchor rods, the primary support steel frames adopt I20a I-shaped steel, the temporary vertical supports and the temporary inverted arches adopt I18I-shaped steel, the distance is 0.5m, two adjacent steel frames are connected by phi 20 steel bars, the circumferential distance of connecting ribs is 0.5m, grooves for mounting steel frame channel steel are reserved at two arch feet and two side wall feet to ensure the arch feet to be solid, wood wedges are driven into the grooves when concrete is sprayed for the first time, connecting plates or channel steel positions are reserved for erecting the steel frames, and the steel frames and the anchor rods are welded together for enhancing the overall stability of the steel frames; (3) arranging longitudinal connecting steel bars and installing steel bar nets, wherein each longitudinal steel arch truss is connected by a phi 8@200 double-layer steel bar net, the inner layer and the outer layer are arranged alternately, and the connecting steel bars are firmly welded with the steel frame; (4) the concrete spraying is fixed, the anchor spraying operation is carried out as soon as possible after the steel frame is erected, the spraying sequence is carried out symmetrically from bottom to top, a gap between the steel frame and surrounding rocks is sprayed firstly, the concrete between the steel frame and the steel frame is sprayed later, the steel frame is covered completely, the thickness of a protective layer of the protective layer is not smaller than 40mm, the steel frame and the spray anchor are stressed together, the spray anchors are carried out in a layered mode, the thickness of each layer is about 50-60 mm, the spray anchors are sprayed upwards from the arch springing or the wall springing position firstly to prevent the upper spray material from covering the arch springing or the wall springing loosely, the strength is insufficient, and the arch spring.
7. The method for constructing a shallow-buried large-section underground excavation rectangular tunnel according to claim 1, wherein the sprayed concrete in the primary support is strength grade C25 concrete with the thickness of 300mm, the construction is performed by a wet spraying method, the sprayed concrete is mixed at the site by a mixing station, transported to a working surface, and subjected to spray anchor construction by a wet spraying machine, the spraying heads slowly and uniformly move in a spiral shape from bottom to top in the sequence of first side wall, rear arch foot and last arch top, each circle presses the front half circle, the diameter of each circle is about 30cm, a large concave part is formed, the sprayed concrete is firstly sprayed and filled, the spraying nozzles are perpendicular to the rock surface and 1.5-2.0 m away from the sprayed surface, the concrete is sprayed in time after excavation, and the concrete is sprayed again in time after slag is discharged; the re-spraying concrete is carried out after the anchor rods, the hanging net and the steel frames are installed, the whole stress of the anchor spraying support is formed as soon as possible to inhibit the change of surrounding rocks, the steel frames are sprayed with the concrete and are leveled by the concrete, enough protective layers are arranged, the concrete spraying is carried out in a segmentation and fragmentation mode from bottom to top, when the re-spraying concrete is carried out, the concrete between the steel frame support and the arch wall is sprayed firstly, and then the concrete between the two arch frames is sprayed.
8. The method for constructing a shallow-buried large-section underground rectangular tunnel according to claim 1, wherein in the step S6, arch back grouting, that is, during primary support construction, the pre-buried Φ 32mm steel of the arch side wall is welded as a grouting pipe, the length of the grouting pipe is generally embedded in one row according to the lining design requirement, 0.8, and the circumferential distance of each row is 1m, and after the primary support is closed into a ring, the grouting pump is used for grouting in time 1: 1 cement mortar, filling the pores after primary backing.
CN202010829595.7A 2020-08-18 2020-08-18 Shallow-buried large-section underground excavation rectangular tunnel construction method Pending CN111997624A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112663625A (en) * 2020-12-29 2021-04-16 哈尔滨工业大学 Construction and protection method for shallow-buried bias-pressure weak surrounding rock tunnel portal in alpine region
CN113803077A (en) * 2021-11-18 2021-12-17 中铁九局集团第七工程有限公司 Advanced support construction method for horizontal joint argillaceous shale water-rich tunnel

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112663625A (en) * 2020-12-29 2021-04-16 哈尔滨工业大学 Construction and protection method for shallow-buried bias-pressure weak surrounding rock tunnel portal in alpine region
CN113803077A (en) * 2021-11-18 2021-12-17 中铁九局集团第七工程有限公司 Advanced support construction method for horizontal joint argillaceous shale water-rich tunnel

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