CN108533272B - Exit construction method for tunnel with extremely small clear distance - Google Patents

Exit construction method for tunnel with extremely small clear distance Download PDF

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Publication number
CN108533272B
CN108533272B CN201810278614.4A CN201810278614A CN108533272B CN 108533272 B CN108533272 B CN 108533272B CN 201810278614 A CN201810278614 A CN 201810278614A CN 108533272 B CN108533272 B CN 108533272B
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China
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line
tunnel
small
constructing
construction
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CN201810278614.4A
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Chinese (zh)
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CN108533272A (en
Inventor
母进伟
张学民
杨旭
陈进
韩光钦
袁立
胡涛
杨国富
许召强
阳军生
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贵州省公路工程集团有限公司
中南大学
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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
    • 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
    • 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
    • E21D20/00Setting anchoring-bolts
    • 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
    • E21D9/00Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
    • E21D9/006Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries by making use of blasting methods

Abstract

The invention provides a tiny clear distance tunnel exit construction method, which belongs to the technical field of small clear distance tunnel exit construction and comprises the following steps: excavating a left line upper step section, and respectively excavating a left line lower step section and a left line lower step right section; constructing a left-line inverted arch and a left-line filling layer, and jumping and beating a left-line secondary lining; excavating a right line small pilot tunnel section, respectively excavating a right section of a right line upper step, a left middle section of the right line upper step and a left edge section of the right line upper step, and constructing a primary right line upper step support; removing the primary support of the small pilot tunnel, excavating a left section of a lower right-line step and a right section of the lower right-line step, and constructing the primary support of the lower right-line end face; and constructing a right-line inverted arch and a right-line filling layer, and integrally molding a right-line secondary lining. The invention adopts the advanced holes to go out in a single direction, thus solving the problem of inconvenient construction of cliff at the outlet section; and reinforcing the middle rock pillar after the left tunnel is excavated, jumping to beat a left line secondary lining, discharging the right tunnel from the tunnel by adopting a small pilot tunnel, expanding and excavating the section, reducing the construction risk and ensuring the safety of tunnel construction.

Description

Exit construction method for tunnel with extremely small clear distance

Technical Field

The invention relates to the technical field of small-clear-distance tunnel exit construction, in particular to a small-clear-distance tunnel exit construction method.

Background

In the prior art, due to the consideration of the requirement of route planning and the limitation of terrain, a traffic route sometimes inevitably adopts a small clear distance tunnel. The traditional small-clear-distance tunnel has the problem that the structure safety and the construction influence each other, and measures must be taken to solve the problem.

The total length of the high-speed old foundation tunnel of the Xingzi city of Guizhou province is 393m, and the tunnel is a branched short tunnel. The tunnel line spacing exit segment is the minimum contour line clear distance of 0.6m, and then gradually separated into the separated tunnel with the minimum clear distance, the small clear distance and the entrance segment line spacing of about 35 m. The tunnel is a gulf river valley after going out of the tunnel, and construction and excavation at an outlet section are inconvenient.

When the thickness of the septal rock in the conventional double-tunnel is less than 2 meters, a composite type mid-partition multi-arch tunnel structure is adopted. This structure has the following disadvantages: (1) the excavation amount is large, and the material input amount is large. The excavation of the small pilot tunnel is firstly carried out, the middle rock pillar is replaced by reinforced concrete with higher strength and rigidity, the excavation amount of earth and stone is increased, and meanwhile, the pouring amount of the concrete is also increased. (2) Temporary support is many, demolish loaded down with trivial details. The excavation of the small pilot tunnel is firstly carried out, the small pilot tunnel is subjected to primary support, and meanwhile, in order to prevent the middle partition wall from being damaged, the right side of the middle pilot tunnel is subjected to unilateral and transverse support; in addition, when the main tunnel side pilot tunnel is excavated, in order to prevent surrounding rocks from generating large settlement convergence and ensure construction safety, temporary support is also carried out. These temporary supports must be removed before applying the second liner. (3) The waterproof problem of the multi-arch tunnel at the top of the middle wall is difficult to solve, a perfect waterproof and drainage system cannot be formed, water leakage is easy to occur after the multi-arch tunnel is built, and the applicability and the durability of the tunnel are seriously influenced. (4) The construction period is long and the cost is high. Constructing a small pilot tunnel, and constructing a main tunnel only after supporting construction; the construction and the removal of the temporary support increase the construction workload and prolong the construction period. And the terrain condition of the exit end of the tunnel is severe, the construction site is difficult to develop, and the cost is high due to the input of materials, the input of labor force and the movement of large machinery and materials (from an inlet to an outlet).

The traditional multi-arch tunnel form is adopted, so that the construction procedures are multiple, the structural stress is complex, the construction period is long, and the construction cost is high.

Patent application No. CN201410708082.5 discloses a tunnel out-of-hole construction method for a steep cliff, wherein a hole body is excavated by a middle partition wall method, and temporary support and primary support are carried out. When the tunnel face is 7-9m away from the exit tunnel forming face, the upper and middle pilot tunnels are adopted to go out of the tunnel from inside to outside to the tunnel mouth, and then the upper and lower sections of the tunnel body are expanded to the tunnel mouth towards two sides.

Patent application No. CN201210036640.9 discloses a method for excavating a tunnel backward-going hole with a minimum clear distance, which comprises the steps of firstly drilling damping holes in rows along one side close to an intermediate wall, and carrying out slotting blasting and slag removal on one side far away from the intermediate wall by deviating 1-2 m. And then blasting and slag removing are carried out on the periphery of the backward hole. And finally, grouting and reinforcing the medium rock wall. On one hand, the method has limited effect of reducing the damping holes, and the control blasting can not reduce the influence of backward hole excavation on the deformation of the surrounding rock of the forward hole.

Disclosure of Invention

The invention aims to provide a tiny clear distance tunnel exit construction method, and aims to solve the technical problems of multiple construction procedures, complex structural stress, long construction period and high construction cost of the existing tiny clear distance tunnel exit construction method.

In order to achieve the purpose, the invention provides a construction method for the exit of a tunnel with extremely small clear distance, which comprises the following steps:

step 1: excavating a left upper step section, constructing a left upper step preliminary support, reinforcing the left upper step preliminary support by using unequal-length anchor rods, respectively excavating a left lower step section and a right lower step section, excavating the left lower step section and the right lower step section in a staggered manner at a staggered distance of about 5-15 m, constructing the left lower step preliminary support, and grouting and reinforcing when the thickness of a middle rock pillar is 0.6-3.0 m;

step 2: constructing a left line inverted arch and a left line filling layer, jumping and beating a left line secondary lining, moving a secondary lining trolley to a left line outlet after the left line opening inverted arch and the left line filling layer are completed, and preferentially constructing a secondary lining of a left line opening section;

and step 3: excavating a right line small pilot tunnel section, and constructing a small pilot tunnel primary support;

and 4, step 4: respectively expanding and digging a right section of the upper step of the right line, a left middle section of the upper step of the right line and a left edge section of the upper step of the right line, and constructing an upper step primary support of the right line, wherein the upper step primary support of the right line is reinforced by using anchor rods with unequal lengths;

and 5: removing the primary support of the small pilot tunnel, respectively excavating a left section of a lower right-line step and a right section of the lower right-line step, and constructing the primary support of the lower right-line end face;

step 6: and constructing a right-line inverted arch and a right-line filling layer, and integrally molding a right-line secondary lining.

The left hole is a hot-rolled seamless steel pipe with a diameter of 42mm, a thickness of 4mm and a length of 4.0m, and the two rows of advanced guide pipes are adopted for discharging; and injecting non-shrinkage cement slurry with the ratio of 1:0.7 into the advanced guide pipe, and plugging the tail end of the advanced guide pipe after grouting is finished.

The double-row advanced guide pipe comprises a row of long advanced small guide pipes and a row of short advanced small guide pipes, wherein the extrapolation angle of the long advanced small guide pipes is 30-40 degrees, the circumferential distance is 40 cm, and the longitudinal distance is 240 cm; the short-advance small guide pipe extrapolation angle is 10-15 degrees, construction is carried out at intervals, the alternate long-advance small guide pipe is arranged, and the circumferential distance is 40 cm and the longitudinal distance is 120 cm.

The advanced guide pipe comprises a steel pipe, grouting holes are formed in the steel pipe, stiffening hoops are welded at the tail of the steel pipe, the distance between each grouting hole and the corresponding grouting hole (15) is 10-20 cm, each grouting hole is in a quincunx shape, and the diameter of each grouting hole is 6-8 mm.

The left hole excavation control process comprises the steps of when the clear distance between the left tunnel and the right tunnel is 1.79m-1.48m, circularly advancing to 2.4m, excavating by adopting a two-step method, and enabling the height of an upper step to be 6.8 m; when the clear distance between the left tunnel and the right tunnel is 1.48m-1.17m, the circulating footage is 1.8m, the two-step method is adopted for excavation, and the height of an upper step is 6.8 m; when the clear distance between the left tunnel and the right tunnel is 1.17-0.88 m, the circulating footage is 1.2m, the three-step method is adopted for excavation, the height of an upper step is 3-4m, and weak blasting is carried out; when the clear distance between the left tunnel and the right tunnel is 0.88-0.59 m, the circulating footage is 0.6m, the three-step method is adopted for excavation, the height of an upper step is 3-4m, weak blasting is carried out, and an active protective net is adopted at an outlet section; two liners of the two molds at the outlet of the left hole are needed to be finished before the right hole is drilled, and the inverted arch of the left hole needs to be ahead of the right hole.

The primary support of the steps on the left line and the right line adopts a method of combining long and short anchor rods, and hollow grouting anchor rods with different lengths (4-6m) are adopted in a triangular area at the top of the middle rock pillar for reinforcement.

The grouting reinforcement of the middle rock pillar adopts grouting small guide pipes with phi of 42mm and thickness of 4mm, the circumferential spacing of the grouting small guide pipes is 120cm, the longitudinal spacing of the grouting small guide pipes is 60cm, the grouting small guide pipes are integrally arranged in a quincunx shape, the grout adopts 1:0.7 of superfine cement single grout, and the grouting pressure is 1-1.5 Mpa; the axial included angle between the small grouting guide pipe and the tunnel is 45 degrees.

And 6 advance probing holes, 3 radial advance probing holes and 3 horizontal advance probing holes are added when the tunnel exits 10m from the entrance to the cave in advance.

Before constructing steel arch frames of the left-line inverted arch and the right-line inverted arch, sealing the excavation surface by adopting sprayed concrete, and connecting the steel arch frames with the steel frame of the lower step; before the left-line inverted arch or the right-line inverted arch is constructed, the virtual slag and the accumulated water need to be cleaned.

The width of the small pilot tunnel is 7.0m, the height of the small pilot tunnel is 4.5m, the distance from the top of the small pilot tunnel to the vault of the tunnel is 2.7m, the distance from the left side to a rock pillar in the tunnel is 3.9m, the small pilot tunnel is excavated for 10-15m, then the expanding excavation of the upper step of the backward tunnel is carried out, when the upper step of the right tunnel is expanded excavation, the right section part of the upper step of the right line is excavated by blasting, the left middle section part of the upper step of the right line is excavated by presplitting blasting, and the left edge section of the upper step of the right line.

After two sections of secondary linings are dug on the left line hole, the manufacturing of the left line secondary lining of the previous section and the left line secondary lining of the next section is returned, blasting parameters are strictly controlled in construction, blasting vibration monitoring is carried out in the blasting process, and meanwhile, data of ground surface settlement, settlement of the top of the hole in the hole, tunnel convergence deformation and steel frame internal stress are monitored on time in the construction process.

The invention has the following beneficial effects:

the pilot hole is led out in a one-way mode, and the problem that construction of the cliff at the outlet section is inconvenient is solved; the steps on the left and right holes are combined by long and short anchor rods to reinforce the triangular area at the upper part of the middle rock pillar and provide the bearing capacity of the surrounding rock; reinforcing the middle rock pillar after the left tunnel is excavated, and effectively reinforcing the middle rock pillar by adopting superfine cement single-liquid slurry; jumping and lining the first left hole, controlling the deformation of surrounding rock at the hole opening section, and avoiding the influence of the backward right hole on the blasting vibration of the first left hole; the backward right tunnel is excavated by adopting an advanced pilot tunnel, the advanced pilot tunnel can effectively reduce the disturbance to the surrounding rock, so that the self bearing capacity of the surrounding rock can be fully exerted, and meanwhile, the later settlement convergence of the surrounding rock can be effectively reduced by releasing part of underground stress in advance; when the right hole is dug, presplitting blasting is adopted, and the blasting vibration speed is controlled; one side close to the middle rock pillar is subjected to mechanical cold excavation, so that the middle rock pillar is prevented from being greatly damaged

In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a plan view showing a lining construction step of the present invention, wherein (a) is a schematic view of a left hole and (b) is a schematic view of a right hole;

FIG. 2 is a schematic illustration of the reinforcement of a middle rock pillar according to the present invention, wherein (a) is a schematic illustration of a left hole and (b) is a schematic illustration of a right hole;

FIG. 3 is a more schematic illustration of the hollow grouting bolt of the present invention with a small grouting conduit;

FIG. 4 is a view of the double-lined advanced ductwork arrangement of the present invention;

FIG. 5 is a sectional view of the stepped section on the left line of the present invention;

FIG. 6 is a construction step diagram of the present invention;

FIG. 7 is a schematic representation of a steel flower structure of the present invention;

fig. 8 is a schematic view of the horizontal bore hole arrangement of the present invention.

Reference numbers in the figures: 1 left line upper step primary support, 2 left line lower step primary support, 21 left line inverted arch, 3 left line filling layer, 4 left line secondary lining, 5 small pilot tunnel primary support, 6 right line upper step primary support, 7 right line lower end face primary support, 71 right line inverted arch, 8 right line filling layer, 9 right line secondary lining, 10 grouting small conduit, 11 hollow grouting anchor rod, 12 long advanced small conduit, 13 short advanced small conduit, 14I-steel, 15 grouting hole, 16 steel pipe, 17 stiffening hoop, I left line upper step section, II 1 left line lower step left section, II 2 left line lower step right section, III right line small pilot tunnel section, IV1 right line upper step right section, IV2 right line upper step left broken section, IV3 right line upper step left edge section, V1 right line lower step left section, and 2 right line lower step right section.

Detailed Description

Embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways, which are defined and covered by the claims.

The embodiment of the construction method for the exit of the tunnel with the minimum clear distance is explained by the tunnel excavation process in practical application. The construction method is implemented by constructing the high-speed old foundation tunnel of the Xingzi city-around of Guizhou province with the total length of 393m and is a branched short tunnel. The tunnel line spacing exit segment is the minimum contour line clear distance of 0.6m, and then gradually separated into the separated tunnel with the minimum clear distance, the small clear distance and the entrance segment line spacing of about 35 m. In the actual construction process, the effect is obvious, the technical problems of multiple construction procedures, complex structural stress, long construction period and high construction cost of the existing minimum clear distance tunnel exit construction method are solved, and the method has good economic benefit. As shown in fig. 1 to 8, the construction process includes the following steps:

step 1: excavating a left line upper step section I, constructing a left line upper step preliminary support 1, respectively excavating a left line lower step left section II 1 and a left line lower step right section II 2, excavating the left line lower step left section II 1 and the left line lower step right section II 2 in a staggered mode, wherein the staggered distance is about 5-15 m, constructing a left line lower step preliminary support 2, and grouting and reinforcing when the thickness of a middle rock pillar is 0.6-3.0 m.

Step 2: and (3) constructing a left-line inverted arch 21 and a left-line filling layer 3, and integrally molding a left-line secondary lining 4.

And step 3: and excavating a right line small pilot tunnel section III, and constructing a small pilot tunnel primary support 5.

And 4, step 4: and respectively digging a right section IV1 of the upper step of the right line, a left middle section IV2 of the upper step of the right line and a left edge section IV3 of the upper step of the right line, and constructing a primary support 6 of the upper step of the right line.

And 5: and (3) removing the primary support 5 of the small pilot tunnel, respectively excavating a left section V1 of the lower right step and a right section V2 of the lower right step, and constructing a primary support 7 of the lower end face of the right line.

Step 6: and constructing a right inverted arch 7 and a right filling layer 8, and integrally molding a right secondary lining 9.

The ultra-small clear distance tunnel exit construction is a construction process combining strengthening treatment of a 'middle rock pillar' and a staggered excavation method of controlling blasting for a left tunnel and a right tunnel. Namely left hole 'upper and lower step excavation, one-way hole outlet'; construction excavation technology for performing 'small pilot tunnel first and rear section expanding excavation' on right hole

And (4) excavating an upper step and a lower step, excavating a left hole by adopting an upper step and a lower step, and grouting and reinforcing the part of the middle rock pillar with the thickness of 0.6-3.0 m. And (3) one-way hole outlet, wherein double-layer small guide pipe advanced support is adopted for hole outlet of the upper step, the height of the upper step is properly reduced when the hole outlet is closed, weak blasting is performed, the influence of uphill slope of the hole is reduced to the maximum extent, and an active protective net is adopted at the outlet end to prevent flying stones from falling into canyons. The small pilot tunnel is firstly excavated in a small area, and then is constructed and supported to form the small pilot tunnel. The excavation of little pilot tunnel can effectively reduce the disturbance to the country rock, makes its full play self bearing capacity, simultaneously to releasing partly underground stress in advance, can effectively reduce the settlement convergence in country rock later stage, guarantees the safety of construction. The construction operation in the small guide tunnel appropriately strengthens the strength of the rock pillar so as to improve the bearing capacity of the rock pillar, reduce the disturbance of subsequent construction to surrounding rocks and avoid roof collapse and collapse accidents. And expanding and digging the section, expanding and digging the small pilot tunnel to the normal section, and constructing the primary tunnel support. After the rock pillar is reinforced, rock mass close to one side of the rock pillar is excavated by a rock drill or manually, the rock mass far away from one side of the rock pillar can be excavated by adopting an explosion mode, and the middle rock pillar is protected (weak explosion is adopted) during excavation. And after excavation, timely supporting is carried out, particularly, a rock mass close to one side of the rock pillar can be added with temporary support or supporting strength if necessary.

Technical assurance measures

1) And the first hole and the left hole are led out by adopting double rows of advanced guide pipes, and the specification of the advanced small guide pipe is a hot-rolled seamless steel pipe with the diameter of 42mm, the thickness of 4mm and the thickness of 4.0 m. The front end of the small conduit is made into a sharp cone shape, and the tail part is weldedThe reinforcing steel bar stiffening hoop is provided with quincunx drilling holes at intervals of 10-20 cm on the pipe wall, the diameter of each drilling hole is 6-8 mm, and the length of the tail part is not less than 30cm and is used as a grout stopping section without drilling holes.

2) The beating angle of the double-layer advanced small guide pipe is that the external plug angle of the oblique advanced guide pipe is 40 degrees, and each roof truss is worked. The horizontal advanced guide pipes are alternately arranged with the external insertion angle of 15 degrees and are constructed at intervals of roof truss. And welding the tail end of the forepoling small conduit with the steel arch after the construction is finished.

3) And (6) grouting. The forepoling small conduit ensures that the pressure injection ratio of cement paste is 1: 0.7. And after grouting is finished, effectively plugging the tail end of the small advanced grouting conduit. The grouting pump and the grouting pipe for grouting cement paste are reliably connected with the small guide pipe.

4) Left hole excavation control

5) And (5) excavating the two sides of the lower step in a staggered manner, wherein the staggered distance is about 5-15 m.

6) The middle reinforcing rock pillar is made of small grouting pipes with the diameter of 42mm and the thickness of 4mm, the circumferential distance of the small grouting pipes is 120cm, the longitudinal distance of the small grouting pipes is 60cm, the whole body is arranged in a quincunx shape, the grouting liquid is made of 1:0.7 superfine cement single liquid, and the grouting pressure is 1-1.5 MPa.

7) The axial included angle between the grouting guide pipe for reinforcing the middle rock pillar and the tunnel is 45 degrees.

8) And 6 advance probing holes, 3 radial advance probing holes and 3 horizontal advance probing holes are added when the tunnel exits 10m from the entrance to the cave in advance.

9) And before the steel arch frame is constructed, the excavated surface is closed by spraying concrete.

9) The inverted arch construction ensures that the steel arch frame is effectively connected with the lower step steel frame.

10) Before the inverted arch is constructed, the deficiency slag and the accumulated water need to be cleaned.

11) And sections YK15+627-YK15+677 of the right tunnel, specific road section marks are shown in the attached drawing of the specification, and the excavation is started by adopting the leading small pilot tunnel.

12) The width of the leading small pilot tunnel is 7.0m, the height of the leading small pilot tunnel is 4.5m, the distance from the top of the leading pilot tunnel to the vault of the tunnel is 2.7m, and the distance from the left side of the leading pilot tunnel to a rock pillar in the tunnel is 3.9 m.

13) Excavating 10-15m of the leading small pilot tunnel of the backward tunnel, and then expanding excavation of the upper step of the backward tunnel

14) When the upper bench of the right tunnel is excavated, blasting excavation is adopted in the part IV1, presplitting blasting excavation is adopted in the part IV2, and mechanical cold excavation is adopted in the part IV 3.

15) And when the second lining of the left hole is excavated to ZK15+640, stopping the construction of the second lining, moving the second lining trolley to the hole, constructing two linings of ZK15+ 697-679 of the hole section, and returning to ZK15+640 to construct the second lining.

16) When the concrete is sprayed, the concrete is guaranteed to be compact and have no cavity at each position;

17) blasting parameters are strictly controlled in construction, blasting vibration monitoring is carried out in the process, and the influence of blasting on the disturbance of the rock wall and the tunnel lining is reduced;

18) the data of surface subsidence, cave roof subsidence in the hole, tunnel convergence deformation, steelframe internal stress and the like are monitored on time in the construction process, so that the construction risk caused by backward hole construction is effectively avoided, and the construction safety is ensured

The invention adopts a small clear distance tunnel construction form instead of a multi-arch tunnel form; and controlling the influence of the backward tunnel on the surrounding rock deformation, the supporting stress and the blasting vibration of the forward tunnel.

And for the pilot tunnel, upper and lower step excavation is adopted, double rows of advanced small guide pipes are used for supporting, and the tunnel is discharged in one direction.

And (3) performing small-duct grouting on the right side of the pilot tunnel to obtain a medium rock pillar, wherein the grout adopts superfine cement single grout, and the grouting pressure is 1.0-1.5 MPa. The circumferential spacing and the longitudinal spacing of the grouting pipes are respectively 0.8m and 0.6m, and the grouting guide pipes are 42 steel perforated pipes.

In the construction process, the pre-grouting construction process and construction parameters, particularly the middle rock wall grouting parameters, are strictly controlled, so that the grouting quality is ensured; blasting parameters are strictly controlled in construction, blasting vibration monitoring is carried out in the process, and the influence of blasting on the disturbance of the rock wall and the tunnel lining is reduced; the excavation step distance is strictly controlled, the support is closely followed, and the surrounding rock exposure time is reduced; when the concrete is sprayed, the concrete is guaranteed to be compact and have no cavity at each position; when the inverted arch is constructed, the steel arch frame is effectively connected with the lower step steel frame, and the virtual slag and accumulated water are cleaned. And before the steel arch frame is constructed, the excavated surface is closed by spraying concrete. When the tunnel goes out of the tunnel, the circulating footage and the excavation height are strictly controlled, the supporting is tightly followed, the erection precision is strictly controlled, and the tunnel bias phenomenon is prevented. And monitoring data such as ground surface settlement, settlement of the top of the tunnel in the hole, tunnel convergence deformation, steel frame internal stress and the like on time in the construction process.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (9)

1. A construction method for enabling a tunnel with an extremely small clear distance to go out of a hole is characterized by comprising the following steps:
step 1: excavating a left-line upper step section (I), constructing a left-line upper step preliminary support (1), reinforcing the left-line upper step preliminary support (1) by using unequal-length anchor rods, respectively excavating a left-line lower step section (II 1) and a left-line lower step right section (II 2), excavating the left-line lower step section (II 1) and the left-line lower step right section (II 2) in a staggered manner, wherein the staggered distance is 5-15 m, constructing a left-line lower step preliminary support (2), and grouting and reinforcing when the thickness of a middle rock pillar is 0.6-3.0 m;
step 2: constructing a left line inverted arch (21) and a left line filling layer (3), jumping and beating a left line secondary lining (4), after the left line inverted arch (21) and the left line filling layer (3) are completed, moving a secondary lining trolley to a left line outlet, and preferentially constructing the secondary lining (4) of the left line cave mouth section;
the left line opening excavation control process is that when the clear distance between the left tunnel and the right tunnel is 1.79m-1.48m, the circulating footage is 2.4m, the two-step method is adopted for excavation, and the height of the upper step is 6.8 m; when the clear distance between the left tunnel and the right tunnel is 1.48m-1.17m, the circulating footage is 1.8m, the two-step method is adopted for excavation, and the height of an upper step is 6.8 m; when the clear distance between the left tunnel and the right tunnel is 1.17-0.88 m, the circulating footage is 1.2m, the three-step method is adopted for excavation, the height of the upper step is 3-4m, and weak blasting is carried out; when the clear distance between the left tunnel and the right tunnel is 0.88-0.59 m, the circulating footage is 0.6m, the three-step method is adopted for excavating, the height of an upper step is 3-4m, weak blasting is carried out, and an active protective net is adopted at an outlet section; two die secondary linings at the left hole outlet are required to be finished before the hole outlet of the right line hole, and the inverted arch of the left line hole needs to be ahead of the right line hole;
and step 3: excavating a right line small pilot tunnel section (III), and constructing a small pilot tunnel primary support (5); realizing left hole 'upper and lower step excavation, one-way hole exit'; the right hole is constructed by expanding and digging a rear section before a small pilot hole;
and 4, step 4: respectively expanding and digging a right section (IV 1) of the upper step of the right line, a left middle section (IV 2) of the upper step of the right line and a left edge section (IV 3) of the upper step of the right line, constructing a primary support (6) of the upper step of the right line, and reinforcing the primary support (6) of the upper step of the right line by using anchor rods with unequal lengths;
and 5: dismantling the primary support (5) of the small pilot tunnel, respectively excavating a left section (V1) of a lower step of the right line and a right section (V2) of the lower step of the right line, and constructing a primary support (7) of the lower end face of the right line;
step 6: and constructing a right-line inverted arch (71) and a right-line filling layer (8), and integrally molding a right-line secondary lining (9).
2. The method for constructing the tunnel with the minimum clear distance as claimed in claim 1, wherein the tunnel is excavated from the left tunnel by adopting a double-row advanced guide pipe, and the specification of the advanced guide pipe is a hot-rolled seamless steel pipe with the diameter of 42mm, the thickness of 4mm and the length of 4.0 m; and injecting non-shrinkage cement slurry with the ratio of 1:0.7 into the advanced guide pipe, and plugging the tail end of the advanced guide pipe after grouting is finished.
3. The extremely-small-distance tunnel cave-discharging construction method as claimed in claim 2, characterized in that the double-row advanced guide pipes comprise a row of long advanced small guide pipes (12) and a row of short advanced small guide pipes (13), the extrapolation angle of the long advanced small guide pipes (12) is 30-40 degrees, each construction is performed, the circumferential distance is 40 cm, and the longitudinal distance is 240 cm; the short advancing small guide pipes (13) are applied at an extrapolation angle of 10-15 degrees at intervals, the alternate long advancing small guide pipes (12) are arranged, and the circumferential distance is 40 cm and the longitudinal distance is 120 cm.
4. The method for constructing the tunnel with the minimum clear distance according to claim 2, wherein the advanced guide pipe comprises a steel pipe (16), grouting holes (15) are formed in the steel pipe (16), stiffening hoops (17) are welded at the tail of the steel pipe (16), the distance between the grouting holes (15) and the grouting holes (15) is 10-20 cm, the grouting holes (15) are in a quincunx shape, and the diameter of each grouting hole (15) is 6-8 mm.
5. The tunnel exit construction method for the extremely-small-clear-distance tunnel according to claim 1, characterized in that grouting small guide pipes (10) with the diameter of 42mm and the thickness of 4mm are adopted for grouting reinforcement of the middle rock pillar, the circumferential spacing of the small grouting guide pipes (10) is 120cm, the longitudinal spacing is 60cm, the whole body is arranged in a quincunx shape, the grout adopts 1:0.7 superfine cement single grout, and the grouting pressure is 1-1.5 MPa; the axial included angle between the small grouting guide pipe (10) and the tunnel is 45 degrees.
6. The method as claimed in claim 1, wherein 6, 3 radial and 3 horizontal advance probe holes are added when the tunnel exits 10m from the entrance.
7. The minimum clear distance tunnel cave-out construction method according to claim 1, characterized in that the excavated surface is closed by spraying concrete before applying steel arches of a left-line inverted arch (21) and a right-line inverted arch (71), and the steel arches are connected with a steel frame of a lower step; before the left-line inverted arch (21) or the right-line inverted arch (71) is constructed, the virtual slag and the accumulated water need to be cleaned.
8. The method for constructing the tunnel with the extremely small clear distance according to claim 1, wherein the small pilot tunnel is 7.0m wide and 4.5m high, the top of the small pilot tunnel is 2.7m far away from the vault of the tunnel, the left side of the small pilot tunnel is 3.9m far away from a rock pillar in the tunnel, and the expanding excavation of the upper step of the following tunnel is carried out after the small pilot tunnel is excavated for 10-15m, when the upper step of the right tunnel is expanded, the right section (IV 1) of the upper step on the right line is excavated by blasting, the left broken section (IV 2) of the upper step on the right line is excavated by presplitting blasting, and the left edge section (IV 3) of the upper step on the right line is excavated by a mechanical cold excavation method.
9. The method for constructing the tunnel with the minimum clear distance as claimed in claim 1, wherein after the step of the left line is excavated, 20m of secondary lining (4) is applied into the tunnel from the outlet of the left tunnel immediately, and then the secondary lining (4) is applied into the tunnel of the left tunnel, the blasting parameters are strictly controlled in the construction, the blasting vibration is monitored in the blasting process, and meanwhile, the data of the ground surface settlement, the displacement of the inner periphery of the tunnel, the strain of the primary support steel frame and the contact pressure between the primary support and the surrounding rock are monitored in time in the construction process.
CN201810278614.4A 2018-03-30 2018-03-30 Exit construction method for tunnel with extremely small clear distance CN108533272B (en)

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CN109184704A (en) * 2018-09-28 2019-01-11 北京市市政三建设工程有限责任公司 A kind of small-clear-distance tunnel excavation and middle folder rock reinforcement technique
CN109707394A (en) * 2018-12-17 2019-05-03 同济大学 A kind of construction method for subway tunnel shield receiving end portal
CN109470101B (en) * 2018-12-27 2020-06-16 中国地质大学(武汉) Method for researching influence of adjacent tunnel blasting on existing tunnel based on field model
CN109630135A (en) * 2019-01-16 2019-04-16 交通运输部公路科学研究所 A kind of method for tunnel construction of system supporting
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