CN116446915A

CN116446915A - Shallow tunnel portal supporting structure and construction method

Info

Publication number: CN116446915A
Application number: CN202310382500.5A
Authority: CN
Inventors: 谢江胜; 冯军武; 郭尚坤; 郭朋超; 张旭辉; 王建军; 申运涛; 余雄军; 董玉中; 祝迎辉
Original assignee: China Railway 20th Bureau Group Corp
Current assignee: China Railway 20th Bureau Group Corp
Priority date: 2023-04-11
Filing date: 2023-04-11
Publication date: 2023-07-18

Abstract

The invention relates to the technical field of tunnel construction, in particular to a shallow tunnel portal supporting structure and a construction method. The method comprises the steps of forming a tunnel opening construction area in an area where a tunnel opening is located, dividing the tunnel opening construction area into an in-tunnel construction section and an in-tunnel construction section with one side communicated with an outside environment through a construction section, inserting a first pipe shed into the first in-tunnel construction section, enabling one end of the first pipe shed, which is close to the outside environment, to extend into the in-tunnel construction section, inserting a second pipe shed into the in-tunnel construction section, and enabling one end of the second pipe shed, which is close to the in-tunnel construction section, to extend into in-tunnel construction section, so that at least part of the first pipe shed is overlapped, and therefore the method can solve the technical defect that when shallow tunnel opening construction is carried out in the related technology, collapse is easy to occur at the position of the tunnel opening, and the safety of the tunnel door construction is finally affected.

Description

Shallow tunnel portal supporting structure and construction method

Technical Field

The invention relates to the technical field of tunnel construction, in particular to a shallow tunnel portal supporting structure and a construction method.

Background

The burial depth of the tunnel portal is generally shallow, and when the tunnel portal is constructed, the hidden danger of easy collapse exists at the portal.

Disclosure of Invention

The invention mainly aims to provide a shallow tunnel portal supporting structure and a construction method, and aims to solve the technical problem that hidden dangers of easy collapse exist at a portal when the portal of a shallow tunnel is constructed in the related technology.

To achieve the above object, according to a first aspect of the embodiments of the present disclosure, a shallow tunnel portal support structure provided by the present disclosure, the tunnel portal is formed in a portal construction area, the portal construction area divides the portal construction area into a portal construction section and an in-tunnel construction section through a construction section, and one side of the portal construction section contacts with an external environment, including:

the first pipe shed is inserted into the hole construction section, and one end of the first pipe shed, which is close to the external environment, extends into the hole construction section; and

the second pipe shed is inserted into the hole construction section, and one end, close to the hole construction section, of the second pipe shed extends into the hole construction section so as to be at least partially overlapped with the first pipe shed.

Optionally, the first pipe shed includes:

35 small ducts in the circumferential direction are distributed with 1 ring at a longitudinal interval of 3 meters, 35 small ducts in each ring,

At least two small ducts and at least one long duct, at least two small ducts and at least two long ducts are alternately arranged at intervals on the circumference of the construction section, and the small ducts and the long ducts are gradually expanded from the external environment towards the construction section in the hole.

Optionally, the overlapping length of the first pipe shed and the second pipe shed is at least 1.4m.

Optionally, the small catheter includes conical end, pipe shaft and the iron hoop that connects gradually, the pipe shaft is including being close to the slip casting section that the conical end set up and keeping away from the end of stopping the thick liquid section of conical end, the iron hoop sets up stopping the periphery of thick liquid section, be formed with at least two-layer slip casting hole layer on the slip casting section, every layer slip casting hole layer all is the quincuncial arrangement.

Optionally, each grouting hole layer comprises at least two grouting holes which are arranged at intervals; the hole spacing between any two grouting holes is at least 15cm, and the aperture of each grouting hole is at least 8mm.

Optionally, the length of the slurry stop section is at least 50cm.

Optionally, the long guide pipe is a hot-rolled seamless steel floral pipe with a wall thickness of at least 6mm and an outer pipe diameter of at least 100mm, and each guide pipe in the second pipe shed is a hot-rolled seamless steel floral pipe with a wall thickness of at least 6mm and an outer pipe diameter of at least 100 mm.

According to a second aspect of the disclosed embodiment of the present invention, the present invention further provides a construction method of the shallow tunnel portal support structure, for constructing the shallow tunnel portal support structure of the first aspect, including the following steps:

applying a first pipe shed in the in-tunnel application section; wherein at least a portion of the first pipe shed extends into the in-tunnel construction section;

performing excavation construction in the hole construction section;

a second pipe shed is applied in the hole application section; wherein at least a portion of the second pipe shed overlaps the first pipe shed;

and excavating construction is carried out in the in-tunnel construction section so as to form the tunnel portal.

Optionally, the step of applying a first pipe shed in the in-tunnel construction section includes:

at least two small guide pipes are inserted into the hole inner construction section at intervals in the circumferential direction so as to form a small guide pipe shed at the hole opening section;

inserting at least one first long guide pipe between every two adjacent small guide pipes at intervals to obtain the long pipe shed;

and grouting the small conduit shed and the long conduit shed simultaneously to form the first conduit shed.

Optionally, the step of applying a second pipe shed in the hole construction section includes:

At least two second long pipes are inserted into the hole construction section at intervals in the circumferential direction, so that the second long pipe shed is obtained;

grouting into the second long pipe shed to form the second long pipe shed.

According to the technical scheme, an opening construction area is formed in an area where a tunnel opening is located, the opening construction area is divided into an in-opening construction section and an in-opening construction section with one side communicated with an outside environment through a construction section, then a first pipe shed is inserted into the first in-opening construction section, one end of the first pipe shed, which is close to an external environment, extends into the opening construction section, and meanwhile a second pipe shed is inserted into the opening construction section, and one end of the second pipe shed, which is close to the in-opening construction section, extends into the in-opening construction section, so that at least part of the first pipe shed is overlapped, and the technical defect that the construction safety of the tunnel opening is affected finally due to the fact that the first pipe shed is easy to collapse when shallow-buried tunnel opening construction is carried out in the related technology is overcome.

Drawings

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

FIG. 1 is a schematic structural view of an exemplary shallow tunnel portal support structure of the present invention;

FIG. 2 is a schematic side structural view of an exemplary support structure;

FIG. 3 is a schematic view of an installation structure of a grout stop section of an example of the present invention;

FIG. 4 is a flow chart of an exemplary method of constructing a shallow tunnel portal structure of the present invention;

FIG. 5 is a detailed flowchart of step S100 in FIG. 4;

fig. 6 is a detailed flowchart of step S300 in fig. 4.

Reference numerals illustrate:

reference numerals	Name of the name	Reference numerals	Name of the name
				100	First pipe shed	200	Second pipe shed
200A	In-tunnel construction section	B	Hole construction section

The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that, in the embodiment of the present invention, all directional indications (such as upper, lower, left, right, front and rear shallow tunnel portal supporting structures, construction methods and roads) are only used to explain the relative positional relationship, movement conditions, etc. between the components in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indication is correspondingly changed.

In the present invention, unless specifically stated and limited otherwise, the terms "connected," "affixed," and the like are to be construed broadly, and for example, "affixed" may be a fixed connection, a removable connection, or an integral body; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

In addition, if there is a description of "first", "second", etc. in the embodiments of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and/or" as it appears throughout includes three parallel schemes, for example "A and/or B", including the A scheme, or the B scheme, or the scheme where A and B are satisfied simultaneously. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.

Referring to fig. 1 to 6, the invention provides a shallow tunnel portal supporting structure, which has the following overall thought:

the tunnel portal is formed in a portal construction area, the portal construction area is divided into a portal construction section B and a portal construction section 200A through a construction section, one side of the portal construction section B is in contact with the external environment, the tunnel portal construction section B comprises a first pipe shed 100 and a second pipe shed 200, the first pipe shed 100 is inserted into the portal construction section 200A, and one end of the first pipe shed 100, which is close to the external environment, extends into the portal construction section B; the second tube nest 200 is inserted into the tunnel portal site B, and one end of the second tube nest 200 adjacent to the in-tunnel site 200A extends into the in-tunnel site 200A to overlap at least a portion of the first tube nest 100.

The method comprises the steps of forming an opening construction area in an area where a tunnel opening is located, dividing the opening construction area into an in-opening construction section 200A and an in-opening construction section 200A with one side communicated with an outside environment through a construction section, inserting a first pipe shed 100 into the first in-opening construction section 200A, enabling one end of the first pipe shed 100 close to the outside environment to extend into an opening construction section B, inserting a second pipe shed 200 into the opening construction section B, and enabling one end of the second pipe shed 200 close to the in-opening construction section 200A to extend into in-opening construction, so that at least part of the first pipe shed 100 can be overlapped, and the technical defect that in the related art, when shallow tunnel opening construction is carried out, collapse is easy to occur at the opening and the safety of the opening construction is finally affected can be solved.

In some embodiments, referring to fig. 1 and 2, the first pipe shed includes at least two small pipes and at least one long pipe, the at least two small pipes and the at least two long pipes are alternately and alternately arranged at intervals in the circumferential direction of the construction section, and the small pipes and the long pipes are gradually expanded from the external environment toward the in-hole construction section 200A.

In this embodiment, the first pipe shed 100 is configured as at least two small pipes and at least one long pipe, and the at least two small pipes and the long pipes are alternately and alternately arranged at intervals in the circumferential direction of the construction section, and the small pipes and the long pipes are gradually expanded from the external environment towards the direction of the in-hole construction section 200A, so that the invention can effectively strengthen the geologic body of the hole construction section B in the implementation process, and further avoid the technical defect that the geologic body is easy to collapse in the construction process.

It is specifically and explicitly stated that in a specific implementation, the angle between the small and long ducts and the central axis of the tunnel may be between 10 ° and 30 °. In practice, the angle is preferably 15 °.

In some embodiments, referring to fig. 2, the overlap length of the first pipe shed 100 and the second pipe shed 200 is at least 3m.

In the embodiment, the longitudinal distance between the steel arches is 0.6m, and the stress structure is better when exactly 5 arch frames are designed according to 3 m.

In some embodiments, the small catheter comprises a conical end head, a pipe body and an iron hoop which are sequentially connected, wherein the pipe body comprises a grouting section close to the conical end head and a grouting section far away from the conical end head, the iron hoop is arranged on the periphery of the grouting section, at least two grouting hole layers are formed on the grouting section, and each grouting hole layer is arranged in a quincunx shape.

In the embodiment, the slurry stopping section and the iron hoop are arranged on the slurry stopping section, so that the small guide pipe can be prevented from falling off through the slurry stopping section and the iron hoop arranged on the slurry stopping section in the implementation process.

In some embodiments, each of the grouting hole layers comprises at least two grouting holes arranged at intervals; the hole spacing between any two grouting holes is at least 15cm, and the aperture of each grouting hole is at least 8mm.

In this example, it is specifically and clearly stated that the grouting holes of the small pipes are 8mm and the grouting holes of the pipe sheds are 10mm.

In this embodiment, at least two grouting holes are formed in each grouting hole layer in a middle mode, and slurry diffusion and slurry solidification are facilitated.

In some embodiments, the length of the slurry stop segment is at least 50cm.

It should be specifically and explicitly stated that in this embodiment, the length of the slurry stop section of the exemplary small conduit is 50cm and the length of the slurry stop section of the pipe shed is 20cm.

In the embodiment, the slurry diffusion radius is 50cm, the 1 st row of grouting holes are 50cm away from the hole bottom, and grouting consolidation can be realized.

In some embodiments, the long conduits are hot rolled seamless steel tubes having a wall thickness of at least 6mm and an outer tube diameter of at least 100mm, and each conduit in the second shed 200 is a hot rolled seamless steel tube having a wall thickness of at least 6mm and an outer tube diameter of at least 100 mm.

In this embodiment, the seamless steel pipe is provided for the purpose of high rigidity and strength.

According to a second aspect of the disclosed embodiment of the present invention, referring to fig. 3 to 5, the present invention further provides a construction method of a shallow tunnel portal support structure, for constructing the shallow tunnel portal support structure of the first aspect, comprising the following steps:

s100, a first pipe shed 100 is applied in an in-tunnel construction section 200A; wherein at least a portion of the first pipe shed 100 extends into the in-tunnel construction section 200A;

in this embodiment, when the first pipe shed 100 is to be applied, the small guide pipe is first driven into the in-tunnel construction section 200A at any angle of 10 ° to 30 °, and then the long guide pipe is driven into the in-tunnel construction section 200A at any angle of 10 ° to 30 °. In specific implementation, the included angle of the small conduit inserted into the geologic body of the in-tunnel construction section 200A may be 10 °, and the included angle of the long conduit inserted into the in-tunnel construction section 200A may be 30 °. After the small and long catheters are completely inserted, grouting is performed simultaneously into the small and long catheters. The slurry used in grouting is cement according to parts by weight: water = 1:1.

S200, excavating construction is carried out in the hole construction section B;

in this embodiment, when the hole construction section B performs excavation construction, a shape matching with the hole in the design drawing needs to be excavated, and the hole construction is performed after the excavation is completed. After the formation of the tunnel portal, the excavation construction of the tunnel portal construction section B is completed.

It should be noted specifically and clearly that in this embodiment, the exemplary construction section is the section of the door on the side that is closer to the outside environment.

S300, constructing a second pipe shed 200 in the hole construction section B; wherein at least a portion of the second tube bay 200 overlaps the first tube bay 100;

in this embodiment, the long conduit is driven into the in-hole construction section 200A at any angle from 10 ° to 30 °. In particular, the included angle of the long catheterization section 200A may be 30. After the long catheter is fully inserted, grouting is performed simultaneously into the long catheter. The slurry used in grouting is cement according to parts by weight: water = 1:1.

s400, excavating construction is carried out in the in-tunnel construction section 200A to form a tunnel portal.

In this embodiment, after the plugging construction of the second pipe shed 200 is completed, the excavation construction is performed at the in-tunnel construction section 200A according to the construction drawing, and finally the tunnel portal structure is formed.

In some embodiments, referring to fig. 4, the step of applying the first tube shed 100 in the in-tunnel application station 200A includes:

s110, at least two small guide pipes are inserted into the in-hole construction section 200A at intervals in the circumferential direction so as to form a small guide pipe shed at the hole section;

in this embodiment, the small conduit is first driven into the in-tunnel construction section 200A at any angle of 10 ° to 30 °, and the included angle of the small conduit in the geologic body inserted into the in-tunnel construction section 200A may be 10 °.

S120, inserting at least one first long guide pipe between every two adjacent small guide pipes at intervals to obtain a long pipe shed;

in this embodiment, the long conduit is driven into the in-hole construction section 200A at any angle from 10 ° to 30 °. In particular, the included angle of the long catheterization section 200A may be 30.

And S130, simultaneously grouting the small pipe shed and the long pipe shed to form the first pipe shed 100.

In this embodiment, during grouting, the slurry is selected from cement in parts by weight: water = 1:1.

in some embodiments, referring to fig. 5, the step of applying a second tube shed 200 in the tunnel portal application station B includes:

s310, at least two second long pipes are inserted into the hole construction section B at intervals in the circumferential direction, so that a second long pipe shed is obtained;

S320, grouting into the second long pipe shed to form the second pipe shed 200.

In this embodiment, after the long catheter is fully inserted, grouting is performed simultaneously into the long catheter. The slurry used in grouting is cement according to parts by weight: water = 1:1.

the specificity of tunnel construction is mainly expressed in the aspect of operation safety, the tunnel construction safety is not only a safety technical problem, but also an engineering quality problem, and the two problems are combined to be comprehensively considered. In order to ensure the construction safety of the tunnel portal section and the shallow buried section, various dangers possibly occurring during construction are analyzed and corresponding technical measures are adopted on the basis of carrying out field investigation and grasping the topography, engineering geology, hydrogeology, environmental conditions and the like near the tunnel in detail.

The construction sequence is as follows: advanced geological forecast, step-by-step excavation and primary support.

And further ascertaining the conditions such as engineering geology, hydrogeology, activity situation and the like in front of the face by adopting geological radar.

The long pipe shed with the hole entering diameter of 30m is pre-supported, the outer diameter phi is 108mm, the wall thickness is 6mm, the advance small guide pipes with the diameter phi of 50mm are adopted for pre-supporting after the hole entering diameter of 30m, the longitudinal row spacing of the small guide pipes is 3.0m, and the horizontal lap joint length of two adjacent rows of small guide pipes is 1.4m. Namely, the overlapping length of two adjacent rows of small guide pipes is 1.4m, and the pipe shed is overlapped with the small guide pipes for 3m.

Advanced small catheter specification: phi 50 hot-rolled seamless steel floral tubes, the wall thickness is 4.0mm, the length of a single tube is 4.5m, 35 tubes are circulated each time, and the distance is 40cm.

Inclination angle: the small catheter adopts an elevation angle of 10 degrees.

Grouting parameters: 1:1 (weight ratio) cement slurry. Grouting pressure: 0.5-1.0 MPa.

The front end of the small guide pipe is processed into a cone shape, the tail end is welded with an iron hoop, grouting holes are drilled at the front part of the small guide pipe, the aperture is 8mm, the hole spacing is 15cm, the small guide pipe is arranged in a quincuncial shape, and the tail part is not drilled with a length of 50cm and is used as a slurry section.

Revealing the condition from the opening surrounding rock: the left and right lines are made of sandstone, and the texture is hard. So a step method is adopted for excavation. The upper step is 0.6m in length per cycle, and the lower step is 1.2m in length per cycle.

The whole ring of the support type is I20a I-steel, the distance is 0.6m, the thickness of C25 sprayed concrete is 26cm, the length of the early-strength mortar anchor rod phi 22 is 3.5m, the longitudinal and circumferential distances are 1m multiplied by 1m, the distance between phi 8 reinforcing steel meshes is 20cm multiplied by 20cm.

The reinforced concrete with the thickness of 50cm and the C30 is adopted, the bar spacing is 38cm, the model is HRB400 phi 22, and the spacing is 20cm.

Before the construction of the entrance portal, measuring and paying off are firstly carried out, a side slope excavation contour line and a water interception gutter are manufactured according to the measuring and paying off, so that surface water is effectively intercepted, the structural damage of the portal and the stability of the side slope are avoided due to the scouring of the surface water, water interception is facilitated, and a water interception gutter is arranged outside the excavation line by 3-5 m. The net size in the water interception gutter is 60cm, the wall thickness is 30cm, and C20 concrete is adopted for cast-in-situ.

And (3) hole excavation:

according to the principle of early entering and late exiting, construction in rainy season is avoided, the excavation height of the side elevation slope is strictly controlled, the excavation of the hole is carried out from outside to inside, the excavation amount is reduced as much as possible, the excavation is carried out in a layered and segmented mode from top to bottom, the step height is 2-3 m, and when the hole has a high steep slope or poor geology, the next excavation can be carried out after adopting measures for stabilizing the side elevation slope.

The earthwork and the strong weathered rock adopt mechanical excavation, the side elevation slope excavation surface is cleaned by manual cooperation, and the local abrupt slope section adopts manual excavation.

The slag is discharged by adopting a loader and an excavator to load slag in a matching way, and the slag is conveyed by a dump truck. And excavating waste slag at the hole, and transporting the waste slag to a specified waste slag field for stacking.

Slope protection:

and (3) performing entrance side slope protection in time after side slope excavation so as to prevent surrounding rock from weathering and rainwater from penetrating and slumping.

Temporary side elevation slope of the tunnel portal adopts an anchor spraying net for protection: phi 22 early-strength mortar anchor rod L=3.5 m, spacing 1.2m×1.2m, phi 8 reinforcing steel mesh 20×20cm, C25 concrete sprayed, and thickness 10cm. The cover layers of the opening section gravelly soil, the block stone soil and the like are thick, and loose rock mass at the top of the opening is removed before construction. The permanent protection of the side elevation slope adopts an anchor spraying slope protection.

The tunnel adopts advanced pre-supporting construction measures through the shallow buried section of the tunnel portal, and follows the principle of 'reinforcing first and then excavating', the advanced supporting measures of the tunnel portal section are 30m, and the 108mm long pipe shed mainly comprises: the device comprises a tunnel portal long pipe shed, an advance small guide pipe and an advance anchor rod.

The guide wall adopts C30 concrete, the cross section size is 0.55m 2m (high x long), the angle and the length of the long pipe shed guide wall are adjusted according to the actual geological conditions revealed by the field excavation, and the guide wall foundation adopts C15 concrete.

4I 20a I-shaped steel is arranged in the guide wall, phi 133 x 4mm guide steel pipes are arranged at the outer edge of the steel frame, and the steel pipes and the steel frame are welded through phi 25 fixed steel bars. The units of the steel frame are formed by welding connecting steel plates, the units are connected by bolts, and welding seams at joints are strictly carried out according to the related requirements of a steel structure. The dimensions of each diameter of the steel frame are marked according to the center line.

Pipe shed parameters:

steel pipe specification: the hot-rolled seamless steel pipe has an outer diameter phi of 108mm, a wall thickness of 6mm and a length of 35m, and is formed by connecting hot-rolled seamless steel pipes with lengths of 3m and 6m in a threaded manner (the effective length is 30 m). The number of joints in the same section in the steel pipe is not more than 50% of the number of pipes, and the joints of adjacent steel pipes need to be staggered by at least 1m. Therefore, the first sections of pipes are alternately arranged in 3m and 6m, the first sections of pipes with odd numbers are 3m long steel pipes, the first sections with even numbers are 6m long steel pipes, each section of pipe is 6m long steel pipes, two sections of steel flower pipes are connected by threads with phi 108mm, and the length of the threads is 30cm.

Tube distance: the circumferential spacing is 40cm.

Drilling grouting holes on the steel floral tube: the aperture is 10mm, the hole spacing is 150mm, the slurry stopping sections are arranged in a quincuncial shape, and the tail parts of the slurry stopping sections are 200cm without drilling holes.

Inclination angle: elevation angle is 2 deg..

And (3) construction errors of the steel pipe: the radial direction is not more than 20cm, and the circumferential direction between adjacent steel pipes is not more than 5cm.

Grouting material: 1:1 (weight ratio) cement slurry.

Before the long pipe shed is applied to the opening section, slope brushing and lofting are needed to be carried out on the opening, an ungrooved soil mold is used as an inner mold of the guide wall, then reinforcing steel bars are bound, and an outer mold is installed. Meanwhile, steel pipes with the diameter of phi 133 mm or 4mm are used as guide pipes, and concrete of the guide wall is poured and positioned accurately and fixed.

The 4 crawler-type down-the-hole drills are adopted to symmetrically carry out from a low hole position to a high hole position, the drilling machine is required to be parallel to the direction of a set orifice pipe, the position of the drilling machine must be accurately checked, and the repeated adjustment is required to ensure that the axis of a drill rod of the drilling machine is matched with the axis of the orifice pipe.

The diameter of the drill bit is phi 130mm. And the dry drill is adopted in the soil layer, the water flushing drill and the flushing hole wall are strictly forbidden, and meanwhile, the drilling speed is strictly controlled, so that the deflection, the distortion or the diameter change of the drilling hole is prevented. When the drilling machine is used for drilling, the drilling speed and the wind pressure can be gradually adjusted according to geological conditions after the hole is formed for 10 m.

The soil can be formed at one time with good quality, the hole collapse and the drill sticking are generated during drilling, and the drilling is performed after the grouting is supplemented. In the drilling process, a geological compass is often used for measuring the position of the drill, the quality of the hole is timely judged according to the drilling phenomenon of a drilling machine, and accidents in the drilling process are timely treated. After the drilling is completed, high-pressure air (wind pressure is 0.2-0.4 MPa) is used for completely removing powder and slag in the hole out of the hole so as to avoid reducing the bonding strength of the cement paste and the wall rock-soil body.

The down-the-hole drill is used for retracing the hole, removing scum to the bottom of the hole, ensuring that the aperture and the hole depth meet the requirements and preventing the hole from being blocked. And blowing out drill slag from the bottom of the hole to the hole by using high-pressure air. The tube housing Kong Qingjiao is inspected with a geological compass.

Screw threads are processed on a special pipe bed, grouting holes with the aperture of 10-16 mm (a shed pipe at the position close to the orifice of 2m is not drilled) are drilled around the guide pipe, the hole spacing is 15cm, the pipe head is arranged in a plum blossom shape, and the pipe head is processed into a cone shape so as to facilitate the hole entering.

And (5) installing a pipe shed in time after pore forming, so as to prevent hole collapse. The shed pipe utilizes the impact force and thrust jacking pipe of the pipe shed drilling machine.

The steel pipe screw threads should be screwed, and the joints of adjacent steel pipes should be staggered front and back. The number of joints in the same cross section is not more than 50%, and adjacent steel pipe joints are staggered by 3m.

Injecting square meter 0 cement mortar into the steel pipe of the pipe shed by adopting a KBY grouting machine, initially pressing the square meter 0.5-1.0 MPa, final pressing the square meter 2MPa, maintaining the pressure for 15min, and stopping grouting. If the grouting amount is not less than 1.5 times of the drilling cylinder and exceeds the limit, the grouting is continued by adjusting the concentration of the slurry until the grouting quality standard is met, so that the filling of the rock mass around the drilling and the holes around the steel pipe is ensured, and the grouting can be stopped. The "single" number hole is poured first and the "double" number hole is poured again during grouting.

Before grouting, an on-site grouting test is carried out, grouting parameters are adjusted according to actual conditions, and grouting construction experience of the pipe shed is obtained. And filling the steel pipe with M30 cement mortar after grouting is finished, and enhancing the rigidity and strength of the pipe shed.

Before the construction of the pipe shed, the tunnel face is sealed by adopting 10-20 cm thick sprayed concrete.

The steel pipe shed is constructed according to the designed position, the inclination measurement of the drilling holes is carried out by using an inclinometer, the drilling direction of the steel pipe shed is strictly controlled, and geological records of each drilling hole are made.

The drilling machine is selected to be suitable for the requirements of drilling depth and aperture, the drilling machine is required to be stable and flexible, the drilling can be performed within 360 degrees in the horizontal direction, and the guide frame is required during drilling.

The construction period should comply with the technical safety rules of tunnel construction and the operation rules of drilling grouting operation.

The construction section of the pipe shed should be reinforced with monitoring measurement to ensure the construction safety.

The figure is a single-layer phi 50 small conduit pre-support of an SC-3 arch part, and is suitable for S V-1 and S V-3 type lining.

Phi 50 lead small guide pipes are matched with a steel frame for use, and the horizontal lap joint length of two adjacent rows of small guide pipes is 1.4m.

Advanced small catheter design parameters:

advanced catheter specification: phi 50 hot rolled seamless steel tube, single length of 4.5m, outer diameter of 50mm and wall thickness of 4mm.

Spacing: the circumferential spacing is 40cm.

Inclination angle: the external insertion angle of the steel pipe is 10 degrees.

Grouting parameters: cement slurry cement ratio 1:1 (weight ratio) and grouting pressure of 0.5-1.0 MPa.

In order to ensure the supporting effect of the small guide pipe, the small guide pipe is erected on the steel frame, and the tail end of the steel pipe is welded with the steel frame.

The small guide pipe is installed by adopting a drilling and driving method, namely, drilling holes with the diameter 3-5 mm larger than the diameter of the steel pipe according to the design requirement, and then jacking the small guide pipe by using a hammering or drilling machine. The jacking length of the steel floral tube is not less than 90% of the length of the steel floral tube, and sand and stone in the steel tube are blown out by high-pressure air.

After the small conduit is installed, the orifice and surrounding cracks are plugged with plastic cement, and if necessary, concrete is sprayed near the small conduit and on the working surface to prevent the working surface from collapsing.

The excavation length of the tunnel is smaller than the grouting length of the small guide pipe, and the reserved part is used as a grout stopping wall of the next circulation.

Before grouting, field tests should be performed to determine final grouting parameters, and grouting sequences are injected from two sides of the arch to the arch.

And when the grouting amount reaches the designed grouting amount or the grouting pressure reaches the designed final pressure, grouting can be ended. In order to obtain a good consolidation effect, a sufficient amount of slurry must be injected to ensure a certain effective diffusion range. The grouting range is designed according to the dimension of 0.3-0.5 m outside the excavation contour line, and the slurry is uniformly diffused in the stratum.

The slurry single hole injection quantity Q is related to the porosity of surrounding rock, and is estimated according to the diffusion radius and the cracks of the rock stratum, and the slurry single hole injection quantity Q is as follows:

Q＝πR2L(m ³ )，

wherein: r—slurry diffusion radius (m);

l-length of grouting section (m);

η -formation porosity, sand 40%, clay 20%, shallow buried section 5%.

Grouting pressure is 0.5-1.0 Mpa, and reasonable grouting parameters are determined according to a construction site test in construction.

In the grouting process, the change of grouting pressure and grouting amount of a grouting pump is observed at any time, grouting conditions are analyzed, and pipe blockage, grouting and grouting leakage are prevented. Grouting records were made to analyze grouting effects.

Step method construction procedure description:

Excavating 1 step, constructing an initial support of the 1-part tunnel structure, spraying 5cm thick concrete, hanging a reinforcing steel bar net, erecting a steel frame, arranging a foot locking steel pipe, drilling a system anchor rod, and spraying concrete again to the designed thickness. b, after the step is constructed to a proper distance, excavating 2 steps by adopting single-side excavation or double-side staggered excavation, excavating a length of 1-3 m, lengthening a steel frame, and performing primary support of a tunnel body structure.

Construction notes:

the tunnel construction should adhere to the principles of weak blasting, short footage, strong support, early closing and measuring.

If auxiliary construction measures such as advance support are adopted, firstly, the construction of the steel frame erected by the previous cycle is finished, and then excavation is carried out. The excavation modes are weak blasting. And during blasting, the depth of the blasthole and the explosive loading quantity are strictly controlled. In construction, monitoring and measurement are carried out according to the requirements of related specifications and standard diagrams, the result is fed back in time, the stability of the structure of the tunnel body is analyzed, and a basis is provided for adjusting supporting parameters and pouring secondary lining time.

According to the design requirement, the anchor rod body and the anchor backing plate are processed on site, and relevant tests are carried out, so that the quality of the anchor rod is ensured. And correcting the construction parameters through experiments to guide large-area construction.

The mortar anchor rod adopts a double-pipe exhaust grouting operation, the slurry adopts cement mortar, the relevant tests and water quality tests of cement and sand materials are mainly completed in the construction preparation stage, and the slurry mixing ratio test is carried out.

And (3) measuring lofting, accurately discharging the anchor rod hole site according to the design requirement, and drilling by adopting a pneumatic rock drill. The system anchor rod allows deviation of + -5 cm when actually lofting.

And the high-pressure air is utilized to clean the holes, and the high-pressure water washing holes are strictly forbidden, so that the artificial hole collapse is avoided. And (5) after hole cleaning is finished, checking the pore channel, and checking the pore diameter, the pore depth and the pore channel gradient of the open pore.

The single-tube grouting process is adopted, the grouting pipe is directly inserted into the hole bottom of the anchor rod, the grouting pipe is repeatedly sent to the hole bottom after grouting is started, so that the mortar extrudes redundant water in the hole out of the hole, and then the grouting pipe is pulled out while grouting, so as to prepare the inserted link.

Cement mortar is used for grouting, and the water-cement ratio is 0.45-0.5. The strength grade of the cement mortar is not lower than square meter 0, the mortar mixing ratio is determined by in-situ test, the principle of mixing and using is maintained, and the mortar exceeding the initial setting time is scrapped. The dry shrinkage of the mortar must be within an allowable range.

And after grouting, an anchor rod is placed in time, and grouting is supplemented according to actual needs after the anchor rod is placed. After the anchor rod Kong Zhuman is pulped, anchor rod reinforcing steel bars are inserted into anchor rod holes, and grout stop plugs are installed.

When the mortar in the anchor rod hole reaches more than 80% of the design strength, the external operation of the installation of the backing plate can be performed. When the backing plate is installed, the backing plate is vertical to the axis of the anchor rod, the backing plate is tightly contacted with concrete, and various incorrect installation methods can have adverse effects on the anchoring performance of the anchor rod. When the axis of the anchor rod hole is not perpendicular to the plane of the orifice, in order to ensure that the backing plate can uniformly compress the rock face, the following steps are adopted: 1. the lower part of the nut adopts an inclined washer; 2. adopting an angular plate for adjustment 3. Adopting a spherical bell-shaped backing plate; 4. one of these four methods is to adjust with mortar or concrete after the pad.

The anchor rod hole is mainly used for checking the projects of the anchor rod such as hole position, kong Xiang, aperture, hole depth, hole cleaning quality and the like, the anchor rod body is mainly used for checking the anchor rod material, length, diameter, slurry performance and the like, and finally, the anchor rod body is sampled according to the standard requirement for checking the anchoring force.

The specification model, the length and the number of the anchor pipes are required to meet the design requirements during the construction of the anchor pipes, and the V-1 pin locking anchor pipes are: and the specification model phi 50 x 4mm hot rolled seamless steel pipes are 3.5m long each, two steel pipes are arranged at each arch foot part, and eight steel pipes are designed for each arch frame. IV-1, locking anchor rod: and the standard model phi 22 steel bars are 3.5m long each, two steel bars are arranged at each arch foot part, and eight arch frames are designed.

Vertical arch centering, drilling, checking and accepting hole depth, manufacturing and installing anchor pipes/blind rods, and welding and fixing U-shaped clamping bars.

And (3) standing: and erecting a steel frame according to design requirements.

Drilling: and (3) immediately carrying out foot locking anchor pipe construction after the vertical frame, marking the position to be drilled before drilling, and drilling at an included angle of 30-45 degrees with the vertical direction, wherein the drilling depth is greater than 95% of the anchoring length of the anchor pipe, but the overlength value is not greater than 10cm.

Manufacturing and installing anchor pipes: adopting a phi 50 wall thickness 4mm hot rolled seamless steel pipe, and directly punching the steel pipe into a hole by a rock drill during installation.

HPB300 phi 20U type clamping bar welded fastening requires the overlap joint length of reinforcing bar and steel bow member and anchor pipe: the width of the arch frame flange plate and the diameter of the anchor pipe are equal to each other, and the arch frame flange plate and the anchor pipe are fully welded with the two sides of the steel frame.

Reinforcing steel bar meshes are reinforced by a mesh welding machine, are laid by manually forming a ring along the excavated rock face by a multifunctional operation bench, are connected by lap joints, the lap joint length is not less than 30d, and the reinforcing steel bar meshes are connected with anchoring devices such as anchor rods by multiple points; the net rib shaking phenomenon which occurs when concrete is sprayed is reduced, and the reinforcing steel bar net can be fixed in an auxiliary mode through drilling equipment in construction, so that the reinforcing steel bar net is closely attached to a rock surface as much as possible.

The reinforcement mesh is paved after being sprayed and applied on the rock face as an anchor rod; the arch part is arranged from the arch top to the arch foot, and the side wall is arranged from top to bottom.

Paving a reinforcing mesh after primary spraying concrete on the excavated surface; the reinforcing mesh should be laid along with the fluctuation of the sprayed surface, and the gap between the reinforcing mesh and the sprayed surface is generally not more than 5cm; the reinforcing mesh is firmly connected with the anchor rods or the steel arch; the steel bar net is provided with a mark for controlling the thickness of sprayed concrete, and a short steel bar is generally arranged on the primary sprayed concrete surface to be welded with the steel bar net, or the mark is arranged by utilizing a steel arch frame.

The sprayed concrete is constructed by adopting a wet spraying mechanical arm and is matched manually. Before secondary repair spraying concrete, the primary spraying surface is blown clean by high-pressure air. When spraying concrete, the nozzle is vertical to the rock surface, the distance from the spray gun head to the sprayed surface is 0.6-1.5 m, when spraying is started, the distance from the spray head to the sprayed surface is reduced, the spraying angle is adjusted, and the concrete is forced to squeeze into the back of the reinforcing steel bar, so that the reinforcing steel bar can be completely wrapped by the concrete and the compactness of a sprayed layer is ensured; if the falling stone or concrete block is blocked by the reinforcing mesh during spraying, the concrete block should be removed in time.

The steel frame should be manufactured in sections, and the length of each section should be determined according to the design size and the excavation method. Each segment should be numbered, indicating the installation location.

The steel frame section is manufactured and formed by adopting a factory processing and manufacturing scheme and a cold bending method. The size and the number of the steel frames are calculated according to the central line, and the reserved deformation value is considered in design.

The thickness of the arch joint steel plate and the specification of the bolts are required to meet the design requirements; the joint steel plate bolt hole must adopt mechanical drilling, the drill hole adopts a grinder to remove burrs and steel slag, and every truss can be exchanged, and gas cutting and punching are strictly forbidden.

The processing size of the steel frame meets the design requirement, and the shape of the steel frame is adapted to the excavation section.

After the processing of the first steel frames with different specifications is finished, the steel frames are put on a flat ground for trial assembly, and the allowable deviation of peripheral assembly is +/-30 mm. When the sizes of the components meet the design requirements, the components can be mass-produced.

The profile, the middle line and the elevation of the excavated section should be checked before the steel frame is installed.

The steel frame installation should ensure that the two side legs must be placed on a firm foundation. The deficiency slag and other sundries at the feet should be thoroughly removed before installation.

The steel frame is installed after the primary spraying concrete, and is wedged by wedge blocks when a gap exists between the steel frame and the primary spraying surface. Considering that the bedrock pressure is transmitted through wedges between the bedrock and the steel frame, the wedges are hard wood wedges with a spacing of 1.0m. The pitch is not more than 2m.

After the steel frame is erected, the steel frame is corrected to a correct position according to the central line and the level, then the steel frame is fixed by using the positioning ribs, and is firmly connected with the adjacent steel frame by using the longitudinal connecting ribs, and the steel frame is vertical to the central line of a tunnel when being installed, and the steel frame is not inclined vertically, is not dislocated in the plane and is not twisted. Steel arch installation tolerance: the transverse sum Gao Chengjun is + -50 mm and the perpendicularity is + -2 deg..

All sections of steel frames are connected by connecting plates and are closely adhered. The installed steel frames are longitudinally connected with the steel frames of the previous truss by adopting phi 22 steel bars according to the design, and the circumferential spacing is 1.0m.

When the steel arch is installed, the steel frame arch foot is constructed in time, and the foot locking anchor rod (or anchor pipe) is arranged. The steel frame should fall to the bottom in time after the lower half is excavated.

And (3) the section with the inverted arch is excavated for 3m each time, after the excavation is completed, the substrate virtual slag is cleaned, and the super-excavated part is backfilled with concrete. Then installing an arch frame, and constructing C25 sprayed concrete to enable the primary support to be sealed into a ring early.

And before concrete is sprayed, the excavated section is detected according to the standard and the standard, and a wet spraying process is adopted. The construction machinery adopts a wet spraying manipulator.

The ordinary silicate cement, the hard clean sand with fineness modulus larger than 2.5 and continuous graded broken stone with particle diameter of 5-10 mm are selected, and the water is used for mixing qualified by test.

The sprayed concrete is strictly mixed according to the designed mixing proportion, and the mixing proportion and the stirring uniformity are checked at least twice per shift.

The tunnel section is carefully inspected before spraying, the underexcavated part and all broken rocks which are cracked, broken, water outlet points and disintegrated are cleaned and treated, pumice and wall corner broken residues are removed, and the rock surface is washed by high-pressure water or wind.

The concrete spraying operation is performed by spraying gaps between the arches and the outlines, spraying the surrounding of the arches, and then spraying gaps among the arches from bottom to top. The spray nozzle makes repeated slow spiral movement, and the spiral diameter is about 20-30 cm so as to ensure the dense concrete spraying. Meanwhile, the wind pressure, the flow and the spraying distance are mastered, and the rebound quantity is reduced. The distance from the spray gun head to the spray surface is generally 0.6-1.5 m, and the working pressure of the sprayer is controlled to be 0.2-0.7 MPa.

The primary spraying thickness is determined according to the design thickness and the spraying position, the primary spraying thickness is controlled to be 2-5 cm, the vault of the primary spraying concrete thickness is not larger than 10cm, the side wall is not larger than 15cm, and the sprayed concrete thickness is ensured to meet the design requirement.

The first injection is performed to level the rock face. The second concrete spraying is carried out after the first layer of concrete is finally set for 1h, and the first layer of concrete surface needs to be washed. And (3) after the sprayed concrete is finally set for 2 hours, carrying out water spraying maintenance, wherein the maintenance time is not less than 7d.

When the sprayed concrete is excavated, the interval between the next blasting and the completion time of the sprayed concrete is not smaller than 4 hours.

When the water gushing points are not more, a guide pipe is arranged to guide water and then the concrete is sprayed; when the water inflow range is larger, the dendritic drainage conduit is arranged and then concrete is sprayed; when the water burst is serious, a water discharge hole can be arranged, and concrete can be sprayed while water is discharged.

The cement consumption is increased, the mixing ratio is changed, the sprayed concrete gradually approaches to the water gushing point from far to near, a guide pipe is arranged at the water gushing point, water is led out, and then the sprayed concrete is sprayed near the guide pipe.

When the rock surface is generally permeable, mortar is sprayed first, the mixing amount of the accelerator is increased, and the construction is carried out according to the original mixing ratio after the primary spraying. When the local water yield is large, measures such as pipe burying, grooving, dendritic drainage blind ditches and the like are adopted, and concrete is sprayed after water is drained.

The treatment is performed when the local asperity size of the sprayed concrete is greater than the following requirements. Side wall: d/l=1/6; arch: d/l=1/8. Wherein: l-the distance between two adjacent convex surfaces of sprayed concrete; d-depth of convex recess of sprayed concrete.

Lining steel bars are processed in a steel bar processing shed, a transport vehicle is transported into a hole, steel bar welding and binding installation forming work are completed on a steel bar rack manually, double-sided lap welding is adopted for the steel bars, single-sided lap welding is adopted for inverted arches and two lining steel bars, positioning fixtures are adopted for inverted arch steel bars, the distance and row spacing of the inverted arches are controlled, and the steel bars are 50cm and 150cm higher than the top surface of a longitudinal construction joint. The steel bar is strictly forbidden to be polluted in the processing and transportation process of the steel bar, the steel bar can be formally used after being processed at the rusted part, and the thickness of the second lining protection layer is not less than 5cm. And C30 concrete cushion blocks are adopted, and the number of the cushion blocks is not less than 4 per square meter.

The V-level surrounding rock section, the inverted arch distance from the face surface is not larger than 40m, the IV-level surrounding rock section, the inverted arch distance from the face surface is not larger than 50m, the III-level surrounding rock section, and the inverted arch distance from the face surface is not larger than 90m.

The inverted arch is cast in full width by adopting an arc steel template, is formed at one time, has a casting length of 4m at one time, is formed by adopting an arc template at the end, is assembled and formed, and is strictly forbidden for half construction, so that the functions of early closing and collapse prevention are achieved, and a good construction environment can be built. In order to ensure the whole construction period requirement, the influence of inverted arch bottoming on the construction progress is reduced, the construction interference is reduced, 19m inverted arch trestle is utilized when concrete is excavated and poured, and the passing of ballasting transporting vehicles and other vehicles is ensured.

The foundation must be cleaned up and care must be taken to drain the water in time when applying inverted arch concrete. Draining accumulated water, binding reinforcing steel bars, ensuring a protective layer by adopting a concrete cushion block, installing an inverted arch template, and pouring concrete after qualified inspection and acceptance by a supervision engineer. The concrete is intensively stirred at a mixing station, a concrete transport vehicle is transported in, a chute is put into a mould, and an inserted vibrator is vibrated to be compact. The form can be removed after the inverted arch concrete reaches 2.5 MPa. For the sections with plain concrete lining, 2 rows of 80cm long sections are embedded inside and outside the joint part of the inverted arch and the secondary lining And connecting the steel bars.

Filling must be performed after the inverted arch concrete has reached strength, supporting the side forms, and casting into place once.

According to the design, the tunnel lining is timely carried out after the primary support is completed according to the principle of a spray anchor construction method. The secondary molding lining time is carried out when the clearance change rate measured by surrounding rock is less than 0.2mm/d, the deformation amount reaches more than 80% of the expected total amount, and the deformation rate has obvious slowing trend.

Firstly, roughening the surface of inverted arch concrete connected with the secondary lining, performing self-checking on the waterproof and drainage system, checking by a field supervision engineer after the checking is qualified, and positioning the movable trolley after the checking is qualified.

The concrete is distributed in different bins, layered horizontally and poured symmetrically, the speed of pouring the concrete and the single-side pouring height are controlled, and the single-side continuous pouring height is not more than 1m. The self-falling height of the pipe orifice of the conveying hose from the pouring surface to the concrete is controlled within 1.5m, so as to prevent the concrete from segregating. The concrete pouring must be continuous, the time interval between two adjacent layers is controlled within the standard allowable range, and the construction needs to leave a facility seam, so that design consent must be obtained and approved by a supervision engineer.

The frequency, amplitude, vibration speed and other parameters of the vibrator for tamping are determined according to the slump of the concrete and the particle diameter of the aggregate; the template, the steel bars and the embedded parts cannot be collided during vibration. The pouring construction adopts full-section one-step pouring molding, and when the concrete is poured to the junction of the wall arch, the interval is about 1h, so that the concrete of the side wall is settled. When the arch ring is closed, the arch ring is filled with the concrete and tamped in time.

The strength of the concrete is not lower than 5Mpa when the lining is removed, and the concrete is maintained within 12h according to the humidity condition, and the maintenance time meets the strength requirement of the concrete.

In order to prevent the occurrence of voids or incompact between the primary support and the secondary lining, grouting is carried out behind the lining before demoulding after the secondary lining pouring of the tunnel is completed for 3 hours.

In the construction, a PVC grouting pipe is reserved on the top of a lining trolley die plate, and 4 radial grouting pipes are arranged on a lining trolley with the number and arrangement principle of 12 m. The grouting pipes at the two ends are required to be positioned at 0.6-1.5 m from the ends, and the grouting pipes in the middle are required to be uniformly arranged. The grouting pipe has the outer diameter of 36mm, the inner diameter of 15mm and the wall thickness of 10.5mm.

And (3) embedding a fixed PVC grouting pipe on the trolley, and timely grouting an arch top through the embedded grouting pipe after lining construction. Grouting is operated by a grouting machine and a stirrer, and grouting materials are micro-expansion cement paste, so that the grouting material has the characteristics of micro-expansion, high fluidity, no bleeding and the like, plays a role in filling cavities, and can also play a role in compensating or repairing the defects of lining concrete.

Before grouting, checking whether grouting pipelines are firm and reliable or not and whether grouting system meters are normal or not.

The monitoring measurement is enhanced, so that the dynamic information and stability of surrounding rock and support in construction are mastered and fed back in time, so that the construction procedure is determined, the construction safety and engineering quality are guaranteed, the monitoring measurement points can be divided into two types of outside and inside the hole according to the position of the measurement, and the outside measurement points are buried on the ground surface and are used for monitoring the ground surface subsidence of a tunnel excavation influence area; the measuring points in the holes are buried around the excavated surrounding rock and inside the support and are used for monitoring deformation of the surrounding rock and internal force of the support.

The outside hole measuring points are arranged on the cross section where the clearance convergence measuring points are located. The observation point spacing is 5m.

The transverse arrangement range of the transverse earth surface settlement measuring points is larger than the width of the range of the predicted sliding fracture surface at two sides, the number of the single transverse section measuring points is not less than 11, the measuring points near the central line of the tunnel are required to be arranged in an encrypted mode, the distance between the adjacent measuring points is required to be controlled to be 2-3 m, the distance between the measuring points can be properly increased away from the central line of the tunnel, and the maximum distance is not more than 5m.

The vault sinking measuring points are used for judging the stability of surrounding rocks of the vault of the tunnel, and the peripheral displacement points are used for judging the stability of the surrounding rocks, whether the design and construction method of the primary support are proper or not and determining the casting time of the secondary lining. The settlement convergence point arrangement is basically closely related to the construction method, the settlement observation points are arranged on a vault, and 1 group of observation points are arranged on a V-stage surrounding rock at intervals of 5m, and each group of 5 observation points are arranged.

Frequency of surface subsidence measurement: the measurement frequency should be increased appropriately in rainy season for 2 times/day. After the earth surface subsidence is converged and stabilized, the measurement time interval can be enlarged or irregular measurement can be carried out until the secondary lining is completed.

Frequency of hole perimeter displacement and dome dip measurements: 2 times per day after excavation for 1-15 days, 1 time per 2 days per 16 days-1 month after excavation, 1 time per 7 days per 7 months per 1-3 months after excavation, and once per month.

Deformation management level: III, displacement U is less than U0/3, and normal construction is performed. And the level II, the displacement U0/3 is not less than U and not more than 2U0/3, and the support is reinforced. The level I displacement U is more than 2U0/3, the excavation of the face is suspended, and special measures are adopted. (U0-design limit displacement; U-measured displacement).

When geological conditions change, such as sand, soft soil and other excessively loose strata, the design institute is timely reported, the support type is adjusted, and the distance between steel frames is reduced. The structural anchor rod should ensure raw materials and construction quality, and the tail ends of various anchor rods (steel pipes) are firmly welded with the steel arch frame. The erection quality of the arch centering and the enough bearing capacity of the foundation at the arch springing are ensured. And the micro-vibration blasting is reasonably applied so as to avoid overlarge disturbance and damage of surrounding rock. The shotcrete support needs to be timely and the quality is guaranteed. Checking and measuring in time to strengthen the place with abnormal shape or large deformation.

The construction site is deployed in detail, and the site which does not pollute the environment and destroy farmlands is arranged on the waste site. The facilities such as wind, water, electric circuits and the like are uniformly arranged and are completed before entering the tunnel.

And before entering the tunnel, the tunnel portal engineering is firstly made, and the side and the upward slope of the tunnel opening are stabilized. Drainage facilities such as intercepting ditches, side ditches and the like are manufactured, and the surface water is ensured not to endanger the construction safety of tunnels and the stability of side and upward slopes.

And (3) setting up earth surface observation points, continuously observing and recording by specially assigned persons, enhancing monitoring and measuring of sinking of the arch tops in the holes, and timely treating the defects such as displacement and the like.

An emergency rescue material reservoir is arranged between the two holes for storing fireproof and waterproof equipment, supporting materials, various tools and the like. The stored equipment guarantees quantity and quality, is not used at will, and is used for supplementing quantity immediately after use. Rescue equipment and equipment list are shown in the rescue equipment and equipment list table 1.

Table 1 rescue equipment, equipment inventory table

The new law principle is strictly adhered to in construction, namely 'early prediction, pre-grouting, pipe advance, half section, core retention, short footage, weak blasting, strong support, tight sealing and duty measurement'.

The multi-arm drilling machine reaches the working surface, firstly, whether the vault and two sides are stable or not is checked, and if loose stones, soil or cracks are found, the working surface is cleaned or supported firstly.

When the excavator is used for discharging the danger, a special person is required to command, a forbidden person moves under the large arm of the excavator, and meanwhile, the excavator arm is prevented from colliding with the applied primary support surface and the temporary support system.

The geological condition changes, adopts dry drilling when encountering loess section stock drilling to strengthen construction water management. And the construction water is strictly controlled, and is not discharged in disorder. According to different geology, we take certain measures to ensure engineering quality.

The TSP203 earthquake emission wave is adopted as the main material, advanced geological forecast is carried out by assisting geophysical prospecting means such as advanced drilling, geological radar, geological sketch and the like, the cave-in and collapse in front are ascertained, and corresponding technical measures are adopted for different situations.

Shallow section of burying in tunnel: the method is characterized in that the phi 108 long pipe shed pre-support is adopted before the hole opening 30m is excavated, the advance small pipe pre-support, the advance small pipe grouting pre-support, the advance anchor rod pre-support and the like are adopted after the hole is introduced for 30m, and the tunnel is steadily and steadily drilled according to the principles of early forecasting, pre-grouting, pipe advance, half section, core reserving, short footage, weak blasting, strong support, tight sealing and duty measurement in construction, and the steps are the same, so that the tunnel quality and construction safety are ensured.

The monitoring and measuring frequency of the surrounding rock is enhanced, and the dynamic state of the surrounding rock is noticed at any time. And (3) carrying out anchor spraying support strictly according to design rules, controlling the deformation of surrounding rock and preventing collapse. The dedicated personnel are responsible for strengthening the safety warning measures and preventing the occurrence of emergency events.

The mechanical ballasting arrangement is ordered by a special person, the section size of the tunnel must meet the safe operation of the ballasting machinery so as to avoid the mechanical breaking of wires or the damage of the prepared primary support, and the following requirements are met: the ballasting is not higher than the carriage; and no person is allowed between the ballast loader and the ballast transporting vehicle.

Vehicles, construction machinery, template trolleys and the like in the holes are provided with low-voltage red flashing lamps at the outer edges to form a limit display facility. The transport vehicle is inspected in detail before use and must not work with the disease.

The following regulations are complied with when the vehicle is traveling: the distance of 50m is kept in the same direction of running, and when the visibility in a hole is poor, the distance is increased; when the vehicle starts, turns to and backs a car, the lamp must be turned on, and the lamp is expected to whistle.

When the vehicle runs in the hole, constructors do not need to rob the vehicle mechanically, do not need to take off the vehicle, track the vehicle and force the vehicle to lift.

After excavation, construction support is timely carried out, monitoring measurement is enhanced, if surrounding rock measurement data have mutation or concrete surface cracking is sprayed, the surrounding rock measurement data are regarded as dangerous warning signals when cracks appear on the earth surface, constructors are immediately informed of withdrawing the site, and construction is carried out after reinforcement treatment.

The primary support is strictly applied according to the design requirement, the function of the anchor spraying support is fully exerted, all the anchor rods are provided with the base plates, grouting quality is guaranteed, the grids and the steel support stand are vertical to ensure the thickness of the concrete protection layer of the steel bars and the steel frame, and the sprayed concrete adopts the wet spraying technology, so that the surface smoothness of the concrete is guaranteed.

The support is carried out in the hole, and the support is carried out along with the digging.

The lining trolley working section is pulled away from the excavation working surface by a proper distance, the clearance under the trolley ensures that vehicles and personnel can smoothly pass through, and an obvious vehicle creep mark is hung.

The workbench of the trolley is provided with a protective railing with the height not lower than 1.2m, the springboard is provided with an anti-skid strip, the workbench is tightly paved, the nailing and paving are firm, the end head of the wood board is lapped on the fulcrum, and the probe board cannot be arranged. The trolley is not stacked with material tools and other sundries, and the baffle plates at the two ends of the lining concrete are firmly installed.

When the concrete conveying hose or pipe is removed, the conveying pump should be stopped. The vibrating machine is provided with a protective cover, and the motor is provided with a grounding device.

And a ventilator is arranged for professional management during construction. Whether the ventilator is operated or not, strictly forbidden personnel stay near the inlet and the outlet of the air pipe, and when the ventilator stops operating, the personnel do not walk close to the ventilation hose and stay beside the hose, and do not put any articles on the ventilation pipe or the pipe orifice.

The ventilation calculation is performed to select the type of the ventilator and the diameter of the air pipe, so that each person of tunnel operators is guaranteed to provide at least 4m ³ Fresh air/min, keeping air flow speed not less than 15 m/min, and silica dust less than 1mg/m ³ The concentration of harmful gases in the air of the excavated working space does not exceed the standards required by the relevant labour regulations.

If the ventilation equipment has a fault or ventilation in the hole is blocked, all people immediately withdraw from the site, and no people enter the hole until the ventilation system does not return to normal operation and no comprehensive inspection confirms no harmful or explosive gas.

The tunnel electricity consumption is protected according to the electricity consumption operation safety measures, and the following measures are adopted:

the power supply circuit adopts 380/220V three-phase five-wire system, all uses dampproofing insulated wire, and the illumination voltage control of each position is: the working area of excavation, support and lining is 36V, the hole forming area is 220V, and the portable working lamp is 12-36V.

When the illumination line and the power line are installed on one side, the lines are erected in layers, and the lines must be firmly fixed on the tunnel wall and are not damaged by tunnel blasting. Each branch line on the power line is provided with a switch and a fuse, and the power line is forbidden to be overlapped with the lighting facilities.

The operation of the electrical equipment in the hole must meet the following specifications: the non-professional electrician cannot operate the electrical equipment, and the operating handle of the handheld electrical equipment is well insulated from the contact part in work, so that insulation inspection is performed before use.

The power supply equipment above 36V and the metal shell, framework and the like of equipment possibly with dangerous voltage due to insulation damage must be provided with grounding protection and an earth leakage protection device. The explosion-proof electrical equipment is inspected by professionals, and the qualified rear part can be installed, and the explosion-proof electrical equipment is periodically tested and inspected during use.

The method comprises the steps of forming a tunnel opening construction area in an area where a tunnel opening is located, dividing the tunnel opening construction area into an in-tunnel construction section and an in-tunnel construction section with one side communicated with an outside environment through a construction section, inserting a first pipe shed into the first in-tunnel construction section, enabling one end of the first pipe shed, which is close to the outside environment, to extend into the in-tunnel construction section, inserting a second pipe shed into the in-tunnel construction section, and enabling one end of the second pipe shed, which is close to the in-tunnel construction section, to extend into in-tunnel construction section, so that at least part of the first pipe shed is overlapped, and therefore the method can solve the technical defect that when shallow tunnel opening construction is carried out in the related technology, collapse is easy to occur at the position of the tunnel opening, and the safety of the tunnel door construction is finally affected.

It should be noted that, the foregoing reference numerals of the embodiments of the present invention are only for describing the embodiments, and do not represent the advantages and disadvantages of the embodiments. The above embodiments are only optional embodiments of the present invention, and not limiting the scope of the present invention, and all equivalent structures or equivalent processes using the descriptions of the present invention and the accompanying drawings or direct or indirect application in other related technical fields are included in the scope of the present invention.

Claims

1. The utility model provides a shallow tunnel portal supporting construction, tunnel portal forms in the entrance to a cave construction area, the entrance to a cave construction area will through the construction section entrance to a cave construction section and the interior construction section of hole are cut apart into to the entrance to a cave construction area, one side and the external environment contact of entrance to a cave construction section, its characterized in that includes:

2. The shallow tunnel portal support structure of claim 1, wherein the first pipe shed comprises:

3. The shallow tunnel portal support structure of claim 2, wherein the overlap length of the first pipe shed and the second pipe shed is at least 3m.

4. A shallow tunnel portal support structure as claimed in claim 3 wherein the small conduit comprises a tapered end, a tubular body and an iron hoop connected in sequence, the tubular body comprises a grouting section arranged close to the tapered end and a grouting section far away from the tapered end, the iron hoop is arranged on the periphery of the grouting section, at least two grouting hole layers are formed on the grouting section, and each grouting hole layer is arranged in a quincuncial shape.

5. The shallow tunnel portal support structure of claim 4, wherein each of the grouting hole layers comprises at least two grouting holes arranged at intervals; the hole spacing between any two grouting holes is at least 15cm, and the aperture of each grouting hole is at least 8mm.

6. A shallow tunnel portal support structure as claimed in claim 5 wherein the length of the grout stop section is at least 50cm.

7. A shallow tunnel portal support structure as claimed in claim 6 wherein the long conduit is a hot rolled seamless steel pipe having a wall thickness of at least 6mm and an outer pipe diameter of at least 100mm, and each conduit in the second pipe shed is a hot rolled seamless steel pipe having a wall thickness of at least 6mm and an outer pipe diameter of at least 100 mm.

8. A construction method of a shallow tunnel portal support structure for constructing the shallow tunnel portal support structure as claimed in claims 1 to 7, comprising the steps of:

performing excavation construction in the hole construction section;

9. The method of constructing a shallow tunnel portal support structure according to claim 8, wherein the step of constructing a first pipe shed in the in-tunnel construction section comprises:

10. The method of constructing a shallow tunnel portal support structure according to claim 8, wherein the step of constructing a second pipe shed in the portal construction section comprises:

grouting into the second long pipe shed to form the second long pipe shed.