CN114278310B - Construction method of micro steel pipe pile lattice beam at shallow buried section of tunnel - Google Patents
Construction method of micro steel pipe pile lattice beam at shallow buried section of tunnel Download PDFInfo
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Abstract
The invention provides a construction method of a miniature steel pipe pile lattice beam at a shallow-buried section of a tunnel, which belongs to the field of tunnel supporting methods. The earth surface protection micro-piles, the concrete lattice beams and the arch center in the hidden tunnel are connected to form a three-dimensional supporting system, and the pressure of primary support in the hidden tunnel is dispersed to bedrocks on two sides to form a stable stress system. The pressure of the preliminary bracing of the hidden tunnel is reduced, and the purpose of reducing the construction risk of the hidden tunnel is achieved. The micro pile lattice beam construction technical achievement is adopted to solve the geological hole digging problem of a shallow buried section accumulation body, a side slope and a heading slope do not need to be excavated to a large extent, original appearance is protected, and any disturbance is not caused to nearby buildings.
Description
Technical Field
The invention relates to the field of tunnel supporting methods, in particular to a construction method of a miniature steel pipe pile lattice beam at a shallow buried section of a tunnel.
Background
The tunnel often meets the shallow section construction in the hole body when being under construction, and the shallow section geological conditions in the hole body is relatively poor, overburden thickness is minimum, and in the tunnel undercut work progress, very easily because of the soil layer vibrations cause the shallow section to cave in, consequently need secretly dig the earth's surface to the shallow section that buries in the hole body before to the shallow section that buries in the tunnel and consolidate to improve the stability of hole body overburden thickness and country rock structure, ensure construction safety. The common ground surface treatment methods are mainly divided into open cut methods and cover cut methods, which are all treatment methods outside holes, but the construction method has a serious problem that various construction equipment and filling materials required by ground surface reinforcement need to be transported from the ground surface to a shallow buried section. Therefore, a better construction method for the shallow buried section of the tunnel needs to be designed.
Disclosure of Invention
The invention aims to provide a construction method of a micro steel pipe pile lattice beam at a shallow-buried section of a tunnel, which solves the technical problems in the background technology. Earth's surface slip casting belongs to the single-point and consolidates, and although the thick liquid possesses the diffusion function, in time encrypts the hole interval, the monoblock accumulation body still is difficult to form wholly in the hole top within range. The risk of overall sinking exists after the hole body is excavated and is near empty, and the problems that the arch change and the like are caused easily in the limit of primary support invasion are solved.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a construction method for a grid beam of a miniature steel pipe pile at a shallow-buried section of a tunnel comprises the steps of cleaning the ground surface of a hole body covering layer of the shallow-buried section of the tunnel, leveling the processing surface, retesting a central axis of the tunnel, mechanically punching the hole body covering layer of the shallow-buried section of the tunnel, detecting the quality of punched holes, preparing a reinforcement cage, placing the reinforcement cage into the punched hole steel pipe, injecting grout into the steel pipe, constructing a concrete grid beam on the ground surface of the hole body covering layer of the shallow-buried section of the tunnel, and constructing a blind hole of the tunnel after the concrete grid beam is hardened.
Further, need carry out a geology and investigate in detail before the earth's surface is handled, confirm the treatment range boundary, extend the treatment range to the accumulation body all around and set for the distance and make stable region play the supporting role to the sash roof beam, need level whole processing face during the earth's surface clearance, avoid unevenness or the step appears, the processing face unevenness can cause final sash roof beam not on same face, easily cause the sash to pull to split under vertical stress condition and lose the function, thereby reduce the wholeness and can not reach and consolidate treatment effect, the processing surface is uphill trend along the dark hole direction, the sash can not need to be carried out along domatic the arranging and excavate into the water plane with the processing face and then cause the destruction of earth's surface by force.
Furthermore, after tunnel central axis retesting, lofting is carried out on the earth's surface so as to determine positions and arrange on two sides of the central axis, and the earth's surface elevation of each pile number along the axis is retested to determine the drilling depth of each section of the miniature pile in the range needing to go deep into the hole body, so that omission and surplus of the reinforced area are avoided.
Further, at mechanical punching's in-process, practical steel pipe punches, because the accumulation body is loose state, the rubble, boulder mix with the ordinary pore-forming mode of earth and easily appear the phenomenon of collapsing hole, shrinkage cavity and sticking and boring, the pore-forming effect does not reach anticipated effect behind the tube drawing, to the pore-forming mode select the root canal to creep into or from advancing pore-forming need not the tube drawing and ensure the pore-forming quality, pore-forming aperture chooses for use
The drill bit makes steel pipe and pore wall have fixed gap and is used for the thick liquid to fill the frictional force that strengthens pipe wall and loose body, need clear up the hole to debris such as downthehole stone bits after the pore-forming, adopts high-pressure air gun to blow the hole, guarantees downthehole unblocked reinforcement cage of being convenient for and lays to end, and miniature steel pipe preparation adopts->
The length of the steel pipe is 2-3 m, the screw openings are connected by adopting a sleeve, the pipe wall is provided with slurry dispersing holes with the spacing of 30cm and arranged in a quincunx shape, the ends of the pipe openings are divided after the holes are formed, the grouting pipes and the slurry stop valves are welded, the grouting diffusion radius of the micro piles is 0.5-1.0 m, and the spacing of the micro piles is preferably controlled to be 0.7-1.4 m.
Further, the hole forming quality is detected by rechecking the drilling depth, and a plumb drop line method is adopted to detect whether the depth is consistent with the design depth, if the drilling depth does not meet the design requirement, secondary hole forming is required, and the hole forming quality detection frequency is 100 percent.
Furthermore, the reinforcement cage adopts three
The method comprises the steps of machining a thread steel bar into a tripod, integrally hoisting the tripod and placing the tripod into a hole, ensuring that the thread steel bar is exposed for 30cm and extends into a frame lattice beam, debugging the mix proportion of slurry on site before grouting of a miniature pile, controlling the grouting pressure to be 1.0-1.5 MPa, judging whether single-hole grouting is finished according to the condition that slurry return occurs on the hole wall at a visual hole opening according to the foundation, coring the middle position of two holes by a core drilling method for grouting quality detection, checking the diffusion condition of the slurry, wherein the core drilling detection frequency is 100% of the total number of the miniature pile and is not less than 3 holes.
Furthermore, in the construction of the concrete lattice beam, the section of the vertical column of the lattice beam of the concrete lattice beam is set to be 2.2 multiplied by 0.4m to accommodate 3 micro-piles, the distance between the cross beams is 3.2cm, and the section is set to be 1.8 multiplied by 0.4m to accommodate 3 micro-piles, after the boundary of the accumulation body is determined, the lattice beam column crosses the accumulation body and is located on the stable foundation rock, the accumulation body is anchored by providing vertical tension for the micro-steel pipe piles under the supporting effect, in the construction of the blind hole, the construction of the blind hole is carried out after the surface treatment is finished, the principles of pipe advancing, short advancing, strong supporting and frequent measurement still need to be followed when the hole is constructed, the inverted arch and two linings are stably propelled, the safety step distance requirement is strict with the specification requirement, the inverted arch distance is not more than 25m from the tunnel face, and the second lining distance is not more than 50m from the tunnel face.
The device of the construction method comprises a concrete lattice beam, a plurality of micro-piles and a primary supporting arch in a hidden hole, wherein the concrete lattice beam is arranged at the top end of a tunnel shallow-buried section tunnel body covering layer, the primary supporting arch in the hidden hole is arranged at the top end of the tunnel shallow-buried section hole, one ends of the micro-piles are connected with the concrete lattice beam and penetrate through the tunnel shallow-buried section tunnel body covering layer to be connected with the primary supporting arch in the hidden hole.
Further, the micropile includes steel pipe, steel reinforcement cage and thick liquid, and the steel pipe setting is in vertical hole, and the steel reinforcement cage setting is in the steel pipe, and the thick liquid is filled in the steel pipe.
Furthermore, the steel reinforcement cage comprises three reinforcing bars, the three reinforcing bars are arranged at intervals, the three reinforcing bars are arranged into a tripod structure, and fixing bars are welded at intervals outside the tripod structure.
Furthermore, the concrete lattice beam comprises vertical bars and transverse bars, wherein the two vertical bars are arranged on a covering layer of the tunnel shallow buried section, the directions of the two vertical bars are the same as the direction of the tunnel, the width of the two vertical bars is larger than that of the tunnel, the transverse bars are arranged between the two vertical bars, and the plurality of miniature piles are connected to the transverse bars and are integrally arranged with the transverse bars.
Furthermore, the vertical bars and the transverse bars are both composed of concrete and lattice beam reinforcement cages, and the lattice beam reinforcement cages are welded with the reinforcement cages.
Due to the adoption of the technical scheme, the invention has the following beneficial effects:
(1) The invention connects the earth surface protection micro-pile, the concrete lattice beam and the arch center in the hidden tunnel to form a three-dimensional supporting system, and disperses the pressure of primary support in the hidden tunnel to bedrocks on two sides to form a stable stress system. The pressure of the preliminary bracing of the hidden tunnel is reduced, and therefore the purpose of reducing the construction risk of the hidden tunnel is achieved. The project eight-hole tunnel adopts the micro pile lattice beam construction technical result to solve the geological hole-out problem of the accumulation body of the shallow buried section, the side and upward slopes do not need to be excavated by a large margin, the original appearance can be protected, and any disturbance is not caused to nearby buildings.
(2) Compared with the traditional shallow-buried section construction technology, the construction technology has the advantages of rapidness, safety, environmental protection and the like, is innovative, is based on the conventional earth surface grouting and introduces the theoretical basis of protecting the anchor rod frame beam of the roadbed slope, combines the conventional earth surface grouting and the conventional earth surface grouting to form advantage complementation, has good reference significance for similar projects, has a positive effect on promoting the innovation of the construction technology, and has remarkable benefit on improving the competitive power of enterprise industries and promoting the high-quality development of companies. And secondly, the later-stage risk can be basically ignored, the side and elevation slope is difficult to avoid by adopting other modes, potential safety hazards are brought to adjacent buildings, original surface vegetation can be restored after construction is completed, and the phenomenon that the driving is oppressed due to the large-area ground surface wound is avoided. The method has remarkable popularization and application values in the construction of the same type of tunnel, is mainly applied to the construction of the shallow buried section of the tunnel portal, provides technical support for the entrance and exit of the tunnel, and particularly has remarkable popularization values for the geological environment of the shallow buried accumulation body. The method has obvious advantages of reducing the construction period, reducing the construction cost and reducing the hidden tunnel construction risk.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a cross-sectional view of the present invention;
FIG. 3 is a transverse cross-sectional view of a micropile of the present invention;
FIG. 4 is a schematic view of a vertical cross-section of a concrete grid and a micro-pile according to the present invention;
fig. 5 is a plan view of the concrete grid of the present invention.
In the attached figure, 1-concrete lattice beam, 1.1-lattice beam reinforcement cage, 1.2-welding spot, 1.3-vertical bar, 1.4-horizontal bar, 2-micro pile, 3-preliminary bracing arch centering in the hidden tunnel, 2.1-hole, 2.2-steel pipe, 2.3-reinforcement cage, 2.4-grout.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings by way of examples of preferred embodiments. It should be noted, however, that the numerous details set forth in the description are merely for the purpose of providing the reader with a thorough understanding of one or more aspects of the present invention, which may be practiced without these specific details.
As shown in fig. 1, the construction method of the micro steel pipe pile lattice beam of the shallow-buried section of the tunnel comprises the following steps:
1) Surface cleaning and surface leveling:
before the earth surface is processed, one geological detail survey needs to be carried out to determine the processing range boundary, and the processing range needs to extend a certain distance to the periphery of a stacking body so that the stable region can play a certain supporting role on the sash beam. Need level whole processing face when the earth's surface clearance, avoid unevenness or step, processing face unevenness can cause final sash roof beam not on same side, easily causes the sash roof beam to pull under vertical stress state and splits the loss function, thereby reduces the wholeness and can not reach and consolidate the treatment effect. The treated surface generally presents an upward slope trend along the direction of the blind hole, and the lattice beams can be arranged along the slope surface, so that the treated surface does not need to be forcibly excavated into a horizontal plane to further cause a certain degree of damage to the ground surface.
2) Tunnel central axis retest
The drilling positions can be arranged on two sides of the central axis accurately by lofting the ground surface after the central axis of the tunnel is retested, and the drilling depth of each section of the miniature pile in the range needing to go deep into the tunnel body is determined by retesting the ground surface elevation of each pile number along the axis. The reinforcement area is not omitted and surplus is avoided.
3) Mechanical hole forming
Because the accumulation body is in a loose state, the phenomena of hole collapse, hole shrinkage, drill sticking and the like easily occur in a common hole forming mode of mixing broken stones and boulders with soil, and the expected effect is difficult to achieve due to poor hole forming effect after pipe drawing. The drilling mode needs to select root canal drilling or self-propelled drilling without pipe drawing to ensure the quality of the drilled hole. The pore diameter of the formed pore is preferably selected
The drill bit enables the steel pipe and the hole wall to form a certain gap for filling slurry to enhance the friction force between the pipe wall and the loose body. After the hole is formed, sundries such as stone chips in the hole need to be cleaned, a high-pressure air gun can be used for blowing the hole, and the smooth hole is ensured, so that the steel reinforcement cage can be conveniently placed on the bottom. The micro-steel pipe is manufactured by
The length of the steel pipe is 2-3 m, the screw openings are connected by adopting a sleeve, and the pipe wall is provided with slurry dispersing holes with the distance of 30cm and arranged in a quincunx shape. After the hole is formed, the pipe port is required to be divided and welded with a grouting pipe and a grout stop valve. The grouting diffusion radius of the micro-piles is generally 0.5-1.0 m, and the space between the micro-piles is preferably controlled to be 0.7-1.4 m.
4) Pore forming quality detection
The quality detection of the formed holes mainly comprises rechecking the depth of the drilled holes, and detecting whether the depth is consistent with the design depth by adopting a plumb drop line method, if the depth of the drilled holes does not meet the design requirements, secondary hole forming is carried out. The detection frequency of pore-forming quality is 100 percent of full detection.
5) Placing of reinforcement cage
The reinforcement cage adopts three
The thread steel bars are processed into a tripod and integrally hoisted and placed into the hole, and the blanking length is ensured to be exposed by 30cm and extend into the lattice beam.
6) Micro pile grouting
The micro-pile grouting is one of the most important processes of the construction method, and plays a decisive role in the treatment effect. The mixing ratio of the slurry on site needs to be adjusted before grouting, and the water-cement ratio is determined by combining the porosity of loose bodies, grouting pressure and other comprehensive factors if the water-cement ratio is not uniformly specified. The grouting pressure is controlled to be 1.0-1.5 MPa, and the single-hole grouting is finished according to the judgment that slurry return occurs on the hole wall at the orifice visible by naked eyes.
The grouting quality detection can adopt a core drilling method to core in the middle of two holes and check the slurry diffusion condition. The core drilling detection frequency is 100% of the total number of the micro-piles and is not less than 3 holes.
7) Construction of lattice beams
If the lattice beams are arranged according to the size of the roadbed slope lattice beams by using anchor rod points, construction is inconvenient due to the fact that the distance is too small, the distance is too large, the overlapping of the diffusion ranges of diagonal steel pipe grout is difficult to achieve, and the lattice beam lattice size setting is different from the arrangement of the roadbed slope lattice beams by taking the anchor rod distance as the standard. The construction method has the advantages that the section size of the lattice beam is large, multiple micro piles can be arranged, and the construction method is not limited by the space between the micro piles. The section of the vertical upright post of the lattice beam is set to be 2.2 multiplied by 0.4m and can contain 3 micro-piles, the distance between the cross beams is 3.2cm, and the section is set to be 1.8 multiplied by 0.4m and can contain 3 micro-piles. After the boundary of the accumulation body is determined, the lattice beam stand columns span the accumulation body and are located on the stable bedrock, and the supporting effect is achieved to provide vertical tension for anchoring the accumulation body to the miniature steel pipe pile.
8) Construction of hidden hole
And after the surface treatment is finished, the construction is carried out in a hidden tunnel, the construction in the tunnel still needs to follow 'pipe advancing, short footage, strong support and frequent measurement', the tunnel is stably propelled, an inverted arch and two linings can follow in time, the safety step distance requirement is strict with the specification requirement, the distance between the inverted arch and the tunnel face is not more than 25m, and the distance between the two linings and the tunnel face is not more than 50m.
Compared with the traditional shallow-buried section construction technology, the method has the advantages of rapidness, safety, environmental protection and the like, is innovative, is based on the conventional earth surface grouting and introduces the theoretical basis of protecting the anchor rod frame beam of the roadbed slope, combines the conventional earth surface grouting and the anchor rod frame beam to form advantage complementation, has good reference significance for similar projects, has a positive effect on promoting the innovation of the construction technology, and has remarkable benefit on improving the competitiveness of enterprise industry and promoting the high-quality development of companies. And secondly, the later-stage risk can be basically ignored, the side and elevation slope is difficult to avoid by adopting other modes, and potential safety hazards are brought to adjacent buildings. After the construction is finished, the original surface vegetation can be restored, and the phenomenon that a large-area ground surface wound is formed to bring oppression to the travelling crane is avoided. The method has obvious popularization and application values in the construction of the same type of tunnels.
In the unfavorable geological treatment of the accumulation body of the shallow-buried section of the tunnel opening, the earth surface protection micro-piles, the concrete lattice beams and the arch center in the dark tunnel are connected to form a three-dimensional supporting system, and the pressure of primary support in the dark tunnel is dispersed to bedrocks on two sides to form a stable stress system. The pressure of the primary support of the hidden tunnel is reduced, so that the purpose of reducing the construction risk of the hidden tunnel is achieved. The project eight-hole tunnel adopts the micro pile lattice beam construction technical result to solve the geological hole-out problem of the accumulation body of the shallow buried section, the side and upward slopes do not need to be excavated by a large margin, the original appearance can be protected, and any disturbance is not caused to nearby buildings.
The frame beams are utilized to pull the downward settled loose bodies through the vertical micro steel pipes, so that the effect of improving the integrity of the loose bodies is achieved, and the purpose of safely discharging holes is achieved.
As shown in figures 2-5, the device formed by the construction method of the micro steel pipe pile lattice beam at the shallow buried section of the tunnel comprises a concrete lattice beam 1, a plurality of micro piles 2 and a preliminary supporting arch 3 in the hidden tunnel, wherein the concrete lattice beam 1 is arranged at the top end of a covering layer of a tunnel body at the shallow buried section of the tunnel, the preliminary supporting arch 3 in the hidden tunnel is arranged at the top end of the tunnel body at the shallow buried section of the tunnel, one end of each of the plurality of micro piles 2 is arranged on the concrete lattice beam 1 and connected with the preliminary supporting arch 3 in the hidden tunnel through the covering layer of the tunnel body at the shallow buried section of the tunnel. The concrete lattice beams, the miniature piles and the primary support arch frames in the hidden tunnel form a spatial three-dimensional support system, the pressure of the primary support of the hidden tunnel is dispersed to bedrocks on two sides through the concrete lattice beams with high rigidity, the support pressure of the primary structure of the hidden tunnel is reduced, and the construction risk of the hidden tunnel is reduced under the condition that the earth surface is not damaged by heavy excavation. The micro-piles 2 penetrate through the preliminary supporting arch 3 in the dark tunnel by about 30cm and are fixedly arranged by welding.
A steel reinforcement cage is arranged in the miniature steel pipe pile to connect with the grid beam at the top, and grouting holes are arranged outside the miniature steel pipe pile to reinforce the accumulation body. And the pipe following drilling process is adopted to avoid hole collapse to influence the hole forming quality and guarantee the reinforcing quality. The depth of the drilled hole is within the range of the hole body, and the transverse radiation range is 5-10 m to the contour line of the tunnel. Set up the steel reinforcement cage in the miniature steel-pipe pile, the intraductal plump slurry of slip casting forms whole with steel pipe and steel reinforcement cage, and in steel pipe and steel reinforcement cage deepened lattice girder, steel reinforcement cage owner muscle and lattice girder reinforcing bar welded into wholly, then pour lattice girder and form vertical atress system. According to actual conditions, certain prestress can be applied to the reinforcing steel bars for extremely loose layers to strengthen the extrusion force on the stacking body. After the construction of the above procedures is completed, the interior of the lattice beam is covered with soil for greening, the original vegetation on the earth surface is quickly recovered, and the effects of environmental protection, no trace and reduction of rainwater washing and soaking are achieved.
In the embodiment of the invention, as shown in fig. 2, the micro pile 2 comprises a steel pipe 2.2, a reinforcement cage 2.3 and grout 2.4, the steel pipe 2.2 is arranged in the vertical hole 2.1, the reinforcement cage 2.3 is arranged in the steel pipe 2.2, and the grout 2.4 is filled in the steel pipe 2.2. The reinforcement cage 2.3 is composed of three reinforcements, the three reinforcements are arranged at intervals, the three reinforcements are arranged to be a tripod structure, and the fixing strips are welded at intervals outside the tripod structure. The micro-pile grouting is one of the most important processes of the construction method, and plays a decisive role in the treatment effect. The mixing ratio of the slurry on site needs to be adjusted before grouting, and the water-cement ratio is determined by combining the porosity of loose bodies, grouting pressure and other comprehensive factors if the water-cement ratio is not uniformly specified. The grouting pressure is controlled to be 1.0-1.5 MPa, and the judgment of the completion of single-hole grouting can be determined according to the occurrence of slurry return on the hole wall at the visual hole opening. The grouting quality detection can adopt a core drilling method to core in the middle of two holes and check the slurry diffusion condition. The core drilling detection frequency is 100% of the total number of the micro-piles and is not less than 3 holes.
In the embodiment of the invention, as shown in fig. 3-4, the concrete lattice beam 1 comprises vertical bars 1.3 and transverse bars 1.4, two vertical bars 1.3 are arranged on a covering layer of a shallow buried section of a tunnel, the direction of the two vertical bars 1.3 is the same as that of the tunnel, the width of the two vertical bars 1.3 is larger than that of the tunnel, a plurality of transverse bars 1.4 are arranged between the two vertical bars 1.3, and a plurality of micro-piles 2 are connected to the transverse bars 1.4 and are integrally arranged with the transverse bars 1.4. Vertical bar 1.3 and horizontal bar 1.4 all comprise concrete and lattice beam steel reinforcement cage 1.1, and lattice beam steel reinforcement cage 1.1 and steel reinforcement cage 2.3 welded connection. Lattice beam construction, the sash roof beam is if use the slope lattice beam size of roadbed to use the stock point to lead to the fact the construction inconvenience because of the interval undersize according to arranging, and the interval is too big to reach the coincidence of diagonal angle steel pipe thick liquid diffusion scope, and sash roof beam net size sets up and is distinguished from the slope lattice beam of roadbed and uses the stock interval to arrange as the standard. The construction method has the advantages that the section size of the lattice beam is large, multiple micro piles can be arranged, and the construction method is not limited by the space between the micro piles. The section of the vertical upright post of the lattice beam is set to be 2.2 multiplied by 0.4m and can contain 3 micro-piles, the distance between the cross beams is 3.2cm, and the section is set to be 1.8 multiplied by 0.4m and can contain 3 micro-piles.
The method is characterized in that a tunnel outlet end shallow buried section with eight interconnected holes is built on an old junction under No6 standard of an old highway from Guangxi south Dan to an old Ante lower expressway, the tunnel outlet is excavated to expose secondary road loose filling soil, the maximum thickness is disclosed to be 16.2m, the tunnel outlet end shallow buried section is mainly made of gray black loose gravel soil, the upper part of the lower place of the loose filling soil layer is clay, the thickness is 1.4-8.2 m, and the lower three-fold system of gray yellow, gray black thin-thick-layer strong-stroke argillaceous rocks, calcium shales and the like belongs to accumulation geology and is basically in a state without self-stabilization capability and belongs to a state of collapsing along with excavation.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be construed as the protection scope of the present invention.
Claims (3)
1. The construction method of the grid beam of the miniature steel pipe pile at the shallow buried section of the tunnel is characterized by comprising the following steps of: cleaning the ground surface of a tunnel shallow-buried section hole body covering layer, leveling the processing surface, retesting the central axis of the tunnel, mechanically perforating the tunnel shallow-buried section hole body covering layer, detecting the quality of the drilled holes, preparing a reinforcement cage, placing the reinforcement cage into the drilled hole steel pipe, injecting grout into the steel pipe, constructing a concrete lattice beam on the ground surface of the tunnel shallow-buried section hole body covering layer, and constructing a tunnel blind hole after the concrete lattice beam is hardened;
before the earth surface is treated, geological detail exploration is needed once, the boundary of a treatment range is determined, the treatment range extends to the periphery of a stack body for a set distance, so that a stable area can support the lattice beams, the whole treatment surface is required to be smooth when the earth surface is cleaned, unevenness or steps are avoided, the final lattice beams are not on the same surface due to the fact that the treatment surface is uneven, the lattice beams are prone to being pulled to crack and lose functions under a vertical stress state, the integrity is reduced, the reinforcement treatment effect cannot be achieved, the treatment surface is in an upward slope trend along the direction of a blind hole, the lattice beams are arranged along the slope surface, and the treatment surface does not need to be forcibly excavated into a horizontal plane so as to damage the earth surface;
in the process of mechanical drilling, a practical steel pipe is drilled, because an accumulation body is in a loose state, the phenomena of hole collapse, hole shrinkage and drill clamping are very easy to occur in a common hole forming mode of mixing broken stones and boulders with soil, the hole forming effect does not reach the expected effect after pipe drawing, the hole forming quality is ensured without pipe drawing for hole forming mode selection of root canal drilling or self-propelled hole forming, the hole forming aperture selects a drill bit with phi 127mm to ensure that a fixed gap exists between the steel pipe and the hole wall for filling slurry to enhance the friction force between the pipe wall and loose bodies, hole cleaning is needed to be carried out on sundries in the hole after hole forming, high-pressure air guns are adopted to blow the hole to ensure the smoothness in the hole and facilitate the placement of a reinforcement cage to the bottom, the miniature steel pipe is manufactured by adopting a steel pipe with phi 108 multiplied by 6mm, the pipe length is 2-3 m, a screw is connected by a sleeve, the scattered slurry holes with the interval of 30cm are arranged in a quincunx shape, the pipe orifice is separated and the slurry injection pipe wall and a slurry stop valve is welded after hole forming, the slurry injection diffusion radius of the miniature pile is 0.5-1.0.0.7-1.4 m;
the steel reinforcement cage adopts three 32mm threaded steel bars to be processed into a tripod and integrally hoisted and placed into a hole, the blanking length ensures that the triangular frame is exposed for 30cm and extends into a frame beam, the on-site grout mixing ratio debugging is required before grouting of a miniature pile, the grouting pressure is controlled to be 1.0-1.5 MPa, the single-hole grouting is finished according to the judgment that the grout return appears on the hole wall at a visual hole opening, the grouting quality is detected by adopting a core drilling method to core in the middle position of two holes, the diffusion condition of the grout is checked, and the core drilling detection frequency is 100% of the total number of the miniature pile and is not less than 3 holes;
in the concrete lattice beam construction, the section of a vertical upright post of a lattice beam of the concrete lattice beam is set to be 2.2 multiplied by 0.4m and contains 3 miniature piles, the distance between cross beams is 3.2cm, the section is set to be 1.8 multiplied by 0.4m and contains 3 miniature piles, the lattice beam upright post crosses an accumulation body and is located on a stable foundation rock after the boundary of the accumulation body is determined, the supporting function is realized to provide vertical tension for anchoring the accumulation body to the miniature steel pipe piles, in the dark hole construction, the ground surface enters the dark hole construction after being treated, the principles of pipe advance, short footage, strong support and measurement are still required to be followed in the hole construction, the inverted arch and the two linings are stably propelled, the safe step distance is strictly required, the inverted arch is not more than 25m away from the face, and the two linings are not more than 50m away from the face;
the device of the construction method comprises a concrete lattice beam (1), a plurality of micro piles (2) and a preliminary bracing arch (3) in a hidden hole, wherein the concrete lattice beam (1) is arranged at the top end of a tunnel shallow buried section tunnel body covering layer, the preliminary bracing arch (3) in the hidden hole is arranged at the top end in a tunnel shallow buried section hole, one end of each of the micro piles (2) is arranged on the concrete lattice beam (1) for connection, and penetrates through the tunnel shallow buried section tunnel body covering layer to be connected with the preliminary bracing arch (3) in the hidden hole;
the micro pile (2) comprises a steel pipe (2.2), a reinforcement cage (2.3) and grout (2.4), the steel pipe (2.2) is arranged in a vertical hole (2.1), the reinforcement cage (2.3) is arranged in the steel pipe (2.2), the grout (2.4) is filled in the steel pipe (2.2), the reinforcement cage (2.3) is composed of three reinforcements, the three reinforcements are arranged at intervals, the three reinforcements are arranged in a tripod structure, and fixing strips are welded at intervals outside the tripod structure;
concrete lattice beam (1) includes vertical bar (1.3) and horizontal bar (1.4), two vertical bar (1.3) set up on the shallow section of burying in tunnel body overburden, the direction of two vertical bar (1.3) is the same with the direction in tunnel, and the width of two vertical bar (1.3) is greater than the width in tunnel, a plurality of horizontal bar (1.4) set up between two vertical bar (1.3), a plurality of miniature stake (2) are connected on horizontal bar (1.4), and set up with horizontal bar (1.4) an organic whole, vertical bar (1.3) and horizontal bar (1.4) all constitute by concrete and lattice beam steel reinforcement cage (1.1), lattice beam steel reinforcement cage (1.1) and steel reinforcement cage (2.3) welded connection.
2. The construction method of the micro steel pipe pile lattice beam at the shallow buried section of the tunnel according to claim 1, characterized in that: the setting out is carried out at the earth's surface after tunnel axis retest and is convenient for confirm the position and arrange in the axis both sides, and the earth's surface elevation of retesting along every stake number of axis confirms that miniature stake needs go deep into every cross section drilling depth in the body of a hole within range, accomplishes that the reinforcement area is not missed, not proud surplus.
3. The construction method of the micro steel pipe pile lattice beam at the shallow buried section of the tunnel according to claim 1, characterized in that: the pore-forming quality detection is to recheck the drilling depth, and adopt a plumb drop line method to detect whether the depth is consistent with the design depth, if the drilling depth does not meet the design requirement, secondary pore-forming is required, and the pore-forming quality detection frequency is 100 percent full detection.
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| CN115030169A (en) * | 2022-05-13 | 2022-09-09 | 中交一公局第四工程有限公司 | Structure applied to hole digging of weak backfill tunnel and construction method |
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| CN106499413B (en) * | 2016-11-19 | 2018-09-21 | 中铁十二局集团有限公司 | A kind of Shallow-buried section tunnel stratum consolidation construction method |
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