CN112663625A - Construction and protection method for shallow-buried bias-pressure weak surrounding rock tunnel portal in alpine region - Google Patents
Construction and protection method for shallow-buried bias-pressure weak surrounding rock tunnel portal in alpine region Download PDFInfo
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Abstract
The invention discloses a construction and protection method for a shallow-buried bias-pressure weak surrounding rock tunnel portal in a high and cold area, which comprises the following steps: firstly, grouting and reinforcing surrounding rock (soil body) through a tunnel top; secondly, excavating a foundation pit of the open cut tunnel to carry out side slope net hanging, shotcrete and anchor supporting; drilling or digging holes, and pouring concrete into the pile holes by using the lower reinforcement cages; step four, erecting a profile steel arch, binding the guide wall reinforcing steel bars and building concrete; fifthly, installing a large pipe shed for grouting, and building a reinforced concrete open cut tunnel structure; step six, filling open cut tunnel foundation pits in a layered mode, and restoring original soil on the ground surface; and seventhly, excavating the underground excavation section by adopting three temporary inverted arches and steps. According to the method, the earth surface grouting, the advanced large pipe shed, the guide wall and the open cut tunnel structure are combined to form the whole tunnel portal supporting structure, the soft soil body section of the tunnel portal side slope can be reinforced and supported, and the side slope collapse, collapse and roof fall in the tunnel, cracking and overturning of the guide wall and primary lining intrusion or collapse in the excavation process are avoided.
Description
Technical Field
The invention belongs to the technical field of cold region tunnel construction, and relates to a construction and protection method for a shallow-buried bias soft surrounding rock tunnel portal in a high and cold region.
Background
With the rapid development of engineering construction in China, the construction of mountain tunnels is generally carried out by using the new Austrian method. The mountain tunnel construction in China inherits the principle of 'early entry and late exit', and meanwhile, the complexity of tunnel site selection is realized, and the tunnel portal cannot avoid the conditions of shallow burying, bias pressure, weak stratum or broken fracture zone and other unfavorable geology. Under such geological conditions, the tunnel portal is excavated, if unfavorable geology is not reinforced and treated, or a traditional tunnel portal excavation construction method is adopted, corresponding construction method adjustment is not needed, slope instability of the tunnel portal is easy to occur, a guide wall at a tunnel light and dark excavation junction is overturned, and the ground surface of the tunnel top is settled and cracked in a large range. Particularly for high-latitude seasonal frozen soil areas, surrounding rocks at a shallow buried tunnel portal of tunnel engineering are in a freeze-thaw environment, if the tunnel portal excavation construction meets the frozen soil thawing period and meets a strong water-rich stratum and has a seepage phenomenon, the strength of the surrounding rocks is rapidly reduced, for example, a strongly weathered argillaceous sandstone, a strongly water-swellable soil surrounding rock is greatly deformed, a weak interlayer exists in the stratum and the like, so that the stability after excavation is extremely poor, the deformation and stress of the surrounding rocks and the tunnel structure are rapidly increased, the advance support failure of a large pipe shed and the collapse invasion limit of primary support are greatly influenced, and the overall construction progress and quality of the tunnel engineering are greatly influenced.
Disclosure of Invention
The invention provides a construction and protection method for a shallow-buried bias-pressure weak surrounding rock tunnel portal in a high and cold area, and aims to solve the problems that a conventional construction method is low in efficiency, and cannot guarantee construction quality and construction period due to potential safety hazards such as cave top collapse and landslide at side walls of a tunnel portal in the construction process. According to the method, the earth surface grouting, the advanced large pipe shed, the guide wall and the open cut tunnel structure are combined to form the whole tunnel portal supporting structure, the weak surrounding rock (soil mass) section of the tunnel portal can be reinforced and supported, and the construction risks of side slope collapse, cave collapse and roof fall, guide wall cracking and overturning, primary anchor spraying lining limit intrusion or collapse and the like can be avoided in the excavation process. In the invention, the surrounding rock grades of the tunnel portal are V and VI grades, and are soft and weak surrounding rocks such as soil bodies or strongly weathered rock bodies and the like.
The purpose of the invention is realized by the following technical scheme:
a construction and protection method for a shallow-buried bias-pressure weak surrounding rock tunnel portal in a high and cold area comprises the following steps:
firstly, grouting and reinforcing surrounding rock (soil body) through a tunnel top.
In this step, carry out hole top earth surface reinforcement construction through squeezing into many sleeve valve pipes slip casting downwards at hole top earth surface, through squeezing into many slip casting sleeve valve pipes downwards at hole top earth surface, can replace the drilling rod and carry out quick pore-forming, use convenient operation, and do not have the hole phenomenon of collapsing, the accurate control sleeve valve pipe location of being convenient for simultaneously.
In the step, the positions of the sleeve valve pipes for grouting at the top of the tunnel are distributed in a quincunx shape along the longitudinal direction and the transverse direction of the tunnel, the distance is 2m multiplied by 2m, and the grouting reinforcement range of the sleeve valve pipes is 5m outside the tunnel excavation outline. The driving depth is adjusted along with the embedding depth of the tunnel, thereby realizing the reinforcement of surrounding rocks (soil mass) of the tunnel and improving the stability of the surrounding rocks (soil mass).
In this step, the sleeve material of the sleeve valve pipe casing adopts expansive soil: cement: the mass ratio of water is 1.5:2: 2; the water cement ratio of the grouting material cement paste is 0.8-1.1.
And secondly, excavating a foundation pit of the open cut tunnel to carry out side slope net hanging, shotcrete and anchor supporting.
In the step, the temporary foundation pit side slope of the tunnel open excavation section is subjected to net hanging anchor spraying support, and the single-stage brush slope with the gradient exceeding 10m is excavated into steps. The construction difficulty is reduced, and open cut construction is facilitated by arranging the slow platforms at each level when the slope is graded. The side slope is supported by adopting a hanging net and jetting, and the open cut construction period can be shortened by supporting and following the excavation construction. The open cut temporary foundation pit provides an enough construction site for the open cut tunnel structure of the tunnel.
And step three, drilling or digging holes, and pouring concrete into the pile holes by using the lower reinforcement cages.
In the step, a bored pile or a manually excavated pile is constructed on the basis of the temporary foundation pit of the open excavation section. The pile foundations are sequentially arranged on two sides of the lower portion of the open cut tunnel and the guide wall along the axis of the tunnel, and the distance S between the pile foundations is determined according to the condition of weak surrounding rock at the tunnel opening.
And fourthly, erecting a profile steel arch, binding the guide wall reinforcing steel bars and building concrete.
In this step, the top of the reinforced concrete pile foundation is connected with the foot of the profile steel arch to form an integral structure. The reserved steel bars on the pile top are anchored with the foot of the profile steel arch frame erected in the open cut tunnel or the guide wall, so that the vertical bearing capacity of the profile steel arch frame is increased. The steel bars are welded on the profile steel arch frame and connected to form a stable structure, and the circumferential arrangement distance does not affect the steel bar binding. The distance between two front and back adjacent profile steel arches is L, wherein the value range of L is 0.8 m-1.6 m. Each steel arch is fixedly connected through a transverse connecting piece (welding steel bars), and the pile foundation is used as a foundation, so that the pile foundation, the steel arch, the reinforced concrete open cut tunnel structure and the reinforced concrete guide wall form an integral frame structure, the horizontal bearing capacity of the guide wall is greatly enhanced, reverse thrust is provided for a weak landslide body or a broken fracture zone of a tunnel opening, large deformation of surrounding rocks (soil bodies) of the tunnel opening is effectively prevented, and the construction risk of tunnel entrance is reduced.
In the step, the profile steel arch frame in the open cut tunnel structure is not provided with a transverse support steel beam, temporary transverse support steel beams are arranged in anchor spraying concrete in the guide wall and the underground excavation section, and the temporary transverse support steel beams are dismantled when a lower soil body is excavated.
And fifthly, installing a large pipe shed for grouting, and building a reinforced concrete open cut tunnel structure.
In the step, a large pipe shed on a guide wall is installed and grouted, a plurality of grouting steel pipes are obliquely inserted forwards within the range of 1-3 degrees in the top and waist supply range of the guide wall, a reinforcement cage is arranged inside the steel pipes of the large pipe shed to improve the rigidity of the steel pipes, and the weak surrounding rock (soil body) of the tunnel excavation section at the rear part of the guide wall is reinforced in advance. The advanced reinforcement of the large pipe shed grouting increases the cohesive force of the weak surrounding rock (soil body) of the tunnel, effectively avoids vault collapse and roof fall, simultaneously ensures that tunnel underground excavation construction can smoothly pass through the soft sliding surface of the surrounding rock (soil body), reduces the stress of preliminary bracing and limits the deformation of the preliminary bracing, and meets the requirement of the tunnel boundary on the air.
And step six, filling the open cut tunnel foundation pit layer by layer, and recovering the original soil on the ground surface.
In the step, the cut open cut tunnel backfill is respectively C20 concrete, C20 pieces of stone concrete, a sand-gravel reverse filter layer, rammed soil, clay, a geotextile water-resisting layer and undisturbed soil from bottom to top. The water-resisting layer and the water filtering layer are arranged in a staggered mode to form the radial and longitudinal effective water intercepting and draining functions of the periphery of the tunnel, and the water draining difficulty of the later operation and maintenance of the tunnel in the geological section with strong water and rich water is reduced. The earth surface is backfilled by using undisturbed soil, so that the damage of construction to the field is minimized, the ecological recovery is quick, and the construction environment recovery cost is saved.
And seventhly, excavating the underground excavation section by adopting three temporary inverted arches and steps.
In the step, the excavation is divided into three steps, and each step is provided with temporary inverted arch shotcrete. Compared with the full-section excavation process, the three-step excavation method has more circulation, but a temporary inverted arch is arranged during excavation, the unloading of the tunnel face and the vault is slow, the phenomena of collapse, mud gushing and the like are avoided, and the construction quality of primary support is ensured.
According to the invention, the horizontal displacement and vertical settlement of the earth surface at the top of the tunnel, the displacement and inclination angle of the plane and section of the guide wall and the convergence of the displacement in the tunnel are matched with the monitoring and measurement of the excavation step sequence.
Compared with the prior art, the invention has the following advantages:
1. the invention obviously reduces the settlement of the earth surface at the top of the tunnel in the construction process of open excavation and hidden entry of the tunnel, and the deformation of the soil body tends to be stable. The guide wall has no overturning phenomenon, and the side wall has fast deformation and convergence. Cave top surrounding rock collapse and side wall surrounding rock landslide are avoided, the safety factor of tunnel construction is effectively increased, the safety of a tunnel structure is ensured, and the requirement of the construction period can be guaranteed after the construction process is optimized.
2. A plurality of grouting sleeve valve pipes are driven downwards into the ground surface at the top of the hole, so that the operation is convenient, the hole collapse is avoided, and the positioning is accurate. The driving depth is adjusted along with the embedding depth of the tunnel, thereby realizing the reinforcement of surrounding rocks (soil mass) of the tunnel and improving the stability of the surrounding rocks (soil mass). The open cut temporary foundation pit provides an enough construction site for the open cut tunnel structure. The pile foundation, the profile steel arch frame, the reinforced concrete open cut tunnel structure and the reinforced concrete guide wall form an integral frame structure. The advanced reinforcement of the large pipe shed grouting avoids vault collapse and roof fall of the underground excavation section, reduces the stress of primary support and limits deformation of the primary support. The three-step excavation method ensures that the phenomena of collapse, mud gushing and the like can not occur, and simultaneously ensures the construction quality of primary support.
3. The waterproof layer and the water filtering layer are arranged in a staggered mode to form the radial and longitudinal effective water intercepting and draining functions of the periphery of the tunnel, and the water preventing and draining difficulty of the later operation and maintenance of the tunnel in the geological section with strong water and rich water is reduced.
4. The earth surface is backfilled by using undisturbed soil, so that the damage of construction to the field is minimized, the ecological recovery is quick, and the construction environment recovery cost is saved.
Drawings
FIG. 1 is a side view of the structure of the present invention;
FIG. 2 is a structural component elevation of the present invention;
FIG. 3 is a plan view of the guide wall, primary support and secondary liner of the present invention;
FIG. 4 is a schematic illustration of open cut hole backfill of the present invention;
FIG. 5 is section 1 (guide wall) of FIG. 2;
FIG. 6 is section 2 (open hole) of FIG. 2;
FIG. 7 is a schematic diagram of three-step excavation of an underground excavated tunnel according to the present invention;
FIG. 8 is a schematic view of the guide wall and open cut tunnel reinforcing bars of the present invention;
FIG. 9 is a schematic view of the steel arch of the present invention;
FIG. 10 is a schematic view of the installation position of the large pipe shed and the steel arch of the present invention;
FIG. 11 is a schematic view of the connection between the steel arch and the pile foundation of the present invention;
FIG. 12 is a schematic view of the reinforcing bars of the reinforced concrete pile of the present invention;
FIG. 13 is a schematic elevation view of the present invention illustrating grouting reinforcement of the roof formation;
FIG. 14 is a plan view of the present invention for grouting reinforcement of the roof formation;
FIG. 15 is a schematic view of the reinforcement cage installed in the large pipe shed according to the present invention;
FIG. 16 is a schematic process diagram of the present invention.
In the figure: 1-a reinforced concrete pile foundation; 2-lining the open cut tunnel with reinforced concrete; 3-reinforced concrete guide wall; 4-pipe shed; 5-a steel arch frame; 6-steel support connections; 7-early-stage spraying concrete lining; 8-reinforced concrete secondary lining; 9-C20 concrete; 10-C20 slate concrete; 11-sand-gravel reverse filtration layer; 12-plain filling; 13-clay water-resisting layer and original soil; 14-sleeve valve tube; 15-hanging net and anchor spraying; 16-digging surface of upper step; 17-excavating surface of middle step; 18-lower step excavation surface; 19-steel reinforcement cage in the large pipe shed.
Detailed Description
The technical solution of the present invention is further described below with reference to the accompanying drawings, but not limited thereto, and any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be covered by the protection scope of the present invention.
A certain tunnel is in a freeze-thaw frozen soil area in the northeast high latitude season of China, and surrounding rocks at the tunnel portal are in V and VI grades. Surrounding rocks of the face to be excavated are completely weathered sandstone, mudstone and basalt, the lithologic contact relation is complex, the weathered layers of the basalt and the mudstone have strong expansibility, and underground water is abundant. And completing the slope support of the open cut tunnel section and the underground excavation section, and integrally entering the winter construction stage. After the underground excavation guide wall is constructed in winter, snow melting on the ground and the underground water level rise in spring, the tunnel face is located in a complicated sand-mud-rock interbedded section, rock mass is broken, water-rich bias voltage is generated, the strength of the sand-mud rock is reduced after the sand-mud rock meets water, the left side pressure of an upper middle step is large, the convergence deformation is serious, the settlement is overlarge, the primary support collapse damage is peeled off from the guide wall, the overturning angle of the guide wall is overlarge, steel supports and large pipe sheds in a tunnel are seriously deformed, the ground surface of a mountain on the top of the tunnel is cracked and greatly displaced, the tunnel construction is forced to stop, and the project becomes a tunnel with extremely high risk on the whole.
Therefore, the invention provides a construction and protection method for weak surrounding rocks at a tunnel portal of a shallow-buried bias tunnel in a high and cold region, which is characterized in that grouting reinforcement is carried out on soil bodies (or strongly weathered rocks) below the earth surface in a guide wall and pipe shed advance support range, so that the stress property of the surrounding rocks (soil bodies) in the range is improved; excavating a temporary foundation pit at the open excavation section of the tunnel to a designed elevation, carrying out net hanging anchor spraying support on a temporary side slope, and excavating steps when the slope of a single-stage brush slope exceeds 10 m; determining the interval of reinforced concrete pile foundations according to the surrounding rock (soil mass) pressure of the underground excavation section, constructing reinforced concrete piles, and reserving anchoring steel bars connected with open cut tunnels or guide walls at pile heads; erecting a guide wall concrete template, binding reinforcing steel bars, pouring concrete, and erecting a profile steel arch before binding the reinforcing steel bars; subsequently, positioning, drilling and installing a large pipe shed on the guide wall to complete grouting of the pipe shed; assembling open cut tunnel lining steel supports while pouring the guide wall, welding each steel support into a frame structure through a plurality of steel bars, and binding open cut tunnel lining steel bars to pour concrete; filling foundation pits of the open cut tunnel section in a layered mode, and enabling the earth surface to be restored to original soil; and after the protective sleeve for the integral underground excavation tunnel is formed in the previous process, the section steel arch frame cross brace is dismantled, and the underground excavation section adopts a three-step temporary inverted arch excavation mode. The excavation construction process and the protection method both meet the requirements of national industry technical specifications. As shown in fig. 16, the method specifically includes the following steps:
firstly, grouting and reinforcing surrounding rock (soil body) through a tunnel top.
As shown in fig. 13 and 14, in this step, a plurality of sleeve valve pipes with a diameter of 50mm are driven downwards into the ground surface of the hole top to perform hole top ground surface grouting construction, and the sleeve valve pipes adopt bidirectional leather cup type grout stop plugs. The sleeve valve pipes above the top of the tunnel are connected to the upper edge of the tunnel structure, and the sleeve valve pipes on the two sides of the tunnel body are connected to the maximum spanning position of the structure. In the grouting range, grouting holes are arranged in a quincunx shape, and the distance is 2m multiplied by 2 m. In order to avoid the influence of drilling on the tunnel structure, 1m safety distance is reserved on the drilling boundary, the drilling end, two sides of the outer edge of the tunnel structure and the top of the structure. The reinforcing range is 5m outside the tunnel excavation contour line. The hole diameter of the drill hole is 60mm, the outer diameter of the sleeve valve pipe is 50mm, the slip casting diffusion is carried out in a permeation-splitting mode, and the diffusion radius is 1.2-1.5 m. The grouting pressure is 2-3 MPa or the grouting speed is determined according to the field test. The sleeve material of the sleeve valve pipe adopts expansive soil: cement: the mass ratio of water is 1.5:2: 2; the water cement ratio of the grouting material cement paste is 0.8-1.1. The sleeve valve pipe construction process comprises the following steps: drilling; pouring a shell material and a lower pipe; waiting for coagulation; grouting; finishing grouting standard; checking the grouting effect; cleaning the hole, roughening the hole wall, and plugging the grouting hole by M15 cement mortar.
And secondly, excavating a foundation pit of the open cut tunnel to carry out side slope net hanging, shotcrete and anchor supporting.
As shown in fig. 1 and 4, in this step, the temporary foundation pit side slope at the open excavation section of the tunnel is subjected to net hanging anchor-spraying support, and single-stage slope brushing with a gradient exceeding 10m is required to be divided into steps for excavation. The slope-releasing rate is 1:2, the early-strength concrete with the concrete grade C25 is sprayed on the surface, the thickness is not less than 100mm, a reinforcing mesh with the diameter of 8@150mm multiplied by 150mm is arranged in the early-strength concrete, the soil nails adopt 22 mm reinforcing steel bars, the spacing is 1500 multiplied by 1500mm, the quincunx arrangement is adopted, the hole-forming diameter of the soil nails is 100mm, cement paste is injected in the early-strength concrete, the water cement ratio is 0.4-0.6, and the cement adopts P.042.5. The lower bottom width of the foundation pit is larger than that of the open cut tunnel structure, and the length is determined according to the open cut section.
And step three, drilling or digging holes, and pouring concrete into the pile holes by using the lower reinforcement cages.
As shown in figures 1 and 2, in the step, the pile foundation is drilled or dug manually by a drilling machine, the pile diameter is 0.8m, the spacing is determined according to the actual geological condition on site, and the pile foundation is arranged at the lower part of the arch springing of the open cut tunnel and the guide wall structure. The pile body adopts uniform reinforcement, and reinforcing stirrups with the diameter of 18 are arranged every 1.5m, and the reinforcement of the pile body is shown in figure 12. The thickness of the protective layer of the steel bar at the outermost side of the pile is 50mm, and in order to ensure that the pile is tightly connected with the profile steel arch frame, a main bar with the length of 29d is reserved at the top of the pile and is used as the anchoring length. The strength grade of the pile body concrete is C30.
And fourthly, erecting a profile steel arch, binding the guide wall reinforcing steel bars and building concrete.
As shown in fig. 2 and 9, the open cut tunnel lining and guide wall structure comprises a plurality of steel arch frames, the two adjacent steel arch frames are identical and are equidistantly arranged along the longitudinal extension direction of the tunnel, and each steel arch frame is positioned on one cross section in the construction axial direction. The distance between two front and back adjacent profile steel arches is L, wherein the value range of L is 0.8 m-1.6 m. The longitudinal connecting pieces 6 are respectively connected between flange plates of two front and rear adjacent steel arch frames, so that the connection is simple and firm. The longitudinal connecting piece 6 is fixedly connected between the phi 22 steel bar and the section steel arch frame in a welding mode. As shown in fig. 11, the top of the pile foundation is provided with reserved steel bars to be anchored in the open cut tunnel and the guide wall, the frame feet are stably supported at the top of the pile foundation, and the shear-resistant pedals can be arranged according to actual needs.
As shown in fig. 5, 6 and 8, in this step, reinforcing steel bars are bound to form a formwork to pour concrete, and a C20 guide wall structure is constructed.
And fifthly, installing a large pipe shed for grouting, and building a reinforced concrete open cut tunnel structure.
As shown in fig. 10, in this step, the grouting process flow of the large pipe shed: manufacturing steel floral tubes → erecting a working platform → positioning a drilling machine → pushing a steel tube shed after drilling or adopting a pipe following drilling process → clearing holes → placing a reinforcement cage 19 → grouting → the pressure flow rate meets the requirement → finishing. The pipe shed is made of phi 108 hot-rolled seamless steel pipes with the wall thickness of 6 mm. Each section is 4-6 m long and is formed by connecting screw threads, grouting holes are drilled in the steel perforated pipe, the hole diameter is 10-16 mm, the hole spacing is 150mm, the steel perforated pipe is arranged in a quincunx shape, and a section which is 1100mm long and stops grouting is left at the tail part without drilling. The steel pipe is arranged along the vault and the waist of supplying of guide wall, and the hoop interval 400mm is arranged, and steel pipe axis and shaped steel bow member outer fringe line contained angle 1 ~3 along tunnel axis direction. In order to improve the bending rigidity of the pipe shed, a steel reinforcement cage is arranged in the steel pipe. The large pipe shed grouting adopts cement slurry with a water-cement ratio of 1:1, and the grouting pressure is 0.5-2.0 MPa. And binding open cut tunnel reinforcing steel bar formwork and pouring concrete after the construction of the large pipe shed is finished, so that the pile, the advance support of the large pipe shed, the open cut tunnel lining and the guide wall are firmly integrated to form a full-section support system.
As shown in fig. 6, the cut-open cut hole cross-section structure in this step is, from inside to outside: reinforced concrete; the M15 mortar leveling layer is 30 mm; 4mm of polyurethane waterproof paint; the thickness of the self-adhesive waterproof coiled material is more than or equal to 3 mm; a 50mm thick polyurethane insulation board + a waterproof board; double-layer geotextile; and a brick protective layer with the thickness of 60 mm.
And step six, filling the open cut tunnel foundation pit layer by layer, and recovering the original soil on the ground surface.
As shown in fig. 4, in this step, the backfill on both sides of the cut-open cut tunnel is, from bottom to top, respectively C20 concrete, C20 pieces of stone concrete, sand-gravel reverse filter, rammed earth, clay, geotextile water barrier and undisturbed soil. The water-resisting layer and the water filtering layer are arranged in a staggered mode to form the radial and longitudinal effective water intercepting and draining functions of the periphery of the tunnel, and the water draining difficulty of the later operation and maintenance of the tunnel in the geological section with strong water and rich water is reduced. The earth surface is backfilled by using undisturbed soil, so that the damage of construction to the field is minimized, the ecological recovery is quick, and the construction environment recovery cost is saved.
And seventhly, excavating the underground excavation section by adopting three temporary inverted arches and steps.
As shown in fig. 7, after the above steps are completed, tunnel construction is started to enter the underground excavation section, the excavation mode adopts a three-step method, temporary steel supports and inverted arch sprayed concrete are arranged on each layer of excavation step, the steps on each layer are staggered, and the profile steel arch frame is fixed by a foot locking anchor rod. And (5) after the section excavation is finished, removing the temporary inverted arch, and continuing to perform the anchor spraying process of the initial lining. Compared with the full-section excavation process, the three-step excavation method has more circulation, but a temporary inverted arch is arranged during excavation, the unloading of the tunnel face and the vault is slow, the phenomena of collapse, mud gushing and the like are avoided, and the construction quality of primary support is ensured.
Claims (10)
1. A construction and protection method for weak surrounding rock at a cave entrance of a shallow-buried bias tunnel in a high and cold region is characterized by comprising the following steps:
firstly, grouting and reinforcing surrounding rock (soil body) through a tunnel top,
step two, excavating a foundation pit of the open cut tunnel to carry out side slope net hanging, spray anchoring and supporting,
step three, drilling or digging holes, placing reinforcement cages in the pile holes for pouring concrete,
step four, erecting a section steel arch frame, binding the guide wall reinforcing steel bars and building concrete in a mold,
fifthly, installing a large pipe shed for grouting, building a reinforced concrete open cut tunnel structure by a mold,
step six, filling the open cut tunnel foundation pit in layers, restoring the original soil on the ground surface,
and seventhly, excavating the underground excavation section by adopting three temporary inverted arches and steps.
2. The construction and protection method for the cave mouth of the shallow-buried bias-pressure weak surrounding rock tunnel in the alpine region according to claim 1, wherein in the first step, the grouting reinforcement construction for the cave top surface is performed by driving a plurality of sleeve valve pipes downwards on the cave top surface and grouting.
3. The method for constructing and protecting the cave entrance of the shallow-buried bias-pressure weak surrounding rock tunnel in the alpine region according to claim 2, wherein the sleeve valve pipes are distributed in a quincunx arrangement along the longitudinal direction and the transverse direction of the tunnel at intervals of 2m x 2 m; grouting reinforcement range of the sleeve valve pipes is 5m outside the tunnel excavation outline; the sleeve material of the sleeve valve pipe adopts expansive soil: cement: the mass ratio of water is 1.5:2: 2; the water cement ratio of the grouting material cement paste is 0.8-1.1.
4. The construction and protection method for the cave entrance of the shallow-buried bias-pressure weak surrounding rock tunnel in the alpine region according to claim 1, wherein in the second step, single-stage slope brushing is performed by step excavation with the slope exceeding 10m, the slope releasing rate is 1:2, and the width of the bottom of a foundation pit of the open cut tunnel is larger than that of the open cut tunnel structure.
5. The construction and protection method for the cave mouth of the shallow-buried bias soft surrounding rock tunnel in the alpine region according to claim 1, wherein in the third step, the pile diameter of the pile hole is 0.8m, and the pile hole is arranged at the lower part of the arch foot of the open cut tunnel and the guide wall structure.
6. The construction and protection method for the cave entrance of the shallow-buried bias soft surrounding rock tunnel in the alpine region as claimed in claim 1, wherein in the fourth step, the open cut tunnel lining and the guide wall structure comprise a plurality of steel arch frames, the two adjacent steel arch frames are the same and are equidistantly arranged along the longitudinal extension direction of the tunnel, and each steel arch frame is located on one cross section in the construction axial direction.
7. The construction and protection method for the cave mouth of the shallow-buried bias soft surrounding rock tunnel in the alpine region according to claim 6, wherein the distance between two adjacent front and rear steel arches is L, wherein the value range of L is 0.8-1.6 m.
8. The construction and protection method for the tunnel portal of the shallow-buried bias-pressure weak surrounding rock in the alpine region according to claim 1, characterized in that in the fifth step, a large pipe shed on a guide wall is installed and grouted, a plurality of grouting steel pipes are obliquely inserted forward within the range of 1-3 degrees of top and waist supply of the guide wall, and the weak surrounding rock at the undercut section of the tunnel at the rear part of the guide wall is reinforced in advance; the large pipe shed grouting adopts cement slurry with a water-cement ratio of 1:1, and the grouting pressure is 0.5-2.0 MPa.
9. The construction and protection method for the shallow-buried bias-pressure weak surrounding rock tunnel portal in the alpine region according to claim 1, wherein in the sixth step, open cut tunnel backfilling is respectively C20 concrete, C20 pieces of stone concrete, sand-gravel reverse filtering layer, rammed soil, clay, geotextile water-resisting layer and undisturbed soil from bottom to top.
10. The construction and protection method for the cave mouth of the shallow-buried bias-pressure weak surrounding rock tunnel in the alpine region according to claim 1, characterized in that in the sixth step, temporary steel supports and inverted arch shotcrete are arranged on each layer of excavation steps of three-step excavation, the steps of each layer are staggered by a distance, and the section steel arch frames are fixed by using foot locking anchor rods.
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| CN112031814A (en) * | 2020-09-17 | 2020-12-04 | 攀钢集团工程技术有限公司 | Cave-entering construction method for crossing shallow-layer high-load highway |
| CN112963177A (en) * | 2021-04-19 | 2021-06-15 | 山东建筑大学 | Supporting method and structure for weak stratum shallow-buried large-section tunnel with hole |
| CN113216980A (en) * | 2021-05-20 | 2021-08-06 | 浙江交工集团股份有限公司 | Complex weak surrounding rock shallow-buried bias tunnel and construction method |
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