CN113266372A - Construction method for soft rock super-large section tunnel step in karst cave development stratum - Google Patents
Construction method for soft rock super-large section tunnel step in karst cave development stratum Download PDFInfo
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- 238000000034 method Methods 0.000 abstract description 27
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/006—Lining anchored in the rock
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/04—Lining with building materials
- E21D11/10—Lining with building materials with concrete cast in situ; Shuttering also lost shutterings, e.g. made of blocks, of metal plates or other equipment adapted therefor
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
- E21D9/006—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries by making use of blasting methods
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
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Abstract
The invention relates to the technical field of tunnel advanced support measure construction, in particular to a construction method of a tunnel step with an extra-large section of soft rock in a karst cave development stratum, which comprises the following steps: (1) confirming the grade of surrounding rock and the surrounding rock condition in front; (2) judging the development condition of karst according to the surrounding rock condition, judging whether a karst cave in front of the tunnel arch part develops according to the development condition of the karst, and determining advanced support measures and design parameters according to the surrounding rock grade and the development condition of the karst cave; (3) synchronously excavating an upper step and a lower step according to the design parameters of the steps; compared with the prior art, the invention has the beneficial effects that: the step construction method is applied to the construction of the tunnel with the extra-large section in the karst cave development stratum, advanced support measures are adopted according to the surrounding rock grade and the karst cave development condition in a classification mode, primary support and karst cave treatment measures are determined according to the tunnel face karst cave exposure condition and the tunnel face state in the geological sketch result, and a specific construction mode is adopted for the karst cave development stratum, so that the method is purposeful and more accurate.
Description
Technical Field
The invention relates to the technical field of tunnel advanced support measure construction, in particular to a construction method of a tunnel step with an extra-large section of soft rock in a karst cave development stratum.
Background
According to the international tunnel co-section division standard, the section area of the tunnel with the extra-large section is more than 100m2The tunnel with the super-large section of the road is generally a three-lane tunnel and a four-lane tunnel. And (3) for IV-level and V-level surrounding rocks of the tunnel with the extra-large section, a CD method, a CRD method and a double-side-wall pit guiding method are generally adopted for the same-part excavation method, namely the whole excavation section is divided into a plurality of parts for excavation, each part adopts temporary support to stabilize the surrounding rocks, the temporary support is dismantled after a supporting structure is closed, wherein the temporary support is mostly formed by supporting and combining a section steel frame, a reinforcing mesh and sprayed concrete.
The karst cave is a typical karst unfavorable geology, and geological disasters such as cave collapse, filler surge, ground surface collapse and the like are easily generated in the exposed tunnel, and the treatment measures mainly comprise closed backfill, concrete backfill, waste slag backfill, grouting reinforcement, wall building or advanced long pipe shed or small guide pipe and the like. When the construction is carried out in a karst stratum in which a karst cave develops, the tunnel with the extra-large section faces various construction problems by adopting a subsection excavation method. Such as: the smaller pilot tunnel can increase the relative size of the karst cave and increase the damage degree of the sudden surge disaster of the karst cave filling; due to a narrow operation space, the difficulty of safe evacuation of constructors is increased, and large-scale machinery cannot operate after a disaster occurs; the karst caves are revealed one by the pilot caves, the karst caves are disturbed for many times, and the implementation difficulty of karst cave treatment measures is increased; the tunnel face tunneling shutdown caused by the disaster of a single pilot tunnel influences the construction progress of other pilot tunnels, and the construction organization difficulty is high. And the working space of the partial excavation method is narrow and small, the working procedure is complex, large-scale mechanical equipment such as a multi-arm drill jumbo, an arch frame installing machine and a wet spraying manipulator cannot be used for operation, the mechanical matching degree is low, and the rapid construction of the large-section tunnel is difficult to realize.
With the development of surrounding rock reinforcement technology and large construction machinery, the technical conditions of large-section or full-section excavation adopted by a soft rock large-section tunnel are gradually mature, and the step method is gradually applied to the construction of the soft rock large-section tunnel.
Therefore, the method for constructing the tunnel step with the extra-large section of the soft rock in the karst cave development stratum has urgent research value, good economic benefit and industrial application potential, and is the basis of the power which can be completed by the method.
Disclosure of Invention
The present inventors have conducted intensive studies to overcome the above-identified drawbacks of the prior art, and as a result, have completed the present invention after having made a great deal of creative efforts.
Specifically, the technical problems to be solved by the present invention are: the construction method of the tunnel step with the extra-large section of the soft rock in the karst cave development stratum is provided, large-section (few-subsection) excavation is carried out under the condition that the stability of IV-grade and V-grade surrounding rocks of the tunnel with the extra-large section and the stability of the karst cave are guaranteed, an operation space is provided for large construction machinery, and the tunnel with the extra-large section is constructed more quickly, safely and economically.
In order to achieve the purpose, the invention provides the following technical scheme:
a construction method for a tunnel step with an extra-large section of soft rock in a karst cave development stratum comprises the following steps:
(1) confirming the grade of surrounding rock and the surrounding rock condition in front;
(2) judging the development condition of karst according to the surrounding rock condition, judging whether a karst cave in front of the tunnel arch part develops according to the development condition of the karst, and determining advanced support measures and design parameters according to the surrounding rock grade and the development condition of the karst cave;
(3) synchronously excavating an upper step and a lower step according to the design parameters of the steps;
(4) carrying out geological sketch on the tunnel face after dust removal and slag discharge, and carrying out karst cave treatment and primary support construction according to the geological sketch result;
(5) adjusting the advance support measure and design parameter of the next cycle and the design parameter of the step according to the geological sketch result;
(6) and (5) repeating the steps (3) to (5).
In the invention, as an improvement, the advance support measures and design parameters in the step (2) include the following modes:
(2-1) when the grade of the surrounding rock is IV, adopting a small advanced guide pipe for supporting, wherein the length of the small advanced guide pipe is at least 4.5 m;
(2-2) when the surrounding rock grade is V grade, adopting an advanced large pipe shed for supporting, wherein the advanced large pipe shed should penetrate through the karst cave and ensure that the rock-entering depth is at least 2.5m, and reinforcing the arch part in an annular manner within 120 degrees;
(2-3) when the surrounding rock grade is IV grade and the karst cave is filled in front of the tunnel arch part to develop, adopting a subarea advanced large pipe shed measure for supporting, wherein the subarea advanced large pipe shed is arranged in the development range of the karst cave filled in front of the tunnel arch part;
the development of the filling karst cave in front of the tunnel arch part shows that the filling karst cave is positioned in the range of 120 degrees of the tunnel arch part, and the filling karst cave scale is more than or equal to 50m3And the distance between the filling karst cave and the tunnel face is less than or equal to 4 m.
In the invention, as an improvement, the method for determining the development range of the karst cave filled in front of the tunnel arch part comprises the following steps:
(2-3-1) preliminarily determining the development range of the karst cave filled in front of the tunnel arch part according to the development condition of the karst in front;
(2-3-2) analyzing the size of the karst cave, the position of the karst cave and the type of the filling materials according to the drilling record of the pipe shed in the primarily determined range, and further determining the development range of the karst cave.
In the invention, as an improvement, the step design parameters in the step (3) comprise step height, step length and circulating footage, wherein the step length is 3-5 m, the step height is 4-6 m, and the circulating footage is a steel frame spacing of 1-2 trusses.
In the invention, as an improvement, the geological sketch result in the step (4) comprises a cavern revealing condition and a cavern state, wherein the cavern revealing condition is the size, the spatial position and the filling type of the cavern.
In the invention, as an improvement, the palm surface state comprises the following steps:
(1) the stable state of the palm surface is as follows: the palm surface has no obvious extrusion deformation, and is stable after a small amount of blocks fall off;
(2) the palm surface is in a stable state and is represented as follows: the face has no obvious extrusion deformation, and the number of falling blocks is increased along with time;
(3) the unstable state of the palm surface is represented as: the extrusion deformation of the tunnel face is obvious, a large amount of vault side walls fall off, local collapse is caused, and the tunnel face cannot be self-stabilized; when the tunnel face is in an unstable state, the primary support adopts the support measures of tunnel face closing and anchor-shotcrete support.
In the invention, as an improvement, the karst cave treatment measure in the step (4) is determined according to the scale, the spatial position and the filler type of the revealed karst cave.
In the invention, as an improvement, the design parameters of the steps in the step (3) should meet the construction conditions of karst cave treatment, the upper step can expose the karst cave vertically and longitudinally by increasing the height of the steps and increasing the length of the steps, the height of the adjusted steps is less than or equal to 6m, and the length of the adjusted steps can be more than 5 m.
Compared with the prior art, the invention has the beneficial effects that:
(1) the step construction method is applied to the construction of the soft rock super-large section tunnel in the karst cave development stratum, advanced support measures are adopted according to the surrounding rock grade and the karst cave development condition in a classification mode, primary support and karst cave treatment measures are determined according to the tunnel face karst cave exposure condition and the tunnel face state in the geological sketch result, and a specific construction mode is adopted for the karst cave development stratum, so that the method is purposeful and more accurate.
(2) Aiming at IV-grade surrounding rocks, the existing large-section tunnel step method construction adopts an advanced large pipe shed pre-reinforcement rear step method for excavation, but numerical analysis research shows that the tunnel face stability is better when the IV-grade surrounding rock extra-large-section tunnel step method is excavated, deformation damage mainly occurs in the primary support construction process, excessive deformation of a primary support structure is mainly controlled, advanced deformation is controlled by adopting an advanced small pipe to stabilize the surrounding rocks aiming at the deformation characteristics of the IV-grade surrounding rocks, a subarea advanced large pipe shed measure is adopted to perform advanced treatment on key areas of an arch part and large-scale filling karst cave development by combining the advanced geological forecast result, the primary support is quickly sealed by adopting a micro-step, the deformation after the support is controlled by adopting measures such as strengthening the strength of the primary support, and the deformation of the primary support structure is mainly controlled, which is the characteristic of the invention for targeted construction.
(3) Aiming at the V-level surrounding rock, numerical analysis research shows that deformation damage during excavation of the V-level surrounding rock super-large section tunnel step method is taken as tunnel face instability, advanced deformation is mainly controlled, the length of the advanced large pipe shed applied by the method is optimized according to the karst cave development condition so as to ensure the shed protection effect of the pipe shed on the front karst cave, the reinforcing range of the advanced large pipe shed is 120 degrees, the method is provided based on the numerical analysis result for improving the optimal reinforcing range of the surrounding rock stability and the case statistical result for easily causing the karst cave with the burst mud burst disaster, and the burst mud burst disaster of the karst cave can be effectively avoided.
(4) The construction design parameters of the existing large-section tunnel step method mainly consider the aspects of the operation space provided by large machinery and the stability of surrounding rocks, the step design parameters provided by the invention ensure that the operation space and the stability of the surrounding rocks of the large machinery are taken as precondition, and simultaneously consider the construction conditions of karst cave treatment, and correspondingly adjust when the karst cave is exposed. Compared with the prior art, the invention has stronger operability and safety.
(5) The existing partial excavation method of IV-level and V-level surrounding rocks of a large-section tunnel forms a supporting system by using a small pilot tunnel and temporary supports, has the problems of narrow working space, complex working procedures, low construction speed and the like, and because the influence of the development condition of the karst cave on the construction is not considered, a series of problems that the karst cave treatment measures are difficult to implement, constructors are difficult to escape when a disaster occurs, large-scale construction machinery cannot be used for disaster treatment and the like exist, the invention adopts advanced support measures such as an advanced large pipe shed or an advanced small pipe to improve the stability of the surrounding rock, adopts treatment measures such as advanced treatment or closed backfill, concrete backfill and the like of the advanced large pipe shed to improve the stability of the karst cave, and ensures that the IV-level and V-level surrounding rock super-large section tunnels can be excavated by adopting micro steps, compared with the existing subsection excavation method, the construction method can adopt large-scale mechanical construction, reduces construction operators and has low construction organization difficulty; temporary supports which cannot be recycled are saved, and the risk of dismantling the temporary supports is avoided; the disturbance times of the surrounding rock and the karst cave are less, and the stability control effect of the karst cave and the surrounding rock is better.
Drawings
In order to more clearly illustrate the detailed description of the invention or the technical solutions in the prior art, the drawings that are needed in the detailed description of the invention or the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.
FIG. 1 is a flow chart of the construction method of the present invention;
FIG. 2 is a schematic diagram of an arrangement of leading greenhouses according to a first embodiment of the present invention;
fig. 3 is a schematic diagram of an arrangement of partitioned advanced large pipe sheds according to a third embodiment of the present invention.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.
A construction method for a tunnel step with an extra-large section of soft rock in a karst cave development stratum comprises the following steps:
(1) the method comprises the following steps of performing work such as advanced geological prediction and face sketch on a tunnel face of a tunnel, and confirming the grade of surrounding rock and the condition of surrounding rock ahead, wherein the grade of the surrounding rock is generally in the IV-grade state and the V-grade state aiming at a soft rock stratum;
(2) judging and analyzing the development condition of karst according to the surrounding rock condition, wherein the development condition of the karst is obtained by judging the surrounding rock condition in front of the tunnel face, judging the development condition of a front karst cave according to the development condition of the karst, and determining advanced support measures and design parameters according to the surrounding rock grade and the development condition of the karst cave;
(3) carrying out blasthole forming and charging operation in the range of the upper step and the lower step, blasting the upper step and the lower step simultaneously, and excavating forwards in parallel, wherein the step design parameters can meet the operation space of large machinery under the condition of ensuring the stability of surrounding rocks;
(4) starting a fan to discharge dust in the tunnel, using an excavator to carry out danger elimination and undermining treatment on dangerous stones around the tunnel, carrying out mucking operation by the excavator matching with a mucking vehicle, carrying out geological sketch on a tunnel face after dust elimination and mucking, and carrying out karst cave treatment and primary support construction according to geological sketch results;
(5) adjusting the advance support measure and design parameter of the next cycle and the design parameter of the step according to the geological sketch result;
(6) and (5) repeating the steps (3) to (5).
The advance support measures and design parameters in the step (2) comprise the following modes:
(2-1) when the grade of the surrounding rock is IV, adopting a small advanced guide pipe for supporting, wherein the length of the small advanced guide pipe is at least 4.5 m;
(2-2) when the surrounding rock grade is V grade, adopting an advanced large pipe shed for supporting, wherein the subarea advanced large pipe shed is arranged in the karst development range in front of the tunnel arch part, the arch part is reinforced in a 120-degree range in the circumferential direction, and the optimal length of the advanced large pipe shed is 20m in a large-section tunnel;
and (2-3) when the surrounding rock grade is IV grade and the karst cave is filled in front of the tunnel arch part to develop, adopting a subarea advanced large pipe shed measure for supporting, wherein the subarea advanced large pipe shed measure is that an advanced large pipe shed is arranged only in the development range of the karst cave filled in front of the tunnel arch part.
The karst development condition is that the karst cave is positioned in the range of 120 degrees of the tunnel arch part, and the scale of the karst cave is more than or equal to 50m3And the distance between the karst cave and the tunnel face is less than or equal to 4m, determining that the karst cave is filled in front of the tunnel arch part to develop.
In the step (2-3), the step of determining the development range of the karst cave filled in front of the tunnel arch part is as follows:
(2-3-1) preliminarily determining the development range of the karst cave filled in front of the tunnel arch part according to the development condition of the karst in front;
(2-3-2) analyzing the size of the karst cave, the position of the karst cave and the type of the filling materials according to the drilling record of the pipe shed in the primarily determined range, and further determining the development range of the karst cave.
The length of the partitioned advanced large pipe shed is optimized after analyzing the scale of the karst cave, the position of the karst cave, the type of fillers and the like according to the drilling record condition of the pipe shed, and the length of the advanced large pipe shed penetrates through the karst cave and ensures that the rock penetration depth is at least 2.5 m.
The design parameters of the steps in the step (3) comprise step height, step length and circulating footage, wherein the step length is generally 3-5 m, the step height is 4-6 m, and the circulating footage is a steel frame spacing of 1-2 steel frames.
Under special conditions, according to the scale of the karst cave, the design parameters of the steps meet the karst cave treatment construction conditions, the height of the steps and the length of the steps are increased, so that the upper steps can expose the karst cave vertically and longitudinally, the height of the adjusted steps is less than or equal to 6m, and the length of the adjusted steps can be more than 5 m.
The lower step should be staggered to excavate, so as to avoid the simultaneous suspension of the primary supports of the upper step and the lower step, and when the solution cavity is exposed on one side of the upper step, the staggered platform of the lower step should excavate the solution cavity side first.
The geological sketch result in the step (4) comprises a cavern exposure condition of the tunnel face and a tunnel face state, wherein the cavern exposure condition of the tunnel face reveals the scale, the spatial position, the filling type and the like of the cavern.
The tunnel face state is divided into three types, namely stable, more stable and unstable, as shown in the following chart:
palm surface state table
And (4) performing preliminary support construction in the step (4) by taking measures of tunnel face sealing, spray anchor support and the like, wherein the spray anchor support comprises a profile steel frame, a steel pipe (phi is more than or equal to 42mm), grouting and locking feet, early strength injection concrete, a system anchor rod and the like.
When the tunnel face is in a stable state or a more stable state, the primary support adopts anchor-shotcrete support;
when the tunnel face is in an unstable state, the primary support adopts the support measures of tunnel face closing and anchor-shotcrete support.
The measures adopted in the karst cave treatment in the step (4) are determined according to the scale, the spatial position and the filling type of the revealed karst cave, and the specific measures are shown in the following table:
karst cave treatment measures
Different treatment measures are adopted according to different parts of different karst cave types, so that the stability of the karst cave and the surrounding rock can be effectively improved.
The first embodiment is as follows: the present embodiment is a three-lane three-center circular tunnel, and the cross-sectional area of the tunnel is about 167m2The technical scheme of the construction method comprises the following steps:
step (1): detecting the range of 30m in front of the tunnel face by adopting a geological radar, wherein the lithology of the tunnel face is soluble rock, the rock mass is hard, the rock mass is broken, and underground water is not developed; and the arch part survey line map shows that radar waves 9-15 m in front of the tunnel face are strongly reflected, a karst cave with a large scale can develop, the underground water of the survey section does not develop, and the surrounding rock level is V level.
Step (2): the method comprises the steps of judging that an advanced large pipe shed is adopted for advanced support according to surrounding rock conditions and karst cave development conditions, wherein the design length of the advanced large pipe shed is 20m, the range of the annular reinforced arch part is 120 degrees, 31 holes are arranged in total, 11-18 m sections of 8-14 holes are analyzed through pipe shed drilling records and filled with karst caves, the length of the 8-14 holes is lengthened to 22m, and the arrangement of the advanced large pipe shed is shown in figure 2.
And (3): carrying out blasthole forming and powder charging operation in the range of an upper step and a lower step, carrying out staggered excavation on the lower step, blasting the upper step and the lower step simultaneously, carrying out parallel forward excavation, wherein the length of the middle step is 3m, the height of the step is 4m, and the circulating footage is 1 steel frame distance.
And (4): and (3) starting a fan to discharge dust in the tunnel, using an excavator to carry out danger elimination and undermining treatment on dangerous stones around the tunnel, and carrying out mucking operation by matching the excavator with a mucking vehicle to carry out geological sketch on the tunnel face.
And (5): the geological sketch result shows that a 3 multiplied by 5m (length multiplied by width multiplied by height) half-filled silty clay karst cave is exposed at the left side wall part of the lower step, and the primary support is closed after filling materials are cleaned and concrete is backfilled; the tunnel face is stable, no obvious extrusion deformation exists, a small amount of blocks fall off, HW 200X 200H section steel, 3.5m long phi 42mm grouting steel pipe locking feet, C20 thick 27cm early strength injection concrete and 5.0m long phi 22mm explosive cartridge anchor rods are adopted for primary support.
And (6): and according to the disclosure condition of the tunnel face karst cave and the tunnel face state, the design parameters of the next excavation circulating step are kept unchanged.
And (7): and (5) carrying out next circulating step excavation.
Second embodiment, the present embodiment is a three-lane three-center circular tunnel, and the cross-sectional area of the tunnel is about 167m2The technical scheme of the construction method comprises the following steps:
step (1): detecting the range of 30m in front of the tunnel face by adopting a geological radar, wherein the rock property of the tunnel face is soluble rock, the rock quality is hard, the rock mass is broken, and underground water is not developed; the atlas shows that the present section basically maintains the present tunnel face condition, the rock quality is harder, the rock mass is broken, no obvious water-bearing body exists, and the surrounding rock grade is grade V.
Step (2): and (3) judging that the advanced support adopts an advanced large pipe shed according to the surrounding rock condition and the karst cave development condition, wherein the design length of the advanced large pipe shed is 20m, the annular reinforcing arch part is 120 degrees, and 31 holes are arranged in total. The lithology in front is analyzed through the pipe shed drilling record, and the karst cave development is not seen.
And (3): carrying out blasthole forming and powder charging operation in the range of an upper step and a lower step, carrying out staggered excavation on the lower step, blasting the upper step and the lower step simultaneously, carrying out parallel forward excavation, wherein the length of the middle step is 3m, the height of the step is 4m, and the circulating footage is 1 steel frame distance.
And (4): and (3) starting a fan to discharge dust in the tunnel, using an excavator to carry out danger elimination and undermining treatment on dangerous stones around the tunnel, and carrying out mucking operation by matching the excavator with a mucking vehicle to carry out geological sketch on the tunnel face.
And (5): the geological sketch result shows that the tunnel face is stable, no obvious extrusion deformation exists, a small amount of blocks fall, no karst cave is exposed, and the primary support adopts HW200 multiplied by 200H section steel, 3.5m long phi 42mm grouting steel pipe locking feet, C20 thick 27cm early strength injection concrete and 5.0m long phi 22mm explosive cartridge anchor rods.
And (6): and according to the disclosure condition of the tunnel face karst cave and the tunnel face state, the design parameters of the next excavation circulating step are kept unchanged.
And (7): and (5) carrying out next circulating step excavation.
Third embodiment, the third embodiment is a three-lane three-center circular tunnel, and the cross-sectional area of the tunnel is about 167m2The technical scheme of the construction method comprises the following steps:
step (1): detecting the range of 30m in front of the tunnel face by adopting a geological radar, wherein the rock property of the tunnel face is soluble rock, the rock quality is hard, the rock mass is broken, and underground water is not developed; the vault survey line atlas displays that a radar reflection strong section exists in a section 3-9 m in front, and a large-scale dissolving cavity is presumed to exist in the section; the side wall line measuring map shows that a section 2 m-5 m in front has a strong radar reflection section, and a weak interlayer or a dissolving cavity is presumed to exist in the section. The stability of the surrounding rock is general, and the grade of the surrounding rock is IV grade.
Step (2): according to the surrounding rock condition and the karst cave development condition, the method judges that a phi 42 advanced small conduit and a phi 76 partitioned advanced large pipe shed are adopted for advanced support, the design length of the advanced small conduit is 4.5m, the circumferential distance is 40cm, the external insertion angle is 10 degrees, the arch part is arranged within the range of 120 degrees, and the lap joint length is more than 1.0 m; the preliminary determination range of the arrangement of the subarea advanced large pipe shed is 30 degrees on the left side of the arch part, then 4-11 m sections of 10-15 holes are determined to be filled karst caves according to the analysis of the drilling records of the pipe shed, the arrangement scheme of the final subarea advanced large pipe shed is 10-15 holes, the length of the subarea advanced large pipe shed is 15m, and the arrangement of the subarea advanced large pipe shed is schematically shown in figure 3.
And (3): carrying out blasthole forming and powder charging operation in the range of an upper step and a lower step, carrying out staggered excavation on the lower step, blasting the upper step and the lower step simultaneously, carrying out parallel forward excavation, wherein the length of the middle step is 5m, the height of the step is 5m, and the circulating footage is 2 steel frame intervals.
And (4): and (3) starting a fan to discharge dust in the tunnel, using an excavator to carry out danger elimination and undermining treatment on dangerous stones around the tunnel, and carrying out mucking operation by matching the excavator with a mucking vehicle to carry out geological sketch on the tunnel face.
And (5): the geological sketch result is that the face is unstable, the face is obviously extruded and deformed, the local part has the phenomenon of block falling and collapse, the face is sealed by spraying concrete with the thickness of 20cm, the primary support adopts I20b I-shaped steel, grouting steel pipe locking feet with the length of 3.5m and the diameter of 42mm, early strength spraying concrete with the thickness of 25cm and the length of 4.0m, and the early strength spraying concrete with the thickness of C20
A cartridge anchor rod; the left arch foot part of the upper step is exposed with a 2 multiplied by 3m (length multiplied by width multiplied by height) half-filled silty clay karst cave, and the filling is cleaned, and the concrete is backfilled to carry out primary support sealing.
And (6): according to the disclosure and the state of the karst cave on the tunnel face, the length and the height of the step of the next cycle are adjusted according to the longitudinal and vertical ranges of the karst cave, the adjusted step length can be more than 5m, and the step height is less than or equal to 6 m; the next circulation advanced small catheter is adjusted to be phi 42, the length of the double layers is 6.0m, the circumferential distance is 40cm, the external insertion angle is 10 degrees, and the arch part is arranged within the range of 120 degrees.
And (7): and performing next circulation advanced small conduit construction and step excavation.
Example four: the present embodiment is a three-lane three-center circular tunnel, and the area of the cross section of the tunnel is about 167m2The technical scheme of the construction method comprises the following steps:
step (1): and detecting the range of 30m in front of the tunnel face of the tunnel by adopting a geological radar. The rock property of the tunnel face is soluble rock, the rock quality is hard, the rock mass is broken, and the underground water is not developed; the atlas shows that the current tunnel face condition of the section is basically maintained, the rock quality is hard, the rock mass is broken, the underground water is not developed, and the surrounding rock grade is IV grade.
Step (2): the advanced support adopts a phi 42 advanced small guide pipe, the design length of the advanced small guide pipe is 4.5m, the circumferential distance is 40cm, the external insertion angle is 10 degrees, the arch part is arranged in the range of 120 degrees, and the lap joint length is more than 1.0 m.
And (3): carrying out blasthole forming and powder charging operation in the range of an upper step and a lower step, carrying out staggered excavation on the lower step, blasting the upper step and the lower step simultaneously, carrying out parallel forward excavation, wherein the length of the middle step is 5m, the height of the step is 5m, and the circulating footage is 2 steel frame intervals.
And (4): and (3) starting a fan to discharge dust in the tunnel, using an excavator to carry out danger elimination and undermining treatment on dangerous stones around the tunnel, and carrying out mucking operation by matching the excavator with a mucking vehicle to carry out geological sketch on the tunnel face.
And (5): the tunnel face is stable, no obvious extrusion deformation exists, a small amount of blocks fall, no karst cave is disclosed, the primary support adopts I20b I-shaped steel, 3.5m long phi 42mm slip casting steel pipe locking feet, C20 thick 25cm early strength shotcrete and 4.0m long
The explosive cartridge anchor rod.
And (6): and according to the disclosure condition of the tunnel face karst cave and the tunnel face state, the design parameters of the next excavation circulating step are kept unchanged.
And (7): and (5) carrying out next circulating step excavation.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.
Claims (8)
1. A construction method for a tunnel step with an extra-large section of soft rock in a karst cave development stratum is characterized by comprising the following steps:
(1) confirming the grade of surrounding rock and the surrounding rock condition in front;
(2) judging the development condition of karst according to the surrounding rock condition, judging whether a karst cave in front of the tunnel arch part develops according to the development condition of the karst, and determining advanced support measures and design parameters according to the surrounding rock grade and the development condition of the karst cave;
(3) synchronously excavating an upper step and a lower step according to the design parameters of the steps;
(4) carrying out geological sketch on the tunnel face after dust removal and slag discharge, and carrying out karst cave treatment and primary support construction according to the geological sketch result;
(5) adjusting the advance support measure and design parameter of the next cycle and the design parameter of the step according to the geological sketch result;
(6) and (5) repeating the steps (3) to (5).
2. The construction method of the extra-large cross-section tunnel step of the soft rock in the karst cave development stratum according to claim 1, wherein the advance support measures and design parameters in the step (2) comprise the following modes:
(2-1) when the grade of the surrounding rock is IV, adopting a small advanced guide pipe for supporting, wherein the length of the small advanced guide pipe is at least 4.5 m;
(2-2) when the surrounding rock grade is V grade, adopting an advanced large pipe shed for supporting, wherein the advanced large pipe shed should penetrate through the karst cave and ensure that the rock-entering depth is at least 2.5m, and reinforcing the arch part in an annular manner within 120 degrees;
(2-3) when the surrounding rock grade is IV grade and the karst cave is filled in front of the tunnel arch part to develop, adopting a subarea advanced large pipe shed measure for supporting, wherein the subarea advanced large pipe shed is arranged in the development range of the karst cave filled in front of the tunnel arch part;
the development of the filling karst cave in front of the tunnel arch part shows that the filling karst cave is positioned in the range of 120 degrees of the tunnel arch part, and the filling karst cave scale is more than or equal to 50m3And the distance between the filling karst cave and the tunnel face is less than or equal to 4 m.
3. The construction method of the soft rock extra-large section tunnel step of the karst cave developmental stratum according to claim 1, characterized in that the determination of the development range of the karst cave filled in front of the tunnel arch is as follows:
(2-3-1) preliminarily determining the development range of the karst cave filled in front of the tunnel arch part according to the development condition of the karst in front;
(2-3-2) analyzing the size of the karst cave, the position of the karst cave and the type of the filling materials according to the drilling record of the pipe shed in the primarily determined range, and further determining the development range of the karst cave.
4. The construction method of the soft rock extra-large section tunnel step of the karst cave development stratum according to claim 1, characterized in that: the design parameters of the steps in the step (3) comprise step height, step length and circulating footage, wherein the step length is 3-5 m, the step height is 4-6 m, and the circulating footage is a steel frame spacing of 1-2.
5. The construction method of the soft rock extra-large section tunnel step of the karst cave development stratum according to claim 1, characterized in that: the geological sketch result in the step (4) comprises a cavern exposure condition of the face and a state of the face, wherein the cavern exposure condition of the face is the scale, the spatial position and the filling type of the cavern.
6. The construction method of the soft rock extra-large section tunnel step in the karst cave development stratum according to claim 5, wherein the tunnel face state comprises the following steps:
(1) the stable state of the palm surface is as follows: the palm surface has no obvious extrusion deformation, and is stable after a small amount of blocks fall off;
(2) the palm surface is in a stable state and is represented as follows: the face has no obvious extrusion deformation, and the number of falling blocks is increased along with time;
(3) the unstable state of the palm surface is represented as: the extrusion deformation of the tunnel face is obvious, a large amount of vault side walls fall off, local collapse is caused, and the tunnel face cannot be self-stabilized; when the tunnel face is in an unstable state, the primary support adopts the support measures of tunnel face closing and anchor-shotcrete support.
7. The construction method of the soft rock extra-large section tunnel step of the karst cave development stratum according to claim 1, characterized in that: and (4) determining the karst cave treatment measures according to the scale, the spatial position and the filler type of the revealed karst cave.
8. The construction method of the soft rock extra-large section tunnel step of the karst cave development stratum according to claim 1, characterized in that: the design parameters of the steps in the step (3) are required to meet the construction conditions of karst cave treatment, the height of the steps and the length of the steps are increased, so that the upper steps can expose the karst cave vertically and longitudinally, the height of the adjusted steps is less than or equal to 6m, and the length of the adjusted steps can be more than 5 m.
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