CN112814686B - Construction method for transverse expansion and excavation conversion during abrupt change of large-span section of tunnel section - Google Patents
Construction method for transverse expansion and excavation conversion during abrupt change of large-span section of tunnel section Download PDFInfo
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- CN112814686B CN112814686B CN202011636914.9A CN202011636914A CN112814686B CN 112814686 B CN112814686 B CN 112814686B CN 202011636914 A CN202011636914 A CN 202011636914A CN 112814686 B CN112814686 B CN 112814686B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH 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
- E21D9/01—Methods or apparatus for enlarging or restoring the cross-section of tunnels, e.g. by restoring the floor to its original level
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- E—FIXED CONSTRUCTIONS
- E21—EARTH 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
- E21D11/003—Linings or provisions thereon, specially adapted for traffic tunnels, e.g. with built-in cleaning devices
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- E—FIXED CONSTRUCTIONS
- E21—EARTH 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 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
- E21D11/14—Lining predominantly with metal
- E21D11/15—Plate linings; Laggings, i.e. linings designed for holding back formation material or for transmitting the load to main supporting members
- E21D11/152—Laggings made of grids or nettings
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- E—FIXED CONSTRUCTIONS
- E21—EARTH 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
- E21D11/14—Lining predominantly with metal
- E21D11/18—Arch members ; Network made of arch members ; Ring elements; Polygon elements; Polygon elements inside arches
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- E—FIXED CONSTRUCTIONS
- E21—EARTH 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
- E21D11/14—Lining predominantly with metal
- E21D11/28—Longitudinal struts, i.e. longitudinal connections between adjoining arches
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D20/00—Setting anchoring-bolts
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/20—Hydro energy
Abstract
The invention belongs to the field of tunnel engineering, and particularly relates to a construction method for transverse expansion and excavation conversion when a tunnel section is suddenly changed into a large-span section. Firstly excavating a pilot pit in advance at a transition section of the abrupt large-span section of the tunnel section, and then excavating the pilot pit later and simultaneously expanding and excavating the arc part of the abrupt large-span section; then, performing 90-degree straight turning pilot pit expansion digging to the side wall direction, and increasing a portal support for temporary protection during expansion digging, wherein a portal beam is arranged outside a large-span section contour line along the line direction; after the arch is excavated to the arch foot position of the side wall with the large-span section, erecting a circumferential arch frame with the large-span section on the lower side of the portal beam at one time; the portal frame is adopted to support the operation space greatly, the safety is high, the construction is convenient, meanwhile, the portal frame beam is arranged on the outer side of the primary arch frame of the main tunnel, the circumferential arch frame of the main tunnel is not influenced to be lengthened or erected, and the portal frame vertical support of the vertical end wall at the junction of the portal frame beam and the two sections can be used as the permanent primary support of the portal frame, so that the dismantling workload of the temporary portal frame is reduced.
Description
Technical Field
The invention belongs to the field of tunnel engineering, and particularly relates to a construction method for transverse expansion and excavation conversion when a large-span section is suddenly changed in a tunnel section, and more particularly relates to a construction method for excavation and support for transverse expansion and excavation conversion when the large-span section is suddenly changed in the tunnel section.
Background
In recent years, the new development concept of the railway in China is fully implemented, the intensive utilization of the underground space is more emphasized, new breakthrough is continuously made on the construction technology of the large-section tunnel and the underground space engineering, and the design of the diameter-variable section in the large-section tunnel is gradually increased. The firewood level mountain tunnel is a new and increased tunnel for regulating the station position of Chongqing east station on Chongqing railway junction east loop line, the tunnel is positioned in Chongqing banan area and south shore area, and the large span construction of leading-out connecting line sections is arranged in the tunnel. The section is A, the large-span section B, and the change position of the section is suddenly changed to the outgoing line side, as shown in figure 1.
The transition procedures of different excavation construction methods at the abrupt section are complex, the operation space is narrow, the equipment construction is difficult, collapse is easily caused by unordered excavation supporting, the safety risk is high, and no mature method exists.
Therefore, the construction method for expanding and excavating transition conversion when the tunnel section is suddenly changed into a large-span section is urgently needed, the work efficiency is improved, and the construction safety is ensured.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a construction method for ensuring construction safety, improving construction efficiency, ensuring enough construction space and facilitating operation when a tunnel section suddenly changes into a large-span section. The construction method for transverse expansion and excavation conversion is provided for overcoming the excavation construction that the tunnel section is suddenly changed into a large-span section and the distance to one side is enlarged by more than 3m under the working condition that surrounding rock is relatively broken when the construction method at the variable section is converted.
In order to achieve the above purpose, the invention provides a construction method for transverse expansion and excavation conversion when a tunnel section is suddenly changed into a large-span section, which comprises the following steps:
sequentially excavating a longitudinal advance pilot pit and a longitudinal backward pilot pit on the upper step of a transition section where the tunnel section enters the abrupt large-span section, wherein the backward pilot pit is excavated and simultaneously the arch part of the abrupt large-span section is excavated;
after the expansion and excavation of the backward guide pits and the arch parts of the abrupt large-span sections are completed, turning 90 degrees straight to the side, needing to be expanded and excavated, of the abrupt large-span sections to expand and excavate the straight guide pits, adopting a portal frame as a temporary support during excavation of the straight guide pits, erecting a portal frame cross beam and a portal frame vertical support, which are closely attached to the surrounding rock of the arch parts, the surrounding rock of the face side and the surrounding rock of the vertical end face side in time, and installing the portal frame cross beam outside the profile line of the large-span sections;
after the straight turning pilot pit is excavated to the arch foot position of the side wall with the large-span section, erecting a circumferential arch frame with the large-span section on the lower side of the portal beam at one time, and lengthening the circumferential arch frame with the circumferential arch frame of the backward pilot pit to the bottom, so that the construction of the step on the transition section is completed;
the subsequent lower steps of the transition section are subjected to excavation, primary support and temporary support construction according to the sequence of the advanced pilot pit, the backward pilot pit, the arch part expansion excavation and the straight turning pilot pit, and finally the temporary support construction of the transition section is removed one by one on the premise of ensuring safety along with the construction promotion of the face direction, so that the transverse expansion excavation construction conversion when the tunnel section is suddenly changed into a large-span section is finally completed.
Preferably, the tunnel section enters a transition section with a sudden change large-span section, and the step on the transition section is constructed according to the following construction procedures:
(1) Excavating a longitudinal pilot pit, constructing a pilot pit primary support, and constructing a pilot pit temporary vertical support;
(2) Excavating a longitudinal backward pilot pit, simultaneously expanding and excavating an abrupt large-span section arch part, constructing a preliminary support of the backward pilot pit, firmly connecting the preliminary support with the preliminary support of the forward pilot pit, and constructing a temporary vertical support of the backward pilot pit; and ensuring that the leading pit face leads the trailing pit face;
(3) After the tunnel face of the backward pilot pit is closed, removing the middle parts of temporary vertical supports of the backward pilot pit one by one, reserving the temporary vertical supports at the two ends of the temporary vertical supports and enabling the temporary vertical supports to form a straight turning door opening, and excavating the straight turning pilot pit through the straight turning door opening, wherein the radius of the excavation outline of the straight turning pilot pit is larger than that of the abrupt change large-span section outline when the straight turning pilot pit is excavated in an expanding manner, so that the erection of a portal beam does not influence the lengthening and erection of a large-span section annular arch frame at the lower side of the beam; the beam and the vertical support of the surrounding rock frame vertical portal at the arch part, the face side and the vertical end face side are clung to each other in time after excavation, and net hanging, anchor rod setting and concrete spraying are sequentially carried out;
(4) After the straight turning pilot pit is reamed to the arch foot position of the large-span section side wall, erecting the annular arch centering in the straight turning pilot pit once, and fully lengthening the annular arch centering with the annular arch centering of the backward pilot pit to the bottom, and punching a locking anchor pipe at the arch foot position;
(5) After the primary support reaches a certain strength, under the condition of ensuring safety, removing temporary vertical supports of the advanced pilot pits one by one and removing vertical supports of the vertical end face sides of the straight turning pilot pits one by one.
Preferably, the step (1) specifically comprises: firstly, a pipe shed at one side of a pilot pit is arranged and grouting is carried out, then the pilot pit is excavated, and the cyclic footage complies with the standard requirement; and the surrounding rock is prevented from being exposed for a long time after excavation by timely supporting, spraying and mixing around the pilot pit; the primary support of the pilot pit is longitudinally connected and reinforced by section steel or channel steel near the arch frame section, and is firmly welded; the bottom of the vertical temporary support is lined with a steel backing plate or a concrete backing block to prevent sinking.
Preferably, the step (2) specifically comprises: excavating a longitudinal backward pilot pit, simultaneously expanding and excavating to a sudden change large-span section arch part, 1-3 truss feet per cycle, timely lengthening a long frame to erect a preliminary supporting arch frame of the backward pilot pit arch part, firmly connecting one end of the preliminary supporting arch frame of the backward pilot pit arch part with the preliminary supporting arch frame of the forward pilot pit through a backing plate and bolts, longitudinally connecting and reinforcing the other end section by using section steel or channel steel, vertically and temporarily supporting each truss arch frame, supporting a steel backing plate or concrete cushion block at the bottom, and arranging anchor rods after the arch frame is circularly installed per arch frame, and spraying and mixing a hanging net to the design thickness.
Preferably, the step (2) ensures that the leading pit face advances by 3-5 arch frames in distance from the trailing pit face.
Preferably, after the back guide pit is excavated for 5-6 m, the face of the back guide pit is sealed.
Preferably, the step (3) removes the middle part of the temporary vertical supports in the line direction of the rear pilot tunnel one by one, and keeps the temporary vertical supports at the two ends of the temporary vertical supports, so that the temporary vertical supports and the channel steel or the section steel longitudinally connected with the primary support arch frame of the rear pilot tunnel arch form a straight turning door opening together, and the width of the door opening is 5-6 m.
Preferably, the radius of the excavation profile of the straight turning pilot pit in the step (3) is at least 35cm larger than that of the excavation profile of the abrupt large-span section design.
Preferably, in the step (3), besides the vertical support of the portal frame at the tunnel face side, the arch part of the straight turning pilot pit and the arch foot of the portal frame at the vertical end face side are respectively provided with a foot locking anchor pipe so as to prevent the arch frame from sinking or falling when the step at the lower part of the transition section is excavated.
Preferably, in the step (5), the longitudinal temporary vertical supports of the prior pilot tunnel and the vertical supports of the face side of the straight turning pilot tunnel are removed one by one, and the vertical supports of the vertical end face side of the straight turning pilot tunnel and the cross beams of the arch part of the portal frame are reserved as permanent supports.
Preferably, the construction method is suitable for working conditions that the tunnel section is suddenly changed into a large-span section, the distance to one side is more than 3m, and the surrounding rock grade is IV grade, V grade or VI grade.
In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:
(1) The construction method for the abrupt change of the tunnel section in the large-span section is essentially an excavation and support construction method for the abrupt change of the tunnel section in the large-span section in the process of 90 DEG left or right straight turning expansion excavation at the junction of two different span sections, wherein the transition section of the tunnel section entering the abrupt change of the large-span section is transversely divided into four longitudinal areas of longitudinal pilot pits, trailing pilot pits, arch expansion excavation and straight turning pilot pit expansion excavation, and the four longitudinal areas are excavated, wherein each part is relatively independent, primary support and temporary support are timely closed, and the stress structure is stable.
(2) In the construction method for transverse expansion and excavation conversion when the tunnel section is suddenly changed into a large-span section, the excavation is performed to the arch part of the suddenly changed large-span section while the post pilot pit is excavated; after the arch part of the rear pilot pit is reamed, 90-degree left-turning or right-turning straight pilot pit is reamed towards the reamed direction, the straight pilot pit is protected by adopting a portal frame support, the excavation safety is high, the operation space is large, meanwhile, a portal frame cross beam is arranged on the outer side of a primary arch frame of a main tunnel, the circumferential arch frame extension or erection of the main tunnel is not influenced, and the portal frame vertical support of the vertical end wall at the junction of the portal frame cross beam and two sections can be used as a permanent primary support of the portal frame vertical support, so that the dismantling workload of a temporary portal frame is reduced.
(3) The arch frame is longitudinally connected at the sections by adopting the section steel or the channel steel, and the steel plates are supported at the bottom of the vertical support or the temporary inverted arch is arranged, so that the deformation and sinking of the arch frame in the weak surrounding rock are avoided.
(4) The straight-turning portal frame supporting method provided by the invention has a large application range, is still suitable for relatively worse surrounding rocks, enables the surrounding rocks with unstable side walls to be safe and controllable through short footage and rapid portal frame supporting, and enables the annular arch frame to be lengthened once after the surrounding rocks are excavated to the arch feet of the straight hole, thereby improving the expanding and excavating safety of the right turning and simultaneously ensuring the installation quality.
(5) The transverse expansion and excavation transition construction method provided by the invention overcomes the defects of difficult equipment unfolding, low construction speed and high safety risk in the process of construction method conversion at the variable section on the whole, and simultaneously, the method is combined permanently, so that the measure cost is greatly reduced, and the cost is saved.
Drawings
FIG. 1 is a schematic view of the variable section excavation floor plan of the present invention.
FIG. 2 is a schematic view of a construction section of the present invention from section A to a large span section B; 1-a foot locking anchor pipe in the figure; 2-longitudinal channel steel or section steel; 3-leading pipe shed; 4-a steel backing plate; a 5-A section midline; a 6-B section midline;
FIG. 3 is a schematic view of a plane of the L-L longitudinal excavation supporting of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The invention provides a construction method for transverse expansion and excavation conversion when a tunnel section is suddenly changed into a large-span section, which comprises the following steps: sequentially excavating a longitudinal advance pilot pit and a longitudinal backward pilot pit on the upper step of a transition section where the tunnel section enters the abrupt large-span section, wherein the backward pilot pit is excavated and simultaneously the arch part of the abrupt large-span section is excavated; after the expansion and excavation of the backward guide pits and the arch parts of the abrupt large-span sections are completed, the expansion and excavation of the straight turning guide pits are carried out by turning 90 degrees to the side, needing to be expanded and excavated, of the abrupt large-span sections, a portal frame is adopted as a temporary support during excavation of the straight turning guide pits, a portal frame beam and a portal frame vertical support, which are tightly attached to the surrounding rock of the arch parts, the surrounding rock of the face side and the surrounding rock of the vertical end face side, are erected in time, and the portal frame beam is arranged outside the profile line of the large-span sections; the straight turning pilot pit is a pilot pit with 90 degrees of left turning or 90 degrees of right turning; after the straight turning pilot pit is excavated to the arch foot position of the side wall with the large-span section, the annular arch frame with the large-span section is erected at one time on the lower side of the portal beam, and the annular arch frame with the backward pilot pit is lengthened to the bottom, so that the construction of the step on the transition section is completed.
The subsequent lower steps of the transition section are subjected to excavation, primary support and temporary support construction according to the sequence of the advanced pilot pit, the backward pilot pit, the arch part expansion excavation and the straight turning pilot pit, and finally the temporary support construction of the transition section is removed one by one along with the progress of the construction in the direction of the face, so that the transition section is subjected to transverse rapid expansion excavation construction conversion when the abrupt change of the tunnel section is large in span section is finally completed under the premise of ensuring safety.
The portal beam is arranged outside the large-span section contour line, namely outside the excavation contour lines of the pilot pit and the postamble, and accordingly, the excavation contour radius of the portal beam is larger than the design contour radius of the abrupt large-span section during the excavation of the straight turning pilot pit. In some embodiments, the radius of the excavation profile of the straight turning pilot pit during the expanding excavation is at least 35cm greater than the radius of the excavation profile of the abrupt large-span section design. On one hand, the erection of the portal beam is ensured, so that the extension and erection of the large-span section circumferential arch on the lower side of the beam are not influenced, and on the other hand, the settlement amount is reserved according to the settlement condition of surrounding rocks, and the settlement limit after the erection is avoided. The radius of the straight turning pilot pit expansion profile can be adjusted according to the actual condition of the site.
In some embodiments, for a tunnel needing to be dug to the right, a transition section of about 5-6 m is arranged at a section change position, in order to ensure the primary support (20 cm) of an upright end face and the lining thickness (100 cm), right turning dug is started at the section change position in advance by a distance of 2 truss, and an upper step is adjusted to a certain safety height before dug according to the stability of surrounding rock and the construction convenience of mechanical equipment. The transition section is divided into 3 small pilot pits after entering the large section, 2 longitudinal pilot pits are firstly excavated, an initial support arch is erected, a temporary vertical support is arranged, see fig. 2, the lower part of the initial support arch connecting point is reinforced by adopting profile steel at 30cm, and the rest is supported according to design parameters. (1) Part excavation is 8-10 m, and (2) part pilot pit excavation is 5-6 m, and the 3 rd pilot pit is extended and excavated transversely and rightwards. The 3 rd pilot tunnel (hole) support portal frame is used as temporary support, arch part cross beams are arranged outside the outline of the primary support steel frame, the portal frames on two sides are vertically supported, the rear part of the tunnel direction is close to the vertical end face, the front part is close to the tunnel face, the arch feet with large cross sections are transversely excavated step by step under the protection of the portal frames and the like, then the arch frames are supported and supported in the circumferential direction on the lower side of the arch frames, the net is hung, anchor rods are arranged, concrete is sprayed, the primary support of the upper steps of the transition section is rapidly completed, and then the excavation and the primary support construction of the middle and lower steps are carried out according to the three-step temporary inverted arch method. The method specifically comprises the following steps:
step one, when a large-span section B is entered from the section A, setting a reasonable step height according to factors such as surrounding rock stability, construction safety, mechanical equipment excavation convenience and the like, and dividing the step on the section B into three parts (1), (2) and (3).
And secondly, arranging a left pipe shed of the part (1) and grouting, and then excavating the part (1), wherein the circulating footage follows the standard requirement. (1) The periphery of the part is supported and sprayed in time, namely 'one support is excavated', so that the surrounding rock is prevented from being exposed for a long time after excavation, as shown in fig. 2 and 3, wherein the primary support I-1 is longitudinally connected and reinforced by section steel or channel steel near the arch frame section, and is firmly welded; the bottom of the vertical temporary support II is lined with a steel backing plate or a concrete backing block to prevent sinking.
And thirdly, excavating the part (2). And (2) -1 is excavated, simultaneously (2) -2 is excavated by expanding to the upper right, 1-2 arch parts are erected on a long frame in time, the primary arch parts I-1 on the left side and the primary arch parts (1) are firmly connected through a backing plate and bolts, meanwhile, the right end section of the primary arch parts I-2 is reinforced by section steel or channel steel in a two-to-two longitudinal mode, corresponding to the vertical temporary support III of each arch part, as shown in fig. 3, the backing steel backing plate or concrete cushion block is erected on the bottom, 3-5 arch parts are lagged on the (2) part in the excavation process, an anchor rod is arranged after the arch parts are circularly installed, and the hanging net is sprayed and mixed to the design thickness.
And fourthly, after a certain distance (5-6 m) is excavated in the part (2), the tunnel face is closed, vertical supports between the right side III-1 and the right side III-N are removed one by one according to monitoring and measuring results, and the III-1, the III-N and channel steel or section steel longitudinally connected with the primary arch frame jointly form a right turning door opening, and the door opening is 5-6 m wide. Before dismantling, the welding of the reinforced channel steel or the steel section longitudinally connected with the arch primary support steel frame is firm, the primary support is sprayed compactly, and the safety is ensured.
Step five, right turning transverse excavation (3) part pilot tunnel, each cycle footage is 0.6-1.5 m (adjustable according to surrounding rock stability condition), the excavation outline radius is not less than 35cm of design outline radius of B section, preferably the excavation outline radius is greater than 35-50 cm of design outline radius of B section, the purpose is to reserve space for B section frame vertical ring arch frame, immediately cling to arch part, face side, beam and vertical support of surrounding rock frame vertical portal of vertical end face side after excavation, hang net, set anchor rod, spray concrete, follow "one excavation one support" principle, wherein at A, B section vertical end face arch foot department corresponds to each roof frame vertical support and sets up 2 lock foot anchor pipes, arch frame subsidence when preventing excavation lower step.
Step six, (3) excavating the part to the arch foot position of the side wall with the section B under the temporary support protection of a portal frame, a net sheet, sprayed concrete and the like, erecting the annular arch centering I-3 with the section B in the small pilot tunnel between III-1 and III-N to the bottom at one time, and punching a foot locking steel pipe, and anchoring and spraying the concrete to the designed thickness according to the design, wherein the design is shown in fig. 2.
And step seven, after the primary support reaches a certain strength, removing temporary vertical supports at the parts of the tunnel direction face side and the like of the part (1) in the longitudinal direction and the part (3) except for the vertical end wall part) one by one according to monitoring and measuring results, and synchronously applying a temporary inverted arch for the upper step.
The method comprises the steps of expanding and digging the upper step of a 5m transition section from the A section to the B section, completing conversion, constructing the lower step of the transition section according to the same method, and carrying out excavation construction of a large-span section by adopting a three-step method, a three-step temporary inverted arch method or a CD method after finishing construction conversion of the transition section.
In some embodiments, for tunnels with weak surrounding rock, the temporary inverted arch of the upper step may be synchronously applied while the temporary vertical support is removed in step seven.
The invention divides the transition section of the tunnel section entering the abrupt large-span section into an upper step and a lower step for construction in sequence, or into an upper step, a middle step and a lower step for construction in sequence.
The construction method provided by the invention is suitable for working conditions that the tunnel section is suddenly changed into a large-span section, the distance to one side is more than 3m, and surrounding rock is broken, for example, the surrounding rock grade is IV, V or VI.
The terms and directions in the description of the present invention have the same meanings as those of the conventional expressions in the art, for example, the term "longitudinal" is referred to as the construction traveling direction. Terms such as "up", "down", "left", "right" and the like refer to directions of up, down, left and right with respect to a tunnel construction face as a reference direction.
Example 1
The firewood lawn mountain tunnel is a new tunnel which is newly added by adjusting the station position of Chongqing east station on Chongqing railway junction east loop line, and the tunnels are positioned in Chongqing banan area and south shore area and are positive line double-line tunnels. Because the east ring positive line is required to be connected to the Chongqing east station, two large spans are required to be arranged in the hole, a Chongqing east station left connecting line and a Chongqing east station right connecting line are respectively led out, and the beginning and ending mileage of the right connecting line large spans is DK43+150-DK43+304, and the length is 154m. The first section is 19.72m wide by 14.29m high and the second section is 24.52m wide by 16.13m high. The embodiment is a first-section large-span transitional construction of a right tie line of a Chongqing east station, and is shown in fig. 1.
The lead-out connecting line section falling bedrock is a sandstone clamp sandstone of a temple group, is close to a syncline core part of a large holding field, is integrally and slowly inclined, has softer mudstone and has more complete rock mass; belongs to weak water-rich rock groups, has poor water-rich property, basically contains no water or little water with fissures, and has better sandstone seepage and water permeability when the atmospheric rainfall is discharged along the slope surface to be collected into a ditch, contains little water with fissures, and predicts the maximum water inflow of 7326.8m 3 And/d, groundwater is not aggressive.
The tunnel construction section and structure are shown in figure 2. The transition section of about 5m is arranged at the section change position, in order to ensure the primary support (20 cm) of the vertical end face and the lining thickness (100 cm), the right turning and the expanding excavation are started at the section change position in advance by a distance of 2 truss (DK43+148.8), and the steps are adjusted to a certain safety height according to the stability of surrounding rock and the convenience of mechanical construction before expanding excavation. The transition section after entering the large section is divided into 3 small pilot pits, a longitudinal (1) part and a longitudinal (2) part are firstly excavated, 2 small pilot pits are firstly excavated, an initial supporting arch frame is erected, a temporary vertical support is arranged, the position 30cm below the connecting point of the initial supporting arch frame is reinforced by section steel, and the rest is supported according to design parameters. (1) Part excavation is 8-10 m, and (2) part pilot pit excavation is 5-6 m, and the 3 rd pilot pit is extended and excavated transversely and rightwards, see figure 2. The 3 rd pilot tunnel (hole) support portal frame is used as temporary support, the arch cross beam is arranged outside a large-span section excavation outline line, the portal frames on two sides are vertically supported, the rear part of the tunnel direction is close to the vertical end face, the front part is close to the tunnel face, the large-section arch foot is transversely and gradually excavated under the protection of the portal frames and the like, then the arch frame is axially stretched at the lower side of the large-section arch foot, the arch frame is hung, anchor rods are arranged, concrete is sprayed, the primary support of the upper step of the transition section is completed, and then the excavation and the primary support construction of the middle step and the lower step are carried out according to the same method.
In the embodiment, the two-section conversion is three-step construction which converts the step method transition of the section A into the section B, the initial support in the support system of the transition section between the section A and the section B adopts an I22B steel arch, the arch sections are longitudinally connected by adopting I16 steel, and the vertical temporary support and the portal frame adopt I18 steel and the like.
Before the excavation, the left side of the part (1) is arrangedAnd (3) grouting the middle pipe shed, and then setting an upper step height according to comprehensive factors such as surrounding rock stability, construction safety, mechanical equipment excavation convenience and the like, and excavating a pilot pit (1), wherein the circulating footage follows the standard requirements. See fig. 2.
In the supporting system of the part (1), the I-1I 22b steel arch frame, the right I18 temporary support and the like are erected around the pilot pit, and are sprayed and mixed to the design thickness, and the principle of 'one excavation and one supporting' is followed, see fig. 2 and 3, and the excavation is strictly forbidden for too long once. The primary support I-1 is longitudinally connected and reinforced by I16 section steel at the position close to the arch centering section, and is firmly welded; the right side temporarily supports the bottom support rigid backing plate or cushion block of the II I18 section steel to prevent sinking.
The (2) part is excavated, the (2) -1 part is excavated simultaneously, the (2) -2 part is excavated in an expanding way to the upper right, 1-2 arch parts are erected in time by lengthening the arch frame of the I-2 arch part primary support, the left side and the (1) part primary support arch frame I-1 are firmly connected through a base plate and bolts, the right end section is reinforced by two-by-two longitudinal connection of I16 steel, the corresponding arch frame of each arch frame is vertically and temporarily supported by III I18 steel, the bottom support lining steel base plate or concrete cushion block, the (2) part is lagged by 3-5 m in the excavation process, an anchor rod is arranged by beating after the arch part is circularly installed, and the hanging net is sprayed and mixed to the design thickness.
After the part (2) is excavated for a certain distance (5-6 m), the face is closed, after the primary support reaches a certain strength, the vertical supports between the right side III-1 and the right side III-N are dismantled one by one according to the monitoring and measuring result, the arch primary support steel frame is ensured to be firmly welded longitudinally by adopting I16 section steel, primary support injection is compact, and safety is ensured. III-1, III-N and I16 section steel longitudinally connected with the primary arch frame form a right-turning door opening, and the width of the door opening is 5 m-6 m.
The pilot tunnel on the right crutch (3) is excavated, each cycle is 0.6-1.5 m (adjustable according to the stability condition of surrounding rock), the excavation contour line is more than or equal to 35cm than the design contour radius of the section B, the vertical I18 portal of the surrounding rock frame on the arch part, the face side and the vertical end face side is tightly attached in time after the excavation, the net is hung, the anchor rod is arranged, and the concrete is sprayed, thereby following the principle of 'one excavation and one support'. Wherein 2 vertical supports corresponding to each portal are arranged at the arch feet of the vertical end face at the junction of the A, B sectionAnd 6m long pin locking anchor pipes. The radius of the annular outline where the elevation of the bottom of the portal beam is located is at least 10cm larger than the radius of the outer side of the outline of the B-section primary support arch frame, so that the B-section primary support arch frame can be erected conveniently during subsequent construction.
After the part (3) is excavated to the arch foot position of the side wall with the section B, the section B in the small pilot tunnel between III-1 and III-N is extended once to the original arch centering I-3 to the bottom, and 2 arch centering are arranged corresponding to each arch centeringAnd the steel pipe with the length of 4m is used for anchoring and spraying concrete to the designed thickness according to the design, and the steel pipe is shown in figure 2.
The vertical temporary support of the portal at the tunnel face of the part (1) and the part (3) is required to be removed from the part (3) one by one according to the monitoring and measuring result after the primary support reaches a certain strength, and the temporary inverted arch of the upper step is synchronously applied.
The expanding, digging and conversion of the upper step of the 5m transition section from the section A to the section B are completed, and the construction of the middle step and the lower step of the section is carried out by adopting the same method.
The construction method improves the safety of the right-turn expanding excavation, reduces the dismantling quantity of the follow-up temporary support, overcomes the defects of difficult equipment unfolding, low construction speed and high safety risk when the construction method at the variable section is converted, reduces the measure cost and saves the cost.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (8)
1. The construction method for transverse expansion and excavation conversion during abrupt change of a tunnel section into a large-span section is characterized by comprising the following steps:
sequentially excavating a longitudinal advance pilot pit and a longitudinal backward pilot pit on the upper step of a transition section where the tunnel section enters the abrupt large-span section, wherein the backward pilot pit is excavated and simultaneously the arch part of the abrupt large-span section is excavated;
after the expansion and excavation of the backward guide pits and the arch parts of the abrupt large-span sections are completed, turning 90 degrees straight to the side, needing to be expanded and excavated, of the abrupt large-span sections to expand and excavate the straight guide pits, adopting a portal frame as a temporary support during excavation of the straight guide pits, erecting a portal frame cross beam and a portal frame vertical support, which are closely attached to the surrounding rock of the arch parts, the surrounding rock of the face side and the surrounding rock of the vertical end face side in time, and installing the portal frame cross beam outside the profile line of the large-span sections;
after the straight turning pilot pit is excavated to the arch foot position of the side wall with the large-span section, erecting a circumferential arch frame with the large-span section on the lower side of the portal beam at one time, and lengthening the circumferential arch frame with the circumferential arch frame of the backward pilot pit to the bottom, so that the construction of the step on the transition section is completed;
the tunnel section enters a transition section with a sudden change large-span section, and the upper step of the transition section is constructed according to the following construction procedures:
(1) Excavating a longitudinal pilot pit, constructing a pilot pit primary support, and constructing a pilot pit temporary vertical support;
(2) Excavating a longitudinal backward pilot pit, simultaneously expanding and excavating an abrupt large-span section arch part, constructing a preliminary support of the backward pilot pit, firmly connecting the preliminary support with the preliminary support of the forward pilot pit, and constructing a temporary vertical support of the backward pilot pit; and ensuring that the leading pit face leads the trailing pit face;
(3) After the tunnel face of the backward pilot pit is closed, removing the middle parts of temporary vertical supports of the backward pilot pit one by one, reserving the temporary vertical supports at the two ends of the temporary vertical supports and enabling the temporary vertical supports to form a straight turning door opening, and excavating the straight turning pilot pit through the straight turning door opening, wherein the radius of the excavation outline of the straight turning pilot pit is larger than that of the abrupt change large-span section outline when the straight turning pilot pit is excavated in an expanding manner, so that the erection of a portal beam does not influence the lengthening and erection of a large-span section annular arch frame at the lower side of the beam; the beam and the vertical support of the surrounding rock frame vertical portal at the arch part, the face side and the vertical end face side are clung to each other in time after excavation, and net hanging, anchor rod setting and concrete spraying are sequentially carried out;
(4) After the straight turning pilot pit is reamed to the arch foot position of the large-span section side wall, erecting the annular arch centering in the straight turning pilot pit once, and fully lengthening the annular arch centering with the annular arch centering of the backward pilot pit to the bottom, and punching a locking anchor pipe at the arch foot position;
(5) After the primary support reaches a certain strength, under the condition of ensuring safety, removing temporary vertical supports of the pilot pit one by one and removing vertical supports of the vertical end face side of the straight turning pilot pit;
the subsequent lower steps of the transition section are subjected to excavation, primary support and temporary support construction according to the sequence of the advanced pilot pit, the backward pilot pit, the arch part expansion excavation and the straight turning pilot pit, and finally the temporary support construction of the transition section is removed one by one on the premise of ensuring safety along with the construction advancement of the face direction, so that the transverse expansion excavation construction conversion when the tunnel section is suddenly changed into a large-span section is finally completed;
the construction method is suitable for working conditions that the tunnel section is suddenly changed into a large-span section, the distance to one side is more than 3m, and the surrounding rock level is IV level, V level or VI level.
2. The construction method according to claim 1, wherein the step (1) is specifically: firstly, a pipe shed at one side of a pilot pit is arranged and grouting is carried out, then the pilot pit is excavated, and the cyclic footage complies with the standard requirement; and the surrounding rock is prevented from being exposed for a long time after excavation by timely supporting, spraying and mixing around the pilot pit; the primary support of the pilot pit is longitudinally connected and reinforced by section steel or channel steel near the arch frame section, and is firmly welded; the bottom of the vertical temporary support is lined with a steel backing plate or a concrete backing block to prevent sinking.
3. The construction method according to claim 1, wherein the step (2) is specifically: excavating a longitudinal backward pilot pit, simultaneously expanding and excavating to a sudden change large-span section arch part, 1-3 truss feet per cycle, timely lengthening a long frame to erect a preliminary supporting arch frame of the backward pilot pit arch part, firmly connecting one end of the preliminary supporting arch frame of the backward pilot pit arch part with the preliminary supporting arch frame of the forward pilot pit through a backing plate and bolts, longitudinally connecting and reinforcing the other end section by using section steel or channel steel, vertically and temporarily supporting each truss arch frame, supporting a steel backing plate or concrete cushion block at the bottom, and arranging anchor rods after the arch frame is circularly installed per arch frame, and spraying and mixing a hanging net to the design thickness.
4. The construction method according to claim 1 or 2, wherein step (2) ensures that the pilot tunnel face leads the post pilot tunnel face by 3 to 5 arch pitches.
5. The construction method according to claim 3, wherein the step (3) comprises the steps of removing the intermediate portions of the temporary vertical supports in the direction of the line of the rear pit, and reserving the temporary vertical supports at the two ends of the intermediate portions so as to form a straight-turning door opening together with the channel steel or the section steel longitudinally connected with the primary support arch frame of the rear pit arch, wherein the width of the door opening is 5-6 m.
6. The method of construction of claim 1, wherein the radius of the excavation profile of the straight corner pilot pit in step (3) is at least 35cm greater than the radius of the excavation profile of the abrupt large-span cross-section design.
7. The construction method according to claim 1, wherein in the step (3), except for the vertical support of the portal frame on the tunnel face side, the leg locking anchor pipes are arranged at the arch part of the straight turning pilot pit and the arch leg of the portal frame on the vertical end face side so as to prevent the arch frame from sinking or falling when the lower step of the transition section is excavated.
8. The construction method according to claim 1, wherein the step (5) removes the temporary vertical supports of the pit longitudinal direction and the vertical supports of the face side of the pit of the straight turning pit one by one, and reserves the vertical supports of the vertical end face side of the pit of the straight turning pit and the gantry arch cross beam as permanent supports.
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