CN112814686A - Construction method for transverse expanding excavation conversion when tunnel section suddenly changes into large-span section - Google Patents
Construction method for transverse expanding excavation conversion when tunnel section suddenly changes into large-span section Download PDFInfo
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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 expanding excavation conversion when a large-span section is suddenly changed on a tunnel section. Firstly excavating a leading pit in advance when the tunnel section enters a transition section of the sudden-change large-span section, and then expanding and excavating towards the arch part of the sudden-change large-span section while excavating a trailing pit; then, performing 90-degree straight-turning pit-guiding expanding excavation in the side wall direction, adding a gantry support as temporary protection during expanding excavation, and installing a gantry beam outside the contour line of the large-span section along the line direction; after excavating to the position of the side wall arch foot of the large-span section, erecting a circumferential arch center of the large-span section at one time on the lower side of the portal beam; the portal support has the advantages that the portal support is large in operation space, high in safety and convenient to construct, meanwhile, the portal beam does not influence the extension of the main tunnel to the arch or erection of the main tunnel to the outer side of the primary arch, the upright end wall portal vertical support at the junction of the portal beam and the two sections can serve as a permanent primary support, and the dismantling workload of the temporary portal is reduced.
Description
Technical Field
The invention belongs to the field of tunnel engineering, and particularly relates to a construction method for transverse expanding excavation conversion when a tunnel section has a sudden change in a large-span section, and more particularly to an excavation and support construction method for transverse expanding excavation conversion when a tunnel section has a sudden change in a large-span section.
Background
In recent years, China's railways are comprehensively developed, intensive utilization of underground spaces is more emphasized, large-section tunnels and underground space engineering construction technologies are continuously broken through, and the design of variable-diameter sections in large-section tunnels is gradually increased. The woodland tunnel is a newly-added tunnel for station position adjustment class I of Chongqing east station of the east circular line of Chongqing railway junction, the tunnel is positioned in Chongqing Banan area and southern bank area, and a connection line section is led out from the tunnel for long-span construction. The section is A, the large-span section B, and the section change part is suddenly changed towards the side of the lead-out line, which is shown in figure 1.
The transition process of different excavation methods at the abrupt cross section is complex, the operation space is narrow, the difficulty of equipment construction is limited, the collapse is easily caused by the disordered excavation supporting, the safety risk is high, and no mature method exists.
Therefore, a construction method for expanding excavation transition conversion when the cross section of the tunnel is suddenly enlarged and the span of the cross section is greatly increased is urgently needed to be explored, 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 tunnel section abrupt change and large-span section, which ensures construction safety, improves construction efficiency, has enough construction space and is convenient to operate. The construction method for transversely expanding excavation conversion of the tunnel section at the time of the large-span section is provided, so that excavation construction that the distance is expanded to one side of the tunnel section at the time of the large-span section is suddenly increased by 3m under the working condition that surrounding rocks are broken when the construction method at the variable section is converted is overcome.
In order to achieve the purpose, the invention provides a construction method for transverse expanding excavation conversion when a tunnel section has a sudden change of a large-span section, which comprises the following steps:
entering a transition section of the abrupt change large-span section on the section of the tunnel, and sequentially excavating a longitudinal leading pit and a longitudinal trailing pit on an upper step of the transition section, wherein the trailing pit is excavated towards an arch part of the abrupt change large-span section at the same time of excavating the trailing pit;
after the arch part expanding excavation of the backward guide pit and the abrupt change large-span section is finished, a portal frame is adopted as a temporary support when the abrupt change large-span section is excavated by directly turning 90 degrees to one side of the abrupt change large-span section which needs expanding excavation so as to carry out expanding excavation of the straight guide pit, the portal frame beam and the portal frame vertical support which are tightly attached to arch part surrounding rocks, tunnel face side surrounding rocks and upright end face side surrounding rocks are erected in time, and the portal frame beam is arranged outside the contour line of the large-span section;
after the straight turning pilot tunnel is excavated to the position of the large-span section side wall arch foot, a circular arch frame of the large-span section is erected at one time at the lower side of the portal beam and is lengthened to the bottom with the circular arch frame of the backward pilot tunnel, so that the construction of the upper step of the transition section is completed;
and finally, along with the construction propulsion in the tunnel face direction, the temporary support of the transition section is dismantled one by one under the premise of ensuring the safety, and finally the transverse expanding excavation construction conversion when the cross section of the tunnel is suddenly enlarged and the span is changed is completed.
Preferably, a transition section of the abrupt change large-span section is entered into the tunnel section, and the upper step of the transition section is constructed according to the following construction procedures:
(1) excavating a longitudinal pilot tunnel, constructing a pilot tunnel primary support, and constructing a temporary vertical support of the pilot tunnel;
(2) excavating a longitudinal backward pilot tunnel, simultaneously expanding and excavating towards the abrupt change large-span section arch part, constructing a backward pilot tunnel primary support and firmly connecting with the forward pilot tunnel primary support, and constructing a backward pilot tunnel temporary vertical support; and the front pit guiding tunnel face is ensured to be ahead of the back pit guiding tunnel face;
(3) after the tunnel face of the backward guide pit is closed, removing the middle part of the temporary vertical support of the backward guide pit one by one, reserving the temporary vertical supports at the two ends of the backward guide pit and enabling the temporary vertical supports to form a straight turning door opening, excavating the straight turning guide pit through the straight turning door opening, wherein the radius of the excavated profile of the straight turning guide pit is larger than that of the expanded span section profile when the straight turning guide pit is excavated, so that the erection of the portal beam does not influence the extension and erection of the large span section annular arch frame at the lower side of the beam; after excavation, timely clinging to the cross beams and the vertical braces of the surrounding rock erecting vertical portal frame on the arch part, the palm side and the upright end face side, and sequentially hanging a net, arranging anchor rods and spraying concrete;
(4) after the straight turning guide pit is expanded and dug to the position of the arch foot of the side wall with the large-span section, a circumferential arch frame in the straight turning guide pit is erected at one time, the circumferential arch frame and the circumferential arch frame of the backward guide pit are all lengthened to the bottom of a building, and a locking anchor pipe is arranged at the arch foot;
(5) after the initial support reaches a certain strength, the temporary vertical supports of the previous pilot pits and the vertical supports on the vertical end face sides of the straight crutch pilot pits are dismantled one by one under the condition of ensuring the safety.
Preferably, step (1) is specifically: firstly, a pipe shed at one side of a pilot tunnel is arranged and grouted, then the pilot tunnel is excavated, and the circulation footage follows the standard requirements; the spraying and mixing are supported and sprayed on the periphery of the pilot tunnel in time, so that the surrounding rock is prevented from being exposed for a long time after excavation; the primary support of the leading pilot tunnel is reinforced by longitudinal connection of section steel or channel steel at the position close to the arch frame section, and the welding is firm; the bottom of the vertical temporary support is supported and lined by a steel backing plate or a concrete backing block to prevent sinking.
Preferably, the step (2) is specifically: excavating a longitudinal backward guide pit and simultaneously expanding and excavating towards a sudden change large-span section arch part, wherein 1-3 arch bolts are fed in each cycle, a backward guide pit arch part primary support arch frame is erected in time in a long way, one end of the backward guide pit arch part primary support arch frame is firmly connected with the forward guide pit primary support arch frame through a backing plate and a bolt, the other end is longitudinally and continuously reinforced by section steel or channel steel corresponding to each arch frame, a vertical temporary support is erected, a steel backing plate or a concrete cushion block is supported at the bottom, a roof bolt is arranged after the arch frame is installed in each cycle of the arch part, and the roof bolt is hung and sprayed to the designed thickness.
Preferably, the step (2) ensures that the front pit guiding tunnel face is 3-5 truss arch pitches ahead of the back pit guiding tunnel face.
Preferably, the tunnel face of the backward guide pit is closed after the backward guide pit is excavated for 5-6 m.
Preferably, in the step (3), the middle part of the temporary vertical support in the backward pit guiding line direction is dismantled one by one, the temporary vertical supports at the two ends of the temporary vertical support are reserved, and the temporary vertical supports and the channel steel or the section steel longitudinally connected with the preliminary bracing arch of the backward pit guiding arch part form a straight-turning door opening, wherein the width of the door opening is 5-6 m.
Preferably, the radius of the excavation profile of the straight-turning pilot tunnel in the step (3) is at least 35cm larger than that of the excavation profile of the abrupt change large-span section design during the enlarging excavation.
Preferably, in step (3), besides the portal vertical brace on the tunnel face side, foot locking anchor pipes are arranged at the arch foot positions of the portal vertical brace on the straight crutch guide pit arch part and the portal vertical brace on the vertical end face side, so that the arch centering is prevented from sinking or falling off when the lower step of the transition section is excavated.
Preferably, the step (5) removes the longitudinal temporary vertical supports of the antecedent pilot pit and the vertical supports on the tunnel face side of the straight pilot pit one by one, and keeps the vertical supports on the vertical end face side of the straight pilot pit and the portal arch part cross beam as permanent supports.
Preferably, the construction method is suitable for the working conditions that the tunnel section has a large-span section, the distance from the large-span section to one side is more than 3m, and the surrounding rock level is IV level, V level or VI level.
Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:
(1) the invention provides a construction method for a tunnel section when a large-span section is suddenly changed, which is an excavation and support construction method for the tunnel when the tunnel is dug by a straight turning and expanding at the left or right angle of 90 degrees at the junction of two different span sections.
(2) In the construction method for the transverse expanding excavation conversion when the tunnel section has the sudden change of the large-span section, the arch part of the sudden change large-span section is expanded and excavated while the guide pit is excavated; after the completion of the expansion excavation of the arch part of the back walking guide pit, 90-degree left-turning or right-turning straight-turning guide pit expansion excavation is carried out in the direction of the expansion excavation, the straight-turning guide pit is supported and protected by the portal frame, the excavation safety is high, the operation space is large, meanwhile, the portal frame beam is arranged on the outer side of the primary portal frame of the main tunnel, the extension or erection of the main tunnel to the portal frame is not influenced, the portal frame beam and the vertical portal frame vertical support of the vertical end wall at the intersection of two sections can be used as a permanent primary support, and the dismantling workload of the temporary portal frame is reduced.
(3) The arch frame is longitudinally connected at the sections by adopting section steel or channel steel, and the bottom of the vertical support is provided with a lining steel plate or a temporary inverted arch, so that the deformation and sinking of the arch frame in the weak surrounding rock are avoided.
(4) The straight-turning portal support method provided by the invention is wide in application range and still applicable to relatively poor surrounding rocks, unstable surrounding rocks of side walls are enabled to be safe and controllable through short-footage and quick portal support, and the annular arch is lengthened once after the arch springing of the main tunnel is excavated, so that the right-turning expanding excavation safety is improved, and meanwhile, the installation quality is guaranteed.
(5) The transverse expanding excavation transition construction method provided by the invention overcomes the defects of difficulty in equipment expansion, low construction speed and high safety risk when the construction method at the variable section is converted on the whole, and simultaneously, the measures cost is greatly reduced and the cost is saved due to the permanent combination.
Drawings
FIG. 1 is a drawing of a variable section excavation floor plan of the present invention.
FIG. 2 is a schematic view of a construction section of the invention with section A entering a large-span section B; FIG. 1-anchor tube of the locking leg; 2-longitudinal channel steel or section steel; 3-advancing a pipe shed; 4-a steel backing plate; 5-A section central line; the center line of the 6-B section;
fig. 3 is a schematic plane view of the L-L longitudinal excavation support of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a construction method for transverse expanding excavation conversion when a tunnel section has a large-span section, which comprises the following steps: entering a transition section of the abrupt change large-span section on the section of the tunnel, and sequentially excavating a longitudinal leading pit and a longitudinal trailing pit on an upper step of the transition section, wherein the trailing pit is excavated towards an arch part of the abrupt change large-span section at the same time of excavating the trailing pit; after the arch part expanding excavation of the backward guide pit and the abrupt change large-span section is finished, a portal frame is adopted as a temporary support when the abrupt change large-span section is excavated, a portal frame beam and a portal frame vertical support which are tightly attached to arch part surrounding rocks, tunnel face side surrounding rocks and upright end face side surrounding rocks are erected in time, and the portal frame beam is installed outside the contour line of the large-span section; the straight turning guide pit is a left turning 90-degree or right turning 90-degree guide pit; after the straight turning pilot tunnel is excavated to the position of the large-span section side wall arch foot, a circular arch frame of the large-span section is erected at the lower side of the portal beam at one time, and the circular arch frame of the backward pilot tunnel is lengthened to the bottom of the transition section, so that the construction of the upper step of the transition section is completed.
And finally, along with the construction propulsion in the tunnel face direction, the temporary support of the transition section is dismantled one by one on the premise of ensuring the safety, and finally the transverse rapid expanding excavation construction conversion when the section of the tunnel is suddenly enlarged to a large-span section is completed.
The portal beam is arranged outside the large-span section contour line, namely outside the excavation contour lines of the leading pit and the trailing pit, and correspondingly, the radius of the excavation contour line of the straight turning pit guide is larger than that of the design contour line of the sudden change large-span section when the straight turning pit guide is used for enlarging excavation. In some embodiments, the radius of the excavation outline of the straight turning pilot tunnel during excavation expanding is at least 35cm larger than that of the excavation outline of the abrupt change large-span section design. Guarantee the frame of portal crossbeam on the one hand, make it not influence the extension and the frame of crossbeam downside large-span section ring arch centering, on the other hand subsides the condition according to the country rock, reserves the settlement volume, subsides behind the avoiding grudging post and invades the limit. The radius of the straight crutch guide pit expanding excavation profile can be adjusted according to the actual situation on site.
In some embodiments, for the tunnel needing to be dug to the right, a transition section of about 5-6 m is arranged at the section change position, in order to ensure the primary support (20cm) of the vertical end face and the thickness (100cm) of the lining, the right turning and digging are started at the section change position 2 trusses ahead, and the upper step is adjusted to a certain safety height according to the stability of surrounding rocks and the construction convenience of mechanical equipment before the digging. Dividing the transition section into 3 small pilot pits after entering the large section, excavating 2 longitudinal small pilot pits firstly, erecting a primary support arch, arranging a temporary vertical support, as shown in figure 2, reinforcing the lower part of the joint point of the primary support arch by adopting section steel 30cm, and supporting the rest according to design parameters. Firstly, excavating 8-10 m, secondly excavating 5-6 m guide pits, and transversely expanding and excavating the 3 rd guide pit in a right-handed way. The 3 rd guide pit (tunnel) supporting portal frame is used as a temporary support, the arch part cross beam is installed outside the outline line 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 foot with the large section is transversely and gradually excavated under the protection of the portal frames and the like, then the primary support arch frame is annularly lengthened on the lower side of the arch frame, a net is hung, an anchor rod is arranged and concrete is sprayed, the primary support of the upper step of the transition section is rapidly completed, and then the excavation and the primary support construction of the middle step and the lower step are carried. The method specifically comprises the following steps:
step one, when entering a large-span section B from a section A, setting a reasonable step height according to factors such as the stability of surrounding rocks, construction safety, excavation convenience of mechanical equipment and the like, and dividing the step on the section B into a first part, a second part and a third part.
And step two, constructing a pipe shed on the left side of the part I, grouting, excavating the part I, and circularly advancing the ruler to conform to the standard requirements. Firstly, timely supporting and spraying the periphery, namely 'one excavation and one supporting', so as to avoid long-term exposure of surrounding rocks after excavation, as shown in a figure 2 and a figure 3, wherein a primary support I-1 is longitudinally reinforced close to an arch frame section through section steel or channel steel and is firmly welded; and the bottom of the vertical temporary support II is supported and lined by a steel base plate or a concrete cushion block to prevent sinking.
Step three, excavating part II. And (2) excavating, namely-1, expanding and excavating towards the right and the upper part, 1-2 arch parts are excavated every time, an I-2 arch part primary support arch frame is erected in time in a long way, the left side of the primary support arch frame is firmly connected with the first part of the primary support arch frame I-1 through a base plate and a bolt, the right end section of the I-2 arch frame is longitudinally reinforced by two steel sections or channel steel sections, a vertical temporary support III is erected corresponding to each arch part, see fig. 3, a steel base plate or a concrete cushion block is lined at the bottom, the second part lags behind the first part by 3-5 arch frame intervals in the excavating process, an anchor rod is arranged after the arch frame is installed in each cycle of the arch parts, and a net is hung and sprayed to the designed thickness.
Fourthly, after a certain distance (5-6 m) is excavated, the tunnel face is closed, vertical supports between III-1 and III-N on the right side are dismantled one by one according to monitoring and measuring results, the III-1 and the III-N and channel steel or profile steel longitudinally connected with the primary arch frame form a right-turn door opening, and the width of the door opening is 5-6 m. Before dismantling, it is necessary to ensure that the reinforced channel steel or section steel longitudinally connected with the arch primary support steel frame is welded firmly, the primary support is sprayed compactly, and the safety is ensured.
And fifthly, transversely excavating a third guide tunnel at a right corner, wherein the footage is 0.6-1.5 m (adjustable according to the stable condition of surrounding rocks) in each circulation, the excavating contour radius is not less than 35cm of the design contour radius of the B section, preferably, the excavating contour radius is more than 35-50 cm of the design contour radius of the B section, so that a space is reserved for the B section erection ring to an arch frame, the B section erection ring is tightly attached to the cross beam and the vertical support of the surrounding rock erection portal frame at the arch part, the palm surface side and the upright end surface side in time after excavation, and the cross beam and the vertical support are hung, laid with anchor rods and sprayed with concrete, and the principle of 'one excavation and one support' is followed, wherein 2 locking anchor pipes are laid at the upright end surface arch foot part of the boundary of A, B section corresponding to each portal frame vertical support, and the arch.
And step six, excavating to the B section side wall arch springing position under temporary support protection of a portal frame, a mesh sheet, sprayed concrete and the like, then erecting the B section annular arch springing I-3 to the bottom of the small pilot tunnel between III-1 and III-N at one time, setting a locking steel pipe, and spraying the concrete to the designed thickness according to the design anchor, and referring to figure 2.
And seventhly, after the primary support reaches a certain strength, removing temporary vertical supports at the parts including the longitudinal direction of the part I and the tunnel face side of the part III (except the vertical end wall) in the tunnel direction one by one according to the monitoring and measuring result, and synchronously constructing an upper-step temporary inverted arch.
And constructing the lower step of the transition section according to the same method after the expansion excavation and conversion of the upper step of the transition section 5m from the section A to the section B are finished, and performing the excavation construction of the large-span section by adopting a three-step method, a three-step temporary inverted arch method or a CD method after the construction conversion of the transition section is finished.
In some embodiments, for the tunnel with weak surrounding rocks, the temporary inverted arch with the upper step can be synchronously constructed while the temporary vertical supports are dismantled in the seventh step.
The invention divides the transition section of the tunnel section entering the abrupt change large-span section into an upper step and a lower step for sequential construction, or an upper step, a middle step and a lower step for sequential construction.
The construction method provided by the invention is suitable for the working condition that the tunnel section has a large span section suddenly, the distance from the large span section to one side is more than 3m, and surrounding rocks are broken, such as the surrounding rocks are in IV grade, V grade or VI grade.
The terms, directions and the like used in the description of the present invention have the same meaning as those commonly expressed in the art, and for example, the term "longitudinal" refers to the direction of travel of construction. The terms "upper", "lower", "left", "right", and the like, which indicate the orientation, are vertical, horizontal, and vertical with respect to the tunnel face as a reference direction.
Example 1
The woodland tunnel is a newly-added tunnel for station position adjustment class I change of an east station of a Chongqing railway junction east-circle line Chongqing, is positioned in a Chongqing Banan area and a southern bank area, and is a main-line double-line tunnel. As the east ring main line needs to be connected to the Chongqing east station, two large spans need 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, the start-end and end-end mileage of the right connecting line large span is DK43+ 150-DK 43+304, and the length is 154 m. 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 the construction of the first section large span transition of the Chongqing Dongting station right connecting line, see figure 1.
The bedrock of the section of the leading-out connecting line is sandstone in mudstone of the group of the Shaxi temple, is close to a large storage area syncline core part, the rock stratum is wholly and slowly inclined, the mudstone is softer in rock quality, and the rock body is more complete; belongs to weak water-rich rock groups, has poor water-rich property, contains no water or a small amount of fracture water basically, is drained away by converging atmospheric rainfall into a ditch along a slope surface, has better sandstone seepage and water permeability and contains a small amount of fracture water, and the maximum water inflow is predicted to be 7326.8m3And/d, underground water is not aggressive.
The construction section and structure of the tunnel are shown in fig. 2. And (3) arranging a transition section of about 5m at the section change position, starting right-turn expanding excavation at the section change position by 2 trusses (DK43+148.8 positions) in advance in order to ensure the primary support (20cm) of the vertical end surface and the thickness (100cm) of the lining, and adjusting the step to a certain safety height according to the stability of surrounding rocks and the convenience of mechanical construction before expanding excavation. The transition section is divided into 3 small pilot pits after entering the large section, firstly, a part I and a part II of the longitudinal pilot pits are dug, a primary supporting arch is erected, a temporary vertical support is arranged, the part 30cm below the connection point of the primary supporting arch is reinforced by profile steel, and the rest is supported according to design parameters. Firstly, excavating 8-10 m, secondly, excavating 5-6 m in a guide pit, and transversely and rightwards turning and expanding and excavating the 3 rd guide pit, which is shown in figure 2. The 3 rd guide pit (tunnel) support portal frame is used as a temporary support, the arch part beam is installed outside a large-span section excavation contour line, portal frames on two sides are erected, the rear part of the tunnel direction is close to an upright end face, the front part of the tunnel direction is close to a tunnel face, the tunnel is transversely excavated to a large-section arch foot step by step under the protection of the portal frames and the like, then the primary support arch frame is annularly lengthened on the lower side of the arch frame, a net is hung, an anchor rod is arranged and concrete is sprayed, primary support of an upper step of a transition section is completed, and then excavation and primary support construction of a middle step and a lower.
In the embodiment, the two-section conversion is a three-step construction for converting the step-method transition of the section A into the section B, the primary support in the support system of the transition section between the section A and the section B adopts an I22B steel arch frame, the sections of the arch frame are longitudinally connected by 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 I is arranged
And (3) grouting the medium pipe shed, setting the height of an upper step according to comprehensive factors such as the stability of surrounding rocks, the construction safety, the excavation convenience of mechanical equipment and the like, excavating a part I of the pilot tunnel, and circularly advancing to follow the standard requirement. See fig. 2.
In the supporting system, I-1I 22b type steel arch center and right I18 temporary support and the like are erected around the pilot tunnel, and are sprayed and mixed to the designed thickness, and the principle of 'one excavation and one supporting' is followed, and the principle that the excavation is carried out for a long time is strictly forbidden according to the principle that the excavation is carried out for one time as shown in figures 2 and 3. Wherein the primary support I-1 is reinforced by I16 steel longitudinal connection near the arch frame section and is welded firmly; the right side temporarily supports II I18 shaped steel bottom support lining steel backing plate or cushion block to prevent sinking.
And secondly, excavating, namely excavating 1-1, simultaneously expanding and excavating 2-2 towards the right upper side, wherein 1-2 arch part primary support arch frames are erected in time by lengthening and erecting 1-2 arch part primary support arch frames in each cycle, the left side of the primary support arch frame I-1 is firmly connected with the first part of the primary support arch frame I-1 through a backing plate and bolts, the right end of each primary support arch frame I-1 is longitudinally reinforced by I16 section steel pairwise at the joints, vertical I18 section steel frames are erected corresponding to each arch frame, a steel backing plate or a concrete cushion block is supported at the bottom of each arch frame, the second part lags behind the first part in the excavating process by 3-5 m, and an anchor rod is arranged after the arch frames are installed in each cycle of the arch parts, and is hung.
And after the second part is excavated for a certain distance (5-6 m), the tunnel face is closed, after the primary support reaches a certain strength, the vertical supports between the right III-1 and the right III-N are dismantled one by one according to the monitoring and measuring result, and before dismantling, the arch primary support steel frame is ensured to be firmly welded longitudinally by I16 type steel, the primary support is sprayed compactly, and the safety is ensured. III-1, III-N and I16 section steel longitudinally connected with the primary arch support form a right-turn door opening with the width of 5-6 m.
And (3) excavating the guide tunnel at the right corner and the palm part, wherein the footage is 0.6-1.5 m (adjustable according to the stable condition of the surrounding rock) in each circulation, the radius of an excavation contour line of the guide tunnel is larger than that of a design contour of a B section by not less than 35cm, the I18 portal is erected by the surrounding rock tightly attached to the arch part, the palm surface side and the upright end surface side in time after excavation, and the principles of 'one excavation and one support' are followed. Wherein 2 vertical props are arranged at the vertical end arch foot position of the cross section boundary of A, B corresponding to each portal frame
A 6m long locking pin anchor pipe. The radius of the circumferential profile where the bottom elevation of the portal beam is located needs to be at least 10cm larger than the radius of the outer side of the profile of the primary arch of the B section, and the erection of the primary supporting arch of the B section during subsequent construction is facilitated.
After excavating to the arch foot position of the side wall of the B section, the annular primary supporting arch frame I of the B section in the small pilot tunnel between III-1 and III-N is lengthened at one time3 to the bottom of the building, and 2 arch frames are arranged corresponding to each arch frame
The length of the lock leg steel pipe is 4m, and concrete is anchored and sprayed to the designed thickness according to the design, and the figure 2 shows.
And the third temporary vertical support and the vertical temporary support of the portal frame at the tunnel face in the tunnel direction need to be detached from the third temporary support one by one according to the monitoring and measuring result after the initial support reaches certain strength, and a temporary upper-step inverted arch is synchronously constructed.
And finishing the expanding excavation and conversion of the upper step of the transition section of 5m from the section A to the section B, and constructing the middle step and the lower step of the section by adopting the same method.
The construction method improves the safety of right-handed expanding excavation, reduces the removal amount of subsequent temporary supports, overcomes the defects of difficult equipment expansion, low construction speed and high safety risk when the construction method at the position of a variable section is converted, reduces the measure cost and saves the cost.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A construction method for transverse expanding excavation conversion when a tunnel section is suddenly enlarged into a large-span section is characterized by comprising the following steps:
entering a transition section of the abrupt change large-span section on the section of the tunnel, and sequentially excavating a longitudinal leading pit and a longitudinal trailing pit on an upper step of the transition section, wherein the trailing pit is excavated towards an arch part of the abrupt change large-span section at the same time of excavating the trailing pit;
after the arch part expanding excavation of the backward guide pit and the abrupt change large-span section is finished, a portal frame is adopted as a temporary support when the abrupt change large-span section is excavated by directly turning 90 degrees to one side of the abrupt change large-span section which needs expanding excavation so as to carry out expanding excavation of the straight guide pit, the portal frame beam and the portal frame vertical support which are tightly attached to arch part surrounding rocks, tunnel face side surrounding rocks and upright end face side surrounding rocks are erected in time, and the portal frame beam is arranged outside the contour line of the large-span section;
after the straight turning pilot tunnel is excavated to the position of the large-span section side wall arch foot, a circular arch frame of the large-span section is erected at one time at the lower side of the portal beam and is lengthened to the bottom with the circular arch frame of the backward pilot tunnel, so that the construction of the upper step of the transition section is completed;
and finally, along with the construction propulsion in the tunnel face direction, the temporary support of the transition section is dismantled one by one under the premise of ensuring the safety, and finally the transverse expanding excavation construction conversion when the cross section of the tunnel is suddenly enlarged and the span is changed is completed.
2. The construction method according to claim 1, wherein the transition section of the tunnel section entering the abrupt change large-span section is constructed by the following steps:
(1) excavating a longitudinal pilot tunnel, constructing a pilot tunnel primary support, and constructing a temporary vertical support of the pilot tunnel;
(2) excavating a longitudinal backward pilot tunnel, simultaneously expanding and excavating towards the abrupt change large-span section arch part, constructing a backward pilot tunnel primary support and firmly connecting with the forward pilot tunnel primary support, and constructing a backward pilot tunnel temporary vertical support; and the front pit guiding tunnel face is ensured to be ahead of the back pit guiding tunnel face;
(3) after the tunnel face of the backward guide pit is closed, removing the middle part of the temporary vertical support of the backward guide pit one by one, reserving the temporary vertical supports at the two ends of the backward guide pit and enabling the temporary vertical supports to form a straight turning door opening, excavating the straight turning guide pit through the straight turning door opening, wherein the radius of the excavated profile of the straight turning guide pit is larger than that of the expanded span section profile when the straight turning guide pit is excavated, so that the erection of the portal beam does not influence the extension and erection of the large span section annular arch frame at the lower side of the beam; after excavation, timely clinging to the cross beams and the vertical braces of the surrounding rock erecting vertical portal frame on the arch part, the palm side and the upright end face side, and sequentially hanging a net, arranging anchor rods and spraying concrete;
(4) after the straight turning guide pit is expanded and dug to the position of the arch foot of the side wall with the large-span section, a circumferential arch frame in the straight turning guide pit is erected at one time, the circumferential arch frame and the circumferential arch frame of the backward guide pit are all lengthened to the bottom of a building, and a locking anchor pipe is arranged at the arch foot;
(5) after the initial support reaches a certain strength, the temporary vertical supports of the previous pilot pits and the vertical supports on the vertical end face sides of the straight crutch pilot pits are dismantled one by one under the condition of ensuring the safety.
3. The construction method according to claim 2, wherein the step (1) is specifically: firstly, a pipe shed at one side of a pilot tunnel is arranged and grouted, then the pilot tunnel is excavated, and the circulation footage follows the standard requirements; the spraying and mixing are supported and sprayed on the periphery of the pilot tunnel in time, so that the surrounding rock is prevented from being exposed for a long time after excavation; the primary support of the leading pilot tunnel is reinforced by longitudinal connection of section steel or channel steel at the position close to the arch frame section, and the welding is firm; the bottom of the vertical temporary support is supported and lined by a steel backing plate or a concrete backing block to prevent sinking.
4. The construction method according to claim 2, wherein the step (2) is specifically: excavating a longitudinal backward guide pit and simultaneously expanding and excavating towards a sudden change large-span section arch part, wherein 1-3 arch bolts are fed in each cycle, a backward guide pit arch part primary support arch frame is erected in time in a long way, one end of the backward guide pit arch part primary support arch frame is firmly connected with the forward guide pit primary support arch frame through a backing plate and a bolt, the other end is longitudinally and continuously reinforced by section steel or channel steel corresponding to each arch frame, a vertical temporary support is erected, a steel backing plate or a concrete cushion block is supported at the bottom, a roof bolt is arranged after the arch frame is installed in each cycle of the arch part, and the roof bolt is hung and sprayed to the designed thickness.
5. The construction method according to claim 2 or 3, wherein the step (2) ensures that the front tunnel face advances by 3-5 truss pitches from the rear tunnel face.
6. The construction method according to claim 4, wherein in the step (3), the middle part of the temporary vertical support in the rear guide pit line direction is dismantled one truss by one, the temporary vertical supports at the two ends of the temporary vertical support are reserved, and the temporary vertical supports and the channel steel or the section steel longitudinally connected with the preliminary support arch of the rear guide pit arch part form a straight-turning door opening, and the width of the door opening is 5-6 m.
7. The construction method according to claim 2, wherein the radius of the excavation profile of the straight-turn pilot tunnel in the step (3) is at least 35cm larger than that of the abrupt change large-span section design excavation profile.
8. The construction method according to claim 2, wherein in step (3), in addition to the portal vertical braces on the tunnel face side, foot-locking anchor pipes are arranged at the arch parts of the straight turning pilot tunnel arch and the portal vertical brace on the vertical end face side so as to prevent the arch from sinking or falling off when the lower step of the transition section is excavated.
9. The construction method according to claim 2, wherein the step (5) removes the longitudinal temporary vertical braces of the leading pilot pit and the vertical braces on the tunnel face side of the straight pilot pit one roof truss by one roof truss, and retains the vertical braces on the upright end face side of the straight pilot pit and the portal arch beams as permanent supports.
10. The construction method according to claim 1 or 2, characterized in that the construction method is suitable for the working condition that the tunnel section has a large-span section and the distance from the large-span section to one side is more than 3m, and the grade of the surrounding rock is IV grade, V grade or VI grade.
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