CN116677419A - Inclined shaft turning positive tunnel three-fork support design of tunnel and roof-picking construction method thereof - Google Patents
Inclined shaft turning positive tunnel three-fork support design of tunnel and roof-picking construction method thereof Download PDFInfo
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- E—FIXED CONSTRUCTIONS
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- 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
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- E21D11/183—Supporting means for arch members, not provided for in E21D11/22
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Abstract
The invention relates to a design of a three-fork support of a inclined shaft turning positive tunnel of a tunnel and a top-picking construction method thereof, belonging to the technical field of tunnel tunneling design and arrangement methods. The method comprises the steps of designing a supporting structure of a three-fork in advance, adopting a double-spliced I-steel arch, establishing a finite element calculation model of the double-spliced I-steel arch and a positive tunnel arch in finite element software, calculating structural parameters of the double-spliced I-steel arch after judging whether the three-fork is shallow or deep buried, substituting the structural parameters into the finite element calculation model of the double-spliced I-steel arch to calculate the strength of the double-spliced I-steel arch, judging whether the double-spliced I-steel arch is reliable or not, and adopting an increased arch model or the three-spliced arch to carry out redesign checking calculation if the double-spliced I-steel arch is unreliable; and if the tunnel roof is reliable, carrying out and completing the tunnel roof-picking construction. According to the method, before tunnel construction, the three-fork support is designed in a trial mode, whether the strength of the three-fork support is reliable or not is checked and calculated by adopting the double-spliced I-steel arch frame, and tunnel roof-picking construction is finished on a reliable basis, so that the stability of the three-fork support structure is guaranteed.
Description
Technical Field
The invention relates to a construction method for supporting and jacking a three-fork of a inclined shaft turning positive tunnel in tunneling, belonging to the technical field of tunnel tunneling design and arrangement methods.
Background
The long tunnel often needs to be additionally provided with auxiliary tunnels such as inclined shafts and the like to increase working surfaces so as to accelerate construction progress, and meanwhile, the inclined shafts can also be used as overhauling and transporting channels of the main tunnel. The space structure of the intersection of the inclined shaft and the positive tunnel at the position of the three-fork is complex, so that a stress concentration area is easy to generate, and the supporting structure at the position needs to be designed and constructed in a key way. The existing design and construction methods mostly depend on the existing experience, and a plurality of support structure forms of brackets and arches are used; the supporting structure form cannot fully utilize the natural arch effect of surrounding rock, and has large excavation square quantity and more construction procedures. The short column is welded between the bracket and the arch frame to effectively transfer the load on the bracket to the arch frame, the welding quality and the perpendicularity cannot be guaranteed in field installation, and a large amount of concrete needs to be sprayed into a cavity between the bracket and the arch frame to fill, so that the load on the arch frame is increased, and the stability of the structure is not facilitated.
In addition, the pilot tunnel is excavated to the side of the pilot tunnel, then primary support is carried out on the pilot tunnel, the working face is formed, and then the pilot tunnel is excavated to the size and the mileage of the pilot tunnel, the process time is long, the pilot tunnel can not be supported in time, and potential safety hazards are buried for tunnel roof-picking construction. Therefore, the construction method of the top picking at the position of the three-fork is required to be specially designed and optimized aiming at the three-fork supporting structure, so that the time of opening and exposing the positive hole is reduced, the safety risk of the conversion of the construction procedure of the top picking is reduced, and the construction method has important practical significance for the safety of tunnel construction.
Disclosure of Invention
The invention aims to solve the technical problems that: the supporting structure of the intersection of the inclined shaft and the positive tunnel is stressed stably, and the top-picking construction process at the intersection is optimized.
The technical scheme provided by the invention for solving the technical problems is as follows: a design and a roof-picking construction method of a inclined shaft turning positive tunnel three-fork support of a tunnel comprise the following steps:
step 1, designing a supporting structure of a three-way fork, specifically designing and checking as follows,
step 1.1, pre-trial design of a supporting structure of the three-fork adopts a double-spliced I-steel arch, a finite element calculation model of the double-spliced I-steel arch is built in finite element software,
the supporting structure of the positive tunnel in the step 1.2 adopts an arch frame to form a positive tunnel arch frame, one side of the positive tunnel arch frame is all arranged on the double-spliced I-steel arch frame, the positive tunnel arch frame is used as a calculating unit according to the supporting distance, and a finite element calculating model of the positive tunnel arch frame is built in finite element software;
step 1.3 checking and calculating to determine structural parameters of double-spliced I-steel arch frame
Step 1.3.1 judging whether the three-way fork belongs to shallow burying or deep burying
Calculating the boundary depth H of the tunnel deep and shallow burial according to the following formula (1) p
H p ＝1.125×2 S-1 w (1)
In the formula (1), S is the surrounding rock grade number; w is a width influence coefficient, calculated according to the following formula (2),
w＝1+i(B-5) (2)
in formula (2), B is the tunnel width (unit m); i is the surrounding rock pressure increase and decrease rate, i=0.2 when B <5m, i=0.1 when B > 5m;
judging shallow burying when the tunnel burying depth h is smaller than Hp, and judging deep burying when the tunnel burying depth h is larger than or equal to Hp;
the structural parameters of the double-spliced I-steel arch frame comprise the dead weight of a supporting structure, the vertical pressure q of surrounding rock, the horizontal pressure e of surrounding rock and the elastic resistance K of the surrounding rock, and the structural parameters are proved to be as follows;
A. when shallow buried
A1. Calculating the surrounding rock vertical pressure q according to the following formula (3)
In the formula (3), gamma is the weight of surrounding rock, and class II surrounding rock takes 27kN/m 3 Grade III surrounding rock is 25kN/m 3 Grade IV 23kN/m 3 V grade 20kN/m 3 ；
θ is the friction angle of the two sides of the top plate column of the supporting structure, when the surrounding rock level is level III,when the surrounding rock level is level IV, < + >>When the surrounding rock level is V level, < -> Calculating a friction angle of surrounding rock; lambda is a side pressure coefficient, calculated according to the following equation (4),
in the formula (4), beta is a rupture angle when the support structure generates maximum thrust;
A2. respectively taking the surrounding rock horizontal pressure e at the top and the bottom of the tunnel in the supporting structure interval, calculating the surrounding rock horizontal pressure e by linear interpolation according to a formula (5),
e＝γhλ (5)；
B. when buried deeply
B1. Calculating the surrounding rock vertical pressure q according to the following formula (6)
q＝γ(0.45×2 S-1 w) (6)
B.2, determining the surrounding rock horizontal pressure e according to the surrounding rock grade, and when the surrounding rock grade is I-II grade, not considering the horizontal pressure; when the surrounding rock grade is grade iii, e=0.15 q; when the surrounding rock level is level iv, e=0.30q; when the surrounding rock grade is v grade, e=0.50q;
C. determination of the elastic resistance K of the surrounding rock
According to the railway tunnel design Specification (TB 10003-2016), K is 1800MPa/m when the grade II surrounding rock, K is 1200MPa/m when the grade III surrounding rock, K is 500MPa/m when the grade IV surrounding rock, and K is 200MPa/m when the grade V surrounding rock;
step 1.4, substituting the dead weight of the supporting structure, the vertical pressure Q of surrounding rock, the horizontal pressure e of surrounding rock and the elastic resistance K of the surrounding rock into a finite element calculation model of the positive arch, wherein the elastic resistance K of the surrounding rock adopts the constraint simulation of a curved surface spring which is only pressed, and calculating the concentrated force Q of each positive arch on the double-spliced arch;
step 1.5, substituting the concentrated force Q into a finite element calculation model of the double-spliced I-steel arch frame, calculating the strength sigma of the double-spliced I-steel arch frame, and when the sigma meets the following formula (7), verifying that the double-spliced I-steel arch frame is reliable, otherwise, adopting an increased I-steel model or adopting a three-spliced I-steel arch frame to repeat the steps to redesign and check;
1.1σ≤f (7)
in the formula (7), 1.1 is a safety coefficient, and f is a material bending resistance and compressive strength design value of the double-spliced I-steel arch;
after the support structure design verification passes, carrying out tunnel roof picking construction according to the following steps of;
step 2.1, when the inclined shaft is excavated to be close to 10m from the side of the positive hole, the upper step is lifted and excavated to a three-fork junction between the inclined shaft and the positive hole with a gradient close to 20%, so that mechanical equipment such as a digging machine, a wet spraying mechanical arm and the like can smoothly climb a slope to carry out ballasting and guniting support;
step 2.2, installing a three-fork arch frame on an upper step, welding a stand column type falling platform and an overhanging type falling platform in advance in the vault range of the three-fork arch frame to provide support for the positive tunnel arch frame, wherein the spacing between the falling platforms is consistent with the supporting spacing of the positive tunnel arch frame, and the arch feet of the three-fork arch frame are provided with three groups of locking anchor pipes and cement slurry for reinforcement, and temporary transverse support connection is arranged on the arch feet of the three-fork arch frame to form a whole;
2.3, excavating a pilot tunnel vertically in the normal tunnel, excavating a flat slope after excavating a certain distance on a broken line of the pilot tunnel, supporting the pilot tunnel by adopting a temporary portal, grouting and reinforcing a foot locking anchor pipe by an arch foot of the temporary portal, and spraying an anchor support; simultaneously installing a main tunnel arch frame, connecting a stand column type falling platform of the three-fork arch frame and a cantilever type falling platform, and installing a temporary portal frame and the main tunnel arch frame until the side edge of the main tunnel while excavating a pilot tunnel;
step 2.4, after the pilot tunnel is excavated, removing the temporary portal frame, excavating and supporting an upper step in the large mileage or small mileage direction of the pilot tunnel to form a large working surface, and excavating other steps of the pilot tunnel after reaching the safe excavation step distance; when the positive hole is excavated to the elevation of the bottom plate of the lower step, the lower step of the inclined shaft top-picking section synchronously starts to be excavated to the position of the three fork and is connected with the elevation of the bottom of the positive hole; the arch foot of the three-fork arch centering of the lower step adopts section steel to enlarge the connecting plate and is tightly poured by concrete after being buried underground, and the arch foot of the three-fork arch centering is provided with an I-steel permanent cross brace;
and 2.5, continuously constructing the positive hole towards the two ends of the positive hole according to a step method, and completing all construction after all primary supports of the positive hole are closed into rings within the range of the falling leg platform of the three-fork arch frame.
In step 2.1, the arch spacing of the inclined shaft of the top-picking section is smaller than that of the arch spacing of the standard section, the arch is supported to the side of the main tunnel along a circular curve in an encrypted manner, and the arch is reinforced according to the anchor spraying support; the height of the upper step is not less than 4.5m.
Further, in step 2.2, the foot locking anchor tube is adopted42mm。
In step 2.3, the width of the pilot tunnel is 4m, the height is 4.5m, the pilot tunnel is supported by an I16 steel temporary portal frame, and the distance is 1m.
Further, in step 2.4, the section steel is expanded to a size of 400mm×400mm×16mm, and buried in the ground by 50cm.
In step 2.5, the I-steel of the permanent transverse support is double-spliced I22a I-steel.
The beneficial effects of the invention are as follows:
(1) The invention firstly tries to design the three-fork supporting structure and check whether the strength of the double-spliced I-steel arch is reliable or not before tunnel construction, if not, redesign the three-spliced I-steel arch or increase the I-steel model of the double-spliced I-steel arch and check the strength of the arch, if so, the construction of tunnel roof picking is implemented and completed, thus ensuring the stability and reliability of the supporting structure at the three-fork position of the inclined shaft turning positive tunnel.
(2) According to the invention, the load structure method is used for designing the three-fork supporting structure, the double-spliced I-steel arch crown is provided with the transverse overhanging type and vertical column type falling platform which is connected with the positive tunnel arch, the structural load is symmetrical, the stress is more reasonable, the temporary cross bracing of the arch feet is used for forming a closed loop supporting system, a sleeve arch is not needed to be applied, and the overall stability of the supporting structure at the intersection is improved.
(3) According to the method, the temporary portal frame and the positive tunnel arch frame unit for the top picking construction are synchronously installed through the temporary bracket reinforcement, and after the pilot tunnel is completed, the positive tunnel arch frame is simultaneously supported, so that the construction period is greatly shortened, and the support system conversion can be rapidly completed.
Drawings
The inclined shaft turning positive tunnel three-fork support design and the roof-picking construction method of the tunnel are further described below with reference to the accompanying drawings.
FIG. 1 is a schematic view of a double-sectional arch structure according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of load calculation of a deep buried tunnel structure according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of load calculation of a shallow tunnel structure according to an embodiment of the present invention;
FIG. 4 is a partial detailed view of node A of FIG. 1 in accordance with an embodiment of the present invention;
FIG. 5 is a partial detailed view of the node B of FIG. 1 in accordance with an embodiment of the present invention;
FIG. 6 is a schematic illustration of a type I joint connection according to an embodiment of the present invention;
FIG. 7 is a longitudinal section view of a slant well rotary positive hole construction according to an embodiment of the present invention;
FIG. 8 is a plan view of a slant well rotary positive hole construction according to an embodiment of the present invention;
fig. 9 is a schematic view of a gantry structure according to an embodiment of the present invention.
The marks in the figure: 1. double-spliced arch frames, cantilever type falling leg platforms, upright type falling leg platforms, connecting plates, expanding connecting plates, cross braces, first locking leg anchor pipes, positive hole arch frames, inclined shaft arch frames, 11 portal frames and second locking leg anchor pipes.
Detailed Description
Example 1
According to the inclined shaft turning positive hole three-fork support design and the top-picking construction method of the tunnel, the total length of the tunnel is 5100m, the cross section size is 14m (width) x 12m (height), all the inclined shaft is formed by IV-level surrounding rocks, the inclined shaft is 200m long, the cross section size is 6m (width) x 7.5m (height), all the inclined shaft is IV-level surrounding rocks, and the burial depth at the intersection of the inclined shaft and the positive tunnel is 35m; the method comprises the following steps:
step 1, designing a supporting structure of a three-way fork, specifically designing and checking as follows,
step 1.1 the support structure of the pre-trial design of the three-fork adopts a double-spliced I-steel arch 1, as shown in figure 1, the arch 1 adopts Q235 steel, and the yield strength is 215MPa. And establishing a calculation model of the double-spliced I-steel arch 1 in finite element software. As shown in fig. 4 and 5, the arch crown of the double-spliced I-steel arch 1 is provided with an overhanging type landing platform 2 and a column type landing platform 3; as shown in fig. 6, the arch 1 is welded together in units and connected into a whole by a connecting plate 4, and the arch legs of the double-spliced i-steel arch 1 are fixed by an enlarged connecting plate 5.
The supporting structure of the positive tunnel in the step 1.2 adopts an arch frame to form a positive tunnel arch frame, one side of the positive tunnel arch frame is all arranged on the double-spliced I-steel arch frame, the positive tunnel arch frame is used as a calculating unit according to the supporting distance, and a finite element calculating model of the positive tunnel arch frame is built in finite element software;
step 1.3 checking and calculating to determine structural parameters of double-spliced I-steel arch frame
Step 1.3.11 judges whether the three-way switch belongs to shallow or deep burying
Calculating the boundary depth H of the tunnel deep and shallow burial according to the following formula (1) p
H p ＝1.125×2 S-1 w (1)
In the formula (1), S is the surrounding rock grade number; w is a width influence coefficient, calculated according to the following formula (2),
w＝1+i(B-5) (2)
in formula (2), B is the tunnel width (unit m); i is the surrounding rock pressure increase and decrease rate, i=0.2 when B <5m, i=0.1 when B > 5m;
when the tunnel burial depth h is smaller than Hp, the shallow burial is judged, and when the tunnel burial depth h is larger than or equal to Hp, the deep burial is judged.
In this embodiment, the above data is substituted to calculate:
the width influence coefficient w=1+i (B-5) =1+0.1× (6-5) =1.1, the demarcation depth hp=1.125×24-1×1.1=9.9 m,
since the tunnel burial depth h=35m > hp=9.9m at the triple junction, the tunnel of this embodiment is judged to be deeply buried.
The structural parameters of the double-spliced I-steel arch frame comprise the dead weight of the supporting structure, the vertical pressure q of surrounding rock, the horizontal pressure e of surrounding rock and the elastic resistance K of the surrounding rock, and the structural parameters are proved and calculated as follows;
B. the tunnel of this embodiment is a deep buried tunnel,
B1. thus, the surrounding rock vertical pressure q of the tunnel is calculated according to the following formula (6)
q＝γ(0.45×2 S-1 w) (6)
In formula (6), γ is the surrounding rock weight (unit kN/m 3 ) Class II surrounding rock is 27kN/m 3 Grade III surrounding rock is 25kN/m 3 Grade IV 23kN/m 3 V grade 20kN/m 3 ；
The surrounding rock of the example IV grade, therefore, the surrounding rock gravity gamma is 23kN/m 3 Surrounding rock grade number s=4, then
q＝γ(0.45×2 S-1 w)＝23×(0.45×2 4-1 ×1.1)×0.6＝91.08kPa。
B2. When the tunnel is deeply buried, the tunnel surrounding rock horizontal pressure e does not consider the influence of the tunnel burial depth because of the natural arch effect, so the surrounding rock horizontal pressure e is determined according to the surrounding rock level, and when the surrounding rock level is I-II, the horizontal pressure is not considered; when the surrounding rock grade is grade iii, e=0.15 q; when the surrounding rock level is level iv, e=0.30q; when the surrounding rock class is v class, e=0.50 q. Since the tunnel of this example is class iv surrounding rock, the surrounding rock level pressure e=0.3q=0.3×91.08=27.32 kPa.
C. Determination of the elastic resistance K of the surrounding rock
According to the railway tunnel design Specification (TB 10003-2016), K is 1800MPa/m for II-level surrounding rock, 1200MPa/m for III-level surrounding rock, 500MPa/m for IV-level surrounding rock, and 200MPa/m for V-level surrounding rock.
Since the tunnel of this embodiment is class iv surrounding rock, the tunnel surrounding rock elastic resistance k=500 MPa/m of this embodiment.
Step 1.4 as shown in fig. 2 and 3, 15 positive hole arches in this embodiment are located on double-spliced i-steel arches, a finite element calculation model of 8 positive hole arches is built according to symmetry requirements, and supporting structures (double-spliced i-steel arches) are substituted into the finite element calculation model of 8 positive hole arches, wherein the surrounding rock elastic resistance K adopts curved surface spring constraint simulation only under compression, so that the concentration force (namely support counter force) Q of each positive hole arch 8 on a landing platform is calculated, and the directions from a vault to the arch feet are 385.5kN,385.6kN, 386.3kN,386.5kN,386.8kN and 387.2kN respectively.
Step 1.5, substituting the concentrated force Q into a finite element calculation model of the double-spliced I-steel arch according to the relation between acting force and reacting force, calculating the strength sigma=170.6 MPa of the double-spliced I-steel arch in the embodiment, and when sigma meets the following (7), verifying that the double-spliced I-steel arch is reliable, otherwise, adopting the I-steel model of the increased double-spliced I-steel arch or adopting the three-spliced I-steel arch to repeat the steps for redesign and checking calculation;
1.1σ≤f (7)
in the formula (7), 1.1 is a safety factor, and f is a material bending resistance and compressive strength design value of the double-spliced I-steel arch frame.
In this embodiment, since 1.1σ= 187.66MPa is less than or equal to f=215 MPa, it is verified that the double-spliced i-steel arch designed in advance is reliable as a supporting structure of the three-way fork.
Step 2, after the structural design verification is passed, carrying out tunnel roof picking construction according to the following steps;
step 2.1, as shown in fig. 7, when the inclined shaft is excavated to a distance of about 10m from the side of the positive hole, the upper step is lifted and excavated to a three-fork junction between the inclined shaft and the positive hole with a gradient of about 20 percent; the height of the upper step is not less than 4.5m, so that mechanical equipment such as a digging machine, a wet spraying manipulator and the like can smoothly climb a slope to carry out ballasting and guniting support; the spacing of the inclined shaft arches 10 of the top-picking section is smaller than that of the standard section, and the inclined shaft arches are encrypted and supported to the side edge of the main tunnel along a circular curve, and are carried out according to anchor spraying and supporting;
step 2.2 As shown in figures 1 and 7, the double-spliced I-steel arch 1 is firstly arranged at the upper step of the three-fork, the vertical column type falling platform 2 and the cantilever type falling platform 3 are welded in advance in the arch crown range of the double-spliced I-steel arch 1 to provide support for the positive tunnel arch 8, the spacing between the falling platforms 2 is consistent with the supporting spacing between the positive tunnel arch 8, and the double-spliced I-steel arch 1 is arranged at the upper step of the three-forkThree groups of arch legs 7 of the arch frame 1 are appliedThe first pin locking anchor pipe 7 with the thickness of 42mm is reinforced by cement slurry, and temporary transverse supports 6 are arranged on the pins of the double-spliced I-steel arch 1 and are connected to form a whole;
step 2.3, as shown in fig. 8, a pilot tunnel is dug in the vertical positive tunnel, the width of the pilot tunnel is 4m, and the height is 4.5m; excavating a guide hole on a broken line for a certain distance, excavating a flat slope, supporting the guide hole by adopting a temporary portal 11 made of I16 section steel, wherein the distance is 1m as shown in fig. 9, and grouting, reinforcing and shotcreting a second locking anchor pipe 12 are arranged on the arch springing of the temporary portal 11; as shown in fig. 8, simultaneously installing a main tunnel arch 8, connecting a stand column type falling platform 2 and a cantilever type falling platform 3 of the three-fork arch, and installing a temporary portal frame 11 and the main tunnel arch 8 until the side of the main tunnel while excavating a pilot tunnel;
step 2.4, as shown in fig. 8, removing the temporary portal 11 after the pilot tunnel is excavated, excavating and supporting an upper step in the large mileage or small mileage direction of the pilot tunnel, forming a large working surface, and excavating other steps of the pilot tunnel after reaching the safe excavation step distance; when the positive hole is excavated to the elevation of the bottom plate of the lower step, the lower step of the inclined shaft top-picking section synchronously starts to be excavated to the position of the three fork and is connected with the elevation of the bottom of the positive hole; the arch foot of the three-fork arch centering of the lower step adopts section steel to enlarge a connecting plate 5 (400 mm is multiplied by 16 mm), and is tightly poured by concrete after being buried under the ground for 50cm, and at the moment, the arch foot of the three-fork arch centering is provided with a double-spliced I22a I-shaped steel permanent transverse strut;
and 2.5, continuously constructing the positive hole towards the two ends of the positive hole according to a step method, and completing all construction after all primary supports of the positive hole are closed into rings within the range of the falling leg platform of the three-fork arch frame.
Example two
This embodiment is a variation on the basis of embodiment one, except that the same as embodiment one is:
(1) The embedded depth at the intersection of the inclined shaft and the tunnel positive hole is 9m.
(2) Since the tunnel burial depth h=35m > hp=9.9m at the triple junction, the tunnel of this embodiment is determined to be shallow.
As shown in fig. 3, the friction angle is calculated by the surrounding rock of the shallow tunnelθ＝0.7/>。
The side pressure coefficient lambda is calculated according to the following formula (4)
A1. Calculating the surrounding rock vertical pressure q according to the following formula (3)
In formula (3), γ is the surrounding rock weight (unit kN/m 3 ) Class II surrounding rock is 27kN/m 3 Grade III surrounding rock is 25kN/m 3 Grade IV 23kN/m 3 V grade 20kN/m 3 The method comprises the steps of carrying out a first treatment on the surface of the The surrounding rock of the example IV grade, therefore, the surrounding rock gravity gamma is 23kN/m 3 。
Calculated q= 161.7kPa.
A2. When the tunnel is shallow buried, taking the influence of formation burial depth into consideration, respectively taking the top and the bottom of the tunnel in the supporting structure interval to calculate the surrounding rock horizontal pressure, and calculating the surrounding rock horizontal pressure e by linear interpolation according to a formula (5).
e＝γhλ (5)，
In this embodiment, the surrounding rock gravity γ of the iv-level surrounding rock is 23kN/m, the height of the supporting structure (double-spliced i-steel arch 1) is equal to 7.5m of the cross section of the inclined shaft, the height h of the top of the supporting structure is equal to 9m of the buried depth of the tunnel, and the height h of the bottom of the supporting structure is equal to 9 m+7.5 m of the buried depth of the tunnel, then
The surrounding rock horizontal pressure e=0.24×9×23=49.68 kPa at the top of the tunnel in the supporting structure section,
surrounding rock horizontal pressure e=0.24× (9+7.5) ×23=91.08 kPa at the tunnel bottom of the supporting structure section.
(3) Referring to the procedure of the first embodiment, the strength σ=241.2mpa of the double-spliced arch 1 of the three-fork is calculated,
in this embodiment, since 1.1σ= 187.66MPa is less than or equal to f=215 MPa, the structural design of the three-fork I22a double-spliced arch 1 does not meet the requirement, and the three-spliced I22a I-steel arch is adopted to repeat the above steps for redesign and checking, so that the specific process is not repeated.
The calculated intensity sigma= 192.96MPa of the three-spelling I22a arch is recalculated,
because 1.1σ= 212.26MPa is less than or equal to f=215 MPa, the three-fork supporting structure adopting the three-spliced I22a I-steel arch frame is safe and reliable.
The subsequent tunnel roof-picking construction is the same as that of the first embodiment, and will not be described again.
The foregoing description is only of the preferred embodiments of the invention, but the invention is not limited thereto, and all equivalents and modifications according to the concept of the invention and the technical solutions thereof are intended to be included in the scope of the invention.
Claims (6)
1. The inclined shaft turning positive tunnel three-fork support design of the tunnel and the roof-picking construction method thereof are characterized by comprising the following steps:
step 1, designing a supporting structure of a three-way fork, specifically designing and checking as follows,
step 1.1, pre-trial design of a supporting structure of the three-fork adopts a double-spliced I-steel arch, a finite element calculation model of the double-spliced I-steel arch is built in finite element software,
the supporting structure of the positive tunnel in the step 1.2 adopts an arch frame to form a positive tunnel arch frame, one side of the positive tunnel arch frame is all arranged on the double-spliced I-steel arch frame, the positive tunnel arch frame is used as a calculating unit according to the supporting distance, and a finite element calculating model of the positive tunnel arch frame is built in finite element software;
step 1.3 checking and calculating to determine structural parameters of double-spliced I-steel arch frame
Step 1.3.1 judging whether the three-way fork belongs to shallow burying or deep burying
Calculating the boundary depth H of the tunnel deep and shallow burial according to the following formula (1) p
H p ＝1.125×2 S-1 w (1)
In the formula (1), S is the surrounding rock grade number; w is a width influence coefficient, calculated according to the following formula (2),
w＝1+i(B-5) (2)
in formula (2), B is the tunnel width (unit m); i is the surrounding rock pressure increase and decrease rate, i=0.2 when B <5m, i=0.1 when B > 5m;
judging shallow burying when the tunnel burying depth h is smaller than Hp, and judging deep burying when the tunnel burying depth h is larger than or equal to Hp;
the structural parameters of the double-spliced I-steel arch frame comprise the dead weight of a supporting structure, the vertical pressure q of surrounding rock, the horizontal pressure e of surrounding rock and the elastic resistance K of the surrounding rock, and the structural parameters are proved to be as follows;
A. when shallow buried
A1. Calculating the surrounding rock vertical pressure q according to the following formula (3)
In the formula (3), gamma is the weight of surrounding rock, and grade II surrounding rock takes 27kN/m 3 Grade III surrounding rock is 25kN/m 3 Grade IV 23kN/m 3 V grade 20kN/m 3 ；
θ is the friction angle of the two sides of the top plate column of the supporting structure, when the surrounding rock level is level III,when the surrounding rock level is level IV, < + >>When the surrounding rock level is V level, < -> Calculating a friction angle of surrounding rock; lambda is a side pressure coefficient, calculated according to the following equation (4),
in the formula (4), beta is a rupture angle when the support structure generates maximum thrust;
A2. respectively taking the surrounding rock horizontal pressure e at the top and the bottom of the tunnel in the supporting structure interval, calculating the surrounding rock horizontal pressure e by linear interpolation according to a formula (5),
e＝γhλ (5)；
B. when buried deeply
B1. Calculating the surrounding rock vertical pressure q according to the following formula (6)
q＝γ(0.45×2 S-1 w) (6)
B.2, determining the surrounding rock horizontal pressure e according to the surrounding rock grade, and when the surrounding rock grade is I-II, not considering the horizontal pressure; when the surrounding rock grade is grade iii, e=0.15 q; when the surrounding rock level is level iv, e=0.30q; when the surrounding rock grade is v grade, e=0.50q;
C. determination of the elastic resistance K of the surrounding rock
K is 1800MPa/m when the grade II surrounding rock is adopted, 1200MPa/m when the grade III surrounding rock is adopted, 500MPa/m when the grade IV surrounding rock is adopted, and 200MPa/m when the grade V surrounding rock is adopted;
step 1.4, substituting the dead weight of the supporting structure, the vertical pressure Q of surrounding rock, the horizontal pressure e of surrounding rock and the elastic resistance K of the surrounding rock into a finite element calculation model of the positive arch, wherein the elastic resistance K of the surrounding rock adopts the constraint simulation of a curved surface spring which is only pressed, and calculating the concentrated force Q of each positive arch on the double-spliced arch;
step 1.5, substituting the concentrated force Q into a finite element calculation model of the double-spliced I-steel arch frame, calculating the strength sigma of the double-spliced I-steel arch frame, and when the sigma meets the following formula (7), verifying that the double-spliced I-steel arch frame is reliable, otherwise, adopting an increased I-steel model or adopting a three-spliced I-steel arch frame to repeat the steps to carry out redesign checking calculation;
1.1σ≤f (7)
in the formula (7), 1.1 is a safety coefficient, and f is a material bending resistance and compressive strength design value of the double-spliced I-steel arch;
step 2, after the design verification of the support structure is passed, carrying out tunnel roof-picking construction according to the following steps;
step 2.1, when the inclined shaft is excavated to be close to 10m from the side of the positive hole, the upper step is lifted and excavated to a three-fork junction between the inclined shaft and the positive hole with a gradient close to 20%, so that mechanical equipment such as a digging machine, a wet spraying mechanical arm and the like can smoothly climb a slope to carry out ballasting and guniting support;
step 2.2, installing a three-fork arch frame on an upper step, welding a stand column type falling platform and an overhanging type falling platform in advance in the vault range of the three-fork arch frame to provide support for the positive tunnel arch frame, wherein the spacing between the falling platforms is consistent with the supporting spacing of the positive tunnel arch frame, and the arch feet of the three-fork arch frame are provided with three groups of locking anchor pipes and cement slurry for reinforcement, and temporary transverse support connection is arranged on the arch feet of the three-fork arch frame to form a whole;
2.3, excavating a pilot tunnel vertically in the normal tunnel, excavating a flat slope after excavating a certain distance on a broken line of the pilot tunnel, supporting the pilot tunnel by adopting a temporary portal, grouting and reinforcing a foot locking anchor pipe by an arch foot of the temporary portal, and spraying an anchor support; simultaneously installing a main tunnel arch frame, connecting a stand column type falling platform of the three-fork arch frame and a cantilever type falling platform, and installing a temporary portal frame and the main tunnel arch frame until the side edge of the main tunnel while excavating a pilot tunnel;
step 2.4, after the pilot tunnel is excavated, removing the temporary portal frame, excavating and supporting an upper step in the large mileage or small mileage direction of the pilot tunnel to form a large working surface, and excavating other steps of the pilot tunnel after reaching the safe excavation step distance; when the positive hole is excavated to the elevation of the bottom plate of the lower step, the lower step of the inclined shaft top-picking section synchronously starts to be excavated to the position of the three fork and is connected with the elevation of the bottom of the positive hole; the arch foot of the three-fork arch centering of the lower step adopts section steel to enlarge the connecting plate and is tightly poured by concrete after being buried underground, and the arch foot of the three-fork arch centering is provided with an I-steel permanent cross brace;
and 2.5, continuously constructing the positive hole towards the two ends of the positive hole according to a step method, and completing all construction after all primary supports of the positive hole are closed into rings within the range of the falling leg platform of the three-fork arch frame.
2. The method according to claim 1, wherein: in the step 2.1, the arch spacing of the inclined shaft of the top-picking section is smaller than that of the arch spacing of the standard section, the arch is supported to the side of the main tunnel along a circular curve in an encrypted manner, and the arch is reinforced according to the anchor spraying support; the height of the upper step is not less than 4.5m.
3. The method according to claim 1, wherein: in the step 2.2, the foot locking anchor tube adopts
4. The method according to claim 1, wherein: in the step 2.3, the width of the pilot tunnel is 4m, the height is 4.5m, the pilot tunnel is supported by an I16 type steel temporary portal frame, and the distance is 1m.
5. The method according to claim 1, wherein: in the step 2.4, the section steel is expanded to a size of 400mm×400mm×16mm and buried in the ground by 50cm.
6. The method according to claim 1, wherein: in the step 2.5, the I-steel of the permanent transverse support adopts double-spliced I22a I-steel.
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| CN117967323A (en) * | 2024-03-21 | 2024-05-03 | 中铁四局集团有限公司 | Reinforcing ring structure at hydraulic tunnel fork-to-branch hole interface and roof-picking construction method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117967323A (en) * | 2024-03-21 | 2024-05-03 | 中铁四局集团有限公司 | Reinforcing ring structure at hydraulic tunnel fork-to-branch hole interface and roof-picking construction method |
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