Tunnel inverted arch postposition mechanized rapid construction method

Abstract

The invention relates to the technical field of tunnel inverted arch mechanized rapid construction, in particular to a tunnel inverted arch rear mechanized rapid construction method. The method includes the following steps that firstly, a tunnel face is excavated; 2, supporting a tunnel face; thirdly, an inverted arch is excavated; fourthly, the undercut position is chiseled away mechanically; fifthly, inverted arch supporting is carried out; sixthly, the third step to the fifth step are repeated for three times, and construction of four circulation sections is completed; seventhly, the hydraulic trestle is moved, the front supporting legs are erected on the initial supporting face of the inverted arch, and after the trestle is in place, inverted arch steel bars and inverted arch filling are synchronously constructed through the two working areas; according to the construction method, the tunnel inverted arch construction efficiency is improved, the initial supporting stability is improved, and the tunnel safety step pitch problem is solved; according to inverted arch rear excavation, the cycle operation time of a tunnel face is mainly considered to be shortened, the construction progress of a rear inverted arch is driven by the excavation cycle time of the tunnel face, the tunnel face plays a role in leading, the construction period is shortened, the construction risk is reduced, the construction difficulty is reduced, and the construction cost is saved.

Description

Technical Field

[0001] The invention relates to the technical field of mechanized rapid construction of tunnel inverts, and in particular to a post-positioned mechanized rapid construction method of a tunnel invert. Background Art

[0002] The inverted arch is a reverse arch structure set at the bottom of the tunnel to improve the stress conditions of the upper supporting structure. It is one of the important components of the tunnel structure and the foundation of the tunnel structure. On the one hand, it effectively transfers the stratum pressure above the tunnel to the underground through the tunnel side wall structure or the load on the road surface, and also effectively resists the reaction force from the stratum below the tunnel. In fact, it is a foundation beam that can withstand permanent stratum loads and temporary road surface loads (dynamic loads). The inverted arch and the secondary lining constitute the whole tunnel and increase the structural stability.

[0003] In traditional technology, the efficiency of tunnel invert construction is generally lower than that of the heading face and secondary lining. The invert construction has become a key link restricting the progress of tunneling. Summary of the invention

[0004] The present invention is to solve the technical problem that the construction efficiency of tunnel invert is lower than that of the face and the secondary lining, and the construction of the invert restricts the progress of tunnel construction. A mechanized rapid construction method for the rear-positioned tunnel invert is provided to improve the construction efficiency of the tunnel invert, improve the stability of the initial support, and solve the problem of safe step distance of the tunnel. The mechanized rapid construction of the rear-positioned tunnel invert is a method based on the independent and parallel advancement of the full process construction of the invert and the face construction, so that the processes of the invert and the face do not intersect each other. The large machine drills holes in the reverse direction at the face position, and the invert part in front of the hydraulic trestle is independently blasted, excavated and supported in batches, and backfilled in time after a single excavation and support. When the invert trestle moves, the overall 12m invert backfill area is excavated at a time to ensure the effective construction space of the last working section of the invert trestle, which is more efficient, standardized and fast, can shorten the construction period, reduce construction risks, reduce construction difficulty, and save construction costs.

[0005] 2. The technical solution adopted by the present invention is: a mechanized rapid construction method for a tunnel invert rear-end, characterized in that it comprises the following steps:

[0006] The first step is to excavate the tunnel face;

[0007] The second step is to support the tunnel face;

[0008] The third step is arch excavation. The end arch is excavated and cleaned by excavators. Then the arch contour is manually measured and set. According to the measured conditions, a three-arm rock drilling rig is used to drill holes. Some parts that are difficult to reach by large machines are manually coordinated. The manual drilling machine uses the large machine's mobile air compressor to supply air, and then blasting is performed to remove slag.

[0009] The fourth step is to use a 3D scanner to scan the contour of the invert after the excavation is completed, and mechanical chiseling is used to remove the under-excavated areas to ensure the arc effect of the invert contour;

[0010] The fifth step is to support the inverted arch by spraying concrete at the bottom of the inverted arch and sealing the inverted arch in time. The strength of the sealed concrete should reach 80% of the design.

[0011] Step 6: Repeat steps 3 to 5 three times to complete the construction of 4 cycles;

[0012] Step 7: Move the hydraulic trestle, and place the front legs on the initial support surface of the invert. After the trestle is in place, use two work areas to simultaneously construct the invert reinforcement and invert filling.

[0013] As a result, within the same time period, the invert excavation, invert reinforcement binding, invert concrete pouring and face construction form independent work areas that do not interfere with each other, becoming a complete set of flow operations, which maximizes the progress of the invert construction. The initial support steel frame can also be closed in time, which improves the initial support stability and solves the problem of safe step distance in the tunnel.

[0014] As a further limitation of the technical solution of the present invention, in the third step, the drilling and blasting design parameters of the rear area of ​​the invert before the invert is excavated include the number of blastholes and the total amount of explosives per cycle;

[0015] The calculation formula for the number of blastholes is: N = qS / ηγ

[0016] Where: N-number of blast holes,

[0017] q-Unit explosive consumption (kg / m 3 ),

[0018] S-excavation cross-sectional area (㎡),

[0019] η-Charge coefficient, i.e. the ratio of charge length to borehole length,

[0020] γ-mass of explosive per meter of cartridge (kg / m);

[0021] The formula for calculating the total explosive consumption per cycle is: Q = qV

[0022] Where: Q-total explosive consumption

[0023] q-Unit explosive consumption (kg / m 3 ),

[0024] V—Total volume of rock blasting during one excavation cycle (m 3 ).

[0025] As a further limitation of the technical solution of the present invention, in the third step, a machine is used to excavate the end arch, which is convenient for measuring operations and for the three-arm drilling rig to drill holes into the working area; during the full-section or step method excavation of the face, the downward depression angle is considered when setting the bottom plate eyes, and the arch can be blasted and excavated to a depth of 0.8m at the same time. After considering the depression angle through the face bottom plate eyes, the rear arch is under-excavated, leaving only the remaining part of the tunnel bottom. The PC220 excavator is used to directly excavate the area with a smaller under-excavation to the designed contour, and the artificial drilling of blastholes is used to supplement the blasting and clear the slag in the area with a larger under-excavation until the design contour line of the arch is cleared.

[0026] As a further limitation of the technical solution of the present invention, 3m of support is provided in each cycle of excavation, and after 4 cycles of excavation, a closed area of ​​the initial support of the entire slab with a length of 12m is formed.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The post-excavation of the invert is mainly to shorten the cycle operation time of the face, so that the face excavation cycle time can drive the construction progress of the rear invert, and make the face play a leading role.

[0029] 2. Reduce the amount of slag discharged from the face at one time. For large-section tunnels or areas with soft surrounding rock, there will be no risk of deformation or collapse due to a single excavation of the face and invert area.

[0030] 3. When excavating the back arch, the back arch should be formed by blasting the curved surface once to reduce over-excavation control.

[0031] 4. After the initial support of the invert is closed, the invert lining can be quickly constructed to minimize tunnel deformation.

[0032] 5. Form one to three working areas, with each area carrying out construction in a continuous flow without affecting each other, thus maximizing the speed of invert construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the sequence diagram for the mechanized rapid excavation of the tunnel invert.

[0034] Figure 2 This is a main process flow chart of the present invention.

[0035] Figure 3 Schematic diagram of the arrangement of inverted blastholes.

[0036] Figure 4 This is a schematic diagram of the rear excavation of the invert. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with specific embodiments.

[0038] Example

[0039] The mechanized rapid construction method for rear-mounted tunnel inverts of the present invention is a specific, scientific and systematic rapid construction method for tunnel inverts, which is specifically described as follows in combination with graphic descriptions:

[0040] 1. Drilling and blasting design of the rear area of ​​the invert

[0041] Number of blastholes: N = qS / ηγ

[0042] In the formula: q—unit explosive consumption;

[0043] S—excavation cross-sectional area (㎡);

[0044] η—Charge coefficient, i.e. the ratio of charge length to borehole length, with a trial value of 0.5;

[0045] γ—mass of explosive per meter of cartridge (kg / m), for emulsion explosive γ=1.

[0046] That is: N = (0.8×17.3) / (0.5×1) = 27.

[0047] Calculation and distribution of charge in each cycle:

[0048] Theoretical total explosive consumption per cycle: Q = qV

[0049] Where: q—unit explosive consumption, q=0.5kg / m 3 ;

[0050] V—Total volume of rock blasting during one excavation cycle (m 3 ).

[0051] That is: Q = 0.8kg / m 3 ×3.0m×17.3m 3 / m = 41.5kg;

[0052] Because when calculating the number of blastholes, try to take: η = 0.5. Assume that the charge coefficient of each blasthole is 0.55 for the bottom plate hole and 0.45 for the auxiliary hole, then:

[0053] 17×0.55+11×0.45=28η

[0054] Calculated: η = 0.51

[0055] The trial selected η value is basically consistent with the calculated η and can be allocated according to the above-mentioned blasthole filling coefficient.

[0056] The amount of medicine for each auxiliary eye = 3 × 0.45 = 1.35 kg;

[0057] The charge amount of each bottom plate eye = 3.2 × 0.55 = 1.92 kg;

[0058] The actual dosage is: 1.35×11+1.76×17=44.77kg.

[0059] The blasting parameters for invert excavation are shown in Table 1.

[0060] Table 1. Blasting parameters for arch excavation Table 2. Arch excavation and cleaning

[0061]

[0062] The end invert is excavated mechanically to facilitate measurement and the drilling of the three-arm drilling rig into the work area. During the full-section or step-method excavation of the face, the downward depression angle is considered when setting the bottom plate hole, and the invert can be blasted and excavated to a depth of about 0.8m. After considering the depression angle through the face bottom plate hole, the rear invert is under-excavated, leaving only the remaining part of the tunnel bottom. The PC220 excavator is used to directly excavate the area with a small under-excavation to the designed contour. The artificial drilling of blast holes is used to supplement the blasting and clear the slag in the area with a large under-excavation until it is cleared to the designed contour line of the invert. After the excavation section is scanned by 3D laser section without intrusion, the excavation and slag removal construction is stopped.

[0063] 3. Forming the rear section of the invert

[0064] The tunnel invert is constructed by blasting + large machinery. 3m of excavation support is provided in each cycle. After 4 cycles of excavation, a closed area of ​​the initial support of the entire 12m invert is formed.

[0065] After each cycle of arch excavation and bottom cleaning is completed, C30 shotcrete sealing is carried out in time. After the sealed concrete strength reaches 80% of the design strength, the tunnel slag is backfilled with counter pressure. After completing four cycles of excavation and support, the front approach bridge is lifted by the hydraulic system when the trestle moves forward, and the excavator is used to excavate 12m of the arch area at a time to backfill the slag. The special arch steel brush configured with 3D scanning is used to perform overall trimming of the local convex surface of the initial support of the arch to ensure the curvature of the arch bottom surface and maximize the over-consumption loss of the arch steel bar protective layer and the arch concrete.

[0066] 4. Materials and Equipment

[0067] (1) Materials

[0068] The main materials for post-excavation of the invert include emulsion explosives, non-electric millisecond tubes, detonating cords, electric detonators, bamboo strips, water bags, and gun mud.

[0069] (2) Equipment

[0070] DJ3E intelligent three-arm rock drilling rig, manual YT-28 pneumatic drill, mobile air compressor, PC220 excavator, invert steel brush (No. 1), pneumatic pick, wet spraying manipulator, 3D cross-section scanner, Wuxin 36m full hydraulic invert trestle, etc., see Table 2 below for details.

[0071] Table 2 Equipment parameters

[0072] Serial number name Specification quantity Remark 1 Drilling rigs DJ3E Intelligent Three-arm 1 2 Pneumatic drill YT-28 1 3 Mobile air compressor <![CDATA[36m 3 / min]]> 1 There is no high-pressure air duct in the hole for large machine operation 4 220 Excavator <![CDATA[1.2m 3 ]]> 2 5 Inverted steel brush (No. 1) <![CDATA[3m 3 ]]> 2 6 Wet spraying machine <![CDATA[30m 3 / h]]> 1～2 7 Pneumatic Pick G1026L / s5kw 3 8 3D cross-sectional scanner ms60 1 9 Inverted Arch Bridge Wuxin 36m fully hydraulic 1 10 Dump Truck <![CDATA[20m 3 ]]> 8 Economic configuration based on transport distance

[0073] 5. Quality Control

[0074] During the construction process, large-scale drilling and bottom cleaning of the invert are used to control the over-excavation and under-excavation of the invert and the flatness of the initial support of the invert, thereby ensuring the overall construction quality of the tunnel invert, thereby achieving the saving of invert concrete under the post-excavation technology of the invert, the quality of the reinforced concrete of the invert structure, and the stability of the initial support arch frame of the side wall, which plays a positive and beneficial role.

[0075] (1) Over-excavation and under-excavation values

[0076] 1) Use a three-arm rock drilling rig to drill holes and excavate, and use a rock drilling hammer to deal with under-excavation.

[0077] 2) Use large machines to excavate the invert to the maximum extent, and use large machine mobile air compressors and pneumatic drills to assist in handling under-excavated areas.

[0078] The invert excavation on site uses a large machine to drill holes, strictly control the spacing of holes around the invert, and reduce the over-excavation and under-excavation values. During the construction process, the blastholes of the invert are arranged by measuring and setting out, and blasting is carried out. After the blasting construction is completed, the excavator + slag truck is used to remove the slag, and the over-excavated part of the tunnel is backfilled with the same grade of shotcrete. The under-excavated position is manually + the invert steel brush machine is used to brush and clean, and the blasting method is no longer used. After the excavation is completed, it is ensured that there is no water accumulation and empty slag at the bottom of the tunnel, and the curvature meets the design outline requirements.

[0079] (2) Flatness of initial support of invert

[0080] Before construction, the invert section should be checked immediately after excavation. The small amount of under-excavation should be handled mainly by excavators and blasting hammers to ensure the thickness of the invert. The excavation of the tunnel invert should be smooth. A 3D scanner or fully automatic Leica total station should be used on site to detect the initial support surface of the invert, analyze its limit intrusion, and use manual methods to deal with the limit intrusion position, and remove the debris at the bottom of the side wall.

[0081] (3) Ensure construction step distance

[0082] According to the requirements for safe step distance for construction in the document "Notice of Beijing-Kunming-Xi'an-Kunming Railway Engineering

[2023] No. 37" issued by Beijing-Kunming High-speed Railway Xikun Company on the issuance of the "Regulations on Safe Step Distance for Construction of Xi'an-Kunming High-speed Railway Tunnel": for inverts with IV and V grade surrounding rock, the distance between the secondary lining of the invert and the face is no more than 100m; for inverts with IV and V grade surrounding rock, the distance between the initial support closure position and the face is no more than 60m when the invert has a steel frame. Under the post-invert working condition, the safe step distance is effectively controlled through the overall excavation operation of the invert partial closure, reducing the disturbance to the side wall support system of the large-section tunnel, and effectively avoiding the safety risks of the operation from the invert to the face.

[0083] 6.Benefit analysis

[0084] The back-placement method of excavation solves the problem of construction difficulties in limited space, making the tunnel back arch excavation and support and the face construction independent of each other and carried out in different areas. The back arch excavation and support are always carried out in a continuous flow with the back arch and filling. The 36m long hydraulic trestle is used to form three blocks for the back arch excavation, back arch reinforcement and filling concrete, and the continuous flow operation is carried out simultaneously. It shortens the construction time, reduces the construction risk and difficulty, is more economical, and makes management more efficient; it provides a reliable basis for decision-making, and reflects good social, technical and environmental benefits.

[0085] Manual excavation is adopted, with an average monthly advance of 110m, 18 people working in each cycle, and a daily wage of 310 yuan / day. The labor cost is: 18*310*30=167,400 yuan.

[0086] Using large excavation machines, the average monthly footage is 120m, and there are 4 people working in each cycle. The labor cost is composed of: basic salary 10,000 yuan + 80 yuan / day subsidy + 80 yuan / daily footage, then the labor cost is: 4*(10,000+80*30+80*120)=132,000 yuan

[0087] Manual excavation of 2000m, 2000 / 110*30=545.5 days

[0088] Using large machine to excavate 2000m, 2000 / 120*30=500 days

[0089] The time saved is: 545.5-500=45.5 days

[0090] In summary, excavating 2000m can save costs: (167400-132000)*(545.5-500)=1.6107 million yuan; and save construction time: 545.5-500=45.5 days.

Claims

1. A mechanized rapid construction method for a tunnel invert, characterized in that: The following steps are involved: The first step is to excavate the tunnel face; the second step is to support the tunnel face; The third step is arch excavation. The end arch is excavated and cleaned by excavators. Then the arch contour is manually measured and set. According to the measured conditions, a three-arm rock drilling rig is used to drill holes. Some parts that are difficult to reach by large machines are manually coordinated. The manual drilling machine uses the large machine's mobile air compressor to supply air, and then blasting is performed to remove slag. The fourth step is to use a 3D scanner to scan the contour of the invert after the excavation is completed, and mechanical chiseling is used to remove the under-excavated areas to ensure the arc effect of the invert contour; The fifth step is to support the inverted arch, spray concrete at the bottom of the inverted arch, and seal the inverted arch in time. The strength of the sealed concrete reaches 80% of the design. The sixth step is to repeat the third to fifth steps three times to complete the construction of four cycles. Step 7: Move the hydraulic trestle, and place the front legs on the initial support surface of the invert. After the trestle is in place, use two work areas to simultaneously construct the invert reinforcement and invert filling. In the same time period, the invert excavation, invert reinforcement binding, invert concrete pouring and face construction form independent work areas that do not interfere with each other, becoming a complete set of flow operations.

2. The mechanized rapid construction method for a tunnel invert according to claim 1, characterized in that: In the third step, the design parameters of drilling and blasting in the rear area of ​​the invert before the invert excavation include the number of blastholes and the total amount of explosives per cycle; The calculation formula for the number of blastholes is: N = qS / ηγ Where: N-number of blast holes, q-unit explosive consumption (kg / m³), S-excavation cross-sectional area (㎡), η-Charge coefficient, i.e. the ratio of charge length to borehole length, γ-mass of explosive per meter of cartridge (kg / m); The total explosive consumption per cycle is calculated as: Q = qV Where: Q-total explosive consumption q-unit explosive consumption (kg / m³), V—Total volume of blasted rock during one excavation cycle (m³).

3. The mechanized rapid construction method for a tunnel invert according to claim 1, characterized in that: In the third step, the end invert is excavated mechanically to facilitate the measurement work and the three-arm drilling rig to drill holes to enter the work area; during the full-section or step method excavation of the face, the downward inclination angle is taken into consideration when setting the bottom plate holes, and the invert can be blasted and excavated to a depth of 0.8m at the same time. After considering the inclination angle through the face bottom plate holes, the rear invert is under-excavated, leaving only the remaining part of the tunnel bottom. The PC220 excavator is used to directly excavate the area with a smaller under-excavation to the designed contour, and the artificial drilling of blastholes is used to supplement the blasting and clear the slag in the area with a larger under-excavation until the design contour line of the invert is cleared.

4. The mechanized rapid construction method for a tunnel invert post-installation according to claim 1, characterized in that: The excavation and support are 3m in each cycle, and after 4 cycles of excavation, a closed area of ​​the initial support of the whole slab with a length of 12m is formed.

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