The tunnel lining construction scheme of the inverting arch and the filling first in the lining is 2 to 3 holes wide from the excavation working face. Invert the arch first, then construct the side wall and arch ring to facilitate the overall force of the lining structure, and to open early, anti-collapse. At the same time, it can ensure the smooth flow of the road inside the cave, and it is very beneficial to do a good job in the drainage of the cave and do a good job in civilized construction. The application of the inverted arch will inevitably affect the operation of the vehicle. This adopts a simple anti-interference platform as a transitional passage to ensure the normal construction of the face. The fill uses a fixed length template. In the section where the section size is unchanged, the secondary lining of the side wall and the arch ring is constructed once by the integral steel mold lining trolley.
If the dimensions of the lining section change, a combined formwork is used. The combined formwork system consists of a steel arch, a longitudinal beam, a steel pipe inner support and a steel formwork. The steel arch is divided into two pieces by bolts to form a backing. When the section changes little, loosen the steel arch butt bolts, by adding or reducing the corresponding steel arches in the middle of the arches, and then tightening with bolts. Section change. The stringer is made of I16 I-beam and joined to the steel arch (I20) to enhance the integrity of the combined formwork. The steel formwork adopts CM03012 (width 300mm, length 1200mm, height 84mm), and the length of each lining is based on the construction plan of each section. Concentrated concrete mixing, concrete tanker transportation, pump pumping, and plug-in vibrator vibrating.
Tunnel lining construction technology
(1) Reinforcement production
A. Straightening and rust removal of steel bars:
The surface of the steel bar should be clean, and the surface oil stains, stains, scales, scales, etc. should be removed before use.
The steel bar is straight and there is no partial bending. The deviation of the center line of the steel bar cannot exceed 1% of its total length.
After the steel bar is straightened on the straightening machine, the surface damage shall not reduce the cross-sectional area of the steel bar by more than 5%.
B. The bending of the steel bars and the hooks at the ends shall comply with the design and specification requirements:
The end of all the round bars of the stretched surface shall be a semi-circular hook of 180°. The inner diameter of the hook shall not be less than 2.5d, and the straight end of the hook end shall be no less than 3d.
C. The minimum turning diameter of Class II steel bars when they are rotated by 90° according to the design requirements meets the following requirements:
When the diameter of the steel bar is less than 16 mm, the minimum turning diameter is 5 times the diameter of the steel bar.
When the diameter of the steel bar is larger than 16 mm, the minimum turning diameter is 7 times the diameter of the steel bar.
The bent steel bar is bent into a smooth curve with a radius of curvature not less than 10 times the diameter of the steel bar (light round bar) or 12 times (ribbed grade II bar). The stirrups made of round steel bars have hooks at the ends, and the length of the hooks meets the technical requirements.
The allowable deviation of the steel bars after processing shall not exceed the values specified in the specification.
The steel bar is responsible for the application according to the technical requirements. The specifications, model and length of the steel bar meet the design requirements. The technical supervisor and the quality inspection engineer are responsible for inspection and acceptance, and check and make records at any time.
The joints of the steel bars are flash butt welded, and when flash butt welding is not possible, mechanical connections are used. Cross-connection of steel bars, using contact spot welding, manual arc welding is not suitable. The joints of the welded steel bars shall be cleaned of the rust, paint, grease and the like in the welding range.
In order to ensure the quality of joints of flash butt welding, two cold bends and two tensile test pieces shall be tested according to the actual welding conditions before the welding or changing the type and diameter of the steel bars, according to the appearance quality of the joints of the test pieces. The welding parameters are verified by inspection and experiment. After the quality of the test welding and the welding parameters are selected, the welding can be carried out in batches. When there is doubt about the welding quality, the sampling will be carried out according to the actual situation.
All flash butt welded joints shall be visually inspected. There shall be no cracks or obvious burns on the surface of the steel bars. The joint bending angle shall not be greater than 4°, and the joint axis eccentricity shall not be greater than 0.1 times the diameter of the steel bars and shall not be greater than 2 mm.
For hot-rolled steel bars with a diameter of 10mm or more, when the joints are welded by lap or gang, they meet the requirements of the specification.
The electrode used for arc welding is used as specified in the design. When the design is not specified, it can be selected according to the specifications. In order to ensure the welding quality of the arc welding, before starting the welding (not before the shift) or each time changing the type, diameter, welding grade of the steel bar and changing the welder, especially in the unfavorable environment that may interfere with the welding operation, during the field welding Two tensile specimens are prepared in advance using the same material, the same welding operating conditions and parameters, and the test results are allowed to be officially welded when the tensile strength of the steel is greater than or equal to that of the steel.
The steel bars are tied with joints and meet the specifications. The steel joints are scattered. The following stress-reinforcing bars disposed in the “same section” shall have a cross-sectional area of the joint that does not exceed 50% of the total cross-sectional area of the stressed steel bar.
(2) Rebar installation
In order to ensure the thickness of the concrete protective layer and ensure the position of the steel bar is accurate, a concrete block with a strength not lower than the design strength is set between the steel bar and the formwork. The blocks are buried with iron wires and tied tightly with the steel bars, and are staggered and dispersed.
The installation position of the ribs, the spacing, the protective layer and the size and size of each part of the reinforcement are in accordance with the design drawings. The deviation shall not exceed the specifications.
The installed steel bars have sufficient rigidity and stability.
After the steel bar is tied, the technical supervisor shall carry out detailed inspection according to the design drawings and the standards of the construction specifications, and make inspection records. After the steel bar inspection is passed, the quality inspection engineer and the resident supervisor must check and confirm before proceeding to the next step.
(3) Formwork construction
A. After the completion of the invert arch excavation, the initial support construction of the invert arch is carried out in time. First spray and close, then hit the anchor rod, install the inverted arch steel frame, and then spray again to the design thickness to cover the steel frame. When there are conditions, after the initial spray sealing at the bottom, the vertical arch can be used for one vertical mold construction.
B. The side wall and arch lining adopts the integral formwork trolley. The secondary lining should be applied after the surrounding rock and initial support deformation are basically stable. When the deformation of the surrounding rock is large and the rheological characteristics are obvious, the initial support should be strengthened. It is also applied as an inverted arch and a secondary lining early. At the same time, the distance between the secondary lining and the face of the hand is in accordance with the requirements of the drawings or technical specifications. Under normal circumstances, it is not more than 200m, and the weak surrounding rock should be followed closely.
C. The surrounding rock and initial support deformation are basically stable and meet the following conditions:
The displacement rate of each test item is obviously converged, and the surrounding rock is basically stable;
The displacements that have been generated have reached 80% to 90% of the estimated total deformation;
The peripheral displacement rate is less than 0.1-0.2 mm/d, or the dome sinking speed is less than 0.07-0.15 mm/d.
(4) lining trolley manufacturing:
A. Formwork support The clearance under the truss door meets the requirements for large-scale equipment required for construction in front of the tunnel lining; the height of each platform of the truss should meet the construction requirements, which is conducive to workers’ construction work such as safety and tamping.
B. The overall template plate of the trolley consists of a panel, a supporting skeleton, an articulated joint, a working window, etc. When the lining section is large and the load is large, the supporting skeleton is made into a truss structure to meet the requirements of the strength and rigidity of the trolley. And try to reduce the number of plate joints.
C. In order to ensure the lining clearance, the outer diameter of the template should be appropriately expanded considering the amount of deformation. The thickness of the steel panel shall not be less than 8mm. Indirect seams of the plates shall be welded and polished.
D. The working window should be set at 2m, 4m, and the vault. The window size is 1250px×1250px, and it should be uniform.
E. The length of the tunnel lining trolley is 9m and 4.5m.
F. The hydraulic support and shrinkage system of the trolley formwork should be arranged reasonably to meet the needs of lining construction.
G. The lining trolley should meet the requirements of automatic walking and have a locking device to ensure accurate positioning.
(5) Prerequisites for concrete construction
A.The initial support of the secondary lining operation section and the waterproof board isolation layer and the circumferential permeable blind ditch have been qualified. The waterproof isolation layer of the hard rock section is at least 2 to 3 times longer than the second lining working surface. The dust on the surface of the waterproof layer should be removed and sprinkled with water.
B.The measurement work is meticulous and accurate, and the center line, elevation, section size and headroom size must meet the requirements of the specification.
C.According to the monitoring and measurement feedback information, the timing of the application of the secondary lining is scientifically determined.
D.The filling layer or the bottoming leveling layer on the inverting arch of the secondary lining operation section has been completed, and the groundwater has been properly routed; in order to facilitate the smooth collection of the foot part of the side mold of the trolley, when constructing the short side wall first, The elevation of the joint with the bottom of the side mould of the trolley and the distance from the centerline of the carriageway are in accordance with the calculated design value, and the allowable deviation is ±5mm; the construction joint has been processed according to the specifications, and the scum and accumulated water in the foundation part must be cleaned up.
E.The overall formwork lining trolley, transfer pump, transport vehicle, tamping machinery, etc. are in normal operation, and the equipment capacity meets the needs of tunnel second lining concrete construction.
F.The lighting, power supply, water supply and drainage systems of the secondary lining operation section meet the normal construction requirements of the lining; the ventilation environment is good.
(6) Construction process
A. All concealed works can only be concealed after the quality inspection and acceptance.
B. In order to ensure the quality of the lining project, the second lining construction of the general section of the tunnel (including the tunnel body, the open hole, and the widening section) must use the full-section formwork trolley and pumping operation.
C. The distance between the working surface of the second lining and the bottom working surface shall not be less than 100m, and the distance from the working surface of the short side wall shall not be less than 60m to ensure the normal construction progress of the second lining.
D. The secondary lining construction of the composite lining structure should be selected under the guidance of monitoring and measurement data.
(7) Construction process of short side wall
Steel stencils must be used for the exposed surfaces of the trench walls on both sides of the cast-in-place tunnel.
The elevation of the top surface of the short side wall is determined according to the bottom elevation of the side mould of the trolley; during construction, the joint reinforcement or vermiculite is pre-buried according to the specification, and the contact surface with the secondary concrete is chiseled, and the settlement joint is set at the change of the surrounding rock; The surface of the crucible is wetted with water before pouring to remove debris.
Note that the longitudinal permeable blind pipe and its connection pipe with the grit well are arranged according to the design, and the ring-shaped flexible permeable blind pipe and the waterproof plate joint are reserved, and the embedded parts and the reserved cavern are set.
(8) Trolley assembly and debugging
The lining trolley factory is manufactured and assembled on site. Thoroughly polish the surface of the stencil before lining to remove rust and oil and rust.
(9) Trolley adjustment
The positioning of the trolley template adopts the five-point positioning method, that is, the plane coordinate system is established with the center of the lining as the origin, and the console is controlled by controlling the center point of the top mold, the hinge point of the top mold and the side mold, and the foot point of the side mold. Bit. The curve tunnel should take into account the change of the length of the left and right side overlap caused by the difference between the inner and outer arcs, so that the arc is rounded and the seam is staggered. Pay special attention to the accuracy of the positioning of the trolley, and avoid the intrusion of the second lining concrete by the error or deviation of the elevation.
The trolley formwork and the concrete have proper overlap (≥250px, the curved section refers to the outside). After the position is opened, check whether the connection of each node of the trolley is firm, whether there is any displacement of the trolley, whether the template is warped or twisted. Whether the position is accurate and the lining is clean. In order to avoid the trolley floating when pouring the wall, it is necessary to add wooden supports or jacks on the top of the trolley. Also check if the working window is in good condition.
(10) Reserved caverns and fixed parts
Reinforced concrete lining section, reserved, embedded parts are fixed on the steel frame.
The non-ribbed lining section is drilled on the lining trolley formwork, and the reserved and embedded parts are fixed by bolts.
(11) Install the head plate and rubber water stop or water stop
Head plate mounting
The stop head template of the end of the trolley should ensure the thickness of the design lining and can be adjusted to suit its irregularity. The structure of the stop head should ensure the joint of the lining ring to ensure the quality of the joint and enhance its water stoppage. Features. A small observation window is left at the top to observe the condition of the covered concrete.
Water stop installation
The waterstop is standing at the lining settlement joint, construction joint or expansion joint. Generally, the medium-buried rubber waterstop is used, and the on-site segmentation installation is fixed on the head plate, and the joint can be hot-contacted or cold-connected according to the site conditions.
Water stop installation
The rubber water stop strip is set at the construction joint, and the water stop strip is installed in the groove reserved for the end surface of the crucible. The installation procedure is: cleaning the surface of the crucible – → coating the neoprene binder – → pasting the water stop strip – → Nail fixation – → infusion of new sputum.
(12) Concrete pouring
A. Review whether the trolley form and the center height meet the requirements, and whether the size in the warehouse meets the requirements;
B. Whether the positioning of the trolley and the stop die is secure;
C. Whether the waterstop and waterstop installation meet the design and specification requirements; the waterstop installation: due to the limited function of the waterstop and the service life, it is now generally changed to P201 waterstop;
D. Whether the template joint is tightly packed;
E. Whether the release agent is evenly applied;
F. Whether the cleaning of the basement is clean and whether the construction joint is treated;
G. Whether the position of the embedded part meets the requirements;
H. Whether the transfer pump joint is sealed and the mechanical operation is normal;
J. Is the distribution of the pipeline reasonable and the joints reliable.
The concrete pouring adopts the pumping and pouring process, and the mechanical vibration is compact:
A. Before the pumping, use the cement slurry mixed according to the design mix ratio or the concrete lubrication pipe prepared by halving the aggregate.
B. Layered from bottom to top, alternating left and right, and symmetrically perfused. The height, order and direction of each layer are determined according to factors such as mixing capacity, transportation distance, filling speed, temperature inside the cave and vibration. In order to prevent the displacement of the trolley caused by excessive pressure deviation on both sides during pouring, the height difference of the perfusion surface on both sides should be controlled within 1250px, and the casting speed should be controlled reasonably.
C. The end of the conveying pipe is connected with the hose to control the vertical distance between the nozzle and the casting surface. The surface of the waterproof plate should not be directly flowed to the pouring position. The vertical distance should be controlled within 1.5m to prevent segregation.
D. During the construction process, the pump should be continuously operated and pumped continuously for construction. It should avoid the “cold seam” caused by the stoppage. When the intermittent time exceeds the specification requirements, it should be treated according to the construction joint.
E. When pouring to 1250px under the working window, before the working window is closed, clean the residue and other materials in the vicinity of the window, apply the release agent, and close it to prevent the unevenness of the surface of the window. Leakage phenomenon.
F. The anti-arc part below the arch line of the tunnel lining is the difficult part of the pouring operation, and the effective performance, slump and tamping method are effectively controlled to reduce the bubble in the reverse arc and effectively improve the surface quality of the lining.
G. The top cover is connected to the conveying pipe by the top mold center top sealer, and the top cover is gradually pressed. When the observation hole on the stop plate has a slurry overflow, the mark is completed.
According to the construction specification, the strength achieved by the last plate capping test piece is used to control. When the external load is not tolerated, the strength of the concrete reaches 5 (2.5) MPa or the surface and edges of the concrete are not damaged when the mold is removed and the mold can be subjected to its own weight. The demoulding sequence is generally first removed, and the first is removed. First, remove the non-bearing part, and then remove the load-bearing part. The major and complicated formwork has a demoulding plan; when it is guaranteed that the lining is applied in advance and is subjected to surrounding rock pressure, it shall be carried out according to the specifications.
Before the mold is removed, the outer surface of the formwork is washed with water. After the mold is removed, the surface of the concrete is sprayed with high-pressure water to reduce the heat of hydration. The number of surface watering should be such that the concrete surface has sufficient wet state. The maintenance period is not less than 14 days.
(15) Defect processing
After the mold is removed, if defects are found, they shall not be repaired without authorization and may be disposed of after being approved by the supervision engineer.
Bubbles: After mixing with white cement and ordinary cement according to the ratio determined by the color contrast test of the lining surface, partially fill the smoothing.
Ring seam treatment: draw the line with a curved ruler, cut the slit of the cutting machine, the seam depth is about 50px, after partial trimming or grinding with the grinder, it is decorated with high-grade cement mortar and smoothed with a steel file. The construction seam is round and tidy.
Use sandpaper to wipe repeatedly for several times if the surface color is inconsistent.
The surrounding area of the reserved cavern should be cleaned first, then sprayed with water, and the mortar with high marking and uniform color should be used to smooth the calender.