Introduction to tunnel lining construction process


First, lining construction preparation

1. The tunnel lining trolley formwork and bracket have sufficient strength, rigidity and stability, the formwork trolley is finished, and the design requirements are met by the commissioned section size;

2. The initial support of the tunnel has been completed, and the surface flatness, clearance size, concrete strength, and bolt pull-out resistance have been accepted and accepted, and the initial support deformation is basically stable after construction;

3. The specifications and quality of various drainage and drainage materials such as circumferential drainage blind pipes, non-woven fabrics and waterproof boards meet the design and specification requirements, and the quantity meets the construction needs;

4. Professional construction personnel conduct pre-job operation technical training;

5. Mechanical equipment such as walkable work bench, automatic running heat welder and welding torch are in place, and the performance status meets the construction needs;

Second, the initial test

1. After the initial support settlement is stable, the initial support clearance is tested to ensure the thickness of the lining.

2. Carefully inspect the base surface of the shotcrete, and there must be no sharp protrusions such as pipe fittings protruding from the steel bar. If it exists, it should be cut off and smoothed with mortar.

3. The angle of the tunnel section or the corner of the corner should be smeared into an arc of not less than 5mm.
4. There should be no clear water on the base of the tunnel. If there is clear water, it should be blocked or led by the breeding measures.

Third, blind tube installation

1. The circumferential drain pipe adopts φ50 double-wall perforated corrugated pipe wrapped with non-woven fabric. Each ring of the lining of the plate is provided with a ring directly connected with the longitudinal bellows by three-way connection. The concentrated water outlet is encrypted according to the size of the water; An outer non-woven perforated corrugated pipe with a diameter of φ100 is arranged on the side, and the longitudinal corrugated pipe and the inverted arch ring are connected by a tee and directly introduced into the central drainage ditch.

2. When the longitudinal blind pipe is installed, the longitudinal slope must be consistent with the slope of the line, and it should be fixed once every 1m to ensure that the position of the blind pipe does not change when the concrete is poured. The slope meets the design requirements.

3. Technical points of blind pipe construction

(1) Longitudinal through-drain blind ditch installation shall be scribed according to the design regulations, so that the position of the blind pipe is accurate and reasonable, and avoiding excessive undulation.

(2) The distance between the drainage blind pipe and the support shall not exceed 5cm, and the blind pipe shall be fixed by wire mesh with a spacing of 100cm.

(3) Drilling the concentrated water outlet point along the water source direction, then inserting a single centralized water diversion blind pipe into it, and sealing the surrounding with a quick-setting mortar to concentrate the groundwater from the pipe;

(4) The blind pipe joint is wrapped with the water-permeable material of the non-woven fabric to prevent concrete or debris from entering the blocked pipe.

(5) The overhanging part of the blind pipe is fixed with steel bars to prevent the position of the blind pipe from changing when pouring concrete.

Fourth, non-woven fabrics and waterproof boards

1. The technical indicators and technical performance of raw materials must meet the design requirements.

2. The laying of the non-woven fabric is laid from the center line of the vault of the working trolley to both sides, and then the non-woven fabric is fixed on the sprayed concrete surface with a nail with a thermoplastic round gasket. The fixed distance of the arch is 0.5m~0.8m, and the side wall 0.8m~1.0m, arranged in a plum pattern.

3, the non-woven fabric should be laid tightly, so that it can be closely attached to the surface of the shotcrete to avoid over-tightening or tearing to form a water storage point. The width of the non-woven fabric overlap is not less than 10 cm, and the longitudinal blind tube is wrapped around the arch.

4. The waterproof board is laid from the center line of the vault of the work trolley to both sides, and the side seam is welded and fixed with a hot seam welding torch and a thermoplastic round washer.

5, the waterproof board should be laid tightly, so that it can fully engage with the non-woven fabric and adhere to the surface of the sprayed concrete to avoid over-tightening and tearing or loosening to form artificial water storage points.

6. The width of the two waterproof boards is not less than 15cm. The joints of the waterproof board are welded by automatic double-slot hot-melt welding machine. The width of each weld is not 2cm. An air passage is left between the two joints after welding for air. The detector detects the weld.

7. Construction control points

(1) Remove the dust on the surface of the waterproof board before welding.

(2) If the waterproof board is damaged, it should be repaired in time. First take a small waterproof board and cut it into rounded corners. The distance between the edge of the patch and the damaged edge should not be less than 7cm. After removing the dust on the two waterproof boards, place it on the damaged part and then weld it with a manual electric fuser.

(3) The joint of the waterproof board should be staggered with the waterproof weakening parts such as the settlement joint, the construction joint and the concentrated water outlet of the surrounding rock.

Fifth, the grouting pipe is buried

1. The grouting pipe and the exhaust pipe are all made of φ30mm PVC pipe. The pipe body is equipped with plum-shaped overflow hole, the hole diameter is 2-3mm, the longitudinal spacing is 20cm, and the fixed strip is made of 40cm×10cm rectangular waterproof board. The grouting pipe and the exhaust pipe fixing strip are welded and fixed to the vault, the distance between the two pipes is 3-5 cm, and the spacing of the fixing bars is ≤80 cm. The PVC pipe is lengthened by direct head connection, the total length is equal to the length of the lining plus 20cm (exposed), and the exposed end should have a connecting pipe device.

2. When the steel bar is tied, the concrete block around the grouting pipe must be encrypted to prevent the grouting pipe from being crushed and destroyed due to the deformation of the steel bar during the pouring process.

3. When the second lining arch top end template is blocked, a specially processed end template is used. The end template is cut at one side, and the grouting tube and the exhaust pipe are passed through the groove to prevent the end die from being damaged and grouted. tube.

Sixth, steel processing and installation

1. The performance of the steel raw materials shall be checked to ensure that the raw materials are qualified. At the same time, the processing and production process of the steel bars shall meet the design and specification requirements.

2, steel construction stakeout: the site with the total station, using five points to locate the position of the steel bar, that is: to establish a plane coordinate system with the center of the lining as the origin, by controlling the center point of the arch table template, the arch lining the trolley The template is the same as the two junction points of the side wall template and the foot points of the two wall templates to control the position of the steel bars.

3. First, the measuring personnel use the coordinate loft to determine the center point of the two steel bars in the range of the self-made trolley in the leveling layer and the vault waterproof board, determine the normal direction, and ensure the verticality of the positioning steel bar and the inverting arch. Reserve the accuracy of the reinforcement connection. The verticality of the steel bar binding is determined by the method of three-point hanging balls.

4. According to the measurement data, the positioning steel bar is arranged, the longitudinal ring spacing of the positioning ribs is 3m*3m, and the longitudinal positioning ribs are located on the side of the waterproof board. When the circumferential main rib is in place according to the specified spacing of the design, it is fixedly connected with the positioning steel bar. The longitudinal reinforcement is then tied as designed.

5. Before the lining inner layer steel bar is in place, it must be based on the measurement of the given midline, elevation, normal and other measurement data, accurately install the steel bar positioning and support steel bars (steel pipes), and evenly distribute the inner layer main ribs on the supporting steel bars (steel pipes). Then, the inner layer longitudinal ribs are evenly arranged at the design pitch and tied tightly.

6. After the main rib is tied, the stirrups are installed, and the stirrups should be tied tightly.

7. After the steel bar is tied, check the contour size according to the height of the center line. After passing the test, hang the 55mm thick ram block on the inner layer of steel (the lining block is prefabricated with the lining of the same level) to ensure the net protective layer of the steel after concrete filling. thickness.

8. Construction control points:

(1) When the steel bars are tied, it is strictly forbidden to damage the waterproof board. When the steel bars are welded, the waterproof board is covered with a fireproof board to prevent the burned waterproof board.

(2) The length of the weld joint of the steel bar should meet the requirements, the double-sided welding is 5d, and the single-sided welding is 10d (d is the diameter of the steel bar).

(3) The steel bar binding must be tied tightly, especially the stirrups, to avoid scattering during concrete pouring and vibrating.

(4) Pre-bending of steel bars needs to be carried out outside the hole, and the transportation of steel bars is carried out by mechanical transportation to ensure that the steel bars are not deformed after bending.

(5) The lining steel bars are arranged on the gantry, which is a high-altitude operation, and workers need to take safety protection measures.

Seventh, the template trolley is in place

1. The track is laid before the trolley is in place, and the sleepers are laid under the track. The distance between the sleepers is 50cm. The center line of the background car roof board coincides with the center line of the tunnel.

2. After the trolley is in position, the rail clamp is locked to fix the trolley on the rail, and then the vertical cylinder and the lateral cylinder are alternately activated to make the template stand at the design position.

3. The trolley is polished and brushed off the mold before adjusting the height.

4. The trolley passes the measurement and positioning. During the measurement, the elevation of the vault design and the distance from the two sides of the side wall to the center line are mainly detected. To meet the settlement requirements, the outer elevation of the vault template of the lining trolley is higher than the net elevation of the tunnel vault by 5 cm. The angle of the arch on both sides of the trolley is 5cm larger than the design outline. After the measurement of the clearance of the trolley reaches the requirements, the reinforcement is locked, the vertical and horizontal jacks are locked, and the reinforcement support is installed to ensure the stable positioning of the trolley.

5. Construction control points:

(1) The movement of the trolley is directed by a special person in the process to avoid collision between the trolley and the pipeline and equipment. At the same time, the person grasps the brake to prevent the trolley from slipping and rushing.

(2) During the reinforcement process of the trolley, carefully inspect each kilogram and cylinder to avoid running the die or the wrong platform due to the bias caused by the individual jacks.

Eighth, install the water stop

1. Buried waterstop installation

(1) Cut the length of 60cm Φ10 steel bar into a steel bar, and bend one end of the steel bar into a circular hook.

(2) A hole of Φ12 is drilled in the head plate at a distance of 50 cm along the contour line of the lining design.

(3) Insert the formed Φ10 steel bar from the side of the concrete to be molded to the other side, the inner test card is tightly closed to the water belt, and the other half of the water stop is flat on the stop plate and fixed by wire. .

(4) After the mold concrete is solidified, remove the stop head plate, straighten the water stop belt to the center steel bar, and then bend the Φ10 steel bar sleeve on the water stop belt.

(5) If the lining trolley is equipped with a flip-type steel-wood composite end die, the inverted rubber-stopped water-stopping belt is accurately positioned by flipping the hinge.

2. Externally attached waterstop installation

(1) According to the deformation joint and the mileage of the construction joint, use the total station to determine the exact position of the waterstop installation on the waterproof board and mark it;

(2) Wipe the waterproof board and the back-mounted water stop with a smooth surface;

(3) Bond the waterstop to the specified position with an adhesive.

3. Water stop installation

(1) Install a hard plastic strip with a width of half the width of the water stop strip on the concrete surface where the water stop strip is required, so that a concrete groove is formed after the concrete is poured, and the water stop strip is embedded in the reserved tank half in the next construction. Exposed half.

(2) After the first concrete pouring of the formwork is removed, the construction joint should be chiseled, and then the rafts on the joint surface should be removed with tweezers or wire brushes. After cleaning, keep it moist and brush the cement slurry 2~5mm thick. After the surface is dry, apply the adhesive on the bottom surface of the water-swellable water-stop strip and the water-stop strip. The adhesive should use the matching products. The liquid is volatilized for a period of time before being pasted.

(3) When the water-expansion water-stopping strip is extended, the joints shall be overlapped by means of overlapping methods, and the butt joints shall be dense and shall not be disengaged.

4. Construction control points

(1) The installation position of the waterstop must meet the design requirements.

(2) The water stop belt shall be connected at the site, and shall be vulcanized and cold bonded by hot pressing. The joint shall be smooth and smooth, and the tensile strength shall not be less than 90% of the base metal.

(3) When tying the steel bars and the formwork, the waterstop must be fixed firmly to avoid displacement when pouring the concrete.

(4) Due to the advancement of the inverting arch and the small side wall, the buried waterstop in the small side wall section should be 15cm higher than the longitudinal construction joint to be docked with the buried waterstop of the post-casting arch wall.

(5) If the water stop strip has a swelling phenomenon, it shall not be used.

Ninth, the end template installation

1. Lining at the contact part of the small side wall, the bottom mold of the lining trolley directly abuts the longitudinal construction joint of the small side wall.

2. The first set of tunnel lining construction requires two ends for sealing.

3. The front end of the lining trolley is generally connected with the lining of the previous rafter to form a closed end. The rear end of the lining trolley is open, and the construction personnel need to assemble the independent template to form the rear end. The closed end of the head.

4. When the end is closed, the longitudinally connected steel bars are reserved. The method of inserting steel bars between the plug plates is reserved, and the spacing and length of the inserted steel bars should meet the requirements of the specification.

Tenth, concrete pouring

1. The perfusion window is arranged symmetrically on the upper, middle and lower layers, with 4 windows on each side of each layer, and the layers are interlaced with the layers. The window size is 0.5*0.5m. Three vertical pumping interface pipes are arranged on the longitudinal section of the highest point of the arch of the trolley, which are arranged at the two ends and the middle part of the trolley.

2. The secondary lining is filled by the concentrated pumping material of the pump pump, and the chute is made of iron. The length of the chute can be adjusted to meet the needs of the concrete conveying windows of the upper, middle and lower concrete pouring windows. According to the distance between the center line of the line and the perfusion window, the length of the chute is determined and fixed by the secondary lining trolley. The chute must be firmly fixed and can support the impact of concrete gravity and concrete pouring.

3. The concrete pouring sequence is the secondary lining of the poured section from the bottom to the top in the direction of the face, and the left and right symmetry is poured window by window, vibrating by window.

4. According to the secondary lining structure, the vibration of the concrete is divided into two parts. The lower part is the part below 0.2m below the lower edge of the third layer window of the trolley, which is mainly the range of the inserted vibrator; the plug-in vibrator cannot be completely covered at both ends and corners of the trolley. Five attached vibrators are added to the side to assist in vibrating. The upper part of the arching line is the range of the attached vibrator, and the attached vibrator is installed on the symmetrical stencil of the secondary lining trolley, and is arranged on the upper, middle and lower layers.

5. In order to achieve the effect of the attached vibrator starting from the bottom to the top, it is necessary to centrally control the same layer attached vibrator.

6. When concrete is poured, the maximum falling height of concrete should not exceed 2m. The height difference between concrete before and after the trolley should not exceed 0.6m. The height difference of concrete pouring surface on the left and right sides should be controlled within 0.5m. It is strictly forbidden to cast more than 0.5m on one side. At the same time, the concrete pouring speed should be reasonably controlled. When pouring concrete, it should not directly rush to the surface of the waterproof board to the pouring position to prevent the concrete from being separated.

7. Construction control points:

(1) When the concrete is vibrated, the vibrating bar shall not touch the waterproof plate to prevent the waterproof plate from being damaged.

(2) The vibrator template has a certain amplitude. In order to avoid the offset of the trolley, the screw rods at both ends of the trolley are reinforced by diagonal bracing.

(3) Before the concrete is poured, carefully check whether the template trolley is in position. The inspection items include the space position and structural size of the trolley comply with the design requirements. The plug reinforcement is firmly locked in the running part, and the bottom support is firm and does not leak.

(4) In order to prevent the occurrence of cavities in the concrete pouring of the arch, the concrete slump should be controlled by 200mm. The slump should not be too large to avoid segregation or bleeding.

(5) When the concrete is poured to the working window 20cm, before the working window is closed, the concrete slurry residue and other dirt near the window should be cleaned, the release agent should be painted, and the sealing agent should be closed tightly to prevent the concrete surface from appearing on the window. Uneven patches and even slurry leakage.

Eleventh, concrete curing

1. After the lining concrete is demolished, the high-strength sprayer is used for timely maintenance to keep the concrete in a wet state.

2. The maintenance period meets the design and specification requirements.