The section with grade IV surrounding rock is excavated by arc heading bench method
.
Good ventilation and adequate lighting
.
4、 NATM is adopted for excavation and support of tunnel body
.
Before construction, check whether the type, specification, quality and performance of anchor rod are consistent with the design
.
The pneumatic mixer is used to drive the anchor rod to rotate rapidly and advance slowly while rotating
.
The V-grade surrounding rock section is excavated by three-step seven step method
.
Bench method is adopted for excavation in grade III surrounding rock section
.
Two hours after the final setting of shotcrete, spray water for curing, and the curing time shall not be less than 7 days.
.
The sprayer should always keep the sprinkler head perpendicular to the surface to be sprayed and the distance should be 0.6-1.0 m, and control the concrete surface flatness
.
Strictly control the drilling size of gusset plate
.
8、 Steel frame fabrication and installation construction, steel frame processing according to different surrounding rock reserves, processing in the steel processing field
.
The charge should be carried out strictly according to the designed charge
.
The mixture is transported to the wet spraying machine by concrete transport tanker, and sprayed to the surface to be sprayed after adding liquid accelerator from the nozzle through the wet spraying machine
.
The air drill is used for drilling, and the hole spacing, depth and layout meet the requirements of design parameters, and its direction is perpendicular to the rock layer
.
When the spraying operation is completed or the spraying is interrupted for some reason, the accumulated materials in the spraying machine and the conveying pipe shall be removed
.
Wash the sprayed surface with high pressure air
.
Finally, the plastic mud is used to seal the surrounding of the pipe and the orifice, and the cracks on the working face are sealed at the same time
.
At the beginning of spraying operation, air is supplied first, then the machine is started, and then the material is fed
.
The grouting holes are arranged in quincunx shape on the pipe wall, the length of the grouting stop section at the tail is not less than 30cm, and the suitable external angle is 10-15 degrees
.
Before spraying operation, the mechanical equipment, wind, water pipes and electric lines shall be fully inspected and trial run
.
5、 Step method is adopted for construction of grade IV and V surrounding rock
.
For the key geological dangerous section mentioned in the drawing, the advanced horizontal drilling is adopted, the survey work is done carefully, and the settlement observation is analyzed
.
Construction process: upper bench excavation → primary shotcreting → arch combined hollow anchor rod → hanging net → re shotcreting → lower bench excavation → primary shotcreting → side wall radial anchor rod → re shotcreting
.
Shotcrete shall cover all lattice steel frames, and the thickness of protective layer shall be greater than or equal to 2cm
.
The steel frame shall be installed after the initial shotcreting according to the design requirements, and the thickness of the steel frame covered by shotcreting shall not be less than 4cm
.
In order to test the installation quality of the anchor rod, the pull-out test of the anchor rod is carried out according to the requirements, the installation tension is timed, and its action line is concentric with the anchor rod and fixed firmly
.
The nonelectric millisecond detonator is inserted into the cartridge and reversely inserted into the eyehole
.
When the machine is in normal operation, enough material is kept in the hopper, and the working air pressure of the machine is controlled at 0.45 ~ 0.7MPa
.
Before drilling, measure the top line and center line of the inner rail, draw the excavation outline, and mark the hole position according to the design (when the geological conditions change, adjust the hole position appropriately)
.
The spraying sequence is symmetrical from the bottom to the top, first spraying the gap between the steel frame and the surrounding rock, then spraying around the steel frame, and then spraying between the steel frames
.
Excavators and manpower are used to excavate soft surrounding rock
.
At the end, the material is stopped first, and then the air is stopped
.
6、 In the construction of mortar anchor rod, the anchor rod is made of Φ 22mm threaded steel bar
.
The grouting pressure should be controlled within 0.5-1.0mpa
.
Two wet shotcreting machines are used for shotcreting from the side walls on both sides at the same time, so as to speed up the construction progress, connect the grid steel frame and shotcrete as a whole in time, and play a supporting role
.
The upper and lower steps are drilled with rock drilling bench and manual hand-held yt-28 rock drill, smooth blasting and non electric millisecond detonator network initiation
.
The diameter of the hole is 50 mm, and the sand is blown out with a blowing pipe
.
The surrounding holes are charged with interval charge and connected with detonating cord, the cut hole is charged with concentrated charge, the bottom 30% length is charged with strengthened charge, and the other holes are charged with concentrated charge
.
3、 Construction technology and construction scheme: the whole section method is adopted for the tunnel with grade III surrounding rock, and the bench method is adopted for the tunnel with grade IV and V surrounding rock
.
The distance between the upper and lower steps shall not be greater than 1.5 times of the excavation width, and the settlement of arch shall be reserved for 5-10cm (appropriate adjustment shall be made according to the measurement)
.
Before charging, clean the mud and stone powder in the blast hole with high-pressure air, check the blast hole, and charge after confirming that it meets the design requirements
.
Step method is adopted for excavation of grade IV and V surrounding rock
.
The lead wire connection of nonel tube adopts “one grasp” type
.
After charging, all the holes were blocked up
.
The diameter of drilling hole is 42mm, the depth of upper bench cut hole and bottom hole is 1.4-1.6m, the depth of other holes is 1.3m, and the depth of lower bench hole is 3.1m
.
After the steel frame of each unit is processed according to the design, the trial assembly is organized to check whether the size and contour of the steel frame are qualified, and the structural test is carried out
.
Then use the pneumatic drill with impact to push the small pipe into the hole, or directly use the hammer to insert into the steel pipe
.
Open the hole with an air drill first
.
The drainage pipe is buried in the dripping part of the spray surface, the blind ditch can be set for the aquifer with poor water diversion effect, and the intercepting circle can be set for the dripping part
.
The spraying operation shall be carried out in pieces, and the spraying sequence shall be from bottom to top; the re spraying shall be carried out after the final setting of the previous layer of concrete
.
The shallow buried section of grade V surrounding rock is located at the entrance of the tunnel, with advanced geological prediction, short footage, weak blasting, early closure and frequent measurement to ensure the construction safety
.
9、 After the section of shotcrete construction tunnel is formed, shotcrete protection shall be carried out in time
.
Construction process: advance conduit support → upper bench excavation → primary spraying → installation of grid or steel frame → arch combined hollow anchor rod → hanging net → re spraying → excavation of lower bench → primary spraying → vertical side wall grid steel frame → side wall radial anchor rod → re spraying
.
7、 In advance small pipe construction, the small pipe is made of steel pipe, the front end is closed and made into a sharp shape, so as to smoothly insert into the drilled hole
.
According to the mix proportion of wet shotcrete provided by the central laboratory, the mixing shall be completed at one time in the mixing station, and the slump shall be checked to keep 5-8cm
.
Excavators and loaders are used to excavate and load the lower steps
.
1、 Before the construction, the weak surrounding rock site should be carefully investigated, the design intention should be deeply understood, and the feasible construction scheme should be prepared according to different geological conditions
.
After drilling, check and record according to the hole layout, and re drill the holes that do not meet the requirements
.
During construction, the left and right steps are staggered by three meters
.
The loading is uniform and slow, and the drawing is stopped when the designed tonnage is reached without destructive test
.
Construction process: advance conduit support → upper bench excavation → primary spraying → installation of grid or steel frame → arch combined hollow anchor → hanging net → re spraying → excavation steps → primary spraying → vertical side wall grid steel frame → hanging net → side wall radial anchor → re spraying → excavation lower bench → primary spraying → vertical side wall grid steel frame → hanging net → side wall radial anchor → re spraying
.
Anchor, mesh and shotcrete are used for primary support, inverted arch is advanced, arch wall is lined once, arch wall full ring grid steel frame and arch double-layer φ 42 small conduit are used for advanced support in seismic fortification lining section of active fault zone, lining trolley is used for lining in tunnel
.
The specific detection method is: assemble the steel frame into a ring on the worktable, use the oil roof and instrument on the outside, pressurize according to the design load, use the steel stress meter and convergence instrument to detect the internal force and deformation of the steel frame
.
Remove the pumice on the excavation face and the rock debris and accumulation at the corner
.
Prepare drilling tools according to the type, specification and surrounding rock condition of anchor rod
.
Millisecond and non electric millisecond detonators are used in blasting network
.
The initial shotcreting thickness is 3cm and the re shotcreting thickness is designed
.
Check the size of excavation section before spraying
.
Wet shotcreting is applied by wet shotcreting machine
.
During the construction, the advance geological prediction of the tunnel, the deepening blasthole detection, the infrared detection method, the advance geological confirmation, whether there are differences in the design
.
Deal with the rock surface, remove the obstacles, repair the under excavated part, and install the working platform if necessary
.
The signs for controlling the thickness of concrete shall be embedded
.
During the construction, the principles of “paying attention to geology, exceeding the front pipe, strict grouting, short footage, strong support, frequent measurement and early closure” should be strictly observed, and the relevant regulations of tunnel construction should be strictly implemented
.
