1、 Method Statement for Pipe Jacking1. Construction of PitsThe jacking pit with a dimension of 6mx5 clear opening with depth of 250mm below invert level of the steel pipe.The floor will be leveled by 100mm thick concrete blinding fixing tow I beams(1.5mx15cm) in the center of the pit for fixing jackin
2、g frame.2. Installation of Jacking FrameAfter the construction of drive, the jacking rig will be lowered into the pit and adjust to the control line and level. The rig will be used on this contract consist of two number of hydraulic cylinders with a capacity of 150 ton each to give a total jacking f
3、orce of 300 tons. The rig will have guided rails, pushing plate and base plate to hydraulic power back with control unit. The hydraulic system will run through a diesel engine installed the top of the pit.The rig will installed to the correct line and level and check by the consultant in respect to
4、level and alignment.3. Thrust WallConstructing a concrete block behind the base plate of the rig to a dimension of 2x1.5x0.5m will be provided to take and distribute the jacking load.4. Pipe Jacking OperationA steel shield is used at the front of the pipe to accommodate the miner and to allow for st
5、eering of the pipe jack. The soil within the shield is manually excavated and loaded into a wheel skip for transport to the pit bottom. The miner does not dig outside the shield (both in front and radically) and the front, or cutting edge, of the shield is always kept buried in the face, so stabilit
6、y is maintained. The shield is thus used to trim the excavation to the size of the pipe thus minimizing the potential for settlement of the ground above the pipe jack.In the pit bottom, the skip is hoisted to the surface, emptied and returned to the used to loosen it prior to digging. The exact diam
7、eter of shield will be selected to suit the pushing pipes.As excavation continues, the shield is jacking forward using two hydraulic jacks thrusting from the back wall. When the shield is buried, the jacks are retracted and the first sleeve pipe lowered on to the rails. This in then pushed up to the
8、 shield and excavation can then continue.When the sleeve pipe is pushed home, the hydraulic jacks are retracted and the services (lighting& ventilation) disconnected. The next sleeve pipe is lowered on to the rails and the services reconnected and the cycle repeated until the shield is pushed into t
9、he receiving pit and the pipeline pushed into final position.5. Maintaining Line and LevelIn order to maintain the correct line and level, a graduated target plate is located within the shield. The site engineer notes the position of the visible sport on the target, this initial position is used as
10、reference value to locate the relative position of the shield at all times during the drive. At each push, the site engineer monitors the position reference value with the help of level instrument and theodalite, thus giving a shield position (high or low, right or left) relative to the design posit
11、ion. Based on this information, the operator manipulates a correct course.Extending or retracting a combination of steering rams causing the front of the shield to articulate in the required direction carries out the steering. As the pipe follows the shield, the correct line and level will be mainta
12、ined. At all times, the amount steering applied is kept to minimum.6. Fixing Carrier PipesAfter completion of the pipe jacking , we check the line and level for the steel pipe and we take the exact line and level for the carrier pipe with the help of survey instruments.A 3 steel angle bar fixed by w
13、elding in the correct bottom level of the carrier pipe, then 3mm thick flat bar half moon claps will fixed through wielding in the correct line after that we put neoprene rubber 3mm thick in the clamp to avoid the scratches of the carrier pipes.Then we start laying the carrier pipe one by one and fi
14、x the clamps through nuts and bolts. After fixing the nuts and bolts we make angle support in between the top of the clamp and top of the pipe. Then we fix the other pipe in the same manner. The same procedure will continues up to the requirement.7. GroutingUpon completion of pipe jacking we make 4
15、2 holes like ventilation in every meter, it helps the concrete fill the gap between the steel pipe and ground. Then we fixed six inch grouting pipe vertically one meter height in the top of the pipe both end jacking and receiving. One side will keep ventilation and the other side for connection and
16、the concrete pump.After that we lay the carrier pipe in the correct line and level then check with the consultant and make the test required from the consultant then we close the both end between steel and carrier pipe by m/s plate welding or masonry, the gap between steel sleeve and ground in the both end we close by cement.During grouting the grout will push through the down string end.Pumping process will continue till the grout reaches the up string end ventilation pipe. When the grout will overflow from the ventilation pipe, grouting process is completed.
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