Due to the partial compression during the jacking process, the ends of jacking pipes are easy to go deformed laterally and become damaged. So the bearing capacity of the ends of jacking pipe should be reinforced. U shape hooping and more latitudinal reinforce wires should be used at the 200mm-300mm ends of the pipes.
The out layer of latitudinal wire should be the priority when doing the reinforcement. After the reinforcement, the span of the latitudinal wires should be 1/3-2/3 of ones on the pipe body. The reinforced u shaped hooping should be equal with the longitudinal wires of the pipe.
You may wonder how we decide the span of latitudinal wires and the length, there are five factors may help you to figure it out:
1.Jacking distance 2.geological conditions of the project 3.drivage (machinery or manually) 4.expirence and skills of the operator 5. straight jacking or curved jacking. The reinforcement should be stronger when factors above are unfavorable.
During the jacking process, the pipes forced stress not only from Poisson’s effect but from the superposition of the deviation as well. Like the picture below: the end faces of the pipe is transmitting the pressure point to point instead of end to end, so the ends of the jacking pipes are very easy to collapse and break.
The end reinforcement in long distance jacommentpe project like the diagram below, the inner and outside wall is covered by the steel ring, the thickness of steel should be 4-8mm, and length from 120-200mm.
Different reinforcement for different joints of jacking pipes:
Leave a comments if I was wrong in this article. Thanks.