Placement of intermediate spaces

Under normal circumstances, the thrust from the main crown of the foundation pit, even at the maximum design value, is insufficient to push the pipe into the receiving well, and the placement of intermediate sections must be considered.

       The general practice for placing relay chambers is: to prevent sudden soil changes and other unforeseen circumstances, a relay chamber should be installed ahead of the pipe jacking machine, with ample room left. Specifically, a relay chamber must be placed when the actual thrust of the main jacking in the foundation pit reaches 50% of the design value. A relay chamber must be activated when the actual thrust reaches 60% of the design value.

       The placement timing for the intermediate stations is as follows: An intermediate station must be installed whenever the actual thrust of the foundation pit's main crown reaches 70% of the large design value. The intermediate station should be activated whenever the actual thrust reaches 80% of the large design value.