Definition - What does Thrust Ring mean?
A thrust ring is a steel ring that is placed at the end of the pipe cross-section to ensure that jacking forces are evenly distributed around the circumference of the pipe.
The jacks that transfer the forces to the thrust ring are hydraulically interconnected to ensure that the thrusting force being applied by each jack is equal in magnitude.
Trenchlesspedia explains Thrust Ring
During pipe jacking, the pipe string is driven from the launch shaft using a system of hydraulic jacks, which in turn push the tunneling machine forward. Once the jacks reach their final position, they are drawn back to make room for the next pipe segment.
The thrust ring, which is attached to the end of the jack head is necessary to mitigate stress concentrations due to uneven force distribution at the end of the pipe string. Without the thrust ring, high local stresses can form on the pipe cross-sectional area, which can lead to cracking or crushing of the pipe ends.