Thanks, yes, he's clearer in the technical section, p.28. (I hadn't read the whole thing.) 4.2.3. Pylons and Tunnels The tube will be supported by pillars

Thanks, yes, he's clearer in the technical section, p.28. (I hadn't read the whole thing.) 4.2.3. Pylons and Tunnels The tube will be supported by pillars which constrain the tube in the vertical direction but allow longitudinal slip for thermal expansion as well as dampened lateral slip to reduce the risk posed by earthquakes. The "longitudinal slip" is what I assumed/guessed with "rollers or similar" (in my comment above).