It seems that the subsidence is because the tunnel does not reproduce the expansion-contraction characteristics of the spoil it replaces. A possible modernizati

It seems that the subsidence is because the tunnel does not reproduce the expansion-contraction characteristics of the spoil it replaces. A possible modernization is massively-dense conditions sampling along the proposed tunnel route, not just in the volume the tunnel replaces, but around it as well, possibly all the way up to the surface. Conditions I can think of off-hand are temperature, ambient moisture/humidity, drainage volume, and groundwater baseline versus historical. Set up the sampling as many years in advance as possible to establish good reference data. Then create hydraulically moveable tunnel rings that push against a static ring, to re-create the desired movement. Use machine learning to refine the model during the pre-construction sampling period, and to refine results during operational period. The sampling of the surrounding volume feeds into the machine learning datastream so the hydraulic movements can be anticipated and performed very slowly over time.