Urban tunneling in sand using pressurized face tunnel boring machines must apply pressures sufficient to avoid large ground losses, comply with surface settlement performance requirements and also avoid ground heave. While empirical methods are commonly used to set performance requirements, these do not adequately address root causes of volume loss at tunnel level. Controlling ground movement at the source has become the primary means of protecting infrastructure through specification of very small settlement or volume loss tolerances. Until the contributions of each ground loss source are quantitatively examined, field control will be dominated by subjective opinion, disparate methodologies and trial and error adjustments. While centrifugal modelling of tunnels in sand has been completed, the results are of limited practical use. This paper summarizes centrifuge and field data in the context of face and annular slurry or grout pressures at ultimate failure and pressure-ground displacement relationships for tunnels driven in sand.