A case study associated with shield-machine bored tunnels in sand is presented in this paper. Observations show that driving the first bored tunnel resulted in up to 10 mm of surface settlement, and the ground between two tunnels seems to have been affected to some extent by the construction of the second, adjacent tunnel. The accumulated maximum surface settlement increases by 12 mm. Back-analyses indicate that excavation of tunnels generates volume loss varying from 0.38 to 0.53%. This volume loss is comparatively smaller than those in cases with the same conditions which might be associated with ground treatment, or performance of the machine, as well as workmanship. Influences on surface settlement from chamber pressure, backfill grout pressure and volume, as well as balance of the volume of materials discharged and inserted into the tunnel were explored. The ground movement might be associated with the imbalance of volume of material discharged and inserted into the tunnel but further data is desired to support the finding.