A three-dimensional centrifuge model test was carried out to investigate tunnelling effects on pile group in expansive clay. A volume loss of 2% was controlled. During the test

ground settlement trough

additional settlement

additional bending moment and axial force of pile due to tunnelling were monitored. The results show that ground settlement troughs are affected obviously by the distance between the centre axis of pile group and tunnel face. The additional settlement of pile shows linear growth with the tunnel excavation from -0.75D to 1.25D; and it continues to settle even when the tunnel excavation reaches 1.25D away. The settlements of front piles and behind piles are different; and the pile cap tilts. Positive additional bending moment presents at the top of front pile while negative bending moment presents at the bottom. However

only positive additional bending moment occurs at the bottom for behind pile. Moreover

the maximum additional bending moment of the front pile occurs near the axis of tunnel; and it is much bigger than that of the behind pile. The additional axial force of the front pile increases with the tunnel construction and reaches maximum near the axis of tunnel. The additional axial force of the behind pile increases too; but it reaches maximum near the top of pile.