GROUND MOVEMENT AROUND SHALLOW TUNNELS IN SOFT CLAY

The prediction of ground movements caused by the construction of shallow tunnels in soft clay is discussed. The article is concerned with methods of predicting displacements (or squeeze) occurring under undrained conditions during tunnel excavation. Both finite element and centrifugal model studies of tunnel deformation behaviour in soft clay have been undertaken at Cambridge University under contract to the Transport and Road Research Laboratory. It is concluded that the combination of finite element analysis and centrifugal model testing suggests that for shallow tunnels, ground loss might be better related to load factor than stability ratio alone enabling surface settlements to be estimated. The studies of tunnel deformation behaviour carried out are said to have provided a useful analytical framework on which field data may be interpreted. (TRRL)