Study on calculation for shield tunneling-induced ground movements in clays

The extent of soil disturbance induced by shield tunneling construction is analyzed. It is considered that the assumed boundary condition of ground loss in Loganathan's formula exists error based on the principle of limit equilibrium. The influence of internal friction angle on ground movements is taken into account. It is considered that the level obliquity about boundary line of the vertical ground formation region should be (45 degrees +phi/2), but not 45 degrees. The modified Loganathan's formula is presented, which is only applicable under the undrained condition in clays. At the same time, the calculation for the extent of the cut disturbance of shield is advanced for the first time. As shown by analytical calculation for a project case, the proposed new approach tends to decrease the width of surface settlement troughs and horizontal ground displacements; and the results are more accordant with the field observations when compared with results of Loganathan's formula.