Following a tunnel excavation in low-permeability soil

it is commonly observed that the ground surface continues to settle with time

as the dissipation of the excess pore pressure leads to the consolidation settlements. For studying the consolidation settlement of soil caused by shield tunneling

an initial excess pore water pressure formula during the tunnel construction is presented based on Henkel pore water pressure theory; and it can be used to calculate the consolidation settlement by means of numerical analysis. This approach has been applied to the engineering case of the Shanghai metro tunnel-line 2; and the calculation results are obtained based on the soil geological condition. As shown in the analytical calculation

the maximum value of the initial excess pore water pressure is located at the spring-line of the tunnel. The calculation results of the consolidation settlements are in good agreement with the field data.