Research on distribution of initial excess pore water pressure due to shield tunnelling

Excess pore water pressure is generated during shield tunnelling, resulting in consolidation settlement. Assuming the disturbance range shape of shield tunnelling is circular arc, the distribution range of excess pore water pressure is determined. The formula of initial excess pore water pressure of soil around tunnel lining is deduced by stress relief theory; and the formula of initial excess pore water pressure of soil within the region of its distribution at any point is subsequently deduced by stress transfer theory. By comparing calculated and measured data, it is shown that they are in good agreement. Based on practical example, a conclusion is drawn that the distribution shape of initial excess pore water pressure of soil around shield tunnel circle is roughly circular (top of small, bottom of large). With the increase of distance from shield tunnel central axis, the initial excess pore water pressure of soil shows a concave curve shape. At the same time, the isopleths at the bottom of shield tunnel changes fastest. Above the top of the tunnel, the initial excess pore water pressure of soil gets the maximum at the tunnel axis in different depths, showing a similar Peck shape.