Based on Peck formula

the calculation approaching to study the three-dimension soil settlement caused by ground loss during double-line parallel shield tunnel (DLPST) construction is proposed. Considering the influence of first tunnel construction on second tunnel and different excavation face positions of two tunnels

modified three-dimensional Peck formula is established. It was used to calculate soil settlement caused by both the first and the second shield tunnel construction and combined the results

then the total soil settlement induced by DLPST is obtained. It is indicated that this method forecast value almost satisfied the measured value. With two tunnels excavation facing before and after distance of approximation

the maximum soil settlement volume will gradually increase. With the depth of z increasing

the settlement slightly increases and the settlement slot width slightly reduces. When the two tunnel axis level distance (L) is small

the soil settlement volume will be larger

and it is accord with normal distribution. The maximum soil settlement volume will gradually reduce and the settlement curve shape will slowly change by V type into W type as the increase of L.