Study of three-dimensional soil deformation caused by double-line parallel shield tunnel construction

Based on the two-dimension calculation approaches of soil deformation caused by ground loss in double-line parallel shield tunnel (DLPST) construction, the three-dimensional calculation approaches of soil deformation caused by DLPST are established. Altering equations of ground loss rate are established by choosing different longitudinal locations as variables. With consideration of the impact of the first shield construction on the second one's, the total soil deformation induced by DLPST is obtained by calculating soil settlement caused by both the first and the second shield tunnel construction. The proposed method is able to calculate the deep soil settlement and horizontal soil displacement, which can reflex the three-dimension soil deformation relatively precisely. The result indicates that the calculated value by the proposed method almost coincides with measured value. As the distance to excavation face x increases, the soil settlement volume tends to increase, and remains stable when x=-40 m approximately in the end. The maximum of total settlement volume increases as the excavation distance between the first and the second shield shortens. With the depth of z increasing, the soil settlement increases slightly, but the settlement slot width slightly reduces. The maximum settlement tends to decrease along with two article tunnel axis level distance L increasing, and the settlement curve shape will slowly change from V-shape into W-shape which is not conform to the normal distribution.