The asymmetric settlement of ground surface caused by the excavation of tunnel in the subway is a key problem in engineering.The settlement trough of saturated loess tunnel with double lines

was monitored by the water level.The surface settlement of the top of right and left tunnels with 30 meter distance between two excavation surfaces changing with time and the characteristics of settlement troughs of single tunnel and double tunnels were analyzed with the monitoring results.It is shown that the settlement can be divided into four stages

including the initial settlement stage

the right tunnel excavation inducing settlement stage

the left tunnel excavation inducing settlement stage and the settlement going to stable stage

and the settlement trough can be described by the Gauss’s distribution curve.Based on the Peck formula of settlement trough and the relationship between settlement trough and burying depth proposed by O’Reilly and New

the width of settlement trough

the maximum settlement of single tunnel and double tunnels

the ratio of settlement trough and maximum settlement of right and left single tunnel was obtained by analyzing the monitoring data.Considering the consolidation deformation of saturated loess

settlement caused by the strata becoming flexible in the stress releasing process of excavation and wall rock of new tunnel disturbed by the excavation of former single tunnel

a calculation model of settlement trough of saturated loess tunnel with double lines was proposed by the addition of settlement trough of two tunnels.