Abstract Considering the unloading stress due to excavation at the bottom and sides of a foundation pit and the shielding effect of the retaining structure at the bottom, a semi-analytical and semi-empirical method is proposed based on the Mindlin formula. A calculation formula for the displacement of an existing metro tunnel caused by excavation of an adjacent foundation pit is deduced, and effects of the foundation pit size, change of relative position to the tunnel and reinforcement measures on existing metro tunnel displacements are analyzed. Results show that the horizontal and vertical displacements of a tunnel increase with an increase of the tunnel overburden, and the displacement increases obviously with a decrease of the clear distance between the foundation pit and the tunnel. Increasing the excavation length of the foundation pit has little effect on tunnel displacement, while the excavation width and depth of the foundation pit have an obvious effect on tunnel displacement. Finally, the effect of reinforcement and control measures could be considered; and the maximum horizontal displacement of the tunnel decreases linearly with a decrease of the stress loss ratio of the retaining structure of the foundation pit, but the vertical dis? placement of the tunnel hardly changes.
Abstract：
Considering the unloading stress due to excavation at the bottom and sides of a foundation pit and the shielding effect of the retaining structure at the bottom, a semi-analytical and semi-empirical method is proposed based on the Mindlin formula. A calculation formula for the displacement of an existing metro tunnel caused by excavation of an adjacent foundation pit is deduced, and effects of the foundation pit size, change of relative position to the tunnel and reinforcement measures on existing metro tunnel displacements are analyzed. Results show that the horizontal and vertical displacements of a tunnel increase with an increase of the tunnel overburden, and the displacement increases obviously with a decrease of the clear distance between the foundation pit and the tunnel. Increasing the excavation length of the foundation pit has little effect on tunnel displacement, while the excavation width and depth of the foundation pit have an obvious effect on tunnel displacement. Finally, the effect of reinforcement and control measures could be considered; and the maximum horizontal displacement of the tunnel decreases linearly with a decrease of the stress loss ratio of the retaining structure of the foundation pit, but the vertical dis? placement of the tunnel hardly changes.
.On Calculation Formula of Existing Metro Tunnel Displacements Induced by Adjacent Foundation Pit Excavation[J] MODERN TUNNELLING TECHNOLOGY, 2018,V55(1): 124-132
2018, Vol. 55 