3-D Elasto-plastic Numerical Simulation of Evolving Regularity of Structural Internal Force of Overlapped Tunnels

To investigate the evolving regularity of structural internal force governed by tunneling of overlapped tunnels,3-D elastic-plastic numerical simulations were conducted on two overlapped tunnels in Laojie-Dajuyuan section of the Shenzhen metro.Two construction schemes,i.e.,up-to-down or down-to-up tunneling procedures,were taken into account.The research result shows that the circumferential internal force of the constructed tunnel deflects when an overlapped tunnel to be constructed is driven,and the longitudinal internal force appears.Evolution in the longitudinal internal force has a fluctuant,local and temporary characteristic with the driving of the subsequent tunnel.The longitudinal effect is confined within three times tunnel diameter in class Ⅲ surrounding rock and five times tunnel diameter in class Ⅴ surrounding rock.