Three-Dimensional Study of Natm Tunneling Near Deep Foundations

Abstract

As the population grew, cities expanded rapidly, requiring Super structures for residents to live in, as well as heavy structures such as bridges for faster population access to various locations. Also in big cities, tunnels are needed for various purposes, such as moving facilities, car lanes and subway tunnels, which is one of the concerns of engineers. On the other hand, most of these tunnels are built in cities in the vicinity of heavy structures that deliberately have deep and semi-deep foundations. Tunnel excavation has caused long-term and short-term displacements at the ground surface, which is more pronounced in piles adjacent to the tunnel excavation site. In such a way that the displacements formed in the ground are transferred to the piles and cause axial force in the piles. All these studies on the effects of drilling on adjacent structures and piles are very important in terms of drilling safety factor. Accordingly, in the present study, a three-dimensional analysis has been performed using ABAQUS finite element software. The effects of tunnel drilling with different diameters and locations on the deep foundation in the bridge near the drilling site have been investigated. The results showed that tunnel location, if improperly selected, has destructive effects on pile tip settlements, axial force changes of piles and tunnel surface settlements. Similarly, as the diameter of the tunnel increases, the number of piles in the pile increases sharply when the tunnel is located just below the tunnel site. Also, as the diameter of the tunnel increases, the number of piles in the pile group increases by about 29% when the tunnel is located just below the pile group. When the construction site of the tunnel is located between the group of piles and at a greater depth than the tip of the piles, the amount of settlements changes to a critical state and with increasing the diameter of the tunnel, the rate of subsidence of the pile tip increases by 48.9% and the amount of subsidence Increases by 54%.

Keywords

• soil and structure of interaction
• pile group
• numerical modeling
• surface settlement
• tip pile settlement