Deformation Stability Response of Adjacent Subway Tunnels considering Excavation and Support of Foundation Pit

Abstract

Since the safety and stability of the original tunnel structure are easily affected by the adjacent foundation pit excavation, it is strongly necessary to study the deformation evolution of tunnels during the adjacent foundation pit excavation. With regard to the two cases that tunnel is adjacently located at the right and bottom of foundation pit, the influence of different supporting methods, including pile support, bolt support, pile-bolt support, and shotcrete-bolt support, on the tunnel stability was investigated on the basis of the whole excavation process numerical simulation of deep foundation pit for determining the best foundation pit supporting beneficial to the stability of adjacent tunnel. The results indicate that both one-step excavation and multistep excavation have great influences on the displacement of adjacent tunnels, wherein the influences on the tunnel located at the right of foundation pit are greater than those at the bottom of foundation pit. Multistep excavation is recommended for the foundation pit adjacent to shallow tunnel. In the case of the tunnel located on the bottom of the foundation pit, the maximum stress generated around the tunnel is small, the maximum stress area is limited, and the displacement of tunnel monitoring points is also small. For the tunnel located at the right of the foundation pit, the pile-bolt supporting can effectively limit the displacement of soil between the tunnel and the foundation pit, reduce the maximum stress and the maximum stress distribution area, and effectively control the tunnel displacement.

Interactions of Foundation Pit on the Underlying Adjacent Existing Underground Structures

“…The cable element is used. There are 7 nodes and 6 construction elements that are numbered 1 ~6 due to the bolt length is 6 m. Component 1 is closest to the edge of the tunnel, and component 6 is farthest from the edge of the tunnel [7], as shown in Figure 3.…”

“…With the increase of exca-vation volume, the original lateral support of rock and soil disappears, so there are more possibilities for instability and damage of the foundation [5,6]. What is more, the lateral displacement also continues to increase [7,8]. At the same time, it leads to the uneven settling of nearby ground surface and the movement of stratum, which affects the stress changes of rock and soil of surrounding tunnel and deformation and seriously even causes the tunnel supporting structure undergoes cracking failure (Figure 1).…”

Review of Research Progresses and Application of Geothermal Disaster Prevention on Large-Buried Tunnels

“…Considering thermal behavior, Rankoth et al [76] proposed a detailed scheme for tunnel by simulation method, which is a powerful tool to execute relevant research in the field of geotechnical engineering [77][78][79]. Figure 1 is the completed model with the heat transfer boundary conditions of a half tunnel, and a detailed cross-section is presented in Figure 2.…”

Characteristics of Deformation and Stability of Ultra-Deep Pit in Plateau Alluvial–Lacustrine Gravel Strata

“…However, the above studies on the deformation of pits have used only one or two of the three above-mentioned methods (numerical simulations, lab-scale geophysical model tests, and field monitoring). In addition, previous studies have focused on deformations in pits surrounded by several buildings that are unimportant compared to the main body of the pit [25][26][27][28].…”