Abstract ▼ AI-Helper

The main risk factors for tunnel excavation through urban areas are ground subsidence and surface sink which caused by ground conditions, excavation method, groundwater condition, excavation length, and support method, etc. As for preliminary measures to prevent the damage caused by these risk facto...

The main risk factors for tunnel excavation through urban areas are ground subsidence and surface sink which caused by ground conditions, excavation method, groundwater condition, excavation length, and support method, etc. As for preliminary measures to prevent the damage caused by these risk factors, Underground Safety Impact Assessment is conducted for underground excavation works. In the process of Underground Safety Impact Assessment, the numerical analysis should be conducted considering not only displacement and stress due to tunnel excavation but also drawdown of groundwater level. However, performing lots of numerical analyses on representative sections for the whole project area, including route and underground facilities with various tunnel depth conditions, are taken too much times and efforts. Therefore a technique that can simplify such process and easily evaluate the influence of tunnel excavation is needed. In this study, parametric numerical analyses were performed considering such parameters as ground conditions, tunnel depth, and lateral distance from tunnel center line, etc. A simplified ground settlement evaluation chart was suggested by analyzing tendency of ground subsidence, lateral influence area and character by depth. Therefore, the evaluation chart can be easily applied to predict the ground settlement induced by tunnel excavation. The applicability of the suggested settlement evaluation chart was verified by comparative numerical analysis of settlement characteristics.
Using the settlement evaluation chart, it is possible to predict the surface subsidence and underground utilities subsidence by location and depth. In addition, the settlement evaluation chart can be applied to proper management of tunnel design and construction as well as to the selection of vulnerable sections with excessive settlements and differential settlement sections for the Underground Safety Impact Assessment.