The surface settlement curves observed from several deep excavation sites are very similar to the ones measured from the shield tunnel sites. Therefore, this paper presents an experiential formula based on the surface settlement curves of shield tunnel excavation to predict the one during a deep excavation. Four cases studies were adopted to check the suitability of the formula to apply on predicting the settlement due to deep excavation. The predicting results indicate that not only the maximum settlement, differential settlement but also the angular distortion correlate the data obtained from the sites well.
The rapidly economical and industrial developments result in significantly increasing the population density and land cost in Taiwan. Especially in the metropolitan areas, such as Taipei and Kaohsiung, constructing high buildings solves the above-mentioned problems. High building requires deep foundation or deep excavation to stabilize the whole building. Hence, the architects and geotechnical engineers must face to the ground settlement problems during deep excavation, especially when the deep excavation is performed at a narrow home site surrounded by other buildings. The earth pressure support design or construction method in a deep excavation might fail and result in severe damage to the surrounding buildings. In addition, many deep excavations are now carried out in very poor subsoil conditions and are approaching to the existing building and infrastructure. The safety of adjacent structure thus must be concerned in designing. This study summarizes the published empirical formulas and methods to estimate ground settlements caused by deep excavation. The conventional formulas employed two straight lines to describe the ground settlement near a deep excavation. Thus, differential settlement and angular distortion are constant, which is different from in-situ status. To evaluate the behavior of ground settlement accurately, this study applies the normal distribution curve for ground subsidence of tunnel excavation proposed by Peck and Schmidt (1969) to the deep excavation.
