|
Abstract
|
Earth response to excavation an underground tunnel appears as changing stress field and displacements around excavation zone and the changes depend on various factors, such as geological conditions, geotechnical characteristics, the drilling process and the implementation of final and temporary maintenance. There also should be a separation between these items: 1) subsidence due to drilling methods in tunnelling, 2) conditions on the ground in terms of construction, 3) loads available for subsidence in cutting face and subsidence that occurs on the backside of cutting face. However, due to the progress on the construction of automated drilling machines, such as the tunnel boring machines (TBM) and Roadheader, paying attention to benefits of each of these devices is important to reduce occurrence of subsidence. Among all a device like TBM can change stress and displacement in the lands around the tunnel via simultaneously putting pressure on cutting face and walls of tunnels using filler injection, and this change should be so that amount of subsidence reach the minimum in short-term and long-term period comparing to the traditional methods of excavation of underground tunnels. In this research, calculation of land subsidence due to a tunnel passing under rail lines and investigation of influencing parameters on subsidence using theoretical relations and modelling by FLAC3D software are implemented. In order to have a real sample, one of the lifelines in Tehran subway was selected and influencing parameters including amount and place of dynamic forces caused by passing trains from the ground, underground tunnel boring method, and in the case of drilling with TBM, pressure changes on cutting face and tunnel walls simultaneous with digging the tunnel were considered. According to local observations and carried out analyses, subsidence of land in short-term using mapping camera readings in long-term using analytical relations and computer modelling is determined, so in
|