A Numerical Modeling Study On EPB Shield Tunneling In Saturated And Unsaturated Soils

Many types of research have been carried out for a better understanding of the EPB-shield tunneling in various types of soils,focusing mainly on the effect of the tunneling process on the related tunnel components.The EPB-shield tunneling comparative numerical analysis in the saturated and unsaturated soils has not received adequate attention.It is important to understand the influence of EPB-shield tunneling on its components regarding the saturated and unsaturated soils that illustrated different results to maintain the integrity of tunnels.This thesis studies the effect of EPB-shield tunneling on its components in saturated and unsaturated soils,using explicit finite volume formulation software,Flac3 D.The important components(muck pressure on the tunnel face,shield conicity,annular gap grouting,and time-dependent setting of the grout and installation of segmental lining)of EPB-shield tunneling simulated by a 3D model in the saturated and unsaturated soils.The numerical simulation is used to model the shield and soil interaction,time-dependent tail void grouting,and the configuration of tunnel lining.Three types of linings are studied: continuous segmental lining without joints,segmental lining with non-rotated joints(3D joint configuration),and segmental lining with rotating joints.The comparison of numerical analysis results to highlight the main features of ground settlement and internal forces of the lining concerning the existence of water in the soil.The result showed that: 1)Changes in the water level had a significant impact on the distribution of axial force and its amount.In such a way that in the case where the soil is saturated,the distribution of axial force is almost uniform in the tunnel lining.2)Ground surface settlement during drilling in saturated soil,due to the reduction of effective soil stress,is less than the settlement in the unsaturated soil.3)Tunneling in saturated soil increases the ground pressure to the shield and the pressure is increasing in saturated increases around twice as much as excavating in unsaturated soil.4)The rotational joints strongly rely on compression;therefore,segment joints are the most critical part of the lining.In other words,regarding ground strength,the amount of bending moment in the saturated state is less than the unsaturated state.5)During the excavation in unsaturated soil,the grout hardening effect increases the flexural stiffness of the tunnel lining.6)Drilling in the saturated soil,most of the inflow to the tunnel is done from the tunnel face(constant permeability),and this flow and infiltration of water causes a decrease in the water pore pressure.Moving away from the tunnel face,the infiltration of water from the walls decreases,and then the water pore pressure increases.7)Increasing the water level in the soil increases the seepage from the face of the tunnel and thus increases the settlement in this section.