Numerical analysis of Static and Dynamic Response of Urban Tunnel Lining

Abstract

Tunnels are one of the high-cost engineering structures, subjected to unexpected problems during the process of the construction, due to the geological conditions, construction technology, structure elements, etc. Previous researchers have addressed two main categories in regard to earthquake. Firstly, tunnel structures have a safer response to earthquake than surface structures (this does not include the special cases of earthquakes that cause a damage to underground structures). Secondly, shallow tunnel suffers higher damage compared to deep tunnel. The present research study highlights the behavior of circular tunnel in different cases, excavated in rock mass under static and dynamic conditions. Numerical simulation using an engineering software program called MIDAS GTS NX (v. 2.1, 2015) is presented. According to the tunnels construction, several points have been considered in the design, including tunnel depth from the ground surface, tunnel dimensions, geological and geotechnical parameters which act on stresses and deformation response of static and dynamic conditions. The outcomes of this research will be helpful in the design and controlled the behaviour of tunnels and rock mass under impact loads, through understanding of the effects of static loads (self-weight, drilling pressure, jack thrust, shield external pressure and segment external pressure). In term to the dynamic forces, the Response Spectrum of UBC (1997) was used as a dynamic load, the dynamic interaction between tunnel structure and the surrounding rock mass was occurred, and response spectrum analysis has an influence on the soft rock due to the inertial force. A comparison of the results of static and dynamic analysis is performed, maximum evaluated values of total displacement and principal stresses, difference of soft rock categories, different tunnel diameters including (D = 4, 6, 8, 10, 12 and 14 m), different of elastic modulus of soft rock including (E = 10, 15, 20, 25, 30, 35 and 40 MPa), different tunnel depth from the ground surface, as well as important parameters influencing the tunnel–ground interaction for all cases, are evaluated. All models of a circle tunnel assumed an elastic tunnel lining. Isotropic, homogeneous and elastic rock mass was assumed for all models. The thickness of tunnel lining for all models was assumed as 30 cm Due to the application of the static load, the stress-strain state around the tunnel periphery is changed, the primary stress state is disrupted and the potential of instability increases, otherwise the result shows that the impact of dynamic stress as an earthquake is not negligible for underground structures.

Tunnels are one of the high-cost engineering structures, subjected to unexpected problems during the process of the construction, due to the geological conditions, construction technology, structure elements, etc. Previous researchers have addressed two main categories in regard to earthquake. Firstly, tunnel structures have a safer response to earthquake than surface structures (this does not include the special cases of earthquakes that cause a damage to underground structures). Secondly, shallow tunnel suffers higher damage compared to deep tunnel. The present research study highlights the behavior of circular tunnel in different cases, excavated in rock mass under static and dynamic conditions. Numerical simulation using an engineering software program called MIDAS GTS NX (v. 2.1, 2015) is presented. According to the tunnels construction, several points have been considered in the design, including tunnel depth from the ground surface, tunnel dimensions, geological and geotechnical parameters which act on stresses and deformation response of static and dynamic conditions. The outcomes of this research will be helpful in the design and controlled the behaviour of tunnels and rock mass under impact loads, through understanding of the effects of static loads (self-weight, drilling pressure, jack thrust, shield external pressure and segment external pressure). In term to the dynamic forces, the Response Spectrum of UBC (1997) was used as a dynamic load, the dynamic interaction between tunnel structure and the surrounding rock mass was occurred, and response spectrum analysis has an influence on the soft rock due to the inertial force. A comparison of the results of static and dynamic analysis is performed, maximum evaluated values of total displacement and principal stresses, difference of soft rock categories, different tunnel diameters including (D = 4, 6, 8, 10, 12 and 14 m), different of elastic modulus of soft rock including (E = 10, 15, 20, 25, 30, 35 and 40 MPa), different tunnel depth from the ground surface, as well as important parameters influencing the tunnel–ground interaction for all cases, are evaluated. All models of a circle tunnel assumed an elastic tunnel lining. Isotropic, homogeneous and elastic rock mass was assumed for all models. The thickness of tunnel lining for all models was assumed as 30 cm Due to the application of the static load, the stress-strain state around the tunnel periphery is changed, the primary stress state is disrupted and the potential of instability increases, otherwise the result shows that the impact of dynamic stress as an earthquake is not negligible for underground structures.