Influence of time-dependent deformation of geo-materials n the convergence characteristic during tunneling
Date Issued
2009
Date
2009
Author(s)
Chu, Huang-Kuei
Abstract
The controlling of convergence deformation is an important concept in modern tunneling technique, and the second lining well be installed when deformation of rock surrounding tunnel is under control as the NATM method. In Taiwan, numbers of tunnels in middle to old ages increase with time rapidly, which deteriorate after years of performance, but there are no ruptures during construction and few numbers of deformations on rock when tunneling. So it is important to know well about the factors affecting their long-term stability. In order to know well about tunnel structure systems in long-term stability characteristics, we must understand how time-dependent deformations occur during tunneling in first. Secondly, it is necessary to consider the influences by visco-elastio-plastic mechanics behavior of geo-materials. Time-dependent deformation behaviors usually appear when geo-materials are abide by stress which is larger than creep critical stress threshold. It is different between time-dependent deformation behaviors and elasto-plastic constitutive model which is been applied extensively in tunnel convergence mechanisms. Some models combine elasto-plastic constitutive law with time-dependent characters which are too many complex procedures for analysis and the parameters are too hard to obtain, so they are difficult to use in engineering application. This research aims to know well about tunnel time-dependent convergence deformations by using: (1) the influences of long-term factors and mechanics mechanisms during tunneling; (2) a non-linear visco-elasto-plastic constitutive model; (3) numerical simulations and monitoring measurements data for parameters by back-analysis; (4) time-dependent constitutive numerical model of different excavation forms and support systems and discuss stress around tunnel and convergence behaviors. Base on the original Burgers rheological model, the model in this research modifies the viscous parameter as a function relative to different stress states. After test and verify confidentially, the model can improved the defects that classic visco-elastic model cannot consider different stress states mechanics mechanisms. The numerical results show that the model can understand the phenomena at time-dependent deformation for geo-materials and underground structures during tunneling, and it also can be used for tunnel long-term stability research.
Subjects
tunnel convergence
time-dependent deformation
elasto-plastic deformation
visco-elasto-plastic constitutive model
long-term stability
Type
thesis
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