EXAMINATION OF EXTENDED PLASTIC ZONE IN THE GROUND WITH THE DEFORMATION OF CYLINDRICAL CAVITY

摘要

Recently, in Japan, the development of underground utilization in urban area provides a lot of case studies on the excavation of cylindrical cavity (e.g. shield tunnel) in the shallow ground. Especially, in center of the cities, the situation of underground has become complicated, so as to excavate new cavities by neighboring construction. However, the present condition is not clear about the influence caused by such situation. It is important to understand the behavior for making clear about that influence. Therefore, the authors try to clarify a mechanism of the ground displacement around the cavity and the earth pressure changes by cavity deformation. It is mainly focused on two factors, namely, the overburden pressure and the extent of the plastic zone caused by the deformation of cavity section. The model tests and theoretical analysis are carried out with taking these factors into consideration. In this paper, it is mainly discussed that the extended plastic zone in the circumference ground with the contraction of cavity is expressed by the cavity expansion theory which introduced the effect of overburden pressure.