ABSTRACT
Oya tuff, which is categorized as soft rock, has been excavated in Oya area of Utsunomiya City, Tochigi Prefecture, Japan, for building stone and retaining walls for several decades. It is one of the most commonly used rock materials in Japan. As a result, there are many abandoned underground quarries existing in this area. After the 2011 East Japan Great Earthquake, the consideration of the seismic responses of underground quarries has become very important. Almost all of Oya underground quarries have been excavated using room and pillar method except some, which are long wall type. In the study, the quarry under investigation is an active room and pillar type and this paper presents the field measurement techniques used to study the seismic response of the quarry. Using the field data, underground dominant frequencies were obtained through analytical solutions. A numerical model was then developed using a Finite Difference method (FDM) program FLAC3D to assess the dynamic stability of the quarry.
