Ryukyu limestone formation is widely distributed over the Ryukyu Archipelago, and it is highly distrubed by the existence of faults resulting from the tectonic movements of the Ryukyu platelet. The faults in the Okinawa Island have generally the normal faulting characteristics. Recently a rock-cut project along the Urasoe fault zone having a NW-SE direction in the Urasoe City was undertaken and rock mass was highly fractured. The authors utilized an elastic wave tomography method to evaluate rock mass conditions besides the boring exploration. In this study, the outcomes of non-destructive elastic wave velocity tomography investigations and geological investigations are presented and they are used in the stability assessment of the rock cut.
Ryukyu limestone formation is widely distributed over the Ryukyu Archipelago. However, it is highly distrubed by the existence of faults resulting from the tectonic movements of the Ryukyu platelet bounded by Phillipine Sea plate in the east and Eurosian plate in the west. The faults in the Okinawa Island have generally the normal faulting characteristics. The authors involved with a rock-cut project along the Urasoe fault zone having a NW-SE direction in the Urasoe City. The rock cut was excavated as two benches, with an overall height ranging between 7-9 m. As the site was situated within the Urasoe Fault Zone, rock mass was highly fractured with a size of gravel and several joints were recognized. The geological condition revealed that a highly fractured rock exist between two Ryukyu limestone layers. The elastic wave tomography method was utilized to evaluate rock mass conditions besides the boring exploration. The rock mass classified as highly fractured rock mass, disturbed rock mass and undisturbed rock mass zone. The authors will report the outcomes of non-destructive elastic wave velocity tomography investigations and how it is used in the stability assessment of the rock cut in this paper.
