In the previous paper, the author summarized results of geotechnical investigation for Ohnaruto Bridge foundation in planning and design stages. In this paper, results of engineering geological survey are described briefly during construction stage of Ohnaruto Bridge.
Inspection of excavated foundation rock was carried out on the basis of geotechnical rock classification by geologist. Some in-situ rock tests were also performed in order to confirm geomechnical parameters used for foundatlon design.
As multi-column foundation is selected for tower pier of Ohnaruto Bridge, a large diameter rotary drilling machine is adopted and it is shown that the drillability is fairly affected by such index properties as rock class and RQD. Field measurements of foundation rock behaviour during construction are planned for the purpose of construction control and improvements of geological investigation and stability analysis method. Main items of monitoring are vertical and horizontal displacements, and contact pressure of foundation rock. Some considerations are presented based on the preliminary measuring results.