Cement-Mixed Soil for Trans-Tokyo Bay Highway and Railway Bridge Abutments

This report describes a number of experiences obtained from two projects. Firstly, among a number of significant geotechnical design and construction issues of the Trans-Tokyo Bay Highway project, large scale ground improvement by cement-mixing in place and construction of large offshore embankments using cement-mixed sand are described. The related strength and deformation characteristics of cement-mixed soil are summarised and compared with those of natural sedimentary soft rocks. A new method to determine the design strength of cement-mixed soil, adopted in this project, is described. Secondly, recent construction of a bridge abutment consisting of the backfill of geogrid-reinforced cement-mixed gravel and a thin RC facing structure supporting a bridge girder for a new bullet train is described. This structure is unique in that the backfill supports laterally the RC facing, rather than exerting static and dynamic earth pressure on the facing. Results from triaxial compression tests on cement-mixed gravel and dynamic loading model tests as well as field full-scale loading tests are reported.