EVALUATION OF HEAVING RESISTANCE FOR DEEP SHAFT USING NODULAR DIAPHRAGM WALL

Abstract

In recent years, an increasing number of plans in Japan have been proposed for large-scale
railway structures to be built deep underground. To construct a large-scale railway structure, it is necessary to
construct vertical shafts that serve as the starting and ending point for the shield machine during the
construction as well as the air vents once it goes into operation. In such situations, it is expected that there
will be an increase in the cases where the vertical shafts will be built to reach deep underground. If typical
diaphragm walls were used to construct these deep shafts, the embedment depth of the diaphragm walls
would have to be made substantially significant in order to control the heaving. Heaving as stated here is a
phenomenon in which pressurized water contained in the permeable layer below the impermeable layer close
to the bottom of the excavated ground breaks through the impermeable layer owing to the upward force of
the water pressure during the excavation process, which then causes the vertical shaft to lose its stability.
Using nodular diaphragm walls that have nodular part on the diaphragm walls of the deep shaft could be
relied upon for the purpose of supporting the embedment depth of the diaphragm walls. In this research, the
influence the nodular part resistivity was examined in resisting heaving when nodular diaphragm walls are
used for the deep shaft. The experiments at gravitational and centrifuge acceleration fields were conducted,
and their effectiveness were confirmed.