An instrumentation observation has been performed during construction of a rubble mound on soft ground improved by the deep soil mixing method. To establish the design criteria for the rubble mound on improved ground, two kinds of analyses for tile soil deformation behavior and the slope stability arc performed on various cases for rubble mounds, soil grounds and backfills with application of the finite element method and the Bishop simplified method. The horizontal displacements and settlements at the crest of rubble mounds are analyzed as a function of the safety ['actor of embankments. The analytical result shows that the soil movement increases considerably when the safety factor of rubble mounds is lower than 1.3.
The deep soil mixing method has been applied to improve the geotechnica[engineering properties of soft alluvial and marine soils in Korea. Recently the deep soil mixing technique was used to stabilize soft seabed deposits during a port construction project in Pusan, Korea. For the shore protection works the deep soil deposits were improved by the deep soil mixing method and the rubble mound was constructed over the improved ground. Then a backfill was executed behind the rubble mound and a landing pier was constructed in front of the rubble mound. After construction of rubble mounds, seabed grounds may undergo deformations such as settlements and horizontal movement', due to the surcharge of embankments and backfills. Sometimes severe settlements and horizontal movements would induce lhilurcs of rubble mounds. To ensure the stability of rubble mounds and port structures during construction, such undesirable movements or 1hilures of both embankments and seabed grounds should be prevented by previous prediction during design (flamilton and flail, 1992). Design criteria or experiences, however, are insufficient lbr coastal development works.
