Ground Improvement. Effect of Cement Stabilization on Prevention of Reddish Soil Flow-Out.

On the northern part of Okinawa Island, the subtropical lateritic soil, so-call “Kunigami Maaji Soils (Reddish Soils)” develops widely on the terraces and terrain. As those soils are the natural residual soil of older metamorphic rocks and the younger gravelly soil of diluvial deposits, the land reclamation and public works cause the soil erosion and flow-out into the sea due to rainfall and also natural environmental problems. The field observation and investigative study of the slope erosion have been carried out to control and prevent the flow-out of reddish soils. The present paper deals with the experimental results of soil stabilization using the cementing material in the laboratory and on the site. The representative reddish soils were sampled and tested for the stabilizing effect on each soil. Also the field experimental study of the artificial slope stabilization under natural weathering condition during one year had been executed. The test results show that soil stabilization with the cementing material is quite effective to protect the soil erosion and improve the stability, consequently to prevent the contamination of river and sea.