在冲绳岛中南部广泛分布着新生代第三纪泥岩。其基岩在未风化状态时是很好的地基,但是一开挖或者钻孔后,由于应力解除、吸水膨胀、干湿循环等作用,其强度就下降;还有开挖出来的土夹有较大粒径的碎块,所以在压实过程中造成施工管理上的问题;泥岩吸水后分解成细颗粒变成了粘土。由于上述种种原因,冲绳岛广泛分布的泥岩土至今未能充分用作填土或路基材料。但是,近年来随着建设工程规模扩大,从经济方面看,特别是冲绳南端延伸新规划的高速道路及填海造地,形势已发展到必须就地取土用作填 Cenozoic mudstone is widely distributed in central and southern Okinawa. The bedrock is a good foundation when unweathered, but its strength declines after excavation or drilling due to stress relieving, water swelling, wetting and drying cycles, etc .; and the soil excavated is sandwiched Larger particle size of the debris, so in the compaction process caused by construction management problems; mudstone after water into fine particles into clay. Due to the above reasons, mudstone so widely distributed in Okinawa has so far failed to be fully used as a fill or subgrade material. However, with the expansion of construction projects in recent years, from an economic point of view, especially the extension of the newly planned high-speed roads and land reclamation at the southern tip of Okinawa, the situation has been to develop a system that requires local use of earth for filling