Study on Geotechnical Properties of Local Soils and Economical Land Reclamation

九州和冲绳当地土壤种类繁多，在开垦土地过程中出现了技术和环境问题。这项工程的目的是为了确保填筑和堤防的安全，并防止施工过程中的水土流失。研究结果总结如下：1。提出了一种新的有限元分析方法，对经典条分法进行了补充，并成功地应用于实际分析。水泥拌和稳定是改善珊瑚礁地区软弱钙质沉积物的可能用途之一。在细粒通过0.075 mm筛分的砂土中，水泥掺入对强度和变形性能的影响显著高于未细粒的砂粒。混凝土配合比设计中的空灰比规律可应用于人工胶结钙质砂土的强度评价。提出了加固软土地基的加固方法--加固箱基法。这种新工艺是一种通过在要建造结构的地面上重叠水泥柱来制作箱形垂直墙的方法。模型地基荷载试验结果与地基承载力理论值吻合较好。从冲绳珊瑚礁地区环境保护的角度来看，防止库尼格玛吉地区的红土流失是非常重要的。在复垦过程中，用化学稳定剂制成的膜覆盖地表是一种有效的控制开挖地表土壤流失的方法。

Various local soils exist in Kyusyu and Okinawa, and both technical and enviromental problems occur during the land reclamation. The purpose of this project is to make the fill and dike safety, and to preserve the soil erosion under the construction. The results are summarized as follws.1. In order to evaluate the stress and pore water pressure acting on the circular cylindrical failure surface of slope with respect to sliding, the new finite element method that complements the classical slice method was proposed, and applied for practical analysis successfuly.2. The cement stabilization through mixing was one of the possible use for improving weak calcareous sediments in coral reef areas. The effect of cement mixing on strength and deformation behavior was significant in sand with fine passing 0.075mm sieves than those with no fine. Void cement ratio law for design of concrete mix proportion could be applied to the evaluation of strength of artifically cemented calcareous sand deposits.3. A stabilized box foundation method for reinforcing soft ground was proposed. This new procedure was a method to make box-shaped vertical walls by overlapping cement colums in the ground on which structures were to be constructed. The loading test results of the model fondation on clay were found to agree well with the theoretical values of bearing capacity of the foundation.4. The prevention of reddish soil loss in Kunigami Maaji area is very important in the light of enviromental conservarion of the coral reef region in Okinawa. The surface covering with a membrain made from a chemical stabilizer was a useful method to control the soil loss in a cutting surface of ground during reclamation.