Yukihiro Kohata

Measurements of Elastic Properties of Geomaterials in Laboratory Compression Tests

Two types of axial loading devices having high and low capacities of axial load, respectively, for use in displacement-controlled compression tests on geomaterials (i.e., natural soils and rocks, and treated soils) in the laboratory are described. They were designed so that the loading direction can be reversed without any noticeable time lag under a highly constant axial strain rate while using a gear system. Results of representative triaxial and plane strain compression tests on a sand, a sedimentary soft rock, and a clay are presented. These results were obtained from very slow monotonic (or one-way) loading tests with several unload/reload cycles measuring axial strains locally along the lateral surfaces of a specimen continuously for a strain range from the order of 0.0001% (10−6) to that at failure. It is demonstrated that initial stiffness at strains less than about 0.001% (10−5) during primary loading is the same as stiffness during small unload/reload cycles applied immediately after the start of loading. Initial deformation properties are rather linear and elastic.

CALCULATION METHOD OF SUBGRADE ELASTIC MODULUS FOR ASPHALT PAVEMENT USING RESILIENT MODULUS

Elastic modulus of subgrade is an important input parameter in the multilayered elastic structural analysis of asphalt pavement, and the resilient modulus measurement of subgrade materials which assumed action of the vehicle load has been examined energetically after 1990s by laboratory testing. However, no design example using the resilient modulus is shown in the Japanese pavement design book because of the resilient modulus is a non-linear elastic modulus depending on a stress state, and structural analysis becomes complicated. In this study, by using the rearranged past data, arranging method of the resilient modulus was examined and furthermore a simple calculation method of the subgrade resilient modulus for the multilayered elasticity structural analysis was proposed. アスファルト舗装の多層弾性構造解析において，路床の弾性係数は重要な入力パラメータであり，1990年代以降には，室内実験によって輪荷重の作用を想定した路床材料のレジリエントモジュラスの測定が精力的に行われてきた．しかし，レジリエントモジュラスは応力状態に依存する非線形弾性係数であり，構造解析が複雑になるため，日本の舗装設計関連図書では設計事例が示されていないのが現状である．本研究では，既往のデータを再整理してレジリエントモジュラスの整理方法について検討するとともに，多層弾性構造解析において簡易にレジリエントモジュラスを用いる方法を提案した．