@techreport{oai:kanazawa-u.repo.nii.ac.jp:00061362,
 month = {Mar},
 note = {地盤に局所載荷を行なうと、荷重に伴う変形の進行が地盤内の局所的なせん断ひずみの卓越を促し、その結果、せん断帯が生成する。せん断帯が顕在化すると、不連続なすべり線が形成され、このすべり線の発達につれて地盤は耐荷力を失い崩壊に至る。従来、この様な問題は、変形問題と安定・破壊問題とに個別に取り扱われていた。すなわち、変形問題には弾性解析・弾塑性解析、安定・破壊問題には極限つりあい・すべり線解析(特性曲線法)・極限解析(上下界定理)などが用いられている。境界値問題として取り扱う場合、変形問題は楕円型、安定・破壊問題は双曲型(放物型)の方程式系に支配されている。しかし、実際の現象は個別に現われるものでなく、連続的・遷移的に変化する。
本研究は、支配方程式の特性の理論的変化と、特性が変化(移行)したときに現われる物理的現象(せん断帯の生成など)に注目して、この変形と安定・破壊の問題を統一的・連続的に首尾一貫したかたちで取り扱う糸口を与えるものである。すなわち、有限変形弾塑性理論に立脚し、せん断帯の生成メカニズムを追跡してゆくことによって、個々の土要素はひずみ硬化しているのだが、全体として地盤にすべり線が入り破壊してゆく現象を解析する。この間、支配方程式は、はじめ楕円型、そのうち双曲型、最後に放物型へと構造が自動的に変化する。地盤が破壊時にたどる種々のプロセスが数学的な構造変化として示される点に理論上の特色がある。従来、変形には楕円型、安定・破壊には双曲型の支配方程式を用いて、別々に解析せざるを得なかったものが、統一的・連続的に取り扱えるようになる。, In order to simulate the formation of localized shear bands, which is commonly observed during large deformation of soils, we first presented a systematic extension of the well known Cam-clay model developed for small strains to the model for finite strain/deformations and then incorporated a non-coaxial tern in the model. Finally, confining the deformation to undrained plane strain conditions, we examined the effects of the non-coaxial term on the shear bands formation. As a result: 1)The incorporation of the non-coaxial term has no effect on the instantaneous shear modulus for the normal stress difference and it makes the instantaneous shear modulus for the shear stress smaller. 2)The non-coaxial term makes easy of access to the elliptic/hyperbolic boundary. 3)The behavior of the simple shearing modulus, which is proposed here as a new measure to see the accessibility to shear bands formation, shows that, in the neighborhood of critical state, the non-coaxial models are. independently of the kinematic constraint, more inclined to instability by localization of deformation than the coaxial model.
Furthermore we investigated the formation of the shear bands by employing the finite element method with a non-coaxial Cam-clay model. This finite element method for finite strains is formulated as a soil/water coupling form based on the updated Lagrangean scheme. A demonstration of shear bands formation is given in a classical rigid punch problem without introducing any initial imperfections into the material elements. We can offer the following remarks as conclusions: 1)Assuming Darcy's law for the notion of pore fluid, we summarized the governing equations for the coupling problem based on the finite strain theory. 2)We derived the finite element formation by discretizing the governing equations based on the updated Lagrangean scheme. The program created here is called SHEBLA. 3)Without introducing any imperfections into the material elements. we demonstrated the formation of shear bands in the ground for the punch problem as the deformation of finite element meshes and also as the localized strain distribution. 4)Observing the process for the formation of shear bands, we found that the shear bands occur for the first time just arround the edge of the loading plate and extend towards the symmetric axis. The stress state of the elements which form the shear bands reaches the hyperbolic region and then finally the parabolic region. The element in which a shear band occurs first, however, does not necessarily pass the E/H boundary first. 5)Observing the effective stress path, we discovered that both the element in the wedge surrounded by the shear bands and the element just beneath the loading plate experience unloading once during the extension of the shear bands. 6)And finally. we found that the distribution of footing stress at bach step is similar to the empirical results for cohesive soils., 研究課題/領域番号:63302045, 研究期間(年度):1988 – 1989, 出典：研究課題「非共軸有限ひずみ論による地盤のすべり機構の解明」課題番号63302045
（KAKEN：科学研究費助成事業データベース（国立情報学研究所）） 
（https://kaken.nii.ac.jp/ja/report/KAKENHI-PROJECT-63302045/633020451989kenkyu_seika_hokoku_gaiyo/）を加工して作成, 金沢大学工学部},
 title = {非共軸有限ひずみ論による地盤のすべり機構の解明},
 year = {1993}
}