Ryosuke Kitamura

Mechanical ^|^amp; Numerical Model for Deformation Behavior of Unsaturated Soil

The mechanical & numerical model for deformation behavior of unsaturated soil is proposed, where the probability theory and statistics are applied to estimate the mechanical behavior at the contact points in unsaturated soil. Adding the consideration on the change in contact angle, i.e., probabilistic motion of soil particles, the energy surface which has been a key physical factor is found not to be needed in the revised model. The numerical experiments are carried out to compare the stress~strain relations with those obtained from the triaxial compression tests on unsaturated sandy soil under drained condition. It is found that the revised new model can express the deformation behavior of unsaturated soil and is promising.

STUDY ON BEHAVIOR OF TUNNEL WITH EXTREMELY LARGE SECTION BY ORIGINAL NONLINEAR CONSTITUTIVE MODEL

Shirasu, which is defined as the non-welded part of pyroclastic flow deposits, is widely distributed in the southern part of Kyushu Island. Shirasu is regarded as soft ground when the mountain tunneling method is applied because its unconfined compression strength is about 50 kN/m2. Nevertheless, it is well known that Shirasu tunnels are comparatively stable. In order to make this mechanism clean, the authors have already proposed a numerical analysis method considering geotechnical nonlinear properties of Shirasu ground. In this paper, they adopted this method to a tunnel with an extremely large section in Shirasu ground and confirmed the validity of this method by comparing the numerical results with those obtained from the field measurement. Further, they analyzed the peculiar behavior of the tunnel with the extremely large section.

A NEW AND SIMPLE IN-SITU TENSILE TEST ON ROCK IN BORE HORE

岩盤の強度パラメータは, ボーリングコアを用いて一軸圧縮強さ試験や超音波速度測定を実施したり, ボーリングコアの状態から岩級区分を行い, 既往資料を参考に設定されるケースが多い. しかし, ボーリングコアを用いた室内試験では, 亀裂等の少ない良質なコアを用いることが多く, 原位置岩盤の強度パラメータを室内試験結果のみで判断することは困難であること, 岩級区分からの強度パラメータ推定では個人誤差が入ることに問題がある. また原位置せん断試験を実施するには, 多額の経費と時間が必要となり, 試験数に自ずと制約が生じる. 本論文では, このような問題点をクリアするため, ボーリング孔内で容易に, 連続的・経済的に実施できる原位置岩盤の引張り強度試験を提案する.