Minoru Matsuo

Reliability analysis of shallow foundations in reference to design codes development

Abstract In this study, FORM analysis is carried out for shallow foundation of a typical building in order to evaluate relative magnitude of uncertainties involved in the force and the resistance sides. The distinguished feature of this study is to take into account the uncertainty of the earthquake force as much as possible. Tthis is because, the seismic design dominates major part of structural design in Japan, and without referring to this problem, no useful information of practical value is gained. The results of the FORM analysis exhibited the reliability index values between 2.0 to 3.5, which is considered to be in a reasonable range. Since the 50 year maximum earthquake force is considered in the reliability calculation, calculated reliability index values are for the period of 50 years. The sensitivity factor obtained in a case more realistic ground variability is taken into account exhibited values not very different from those obtained in the upper structures.

Bayesian calibration of embankment safety under earthquake loading

Abstract This study provides a probabilistic procedure for the back-calculation of factors of safety of embankment slopes during seismic loading. The slope stability is analyzed by the conventional circular arc slip surface method in which the seismic load is introduced in terms of a horizontal body force. The factor of safety of an embankment is inversely estimated using information whether the embankment is still safe or not after the occurrence of an earthquake. In this back-calculation, soil strengths and seismic loads are treated as random variables. This is because, in many actual situations, these two factors are usually uncertain even after the occurrence of an earthquake. The developed procedure is applied to the case records of embankment behavior during the Niigata earthquake of 1964. Six embankments are analyzed. Four of them are damaged embankments while the others are non-damaged. The factors of safety are inversely estimated and they are compared with the state of damage described in the case records.

EXPERIMENTAL ANALYSIS ON THE USE OF FLY ASH TO IMPROVE SOIL QUALITY

大量に搬出される建設発生土, 泥土, 浚渫土などの建設副産物や石炭灰, 脱硫石膏などの電力副産物は品質などの制約で十分に利用されずに埋立・処分され, 資源・環境面で大きな社会問題になっている.このうち, 石炭灰は昔から自硬性のあることが知られている. 本研究では, 石炭灰及び石膏を低品質な土砂の土質改良材として利用することを目的に, 改良要因とその効果の度合い, 最適な配合を把握した. その解析手法として統計手法 (実験計画法と重回帰分析法) を適用し, 少ない実験回数で不良土の初期含水比W0, 生石灰添加率L, 石炭灰添加率F, 交互作用L×F, 石膏添加率Gが不良土改良の重要要因であることを確認するとともに, その添加量の範囲を絞り込んだ.

IN-SITU TEST OF GROUND IMPROVEMENT SAND PILES METHOD BY MEASURING THE PROCESS OF DEWATERING

川越火力発電所では, 軟弱な沖積層上に造成された埋立地盤に, LNG設備を建設中である. このため, タンクなど主要構造物を杭基礎とする場合でも, 杭の横抵抗の不足, 地震時の液状化, 完成後の残留沈下の問題が複合的に発生する. この対策として, 揚水井を併用した新しい地盤改良工法を適用した. 揚水井を沖積砂層に設置することで, 砂杭が打設された埋立粘土層の水位低下を強制的に促進し, 合せて, 下部の沖積粘土層の圧密促進を図った. しかし, 設計に必要な水位低下に要する時間の予測手法なども確立されていない. そこで, 本工事に先立ち試験工事を行いそこで得られた知見を, 本工事の設計と施工に反映した. その結果, 所要の強度を満足でき, 残留沈下が発生しない地盤を経済的に造成することができた.

A method for estimation of ground layered systems for the control of steel pipe pile group driving

Abstract A new method for the estimation of ground layered systems, which is to suggest the dynamic design method of steel pipe pile groups, is proposed, in a probabilistic manner. The distinctive features of the method are as follows: (1) The method is safer and easier than other methods, as it needs only a general soil boring investigation prior to, and measurement of blow count data during, the pile driving. (2) Not only is the pile bearing capacity estimated, but the accuracy of the estimation can be evaluated. (3) Attention is given to the regulation of sedimentation layers from the geological point of view. (4) It can make a higher accurate estimation than a current design method. Real ground layered systems are estimated by the method, and it becomes clear that the variation of pile bearing capacities, and of the uncertainty of these, cannot be ignored even within one site. A chart, to use the arrangement of the variations, is also provided. Its applicability is examined by real pile driving data, and it becomes clear, that the effect of the magnitude of bearing capacity, and also the accuracy of the estimation to the design alteration, is well presented in the chart.