Yukiyoshi Kitamoto

Impact Based Testing Technique for Measuring Strength of Geomaterials

This paper presents a rapid geomaterial strength testing method that measures the impact process of a spherical object colliding with a test material. This method is based on Vesic (1977) cavity expansion theory and combines with the technology developed for measuring deformation characteristics (in a companion paper by the authors). In this new method, a geomaterials strength parameters including its internal friction angle Φ and cohesion c are directly calculated. Results from validation tests demonstrated satisfactory testing accuracy of this method and its unique advantages comparing with conventional laboratory strength tests.

Impact Based Testing Technique for Measuring Moduli of Geomaterials

This paper presents a method that measures an impact process of a spherical object colliding with on a testing material and, through analytical techniques based on Hertzs theory of impact, deduces the elastic modulus of the tested material. Furthermore, by distinguishing the compress and rebound phrases, and by accounting for the plastic deformation characteristics of the tested material, this method can measure the compressive modulus and rebound modulus simultaneously. This method is suitable for testing various materials, such as steel, concrete, and geomaterials including cement-treated soils. Various deformation parameters can be deduced from this method, including compressive modulus, subgrade soil modulus K30, California Bearing Ratio (CBR) value, and Benkelman Beam Deflection value. This method is shown to be very accurate in a large number of validation tests performed by the authors. Its advantages include broad applicability, high efficiency, and relatively large strain (thus also capable of evaluate material strength). Results from field implementation in actual civil projects show that this method has great potential in many applications, particularly real-time fill materials quality assurance and construction optimization.

CONSTRUCTION OF A LATTICE-FRAME-REINFORCED SHEET ON THE SOFT GROUND

格子ジャケットを用いたシート工法は，筒状織物に流動性の高いモルタルを充填して格子状の補強枠を形成する表層安定処理工法で，格子構造が荷重分散効果を有し，軟弱地盤上に施工することで不同沈下の抑制が行える．これまでに水田上におけるトラフィカビリティーの改善実験や鉄道路床の試験施工，および河川護岸工事における短期間の仮設道路としての使用などの実績がある．本報告では深さ10m近くまでN値の低い地盤が堆積している軟弱地盤上に一般道路の仮設道路として施工した例を紹介すると共に，使用期間が1年以上と比較的長期にわたるため，追跡調査を行い施工後の状況について詳細調査を行った結果を報告する．

SUPPORTING EFFECT OF TUNNEL FOREPILING WITH INJECTION

断層や破砕帯あるいは都市部の未固結地山といった地質条件の悪い場所に, 山岳トンネル工法を適用する工事が増加している. このような施工条件では, 切羽の安定性確保や地表面の沈下抑制を図ることが重要であり, 補助工法の中でも先受工は大きな進歩を遂げてきた. そこで現在, 施工技術の進歩に対応すべく, 補強メカニズムに立脚した合理的な設計法の開発が求められている. 本論文では, 三次元的な円筒シェル解に着目し, 施工条件的にも適用性が高いことから注入式鋼管フォアパイリングの評価手法として提案した. さらに, 遠心模型実験によって円筒シェル解の適用性を検討し, 先受け領域の変形特性を室内載荷実験により確認するとともに現場計測データとの比較から提案手法の妥当性を検証した.

EFFECT OF THE NEW FORE PILING METHOD WITH MIDDLE LENGTH PIPES

With regard to the current practice of tunnelling construction for railways and roads it is desired that a more practical method be developed so as to save time and cost as well as more safety. Lecentry, long forepiling method has been used widely so that the tunnel crown settlement in soil ground, can be restrained. On the other hand, cost by such method is generally high in case special technique or machine must be adopted. In addition, the effect by reinforcement using forepiling method is difficult to be made clear theoretically. We developed a new forepiling method using middle length steel gas pipes for the purpose of lowering the construction cost with enough reinforcement effect. These reinforcement can be easily installed by conventional tunnelling machine. This paper reports the technical features and construction procedure. Next, the practical measuring results are shown. As a result, it is proved that the new forepiling method is effective in cost and reinforcement.