Kensuke Date

Experimental and Numerical Study on the Interface Behaviour Between the Rock Bolt and Bond Material

Conventional tunnelling methods (i.e., the drill and blast tunnelling method or the new Austrian tunnelling method) have been frequently applied for the construction of tunnels/caverns under a high overburden and with a large cross section. Under such adverse conditions, tunnel support materials may yield because of ground pressure and tunnel deformation. As a result, a tunnel may lose its stability due to a reduced effectiveness of the tunnel supports. Rock bolts have been widely used as an essential component of tunnel support, and many studies have been conducted on the performance of rock bolts in strengthening the jointed rock mass. However, there is a lack of understanding on the interface behaviour between the rock bolt and the bond material, especially the crack initiation and propagation inside the bond material. This study aims to investigate the interface behaviour between rock bolts and bond materials using laboratory tests (shear tests) and numerical simulations (Discontinuous deformation analysis). By assessing the impact of the key parameters in the rock bolting system, such as the ribs, rib angle, strength of the bond material and the confining pressure, we are able to better understand the supporting mechanism and the effects of rock bolting.

A STUDY FOR EVALUATION OF DRAINAGE USING PIPE JACKET

従来より地すべり対策として施工されている保孔管は,塩ビパイプが一般に使用されているが,対象が砂質地盤の場合,土砂流出による地山崩壊や,目詰まりが懸念される.本研究ではジオテキスタイルを筒状に加工したパイプジャケット1）を用いて,保孔管としての適用性を検討した.室内実験においてパイプジャケットは表面に無数の小さな孔が開いており集水効果が高く,ジオテキスタイルの特徴であるフィルター層がパイプジャケット表面に形成されてろ過機能が発現されることが確認された.これらの知見をもとに地すべり地帯において試験施工を行い有孔塩ビパイプとの比較試験を行った.この結果パイプジャケットは土砂流出抑制,排水量供に有孔塩ビパイプよりも優れることが確認できた.

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.