TFT survey is a kind of survey that generated seismic waves induced by blasting during excavation. This method allows engineers to carry out a geological survey without interrupting the tunnel excavation work. The geological condition around the face of the tunnel can be evaluated in real time using direct waves. On the other hand, this method allows the prediction of geological changes for instance fault or fracture zones ahead of the tunnel face through the analysis of reflecting waves. As a result, the TFT survey is considered as an advantageous and effective way to obtain various types of geological information.
 Furthermore, this paper introduces the outline of the TFT survey and shows the results of the TFT survey carried out during the construction work of a road tunnel in Japan. In this experiment, changes of the geological condition are confirmed from the evaluation of direct waves. The predictions ahead of the tunnel face are carried out after the characteristics of the TFT survey system and parameters of the analysis are reviewed. And the comparison of the TFT survey with other commonly adopted face forward exploration techniques confirming to yield equivalent performance. Results of the experiment estimate that about 70% of the predictions confirm with real geological conditions.

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 Although the mechanical functions and effects of shotcrete have been studied much by experimental or numerical method, they aren't still quantitatively evaluated. Therefore, the mechanism that reinforces the rock mass around tunnel isn't made clear. Authors derived the analytical solution of an elliptical tunnel reinforced by ring considering initial displacements under semi three dimensional loads. This paper presents quantitative evaluation of functions and effects of shotcrete for an elliptical tunnel from numerical calculation results using above solution in the level of stresses, displacements and sectional forces, and make its mechanism of reinforcement clear.

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 The study aims at examining the effect of covering sheet on surface quality of concrete. The study uses a concrete-form simulating tunnel sidewall of negative angle and various sheets covering the form, and investigates bugholes and color irregularity of the concrete made in the form covered with the sheet. The primary parameters in the comparative test are water-pressure resistance and air-permeability of the covering sheet. The experimental study shows that water-proofing material sheet contribute decrease color-irregularity as well as bugholes. Based on the laboratory test, this paper presents appropriate properties of sheet to improve concrete surface quality.

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