The new ventilation system for reducing the dust concentration has developing in order to cope with the enlargement of the cross section of the mountain tunnel. Now a new ventilation method called “the dust collection system with air supply and suction” is proposed at various sites. This method is expected large dust collection effect by isolating the dirty and clean air to form the wall of air flow called “Air curtain” by using dust collector near the tunnel face. However, this method is experimental method, it is necessary to clear the optimal design of ventilation system. The indoor wind tunnel experiments were executed the formation characteristic of “Air curtain” by the wind tunnel experiment. And, the possibility of further improvement of dust collection efficiency is examined by in-site experiment at the tunneling site.

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 Thus far, there has never been any cases where infrared thermography (passive method) was applied to detect flaking near the surface of the concrete in subway tunnels, which are not affected by sunlight. Through this research, a method was developed, which can actually be put into practice to detect flaking of the decking concrete used in subway tunnels using infrared thermography. At first the temperature conditions (and other elements) that would allow detection of flaking in a box-type tunnel and in a shield tunnel, both in use, were analyzed.
 Then, detection of flaking inside a box-type tunnel was carried out, and a method to identify the day that was appropriate for infrared thermography measurement was developed based on the temperature outside, having considered accuracy of infrared thermography measurements and the relationship between temperature outside and temperature in the tunnel.
 Furthermore, on the same section meticulous concrete surface hammering tests were carried out besides the infrared thermography measurement, and the effectiveness of this method was verified having compared those results with results of special general inspection based on the maintenance standards for railway structures.

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 The squeezing and swelling deformation is a major threat in tunnel engineering. It can often cause serious damage to tunnel linings and produce high additional costs during tunnel construction and operation. The squeezing and swelling may result in a heave of the tunnel floor or the tunnel invert, or destruction of the lining or the invert, or uplift of the entire tunnel section. For an optical design of the tunnel and the countermeasures, it is necessary to predict the tunnel deformation. For that, it is necessary to understand the mechanical behaviour of squeezing and swelling rock as a basis.
 In this paper, the relationship between swelling strain, pressure and time are introduced. And the strength reduction law is considered to this relation. In addition, this relationship is incorporated into elasto-plastic analysis considering the tension off by finite element method.
 Consequently, this paper presents the results of a numerical back analysis of measured deformation in the ground and surface with a simple constitutive model using field observation and laboratory tests.

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 In tunnel rock classification, seismic velocity has been long used as one of important classification indices. However, seismic velocities measured before and after excavation of the tunnel may differ largely, and as a result, there may be a large difference in the rock mass classification of the tunnel, and it is often imperative to change the tunnel support pattern at the time of construction. We have, therefore, studied a method to predict the seismic velocity and tunnel rock classification after excavation by applying rock physics models to geophysical data obtained in the site characterization stage before excavation. In this paper, we applied the proposed method to seismic velocity and resistivity profiles measured along the formation level of a planned tunnel and predicted P-wave velocity reduction due to loosening by excavation for estimating the tunnel rock classification after excavation. This application demonstrates that predicted and actual tunnel rock classifications agree each other very well.

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 Soundness evaluation method for concrete structures is newly developed by non-contact inspection method by laser Doppler vibrometer and pulsed laser. The results by laboratory tests using concrete specimen revealed the following. The presence of defects can be estimated by the presence of damped waves. The presence or absence of defects can be judged with high accuracy even under the noisy measurement data by the assumption that the measurement data is impulse response and the LSCF, which is a kind of system identification algorithms. Moreover, vibration characteristic of the defects with physical significance can be quantified when there are defects. In addition to laboratory tests, field tests in Shinkansen tunnels are performed. The results demonstrated the availability of the soundness evaluation method and suggested that natural frequency of the lowest mode is one of the most useful indexes to evaluate the soundness from the vibration characteristic.

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 Monitoring system of Japan expressway corporation (NEXCO) consists two stages. The first stage is the screening system by using tunnel lining photo image at the periodic tunnel health inspection. The second stage is the onsite detailed inspection by engineer. The main evaluation item of both system is called evaluation value effected by external force and exfoliation based on Tunnel lining Crack Index (TCI). In this research, inspection results over 85,000 lining spans managed by NEXCO was analyzed for the purpose of high accuracy and efficiency of tunnel health monitoring system for expressway. In the data analysis, it was found that there is a high relationship with tendency between the first and second stage. In addition, a comparative analysis of the both stage is performed. The practicality of the current inspection system is high, the efficiency of detailed inspection needs to be examined in the future.

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