The Blasting vibration can be reduced substantially by the employment of the controled blasting with continuous slot. Despite of this capability, the behavior concerning the dynamic fracture and vibration during the blasting process have not been clarified, and a numerical analysis method which can estimate these phenomena appropriately has not been developed. We propose a DEM-based analysis method which simulates the dynamic process consisting of both dynamic fracture and vibration. In this study a blasting experiment is also achieved for concrete blocks. The developed numerical method is then applied to its simulation. Through these analyses, the validity of the present method is discussed.

View full abstract

 In the study, we carried out laboratory experiments and numerical analysis to verify how the curing environment and construction method of lining concrete cause cracks, so that we may prevent concrete pieces from falling and improve the long-term health of lining concrete. As a result, we found that the necessary compactness of concrete surface can be secured, if the concrete is cured in a wet condition for 7 days. As for the construction method, applying excessive compaction energy did not have a major impact on the quality of concrete. We also analyzed the crack propagation based on the physical properties obtained from laboratory tests. It was found that harmful cracks were not generated in the short-term (50 days), and in the long-term (50 years), occurrence and crack propagation caused by shrinkage strain of the concrete were not influenced by the curing environment. Based on these findings, we will propose construction management guidelines for medium-fluidity lining concrete.

View full abstract

 Assessing and accurately predicting geological conditions ahead of a tunnel face are important in constructing mountain tunnels reasonably and safely. The authors have developed a new type of seismic tomography technique between tunnel and ground surface using a precise time synchronization wireless system with GPS, a vibration of blasting excavation and an automatic data acquisition system. This system enable to illustrate P-wave velocity contour ahead of a tunnel face without stopping an excavation. Based on its velocity distribution, not only a location but also a velocity value of geological change can be evaluated. This paper presents that details of each development and an actual employment of new technique to a construction site.

View full abstract

 Various auxiliary methods have been carried out in tunneling sites due to increasing in the size of the tunneling machines and developing their technology. Thus, full-face tunnel excavation has been increasingly employed for sequential excavated method tunneling as well as the ground control effect of early ring closure. As the stability of the tunnel face is essential to full-face tunnel excavation, the tunnel stabilizing method utilizing curved tunnel faces, which would naturally form as part of the tunnel excavation sequences, can be considered effectively.
 This paper addresses an investigation into the stability of various shapes of tunnel face considering full-face and bench cut methods. In order to clarify the stability, we carried out the model tests using base friction apparatus and numerical simulations with discrete element method (DEM). As a result, it was confirmed that curved tunnel faces were advantageous and the stability of the tunnel face could be improved by a simple reinforcing method such as shotcrete on tunnel face. In addition, we concluded that there was a difference in the reinforcing effect by the shape of the tunnel face or excavation method.

View full abstract

 Deformation measurement is usually one of the key elements of measurement carried out in tunnel construction. A new mechanical method is proposed to measure the relative displacement between two points, and to visualize the results in real-time based on the concept of “On-site Visualization”. The mechanism of the method lies in that a rotational structure is used to translate the linear displacement into the rotation. Since the simple method performs in a mechanical way without using electricity, it would reduce the purchase&use cost to an acceptable degree.
 This paper presents the laboratory tests and a field experiment to verify the possibility and feasibility of the method. In the field experiment, the shotcrete cracks, the heave of invert and so on in the tunnel during construction were monitored by this method. The measured results are analyzed in comparison with those from Total Station, which shows the deformation of the tunnel during construction could be detected and visualized availably. Finally, the applications of this mechanical method are discussed briefly.

View full abstract

 By the collapse of ceiling panels in Sasago tunnel, it turn out completely inevitable the falling of the appendage by periodic inspection. In conventional inspection method, it can't fully grasp the soundness of the bolt for securing the appendage. While, with technology improvement of economical, high-performance sensors and handling of big data, it has been promoting the social device in the infrastructure field called "anywhere sensor". This paper focused on lumps in load tunnel, proposes a sensing method utilizing commercial sensors with MEMS technology and verifies its practicality. And proposes the tunnel conservation monitoring system with organizing the relationship with periodic inspection.

View full abstract

 Some mountain tunnels suffer from floor heave after completion, and some of them require countermeasures. This phenomenon occurs if there are no big deformation during construction, therefore, under existing circumstances, based on preliminary survey and condition of excavation, to predict the floor heave deformation after completion is difficult.
 In this study, to help the improvement of the prediction accuracy, first, construction data of Shinkansen tunnels suffered from floor heave were analyzed, so that the concernment between deterioration of ground by water and floor heave was confirmed. Second, make the model ground using the rock of actual tunnel, and recreate the floor heave by adding the water to model ground. Finally, tunnel excavation and floor heave after construction are consistently modeled in the numerical analysis. As the result, the effect of early closure and invert shape for floor heave were confirmed.

View full abstract

 The effect of construction load due to shield tunnel excavation is not necessarily temporary rather it continues as a residual effect. The construction loads include the load at the time of assembling the segment associated with the deformation of the previous segment, the load during insertion of the key segment, the load due to the scraping and thrusting between shield tail and segments during tail passing, and so on.
 In this paper, by quantitative evaluation of the monitoring data starting from assembling the segment to the tail passing, it is obsered that there is a significant influence of the above mentioned construction loads in shield tunneling. Based on the evaluation of the monitoring data a simulation model has been proposed considering the construction loads, and the validity and applicability of the model is verified.

View full abstract

 The state of temperature environment in our tunnel was cleared due to long term measurement of tem-perature in the tunnel by fixed thermometers in a section of a shield tunnel with box-type segments for the purpose of developing a non-destructive and contact free method using infrared thermometry to detect non-visual voids effectively. Moreover, we carried out every seasonal movement measurement by an infrared thermography and compared with results of hammering tests found some voids. From the results, follows were cleared. Winter season was suitable for the detection with the method in the area of the investigation. Accuracy of voids by infrared thermometry was approximately equal with it by hammering test when the temperature at measurement satisfied temperature environmental conditions.

View full abstract

 We conducted stress measurement of the reinforcing bar stress transducer which made before structure concrete of cut and cover tunnel placing defaults until the structure construction completion in on a specific site in Fukutoshin line, and presumed the static load of the structure by executing the back analysis about a result which separated thermal stress and the dry shrinkage stress from a measurement stress of reinforcing bar stress transducer. As a result, it was found out that static load of the side wall is lower than the design load and it seemed to be caused by effect of decreasing static load by leaving retaining wall.

View full abstract

 There were the following typos in the article, "Journal of Japan Society of Civil Engineers, Ser. F1 (Tunnel Engineering) Vol. 69 (2013), No. 3 pp. 21-30"

View full abstract

 There were the following typos in the article, "Journal of Japan Society of Civil Engineers, Ser. F1 (Tunnel Engineering) Vol. 70 (2014), No. 3 pp. 32"

View full abstract