Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Results
Japanese State of the Art On Tunnel Maintenance Technology
Asakura, Toshihiro (Kyoto University) | Kojima, Yoshiyuki (Railway Technical Research Institute) | Matsunaga, Takeshi (Kyoto University)
ABSTRACT Recent maintenance technology of Japanese railway tunnels is written in this paper. In the first place, inspection of tunnel lining is divided into primary inspection and secondary inspection and shown in this paper. New technology of non-destructive inspection which is in the process of practicable inspection to make this automatic is introduced.Inspection techniques of lining surface deformation based on the analysis of images obtained by laser beams, line-sensor cameras, CCD cameras, etc. Inspection techniques of lining internal deficiency by non-destructive tests using infrared rays, hammer testing using an acoustic analysis of the strike sounds, and ground radar. An observation system to measure the progress of the deformation using optical fiber. An expert system of tunnel diagnosis. 1 INTRODUCTION Since seventy percent of the land in Japan exhibits mountainous topography, tunnels have been built from place to place in order to secure traffic paths for railways and roadways. In urban areas, in addition to subways, tunnels for lifelines such as sewerage, waterworks, etc. have been built in many areas. Table 1 and Figure 1 show Length of tunnels in Japan. Tunnels do not deteriorate easily; they generally have a very long service life compared with on-ground structures, since they are constructed in the ground and experience little environmental change. For instance, about one third of all railway tunnels in Japan were built before the Second World War, but most of them still serve under proper maintenance today. When internal factors resulting from the lining material and the execution works are influential, deformation due to material deterioration becomes noticeable with time because of water leakage (acid water and the cycle of drying and wetting), environmental factors such as frost damage, and so on. The progress of the deterioration causes the spalling of the lining and leads to a decrease in the structural strength of the lining. Even when the deterioration factor is less noticeable, if cracks and poor quality materials at the construction stage were obvious, the deterioration may progress with time and lead to the spalling of the lining. 2 PRESENT INSPECTION SYSTEM AND TECHNIQUE The inspection of tunnels are conducted in order to grasp whether or not deformation has an influence on structural safety and durability, and then to take proper countermeasures to secure the functions of the tunnels based on the evaluation results. Thus, the inspection of a tunnel and the resultant diagnosis are the most basic parts of the maintenance and the management of a tunnel. Figure 3 shows a general flow chart of tunnel maintenance. Inspections are divided into two groups, the primary inspection and secondary inspection. 2.1 Primary inspection The primary inspection is done to discover whether or not deformation exists, and to judge, if deformation is detected, whether or not a secondary inspection and/or temporary countermeasures or actions are necessary by making an estimate of the magnitude of the deformation.
Guideline For Influence Estimation On Existing Tunnel Due to Embankment And Excavation Above a Tunnel
Kojima, Y. (Railway Technical Research Institute) | Yashiro, K. (Railway Technical Research Institute) | Yoshikawa, K. (Fujita Co. Ltd) | Shigeta, Y. (DIA Consultants Co. Ltd) | Asakura, T. (Kyoto University)
ABSTRACT Recently, a number of construction projects including a large-scale embankment and surface excavation have been planned and executed at locations adjacent to existing tunnels. In these cases, it is essential to estimate adverse effects due to the neighboring construction works on the tunnels. At first, we carried out case studies of embankment and ground surface excavation above railway mountain tunnels.We therefore carried out FEM simulation analyses for such cases to clarify tunnel deformation behaviors due to embankment and ground surface excavation above the tunnel. This paper presents a summary of these results obtained from the case studies and the simulation analyses, and proposes a guideline for criteria to judge proximity levels to embankment or excavation above existing mountain railway tunnel. 1 INTRODUCTION Recently, in Japan, a number of construction projects including a large-scale embankment and surface excavation have been planned and executed at locations adjacent to existing tunnels. In these cases, it is essential to estimate adverse effects due to the neighboring construction works on the tunnels. Therefore, Railway Technical Research Institute (RTRI) presented a draft of "Manual for Precautionary Measures in Construction Adjacent to an Existing Tunnel" in 1995, for maintenance of railway tunnels. The manual frequently has been applicable to predict adverse effects of the adjacent construction work to existing railway mountain tunnels. In this manual, however, there is no provision of methods of numerical analysis to estimate adequately the tunnel deformation behavior. In view of such a situation, the authors initially carried out case studies using eighteen cases of embankment and thirtyone cases of ground surface excavation above railway mountain tunnels.We also carried out FEM simulation analyses for such cases to clarify the tunnel deformation behaviors due to embankment and ground surface excavation above the tunnels. This paper presents a summary of these results obtained from the case studies and the simulation analyses, and proposes a guideline for criteria to judge proximity levels to embankment or excavation above existing mountain railway tunnels. 2 DEFORMATION BEHAVIOR OF TUNNEL DUE TO SURFACE EXCAVATION Prior to proceeding to the subject, the authors briefly describe on a typical case of deformation behavior of an existing railway tunnel due to surface excavation.The tunnel is a railway tunnel with cast-in-place concrete lining constructed on a doubletrack in 1929 by a conventional mountain tunneling method, approximately 200-m in length and 40-m maximum overburden. The surrounding medium of the tunnel is of Tertiary soft mud rock of unconfined compressive strength q u = 5-MPa and deformation modulus in unloading D =1,000-MPa. Photograph 1 shows a view of the surface excavation above the tunnel. Figure 1 shows a longitudinal cross section of the surface excavation. As shown in Fig. 1, the original maximum overburden of the tunnel H is 40-m and residual overburden h is 10-m, then the height of excavation _ H is 30-m. Figure 2 shows raise and convergence progress of the tunnel during excavation.
Damage to Mountain Tunnels By Earthquake And Deformation Mechanism
Asakura, Toshihiro (Kyoto University) | Kojima, Yoshiyuki (DIA Consultants Co. Ltd) | Matsunaga, Takeshi (Kyoto University) | Shigeta, Yoshiyuki (Railway Technical Research Institute) | Tsukada, Kazuhiko (Kyoto University)
ABSTRACT Generally the mountain tunnels are little damaged by earthquake. However, recent case studies of the damage of mountain tunnels caused by earthquakes also show that they are likely to be damaged whenthe energy scale of earthquake is large, the tunnel is near the earthquake faults and the tunnel has special conditions, such as bad geological condition and structural deficiency of tunnel. We collected information on the tunnels which suffered damage from earthquakes, and surveys of the tunnels damaged by the 2004 Niigata Chuetsu Earthquake to study the damage mechanism of mountain tunnels. And we mainly focused on grasped the deformation mechanism of the lining qualitatively and simplified the modes of shear deformation of the ground during an earthquake into the following two cases;when the angle of incidence of shear wave is vertical, and when the angle of incidence of shear wave is 45° against the vertical line. This paper presents a summary of these results obtained from the case studies and the simulation analyses. 1 INTRODUCTION As tunnels are surrounded by the ground, they have good earthquake-resistance if the ground is stable during an earthquake. Therefore, it is generally said that the earthquakeresistance is not necessarily required for tunnels in the stable ground. In the 1995 Hyogoken-Nanbu Earthquake, however, 10 tunnels among at least one hundred mountain tunnels in service in and around the disaster area had serious damage to need repair and reinforcement. We reconfirmed that if an earthquake was larger, even mountain tunnels would have been damaged. Damage survey of the regions affected by the 2004 Niigataken-Chuetsu Earthquake is still underway, but so far it has been revealed that among over 100 mountain tunnels, approximately 50 were damaged, including 25 or so that required repair and reinforcement, as well as those that sustained minor impacts. There are few studies on the earthquake damage mechanism of mountain tunnels. On the other hand, more and more tunnels have been constructed recently in the ground of low strength and low earth covering, to require the establishment of a method to design mountain tunnels in consideration of the effect of earthquake. We performed this study to acquire the basic knowledge of the earthquake damage mechanism of mountain tunnels. 2 DAMAGE TO MOUNTAIN TUNNELS BY EARTHQUAKE 2.1 Tunnels surveyed Asurveywas conducted on the tunnels used for highways, railways and aqueducts for power plants situated within regions affected by the 2004 Niigata Chuetsu Earthquake (hereinafter, the "Chuetsu Earthquake") in order to determine the level of damages. Table 1 show the basic data on the tunnels surveyed and outline of their damages. 2.2 Outline of earthquake damage to the tunnels Fig. 2 shows the level of damage in percentages. The damages were categorized into 4 levels, from "Tunnels requiring major repair/reinforcement (A1 Tunnels)" to "Undamaged tunnels".