Development of new tunneling method using X-ray CT

近年来，即使在城市地区，也已经将诸如新奥隧道法（新奥隧道法）的山岭隧道法用于隧道建设。在国土面积小的日本，要求隧道在松散地层或低覆盖层地层中施工。隧道开挖过程中，开挖引起的应力释放使掌子面变得非常不稳定。隧道掌子面的稳定性是施工过程中的主要问题。为了给安全施工创造条件，有必要对隧道掌子面进行辅助加固。然而，由于隧道开挖引起的破坏区是一个三维的行为，在三维的工作面破坏的机制还没有得到很好的了解，本研究的目的是在三维的隧道工作面破坏和评价的辅助方法的机制。最后提出了辅助法施工的新方法。在这项研究中，使用工业X射线CT来研究土壤中的行为。并利用离心模型试验对模型试验结果进行了验证，以确定地应力水平。本文的主要结论如下：1.开发了一套模型试验与X射线CT相结合的新型试验系统;提出了获得正确X线图像的效果图像分析方法;利用本研究开发的试验系统，对隧道掌子面破坏机理进行了研究。进行了一系列的离心模型试验，目的是检查在原地应力水平的行为;5。根据本研究的结果，提出了一种隧道施工方法;6.采用一种新的试验装置--CT扫描直剪试验，对辅助方法的效果进行了研究。通过1G模型试验和离心试验研究了辅助方法的效果。最后，总结了本研究的成果。

In recent years, mountain tunneling method such as NATM (New Austrian Tunneling Method) has been used for tunnel construction even in the urban area. In Japan where land area is small, it is required that tunnel is constructed into unconsolidated ground or low overburden ground. When excavating a tunnel, tunnel face becomes very unstable due to stress release caused by excavation. It is a main issue to maintain the stability in tunnel face during construction. To create the condition for safe construction, it is necessary that tunnel face is reinforced by auxiliary method. However, failure zone due to tunneling is a behavior in three dimensions and the mechanism of face failure in three dimensions has not been well known yet.The objective of this research is to investigate tunnel face failure in three dimensions and to evaluate the mechanism of the auxiliary method. And finally, the new tunneling method with the auxiliary method is proposed. Here in this study, an Industrial X-ray CT was used in order to investigate the behavior in the soils. And the results of model test were checked with centrifuge modeling test for the purpose of in-situ stress level. Followings are the list of conclusions :1. A new testing system combining model test with X-ray CT was developed ;2. Effect image analysis method for getting proper X-ray image was developed ;3. The mechanism of tunnel face failure was well investigated using the test system developed in this research ;4. A series of centrifuge model tests were conducted for the purpose of checking the behavior of in-situ stress level ;5. One tunneling method was proposed based on the results of this research ;6. The effect of the auxiliary method was well investigated using a new test apparatus, direct shear test with CT scanning ;7. The effect cf the auxiliary method was also investigated with 1G model test and centrifuge test ;8. and finally, all the results obtained here in this research were summarized.