It has been widely reported that fault zones are the most influencing factor of tunnel collapse. This study reviewed the applicability of the 3-D absolute displacement measurement of a tunnel by using digital vision monitoring. Also analyzed is the behavior of a tunnel displacement when passing through a fault zone with various orientations by using 3-D finite element analysis. As a result of analyzing 3-D deformation, it was found that the variation of displacement trend on horizontal/vertical section per measurement section would be larger as it approaches to the core of the fault zone. It was also examined that the variation of crown settlement and trend line would be the most influenced at a point where a tunnel meets fault zone. However, since the variation of crown settlement trend line starts as it is very close to a fault zone(0.5D ~ 1D), it may be difficult to anticipate a fault zone from crown settlement trend line. It was also proposed the move vector concept of a center point in a plane, which is created by connecting displacement measuring points. After applying the proposed monitoring center vector(MCV) to a tunnel section through which a fault zone passes, it was found that the influence would be well reflected depending on the fault zone orientation. In addition, the study suggested the ‘stereonet projection’ as a method to express the move behavior of MCV in a 3-D space and suggested how to anticipate front fault zone through variations of measuring section center point vector on the stereonet projection diagram. The 3-D absolute displacement measurement of tunnel and the displacement analysis using the digital vision measurement developed in the study were applied to a tunnel site. Comparison with the survey results of fault zone showed good
For safe and economic construction of a tunnel in a fault zone, appropriate method have to be employed to predict and prepare for sudden change in ground condition ahead of the tunnel face as early as possible. Studies on the prediction of fault zone ahead of tunnel face using the convergence of tunnel have been conducted since late 1980s. Various methods have been tried, including analysis on the trend line and influence line of the displacement in tunnel axis, analysis on the change trend of the vector orientation which is the ratio between the displacements in radial and advance directions, and so on. Most of the studies on the prediction of fault ahead of tunnel face using tunnel convergence have been focused on the investigation of the deformation behavior of the displacement by excavation at the measuring point. However, it was not possible to take full consideration of the 3-dimensional behavior of displacement by fault zone ahead since the analyses were only limited to the displacement in single or two directions,. In this paper, a 3-dimensional displacement analysis method which can efficiently represent behavior of rock in fault zone is proposed.
