Estimation of Natural Ground Behavior Ahead of Face by Measuring Deformation Which Utilized TBM Drift Tunnel

摘要

In Japan, 3-lane highway is building by Japan Highway Public Corporation. The area of 3-lane tunnel rncross-section is about 200m2 and is about 2 times as large as the cross-sectional area of a standard rnmountain tunnel in Japan. The tunnel construction method of excavation with which TBM (Tunnel rnBoring Machine) drift tunnel (the diameter is 5m) is made preceding was newly adopted as the standard rnexcavation method of mountain tunnel. Then the cross-section of its TBM drift tunnel is enlarging by rnexcavation of NATM. In order to measure all displacement of axial direction of tunnel continually rnduring excavation, the deformation is monitored inside TBM drift tunnel until the enlarged excavation rnreached. When the enlarged tunnel face arrived just before monitoring point, the measuring points have rnplaced inside wall of enlarged tunnel at less than one-cycle length. Then displacement is measured rncontinually. Therefore, to predict of natural ground behavior after enlarged becomes possible, utilizing rndeformation measurement in TBM drift tunnel, on the basis of behavior of excavated natural ground. By rncontinuous deformation measuring from the enlarge excavation before and after, continuous estimation rnof natural ground behavior, prediction generally the last displacement from displacement of enlarge rnexcavation immediately and evaluation the good or bad condition of tunnel face and natural ground rnahead of face relatively become possible. Besides effect of TBM drift tunnel thought about heretofore, rnpossible to add role of estimate of mechanical property of natural ground, evaluate behavior of natural rnground ahead of face before enlarge excavation, necessity examination of simple reinforcement and rnauxiliary method get possible.