NATURAL GROUND REINFORCEMENT METHOD

To obviate natural ground collapse in tunnel excavation and secure tunnel excavation safety by simply and surly getting hold of filling state of an injection material injected into an unexcavated natural ground of the tunnel in preceding natural ground reinforcement work and by reinforcing an unimproved area.SOLUTION: The natural ground reinforcement method includes placing a long steel pipe 3 for detection adjacent to a placed long steel pipe 1 before injection of a urethane injection material 10 into the natural ground, providing temperature sensors 5a to 5c inside the long steel pipe for detection, getting hold of an improved area in the natural ground by measuring temperature with the temperature sensors after the urethane injection material is injected from the long steel pipe to the natural ground, and conducting supplemental injection to the place judged that it is an unimproved area through the long steel pipe for detection.SELECTED DRAWING: Figure 5 【課題】先行地山補強工に際し、トンネルの未掘削地山に注入された注入材の充填状況を簡便かつ確実に把握し、かつ未改良領域を補強することにより、トンネル掘削時の地山の崩落を未然に防止してトンネル掘削の安全性を確保する。【解決手段】本地山補強工法は、地山へのウレタン注入材１０の注入に先立って、打設された長尺鋼管１に隣接して検知用長尺鋼管３を打設し、検知用長尺鋼管内には温度センサー５ａ～５ｃを設置し、長尺鋼管から地山へウレタン注入材を注入した後に温度センサーで温度を測定することによって地山内の改良領域を把握し、未改良領域と判断される箇所には検知用長尺鋼管を通じて補足注入を行う。【選択図】図５