METHOD AND DEVICE FOR DETECTING LOOSENESS IN NATURAL GROUND ON WORKING FACE SIDE OF SHIELD MACHINE

PROBLEM TO BE SOLVED: To provide a method and a device for detecting looseness in a natural ground on a working face side of a shield machine for detecting looseness that induces collapse instead of detecting a collapse, thereby calling for attention before a collapse occurs.SOLUTION: A collapsing surface of a natural ground is forecasted by clarifying wet density and moisture density (moisture content) of soil with wet density and moisture density (moisture content) detection means for the soil installed in a front part of a shield machine. The wet density detection means and the moisture density (moisture content) detection means for the soil has a radiation source rod that radiates gamma rays and neutron rays from the front part of the shield machine, and the gamma rays and the neutron rays are scattered repeatedly while advancing in the soil. The wet density and the moisture content are derived from a radiation dose that reaches the detector.SELECTED DRAWING: Figure 1 【課題】崩落の検出でなく、崩落を誘引する緩みの存在を検出し、崩落の前段階での注意喚起ができるシールド機の切羽地山緩み検出方法および装置を提供する。【解決手段】土の湿潤密度検出手段と土の湿潤密度と水分密度（含水量）検出手段をシールド機の前部に設け、これら土の湿潤密度と水分密度（含水量）を把握することで地山崩落面の予測を行う。土の湿潤密度検出手段と水分密度（含水量）検出手段は、線源棒を設けてシールド機の前部からガンマ線と中性子線を発し、線源棒から出たガンマ線と中性子線が、土の中を進行する過程で散乱を繰り返し、検出器に到達する放射線量から湿潤密度と含水量を求める。【選択図】 図１