NATURAL GROUND REINFORCING METHOD

To provide technology related to a natural ground reinforcement method that can suppress subsidence of a tunnel prior to the excavation of the front natural ground in a tunnel excavation direction.SOLUTION: A natural ground reinforcement method that a drilling hole is drilled in the natural ground on the side from the side wall of a tunnel located near the cutting face of the tunnel, a core material for reinforcing the natural ground is injected into the drilling hole, a solidification material is injected in the drilling hole, or a core material for reinforcing the natural ground is injected into the drilling hole after filling the drilling hole with the solidification material, and a natural ground reinforcement part in the natural ground is formed, comprising : in the natural ground reinforcement part, a natural ground drilling angle between a drilling direction and a tunnel excavation direction with respect to the natural ground on the side is set to an acute angle, at least part of the natural ground is formed so as to extend to the natural ground in front of the cutting face.SELECTED DRAWING: Figure 3 【課題】トンネルの掘進方向における前方地山の掘削に先立ってトンネルの沈下を抑制することの可能な地山補強工法に関する技術を提供する。【解決手段】トンネルの切羽近傍に位置するトンネル側壁部から側方の地山に削孔を施し、削孔内に地山補強用芯材を挿入した状態で削孔内に固結材を注入、又は、削孔内に固結材を充填した後に削孔内に地山補強用芯材を挿入することで地山内に地山補強部を形成する地山補強工法であって、地山補強部は、側方の地山に対する削孔方向とトンネル掘進方向とのなす地山削孔角度が鋭角に設定され、少なくとも一部が切羽前方地山に延在するように形成される。【選択図】図３