A.30 B.28 C.26 D.24
A.0.15~0.50倍洞跨 B.0.15~0.60倍洞跨 C.0.15~0.50倍水頭 D.0.15~0.60倍水頭
A.滑動與塌落、彎曲與折斷、松動脫落、變形與膨脹、巖爆 B.滑動與塌落、彎曲與折斷、松動與膨脹、巖爆 C.滑動與塌落、彎曲與折斷、脫落與膨脹、巖爆 D.滑動與塌落、彎曲與折斷、松動與變形、巖爆