隧道中用陆地声纳法在开挖的岩面或衬砌表面测围岩松弛带深度

DETECTING DEPTH OF RELAXATION ZONE OF TUNNEL SURROUNDING ROCK BY USING LANDSONAR ON SURFACE OF ROCK OR LINING

陆地声纳法在浅层勘查、隧道地质预报等方面已有大量应用,它可用锤击震源在隧道壁测量围岩松弛带的深度,经与双孔对穿声波测量法对比,二者所测结果相符。陆地声纳法现场采集简便,所需时间远少于声波测量法,还可在钢筋混凝土衬砌完成后进行。陆地声纳法可在围岩面、喷层表面或衬砌表面测出松弛带的界线及其反射时,并用折射波法或共中心点法测出松弛带岩体的平均波速,由此计算松弛带的深度。

Landsonar method is a new survey method that has been successfully used in shallow layer survey and geological prediction of condition before of tunnel working face. It can be used to detect the depth of relaxation zone of surrounding rock of a tunnel with a wave source induced by hammering on the surface of rock or lining. The results by landsonar method and acoustic wave measurement method with boreholes are compared, which shows that they are consistent. In the detection of the depth of relaxation zone of surrounding rock by landsonar method, the geophones are set near by the wave source point. The measuring stations are arranged in a measuring line of 2-4 m long with a distance of 20-30 cm to one another. The data of all stations in a line are treated to a time-section on that the reflection image of the boundary line of relaxation zone can be clearly differentiated. Wave velocity can be measured by refracted wave method or common center point method on surface of rock mass or lining; and the depth of the boundary line of the relaxation zone can be calculated. Landsonar is more time-saving and convenient because it does not need boreholes which are needed in acoustic wave measurement method.