Effect of ground settlement restraint by soil nail in a soft ground tunneling

摘要

One of the most important factors in the soft ground tunneling is the restraint of the ground settlement. In this study, soil nailing method is used as a method of ground settlement restraint. The effects of nails are analyzed by the laboratory model tests. Several tests concerning the effect of position and length of the nail are analyzed with respect to the ground settlement. Air dried Gupo sand, which is dumped into a soil box by air-pluviation method under the plane strain condition, is used as a model ground. In order to analyze the position effect of the nail, the tests are performed for three different cases. Locations of the nail for each case are as follows; (1) the nail is located in the upper part of the tunnel, heading to the ground surface (2) the nail is located in the center of the tunnel, laid in the horizontal direction (3) the nail is located in the lower part of the tunnel, heading to underground. As the results of the tests, the following facts are found. The effective length of the nail is 0.5D. Where, D is diameter of the tunnel. The nail of the lower position is more effective than that of the upper position for reducing the ground settlement.