A NEW EVALUATION METHOD OF EARTH PRESSURE ON MULTI-CIRCULAR FACE SHIELD TUNNEL BASED ON CENTRIFUGE MODEL TESTS

The multi-circular face shield tunneling method is a method which makes it possible to construct various shapes of section. In this method, several cutter faces are horizontally or vertically combined to construct double, triple or more circular sections. Therefore, the necessary section could be efficiently assured in the over densely occupied underground space of cities, and the construction term could be shortened with the amount of the excavated earth being reduced. Because of the complicated shape of section, however, for the design of segment lining, it is necessary to verify the applicability of conventional earth pressure evaluation method (for total earth pressure, loosen earth pressure of Terzaghi), which has been adopted for the single circular section. In this study, the earth pressures on a horizontal triple circular tunnel and a vertical double one were investigated through centrifuge model tests, and a new evaluation method of earth pressure on segment lining was proposed based on the behavior of surrounding ground during the shield driving.