ABSTRACT
In the apparatus 12 load cells are used to measure earth pressure acting on the tunnel. The load cells are attached with the block which is placed surrounding the segments of the tunnel. Each load cell block is 2.35cm in width and 5.0 cm in length. The blocks are tightly fastened with rubber band. Therefore, earth pressure can be obtained at 12 points on the periphery of the tunnel at a time. Earth pressure can also be obtained at other positions by rotating the tunnel. However, in this case it will be required to make the model ground once again. Including the load cell bocks the total diameter of the model tunnel is 10.0 cm. The circular tunnel device is placed on an iron table that was used for the trap door tunnel apparatus (Nakai et al., 1997; Shahin et al., 2004). It has 10 moveable blocks above which the ground is made. The reason of using this type of base is to adjust the initial stress condition of the ground such a way that the stress distribution becomes similar to the ground without tunnel. The surface settlement of the ground is measured using a laser type displacement transducer with an accuracy of 0.0 1mm and its position in the horizontal direction is incurred with a supersonic wave transducer. Photographs are taken during experiments which are later on used as input data for the simulation of ground movements with Particle Image Velocimetry.
