FLOOR LEVEL MOTION OBSERVED IN THE KEKB TUNNEL

The level of the KEKB tunnel floor has been monitored using tilt meters. A clear diurnal effect, which seems to have a strong correlation with the outside air temperature, has been seen. The tunnel level appears to be affected by atmospheric pressure as well. Simultaneous measurements in the basement floor and at four locations along the beam line were carried out. They show that the amplitude of the daily floor motion is largest on the basement floor of the experimental buildings and is reduced on the far side of the expansion joint away from the building. Measurement results are shown.