Application of freezing method to shift down an exiting tunnel

To construct the subway KAIGAN line crossing an existing ITT cable tunnel line, the cable tunnel cross sections as 40.7m are shift down at 4.55m with freezing method. In order to create the minimum volume of frozen soil wall around an existing tunnel, total numbers of 106 curve freezing pipes with length of about 10m are installed from the both sides of an existing tunnel circularity. To obtain the effect of excavation for frozen soil, a new machine with twin-header provided 60hard-bits is used. As these new techniques the construction was completed safely within construction period.