Abstract: A general segment 20 which is propelled and set in an excavated hole by a propulsion excavating machine, and a flexible segment where flexible members 4 and rigid ring members are alternately installed and connected inside the skin-plate 7 provided on the outer periphery side of the side rings 5 having the same thickness as the general segment and a thrust-receiving member 9 is provided inside the flexible portion, are propelled and set by the propulsion excavating machine and then secondary coating concrete 30 including a secondary watertight band 15 is applied to said side ring. As a segment for a shield tunneling method, the flexible segment appropriately provides flexibility to quickly cope with earthquakes and uneven settlement. The flexible segment may be handled in the same manner as a standard general segment during excavation work, providing excellent application potential.

Abstract: For a bearing mechanism, a pair of oil seals are installed within an outer cylindrical housing and elastically encircle a rotating or reciprocating shaft extending concentrically through the housing. Each of the oil seal is made of rubber or synthetic resin and has a prop ring made of steel wire extending underground through a radially outer portion of the oil seal. The prop ring is partly cut out and thus provides a radially outwardly directed elasticity for close adhesion to the inner surface of the housing. The radially outer portion of the oil seal extends in a radially inward direction to form an oil sealing lip and a dust sealing lip, with a narrow dog-legged portion at an intermediate portion of the oil seal which permits the oil seal to be flexible in a radial direction. An additional seal having substantially a similar elements and structure may be installed as a dust seal.