Abstract: A smalldiameter conventional pipejacking machine cannot be dismantled and maintained in tunnels, and the cutters on the cutterhead cannot be replaced after failure. Therefore, a reversible cutterhead that can be used in a smalldiameter pipejacking machine is designed. A numerical calculation method is used to determine the correlation factors of the turning arm′s angle. Furthermore, three structural designs for the key components of the reversible cutterhead are proposed. The structural strength is examined, and the muck fluidity is analyzed through numerical simulation. Finally, the feasibility of the reversible cutterhead is validated through indoor tests and site application. The results are summarized as follows: (1) Factors, such as the position of the rotation center, gravity center, allowable limit position, size and bearing capacity of cutters, and structural strength, should be considered for the turning arm. (2) Three key-targeted designs of the turning arm, i.e., separation design of connection and torsion, twoway limit design, and eccentricity design of the edge disc cutter, can meet the requirements of engineering geology and equipment reliability.

Key words: pipejacking machine, reversible cutterhead, turning arm, structural strength, muck fluidity