Shield supporting cycle. (a) Temporal evolution of shield resistance and loading rate in a typical shield-supporting cycle without yielding. The three periods are (I) initial period, (II) relatively stable period, and (III) cutting-influenced and neighboring shield advance period. (b) An example determination of shield-supporting cycle by SSRI (Panel LW22306 of Bulianta mine). ps, psr, and pf denote setting pressure, revised setting pressure, and final pressure, respectively.