Undrained adhesion of consolidated mudstone muck under varying water contents and stress histories for shield tunnelling

During shield tunneling, muck adhesion can readily leads to shield clogging. To investigate the effects of effective consolidation stress, water content, and stress history on adhesion strength, consolidated undrained rotary shear tests were conducted on saturated moderately weathered mudstone muck using a modified rotary shear apparatus. The results indicated that as the rotational shear angle increased, the interfacial shear stress between normally consolidated muck and metal decreased by 30–40% after reaching its peak. In contrast, the interfacial shear stress of overconsolidated muck remained near its maximum. For normally consolidated muck, adhesion strength increased linearly with effective consolidation stress, with an effective interfacial friction angle of 10°. At zero effective consolidation stress, the muck exhibited high water content and zero effective interfacial adhesion force. For overconsolidated muck, unloading resulted in progressively faster decreases in adhesion strength as effective consolidation stress decreased, while reloading caused progressively faster increases as effective consolidation stress rose. Overconsolidated muck exhibited higher interfacial effective stress than normally consolidated muck due to the presence of water pressure, leading to higher adhesion strength. Additionally, higher water content reduced adhesion strength. The mechanical mechanism of muck adhesion and possible engineering measures for mitigating shield clogging are analyzed.