Mechanical Performance of Circumferential Yielding Components and Their Adaptability in Steeply Inclined Rock Tunnelling

To address the frequent failure of initial support structures in steeply inclined rock strata, unconfined compression tests were conducted on steel tube components, vertical SRLD elements, and V-SRLD elements. Based on the test results, numerical simulation methods for steel tube components and vertical SRLD elements were established using a tri-linear elastic constitutive model combined with Euler′s buckling formula for compression members. Numerical simulations of a steeply inclined phyllite Tunnelling were then performed to evaluate the applicability of circumferential yielding support. The results show that: (1) circumferential yielding support promotes stress relief and energy release of the surrounding rock, thereby reducing damage to the shotcrete layer; (2) under the bench excavation method, shotcrete damage at sidewalls caused by bending is difficult to prevent using yielding support, whereas under full-face excavation, shotcrete damage is effectively controlled when combined with circumferential yielding support; (3) when installed at the vault, vertical SRLD elements, owing to their higher initial stiffness, are more effective in resisting interlayer slip of steeply inclined phyllite; and (4) under circumferential yielding support, slip between the shotcrete layer and surrounding rock readily induces tensile yielding of rock bolts.