Numerical investigation of the influence of the yield stress of the yielding element on the behaviour of the shotcrete liner for yielding support

When tunneling in squeezing rock, the use of yielding support is recommended. In the yielding supports, the shotcrete liner is often divided into several segments with the yielding elements installed between them. The deformation ability of the yielding element is considerably greater than that of the shotcrete, and the yield stress of the yielding element can be adjusted as the support requirements. To investigate the influence of the yield stress of the yielding element on the behaviours of the shotcrete liner, a number of numerical analyses were conducted. In all of these numerical analyses, a connector element that can simulate the large deformation ability of the yielding element was used. According to the numerical results, the yield stress of the yielding element has a significant influences on the internal forces and failure behaviours of the liner. With the decrease of the yield stress, the axial force of the liner clearly decreases, while the bending moment concentration of the liner obviously increases. When the yield stress is extremely low, obvious tensile failure of the liner will occur because of the large bending moment of the liner, whereas when the yield stress is extremely high, clear shear failure of the liner will occur due to high axial forces of the liner. According to the total failure zone of the shotcrete liner, the optimum yield stress of the yielding element for the Xiakou tunnel is determined.