The double‐row capsule grouting (DRCG) is an innovative technique which can restrain the horizontal and vertical tunnel deformations induced by excavation simultaneously. The real‐time and active control capacity of DRCG can overcome the shortcomings in invariance and inefficiency of the traditional protective approaches. However, the performance of DRCG and the prediction method of control effectiveness have not been investigated. A numerical analysis using the hardening soil model with small‐strain stiffness (HSS model) is conducted to investigate the influences of the relative buried depth and the grouting volume of capsule on the control effect of DRCG in relation to the restoration ratio of horizontal deformation (R_h), and restoration ratio of vertical deformation (R_v). A polynomial relationship between parameters and restoration ratio is observed. Furthermore, a dimensionless formula, developed from hypothetical cases, shows a high conformity between predicted and numerical results. It can accurately predict the control effectiveness of DRCG.

To enhance the seismic performance of reinforced concrete (RC) elements, it is essential to consider both strength and ductility post-yielding. This study proposed a novel method to improve the ductility of RC piers by using preformed inward-bending longitudinal reinforcements at the plastic hinges. Two full-scale model tests of standard and ductility-enhanced (DE) RC piers and numerical simulations were conducted. The lateral reversed cyclic loading experiments were conducted to assess the effectiveness of this new approach. The performance was evaluated regarding failure mode, plastic hinge distribution, hysteretic properties, normalized stiffness degradation, normalized energy dissipation capacity, bearing capacity, and ductility. Non-linear finite element method (FEM) analyses were also carried out to investigate the usefulness of the proposed method by DIANA, and simulation was validated against the experiment results by hysteretic curves, skeleton curves, failure mode crack pattern, ductility coefficient, and bearing capacity. The results indicated that the proposed method enhanced bearing capacity, resistance to stiffness degradation, energy dissipation capacity, and ductility. Additionally, it was observed that the preformed positions and curvature of the main steel bars influenced the plastic hinge location and the buckling of longitudinal reinforcements. FEM analysis revealed that it might be reasonable to deduce the other factors that influenced the ductility of the specimens by using the same material parameters and models.