In braced excavations retained by piles, insufficient embedment depth or pile tips ending in soft soils can cause kick-in failure, potentially leading to progressive collapse. This study examines a real excavation failure caused by kick-in instability. A three-dimensional finite difference model was developed to investigate the effects of insufficient pile length, stratigraphic heterogeneity, and strut–pile connections on the kick-in failure mechanism. Based on these analyses, a resilient design method using combined long and short piles is proposed to mitigate progressive collapse, and its performance is evaluated in terms of deformation control, internal force distribution, anti-kick-in stability, and cost-effectiveness. The results show that kick-in failure occurs suddenly, with little pre-failure deformation, and a slip surface initiates at the pile toe and propagates upward. Stratigraphic heterogeneity is identified as a key factor contributing to localised kick-in failures. The proposed long–short pile design—where long piles provide embedment and short piles retain soil—significantly improves anti-kick-in stability while maintaining the total pile length. Although bending moments in the long piles increase, this can be managed through proper reinforcement. Compared with a full-short-pile scheme, the long–short pile scheme increases construction cost by about 50%, but reduces cost by about 5% compared with a full-long-pile scheme. These findings provide a theoretical basis for resilient design against kick-in failure in braced excavations in soft soil areas.