Assessment of two-component backfill grouting quality for TBM tail voids via scaled physical modeling: Effects of injection flow rate, hardener dosage, and water-to-cement ratio - Hyun-Jun Kim; JunHyuk Jang; Daehui Kim; Tae-Hyuk Kwon; Tae-Young Kim; Song-Hun Chong; Min-Ji Kim; Tae-Min Oh; Hee-Hwan Ryu (Tunnelling and Underground Space Technology, 2026)